Cleaning PCBs: works ... but ...

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(I have read other "cleaning PCB" posts but I don't see an answer to this aspect of the issue)

 

I use a combination of solder paste and rosin-core solder (what can I say, I was given a bunch of it).

 

I clean the boards with 99% alcohol and it works well, except ...

 

After I have done several boards a sticky film is left behind which, I assume, is flux that was cleaned off but left in suspension.

 

I tried filtering the used alcohol but the filter material quickly clogged up and became useless.

 

Using several staged baths as someone suggested would help but is not a long-term solution if doing a lot of boards.

 

I can only think of two solutions:

 

1) Distill the used solution to remove the suspended flux (this assumes a lower boiling point for the alcohol) ... heat and alcohol - this sounds like a recipe for disaster ...

 

2) Use a centrifuge to remove the heavier (?) flux (isolate to the bottom of the container) ... complicated but doable

 

Other ideas?

 

Regards,

 

Chuck Hackett

 

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ChuckH wrote:

I can only think of two solutions:

[:facepalm:]

"Experience is what enables you to recognise a mistake the second time you make it."

"Good judgement comes from experience.  Experience comes from bad judgement."

"Wisdom is always wont to arrive late, and to be a little approximate on first possession."

"When you hear hoofbeats, think horses, not unicorns."

"Fast.  Cheap.  Good.  Pick two."

"We see a lot of arses on handlebars around here." - [J Ekdahl]

 

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Rosin based solder does not need to be cleaned, it may look messy, but does no harm. 
if you want clean boards, you should be using water based fluxes, then hot water will clean your boards.

Either live with the chemicals you have or switch to a better process!

jim

 

 

Keys to wealth:

Invest for cash flow, not capital gains!

Wealth is attracted, not chased! 

Income is proportional to how many you serve!

 

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ChuckH wrote:
Other ideas?
Elbow grease wink

PCBA manufacturers probably agitate the assemblies in a solvent bath; could try a brush for a quick evaluation.

 

Affordable PCB Etching System with Agitator and Heater

 

"Dare to be naïve." - Buckminster Fuller

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What does the solder datasheet say? I am using a mildly activated rosin core (RMA); it is no clean.

 

https://www.kester.com/products/product/285-flux-cored-wire

 

There is also activated rosin (RA), which I have seen removed with de-greasers. Still, the datasheet says it is "non-corrosive, non-conductive and does not require removal for most applications."

 

https://www.kester.com/products/product/44-flux-cored-wire

 

I would get some solder that does not need cleaning rather than sort out a de-greaser and distillation process.

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gchapman wrote:

Elbow grease wink

PCBA manufacturers probably agitate the assemblies in a solvent bath; could try a brush for a quick evaluation.

 

Affordable PCB Etching System with Agitator and Heater

 

 

I use an ultrasonic cleaner followed by vigorous brushing (while still submerged) with a toothbrush.  The boards are getting 'clean' in that the flux accumulations are being removed ... the issue is that, upon removal from the alcohol bath a thin layer of flux is being left behind because the alcohol contains flux in uniform suspension.  No amount of agitation is going to fix that as far as I know.

 

Regards,

 

Chuck Hackett

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Can flux become a powder?

(wash, bake, wash)

 

"Dare to be naïve." - Buckminster Fuller

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ChuckH wrote:

1) Distill the used solution to remove the suspended flux (this assumes a lower boiling point for the alcohol) ... heat and alcohol - this sounds like a recipe for disaster ...

This is exactly how big cleaning baths we used n the old days kept the (now banned) tri-chloroethane solution clean. It was a continuous process with a dirty tank and a clean tank. After cleaning a  large qty of boards you had to leave the machine a few hours for the cleaning tank to re-generate.

 

 

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Citrus rind are for some industrial solvents and medicines.

You searched for citrus - MicroCare Electronics

 

"Dare to be naïve." - Buckminster Fuller

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At the hobbyist level, I use wipes to wick up the IPA from the board, so as not to leave any sticky residue. 

 

Method: flood with IPA, agitate with a stiff brush, lay a piece of wipe over the board, then use the brush in a stippling motion to soak it up into the wipe. Repeat if necessary.

 

This works too: https://youtu.be/BvhE16vBfX4?t=224

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ChuckH wrote:
I clean the boards with 99% alcohol and it works well, except ...

it's highly flammable and leaves the boards messier then when they started....

