Mixed Cleaning - No Clean and Water Soluble

Mixed Cleaning - No Clean and Water Soluble
What problems might we encounter if we clean no clean boards using a water wash systems set up to clean water soluble fluxes. The Assembly Brothers, Jim Hall and Phil Zarrow, discuss the problems that can occur.
Board Talk
Board Talk is presented by Phil Zarrow and Jim Hall of ITM Consulting.
Process Troubleshooting, Failure Analysis, Process Audits, Process Set-up
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Phil Zarrow
Phil Zarrow
With over 50 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. This is Phil Zarrow and Jim Hall, the Assembly Brothers, also known by day as ITM Consulting. We're here to answer process questions to do with SMT. Today's question comes from a Mr. P.H., in Texas, who writes,

I have a closed-loop batch wash system used in SMT, running a water-soluble process. An associate wants to clean assemblies that were hand-soldered with a no-clean through our batch wash.

The solder chemistry is the same, 63/37, but the manufacturers are different. Of course, one is no-clean and one is water-soluble. Does this pose potential problems for the assembly or equipment? I prefer not to introduce the no-clean into my SMT environment, since the system is closed-loop.

Hey, good for you, Mr. P.H. Keep them the heck away from your cleaner with that stuff. What the heck? You don't want him messing that thing up.

Well, the most important thing, though, is that he's not going to clean his no-clean residues with a straight water cleaner.

No, he's going to make one hell of a mess, is what he's going to do.

Well, he might. It really depends on the individual no-clean chemistry. No-clean is not one thing, it is a wide family of many different formulations using many chemicals.

Some can be cleaned with water and a saponifier, others require very special solvents and cleaning processes so you have to match the cleaning processes for no-clean to the specific no-clean flux formulation you're dealing with.

There is no universal solvent, IPA, or anything else that's going to get it all off. It's a common mistake that any people make. But most importantly you're not going to clean it with pure water.

So that's the bottom line. If you want to allow him to introduce his boards with a no-clean flux that he's planning to wash off he would have to introduce a saponifier to the system.

As far as changing it over from running straight aqueous, he would have to talk to the saponifier companies as to what proportion of saponifier to put in there.

I suppose that you could say, "I'll run everything with a saponifier," but that's an additional cost and maintenance, and you've got to make sure that your closed-loop system will handle it. There are just a whole lot of issues. So I guess our advice is no, don't try it. It's not going to clean a no-clean, and it could potentially mess up your pure water batch system, even with a closed-loop.

Yep, and that hopefully answers this question. And on that note, this is Phil Zarrow with Jim Hall, your Assembly Brothers, bidding you farewell, and remember, whatever you do,

Don't solder like my brother.

And don't solder like my brother.


Applying WS flux after any no clean process is not recommended for a number of reasons. Many no clean fluxes cannot be removed by water alone and the residue properties can be adversely impacted with exposure to liquid water at pressure and temperature. Also, the ionic components of the WS flux can be absorbed by the remaining no clean residue and alter the residue properties. If cleaning must be performed, all residues should be removed which usually requires the addition of wash chemistry to the cleaning process.
Timothy ONeill, AIM
We are exploring something similar to what Bill @ Smart Sonic mentioned. Is there a problem with cleaning a No-clean board?

On some of our products we would like to build the double side SMT with No-Clean but later install some hand soldered parts with OA. Followed by washing the assembly.

The reasoning behind this would that hand soldering with no-clean tends to have more residue than OA and in addition using no-clean for double side SMT does not require an immediate wash.

We are evaluating the process. Some no-clean materials show the white residue when cleaned.

Any experience?

Gregory Cronin, CASE Assembly Solutions Inc
Regarding mixing OA with No-clean. You say water will not clean the no-clean, but as no-clean does NOT require cleaning, my question is: will the water "hurt" the no-clean? If not, you should end up with the water washable being cleaned and the no-clean still "no-clean (not cleaned). Or, will the no-clean develop a "white residue", etc.?
Bill Schreiber, Smart Sonic, USA
At one time we used Alpha 6100 series no clean. It had a very long stencil life and it never dried to a hard crusty material. You could place "Late Parts" a couple days later and things would solder OK.

The big problem was cleaning a board after rework, you can not remove the no clean flux, it makes a mess. So we gave up and used WS, late parts became hand soldered parts.

Is there anything out there that you know of that is a "None Complete Dry Out" WS flux? I would love to know.

I deal with loads of quick turn proto and short runs. Holding a placed job before reflow is important.
Bob Kondner

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