Semiconductor devices - Mechanical and climatic test methods - Part 39: Measurement of moisture diffusivity and water solubility in organic materials used for semiconductor components

IEC 60749-39:2021 is available as IEC 60749-39:2021 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 60749-39:2021 details the procedures for the measurement of the characteristic properties of moisture diffusivity and water solubility in organic materials used in the packaging of semiconductor components. These two material properties are important parameters for the effective reliability performance of plastic packaged semiconductors after exposure to moisture and being subjected to high-temperature solder reflow. This edition includes the following significant technical changes with respect to the previous edition:
- updated procedure for "dry weight" determination.

Dispositifs à semiconducteurs - Méthodes d'essais mécaniques et climatiques - Partie 39: Mesure de la diffusivité d'humidité et de l'hydrosolubilité dans les matériaux organiques utilisés dans les composants à semiconducteurs

IEC 60749-39:2021 est disponible sous forme de IEC 60749-39:2021 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.L’IEC 60749-39:2021 détaille les modes opératoires pour la mesure des propriétés caractéristiques de la diffusivité d’humidité et de l’hydrosolubilité dans les matériaux organiques utilisés dans l’encapsulation des composants à semiconducteurs. Ces deux propriétés des matériaux sont des paramètres importants pour la performance de fiabilité réelle des semiconducteurs sous boîtier en plastique après exposition à l’humidité et qui sont soumis à une refusion à température élevée au moment du brasage. Cette édition inclut les modifications techniques majeures suivantes par rapport à l’édition précédente:
- mise à jour du mode opératoire relatif à la détermination du "poids sec".

General Information

Status
Published
Publication Date
28-Nov-2021
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
29-Nov-2021
Ref Project

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IEC 60749-39
Edition 2.0 2021-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Semiconductor devices – Mechanical and climatic test methods –
Part 39: Measurement of moisture diffusivity and water solubility in organic
materials used for semiconductor components
Dispositifs à semiconducteurs – Méthodes d’essais mécaniques et
climatiques –
Partie 39: Mesure de la diffusivité d’humidité et de l’hydrosolubilité dans les
matériaux organiques utilisés dans les composants à semiconducteurs
IEC 60749-39:2021-11(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60749-39
Edition 2.0 2021-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Semiconductor devices – Mechanical and climatic test methods –
Part 39: Measurement of moisture diffusivity and water solubility in organic
materials used for semiconductor components
Dispositifs à semiconducteurs – Méthodes d’essais mécaniques et
climatiques –
Partie 39: Mesure de la diffusivité d’humidité et de l’hydrosolubilité dans les
matériaux organiques utilisés dans les composants à semiconducteurs
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 31.080.01 ISBN 978-2-8322-1046-7

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

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60749-39:2021 © IEC 2021
CONTENTS

FOREWORD ........................................................................................................................... 3

1 Scope .............................................................................................................................. 5

2 Normative references ...................................................................................................... 5

3 Terms and definitions ...................................................................................................... 5

4 Apparatus ........................................................................................................................ 5

5 Samples .......................................................................................................................... 6

6 Procedure ........................................................................................................................ 6

6.1 Sample preparation ................................................................................................. 6

6.2 Absorption measurements below 100 °C ................................................................. 6

6.3 Solubility and diffusivity calculation ......................................................................... 9

6.4 Desorption measurements above 100 °C .............................................................. 10

7 Calculation of activation energy for moisture diffusion ................................................... 11

8 Calculation of functional fit for solubility ......................................................................... 11

9 Summary ....................................................................................................................... 11

Bibliography .......................................................................................................................... 12

Figure 1 – Example of linearly increasing mass gain ............................................................... 8

Figure 2 – Alternative intercept method to estimate the reversible Fickian moisture

mass ....................................................................................................................................... 9

---------------------- Page: 4 ----------------------
IEC 60749-39:2021 © IEC 2021 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SEMICONDUCTOR DEVICES –
MECHANICAL AND CLIMATIC TEST METHODS –
Part 39: Measurement of moisture diffusivity and water solubility in
organic materials used for semiconductor components
FOREWORD

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

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

IEC 60749-39 has been prepared by IEC technical committee 47: Semiconductor devices. It is

an International Standard.

