SSC P7 Leads?

[LEDobsession]

Hey I was just courious, how do you tell the anode and cathode apart on the P7 emitter? I'm sure it has something to do with the small small hole on one side of the leads but which is positive and which is negative?

 

[Morelite]

The small hole is on the cathode (negative) side.

 

[Morelite]

The slug is also positive so keep that is mind when mounting so it doesn't make contact with a bare heatsink that may be negative.

 

[LEDobsession]

The small hole is on the cathode (negative) side.

I figured that would be the negative side.

The slug is also positive so keep that is mind when mounting so it doesn't make contact with a bare heatsink that may be negative.

Crap. I was going to mount the LEDs to the heatsink using thermal epoxy and ground everything to the heatsink. I guess that wont work.

Thanks for the info!

 

[Morelite]

I figured that would be the negative side.



Crap. I was going to mount the LEDs to the heatsink using thermal epoxy and ground everything to the heatsink. I guess that wont work.

Thanks for the info!

That will still work, the thermal epoxy will insolate the electrical connection. I would use AA (arctic alumima) for mounting.

 

[LEDobsession]

That will still work, the thermal epoxy will insolate the electrical connection. I would use AA (arctic alumima) for mounting.

Ok great. The Arctic Alumina Thermal Adhesive is what I'm gonna use. I bought some with the LEDs from Photonfanatic over on MP with the p7 sale a few weeks back.

 

[Oznog]

The thermal epoxy is an electrically insulating material in itself, but it generally does NOT reliably create a electrical in itself.

The two sides will generally have some point touching. You can "sort of" avoid this by placing it really carefully, not pressing down, and keep checking it with an ohmmeter. However- even Arctic Silver (and worse with AA) has significant thermal resistance as the thickness increases and if you don't press it down it could easily be 10x thicker than the minimal layer, with 10x the thermal resistance. This may not be such a big deal for 1W devices but a much more powerful one like the P7- and trying to push it all through the small thermal pad area- I'd expect would end up with a really bad thermal resistance. Is there some reason you're not using the MCPCB designed for it?

I figured the best chances for a low thermal resistance would be to take some fiberglass boat cloth, unweave a bit, and separate out a couple single glass threads. Tape (or superglue) on one side of the sink's mounting area, pull across the mounting area tight, and tape/glue to the other side. So like you'd have 1/4 the pad area to the left of one thread, 1/2rd between the threads, and 1/4 to the right. Then you should be able to mount the LED and apply pressure and still guarantee a minimal spacing without a lot of extra spacing. In theory, at least. But it's still gonna be thicker than the very thin layers they recommend.

Contact the Arctic company and ask for their recommendations. They know their stuff pretty darn well.

 

[LEDobsession]

Is there some reason you're not using the MCPCB designed for it?

I figured the best chances for a low thermal resistance would be to take some fiberglass boat cloth, unweave a bit, and separate out a couple single glass threads. Tape (or superglue) on one side of the sink's mounting area, pull across the mounting area tight, and tape/glue to the other side. So like you'd have 1/4 the pad area to the left of one thread, 1/2rd between the threads, and 1/4 to the right. Then you should be able to mount the LED and apply pressure and still guarantee a minimal spacing without a lot of extra spacing. In theory, at least. But it's still gonna be thicker than the very thin layers they recommend.

Contact the Arctic company and ask for their recommendations. They know their stuff pretty darn well.

The reason Im not using the PCB is because Photonfanatic didnt have any with the emitters when I bought them from him (on CPF MP). I could buy some and just mill off the top of my heatsink spots to put them on but if I dont do that and stick with what I have, then I need to keep the space between the LEDs and the heatsink spots relatively thin because I only left a .100" gap between the relector plate and my heatsink. Check out my other thread and you can see what it is Im making.

 

[yellow]

... as You type "heatsink" and not "thermal/mounting plate" as I would call a bare aluminium sheet that holds the led and is pressed into the housing ...

when Your sink is anodized: this is isolation!
Just place the led (with thermal PASTE) and glue it in with epoxy around the led body

another (and the only sure way) is, to place 2 hair into the compound (paste, or arctic - if You insist on using it) and put the led onto.
This ensures no direct contact slug <-> sink
... less than ideal, but safe and working

 

[LEDobsession]

Well, its not really a "plate" but rather a big piece of CNC'd 6061 alum. part that I threw together at school.

I think I may just get it anodized. It will be cool looking and provide isolation. Ill have to ask around at work to see where we send our parts to be anodized and if I could throw in my base/heatsink with some other order too.

 

[ktafil]

All info you need in PDF's here