[Fwd: LF: Soldering down fine-pitch parts]

[Andre Kesteloot]

Steve Dove wrote:

> Greetings,
>
> I find the best tool for sticking down fine-pitch parts is an intern.
> But that's cheating, really.  There is one truly gruesome,
> cringe-worthy technique that I've used when pushed, and always
> successfully, to stick dsps and fpgas down.  It takes a bit of nerve.
>
> With best eyeballs, aided or otherwise, line up the chip onto the
> pads; restrain it (g-cramp etc.) such that it won't budge.  With a
> normal-sized iron (no need for a really teensy tip at this point)
> solder all the pins along each side in turn down onto all the pads;
> the result will be a solid bar of solder along each side of the chip,
> engulfing the pins.  Naturally, don't go overboard, but all the
> adjacent pins will be stuck to each other as well as the pins being
> stuck to their appropriate pads.  Try not to panic or cry.
>
> The next phase is to use solder-wick (the real stuff, not coax
> braid) to drain off the excess solder;  gently slide the wick in line
> with the pins, not sideways 'against the grain', methodically around
> the chip.  Use a magnifying glass to peer between the pins for
> sneaky bridges;  wick more if you have to.
>
> Any human attempt at laying these things down will always result
> in a long period of squinting, cleaning and picking between its teeth
> with a scalpel, including this,  but it is amazing how well this horrible
> method works.  Never lost a device.  Oh, except for the dsp on which
> a mold ejection dimple was more prominent than the 'pin 1' marker,
> resulting in an 80-pin part glued on 180 degrees out . . .
>
>         Cheers,
>
>                 Steve