Hi All
I have been evaluating solder pastes for QFN packages and these are my
findings and
observations. Everybody are welcome to provide comments.

Vehicle: QFN 5 x 6 8 leads (Powerpak footprint) also evaluated those from
Infineon footprint

1. Observed that NiPdAu plating finish- voiding is less compared to matte
Sn? Infineon solders well compared to a matte Sn plating QFN.

2. Of all the paste evaluated--Shenmao, Alpha metals, indium, henkel--->
Shenmao has the biggest voiding. But it works Ok with NiPdAu plated QFNs
compared to Matte Sn plating.

3. Stencil opening is varied. Observed no significant effect.

4. All pastes are lead free. SAC305



Questions:

1. Does anyone had experience of using shenmao paste? How does it perform in
terms of voiding. Why it doesnt work well on Matte Sn finish?

2. Is the compostion of solder paste (Cu content) affect the soldering
performance ex. voids?

3. It seems the paste quality had the biggest impact on voding, any
comments?

4. Evaluation uses the same PCB pattern and stencil openings for different
type of paste but Shenmao had the largest voids. Do you have
some experience?

We want to improve the voiding quality, any more suggestions.


Thank you for your kind help

Thanks


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