Interesting thought
----- Original Message -----
From: Jac Kroeker <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, April 10, 2002 12:42 PM
Subject: Re: [TN] 0402 tombstone problem
> Hi TN assemblers;
> Having followed this thread, I haven't seen any body point a finger at the
> board finish as a cause of tombstoneing. I always thought that HASL or
> poorly HASSLED boards contributed to tombstoneing. We went to immersion
> White Tin years ago in order to make our boards more manufacturable. Is
> there a comment from the assembly community about tombstoning and the
> topography of the bare board?
> Jac Kroeker
> Omni Graphics Ltd.
> www.omnigraph.com
>
> At 11:16 AM 04/10/2002 -0400, you wrote:
> >Hi Dan,
> >
> >can you give the exact dimensions of the round land pattern?
> >
> >Thanks,
> >Ioan
> >
> > > -----Original Message-----
> > > From: Dan R. Johnson [SMTP:[log in to unmask]]
> > > Sent: Wednesday, April 10, 2002 10:22 AM
> > > To: [log in to unmask]
> > > Subject: Re: [TN] 0402 tombstone problem
> > >
> > > Steve,
> > > I use round pads to decrease pad size (increase circuit density). A
side
> > > benefit seems to be less chance of skew, I don't have numbers on
> > > tombstoning/drawbridging, but product hasn't yelled. I have also been
> > > tinkering with the idea of other geometries just haven't come across
the
> > > right application yet.
> > > Dan
> > >
> > > ----- Original Message -----
> > > From: [log in to unmask] <mailto:[log in to unmask]>
> > > To: [log in to unmask] <mailto:[log in to unmask]>
> > > Sent: Tuesday, April 09, 2002 8:12 PM
> > > Subject: Re: [TN] 0402 tombstone problem
> > >
> > > I just heard something not too long ago, that round pads for
0402's
> > > are the way to go.
> > >
> > > Never heard of that before, but just recently received a board
for
> > > quote that uses round pads for the 0402 components...anybody else ever
> > > heard of this?
> > >
> > > Guess I'll find out how it works inna little while, while
pondering
> > > why a round pad would work better than a square pad....
> > >
> > > -Steve Gregory-
> > >
> > >
> > >
> > >
> > > Edward,
> > >
> > > When we do everything correct on 0402 and 0201 and still
> > > have components
> > > standing-up, we often look to the component terminations
and
> > > find poor
> > > plating.
> > >
> > > Good luck
> > > Dave Fish
> > >
> > > ----- Original Message -----
> > > From: "Edward S. Wheeler" <[log in to unmask]>
> > > To: <[log in to unmask]>
> > > Sent: Tuesday, April 09, 2002 10:59 AM
> > > Subject: [TN] 0402 tombstone problem
> > >
> > >
> > > > Hi folks, we are running a new board with 0402 parts
on
> > > it. It seems that
> > > > we are having a tombstone problem as well as a problem
> > > with parts not
> > > > staying centered on the pads. We are currently using
20
> > > mil square pads on
> > > > the board, with 20 mils of spacing between them. Our
> > > stencil is 6 mils
> > > > thick, laser cut and electro polished. The trapezoidal
> > > walled apertures
> > > are
> > > > slightly reduced, 17 mils square, and centered on the
> > > pads. It appears the
> > > > chip shooter is placing the parts perfectly. We are
using
> > > eutectic solder
> > > > paste with an OA flux, and reflowing the parts using
the
> > > recommended
> > > profile.
> > > >
> > > > Are there any suggestions any of you might have
concerning
> > > this size of a
> > > > part? Is there a better stencil design, reflow
profile, or
> > > pad design that
> > > > could help us out? I would appreciate any suggestions.
> > > >
> > > > Thanks.
> > > >
> > > > Ed
> > >
> > >
>
> ========================================================
> Omni Graphics Ltd. 2 - 12760 Bathgate Way, Richmond BC, Canada V6V 1Z4
> Tel 604-276-9717 Fax 604-276-2514
> [log in to unmask] www.omnigraph.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 e-mail to [log in to unmask]:
SET Technet NOMAIL
> 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 1.8d
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 e-mail to [log in to unmask]: SET Technet NOMAIL
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
---------------------------------------------------------------------------------
|