Most effective rosin flex removers have been removed from the market, because environmentally friendly methods have been developed.

Best to just leave it, it does no harm, it just does not look as nice as boards soldered with water soluble flux methods.

 

Jim

 

 

Keys to wealth:

Invest for cash flow, not capital gains!

Wealth is attracted, not chased! 

Income is proportional to how many you serve!

 

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ChipQuik makes water washable solder paste.  I haven't used it.  I don't solder much lately.  I have used ChipQuik's water washable paste flux.  It's easy to clean under the kitchen faucet.  I use a toothbrush to get into the nooks and crannies. 

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Thanks for the input.  Looks like I will use a combination of a) purchase some 'no clean' solder, b) IPA and wipes for some cases, and c) just leave it if not for sale to customer.

 

Regards,

 

Chuck Hackett

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Go to your local auto paint supplies and get acrylic thinners. You want the one with more 'bite'. Warm up your boards a little and give them a wash in this stuff. Clean as a whistle. Note the thinners is nasty stuff - the solution might well be worse than the problem.

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ChuckH wrote:

...c) just leave it if not for sale to customer.

 

Or leave it and sell it anyways. Make a selling point of it, people like products that are made in an environmentally friendly way. Cleaning PCBs uses chemicals and /or water, and the waste product needs to be disposed of.

#1 Hardware Problem? https://www.avrfreaks.net/forum/...

#2 Hardware Problem? Read AVR042.

#3 All grounds are not created equal

#4 Have you proved your chip is running at xxMHz?

#5 "If you think you need floating point to solve the problem then you don't understand the problem. If you really do need floating point then you have a problem you do not understand."

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Kartman wrote:

Go to your local auto paint supplies and get acrylic thinners. You want the one with more 'bite'. Warm up your boards a little and give them a wash in this stuff. Clean as a whistle. Note the thinners is nasty stuff - the solution might well be worse than the problem.

It can also remove signage on components.

 

As a teenager, last millenium, I used a spray can of tricho when making boards in my bedroom. Surprised I am still alive.

Ross McKenzie ValuSoft Melbourne Australia

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ChuckH wrote:
I clean the boards with 99% alcohol and it works well 

I am no longer able to find 99% alcohol (isoproply I assume)

Even years before Covid, can only find 91% or 70% isopropyl alcohol.

Any ideas where I can buy this? I am in Canada.

I don't do a lot of boards, but the 99% isopropyl alcohol works good after soaking the board

then use compressed air. Sometimes a small toothbrush is needed to clean stubborn areas.

 

Last Edited: Tue. Sep 8, 2020 - 08:04 PM
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Plenty of 99.9% on eBay UK. Maybe a temporary shortage due to the pandemic ?

 

Also known as isopropyl alcohol, IPA, or isopropanol. 

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Amazon!

 

 

Keys to wealth:

Invest for cash flow, not capital gains!

Wealth is attracted, not chased! 

Income is proportional to how many you serve!

 

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"Experience is what enables you to recognise a mistake the second time you make it."

"Good judgement comes from experience.  Experience comes from bad judgement."

"Wisdom is always wont to arrive late, and to be a little approximate on first possession."

"When you hear hoofbeats, think horses, not unicorns."

"Fast.  Cheap.  Good.  Pick two."

"We see a lot of arses on handlebars around here." - [J Ekdahl]

 

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"Dare to be naïve." - Buckminster Fuller

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Home Depot and Lowe's sells all kinds of solvents.  You can get the alcohol by the gallon (when it's available), and there's several other pain thinners.

 

After you clean them and they have that thin sticky film, that will dry up and not be sticky after a while.   So once you get to that point, I wouldn't worry about it.  You could bake it to speed up the process and help dry it. (fairly low temps work).

Just gettin' started, again....

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Keep it sealed tight & away from your sauna, it loves to abssorb moisture

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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ki0bk wrote:
if you want clean boards, you should be using water based fluxes, then hot water will clean your boards.
otherwise

Is It Necessary to Clean No-Clean Flux? | Electronic Design

by Akber Roy [CEO of Rush PCB]

Most assemblers in the electronic industry use no-clean solder paste mainly to eliminate the requirement of cleaning the circuit board assemblies.

...

 

Why Clean No-Clean Flux

[1GHz clock signals, conformal coating and/or underfill, appearance]

 

How to Clean No-Clean Flux

Simple water can’t clean the flux residue left behind by no-clean solder paste—it requires a solution of saponifier in water.

