Hi Martin!

Here's an idea; maybe you could "Pre-bump" the pads you need the extra
solder by getting a stencil with openings only for the pads that need
the extra solder, print and reflow them, clean, then process the boards
as you normally would.

I've done that before when I needed more solder than I could get from a
6-mil stencil for a PTH-to-SMT socket that a PGA plugged into. The
socket
sat on what looked like BGA pads. It worked pretty good, but luckily it
wasn't a high volume product.

-Steve Gregory-

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Martin Butcher
Sent: Friday, January 20, 2006 1:08 PM
To: [log in to unmask]
Subject: [TN] Solder preforms

I have an application where we are forced to add solder to pads after
paste
printing to ensure a good fillet.  We have opened up the apertures as
much
as the surrounding parts will allow and due to 0402's near by increasing
the
paste height with the stencil is not practical.

My questions concern solder preforms as I have never seen them used.
One of
the components to be placed is a cylindrical surface mount fuse with
three
rectangular pads measuring about .125" x .375".  Can someone please
explain
how the process works?  Is the preform placed in the paste after
printing?
Are they tape and real for automated placement?  What holds the
component on
the preform during any handling that might be required prior to reflow?
We
are building in volume so the objective is to reduce the operator
variable
and additional handling.

Any comments, expertise, or quirks would be greatly appreciated.

Regards,
Martin Butcher,
Process Engineering

---------------------------------------------------
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
-----------------------------------------------------