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no-clean flux vs. impedance

no-clean flux vs. impedance

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A PCBA contains a couple of parts that are not sealed and ca... - Feb 18, 2008 by kennyg

In theory, no clean flux residues are electrically benign...... - Feb 18, 2008 by Dirk Nuendyke

If the hand soldering is done right and you use little to no... - Feb 18, 2008 by jdumont

I should have mentioned... the only flux we use for the hand... - Feb 18, 2008 by kennyg

Get the ionic specs from your flux manufacturer, and show it... - Feb 19, 2008 by robgd3

The low solids flux that is commonly called no-clean can aff... - Feb 19, 2008 by jdengler

KRIKIES, a designer insisting on cleaning no-clean residues!... - Feb 20, 2008 by Chim Richalds

kennyg

#53692

no-clean flux vs. impedance | 18 February, 2008

A PCBA contains a couple of parts that are not sealed and can't be water washed. We hand solder these with no-clean after everything else is water washed. The designer says the no-clean residue must be completely removed so that it will not affect the circuit impedance. Does this sound accurate, or is he being too carefull? Is there any way to quantitatively argue a case for not cleaning?

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Dirk Nuendyke

#53696

no-clean flux vs. impedance | 18 February, 2008

In theory, no clean flux residues are electrically benign...period.

Here's a good test. Subject the board to some moisture/humidity, and have your circuit designer ohm-out any areas that may be affected by conductive material.

Option B: Have a lab, like Trace Labs, verify ionic cleanliness.

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jdumont

#53699

no-clean flux vs. impedance | 18 February, 2008

If the hand soldering is done right and you use little to no extra flux (other than whats in the solder wire) you should be ok. You should still verify with some testing however... You need to make sure any flux used is activated, thus rendered benign.

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kennyg

#53700

no-clean flux vs. impedance | 18 February, 2008

I should have mentioned... the only flux we use for the hand soldering is wire-core, no bottle flux. I think it should be a non-issue to leave the activated wire core flux residue. I'm just looking for some way to prove it to the designer.

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robgd3

#53707

no-clean flux vs. impedance | 19 February, 2008

Get the ionic specs from your flux manufacturer, and show it to the designer. No-clean flux/solder is supposed to be low to minimal in ionic contamination, which allow the whole no-clean thing.

If he needs further proof, you can have the board ionically tested. Test it before and after soldering, to show the difference in the ionic contamination. It should be low enough to not effect his impedences.

Although, I will say that I've heard of cases of high frequency RF boards having super-sensitivity to ionic contamination.

Cheers ..rob

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jdengler

#53708

no-clean flux vs. impedance | 19 February, 2008

The low solids flux that is commonly called no-clean can affect some circuits.

We are building a PCB that measures pico amps. The customer required that it be cleaned. We would rather used the low solids and eliminate a step.

The customer had us build 1 PCB with low solids flux paste. The board gets reflowed and the profile was to the paste manufacturers spec so we were sure that the flux was completely activated.

The customer then showed us the measurements this board was capable of and what a cleaned board was capable of. The clean board was more than twice as sensitive.

So a test would have to be conducted to prove whether it will actually cause problems.

Jerry

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Chim Richalds

#53737

no-clean flux vs. impedance | 20 February, 2008

KRIKIES, a designer insisting on cleaning no-clean residues!

the BLAME-THE-PROCESS bandwagon travels everywhere, me lad!

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