Ken,
There exists in the TechNet archives lots of info about ENIG (electroless
nickel/immersion gold) and the pros and cons of using such. There seems to
be some debate about its use with BGAs, but for the most part many find
ENIG acceptable. We have been getting some boards from a fab house with
ENIG, with no problems so far, with the possibility of using ENIG in the
future for new products.
Solderability is excellent, durability is good, reliability is good. The
gold finish provides a basically oxide-free surface, to allow good wetting
to the nickel plating underneath. Solder embrittlement becomes an issue
with heavy gold plating. (Of course, HP has been using ENIG on their
boards for years. Saw that even 24 years ago with an inexpensive 3-1/2
digit DVM from HP: an Au-plated board. Made all the techs at now-defunct
company jealous...)
Would this board supplier be in Canada, per chance?
BTW, I think you meant to say 30 micro-inch electroless gold finish. 1
micron = 1 micrometer = 39.4 micro-inches. Just a thought: if you are not
using edge-fingers (probably not, considering the end use), you might be
just as well off with 4 to 10 micro-inches of Au over 100uin of Nickel.
Roger M. Stoops, C.I.D., PCB Designer
Trimble
Engineering and Construction Division
5475 Kellenburger Rd.
Dayton, OH 45424-1099 USA
Ph: +01 937.233.8921 or +01 937.233.4574 ext 288
Fax: +01 937.233.7511
"Chafin, Ken
G." To: [log in to unmask]
<kgchafin@SWI cc:
TCH.COM> Subject: [TN] Solder vs Gold Pads on SMT
Sent by:
TechNet
<[log in to unmask]
ORG>
08/20/01
02:30 PM
Please
respond to
"TechNet
E-Mail
Forum."
We presently use SMT printed wiring boards with 60/40 tin-lead solder
finish
on the pads.
Our PWB supplier has offered to supply our boards with a 30 micron
electroless gold finish on the pads at the same price.
Does anyone have any views on the relative merits of the two finishes?
Solderability? Durability? Reliability?
We manufacture electronic control and signaling systems for the rail and
rapid transit industry and our equipment is often in harsh environments.
Thanks for any information on the subject.
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