Material costs of solderability preservation materials based on weight are (highest to lowest) Ni/Au, Pd, Ag, Sn, SnPb, OSP. This is based on the in-bound material cost to a fabricator.  I don’t know how that cost plays-out as a cost to
"properly" coat a pad.

Fabricators price white tin to match-up with SnPb.  Based on that, I’d guess their material cost is somewhere between SnPb and OSP.

The chunks of white tin stuff that fabricators spray or dip onto boards are BIG.  So, the process uses an OSP to protect the solderability of copper pads.  Given that immersion / spray processes are not a core skill of and difficult to control
for many fabricators … why not skip the white tin chunks and just stick with the benefits and problems of an OSP?

Dave Fish

"Lefebvre, Scott" wrote:

> I wanted to know what is the consensus on White Tin finish for replacement of tin lead HASL.  Is it compatible with today's component finishes and the Lead free finishes of tomorrow.
>
> I was told Nickel Gold is preferred but I've had issues with gold embattlement, and the cost is also a factor.  The gold we have on some of our assemblies has about 5 micro inches and I still do not get as nice of a solder joint as tin lead.
>
> Scott Lefebvre
> Process Engineer
>
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