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The Versatile Preform

Cleaning No Clean Boards With IPA

Cleaning No Clean Boards With IPA
Are there specific instructions for cleaning no-clean circuit boards using IPA? The Assembly Brothers, Phil Zarrow and Jim Hall, cover the bases answering these pressing questions and more.
Board Talk
Board Talk is presented by Phil Zarrow and Jim Hall of ITM Consulting.
Process Troubleshooting, Failure Analysis, Process Audits, Process Set-up
CEM Selection/Qualification, SMT Training/Seminars, Legal Disputes
Phil Zarrow
Phil Zarrow
With over 35 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis. He has vast experience in SMT equipment, materials and processes.
Jim Hall
Jim Hall
A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics. He is a pioneer in the science of reflow.


Welcome to Board Talk. We are the Assembly Brothers, Phil Zarrow and Jim Hall, of ITM Consulting.

Today, we're working at the car wash

Working at the car wash. Da, da, da. That's right. We've got some clean questions and clean thoughts for you.

What do we have here? Well, here is a question. This is from Mr. RP in India. Land of enchantment. He says, "In our company, all our products are RoHS compliant. For some of them, we're using lead-free no clean flux and lead-free solder. Is there a specific IPA, isopropyl alcohol, to clean lead-free PCBs? Is it needed?"

Oh, I'm sorry you ask that question.

But it's a good question.

There are a lot of issues here and we're just going to cover them briefly. First off, IPA refers to isopropyl alcohol. It's just a specific chemical. If you're talking about a solvent blend, which there are many, the answer is yes, there are specific solvents. Some of them use IPA. Some of them don't. We'll just call them specific cleaning solvents or cleaning materials, which can remove virtually any flux.

The problem is there are no universal ones. So you need to know exactly what you're doing, what flux you're using, in order to choose the right solvent and the right cleaning process.

Let's talk some generalities. No clean fluxes are designed not to be cleaned. Generally, they're designed to have a residue that's safe to leave on the board without any other coating.

So typically, they're designed not to absorb moisture. So they're not very soluble in moisture. So most of the water-based things, which include a lot of the IPA blends, are not particularly good.

You have to decide do you really need to clean it? If you are, why are you using a no clean. Should you go to a cleanable, water soluble flux that's designed to be cleaned?

But assuming that you have your reasons for cleaning and no clean you need to realize that it's going to be more difficult, and the fact that you're soldering for lead-free, therefore, you're soldering at temperatures that are probably 30 degrees higher. Therefore, in general, the residues are going to be more difficult to clean.

So understanding that you've created a situation where you've stacked the dice against yourself, you've raised your degree of difficulty, you've got a no clean flux, which are harder to clean, you got lead-free temperatures, which are typically harder to clean.

That being said, you need to find a solvent that is specific for the flux that you're using, be it whether it's a wave soldering flux or whether you're reflow soldering and it's in a paste, you need to talk to your solder paste manufacturer or the flux supplier, and then to one of the cleaning chemical companies to find out. They're probably the best source because that's their job to supply you with cleaning chemicals.

They should know what is good and best for your specific flux that you're using. They'll probably run some tests for you.

If you're going to endeavor to clean the no clean, as we said, for whatever reason, you definitely want the right tool for the job. And IPA, it's kind of squeezing by.

IPA will not clean a lot of flux residues. There's a lot of confusion, People say, "Oh, IPA cleans everything." This is really typical at the repair and rework benches. They get IPA, throw it on there, and it cleans it. In a lot of cases, it just doesn't. So don't make that mistake, and particularly for no clean. If you've got a no clean, you're going to have to find the specific system.

Some of them may require a heating, agitation, multiple soaks, and so forth, because, again, many of the no clean residues are not designed to be cleaned.

As Jim mentioned before, there are specific solvents made for doing exactly what you need. Go to the experts. Go to the companies that exist just for this purpose, companies like Kyzen, Zestron, and some of the others. They're the experts on the area. They have the right stuff that will work with a particular formulation that you're using.

The worst thing you want to do is use something that sort of dissolves this stuff and spreads it around on the board and maybe de-encapsulate some of the active chemicals. So the bottom line is if you use the wrong solvent, you end up with a board that's, in chemical terms, dirtier than you started with because the flux, active chemicals are no longer encapsulated as they would be with a properly activated no clean residue.

So use the right formulation. Don't go wishing you didn't.

That's it for this session of Board Talk. Phil and Jim would like to thank you for joining us today.

This has been Phil and Jim at Board Talk. And remember, whatever you do ...

Don't solder like my brother.

And don't solder like my brother.

Keep the kids away from that flux spot.

Yeah. Don't let them drink that IPA either.


This is not so much an assembly question as a repair question. I understand a lot of remote controls use a carbon connector switch. These can get dirty and become intermittent or open all the time. What is the proper way to clean them?
Bill Chase, Starkey Labs., Inc.

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