I do not like the term "activated" to describe flux that has been heated,
and thereby partially inerted. From what I understand, the older rosin
fluxes needed to be heated for the flux to liquify and do its job, hence
activated. Additionally, some of the organic halides in the fluxes
remained inactive until they were heated and the halide liberated to do its
job.
Low VOC, i.e. mostly water, liquid fluxes are active right out of the
bottle, and will clean oxide off copper. Residues that absorb water are
problematic. This is why we do SIR and ECM testing. Ask for the data.
Low solids liquid fluxes intended for no-clean assembly generally use
dicarboxylic acids that partially volatilize during the heat of soldering,
so that the longer it is heated the lest active it becomes, These fluxes
are designed to have just enough activity to allow good soldering, but
after the soldering operation, enough of the activator has been driven off
so that the remaining residue does not promote electrochemical failure in
most service environments, For many applications, these materials work
very well, and their manufacturers test a flux's soldering functionality
AND its propensity to promote electrochemical failures (it should be
minimal) before it is sold. Soldering promotion and reliability need to be
balanced to provide the best product for the application. Most
manufacturers have a range of products with different activity levels for
different applications.
Karen Tellefsen - Electrical Testing
[log in to unmask]
908-791-3069
Re: [TN] Cleaning non-clean paste
Robert Kondner
to:
TechNet
04/26/2012 06:03 PM
Sent by:
TechNet <[log in to unmask]>
Please respond to rkondner
Well
You wrote:
"Yes, but after it is ACTIVATED it becomes inert,"
"Flux residues never heated are still very active"
So are you saying these No Cleans are "Activated" (Active???) before use
or
are you saying heating "Activates" and more heating makes inert? Or maybe
both?
Can you identify where you are getting this information? I just asked 4
questions, you are the one suggestion how things work and what you are
suggesting would indicate many no clean flux suppliers are leasing customer
astray.
Please site some references or just say "I don't know for sure."
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, April 26, 2012 5:05 PM
To: [log in to unmask]
Subject: Re: [TN] Cleaning non-clean paste
Yes, but after it is ACTIVATED it becomes inert, but never completely.
Solder paste flux residues are pretty inert after going through reflow.
Liquid benchtop fluxes are still active if left on because not all of the
flux is activated by the heat from a soldering iron, and thus inerted.
Flux residues never heated are still very active.
Flux residues from cored wire solder are so concentrated that they are
fully
heated during soldering, thus are activated, and when finished soldering
are
pretty much inert but again, no flux is ever 100% activated/inerted by a
thermal cycle.
-----Original Message-----
From: Robert Kondner [mailto:[log in to unmask]]
Sent: Thursday, April 26, 2012 3:36 PM
To: 'TechNet E-Mail Forum'; Stadem, Richard D.
Subject: RE: [TN] Cleaning non-clean paste
Well,
1 You heat flux to ACTIVATE flux. (Activate as in make chemically active
for oxide film removal.)
2 Not heating a No Clean flux does not leave activated chemicals. If so No
Clean wire solder would be useless as hand soldering does not chemically
react all the flux in the solder. RMA wire solder is a good example.
If anyone can site a manufacturers data sheet or any No Clean flux product
that requires cleaning after use that would be serious input to this
discussion.
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, April 26, 2012 4:23 PM
To: [log in to unmask]
Subject: Re: [TN] Cleaning non-clean paste
May I amend that a little bit?
Here is what I would say:
Ideal scenario would be to either use a flux meant to be cleaned, then
clean, or to not clean a no-clean flux, PROVIDED IT HAS BEEN SUBJECTED TO
HEAT TO INERT (DE-ACTIVATE) IT.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak
Sent: Thursday, April 26, 2012 3:09 PM
To: [log in to unmask]
Subject: Re: [TN] Cleaning non-clean paste
Fabien: All replies so far have been excellent. I want to underline that
a
no-clean flux, being formulated to not require cleaning, will by its nature
be much more difficult to clean than a flux meant to be cleaned, so it is
highly probable you are leaving at least some flux residue on the board.
Ideal scenario would be to either use a flux meant to be cleaned, then
clean, or to not clean a no-clean flux.
Rudy Sedlak
RD Chemical Company
--- On Thu, 4/26/12, Fabien Guizelin <[log in to unmask]> wrote:
From: Fabien Guizelin <[log in to unmask]>
Subject: [TN] Cleaning non-clean paste
To: [log in to unmask]
Date: Thursday, April 26, 2012, 6:40 AM
Hi,
Can you summarize the risks linked to cleaning a non-clean paste ?
I am concerned by incomplete cleaning of the non-clean leaving active
residue on the board.
We are using Inudium 5.1 (non-clean, Pb free), cleaned with Vigon A250.
We are using non-clean because of experience of that paste (internally and
at EMS shop) and we are cleaning to promote underfill bonding.
Thanks,
Fabien
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