How to demonstrate leaded verses lead-free microsoldering performance? - Page 1
Forum section: electronics / general

author: lukego
author_rank: Frequent Contributor
timestamp: September 17, 2020, 12:22:38 pm
content: I would like to experience first hand the major differences between leaded and lead-free solder alloy performance in my domain of interest, which is micro-soldering motherboard/PCIe/laptop/phone type of devices. I'm always working in the presence of a preheater and good tacky flux.Can someone suggest a benchmark that would clearly demonstrate the relative strengths and weaknesses of one alloy over another?So far I have tried soldering 01005 parts and I found that both 63/37 and SAC305 seemed to perform fine, despite my own clumsiness and lack of more suitable pads to practice on. This was not a completely scientific test, having used a preheater and slightly different flux variant and quantity with SAC305, but it really feels like both alloys perform quite well and my only real limitation is dexterity.Leaded (no preheater, modest amount of flux):Lead-free (board preheated to 100C, plenty of flux):So if ad-hoc soldering of 01005's doesn't clearly demonstrate the superiority of one alloy over another, what else might? Or am I simply overlooking important differences illustrated in the videos?(Separately I'd also be interested in any serious empirical studies of relative failure rates of SnPb vs RoHS and their relative contributions to soldering iron tip lifetime, but that might be a question for another thread!)

author: thm_w
author_rank: Super Contributor
timestamp: September 17, 2020, 09:10:55 pm
content: I am heavily biased, but from those videos you seem to have more problems soldering with SAC305, where multiple touches of the iron of required.Of course this is not conclusive that one is better or worse though.Try adding some fine pin pitch parts like TSSOP, etc.What temperature was used in both cases?

author: lukego
author_rank: Frequent Contributor
timestamp: September 18, 2020, 11:47:14 am
content: Quote from: thm_w on September 17, 2020, 09:10:55 pmI suppose this scant data can at least be used for generating hypotheses that would then need to be tested later (e.g. one wets better than the other), or to disprove really extreme hypotheses (e.g. "it's not possible to solder 01005 with SAC305.")Temp here was cold board and 280C iron for SnPb verses 100C board and 350C iron for SAC305. So the leaded was on the cold side and lead-free on the hot side. The reason for the wildly different choices is that I'm just feeling around for what works best for me in terms of tools/alloys/temps and I am still early in that process (n00b.)Quote from: thm_w on September 17, 2020, 09:10:55 pmI have done three more exercises now.I soldered a QFP with ~0.6mm pitch using SAC305. That was a really pleasant experience from beginning to end with good results. Subjectively it felt similar to my experience of 63/37. (Sorry, no video of that one.)I made a ham-fisted attempt to A/B compare 63/37 and SAC305 on separate quadrants of a significantly larger QFP. I made a total mess of both, partly due to choosing the wrong tips for such a large part, partly perhaps my soldering beginners' luck wearing off. I made a video that I haven't edited but could be scrubbed through:https://youtu.be/j4WVN0HAKSoI then reworked that same messy chip with SAC305 and a better-suited tip. Just added LOTS of solder to dilute out the SnPb and tried to drag the solder blobs to the sides where I could suck them up. I did struggle with removing bridges and it's possible (hypothesis) that SAC305 was a contributing factor. Sorry, unedited video again:https://youtu.be/jOhPbCtoYeYHere's one short highlight from the previous video of having fun playing with SAC305. It seems nice and playful in Amtech flux:I'm not sure how far to pursue this now. My root problem is deciding whether to use SnPb or SAC305 for my own microsoldering that will be mostly assembling prototypes of e.g. PCIe cards. I have started with SnPb for fear that lead-free would be too frustrating and deter me from learning soldering at all. Currently though it seems like I could pick either one and successfully assemble my prototypes.SAC305 is then attractive because I'd be able to sell my boards here in Europe (RoHS), I wouldn't have to worry about so much about contamination (using solder paste in a home office that my young kids can visit), and my techniques would transfer onto all the random electronics that I encounter e.g. laptops, phones, soldering stations, etc.One further observation: I find that solder bridges stick out like a sore thumb with SAC305 because of the strong diffuse reflection. With SnPb I'm sometimes in doubt about whether I'm seeing a bridge or just wet flux in the shadow between pins because both produces mostly direct reflections. Sorry that I don't have a reference image for this at the moment, I know that would be more in keeping with the empirical theme here, so let's call that a hypothesis. This would be an advantage for SAC305 because I wouldn't even mind making a few extra mistakes if I were more confident that I would catch them earlier.

