INVESTIGATING TEMPERATURE MEASUREMENT METHODS AND THEIR IMPACT IN EMBEDDED SYSTEMS

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V¨

aster˚

as, Sweden

Thesis for the Degree of Master of Science in Computer Science with

specialization in Embedded Systems 15.0 credits

INVESTIGATING TEMPERATURE

MEASUREMENT METHODS AND

THEIR IMPACT IN EMBEDDED

SYSTEMS

Zhaneta Nene

zne19001@student.mdh.se

Examiner: Thomas Nolte

M¨

alardalen University, V¨

aster˚

as, Sweden

Supervisor: Nandinbaatar Tsog

M¨

alardalen University, V¨

aster˚

as, Sweden

Company supervisor: Pontus Eriksson

Westermo, V¨

aster˚

as, Sweden

May 20, 2020

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Testing is one of the most important aspects in the development of new products. There are different types of testing a product can undergo, either hardware durability tests or software tests. Embedded systems are closely related to hardware and a key feature of them is the reliability and dependability. In order to assure that these features will remain intact no matter where the embedded systems operate it is very important to conduct standardized testing and give validation. The purpose of this thesis is to research the temperature testing procedure and develop a measurement guideline based on several key moments. The guideline is closely related to the standards and due to this reason some of the most frequently used standards are taken in consideration. The temperature measurement technology involves different tools or equipment. One interesting technology used for this purpose is the infrared technology through the investigation provided by the IR cameras. It is beneficial to integrate this technology in the contact measurements because it describes the temperature variation by colors, information which is very important in the first steps of the test procedure.

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Acknowledgement

I would like to express my deep appreciation to my supervisor Nandinbaatar Tsog who has guided and encouraged me throughout the work of this master thesis. Next I would like to show my gratitude to my company supervisor, Pontus Eriksson for the technical help and valuable discussions. A special thank you also goes to the Westermo company and the engineers there who have shown great support and provided all the necessary resources without which this work would not have been possible. Finally a great thank you goes for my family for all the support and love throughout the years of my studies.

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*List of Abbreviations

PCB Printed Circuit Board

HALT Highly Accelerated Life Test

HASS Highly Accelerated Stress Screening

IRT Infrared Thermography

SDO Standards Development Organisation

IEEE Institute of Electrical and Electronics Engineers

JIS Japanese Industrial Standard

SA Standards Australia

CEN European Committee for Standardization

EN European Standard

IEC International Electrotechnical Commission

IC Integrated Circuit

RTD Resistance Temperature Detector

IR Infra Red

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List of Figures

1 Principle of the test [1] . . . 10

2 The HALT process [2] . . . 10

3 Process of developing an IEEE standard [3] . . . 13

4 Process of developing an JIS standard [4] . . . 14

5 Process of developing a SA standard [5] . . . 14

6 Process of developing CEN standard [6] . . . 15

7 A multi-methodological research approach [7] . . . 18

8 Dry heat test [8] . . . 20

9 Cold test [9] . . . 22

10 Loctite 416 and PT 1000 . . . 29

11 Loctite 454 and PT 1000 . . . 29

12 UV light glue . . . 30

13 Normalisation of probes . . . 32

14 Loctite 416 steady state with no airflow result . . . 33

15 Steady state with 50% airflow result . . . 34

16 Steady state with 100% airflow result . . . 34

17 Steady state with 50% airflow and changed input . . . 34

18 Steady state with 100% airflow and changed input . . . 35

19 Loctite 454 steady state with no airflow result . . . 36

20 Steady state with 50% airflow and 30°C chamber . . . 37

21 Steady state at 100% airflow and 30°C chamber . . . 37

24 Steady state at 100% airflow at 70°C ambient . . . 38

25 Loctite 454 steady state with 50% airflow and changed input . . . 38

26 Loctite 454 steady state with 100% airflow and changed input . . . 39

27 UV glue steady state with no airflow result . . . 40

28 UV glue steady state with 50% airflow at 30°C chamber . . . 40

29 UV glue steady state with 100% airflow at 30 °C chamber . . . 41

32 UV glue steady state with 100%airflow at 70 °C chamber . . . 42

33 UV glue steady state with 50% airflow and changed input . . . 42

34 UV glue steady state with 100% airflow and changed input . . . 43

35 Epoxy glue steady state with no airflow result . . . 44

36 Epoxy glue steady state at 50% airflow . . . 44

37 Epoxy glue steady state at 100% airflow . . . 45

38 Epoxy glue steady state at 50% airflow and 40°C chamber . . . 45

41 IR camera experiment results . . . 47

List of Tables

1 Temperatures for dry heat test . . . 19

2 Duration for dry heat test . . . 20

3 Temperatures for cold test . . . 21

4 Duration for cold test . . . 22

5 Temperature range and accuracy of thermocouples . . . 24

6 Comparison between temperature probes . . . 25

7 Normalisation values . . . 32

8 Offset values of probes . . . 32

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1 Introduction

Embedded systems are one of the most essential subjects in the digital world. The presence of them is noticed from the consumer electronics of the everyday lifestyle such as mobile phones and laptops followed by household appliances, to automobile or aerospace industry and communications area. Their broad range of usage often puts embedded systems in environments where the temperature differs by many degrees from the normal condition temperature of 20 degrees Celsius. In this scenario the manufacturer should validate the product and guarantee its reliability.

Embedded systems should be reliable. This means that the company that is producing them should make sure that their products will comply to certain standards and will behave according to them. This is why testing in industry is very important. The manufacturers use different testing methods and from the obtained results verify the products. One of the many possible tests a product might undergo is temperature testing.

These kind of tests specify the temperature range a product can support without changing its functionality. In a scenario where a product is part of a larger embedded system which operates in extreme temperatures verifying the temperature range of it is very important. There exists a number of temperature tests as well as environmental standards, each of them derives from the scientific knowledge and understanding of physical principles, hardware development and testing. Despite the existence of many testing methods there is often not followed only one particular way of performing it. This fact might affect the quality of measurement. Throughout this master thesis, these methods will be studied, together with a way of developing a new guideline to facilitate the testing procedure. This guideline will take into consideration the key moments of temperature testing, from choosing the right temperature probe to the effect that airflow has in a product and based on the results of several experiments, will give a solution. Except the common temperature testing materials such as temperature chambers, temperature sensors and conversion equipment, on this master thesis the infrared thermography will be investigated and aimed to be included as a standard step when performing this type of tests.

