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WIGGLING 'LITE' IN GUEST MODE

Why wash PCBs?
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2  Next [all]
Author Why wash PCBs?
electricanada
Does flux really need to be removed? Is it only unsightly, or does it impair functionality in some way?
devinw1
Well, you do realize they make solder with literally named "no clean" flux, right?

wink
thetwlo
http://orbit.dtu.dk/files/100370544/Corrosion_in_electronics.pdf
sduck
It all depends on what kind of flux is in the solder you use. If you're using Kester 245 No-Clean, you can go ahead and... well, not clean it after soldering. If you use Kester 331 organic water-soluble flux solder, you NEED to clean it with hot water (and perhaps scrubbing with an old toothbrush) to get the flux off, as it's extremely corrosive over time, and will eat through your pads and such eventually if you leave it.
ranix
I have a test in progress now where I soldered a bunch of surface mount components to a board with corrosive solder without cleaning it and am observing the behavior. So far nothing visible, it's been about a month. I am sure over time it will damage the board, though.

I wouldn't "wash" the pcb, I'd just remove the excess flux with a swab and some alcohol.
electricanada
devinw1 wrote:
Well, you do realize they make solder with literally named "no clean" flux, right?

wink


No, I don’t know much about solder at all. This is what I’ve been using:

https://www.amazon.com/KESTER-SOLDER-32117-24-6040-0027-Diameter/dp/B0 0068IJPO/ref=pd_rhf_ee_s_rp_0_3/146-3427580-1981718?_encoding=UTF8&pd_ rd_i=B00068IJPO&pd_rd_r=e8c51df0-a54a-490e-b693-64868a7f2402&pd_rd_w=E ZDVa&pd_rd_wg=NQuJn&pf_rd_p=f4c63947-4e8b-4aeb-a925-1d4e1a211124&pf_rd _r=7VSPMYMR0A5KJNTF9ZFX&psc=1&refRID=7VSPMYMR0A5KJNTF9ZFX

It says on Amazon: “Kester ""44"" 60/40 Solder Rosin ""44"" Is A High Activity Ra Core Flux Designed For Excellent Instant Wetting Action, Even On Nickel Surfaces. Although ""44"" Is A Ra-Based Material, The Residues Are Non-Corrosive If Not Cleaned. Per J-Std-004, ""44"" Is Classified As Rom1 Flux.• Type: Wire• Alloy: 60/40 (60% Tin, 40% Lead)• Description/Function: Wire Solder• Diameter: 0.031" (1.57 Mm)• Core Size: 66• Contains Lead: Yes• Package Type: Spool• Weight: 1 Lb Also Available In Diameter Size 0.062"".

So this is no clean solder, and I can just leave the flux residue? Thanks very much guys.
ultravox
electricanada wrote:
Does flux really need to be removed? Is it only unsightly, or does it impair functionality in some way?


It depends on they type of solder / flux you're using. Some flux can be corrosive and even conductive if left on a PCB. When I built the TTSH I was getting S&H droop (sample & hold cap would not maintain it's charge and the voltage drooped over time). After thoroughly cleaning off the flux the S&H was rock solid.

I use Kester 331 and 245 Flux-Cored solder. This is a good combination for how I work.
Revok
Looks like you're good to leave it on there.

"The “44” flux residues are non-conductive and non-corrosive to temperatures up to 85°C (185°F) and 85%RH as determined by IPC Surface Insulation Resistance (SIR) test method 2.6.3.3. Residue removal would normally be for cosmetic reasons. If the end application of the assembly will be in a heated environment and seeing temperatures of over 185°F, then product specific testing should be performed by the designer/assembler."

https://www.kester.com/knowledge-base/faq#46138-44-flux-residues-the-q uestion-is-frequently-asked-are-44-flux-residues-harmful-to-an-assembl y
davebr
People send me DIY projects to repair when they don't work after building. Flux can cause havoc with high impedance circuits and sometimes I just need to wash the board to get it to operate correctly.

The larger issue is with so much flux on a board, one can't see the cold and incomplete soldering. It makes it more difficult to inspect soldering. A washed board should have a sea of shiny and smooth soldering. You can't see that with flux everywhere.

Finally, it moves the build from amateur looking to professional looking. There is a reason most professional companies wash their boards.

