Soldering Flux

[slikrx]

I have heard time & again that using acid flux (usually used in copper plumbing) is very bad to use for electronics.

Now, back when I took my first electronics class (1985) we used a paste/gel flux that came in a tin, and later used some of my dad's similar stuff. I assume it was acid based, because I cannot find it anymore. too bad, because it wokred great for me.

Anyhow, on to the question:

How the **** do you get a decent solder joint using resin flux (or resin core solder)? :dontknow

With acid flux, I can make a BEAUTIFUL pre-tinned wire and great looking joints. Everything just wicks in and goes where I want, minimal overheating and looks pretty good. :D

With rosin flux or cored solder, I end up with lumpy, inconsistent solders joints, I can't pre-tin a wire to save my life, and nearly half my solder joints end up being cold-soldered and bound to fail.

I get better results by washing the wire/etc in acetone then abrading it to get fresh metal. Rosin just seems to be a waste and a hinderance for me.

I guess a second questuion is this: is acid flux REALLY that bad for electronics? I still use it because a chemically etched, but solid solder joint is much better than a cold soldered joint that isn't etched. :oops:

Anyhow, sorry for the rant, and thanks for any help/ideas!

[Jermo]

4 keys to soldering

Cleanliness - no matter how shiney it looks always clean the surfaces to be soldered. I keep a fine piece of scotchbright in my kit exactly for this purpose.

Heat Control- too much heat or too little heat creates bad solder joints.

Solder Control - apply the solder to the work not the soldering iron.

Cooling - Most electronics solder has 3 states, solid, plastic, and liquid. It goes through these states every time it's melted. Any movement in the joint as it cools can weaken the joint and create a cold solder joint. Some solders (subeutechnic<sp?>) only have two states; solid and liquid. these are harder to find but are easier to work with.

Are you working with 60/40 rosen core solder or solid core solder and seperate flux?

Acid based flux is bad for electronics/wiring regardless.

Jermo

[DebianDog]

A good BIG HOT iron help my joints but they are still poor in the grand scheme of things. Do not feel bad.

[slikrx]

I have the 40 watt iron from Radio Shack as well as 60:40 (also from RS) and non-cored solder.

What brand of flux is any good?

I can use identical technique with acid vs rosin fluxes and the results simply do not compare. My acid flux connections look pretty good. The rosin fluxed joints are almost unusable.

I simply cannot get solder to wet the surfaces properly and penetrate the strands of wire with rosin. I get better results with NO flux and jest scuff the surface. Which is a royal pain with stranded wire :arggg:

Rosin core solder isn't really any better. (for me)

I have a couple small items I soldered together 20 years ago with that old flux, and the joints are still look solid. I think one or two traces came off the PCB, but whether that was flux related or more related to the fact that I have hand etched PCBs that have been carted around and abused for 20 years is hard to say :dontknow

[Jermo]

I've been soldering since I was 15 (27 years) and can tell you 100% if you're having that much trouble you're doing something wrong.

Keep the tip of the soldering iron clean and tinned, the items to be soldered clean (and you can tin them depending on the application).

I use radio shack irons and 60/40 rosen core solder. Use the cored solder, it's easier to work with. I've worked with solid solder wire and liquid flux in the Navy. It's a bit harder to deal with IMHO but does a superior job. When learning to solder use the 60/40. It's perfect for most electrical/electronics applications and is easier to deal with.

NOTE: you only need a small amount of solder. The idea is to join the surfaces not see how high a mountain you can make :D

When you solder you aren't looking for flux you are looking for solder. Please post pictures to help us get an idea of your struggle. Post the exact proceedure you are using. For most electronics soldering a 20w iron is fine. For connectors (like deans) I use a 40W (but you have to be darn careful or you'll burn/melt the connectors).

