Damp heat, steady state (unsaturated pressurized vapour with air)

IEC TR 63141:2020(E) describes a new test method to control the volume of air injected into a conventional HAST chamber filled with water vapour. This document provides an overview of the conventional HAST chamber, an overview of the air-HAST equipment where air is incorporated into the HAST chamber, an example of an air-HAST test apparatus, and application examples of air-HAST.

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Status
Published
Publication Date
08-Apr-2020
Current Stage
PPUB - Publication issued
Completion Date
09-Apr-2020
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IEC TR 63141
Edition 1.0 2020-04
TECHNICAL
REPORT
colour
inside
Damp heat, steady state (unsaturated pressurized vapour with air)
IEC TR 63141:2020-04(en)
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IEC TR 63141
Edition 1.0 2020-04
TECHNICAL
REPORT
colour
inside
Damp heat, steady state (unsaturated pressurized vapour with air)
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 19.040 ISBN 978-2-8322-8090-4

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TR 63141:2020 © IEC 2020
CONTENTS

FOREWORD ........................................................................................................................... 5

INTRODUCTION ..................................................................................................................... 7

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms and definitions ...................................................................................................... 8

4 Overview of HAST and air-HAST ..................................................................................... 9

4.1 Overview of HAST chamber .................................................................................... 9

4.1.1 Structure of HAST chamber ............................................................................. 9

4.1.2 Definition of humidity ..................................................................................... 10

4.2 Structure of air-HAST equipment .......................................................................... 12

4.2.1 General ......................................................................................................... 12

4.2.2 Air concentration and relative humidity .......................................................... 14

5 Evaluation of tin whisker growth from lead-free plating and solder-joints ........................ 14

5.1 Whisker of lead-free solder (comb-type substrate) ................................................ 14

5.1.1 General ......................................................................................................... 14

5.1.2 Summary of evaluation results of solder-joint whisker growth [3] [4] .............. 15

5.1.3 Conclusion .................................................................................................... 24

5.2 Lead-free whisker of plating (mounting substrate) ................................................. 25

5.2.1 General ......................................................................................................... 25

5.2.2 Test method .................................................................................................. 25

5.2.3 Test results.................................................................................................... 26

5.2.4 Observations ................................................................................................. 27

5.2.5 Conclusion .................................................................................................... 29

6 Applied case of JISSO using electrically-conductive adhesive and acceleration

test under humidity environments for joining parts ......................................................... 29

6.1 General ................................................................................................................. 30

6.2 Experiment method ............................................................................................... 30

6.2.1 Testing material ............................................................................................. 30

6.2.2 Test conditions .............................................................................................. 30

6.2.3 Measurement and evaluation method ............................................................ 31

6.3 Test results ........................................................................................................... 31

6.3.1 Experimental result ........................................................................................ 31

6.3.2 Test result (1608R/paste A) ........................................................................... 36

6.4 Points of attention ................................................................................................. 38

6.5 Summary .............................................................................................................. 38

7 Applied air-HAST to c-Si PV modules evaluation tests ................................................... 39

7.1 Background and objective ..................................................................................... 39

7.2 Photovoltaic module structure and deterioration factors ........................................ 39

7.3 Test methods ........................................................................................................ 40

7.3.1 Crystalline silicon photovoltaic module type-approval international

standard ........................................................................................................ 40

7.3.2 Air-HAST work ............................................................................................... 41

7.3.3 Test samples ................................................................................................. 41

7.3.4 Test conditions .............................................................................................. 42

7.3.5 Measurement and analysis ............................................................................ 44

7.4 Test results ........................................................................................................... 44

7.4.1 DHT testing ................................................................................................... 44

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IEC TR 63141:2020 © IEC 2020 – 3 –

7.4.2 Saturated HAST............................................................................................. 46

7.4.3 Air-HAST ....................................................................................................... 47

7.4.4 External appearance comparison ................................................................... 48

7.4.5 Use of dark I-V measurement to infer deterioration factors ............................ 50

7.4.6 Use of ion chromatography to quantify residual acetic acid ions .................... 50

7.5 Discussion ............................................................................................................ 51

