Soldering - irons - solder - fluxes - techniques

[Argos]

Having conducted a quick search of the site  I was surprise to discover there is no general thread for capturing help and advice with soldering.

Doubly surprised given this is such an important skill for constructing most of the kits we attempt.

There are plenty of specific questions that I'll try to link to below.

 

For my own part the skills I do possess are largely thanks to this site and the encouragement of what others have achieved.  

"learn by doing", as Jazz of this parish says.

 

Hopefully this thread will encourage others to have a go.

 

I am firmly convinced there is no "dark art".

The hardest part of soldering I've found is holding part in a rigid enough manner to enable the joint, this just takes a bit of thought. 

The biggest difference between experienced and learner is about half an hour of clean up!

 

Other threads:-

 

Having trouble linking content at present, I'll post the links as I get this to work.

 

Post 39 on page 2 has links to previous soldering threads

 

Thanks to Dhig

[brossard]

There are many threads where soldering has been discussed but, perhaps no one specific thread to cover the topic, so I say go for it.

 

I've been soldering for several years now and developed techniques that I am comfortable with and that work for me.  I think you'll find there are diverse opinions on methods so find the best one by doing.   Probably the most influential thing that taught me soldering was Iain Rice's Etched Loco Chassis book from Wild Swan.

 

Probably the best advice is to get the right kit in the form of a good (that means you'll have to shell out some dosh) soldering iron, flux and solder designed for the job you want to do.

 

I agree that one of the challenging aspects can be holding parts together so they can be joined.  Sometimes use of a "third" hand device, other times a purpose built fixture and even occasionally fingers while gritting teeth.

 

Looking forward to seeing more of your thoughts.

 

John 

[Argos]

Just to show and ulterior motive I'll pose the first question:-

 

To date my soldering has been done using two irons, both Weller one 25w for smaller kits (2mm) and an 80w for larger (7mm), I have also been using Weller solder with a melt point of 180 or 212 degrees C (depending which web site you read). This choice was purely on the basis of a closing down sale at a local tool shop at the point I dived into my first kit construction. The 80w iron and the a large reel of solder were half price......  

 

The flux I use is the yellow tub "Powerflux" again chosen because I had large quantity left from a bathroom plumbing project.

It works fine as long a clean up is done at the end of each session otherwise things turn a bit green.

 

I have always been a bit concerned that this combination seem to require a lot of heat to be put into the joint to get the solder to flow.

 

Reading around several of the more experienced builders on this forum, there seemed to be a general consensus that 145 degree solder and carrs red liquid flux (or equivalent) was the way to go.

 

The liquid solder seem to work fine with the Weller solder, albeit with no discernible difference from the Powerflux.

Until the end of the second days soldering when the plating blew off my soldering bit, co-incidence?

 

When I try to use the 145 degree solder I cannot get it to coat the tip (prior to the plating blowing).

I've carefully cleaned and refluxed the tip but to no avail, I just finish up chasing a blob of molten solder around in a liquid ball, I cannot get it flow.

 

Do I need to change bit completely, am I using the wrong flux or is the 80w iron too hot for the solder, or is it some thing else completely?

 

Flummoxed.

 

Any help appreciated.

 

Angus

 

 

[brossard]

For myself, 60/40 uncored solder seems to work fine on brass/NS models.  It melts at ~ 190C from what I've read.  I generally use Carr's Green phosphoric acid.  I also use 145C solder.  I've tried plumber's water based paste flux, which works well on all solders including 70C.  It does need cleaning up but, on the bright side, it is non corrosive.

 

I can never get solder to stick to the tip so I have developed a habit of cutting off tiny amounts and picking that up with the tip.  The other advantage is that you can control how much solder goes on.  The tip needs to be clean and I find a wipe with a damp sponge does that job just fine.

 

I now have a Weller 50W digital soldering station which I think is wonderful.  I can set the temp I need (currently 340C) and I get feedback of actual tip temp.  It really is about tip temp. and power means the rate at which at which the tip recovers after losing heat to the workpiece.  I don't know what temp. your 80W produces, but for large areas of metal (like 7mm) more power is appropriate I think.

 

A question I have is the use of solder paint (C&L stuff).  I have tried it a couple of times but the joint seems weak and I've had to remake using regular solder.  Any tips out there?

