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Soldering help


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Hi, I bought a new iron not long ago and I just got around to trying it out. I'm a beginner to building brass kits. But I had a wagon which I figured was simply enough to try it out on. First joint here using 145° solder with flux and my iron set at 345°. It produced almost an immediate "blob joint" and would not spread. I set the temperature around 100 degrees higher and was able to get it to flow a bit more which produced what you see in the picture. It's very messy and I shouldn't have had to use that much solder. So the question is: how do I get it to flow? What am I doing wrong?

 

Thanks,

 

Matti

Edited by Matti8
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Cleanliness is everything, so I tend to brush a decent amount of flux along the joint.

 

In the case of the above I would initially place 3 blobs of solder (2 ends and middle) so that the heat is averaged out, then when tacked hit them with the iron to make them flow. I'd probably have the iron set at 370-390.

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Posted (edited)

That looks like a lot of brass, and the brass will draw heat away from the soldering iron tip.

 

So, what size tip are you using? A larger tip will hold more heat, and an iron with a higher wattage rating will recover its temperature quicker.

 

The brass looks shiny, but have you handled it? Any grease / dirt / oil will prevent the solder flowing. Ideally a fibreglass burnishing pen can be used to clean the surface, but take care if any splinters of fibreglass get into your fingers.

 

You may also need a liquid flux, some can be very corrosive and need to be washed after use, I use IPA with an old toothbrush, even when using a “non-clean” type flux.

 

Ideally the solder should just be a river of silver which flows along the seam.

Edited by Tim123
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16 minutes ago, Tim123 said:

That looks like a lot of brass, and the brass will draw heat away from the soldering iron tip.

 

So, what size tip are you using? A larger tip will hold more heat, and an iron with a higher wattage rating will recover its temperature quicker.

 

The brass looks shiny, but have you handled it? Any grease / dirt / oil will prevent the solder flowing. Ideally a fibreglass burnishing pen can be used to clean the surface, but take care if any splinters of fibreglass get into your fingers.

 

You may also need a liquid flux, some can be very corrosive and need to be washed after use, I use IPA with an old toothbrush, even when using a “non-clean” type flux.

 

Ideally the solder should just be a river of silver which flows along the seam.

 

The tip looks to be about 1.25mm. I have handled it but not around the joint. I should probably look into a fiberglass brush either way. I am using Slater's Liquid Flux which is 9% phosphoric.

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Is the tip pointed like a pencil or a chisel shape? 1.25mm is more for soldering electrical items. Hopefully your soldering iron has changeable tips and larger sizes are available, I'd go for a 3mm chisel tip if possible.

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That brass looks a bit yellow . Straight off the etch brass tends to have a coat of the varnish used as an etch resist, it is essential that you clean that off before you start. I use the kind of abrasive block sold as pcb cleaners and give the whole etch a really good going over on the flat before anything else. Then wash it , dry it and wipe any fingerprints off with ipa or similar. 

 

As has been said many times, clean metal is essential if you want to solder it. 

 

 

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I decided to have another go using the advice given. I absolutely scrubbed the thing inside and out as well as giving it another light sanding. Yet still will not melt at 380ish after applying. Very strange, perhaps there is a setting that needs changing or perhaps I did not tin the iron properly?

 

Anyways thanks for any help,

 

Matti

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1 hour ago, Matti8 said:

I decided to have another go using the advice given. I absolutely scrubbed the thing inside and out as well as giving it another light sanding. Yet still will not melt at 380ish after applying. Very strange, perhaps there is a setting that needs changing or perhaps I did not tin the iron properly?

 

Anyways thanks for any help,

 

Matti

are you using lead free solder or lead solder ?

 

others may argue but I find lead free solder totally unfit for purpose

 

Nick B

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Two points not already raised - is your iron tip clean? And are you using an appropriate flux for brass, such as Carrs Green? I'd also suggest you start by practising spot welds on smaller pieces of scrap etch.   

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8 hours ago, Dave John said:

That brass looks a bit yellow . Straight off the etch brass tends to have a coat of the varnish used as an etch resist, it is essential that you clean that off before you start. I use the kind of abrasive block sold as pcb cleaners and give the whole etch a really good going over on the flat before anything else. Then wash it , dry it and wipe any fingerprints off with ipa or similar. 

 

As has been said many times, clean metal is essential if you want to solder it. 

