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PD IEC TR 61191-7:2020 Printed board assemblies - Technical cleanliness of components and printed board assemblies, 2020
- undefined
- CONTENTS
- FOREWORD
- INTRODUCTION
- 1 Scope
- 2 Normative references
- 3 Terms and definitions
- 4 Technical cleanliness [Go to Page]
- 4.1 What is technical cleanliness?
- 4.2 History – standardisation of technical cleanliness
- 4.3 Technical cleanliness in the electronics industry
- 4.4 Potential particle-related malfunctions
- 5 Technical cleanliness as a challenge for the supply chain [Go to Page]
- 5.1 General
- 5.2 Contamination [Go to Page]
- 5.2.1 Definition of particles
- 5.2.2 Definition of fibres
- 5.3 Test procedure to determine technical cleanliness [Go to Page]
- 5.3.1 Fundamentals
- 5.3.2 Clarification form
- Figures [Go to Page]
- Figure 1 – Test method as per VDA 19 Part 1 [Go to Page]
- 5.3.3 System technology
- Figure 2 – Examples of extraction systems [Go to Page]
- 5.3.4 Process parameters for pressure rinsing extraction
- 5.3.5 Pressure rinsing process
- 5.3.6 Preparing membrane filters for measurement analysis
- Figure 3 – Component holder during manual pressure rinsing
- Figure 4 – Examples of different options for drying membrane filters
- Figure 5 – Slide frame with membrane filter
- 5.4 Measurement analysis
- 5.5 Evaluating the results of cleanliness analyses [Go to Page]
- 5.5.1 Overview
- 5.5.2 Particle count relative to component surface
- 5.5.3 Procedure for violation of action control limits
- Figure 6 – Example procedure if specifications are exceeded
- Tables [Go to Page]
- Table 1 – Influence of the blank value on the measurement results for different material surfaces (examples for a blank value fraction of 2,2 % and above)
- 5.6 Extended risk assessment [Go to Page]
- 5.6.1 General
- 5.6.2 Example
- Figure 7 – Particle size distribution and corresponding process capability
- 5.7 Component cleanliness – Data management and visualization [Go to Page]
- 5.7.1 Component cleanliness analysis – flow diagram
- Figure 8 – Flow diagram for component cleanliness analysis
- Figure 9 – Scope of analytical report [Go to Page]
- 5.7.2 Explanation of SCI (Surface Cleanliness Index)
- Figure 10 – Derivation of Illig value
- Figure 11 – Derivation of SCI
- Figure 12 – Evaluation of 7-pin HV strip connector
- Figure 13 – Graph showing cleaning effect based on SCIs [Go to Page]
- 5.7.3 Creating a database
- Figure 14 – Comparison of the three largest particles
- Figure 15 – Structural levels of a database
- Figure 16 – Option A – Evaluation of the largest particles by length and width
- Figure 17 – Option B – Extension to include the degree of contamination – SCI
- Figure 18 – Option C – Extension to include a separate data sheet "direct comparison of test series" [Go to Page]
- 5.7.4 Summary
- Figure 19 – Option D – Extension of the database "to include'comparison with customer standards'"
- 6 State of the art – Technical cleanliness in the electronics industry [Go to Page]
- 6.1 Process flow (per cluster) [Go to Page]
- 6.1.1 General
- 6.1.2 Electronics manufacturing cluster
- Table 2 – Electronics manufacturing cluster process flow [Go to Page]
- 6.1.3 Passive components cluster (e.g. for inductors and aluminium electrolytic capacitors)
- Table 3 – Process flow for inductors [Go to Page]
- 6.1.4 Electromechanical components cluster
- Table 4 – Aluminium electrolytic capacitors
- Table 5 – Stamped contact production/plastic production (housing) process flow
- Table 6 – Housing assembly process flow [Go to Page]
- 6.1.5 PCB cluster
- 6.2 Technical cleanliness in the electronics industry – current situation [Go to Page]
- 6.2.1 General
- Table 7 – PCB cluster process flow [Go to Page]
- 6.2.2 Electronics manufacturing
- Table 8 – Empirical data from electronics manufacturing cluster [Go to Page]
- 6.2.3 Electronic components
- Table 9 – Empirical data from inductors
- Table 10 – Empirical data from aluminium electrolytic capacitors
- Table 11 – Empirical data from tantalum capacitors
