AMC7135 Stacking chips... First attempt photo

I think it turned out good.... I'm pretty happy.

Hope it still works. :thinking:

Very nice clean job.
So this is ~4.5A now, what LED and light will you be using this with?

Thanks.

I think 4.2A now. 2800ma board + 4x350ma chips. The light is just and ultra cheap ebay UF C8 with XML-T6.

Nice soldering job :twothumbs and looks good too.

But it's technically not sound:

• The upper IC's have a very poor thermal path (that already sits at elevated temps).
• The bottom IC's loose the air cooling part which they'd otherwise have (however insignificant that may be) AND get an heater strapped to their back. :sweat:
• The circuit board will have double the heat to transport to flashlight housing & will therefore get a lot hotter. You are running experiments with this strapped to a cooler / flashlight host, are you? (that is, not a loose pcb hanging in the air).

Don't expect this to live long when running @ full power (but maybe you're lucky). Whatever you're trying to achieve: this screams "buck regulator!" to me.

Funny, when I read the reply above on the thread I thought "This almost looks like a dutch forum". Guess I was half right .

TS: very clean job! Did you do this by hand or with soldering paste?

I have to agree with RetroTechie above concerning heat management. It can be used (and in fact it has been used multiple times), but keep in mind that you have limited heat dissipation. Do not try to use it on a single LED with 4xNiMH cells, it will not be able to get rid of the heat.

Potting it will help tremendously to improve the thermal pathway.

I do not agree with RetroTechie about the buck driver thought.
This 7135 based driver is for single cell use. It basically is just a current limiter with a PWM function.

Buck drivers are only for multi cell operation basically. Not to mention it is near impossible to find one with 4A driver current, multimode that changes modes by disconnecting and reconnecting the power with the tail switch and with a 17mm size. Believe me, I know .

Thanks again. I did this by hand and getting just the right amount of solder on the tip will take some practice.

I'm just tinkering and I'm sure most here know way more than I. Light is just a single 18650 C8 with aluminum pill that I'm filling with 2 -95% copper pennies to help heat dissipation. I'm not sure the pennies are even necessary?

2 pennies soldered together and sanding the diameter to get a slight press fit. Also will be using Arctic Silver A+B adhesive.

just a sec...Next to the controler chip there should be a diode. (on the right)
I see two of them stacked?

No, there aren't two stacked. That's a mold line you're seeing, not a space between two parts.

nice work! I've never done this, but why don't the middle pins get bridged?

tobrien said:

nice work! I've never done this, but why don't the middle pins get bridged?

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Middle pin is shorted to the pin at the back.
So connecting either one will get it connected.

- JonK

IIRC, you can get a brass C8 pill from FastTech.
It might be a better option to increase the thermal property of ur light.

And by adding the 2 pennies, i am assuming u are trying to increase the mass so that it can take more heat, right?
I do the same thing, but i took some cheap 16mm copper MCPCB (FastTech has them), solder 2 pieces together & they fit into a P60 pill just nicely. Plus they have the groove for the wires to go thru them nicely.

- JonK

DellSuperman said:

And by adding the 2 pennies, i am assuming u are trying to increase the mass so that it can take more heat, right?

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Adding mass by itself only helps to increase "run @ full power for a few seconds" (or minutes) to "run full power for a few seconds more".

If it helps with transporting heat: excellent! If not: don't bother.

This got me thinking though... afaik most drivers will have low modes by PWM-ing these current sink IC's, correct? If so: do there exist drivers that control lower modes by changing the number of IC's that are "on" ?

So (for example) not "switch on all IC's for 1/6 of the time, off the rest of each cycle", but "1 IC on @ low mode, 6 IC's on @ high mode". That would obviously limit available settings for low modes, but do away with PWM-related flickering.

RetroTechie said:

Adding mass by itself only helps to increase "run @ full power for a few seconds" (or minutes) to "run full power for a few seconds more".

If it helps with transporting heat: excellent! If not: don't bother.

Click to expand...

Hmm, my understanding is that it does help to run at full power longer because it can transport the heat from the emitter to the pill & whatsoever that absorbs heats away, including the host & pill & blah blah blah..

- JonK

Epsilon said:

Potting it will help tremendously to improve the thermal pathway.

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I plan to use a similar setup, stacked AMC's. I dont see it feasible to solder the AMC's to a heatsink. But potting would be easy.

Anyone suggestions for good potting material? Thermal glue like arctic silver? What would a professional use?

Walterk said:

I plan to use a similar setup, stacked AMC's. I dont see it feasible to solder the AMC's to a heatsink. But potting would be easy.

Anyone suggestions for good potting material? Thermal glue like arctic silver? What would a professional use?

Click to expand...

Check this out.
Someone machined a circular copper sheet as a heatsink for AMC7135 chips.

https://www.candlepowerforums.com/posts/4298904

As for potting, i have been using this Fujik thermal paste. So far so good..

- JonK

I've used the cheap Fujik Thermal paste too and it does actually pretty well. But that will almost certainly not be the stuff that "a professional" uses. It will also not get totally hard and smooth, which I would like.

But I would rather use Artic Alumina Adhesive as a potting compound or something else. But finding Artic Alumina Adhesive appears to be dificult in NL for a decent price.

The Artic Silver Adhesive is not suitable for potting; it is electrically conductive.

Walterk said:

Anyone suggestions for good potting material?

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You might try a 2-component epoxy resin like what's used to repair holes / dents in car or boat bodies. Mostly resin, with a small percentage of "harder" added it becomes a semi-transparent, plastic-like block. Stores that sell various hobby materials might have similar stuff. Hell, perhaps even a 2-component epoxy based glue might work.

Not a good thermal conductor tbh, but still much better than air. And electrically non-conductive afaik (depending on what's mixed in - coloring etc). Not hot glue though, that's usually an awful thermal conductor!

I would not use a regular epoxy. While it would be 10x better than air, metal oxides are 1000x better than air. I would use a proper heat sinking compound to wick the heat away, preferably with a short path to some substantial heatsinking material as well.

You used a 45 year old penny in a flashlight..... i like old stuff, wouldve put it in the safe. lol