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Testing effect of non-clean flux residue on solder joints

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#77287

Testing effect of non-clean flux residue on solder joints | 20 March, 2017

We're currently using no-clean flux (SR-12) in a no-clean manual soldering process.

The brownish flux residue impedes direct visual inspection of the solder joints. Therefore, we're forced to clean the residue off.

(1) Is there testing we can do (environmental stress chambers) with which we can see the long-term effects of flux residue on solder joints?

(2) Has anyone else seen this problem with no-clean flux residue and how do you handle it?

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#77293

Testing effect of non-clean flux residue on solder joints | 21 March, 2017

No clean is giving us problem in ICT. Other than that, a coating of flux should remain there to pretect the solder joint from the environment. In general you should not clean NO clean - it is supposed to be there.

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#79284

Testing effect of non-clean flux residue on solder joints | 2 November, 2017

Hi...i have a question. After you solder a circuit board, what do you wash the flux residue off with? I am hesitant to use water for fear of subsequent corrosion, and have no clue as to what kind of flux is in my solder wire.

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dwl

#79285

Testing effect of non-clean flux residue on solder joints | 2 November, 2017

For low volume hand assembly, deionized water or IPA should work fine.

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#79286

Testing effect of non-clean flux residue on solder joints | 3 November, 2017

On the flux reside issue that is gumming up your test probe pogos ...

Short term, clean what's in process with a aerosol flux cleaner solvent. Ask your flux supplier for recommendations.

Longer term, recognizing that there is no fix, your improvement plan should include:

* Apply less flux. Take squeeze bottle applicators away from your operators.

* Use a proper cored solder for hand soldering

* Change test fixture probes to suit the flux reside in your operation

* Implement a proper probe maintenance program

* Work with your test fixture designer

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#79287

Testing effect of non-clean flux residue on solder joints | 3 November, 2017

On your question about reliability ... " Is there testing we can do (environmental stress chambers) with which we can see the long-term effects of flux residue on solder joints?"

Sure, incompletely activated low residue flux residues are potentially corrosive, just like poorly cleaned, cleanable flux.

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#79288

Testing effect of non-clean flux residue on solder joints | 3 November, 2017

regarding dwl comment, "For low volume hand assembly, deionized water or IPA should work fine."

Deionized water: Deionized water is corrosive. It needs to be removed. Proof? Drop a copper coin into a covered jar of DI water and watch what happens over time.

IPA: Isopropal alcohol [IPA]:

* IPA is ionic and still needs to be cleaned

* IPA and empty containers are a hazardous material by RCRA criteria (40CFR 261)

* Fire hazard with a flash point (~12*C TCC)

* IPA is a volatile organic compound (VOC) at 1000 g/l

* IPA is harmful to people, requiring personal protective equipment including: chemical resistant gloves for skin protection, eye & face protection, and respiratory protection.

Proof??? Read the IPA SDS: http://www.tsi.com/uploadedFiles/_Site_Root/Products/Literature/MSDS/Isopropyl_Alcohol_SDS_Sheet_EU_6010486.pdf

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dwl

#79290

Testing effect of non-clean flux residue on solder joints | 3 November, 2017

IPA and DI water are both very common and effective methods of cleaning PCBAs.

http://www.zestron.com/sa/cleaning-applications/smt-electronic-cleaning/pcba-cleaning/aqueous-cleaning.html

http://blog.gotopac.com/2010/11/18/ipa-as-a-universal-cleaner-advantages-disadvantages-2/

Yes DI water is corrosive, but you aren't soaking the PCB in it for a long time. For cleaning the board is immersed for a few minutes, then allowed to dry. This level of exposure isn't enough to harm the PCB.

IPA is a common house hold chemical used in numerous products. Rubbing Alcohol is just IPA with an extra chemical mixed in it to discourage human consumption (at least in the USA). The government would rather blind drunks than lose tax money, but I digress...

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