A year or so ago we had a problem with units failing that had been exported
to China. It was found with some 85/85 tests that a process that added
liquid flux that did not see a full heat cycle caused component leg
corrosion and failure. We use no-clean flux and normally, our process is
totally no-clean. We corrected the problem with more judicious use of the
flux ( for a terminal dipping process )but it does show that no-cleans have
to see the proper thermal excursions to be benign. For that reason, I am
not a big fan of post-wave assembly, modification or repair operations with
or without added flux. Cleaning uncured flux residues would be time
consuming and, in some cases, impossible.
George
-----Original Message-----
From: Phil Nutting [mailto:[log in to unmask]]
Sent: Thursday, February 27, 2003 8:43 AM
To: [log in to unmask]
Subject: Re: [TN] Adding liquid flux when hand soldering
Brian,
I can't argue with your statements. I can only speak from personal
experience (including a test last night) that adding the liquid flux makes a
much better solder joint with less heat applied to the joint. In a quick
poll of some of my fellow old-timers who worked on military stuff all
agreed.
Gee, what would Moonman say to this one?
Phil
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Thursday, February 27, 2003 3:17 AM
To: TechNet E-Mail Forum.; Phil Nutting
Subject: Re: [TN] Adding liquid flux when hand soldering
If you are using cored solder, you should never add flux. Because:
a) liquid flux will spread beyond where you need it and add to contamination
b) the chances are the two fluxes will be incompatible with each other
c) there is a distinct possibility the residues will be impossible to
clean off correctly or, if they are both "no-clean", they will form a
dangerous flux porridge which could be ionically incompatible with
reliability
d) you are insulting the wire manufacturer who has determined the
quantity and type of flux, through scientific lab tests, to optimise
what you are trying to do.
IOW, you will cause far more harm than good.
Brian
Phil Nutting wrote:
> Is it a common practice to add liquid flux when soldering by hand or do
you rely on the flux core of the solder? My 30+ years says add the liquid
flux for the best solder joint, but that was back when I was involved with
rocket science.
>
> Phil Nutting
>
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