Electronics > Projects, Designs, and Technical Stuff
Using Kapton with phase change layer - Is it as great as advertised in papers ?
Miyuki:
Hi folks,
I have a question, have you experience with Kapton film pads with phase change layer ? Like this DiaPhase60
They are advertising about 0.13 K-in2/W for thinnest version
This should give me about 0.2 K/W at TO247 package
Is that realistic or too optimistic ?
Siwastaja:
Note that people here have reported bad experience using very thin layers of Kapton for thermal insulation, because any surface defect on the heatsink or component punctures through the thin Kapton layer, given some time and vibration. I wouldn't use the 0.025mm version at least unless I could guarantee perfect rounding and deburring of the device edges, smooth surfaces, balanced clamp force, and the cleanliness standard of the assembly. A tiny little metal dust particle is everything that's needed to cause a nasty, latent damage.
Thin kapton would offer more safety, but the thermal conductivity starts sucking. At 0.46W/(mK), the Kapton kind of sucks if you want to have the physical distance (and not rely on the perfect insulation properties of the thin, undamaged material). Note that classical enforced, tough thermal pad materials exist up to about 3 W/(mK), so they could be 6 times thicker for the same thermal resistance.
Miyuki:
For mass production it can be a problem
This I want for single piece prototype where I can polish devices and heatsink surfaces
Main problem is I want to cool 150W in TO247 case IGBTs what is on extreme side, and should last about 1000 hours on bench
H713:
I used .001" Kapton film for my HV bench supply. It works great, but it's quite tricky to use. The film is incredibly fragile, so careful prep is necessary. I ended up polishing the heatsink surface and the transistors to make absolutely sure there were no sharp edges. Be incredibly careful applying the compound- it MUST be clean. A little spec of dirt in the compound from being careless is enough to puncture the Kapton.
When I blew up the supply a few weeks ago, I used the white ceramic insulators. I don't remember if these particular ones were Beryllium or Aluminum Oxide, but they have great thermal properties. Significantly better than Mica.
Keep in mind that Kapton is a rather lousy thermal conductor, we just use it for insulators because we can make it so thin.
Miyuki:
Aluminum Oxide ceramic pad must be 0.5mm thin to reach desired conductivity
They are not commonly available
Navigation
[0] Message Index
[#] Next page
Go to full version