:Pics

[WayneBrown]

tin the tip of the iron, apply to the work and add more solder (to the work) slowly until it flows.
Solder itself will transfer heat better in a 'wetted' state than you will get with a bare iron tip BTW.
Tin both pieces of the work evenly, ending with a shiney, smooth tinned end.
Place both pieces of work in a jig, re-tin soldering iron and apply to work. When the solder flows add more ( to the work) to create the joint that you need. If you are too hasty, the joint will look cold, apply heat and more solder until the joint looks wet and shiney.
I redress the iron tip every few uses with a file followed by emory cloth or sandpaper and re-tin.
I use either a 30W iron in the field, or a 20/40W station at the shop. All the proper preparation work in the world is useless if the iron cannot maintain the temp, or you are too impatient and don't allow it to heat up.

[slikrx]

I'll try to get stuff to make a quick video of my "technique" and show the results, both good & bad. It'll take a few days.

But, as a rule I do the following:

Clean the tip every 5-10 uses with sandpaper.
Pre-tin the tip every time I heat it up.
use a wet sponge to clean slag/gunk off during soldering -then re-tin the tip.
Pool solder on the tip and let it flow into the joint/sire/etc.

Acid based flux works VERY well for me and I'm really happy with the results I get. So, I assume I'm not totally off base in my technique. It's just that the resin based ones I have tried to date are 99% worthless, IMHO :oops:

Let me ask you guys this: what BRAND of flux do you use?

Anyhow, thanks for the input/help and your responses!

[Jermo]

I use standard 60/40 radio shack rosen core solder.

do what's best for you. Personally I'll never use acid core solder or acid based flux on anything electrical under normal (non-emergency) conditions.
Jermo

[Pinecone]

The stuff in a tin is probably resin flus. The same stuff that is inside the solder. Just more of it. Last time I looked it was still available.

Heck, Amazon has it: http://www.amazon.com/exec/obidos/search-handle-url/index=blended&field-keywords=rosin%20flux&results-process=default&dispatch=search/ref=pd_sl_aw_tops-1_blended_26033529_1&results-process=default

[don_87]

I use resin core wire solder. Works great for me, but 1 tip for ya......always make sure the hole in the tip of the roll of solder is melted shut before putting the solder away(the flux will come out of the end leaving you with nothing the next time you use it).

[slikrx]

After bugging the EE's at work, I tried a few of their fluxes.

I actually found one I like and can use. "Kester" brand rosin paste flux. From Fry's Electronics.

I tried 3 other fluxes (including a liquid one) and couldn't solder worth a darn with them.

I plan on hitting Fry's for 3 or 4 jars of the stuff. :mrgreen:

[monty666]

Without reading all the posts i may be just saying what has already been said. I work on printed circuit boards all day hand building guitar effect pedals and i find the best way to solder ie having a clean shiny and strong join,

- black crap on the tip of your iron is no good
- a goldish colour from a very clean iron is also no good you want to have a small ammount of shiny silver coloured solder on your tip this makes the best conditions to flow solder

1. Hot iron if you have a temp controlled iron you want it around 380 for tinning wires.
2. use THIN solder with a flux core your working with wire that is like 2 or 3 mm not mains cable so no need for the really thick solder
3. the very point of the iron is not actually the hottest part you want to use the side of the tip about 3mm up from the very tip
4. Tin you iron so just melt a tiny bit of solder to the iron that way there is already some solder melted ready to flow this also allows for the best transfer of heat to the still solid solder.
5. when you go to tin a wire touch the wire with the melted solder on the iron then feed the solder onto the part where the melted solder, wires and iron are contacting.

The biggest mistake people make is they try to 'Paint' on the solder which is wrong in order for the solder to flow you need heat .. the iron is the catalyst in this equasion with out the iron nothing happens

6. to make a good solder join you need the surfaces you want to join to be hot so dont put a huge blob of solder on the iron and sick the wire in it .. that wont work .. the solder wont flow through the copper wires and bind them together it will only coat the outside which will give you a dry join


Anyway my 2 c :)

its a 3 part process

1. contact the 2 things you want to join with the iron to heat them up this is a 1 1/2 second process
2. feed the solder onto where the iron and the 2 things you want to join meet
3. once you are happy pull the solder away and then pull the iron away