In a message dated 10/6/98 1:26:44 PM Pacific Daylight Time,
[log in to unmask] writes:

<< Hello, TechNetters!
 I am looking for information concerning design rules for ceramic chip
 capacitors on the
 wave soldering side of printed circuits.
 I am interested in rules concerning the size, the termination finish and
 general manufacturing technology.
 If you can help me by giving any information, web sites or recommend
 articles , I'll be
 very grateful.
 Thank you,
 Gaby
 ok >>

Hi Gaby!

The IPC-782 manual is pretty good as far as footprints go, just follow what's
recommended there. As far as size goes, I've heard a lot of different things
about waving capacitors, mostly about the larger ones...I think I would want
to stay the same size or smaller as a 1206.

You want them oriented perpendicular to the direction of travel, that is if
your board is running down the wave from left to right, you want the long
dimension of the cap pointing north and south...that way you're ensuring that
the wave will be able to reach both pads.

You don't want to put them in the "shadow" of larger parts, or close to the
trailing edge of a taller part as it travels down the wave. The taller part
could prevent the solder from reaching the smaller cap.

Another thing, NO VIA's between the pads! I see this a lot, but what the
designers don't realize is that I'm trying to put a dot of epoxy to hold the
component for wave right where they've put a hole...that don't work too good!

One last thing that I've seen before that maybe somebody else can give some
feedback on, and that's with using narrow pads for waving chips...'scuse me
whilst I fire up the ol' ascii cad:


                  __
             __|__|__
             |           |
             |           |
             |           |        DIRECTION OF TRAVEL--------->
             |           |
             |______|
                 |__|

Has anybody else used small pads like what's shown above? I've seen it a few
times with different customer boards,and they wave GREAT!! I think I also read
someplace (It may have even been something that our own solderjoint guru
Werner had written) that smaller is better...the solderjoint is more forgiving
when it's small from what I read.

-Steve Gregory-

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