Led soldering - MCPCB / 3M Tape

I'm thinking about one thing, when you have cree soldered on the MCPCB - between led and the metal base is usually FR4 (epoxy & fiberglas) – 8 to 12 mils :thumbsdow.
What if instead of that I'll use 2 mils (0,05mm) adhesive transfer tape (3M 467MP) to solder emitter directly to heatsink ??

FR4 - thermal conductivity 0.03 to 0.04 W/mK
3M Tape - thermal conductivity 0.17 W/mK

High Performance Adhesive Transfer Tapes with 3M Adhesive 200MP - Data Sheet

+ very easy soldering (easier than arctic alumina).
+ electrical isolation
+ better thermal transfer parameters than MCPCB

It looks good for me :twothumbs, but what do you think ?

Ok I'll reply myself...

First impression:
Cut appropriate shape from the tape, take a top cover and stick glued side with emitter, then take off backtape (the glue layer is almost invisible) and put wher you want to solder it, tighten.

Soldering :
Fitting emitters with Ledil CRS optics newer was easier - you are simply putting preglued emitter in optics and then put that on degreased case/radiator – emitter will stick to case/radiator. Then the only thing to do is to solder the wires . There was no electrical problems - no short-circuit between radiator/emitter – I didn't do anything with emitter as is recommended when you are soldering with AA .

Thermal properties :
on similar radiator star screwed to it make radiator only a bit warm
after soldering emitter directly I assure you the radiator was a lot warmer :thumbsup:

So the presumed effect was achieved I think...

Costs :
peace of tape that cost me 2$ is enough for soldering about 160 emiters

Interesting idea....following your link...I found this
http://tapeinfo.com/TapeInfo/Brands/ThreeM.aspx
Check out...9882,9885,9892fr & 9890....

Specifically thermal tapes, pity the maximum temperature is not given.

Which tape did you actually use?...the 200mp is the glue type only.

eng hoe

I've used 467MP - 2 mils it have thermal impedance 0.16 compared to 0.20 – 9882 - but it is easy to get in Poland. I'll try to get 9882 in small quantities but I don't know if it will be possible.

Are you sure about your FR4 thermal conductivity values? Most places around the web quote it around 0.3W/mK. If it was 0.04W/mK, then the cree star would give a thermal resistance of over 100C/W, which certianly isn't true.

The thermal conductivity of air is around 0.025 - according to you, FR4 is just barely better than air, which we know isn't true at all.


So we'll use the real value of 0.3W/mK

The Cree's thermal pad is 5.6x6.5mm.

With the FR4, 10 mils at 0.3W/mK gives an additional 21C/W of thermal resistance (ignore the solder and aluminum, since it's only minor)

With the tape, you're going to have about 8C/W of additional thermal resistance. So quite a bit better than the star.

Arctic alumina thermal epoxy is has a thermal conductivity of about 7.5 W/mK.
Even if you end up with a 1mm thick layer, that will only be an additional 3.6C/W of thermal resistance.
You can easily make an 0.5mm thick layer or thinner while still maintaining electrical isolation, and get only 1.8C/W additional thermal resistance.

Or, grind off the vias to the bottom contacts, and squeeze everything out to get only an 0.1mm thick layer, for about 0.4C/W extra.


The tape sounds like a nice improvment over the stars.

evan9162 Thanks for noticing I probably messed with units W/mK W/cmK oo: it should be "0.3 to 0.4".

Szemhazai said:

I'm thinking about one thing, when you have cree soldered on the MCPCB - between led and the metal base is usually FR4 (epoxy & fiberglas) – 8 to 12 mils :thumbsdow.
What if instead of that I'll use 2 mils (0,05mm) adhesive transfer tape (3M 467MP) to solder emitter directly to heatsink ??

FR4 - thermal conductivity 0.03 to 0.04 W/mK
3M Tape - thermal conductivity 0.17 W/mK

High Performance Adhesive Transfer Tapes with 3M Adhesive 200MP - Data Sheet

+ very easy soldering (easier than arctic alumina).
+ electrical isolation
+ better thermal transfer parameters than MCPCB

It looks good for me :twothumbs, but what do you think ?

Click to expand...

Why don't u just buy the LED tape with the 3M tape already on it???? I bought mine from LED Tape and they even cut it and soldered it to the right size for me.

This dude is talking about using 3M thermal transfer tape, not 3M double-sided tape, for use in mounting a high power emitter to its heatsink... 3 years ago.

Although it would be interesting to see what people concluded about that 9882 tape...