Which solder/flux combination do you use for etched kit construction?

chigley

Western Thunderer
60/40 typically melts at 188°C, use 145°C and that'll help.

However, I suspect your biggest problem is simply lack of heat or sustained heat.

Nickel silver is a very good conductor of heat and will sap the heat away from the iron very quickly, that's why once you have the solder flowing it'll zap down a joint in a flash.

Lots of folks get by with a 50W iron, I never could and up rated to 80W and solder pretty much everything with it set to 400°C, get in and out fast. Though to be fair, nearly all of my work now, except detail work, is done with a micro flame.

The only down side is super heated flux which spatters and is a bit of a devil to clean afterward.

I use safety flux from Building O gauge on line Building O Gauge Online - Soldering and apply with a small pint brush.

Just about every reply you get will be different here, all good and well and I went through the exact same process a few years back; the trick is to try a few and find one that works best for you, but I do think your iron is going to be your main culprit.

As a quick test, buy a small cheap micro flame, waft it over a test piece and see if the solder then runs okay, if it does, then it's a lack of heat issue, if not it's your flux or solder.
60/40 typically melts at 188°C, use 145°C and that'll help.

However, I suspect your biggest problem is simply lack of heat or sustained heat.

Nickel silver is a very good conductor of heat and will sap the heat away from the iron very quickly, that's why once you have the solder flowing it'll zap down a joint in a flash.

Lots of folks get by with a 50W iron, I never could and up rated to 80W and solder pretty much everything with it set to 400°C, get in and out fast. Though to be fair, nearly all of my work now, except detail work, is done with a micro flame.

The only down side is super heated flux which spatters and is a bit of a devil to clean afterward.

I use safety flux from Building O gauge on line Building O Gauge Online - Soldering and apply with a small pint brush.

Just about every reply you get will be different here, all good and well and I went through the exact same process a few years back; the trick is to try a few and find one that works best for you, but I do think your iron is going to be your main culprit.

As a quick test, buy a small cheap micro flame, waft it over a test piece and see if the solder then runs okay, if it does, then it's a lack of heat issue, if not it's your flux or solder.
 

mickoo

Western Thunderer
I'm fortunate, I bought two bottles a few years back, both still unopened and should keep me going for a couple of years at my current build rate.

I do often wonder what the base component is for safety flux and idly wondered if it was available elsewhere, precisely for this type of situation or it goes off the market completely.

I might try citric acid as an experiment, as a fall back solution, or if acceptable, a replacement.

I've tried many fluxes in the past, all left sticky residue or some sort of residue that made paint adhesion problematical, worst of all, most turned green after while, even when washed thoroughly after use.
 

simond

Western Thunderer
Mick,

citric acid will leave a sticky residue, rather like sugar syrup, it washes off very easily in warm water.

I add ipa to mine, seems to aid wetting.

Atb
Simon
 

Longbow

Western Thunderer
Simon - that makes sense as I have heard that commercial phosphoric fluxes use a surfactant. How much IPA do you add?
 
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mickoo

Western Thunderer
Thanks for the heads up, I did wonder if there was a residue as it's primarily lemon and orange juice as far as I can tell, though I wouldn't consume it :p

Over the years I tend to find it's flux spatter that seems to turn green the most, that in the area of the actual joint is usually fine but can leave a iced sugar (oxidisation) effect on solder over time, however, flux flashed off and spattered further away from the joint rapidly turns into green spots.

The Iron temp is a big factor and I'm a victim of my own methods as I generally run with a hot tip, ergo more spatter as the flux flashes off and occasionally it'll tarnish the work and the solder will not run.
 

simond

Western Thunderer
It doesn’t turn green, however long I’ve left it, despite being the acid from fruit! It is mildly corrosive according to Wikipedia. Citric acid - Wikipedia. The MSDS etc is available there, and Citric acid will tell you anything else you might want to know.

My mix is add citric acid & water, until it won’t dissolve any more - saturated solution - 50-60g / 100g, and then add some IPA, about half again. It dissolves in ethanol too, and melts at 150C, though I’ve never tried using it as a dry flux.

I recall comments on here when this has been discussed, suggesting a much lower percentage of IPA might be better, 10% maybe.

I don’t think the mix is too critical, and the ingredients are cheap, and if it’s a complete b.....x then it’s pretty environmentally friendly if well watered down before flushing down the loo or sink.

hth
Simon
 

SimonT

Western Thunderer
I'm using the citric acid flux with 10%ish IPA. My solution is about half the strength of Simon's. Its good for NS and ok but not brill for brass. The real surprise was finding it is really good for soldering steel.
Simon
 

Deano747

Western Thunderer
Apart from IPA, are there any other wetting agents, and approximate percentage to use in diluted phosphoric acid?

Regards, Rob (Deano)
 
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Longbow

Western Thunderer
Iain Rice gave the following recipe for ~11% phosphoric acid flux:

800ml distilled water
120ml 85-95% phosphoric acid (adjust pro-rata for other strengths)
20ml IPA as wetting agent

For whitemetal this should be diluted by 30%-50%.

Clean-up with a mild alkaline solution eg washing soda.

I suspect that as a water-based flux this will be less effective with very hot irons or micro-burners - the solvents will boil off too fast, meaning less wetting and more spattering.

Citric acid is a weaker acid than phosphoric, so you would need more of it.
 

Longbow

Western Thunderer
I priced Iain's flux recipe above at ~12p per 50ml. I don't know if it's as good as Carr's flux, but that costs GBP7.20 for 50ml.
 
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