We had a similar problem with one of our assemblies and the only way we
managed to cure it was to setup the chip wave on the solder machine as
well as the lamda wave {even though there are no components on the
bottomside}. This added turbulance managed to dislodge any flux build
ups and allowed the soldering to occur.

Best Regards

Gordon McAlpine
Manufacturing Manager
Telspec Scotland Ltd

Tel :- 01738 494500
DDI :- 01738 494506
Mobile :- 07710-477336
Fax :- 01738-630012
E-Mail :- [log in to unmask]

============================================

DISCLAIMER

This message is intended only for the use of the individual(s) or entity
named above. It may contain information which is privileged or
confidential. If you are not the intended recipient, please return it to
the sender as soon as possible and be aware that any disclosure,
copying, distribution or use of the contents is prohibited. The views
expressed in this communication may not necessarily be the views held by
the Company.

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Alistair Murray
Sent: 11 August 2004 08:59
To: [log in to unmask]
Subject: [TN] Solder skipping on ENIG finish


Hi to all. This is my first visit to this forum and I apologise if this
subject has been aired and exhausted in previous correspondence.

My customer has an issue with a simple double sided PTH board (no
surface mount pads) with ENIG finish all over. After standard wave
soldering, he is experience random skipping of test pads on the solder
side. Normally, this would not be a problem but some of these test pads
do not provide a good electrical contact when subjected to electronic
testing. Again, this phenomenon is quite random. The wave soldering
parameters have been modified but with little success as the skipping
persists in a random fashion. We have carried out SEM analysis on good
and suspect pads and have concluded that (1) there are no unexpected
elements present thereby eliminating contamination such as solder resist
(2) evidence of nickel oxide is present on the suspect pads (3) there is
a physical difference in the material structure of the good and suspect
pads - the good test pad has an homogenous structure with no
discontinuities whilst the suspect pad is not homogenous and has a
series of parallel lines which are boundaries in the material deposition
(4) SEM analysis on the test pin found no insulating material.

Can anyone explain how such skipping can occur and how it can be
prevented? The random failure to make electrical contact on non soldered
pads is puzzling. We are convinced that there are no insulating elements
present. Could the different structures be a clue? Could the deposition
rate differ from pad to pad? Could the process control parameters of the
nickel and gold solutions be a factor here?

Thank you for your anticipated help.

Alistair F Murray
Technical  Manager
Artetch Circuits Limited
Tel: 01903 725365
Voice Mail Ext. 1260
e-mail: [log in to unmask]
www.artetch.co.uk

---------------------------------------------------
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
-----------------------------------------------------


Disclaimer:
This message is intended for the use of the individual(s) or entity named above. It may contain information which is privileged or confidential.
If you are not the intended recipient, please return it to sender as soon as possible and be aware that any disclosure, copying, distribution or use of its contents is prohibited. The views expressed in this communication may not necessarily be the views held by the company.

---------------------------------------------------
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
-----------------------------------------------------