Hi, Darrel,
In my former existence, we used flexi wrap-over and wrap-under connectors,
custom made by Hypertac, to connect pairs of boards to form a cassette
around a coldwall. It took a while to get the tolerancing right so that the
flexi contacts all lined up well with the mating fingers on the board, and
as a result we had to hand solder them. There were 144 contacts between the
two sides of each conn.
Eventually all the dimensioning and tolerancing problems were sorted and we
took to Hot Bar soldering the connectors, SMY style onto the boards. We
couldn't use normal reflow soldering methods as the requried coplanarity
just wasn't there. Hot Bar was successful, although the solder joint
formation is quite different from more conventional forms of soldering. If
you go down that route, involve your QA so that they are happy with the
results.
We also had some power supply boards with flexi connectors to the outside
world. These were inserted into plated through holes, half clinched and
wave soldered, again very successfully. The only thing we had to watch out
for was solder wicking up between the flexi layers, but there was little
evidence of this in practice after fine-tuning the wave height and level
and making sure the flexis were made properly.
Just make sure you don't try to route the flexi through tight bends (unless
it's pre-formed to do so), as the region around the solder joints is quite
rigid and prone to cracking if you try to bend the flexis too sharply too
close to this zone. If the flexis are longer then say about 3 inches,
include some form of support for them that holds them securely across their
full width without crushing them.
On the whole no real horror stories with processing - just getting the
flexis themselves designed and made right to start with.
Regards
Peter Duncan
ST Aero
Darrel
Therriault To: [log in to unmask]
<DTherriault@ cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST
INCEP.COM> Aero/ST Group)
Sent by: Subject: [TN] Flex and Soldering
TechNet
<[log in to unmask]
ORG>
10/01/01
09:26 AM
Please
respond to
"TechNet
E-Mail
Forum."
Technet,
Does anyone have any guidelines for soldering flex circuit directly to a
PWB? We currently connect it mechanically and with a connector, but
were toying with the idea of direct solder attach.
Any experience, do's and don't, especially horror stories, appreciated.
Thanks......DT
--
Darrel Therriault
VP, Mfg. Operations
INCEP Technologies, Inc
(858)547-9925 223
[log in to unmask]
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