Flux

[Thorskin]

I want to try my hand at some DIY Audio and I got myself a TS100 soldering iron, I just need to get some solder and flux now.

For the solder I think I will go for some Duratools 63/37 0.64mm, 3.3% Flux RA Solder which is cheaper than the popular Kester 44 solder but seems similar in spec?

The flux is where I have been struggling for hours as I keep reading different advice.

Should I stick with a Rosin Flux like MG Chemicals Rosin liquid 835 or MG Chemicals 8342 RA Rosin Flux Paste
or get some MG Chemicals 8341 No Clean Flux Paste?

There is some cheaper Polish products from TermoPlasty ( Topnik RF800, Topnik TK83 or TermoPlasty Soldering Paste ) but im not sure if they are any good.

Some people recommend only using No Clean flux and some say use Rosin flux if you use RA Solder?

I have been researching for hours now and am still confused as to what to buy.

Ill be making DIY headphone amps , cables and other small projects for now to learn to solder, eventually maybe recapping some old amplifiers.

 

[Omar Cumming]

Whatever you do, do not use an acid based flux (such as Stay-Clean) on electronics, stick with rosin!

Cheers

 

[SIY]

You shouldn't need extra flux if you use rosin-core solder. At least I never have (veteran of >1000 projects).

 

[Thorskin]

You shouldn't need extra flux if you use rosin-core solder. At least I never have (veteran of >1000 projects).

Oh really? So many videos say its super important even if you use rosin cored solder.
I could try just using rosin core solder for now and get some flux if I struggle.

 

[DonH56]

Most of the time I have not needed flux. The times I have, the components have been very tiny (like 0201 specs of resistor dust), or very large (booster cables to large metal connectors). Or when I was doing plumbing and soldering copper pipes (with acid flux, do NOT miss that job!) I would not get it. I am pretty sure I have a tin I bought 40+ years ago that still has most of it inside, probably all dried out.

FWIWFM - Don

 

[Thorskin]

Most of the time I have not needed flux. The times I have, the components have been very tiny (like 0201 specs of resistor dust), or very large (booster cables to large metal connectors). Or when I was doing plumbing and soldering copper pipes (with acid flux, do NOT miss that job!) I would not get it. I am pretty sure I have a tin I bought 40+ years ago that still has most of it inside, probably all dried out.

FWIWFM - Don

Thanks, it seems like its not necessary then. I hope as a beginner I will find the rosin core solder easy enough to use without additional flux.

 

[Doodski]

For surface mount printed circuit board work you need extra flux. Especially for a newbie. Do yourself a favor and use it from a small squirt bottle or just a drop off the end of a small screwdriver. It saves the printed circuit board and components from excess heat and gives-lends a nice liquid meniscus property to the solder so it flows better and can be reworked easily if required. If you use flux oftentimes you won't need extra solder if it is a rework job. You'll need a toothbrush, Q-Tips and isopropyl alcohol for cleanup. I only use Kester for the sole reason that's all I've ever used and I know it. Saving money by not using flux and good quality solder is not the way to go.

 

[SIY]

Thanks, it seems like its not necessary then. I hope as a beginner I will find the rosin core solder easy enough to use without additional flux.

You made your life easier with 63/37. Good choice for anything other than silver or silver plated metals. There, you'll need something like 62/36/2 silver-bearing solder, rosin core.

 

[mansr]

You also will need some for SMD.

Solder paste is the way to go there.

 

[solderdude]

I never used extra flux.
The flux inside solder works well.
There are many different types of solder/flux.
Not all work equally well or are as easy to clean afterwards.

When soldering do it quickly. Make sure your tip is well wetted.
Heat up the pad + component lead and then apply the solder.
Keep the last part short. When the solder flowed nicely remove the tip.

I see many people putting solder on their tip and then press that against the to be soldered parts.
This is not the correct way and the flux already is gone.

 

[mansr]

it depends. I don’t have hot air(not using enough). Using solder paste with iron risks partial activation of no clean flux and nasty residue. I use iron and flux paste for solder transfer while doing my opamp installation.

Hot air (or reflow oven) is also the way to go with SMD. A pre-heating plate is useful too.

 

[mansr]

I never used extra flux.
The flux inside solder works well.
There are many different types of solder/flux.
Not all work equally well or are as easy to clean afterwards.