7.5.1 Environment test method comparisons .......................................................... 51

7.5.2 Power-loss profiles by moisture permeation ................................................... 52

7.5.3 Comparisons by ion chromatography acetic acid quantification ...................... 52

7.6 Conclusion ............................................................................................................ 53

8 Summary ....................................................................................................................... 54

Bibliography .......................................................................................................................... 55

Figure 1 – Two types of HAST equipment and their structures ................................................ 9

Figure 2 – Image of air vent process ..................................................................................... 11

Figure 3 – Saturated test ...................................................................................................... 11

Figure 4 – Unsaturated test................................................................................................... 12

Figure 5 – Structure of two-vessel type air-HAST chamber ................................................... 13

Figure 6 – Structure of one-vessel type air-HAST chamber ................................................... 14

Figure 7 – Example of test vehicle with comb pattern ............................................................ 15

Figure 8 – Process flow for sample build ............................................................................... 16

Figure 9 – Temperature/relative humidity profiles of HAST and air-HAST .............................. 17

Figure 10 – Whisker generation situation in air-HAST ........................................................... 19

Figure 11 – Mapping of the cross-section at the solder fillet in HAST .................................... 20

Figure 12 – Mapping of the cross-section at the solder fillet in air-HAST ............................... 20

Figure 13 – Arrhenius plot of the bromine-based flux ............................................................ 22

Figure 14 – Reciprocal of relative humidity of whisker generation on solder .......................... 22

Figure 15 – Humidity properties of whisker generation on solder (pt.2) ................................. 23

Figure 16 – Evaluated sample ............................................................................................... 25

Figure 17 – Whisker formation (Substrate: Cu) ..................................................................... 27

Figure 18 – Cross-section inspection results with electron-imaging (Substrate: Cu) .............. 28

Figure 19 – Elements analysis .............................................................................................. 29

Figure 20 – Substrate for conductive resistance measurement and example of

component mounting ............................................................................................................. 30

Figure 21 – Humidity test conductive resistance monitor test status ...................................... 31

Figure 22 – Example of the conductive resistance value change ........................................... 32

Figure 23 – Weibull plot of temperature acceleration (under fixed humidity conditions) ......... 32

Figure 24 – Arrhenius plot (fixed humidity) ............................................................................ 33

Figure 25 – Weibull plot of humidity acceleration (under fixed temperature conditions) ......... 34

Figure 26 – Arrhenius plot (fixed temperature) ...................................................................... 35

Figure 27 – Eyring plot of all conditions ................................................................................ 35

Figure 28 – Comparison of paste (120 °C/85 % RH Air-HAST) .............................................. 36

Figure 29 – Cross-section analysis of 1608R after a humidity test (SEM image) ................... 37

Figure 30 – Magnified image of cross-section analysis of 1608R after a humidity test

(SEM image) ......................................................................................................................... 37

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– 4 – IEC TR 63141:2020 © IEC 2020

Figure 31 – Cross-section analysis of 1608R after a humidity test (SEM image) and

examples of componential analysis by EDX .......................................................................... 38

Figure 32 – Structure of c-Si PV module ............................................................................... 40

Figure 33 – Qualification test sequence in IEC 61215-1 [23] ................................................. 41

Figure 34 – Appearance of modules ...................................................................................... 42

Figure 35 – EL images after DHT .......................................................................................... 45

Figure 36 – Degradation profiles with DHT ............................................................................ 46

Figure 37 – EL images of HAST 105 °C/100 % RH ................................................................ 46

Figure 38 – EL images after HAST 120 C/100 % RH ........................................................... 47

Figure 39 – Degradation profiles with HAST .......................................................................... 47

Figure 40 – EL images after air-HAST ................................................................................... 48

Figure 41 – Degradation profiles with air-HAST .................................................................... 48

Figure 42 – Appearance of modules after each test .............................................................. 49

