IPC-4556 印制板化学镍钯浸金（ENEPIG）规范ENG - 第57页
CONCLUSIONS The solder spread on ENEPIG with the Sn/Pb/Ag solder paste (ROL1) was very high (good), regardless of ENEPIG chem- istry , deposit layer thickness, or damp heat conditioning. • The solder spread on ENEPIG wit…
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110
100
90
80
Figure A6-7 Solder Spread Results for Pb-free Solder Paste as a Function of the EN Layer Thickness in the ENEPIG Deposit
%
%
%
%
70%
60%
50%
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00
Solder Spread (%
8.00 9.00 10.00
)
Actual Ni Thickness (um)
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00
Solder S
pread (%
8.00 9.00 10.00
)
Actual Ni Thickness (um)
Pb-free ROL0 – No Condioning
Chem A
Chem B
Chem C
Chem D
Chem E
Chem F
Chem G
Pb-free ROL0 – Post 72 C/85% RH
Chem A
Chem B
Chem C
Chem D
Chem E
Chem F
Chem G
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CONCLUSIONS
The solder spread on ENEPIG with the Sn/Pb/Ag solder paste (ROL1) was very high (good), regardless of ENEPIG chem-
istry, deposit layer thickness, or damp heat conditioning.
• The solder spread on ENEPIG with the Pb-free solder paste (ROL0) was lower than the Sn-Pb results.
• Damp heat conditioning prior to solder paste printing negatively impacted the spread for the Pb-free solder paste. The worst
samples exhibited localized areas of dewetting.
• No correlation (linear R
2
<0.1) was found between the solder spread and the electroless palladium layer thickness (range
tested: 0.05-0.45 µm) or IG layer thickness (range tested: 0.015-0.085 µm).
• Some correlation (linear R
2
~ 0.45) was observed between the Pb-free solder spread and the EN layer thickness (range
tested: 4.5-9.5 µm), with the thickest EN deposits having the highest spread and the lowest spread observed for low EN
thicknesses.
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APPENDIX 7
ENEPIG PWB Surface Finish Shear Test Project
Dave Hillman, Brad Williams, Tim Pearson, Ross Wilcoxon and Jennet Volden
Rockwell Collins Inc.
INTRODUCTION
Rockwell Collins conducted solderball shear testing for the IPC 4-14 Plating Processes Subcommittee as part of their efforts
to create a specification for electroless nickel/electroless palladium/immersion gold (ENEPIG) circuit card finishes. A test
program was conducted to assess the solderball shear strength of a series of test coupons with different electroless palladium
plating thicknesses using both tin/lead and lead-free soldering processes.
Test Vehicle The IPC 4-14 subcommittee supplied solderball shear test coupons that were 2.4 inches long x 0.93 inches
wide x 0.063 inches thick. The solderball pad was 0.025 inches in diameter. The palladium thickness varied for each coupon.
Table A7-1 lists the measured palladium thickness/coupon combinations and Figure A7-1 illustrates the shear test coupon.
Solder Processes The shear test coupons were manually stenciled using low residue tin/lead (Sn63Pb37) and lead-free
(SAC305) solder pastes per IPC-JSTD-004 and a 0.005 inch thick stainless steel stencil. A 0.025 inch diameter Sn63Pb37
alloy solder sphere and a 0.035 inch diameter SAC305 alloy solder sphere were manually placed on a random selection of
stenciled deposits. The test coupons were then processed in a five zone Electrovert Omniflow reflow oven using a nitrogen
reflow atmosphere. The peak reflow temperature for the Sn63Pb37 alloy was 220 °C and for the SAC305 alloy was 245 °C.
The Time Above Liquidus for the Sn63Pb37 alloy was 30-60 seconds and for the SAC305 alloy was 45-90 seconds. The test
coupons were cleaned using an in-line cleaner that used Kyzen Aquanox A4625 saponifier/deionized water solution.
Table A7-1 Test Coupon Serial Number and Palladium Thickness
Sample Number Pallidium Thickness (µinches)
1 3.48
2 5.49
3 6.84
4 1.57
5 6.38
6 8.32
16 3.8
17 5.93
18 6.9
19 17.95
Figure A7-1 Shear Test Coupon – Note right portion of the test coupon is missing due to removal for cross-sectional analysis (left view)
and close up view of solder paste deposit reflowed on coupon pads (smaller solder joints) and a pad with a solderball reflowed on pad (large sol-
der joint) (right view)
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