The nails from a bare board tester may be proven to be the
culprit if the CC has been perforated, assuming the board was CCed.
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kerry McMullen
Sent: Friday, March 09, 2007 12:17 PM
To: [log in to unmask]
Subject: Re: [TN] whodunit?
Seen that before. That is the test point indent from a bed of nails
bareboard tester. The force is too great. This can also be caused by
too many test points in the fixture and the operator not being able to
dial in the force required to make all the probes achieve good contact.
Kerry McMullen
Principal New Product Mfg. Engineer
LTX Corporation
825 University Avenue
Norwood, MA 02062-2643
(T) 781-467-5468
(C) 508-631-1832
(F) 781-461-0993
Steve Gregory <[log in to unmask]> Sent by: TechNet
<[log in to unmask]>
03/09/2007 11:48 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to Steve Gregory
<[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] whodunit?
Hi Graham!
Got a picture of your "Whodunnit" up, it's at:
http://stevezeva.homestead.com/files/whodunnit.JPG
Sure looks like a probe mark to me...a chisel type tipped probe. Here's
one they call a "Flux Buster":
http://www.isiconnectors.com/mfrs/idi/catalog/so25.jpg
Looks like it would leave a similar mark...
-Steve Gregory-
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins
Sent: Friday, March 09, 2007 9:40 AM
To: [log in to unmask]
Subject: [TN] whodunit?
Hello Technet!
I've got a mystery today. A colleague showed me a board, it's got some
unique damage on it. It is the only one of maybe a thousand identical
assemblies, the rest do not have this damage.
Throughout the bottom side of the board there are damaged through-hole
pads. The damage is an impact hole, where something triangular in shape
has in some cases literally punched through the pad. In some cases
there is a lighter mark on the pad and/or on adjacent solder mask. The
damaged pads are scattered throughout the board, they aren't restricted
to one area. In some cases where there is damage there is visible
exposed copper.
Some facts
1) the board went through our assembly process without incident until
inspection
2) no unusual equipment malfunctions have been reported recently here -
so I don't think it is something we did.
3) The board is received with HASL finish on the pads, and is wave
soldered.
4) In all cases the damage is at a through-hole pad, some overlaps the
pad onto bare FR4/solder mask, but in all cases the damage at least
touches a pad.
5) the board also has SMT parts on the bottom side, we glue parts on and
wave solder attach them. No damage has been identified on these pads.
I'm concluding that:
- we don't have any equipment capable of doing this type of damage to a
PWB with such precision.
- because there is exposed copper, whatever happened likely took place
after HASL coating.
At this point my theory is that the electrical test at the PWB shop did
this, but it's a theory. Can you PWB guys advise, is this possible?
Where else would something triangular have the potential to whack the
pads?
As I said already, it's only one - but I hate an unsolved mystery!
Please help.
regards,
Graham Collins
Process Engineer,
L-3 Communications Electronic Systems Inc.
Halifax
(902) 873-2000 ext 6215
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