Rudy,
Thanks for your reply. Any thoughts on solderability after
multiple heat cycles. Our current involve 2 reflow cycles as well as some
postwave handsoldering. We encounter problems with the handsoldering
operations, particularly when boards have been sitting in storage 4+
months.
Wendy
Worth
Harris
Corporation
585-242-4543
Wendy:
The chemical that is the real "cause",
or engine, of immersion Tin is:
Stannous Chloride (Thiourea
Complex) and this item is not real soluble, (read that as
rinseable). You want thick Tin plate (for shelf life reasons), and in
order to have thick Tin, your fabricator needs a lot of this chemical in
solution, usually held in solution by it being heated. When this stuff
hits cold rinse water, it can set up like a gooey gel, and be difficult to
rinse.
Back in the days when we used to use immersion Tin to cover
dewetting on reflowed boards...this is really the stone age, most readers will
be too young to remember, we used to use hot water first rinse, to assure
getting good rinsing.
I do not recommend HOT rinsing, but I do think
WARM rinsing is not a bad idea.
Rudy Sedlak
RD Chemical
Company
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