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| How to demonstrate leaded verses lead-free microsoldering performance? |
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| lukego:
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!) |
| thm_w:
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? |
| lukego:
--- Quote from: thm_w on September 17, 2020, 09:10:55 pm ---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. --- End quote --- I 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 pm ---Try adding some fine pin pitch parts like TSSOP, etc. --- End quote --- I 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/j4WVN0HAKSo I 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/jOhPbCtoYeY Here'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. |
| SerieZ:
Have you tried a soldering Iron with a Soldering Depot tip? When you get the hang with it it is like magic. ::) |
| tooki:
--- Quote from: lukego on September 17, 2020, 12:22:38 pm ---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!) --- End quote --- I 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. |
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