Soldering woes....

[Crosland]

High power is good but you want controllability (temperature) at the 50 - 100W range.

 

This is especially important for soldering droppers where the rail acts as a heatsink and conducts the heat away. A higher power iron can replace the heat and let you quickly get the job up to temperature for the solder to flow, and then remove the iron, before you melt the sleepers. You are more likely to cause damage by lingering on the joint with an underpowered iron.

[Kenton]

 

High power is good but you want controllability (temperature) at the 50 - 100W range.

 

Isn't that a contradiction. Power does not equal temperature. So a temperature control unit does not control the wattage range.

 

AFAIC the only use a temperature controlled iron has is to reassure the uninitiated into belief that soldering low melt solder on white metal kits also has something to do with 70'C and 150'C instead of getting sufficient heat into the job to make the solder stick two great lumps of heat sinks together. You can have your iron set at 450'C and still have a dry solder join. If the metal is too bulky (a big heavy brass chassis or boiler in 7mm) the heat from a puny 25W iron set at 450'C will struggle to even melt 180'C solder let alone put enough heat into the brass to form a join.

[cliff park]

I have to agree with Crosland, but it seems to me there are two seperate issues here. Soldering an LED into a PCB and soldering a white metal kit together are so dissimilar that they ought to have different names. I worked in electronic telephone exchanges for 35 years, and only ever used a 50 watt iron, temperature controlled, but not adjustable. The idea is that it can supply the amount of heat when needed, but doesn't get too hot. I have a 120 watt iron, uncontrolled, but physically big that I use for 'mechanical' soldering, it has the grunt to heat up the big heat sinks that whitemetal kits effectively are.

[Tricky Dicky]

I have to agree with Crosland, but it seems to me there are two seperate issues here. Soldering an LED into a PCB and soldering a white metal kit together are so dissimilar that they ought to have different names. I worked in electronic telephone exchanges for 35 years, and only ever used a 50 watt iron, temperature controlled, but not adjustable. The idea is that it can supply the amount of heat when needed, but doesn't get too hot. I have a 120 watt iron, uncontrolled, but physically big that I use for 'mechanical' soldering, it has the grunt to heat up the big heat sinks that whitemetal kits effectively are.

The temperature control is really a non-issue, whatever form of soldering you do the essence is to deliver heat faster than it disapates into the metal and getting the metal being soldered up to the temperature that the solder melts in order for fusing to occur. In the days when I did a lot of silver soldering with gas torches, the gas burned at the same temperature no matter what size nozzle or valve setting used. The only difference different nozzles and valve settings made was how localised the heat was.

 

Richard

[Crosland]

  Isn't that a contradiction. Power does not equal temperature. So a temperature control unit does not control the wattage range.

 

AFAIC the only use a temperature controlled iron has is to reassure the uninitiated into belief that soldering low melt solder on white metal kits also has something to do with 70'C and 150'C instead of getting sufficient heat into the job to make the solder stick two great lumps of heat sinks together. You can have your iron set at 450'C and still have a dry solder join. If the metal is too bulky (a big heavy brass chassis or boiler in 7mm) the heat from a puny 25W iron set at 450'C will struggle to even melt 180'C solder let alone put enough heat into the brass to form a join.

 

You answered your own question

 

Power is the ability to pump heat into the job and maintain the set temperature. Once you have an iron capable of actually maintaining the bit temperature then temperature control becomes essential. Anything else is "suck it and see, OH **** I just melted a hole in the side of the cab".

 

It's like voltage and current. Higher power is the ability to supply higher current and maintain the voltage. In this analogy voltage is temperature and current is heat flow.

[Kenton]

 

Anything else is "suck it and see, OH **** I just melted a hole in the side of the cab".

 

That is funny, never had that problem. I have used, (and still do) gas torches, a RSU, 50 or 100W irons on a daily basis. I have never had the need, or slightest desire, to control temperature. I have used a 25W iron for some 2mm kits and for some electronic stuff where I needed a very fine tip, but wouldn't even dream of wasting my time with one for 4mm or 7mm work.

 

Sure, the gas torch if misused will anneal the brass, and the RSU on an incorrect setting (also misused) will vapourise things like brass wire.

 

Soldering, in the end will always come down to the application of heat at the join and understanding how heat is dissipated within the join. If there is insufficient heat being applied (or even applied for too long) then something is going to go wrong. It is something that you learn by experience not by just dialling up a temperature and thinking it just happens at some meaningless setting.

 

I have seen beginners failing to think it through, setting the temperature of the iron at some arbitrarily selected temperature based on the temperature of the solder or definition of "hot" then sitting there with the tip of the iron on a blob of solder wondering why it isn't melting, watching the flux boiling away and then blaming the solder, the flux, themselves, the metal, the world and anything other than the "temperature" setting. After all it is set higher than the melting point temperature so it cannot be that can it?

 

Get in fast with heat too do the job [1], the solder will melt and flow [2], then get out fast without disturbing what you have achieved [3] if you count to [4] you have probably been there too long.

[HowardGreen]

Sounds like too cold an iron and probably lead free solder. No need for flux if you use rosin multicore solder. But the fact it worked and then didn't it is typical symptom of an iron under-powered or not kept tinned or has become contaminated with rubbish from the sponge (I never use a sponge)

 

It is often thought that a low power iron will do but then forget that track is a big heat sink. Of course too much heat will melt plastic sleepers and the plastic coating on the wire but part of the problem there is that you shouldn't be lingering around so long to let that happen. Soldering is all about going in fast with everything clean and applying enough heat for the job.

I clean mine with a file.

[HowardGreen]

I find that I get a good joint by the following method: I load the tip of the soldering iron with a drop of solder from a coil then transfer some of it to the wire dropper; then I do the same with the rail; finally, I bring the tinned wire into contact with the tinned rail then apply heat from the (tinned) soldering iron bit.  In all cases, I first of all apply some solder paste to the bit/wire/rail.  Now all I need to do is find out how to clear up the mess of melted & re-solidified flux.

[HowardGreen]

In all the discussion about temperature, heat and power, I think at least some people have lost sight of the difference between heat and temperature.  The amount of Heat in an object is related not only to its temperature but also its mass; it has been said that the iceberg that sank the Titanic contained more heat than a kettle of boiling water.  In fact, I suspect it contained more heat than the boiler of "Mallard" when it set it's world record.  Another aspect (already touched on) is the soldering iron's ability to replace the heat being conducted away from the bit by the heat sink action of the work pieces being soldered.  As in many other things, a good big 'un will beat a good little 'un; mass and wattage will both play a role here.  (My Dad had a soldering iron that had to be heated in a fire, but it was so heavy he could solder lead pipes with it.)

[ajaxjones]

I've had plenty of success with a 25W Antex and lead free solder from maplins. A dab of carrs yellow flux for obstinate joints. I'm not worried about scraping the crud from the tip of the iron either when hot to clean it up with and get it tinned again (needle file or scalpel). Boiled clean water on the sponge but doesnt matter too much for hobby soldering. I find getting the joint hot enough to flow into a concave meniscus can be easier with a lower temp instead of melting all the sleepers with a big un, but I've probably had more practice   Pre soldering the wires helps as does tinning the track and then just melt the two together. Pulling the entire tip off and twisting about (when cold) also seems to clean up the carbon (?) deposits inside and the crud to make sure all the heat gets into the tip too. 

[Kenton]

 

I clean mine with a file.

 

Only with the old style (copper) solid tips, do that with a plated tip and you will be soon through to the core and it will be near impossible to tin it again.