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How to demonstrate leaded verses lead-free microsoldering performance?
lukego:
The JBC "precision" tweezers don't perform that much differently than the JBC "nano" tweezers.
This makes sense in hindsight. The nano tweezers are ~15W per tip while the precision tweezers at ~20W per tip. So only 33% more power and in practice still mostly limited by the heat transfer to the joint (showing only ~50% load when using the tips that I like.) I had been under the mistaken impression that the difference was larger (14W vs 7W) but I don't know where I got that idea from.
This means that despite having a whole desk full of soldering tools I'll have a bit of a struggle to find a suitable tool for soldering bypass caps on dense boards using lead-free solder. The 20W tweezers will probably get the job done but I'll need the bigger tips that will be harder to maneuver between dense placements.
That's crazy! I reckon it'll be leaded solder on those kinds of boards for me. I'll have to decide whether to use lead-free for hand-soldering smaller boards or only for production work (in the future, likely done with paste in a reflow oven or contracted out.)
EDIT: I am actually not sure of the power of each JBC tool. They don't write it on the tin and I am seeing conflicting messages on sellers' pages. Anybody know for sure what the power draw is on precision and nano irons and tweezers?
lukego:
--- Quote from: lukego on September 20, 2020, 01:53:13 pm ---Overall it seems reasonable to say that the main difference between leaded and lead-free is what tool is appropriate for each job.
--- End quote ---
I realize that I'm talking to myself like a crazy person here but I think that ^^^ is the summary. Leaded and lead-free both work but lead-free is much more challenging with small parts connected to power/ground on boards with high thermal mass. The rework I'm describing as "a struggle" can surely be done with more practice and careful selection of tips and working angles that maximize heat transfer. On the nano tweezers my comfortable working style with sharp tips only gets the iron up to 50% power delivery which is not sufficient for this work, while working with larger chisel tips coming over the top gets the job done with about 70% power delivery.
So the difference in my eyes is that with leaded solder on a preheated board I can pretty much get anything done using 0.1mm tips and free choice of working angle, while with lead-free solder I need to be much more deliberate about restricting myself to a narrower range of applicable tips and angles of attack. I think in this context that working leaded and lead-free are two different skill-sets and I'll probably develop both of them separately, leaded for assembling my own prototypes, lead-free for things going out into the world.
The people on the forum who recommend throwing lead-free solder out the window and sticking with leaded are talking sense in my opinion! :-+
I'm not sure that I want to touch leaded solder paste though... that's a heck of a contamination risk with those tiny little spheres... but that's another tipic.
exe:
In my experience the difference between leaded and lead-free solder is quite noticeable. Lead-free is harder to handle, flows worse, and requires higher temperatures. A good flux helps a lot with lead-free. Soldering ground planes and large parts with it is challenging with equipment I have (I don't have bottom heating).
lukego:
--- Quote from: exe on September 21, 2020, 08:14:08 am ---In my experience the difference between leaded and lead-free solder is quite noticeable. Lead-free is harder to handle, flows worse, and requires higher temperatures. A good flux helps a lot with lead-free. Soldering ground planes and large parts with it is challenging with equipment I have (I don't have bottom heating).
--- End quote ---
There are so many confounding variables to take into account, right?
On my first foray into lead-free soldering I was already using preheated PCBs, good flux, and knew to turn the iron up to 350C. I didn't notice much difference at all... until I reached small parts connected to ground/power planes on dense boards and got into trouble.
Just now I realized that there is an easy fix for that too: crank up the preheater. If the top of the board is raised from 100C to 135C then it's suddenly easy to rework all the 0402s using nano tweezers with sharp tips. Problem solved? I'll have to look at the underside of the PCB, that's now spend about fifteen minutes at ~200C, to decide that...
lukego:
Pardon my endless musing...
I've framed it differently in my mind now: leaded soldering is "easy mode" and lead-free is "hard mode." So which one do you prefer to play?
On the one hand it's tempting to take the easy path with leaded soldering because you pick up the skills faster, you don't need so much expensive gear, and you can get on with other things.
On the other hand with lead-free you have more opportunity to rise to challenges and developed tricky techniques, you have an excuse to buy professional gear and learn how to use it properly, and the soldering skills you develop will transfer directly into reworking production commercial hardware.
This perspective actually makes me want to pursue the lead-free path. I'm interested in developing soldering skills and enjoying the process of assembling boards by hand, and my excuse for spending so much time and money on this is that it will help me with e.g. fixing production problems in the future.
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