IPC-4552A: Performance Specification for Electroless ...

1 IPC-4552 APerformance Specificationfor Electroless Nickel/Immersion Gold (ENIG)Plating for Printed BoardsDeveloped by the Plating Processes Subcommittee (4-14) of the Fabrication Processes Committee (4-10) of IPCU sers of this publication are encouraged to participate in the development of future :IPCS upersedes:IPC-4552 with Amendments1&2 December 2012 IPC-4552 October 2002 Table of Contents1 of Scope .. Size for Thickness Measurement .. Nickel Reducing Agents Phosphorus Content .. of Precedence .. 22 APPLICABLE .. International (ASTM) .. Standardization Program.

2 Technologies, Inc.. Organization forStandardization (ISO) .. , Definitions and Acronyms .. Turnover (MTO) .. Corrosion Deposit .. Annular Ring Dewetting (SAD) .. 33 REQUIREMENTS OF ENIG Board Fabrication Supplier ProcessRequirements .. Plating Line Requirements .. Deposit Thickness Measurement .. Capability Gauge R&RType 1 Study .. Size and Measurement Times .. Bands and Lot ConformanceTesting .. XRF Calibration Standards .. Zero Offset Acceptability .. Qualification MeasurementRequirements .. Phosphorus Content in anENIG Deposit.

3 Of % Phosphorous (P)Content in Electroless Nickel (EN)Layers with Energy Dispersive X-RaySpectroscopy (EDS) .. of % Phosphorous (P)Content in Electroless Nickel (EN)Layers with Energy Dispersive X-RayFluorescence (EDXRF) .. Instrument Calibration for PhosphorusContent .. Stripping of Plated Deposits forEvaluation of Hyper-Corrosion .. Methods for Gold Stripping .. Stripping Solution DwellTimes and Process Steps .. Using SEM .. Boundary Enhancement .. of Hyper-Corrosion .. Functions .. Life .. Embrittlement .. and Copper Wire (Wedge)Bonding.

4 Wire Bonding .. Surface .. Membrane Switches .. Dome Contacts .. Shielding .. and/or Anisotropic AdhesiveInterface (Replacement for Solder) .. Fit Connectors .. Tab .. of ENIG .. Corrosion/Chemical Resistance .. Frequency Signal Loss .. Annular Ring Dewetting (SAD) .. Thickness .. Nickel Thickness .. Nickel for Rigid PrintedBoards .. More Than the Upper Limit .. Less Than the MinimumThickness Limit .. Nickel for Flexible Circuits .. to the Base Structure of theElectroless Nickel Deposits with FlexibleCircuits .. Gold Thickness.

5 Category B Coating Durabilityper IPC J-STD-003 .. 21 August to the Required ThicknessRanges .. Gold Thicker Than Specificationby Design .. Conformance Testing .. Measurement Exceptions .. Process Control .. Sizes of Ten Printed Boards or Less .. Overruns and/or InventoryItems .. of ENIG .. Hyper-Corrosion .. of the ENIG Deposit byCross Section .. ENIG Free of Hyper-CorrosionDefects .. Conditions with SomeEvidence of Hyper-Corrosion .. Conditions with End UserSign-Off/Acceptance .. Conditions .. Rating Level Table .. Non-Failure Analysis Testingto Determine Acceptance or Rejection forLevel 2 Hyper-Corrosion.

