Most reliable solder type? - Page 1
Forum section: electronics / projects

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: August 12, 2022, 11:13:42 am
content: What would be the most reliable solder, one that will take the longest to deteriorate and crack?and also with flux, I saw that some solders are "glow core" and don't need the flux to be cleaned, but do different types of flux lead to faster deterioration of the solder?and why isn't 63/37 the most popular solder type? rather than 60/40?

author: mariush
author_rank: Super Contributor
timestamp: August 12, 2022, 11:57:38 am
content: 63/37 is euctetic, 60/40 isn't. Euctetic means solder transitions between liquid and solid almost in an instant.63/37 is better as it "snaps" to solid state at an instant when 183c is reached, but 60/40 stays semi-liquid / liquid for a longer temperature range (around 180c) making it easier for beginners or people with low quality irons.63/37 is often recommended to be used in environments where there's lots of vibrations or other noise or issues that could affect how the joint solidified. For example, on a ship where the ship engines vibrate all the time you wouldn't want a tall capacitor's leads to vibrate and move around while the solder becomes solid, that can result in a weak/bad solder joint .. with 63/37 you can apply solder and hold part for a second or so until solder cools down and snaps to solid.There's also other formulations which are euctetic, for example I think - from memory, but fairly sure it is euctetic - 63/36/2 Ag - they use 2% silver. The added silver helped when a lot of surface mounted components had silver in their terminals.Don't know what "glow core" means.There's rosin core flux, there's RMA flux (rosin mildly activated) which has some additives which makes the flux more active but rarely it's required to clean the flux from the board and there's RA flux (rosin activated) which is rosin with extra stuff, and depending on formula it's sometimes recommended to clean the flux off with isopropyl alcohol or other solvents because otherwise over time, the flux could still work and affect the circuit.There's no-clean fluxes which as the name says don't have to be cleaned off the board and usually leave very little residue. A lot of no-clean fluxes are as strong as rosin or RMA fluxes.Then there's organic and water soluble fluxes which you should avoid - they're stronger fluxes but the smoke is also worse for your lungs and those water soluble fluxes are not quite as easy to clean off the boards as the name says, you can't just wipe the board with a wet towel. You're supposed to be more thorough, and even use distilled water, make sure there's no flux under chips... it's a pain in the ass.Some solders have a single core of flux along the length of the wire, other solders have several cores (multicore has 5 for example) - the flux is supposed to liquify faster than the actual solder and drop on the parts you want to solder and remove/attack the oxides and corrosion on the surface of the metals, making it possible to transfer heat better and for the actual solder to form a chemical reaction with the pads /other solder on the leads. Liquid/gel flux on the components leads/pads that you want to solder always helps, as sometimes the flux inside the solder burns too fast or is too low amount.

author: mariush
author_rank: Super Contributor
timestamp: August 12, 2022, 01:35:13 pm
content: Tin whiskers can form no matter what, but in lead based solders the effect is much less pronouncedAs for effect of other alloys... how about you do some of your own research ... may I suggest wikipedia's page for solder alloys :https://en.wikipedia.org/wiki/Solder_alloys

author: MathWizard
author_rank: Super Contributor
timestamp: August 12, 2022, 04:17:16 pm
content: Is there much difference between thermal expansion and stress, in say a BGA done with Pb/Sn vs non-leaded ? Besides the brittleness or whatever as it ages ? How much of that is tin whisker related, and how does heat affect them ?

author: jonpaul
author_rank: Super Contributor
timestamp: August 13, 2022, 01:07:03 am
content: Leaded 63/37 Eutectic Kester rosin coreWorse: Any lead free, or 50/50, 60/40

author: Gregg
author_rank: Super Contributor
timestamp: August 14, 2022, 04:25:32 am
content: The strongest, best ductility and most reliable soft solder I have ever used is 94%Sn-6%Ag. About 50 years ago I soldered a seam on a stainless steel back splash on a wall behind the stove in a neighbor's kitchen; it is still in great shape in a fairly poor environment for solder.

author: Haenk
author_rank: Super Contributor
timestamp: August 14, 2022, 06:11:09 am
content: Good old 60/40 (or 63 eutectic) should be fine for everything. Clean the flux, even if it is "no clean". Most importantly: Avoid stress - use heatsinking against thermal stress and mechanical fixture (screws, zipties, silicone). Coat the completed board, put it in a sealed metal box with overpressured gas filling. Or pot it in.Have a read:https://nepp.nasa.gov/docuploads/06AA01BA-FC7E-4094-AE829CE371A7B05D/NASA-STD-8739.3.pdfQuote "All solder used for tinning and solder connections shall conform toANSI/J-STD-006. Flux-cored solder shall be either composition SN60 or SN63 containing fluxtypes R or RMA, or equivalent. For all soldering applications where adequate subsequent cleaningis not practical, only solder containing flux type R shall be used. Solid solders (no flux) for use insolder pots shall be of the same composition."If 60/63 is good enough for NASA operations, it shall be good enough for you