Figure 43 – Dark I-V ............................................................................................................. 50

Figure 44 – Residue of acetate ion and retention of P after each test ............................ 51

max

Table 1 – Test conditions ...................................................................................................... 15

Table 2 – Influence of fluxes and circumstances to whisker growth ....................................... 18

Table 3 – Whisker generation in HAST.................................................................................. 18

Table 4 – Whisker generation in air-HAST ............................................................................ 19

Table 5 – Comparison of coefficients for Equations (5), (6) and (7) ....................................... 24

Table 6 – Details of evaluated samples ................................................................................. 26

Table 7 – Lead frames composition ....................................................................................... 26

Table 8 – Environmental test conditions ................................................................................ 26

Table 9 – Electrically-conductive adhesives .......................................................................... 30

Table 10 – Testing material ................................................................................................... 31

Table 11 – Test conditions .................................................................................................... 36

Table 12 – Example of failure modes of PV module via materials .......................................... 40

Table 13 – Specifications of materials used in PV module ..................................................... 42

Table 14 – Test conditions .................................................................................................... 43

Table 15 – Test conditions and partial pressures .................................................................. 43

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IEC TR 63141:2020 © IEC 2020 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
DAMP HEAT, STEADY STATE
(UNSATURATED PRESSURIZED VAPOUR WITH AIR)
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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The main task of IEC technical committees is to prepare International Standards. However, a

technical committee may propose the publication of a Technical Report when it has collected

data of a different kind from that which is normally published as an International Standard, for

example "state of the art".

IEC TR 63141, which is a Technical Report, has been prepared by IEC technical committee

104: Environmental conditions, classification and methods of test.
The text of this Technical Report is based on the following documents:
Draft TR Report on voting
104/834/DTR 104/853A/RVDTR

Full information on the voting for the approval of this Technical Report can be found in the

report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

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– 6 – IEC TR 63141:2020 © IEC 2020

The committee has decided that the contents of this document will remain unchanged until the

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IEC TR 63141:2020 © IEC 2020 – 7 –
INTRODUCTION

Highly accelerated stress test (HAST), is a high temperature (100 °C or more), high humidity

steady test of unsaturated pressurized steam of 85 % RH, and is the original test method that

was developed for the evaluation of corrosion of packaged semiconductor wiring. This test

method, often referred to as HAST, is applied to primarily non-hermetically sealed small

electronic components, and has been standardized as a standard test method for evaluating,

in an accelerated manner, the resistance to the deteriorative effect of high temperature and

high humidity (IEC 60068-2-66). The equipment used for this test method is a chamber, filled

with unsaturated water vapour, called a HAST chamber.

However, in life evaluation test conditions, acceleration cannot be obtained without air from

the environment being incorporated into the HAST chamber. This test method is referred to as

air-HAST.

Examples of the application of air-HAST are whiskers evaluation of lead-free solder,

deterioration life evaluation of conductive paste, and deterioration life evaluation of solar cells

and are given in this document in order to provide an understanding of air-HAST with the aim,

in future, to standardize air-HAST.

The International Electrotechnical Commission (IEC) draws attention to the fact that it is

claimed that compliance with this document may involve the use of a patent concerning

whisker evaluation given in Clause5.

IEC takes no position concerning the evidence, validity and scope of this patent right.

The holder of this patent right has assured the IEC that he/she is willing to negotiate licences

under reasonable and non-discriminatory terms and conditions with applicants throughout the

world. In this respect, the statement of the holder of this patent right is registered with IEC.

Information may be obtained from:
ESPEC CORP.
3-5-6,Tenjinbashi,Kita-ku
Osaka,530-8550
Japan

Attention is drawn to the possibility that some of the elements of this document may be the

subject of patent rights other than those identified above. IEC shall not be held responsible for

identifying any or all such patent rights.

