Rick,

You cannot use Durapol in the reflow oven. It will burn up in just a hundred
or so passes. You need to use Durastone or Delmat.

You may also want to consider using a fixture that you can run through the
screen printer to avoid handling after printing.

Jim

----- Original Message -----
From: "Rick Thompson" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, May 07, 2003 12:48 PM
Subject: [TN] Reflow Fixture Opinions Sought


We have a customer who is requesting that we use a reflow fixture consisting
of a Durapol plate with removable tooling pins to accomodate several
different large PWBs through the reflow process. These fixtures would run on
the flat belt rather than edge rails and would require that we remove large
(16"x12") fully loaded boards from the conveyor rails to install on these
fixtures prior to reflow. Components on the board range include a number of
BGAs and micro-BGAs.  The intent of the fixtures is to keep the board from
flexing during reflow. My concern is that all the handling and flexing of
boards with components in solder paste is going to increase the chances of
soldering problems due to part separation from the paste if the board is
flexed.

Question: Has anyone used this type of concept on large, densely populated
boards. Comments on pros and cons? Any other insights would be appreciated
as I'm looking for supporting evidence to dissuade them from this approach
which is primarily aimed as saving fixture costs over dedicated SMT
fixtures.

Thanks in advance.


Rick Thompson

Sr. SMT Process Engineer
SMTEK International, Inc.
+1 (805) 532-2800
[log in to unmask]

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