 

John

[Arthur]

Well, firstly there's no point using a higher melting point solder than you need to. It just makes the job more difficult as you have to get more heat energy into the joint. For virtually all etched kit construction 145 is all you need. Understandably, if you've got a job lot of high melting point solder, you'll want to use it, but it will make the job harder, as you 've found.

 

A higher melting point solder can be handy if you are soldering an item to close to which you will make a second joint. It reduces the chance of the first item becoming unsoldered, though I have to say it's technique I very rarely resort to.

 

 

As for your problem with plating the tip.

 

I've never used Powerflow flux, nor an iron of 80watts, (well, not for model making, I've soldered plumbing joints with it) so I don't know how it behaves.

 

Just wondering if there's something in the Poweflux that's incompatible with 145 solder which is why you cannot tin the tip? 80 watts is a powerful iron, I rarely use anything other than 25 watts albeit I work in 4mm. Again, is it boiling off the flux too quickly?

 

With soldering, cleanliness is not next to, but above, Godliness but you say the tip is clean. I've overused tips which have lost their plating, I file them down to clean copper, dip in flux and coat with solder, they work fine then and I can pick up enough solder on the tip to make most joints.

 

I'd try the liquid flux and 145 with your 25 watt iron first and, if all that is okay, try the 80 watt iron but with a new tip.

[Torr Giffard LSWR 1951-71]

....if you're in any doubt as to how important it is to keep all areas to be soldered clean and just how much crap comes off once you've finished soldering, then consider a decent Ultrasound bath and correct cleaning solution. Many of the issues associated with soldering vanish if you ensure that everything is clean at all times...also it prevents the flux oxidising/attacking the soldered/surrounding surfaces. The vibration within the bath will also detach anything that isn't soldered securely....at least you won't lose the part.

Use of heatsinks and how to limit temperature build up is also useful associated knowledge. It is always best to get all soldering done before adding any other parts where possible, however, it is sometimes unavoidable to need to solder afterwards and knowing how to get the job done quickly with a hot iron & without prolonged contact between iron and work area is crucial in avoiding damaging heat build up. Heatsinks are useful too...i.e. using a better conductor of heat to absorb/divert heat in order to avoid melting/softening delicate parts nearby.

 

In some situations requiring max heat instantly, an aerosol sized gas burner is the best type of heat source for soldering but practice is required and obviously any flammable materials have to be kept well away.

 

UNDER NO CIRCUMSTANCES SHOULD YOU SOLDER NEAR TO SUPERGLUED AREAS BECAUSE THE FUMES GIVEN OFF ARE HIGHLY TOXIC   

 

Dave 

[Raised On Steam]

I think the inital frustrations I had were all 'not enough heat' related ha ha.

 

I had a real problem getting my hands on phosphoric acid flux earlier this year…as in no-one near me was stocking it at the time and it would have cost a fortune to have a bottle courier-ed to me. I even contemplated using coca cola (seriously). Thanks to advice from folk on here I managed to make my own. I found that my local 'head' shop (hydroponics suppliers - ahem) sold me a great big bottle of 81% phosphoric acid for a fiver, which, again thanks to fellas on here, I successfully diluted and it works a treat. Years and years' worth :-)

I've also since found limescale remover in The Range which is basically phosphoric acid in a great big bottle for cheap money. Of course after all this I've found a few local supplies of ready made. Too late ha ha!

 

I find wooden clothes pegs are handy for holding things together if not too much pressure is needed, with the benefit that they don't draw heat from the joint.

Similarly I was after a parallel action vice….made from wood…sort of a bigger, stronger clothes peg. I came up with this fella:

 

[Quarryscapes]

I'd love to know what the difference would be between the various carrs fluxes in etched kit construction, All I know from experience is Red didn't impress me at all when I tried it years ago (But did sterling service as a rust converter elsewhere!) 

 

I generally use Fry's fluxite paste old school plumbing stuff, most definitely corrosive but works well. I also use a lot of Carr's 'No clean' solder cream (179) but find it most certainly does need cleaning, in fact it leaves a sticky residue behind that is incredibly difficult to clean off! 

 

I'm still searching for the holy grail for getting into difficult detail areas. 

