Author Topic: Which solder flux pen? (Read 9377 times)

theleakydiode · « **on:** January 28, 2018, 06:54:52 pm »

Looking on amazon for a flux dispensing pen to aide with some SMD soldering I've come across a few different variants and don't really know what to buy.

The main ones I can find are "R" type "RA" rosin type, a "No clean" type", "Rosin RMA" and "water soluble". Having not done any SMD work before I have no idea which one to select, can someone help me out?

I normally use rosin 60/40 lead based solder and I'm a hobbyist so don't need a big expensive jar of the stuff, the main aim here is to get those SMD pads to take solder correctly. Also I live in a humid and cold place and I've read that moisture can be a problem with some types of flux.

Right now I'm looking at this one https://www.amazon.co.uk/MG-Chemicals-Rosin-Flux-Pen/dp/B0080X79HG

Any help on which one to buy would be great.

Thanks!

wraper · « **Reply #1 on:** January 29, 2018, 01:01:23 am »

You should never use water soluble flux unless you can wash bards professional way in a special machine.

theleakydiode · « **Reply #2 on:** January 29, 2018, 01:38:16 am »

Ok then so I'll be crossing that one off my list!

Which one would you pick for general hobbyist use?

GreyWoolfe · « **Reply #3 on:** January 29, 2018, 02:18:04 am »

I use RMA flux. I don't use a pen but a squeeze bottle with a needle tip and a nail polish type bottle with a brush. MG Chemicals 835.

theleakydiode · « **Reply #4 on:** January 29, 2018, 02:23:11 am »

Thanks.

Is RMA the best all purpose type? I'm going to get a pen as I can stuff it in my toolbox when its time to pack up since I don't have a permanent setup.

David Hess · « **Reply #5 on:** January 29, 2018, 03:32:54 am »

If you need additional flux then I would assume the board or leads are already tarnished so RA (rosin activated) would be my first choice. RMA would be more appropriate where boards and parts which are new and have not aged.

wraper · « **Reply #6 on:** January 29, 2018, 08:08:47 am »

Quote from: David Hess on January 29, 2018, 03:32:54 am

If you need additional flux then I would assume the board or leads are already tarnished so RA (rosin activated) would be my first choice.

RA is more active than needed for general work and needs cleaning. Which in hobbyist conditions in case of SMT parts usually is not possible to do properly under SMT parts.

theleakydiode · « **Reply #7 on:** January 29, 2018, 04:48:00 pm »

I think it might be easier if I just showed you all what I'm going to be doing.

What kind of flux would be best for this and do I need to worry about cleaning it up and if so what do I need for that? Like I said I'm a total beginner when it comes to SMD.

Pic related is the board in question and the small bag underneath shows the SMD parts.

tooki · « **Reply #8 on:** January 29, 2018, 07:24:39 pm »

I’d actually suggest a flux gel/paste. Since it’s tacky, it helps prevent SMD parts from blowing away until you’ve soldered them down.

I use this one from MG: https://www.amazon.co.uk/MG-Chemicals-Clean-Paste-Syringe/dp/B00425FUW2

You should still get a flux pen, though, they’re handy for lots of stuff.

theleakydiode · « **Reply #9 on:** January 30, 2018, 12:00:02 am »

Its odd but I can't find any RMA flux pens on UK websites, do they have banned materials in them or something?

Only ones I can find are R type and RA, I'm avoiding no clean and water soluble because of reasons mentioned.

wraper · « **Reply #10 on:** January 30, 2018, 12:44:09 am »

Quote from: theleakydiode on January 30, 2018, 12:00:02 am

Its odd but I can't find any RMA flux pens on UK websites, do they have banned materials in them or something?

Only ones I can find are R type and RA, I'm avoiding no clean and water soluble because of reasons mentioned.

What's wrong with no-clean, what reasons?

theleakydiode · « **Reply #11 on:** January 30, 2018, 01:28:13 am »

Quote from: DiligentMinds.com on December 20, 2014, 01:51:15 am

"No-Clean" flux is all "the rage" these days, and if you are having your boards built by an outside assembly contractor, they probably use this by default.

There is a slight problem with "no clean" flux though-- on very high impedance circuits [above ~1M-ohms], or high voltage [above ~300Vp], the no-clean flux can cause problems. This is due to the fact that it leaves a slightly conductive residue behind. The worst part is that you can *try* to clean a board that has been soldered with no-clean flux using water or whatever chemicals you might have in your kit, but it is almost impossible to get it all off of the board, and it still causes problems with high voltage and/or impedance circuitry. I think the no-clean flux actually eats into the solder mask or something. Very nasty stuff.

If your board is just popcorn analog or digital stuff with no high voltage, no high impedance, no precision requirements, etc.-- then by all means, go ahead and use no-clean flux.

