For manual reflow we strongly suggest Pb63Sn37 solder paste. Poorer wetting of leadfree solder paste requires precise dispensing and LEDs placement.
The ultra thin solder mask/solder resist is somewhat fragile, especially in hot temperature during reflow process. Avoid any hard and sharp objects on it.
Solder mask is rated to survive multiple reflows up to 300°C only for a brief moment (< 30 seconds). Prolonged high temperature exposure above 240°C will make it less white while still functional
Soldering LED wire can be difficult because the board is very thermally conductive.
Fixes: Use more powerful solder iron with as big as possible tip, pre-heat the base (or the case/host), use intermediate wire (solder a short slave wire to the pad first).
Note: I successfuly solder all the boards using 30 watt solder iron with board temperature of 150C or...
200 watt solder iron at base temp of 100C. I use cheap Dekko 30 - 200 watt iron with big pointy (blunt) tip. My more expensive 20 - 130 watt Hakko Presto is too weak after I modified it to finer tip.
Just to add to the soldering discussion:
For soldering wires to the MCPCB pads, I use a faulty 60W soldering iron.
It doesn’t stop heating, keeps going hotter and hotter, until it glows dark red (you can see it when you turn the lights off). When you then touch some solder wire, the solder evaporates or something, at least it’s not on the soldering tip.
But holding the tip on the mcpcb, and then adding solder works perfectly, like working on a normal pcb.
Thanks for clarifying. I also notice the 3 steps Macadam Optisolis adheres closer to the BBL than earlier Nichias.
As a side note: looks like the Optisolis use two different blue pumps (or violet), 420nm for CW and 440nm for WW
I received my sm203 E21A today and immediately put it in an S2+, together with a 4x7135 biscotti driver. The reflow went well and soldering the wires was hard (as expected), I had to hold my 60W soldering iron on the pcb until the whole pill heated up.
The tint is not as orange as I thought it would be, but it is the warmest I’ve seen yet from a led and it’s very easy on the eyes, I think this will be my bedside lamp from now on. The beam shape with an orange peel reflector is pretty good.
Some pics (tint is warmer in reality):
Spent an hour playing with the 3k, 4k and 5k e21s. Somehow the soldering just went easily this time.
Now I can say that the funny patterns of tint shift I reported earlier were not real. Each cct has very visible tint shift. On the other hand, it is much less of a problem to me as compared to that of 219b 9080. First, the shift is from neutral to green rather than from rosy to green, and this is much less annoying. Second, the green rim starts developing considerably farther from axis, so it would be better cut off in a mule head.
Overall, I am very pleased with the 3k and 5k, not that much withthe 4k but I think this is just me. I just prefer either incand like or true daylight tints.
Will be ordering the 6.5k and 2k versions right after I got the incoming drivers and finalize the host.
Clemence, thanks much again for making these leds and the boards available!