TECHNET Archives

March 2001

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Brad Kendall <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 2 Mar 2001 05:59:33 -0800
Content-Type:
text/plain
Parts/Attachments:
text/plain (176 lines)
Steve,
Do the parts look like the center of the part has been
pushed out?  This is likely something that your rework
house could tell you.  If your parts were exposed to
air for too long and absorbed moisture, they could
popcorn during reflow and that causes the center of
the bottom of the part to bulge.  When that happens,
you may lift the outside leads, or, you could squeeze
the inner leads enough to cause bridging.  The area
inside the part that bulges could also be the same,
thus similar bridge areas.  Just a thought.

Brad Kendall
--- Bob Perkins <[log in to unmask]> wrote:
> Hi Steve
>
> One thing I have noticed is that if you do not have
> your voiding under
> control you can create bridging.  I have seen a
> voids large enough to
> expanded the ball enough to invade in the space of
> the next ball, and if
> that ball has a large void also a bridge can occur.
> If this is an known
> issue then a new paste may be in order.
>
> I see two issues with your profile that could
> possibly be causing a
> problem, I don't think all the balls on the BGA are
> reflowing at the same
> time.  I think you can improve this by setting up
> your reflow closer to 183
> before spike. There could also be a hot slump issue
> also at the beginning or
> reflow, I would recommend you try this to get a more
> simultaneous reflow.
>
> 130 160 180 183 240
> 130 160 180 183 240
>
>
> How you guys doing in Seattle after that shake up?
> We felt it up here in Vancouver.
>
> Bob Perkins
> SMT Manufacturing Process /
> Automation Technician
> Aitmronics-Delta
>
>
>
>
> -----Original Message-----
> From: Stephen R. Gregory [mailto:[log in to unmask]]
> Sent: Tuesday, February 27, 2001 1:34 PM
> To: [log in to unmask]
> Subject: [TN] Heat-sinked BGA Bridging...
>
>
> Hi all!
>
> This topic is a "moldy-oldie", but I've started to
> experience bridges again
> with this TI DSP (TMS320C6201GJC200). I've been
> doing okay up unil recently.
> We build these boards in work orders of around 25
> pieces.
>
> Our last run we had 7 boards bridged out of 25!!
> Sent the boards out to be
> reworked. I asked that they be x-rayed before and
> after, and to my surprise
> after looking at the x-ray images, they were all
> bridging in the same
> general
> area.
>
> It's a 4-row periphery BGA, and the bridges are
> occuring on the inner two
> rows, around the center of the part, at the same
> side of the part.
>
> What's funny, is that the vendor we use to rework
> the boards for us is
> having
> difficulty as well. We've been asking him to remove,
> re-ball, and re-install
> the part, they said they've been having about a 50%
> success rate doing
> this...they've been getting the bridges too. They
> have a nice full-blown SRT
> BGA rework station and do this for a living.
>
> I print 6-mils of paste (square apertures for the
> BGA), have a Conceptronic
> HVN-70 which I run:
>
> 150     160     170     180     240
> 150     160     170     180     240
>
> 25-in. per min
>
> We never have had these problems before...it all
> started when TI put the
> heatsink into the top of the part. I've looked at
> our paste print and it's
> dead on, placement is dead on too, we verify that
> with a Ersascope.
>
> My question is could there be something wrong with
> the part? Warping causes
> bridges at the corners, right? Why would it bridge
> in the interior rows at
> the same general area?
>
> Thanks in advance!
>
> -Steve Gregory-
>
>
----------------------------------------------------------------------------
> -----
> Technet Mail List provided as a free service by IPC
> using LISTSERV 1.8d
> 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 delivery of Technet send the
> following message: SET
> Technet NOMAIL
> Search previous postings at: www.ipc.org > On-Line
> Resources & Databases >
> E-mail 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 1.8d
> 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 delivery of Technet send the
> following message: SET Technet NOMAIL
> Search previous postings at: www.ipc.org > On-Line
> Resources & Databases > E-mail 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
>
---------------------------------------------------------------------------------


__________________________________________________
Do You Yahoo!?
Get email at your own domain with Yahoo! Mail.
http://personal.mail.yahoo.com/

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
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 delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail 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
---------------------------------------------------------------------------------

ATOM RSS1 RSS2