1.1 Motivation

This master thesis work will investigate on different temperature measurement methods as well as temperature testing standards and understand the properties of them. This will serve the purpose of exploring how a temperature testing standard is created and what are the key moments that have to be taken in consideration in this type of procedure. In the end, the goal will be to propose a guideline which will be built on top of the existing knowledge and after investigating on the uncertainties of existing ones. The guideline will be comprised of several steps which will be validated after performing the respective experiments. This steps resemble those found in standards created by well known organizations but the difference will be that the guideline proposed by this master thesis is more simplified and will investigate only towards certain topics which are of interest by the company in collaboration. Another investigation will be made towards the infrared thermography technology, its benefits and how it can be integrated in a temperature testing procedure.

1.2 Problem formulation

Embedded systems industry, being one of the most popular and powerful industries nowadays, will continue to grow in the following years which points out even more the importance of research to-wards guaranteeing the reliability of their products. This thesis will be focused on the temperature testing methods which are closely related to temperature testing standards and in this context will aim to answer the following research questions:

• How is a temperature testing standard created?

• What is infrared thermography, and how can it be integrated in a temperature testing guide-line?

In order to answer these research questions there will first be an evaluation of existing tem-perature tests and standards as well as relevant literature related to infrared thermography will

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be taken in consideration and afterwards discussions will take place with company specialists. The experimental procedure, will in the end aim to develop a guideline related to temperature measurement methods.

To provide an accurate answer related to measurement guideline, the following concrete problems will be addressed considering the practical part:

• Tests with Lynx-NG[10] • Tests with PCB-s [10]

• Tests with electronic components[10] • Temperature probe placement[10]

During testing it has been noted that depending on the way the temperature probe is fastened in the product, the temperature of the air in the product differs by up to 9 degrees. This difference is even higher if the wires are glued to the chassis rather than the PCB. This leads to the question, which is the correct way to mount the temperature probe?

By combining the theoretical knowledge and the result from experimenting with the practical problems, which will be performed in an industrial environment, a new guideline will be created on how to perform temperature testing. The term quality of measurement refers to the factors influencing the accuracy of measurement such as the environment where the measurement takes place, errors in calibration, choice of temperature probes and glues or other factors which may be identified during the work.

These problems are of interest because they represent common methods of temperature testing in today’s industry and the situations described above are often met in many industrial environments.

1.3 Limitations

This master thesis is done in collaboration with the Westermo Company. The hardware, measuring equipment and industry standards taken in reference are based on the company’s production and field of interest. Therefore the guideline proposed in the end and the research towards infrared thermography and standards comply only with this company.

1.4 Thesis outline

This report is constructed as follows:

• In section 2 the background is presented. The background topics covered are definition and examples of embedded systems, thermal fundamentals, temperature testing inspection and related work.

• Section 3 presents the process of creating a standard according to some well known standard creating organizations such as IEEE, JIS, SA, CEN and IEC. In the end a summary related to this process is given.

• Section 4 describes the methodology that will be followed to solve the problem in the form of steps as well as the research method.

• Section 5 aims to answer the research question of how temperature testing standards are created. Two standards that are used often in industry such as dry heat testing standard and cold test standard are taken in consideration.

• Section 6 discusses some background information on the key topics that have to be taken in consideration when performing temperature tests. Among these topics critical components, temperature probes, probe mounting methods and the meaning of steady state are discussed. • Section 7 discusses the second research question related to Infrared Thermography and how

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• Section 8 presents the experimentation conducted in the company. The experimentation was focused on several topics such as probe types, glue types, and infrared thermography. • Section 9 summarizes the results of this master thesis, as well as discusses the guideline. • Finally in section 10 future work will be discussed.

2 Background

This section will introduce the key subjects related to this thesis work. Section 2.1 provides a definition of embedded systems together with some examples of embedded systems usage in real life. Section 2.2 describes some thermal fundamentals, how heat is transferred between two bodies and finally an important physical quantity related to temperature. Section 2.3 presents an inspection of temperature testing which considers of some industrial scenarios where it applies and some examples of how temperature testing methods work. In the end there will also be a section about the related work.

2.1 Embedded systems

A general definition of embedded systems is: Embedded systems are computing systems with tightly coupled hardware and software integration, that are designed to perform a dedicated func-tion [11]. The word ”embedded” clarifies the fact that these systems are integrated on a larger system, known as the embedding system. Also many embedded systems can coexist in one single embedding system.

In the majority of cases, embedded systems do not function on their own, for example the digital audio/video decoding system or A/V decoder which is part of the digital set-top (DST) box. In other cases embedded systems can function as a standalone system. The network router for example, is built using a communication processor, memory, network access interfaces or ports and a special software. This system manages to route packets that come from one port to another, based on the routing algorithm that is implemented.

Embedded systems are also seen as dedicated computers which are designed to perform a few specific functions. Because of this fact engineers tend to optimize factors such as size, cost, power consumption, performance and reliability. Embedded systems software is very hardware specific. This means that the software developed for one hardware cannot operate on another because of the differences in port addresses or other specifications.

2.1.1 Real life examples of embedded systems

Embedded systems are present in numerous industries varying from automation, defense, trans-portation, aerospace or communication. Embedded systems can also be found at home, work or in consumer electronic devices. It is difficult to find a part of daily life that does not involve embedded systems in a way. As an example there are cable and satellite boxes for televisions, home cinema systems, telephones, printers, modems, music players etc. Embedded systems in combination with other technologies deliver benefits to other aspects of human’s lives as well. GPS technology, for example is one of the cases. GPS uses satellites to pinpoint locations to centimeter level accuracy [11]. This allows people to move freely in unknown territories without getting lost.

Embedded systems are also noticed in the radio-control airplanes, race-cars or boats. These devices take command input from joysticks and pass them wirelessly to the receiver of the device which allows them to perform safe journeys. Some other well-known applications of embedded systems are NASAs Mars Path Finder and Lockhead Martin’s missile guidance system.

2.2 Thermal fundamentals

In thermodynamics, from a macroscopic viewpoint the temperature is defined as the property that is shared by two systems, initially at different states, after they have been placed in thermal contact and allowed to come to thermal equilibrium [12]. Another definition from the microscopic viewpoint for the special case of an ideal gas is: ”Temperature is directly proportional to the square

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of the mean molecular speed. Higher temperature means faster moving molecules [12]. From these definitions we can realise that temperature is a state variable that reflects the level of internal energy possessed by a system.

Another important concept is the difference between heat transfer and thermodynamics. Ther-modynamics deals with systems in equilibrium and can be used to determine the energy required to change a system from one equilibrium state to another. Thermodynamics cannot, however, enable us to determine the rate at which the change occurs [13]. On the contrary, heat transfer analysis can tell us the time-dependent process of the state change [13].

