how to isolate +ve slug on Seoul SC emitters?

[roguesw]

Hi guys, sorry for another question
i just read up on the specs of the Seoul SC emitters and they note they are
+ve polarity on the slug
how do i isolate the slug as most flashlights are -ve polarity on the body
Is arctic alumina enough or
should i put kapton tape on the bottom of the Pr-T and use AA between
the emitter and the kapton?
thanks again for your help
best regards
Des

 

[ginaz]

i've heard of people using nail polish.

 

[EngrPaul]

First, make sure you flatten the copper slug in a smooth vice. As supplied from the Sandwich Shoppe, mine were severely cupped.

Second, you can cut strips of Kapton tape and lay them across the slug. This defines a .001" thick plane that the emitter cannot cross. Just make sure you leave plenty of open copper so that the heat transfers around the Kapton.

 

[Anglepoise]

A thin single layer of Arctic Alumina Epoxy will electrically insulate the LED base from the metal you wish to mount the LED to.

Also it will conduct the heat away to the metal.

 

[IsaacHayes]

yeah, thin layer of AA. it wont be near as good as if it were pressed hard so its a metal to metal connection, with just AA to fill in the microscopic holes, but you gotta isolate so what can you do?

I've done several red/amber/etc luxeons before without issue. Even a R/O one driven at 1.4amp and it was still bright, so you may loose some lumens but still be bright...

 

[EngrPaul]

I've had success with just not pushing on the emitter while it cures, and then also not allowing anything to push on it in the flashlight (like the reflector base).

 

[roguesw]

thanks guys for all the great responses, so there are several methods i can choose, and luckily all are available to me
i think EngPaul has a fairly easy to use method, the two step epoxy method, initial layer and then epoxy emitter
thanks again for the great responses guys
best regards
Des

 

[Led_Blind]

Why Arctic aluminia rather than arctic silver?

 

[ViReN]

for low current applications (like below 200 mA) there is very less heat generated anyway you can simply use an insulator (plastic disc etc) even a FR4 PCB (without the copper) will do...

heat comes in to major play after 300 mA .... and SP4 turns blue after 1000 mA (with heat sinking)

 

[EngrPaul]

Why Arctic aluminia rather than arctic silver?

My only guess is that AA has been around for a while... isn't AS newer?

I use AS.

 

[Sengoku]

Taken from http://www.articsilver.com/arctic_silver_thermal_adhesive.htm

NOTE: Even though Arctic Silver Thermal Adhesive is specifically engineered for high electrical resistance, it should be keep away from electrical traces, pins, and leads. The cured adhesive is slightly capacitive and could potentially cause
problems if it bridged two close-proximityelectrical paths.

 

[Mike abcd]

Taken from http://www.articsilver.com/arctic_silver_thermal_adhesive.htm

NOTE: Even though Arctic Silver Thermal Adhesive is specifically engineered for high electrical resistance, it should be keep away from electrical traces, pins, and leads. The cured adhesive is slightly capacitive and could potentially cause
problems if it bridged two close-proximityelectrical paths.

I wonder if the slight capacitance of the artic silver adhesive or its "negligible" conductivity is enough to actually cause an issue with most drivers. I suspect it might be more likely with PWM or possibly on initial turn on.

I noticed that they spec the thermal conductivity for Arctic Silver Thermal Adhesive but not for Arctic Alumina Thermal Adhesive...

Mike

 

[EngrPaul]

I wonder if the slight capacitance of the artic silver adhesive or its "negligible" conductivity is enough to actually cause an issue with most drivers. I suspect it might be more likely with PWM or possibly on initial turn on.

I noticed that they spec the thermal conductivity for Arctic Silver Thermal Adhesive but not for Arctic Alumina Thermal Adhesive...

Mike

It didn't cause any problems with my L0-Ti or L0P-SE.

 

[Gnufsh]

The "negligible" conductivity of AS epoxy is not detectable on my DMM. I think the capacitance is more of an issue with high frequency, tight tolerance signals when things that are close together are bridged with it (eg cpu pins, etc).

 

[carbine15]

why the hell dont they design these slugs to be electrically neutral or -neg at least. I'ts like they have no idea what they might be used for.

 

[vacuum3d]

If you're using the Aleph e-screw, you don't need to worry about the isolation since the e-screw is anodized.

 

[Mike abcd]

It didn't cause any problems with my L0-Ti or L0P-SE.

Thanks for the reply Paul. You seem to have done FAR more SSC mods than anyone else.

Any advice on what to use? Do you think the better thermal conductivity of the Artic Silver adhesive is noticable in reducing the emitter temperature at 350 and 700 mA drive levels? Worth the extra cost?

Mike

 

[EngrPaul]

Hi Mike,

I have not comparee the benefits of AS over other adhesives. It only ends up being a few cents per light, so I just use what's best of what's available.

 

[The-David]

I used a thin layer of cleer nailpolish and checked to make sure it covered evereywhere with a DVM.

 

[dat2zip]

Be careful with Artic silver. You can expose the silver with a soldering iron or other heat methods like IR reflow. The silver component can separate out and become a blob. Under certain conditions of compression you can get the silver to make contact as well.

I use a thin coat of nail polishon all my emitters that need isolation. Just need to have patience and let it dry thoroughly.

You can get thin Kapton tape and use that for an insulator. You can probably use saran wrap or some super thin plastic.