In article ,
Michael Kennedy mike@com wrote:

They did use white goop on both sides, but very little and it was already
dried. The heat sinks are milled flat where they make contact with the
Peltier device, so my thinking is they need new goop.

Too much of the stuff will be a problem whether you are trying to heat or
cool. I have some major doubts that a thin coating of that stuff would be
enough to make any major difference in the performance of peteler junction.
Now on the other hand, if the heatsink is loose... That could give you some
real issues.

Michael is quite correct.

The thing about heatsink compound, is that you should only use a
*very* thin layer, and use it between surfaces which are already flat
and well-fitting. Adding a thicker layer of heatsink compound than is
necessary, will actually reduce thermal conductivity.

You want as much direct metal-to-metal or metal-to-ceramic contact as
you can get - enthusiasts who "overclock" their PCs will often flatten
and polish the top of the CPU and the bottom of the heatsink to
increase direct contact. A *thin* smear of heatsink compound is
appropriate... just enough to fill the remaining gaps between the
heatsink and the heat-sunk :-). You almost want to smear it on, and
then wipe most of it off gently with a single-edged razor blade, so
that there is no excess buildup between the two surfaces.

And, yes, if the heatsink actually comes loose from the Peltier
junction (e.g. if it was originally spring-clipped in place, and the
clips are loose or have fatigued and lost pressure) then you've got
problems... you'll get a layer of air between the two surfaces, and
thermal conductivity will become quite poor. Adding a thicker layer
of goop to try to fill the gap isn't the right thing to do - instead,
fix whatever caused the devices to become loose, clean the surfaces,
reapply a *thin* layer of compound, and secure the devices back
together with the proper amount of pressure.

If there was (apparently) nothing holding the two surfaces together -
no clips or retainers - then you're probably dealing with a "thermally
conductive adhesive". Some of these are good, some are poor... and
you'll have to strip off all of the remains, and then reapply (again)
a very thin layer of a suitable thermal adhesive, and fasten the parts
back together with appropriate pressure until the adhesive cures.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!