Can someone share their experience with solder?

At my local electronics, I see 97% Sn (very expensive), 63/37, 60/40, etc.

I presume that we are talking about the ratio of Tin to Lead. But what are the practical differences that I, as a consumer, would notice? I am tempted to just get the cheapest solder but don't mind paying a little more if there are observable differences. Thanks.

 

There are lots of resources on the web to answer your question. Major solder makers such as Kester come to mind. There have also been several threads on this and other fora discussing your topic.

 

I prefer Sn63/Pb37. It's eutectic; which means that it has no "plastic" state.

 

I prefer Sn63/Pb37. It's eutectic; which means that it has no "plastic" state.

"plastic" state? I've always just bought solder and looking at what I have left, it's 60/40 and worked well. Truth is I haven't bought solder since the 1lb. rolls I used lasts like forever but now that I'm out shopping, I'm a little overwhelmed by all the choices which I don't recall seeing in the past.

 

60/40 works well for electronics, too. I simply prefer 63/37.

When most other solder alloys are cooled from a liquid to a solid, they go through a semi-liquid state that's sort of like a plastic. If you move the solder when it's in that plastic state, the resulting solder joint will be physically weak and high in resistance.
The 63/37 doesn't have that plastic state; it goes directly from liquid to solid.

 

I see. I do notice that semi-solid cooling period you speak of. So is the 63/37 solder completely immune to that? Because I imagine the actual temperature during the soldering process will be somewhat higher than the actual melting temperature of the solder. So it will still require a cooling period before solidifying anyhow, correct?

 

I see. I do notice that semi-solid cooling period you speak of. So is the 63/37 solder completely immune to that?

If you are soldering new components to a new board or other new components where old solder isn't present to contaminate the alloy, then Sn63/Pb37 won't have a plastic state. Can we just go forward with that premise?

Because I imagine the actual temperature during the soldering process will be somewhat higher than the actual melting temperature of the solder. So it will still require a cooling period before solidifying anyhow, correct?

You want to heat the component rapidly, apply just enough solder to make the joint, and let it cool immediately. You don't want to let the parts get hotter for longer than necessary.

If the solder stays liquid for awhile, you're getting things too hot.

Sn63/Pb37 has a relatively low melting point. Sn96 is a good bit higher. I don't have the numbers offhand.

 

I like 63/37 because it has the lowest melting point and is easiest to work with. Tin/lead is the best electronics solder, but is limited in use due to RoHS. However, for personal use, you still have the option. Hopefully that isn't going to change soon. I have a an extra pound of 63/37 stored away just in case.

The type of flux core is also a big consideration. There's a bunch different ones. I use a mildly activated rosin core with an active liquid rosin dispensed from a flux pen to supplement as required. There are no-clean fluxes and water soluable fluxes, but I don't mind cleaning so the rosin is fine for me.

My favorite electronics solder is Kester part number 24-6337-9703. The stuff is crazy expensive now. It's more than doubled in price since the last time I bought it. Wonder what's up with that? RoHS maybe?

 

Solder containing lead is being discontinued in some regions because of concerns about toxicity. Unfortunately, as well as performance issues during initial application, tin coatings have been associated in the past with long-term reliability problems due to slowly growing tin "whiskers" causing short-circuits.

I do not know how well these problems have been addressed with the present crop of "lead-free" solders - time will tell.

 

My understanding is the whiskering has been reduced to a tolerable level with modern lead free solders. The big down side with those is they are much harder to work with by hand due to the higher melting point. It's a lot higher.

They still use tin/lead solder in assemblies for aerospace (like satellites) because of the concern over whiskering. For consumer stuff, it's not as big of a concern.

 

It's a pretty big deal when a satellite fails due to whiskers. It's also a big deal when fighter aircraft stop working due to whiskers. This started happening to the F-15 program in the mid-80's. They went back to tin/lead, and the problem went away.

 

62%Sn/36%Pb/2%Ag is the best.

 

62%Sn/36%Pb/2%Ag is the best.

Please explain.

 

It melts real nice and it's shiny and strong. It's the prettiest solder I've ever used.

Oh yeah, it also doesn't leach silver from component leads. Did I mention how pretty and shiny it is?

That RoHS (Reduction of Human Satisfaction) stuff looks like gray mud and takes hellfire to melt. You can lick your fingers while using it and hold it in your teeth but your lungs will fall out since the fluxes you have to use with it are so nasty.

 

Never saw that formulation at my local electronics shop. Must be hard to find.

 

There are many diferent tipes of soldering wire. The difrence mostly consist in the melting temperature. Lead has a lower melting temperature then Sn so the more lead the quicker it melts. But some people choose soldering wire with less lead because it's healthier.

 

One of the easiest to use is Chip Quik, low temp solder 63sn/37pb paste. I use three types of solder here. SMD gets Chip Quik most of the time since its easy to put a dab on the board and use hot air.

I use core 60/40 in two different sizes. Flux in paste and liquid form.

 

I worked on a MIL-Aerospace power supply we had to use high temp solder to keep parts from sliding off.

 

62%Sn/36%Pb/2%Ag is the best.

I have several syringes of this stuff and it is most excellent.