Christian, SSD, solid solder deposits, refers to the pre-placement of
solder, usually at the bare board fabrication stage. A variety of
methods have been used to place the solder, including
electrodeposition (plating), and molten deposition, then flattening
them. I was one of 4-5 speakers who talked about it at last year's
Nepcon West/Anaheim; suggest you see the Proceedings. Since I was
invited too late to submit a written paper, permit me to tell you
about "Deep" Solid Solder Deposits. DSSD has solder that goes INTO
the board. Happens as follows: Using IMPRINT Patterning (sort of a
precision "hot stamping" into special PWB uncured "laminte"), U-
shaped recessed pads (and grooved, X-Y traces) are formed, plated,
etched. The unexpected result of this work is that, for ordinary
fine-pitch designs, the "cups" fill up with solder and the top of the
solder is quite flat. In assembly, as with other SSDs, a sticky flux
is used to hold the component's leads in place. In the case of DSSDs,
the leads move down and into the molten solder during reflow. For a
much more thorough explanation, please see the issue of PC Fab
magazine that just came out (I authored a 2-p. article on IMPRINT
Patterning here). Hope this is not too commercial and informatiive.
Sincerely, George Gregoire
(President, Dimensional Circuits Corp., San Diego, CA; DCC is the
inventor of the Imprint process, which is expected to be licensed)
|