Re: Soldering bypass caps to QFP possible?

John Larkin wrote:
On Sat, 26 Jan 2008 01:00:17 GMT, Joerg
<notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:

Joel Koltner wrote:
"Joerg" <notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote in message news:Grvmj.664$R84.277@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Except that there aren't any vias. The next one is about 1-1/2 inches away and that's also where the lone bypass cap dwelleth. Ground is almost as long and takes a different path :-(
Something I've done in the past is to make cover the top of the chip in solid copper foil tape, soldering the outer tape edges to all the ground pins you have available (using 30 ga. wire). Then, solder a cap to this new ground plane on one side and run a 30 ga. wire from the other side down the few mm to the power pins (or any other pin you're looking to bypass).

This also makes for an excellent ground point if you're using, e.g., FET probes with a ground "leg" that needs to be within a few cm of the probe tip because you actually want 1GHz response or whatever.

I thought about a copper tape lash-up. Unfortunately this stuff is used in a rather hot and humid climate and I am afraid the glue on that tape won't hold up.

Copper tape will stick forever.

But the main issue is soldering to those 0.5mm pitch pins.

Make a tiny PCB that has bypass caps, and glue it on top of the chip,
and drop down ground and vcc wires.


That's a good idea, could be epoxied down. The wires would be a royal pain in the neck though. I know catheter assemblers who could do that but they are all cranking overtime as it is because there aren't enough of them. Pretty much all my clients with catheter manufacturing have permanent ads out.

--
Regards, Joerg

http://www.analogconsultants.com/
.

Relevant Pages

  • Re: Soldering bypass caps to QFP possible?
    ... Something I've done in the past is to make cover the top of the chip in solid copper foil tape, soldering the outer tape edges to all the ground pins you have available (using 30 ga. ... solder a cap to this new ground plane on one side and run a 30 ga. ... wire from the other side down the few mm to the power pins. ...
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  • Re: Soldering bypass caps to QFP possible?
    ... and that's also where the lone bypass cap dwelleth. ... Something I've done in the past is to make cover the top of the chip in solid copper foil tape, soldering the outer tape edges to all the ground pins you have available (using 30 ga. ...
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  • Re: Soldering bypass caps to QFP possible?
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