# Another way to isolate a P4 emitter base??



## Anglepoise (Mar 15, 2007)

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??..........


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## PhotonFanatic (Mar 15, 2007)

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.


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## lasercrazy (Mar 15, 2007)

I looked through the site but I couldn't find the dust you were talking about.


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## PhotonFanatic (Mar 15, 2007)

lasercrazy,

Try searching on this site--it might be easier to find.


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## cy (Mar 15, 2007)

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


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## lasercrazy (Mar 15, 2007)

:lolsign: Good one.


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## Morelite (Mar 15, 2007)

You can find it here too.


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## H22A (Mar 15, 2007)

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:


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## lasercrazy (Mar 15, 2007)

Morelite said:


> You can find it here too.


 I wonder which micron size would work best?


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## tvodrd (Mar 15, 2007)

Been done here.

Larry


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## Anglepoise (Mar 15, 2007)

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.


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## tvodrd (Mar 16, 2007)

David, you don't need Don's approval! Any IP preceeds you, Don, me. etc!  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


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## mobile1 (Mar 16, 2007)

At $9/carat I wonder how much diamond is really in there and how much of the heat conductive properties you really get....


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## Anglepoise (Mar 16, 2007)

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>


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## gadget_lover (Mar 16, 2007)

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


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## Nereus (Mar 16, 2007)

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

-N


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## KDOG3 (Mar 16, 2007)

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


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## Nitroz (Mar 16, 2007)

Nereus said:


> How do I explain to my SO why on earth do I buy diamonds for my flashlights, not for her?
> 
> -N



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


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## Anglepoise (Mar 18, 2007)

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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## benighted (Mar 18, 2007)

Is it possible the current could arc across 30 microns?


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## Morelite (Mar 18, 2007)

benighted said:


> Is it possible the current could arc across 30 microns?


 
Not at this low voltage level, plus there is still a physical barrier between the two surfaces.


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## gadget_lover (Mar 19, 2007)

Just a stray thought or two.

First, if the idea of the diamond dust is to prevent the touching of irregularities in the heatsink or emitter slug, then lapping both should eleminate the problem.

Second, The P4 data sheet explicitly requires that you solder the slug to the heatink. I imagine the heat transfer from slug to base would be much, much better using solder instead of AA. You could use a lapped copper slug ( as you would a star) and AA epoxy that to the flashlight's heatsink Also lapped) after soldering the emitter slug to the "star". The increased area for the AA epoxy should conduct much more heat than the simple back of the emitter.

I have some P4s, so I guess I should just do it, huh?

Daniel


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## Anglepoise (Mar 19, 2007)

gadget_lover said:


> Just a stray thought or two.
> 
> The P4 data sheet explicitly requires that you solder the slug to the heatink. I imagine the heat transfer from slug to base would be much, much better using solder instead of AA. You could use a lapped copper slug ( as you would a star) and AA epoxy that to the flashlight's heatsink Also lapped) after soldering the emitter slug to the "star". The increased area for the AA epoxy should conduct much more heat than the simple back of the emitter.
> 
> Daniel



If you solder the slug to the heatsink , you still have to deal with the + 
( positive) base. So another layer of insulating material would be needed.

Not for me. I like to glue directly to the heat sink.


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## gadget_lover (Mar 19, 2007)

I shoudl have been more clear in my post. 

My thinking is thus; Heat transfer is based on the temperature difference, the thermal resisitance of of the joint and the area involved. The thermal resistance of a joint is determined by the thickness of the material as well as the area of the joint. 

A small contact area will always move less leat than a large one with the same resistance. That would mean that you want the best possible heat transfer at the point where you have the least contact area. The 1 sq cm of the P4 slug is that spot. A 1 inch diameter copper slug will conduct a lot more heat through a layer of AA to an aluminum heat sink than the slug would.

I think.

Daniel


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## benighted (Mar 20, 2007)

Theres been some contraversy on this subject, I'd just use a star for reliability purposes. You aren't going to notice the 2% output decrease anyway.


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## Anglepoise (Mar 20, 2007)

benighted said:


> I'd just use a star for reliability purposes. You aren't going to notice the 2% output decrease anyway.



Well if you expect reliability, watch out for the some P4s that were sold by Dealer Extreme. They were a star base with the emitter soldered only on it's two electrical contacts . The actual base was just 'resting' on the star with some thermal paste, not glue. 
In another post, members were complaining that they could clearly see the gap.
Turns out that their Chinese supplier was responsible and credits have/are/will be forthcoming.


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## Ra (Mar 21, 2007)

Why oh why, do I never hear someone about reversing the polarity within the flashlight and simply turn the battery 180 degrees ??

Or are you talking about exsisting flashlights with embedded electronics of which the polarity cannot be switched??

With my upcomming designs involving SSC-emitters, I connect the + of the battery to the body and heatsink of the flashlight.


Please help me on this one, and tell me why that isn't possible in your case..


Regards,

Ra


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## lasercrazy (Mar 25, 2007)

Ra said:


> Why oh why, do I never hear someone about reversing the polarity within the flashlight and simply turn the battery 180 degrees ??
> 
> Or are you talking about exsisting flashlights with embedded electronics of which the polarity cannot be switched??
> 
> ...