[Arthur]

 

The fumes given off by cyanoacrylates, even if heated, are not highly toxic but they are highly irritant especially on mucous membranes, e.g. eyes, nasal and respiratory passages. Superglue does not, as some claim, contain cyanide though it is used in the manufacture.

 

The effect on the eyes is not unlike tear gas. It is highly unpleasant if breathed in and in a few individuals it has been known to bring on asthma.

 

I am NOT suggesting that you go around heating it, and certainly not that breathing in the fumes is a good idea, I am just clarifying that if you do accidentally heat it, the fumes will not kill you.

[John_Miles]

I've never used Powerflow flux, nor an iron of 80watts,

 

I mostly use Antex irons. I have a 25 watt and a 50 watt and use the latter a lot. It means you can be in and out quickly because generally the less you heat things up the better. You can build in stresses if things get too hot which can result in things like footplates not being flat. That said, there are occasions when I used a 75 watt Weller iron. For example, smokebox wrappers which are going on a tube which then has another layer of material on the outside of it and on this you need to fix a wrapper. It takes a lot of heat so I generally build boilers as completely separate items and fix them in place after painting so the heat doesn't cause problems elsewhere.

 

Flux - usuaully phosphoric acid with non-corrosive flux used where cleaning is a problem (e.g. wiring)

 

Finally there was a question about holding things. One thing that means you are a real modeller is when you get the great smell of roasting flesh and then you realise it's your fingers. Use jigs. Bits of cardboard, plywood, whatever is handy. Blutack is also handy.

[Graham Hughes]

For keeping the tip clean you want one of the little tins of tip tinner and cleaner as made by Multicore, Weller and others. In the smaller scales "not enough heat" is more likely to be down to an oxide coating on the tip which is a wonderful barrier to the transfer of heat than to the iron being too small. Although when I tried building a loco in 7mm for the first time after years of modelling in 2mm and 3mm scales My soldering iron, and indeed most of my tools, were just not big enough for the job. The 50W Antex I have now is fine but Antex irons have the element in the shaft rather than the handle so the tip has more heat for the same power. It is not just down to the tip temperature but the rate of heat flow. If the iron can't supply heat fast enough the tip cools and you can't make the joint.

Don't try and hold the bits in place with either your fingers or the soldering iron. You need one hand to hold the iron and one to hold the solder, so unless you have an unusually generous endowment of hands get the parts to stay in place before you make the joint. If you are fiddling around trying to get the parts lined up while you are making the soldered joint you will put too much heat in and bits will start falling off elsewhere. If you do need to hold something in place manually, use solder paste or paint. If the joint goes wrong let everything cool down and then try again. You don't want any heat stored in the parts or again, other bits start falling off as nearby joints melt.

 

Clean and tin the parts, apply plenty of flux (I use Carr's Green Label), heat the joint with the iron and melt the solder into the joint. Don't heat the solder with the iron and don't carry solder to the joint on the tip. That is how to get "dry" joints where the parts didn't get hot enough for the solder to bond properly and you have effectively "glued" the joint with the solder. Dry joints are brittle and will fail.

 

My choice of solder is Carr's 188. Either in coil form or the paint, as mentioned above. 60/40 and similar do not have such good "wetting" properties and therefore makes a thicker bead which needs more cleaning up. It has its uses if you need to fill gaps, badly fitting joints or something like the "fingers" sometimes used in etched kits to form rounded tender corners and such like but 188 is nicer to use if you are soldering well fitting parts. It also has a shorter melting range so needs less heat. I also use Carrs 145 occasionally for adding details if there is a risk that other joints will come apart from the heat needed for the 188 and 70 for whitemetal work although that is funny stuff, more like a metallic glue than soldering.

I see the OP has a 2mm logo on his profile pic. You can completely bury smaller 2mm details with 60/40 solder. I have used it for 2mm work when I hadn't got anything else available but it needs a lot more care and it is not the best solder for the job. Why would it be? It is designed for soldering pipes and tinware. You wouldn't use a plumber's stilson wrench to tighten crankpin nuts so why expect plumber's solder to be the best stuff for soldering models. I think part of the reason some people find soldering difficult is because they don't realise that, just like any other tools and materials, those for soldering come in different types suited to different applications. 

