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April 1999

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Subject:
From:
"Tempea, Ioan" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 20 Apr 1999 08:28:55 -0400
Content-Type:
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text/plain (72 lines)
Well, Joseph,

you may try to use a slightly different technology. That is, screening the
flat pack, if not the whole solder side, go through reflow and for the wave
cover the QFP with some peelable stuff.

That won't solve the connector, but it might give some ideas.

Good luck, Ioan

> -----Original Message-----
> From: Kane, Joseph [SMTP:[log in to unmask]]
> Sent: Monday, April 19, 1999 6:24 PM
> To:   [log in to unmask]
> Subject:      [TN] Hot Air Knife
>
> TN'ers:
>
> We're getting a handful of bridges at wave solder on a few designs.  We've
> tried A, B, and C, but they continue to show up consistently on some
> styles
> of connector behind chip components, and on trailing leads of flatpacks.
>
> The machines is a fairly new Electrovert with convection preheat, Lambda
> wave, and chip wave.  We're using Sn63 at 500F with RMA 25%.
>
> We're looking at a hot air knife retrofit, which would be turned off on
> everything but problem boards.  We've had a demo, with mixed results.
> Good:
> bridges were much improved, and no insufficients.  Not-So: some frosty
> looking joints, which we expected, but also a lot of solder balls and
> splashes.
>
> We've heard that setup can be touchy, and we didn't expect to optimize on
> a
> two board sample, but we're not sure what we can conclude here.
> Unfortunately, the demo was not apples-to-apples - it was performed on an
> inerted machine with an A-type wave, and we're not sure if the splashing
> and
> balls could be attributable to the increased surface tension.
>
> Anyone out there have good things to say about their hot air knife?
>
> Joe Kane
> Lockheed Martin Control Systems
>
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