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Ni and SnPb Electroplating of Surface Mount Chip Resistors




I am a new engineering engineer in chip resistor (surface mount devices) industry. Now I need to seek the root cause of a defect which randomly occurs during electroplating ( Ni and SnPb plating) process. The defect only can be seen after solderability test or leaching. The defect looks like a big hole at the center of terminal site of the chip. When I am using X-ray to measure the Ni and Sn thickness I found there is no Ni and Sn on the terminal site, we only found base material (NiCr) with thickness 0.22 microns. We face this problem more that 2 years and try many ways but still cannot solve this problem. Can anyone out there advise me?

I want to know what is the industrial recommended thickness for Ni/Au electroplating for surface mount devices of size 0603, 0402 and 0201. Can anyone out there advise me?

Thanks,

W.Y.Ho
- Johor Bahru, Senai, Malaysia
2003



"Modern Electroplating
Schlesinger & Paunovic"


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A. Hello Ho,

Hope you are doing sputtering on the edge termination of chip resistors. It seems the void (as you say) is covered by thin layer of plating and gets leached out during solderability or leach test. The probable cause is contamination on the surface of base metal. Check your handling or check your pre-cleaning process. 3-5 microns of plated nickel will withstand solderability and 1 min leach test. To prevent Nickel from getting oxidised you can apply 0.5 to 1 micron of Au flash. For 0201, 0402 and 0603 the above should be good.

Good luck,

Karthik Thambidurai
electronic components - Norwood, Massachusetts
2003



Q. Thank you for your advise. I use 96% sulfuric Acid to do pre-cleaning in 6% sulfuric acid tank, it is enough to do preparation before plating nickel on sputtering surface (NiCr).

W.Y.Ho
- Johor Bahru, Senai, Malaysia
2003


A. Hi,

5-10% Sulfuric acid should be sufficient enough to activate the surface, but it will not be able to remove any mask or organics which come into contact after sputtering. Do you use any mask during sputtering process? check for contamination getting onto the surface; if those are not removed you will have voids like these.

Good luck ...

Karthik Thambidurai
electronic components - Norwood, Massachusetts
2003




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