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PD IEC TR 61191-9:2023 Printed board assemblies - Electrochemical reliability and ionic contamination on printed circuit board assemblies for use in automotive applications. Best practices, 2023
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- CONTENTS
- FOREWORD
- INTRODUCTION
- 1 Scope
- 2 Normative references
- 3 Terms, definitions and abbreviated terms [Go to Page]
- 3.1 Terms and definitions related to management
- 3.2 Technical terms and definitions
- 3.3 Abbreviated terms
- 4 Failure mode electrochemical migration [Go to Page]
- 4.1 Background of electrochemical migration
- Figures [Go to Page]
- Figure 1 – Principal reaction mechanism of ECM
- Figure 2 – Uncertainty in local conditions determines ECM failures
- 4.2 Complexity of electrochemical migration
- Figure 3 – Occurrence of ECM failures during humidity tests
- 4.3 Conductive anodic filament (CAF) and anodic migration phenomena (AMP)
- Figure 4 – VENN diagram showing the factors influencing ECM
- 4.4 Creep corrosion
- Figure 5 – Occurrence of CAF and AMP
- 5 Electrochemical migration and relevance of ionic contamination [Go to Page]
- 5.1 General aspects
- 5.2 Background of ionic contamination measurement
- Figure 6 – Creep corrosion caused by corrosive gases
- Figure 7 – Ionic contamination measurement
- 5.3 Restrictions and limitations of ionic contamination measurement for no-clean assemblies [Go to Page]
- 5.3.1 Factors determining the result
- Figure 8 – Principal operation mode (fluid flow) of ROSE [Go to Page]
- 5.3.2 Influence by solvent on measurement of no-clean assemblies
- Figure 9 – Effect of solvent composition on the obtained ROSE results
- Figure 10 – Effect of solvent composition on the obtained ion chromatography result [Go to Page]
- 5.3.3 Influence of extraction time on measurement of no-clean assemblies
- Figure 11 – Comparison of ROSE values with different solvent mixtures and material variations of the CBA [Go to Page]
- 5.3.4 Influence by assembly and interconnect technology on measurement of no-clean assemblies
- Figure 12 – Variation in ROSE values depending on technology used
- Figure 13 – Destructive action of solvent on resin matrix
- Figure 14 – Comparison of the resin change [Go to Page]
- 5.3.5 Ion chromatography of no-clean assemblies CBA
- Figure 15 – Destructive action of solvent on resin matrix and chipping effect
- Tables [Go to Page]
- Table 1 – List of ions based on IPC-TM650, 2.3.28 [21]
- Table 2 – Fingerprint after ion chromatography of no-clean assembly shown in Figure 16
- 5.4 Restrictions and limitations of Ionic contamination measurement for cleaned products [Go to Page]
- 5.4.1 Ionic contamination of unpopulated CBs (bare board, state of delivery)
- Figure 16 – Assembly manufactured with 2x SMT and 1x THT process for the connector
- Figure 17 – Comparison of SPC-charts from 1-year monitoring of different CB suppliers and two different iSn final finish processes
- Figure 18 – Differences in ROSE values for unpopulated CBs depending on the extraction method
- Table 3 – Fingerprint after ion chromatography of bare CBs (state of delivery) [Go to Page]
- 5.4.2 Ionic contamination of electronic and electromechanic components
- Figure 19 – Reduction of ionic contamination on bare CBs (state of delivery from CB supplier) by leadfree reflow step without solder paste or components
- Figure 20 – Influence of components on the ionic contamination based on B52‑standard [Go to Page]
- 5.4.3 Ionic contamination of cleaned CBAs
- Figure 21 – Formation of a white veil or residue on MLCCs during active humidity test
- Table 4 – Fingerprint after ion chromatography of a bare CB and the respective PBA in uncleaned and cleaned condition
- Figure 22 – Chromatogram derived from ion chromatography measurement of a cleaned CBA
- 5.5 How to do – Guidance to use cases [Go to Page]
- 5.5.1 When is the use of ROSE measurements reasonable?
- Table 5 – Fingerprint after ion chromatography of an uncleaned CBA compared to the cleaned CBA and after removing the components [Go to Page]
- 5.5.2 When is the use of ion chromatography reasonable?