Dave
electricanada
I have a box of Kimwipes. Will that work, or do I need to buy some rubbing alcohol too?
TheMentat
sduck wrote:
It all depends on what kind of flux is in the solder you use. If you're using Kester 245 No-Clean, you can go ahead and... well, not clean it after soldering.


Interestingly enough, "No-clean" has a double meaning with this stuff... it doesn't come off easily!
moogah
For the love of god clean the flux off your boards. Why would you spend 5 hours building a module only to skip the 30 seconds it requires to actually make sure it will function properly.

Kester 245 no clean is fine for pots, switches and jacks on a faceplate board where you really don't have a choice, but really if your PCB is covered in flux spooge and doesn't perform correctly.. well.. fix that.

Water soluable flux core wire is great. It'll make nice clear joints even on old and somewhat dirty PCBs.. And a _pound_ of it is cheap. I bought one of these 10 years ago and only recently ran out.

https://www.amazon.com/Kester-331-Lead-Solder-Wire/dp/B0032US9SA/ref=a sc_df_B0032US9SA/?tag=hyprod-20&linkCode=df0&hvadid=312125823820&hvpos =1o5&hvnetw=g&hvrand=16851554826709575810&hvpone=&hvptwo=&hvqmt=&hvdev =c&hvdvcmdl=&hvlocint=&hvlocphy=9061331&hvtargid=pla-569455021663&psc= 1
electricanada
moogah wrote:
For the love of god clean the flux off your boards. Why would you spend 5 hours building a module only to skip the 30 seconds it requires to actually make sure it will function properly.


Honestly, because I'm a total noob who's only ever built three modules and don't know how to clean the flux up. What stuff do I need?
thx2112
electricanada wrote:
I have a box of Kimwipes. Will that work, or do I need to buy some rubbing alcohol too?


Use both together. Put a Kimwipe over the PCB and then put IPA on the Kimwipe and rub it around with a stiff brush. IPA will dissolve the flux, but it needs to get absorbed into something or else it'll just get smeared around and make a big ugly mess.

Look at 10:20 here:

EATyourGUITAR
kimwipes + rubbing alcohol + an old toothbrush to push it around. if your leads are not clipped tight and straight then you could really tear up your kimwipes pretty fast. alcohol is not the most effective thing I have tried to clean flux but it is the most safe for your health and the environment. it is also cheap. I used a specialty spray to clean flux from a DIY power supply because I don't ever want a power supply to kill all my modules no matter how many decades have passed.
moogah
electricanada wrote:
moogah wrote:
For the love of god clean the flux off your boards. Why would you spend 5 hours building a module only to skip the 30 seconds it requires to actually make sure it will function properly.


Honestly, because I'm a total noob who's only ever built three modules and don't know how to clean the flux up. What stuff do I need?


Totally fair, everything I recommend comes from advice given to me from more experienced builders when I was a noob smile Kester 331 solder is perfect for the main build of a PCB, solder everything in except pots, trimpots, switches, sliders jacks etc. Once all those are fully soldered, take it to your sink with some nice hot water and literally wash it like it was a dish, I use an old tooth brush to help scrub the flux off and it takes maybe a minute to get all clean (you can tell it's clean because the flux makes little bubbles when it's present, and when no more little bubbles are there, you're done.. just like washing dishes).

Kester 245 "no-clean" is perfect for all the components that shouldn't be washed like this. Note that many parts can handle warm water, but washing off flux would mean that you'd get the chemicals in the flux deep into the parts which is bad for pots, switches.. etc. They all have lubricants and other things that would be damaged by this so better to just not do that. No-clean solder has a gentle flux that is generally OK to have left on the boards, and for the most part the components you solder in with it have wide spacing between their solder pads so the flux isn't going to connect with another pad and potentially cause an issue.

Part numbers I use:
Kester 24-6337-6401
Kester 24-6337-8800

(Thanks to Paul Schreiber from synthtech for this advice given nearly 15 years ago smile)
mskala
I use no-clean flux, but after someone started a thread (not here, Wigglers are smarter than that) calling me out for "sloppy" soldering that "looks like a how not to solder guide" - apparently just because of the flux left on the boards - I clean it off anyway. When I'm selling my work I can't afford to have that going on, and I can't get into arguments with such people either.
electricanada
Thanks a lot everyone. You guys are the best.
thetwlo
sduck wrote:
It all depends on what kind of flux is in the solder you use. If you're using Kester 245 No-Clean, you can go ahead and... well, not clean it after soldering.


kinda, the article I posted to, stated that "no clean" needs to reach a certain temp, before that is true/effective. I always wondered why Paul S. MOTM said to use both, why not just 245? Maybe it's not as easy to work with? -I guessed.

