I would expect flux to make its way up through the holes.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Dave Seymour
Sent: Tuesday, January 04, 2005 2:09 PM
To: [log in to unmask]
Subject: [TN] flux wick-up?


We had a batch of boards with high fall out. Below are a couple of
statements
from the CM building our cards. The socket mentioned below is a 370 pin CPU
ZIF
socket with a locking arm. We have manufactured this double sided
SMT/Through
hole mix card for 4 years.

My questions are,

Is there such a thing as "flux wick-up"?

Is the hole supposed to stop flux from getting onto the top side of the
PCBA?


I figured that flux is supposed to go up into the PCB hole ( and maybe even
getting into the socket contact area) to prepare the hole for soldering.
Then
the cleaning operation washes away any residue.

Any comments or help would be appreciated.

Thanks
Dave Seymour


>From CM:
"On a failed board we reviewed CPU sockets and removed the lid off the
socket
and viewed the gold contacts under a microscope and found some evidence of
contaminants/foreign matter on the gold contacts. "

"Got 23 CPU sockets from Stock and removed lids and there was no
contaminants found on sample of 4 parts."

"MFRG's data sheet and hole pattern recommendation is .030" 2 plc's = 0
tolerance.
Fab DWG shows hole dia to be .033" +.004 -.001.
Board hole dia is oversized compared to mfgr recommendations. "

"Can this possibly allow flux to wick-up?"

"We are continuing to investigate the findings and working to
determine what the contamination is...."

--
Dave Seymour, CID+
Catapult Communications Inc.
800 Perimeter Park Dr, Suite A
Morrisville, NC 27560

Direct: (919)653-4249
Main: (919)653-4180
Fax: (919)653-4297

[log in to unmask]

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