Slightly OT: TQFP mounting

Patrick Finnegan pat at computer-refuge.org
Sat Dec 22 13:15:27 CST 2007


On Saturday 22 December 2007 02:52, Roy J. Tellason wrote:
> On Friday 21 December 2007 16:54, Chuck Guzis wrote:
> > Two approaches that I've seen for conventional soldering iron
> > mounting involve what I'll call "flood and suck" that involves
> > covering all of the leads on one side of the QFP on the PCB with
> > solder and then using a solder "sucker" (such as a Soldapullt) to
> > remove the excess.
>
> I've *never* heard this recommended.  And with that setup you're
> talking about pulling the solder out between the part lead and the
> trace without pulling the trace off the board.  I wouldn't care to
> try it.

The way that they taught us to do it in college was basically the same 
way, except using solderwick to pull up the excess, instead of a solder 
sucker.

The technique was basically to tack down the corners of the chip first, 
so that the chip is/stays properly aligned with the board, and then 
drag the soldering iron along each side (using a wedge tip), with the 
solder along the trailing edge.. if you get just the right speed, 
you'll get a good connection.  Then, just take solderbraid and an iron 
to pick up the excess.

It works, and unless you're careless (or using a 100W soldering gun or 
something), it works pretty well, once you've tried it a time or two.

Pat
-- 
Purdue University ITAP/RCAC       --- http://www.rcac.purdue.edu/
The Computer Refuge               --- http://computer-refuge.org



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