After disassembling a number of my lights I noticed that some have the MCPCB glued in while others have a white paste that stays in a pliable unhardened non adhesive form.
Being fairly new to this, I have so far only used Fujik thermal glue. At least I think it's glue as I have never waited for it to dry before soldering wires and installing the reflector.
What I want to know is, what is the difference between the adhesive, and non adhesive thermal compounds? It seems to me that a non adhesive compound would be better just for the ease of removal of the MCPCB for later emitter swaps.
It also seem to me that non adhesive compound would make it easier for the MCPCB to shift around a little so it can be perfectly centered while installing the reflector. Once the reflector is screwed down, the MCPCB can't move anyway, so what's the point of glue.
I would also like to know the best way to remove an MCPCB that is glued in.
I never had the patience to find out the best way, I just applied brute force with whatever was at hand .
I am also interested in the different thermal compounts, perhaps there is someone who is less lazy and more knowledgable than me who can make a small table with the different compount and their properties (glue or not, thermal conductivity , conformability, biohazards or whatever)
From my reading (and don't quote me here) I understand that thermal paste;compound has better heat transfer than thermal adhesive. If you don't need to have the emitter immobile i.e. if it will be held down by pressure from either an optic or reflector, then go with thermal paste/compound. If you need it stuck down, you go with the adhesive. In either case, use as thin a layer as possible.
I tried to get the benefits of both when I need to glue the emitter down: I use paste under the emitter, make any fine adjustments to position, then glue the edges with thermal adhesive. In this way, if I need to remove it, I can take a razor and very easily slice through the adhesive later around the edge.
It doesn't look as pretty, but here are some end results of emitters using both compound and adhesive:
Fujik (brand) or more precisely the product BAB900, has a thermal conductivity of 0.9W/m.K. Use a thermal paste that has 6+W/m.K and use the reflector to apply pressure, as thermal greases need pressure to work well. The thinnest possible layer, just to fill the air gaps otherwise it will work against you.
Artic silver 5 is recommended by many. But that is not very budget.
I currenty use Noctua NT-H1.
+1
Anyone have good tips?
If I have a larger surface I just use a small flat screwdriver or three. Get them under the side of the pcb and hit it lightly or just use force. Try to to it as gently as possible and from many angles so that you dont bend the pcb.
As for removing emitters in P60 pills and such. Tips are appreciated, because there is no way to get a screwdriver under it.
Could always use a dremel and cut away some of the side of the P60 pill so that you could get a screwdriver under the emitter…
AS5 is like the hype of 6 years ago. There are other pastes that are very good, MX-2 is also appreciated today even the specs are not the best in the world.
As far as I am concerned, it does not really matter which paste. As long as the star and the surface of the heat sink are lapped, then you only need to wipe a film of paste on the surface. Thin meaning so thin that it is translucent and you can hardly see it at all. If you use enough paste to "hold the star on", then you have made it an insulating layer, not a heat transfer layer. And..... if you do not use some type of clamping mechanism (such as screws), to put pressure on the joint, then heat transfer is no good.
Ok, that's the stock "I am a perfectionist and extremist" answer. My personal feeling is, "it's a flashlight". We turn it on and we turn it off and 95% of the time, for 95% of the people (truth be known), don't ever get the thing hot enough to make use of all that anal heat transfer thinking. Just glue the derned thing on and be done with it. In that case, most any thermal paste will work ok.
CPUs have have huge and active heatsinks and still thermal paste paste matters. Some of the coolers (heastink+fan) I've used were so tight fitted that needed an additional 3mm steel backplate on the mainboard PCB to take that pressure. Considering all that you can still see performance difference between thermal pastes. Not only that but most high end heatsinks are lapped to a mirror finish. Those are the conditions the thermal pastes are tested on CPUs and yet you cam still see performance differences.
With CPU's is not like the LEDs that they will not be bright enough, but if you overclock the CPU there a huge chance it will freeze, reset, give you BSODs, ect.
+1, I have AS5 adhesive, AS compound, Fujik glue, and Fujik grease. Since most of my builds are twisty’s I use some kind of adhesive to prevent wire movement with the lens but otherwise whatever makes sense at the time(and don’t ask me to explain why later ’cause I won’t remember).
Not trying to hijack the thread but talking of tooth paste, used in an inwards to outwards or visa versa movement on CD's and DVD's can also remove scratches. It does take a lot of effort though. Apparently it has another use but I dont recall what it is. Yes that is what it is. For kids to leave white stains all over the basin.
I use plain ol JB Weld on p60 pills, and it's good enough that you can reflow an emitter with the board still glued into the pill. Doesn't take any longer for the solder to flow than doing it on a bare MCPCB, might even be quicker due to the cup shape on the underside catching more of the hot air. I use a butane soldering torch with the tip adapter/heating element adapter, but no actual soldering tip screwed in, so it just blows hot air out the end.
If I can’t reflow the emitter base to the pill (Aluminum base or pill, etc), I use this stuff because it’s cheap. $9 for 3 ozs. Seems to work fine, but I haven’t scientifically tested it. Who am I kidding? I couldn’t scientifically test something if I wanted to.
Post I made on another thread about thermal paste
Credit for the table goes to Anandtech forum member Idontcare, links can be found on the quoted post.
.
