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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
im thinking of using double sided tape to hold copper foil insulated via the kapton to an aluminum plate. im not sure if this is wise or possible.
the Kapton would be 2.7 mil for 1 mil of kapton. So i dont know if 1.4 mils of silicone adhesive on each side matters, but thickness worries me, as thermal resistance is non-linear with thickness right?
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714
Nope, thermal conduction behaves like ohmic electrical conduction. Resistance is proportional to thickness (length in direction of heat flow). It's not hard to find the material properties (thermal conductivity) and run the numbers.
You might be interested in the results of an Internet search for Thermal Interface Material.
Registered Member #108
Joined: Thu Feb 09 2006, 11:44PM
Location: Billings, MT
Posts: 61
Echoing the previous comment, this might help. The temperature profile through the solid is linear (conduction only), but through the fluid it is not (conduction plus convection).
Registered Member #56
Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445
I wouldn't recommend it for a really high performance application, but for light heat loads kapton is fine, and I have even seen it used in a few commercial products. I have seen the thermal conductivity specified as roughly 1W/m*k (compare to 30 for alumina, but keep in mind you can get away with a much thinner piece due to its better electrical/mechanical properties), although different brands will differ by about a factor of 2 or so. IIRC Dupont even makes a special 'high thermal conductivity' version for such applications.
One thing worth mentioning--1 mil layer of kapton, while specified to hold off about 5kv, will be very fragile and it is easy to poke a hole through it due to overtightening/spec of dust/etc. I have seen some products get around this by using 2 layers of kapton (by the looks of it, they just had the assembly line workers put 2 layers of kapton tape on the heatsink, then use a knife or drill to clear out the holes).
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Kapton Tape for Attaching Heat Sinks