author: SerieZ
author_rank: Regular Contributor
timestamp: September 18, 2020, 01:14:10 pm
content: Have you tried a soldering Iron with a Soldering Depot tip?When you get the hang with it it is like magic.

author: tooki
author_rank: Super Contributor
timestamp: September 18, 2020, 03:04:40 pm
content: Quote from: lukego on September 17, 2020, 12:22:38 pmI think what you managed to prove is that a) flux is good, and b) lead-free solder isn’t the horror some people make it out to be. Yes, leaded flows better. And yes, especially in very large joints that suck away heat, leaded is a bit easier to work with. But lead-free does work, and in small joints its higher melting point is not noticeable.

author: lukego
author_rank: Frequent Contributor
timestamp: September 19, 2020, 05:25:01 am
content: Quote from: tooki on September 18, 2020, 03:04:40 pmSurely I'm missing some important details here though?Louis Rossmann for example works all day long with lead-free Macbooks but still takes the trouble to dilute out all the lead-free solder and replace it with leaded at the points where he is doing rework. He's a results-oriented guy who doesn't follow the crowd and that seems like a significant hassle that he's undertaking. So what's the payoff? Maybe the difference between alloys is more pronounced on Macbook motherboards due to greater thermal mass of ground planes compared with my test boards? That would be one testable hypothesis.One other hypothesis is that low-power tools like JBC nano irons may be less useful on lead-free boards because they won't produce enough heat for (say) 0804 or 0603 parts which they could handle on leaded boards. That's also a testable hypothesis.One variable is the use of a preheater. I used to see preheater as a last resort because I had a big and clunky one. I have a little Hakko FR-830 now though and I'm happy to use that all the time. I start my sessions by giving the board and ultrasonic bath and then drying it on the preheater. Then it's ready for action: the preheater is right underneath the microscope. So maybe my willingness to work with a preheater masks some potential weaknesses of lead-free alloys.

author: lukego
author_rank: Frequent Contributor
timestamp: September 19, 2020, 04:28:18 pm
content: PLOT TWIST!Here is a demonstration of where lead-free is miserable on a peculiar use case that happens to be important to me, reworking bypass capacitors under large FPGAs using 7W JBC AN115-A nano tweezers:The nano tweezers are really struggling and failing to reflow the solder here, even with the PCB preheater cranked up pretty high. There's no way they can cope with the larger parts like 0603 and 0804. And this is while using the broad chisel tips rather than my preferred ultra-fine 0.1mm conicals.I tried diluting this solder with 63/37 and then everything flowed like butter, even the large caps on the left, even with my finest tips. (Sorry, haven't made a video clip of that.)So... maybe this lead-free solder really is horrible muck for the applications that I care about?!?!(I'm planning to mostly hand-solder prototype FPGA boards for in-house development. I would like to be able to turn those into products to sell but that's much further down the line and may well involve contracting out the assembly. From this perspective at the moment it now suddenly seems like a no-brainer to switch back to leaded solder if that means I can do a lot more work using the gorgeous nano tools.)

author: lukego
author_rank: Frequent Contributor
timestamp: September 19, 2020, 07:18:38 pm
content: Here's how smooth and slippery it gets once I add some leaded solder to dilute the lead-free, even after switching to much finer tips (iron still at 350C as before though):I'll need to re-test to control for the amount of solder, e.g. whether the leaded was benefiting from more solder improving heat transfer from the iron, to see if that levels the playing field. Anything else to consider?

author: lukego
author_rank: Frequent Contributor
timestamp: September 20, 2020, 10:19:12 am
content: I experimented a little more on that same board and the results tend to confirm what the last couple of videos showed. I tested with more and less solder and flux but that didn't seem to make much difference.Cold board and lead-free: Can't rework anything at all here with the nano tweezers and sharp tips.Cold board and leaded: Can rework the 0402s okay but not the larger parts.Heated board with lead-free: Can sort-of rework 0402 but it's a struggle.Heated board with leaded: Can easily rework all the parts with the nano tweezers and sharp tips.So in summary I'd say that it's pretty miserable trying to rework small parts connected to power/ground using nano tweezers, even with good flux and a preheater. In contrast, it's perfectly heavenly to do the same work with the same tools with leaded solder.I think that I'll end my flirtation with lead-free solder here and return to 63/37 for the sake of bringing more enjoyment to the time I spend hand soldering, which is currently my favorite hobby.