- Table 12 – Empirical data from chip components
- Table 13 – Empirical data from shunts
- Table 14 – Empirical data from quartz [Go to Page]
- 6.2.4 Electromechanical components
- Table 15 – Empirical data from semiconductors
- Table 16 – Empirical data from metallic components –stamping from pre-treated strip stock
- Table 17 – Empirical data from metallic components – stamping of contact from untreated strip stock and subsequent electroplating process
- Table 18 – Empirical data from metallic components – turning of pins andsubsequent electroplating process
- Table 19 – Empirical data from pure plastic parts
- Table 20 – Empirical data from joined strip connectors
- Table 21 – Empirical data from high-voltage connectors (typically shielded)
- Table 22 – Empirical data from the assembly process of non-metallic components [Go to Page]
- 6.2.5 Metal housings
- Table 23 – Empirical data from die-cast aluminium housing [Go to Page]
- 6.2.6 Packaging
- 6.2.7 Printed circuit boards (PCBs)
- Figure 20 – Flexible circuit board
- Table 24 – Empirical data from deep-drawn trays (new)
- Figure 21 – Rigid circuit board
- Table 25 – Empirical data from flexible PCBs without cleaning step
- Table 26 – Empirical data from bare, flexible PCBs with cleaning step
- Table 27 – Empirical data from bare, rigid PCBs
- 6.3 Determining potential particle sources in production areas [Go to Page]
- 6.3.1 General
- 6.3.2 Particle generation
- 6.3.3 Electronics manufacturing cluster
- 6.3.4 Passive components cluster
- Figure 22 – Burr formation on copper wire (D = 2,25 mm) after use of wire-cutter
- Figure 23 – Particles generated by wire cutting D = 1,8 mm (tinned copper)
- Figure 24 – Particles generated by wire cutting D = 1,8 mm (tinned copper)
- Figure 25 – Particle (tin) adhering to a tinned copper wire D = 2,25 mm
- Figure 26 – Hair-like particle (tin whiskers) chipped off a tinned wire (655 µm long)
- Figure 27 – Milled enamel wires
- Figure 28 – Molten solder balls fused to plastic housings
- Figure 29 – Ferrite particle, identified as metallic (419 µm)
- Figure 30 – Ferrite particle, identified as non-metallic (558 µm) [Go to Page]
- 6.3.5 Electromechanical components cluster
- Figure 31 – Non-metallic particle, probably burr or plastic residue (217 µm)
- Figure 32 – Non-metallic particle, probably pink polystyrene packaging material
- Figure 33 – Shielding plate
- Figure 34 – Stamped contacts
- Figure 35 – Connector pin
- Figure 36 – Connector housing
- Figure 37 – 58-pin connector housing [Go to Page]
- 6.3.6 PCB cluster
- Figure 38 – 12-pin connector with bridged contacts
- Figure 39 – Plastic particles + fibres
- Figure 40 – Plastic particles
- Figure 41 – Metallic particle
- Figure 42 – Milling crosses V-scoring line
- Figure 43 – V-scoring line on milling edge
- Figure 44 – Chip formation in milled hole
- Figure 45 – Edge plating
- Figure 46 – Connections for electroplated gold areas
- Figure 47 – Deep milling
- Figure 48 – Chip formation caused by stamping
- Figure 49 – Flexible circuit board with undercut
- Figure 50 – Punching burr in hole
- Figure 51 – Punching burr
- Figure 52 – Damaged metallic stiffener
- Figure 53 – Stamping residue along stamped edge
- Figure 54 – Stamping residue loosened by pickling bath
- 6.4 Cleanliness-controlled design and process selection [Go to Page]
- 6.4.1 Aspects of cleanliness-controlled design/production with regard to metallic particles
- Figure 55 – Plastic element with burr
- Figure 56 – Particles on externally supplied plastic elements [Go to Page]
- 6.4.2 Environmental cleanliness and internal production processes
- Figure 57 – Process chain analysis as per VDA 19 Part 2
- 6.5 Environmental cleanliness analysis and visualisation [Go to Page]
- 6.5.1 General
- 6.5.2 Procedure for environmental analysis
- Figure 58 – Cleanroom production
- Figure 59 – Example particle trap
- Figure 60 – Position of particle trap
- Figure 61 – Database – Visualisation
- Figure 62 – Illustration of the Illig value with max. three particles
- Figure 63 – Airborne dispersion diagram