This second edition, based on JEDEC document JESD22-A120B, cancels and replaces the

first edition published in 2006. lt is used with permission of the copyright holder, JEDEC Solid

State Technology Association. This edition constitutes a technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:
a) updated procedure for "dry weight" determination.
---------------------- Page: 5 ----------------------
– 4 – IEC 60749-39:2021 © IEC 2021
The text of this International Standard is based on the following documents:
Draft Report on voting
47/2652/CDV 47/2725/RVC

Full information on the voting for its approval can be found in the report on voting indicated in

the above table.
The language used for the development of this International Standard is English.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in

accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,

available at www.iec.ch/members_experts/refdocs. The main document types developed by

IEC are described in greater detail at www.iec.ch/standardsdev/publications.

A list of all the parts of the IEC 60749 series, under the general title Semiconductor devices –

Mechanical and climatic test methods, can be found on the IEC website.

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

stability date indicated on the IEC website under webstore.iec.ch in the data related to the

specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 6 ----------------------
IEC 60749-39:2021 © IEC 2021 – 5 –
SEMICONDUCTOR DEVICES –
MECHANICAL AND CLIMATIC TEST METHODS –
Part 39: Measurement of moisture diffusivity and water solubility in
organic materials used for semiconductor components
1 Scope

This part of IEC 60749 details the procedures for the measurement of the characteristic

properties of moisture diffusivity and water solubility in organic materials used in the

packaging of semiconductor components.

These two material properties are important parameters for the effective reliability

performance of plastic packaged semiconductors after exposure to moisture and being

subjected to high-temperature solder reflow.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their

content constitutes requirements of this document. For dated references, only the edition

cited applies. For undated references, the latest edition of the referenced document (including

any amendments) applies.

IEC 60749-20, Semiconductor devices – Mechanical and climatic test methods – Part 20:

Resistance of plastic encapsulated SMDs to the combined effect of moisture and soldering

heat
3 Terms and definitions
No terms and definitions are listed in this document.

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
4 Apparatus

4.1 Analytical balance capable of a resolution of either 0,000 01 g or 0,001 % of sample

mass.

4.2 High-temperature oven capable of maintaining uniform temperatures from 100 °C to

250 °C ± 2 °C.

4.3 Temperature/humidity chamber(s) capable of maintaining temperatures in a range from

30 °C to 85 °C and relative humidities (H ) in a range from 60 % H to 85 % H . Within the

R R R

chamber working area, temperature tolerance shall be ±2 °C and the H tolerance shall be

±3 % H .
---------------------- Page: 7 ----------------------
– 6 – IEC 60749-39:2021 © IEC 2021

4.4 Perforated stainless steel trays or stainless steel wire mesh baskets used for holding

samples and for placement into ovens.
4.5 Large aluminium plate or disk used for heat sink capability.
4.6 Desiccator for holding dry samples.
5 Samples

Samples of mould compound shall be flat parallel-sided discs or coupons. The linear

dimensions shall be accurately measured to within ±0,02 mm.

To approximate one-dimensional diffusion behaviour with edge effects limited to less than 5 %

of the total diffusional moisture mass uptake, the free surface area in the thickness dimension

shall be less than 5 % of the flat-sided free surface area of the sample. For a disc of radius, r,

and thickness, h, the following relation shall be met:
h < 0,05r (1)
for a coupon of length, L, and width, W,
0,05(WL)
(2)
()WL+
Recommended sample thickness should be in the range from 0,3 mm to 1,0 mm. The

maximum sample thickness should not exceed 1,0 mm, because the time to achieve moisture

saturation at temperatures below 60 °C will be excessively long for compounds with slow

diffusivity.

