Have to get one off a can without my wife finding out then :)!
I think a lid might be too thin to hold adequate heat. You want the heating surface to be relatively stable, so I think you’ll need something with at least a little bit more mass.
What about this:
I could cut it to 2”, so it’d be 2” x 2” x 1/8” (thickness)?
I think you’re fine with placing the star in a vice and using your iron to heat it from the bottom. The addition of an aluminum block intermediary, while it is a good idea*, seems like an unneeded expense to me, unless you plan to do a bunch of these.
*The alu block is sorta like turning your iron into a mini-hotplate, or you could look at it as a big custom-made tip for your iron.
I’ve been practicing using an old XP-G on a 16mm aluminum star (since I destroyed the two XM-L ones), in a vise, and a soldering iron directly on the bottom of the star, but for example, to remove the emitter, it’s taking forever (like several minutes) for the solder to melt to the point that I can pick off the emitter.
And that’s with my relatively new Aouyue iron turned up to 480C, and using a chisel tip, applied directly to the bottom.
Is it suppose to take that long?
Use the tip that gives the most contact area. When removing the led, try sliding it sideways rather than pulling it up. They seem to suction down.
It shouldn’t take more than a minute. If you’re using metal jaws on your vice, that could be acting as a heatsink.
That was what I was thinking, but I don’t really have anything to cover the jaws of the vise that wouldn’t either be metal or would melt. Would cutting up an old belt and clamping the star between one piece of leather on each side work?
Probably.
This is just a thought. Maybe you could repurpose one or your busted XML boards into a mini-hotplate.
You can smooth out the top, flip it upside down, and it’s basically a mini alu block. You would have to set one side of the triple board off the edge a little, but it should work the same as lilkevin’s method.
It would save you the trouble of finding a way to pad your vice.
I already cut up some pieces of leather, and will give those a try with the soldering iron and see if it heats things up faster.
Thanks,
Jim
Edit: Tried it with the leather on the vise jaws, and I guess it was a little faster, but not by much. Nevertheless, I think that for the first one I try (tomorrow - solder paste arriving), I think I will go with the iron-on-bottom-of-star, as it just seems safer for me.
BTW, re. the can top - no good, and actually bad! The problem is that when the thin metal heats up, it pops, and it threw both the star and emitter. Luckily, both missed me :(… So, lesson learned - no can tops!
Edit 1: I was re-watching Old-Lumens’ video:
and he doesn’t have anything on his vise’s jaws. Also, he did one thing that I didn’t do… he put some solder on the soldering iron tip before using it to heat the star… I didn’t do that, in fact I cleaned the tip off before heating the star, because I was worried that solder from the tip would stick to the bottom of the star.
That may’ve been the problem, because the heat transfer from the iron tip to the star would not be as good with the dry tip?
You should always tin the tip. It improves heat transfer a lot. Solder doesn’t stick to aluminum, so it won’t stick to the underside of the star.
NOW you tell me…
JUST KIDDING :)!!
Yes, next time I try this, I’ll tin the tip.
Thanks,
Jim
The vise is made of iron, it does not conduct heat very well, so you get away with that.
JonnyC wrote:
ImA4Wheelr wrote:Great info in this thread. I think I have reflowed almost every way except with a reflow oven. For me, a heat gun used under the base while in Helping Hands works best. I just have a cheapo heat gun from Harbor Freight and it works great for all kinds of things.
Hmm, I was just going to buy a cheap hotplate, but I might go with this method. I have the same heat gun. How close do you get it to the MCPCB?
Sorry, I missed this post. Not sure. Probably about 3 to 6 inches. The great thing about the heat gun is that you can rapidly adjust the heat be using distance and power level. Every heat gun, base, solder, etc is going to be different. So you can't just use the same exact approach each time. That applies to almost all of the methods. Watching for flux boil off and for the solder changing states (solid to liquid) are how to gauge the best distance. I always use the low level on my heat gun.
I just found that I had a couple of these:
That’s an old Thermaltake CPU heatsink. The neat part is the copper plate is screwed onto the aluminum heatsink, so it’s easily removeable.
So I’m going to put the star on top of the copper plate that I removed, and heat from under that, either with my soldering iron or small butane torch.
Still waiting for the solder paste to arrive…
Comments?
Comment: that is quite some copper with quite some surface, thus requires quite some heat to get it to temperature
Yes, it’s a nice chunk :). FYI, I’ve tested with both a small torch and a el-cheapo 60W soldering iron (not at the same time) underneath the copper plate (which is in a bare vise), and I was able to remove and then reseat/reflow an emitter onto a single-emitter PCB so far. I’ve done it a couple of times now.
With the 60W soldering iron, it takes quite awhile to heat it up enough to get the solder on the PCB to melt.
The torch is much faster, and with the copper plate between the torch and PCB, I feel like I have enough control and don’t burn the top layer off of the PCB, so I’m leaning towards this vs. the soldering iron at this point.
The Kester solder paste should get here any minute now, so I’ll need to make a decision soon :)…
It’s like a miniature frying pan. 
Yes, it is, and I was kind of surprised how heavy it is. It’s only about 1.5 - 2” square, maybe 1/8” thick, but it is heavy!
BTW, a little off-topic for this thread, but I have some XP-G2s coming in, probably next week. I’m hoping I get the XP-E2s reflowed ok the 1st time, so that I can use the 2nd IS 3up PCB for the XP-G2s.
So the pressure’s on :)!