author: lukego
author_rank: Frequent Contributor
timestamp: September 20, 2020, 01:53:13 pm
content: Maybe not so fast...I'm also experimenting a little more with slightly larger tweezers (14W vs 7W) and thinking about how high I dare to bring up the temperature on the irons (I've maxed at 350C but induction irons from Metcal/Hakko would run at 400C+.)Overall it seems reasonable to say that the main difference between leaded and lead-free is what tool is appropriate for each job. For example what you do with fine hot tweezers on leaded solder may require a couple of proper irons with lead-free. This will depend on the board you are working on (e.g. its thermal mass) and on the specific part (e.g. whether it is connected to power/ground planes.)

author: lukego
author_rank: Frequent Contributor
timestamp: September 20, 2020, 03:14:38 pm
content: 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?

author: lukego
author_rank: Frequent Contributor
timestamp: September 21, 2020, 04:54:12 am
content: Quote from: lukego on September 20, 2020, 01:53:13 pmI 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.

author: exe
author_rank: Unknown
timestamp: September 21, 2020, 08:14:08 am
content: 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).

author: lukego
author_rank: Frequent Contributor
timestamp: September 21, 2020, 10:39:36 am
content: Quote from: exe on September 21, 2020, 08:14:08 amThere 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...

author: lukego
author_rank: Frequent Contributor
timestamp: September 21, 2020, 05:59:42 pm
content: 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.

author: SerieZ
author_rank: Regular Contributor
timestamp: September 22, 2020, 01:10:00 pm
content: Almost everything produced this day (at least in Europe) is done without Pb.Even Military Applications are slowly but steadily switching to Pb Free.I myself have only soldered like 1 or 2 Boards with Pb last year.

author: lukego
author_rank: Frequent Contributor
timestamp: September 24, 2020, 06:44:21 pm
content: Follow up: I had been disappointed in the way my SAC305 solder flowed and especially the way it clumped up while tinning tips. I had wrongly attributed this to the surface tension of the alloy but it was in fact due to poor wetting properties of the flux core.Specifically I had bad results with ChipQuik SAC305 with "No Clean Water Washable" flux core (and several no-name Chinese solder wires.)I have now switched to ChipQuik and Multicore SAC305 solder wire with RA flux core and the performance is much better, comparable to Kester 44 in my opinion so far.So now I'm able to properly tin my tips with lead-free solder and should avoid some expensive dewetting failures of my tips.

author: exe
author_rank: Unknown
timestamp: September 24, 2020, 08:07:11 pm
content: I'd avoid any water-soluble fluxes as chances are they absorb moisture. I know it's claimed "no-clean", but I don't trust this label unless proven otherwise. That's because I haven't seen a water-soluble flux that doesn't require cleaning and doesn't conduct.In many cases "no-clean" means something else than most people think: it means flux can be left uncleanedif flux goes through the thermal profile in reflow owen. Such fluxes are not suitable for hand-soldering with an iron due to incomplete flux activation.

author: lukego
author_rank: Frequent Contributor
timestamp: September 25, 2020, 03:26:59 pm
content: Here's another demo video showing that I can still do playful hand-soldering using hot tweezers and 0402s on the "new normal" of lead-free/SAC305:I'm really happy about that because I'm experimenting with a bunch of different personal soldering techniques and I'd worried that lead-free would be more limiting but so far nope.

author: lukego
author_rank: Frequent Contributor
timestamp: September 28, 2020, 04:31:35 pm
content: Today I soldered a ground pad on a small 4 layer PCB using lead-free solder, both with an iron to deposit solder and then with hot air to reflow. It was hard work (with a preheater cranked up below too) and I'm not convinced that it actually worked out yet! This exact same chip/board is child's play with 63/37 which flows like melted butter.Definitely hard-mode with lead-free.