...

 

Cleaning Lead-Free No-Clean Flux

...

 

How Cleaning No-Clean Flux Helps

[high-frequency, high-voltage, high-impedance]

[solder balls]

[ease QC]

...

 

Selecting No-Clean Flux Removers

[strong enough yet no damage, non-flammable, dispenser]

 

Conclusion

...

 


San Jose, CA

PCB, Printed Circuit Board Manufacturer & Assembly | RushPCB USA

 

Underfill revisited: How a decades-old technique enables smaller, more durable PCBs | Embedded

Underfill for CSP and BGA - Epoxyset

Underfill for CSP and BGA (EpoxySet)

 

Flux Cleaner, Saponifier, and Descaler | Superior Flux & Mfg. Co.

 

"Dare to be naïve." - Buckminster Fuller

Last Edited: Tue. Dec 1, 2020 - 07:35 PM
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this seems ok...I use it in an ultrasonic.  A really hardened flus is still a tough job

 

However, this reminds me of  "soap" , doesn't have the nice knockout vapors of the good old cleaners.

 

http://www.techni-tool.com/237CH...

 

here is the GOOD stuff: flux off ROSIN

http://www.techni-tool.com/237OZ...

 

note the hazmat warnings---so you know it's good!

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Tue. Dec 1, 2020 - 08:10 PM
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You all may think I'm nuts, but here's what I do:

 

1: Submerge the PCB in "Klean Strip" lacquer thinner. Use an old toothbrush to scrub areas clean. The lacquer thinner works very quickly - the board only needs a few minutes at most here. Residual flux from previous cleanings is no problem since the next step removes any residue.

 

2: Rinse the PCB in clean 99% isopropyl alcohol. 

 

3: Blow dry with a vacuum cleaner blower.

 

Never had any problems with any board - ever.

 

NOTE: Both solvents are extremely flammable (even their vapors). Work in a well ventilated area or outside and, obviously, no smoking or any other ignition danger.

 

NOTE: Both solvents can irritate skin. Use gloves. Don't inhale the vapors either.

 

Gentlemen may prefer Blondes, but Real Men prefer Redheads!

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Krupski wrote:
You all may think I'm nuts,
unaware?

Krupski wrote:
1: Submerge the PCB in "Klean Strip" lacquer thinner. ...

...

... Use gloves. Don't inhale the vapors either.

  • Approximately 5% benzene
  • PPE on page 5

Klean Strip Paint Thinner | MSDS

 

"Dare to be naïve." - Buckminster Fuller

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Just curious - doesn't the lacquer thinner eat the solder resist?

 

Neil

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I used to buy Klean Strip shellac thinner, which is ethanol denatured with methanol.  I used it to clean boards before it became unavailable in California because it was deemed a carcinogen, probably because of the methanol.  Now I use 200 proof anhydrous ethanol, which is actually 95% ethanol denatured with 5% isopropanol.  Proof is a measure of water in the mixture, not the amount of ethanol.  When I could no longer get the Klean Strip I bought a gallon of 200 proof ethanol denatured to Govt formula No. 40-B, which is 1/16oz of Denatonium Benzoate per 100 gallons of ethanol.  Denatonium Benzoate is supposedly the bitterest substance known to man.  I dipped my finger in it and thought it tasted sort of good, but when I sprayed down boards and scrubbed them with a flux brush I didn't like the smell, so I set it aside and bought a gallon of ethanol with the isopropanol denaturant, which smells more like it should.  Lacquer thinner has a lot of toluene in it along with other harsh solvents.  It's good if you want to huff glue, but not so good on internal organs like the brain.  It smells good. The Klean Strip shellac thinner left behind a powdery layer on the board that could be brushed off with a paint brush.  The 200 proof ethanol doesn't leave anything behind, and evaporates quickly because there is no water in the mixture.  I figure the fumes are not so dangerous since a lot of people drink ethanol, and the 5% isopropanol isn't too worrisome.

 

99% isopropanol is readily available again on eBay for $30 / gallon after the initial rush for it to decontaminate surfaces from covid.  A lot of people use it to clean boards, so I guess it must work.  I have never used it, but may start when I use up the gallon of ethanol I have now.  Ethanol costs more than isopropanol.  It turns out the 70% isopropyl rubbing alcohol actually kills more germs than 99% isopropyl.  For some reason the extra water makes it more effective.  At least that was what I was told when I worked in the medical device industry.