2.2.1 Heat transfer theory

Integrated circuits generate heat that must be removed, or transferred to the outer environment. If this does not happen, the operating temperature will accumulate and cause malfunction which will eventually destroy the system. Heat transfer is the transport of thermal energy from one region to another. In order for heat transfer to occur, there must be a temperature difference between the two regions [13]. The first law of thermodynamics related to conservation of energy states that the heat given by the hot region has to be equal to the heat absorbed by the cold region. In addition the second law defines that the heat transferred, is transferred from the hot region to the cold one or heat flows in the direction of decreasing temperature.

There are three ways in which heat transfer happens: • Conduction The heat transfer in solids.

• Convection The heat transfer between a solid surface and a moving fluid touching the solid surface.

• Radiation The heat transfer mode in which thermal energy is transported by electromagnetic waves.

2.2.2 Physical interpretation of temperature gradient

When studying on the temperature testing a popularly known physical quantity is the temperature gradient. The temperature gradient on itself is defined by two physical quantities, temperature and length. Temperature is known as the degree of hotness or coldness of an object or body. So finally the temperature gradient is defined as the ratio of the temperature difference between two points and the distance between these two points [14]. In the basis of temperature gradient, uniform heating tests and thermal shock tests are used today to evaluate the heat resistance. These methods are capable of realizing necessary temperature gradient by controlling both the surface and rear face temperatures of the tested piece, as described in [1].

2.3 Temperature testing inspection

This section provides information related to industrial scenarios where temperature testing is applied and some of the methods used to perform it.

2.3.1 Temperature testing applicability

An industrial scenario where temperature testing applies is in temperature sensors used in trains which operate in Scandinavian countries, described in [15]. When the train is put into operation every day the sensor might be exposed to temperatures deep below zero during winter while during the drive it will heat to a relatively high temperature and finally at the end of the day it will decrease again to the ambient temperature. These sensors are part of a larger system whose reliability depends on the correct functionality of their components, which implies the importance of verifying the sustainability of them. In order to verify their sustainability, an accelerated test based on cyclic thermal changes is used. This test aims to verify the sensor’s functionality for 10 years of technical life operating 18 hours per day on average and being subjected to temperatures ranging from -50 degrees to 180 degrees.

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In order to perform this test a climatic chamber is used. After the test starts the sensors are heated to 180 degrees and when this temperature is achieved it levels off and is kept in the chamber for 45 minutes. After 45 minutes elapse the cooling part begins and the sensors are gradually cooled off to -50 degrees. This temperature is again kept for another 45 minutes. This process is repeated for nearly 9 months and each cycle takes 230 minutes. This test reveals two failure modes:

• Complete failure- The sensor has lost all sensor functions.

• Decreased accuracy of temperature measuring- A lot of measurement errors were recorded. A certain disadvantage of this test is that only one kind of load is simulated and other kinds of operations which might affect the temperature sensor’s reliability such as vibrations or humidity are not taken in account.

Other industrial components such as air-craft engines or gas turbines are subject to temperature gradient. The temperature gradient influences thermal cycle damage from the continuous start and shut down operations. Therefore these components require a testing method which will guarantee their functionality. This problem is described in [1] where is also presented a testing method which is a Japanese Industrial Standard (JIS) named ”Testing method for heat resistance under temperature gradient”. This testing method will be described briefly in the section below. 2.3.2 Existing test methods

• Testing method for heat resistance under temperature gradient

Testing method for heat resistance under temperature gradient is a japanese industrial standard established by the Minister of Economy, Trade and Industry. According to this standard a testing method for heat resistance of materials exposed to high temperature under temperature gradi-ent is specified. This test aims to be used on equipmgradi-ent such as aircraft engines, gas turbines, accelerators, power switch-gears etc.

The test can be described as following: The test piece mounted on the jig is subjected to temperature gradient by heating its surface and cooling the rear surface of the jig. The heating source shall be chosen from among burner heating, arc heating, plasma heating and beam heating by lamp, laser or electron beam. The cooling source, such as water and gas, should have the performance enough to obtain the required temperature gradient [1]. This is represented in figure 1.

Both surface and inner temperatures of the jig must be measured in real time using a radiation thermometer and thermocouples respectively. After the test is conducted, evaluations of the dam-age state and fracture morphology are made. This can determine the cyclic thermal resistance of the test pieces.

In 1957 IPC (Institute for Printed Circuits) was formed. The mission of IPC is to represent all facets of the electronic industry, including design, printed circuit board manufacturing, and electronics assembly [2]. IPC is a leader in industry standards, training and market research.

• Highly accelerated life test (HALT)

HALT was developed by Hobbs Engineering Corporation and is defined as ”HALT is a series of tests performed on a product as part of the design process to aid in improving product robustness. The principal idea of HALT is to find design weaknesses as quickly as possible and then fix them. After improving one weakness, the next design weakness is found and improved and so on until no design weaknesses remain that could result in field failures. During HALT a product is stressed beyond the product specifications” [2].

The 9592A IPC standard requires a test system capable of stressing the product in a combined thermal and vibration environment, using repetitive shock (RS) 6 degree of freedom (DOF) vibra-tion1_[₂_{]. The minimum vibration level specified is 50gRMS}2_{and the temperature range is between}

-80 degrees to 170 degrees. The thermal change rate is at least 40 degrees per minute. In order to achieve this rate the direct injection of liquid nitrogen cooling technique is required.

1_{Repetitive shock (RS) 6 degree of freedom (DOF) vibration means that the unit under test is simultaneously}

stimulated in the three axes and rotations around axes as well.

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Figure 1: Principle of the test [1]

Figure 2: The HALT process [2]

• The HALT process

HALT process incorporates thermal and vibration stresses. These stresses are applied separately and then in combination. According to 9592A the description of the HALT process can be schema-tized as follows: The completion of the actual HALT test which includes the identification of failure modes is only the beginning of the work. The most important part of the process is to perform root cause failure analysis to implement corrective actions [2].

• Highly accelerated stress screening (HASS)

HASS is a test used in the production phase which helps reduce the number of infant mortality types of failures [16]. HASS was developed by Hobbs Engineering Corporation. It uses the highest possible stresses in order to reduce the time of the screen [16]. The screen must be proven using the HASS Development process, prior to using it in manufacturing. HASS is performed on all units shipped for screening the product.

The equipment needed for HASS is very similar to the equipment used for HALT but with some key differences. The limits for HASS are by definition lower than those found in HALT, so the HASS system may not need the extreme temperature range, rates of change or high vibration levels used in HALT [2]. The standard states that the test must be performed in industry standard HASS/HALT chambers but the thermal change rate is reduced to 30 degrees. A very important equipment for the HASS testing is the HASS fixture. The 9592A IPC standard implies that the

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fixture should be designed and fabricated to support the products through-put testing and provide proper vibration transmissibility, thermal uniformity and a balanced thermal rate of change [2].

