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Cleanning no clean residu

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#52125

Cleanning no clean residu | 19 October, 2007

Hi I will like to know what do you think about cleaning hand solder, my employee spend about 25% of they time to brush they hand solder with teddy pen cleaner, we used no clean solder wire. It�s not been the first time that I try to eliminate those cleaning but no one want to take that decision because we always clean it. I made several test by not cleaning some PCB never had any bad feed back. Want do you think?

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#52126

Cleanning no clean residu | 19 October, 2007

By definition, no clean solder can be not-cleaned. The solder/flux are formulated to result in low ionic-contamination, hence, no cleaning.

I have, however, always had at least one customer that requests their no-clean solder get cleaned. No-clean solder is used post aqueous wash, for parts that are wash incompatible, but the customer wanted no visible residue.

If this is your own product, you can prove out the efficiency of not cleaning the no-clean operations by a. conducting ionic contamination testing, and b. conducting accelerated life-cycle testing without cleaning the board. If these are boards supplied to a customer, you'd need to get your customers' input on the evolution. If they've been seeing clean boards all this time, they may balk at suddenly seeing boards with flux residue on them.

cheers, ..rob

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#52128

Cleanning no clean residu | 19 October, 2007

Thank Rob those are our own product, try few test by not clean some PCB never had any issue except on compoment under faraday cage. Did you know any norm that could persuade my boss and the R&D department that cleanning no clean is a waste of time. Thank again Bruno

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#52129

Cleanning no clean residu | 19 October, 2007

Hi Rob,

I must take issue with your statement �By definition, no clean solder can be not-cleaned�.

All no-clean fluxes can be cleaned. Whether or not one cleans no-clean depends on a variety of factors. More than eighty percent of all post reflow flux residues being cleaned today are no-clean. Although that sounds like a strange irony, there is a logical reason.

While many applications do not require cleaning, some do. Many contract assemblers operate a no-clean line and just clean the assemblies that require cleaning due to customer, application, or environmental demands. Rather than running two lines, one no-clean and the other water soluble or RMA, all assemblies are reflowed (or wave or hand soldered) with no-clean pastes. The assemblies that require defluxing are then cleaned.

Exfo� Cleaning is never a waste of time. A no-clean process leaves some degree of ionic residue. That is a fact. Eliminating ionic residues will make your board (and application) no reliable. Cleaning either reduces or eliminates ionic and other forms of contamination. The big question is whether your specific application will be negatively effected by the level of ionic contamination left behind on the board. While is true that many applications are not negatively effected by residual contamination, it is likewise true that all high reliability applications (military, flight, space, medical, etc) require cleaning and not-to-exceed levels of contamination.

I am not suggesting that your boards require cleaning. In fact, they may not. But you need to realize that by not removing the flux, you are leaving ionic residue on the boards. You need to determine if this level of residue can cause a failure. Then, you need to determine the cost of a failure. That will determine the value (or lack thereof) of cleaning.

Michael Konrad Aqueous Technologies www.aqueoustech.com konrad@aqueoustech.com

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#52130

Cleanning no clean residu | 19 October, 2007

Really, if you start out from the beginning planning to clean the boards, then DON'T use the no-clean flux! The way that stuff is made, it leaves a hard, low-solubility residue that takes a LOT of effort to get clean. If you plan to clean, use a water soluble flux, it will wash off with MUCH less effort.

On some specific boards, we have used no-clean flux, but needed to clean just a couple components, and found it to be very hard to get it clean.

Jon

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#52135

Cleanning no clean residu | 22 October, 2007

Michael,

You're right, of course. A major mis-type on my end.

What I meant to say is that no-clean fluxes are designed to not _require_ cleaning to meet industry cleanliness standards.

Cheers ..rob

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#52145

Cleanning no clean residu | 22 October, 2007

Thank you guys for your help, I do not clean any on my assemblies who are build by the SMT an wave soldering department, we do used liquid fluxes Kester 951 and cored wire keester 245, usually it�s for batteries connector, led, terminal and wire rap wire, a few IC and that all, some of my employees used both on then. It�s the long term quality, who worries me; if I do not clean those passive components did those contaminations could cause failure? Best regards Bruno

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#52146

Cleanning no clean residu | 22 October, 2007

Bruno

The real question about your troop using Kester 951 wave solder flux on boards is: how is the flux applied and controlled. See, when you apply this flux with your wave solder fluxer, it is ideally applied in a metered fashion with your fluxer. Next, as the board is processed through the machine, it brings the flux to the proper activation temperature. These two actions, precise amount and proper heater, are assumed conditions of low residue soldering. In other words, raw low residue flux isn't low residue.

If your troop are applying this flux with uncontrolled methods, like with squirt bottles, the flux is probably end-up in some unintended places, because: * Application method is not precise. * Liquid flux will move away from the heat of the soldering iron durning hand operations. So, it will not receive the proper activation temperature and will be under components.

Old timers used to keep squirt bottles of OA wave solder flux on the bench for use during hand soldering. Doing this was not BIG deal because the board was washed after hand soldering. With low residue fluxes, this is poor practice.

Further, you troop are elbow deep in the stuff, presenting some potential personnel safety issues.

Get suggestions from your flux supplier.

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bob

#52209

Cleanning no clean residu | 26 October, 2007

We recently changed to an Amtech no clean paste and flux that is washable. So far excellent results. Far superior to the water soluable paste we were using. Fewer solder balls, longer life in printer, boards can be left up to 5 days and still come clean in either our Orbi or Aqueous wash. Check their website. For hand solder, use the 4% flux. The 2% didn't seem to work very well for us.

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