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Low temp solder paste


Borez

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Anyone have any experience of this?

 

Bought a syringe of it and did an experiment trying to solder 2 x 1mm metal tubes together. Heated the soldering iron to 150ºC ( the lowest it goes ) it didn't melt the paste, set it to 165ºC and it seemed to.

 

OK put a dab of paste on the joint, melted it and... nothing. It didn't form anything near a solid joint, just seemed to reform as a paste.

 

What am I doing wrong here?

 

I did buy it over a year ago, haven't never used it since buying, does it expire or something?

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12 minutes ago, colin said:

Did you use any flux with it

 

Ahh, I presumed the flux was in with the paste. What kind of flux do you use with this?

 

Sorry for being naive, there really isn't a lot of info online about this.

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I think there is a rosin flux in the paste but like rosin cored solder wire, a bit of extra flux is often needed to make a sound joint. I use Fry Powerflow Flux which can be obtained in the plumbing section of your local DIY shop.

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3 minutes ago, Nigel Heath said:

I think there is a rosin flux in the paste but like rosin cored solder wire, a bit of extra flux is often needed to make a sound joint. I use Fry Powerflow Flux which can be obtained in the plumbing section of your local DIY shop.

 

Thanks, I'll look into that.

 

I'm still a little confused as to why this would basically reform as a crumbly paste though? Would extra flux prevent this?

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17 minutes ago, Borez said:

 

Thanks, I'll look into that.

 

I'm still a little confused as to why this would basically reform as a crumbly paste though? Would extra flux prevent this?

As  Nigel says, your iron is not hot enough..............before you start, touch the tip of the paste to the tip of the iron, just to see what temperature it will melt at...........if I use a paste, which I rarely do, I always flux it as well with Carrs.  Be aware, there are different low temperature solders ranging from 65 upto about 140.........test the solder on the tip of the iron before soldering, just to check that your iron will melt the solder and ALWAYS make sure that the tip of the soldering iron is clean.  On some tips I have - when the iron is hot, I will wipe the dirt off on a wet sponge, with well worn but favourite tips that love to hold onto crud and sponge doesnt work, I use a fine file and file off the dead solder and flux until tip is shiny, then I dip in flux and tin the tip with a touch of solder.

 

If you run out of flux and have a bottle of Coke handy, this also can be used as a flux!!!!

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16 minutes ago, Head in the clouds. said:

I use Carrs Green Flux with Carrs 188 solder heating with a simple iron, no problems, as to your woes, not sure what the problem is so trying another product may be your answer.

 

Yep, that's pretty much what I'm thinking. I've soldered plenty of leads/cable/patchbays/electronic stuff in my lifetime ( as a touring live sound engineer ) but this stuff just doesn't look right to me at all.

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5 minutes ago, rayprit said:

As  Nigel says, your iron is not hot enough..............before you start, touch the tip of the paste to the tip of the iron, just to see what temperature it will melt at...........if I use a paste, which I rarely do, I always flux it as well with Carrs.  Be aware, there are different low temperature solders ranging from 65 upto about 140.........test the solder on the tip of the iron before soldering, just to check that your iron will melt the solder and ALWAYS make sure that the tip of the soldering iron is clean.  On some tips I have - when the iron is hot, I will wipe the dirt off on a wet sponge, with well worn but favourite tips that love to hold onto crud and sponge doesnt work, I use a fine file and file off the dead solder and flux until tip is shiny, then I dip in flux and tin the tip with a touch of solder.

 

If you run out of flux and have a bottle of Coke handy, this also can be used as a flux!!!!

 

I hear that, but this stuff was supposed to have a 138C melting point. That was the whole point, so I could use it on a 1mm white metal frame without disintegrating the metal itself.

Edited by Borez
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Sounds like the paste needs a high temperature to melt the paste and your iron, due to using a low temperature is not reaching the temperature required to melt that paste.  Go for Carrs liquid...............I have never had a problem with it after many years of making white metal rolling stock and various commercial vehicle kits...............be careful though, linger too long near those tubes and they will melt..........

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7 minutes ago, rayprit said:

Sounds like the paste needs a high temperature to melt the paste and your iron, due to using a low temperature is not reaching the temperature required to melt that paste.  Go for Carrs liquid...............I have never had a problem with it after many years of making white metal rolling stock and various commercial vehicle kits...............be careful though, linger too long near those tubes and they will melt..........

 

Thanks. I'm looking into the Carrs liquid.

 

Maybe I'm asking too much to try and solder these tubes at this scale, melting them is the last thing I want to be honest and some of the ( double and triple ) joints are tiny in places. I'll probably just go with epoxy instead. Although I'll buy some Carrs and experiment away from the model too.

 

Thanks guys. :thumbsup:

Edited by Borez
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Carrs flux, and shave some small pieces off the solid low temp solder that you get. Get a small paint brush and put some flux where you want the solder to go, put the some pieces of solder on the part, now it helps if you have three hands but most around here don't so a jig helps, bring the iron to the work and it should flow nicely, if not, a little more flux.

Soldering white metal is a bit perilous so most use super glues or epoxy if you want more strength

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