• Infrared thermography for temperature measurement and non-destructive test-ing

Infrared thermography is based on infrared radiation which is the energy radiating by the surface of an object whose temperature is above absolute zero [17]. The radiation, which is emitted, is a function of the temperature of the material, which can be described as: the higher the temperature is, the greater is the intensity of the infrared energy.

When using IRT not all the radiation received comes from the target object, so in order to have an accurate measurement the radiation that comes from other sources must be removed. This process is called compensation. The total radiation is composed of three sources: emission of the target object, emission of the surrounding environment and emission of the atmosphere. The most important calibration parameter is emissivity. Emissivity indicates how much radiation is emitted from the target object compared to that from a black body at the same temperature [17]. Infrared thermography used for non-destructive testing measures and interprets the temperature field of the surface of the body being studied [17]. The theoretical principle is based on the fact that the internal structure of the inspected object and its flaws will have a different thermal behavior [17]. The defects affect the flow of a previously applied heat source, which will be heated or cooled at different rates. The result is temperature differences on the surface of the object, resulting from differences in radiation emission captured by the infrared camera [17].

• Multi-temperature testing

Other researches have also shown that different defects can appear as failures when exposed to different temperature ranges in core based systems-on-chip. This brings out the need to perform multi-temperature tests. Some defects may be sensitive to a certain temperature level, for example, metal interconnections may pass a test in nominal temperature but fail the exact same test in a higher temperature.

Temperature has a big impact on electrical properties of transistors and other electronic com-ponents. In high temperatures carrier mobility in the thin metal lines connecting the transistors decreases and as result the interconnection resistance increases. This leads to performance degra-dation which is why integrated circuits should be tested in high temperatures in order to guarantee a reliable functionality in a wide temperature range. Multi-temperature testing is described in [18].

• Temperature testing method for very low temperatures

There are many embedded systems which operate in very low temperatures, for example integrated circuit chips of satellites. This presents the need to test the functionality of these circuits in very depressed temperatures. When the temperature is lowered under atmospheric conditions, condensation or frost can develop and accrete on the exposed surface of the integrated circuit chip [19]. Motivated by these reasons the inventor Kenneth F. Hollman patented a method and apparatus for performing depressed temperature tests on electronic components which is described in [19].

2.4 Related work

This master thesis will rely on the knowledge related to embedded systems and temperature test-ing methods. For this purpose the followtest-ing papers have been chosen which describe existtest-ing temperature testing methods. In paper [15] authors describe the methodology of performing and evaluating the accelerated life test of temperature sensors. The sensors under study are designed for trains in Scandinavian countries which undergo significant temperature changes. The test method described in this paper consists of undergoing thermal changes ranging from -50 degrees to 180 degrees. Keeping in mind that these sensors are applied in a similar manner in other applications of embedded systems the importance of testing their reliability emerges.

In paper [1] the authors have described a Japanese Industrial Standard (JIS) which is strongly related to the physical quantity of the temperature gradient. They have described the testing

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process together with the outcomes. This is useful for understanding how to set up a testing environment and also understand the factors that affect the result.

As part of the existing temperature testing methods in this thesis, there are mentioned two methods which are used in the industry to evaluate the performance of the products. These methods, HASS and HALT are stimulating tests in which the product is exposed to environmental stress beyond what it would normally experience. The stress in HALT consists of thermal and vibration changes stimulated by repetitive shock(RS) 6 degree of freedom (DOF). HALT aims to find problems related to the design of the product and are described in paper [16] and [2]. HASS is applied in the production phase. The equipment needed for HASS is very similar to HALT but with some key differences as described in [2].

In order to understand more about the way how temperature testing methods work, paper [17] is chosen. Here the authors have presented infrared technology for measuring the temperature. This technology allows non-destructive testing and leans on the infrared energy, which is the energy radiated by an object whose temperature is higher than the absolute zero. The investigation at [20] also discusses infrared thermography. It provides insight about this technology as well as how to integrate it in the temperature measurement process.

In embedded systems different electronic components might have specific behaviours in different temperatures. In paper [18] the authors have presented the importance of a multi-temperature test for electronic components. Many electronic components that make up integrated circuits change their electronic properties in different temperatures. For example the carrier mobility decreases in the thin metal layers which connect the transistors. This leads to interconnect resistance. Threshold-voltage is another temperature dependent parameter in transistors which increases with rising temperature. The test proposed in this paper is done through a scheduling algorithm which uses a finite state machine to manage the temperatures of cores and a thermal simulator which obtains instantaneous temperatures of all individual cores [18]. In paper [21] the authors describe the concern about thermal performance of microelectronics related to the failures caused by over-heating and the importance of heat sink device to reduce the overover-heating. This paper provides knowledge related to the importance of validating the products thermally and gives insight into the methods that designers use to reduce the overheating in their products. In paper [19] the author has presented a method and an apparatus to perform low temperature testing of electronic components which make up larger systems used in very low temperatures such as satellites.

As one of the goals of this thesis is to propose a new standard, several standards associations (SA) processes of making a new standard will be taken into account. IEEE is part of Stan-dards Development Organization (SDO) together with IEC, ISO and others and offers rules and methodologies for developing, distributing and maintaining standards. The process of developing a standard is comprised of a number of phases such as:

• Initiating the project

• Mobilizing the working group • Drafting the standard • Balloting the standard • Gaining final approval • Maintaining the standard

These steps are described in [3]. As a knowledge contribution for this master thesis there were also used documents which were provided by the Westermo company such as the IEC dry heat standard[8], IEC cold test [9] standard which provided an insight on how a standardized test is built and what are the important points that should be defined in a similar guideline.

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3 Standard creation process

The process of creating a standard is handled by a standards development organization (SDO) such as ISO, IEC, IEEE, JIS ect. The goals of each SDO are the same but each of them applies their own rules, processes and terminologies to the development process of a standard. Each SDO is made of boards, committees and staff who establish and follow the guidelines and procedures. This section will describe the process of standard creation according to five different SDO-s such as IEEE, JIS, SA, CEN and IEC.

3.1 IEEE standard

The development of a new standard is triggered by a formal request which is submitted to IEEE. Once the request is approved, the process of assembling a collaborative team starts. This team is made of individuals and/or entities who volunteer to support the development of standards. Based on the rules established by the IEEE, participants may contribute at varying levels to the development process. The rules ensure that highly dedicated individuals will participate and no interest will dominate in the standards development process.

