IPC-4556 印制板化学镍钯浸金（ENEPIG）规范ENG - 第10页

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Figure A7-7 Sn63Pb37 Test Coupons5&6 ................... 53

Figure A7-8 Sn63Pb37 Test Coupons7&8 ................... 53

Figure A7-9 Sn63Pb37 Test Coupon 18 .......................... 53

Figure A7-10 Sn63Pb37 Test Coupon 19 .......................... 54

Figure A7-11 SAC305 Test Coupons1&2....................... 54

Figure A7-12 SAC305 Test Coupons3&4....................... 54

Figure A7-13 SAC305 Test Coupons5&6....................... 55

Figure A7-14 SAC305 Test Coupons 16 & 17 ................... 55

Figure A7-15 SAC305 Test Coupon 18 ............................. 55

Figure A7-16 SAC305 Test Coupon 19 ............................. 56

Figure A7-17 Solderball Shear Force as a Function of

Palladium Plating Thickness ........................ 56

Figure A8-1 Wire Bond Test Vehicle Showing pin #1,

quadrants 1, 2, 3 and 4 ............................... 58

Figure A8-2 Example of 6 inx8inPanel Containing

1 in x 1in ENEPIG Wire Bond Coupons ...... 60

Figure A8-3 Visual Evaluation of Wire Bonding

Showing Classical Crescents Resulting

in Neck Breaks ............................................. 61

Figure A8-4 (Top) Summary of 1 mil Gold Wire

ENEPIG Destructive Pull Test (DPT)

Results and (Lower) Comparison of

X-Y Directional DPT Values ......................... 62

Figure A11-1a Meniscometer ............................................... 70

Figure A11-1b

Wetting Balance ........................................... 70

Figure A11-2 ENEPIG with Thin and Thick Pd from

Vendors1&2 .............................................. 71

Figure A11-3 Wetting Rate as a Function of Battelle

Class 2 Aging ............................................... 72

Tables

Table 3-1 Requirements of Electroless Nickel Electroless

Palladium Immersion Gold (ENEPIG) Plating ... 4

Table 4-1

Suggested Fabricator Qualiﬁcation Plan ......... 10

Table 4-2 C=0 Sampling Plan (Sample Size for Speciﬁc

Index Value

) .................................................... 11

Table A3-1 Comparison of the Accuracy of Measurements

Relative to the C Readings for All Three

Deposits ........................................................... 21

Table A4-1 Summary of XRF Conﬁguration Solutions

Offered for Measurement of ENEPIG

Plating on PCB’s with Advantages and

Disadvantages ................................................. 27

Table A5-1 XRF Measurements of the Nominal

0.5 micron Electroless Palladium

Samples ........................................................... 32

Table A6-S1 Preconditioning and Solder Paste Matrix

Used for Solder Spread Testing for a

Given ENEPIG Chemistry and Electroless

Palladium Thickness ........................................ 40

Table A7-1 Test Coupon Serial Number and Palladium

Thickness ......................................................... 48

Table A7-2 Sn63Pb37 Solderball Shear Test Results

Coupon Set 1 (grams) ..................................... 50

Table A7-3 Sn63Pb37 Solderball Shear Test Results

Coupon Set 2 (grams) ..................................... 50

Table A7-4 SAC305 Solderball Shear Test Results

Coupon Set 1 (grams) ..................................... 51

Table A7-5 SAC305 Solderball Shear Test Results

Coupon Set 2 (grams) ..................................... 51

Table A8-I Twenty-one Panels Marked (a) Whole

Panel, (b) Array and (c) Hand Cut ................... 59

Table A8-II Destructive Wire Bond Pull Test Force

(grams) Results for All 21 ENEPIG

Test Groups ..................................................... 60

Table A8-III Summary of Plating Finish Thicknesses for

Samples Wire Bonded ..................................... 63

Table A9-1 XRF Detectors and Their Limitations at

Typical Count Rates ......................................... 64

Table A11-1 ‘‘Relative Wettability Guideline,’’ Using

Contact Angle (θ

) As ‘‘General’’ Metric .......... 70

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Specification for Electroless Nickel/Electroless Palladium/

Immersion Gold (ENEPIG) Plating for Printed Circuit Boards

1 SCOPE

1.1 Statement of Scope

This speciﬁcation sets the requirements for the use of Electroless Nickel/Electroless Palladium/

Immersion Gold (ENEPIG) as a surface ﬁnish for printed boards. This speciﬁcation sets requirements for ENEPIG deposit

thicknesses for applications including soldering, wire bonding and as a contact ﬁnish. It is intended for use by chemical

suppliers, printed board manufacturers, electronics manufacturing services (EMS) and original equipment manufacturers

(OEM).