 

 

I cannot echo this too loudly. Cleanliness IS godliness. Then apply flux and turn the iron up to 11. Keep the tip of the iron clean. Some have a fancy wet sponge, I have a ball of wet kitchen towel. If the solder is not running easily across the tip you will struggle. Practice on some thin scrap. If this works easily perhaps a bigger iron might be needed.

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Another area that can draw heat away is if you are using a metal "square" or block or surface to hold the items in place. They will suck the heat out and make it very difficult for the solder to flow.  I put my iron on max (440 degrees), use 188 solder, 12% phosphoric acid flux, wooden block to hold it square and make sure i clean the brass well using a fibreglass brush first. For thick brass (0.8mm and above smoke box bands/boilers etc) i use my 80 watt iron with large chisel tip. For thinner brass such as wagon kits and fine etches i use my temp controlled iron.

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  • 3 weeks later...

I would think a fine nozzle butane torch would be better. clean and flux the joint, then lay a strip or a line of solder snippets and just hit it with a torch until it is drawn into the joint. 

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On 26/04/2021 at 11:38, ianLMS said:

Another area that can draw heat away is if you are using a metal "square" or block or surface to hold the items in place. They will suck the heat out and make it very difficult for the solder to flow.  I put my iron on max (440 degrees), use 188 solder, 12% phosphoric acid flux, wooden block to hold it square and make sure i clean the brass well using a fibreglass brush first. For thick brass (0.8mm and above smoke box bands/boilers etc) i use my 80 watt iron with large chisel tip. For thinner brass such as wagon kits and fine etches i use my temp controlled iron.

Lollipop sticks. Great for insulating the clamps when soldering to avoid heat drain.

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I agree with Esmedune - for soldering large pieces a fine nozzle butane torch is better. I have a Dremel 2200, but there are other equivalent ones out there.

 

My trick is to use solder paste in these situations - literally paint it onto the two surfaces before bringing them together and then heating them. Solder paste is a combination of solder and flux. It is obvious when you have reached the right temperature since the paste is dull grey but it changes to silver as the solder melts and binds to the surfaces. Using paste means that you can concentrate on heating the surfaces and you don't need to hold any solder wire with one hand.

 

Yours, Mike.

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It was quitea long time ago and I don't know if things have changed since, but lead-free solder was a no-no when I was working on electronics for military use. If it's no good for them....

 

IIRC the approved solvent for flux removal was 'Arklone', but we won't go into that!

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On 26/04/2021 at 03:21, nick_bastable said:

are you using lead free solder or lead solder ?

 

others may argue but I find lead free solder totally unfit for purpose

 

Nick B

I agree, lead free solder is a waste of time.  I Use Powerflow flux it is very good.  

Rob

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IT also depends on the wattage of the soldring iron, for 'O' gauge I use a 60watt iron, but for smallerbrass kits 25 watts is the minimum I would use.

 

Brass kits drain the heat from the tip like water going down a plug hole.

 

Terry.  

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14 hours ago, Trainshed Terry said:

IT also depends on the wattage of the soldring iron,

 

This could be - indeed, probably is - one of the most important aspects of this discussion.  Some posts back I asked the OP what wattage his iron but he has not replied.  The situation he describes suggest to me that it's nothing to do with the heat of his iron, but much more to do with its power in watts.

 

DT

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Patience. We live in a world of expected instant results. Larger irons take longer to heat up to working temperature. I have an old 80W Weller that takes around ten minutes to reach full temperature but then delivers heat faster than the brass can lose it. I also have cheap and cheerful irons that are ready to solder wires in a minute but can struggle with large chunks of brass like old school loco frames.

Then there is the RSU but you still need to be able to tin one of the surfaces.

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Neither piece is tinned in the OP's picture. I predict that things would be smoother with tinned parts.

 

When soldering a small thing to a large thing, I find it works best to tin the large thing and leave the small thing free of solder. Tinning the large part makes for a reliable joint and not tinning the small part reduces the cleaning up. This works better for me than sweating parts into place.

 

I also find that old-fashioned, leaded, 60/40 solder flows better than 145-degree solder, even when the 145 is the leaded kind. This is contrary to published findings, so I wonder if some kinds of 145 solder flow better than others.

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1 hour ago, doilum said:

Patience. We live in a world of expected instant results. Larger irons take longer to heat up to working temperature. I have an old 80W Weller that takes around ten minutes to reach full temperature

 

Modern irons are a bit faster than that.  My 70 watt Hakko takes 42 seconds to reach 450 degrees from cold.

 

DT

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