IPC 4552 Table Of Contents
User Manual: 4552
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IPC-4552 ASSOCIATION CONNECTING ELECTRONICS INDUSTRIES ® Specification for Electroless Nickel/ Immersion Gold (ENIG) Plating for Printed Circuit Boards Developed by the Plating Processes Subcommittee (4-14) of the Fabrication Processes Committee (4-10) of IPC November 6, 2002 Users of this standard are encouraged to participate in the development of future revisions. Contact: IPC 2215 Sanders Road Northbrook, Illinois 60062-6135 Tel 847 509.9700 Fax 847 509.9798 IPC-4552 October 2002 Table of Contents SCOPE ....................................................................... 1 APPENDIX 2 Process Sequence ................................ 7 1.1 1.2 Scope ................................................................... 1 Description .......................................................... 1 APPENDIX 3 Qualification of ENIG Process by the Board Supplier .......................... 8 1.2.1 1.3 1.4 1.4.1 1.4.2 1.4.2.1 Phosphorus/Boron Content ................................. Objective ............................................................. Performance Functions ....................................... Solderability ........................................................ Contact Surface .................................................. Membrane Switches ........................................... APPENDIX 4 Recommendation For Thickness Measurement ......................................... 9 APPENDIX 5 Standard Developments Efforts of Electroless Nickel Immersion Gold ...................................................... 10 1 1 1 2 2 2 2 Figures 1.4.2.2 Metallic Dome Contacts ..................................... 2 1.4.3 EMI Shielding .................................................... 2 Figure 3-1 Uniform Plating ................................................. 3 Figure 3-2 Extraneous Plating or Nickel Foot .................... 3 1.4.4 Figure 3-3 Edge Pull Back ................................................. 4 Figure 3-4 Skip Plating ....................................................... 4 Figure 4-1 IPC-2221 Test Speciman M, Surface Mount Solderability Testing, mm [in] ............................ 5 Figure 1 Results from Gold Thickness Survey ............. 11 Figure 2 Results from Nickel Thickness Survey ........... 12 Figure 3 Comparison of Gold Thickness Values by XRF Machine Type .................................... 14 Figure 4 Comparison of Gold Plating Thickness Variation by Vendor for Similar Bath Life Conditions ....................................................... 15 Figure 5 Comparison of Nickel Plating Thickness Variation by Vendor for Similar Bath Life Conditions ....................................................... 16 1.4.5 Conductive (Replacement for Solder) and/or Anisotropic Adhesive Interface .............. 2 Connectors .......................................................... 2 1.4.5.1 Press Fit .............................................................. 2 1.4.5.2 Edge Tab ............................................................. 2 1.4.6 Aluminum Wire Bonding ................................... 2 2 APPLICABLE DOCUMENTS ................................... 2 2.1 2.2 2.3 2.4 IPC ...................................................................... ASTM International (ASTM) ............................ Defense Standardization Program ...................... Telcordia Technologies, Inc. .............................. 2.5 International Organization for Standardization (ISO) ......................................... 2 Figure 6 Wetting Times as a Function of Plating Dwell Times for Vendor D, 90 Days Old ........ 17 REQUIREMENTS ...................................................... 3 Figure 7 Wetting Times as a Function of Plating Dwell Times for Vendor D, 90 Days Old ........ 18 Figure 9 Wetting Balance Data for Vendor D Post 18 Hours 85/85 Conditioning .......................... 20 Figure 10 Comparison of One Microinch Gold Deposit Tested at 8 Months Shelf Life vs as Received and 85/85 .............................. 21 Figure 11 Comparison of One Microinch Gold Deposit after Various Storage Times/ Conditions ....................................................... 21 Figure 12 Contact Resistance Data for Vendor D for Interlocking Square Contacts .................... 22 Figure 13 Contact Resistance Data for Vendor C for Interlocking Square Contacts .................... 