Hi. Net:

Recently we have been experiencing some void holes problems

Our process is following:

manual medium PTH build 60 "
primary image 
Automated pattern plating copper and etchresist pure Sn
Striping and Etching

After striping Sn, we find plated copper very low and almost none especially along the edge (vertical direction). then after we chemically prepare the surface for LPI, Void comes out.

It seems surface have no trouble picking up Sn, but for Cu plating. 

We try our best to control developing . Everything not too bad except temp and pressure a little low. Surface still look clean!

For preclean cycle we are using methanesulfnoic chemistry, total etch rate may be a little low < 10" (we have problem with acid soak solution which kind functions as etch inhibitor rather promoter)

For copper plating tank. Analysis and hull cell indicate everything OK.

Since it random happen on different jobs with low percentage, It make quite difficult to quickly point to one stage. Any thoughts?


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