Identifying type of solder

[Hillbilly]

I have a couple rolls of solder BUT there is no label on the spool to tell whether it is acid or rosin core.

Rather than buy more solder (which I don't mind doing), is there a way to determine which type it is ... does the flux melt differently for example?

Many thanks.

 

[Boncuk]

I don't know if plumbers use soldering tin with an acid core - I doubt it. They normally use acid separately from the tin and a brush to prepare the material for soldering.

You can make a smell test though. If the soldering tin causes slight smoke and smells a bit sweet it contains rosin.

If it bytes the eyes it contains acid.

Boncuk

 

[Sceadwian]

I don't know of any solders that have a built in acid core, I'm not even sure if it's possible because most acid fluxes are pastes. If you cut the solder and look at it's cross section and see a smaller tube in the middle it's should be rosin core.

 

[Vizier87]

What's the significance of choosing either?

 

[Sceadwian]

Acid flux can't be used on electronics generally... it's acidic, if it ever gets damp, or simply over time the acid in the flux (that's left on the surface) will corrode components and traces. The only way to avoid this is to use rosin flux (not as effective but on a clean solder joint it doesn't need to be) or wash the flux residue away after use, which has all it's own problems.

 

[jpanhalt]

I don't know of any solders that have a built in acid core, I'm not even sure if it's possible because most acid fluxes are pastes. If you cut the solder and look at it's cross section and see a smaller tube in the middle it's should be rosin core.

Acid core solder is made and relatively common. I have some. Check out:McMaster-Carr

See: part numbers 7658A(x)

John

 

[Mr RB]

Acid core is very rare in fine solder on reels!

With rosin core the flux will build up on your PCB and quickly cool to form a hard deposit usually clearish or browny colour (it can then be chipped off).

 

[Boncuk]

What's the significance of choosing either?

The most significant difference is increasing sales.

Using acid instead of rosin you've made a circuit with self-destruction ability.

Boncuk

 

[Vizier87]

The most significant difference is increasing sales.

Using acid instead of rosin you've made a circuit with self-destruction ability.

Boncuk

Touche, Hans. It's like those tech guys who flood their PCB with goo to prevent people reverse engineering their stuff. Goons.

 

[mneary]

"Active" flux is used a lot in mass production. Don't know what the pH is, but it attracts moisture and promotes corrosion. The benefit is, that it washes off with water instead of requiring VOCs, or CFCs. Yes, it must be washed and dried thoroughly but it is commonplace.

You can tell if a manufactured product has no flux residue, it probably didn't use the old fashioned rosin.

 

[Boncuk]

I remember the early days of "flux" inside the solder. It was "Kolophonium" (colophony), a syrup like juice coming from the stems of pine trees.

Violine players use colophony to wax their bows.

Boncuk

 

[stevez]

My experience, for what it's worth: rosin or acid core flux solder was common and abundant (probably still is) in the larger sizes, such as one might use in plumbing. I've not seen acid core solder in the smaller gages though it may be available.

 

[jpanhalt]

My experience, for what it's worth: rosin or acid core flux solder was common and abundant (probably still is) in the larger sizes, such as one might use in plumbing. I've not seen acid core solder in the smaller gages though it may be available.

Small and large are somewhat hard to measure.

The acid core solders I have are 0.062" and 0.038". The latter is a little finer than a very old spool of rosin core solder that I have for TH construction. True, I have not seen acid-core solder in the very fine (0.015") size used for SMD.

The point is, acid core solders do exist, and the distinction between paste and liquid fluxes is irrelevant with respect to whether the flux is acid, rosin, or organic base. BTW, the acid in low-temp fluxes is often zinc chloride or a similar acidic salt in paste.

A simple test for acid or chloride should help distinguish the solders.

John