Are the heatsinks clear coated underneath?

[pinoy]

I'm in the process of improving the heat sinking of the pill on my flashlight. I read aluminum oxide has low thermal conduction and I was thinking of sanding the bottom of the LED heastink a bit. I noticed that when I'm making continuity test with a multimeter I have problems making connection with both probes touching the bottom of the heatsink. Is there a clear coat on the heatsink so it doesn't form an electrical path to the pill? Or is it aluminum oxide?

 

[kramer5150]

Its most likely a clear chromate conversion coating. A process to coat the Aluminum and help reduce corrosion. I always fabricate an insulator disk to isolate the +V from the backside of the reflector.

 

[mcnair55]

I have no idea if this would work but many motorsport companies use a brake heat agent of aluminum rather than copper slip due to higher brake temps.You can buy it in a small aerosol can,or contact a friendly work shop that tune the bigger output engines, they may give you a squirt or 2 for free.It is a similar product to heat shrink paste but designed for auto and other high temp work shop use.I just fill little poly bags up of many free squirts from garages of many items like a decent silicone grease etc.

Hope a member with more electrical knowledge will say a yay or a no to this paste before you try it though.

 

[Light-Brite]

Coated or not I would sand it down, polish it to a mirror finish and use Arctic Silver 5.

 

[pinoy]

I'm just wondering if the heatsink is meant to be insulated from the electrical path.

 

[AnAppleSnail]

I'm just wondering if the heatsink is meant to be insulated from the electrical path.

Depends on the LED. With most XP Crees it doesn't seem to matter. I've got one built where the LED- lead just goes to the copper the LED is soldered to.

 

[qwertyydude]

Ideally, like with high performance computer tuning, both heat conducting surfaces should be lapped and the thinnest possible layer of heat sink compound used. Lapping means using sandpaper on top of a flat sheet of glass to sand on, going progressively finer until you get to 2000 grit or so. You can then polish the surface. This is done to both mating surfaces. In order to put the thinnest possible layer of heat sink compound like arctic silver I put a tiny drop of the stuff, the get some lacquer thinner and use that and your finger to spread it to an even and very thin coat, let dry completely and press the two parts together. Using this method I've measured up to a 20F drop in temperature on my computer hardware. This is very significant temperature differences with no other change in cooling equipment, just lapping and spreading thin heat sink compound. It seems crazy to take a $500 processor and start sanding on it before even installing it but it makes a big difference.

 

[mcnair55]

Ideally, like with high performance computer tuning, both heat conducting surfaces should be lapped and the thinnest possible layer of heat sink compound used. Lapping means using sandpaper on top of a flat sheet of glass to sand on, going progressively finer until you get to 2000 grit or so. You can then polish the surface. This is done to both mating surfaces. In order to put the thinnest possible layer of heat sink compound like arctic silver I put a tiny drop of the stuff, the get some lacquer thinner and use that and your finger to spread it to an even and very thin coat, let dry completely and press the two parts together. Using this method I've measured up to a 20F drop in temperature on my computer hardware. This is very significant temperature differences with no other change in cooling equipment, just lapping and spreading thin heat sink compound. It seems crazy to take a $500 processor and start sanding on it before even installing it but it makes a big difference.

Sounds good to me,that is also how you get a scratch out of a car using 2400 grit paper and 2 different polishing compounds,it started its life as a product for polishing diamonds and aircraft screens but now has spread to the auto world,compounds are very expensive but highly effective.

 

[qwertyydude]

It's not exactly how you get rid of scratches, it's how you get rid of orange peel on paint. Scratches you want to sand by hand to round off the scratch edges and reduce visibility, you definitely do not want to remove the entire top layer to the same level as the depth of the scratch. Orange peel you use a stiff sanding block to level the paint, basically knock off the high points of the clear.

But with heatsinks you want to remove all the high points, hence the flat glass, the paper ends up only taking off the high points.

 

[mcnair55]

It's not exactly how you get rid of scratches, it's how you get rid of orange peel on paint. Scratches you want to sand by hand to round off the scratch edges and reduce visibility, you definitely do not want to remove the entire top layer to the same level as the depth of the scratch. Orange peel you use a stiff sanding block to level the paint, basically knock off the high points of the clear.

But with heatsinks you want to remove all the high points, hence the flat glass, the paper ends up only taking off the high points.

I sell this new system,trust me it works and you use a totally new concept involving other items which I did not mention due to being an off topic subject,it is all about open cell technology regarding the polishing and finishing buffers but the 2400 grit is the start of the process with a special compound,we were the first company in the world to get a head start on the competition but after 6 months many companies have a similar idea,long story short it saves time and money and very effective.