[scotcent]

In  my  experience  a  lot  of  beginners  problems  arise  because  the  tip  is  not  properly  prepared,  and  I  have  found  very  helpful  an  article  written  by  Brian  Lewis  and  available  on  the  C & L  website.  Look  under  "Knowledge  Centre".  I  went  through  a  lot  of  soldering  irons  before  I  worked  this  out!  Clean  the  tip  before  every  use  on  the  brass  potscourer  type  of  cleaner -- much  more  effective  than  the  wet  cloth.  Cleanliness  of  work  and  tip  are  paramount,  as  is  the  maintenance  of  a  sufficient  temperature  throughout  the  soldering  operation -- this  is  where  smaller  irons  on  bigger  jobs  fall  down.  For  the  same  reason  a  bigger  tip  will  usually  do  better  than  a  smaller  tip -- it  stores  more  heat.

 

Allan  F

[Torr Giffard LSWR 1951-71]

....make sure that you have a solder 'wick'....ideal for removing excess solder when the inevitable happens.

 

Dave

[ColinK]

While I'm adequatly competant at soldering wires together, soldering rolling stock kits is an art I've not yet mastered, so thanks for this thread.

 

Advice on how to do the following appreciated.

 

First, If coupling rods consist of two layers which have to be soldered together, how?

 

Second, how do you solder panels, eg engine room doors, onto a brass loco bodyshell?

 

Cheers

[EKR]

Clip coupling rods together with cocktail sticks through the holes to align them leaving the edges exposed.

Flux the edges and when solder is applied the flux will draw the solder between the layers. File to finish.

You could also tin the backs of each then flux, align and add heat, but the formers quicker.

 

With panels you can do the same by fluxing around the edges and applying solder so that it gets drawn under the edges,or use solder paste. Theres always more than one way to do most jobs.

Find what works for you. 

[bagpipes331]

Up until last November, I had never built an etched brass kit, and had relied on others to do it for me. (Quite expensive!) The final straw was a kit that I waited 3 years to be completed, and gave nothing but huge disappointment.

I had been a gas engineer for 36 years, and was very experienced and very good at soldering pipework, all be it with a gas blow torch.

 

So, as with many others who had quivered and worried over the 'black art', I decided to have a go myself.

 

The 1st kit was a connoisseur BR brake van. Tools consisted of a cheap 40W iron from Halfords, 140 Carrs solder and Yellow label flux. I managed to make the frames resemble bananas, and Jim kindly sent me spares FOC. What a gent!!

 

 

 

I was so pleased with the finished kit, I agreed to build a Dogfish for a friend, followed by a 16T coal truck from MMP.

 

By now, I changed irons for an Antex 50w and 25w irons for the smaller parts, and built a couple of class B tankers. (Dave Parkins is also a gent and great to deal with)

 

One thing that annoyed me, despite thorough cleaning after each session, the kit became heavily stained due to the flux. (Not green corrosion, just staining).

 

I decided to experiment with my next kit, a Peter Clark thumper. I built the driving coach, under frames etc using the above method, although I used a 100w Weller iron for the compartment bulkheads.

 

For the trailer coach I have used La Co flux. I used all sorts of flux as an engineer, and between Power Flux (Yellow tub) and La Co (Black tub, red lid) I found La Co less aggressive. 

 

What I found was that for the 1st coach (and previous kits) the tip of the iron required reasonably frequent tinning. For the whole build of the trailer coach, I have not tinned the iron once. Cleaning up is easier, and as long as I dry the kit thoroughly, no staining is evident. Also by using a very small brush, the aplication of flux is very precise, and helps very small components to stay put whilst soldering.

These are my findings, and it all works for me. As others have said, we all develop our own ways. I am by no means an expert, but I have not had a single component fall off while soldering adjacent or in the cleaning process.

 

Good luck, and enjoy!!!

[brossard]

Great stuff!  It is marvellously satisfying to complete a brass kit.  Glad you're a convert. 

 

John

[halfwit]

....make sure that you have a solder 'wick'....ideal for removing excess solder when the inevitable happens.

 

And here's how you use it.

 

On solder - I prefer Eileen's 188 degree solder wire, especially for structural work (loco bodyshells for example), I find that it flows better than 145 degree making for a neater joint with less effort. 145 still has a place on my workbench though, I use it for adding detail without affecting nearby structural joints ('step soldering').

