Dwight,
Great feedback. Many of our new designs are locating vias in the solder
pads due to space limitations which are causing solder problems as you would
expect.
I read the PETERS tech data sheet for PP 2795-SD plugging paste. Sounds
like it is formulated for plugging buried vias and does not address blind or
through vias. What has been your experience plugging blind vias in solder
pads?
joe
-----Original Message-----
From: Dwight Mattix [mailto:[log in to unmask]]
Sent: Monday, January 27, 2003 1:58 PM
To: [log in to unmask]
Subject: Re: [TN] Completely Plugging Vias.
At 09:47 AM 1/27/2003 -0800, Jindra, Larry wrote:
Dwight, et al-
We're looking at plating over conductive filled via-in-pad for 1mm pitch
BGAs (small vias, thick boards). How much trouble are we going to get into?
Keep the CTE match in mind. It's the main issue...
Conductive pastes typically have a CTE around 75 ppm.
Non-conductive pastes are on the order of 25ppm and therefore more closely
matched to the FR4/Cu combination.
In general, it depends on how good a job your supplier does of filling
without entrapment of bubbles and curing the paste (gotta get the volatiles
out). Most of the conductive pastes we've encountered are ~3% volatiles and
something like peanut butter in consistency so it's a nice trick getting the
toothpaste back in the tube without entrapped bubbles. It can be done but
very ew North American fabs have the tools and a repeatable procedure for
via fill (high end Asian shops have via fill nailed). You should be
alright if the paste is in individual holes with individual annular rings.
Even better if the fill is not plated over. Plating over the fill provides a
surface for the fill to act on in the Z axis.
Most of the problems we've had have been when filling tight clusters of
gnd/thermal vias located all in the same pad or piece of foil; then plated
over to make a planar, pretty finished surface.
The surface plating acts like a head over a gang of expanding "pistons." All
the Z axis force of the vias acting together sometimes lifts that pad
(usually a gnd slug under some high temp IC). It's not it's an everyday
occurrence but frequent enough that it's not our preferred solution.
The only real advantage I see to the conductive fill is that plating
adhesion has been better that for the non-conductive fills. As a result
conductive fill has pretty much been relegated to the province of ATE DUT
cards that need a perfect planar (filled via) surface for their delicate
probes (IC test sockets). Even so our suppliers are getting to the point
where plating adhesion over non-conductive fill is getting good enough that
we'll probably get away from conductive fill all together.
cheers,
Dwight
Larry Jindra
Mfg Engr Group Lead
[log in to unmask]
-----Original Message-----
From: Dwight Mattix [ mailto:[log in to unmask]
<mailto:[log in to unmask]> ]
Sent: Friday, January 24, 2003 2:01 PM
To: [log in to unmask]
Subject: Re: [TN] Completely Plugging Vias.
Consider using a 100% solids via fill material. There's several good ones
available. Peters and Taiyo (HBI-200DB4/TA20DB4) probably have the best and
MacuVia should be fine for this requirement as well. Stay away from the
conductive fills if possible (CB100 et al).
dw
At 09:54 AM 1/24/2003 -0500, you wrote:
Greeting mighty TechNetters.
Here's a common question, I think, but not common enough that I found it in
a search.
Scenario-Small PWB fab shop. Customer wants vias (no larger than .016 inch)
plugged to prevent light, vacuum, you name it, from escaping through. Must
be plugged from at least one side, and tented on the other. We build it on
an 16x18 panel, probably .063 finished thickness with 1/1 outers. LPI and
SMOBC ink are applied manually at this time. (squeegee, squeegee, bake [or
tack]) We have not come up with a reliable process. New equipment is
probably not an option yet, unless its like a bigger squeegee. (ha ha).
Any assistance is appreciated.
Steve MacDonald
---------------------------------------------------
Technet Mail List provided as a free 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
<http://listserv.ipc.org/archives>
Please visit IPC web site http://www.ipc.org/html/forum.htm
<http://www.ipc.org/html/forum.htm> for additional information, or contact
Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a free 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
<http://listserv.ipc.org/archives>
Please visit IPC web site http://www.ipc.org/html/forum.htm
<http://www.ipc.org/html/forum.htm> for additional information, or contact
Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a free 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
<http://listserv.ipc.org/archives>
Please visit IPC web site http://www.ipc.org/html/forum.htm
<http://www.ipc.org/html/forum.htm> for additional information, or contact
Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a free 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/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a free 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/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
|