But it seems like you want to use 245 for jacks and hardware that can not be washed, but can withstand the higher temps.
EOTS
moogah wrote:
Kester 331 solder is perfect for the main build of a PCB, solder everything in except pots, trimpots, switches, sliders jacks etc. Once all those are fully soldered, take it to your sink with some nice hot water and literally wash it like it was a dish, I use an old tooth brush to help scrub the flux off and it takes maybe a minute to get all clean (you can tell it's clean because the flux makes little bubbles when it's present, and when no more little bubbles are there, you're done.. just like washing dishes).

… "no-clean" is perfect for all the components that shouldn't be washed like this.


(Thanks to Paul Schreiber from synthtech for this advice given nearly 15 years ago smile)


+1

I also do it like that.
BTW, there are also lead-free variants with those flux types available, dual process is also possible there!
EOTS
But I'm still searching for a flux pen/bottle perhaps with a brush to apply in the EU.

There are fine products for no-clean/rosin removal, but they contain ammoniak and stink like hell: http://dr-stamm.de/pinf/tr14_8538-8.pdf

So I'd really prefer to avoid this using as much water soluable stuff as possible.
fuzzbass
EOTS wrote:
But I'm still searching for a flux pen/bottle perhaps with a brush to apply in the EU.

There are fine products for no-clean/rosin removal, but they contain ammoniak and stink like hell: http://dr-stamm.de/pinf/tr14_8538-8.pdf

So I'd really prefer to avoid this using as much water soluable stuff as possible.


Kester 186 is available in liquid squeeze bottles, and is a mildly activated, no clean formula. Useful for smd, rework or fixing cheap-ass desoldering braid that does not have enough built in. It is rosin based so you can still clean it with isopropyl alcohol + all the usual caveats. The package I bough came with a rather big dispensing needle, but it will flow through the smallest needles available. The bottle says Tekline supply/CMLsupply.com on it and I think I found it on Amazon.

Also, and I think most folks know this - but was not stated above. Always use no-clean flux when soldering wire to board connections, especially with stranded hookup wire. The flux will wick up under the insulation so you don't want organic flux there.
defalut
EOTS wrote:
But I'm still searching for a flux pen/bottle perhaps with a brush to apply in the EU.

There are fine products for no-clean/rosin removal, but they contain ammoniak and stink like hell: http://dr-stamm.de/pinf/tr14_8538-8.pdf

So I'd really prefer to avoid this using as much water soluable stuff as possible.


https://www.electrokit.com/produkt/flussmedel-penna-10ml/ this what i use. Sweden, so inside EU.
Alright it´s no brush but rather a felt stick that when you press it it gets "wet".
Not cheap but small and useful.
deepblackjoe@gmail.com
Let's say I have some modules working fine that I used Kester 331 on in the last year and didn't clean because I wanted to believe the "organic" flux would just be protecting the joints from oxidization, or just balked at the idea on running this device under the sinktap that normally you would never get wet. A little late I realize my folly and want to go back and take them from their cases to clean them right - is this OK to do? Should I maybe just pop the IC's or does that not even matter? Avoid the trimmers? I guess put them in front of a fan to dry them faster. Anything else I should watch for, or is it a bad idea at this point? I'd be sad if I put it all back together and I just had new problems
cornutt
thetwlo wrote:


But it seems like you want to use 245 for jacks and hardware that can not be washed, but can withstand the higher temps.


The 331 organic flux is a lot more aggressive at cleaning up oxidation and gunk. Most metals will oxidize slowly in non-dry air, and when you handle parts and leads, moisture from your finger is going to accelerate that to an extent. Boards and parts that have been sitting in a warehouse for a while are going to have some oxide on them. 331 makes it easier to get a good clean joint.

As others have pointed out, with Paul's method, you're going to be using the 245 mainly for parts that have larger leads, more widely spaced. With those, it's not as critical to get an absolutely clean joint.
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