The moisture absorption parameters used in this standard can be obtained from the material

suppliers (such as the resin supplier).
6 Procedure
6.1 Sample preparation
6.1.1 Process and cure the samples using recommended processing conditions in
accordance with the manufacturer’s specification.

6.1.2 To obtain the appropriate sample thickness as given by Formulae (1) or (2), samples

can be sectioned and finely polished from larger specimens. Near parallel-sided flatness shall

be maintained for samples prepared in this manner.

The prepared samples should be inspected for voids, both internal and surface, using

acoustic microscopy or x-ray. The ideal samples should be nearly void-free.
6.2 Absorption measurements below 100 °C

6.2.1 Measure the linear dimensions of the prepared sample to the nearest ±0,02 mm.

Record the sample thickness, h, and calculate the sample volume, V, using the appropriate

geometric relationship based on the sample shape.
---------------------- Page: 8 ----------------------
IEC 60749-39:2021 © IEC 2021 – 7 –

NOTE Calculating the volume by measuring the linear dimensions is never accurate. The error is smaller when

the sample is big. One accurate way of determining the volume is to use Archimedes’s principle, which is to

measure the sample weight in air and immersed in a liquid with known density (ethyl alcohol, IPA, etc.). In this

way, the volume of a sample with irregular shape can also be determined.

6.2.2 The dry weight of the sample shall be determined, in accordance with IEC 60749-20,

firstly by baking the sample for 24 h at 125 +5/-0 °C and continuing to bake and weigh the

sample every 12 hours until no further weight loss is observed to ensure that the sample(s)

are dry. The dry weight is determined when no further weight loss is observed, less than

0,002 % difference, after two consecutive measurements with a minimum baking interval of

12 h. Within 30 minutes after removal from the oven, weigh the sample(s) using the analytical

balance equipment described in 4.1 and determine the dry weight in accordance with 6.2.4.

In accordance with IEC 60749-20, small sample(s) (less than 1,5 mm total height), devices

should be weighed within 30 minutes after removal from oven.

6.2.3 Remove the sample from the bake oven and immediately cool by placing in contact

with the heat sink of 4.5.

If more than one sample is to be measured, the samples and heat sink should be placed into

a desiccator to limit moisture uptake during the mass measurements.
6.2.4 Weigh the sample using the balance described in 4.1 and record the mass as
M .
Comp,dry,1

Read points: At the desired read point; remove the sample(s) from the bake oven. Within

30 minutes after removal of the sample(s) from the bake oven, remove the sample(s) from the

container and determine their weight using the analytical balance equipment in 4.1. Within

30 minutes after weighing the samples, place them in a clean, dry, shallow container so that

the sample bodies do not touch each other. Return the sample(s) to the bake oven for the

desired time. Continue until the sample(s) have lost all their moisture as determined by the

dry weight in 6.2.2.
6.2.5 Place the sample(s) into a stainless steel holder and transfer to a
temperature/humidity chamber stabilized at a pre-set temperature and humidity.

The sample should be transferred into a stainless-steel holder that has been preheated and

stabilized to the set chamber temperature.

6.2.6 At accumulative times, remove the sample from the temperature/humidity chamber,

cool and measure the sample mass in accordance with 6.2.4. Record the mass as M
Comp,wet,t

6.2.7 Read Points: The X-axis (time) read points, in accordance with IEC 60749-20, are

selected for plotting the absorption curve. For the early readings, points should be relatively

short (24 h or less) because the curve will have a steep initial slope. Later readings can be

spread out further (10 days or more) as the curve becomes asymptotic. The Y-axis (weight

gain) should start with ‘‘0’’and increase to the saturated weight gain. Most sample(s) will

reach saturation between 0,3 % and 0,4 % when stored at 85 °C/85 % RH. Devices shall be

kept at room ambient between removal from the oven or chamber and weighing and
subsequent reinsertion into the oven or chamber.