When soldering do it quickly. Make sure your tip is well wetted.
Heat up the pad + component lead and then apply the solder.
Keep the last part short. When the solder flowed nicely remove the tip.

I see many people putting solder on their tip and then press that against the to be soldered parts.
This is not the correct way and the flux already is gone.

Gullwing SMD ICs can be soldered by adding some flux to the pads, then using the iron to drag a blob of solder across the pins. Much quicker than applying wire solder to the pins one by one.

 

[mansr]

i know. However for someone probably only do one project, or mainly through hole like myself, i stick to iron. My smd skills with iron is good enough with dip items that you cannot tell wether i used hot air or not, if i spend the time rinsing rosin completely off.

It's worthwhile getting comfortable with fine-pitch DFN/QFN packages. Lots of nice ICs available in those.

 

[March Audio]

Hot air (or reflow oven) is also the way to go with SMD. A pre-heating plate is useful too.

This.

Get PCBs made in China and a solder stencil. You can spread solder paste over stencil then place the components with fine tweezers. Use easyeda. Jlcpcb.com are spectacularly quick, cheap and good quality.

Modify a toaster oven to bake (reflow) the board. A bit of practice and you can get quite professional, well entirely professional in fact, results.

I can give more detail and video if needed.

Normal soldering (non smd) rarely needs extra flux.

Don't use silver solder, total waste of time. Lead free is also more challenging.

Practice general soldering on a pice of veroboard and some resistors. I have no doubt there are tons of YouTube videos that can help.

 

[March Audio]

It is possible to use a fry pan.

It is, but more challenging, in fact I would say very difficult to get the correct temperature profile, ramp and control. I wouldn't recommend the method. Raspberry pi as a controller plus toaster oven is dirt cheap and extremely effective.

I'll do a video tomorrow. I do this for development and test PCBs. It's cheap, quick and allows me to try out ideas without resorting to the cost and lead times of "professional" manufacture.

 

[March Audio]

I agree with the control part of it. But since handheld hot air doesn't have ramp control either and works, I would say it is probably fine. Just be careful.

Yeah hot air guns are equally difficult, underheat, roast it for 5 mins then overheat.

 

[solderdude]

Gullwing SMD ICs can be soldered by adding some flux to the pads, then using the iron to drag a blob of solder across the pins. Much quicker than applying wire solder to the pins one by one.

I always solder all pins together, then use desolderwick and afterwards reflow each pin.
Don't have flux anyway but if I had would give it a try.

 

[Doodski]

Don't have flux anyway but if I had would give it a try.

It makes life way easier especially for flat packs. Much less heat is req'd and the result is nicer solder joints with less reworking and it's faster. It cleans up pretty easy too with some isopropyl or methyl hydrate if you're so inclined. I would not do it any other way.

 

[mansr]

I agree with the control part of it. But since handheld hot air doesn't have ramp control either and works, I would say it is probably fine. Just be careful.

My hot air station has a programmable sequence. Even without that, varying the distance from the nozzle to the board gives you some control. A hotplate is useful for pre-heating, less so for actual soldering.

 

[DonH56]

For surface mount printed circuit board work you need extra flux. Especially for a newbie. Do yourself a favor and use it from a small squirt bottle or just a drop off the end of a small screwdriver. It saves the printed circuit board and components from excess heat and gives-lends a nice liquid meniscus property to the solder so it flows better and can be reworked easily if required. If you use flux oftentimes you won't need extra solder if it is a rework job. You'll need a toothbrush, Q-Tips and isopropyl alcohol for cleanup. I only use Kester for the sole reason that's all I've ever used and I know it. Saving money by not using flux and good quality solder is not the way to go.

I personally would steer a newbie away from SMDs as a project to learn soldering skills. Find some point-to-point or through-hole projects first.

For SMD rework we have Metcals (conventional soldering units), hot-air units, and big bench units that allow us to place and replace large (1000+ ball) ASICs on larger PCBs and such. The bench units have programmable temperature profiles and all that jazz. Maybe when I have $100k to play with I'll get one of my own. For personal use I bought an inexpensive Weller with controlled tip temp but rarely do soldering at home anymore unless something is broken. Maybe when I retire, though I am leaning toward the woodshop instead. Bigger stuff, easier to see, fewer burns (but deeper cuts).