Hello, Technetters

I have been following the forum for a while and I have benefited a lot from
all those who contribute their knowledge and know-how.

Now I have some questions that need an answer urgently. We have a SMT board
which requires flash gold finish typically in the range of 4 - 10 u".
However our PCB fab used electrolytic Au that caused the Au thickness at the
component side gone up to as high as 21 u" and as a result solder joint
embrittlement occurred.
I know that eletroless Au would be the answer to this problem. When I
suggest this to the fab house, they replied that electroless Au has to go
with electroless Ni. And this is due to compatibility of the resist and
plating bath. Could someone explain what is actually happening.
However our product engineer some comments that it is not recommended to use
eletroless Ni as phosphorous in the bath may codeposit with Ni which will
cause soldering issue. I am not sure if this is the real case.
Lastly, I have a few questions.

1. Is the porosity level same for a given thickness for both type of Au
   finishes (electrolytic Vs eletroless) ?
2. What is the Minimum Au thickness which provide sufficient protection on
   the Ni surface ?Pls. provide separate figure if there is any different
for
   both type of finish.

Cheers....

CL Chong
Materials Engineer
Agilent Technologies
.

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################