SK98 Pill Penny Reflow Question

Hello Friends,
I’ve built a reflow hot plate and reflowed my first part. However, I am not sure if I had it hot enough or not? I stacked the pennies in the pill with a layer of solder paste inbetween each penny. I put it on the hot plate when the temperature reached 220C. Then as the solder started melting I pushed on the pennies to try and even out the solder. It seemed to work. I then put some past on the mcpcb of an xml2 and placed it on the top penny. As the solder started melting I centered the mcpcb and held it down for about 30s. I then transfered a pill to another block of aluminum that was cool. I held the mcpcb in place by pressing down with my tweezers.

Now, when I pressed down on the mcpcb the excess solder squished out the sides and formed a bubble or blob of solder. I was expecting it to flow more like a liquid.

Can anyone tell by the photo if enough heat was applied and if this reflow job is acceptable? The temp of the hot plate when I removed the pill was 240C, but I’m not sure of the temperature of the pill around the mcpcb?

I think you put too much solder paste. Reheat the pill. Press down you led star and remove the excess of solder with solder braid or a solder pump. For me I think more the layer between star and the penny be thinner better will be the heat transfer.

I pushed down pretty hard on the mcpcb and the solder you see was pushed out from underneath. Do you think that there is too much under the mcpcb even after “squishing” it down?

Oh well. I think the layer is thin now. It’s only the excess of solder. You can remove excess or let it like this. If you want to remove the excess without reheating all the pill. You can do it with a soldering iron and desoldering bread just to get the jod more cleaner. And remove as much as you can.

And for me you made a great job on this reflow

Ok. thank you. I was expecting the excess solder to flow more and “wet” the top penny like when soldering a spring to a driver using lots of flux. Maybe this will be ok then. I will try to clean up the solder and do some testing to make sure the heat is transferring. Thanks for your help!

When I modded my sk68 like this I expected the same. But If you penny is not copper and deoxidised solder will not stick to it.
Sometime when I get some solder blob like this I heat the pill for more time it need because flux need time to clean the surface and tin got to the surface by itself.
What solder paste did you use? I’m using The XG-Z40 solder paste from banggood.It give really shinny effect.

The paste I used is MG Chemicals 73/27 no clean paste. I think it’s good paste, but maybe the flux is not so strong for this application. I took a magnifying glass and looked at it a bit closer. Around the edge of the mcpcb there is a good concave solder joint. It has a nice wet look to it so I think I might be ok without reheating. However, I think you are right and I should have left it get hotter to let the flux do its work. I will leave it on longer next time.

If it have solder all around the edge of the mpcb it’s perfect.
Poste more picture of your build if you can. It will be cool to see your work.

Ps: a friend use mg chemical solder paste. He’s happy with it.

You checked the date on each penny? You want 1981 or earlier:

If you have 1982s, weigh each one and you’ll be able to separate them.
(and if you don’t have a gram scale a simple teeter-totter will let you compare each 1982 to 1981 and 1983 to see which is which.)

Wouldn’t it be easier to just go through your pocket change, pick out the pre-1982 pennies, and set them aside for use?

Ya… I’ve got a pile of pennies from 1963-1981. I just learned that the pre 1962 pennies are pretty much just as good. They have a little bit of tin instead of some of the 5% zinc. The rest of the penny is still 95% copper. For the most part…

I have 5 pennies in this pill filling every bit of space to fhe driver. The led lead wires go straight up to the pads. No room for coiling up wire. I just fit the driver in and the holes line up perfect! Lucky drilling!

I will post some pics. Maybe tomorrow. I hate that all I have is my iOS camara, but I should be able to get some shots decent enough.

Here is a pic of the back of the pill where the driver will go. The pic shows my first effort in stacking amc7135 chips. It now has a total of 11 chips.

Nice work. The pill Is perfect for high current now. Great.
Did you planned to change the lens ? I do this for my sk68. It give litle more throw.
And kaidomain sell the lens for 2.48$
The driver is clean.

Do you have a link?
How do you change it? Mine is glued in…

Mine was totaly free. No glue.
I changed between these 3 lens (this one is too big but great throw) (I tried this one too but it’s an horror it need too much focusing space)

This one is the one I keep after all test.

Its better to test by yourself. Juste take measur of your original lens go to kaidomain and choose every lens you want I buyed 10 or more for all my light and test :party:
Can you give me a picture of the lens in the host part?

I can come up with a pic soon.

I have planned to adjust the focus range for the lense I have now. If you look and the photo above you will see that I lowered the led about 1.75mm down into the pill. I am planning on both filing down the top rim of the pill and adding a 2mm spacer between the body and the edge of the pill that stops the head from sliding out. This will add range to both ends of the zooming range for a focus past a crisp square when extended and a nice round flood when retracted. I don’t know if I explained that well or not? I will post pics when I can. A real glass lens would be nice!

Hum great. It’s a great idea to lower the led. I wanted to do the same when I modded my little sk68. But I didn’t get the idea when I modded the light.
And a glass lens is definitely better than the plastic lens.

This is the lens. After looking at it again, I don’t think it is glued. It looks like it is held in by some punch marks. If I had another lens, I think I could get it out. I Have not yet decided for sure, but I think I will place an order for the lens you suggested.

i wonder if the lens that gave you trouble would work for me since I have extended the focal range? What do you think? I’m not sure of the differences anyway…

Yeah she’s crimped. she’s a plastic lens. You can remove it you don’t care of the plastique lens and remove the steel to put the glass lens in. (If you need to keep it in place the artic thermal adhesive can help you or every epoxy or resin.
If I remember i’ve measured the focal of the ‘bad’ lens (bad for me) to 3.3cm from led to the lens.
To be sure buy the two lens.
Do you measured the max lens diameter?

Edit:After little reflexion I didn’t recommend you the ‘bad’ lens. Because the original focusing space is little. you got +1.75 mm with the led and some little space with the head too. But I definitely think it’s not enough. But I can be wrong. To be sur you can tested it. For less than 3 dollar. But sometime budget can be tight.

I got the light finished. It works great! It focuses just past the square shape of the die and actually gives a semi round beam that way. When in flood mode the die nearly touches the lense. it has nearly a round circle using an xml2 die. Oh ya… It gets hot fast. It measures about 3.4amps at the tail. Now I just need that glass lens:)