This doesn’t make much sense to me. The LED and pcb radiate into the air inside the flashligth head. Air is a very bad conductor of heat. After this the heat would still need to go through the metal of the head or through the glass lens (glass is somewhat good at conducting heat). You would need to replace the air inside the head with something else that doesn’t transmit light any worse, but has a noticeably better thermal conductivity.
Agro
(Agro)
October 5, 2018, 4:17pm
30
The_Driver:
This doesn’t make much sense to me. The LED and pcb radiate into the air inside the flashligth head. Air is a very bad conductor of heat. After this the heat would still need to go through the metal of the head or through the glass lens (glass is somewhat good at conducting heat). You would need to replace the air inside the head with something else that doesn’t transmit light any worse, but has a noticeably better thermal conductivity.
Would air absorb significant part of the radiation? I assumed no, but maybe incorrectly.
Otherwise goes towards the optics or towards the head sides or both, depending on what radiates it and what’s the optic.
Head can absorb it, conduct it towards the edges and remove.
No, not in such a short distance.
Maybe a solid glass TIR lens which touches the PCB with as large of an area as possible might improve the heat transfer a bit.
Agro
(Agro)
October 10, 2018, 11:44am
33
Thermal conductivity of 65.73 K/W. Better than SnPb or SAC305, worse than Indium. Melting temp of 227C, slightly higher than SAC305.
Barkuti
(Barkuti)
October 10, 2018, 12:05pm
34
Soldering with Sn99.3Pb0.7 is like sailing with a headwind, and it also increases stress in the soldering iron's tips. Check here: Why do tips easily oxidize when they are used with lead-free solder? @ hakko.com
I recommend standard eutectic Sn63Pb37 or Sn60Pb40 classic solder alloys, namely if newbie.
Cheers ^:)
P.S.: editing Niko's above post to reduce image size would be nice, somehow messes up with the page view on mobile or small screen devices.
Niko
(Niko)
October 10, 2018, 12:21pm
35
How is S-Bi57sn43 ?
I also have this.
…sorry for extra big photo
Agro
(Agro)
October 10, 2018, 12:31pm
36
I remember it’s worse than SnPb.
Barkuti
(Barkuti)
October 10, 2018, 8:44pm
37
Niko, you can fix the extra big photo by inserting a {width:100%} format tag in your photo link code. Example:
Before:
!https://www.nikohostwebsite.org/nikopicture.jpg!
After:
!{width:100%}https://www.nikohostwebsite.org/nikopicture.jpg!
Bi57 Sn43 /Bi58 Sn42 should make your life a lot easier when soldering. Versus standard Sn63 Pb37 or Sn60 Pb40 you can do with around 50°C less in your iron.
Cheers :-)
Originally posted on Wed, 10/10/2018 - 19:06. Edited for a tiny explanatory addition.
Agro
(Agro)
October 16, 2018, 1:49pm
39
I found an article which largely rehashes what we’ve already found, but may be interesting for some. I only skimmed over it, so there may be some gems that I missed.
https://www.ledsmagazine.com/articles/print/volume-14/issue-8/features/manufacturing/understand-thermal-characterization-of-high-power-leds-for-reliable-ssl.html
Yes, Luminus makes great LEDs.
Agro
(Agro)
November 13, 2018, 5:11pm
41
The_Driver:
I just remembered an additional material upgrade. Normal dtp pcbs are made out of copper or aluminium. There is another possible material onto which the LED can be directly soldered which transfers heat even better than copper: silver. Basti in the German TLF forum made such a pcb a few years ago . He made it just for the looks though.
The thermal conductivity of silver is 7 higher than that of the best possible (most pure) copper. Most common copper alloys are not 99.99 pure though, making the difference for pronounced.
I asked him if he would make one for me for my big thrower when I was planning the build, but he is not an active flashahlic anymore.
There is even better material than silver:
It’s even readily available for purchase. The price is a little high ($14K minimal order, good for 400 PCBs), but maybe one could get some samples?
BTW, silver-diamond works even better but copper-diamond doesn’t: https://www.electronics-cooling.com/2008/11/advanced-metal-diamond-composites-love-and-heat-relationship/
Agro:
The_Driver:
I just remembered an additional material upgrade. Normal dtp pcbs are made out of copper or aluminium. There is another possible material onto which the LED can be directly soldered which transfers heat even better than copper: silver. Basti in the German TLF forum made such a pcb a few years ago . He made it just for the looks though.
The thermal conductivity of silver is 7 higher than that of the best possible (most pure) copper. Most common copper alloys are not 99.99 pure though, making the difference for pronounced.
I asked him if he would make one for me for my big thrower when I was planning the build, but he is not an active flashahlic anymore.
There is even better material than silver:
Aluminum Diamond Thermal Management Material - NANO MATERIALS INTERNATIONAL CORPORATION
It’s even readily available for purchase. The price is a little high ($14K minimal order, good for 400 PCBs), but maybe one could get some samples?
BTW, silver-diamond works even better but copper-diamond doesn’t: https://www.electronics-cooling.com/2008/11/advanced-metal-diamond-composites-love-and-heat-relationship/
Can you solder it?
The benefit of Silver is that you can solder the LED onto it just like with copper pcbs.
Agro
(Agro)
November 13, 2018, 9:41pm
43
It’s gold plated, so you probably can solder to it.
clemence
(clemence)
November 28, 2018, 7:12pm
44
Niko:
Opinion for this wire?
Known as SC07. Good for soldering aluminum. High melting point, but very strong joint. I have 250gr 0,7mm spool lying unused. Bought for it’s “slightly” better thermal conductivity but the higher melting point made it my last choice.
- Clemence
clemence
(clemence)
November 28, 2018, 5:53pm
45
If you don’t plan to remove the LED later, then we can easily braze the chip directly to almost any metal. The brazing material can be anything with melting temp lower than 1500°C. Copper or Silver is a good candidate.
- Clemence
Agro
(Agro)
November 29, 2018, 10:38am
46
But such temp will destroy the phosphor. Maybe a die as well.
Barkuti
(Barkuti)
November 29, 2018, 10:50am
47
Can someone explain how to wet aluminium with Sn99.3Cu0.7? Tried to do it over heatsink material in the past, to no avail. I can understand it has to do with the particular aluminium alloy of the heatsink, maybe some 6061 crap, and insufficient surface sanding down. Hello?
Cheers ^:)
clemence
(clemence)
November 29, 2018, 5:20pm
48
Nanofoil
Asked for sample but heldback because the solder still limited to Sn based
https://www.indium.com/assets/videos/nanofoil/nanofoil-reaction.mp4
- Clemence