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From [log in to unmask] Sat Apr 27 14: |
21:04 1996 |
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Our major problems were in the areas of controlling part placement and lead
misalignment to prevent opens during assembly. This was mostly equipment and
training related and essentially had to do with getting people used to the
fragility of these leads when placing the devices (we autoplaced but VERY SMALL
forces can move leads out of alignment (vertically or horizontally).
As we conquered this, we also had some problems on "mixed technology" PWAs with
fine pitch on top and also wave soldered (PTH) devices. Problem was that the
wave solder schedule was "too hot" and tended to cause localized reflow/voiding
under the fine pitch device leads. These joints would look OK but have very
little mechanical strength. We had to lower wave solder preheats/dwells to
overcome this. IBM has had similar issues (I believe this was reported in a
recent IPC Tech Review article.
Jim Maguire
Boeing Defense & Space Group
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______________________________ Reply Separator _________________________________
Subject: transition to fine pitch
Author: [log in to unmask] at esdigate
Date: 7/5/95 8:56 AM
Hello,
Our design requirements are driving us to finer pitch technologies. We
currently assemble 50mil pitch devices. My expectation is that our next
generation of products will be 20 to 25 mil pitch. I am interested in hearing
war stories of people who have been through this process. Specifically, what
was the number one problem encountered and how was it overcome?
Thanks
Mitch Austin
Itron
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