maxflex heatsink solder or epoxy?

[VegasF6]

I have gathered all the parts for a penta cree mag, and assembly is going slowly. I would like to make this light as durable as possible since as you can imagine there is quite a bit of money in parts.

Maxflex V2 driving 5 Q5 from 3x18650. So, max input amps should be in the neighborhood of 2.3 amps worst case scenario I am thinking.

Using the formula provided for output power I entered 3.75x5x1=18.75x.09= 1.69 watts of dissipate. Hopefully VF will be lower.

To heatsink the driver, I plan on borrowing this idea:
http://www.candlepowerforums.com/vb/showthread.php?t=192418

I want to try and keep everything somewhat reversible as I may want a nicer host in the future.

So, that heatsink and some AA epoxy would probably be good enough, but I am debating soldering the sink to the board. I have some solder paste, and a very hot iron that I think can handle it, but I am concerned of either delam-ing the board, or damaging the IC.

George states: When running at high output power it is recommended to solder or use thermal epoxy to mount a tab to the pad on the back of the MaxFlex2 board
And: Soldering is also another option if copper or tinplated material is to be used as the tab. Please ensure that the board is not overheated during the soldering process - if in doubt use thermal epoxy instead.

I guess it is safe to say I am in doubt, put perhaps with the help of the fine people here I won't be

*edit* I ran the output formula again for an even worse case.
5x3.75x1.2=22.5
22.5/.88=25.57
25.57/9=2.84 amps driving current.
But, I will enable the low voltage cutoff to be higher than 9 volts. Plus, I am not even clear if V2 will drive at 1.2 amps.

 

[steve6690]

I fried my last maxflex attempting to solder it to a copper tab. I pre-tinned the copper tab, applied a small amount of flux to the heatsink pad on the maxflex, heated up the tab until the solder melted and then quickly pressed the tab onto the maxflex. The joint was good but the maxflex was killed. If I were to try it again I'd use a much hotter iron ( mine is 35W ) and I'd ensure the copper tab was attached to a heatsink of fairly large area so that once the iron is removed from the tab the heat is wicked quickly away from the driver.

 

[nailbender]

a thin layer a AA works great and no heat issues as long as you get a good contact point. George at Task Led even recommends this if you can get good contact to the copper area and just use a thin layer.

Dave

 

[VegasF6]

I suppose AA it is, just wanted to be a little different.

...Unless, maybe I should drill a couple holes through the board and bolt it on? Naw... I guess my maxflex doesn't need vents