 

For flux I find that Eileen's Strong Flux works well, its 12% phos. acid rather than the more usual 9%.

 

After every session I thoroughly clean the job with Cif and an old toothbrush.

[Mrkirtley800]

Reading through this thread has been fascinating.  I first started going through the motions of soldering when I was four years old (according to my mother) and that is 75 years ago.  My dad was a sheet metal worker so soldering was a way of life for him.  His run lead joints in household plumbing were the neatest I have seen.  Of course back in the 1940's the soldering irons had to be heated in the fire, on the gas stove or by blowlamp.  To make sure it was hot enough he used to hold it a few inches from his face. You can probably guess what happened when I tried that trick.

Flux was 'killed spirits' -  pieces of zinc thrown into strong hydrochloric acid until the reaction subsides.  Very effective flux but very corrosive.  Solder came off a big stick.

Happy Days

[Jol Wilkinson]

Most people that struggle do so because they use the wrong solder and flux and don't have an iron with sufficient power.

 

The following works for me;

 

1. Ensure the parts are mechanically clean - remove tarnish, etc. with a clean fibre glass brush tip.

2. Ensure they are chemically clean - use a good and appropriate liquid flux applied to the area to de soldered.

3. Use plenty of heat - a soldering iron with sufficient power (watts) to heat up the area and parts being soldered. Minimum 25 watts in 4mm, preferably more. Use a bit of at least 3mm diameter unless soldering on fine detail. A narrow bit acts as a heat restrictor.

4. Work at the correct temperature - too cold and the solder will not melt and flow, too hot and impurities sometimes formed which coat the tip and hinder the process.  A temperature controlled iron such as the Antex unit is ideal.

5. Use suitable solder - I use London Road Models 145 on brass and n/s as it has good flow characteristics or Carrs/C&L 100 degree for white metal.

 

Here is an example of a 4mm tender assembled using a 50W Antex TCU, LRM 145 solder, LRM 12% phosphoric acid flux and, for some some of the detailed overlays, an RSU. 

 

 

 

 

 

[Adie89]

Many on here mention temperature controlled soldering irons and different solder melting points.

Is there a rule of thumb/ hard and fast rule relating soldering iron to solder temps?

I only ask, not to sound stupid, but because in my head if the solder melts at 145 deg my iron will need to hotter than that to transfer 145 deg to the part in question and then to the solder, but how much hotter?

[0_gauge_novice]

Hi Adie89,

 

I use double the temp. 145 solder I set the iron at 300. For 188 at 350. For 70 low melt at 150. If the parts are cast brass and you lose heat I might go up to 400.

 

Cheera

Andeas

[Jeff Smith]

For white metal kits I usually set the iron temp below the white metal melting point by testing on a bit of sprue or similar. This is particularly important when attaching small white metal parts. For main body assembly you can get away with a hotter iron because of the heat-sink effect but you have to be quick.....

 

Lately I have been using liquid flux sold for stained glass window assembly. Low temp solder and flux does not seem to be readily available in the US.....I guess white metal kits are normally super-glued and brass kits assembled using multi-core....

[Jol Wilkinson]

Many on here mention temperature controlled soldering irons and different solder melting points.

Is there a rule of thumb/ hard and fast rule relating soldering iron to solder temps?

I only ask, not to sound stupid, but because in my head if the solder melts at 145 deg my iron will need to hotter than that to transfer 145 deg to the part in question and then to the solder, but how much hotter?

Generally I set the Antex 50w TCU iron temp about 80/100 deg above the solder temp. It will depend on the power of the iron. The tip temp drops when it is applied so the more easily it can "heat up" again, then the lower the setting needs to be, although some differential will always be needed.

 

If the iron is lower wattage then a higher temperature provides a bigger "reservoir" to stop the temperature from falling too low. That's okay up to a point but there is really no substitute for wattage.

[sagaguy]

At last iv`e made a start on my DJH 7mm Fairburn tank,I bought one of these from Maplin & it`s just the job.

 

http://www.maplin.co.uk/p/60w-professional-lcd-solder-station-with-esd-protection-a55kj

 

 for soldering in the axle bushes,I use 145 deg.solder with the temp set to 450 as the frames are quite thick.

Best of all,it`s still on offer at £39.99.

 

   Ray.