IEC TR 61191-8:2021
(Main)Printed board assemblies - Part 8: Voiding in solder joints of printed board assemblies for use in automotive electronic control units - Best practices
Printed board assemblies - Part 8: Voiding in solder joints of printed board assemblies for use in automotive electronic control units - Best practices
IEC TR 61191-8:2021(E) gives guidelines for dealing with voiding in surface-mount solder joints of printed board assemblies for use in automotive electronics. This technical report focuses exclusively on voids in solder joints connecting packaged electronic or electromechanical components with printed boards (PBs). Voids in other solder joints (e.g. in a joint between a silicon die and a substrate within an electronic component, solder joints of through-hole components, etc.) are not considered. The technical background for the occurrence of voids in solder joints, the potential impact of voiding on printed board assembly reliability and functionality, the investigation of voiding levels in sample- and series-production by use of X‑ray inspection as well as typical voiding levels in different types of solder joints are discussed. Recommendations for the control of voiding in series production are also given. Annex A collects typical voiding levels of components and recommendations for acceptability.
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Standards Content (Sample)
IEC TR 61191-8 ®
Edition 1.0 2021-03
TECHNICAL
REPORT
colour
inside
Printed board assemblies –
Part 8: Voiding in solder joints of printed board assemblies for use in automotive
electronic control units – Best practices
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IEC TR 61191-8 ®
Edition 1.0 2021-03
TECHNICAL
REPORT
colour
inside
Printed board assemblies –
Part 8: Voiding in solder joints of printed board assemblies for use in automotive
electronic control units – Best practices
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.180; 31.190 ISBN 978-2-8322-9575-5
– 2 – IEC TR 61191-8:2021 IEC 2021
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Technical background of voiding in solder joints and potential impact on assembly
reliability . 8
4.1 Void categories . 8
4.2 Void occurrence in surface-mount technology solder joints . 11
4.3 Influence of voiding on solder joint performance . 14
4.3.1 Introductory remarks . 14
4.3.2 Thermomechanical reliability . 15
4.3.3 Mechanical reliability . 17
4.3.4 Thermal functionality . 18
4.3.5 Electrical functionality . 19
5 Determination of voiding levels in solder joints . 20
5.1 Instrumentation available for investigation of voiding in solder joints . 20
5.1.1 General . 20
5.1.2 X-ray inspection equipment operating in two-dimensional mode. 20
5.1.3 X-ray inspection equipment operating in three-dimensional mode . 21
5.2 Challenges for the X-ray inspection of voiding: two case studies . 22
5.2.1 Influence of shadowing effects on measuring reproducibility – first
results for 3D X-ray inspection equipment . 22
5.2.2 Influence of X-ray parameters . 23
5.2.3 Manual determination of voiding levels in solder joints in sample
production . 24
6 Recommendations for sample qualification . 25
7 Recommendations for mass production . 26
7.1 General remarks . 26
7.2 Ramp-up quality assurance for voiding . 26
7.3 X-ray sampling inspection . 26
7.3.1 General . 26
7.3.2 Control limits . 26
7.3.3 Exceeding the control limits . 26
7.4 Process control without X-ray sampling inspection . 27
Annex A (informative) Types of voids and guidelines for acceptability . 28
A.1 Types of voids – Summary . 28
A.2 Typical voiding levels of components and guidelines for acceptability . 29
A.2.1 General . 29
A.2.2 Ball-grid array (BGA) components with collapsing balls . 30
A.2.3 Bottom-termination components involving a lead-frame construction, as
quad-flat no lead packages, dual-flat no lead packages . 30
A.2.4 Exposed pads of components with gull wing solder joints as quad-flat
packages . 31
A.2.5 Transistors with thermal plane as D2PAK and TOLL (TO lead-less) . 31
A.2.6 Rectangular or square end chip components (2, 3 or 5 side
terminations) . 32
A.2.7 Light-emitting diodes . 32
A.3 Further components currently under discussion . 32
A.4 Tabular summary . 32
Bibliography . 34
Figure 1 – Example of inclusion/macro void . 8
Figure 2 – Example of design induced void . 9
Figure 3 – Example of shrinkage void . 9
Figure 4 – Example of planar micro voids . 10
Figure 5 – Example of intermetallic voids . 10
Figure 6 – Example of pinholes . 11
Figure 7 – Example of blowhole voids . 11
Figure 8 – Theoretical model for voiding behaviour of preballed components . 12
Figure 9 – Online X-ray images and trend of void level during melting phase . 13
Figure 10 – Principal influencing parameters affecting solder joint reliability . 14
Figure 11 – Correlation of BGA lifetime with average and maximum void levels . 16
Figure 12 – Correlation void level standoff chip resistor 1206 and shear force after TC. 17
Figure 13 – Sketch of heat transfer with exposed pad solder joints . 18
th
Figure 14 – Calculation of void influence within exposed pads on overall R . 19
Figure 15 – Average voiding results for different shadowing conditions . 22
Figure 16 – Gauge reproducibility of void measurement with different shadowing . 23
Figure 17 – Void measurement of BGA region with varying X-ray parameters . 24
Table A.1 – Types of voids with indication of root cause, occurrence in automotive
electronic assemblies, detectability, effect on thermomechanical reliability, thermal and
electrical function and overall assessment . 28
Table A.2 – Recommendations for acceptable minimum solder coverage or maximum
void level as well as ranges for process indicators . 33
– 4 – IEC TR 61191-8:2021 IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PRINTED BOARD ASSEMBLIES –
Part 8: Voiding in solder joints of printed board assemblies
for use in automotive electronic control units – Best practices
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