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July 2004

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Subject:
From:
Charlie Pitarys <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 2 Jul 2004 10:43:03 -0400
Content-Type:
text/plain
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text/plain (195 lines)
Yes I am lurking ;-)
In the world of "bench-top" cleaning I believe most CM's have painted
themselves into a corner.
The driving force can be cost and resistance to change. All spelled out
in the short reply from Bill K.

Almost weekly I hear "We use IPA because it's.....
"Cheap"
"We have always done it this way" 
"The operators are used to it"
"we cut it w/water cause we have had fires"
"we have used it before but now we are seeing white residue with the
no-clean flux/paste"
And ....
"Spray cans are expensive, the operators use way to much and waste it." 

But are they?? More likely the cans clean well but now they are RINSING
with it. And I believe here is another key subject. Do I or should I
rinse? We did hear IPA does not clean well, only "smears" it around. So
the first need is to find a solution that will actually clean the flux.
Then maybe we can rinse w/DI water or IPA (note process change)If there
is already an aqueous wash process or gear in house then this change is
certainly a whole lot easier.

And to quote Brian E. "Would not a "no-clean" process be more suitable
for your products? Please give your technically justified reasons for
cleaning." 

Why clean if you do not have to? With the newest technology flux
formulas, this is great, but still after my 20+ years in the biz a lot
still has not changed.
What assembly guru deemed "though shall use IPA and like it" Maybe the
same person who told my mother we should wait an hour after eating
before we jump in the pool !! Made you sit there and play checkers or
something. Ah you laugh but how many of you have told your kids the
same?

Cleaning is a value added process. 
Am I building a garage door opener or an aerospace component? 
Will the garage door opener work well for years if I used a "low
reside/no-clean" process on the rework, YES, but oh oh I build these
HUD's over on the next line maybe that's not the right method?
I can offer alternate cleaning solutions and bench top cleaning process
methods. But it requires CHANGE.

 Contact me offline if you wish. Have a great and safe long holiday
weekend.

Charlie Pitarys
Director of Application Technologies
[log in to unmask]
603.622.2900 x-115




-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kasprzak, Bill (sys)
USX
Sent: Friday, July 02, 2004 7:38 AM
To: [log in to unmask]
Subject: Re: [TN] cleaning solvent

Brian,

You have certainly opened the forum for the larger question of the
"need" of cleaning.

Our surface mount reflow and wave soldering operations use water soluble
fluxes and obviously there is a definite need to clean when using these
aggressive fluxes.

However, for secondary operations (Hand soldering, soldering stranded
wire,
etc.) we use Rosin cored solder and RMA fluxes for these operations.
Most programs that we work with require ionic contamination testing so,
cleaning is necessary. In addition, it is good practice to have clean
assemblies when conformal coating needs to be applied.

Since Freon and similar products have been banned, IPA has become the
solvent of choice for these applications even though the IPA only
"smears"
the material around. It does allow us to "get by".

I have used Flux-off CZ in limited applications. It removes flux
residues nicely but its drawback is the high cost.

So, there is a definite need for cleaning. Use of no-cleans requires
pristine parts, boards and has a tight process window. For me it's not a
practical choice. It can't be used everywhere just as water solubles
can't be used everywhere. So IPA has become a popular choice only
because there is nothing else when dealing with rosin fluxes even though
it's marginally effective.

Any suggestions for an alternative would be welcomed.

Bill Kasprzak
Moog Inc., Systems Group, Process Engineer





-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Friday, July 02, 2004 6:40 AM
To: [log in to unmask]
Subject: Re: [TN] cleaning solvent


Despite popular belief, IPA and other light alcohols are not good
solvents for removing flux residues. However, I cannot answer your
question without knowing a lot more about your products and the
flux/paste used, quantities, equipment etc. However, my first question
is: Are you sure you **need** to clean? Would not a "no-clean" process
be more suitable for your products? Please give your technically
justified reasons for cleaning.

Brian

Murulidhara wrote:
> Dear Technetters,
>
> I want to know what are the better solvents to clean PCB assemblies 
> better
than IPA.
> Also give the sources.
>
> Thanks in advence.
>
>
>
>
>
>
>
>
>
>
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