Personally, I use liquid [and paste sometimes] rosin-type flux. It is tried and true, even if it does leave a sticky mess behind. I clean up the board when I'm done with 99% IPA, and blow it dry with air [or just let it air dry].

My circuit has high voltage and high impedance on it, plus I use rosin based solder and I read elsewhere that its best not to mix them.

theleakydiode · « **Reply #12 on:** January 30, 2018, 09:00:35 pm »

Anyone tried any of these two flux pens? https://www.ebay.co.uk/itm/Flux-Pen-No-clean-or-RMA-for-PCB-repairs-SMD-rework-pen-various/112162785290

Are they likely to be too cheap to be good?

frozenfrogz · « **Reply #13 on:** January 30, 2018, 10:57:34 pm »

For small rework and manual soldering of SMD components I am getting good results with the Stannol Mini-Fluxer X32-10i.
It is no-clean and halogen free. It contains quite a bit of solvent and is very thin fluid.
As a general purpose jelly type I can recommend "Löthonig" and Amtech NC-559-V2-TF for more serious jobs. Keep in mind though to buy Amtech from a reputable dealer. Most Amtech stuff on eBay / Amazon et.al. is fake.

https://www.eevblog.com/forum/beginners/flux-in-europe/ ...might be of interest as well

theleakydiode · « **Reply #14 on:** January 30, 2018, 11:27:54 pm »

>Stannol Mini-Fluxer X32-10i
Is that RMA type? I had a look in the datasheet but its quite cryptic about the rosin type.

Regarding the ebay thing this is why I was hesitant to pull the trigger, there is just so much crap out there and people looking to make quick cash. Times like this make me wish I lived in the US because of the range and choice you get when shopping online, plus prices are better.

I'm probably overthinking all this.

frozenfrogz · « **Reply #15 on:** January 30, 2018, 11:52:18 pm »

X32-10i is not rosin based but mixing with rosin filled solder does not seem to be a problem (from the datasheet), other than you need to clean the board afterwards - if that was the question.
What I like a lot is that I can get away with a very small amount of this stuff to produce good results. Less flux == less expenses == less fume == less stink == less work for the fume extractor ==

HwAoRrDk · « **Reply #16 on:** February 01, 2018, 07:59:20 pm »

Quote from: theleakydiode on January 30, 2018, 12:00:02 am

Its odd but I can't find any RMA flux pens on UK websites, do they have banned materials in them or something?

CPC sell one: http://cpc.farnell.com/qualitek/rework-wand-rma/rework-pen-rma/dp/SD01930

I have one. No complaints about it. (Well, apart from the silly name: 'rework wand'. What is this, Hogwarts? Fluxus Scourgify!

)

It's even made in the UK, so no, I can only conclude RMA isn't banned.

jasonbrent · « **Reply #17 on:** February 03, 2018, 05:10:30 pm »

This isn't strictly a pen, but is what I've been using lately...

Amtech Solder Flux NC-559-V2-TF 10cc 16150 Kit USA

https://www.amazon.com/dp/B01N8ZX7ZQ

-j

Sent from my SM-N950U using Tapatalk

theleakydiode · « **Reply #18 on:** February 05, 2018, 08:31:37 am »

Quote from: HwAoRrDk on February 01, 2018, 07:59:20 pm

Quote from: theleakydiode on January 30, 2018, 12:00:02 am
Its odd but I can't find any RMA flux pens on UK websites, do they have banned materials in them or something?

CPC sell one: http://cpc.farnell.com/qualitek/rework-wand-rma/rework-pen-rma/dp/SD01930

I have one. No complaints about it. (Well, apart from the silly name: 'rework wand'. What is this, Hogwarts? Fluxus Scourgify! )

It's even made in the UK, so no, I can only conclude RMA isn't banned.

I ended up getting that one since I was ordering from there anyway.

Should it hiss and boil as soon as the soldering iron it touched to it?

Quote from: jasonbrent on February 03, 2018, 05:10:30 pm

This isn't strictly a pen, but is what I've been using lately...

Amtech Solder Flux NC-559-V2-TF 10cc 16150 Kit USA

https://www.amazon.com/dp/B01N8ZX7ZQ

-j

Sent from my SM-N950U using Tapatalk

Wow that's kind of expensive, is it better than the regular RMA flux pens?

Quote from: frozenfrogz on January 30, 2018, 11:52:18 pm

X32-10i is not rosin based but mixing with rosin filled solder does not seem to be a problem (from the datasheet), other than you need to clean the board afterwards - if that was the question.
What I like a lot is that I can get away with a very small amount of this stuff to produce good results. Less flux == less expenses == less fume == less stink == less work for the fume extractor ==

My nose is the only fume extractor in this house

How do you clean off the residue without making an even bigger mess?


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Author Topic: Which solder flux pen? (Read 9377 times)

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