Soldering material, need advice.

[Serge125]

Hi all!!

    Ok need some advice on what can I buy at Amazon (can) for soldering. I used to buy it at Radio Shack but that store doesn't exist no more and I'm starting to be very low on solder. I still have some 60/40 rosin core solder left but not much and I would like to buy the same so what can I buy at Amazon that would be a good all around solder to be used on general electronics (audio, tv, etc...) and computer repair (mostly recapping ps repair). And while I'm on this subject what do you recommend for smd soldering doesn't need to be the best just an all around good and dependable solder. So any advice is welcomed and THANKS!!!

[wizard69]

First off buying from Amazon, for electronic repair supplies, is a bit silly when you have companies that specialize in this sort of material.   Have you not heard of Mouser, DigiKey, Newark and a whole host of other suppliers?   Generally Amazon is a hotbed of ripoff pricing, you are far better off on average to go with a supplier that functions in this niche.

As for general repair I tend to used 60/40 rosin core solder often aided by an external flux.   For electronics repair these days it pays to have rolls in two diameters.   A heavier gage for more traditional hook ups and the smaller diameter for fine printed circuit board work.

For surface mount devices it really depends, in some cases you will need to reflow solder paste in others you can do fine with the fine wire 60/40.   

Frankly the whole question of solder comes down to "it depends".   By the way preferences are also a factor.

[MosherIV]

Yes, go look at reputable electronics supplier like the ones mentioned.

All electronics is done with lead free solder now. It is not a good idea to mix lead and unleaded solder, it corrodes the pcb traces long term.

Best to get both 60/40 and unleaded solder.

Yes get thick  ( >1mm ) and thin (  <1mm ).

[Ian.M]

All electronics is done with lead free solder now. It is not a good idea to mix lead and unleaded solder, it corrodes the pcb traces long term.

WTF???  Please explain how mixing Sn60/Pb40 or Sn63/Pb37 lead containing solder with lead-free solder which is usually >96% Sn (tin). alloyed with copper, silver or other metals can cause PCB corrosion.

Sn/Pb solders tolerate a significant variation from their nominal composition without major adverse effects and both copper and silver have been used as components of Sn/Pb solder alloys so the chances of a small remaining quantity of Pb-free solder on a joint mixed with many times its volume of new Sn/Pb solder causing a bad joint are negligible.

OTOH Pb at concentrations as low as 1% can result in joint failure of many Pb-free alloys (see https://www.bomir.com/downloads/aim/Lead_Contamination_in_Lead-Free_Electronics_Assembly.pdf ) so even 'touching up' a Pb-free joint with a bit that has just come from a Sn/Pb joint can cause failure.  Therefore a Sn/Pb joint on an otherwise Pb-free board is a booby trap waiting for any future repair worker, and if you intend to repair modern Pb-free electronics, even setting aside ROHS legal issues, you should still use Pb-free solder. 

Also, the fluxes use for lead free soldering can be more aggressive and can cause corrosion problems, especially if the board has been manually soldered. if their residue is not cleaned off well enough afterwards, but that's always been a problem even with fluxes intended for Sn/Pb if you choose a high activity flux.

[Doctorandus_P]

Thank you Ian, I wanted to post a similar response the "corroding" thing is nonsense.
I did want to post that a little bit of lead contamination can give a 90% strength reduction in the solder joint, but did not have a rearl reference. The document you linked from bomir does confirm this though, and is therefore a much better post than I could have done.

So the conclusion is:
Use leaded solder for repair if there is any doubt about the product's solder joints containing lead or not, and clean off most of the old solder (as usual anyways). Very small quantities of lead are very bad for the solder joints, but in normal leaded concentrations, a bit more or less lead does not matter.

When RoHS first started I was all in of the lead-free solder when it came available. I don't like lead, it killed the Romans. The stuff was however very difficult to work with (this was solder from Stannol, and before  cheap china) Then I abandoned it and went back to leaded solder for everything. (As a hobbyist I do not solder much)

Small tip:
When you have an empty spool of solder wick, do not throw them away, but fill them with regular solder wire.
This is by far the most convenient way for using small amounts of solder. Just try it. It's the best method I know in my 35 years of soldering.

[Ian.M]

If you use Sn/Pb solder for repair of a ROHS or questionable ROHS status board, *DO* *NOT* even touch with the bit any joints that you don't have to, and if you rework a joint suck off the old solder first.  Don't allow such boards to leave your ownership. Flag joints reworked with Sn/Pb with a red marker pen so you don't form a trap for yourself. 

Personally I keep a small quantity of SAC305 solder for Pb-free rework, so I can legally give away or resell repaired items and charge for repair.  If you cant keep separate bits, (or better, as the pros do, have separate solder stations and work areas)  for Sn/Pb and Pb-free rework, as a DIYer, wipe your bit thoroughly and re-tin with Pb-free solder *THREE* times if going from Sn/Pb to Pb-free to reduce trace Pb contamination on your bit below the 0.1% limit mandated by ROHS.