Re: Soldering bypass caps to QFP possible?

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.

John

.

Relevant Pages

  • 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. ... wire from the other side down the few mm to the power pins. ... 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. ...
    (sci.electronics.design)
  • 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. ... The wires would be a royal pain in the neck though. ...
    (sci.electronics.design)
  • 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. ... wire from the other side down the few mm to the power pins. ...
    (sci.electronics.design)
  • 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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