Another way to isolate a P4 emitter base??

Anglepoise

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Here is another method for consideration.

In the past, my preferred method of using an LED was as a bare emitter, as opposed to a star or round board.

My logic was that there would be a better transmission of heat with the minimum of glued or soldered surfaces.

This worked fine for Lux III's and using Arctic Alumina ( 2 part epoxy) I have never had one 'come off'.

Then along comes the P4 with it's positive base. Now some members are becoming concerned about the possibility that a thin layer of AA might not be enough and over time one could possibly get a direct electrical short. So I have read about all sorts of methods to avoid this possibility. Sadly all these required increasing the thickness of the AA or adding additional insulating layers.

I am told that Diamond transmits heat very well and is also
a good electrical insulator. I had a small vial of 30 micron Diamond dust that was absolutely clean and calibrated to size. Used in the Faceting business to cut and polish gem stones. This vial was purchased from Beta Diamond Products Click for Website and If memory serves was about $9.00 a carat.

If a tiny bit of Diamond was mixed in with the AA, there would be absolutely no way that the two metal surfaces could ever touch ( presuming both surfaces were clean and flat ) and the Diamond dust, due to it's properties, would not hinder the heat transmission ( I am guessing here ). I use a spring loaded alignment tool to assist when gluing emitters and in theory the spring will force out the glue mixture until the individual diamonds are resting on the emitter and heat sink surfaces with full electrical insulation for ever.

In my simple tests, the adhesive qualities of AA have not changed, presumably due to the very tiny amount of Diamond well mixed in to the AA.
A Carat of Diamond Dust should probably last the average modder a lifetime.

In a post last year,Newbie recommended SIC could be used, but the Diamond dust, while a little more expensive, is absolutely pure and exactly calibrated for size so IMHO would be the preferd material to add to your favorite epoxy.

Any long term problems with this method??..........
 

PhotonFanatic

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David,

I see no problems with your addition of the diamond dust at all; in fact, the diamond dust will probably help with the thermal transfer since diamond is the best material for that.

From Wikipedia:

Thermal properties

Unlike most electrical insulators, diamond is a good conductor of heat because of the strong covalent bonding within the crystal. Most natural blue diamonds contain boron atoms which replace carbon atoms in the crystal matrix, and also have high thermal conductance. .999-12C monocrystalline synthetic diamond has the highest thermal conductivity of any known solid at room temperature: 2000–2500 W·m/m2·K (200–250 W·mm/cm2·K)[2], five times more than copper. Because diamond has such high thermal conductance it is already used in semiconductor manufacture to prevent silicon and other semiconducting materials from overheating.

Still, if you properly use the Arctic Alumina Thermal Adhesive, one should not have any problem isolating the slug of the P4. :D
 

cy

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hmmm diamond dust sounds great!
need to order some..
 

H22A

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Thank you Anglepoise for sharing this valuable information. I always thought copper is the best heat conductor, but diamond never cross my mind. :thinking: I guess you learn something everyday. :thanks:
 

Anglepoise

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I should not be surprised that Don had done something like this before.
If he stamps his approval on this mod then I will feel my question has been answered.
 

tvodrd

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David, you don't need Don's approval! Any IP preceeds you, Don, me. etc! :D Did you read the link as far as my post #46 where published thermal conductivity numbers indicate the matrix material rules over the thermally-conductive filler stuff? What's your read on that?

Larry
 

Anglepoise

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tvodrd said:
D Did you read the link as far as my post #46 where published thermal conductivity numbers indicate the matrix material rules over the thermally-conductive filler stuff? What's your read on that?

Larry

Yes......I read all the posts and found lots more good info within.Thanks.
I would tend to agree with the statement ..."matrix material rules over the thermally-conductive filler stuff". I have been absolutely delighted with the performance of Arctic Alumina 2 part epoxy, both in adhesion and heat transmittal. I came to this conclusion in a simplistic way..... the emitters stay put and the flashlights get hot.

My reason to try mixing in some Diamond grit was purely as a means of guaranteeing the physical separation of the two flat surfaces so there could never be a possibility of electrical contact. That was my concern with the P4, arrived at through reading some members posts.

However the addition of Diamond grit is probably 'overkill' if just a thicker layer of AA will do the trick. It just sounded like a neat idea. < grin>
 

gadget_lover

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Since they are selling 1 carat of diamond dust for $9, I'm pretty sure you get 100% diamond.

As for the pastes, well that would have to depend on other factors.

The second source (Diamond Technologies) has prices around $1 per carat! That sounds interesting.

Daniel
 

Nitroz

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Nereus said:
How do I explain to my SO why on earth do I buy diamonds for my flashlights, not for her? :ohgeez:

-N

Tell her she can have a 4 carat diamond (dust) ring. :)
 

Anglepoise

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KDOG3 said:
Ok this if very interesting. Where would be a good vendor to get it and what micron would you get?

I happened to have on hand for my experimenting a one carat vial of 325 grit ( approx 30 microns I think ). I purchased it from Beta Diamond Products in CA but any local lapidary shop will have it. 325 grit is quite coarse and this was beneficial as my objective here was to separate the two electrical surfaces and NOT to attempt to improve the thermal characteristics of an already good product.( AA)
 
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