The standard is compiled into a draft standard that undergoes multiple revisions. Once the draft has been finalized it is submitted to the standards committee for the standards association (SA) ballot. After SA ballot successfully finishes with it, the draft is submitted to the review committee and finally to the standards board for approval. Finally after approval the standard is published and made available for distribution. This process can be described by the figure below:

Figure 3: Process of developing an IEEE standard [3]

3.2 JIS standard

JIS is the abbreviation for Japanese Industrial Standards and is used for standardizing the indus-trial activities in Japan. The standardization process is coordinated by the Japanese indusindus-trial standards committee and published through the Japanese standards association.

In the process of JIS standards, firstly a draft is prepared by an industrial association entrusted by the relevant ministry or an interested party. The draft is submitted to the relevant minister and the Japan Industrial Standards Committee (JISC) starts the discussion and observation process. After being consulted with a board and technical committee of the JISC, the draft is established as JIS. The standard is published through the Japanese Standards Association. In 2018 Ministry of Economy, Trade and Industry (METI) started the process of revising the Japanese industrial standardization act (JIS) for the following reasons: expansion of the scope into services and other sectors, acceleration of the JIS development process, promotion of international standardization activities, and enhancement of penalties as described in [22]. The process is summarized in the figure below:

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Figure 4: Process of developing an JIS standard [4]

3.3 SA standard

SA is the abbreviation of Standards Australia which is a standards organisation established in 1922 and is recognised by the Australian government for the purpose of developing new standards. The process of developing a standard according to SA goes to 6 stages as described in the figure below:

Figure 5: Process of developing a SA standard [5]

The project proposal comes from the Australian community and is required to go through a selection process. Once it is approved a technical committee is assigned. The committee discusses the scope of the project, drafting tasks, time frames and means of monitoring project progress.

In the drafting stage, the working groups provide the technical content to write the standard. During the process they report to the technical committee on the scope and realisation of the work. After this stage, the public comment stage ensures that a broader community has an opportunity to review the content and direction of the document before being completed. Drafts stay available to the public for 9 weeks.

Prior to publication, the committee votes on the final draft. Committee members may approve or disapprove the draft and negative votes must be accompanied with technical explanations. Finally once the approval is given by the Standards Development and Accreditation Committee (SADC), the standard is ready for publication.

3.4 CEN standard

The European Committee for Standardization(French:Comit´e Europ´een de Normalisation ) is one of the three European Standardization Organizations together with CENELEC and ETSI that have been recognized by the European Union and the European Free Trade Association (EFTA) as responsible for developing standards at European Level. The sectors where CEN is applied are air

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and space, chemicals, construction, consumer products, defence and security, energy, environment etc. The development of an European Standard (EN) is governed by principles of consensus, openness, transparency, national commitment and technical coherence [6]. This process goes into several steps, described below:

1. Proposal to develop an EN

In this step interested parties introduce a proposal for a new work. 2. Acceptance of the proposal

The new proposed project should be accepted by the relevant Technical Body, or Technical Board.

3. Drafting

The EN is developed by experts within a Technical Body [6]. 4. Enquiry-Public comment at national level and weighted vote

Once the draft is prepared, it is released for public comment and vote. This process is known as ”Enquiry”. During this stage, everyone who is part of a relevant field such as manufacturers, public authorities or consumers can comment on the draft. These views are gathered by the members who then submit a national position by means of weighted vote and which is subsequently analyzed by the CEN technical body [6]. If the results are positive, the technical body can decide to publish the Standard.

5. Adoption by weighted formal vote

If the enquiry results show that the draft requires technical reworking, the technical body can decide to update the draft and resubmit it for another weighted vote, called the formal vote [6].

6. Publication of the EN

After the approval of the EN, either from the enquiry or the formal vote, the EN then is published. A published European Standard must be given the status of national standard in all member countries, who also have the obligation to withdraw any national standards that conflict with it [6]. This guarantees that a manufacturer has easier access to the market of all the member countries when applying European Standards and this also applies whether the manufacturer is based in a member’s territory or not [6].

7. Review of the EN

To make sure that a European Standard is still current, it is reviewed within five years of its publication. This review results in one of the following possibilities, confirmation, modification, revision or withdrawal of the EN.

The process of developing an European Standard is summarized in the figure below:

Figure 6: Process of developing CEN standard [6]

3.5 IEC standard

The International Electrotechnical Commission (IEC) is a worldwide organization for standard-ization comprising all national electrotechnical committees [8]. The object of IEC is to promote international co-operation on all questions concerning standardization in electrical and electronic fields. The IEC activity consists of publishing international standards, technical specifications,

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technical reports and guides. IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations [8].

IEC publications have the form of recommendations for international use and are accepted by IEC National Committees, but IEC is not held responsible for the way they are used or for misinterpretations by the users. IEC has issued guidelines for dry heat testing, cold testing, vibration, salt testing, many temperatures testing etc.

After developing a new standard it is expected to remain unchanged until a predefined date which is specified in the IEC website. At this date the standard will go through a process which consists of the following steps reconfirmation, withdrawal, replacement by a new revised edition and amendment.

3.6 Summary of standard organizations

A standard is a technical document designed to be used as a rule, guideline or definition which unites interested parties in a way of doing something. All parties benefit from standardization through increased product safety and quality.

There exist a lot of Standards Development Organizations (SDOs), each of them working towards a common goal, that of providing guidelines that will verify safer products. The above mentioned SDO-s, provide a general idea of the standard creation process according to different parts of the world. They share a similar creation procedure and waiting process as well as revision until the standard is published.

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4 Method

This section introduces the main idea for this master thesis. Firstly, an overall description in section 4.1 is presented, which describes the steps that will be followed throughout the process. Section 4.2 describes the research methodology that will be used.

4.1 Overall description

The main focus of this thesis is directed at developing a temperature testing guideline which will come on top of the existing techniques used in industry and after studying them and identifying their possible weak points. This guideline should provide better results which will eventually identify the importance of a standardized temperature testing.

This guideline will come as an optimization process, that is why it is necessary to analyse firstly the existing methods, understand their principles and evaluate their strong and weak points. The objective of this process will be to understand the causes of their limitations. Furthermore, the work will be focused on experimenting the new ideas related to temperature measurement methods. This step is key in understanding the effectiveness of the proposed guideline. This experimentation process will take place in the experimental setup of the company.

The planned work can be summarized according to the following steps:

1. Qualitative analysis of literature supporting actual temperature testing methods.

2. Distinguishing temperature testing methods and standards that are used today in industry and investigating their nature.

3. Discussing with specialists the importance of standardized testing as well as identifying pos-sible weak points of actual testing methods.

