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Wed, 5 Nov 1997 07:00:55 -0700 |
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Yes Graham, there are washable spacers available from several sources.
We used them extensively in the past with mixed results. I will point
out the problems I have experienced with them:
The ones we used were brittle and occasionally broke prior to wave
soldering. This resulted in unnecessary rework and a tendancy for
operators to over-inspect boards prior to wave.
They are tiny and a pain to put on the leads. Way to much labor
involved.
They washed off in the in-line cleaner, resulting in increased waste and
maintenance on the cleaner.
I would really suggest you consider setting up a component forming
operation to handle this. Most parts commonly requiring standoff can be
formed using a couple of relatively inexpensive machines. You might also
consider revisiting lead to hole diameters from a PCB design
perspective. Also recheck the packages available on your parts, many
styles are available with standoffs built into them. Finally, I would
ask just why a component needs to standoff the board. You may find a lot
of "because thats the way we've always done it."
Best of luck.
Steve Tucker
AlliedSignal Aerospace
(785) 838-5116
>----------
>From: COLLINS, GRAHAM[SMTP:[log in to unmask]]
>Sent: Monday, November 03, 1997 12:03 PM
>To: [log in to unmask]
>Subject: Mechanical standoff
>
>Good Day Technet!
>In wavesolder attachment of some through hole components, we have to provide
>a temporary standoff to keep the part off the board surface. Currently we
>are doing this with bits of wire or other mechanical means, which are then
>removed after wavesolder. Some components we keep off the board with a
>washable solder masking material, but this is not a precise or quick method.
>Is there such a thing as a preformed standoff that will dissolve when the
>assembly is washed, that would be put on the lead before insertion into the
>board?
>
>Thanks!
>
>Graham Collins
>Process Engineer,
>Litton Systems Limited, Atlantic Division
>(902) 873-2000 ext 215
>
>
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