Where to get Q4-R2 on a small board (16mm or so)

[moon lander]

I cant seem to find higher bin Crees on a board small enough to mod AA sized lights. i believe anything smaller than 16mm would work. specifically, im looking to replace the led in my rexlight and a couple others with a Q or R bin cree, or even Rebel100.

You can get bare emitters, you can get them pre-mounted on stars, but i cant find them pre-mounted on a small board. apparently cutters round boards are too big to fit in AA sized lights. DX has these small boards, but with P4 only.

Any ideas where to find them? if not, are there any other options? like triming down a star or desoldering an emitter from a small board and resoldering the newer bin to the old board? both of these options seem very hard to do, any advice? thanks for the help!

 

[starburst]

With a new file and some patience it has been done

 

[richdsu]

Actually desoldering and soldering a Cree Emitter to Star Board is not very difficult.

You will need to have a Hot Air Gun ( I am using a Bosch Hot Air Gun).

To desolder : Hold the Star Board with a long nose plier, heat up the Star board ( hot air gun pointing at the bare aluminium side of the star board about 2 inches apart), when it is hot enought after 10 seconds of heating, tap the plier holding the emitter by the edge of a table and the emitter will pop-off the star board.


To solder : First use a soldering iron to apply a very thin film of solder onto the solder pads on the emitter board. Next place and locate the cree emitter onto the solder pads of the star board. You can use Kapton Tape or Glass-cloth tape or thin copper wire to help you hold the cree emitter properly onto the star board. Next place and hold the star board assembly properly to a vise with cree emitter face up. Heat up the star board bare aluminium side from underneath about 10 seconds. When the solder reaches melting temperature, the cree emitter will fuse up with star board. ( you may want to use a flat tip screw driver to depress lightly on the cree emitter when the solder is still molten to ensure good bonding).


:devil:

 

[moon lander]

thanks for the advice, ill definately try that, but ill have to get a hot air gun first. can this be done with a soldering iron? and does the cree handle the temperature? also, any idea where to get a bare board that small, other than the one in the light itself? thanks again.

 

[Mash]

I tried the soldering/desoldering of the emitter to the star when I blew one emitter.
I used a jet lighter and a the flame attachment of a gas soldering iron. BUT I dont really know what temperatures I was getting and whether this would ahve damagd the emitter.
My rough guess would be that yes, this would damage the emitter, since the white coating on top the star started turning brown!
So I would ask the knowledgable members here, for their maximum temp recommendations.

 

[mds82]

I know 2 other ways you can do this are with a hot plate or a toaster oven. i tried using a hot plate once and its not too bad.
Once i even put it right on top of a stove top range ( the one with metal coils)

 

[SteveDavis]

For XR-E sampling on stars, we use a hot plate set to 230 deg C, with a thin application of 10% flux solder paste on the star (or whatever board). Place the XR-E on top of the solder paste and wait until the weight of the LED self settles the package onto the pads. Quickly remove the board from the hot plate and allow to cool. We have had a 100% success rate so far with this method.

UPDATE: Got the temp scale wrong. It didn't feel right to be saying F, but somehow I said it anyway.

 

[richdsu]

You can do a dry-run first without the cree emitter:

Pre-solder a thin layer of solder on the pads of the star board, attach it to a vise. Start heating up the star board ( use a stopwatch ), take note of the time taken when the solder on the board begin to molten.

 

[moon lander]

Once i even put it right on top of a stove top range ( the one with metal coils)

Good idea. Medium? Medium high? I think the melting point of solder is like 360ºF. Ill try a dry run to see what setting melts it.

i figure if i move it from the stove strait to an aluminum slab the instant it melts then the emitter should be ok. isnt this similar to what they do at the fatory anyway?

im guessing a soldering iron wouldnt work well since it might heat only part of the star board up enough to damage the emitter while the rest is cool enough that the solder stays solid.

thanks for all the replies folks!

 

[moon lander]

ok that worked! i did it on the stove, set to medium. took about 10 seconds to melt the solder, than i moved it strait to an aluminum slab sitting on an icepack.

now my rexlight has a WC Q5 driven by RV7s AA board and gets 500ma at the led. the Q5 i used has a high vf. i need to find one with a better vf because the P4s i have can get up to 950ma from just a AA thru the RV7 board. either way, judging by eye, it looks about twice as bright as my Jetbeam MKIIx, both on AA. thanks again for the help.