Ensure that no condensed moisture from the chamber walls comes into contact with a sample

during removal from the temperature/humidity chamber. If condensed water should contact a

sample, immediately dry the sample using nitrogen or dry air. The sample should then be

returned to the chamber for re-equilibration and another data point taken at a later time.

The sample weight measurement shall be made within a few minutes after removal of the

sample from the temperature/humidity chamber. Time delays longer than 5 minutes after

removal from the temperature/humidity chamber could affect the sample weight
measurements.
---------------------- Page: 9 ----------------------
– 8 – IEC 60749-39:2021 © IEC 2021

Within 30 minutes after weighing the samples, place them in a clean, dry, shallow container

so that the sample bodies do not touch each other. Return the sample(s) to the
temperature/humidity chamber for the desired time.

6.2.8 Place the sample back into the temperature/humidity chamber and continue mass

measurements until either of the following conditions are met:

a) additional weight gain after a 24 h period is less than 0,002 % from the previous

measurement;

b) a plot of the weight gain versus time shows a linearly increasing weight gain after an initial

decreasing change in mass with time (dM/dt), as depicted in Figure 1.
Figure 1 – Example of linearly increasing mass gain
6.2.9 Record the final wet mass of the sample as M .
Comp,wet,f
6.2.10 Bake the sample again at 125 °C until dry as determined by 6.2.2.
6.2.11 Record the second final dry mass as M .
Comp,dry,2
6.2.12 Record the saturated moisture mass as, M = M – M .
Sat Comp,wet,f Comp,dry,2

NOTE An alternative method to estimate the reversible saturated moisture mass can be determined by an

intercept approach as shown in Figure 2. Using this method the intercept point between the weight gain curve and

a linear extrapolation of the linear varying portion of the weight gain curve can be used to estimate the reversible

Fickian moisture weight gain response.
---------------------- Page: 10 ----------------------
IEC 60749-39:2021 © IEC 2021 – 9 –
Figure 2 – Alternative intercept method to estimate
the reversible Fickian moisture mass
6.3 Solubility and diffusivity calculation
6.3.1 Calculate the solubility at the given temperature and humidity by using:
M − M
M (T, H )
Comp,wet,f Comp,dry,2
sat R
(3)
C (T, H )= =
sat R
V V
where
C (T,H ) is the moisture solubility at temperature T and H (in mg cm );
sat R R
M is the final wet sample mass (in mg);
Comp,wet,f
M is the final dry sample mass after the second bake (in mg);
Comp,dry,2
V is the sample volume (in cm );

M (T,H ) is the reversible saturated moisture content at temperature T and H (in mg).

sat R R
6.3.2 Plot mass gain curve versus time using change in mass as M(t) − M
Comp,dry,1
6.3.3 Using the plotted curve, calculate the moisture diffusivity from
0,049 19 h
DT()=
(4)
0,5
where
2 −1
D(T) is the diffusivity at temperature T (in mm s );
H is the sample thickness (in mm);

t is the absorption half-time defined as the time at which the absorbed mass of moisture is

0,5
equal to one-half the saturated mass, for example, M /M = 0,5;
t sat
M is the mass of moisture at time t.

NOTE Formula (4) is recognized as an approximation to the analytical closed form solution, however, it will

provide an accurate approximation to less than a few percent error. An alternate method for determining D(T) is to

use a best fit curve fitting approach of the experimental weight gain data. The following solution for rectangular or

square samples can be used:
---------------------- Page: 11 ----------------------
– 10 – IEC 60749-39:2021 © IEC 2021
∞ ∞ ∞
exp(−Dt L )
M 512
eqv
1 −
(5)
∑∑ ∑
6 2 22
sat π (2l+1) (2mn++1) (2 1)
l 0 mn00
2 2
     
(2l+1) (2m+1) (2n+1) 
where L = + +
     
eqv
x y z
0 0 0 
     

Here, x , y , and z are the width, length, and thickness of the sample, respectively. l, m and n represent integers

o o o

relating to calculation of diffusion/concentration steps solved by iterative calculations in each principal direction.

