Why is 60/40 solder so popular?

MaximRecoil

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63/37 is the eutectic alloy, so why use anything else? I can only see potential disadvantages to using 60/40 (like wrinkled joints due to it taking longer to solidify) and no advantages.

63/37 is the only solder alloy we ever used at the PCB factory I used to work at (which was before the whole lead-free horseshit, thank God).
 
Didn't know it was popular. I always buy 63/37, .032", 2.2% Flux, No Clean myself...
 
I buy whatever I can get cheap... either one works fine in my hands. :D

Picked up 5 rolls of solder this weekend for 3 forum members for $10 a 1lb roll. It was all 63/37 no-clean.
 
I've never actually bought solder (except for plumbing solder) because I still have the 1 lb. roll I brought home from the PCB factory over a dozen years ago (it still solders perfectly; the flux core hasn't gone "bad" over the years like I've heard happens with some brands). The only problem is that it is .015". We didn't use a lot of .015" solder at work, which is why my supervisor let me have a roll of it. We used .025" for most stuff. So sometimes I have to twist 2 or more strands of this tiny solder together, which is a pain.

This is the stuff:

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I'd like to get a roll of the exact stuff but in .025" diameter, but I think they've changed product names around and I don't know what the equivalent is. I do know that it is perfect solder though, and I don't want to gamble on anything else. I have a friend that still works there; I need to talk to her and find out what they are using now (not counting the lead-free stuff that they are required to use on certain things).

All of my soldering stuff at home is the same as I used to use at the factory, because that is where I learned to solder in the first place, and everything worked so well (it all had to work well, because not only was it a factory, but we built PCBs for "life saving equipment", which carries extra red tape with regard to procedures):

- Metcal STSS-002 solder station
- Edsyn Soldapullt DS017LS
- Xuron Micro-Shear 170 II flush cutters
- Excelta 00-SA tweezers
- Alpha Metals SMT Core Plus solder

If anyone knows what the current Alpha Metals equivalent of that solder is I'd like to know.
 

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I don't think it is really popular, but it is available at radio shack. That is why I keep using it. It works fine, and I just grab it when I need it. I don't solder enough anymore to keep a 1 lb roll sitting around.
 
I've used both and honestly... for how little I solder I don't notice a difference. I just make shiny little volcanos on all my connections and move on. :D
 
I don't think it is really popular, but it is available at radio shack. That is why I keep using it.

In every thread on here that asks about solder, 60/40 is most often mentioned.

Also:

60/40 solder Solder that is made of 60% tin and 40% lead. 60/40 is the most commonly used type of solder for hand soldering.

63/37 solder Solder that is made of 63% tin and 37% lead. 63/37 solder is also known as eutectic solder and is often preferred because it goes directly from a solid to liquid state when melted.

http://www.toolingu.com/definition-660210-28725-60-40-solder.html

I'm wondering why "60/40 is the most commonly used type of solder for hand soldering" even though 63/37 is better. Is 63/37 more expensive than 60/40? It has more tin than 60/40, and tin is ~10 times more expensive than lead, but in a pound of solder, 63/37 only has about half an ounce more tin, which only amounts to about 30 cents at current tin prices.
 
I'd guess it's just because of cost... 60/40 is close enough to eutectic, and saves a little bit of money. Wikipedia ( http://en.wikipedia.org/wiki/Solder ) says: "Sn60Pb40 is slightly cheaper and is often used instead for cost reasons, as the melting point difference is insignificant in practice."

I personally like the silver bearing solder - Sn62Pb36Ag2... it has a slightly lower melting point than eutectic, but overall just feels nice (can't really put my finger on exactly what, but I like it). I also use a really old roll of Alpha solder with no problems... from 1986. Solders better than new Radio Shack silver bearing solder (though theirs may be from the '80s as well ;) ).

DogP
 
I'd guess it's just because of cost... 60/40 is close enough to eutectic, and saves a little bit of money. Wikipedia ( http://en.wikipedia.org/wiki/Solder ) says: "Sn60Pb40 is slightly cheaper and is often used instead for cost reasons, as the melting point difference is insignificant in practice."

