Dave,
That is a good print note. I avoid via-in-pad unless it is either filled
and plated over, or plated up to the surface. Small dimples less than
2-3 mils deep don't hurt, but anything more than that is an automatic
void in the solder joint, especially on the BGAs. I have actually had
them explode, scattering a single solder ball all over under the BGA. It
is because deep holes in the pads collect moisture and crud, and during
reflow they outgas like crazy.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dave Seymour
Sent: Tuesday, February 27, 2007 12:11 PM
To: [log in to unmask]
Subject: Re: [TN] Via in Pad question
Here is an earlier email trail.....
-------- Original Message --------
Subject: Re: [TN] Via in (SMT) pad
Date: Wed, 18 May 2005 11:09:44 -0400
From: Dave Seymour <[log in to unmask]>
Reply-To: TechNet E-Mail Forum <[log in to unmask]>, Dave Seymour
<[log in to unmask]>
To: [log in to unmask]
References: <[log in to unmask]>
Here is a fabrication note I worked up with the fab shop.
"All vias drilled equal to or less than .0xx shall be plated, then
filled with non conductive material, such as Peter's paste # SD-2361, or
equivalent. Surface to be planar prior to final plating and
metallization.
Boards must be suitable for via in pad technology."
http://www.peters.de/
I would recommend working with your fabricators to find the best
solution to your requirement. Without mentioning names, Most large fab
houses can handle this either internally or through subcontractors.
.028 is pretty big these days to fill. (?)
Most prefer to flood the entire board, rather than be selective.
Hope this helps,
Dave
Allen T. Maddox wrote:
>We have a couple engineers who are insisting on using Via in (SMT) pad.
I'm not talking about micro via in a BGA pad. I'm talking about vias
with a 10 to 28 mil hole in a 0805, PLCC, QFP, and other SMT pad.
>In order for this to work in manufacturing they must be filled, without
voids, and capped flush on the solder surface.
>Does anyone know of a board house that does this process?
>
>Would you have an idea what the general cost effect to a board for this
process and does it make a difference if it's one via or 500 vias? Cost
difference between electrically conductive and thermally conductive
fill?
>
>Any information would be helpful,
>
>
>Allen Maddox C.I.D.
>Sr. PC Board Designer
>GAI-Tronics, Corp
>610-796-5854
>PO Box 1060
>Reading, PA 19607-1060
>
>[log in to unmask]
>www.gai-tronics.com
>
>
>
--
Dave Seymour, CID+
Catapult Communications Inc.
800 Perimeter Park Dr, Suite A
Morrisville, NC 27560
Direct: (919)653-4249
Main: (919)653-4180
Fax: (919)653-4297
[log in to unmask]
Carl VanWormer wrote:
>I am looking for guidance on using vias in pads of surface mount
>components. The concept is great for high speed design, since it gives
>the least inductance for mounting bypass caps. It sounds easy, but I'm
>sure there are some pitfalls and there may be some rules I will break.
>Any guidance towards documents on this combination would be
appreciated.
>Also, any stories to scare me away from this approach will be fun to
>hear.
>
>Later,
>Carl
>
>
>
>
>
>Carl Van Wormer
>Cipher Systems
>1800 NW 169th Place, Suite B-100
>Beaverton, OR 97006
>Phone (503)-617-7447 extension 20
>
>---------------------------------------------------
>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
>847-615-7100 ext.2815
>-----------------------------------------------------
>
>
>
--
Dave Seymour, CID+
Catapult Communications Inc.
800 Perimeter Park Dr, Suite A
Morrisville, NC 27560
Direct: (919)653-4249
Main: (919)653-4180
Fax: (919)653-4297
[log in to unmask]
*************************************************************
"This e-mail (and any attachments) may contain confidential and
privileged information. If you are not the intended recipient, please
notify the sender immediately by return e-mail, delete this e-mail and
destroy any copies. Any dissemination or use of this information by a
person other than the intended recipient is unauthorized and may be
illegal. Thank you."
*************************************************************
---------------------------------------------------
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
847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------
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 847-615-7100 ext.2815
-----------------------------------------------------
|