1.2 Description ENEPIG is a tertiary layered surface ﬁnish plated over copper as the basis metal. ENEPIG consists of an

electroless nickel base layer over which is plated an electroless palladium barrier layer followed by a deposit of a thin

immersion gold as the ﬁnal outer layer. For deposition process details, see APPENDIX 1 of this speciﬁcation. It is a multi-

functional surface ﬁnish, applicable to soldering and to gold, aluminum and copper wire bonding. It is also suitable as the

mating surface for soft membrane and steel dome contacts. Additional applications include use in Low Insertion Force (LIF)

and Zero Insertion Force (ZIF) edge connectors and for press-ﬁt applications. The electroless palladium layer forms a dif-

fusion barrier that impedes nickel diffusion to the gold surface. The immersion gold protects the palladium layer from react-

ing with contaminants prior to processing that might otherwise affect joining processes, such as wire bonding and soldering.

1.2.1 Electroless Nickel Reducing Agents - Phosphorus Content Phosphorus-containing, reducing agents are typically

used for the reduction of the electroless nickel during the deposition process and phosphorus is incorporated in the nickel

deposit. The level of this co-deposited element should be controlled within the suppliers speciﬁed process limits. Variation of

phosphorus levels outside the speciﬁed process limits may have adverse effects on the performance of the ﬁnish.

1.2.2 Electroless Palladium Reducing Agents There are two distinct classes of reducing agents used in electroless pal-

ladium baths currently available for use in the ENEPIG process, those that produce deposits that contain a co-deposited ele-

ment such as phosphorus, and those that produce an essentially pure palladium deposit. The level of the co-deposited ele-

ments should be controlled within the speciﬁed process limits. Examples of electroless palladium deposit from both these

classes have been evaluated during the development of this speciﬁcation and no perceivable differences in performance were

observed in the tests of solderability or wire bondability

1.3 Objective This speciﬁcation sets the requirements for ENEPIG as a surface ﬁnish (see Table 3-1 for a summary of

these requirements). As additional surface ﬁnishes require speciﬁcations, they will be addressed by the IPC Plating Processes

Subcommittee as part of the IPC-455X speciﬁcation family. This and other surface ﬁnish speciﬁcations are under continuous

review. The 4-14 subcommittee will make appropriate amendments or revisions to these documents as required. The 4-14

Plating Processes Subcommittee undertook a ‘‘Round Robin’’ study to generate data to support the recommendations sited

for the various aspects of this speciﬁcation. For an outline of the study, refer to APPENDIX 2.

1.3.1 Order of Precedence In the event of conﬂict, the following order of precedence shall apply:

1. The purchase order. This includes AABUS exceptions to this speciﬁcation.

2. The master drawing. This includes AABUS exceptions to this speciﬁcation.

3. This speciﬁcation.

4. Applicable documents as detailed in Section 2 of this document.

1.3.1.1 Appendices This speciﬁcation contains eleven Appendices provided for information which are included after the

main body of this document. Be aware that none of the content of these appendices are binding requirements unless sepa-

rately and speciﬁcally speciﬁed herein, or as required by purchase order, master drawing, other applicable documents, or as

established AABUS.

1.4 Performance Functions

1.4.1 Solderability

One of the two primary functions of ENEPIG is to provide a solderable surface ﬁnish capable of pro-

viding IPC Category 3 shelf life (minimum 12 months) per IPC-J-STD-003 testing. This shelf life is suitable for all surface

mount, hybrid and through-hole assembly applications. The use of electroless palladium as a diffusion barrier between the

January 2013 IPC-4556