 Would that work? Say you had a series setup, what would stop the voltage from just skipping everywhere and possibly even bypassing an led or 2?


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## starfiretoo (Apr 2, 2007)

In the days of dinosaurs thin mica sheets were used to electrically isolate power transistors from the heatsinks. Any comments on this for this application?


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## TaschenlampeMann (Apr 2, 2007)

I must be one of the dinosaurs because I used to use the mica insulators in the good ol days. Anyway, I used them as insulators when I upgraded my FireFlyIII, HDS B60 and Orb RAW to Seoul P4s. If I recall, the mica I used was only .08mm thick. Of course I still used the Arctic heatsink compounds. I didn't notice any negative effects on the beam by the change in height.


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## tesseract (Apr 2, 2007)

lasercrazy: the laws of physics.


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## bombelman (Apr 3, 2007)

Nice, time to get some diamond dust...


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## Blindasabat (Apr 4, 2007)

I believe the purpose here is to make as THIN a layer of AA as possible while still remaining reliably non conductive (the physical separation Anglepoise mentioned). At least it will be for me. 



Anglepoise said:


> 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>


Just slathering on AA decreases efficiency and will drop thermal transfer as AA is far less thermally conductive than any direct metal contact. AA is meant to add thermal paths that would not otherwise be touching (air is even less conductive than AA), and lapping is desireable as it decreases the reliance on AA. The diamond powder is primarily a very thin but reliable (size-wise) non-conductive barrier, then thermally conductive only as a bonus. For that alone, it is worth exploring. 

If sand (Si or other) can be bought at the same grit quality for less, then I think that would be just as good an alternative. But you lose the bragging rights that you have the most thermally conductive material, diamond, in your light. 

Ra has a good point about reversing the batteries, but ONLY if your light is direct drive and you have a nub for the negative contact. Just mark it very well that way very well so you don't fry it at some other point.


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## Anglepoise (Apr 5, 2007)

Here is a fun picture. It consist of a small 'blob' of AA + 325 grit diamond that can be clearly seen in the picture. The disk is only 0.005" thou thick and it was produced by squeezing between two flat, waxed and highly polished surfaces.

Once cured, the AA disk separated easily and was undamaged.
I am presuming the very poor adhesion was entirely due to the wax on the two flat surfaces and not the inclusion a few diamond particles in the mix.


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## Tritium (Apr 6, 2007)

Guys don't pay high prices for diamond bort (grit).
Ebersoles has an e-bay store and is selling 50 ct containers of grit for less than $1 per ct. Here is the link.

http://stores.ebay.com/Ebersole-Roc...d-Grit_W0QQcolZ4QQdirZ1QQfsubZ9QQftidZ2QQtZkm

Thurmond


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## PEU (Apr 6, 2007)

David, what's the point of using artic alumina (aluminate filled epoxy) with diamond dust? 
Why not use common epoxy mixed with diamond dust directly?


Pablo


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## Anglepoise (Apr 6, 2007)

PEU said:


> David, what's the point of using artic alumina (aluminate filled epoxy) with diamond dust?
> Why not use common epoxy mixed with diamond dust directly?
> 
> 
> Pablo



I am adding diamond solely to guarantee the electrical separation.
AA has always worked well for me , so why change. I am NOT suggesting that the use of diamond will alter in any way the heat transfer of the 'glue' used.

I am NOT advocating this. Just experimenting and offering an alternative to members that have had problems ( various posts ) with shorting out between Seoul P4 base and heat sink.


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## photon555 (Apr 12, 2007)

Hi, I am thinking of Seouling my VIP. Any thoughts or advice would be appreciated. If I can do that sucessfully I will mod my Gladius. The idea of diamond dust as a uniform separation regulator appears appealing. I have a few questions if anyone is willing to give advice.

Is there any advantage to using the Artic Silver with the diamond grit?
What's the best way to pry off the old emitter in my VIP/Gladius?
Does anyone have any thoughts on the quality of the DE Seoul P4 emitters, not stars? Is DE an acceptable source for Seoul emitters?
Is it possible to order or acquire a low Vf Seoul emitter, or is it a lottery?
Does anyone have an opinion on the timing/availability of the next step up in led output?

I have a soldering station and experience in testing, debugging, and repairing digital and RF circuits/devices. 



Anglepoise said:


> Well if you expect reliability, watch out for the some P4s that were sold by Dealer Extreme. They were a star base with the emitter soldered only on it's two electrical contacts . The actual base was just 'resting' on the star with some thermal paste, not glue.
> In another post, members were complaining that they could clearly see the gap.
> Turns out that their Chinese supplier was responsible and credits have/are/will be forthcoming.


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## Anglepoise (Apr 12, 2007)

photon555 said:


> Does anyone have any thoughts on the quality of the DE Seoul P4 emitters, not stars? Is DE an acceptable source for Seoul emitters?



The problems with some of the DE supplied LEDs, only surfaced with the stars. The emitter was not making a good contact to the star. 
I have been very happy with Seouls purchased from member PhotonFanatic.
He seems to have a well deserved, good reputation.


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## photon555 (Apr 12, 2007)

Thanks for the info.


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