I personally like the silver bearing solder - Sn62Pb36Ag2... it has a slightly lower melting point than eutectic, but overall just feels nice (can't really put my finger on exactly what, but I like it). I also use a really old roll of Alpha solder with no problems... from 1986. Solders better than new Radio Shack silver bearing solder (though theirs may be from the '80s as well ;) ).

So it is a price thing.

I've never tried Sn62Pb36Ag2 before, but I've never had any problems with the solder I used at the factory (and now use at home). It is predictable, consistent, flows and solidifies perfectly, doesn't make a mess, works perfectly with a 700°F Metcal tip (STTC-1xx), and apparently has no expiration date.

I can't remember if the normal size we used at the factory was .025" or .020" (it was definitely one of those 2; I sent an email to my friend that still works there asking about it); whatever it was, it was the perfect size for typical through-hole PCB soldering:

0.00018 sq. in. (area of 1 strand of .015" solder)

0.00035 sq. in. (area of 2 strands of .015" solder)

0.00031 sq. in. (area of 1 strand of .020" solder)

0.00049 sq. in. (area of 1 strand of .025" solder)

0.00080 sq. in. (area of 1 strand of .032" solder)

The common .032" size is way too big; that is equal to about 4.5 strands of .015" twisted together. Twisting 4 strands of .015" together is what I do for soldering flyback transformers to the board, which is a significantly heavier job than average.

On the other hand, .015" is too small for typical through-hole stuff, though it is fine for small capacitors and ICs. For more typical sized through-hole stuff I twist 2 strands together, and that is about right, and doing that is closest in size to .020", so I'm thinking .020" is what we probably used at the factory for typical through-hole (like common terminal blocks), rather than .025".

I don't see how anyone could do e.g. a capacitor kit on a typical monitor chassis with .032" solder. That stuff is so thick relative to the size of a typical monitor chassis capacitor leg and pad, that the instant you touched it to the joint it would melt enough (or more than enough) solder into it, and then you'd have to hold your iron there until it flowed down and into the joint properly; but you wouldn't be feeding fresh solder and flux while that was happening, so it would be boiling away the existing flux. That would make it tricky to get perfect joints. A proper solder joint is made by using a solder wire size that requires you to feed the wire about an inch in order to get enough in there, because this keeps fresh flux coming steadily as the heat draws the solder down and into the joint, and allows you to remove the iron and solder wire at the same time.
 
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Yep... I agree that .015 is too small for the typical through-hole stuff. I like .022, like this stuff: http://www.radioshack.com/product/index.jsp?productId=2062717 , though I typically end up using 60/40 .032 for cap kits, because I hate wasting the good stuff for such a low-tech job... but I always keep a bottle of flux handy. The .015 is really nice for hand soldering 0402s and other fine pitch SMT, when I don't feel like using paste and hot air.

DogP
 
Odd... I use .032 on almost everything. I also use liquid rosin flux and a small ball of solder on a 1/8" chisel tip to reflow even 1/2 mm pitch SMT devices and it works just fine.

For chip resistors/caps I just use a tiny tiny bit on the tip of the iron and some liquid rosin flux on the part/board to flow 'em into place.
 
Odd... I use .032 on almost everything. I also use liquid rosin flux and a small ball of solder on a 1/8" chisel tip to reflow even 1/2 mm pitch SMT devices and it works just fine.

For chip resistors/caps I just use a tiny tiny bit on the tip of the iron and some liquid rosin flux on the part/board to flow 'em into place.

Yeah, that's a different technique than what I do. I like to be able to feed (about an inch of feed) flux core solder into a joint and pull away the iron and solder wire at the same time; and to do that, you need solder wire size that is roughly matched to the job. I don't even have separate flux on hand, nor have I ever used it before (aside from soldering copper water pipes, which is a type of flux you wouldn't want to use on PCBs anyway).
 
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