isolating bottom of SSC P4 from heatsink.

Is this product OK for isolating the base of the SSC P4 from a copper heatsink: (I believe the bottom of the SSC P4 is tied positive).

http://www.overclockers.co.uk/showproduct.php?prodid=OA-001-AC

It is Artec silver epoyx.

If not, what can i sink the heat with yet keep it electrically isolated. I dont see any way to screw the emitter down.


Many thanks.

forget these "isolation" ideas
A high powered Led must be sinked in a way that as much heat as possible goes away.
To add a heat border is something not even beginners should "have to" do.

solution: use an anodized sink --> anodizing is an isolation

yellow said:

forget these "isolation" ideas
A high powered Led must be sinked in a way that as much heat as possible goes away.
To add a heat border is something not even beginners should "have to" do.

solution: use an anodized sink --> anodizing is an isolation

Click to expand...

Ehh - it's actually not that big of a deal.

Arctic Silver Epoxy can provide enough heat transfer to mount a videocard heatsink that will need to dissipate >100W of heat. Certainly it can handle the heat from an LED.

I actually didn't even bother with the brand name. My Arctic Silver Epoxy went bad, and I didn't want to wait for it to get shipped to me before starting on a project, so I just got a $3 epoxy from my hardware store (clear gels) and mixed 2 parts epoxy A, 2 parts epoxy B, and 1 part Arctic Silver 5 thermal compound. I then mounted an SSC on the heatsink using about 1/4mm of this goop.

The result = resistance between heatsink and (-) was >2M ohms, so the bottom was electrically-isolated.

Heat-wise, I was driving an SSC to about 600mA with a single Eneloop AA, and it ran the batteries down just fine, with the light getting warm on the outside, indicating fine heat transfer.

To ask a related question on the same thread - if I was using say a Cree xr-e R2 whose base is tied -ve, would I be correct in assuming that it would be Ok for my light housing to be -ve also? (assuming I was lazy and didn't want to go to the trouble of isolating the base.

Many thanks.

marcopolo said:

To ask a related question on the same thread - if I was using say a Cree xr-e R2 whose base is tied -ve, would I be correct in assuming that it would be Ok for my light housing to be -ve also? (assuming I was lazy and didn't want to go to the trouble of isolating the base.

Many thanks.

Click to expand...

The central pad of the XR-E is already electircally isolated.

My best advice is to get everything hard anodized. I'm using H22A's heatsinks, and I've used both HA and non-HA, and the HA makes like SO much easier. I fried 2 drivers and 2 LEDs on a non-HA sink. Its just too easy to short out something.

If HA is not an option, I have started using super glue. The real thin stuff. I'll put a drop right in the middle of where the LED is going to set. It will spread out and cover enough of the sink. Once its set, you can use arctic alumina or whatever you chose to mount the LED (I did mount one with the super glue, so we'll see how well that works for heat transfer).

There is nothing worse than chasing wiring gremlins and shorts in something that should be so simple.

yellow said:

solution: use an anodized sink --> anodizing is an isolation

Click to expand...

That is impractical for some of the mods we do, especially when the emitter is mounted directly onto the circuit board (Arc LS, PT Apex, etc.).

Some folks use a thin layer of Artic Alumina epoxy on the slug that is allowed to set before installation with more AA or other thermal bog.

My favorite methods are mica flakes in the thermal paste between the slug and the heatsink, or double-sided adhesive heatsink tape. If you can't find an easy source of mica, thin mica flakes are available as "fake snow" in craft or christmas stores. You'll have to pick out the larger flakes for use, but a teaspoon of the material is enough for a lifetime supply for most modders

+1 on the mica,either the flakes or the mica transistor washer discussed in the thread below.

This thread may be of interest:
https://www.candlepowerforums.com/threads/149734

hello,

i had the same problem with my bigmag³. anodizing was also my idea, but i never do it by myself. i will try this in the feature.
so i only make a thin layer of heat resistant paint under the ssc p4. then i stick the p4´s with loctite heatadhesion to the head.
untill now, after many hours of runtime to test, messure and so on, no problems with heat.

markus

I dont like to trust just Artic Alumina epoxy to provide isolation so I use two very narrow strips of Kapton tape under the die then AA.

It is a similar method to the mica flakes but allows the AA to flow between and around the tape.

LukeA said:

The central pad of the XR-E is already electircally isolated.

Click to expand...

Some people may get the wrong idea from that. On the bottom toward the outside corners, there are vias connected through the substrate to the solder pads on top. Therefore, Cree XR-E's conduct both pos and neg to the bottom, and need to be isolated as well.

Either that, or the corners can be clipped or ground off... which is great because then no isolation is needed at all.

Is there any simple chemical way of producing a thin insulating layer on aluminium without anodizing - something that can be painted on, left, and then rinsed off later?

I just try this one on my new project,...

http://www.bergquistcompany.com/tm_sil_pad_list.cfm

and works perfect,...

uk_caver said:

Is there any simple chemical way of producing a thin insulating layer on aluminium without anodizing - something that can be painted on, left, and then rinsed off later?

Click to expand...

It seems like one could affix and seal a bottomless cylinder to the heatsink, fill it with the proper acid, run current through it, and place the setup in the refrigerator for an hour or so, or until there was a nice layer.