On low melt solder - Page 1
Forum section: electronics / projects

author: Haenk
author_rank: Super Contributor
timestamp: October 12, 2025, 09:11:26 pm
content: Just randomly found this excellent article about low melt solder:https://www.sciencedirect.com/science/article/pii/S259004982030062X

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: October 12, 2025, 09:22:14 pm
content: Interesting article, though I can't claim to have read and understood every word. We spend a lot of time where I work investigating solder alloys suitable for the very thin and fragile electrodes on PZT elements. There is no perfect solution as yet, that keeps temperature reasonably low, isn't so low as to prevent sterilization in a medical environment and doesn't dissolve the electrode. Wikipedia has a nice list of most known alloys and when you remove leaded solders, there's a distinct no man's land of temperature with almost no usable alloys available. I do think lead wasn't as big an issue as was made of it, especially if recycling is enforced, and it should be allowed for some applications where temperature, reliability and tin whiskers are of concern.

author: TimFox
author_rank: Super Contributor
timestamp: October 12, 2025, 11:37:25 pm
content: If I remember correctly, one of the first exceptions to Pb-free solder requirements was cardiac pacemakers, which are implanted in the body but must be reliable.

author: Haenk
author_rank: Super Contributor
timestamp: October 13, 2025, 06:37:04 am
content: Quote from: TimFox on October 12, 2025, 11:37:25 pmI think medical, military and avionics were/are exempt.But honestly the leaded fuel was *way* worse than discarded leaded electronics. In most cases, the lead passivates and stays intact for decades or centuries.

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: October 13, 2025, 08:07:37 am
content: Hi Haenk,have you ever heard of "Eutektikum"?Melts at 79°C and is ROHS.Scroll down a bit:https://amplifier.cd/Technische_Berichte/Real-Time-Clock-Ersatzakku/Real-Time-Clock-Ersatzakku.htmlExcellent website by the way....Best regards

author: jpanhalt
author_rank: Super Contributor
timestamp: October 13, 2025, 09:11:00 am
content: Quote from: Conrad Hoffman on October 12, 2025, 09:22:14 pmIsn't reliability always a concern? Would you knowingly buy any device marked "function cannot be guaranteed," if you had an option? Cell phones today are the lifeline of many people as are the cars we drive. Should either be allowed to be disabled because of unreliable soldering?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: October 13, 2025, 09:44:02 am
content: Quote from: Roehrenonkel on October 13, 2025, 08:07:37 amThat would not be compatible with "sterilization temperatures".Quote from: Conrad Hoffman on October 12, 2025, 09:22:14 pmPZT, is that this stuff:https://en.wikipedia.org/wiki/Lead_zirconate_titanateMaking a fuss about a leaded soldering alloy to solder lead containing materials is an exercise in bureaucracy.

author: Haenk
author_rank: Super Contributor
timestamp: October 13, 2025, 02:15:53 pm
content: Quote from: Roehrenonkel on October 13, 2025, 08:07:37 am

author: jpanhalt
author_rank: Super Contributor
timestamp: October 13, 2025, 02:56:33 pm
content: If you are bonding only a few things, have you considered using a nanoparticle pure silver ink (recipe attached) as a glue? The ACS decided to make the abstract useless, thus my version of the method as described is attached. It's supposed to be solderable and conduct almost as well as silver. It is a modification of the very old Tollens reagent that was (maybe still is) used to silver mirrors. As an aside, it sticks to glass really well. We used to do it as a practical joke on an occasional colleague in school. The only practical way to remove it is chemical.I have not kept track of its commercial uses, but suspect once cured, it would be stable to quite high temperatures.

author: moffy
author_rank: Super Contributor
timestamp: October 13, 2025, 10:48:55 pm
content: Quote from: jpanhalt on October 13, 2025, 02:56:33 pmWhen working on laser gyroscopes, which have a spoked wheel at the centre with PZT elements epoxied to the spokes, we used a silver loaded epoxy/glue for the electrical connections to the PZT. The PZTs had a silver layer already coated top and bottom.

author: Stray Electron
author_rank: Super Contributor
timestamp: October 14, 2025, 12:33:42 am
content: We used silver loaded epoxy made by Traybond to attach an M100 micro detonator to the steel rupture diaphragm used in the prototype cold gas infiltrators for air bags. The micro dets are tiny and only have one lead and the case is used for the return side so we had to find a way to attach them that was conductive and that wouldn't block the gas flow yet we couldn't solder to them. Silver loaded epoxy worked fine and as far as I know, that's what the auto manufacturers and others who use that system still use to today. The patent for that is online but I don't remember if it talks about the epoxy or not.That was about 25 years ago and I don't know if Traybond is still around or not but the epoxy that we used was one of their standard products and was used to attach chip LEDS to circuit boards.