23 Figure 14 Comparison of Gold Thickness by Vendor for the Interlocking Square Contact Test ........ 24 Figure 15 Interlocking Square Contact Test Coupon ...... 25 3 2 2 2 2 3.1 3.2 3.2.1 3.2.2 Visual .................................................................. Finish Thickness ................................................. Electroless Nickel Thickness ............................. Immersion Gold Thickness ................................ 3.3 3.4 Porosity ............................................................... 3 Adhesion ............................................................. 3 3.5 3.6 3.7 3.8 Solderability ........................................................ Cleanliness .......................................................... Chemical Resistance ........................................... High Frequency Signal Loss .............................. 4 3 3 3 3 3 4 4 4 QUALITY ASSURANCE PROVISIONS ................... 4 4.1 Qualification ........................................................ 4 4.1.1 Sample Test Coupons ......................................... 5 4.2 Acceptance Tests ................................................ 5 4.3 Quality Conformance Testing ............................ 5 Table 3-1 Requirements of Electroless Nickel Immersion Gold Plating ......................................................... 1 Chemical Definitions ............................ 6 Table 4-1 Qualification Test Coupons ................................. 5 APPENDIX 1 iv Tables October 2002 IPC-4552 Specification for Electroless Nickel/Immersion Gold (ENIG) Plating for Printed Circuit Boards 1 SCOPE 1.2.1 Phosphorus/Boron Content Phosphorus or boron containing reducing agents are used for the reduction of the electroless nickel during the deposition process. Phosphorus or boron is thus incorporated in the nickel deposit. The level of these co-deposited elements should be controlled within the specified process limit. Variation of phosphorus or boron level, outside the specified process limits, may have adverse effects on the solderability of the finish. 1.1 Scope This specification sets the requirements for the use of Electroless Nickel/Immersion Gold (ENIG) as a surface finish for printed circuit boards. This specification is intended to set requirements for ENIG deposit thicknesses based on performance criteria. It is intended for use by supplier, printed circuit manufacturer, electronics manufacturing services (EMS) and original equipment manufacturer (OEM). 1.3 Objective This specification sets the requirements specific to ENIG as a surface finish (see Table 3-1 for a summary of these requirements). As other finishes require specifications, they will be addressed by the IPC Plating Processes Subcommittee as part of the IPC-4550 specification family. As this and other applicable specifications are under continuous review, the subcommittee will add appropriate amendments and make necessary revisions to these documents. ENIG is an electroless nickel layer capped with a thin layer of immersion gold. It is a multifunctional surface finish, applicable to soldering, aluminum wire bonding, press fit connections, and as a contact surface. The immersion gold protects the underlying nickel from oxidation/passivation over its intended life. However, this layer is not totally impervious and it will not pass the requirements of a ‘classic’ porosity test. 1.2 Description Table 3-1 Requirements of Electroless Nickel Immersion Gold Plating Test Method Requirement Paragraph Visual 3.1 Uniform plating and complete coverage of surface to be plated. Electroless Nickel Thickness APPENDIX 4 3.2.1 3 to 6 µm [118.1 to 236.2 µin] Immersion Gold Thickness APPENDIX 4 0 0.05 µm minimum [1.97 µin minimum] N/A 3.3 N/A IPC-TM-650 TM 2.4.1 3.4 No evidence of plating removed. J-STD-003 3.5 Meet solderabiltiy requirements of Category 3 durability with six months shelf life. ASTM B-733-97 & ASTM B607-91 (1998) 1.2.1 (Reference Only; Supplier Dependent No Testing Required) N/A 3.7 N/A Tests Class 1 Class 2 Class 3 General Visual Porosity Physical Adhesion/Tape Test Solderability Chemical Phosphorous/Boron Content Chemical Resistance Electrical High Frequency Signal Loss Contact Resistance (1) (1) 3.8 TBD 1.4.2 TBD 3.6 Max. 1.56 µg/cm2 Environmental Cleanliness IPC-TM-650 TM 2.3.25 (1) An appropriate IPC-TM-650 test method used to generate data for this electrical property is not available at the time of this writing. 1
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