I did a search on this but came up more or less empty handed.... I prefer to use thermal pads on my projects and have searched high and low for thermal pads to fit these. They are TO-220-11 size. Although I realize I can go with the completely insulated version of the 3886 I still feel I prefer to use the metal tab version for a number of thermal reasons. What have all you chip amp builders been using for insulators or thermal pads???
Thanks!
Mark
Thanks!
Mark
Mica. We get it cheap locally, and I cut a TO3 pad to size and separate the layers. One TO3 pad usually yields enough insulation for three chips 🙂
Well, I don't kow where to get Mica around here locally although I know where there are a cople of abandoned Mica Mines out in the West Desert. I was thinking of Kapton insulation or Kapton tape... I know where to get both of those but I'm not sure of it's thermal characteristics... although it's an excellent insulator and very heat resistant. I wish Bergquist made thermal pads for these.... perhapos I'll call them tommrrow and inquire...
Mark
Mark
Last edited:
http://www.bergquistcompany.com/
SIL Pad 400 (7 mils & 9 mils)
have to cut a hole in the PAD..I've used successfully for LM3876
SIL Pad 400 (7 mils & 9 mils)
have to cut a hole in the PAD..I've used successfully for LM3876
Kapton tape is very good for semiconductor insulator use, in fact the only usual problem is its price. To cover an LM3886 you would need something like TO-264 sized pads.
I thought about just using the insulated version but I don't think the thermal transfer ability of plastic is all that good. I will just go the route of the Kapton since it is easily available... even WW Grainger stocks it. You can also get Kapton tape at just about any Powder Coating facility. Since it is extremely heat resistant they use it for masking off things to be powder coated.
Mark
Mark
The trick with Kapton tape is to keep it thin. Also, the adhesive is not a good thermal transfer agent. It's design is to withstand heat, you want heat transfer. Try to find non-adhesive kapton, then use thermal paste on both sides.
Bergquist also makes great kapton-based thermal pads. K-10 is what I use for high-heat apps.
Bergquist also makes great kapton-based thermal pads. K-10 is what I use for high-heat apps.
Kapton isolation comes in thicknesses that vary from 0.001inch (1mil=0.025mm) to 0.006inch (6mil=0.15mm).
The adhesive seems to vary between 0.001inch and 0.003inch.
0.002inch mica performs better than 0.002inch Kapton.
Buying the thicker Kapton will do you no favours.
You will be better with a TF package than with 6mil Kapton.
The adhesive seems to vary between 0.001inch and 0.003inch.
0.002inch mica performs better than 0.002inch Kapton.
Buying the thicker Kapton will do you no favours.
You will be better with a TF package than with 6mil Kapton.
jormajj is right! Those are the correct Bergquists for the 3886. Thanks, I will order some today!
Andrew, Nothing against mica except the silicon compound required and the mess it creates. It's certaily less expensive....
By the way... Arrow electronics has LM-3886Ts for 3.65 each!!!
Mark
Andrew, Nothing against mica except the silicon compound required and the mess it creates. It's certaily less expensive....
By the way... Arrow electronics has LM-3886Ts for 3.65 each!!!
Mark
Last edited:
if you use Kapton, you will need some form of thermal compound to exclude air from the two interfaces, either side of the Kapton film.
I ordered the BER-180 pads. I use these same pads on Xenon switching rectifier repairs that I do although the ones I normally use for the repairs are for TO-247. It's kind of ironic because the Switching rectifiers come with Kapton insulators from the factory... yellow colored ones.
Mark
Mark
Well, after all the hoopla on thermal pads and such I received my LM-3886's today and they are the plastic insulated style. I think Arrow goofed up the order because I definately ordered the metal tab variety. They are only like 3.26 each so I might just keep these and have them also ship the correct ones.
Mark
Mark
If you can find a broken PC power supply, there may well be something that you can use in there. 
How do you tie the LM3886 to the heatsink when thermal pad is used. Can 6-32 Nylon or plastic screw really do a solid job ? Or you still need metal screw with some kind of insulation.?
There are little isolation rings that fit on the bolt you use to fasten the Chip to the heatsink , they isolate the bolt from the chip , most electronics stores sell transistor mounting kits , I get the To-264 Mounting kit and it come with the nut/bolt , Isolation ring and a mica themal pad that fits the LM3886, they cost like $1 ....
Cheers
Cheers