 

Most of the commercial hand sanitizers are 60-70% ethanol.

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gchapman wrote:
Approximately 5% benzene
One of only 4 controlled substances in automotive assembly plants in North America.  The other three are lead (in some body work), cyanoacrylate (in paints), and Tanner's solvent (the main component in WD-40).
Krupski wrote:

You all may think I'm nuts, but here's what I do:

Well, >>I<< do ;-)

 

"Experience is what enables you to recognise a mistake the second time you make it."

"Good judgement comes from experience.  Experience comes from bad judgement."

"Wisdom is always wont to arrive late, and to be a little approximate on first possession."

"When you hear hoofbeats, think horses, not unicorns."

"Fast.  Cheap.  Good.  Pick two."

"We see a lot of arses on handlebars around here." - [J Ekdahl]

 

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Have you tried sand blasting?  Has the government classified sand as toxic?  smiley

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steve17 wrote:
sand as toxic
Long known to be so.

"Experience is what enables you to recognise a mistake the second time you make it."

"Good judgement comes from experience.  Experience comes from bad judgement."

"Wisdom is always wont to arrive late, and to be a little approximate on first possession."

"When you hear hoofbeats, think horses, not unicorns."

"Fast.  Cheap.  Good.  Pick two."

"We see a lot of arses on handlebars around here." - [J Ekdahl]

 

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joeymorin wrote:

steve17 wrote:

sand as toxic

 

Long known to be so.

Oh oh, I didn't know.  Have they closed the beaches or maybe they just paved them over.  smiley

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barnacle wrote:

Just curious - doesn't the lacquer thinner eat the solder resist?

 

Neil

 

Nope.

Gentlemen may prefer Blondes, but Real Men prefer Redheads!

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gchapman wrote:

Krupski wrote:
You all may think I'm nuts,
unaware?

Krupski wrote:
1: Submerge the PCB in "Klean Strip" lacquer thinner. ...

...

... Use gloves. Don't inhale the vapors either.

  • Approximately 5% benzene
  • PPE on page 5

Klean Strip Paint Thinner | MSDS

 

 

The point? I DID warn about flammability, to use gloves, to not inhale the vapors, not to smoke, etc...

 

I think people are overcautious about "safety", especially now with the "highly communicable flu" going around.

 

How about wearing a complete SCAPE suit while cleaning a PC board? How about a SCAPE suit under a complete NASA spacesuit? Never can be too careful!

 

And don't forget, wear your symbolic mask!

 

Gentlemen may prefer Blondes, but Real Men prefer Redheads!

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Krupski wrote:
The point?
That post was due to me recalling what an automobile painter said.

He is the survivor among other such painters as only he wore PPE; his colleagues passed on early due to cancer.

He's a senior though not yet an elder; IIRC, automobile paints are now water-based.

 

 

"Dare to be naïve." - Buckminster Fuller

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PPE? The main this is...don't forget to discharge your picture tube!!!

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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gchapman wrote:

Krupski wrote:
The point?
That post was due to me recalling what an automobile painter said.

He is the survivor among other such painters as only he wore PPE; his colleagues passed on early due to cancer.

He's a senior though not yet an elder; IIRC, automobile paints are now water-based.

 

 

 

Well, I can see how breathing in paint vapors for a living could be hazardous to one's health, but an occasional 3 minute exposure to a solvent that's freely sold in a hardware store is not (IMHO) anywhere near the same thing.

 

If I do get sick from cleaning a PC board, you can say "told ya so".  smiley

 

Gentlemen may prefer Blondes, but Real Men prefer Redheads!

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avrcandies wrote:

 

PPE? The main this is...don't forget to discharge your picture tube!!!

 

 

Haven't worked on one of those in a long, long time. But I will admit getting a shock from a CRT anode once. Not because I didn't know it held a charge, but because my thumb was too close to the metal part of the screwdriver. I slid under the rubber cap and SNAP a 1/2 inch spark jumped to my thumb. Didn't hurt but it startled me. Now if I had half a brain I would have clipleaded the screwdriver to ground....

Gentlemen may prefer Blondes, but Real Men prefer Redheads!

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But I will admit getting a shock from a CRT anode once

One of our techs was tasked to clean up the eng lab...he was going about it & suddenly there was a huge crash...He had picked up a 20" picture tube and launched it across the room as it touched his belly and gave him a 10KV surprise. 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!