4. Performing experiments on the above specified parts. 5. Developing the guideline.

6. Giving conclusions.

4.2 Research method

The multi-methodological approach proposed by Nunamaker, Chen and Purdin [7] will be used in this master thesis. A research methodology in general consists of the combination of the process, method and tools that will be used in performing the research in a research domain. A research process involves understanding the research domains and research methodologies [7]. If the research project provides good results it contributes in the body of knowledge by expanding the existing knowledge of the given domain.

The multi-methodological approach proposed in [7] incorporates four stages: 1. Theory building

2. Experimentation 3. Observation

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Figure 7: A multi-methodological research approach [7]

Theory building is used to construct research questions and motivate their significance in the body of knowledge. Research questions can not always be solved mathematically and in those cases developing a system provides the answers. System development leads to new theories and improvements of existing ones. After the system is built the researchers use it for experimentation. System development is an essential strategy and is interconnected with other strategies. Exper-imentation includes research strategies such as laboratory and field experiments or computer simulations. Experimental designs are lead by theories and simplified by system’s development. The experimental outcome can be used to refine theories and improve systems. Observation includes research methodologies such as case studies, field studies and surveys. It is used when there is not a lot of information available and the researcher wants ”to get a general feeling for what is involved in a research domain” [7].

The steps of this process fit in better with the goal and the development of this master thesis work and for this reason this research method was chosen. One of the goals of this thesis is to develop a new guideline for temperature testing in industry. This part can be considered as system development. The purpose of developing a new guideline is to facilitate the temperature testing procedure and provide an accurate validation of the functionality. In order to confirm ideas and concepts related to the importance of guidelines, as part of theory building, observations related to the existing standards will be made. Observations will be performed following a combination between case studies and surveys methodology, where case studies consist of independent research and survey consists of discussing with company experts about the performance of the test standards and methods they use. Experimentation consists of using the industrial company to test the new proposed standard. In order to test the performance of this guideline several metrics will be tracked such as ambient temperature, airflow speed, component temperature, thermal conductivity, strength of bond (in glues) etc. These are dependent variables because they are being observed. Their change represents a result of experimental manipulation of the independent variables [23]. Independent variables are climate chamber characteristics such as the value of set temperature, the value of the fan speed, the humidity percentage etc. They can be manipulated by the experimenter and are unaffected by other variables.

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5 Standards used in industry

Industry has to test the products in different conditions. Some of the most common tests that can be performed are the high temperature tests and the low temperature tests. When it comes to these type of tests, it is very important to define if the device under test is heat-dissipated or not. Heat dissipation may be defined as “short distance” dissipation within the source of frictional heat and in its immediate vicinity [24]. It is a type of heat transfer which occurs when an object that is hotter than other objects is placed in an environment where the heat of the hotter object is transferred to the colder objects and the surrounding environment.

Heat sink is a structural device that dissipates heat from a functional electronic package to the environment to ensure the device operates within safe temperature limits[25]. Heat sinks are mostly made of aluminum because of its good thermal conduction properties. Their usage is very common in industry.

In order to make sure that the results of the tests are valid and that the product is within a certain pre-defined quality, different SDO-s (Standards Development Organizations), as described in the previous section, have created guidelines to facilitate the testing of products in industrial environments. Some of these standards will be described in the subsections below.

5.1 IEC 60068-2-2 environmental testing: Dry heat

Dry heat testing is a test used to verify the functionality of electronic components or devices under exposure in relatively high temperatures for a defined period of time. In this test procedure some concepts and definitions are taken into account such as:

• Heat dissipation: The specimen is considered heat-dissipating only if the hottest point on its surface, measured in free air conditions is more than 5 K above the ambient temperature of the surrounding atmosphere after temperature stability has been reached [8].

• Ambient temperature: The air temperature of the chamber should be measured by tem-perature sensors located at such a distance from the specimen that the effect of dissipation is negligible [8].

• Low velocity air: The air in the working space is considered of low velocity if the temper-ature of the specimen is not lowered by more than 5 K by the influence of its circulation in the chamber and the speed of it is less than 0.5 m/s [8].

• High velocity air: The air in the working space is considered of high velocity if the tem-perature of the specimen is lowered by more than 5 K by the influence of its circulation in the chamber and the speed of it is more than 0.5 m/s [8].

• Severities: Severities describe conditions of the test and measurements made before, during and after the test. These conditions are summarized below.

Temperatures

Temperature condition and duration for this test can be chosen from the values below:

+ 1000 degrees +400 degrees +70 degrees +50 degrees +155 degrees +800 degrees +315 degrees +125 degrees +45 degrees +65 degrees +630 degrees +250 degrees +100 degrees +60 degrees +35 degrees +500 degrees +175 degrees +85 degrees +55 degrees +30 degrees

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Duration

7 hours 72 hours 168 hours 336 hours 16 hours 96 hours 240 hours 1000 hours

Table 2: Duration for dry heat test

Before starting the test, the initial state of the specimen should be known. This may be achieved by visual inspection or functional tests. After specifying the temperature and the duration of the test the procedure begins. Care should be taken for the absolute humidity which should not exceed 20 g of water vapour per cubic metre of air or relatively 50 percent at 35 degrees.

If intermediate measurements are required the specimen should not be removed from the cham-ber while performing them. At the end of the test the final measurements are made as well as a visual inspection.

Depending on the conditions of testing, the dry heat test can be summarized by the block diagram below:

Figure 8: Dry heat test [8]

Tests Bd/2, Bd/3 and Be are similar. The rate of temperature change inside the chamber should not exceed 1 K per minute, averaged over a period of not more than 5 minutes. [8]. 5.1.1 Test Bd/2: Dry heat for non heat-dissipating specimens with a gradual change

of temperature

In this test the specimen is introduced into the chamber, which is at the temperature of the laboratory. The temperature is adjusted to the temperature appropriate to the degree of severity as specified in the relevant specification. After temperature stability of the test specimen has been

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reached, the specimen is exposed to these conditions for the specified duration. For specimens that are required to be operational (even though they do not meet the requirements of being heat dissipating) power shall then be applied to the specimen and a functional test is performed as necessary. A further period of stabilization may be necessary and the specimen shall then be exposed to the high temperature conditions for a duration as specified in the relevant specification. High air velocity circulation is normally used for this test [8].

