Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!bloom-beacon!tut.cis.ohio-state.edu!husc6!encore!maxzilla!waltm
From: waltm@maxzilla.Encore.COM (Walt Mattison)
Newsgroups: sci.electronics
Subject: Re: Warp Factor 5
Keywords: Help!
Message-ID: <10326@xenna.Encore.COM>
Date: 7 Jul 89 13:58:57 GMT
References: <753@fibercom.UUCP>
Sender: news@Encore.COM
Reply-To: waltm@maxzilla.UUCP (Walt Mattison)
Organization: Encore Computer Corp, Marlboro, MA
Lines: 49

In article <753@fibercom.UUCP> lab@fibercom.UUCP (Lance Beckner) writes:
>
>Can anybody give me some info on how to best eliminate warping that
>results when a PC board goes through flow soldering?  We have a
>good number of eight layer boards (6.3" X 9.2" X .063") and so far,
>every one has come out warped.  Other than just playing around with
>solder temperature and time, is there anything I could/should do?
>
>Please E-mail me any suggestions, and I'll post a summary later.
>
>Thanks in advance.
>-- 
>Lance A. Beckner                   INTERNET: lab@fibercom.com
>FiberCom, Inc.                     UUCP: ...!uunet!fibercom!lab
>P.O. Box 11966                     FAX: (703) 342-5961
>Roanoke, VA  24022-1966            PHONE:  (703) 342-6700

Lance,

Warpage is a common problem with board assembly and is always curable.
First the boards you are talking about are not that large so a board thickness
of 0.063" is not a problem.

Do these boards have tooling holes at each corner? 

Tooling holes or some other type of secure fastening method must be used to

firmly attach the board to a sturdy fixture for wave soldering. This fixture

will keep the board from warping during the actual wave process. Remember that

enough fixtures must be built so that you can allow the boards that have been

waved to cool to room temperature slowly while still firmly in the fixture.

Fixturing is the key to reducing warpage in wave soldering, temp and time

are contributors but play a much lower role than fixturing. Are you doing

these boards in-house? Why don't you just send them out to be waved and not

worry or does your company own the equipment to do it infrequently? If you have

any problems or questions with this feel free to call, I will give you a hand.

Walt Mattison

Phone 508-460-0500
Fax   508-485-0709