ISO (www.iso.org/patents) and IEC (http://patents.iec.ch) maintain on-line data bases of

patents relevant to their standards. Users are encouraged to consult the data bases for the

most up to date information concerning patents.
---------------------- Page: 9 ----------------------
– 8 – IEC TR 63141:2020 © IEC 2020
DAMP HEAT, STEADY STATE
(UNSATURATED PRESSURIZED VAPOUR WITH AIR)
1 Scope

This document describes a new test method to control the volume of air injected into a

conventional HAST chamber filled with water vapour. This document provides an overview of

the conventional HAST chamber, an overview of the air-HAST equipment where air is

incorporated into the HAST chamber, an example of an air-HAST test apparatus, and

application examples of air-HAST.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
galvanic corrosion

corrosion damage induced when two dissimilar materials are coupled in a corrosive electrolyte

3.2
Kirkendall effect

motion of the boundary layer between two metals that occurs as a consequence of the

difference in diffusion rates of the metal atoms
3.3
whisker
metallic protrusion which grows up naturally during storage or in use
3.4
HAST
highly accelerated stress test

original test method developed to evaluate the corrosion of the semiconductor wiring at a high

temperature of 100 °C or more
3.5
air-HAST

HAST test method with the addition of further air partial pressure in a HAST chamber

---------------------- Page: 10 ----------------------
IEC TR 63141:2020 © IEC 2020 – 9 –
4 Overview of HAST and air-HAST
4.1 Overview of HAST chamber
4.1.1 Structure of HAST chamber

HAST is an evaluation test at a high-temperature and high-humidity unsaturated pressurized

steam atmosphere environment of more than 100 °C. The test apparatus is roughly divided

into a one-vessel type and a two-vessel type, as shown in Figure 1.
a) One-vessel type b) Two-vessel type
Key
1 pressure gauge
2 pressure vessel
2 temperature sensor for moisture
4 safety valve
5 door
6 working space
7 heater for humidifying water
8 humidifying water
9 temperature sensor for humidifying water
10 air-exhaust valve
11 fan
12 heater for moisture fan for air
13 magnetic coupling
14 pressure vessel 2
Figure 1 – Two types of HAST equipment and their structures

The configuration of the one-vessel type and the configuration of the two-vessel type are

explained as follows.
a) Configuration of the one-vessel type (See Figure 1 a))

This type of chamber is called a one-vessel type because it has only one pressure vessel.

The inner cylinder provided inside the pressure vessel is divided into a steam generator

for supplying humidifying water vapour and a working space to set the sample. A fan for

generating a flow of steam from the steam generator to the working space is provided in

the back of the inner cylinder. Heaters are arranged outside of this fan and in the steam

generator. Steam flow rate of this system is suppressed to about the flow rate of natural

convection.
b) Configuration of the two-vessel type (See Figure 1 b))
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– 10 – IEC TR 63141:2020 © IEC 2020

This type of chamber is called a two-vessel type because it is composed of two different

pressure vessels: the test chamber which sets the sample and the steam generation chamber

which supplies humidifying water vapour. Heaters are respectively located in the test chamber

and the steam generation chamber. Water vapour is fed by boiling water vapour pressure to

the test chamber from the steam generation chamber holding the humidifying water, the

amount that was the condensed water goes back into the steam generation chamber. There is

an inner cylinder in the test chamber, and a heater is provided on the outside of this inner

cylinder. Heat from the heater is transmitted to the inner cylinder, keeping the temperature of

the entire working space at a constant level. This system is also referred to as a natural

convection because it does not require a fan for the circulation of water vapour.

4.1.2 Definition of humidity

HAST is carried out in a closed vessel which is isolated from the atmosphere of the

atmospheric pressure (pressure vessel), under the assumption that air is absent from the

filled water vapour atmosphere. Therefore during the start of HAST, steps to eliminate air

(Figure 2 air vent process) are always taken. The humidifying water is heated and boiled by

the heater, the exhaust valve is opened and the test vessel is filled with 100 % water vapour

until all air is discharged. Then the exhaust valve is closed to perform heating until the test

temperature in the vessel is reached again. The difference between the saturated test and

unsaturated test in the working space in the chamber is then
...

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