# Led soldering - MCPCB / 3M Tape



## Szemhazai (Sep 24, 2007)

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 ?


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## Szemhazai (Sep 28, 2007)

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


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## Wok (Sep 28, 2007)

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


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## Szemhazai (Sep 28, 2007)

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.


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## evan9162 (Sep 28, 2007)

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.


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## Szemhazai (Sep 28, 2007)

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


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## joewatts (May 20, 2010)

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
> ...



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.


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## bshanahan14rulz (May 20, 2010)

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...


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