-----Original Message-----
From: Wenger, George M.
Sent: Monday, September 12, 2005 8:23 PM
To: 'John Burke'; 'TechNet E-Mail Forum'
Subject: RE: [TN] raised vias...
John,
We won't know for sure until Steve does a cross section but my
assessment right now is that the raised ant hills are all too uniform to
be unfilled vias that have solder being pushed out. When I look at the
photograph it looks like a continuous sheet of copper that has bulged
areas rather than ant hills with an opening due to outgassing.
Regards,
George
George M. Wenger, Andrew Corporation
Reliability / FMA Engineer
Base Station & Subsystems Group
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 [log in to unmask]
-----Original Message-----
From: John Burke [mailto:[log in to unmask]]
Sent: Monday, September 12, 2005 8:15 PM
To: 'TechNet E-Mail Forum'; Wenger, George M.
Subject: RE: [TN] raised vias...
I think they are not filled, I believe the HASL process filled the vias
(horizontal HASL). I also think that the very thick core kept the via
hole solder molten long enough after process for the outgassing taking
place in the via holes to push the solder back out of the via forming
the ant hills.
Who knows...............Section it Steve...................
John
------------------------------------
Avanex
John Burke
Senior Manager RoHS Compliance
[log in to unmask]
40919 Encyclopedia Circle
Fremont
CA 94538
tel: 510 897 4250
fax: 510 979 0189
mobile: 510 676 6312
------------------------------------
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Wenger, George M.
Sent: Monday, September 12, 2005 4:57 PM
To: [log in to unmask]
Subject: Re: [TN] raised vias...
Michael,
I've taken a closer look at the raised via photo on Steve's site and I
agree the board does appear to have HASL surface finish and a cross
section should eliminate any guess work as to the cause for the raised
via. I would be more worried with Layer 1 copper plating attachment to
the via barrel plating than I would to the via fill material.
Regards,
George
George M. Wenger, Andrew Corporation
Reliability / FMA Engineer
Base Station & Subsystems Group
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 [log in to unmask]
-----Original Message-----
From: Mcmaster, Michael [mailto:[log in to unmask]]
Sent: Monday, September 12, 2005 7:44 PM
To: 'TechNet E-Mail Forum'; Wenger, George M.
Subject: RE: [TN] raised vias...
I would bet they were planarized down to the surface initially. It
looks like the board has HASL surface finish and I would bet the resin
in the vias expanded, pushing out the copper which then stayed there.
Cross section should show whether the copper is still attached to the
via fill.
This is one of the problems of trying to use prepreg resin to fill vias.
The resins meant to fill vias generally give better plating adhesion and
don't show this "bullet hole" appearance.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
Sent: Monday, September 12, 2005 4:36 PM
To: [log in to unmask]
Subject: Re: [TN] raised vias...
Valerie,
I think I agree with you that the bumps are prepreg and that the
fabricator needs to plane the prepreg back down to the copper level.
However, the problem with doing that is control of the plane operation
so it doesn't remove too much copper and weaken the Layer 1 via knees.
My suggestion to Steve is to cross section some of the raised vias and
examine the integrity of the Layer 1 plating to the blind via barrel
plating. And I would also repeat the cross sectioning process on
reflowed bare boards after the fabricator eliminates the raise vias to
insure he has good interconnect integrity/reliability.
Regards,
George
George M. Wenger, Andrew Corporation
Reliability / FMA Engineer
Base Station & Subsystems Group
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Valerie St.Cyr
Sent: Monday, September 12, 2005 7:18 PM
To: [log in to unmask]
Subject: Re: [TN] raised vias...
Nope .... those vias are filled with prepreg from the lamination cycle.
It
had nowhere to go ... it melts and floods up the hole, capillary action.
The fabricator should have planed the surfaces to bring the prepreg back
down level to the copper layer.
Valerie
stephen gregory <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
09/12/2005 07:02 PM
Please respond to TechNet E-Mail Forum; Please respond to stephen
gregory
To: [log in to unmask]
cc:
Subject: Re: [TN] raised vias...
Hi Everyone!
I'm home now, but I can answer some of the questions.
The picture of the board is as it was given to us. It hasn't been
through
reflow...this is how the bare board looks.
The vias aren't filled.This is a 10-layer board that is made from
IPC-4101/26
(GF) material. BUT, there is 5-layers on one side of a .045" thick
copper
core,
and on the other side of the core is the other 5-layers. There is
double-sided
SMT on the board, and both sides have the "anthills" like you see in the
picture.
Pretty strange, huh?
-Steve Gregory-
"Brooks,Bill" <[log in to unmask]> wrote:
I'm just passing the message on... it's Steve's board...
Thanks,
Bill Brooks
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