TECHNET Archives

December 2003

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Joe Fjelstad <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 12 Dec 2003 11:06:42 EST
Content-Type:
text/plain
Parts/Attachments:
text/plain (56 lines)
Hi Steve,

Interesting discussion you have brought to the fore and you have gotten some
excellent advice on cleaning. It was not stated but I am assuming gold wire
bonding based on the thickness and as well assuming that the gold is not
selectively plated on the wire bonding pads.

My experience from past lives was that 1 micron was normally enough, however,
there were not two extra press cycles (with attendant volatilization and
deposition of organic materials and a reflow operation that preceded wire
bonding).

I have worked with folks wherein millions of devices were wire bonded post
reflow assembly using aluminum wedge bonding. The gold for such was about 1/5
micron

Brian has suggested and it has been seconded that porosity might be in the
mix.

I am left with a few questions whose answers that might lead me to ask better
questions.

Is the soldering leadfree? (higher temperatures? volatilized organics? )

Have you looked at the positity/diffusion issue? (i.e. Is Ni really there?)

Or is the offending layer organic by analysis?

Last (for the moment anyway... ;-) what thickness of gold would be considered
pore free? 1.5 microns?,  2.0?  2.1?  (I know that there are plating related
issues that mitigate any answer) and would that work for all steps in the
process? (embrittlement has already been cited as a concern but where is the wall
for this process combination?)

Gold is expensive but not so expensive as the board. I have had customers in
the past that specified 1.5 microns and never had a problem (make that never
reported back a problem)

We all like a good problem but the real objective is to find a way to make
them never show their faces in production. It's pretty boring but very cost
effective :-)

Good luck,
Joe


---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------

ATOM RSS1 RSS2