I have years of soldering skill, but never solder any audio equipment. For years, I bought cheapest solder that I can get and many of them are from surplus center.

My question is which type of solder wire are the best for audio application?
(alloy, diameter, gauge...)

The solder wire that I am using now have some 'yellow crystal' like amber form and it is quite annoying. It makes the PC board looks 'drity'.

Yes, I am getting the PORTA CORDA!!

The highest quality solder is supposed to be silver solder. It is more expensive than the tin/lead solder. I have never used it and don't know if there are any difficulties working with silver solder (such as maybe a higher melting point, joints that oxidize easily, etc).

In terms of ease of use and sonic quality you can't go wrong with either the Wonder Solder or Cardas Solder. They are both excellent for audio, and both are highly regarded.

FWIW: Audible Illusions uses Wonder Solder in their preamps. While Moth Audio uses Cardas in their amps.

Please note: I edited out the Radio Shack silver solder info I posted before. Why? It's not so hot.

BTW: The "quad" in the Cardas Solder refers to the use of 4 metals: Tin, lead, 2% silver, and 1% copper. However, the melting point is 190 degrees Centigrade, which is low for a silver solder.

[Edited by Gariver on 11-08-2001 at 04:34 PM.]

Cardas.com has some info on this solder...
www.cardas.com/insights/solder.html

Here's the link to Welborne's site. Please note that there's an interesting solder primer on that page. Take a look...
www.welbornelabs.com/solder.htm

Oops...I almost forgot. You will get your Welborne order right away. A Michael Percy order might take a while.

[Edited by Gariver on 11-08-2001 at 03:04 PM.]

An additional advantage is this: The rapid change from liquid to solid gives the solidified solder a finer grain. Results? This fine-grain solder joint is stronger and transmits your signals better! Thus, cold solder joints are easily avoided when you use an eutectic solder.

Standard 60%Tin/40%Lead Solder:
Goes from solid state to a pasty state, and then to a liquid state. So there's 3 steps.

Eutectic Solder:
Goes directly from solid state to liquid state. Just two quick steps.

The Bottom Line...
Eutectic Solders are more expensive. However, they are a joy to use. Plus the joints are clean and strong, usually free of cold solder joint. Results? Great sonics! Thus, you pay more for an eutectic solder, but you get more of everything with them.

BTW, Wonder Solder is not an eutectic solder. However, it's very close to being one. So it does not have too much of the dreaded pasty state. Reasons? Wonder does not contain silver. So that keeps the melting temp down a bit and makes it an easy flow solder! On the other hand, Cardas is a completely eutectic solder with a 2% silver content.

My solder pick: Cardas Quad Eutectic Solder!!! It costs $10 for a 30ft roll from Welborne Labs, but it's worth it!

[Edited by Gariver on 11-08-2001 at 07:17 PM.]

A solder defined as being eutectic does not mean that it is special in any way except that its metals composition ratio results in a near instantaneous liquid to solid transistion phase.

There are actually MANY eutectic formulations. But by far the single most commonly used is simple 63/37 tin/lead.

I fail to see how any type of solder, when a joint is properly made, can affect sonic performance; at least for those of us w/o magical golden ears.

As far as the yellow discoloration, this is indicative of a rosin based flux. Depending on the type rosin formulation used, it may or may not be good to leave on. Some rosin fluxes remain 'active' long after the joint has been formed. The flux will, over time, begin to do damage to the joint and surrounding surfaces. In the manufacturing industry, these types of rosin fluxes require removal by a water cleaning process before shipping.

The other fluxes that are almost clear are what's called 'no-clean' fluxes. Without going into the boring details, these fluxes were primarily developed as a way for the manuf. industry to get around the washing process($$).

Initially, the no-clean fluxes did not perform as well as fluxes which require washing (Organic acid and rosin based). But over the years, they've been developed to a point where they come very close in many cases.

Just FYI, fluxes are used to remove oxides from the metal surfaces prior to being soldered. Once the oxides are removed, the solder is able to 'wet' onto the metal and form a better solder joint. The analogy I always liked to use when teaching classes is the water/wax illustration. You know how water beads up on a fresh coat of wax on your car? That fresh coat of was is the equivalent to oxides. Once the wax is removed, the water flow evenly and spreads out over the paint. THIS is what you WANT when soldering. So, the flux, in a sense, removes the wax so the solder will 'flow/wet' onto the metal surfaces smoothly.

...how I do know such boring details? I am/was an expert in the field of flux/solder process methodologies. It was my job.

[Edited by ck42 on 11-09-2001 at 08:28 PM.]

Like I had said, it really depends on the actual type of rosin flux used. In some types cases, the 'left on' flux actually performs a protective type of service; almost a poor man's conformal coating.

As for alcohol solutions for cleaning....one word: NO. This is ESPECIALLY the case for the no-clean fluxes. You'll end up with a board that looks like it has a permanent white haze to it. This really starts to get into the chemistry side of things. But in short, don't use IPA or other types of alcohols. There ARE low cost cleaning solutions....I'm thinking that RadioCrack even caries something like this.

The only thing I can do is find out what the make and model is of your flux and check with the manufacturer on cleaning recommendations.

All the above info is regarding the use of flux as a separate solution, ie. liquid flux in a container and solder wire w/o flux built into it.

A LOT of solder wire has rosin core flux 'built-in' to the solder wire itself (the solder wire is hollow). If this is the case, then it makes finding out what type of flux it is even more difficult. Again, I would ask what is the make/model of the rosin core flux/solder wire and would consult with the manufacturer.

I don't mean to create any type of panic here. When I speak of joint/board damage, I'm talking in terms of years....longer term stuff which a company selling thousands of a product cares about.

So, if you're building something nice that you want to keep for a while, then it WOULD be prudent to consider this matter.

---

quote:

The Bottom Line...
Eutectic Solders are more expensive. However, they are a joy to use. Plus the joints are clean and strong, usually free of cold solder joint. Results? Great sonics! Thus, you pay more for an eutectic solder, but you get more of everything with them.

---

The kester stuff isn't expensive, i got mine for $15cdn/pound, and if i looked around i could get an even lower price from local surplus stores. As for sound, it sounds exactly the same as every other solder i've "heard" in my life...

You are right about that. 63/37 is the 'norm' and it's cheap. There's nothing special about it.

If someone wanted to get a little more picky about what they bought, they could go the separate solder/liquid flux route.

This would mean buying solder wire w/o flux in it and buying little bottles of flux separately. The advantage in this is being able to choose your flux. By far, the biggest determining factor in solder joint quality formation, BESIDES the skill level of the person doing it, is the 'performance' of the flux. And all fluxes CERTAINLY ain't created equal. Believe me, I've worked with literally dozens of different types and they all have their own peculiar behaviors and performance.

I'm an almost-total newbie at this, but I'll throw one more solder/flux combo into the mix...Multicore Hydro-X Solder. The flux washes off under water, for easy cleaning. It's pretty nice to work with (hand-built BEAM circuits are evil messes of twisty deadbug construction, so nice solder really helps a lot...)

I obtained mine from http://www.solarbotics.com (it's under Misc. Items, product ID SHX). $1 for a 12 foot length. Note that, as indicated by solarbotics, cleaning is recommended as the flux has low resistance.

I'm sure there are other distributors as well.

-jP