I totally agree with Andrew's comments, we have recently started a move over
to water based fluxes and the hardest part is ensuring you get a good even
coat of flux whilst applying a small enough qty.
However, by reducing the flux qty you can achieve excellent results with
water based fluxes and reduce your overall flux spend.
I would also recommend measuring flux qty by measuring the amount of dried
flux being applied. This can be done by putting a number of small panels in
a pallet with a known weight over the wave soldering machine with the solder
wave switched off. The difference in the weight of the panels afterwards
can be used to quantify the amount of flux being applied and by comparing
different panels in different positions in the pallet it is possible to
determine how evenly the flux is being distributed. See Page 537of
"Soldering in Electronics", Klein Wassink.
"If you don't measure it, you can't control it!"
I would be interested in hearing anyone else's comments on the control of
flux qty.
Neil Atkinson - Quality Manager
Stadium Electronic Controls Division
Stephen House, Brenda Road, Hartlepool TS25 2BQ (UK)
-----Original Message-----
From: Andrew Hoggan [mailto:[log in to unmask]]
Sent: 31 July 2001 13:29
Subject: Re: Water based fluxes
A little note on water based fluxes.
It is my and my colleagues experience that many assemblers
use too much flux
especially in the case of water based fluxes. It's always a
good idea to put
the extra effort into running a few trials turning down the
application rate
or application pressure to reduce the volume of flux
applied. As implied
below it is also critical to dry the boards with sufficient
preheat, but the
first step should be to turn down the flux volume.
Best regards,
Andrew Hoggan
BBA Associates Ltd
www.bba-associates.ltd
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Kasprzak,
Bill (sys)
USX
Sent: 31 July 2001 12:56
To: [log in to unmask]
Subject: Re: [TN] Fluxes
Ray:
One key factor in selecting an OA (water soluble) flux is
whether the
material is alcohol based or water based. During a
qualification test that I
ran years ago to qualify us for J-Std-001A, we selected a
material which was
a water based material. We ran some initial test runs using
our typical
solder profiles. When the circuit boards reached the wave,
there was still
enough moisture left on the boards from the flux. This
resulted in a
splattering effect similar to water in a hot frying pan
except in this case,
solder balls were evrywhere from the splattering effect!
Making a long story
short, I was finally able to correct for the situation but
it took a while
for me to accept and break the solder process paradigms.
So if selecting an OA flux, and you want the make the
process transition
virtually seamless from RMA, select an alcohol based OA
flux.
By the way, you can never eliminate RMA. Do not solder
stranded wires using
OA flux!! Corrosive residues will be trapped under wire
insulation resulting
in broken wires at the wrong time.
Bill Kasprzak
Moog Inc., Electronic Assembly Engineering
> -----Original Message-----
> From: Golembiewski, Ray [SMTP:[log in to unmask]]
> Sent: Friday, July 27, 2001 9:13 AM
> To: [log in to unmask]
> Subject: [TN] Fluxes
>
> I am looking for data analysis between a water
soluble flux, and
> an RMA. What are the major effects each has on a PCB. What
do I have to
> know before I make a switch from RMA to water soluble. If
you might be
> able to direct me to a link, or send me some information
it would be
> greatly appreciated. Thanks again,
>
> Ray Golembiewski C.I.D.
> IPC Certified Interconnect Designer
> Manufacturing Test Engineer
> Projects Unlimited, Inc.
> (937) 918-2200
>
>
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