5.1.2 Test Bd/3: Dry heat for heat-dissipating specimens with gradual change of temperature that are not powered during the conditioning period

After installing the specimen into the temperature chamber it is switched on or electrically loaded and checked to verify whether it is capable of performing its functions in accordance with the relevant specification. It will remain in the operating condition in accordance with the duty cycle and after the temperature stability has been reached, the specimen will be exposed to the temperature conditions described above. For this test low air velocity is normally used [8]. 5.1.3 Test Be: Dry heat for heat-dissipating specimens with gradual change of

tem-perature that are required to be powered throughout the test

The specimen is introduced into the chamber which is at the temperature of the laboratory. It will then be switched on or electrically loaded and the verification of its functionality will be made. The specimen will remain in the operating condition in accordance with the duty cycle. The temperature of the chamber is then adjusted to the temperature appropriate to the degree of severity and the specimen is exposed to it for the specified duration. For this test low air velocity circulation is normally used [8].

5.2 IEC 60068-2-1 environmental testing: Cold test

Cold testing is an environmental test used to determine the ability of components or equipment to be used, transported or stored at low temperatures. In this test some definitions are taken into account such as:

• Low air velocity in the working space: The air in the working space is considered of low velocity if the temperature of the specimen is not lowered by more than 5 K by the influence of its circulation in the chamber [9].

• High air velocity in the working space: The air in the working space is considered of high velocity if the temperature of the specimen is lowered by more than 5 K by the influence of its circulation in the chamber [9].

• Severities: Severities describe conditions of the test and measurements made before, during and after the test. These conditions are summarized below.

Temperatures

Temperature condition and duration for this test can be chosen from the values below:

-65 degrees -40 degrees -20 degrees -56 degrees -33 degrees -10 degrees -50 degrees -25 degrees -5 degrees Table 3: Temperatures for cold test

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Duration

2 hours 72 hours 16 hours 96 hours Table 4: Duration for cold test

Depending on the conditions of testing, the dry heat test can be summarized by the block diagram below: Tests Ab, Ad and Ae are similar. The rate of temperature change inside the

Figure 9: Cold test [9]

chamber should not exceed 1 K per minute, averaged over a period of not more than 5 minutes. 5.2.1 Test Ad: Cold test for non heat-dissipating specimens with a gradual change

of temperature

In this test the specimen is introduced into the chamber, which is at the temperature of the laboratory. The temperature is adjusted to the temperature appropriate to the degree of severity as specified in the relevant specification. After temperature stability of the test specimen has been reached, the specimen is exposed to these conditions for the specified duration. For specimens that are required to be operational (even though they do not meet the requirements of being heat dissipating) power shall then be applied to the specimen and a functional test is performed as necessary. A further period of stabilization may be necessary and the specimen shall then be exposed to the low temperature conditions for a duration as specified in the relevant specification. High air velocity circulation is normally used for this test [9].

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5.2.2 Test Ad: Cold test for heat-dissipating specimens with gradual change of tem-perature that are powered after the initial temtem-perature stabilization

The specimen is introduced into the chamber which is at the temperature of the laboratory and the temperature is adjusted to the appropriate degree of severity chosen from the values above. After temperature stability of the test specimen has been reached, the specimen is powered on and stabilized again and then exposed to these conditions for the specified duration. The specimen shall remain in the operating condition in accordance with the duty cycle and at the loading condition (if applicable) as prescribed by the relevant specification [9].

5.2.3 Test Ae: Cold test for heat-dissipating specimens with gradual change of tem-perature that are required to be powered throughout the test

The specimen is introduced into the chamber which is at the temperature of the laboratory. Power is then applied to the specimen and a functional test is performed, as necessary. The temperature is then adjusted to the temperature appropriate to the degree of severity as specified in the relevant specification [9].

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6 Important aspects of temperature testing

In this section a description of critical components will be made, in the sense of their importance when performing temperature testing and also an insight of different temperature probes used in industry together with their properties will be given. The meaning of steady state will also be discussed.

6.1 Critical components

In an integrated circuit board there are many different components such as resistors, capacitors, transistors, inductors, diodes, LED-s etc. Each of them has different thermal properties and depending on the application where the board is used, they are likely to heat up. It is the duty of the testing engineers and hardware designers to figure out which components are important to be measured. A sensible way to detect the critical components is to divide them into two categories, the ones that generate heat and the ones that are sensitive to heat. Among those that are sensitive to heat, transformers and optocouplers are usually distinguished while in the group of heat generating ones, the processor is included.

6.2 Temperature probes

Temperature probes are a type of temperature sensors. There are many kind of temperature probes used today, such as thermocouples, thermistors, RTD-s (Resistance Temperature Dedectors), IC sensors etc.

6.2.1 Thermocouples

A thermocouple is a device whose principal application is temperature measurement [26]. They are composed of two legs, each of them made of different metals and joined together at one to create a junction. The temperature is measured in the junction, when it experiences a change in temperature, a voltage is created. The voltage is then interpreted using a thermocouple reference table to calculate the temperature. There are many kinds of thermocouples such as:

• Type J,K,T,E (base metal) used for common applications • Type R,S,B (noble metal) used for high temperature applications The temperature range and accuracy of them is specified in the table below:

Type Range(degrees) Accuracy (degrees)

K -270 to 1260°C ± 2.2°C J -210 to 760°C ± 2.2°C T -270 to 370°C ± 1°C E -270 to 870°C ± 1.7°C N -270 to 392°C ± 2.2°C S -50 to 1480°C ± 1.5°C R -50 to 1480°C ± 1.5°C B 0 to 1700°C ± 0.5°C

Table 5: Temperature range and accuracy of thermocouples

6.2.2 RTDs- Resistance Temperature Detectors

Resistance temperature detectors are a type of temperature sensors that measure the temperature by the change of resistance. When the temperature of metal increases, the resistance to the flow of electricity increases as well. This resistance is converted to temperature. There are many types

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of RTD-s. The most used are PT 1000 and PT 100. PT 1000 and PT 100 are both platinum resistance thermometers. At 0 degrees PT 1000 has 1000 ohms resistance while PT 100 has 100 ohms resistance. PT 100 has a higher level of self generated heat compared to PT 1000. For this reason, PT 1000 is preferred when measurements of high accuracy are required.

6.2.3 Thermistors

Thermistors are similar to RTD-s but contain a polymer resistor instead of metal. They are exponential and don’t work well with excessively hot or cold temperatures. Thermistors can be NTC- Negative Temperature Coefficient or PTC- Positive Temperature Coefficient. In a NTC, temperature increases as resistance decreases and temperature decreases as resistance increases while in a PTC a decrease in temperature leads to an decrease in resistance and an increase in temperature leads to an increase in resistance.

