Penny heatsink: better to solder or use AA or paste?

Flashlight Modding and DIY Parts
1

I am modding a D25C clicky to use a TIR with a neutral XML2 but the TIR is shorter than the stock reflector so I need to make a heat sink to sit under the LED board. Im using a few pennies, filed and sanded to fit, but I don’t know what to use between them for the best heat transfer. Should I try to solder them or just use Arctic Alumina or thermal paste?

Thanks!

2

Solder is best. Perhaps use a butane “jet” lighter if your soldering iron won’t get them hot enough.

3

I’ve done several projects recently using different sizes of Cu rounds. The easiest method I’ve found is to “frost” them (like a cake) with a thin layer of solder paste and stack them all together and heat them all at once with pressure (steel vice-grips work great cause they don’t stick). It’s also the cleanest method and leaves the least amount of extra solder and very little flux to clean up.

I do use a full size mapp gas torch, not a lighter/ mini-torch but it takes a minute or two even for the 2”+ multi-layer pucks I make.

4

I dont have any solder paste, do you think I can just shave some solder off of a roll really thin and make that work?

5

It works with solder, I did my first few that way, it just leaves extra to clean off the edges and it may not get the disks quite as close to each other if you add to much but it will still work no problem.

You may look around on google and find a DIY solder paste recipe using regular solder and flux, but the real stuff can be bought from eBay from a US seller for <$5 shipped.

6

Thanks!

7

How many pennies?
Since solder is soft & malleable you could flatten out a coil of solder, place it between then heat.

Solder paste is great stuff. $3.28 fasttech, china.

8

That’s the same exact stuff I get off eBay for $5, comes in a few days from a wearhouse in NJ.

9

Its either going to be 2 or 3 pennies, depending on how much I have to file off to get them flat and smooth.

10

Quick way to make solder sheet for bonding the pennies

Take regular stick solder, hold it over a flat non porous surface maybe a foot…melt with soldering iron till it drips…when it lands…kerplop will make a funny solder sheet design…it might take some force to de-stick it from the surface, put on penny with a light coating of flux

Put pennies sanded smooth on top of each other after making solder sheet, put in stainless steel pan, set on stove, it will eventually heat and bond them all together

To make it faster take your torch and heat up and down the sides to make sure the top is getting good heat too

I used the above solder paste though…just put a blob…mooshed the pennies together spreading the paste…heated on stove…voila

11

Keep in mind, a penny is not a penny.
In 1982, the composition was changed to 97.5 percent zinc and 2.5 percent copper (copper-plated zinc).
And buy the way, to mint a penny, it costs 1.83 cents as of 2014.

12

Which pan was my solder reflow pan and which is my scrambled egg pan? :~

13

The one your wife won’t smack you in the head with for reflowing your emitters :smiley:

14

I went by the welding shop and asked if he had any SS scraps. He’d made something fairly recently that had 6” holes cut out of 1/8” thick 314 Stainless, gave me one of those rounds. So I use the 6” round disc of stainless on the glass stove top to re-flow. It’s golden now from the heat, with some splashes of flux stain on it. :slight_smile: Works beautifully! (And I’m safe from the head smashing pans)

15

If I use the wrong one I think I’ll lose more brain cells from the lead in my scrambled eggs then from a single smack in the head.

16

I reflow directly on my glass top stove, no pan needed (obviously not everyone has a glass cook-top). First I turn the burner on and heat it to 5 for a minute or two then I turn it down to 3-4 and reflow.

After I reflow I slide the star off to the side then use needle-nose pliers to pick it up and set it on a 2mm thick solid sterling silver platter I have for a heatsink, within 60 seconds on the silver you can pick the star up with your bare fingers.

17

Yep, make sure your pennies are from 1981 or earlier.

18

Actually those are probably bronze, not pure copper. From the US Mint’s website The Composition of the Cent :

  • The composition was pure copper from 1793 to 1837.
  • From 1837 to 1857, the cent was made of bronze (95 percent copper, and five percent tin and zinc).
  • From 1857, the cent was 88 percent copper and 12 percent nickel, giving the coin a whitish appearance.
  • The cent was again bronze (95 percent copper, and five percent tin and zinc) from 1864 to 1962. (Note: In 1943, the coin’s composition was changed to zinc-coated steel. This change was only for the year 1943 and was due to the critical use of copper for the war effort. However, a limited number of copper pennies were minted that year. You can read more about the rare, collectible 1943 copper penny in “What’s So Special about the 1943 Copper Penny.”)
  • In 1962, the cent’s tin content, which was quite small, was removed. That made the metal composition of the cent 95 percent copper and 5 percent zinc.
  • The alloy remained 95 percent copper and 5 percent zinc until 1982, when the composition was changed to 97.5 percent zinc and 2.5 percent copper (copper-plated zinc). Cents of both compositions appeared in that year.
19

Can I buy one from you?
Seriously!

I might get out of the dog house finally :smiley:

20

P.S. go to Etsy…search 16mm copper disks