Graham,
Since you are looking at SIR/EM type testing an not solder joint testing,
then things like spacing and voltage gradient, etc are more important than
part type.  So to cut cost (if you have not already bought your coupons),
design a board with fewer component types, use all surface finishes and run
it as a DOE so you do not have to use every different combination of
variables.

regards,
Bev Christian
Research in Motion

-----Original Message-----
From: Graham Naisbitt [mailto:[log in to unmask]]
Sent: October 15, 2001 6:52 AM
To: [log in to unmask]
Subject: [TN] Lead Free Surface finishes


Techies and (I guess - Leadies?)

We are about to carry out some reliability test work, examining the
influences of electro-chemical reactions using SIR techniques.

The manufacturing process that will be employed involves lead-free soldering
materials, water based fluxes and water based conformal coatings. The
methodology we shall employ shall be as drafted in a new IEC draft spec
6-1189.

The coupon we will use is intended to model mixed technology as closely as
possible. We include through-hole connectors, J lead SOIC's, BGA 225, SMT
Capacitors and QFP 160.

We will use an LPIM resist and were going to examine 4 different surface
finishes:

NiAu (ENIG)
ImSn - Immersion Tin
ImAg - Immersion Silver
OSP

However, and to get to the question: We can't afford all these permutations
so, we shall select only one surface finish. Can you folks advise the most
popular surface finish that is likely to be used for lead-free processing?

Please, we would REALLY like a simple answer rather than to open a huge
dialogue - 'cos we have to get the testing done by Mid November and we have
yet to have the coupons made!!

Awaiting your replies with interest.

Regards, Graham Naisbitt

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