6.2.4 IC sensors

An IC Sensor is a two terminal integrated circuit temperature transducer that produces an output current proportional to absolute temperature [27]. Most common temperature range is -55 to 150 °C. Has an accuracy within ± 0.3°C. IC Sensors are used in circuit boards to monitor and control temperature. They are present in computers to control the CPU temperature, telecommunications applications etc. They can be used in PCB-s (Printed Circuit Boards) to monitor the heat sink temperature. The problem with them is that their accuracy varies between different models. 6.2.5 Comparison between temperature probes

When choosing a temperature probe certain factors have to be taken into consideration such as the range of temperature that has to be measured, the accuracy wished to be obtained, linearity of the probe, the response time etc. Because of the exponential nature of thermistors and their poor performance with excessively hot or cold temperatures, the most frequently used probes are RTD-s and thermocouples. A general comparison between RTD-s and thermocouples is presented in the table 6:

Parameter RTD Thermocouples

Typical measuring range -240 to 650 degrees -270 to 2320 degrees

Long term stability Excellent Poor to fair

Accuracy Excellent Good to medium

Response time Good Medium to excellent

Linearity Good Fair

Undesirable self heating Medium to excellent Excellent

Tip sensitivity Fair Excellent

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Based on the comparison from the table 6 and considering the temperature range in which electronic circuits are tested, RTD-s are the most reliable and accurate probes. Their linearity provides a better result than thermocouples and the temperature range in which they operate fits better with the purpose of temperature testing of electronic equipment.

6.3 Probe mounting methods

Probe mounting means the approach followed to install the probe into the PCB (printed board circuit) or the product. It can be glued, taped or loosely attached. There are certain factors that have to be taken into consideration before choosing a method.

• The size of the component. The size of the component plays a great role in determining the mounting method of the probe. If the component is too small and glue is used to install the probe, the result will not be accurate because the glue will take up heat from the component. In this case the best approach is to use an IR camera. IR camera reflects in response to heat and this reflection corresponds to a temperature. The infrared thermography is described in [17]. In other cases where tape is used, attention should be paid when applying the tape and not touching the tape’s surface in order to minimize the impurities which affect the quality of measurement.

• The material of the component. If the component is made of metal and the IR camera used, it should be painted black before performing the measurement. In this way the reflection will be obtained and the result is more accurate.

• The location of the component. If the component is located in such place that is sur-rounded by other components and inserting a probe in it is difficult, an alternative approach is followed either by using IR camera or finding another place to perform the measurement.

6.4 Steady state

Steady state is the condition of having reached a steady value of temperature. This is different from thermal equilibrum, where a body has regulated the temperature according to the environment temperature and does not perform any more temperature exchange. The steady state temperature is different from the environment temperature. In the steady state, the electronic device has reached a certain point where it does not get further heated.

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7 Infrared thermography as part of a temperature testing

procedure

7.1 What is infrared thermography

Thermography has become an interesting tool for the investigation of thermal conditions in elec-tronic devices. The trend towards smaller elecelec-tronic devices with more built-in functions means a greater power density [20]. There are a few concepts related to thermography such as radiom-etry and emissivity. Radiomradiom-etry is concerned with the measurement of radiated electromagnetic energy [28]. By respecting some hypotheses and with a proper calibration, it becomes possible to translate radiometric values measured by the camera into temperature values [28]. Emissivity is closely related to the black body and Plank’s law. The black body is the reference for the thermal emission of solids [28]. It is capable of absorbing totally all incident radiations, it re-emits also these radiations uniformly in all directions [28]. Compared to this value, the ability that other materials have towards emitting the light, their emissivity value is calculated.

7.2 Integration of infrared thermography in temperature testing

Infrared thermography becomes a valuable tool when it comes to temperature measurement. There are cases when the contact measurement is impossible and in these cases using an IR camera is the best solution. The accuracy is on satisfying levels so engineers can use it as an alternative solution to verify their contact measurements.

In the temperature testing area where this master thesis is focused, it is of great importance to identify hot spots and potential overheated components. The theoretical identification often provides insufficient results because one should take in consideration also the effect that several close components have on each other. Under these circumstances the idea of using IR thermography is investigated.

The main idea of integrating this technology in the temperature testing procedure lies in using it to identify hot spots before performing contact measurements (measurements using probes), in order to make sure that all the critical components will be identified.

The process can be described as follows, a PCB is taken into consideration and is powered according to respective data sheet. An undefined amount of time is then allowed to elapse during which the experimenter investigates the surface with the IR camera. A scenario with various colours appears each of them corresponding to a temperature, and based on this information the hottest points are identified. After this step the experimenter is able to place probes into these components and submit the unit under test into various severities which might be of interest depending on the application. A very important aspect when using an IR camera is to consider the components with shiny surfaces, such as transformers. A shiny surface will lead to an inaccurate measurement from the IR camera due to the big reflection it has. This is why it is important to paint these components with a black paint that has a high emissivity coefficient.

Infrared thermography is an approach that is known and discussed by several companies which perform similar tasks. One of these companies is Delta Development Technology AB, an accredited test and consulting company which among different types of tests performs temperature testing. After discussing with some of their specialists over the usability of IR camera in the above described manner, it was concluded that this approach would benefit the process. Section 8.3.6 describes the process in an experimental manner.

INVESTIGATING TEMPERATURE MEASUREMENT METHODS AND THEIR IMPACT IN EMBEDDED SYSTEMS

V¨

aster˚

as, Sweden

Thesis for the Degree of Master of Science in Computer Science with

specialization in Embedded Systems 15.0 credits

INVESTIGATING TEMPERATURE

MEASUREMENT METHODS AND

THEIR IMPACT IN EMBEDDED

SYSTEMS

Zhaneta Nene

zne19001@student.mdh.se

Examiner: Thomas Nolte

M¨

alardalen University, V¨

aster˚

as, Sweden

Supervisor: Nandinbaatar Tsog

M¨

alardalen University, V¨

aster˚

as, Sweden

Company supervisor: Pontus Eriksson

Westermo, V¨

aster˚

as, Sweden

May 20, 2020

Table of Contents

Acknowledgement

List of Figures

List of Tables

1

Introduction

1.1

Motivation

1.2

Problem formulation

1.3

Limitations

1.4

Thesis outline

2

Background

2.1

Embedded systems

2.2

Thermal fundamentals

2.3

Temperature testing inspection

2.4

Related work

3

Standard creation process

3.1

IEEE standard

3.2

JIS standard

3.3

SA standard

3.4

CEN standard

3.5

IEC standard

3.6

Summary of standard organizations

4

Method

4.1

Overall description

4.2

Research method

5

Standards used in industry

5.1

IEC 60068-2-2 environmental testing: Dry heat

5.2

IEC 60068-2-1 environmental testing: Cold test

6

Important aspects of temperature testing

6.1