- 5.5.3 At what point in the manufacturing sequence ionic contamination measurements are carried out, if a fingerprint or the basis for process control is to be established?
- 5.5.4 How is the sampling for ROSE and IC done?
- 5.5.5 How is a product-specific process control limit based on ROSE determined?
- 5.6 Examples for good practice [Go to Page]
- 5.6.1 Ways to achieve objective evidence
- 5.6.2 Introduction of a new product family with new materials
- Figure 23 – Approach for achieving objective evidence for a qualified manufacturing process in the automotive industry [Go to Page]
- 5.6.3 Adaptation of an ECU for a new vehicle type
- Figure 24 – ROSE as process control tool
- 6 Surface insulation resistance (SIR) [Go to Page]
- 6.1 SIR – An early stage method to identify critical material combinations and faulty processing
- 6.2 Fundamental parameters of influence on SIR [Go to Page]
- 6.2.1 General aspects
- Figure 25 – View on SIR measurement
- Figure 26 – Principal course of SIR curves
- Figure 27 – Response graph concerning stabilized SIR-value after 168 h from a DoE with B53-similar test coupons (bare CB) [Go to Page]
- 6.2.2 Influence of climate
- Figure 28 – SIR measurement with B24-CB, no-clean SMT solder paste [Go to Page]
- 6.2.3 Influence of voltage
- 6.2.4 Influence of distance
- Figure 29 – Increase in ECM propensity depending on voltage applied (U) and Cu-Cu distances (d) of comb structures [Go to Page]
- 6.2.5 The limit 100 MΩ and optical inspection
- Figure 30 – Layout of B53 test coupon [Go to Page]
- 6.2.6 Influence of materials
- 6.3 Harmonization of SIR test conditions for characterization of materials for automotive applications
- 6.4 Different steps of SIR testing [Go to Page]
- 6.4.1 General procedure
- Table 6 – Common test conditions for basic material evaluation [Go to Page]
- 6.4.2 Base material
- 6.4.3 Solder mask and final finish
- 6.4.4 SMT solder paste
- 6.4.5 THT fluxes
- Figure 31 – B53 with solder mask, partially covered and fully covered comb structures [Go to Page]
- 6.4.6 Encapsulations and adhesives
- 6.4.7 Process qualification at CB manufacturer
- 7 Comprehensive SIR testing – B52-approach [Go to Page]
- 7.1 General aspects
- Table 7 – Recommended SIR test conditions for basic material- and process release for the outer layer manufactured by a CB supplier
- 7.2 The main B52 test board
- Figure 32 – B52 CBA after SMT process, layout slightly adapted to fulfil company internal layout rules
- 7.3 The test patterns
- Figure 33 – Pattern of B52 CB, layout slightly adapted to fulfill company internal layout rules
- Table 8 – List of materials for components with recommendations for minor adaptations
- 7.4 Processing of B52 boards
- 7.5 Sample size for SIR testing of B52 test coupons
- 7.6 Preparation for SIR testing
- 7.7 Sequence of SIR testing
- Table 9 – Sequence for SIR testing of B52-CBAs for general material- and process qualification
- Figure 34 – Positive example of comprehensive SIR tests obtained for qualification of a SMT process
- Figure 35 – Negative example of a contaminated B52-sample, tested by the sequence of constant climate and cyclic damp heat climate
- 7.8 Evaluation
- 8 Example for good practice [Go to Page]
- 8.1 Methodology for material and process qualification, process control
- 8.2 Step 1 – Material qualification
- Figure 36 – SIR test coupon, similar to B53, for principal material qualification
- Figure 37 – SIR test with constant climate and cyclic damp heat condition
- 8.3 Step 2 – Product design verification and process validation
- Figure 38 – B52 test board and example of SIR curve
- Figure 39 – Example of the product that was realized by the released materials and process
- 8.4 Step 3 – Definition of process control limits
- Figure 40 – Ionic contamination test results from 4 repetitions of PV samples
- Figure 41 – Results of ionic residue testing and calculation of upper control limit (UCL)
- Figure 42 – Run chart derived from 2 samples per month during mass production
- Annex A (informative)SIR measurement for SMT solder paste – Representative example [Go to Page]
- A.1 Purpose
- A.2 Equipment
- A.3 Example of an instruction how to perform the test
- Bibliography [Go to Page]
