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Reply To: | TechNet E-Mail Forum. |
Date: | Tue, 6 Apr 2004 10:03:01 EDT |
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Hi Siegfried!
From experience at a past job, concave terminations are best for reflow
soldering. I worked for a company named SMART Modular Technologies where we built
memory modules. The one I remember well that used chip resistor networks was a
Pipeline Burst Cache Module that had 21 chip resistor networks on the
backside...this was a double-sided reflow assembly. When we first started building it,
we had many bridges and mis-alignments. The footprint was what was
recommended by the manufacturer of the resistor network that we were using at the time,
and it was a convex terminated network. I think I must have bought 2-3
different stencils all with different aperture openings to try and improve yields.
Things got a little better, but the problems never really went away.
Then we had this Panasonic Rep in, and I started talking with him about the
problems we were having. He immediately pulls this paper out of a study that
was done by Panasonic on concave vs. convex chip resistor networks reflow
soldering performance, and it showed that concave network terminations had better
self-centering characteristics, and less bridging. I tried to find that paper up
on the web, but no joy. Here is a link to a page in Digikeys catalog to a
Panasonic resistor network that says that concave terminations solder better:
http://dkc3.digikey.com/pdf/EU041/0601.pdf
In my case at SMART Modular, switching to networks with concave terminations
almost completely eliminated the solder defects we were experiencing with chip
resistor networks.
I've requested the paper I remember from Panasonic, it's pretty good with
some nice images. If they still have it, and I get it, I'll share with everybody.
-Steve Gregory-
> Dear TechNetters,
>
> we are using more and more chip resistor arrays. They are available in
> concave and two convex (scalloped edge, square edge) types. The concave one is
> some expensive and less disposable, but I heard that it is easier to solder
> giving better quality.
>
> Any opinions and informations comparing the different types (concave,
> convex) are welcome.
>
> Thank you in advance for your help.
>
> Siegfried Meier
> Dipl.-Ing.
>
> Entwicklung selbstfahrende Erntemaschinen
> Müller-Elektronik GmbH u. Co.
> Franz-Kleine-Str. 18
> D-33154 Salzkotten
>
> Tel: +49 5258 9834-70
> Fax: +49 5258 9834-94
> email: [log in to unmask]
> Internet: http://www.mueller-elektronik.de
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