Seeking solder/flux recommendation

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My standard soldering "recipe" is Kester 245 flux cored solder with Kester 951 liquid flux.  Most of my work is SMD by hand (little through-hole, no reflow).  My goal is as pristine a PCB as possible after soldering, with as little post-processing as possible.  Nevertheless, while Kester describes the results of 245 as "visually acceptable," there's still plenty of residue (either from the 245 or 951), most of which comes off with some mild isopropyl scrubbing with an anti-static brush.  Unless I put in a lot of effort, there's still residue visible.  Just wondering if someone here has a better recipe/process.  Thanks.

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I've used water soluble flux for a long time and it is by far my favorite.  A water rinse and blast with compressed air is all it takes for pristine clean boards.

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Might try a Kester 951 flux pen to limit the amount of flux applied.

Could try drag soldering in lieu of flux-cored solder (manual equivalent of automated wave soldering)

Gel rework flux Kester RF550 states easy removal of flux by automated means (ultrasonic bath?)

Kester 2331-ZX flux pen states it must be water washed (hot water typical)

No clean flux residue is usually acceptable unless conformal coat will be applied to the PCBA.


http://www.kester.com/

 

"Dare to be naïve." - Buckminster Fuller

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>  aerosol flux remover

 

Which one?

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> Might try a Kester 951 flux pen

 

That's what I'm using.

 

> Kester 2331-ZX flux pen

 

I've used that before, but cleaned with isopropyl, leaving residue.  I guess I should try water if that's what it calls for, but I'd think isopropyl would be at least as effective as water (though I'm no chemist).

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I've used water soluble flux for a long time

Same here for about 20 years but not allowed to say here as one gets ridiculed. wink

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Why is it cause for ridicule?

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alank2 wrote:
water soluble flux


Which one?

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Water soluble fluxes are of the "MUST wash" variety, aren't they?  I'd rather have ugly residue...

 

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Kester 951 contains "proprietary organic acids". Personally, I use solutions of oleic acid (about 50%) in ethanol or isopropanol as liquid flux, it's very easy to clean with alcohols. Since I have a degree in chemistry and access to "ingredients", I like to concoct my own fluxes cheeky

 

It's very easy, really, you just mix organic acids to adjust the desired properties:

Mild: Rosin and/or fatty acids like oleic (soluble in alcohol). Ratio of rosin to oleic acid determines how fluid the flux becomes during soldering. More rosin = more difficult cleaning and more viscosity.

Aggressive: Lactic, citric and other water soluble organic acids. I actually don't use this kind of flux, so can't give details.

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El Tangas wrote:
Kester 951 contains "proprietary organic acids". Personally, I use solutions of oleic acid (about 50%) in ethanol or isopropanol as liquid flux
Thanks for the tip. Time to order some C18H34O2.

- John

Last Edited: Tue. Dec 27, 2016 - 11:25 AM
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I use:

 

http://www.mouser.com/ProductDet...

 

http://www.mouser.com/ProductDet...

 

If you want to try the solder (0.031"), this is much cheaper:

 

http://www.ebay.com/itm/27228394...

 

The date of manufacture is 2011 I think, but I'm using a spool from 2011 right now and it is working fine...

 

Thanks,

 

Alan

 

p.s. The datasheet they have at Mouser is wrong - the above part number uses the 331 water soluble flux.

Last Edited: Tue. Dec 27, 2016 - 05:22 PM
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I use water washable no-clean tack flux.  It cleans easily under the faucet.  I use 64/40 rosin core solder.  It may be harder to clean if you use high temperature (350C?) no-lead solder.

 

http://www.chipquik.com/store/product_info.php?products_id=310004

 

 

Last Edited: Tue. Dec 27, 2016 - 08:39 PM
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lautman wrote:
Why is it cause for ridicule?

 

Because we're freaks

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut. 

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Torby wrote:

lautman wrote:Why is it cause for ridicule?

 

Because we're freaks

I've been mentioning for years that I like my water washable flux.  I had got nothing but disparaging remarks.  Now I learn that I'm not the only one around here that knows his azz from his elbow.  laugh

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I've been mentioning for years that I like my water washable flux.  I had got nothing but disparaging remarks.

When I first started working for myself full time I used "normal" solder and alcohol to clean them. Then the quantities of boards got rather large and I had to spend some time in rehab with AA meetings attendance....but it was fun. cheeky

 

Then we started to use a lady subcontractress and she said that she only used solder with water soluble flux, made about 10,000 boards in about 10 years and no problems. Yes you need to clean it, it maybe highly corrosive etc. but that's part of the game.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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I use ethanol to clean my boards using rosin core 63/37 solder.  It tends to leave a powdery residue that I brush off with a cheap paint brush.  I wonder if I should start going to AA meetings again.