Can you recommend which BiSn to buy?
Chipquik Sn42/Bi57.6/Ag0.4 is what I use.
It’s the flux fumes that get to me after an extended session. Unless I take some measure to suck them away from my work area.
Haven’t tried any lead free solder yet. The early versions were a pain to work with when re-flowing joints on motherboards.
All the Best,
Jeff
For me the cause was poor posturing, poor lighting and inadequate ventilation. I still use leaded solder but I no longer get headaches, eye strain or feel malaise after I have better lighting, a better fume ventilating/extracting and a standing magnifier help to stop the slouching.
Have you tried use this alloy on pcb drivers as button top or it blackens with false contact on the + battery like Sn60 / Pb40 ?
i find the lead free to be a pain to solder and it tends to ball up instead of wetting the surfaces. It might be okay for wave soldering on production lines, but for repair and mod work it is not as easy to use.
Did you tried low melting point lead free solder like above mentioned Sn42/Bi57.6/Ag0.4 ?
I have difficulty to find mentioned one on my market.
On my market there is only S-Sn99Cu1 whatever that means :question:
Here is a table of different alloy properties
Ag content decreases slightly the melting temperature compared to SnCu.
The issue with BiSn is that if it’s contaminated with lead the melting temperature decreases a lot, down to 95°C in the right proportion (rose’s metal) and it makes weak joints, if you plan to solder on existing joint you have to check if it’s leaded or lead free first.
I did use it to make solder blobs a button contact but I don’t trust it to keep a low contact resistance, I’ll swap with gold plated constacts as soon as I receive them.
i’ve not tried it, but it has a low melting point and that should make it easier to use as long as the flux will remove oxides and allow proper wetting.
The S-Sn99Cu1 is almost pure tin, at 99% tin and 1% copper.
I tried it a while ago, and maybe I got cheap stuff, but I hated it. I tried some quality 60/40sn/pb and never went back. Now I only use 63/17 Kester 44. The lead-free melted too hot, does’t flow well, and the joints oxidized too fast. The high melting temperature was the main issue. My smaller pieces got heated too hot for my liking to get good joints and wetting. I’m sure there are really expensive brands of lead-free (I hear some places are banning leaded sder) that work great, but I’m stuck on the leaded stuff. Just use it in a well ventilated area and wash your hands after use.
My preferred solder is Mechanic’s Solder paste.
It has lead in it, but it’s very easy to work with. Much better than Chipquik.
Hello my fellow nsolder freaks. In manufacturing you must (?) be lead free. Those of us occasional users still have leaded solder. suck the fumes away! it is the flux. Not sure if any lead is in the flux fumes, we melt the solder, not vaporize it.
I prefer to use solder with some silver in it. It works a lot better for me. Leaded or lead free.
There is a thread where Led4Power said that he uses lead free solder for everything he does and that it has better properties than leaded we mostly use here.
I think someone could do solder joint tests for our flashlight modding purpose: Lead vs Lead free solder strength test… Someone like Djozz with “touch” for doing experiments. 
Sounds good for a test. Way back, I wound two solenoids (springs) from solder, leaded and silver tin lead. Pulling the leaded solder, it stayed pulled, no strength. The silver / lead / tin “spring” had resilancey, it went most of the way back to original. I also find it to tack better. And someone may comment, don’t use the solder to hold the connection, it needs to be mechanically attached first. This goes back to chassis wiring, point to point. Now surface mount, it is the mechanical attachment also. Will be interested in the test results.
Not a test, per se, but some of those pertinent qualities are listed here: [Reference] Physical and Mechanical Properties of Solder Alloys
I’m in agreement about source of irritation being the flux rather than the lead. Active fume reduction/movement is pretty much standard at pro benches and you can get decent cheaper units these days for $45 to $80 without going all in on a commercial unit ($$:money_mouth_face:. It’s been a long time since I’ve done enough soldering for a length of time to really bother me, but it used to get me a little with sinuses and a headache…most of that was acid core and non-electronics rosin core, though.
It also has terrible thermal conductivity which may be an issue for LEDs. That’s why Clemence uses indium for his low temp Nichia reflows.
[Reference] Physical and Mechanical Properties of Solder Alloys :+1: , although not all are listed here for example the one I use is Sn60Pb39Cu1 which could be similar to Sn60Pb40 which has melting point 183 / 191 °C, solidus / liquidus and 535 kgf/cm² of Tensile Strength at Break which is one of the best from the table.
Also the one that thefreeman mentioned Sn42/Bi57.6/Ag0.4 could be similar to Bi58Sn42 from mentioned table which has lower melting point 138 / 138 °C solidus / liquidus and 565 kgf/cm² Tensile Strength at Break which seems like the best properties for our modding job if we look the table - very low melting point and excellent tensile strength! But lower thermal conductivity…
The question is: Should we use Bi58Sn42 instead Sn60Pb40? Bi58 has very bad thermal conductivity at 19 W/m⋅K while Sn60 has 49!
So real question: Is thermal conductivity more important than lower melting point and Tensile strength properties? If that is not so important than Bi58Sn42 is winner here?!
Yes. This certainly is an issue if we repair over existing setup but it should not be an issue if we do build from scratch?
True but he uses BiSn for the wires IIRC, his MCPCB are so good that when using high temp solder for the wires, or even SnPb, it can reflow the indium. I also use indium for the non DTP LEDs but I’m not sure it matters that much vs SnPb or SAC.
It shouldn’t, all the drivers I’ve made where soldered with BiSnAg (paste and wire)
Shouldn’t matter for things that don’t produce a lot of heat.
I do need to check if it has an effect on dc/dc regulators with integrated switches on my drivers, which also produce heat (not as much as an LED), on one of my driver the regulator I used went into thermal protection at high current, I’ll need to test if it does the same with SnPB or SAC. (It’s possible it was also inadequate thermal design).
There are many lead free solder alloys. I don't know what Led4Power uses but, in my experience, Sn99.3Cu0.7 just sucks.
Sn63Pb37 has always been the golden standard for electronics work, and for me it continues to be so. Right now I am using Sn60Pb40 I got from AliExpress, which is veery close but not quite.
I currently find little to no reason to do away with leaded solders, at least for our usage. As far as I know it all started with RoHS, which excluded :!!!: batteries; so at least in this respect I don't give a damn about it.
Concerning the above solders, no one noticed Sn91Zn09? Its resistance is lower than that of Sn63Pb37 or Sn60Pb40, so higher conductance, while its thermal conductivity is also better (22%/24.49% higher). It also is a good alloy for soldering over aluminium, according to this Kester's 2600 aluminum soldering flux document.
Solder alloys @ Wikipedia adds the following information about Sn91Zn09:
KappAloy9 Designed specifically for Aluminum-to-Aluminum and Aluminum-to-Copper soldering. It has good corrosion resistance and tensile strength. Lies between soft solder and silver brazing alloys, thereby avoiding damage to critical electronics and substrate deformation and segregation. Best solder for Aluminum wire to Copper busses or Copper wire to Aluminum busses or contacts.[54] UNS#: L91090
I'm using Stannol Sn95Ag4Cu1 0.8mm wire (Manuf. nr: 593410), silver makes a lot of difference, and this alloy has 4% of it. 100gr spool can last for years, so it's a very bad idea trying to save some money on solder wire/paste.
Avoid any kind of cheap no-name junk from Aliexpress etc., most of them have no silver (even if they claim they do), and contain so much impurities/junk that soldering is not possible.