Constantino,
Please forward the cross section photo because it should show what is going
on inside the board.  I hear what you are saying, that it appears to be a
dent, but the top and bottom photos look like delamination.  If this is
standard FR4 material then you are far exceeding the glass transition
temperature of the material which is probably about 140 degrees C.
Localized applied heat of 290C - 350C for 15 seconds sure has the potential
to cause a blister/delamination.  Are you able to verify/calibrate the
temperature of the hot air blower?  What is your bare board supplier telling
you the defect is?
Regards,
Scott A. Bowles
Director of Quality and Technology
Sovereign Circuits Inc.
12080 DeBartolo Drive
North Jackson, OH 44451

Phone: (330) 538-3900 x211
Fax:   (330) 538-2434
Cell:  (330) 717-2125
email: [log in to unmask]

-----Original Message-----
From: IPC-600-6012 [mailto:[log in to unmask]]On Behalf Of Constantino
J. Gonzalez
Sent: Friday, October 28, 2005 5:50 PM
To: [log in to unmask]
Subject: [IPC-600-6012] Dent


Hello does anybody has a clue what this can be if it is not a blister?
Please read below and see attachments



Attached is the best photo I can get.

Fr top it sinking down, fr bottom it's budging up.

We see this right after reflow on random location.

It is not blister, the cross section photo does not show that.

Only abnormalities is difference in Cu thickness ( slight thinner on dent
area).



Any clue??



Hello Constantino,
How are you ??
I need your advise on recent issue I'm facing in our line.  It pretty new
for me ..
I hv  this PCA which produce "dent mark" during rework.

This dent appeared after performing rework to remove the SRAM (the location
that you see dent) with hot air blower, the temp is set to 350 deg C, blow
time is around 15 seconds (dent will be created - in shape of circle about
10mils diameter ), effective temperature on the comp is 290 deg C.

Every single board which we rework produce this condition.
It's not d/c related as we see similar condition on other d/c as well.
More then one d/c and more one location.
We try to simulate the hot air rework on raw card and the dent appears too.

Today line found 2 more boards with dent after going through IR reflow only
( no rework involved ).

The PCB supplier perform cross section on the dent location,  there is no
abnormalities seen expect for a difference in the copper thickness before
and after the dent.

I hv attached the cross section photo.. I can not get a snap shot of  the
dent due to glossy appearance and light reflection.

I can not figure out the root cause..
1) What actually caused this dent ?? Mechanical or thermal
2) Thermal should expand not contract !!
3) Why the dent appear only after reflow / rework ??

Even the PCB suppliers cracking their head.
This board is not failing   ICT/ FVT however it not as simple as cosmetic
defect !!!

I really hope to hear fr you.