6 Of the Deposit Prior to SolderabilityTesting .. Measurement Testing (Wetting BalanceTesting) .. Corrosion .. Resistance .. 294 QUALITY ASSURANCE Quality Assurance Provisions .. Recommendations .. Test Coupons .. Conformance Testing .. of Thickness Measurements .. Qualified Process .. 30 APPENDIX 1 Terms and Definitions NotCurrently in 33 APPENDIX 2 ENIG Process 34 APPENDIX 3 XRF Thickness Measurements ofThin Au (ENIG): Recommendationsfor Instrumentation (Detectors)and Their 35 APPENDIX 4 ENIG PWB Surface Finish WettingBalance 37 APPENDIX 5 IPC 4-14 SC ENIG Round RobinSolder Spread 55 APPENDIX 6 Wire Bonding to 61 APPENDIX 7 Through Hole 62 APPENDIX 8 Evaluation of Electroless NickelCorrosion Due to Immersion GoldPlating, Using 3000X MagnificationAfter Gold 77 APPENDIX 9-A Cyanide Gold Stripping 82 APPENDIX 9-B Test Method for Potassium Iodide/Iodine (Non-Cyanide)

7 ENIG GoldStripping 83 APPENDIX 9-C Method for Stripping Gold Platingfrom ENIG Finished PCBs byBroad Beam Argon Ion 85 APPENDIX 10 Determination of Thicknessand Phosphorus Content InElectroless Nickel (EN) LayersX-Ray Fluorescence (XRF)Spectrometry [IPC-TM-650,Method ].. 90 APPENDIX 11 Phosphorus Content Measure-ment in ENIG Using ElectronDispersive Spectroscopy EDS Initial 97 APPENDIX 12 Standard Developments Effortsof Electroless Nickel 102 APPENDIX 13 Using Guard Bands or a GaugeCorrection Factor to AccommodateType 1 Gauge Study 102 FiguresFigure AExample of Repeat Measurement Data fromThree Different XRF Tools.

8 6 Figure BGraphical and Statistical Evaluation of Datafrom XRF Tool # 1 .. 7 Figure CGraphical and Statistical Evaluation of Datafrom XRF Tool # 2 .. 8 Figure DGraphical and Statistical Evaluation of Datafrom XRF Tool # 3 .. 9 Figure 3-1 Potassium Iodide/Iodine (KI / I2) at 15 (left) vs. 60 sec. dwell (right) .. 14 IPC-4552 AAugust 2017viiiFigure 3-2 Cyanide-Based Stripping at 15 sec. dwell(left) vs. 60 sec. dwell (right) .. 15 Figure 3-3 Cyanide Stripping (left) vs. KI/I2 Stripping(right) Using Focused Ion Beam (FIB) .. 15 Figure 3-425,000X FIB Images Cyanide (left) (right) Same Dwell Time.

9 15 Figure 3-5 Ion Mill Stripping of Defect-Free Nickel (left)vs. Hyper-Corroded Nickel (right) .. 16 Figure 3-6 Uniform Plating .. 18 Figure 3-7 Extraneous Plating or Nickel Foot .. 18 Figure 3-8 Skip Plating (No Ni plating) .. 18 Figure 3-9 Edge Pull Back .. 19 Figure 3-10 Example of SAD (Selective Annular ringDewetting) .. 20 Figure 3-11 Another Example of the SAD Defect .. 20 Figure 3-12 Selective Annular Ring Dewetting Defect .. 20 Figure 3-13 Grain Structure of Conventional NickelDeposit .. 21 Figure 3-14 Grain Structure of Nickel Deposit Modifiedfor Dynamic Flex Applications.

10 21 Figure 3-15 Example of Fracture in Conventional NickelDeposit .. 21 Figure 3-16 Modified Nickel Deposit of Cycles ShowingNo Fracture with Same Number .. 21 Figure 3-17 Defect Free ENIG Deposit Knee of Hole .. 25 Figure 3-18 Defect Free ENIG Deposit SMT Feature .. 25 Figure 3-19 Level 1 Hyper-Corrosion SMT Feature .. 25 Figure 3-20 Level 1 Hyper-Corrosion Knee of Hole .. 25 Figure 3-21 Level 2 Hyper-Corrosion Knee of Hole .. 25 Figure 3-22 Level 2 Hyper-Corrosion SMT Feature .. 25 Figure 3-23 Level 3 Hyper-Corrosion Knee of Hole .. 26 Figure 3-24 Level 3 Hyper-Corrosion SMT Feature.