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IEC TR 61191-7
Edition 1.0 2020-03
TECHNICAL
REPORT
colour
inside
Printed board assemblies –
Part 7: Technical cleanliness of components and printed board assemblies
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IEC TR 61191-7
Edition 1.0 2020-03
TECHNICAL
REPORT
colour
inside
Printed board assemblies –
Part 7: Technical cleanliness of components and printed board assemblies
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 31.180; 31.190 ISBN 978-2-8322-7901-4
– 2 – IEC TR 61191-7:2020 © IEC 2020
CONTENTS
FOREWORD . 8
INTRODUCTION . 10
1 Scope . 11
2 Normative references . 11
3 Terms and definitions . 11
4 Technical cleanliness . 11
4.1 What is technical cleanliness? . 11
4.2 History – standardisation of technical cleanliness . 12
4.3 Technical cleanliness in the electronics industry . 12
4.4 Potential particle-related malfunctions . 12
5 Technical cleanliness as a challenge for the supply chain . 13
5.1 General . 13
5.2 Contamination . 14
5.2.1 Definition of particles . 14
5.2.2 Definition of fibres . 14
5.3 Test procedure to determine technical cleanliness . 15
5.3.1 Fundamentals . 15
5.3.2 Clarification form . 16
5.3.3 System technology . 18
5.3.4 Process parameters for pressure rinsing extraction . 19
5.3.5 Pressure rinsing process . 19
5.3.6 Preparing membrane filters for measurement analysis . 20
5.4 Measurement analysis . 22
5.5 Evaluating the results of cleanliness analyses. 22
5.5.1 Overview . 22
5.5.2 Particle count relative to component surface . 23
5.5.3 Procedure for violation of action control limits . 24
5.6 Extended risk assessment . 25
5.6.1 General . 25
5.6.2 Example . 25
5.7 Component cleanliness – Data management and visualization . 27
5.7.1 Component cleanliness analysis – flow diagram . 27
5.7.2 Explanation of SCI (Surface Cleanliness Index) . 28
5.7.3 Creating a database . 31
5.7.4 Summary . 34
6 State of the art – Technical cleanliness in the electronics industry . 35
6.1 Process flow (per cluster) . 35
6.1.1 General . 35
6.1.2 Electronics manufacturing cluster . 35
6.1.3 Passive components cluster (e.g. for inductors and aluminium
electrolytic capacitors) . 36
6.1.4 Electromechanical components cluster . 37
6.1.5 PCB cluster . 39
6.2 Technical cleanliness in the electronics industry – current situation . 39
6.2.1 General . 39
6.2.2 Electronics manufacturing . 40
6.2.3 Electronic components. 41
6.2.4 Electromechanical components. 44
6.2.5 Metal housings . 48
6.2.6 Packaging. 49
6.2.7 Printed circuit boards (PCBs) . 49
6.3 Determining potential particle sources in production areas . 52
6.3.1 General . 52
6.3.2 Particle generation . 52
6.3.3 Electronics manufacturing cluster . 52
6.3.4 Passive components cluster . 53
6.3.5 Electromechanical components cluster . 59
6.3.6 PCB cluster . 63
6.4 Cleanliness-controlled design and process selection . 72
6.4.1 Aspects of cleanliness-controlled design/production with regard to
metallic particles . 72
6.4.2 Environmental cleanliness and internal production processes . 74
6.5 Environmental cleanliness analysis and visualisation . 76
6.5.1 General . 76
6.5.2 Procedure for environmental analysis . 76
6.5.3 Conclusions: . 80
6.6 Cleaning tips . 81
6.6.1 General . 81
6.6.2 Washing . 81
6.6.3 Brushing . 81
6.6.4 Suction-cleaning . 82
6.6.5 Blowing. 83
6.6.6 Reducing carry-over and controlling cleanliness in workplace design . 83
6.6.7 Adhesive methods . 84
6.7 Packaging and logistics requirements . 84
7 Why do metallic particles in assemblies so rarely cause short circuits? . 84
7.1 General . 84
7.2 Probability of contact . 85
7.2.1 Introduction and theory . 85
7.2.2 Testing the probability of contact . 88
7.2.3 Results . 90
7.3 Rinsing extraction versus actual mobility . 92
7.4 Particle sinks . 92
7.5 Effect of short circuits on ICs . 93
7.6 Tool for estimating the risk of short circuit . 93
7.6.1 Overview . 93
7.6.2 Model hypotheses . 94
7.6.3 Calculation methods . 95
7.6.4 Orientation factor . 95
7.6.5 Critical area . 96
7.6.6 Number of particles per size class . 97
7.6.7 Weighting factors . 98
7.7 Example use of the risk assessment tool . 99
7.7.1 Example use of the risk assessment tool for calculating failure rate . 99
7.7.2 Example use of the risk assessment tool for design changes . 100
– 4 – IEC TR 61191-7:2020 © IEC 2020
7.7.3 Example use of the risk assessment tool for specification violations . 101
8 Summary . 102
9 Outlook . 102
10 Related topics .
...