John,

A number of years ago we tried DFSM over tin plate followed by HAL. There
were issues with solder wicking resulting in lifting mask on traces adjacent
to surface mount pads. With no HAL, defects were still evident but not as severe.
This was primarily due to the lower available volume of solder. Since that
time we have only utilized SMOBC for our surface mount product (LPI or DFSM).

We still use some DFSM over reflowed PbSn for a some through hole products, using
the mask only to minimize shorts at wave.

Bob Smith
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Phil,

We are also considering making the switch from tin/lead to tin plating =
as initially an etch resist only.  We are however interested in your =
comment on using tin only as a final finish.  Standard production would =
remain SMOBC...

1. Can tin plating be offered as an alternative to our customers =
concerned about pad finish for SMT applications?

2.  Are there problems with bonding between LPI mask and the tin =
plating?

Any information, pro's con's, on this with respect to fabrication and =
assembly would be appreciated.

Regards
John Parsons
Circuit Graphics Ltd.
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