The value of D(T)) determined by a curve fitting technique using Formula (5) should be compared to the value

determined by Formula (4) as a reference check.

6.3.4 Repeat the absorption measurements 6.2 to 6.3.3 using different temperature and

humidity conditions. The following environmental conditions shall be used: 30 °C/60 % H ,

60 °C/60 % H , and 85 °C/60 % H .
R R
6.4 Desorption measurements above 100 °C

6.4.1 Place the sample in a chamber maintained at 85 °C/60 % H or 85 °C/85 % H for

R R

168 h or until M is achieved as determined by a calculation using a previously determined

sat
diffusivity at 85 °C.

6.4.2 Remove the sample from the temperature/humidity chamber, cool in accordance with

6.2.3 and record the saturated sample weight, M .
sat

6.4.3 Immediately transfer the sample into a stainless-steel holder that has been

preheated and stabilized at the set bake temperature and place in a bake oven stabilized at a

temperature greater than 100 °C.

6.4.4 Remove the sample after a recorded elapsed period of time, immediately cool in

accordance with 6.2.3 and measure the sample weight in accordance with 6.2.4.
6.4.5 Repeat steps 6.4.3 and 6.4.4 until the sample is dry.

Appropriate times for recording weight losses can be determined by using a first-order

extrapolation of the value for the diffusivity by using an Arrhenius fit (see Clause 7 and

Clause 8) of the absorption diffusivities determined in 6.3.3.
Estimated weight losses can be assessed by using the following equation:
∞ 22
M 8 1 (2n+1) π Dt
=1−−exp
(6)
22 2
π (2n+1) h
sat 
n=0
where
D is the diffusivity;
t is the time.

6.4.6 Calculate D(T) using Formula (4), where t is now defined as the time at which the

0,5
desorbed mass of moisture is equal to one-half of the saturated mass.
===
---------------------- Page: 12 ----------------------
IEC 60749-39:2021 © IEC 2021 – 11 –
6.4.7 Reset the bake oven to a higher bake temperature and repeat measurements
following 6.4.1 to 6.4.6.
7 Calculation of activation energy for moisture diffusion

The activation energy for moisture diffusion is calculated from the slope of a plot of ln{D(T)}

versus 1/T where T is in degrees Kelvin. Report the best fit line as:
 
D(T )= D exp −
(7)
 
 
where
D is the pre-exponential factor for fitted line (in mm /s);
E is the activation energy (in eV);
k is Boltzman’s constant, 8,617 × 10 eV/K.

Diffusion of moisture can show a dependency on the glass transition temperature (T ) of the

material. Measurements above the T of the material should be reported as a separate

activation energy and pre-exponential factor.

NOTE For accurate determination of the activation energy, a minimum of three temperatures differing by 20 °C to

30 °C for both above and below T is used.
8 Calculation of functional fit for solubility
The solubility can be fitted to the following formula:
C (T,P) PS exp−
(8)
sat 0
where
2 −3
S is the pre-exponential factor for fitted line (in mg cm Pa);
E is the activation energy (in eV);
k is Boltzman’s constant, 8,617 × 10 eV/K.
9 Summary
The following information shall be tabulated:
a) mould compound identification (see Clause 5);
b) test temperature and relative humidities (see Clause 6);
c) D (see Clause 7);
d) E , activation energy (eV) (see Clause 7);
e) C (T,H ), solubility at a given temperature and humidity (see 6.3);
sat R
f) D(T), diffusivity at temperature (see 6.3).
---------------------- Page: 13 ----------------------
– 12 – IEC 60749-39:2021 © IEC 2021
Bibliography

JESD22-A120B, Test Method for the Measurement of Moisture Diffusivity and Water Solubility

in Organic Materials Used in Electronic Devices
___________
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SOMMAIRE
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