- Figure 64 – Analysis results in the cleanroom [Go to Page]
- 6.5.3 Conclusions:
- Figure 65 – Analysis results in the area not governed by VDA 19
- Figure 66 – Weighting of factors influencing technical cleanliness
- 6.6 Cleaning tips [Go to Page]
- 6.6.1 General
- 6.6.2 Washing
- 6.6.3 Brushing
- 6.6.4 Suction-cleaning
- Figure 67 – Manual cleaning with brush and illuminated magnifier
- Figure 68 – ESD brush [Go to Page]
- 6.6.5 Blowing
- 6.6.6 Reducing carry-over and controlling cleanliness in workplace design
- Figure 69 – Workstations designed for cleanliness control [Go to Page]
- 6.6.7 Adhesive methods
- 6.7 Packaging and logistics requirements
- 7 Why do metallic particles in assemblies so rarely cause short circuits? [Go to Page]
- 7.1 General
- Figure 70 – Adhesive roller system for PCB contact cleaning
- 7.2 Probability of contact [Go to Page]
- 7.2.1 Introduction and theory
- Figure 71 – Diagram showing failure risks based on metallic particles on assemblies
- Figure 72 – Sketch of electrical arrangement (particle forming "bridge" between two conductors)
- Figure 73 – Diagram showing contact point of a particle on a conductor –nickel-gold conductor and copper particle [Go to Page]
- 7.2.2 Testing the probability of contact
- Table 28 – List of materials used in the test
- Figure 74 – SIR test circuit boards (interleaving comb pattern layout)
- Figure 75 – Voltage source that measures current with an analogue picoamperemeter [Go to Page]
- 7.2.3 Results
- Figure 76 – Automated current measurement with software
- Figure 77 – Comparison of CU particles in three conditions on SAC305 PCBs
- Figure 78 – Overview of all metals in the voltage classes, rounded
- 7.3 Rinsing extraction versus actual mobility
- 7.4 Particle sinks
- 7.5 Effect of short circuits on ICs
- 7.6 Tool for estimating the risk of short circuit [Go to Page]
- 7.6.1 Overview
- 7.6.2 Model hypotheses
- Figure 79 – Functional structure of risk assessment tool [Go to Page]
- 7.6.3 Calculation methods
- 7.6.4 Orientation factor
- 7.6.5 Critical area
- Figure 80 – Geometric constraints at a contact pair [Go to Page]
- 7.6.6 Number of particles per size class
- Figure 81 – Clearance areas up to 400 µm (in white)
- Figure 82 – Clearance areas up to 600 µm (in white)
- Figure 83 – Clearance areas up to 1000 µm (in white) [Go to Page]
- 7.6.7 Weighting factors
- 7.7 Example use of the risk assessment tool [Go to Page]
- 7.7.1 Example use of the risk assessment tool for calculating failure rate
- Figure 84 – Example calculation 1 – Calculating an absolute probability of failure [Go to Page]
- 7.7.2 Example use of the risk assessment tool for design changes
- Figure 85 – Example calculation 2 – Calculating probabilities of failurefor layout changes e.g. for a new generation component [Go to Page]
- 7.7.3 Example use of the risk assessment tool for specification violations
- Figure 86 – Example calculation 3 – Optimising the main variables
- Figure 87 – Example calculation 3 – Calculating the changed probabilityof failure in the event of specification violation
- 8 Summary
- 9 Outlook
- 10 Related topics [Go to Page]
- 10.1 Filmic contamination [Go to Page]
- 10.1.1 General
- 10.1.2 Biological films
- 10.1.3 Chemical films
- 10.2 Whiskers
- Figure 88 – Whiskers growth of > 8 mm over a period of 10 years
- Figure 89 – Whiskers growth of > 2 mm over a period of 6 months
- Annex A (informative)Determining the surface area of componentsand assembled circuit boards [Go to Page]
- Figure A.1 – Dimensions of cuboid components
- Figure A.2 – Dimensions of cylindrical components
- Table A.1 – Sample values of standard components to determinethe component surface area
- Annex B (informative)Examples of cleanliness clarification forms [Go to Page]
- Figure B.1 – Ambient cleanliness clarification form
- Figure B.2 – Ambient cleanliness clarification form
- Figure B.3 – Component cleanliness clarification form
- Figure B.4 – Component cleanliness clarification form
- Figure B.5 – Component cleanliness clarification form
- Bibliography [Go to Page]
