Hi Kevin,
Sorry for my delayed response, I have not been following TechNet for a
couple of days. I will try to answer concisely. First of all, Kenny is
concerned that the no clean flux used by his component manufacturer inflates
the ROSE test results for his assemblies. His concern is valid. Any easily
soluble ionic residues left by the boards, fluxes, components, etc can
inflate the resulting residue picture for a finished assembly in any
cleanliness test. The trick is knowing what residues are related to what
materials so that you can make distinctions between those materials. ROSE
does not have the capacity to distinguish the different ionic species. So it
is impossible to determine what residues are contributed by what material.
This is one big reason that I don't like ROSE testing. It is simply not a
good tool for assessing cleanliness. As a process control tool it's okay,
provided it has been verified by another more accurate method, such as IC.
As for precleaning components, that may or may not be advantageous. It
depends on the residue and how easily removed it is. In Kenny's case his
vendor is using a no clean flux. Most no cleans are designed to be left
alone and cleaning them can sometimes cause more issues than if you had just
left them be. He would need to talk with his component vendor to determine
what flux is being used and find out from the flux vendor if it can be
effectively removed.
As a game plan, I would:
1) Find out all the info I could about the flux used by the component
vendor.
2) Check with the flux vendor to determine if it could be removed and with
what.
3) Clean some of the components prior to assembly.
4) Test via IC, the starting and post-cleaning cleanliness of the
components
to verify that cleaning was beneficial.
5) Process some assemblies with the cleaned components and check using ROSE.
I would also check a few assemblies via IC to verify the ROSE results.
Just a few quick thoughts.
Best Regards,
Joe Russeau
Process Analyst
Precision Analytical Laboratory, Inc.
4106 Cartwright Dr. Ste. A
Kokomo, IN 46902
P: 765-455-1993
F: 765-455-1996
E: [log in to unmask]
www.precisionanalysts.com
>
> ----- Original Message -----
> From: "Kevin Glidden" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, November 30, 2006 3:55 PM
> Subject: Re: [TN] Question about J-STD-001 cleanliness designator C-22
>
>
> > I guess I don't fully understand. If you need to pass ionic cleanliness
> > testing, than you need to pass. That includes the components used, not
> just
> > the joints you made. Ionics are detrimental on the PCB and on the
> > components- no discrimination there. I would either pre-clean the
> > components or find different supplier. If neither are feasible, you
would
> > need to do some sort of investigation with IC testing and/or SIR testing
> to
> > prove the residues are not detrimental, wherever they may lie. Then if
> > validated by that testing, you could put in the documentation that the
P/F
> > limit is higher, just so long as you have the data behind it. The
> Rockwell
> > Gang or P.A.L pals might have a valid opinion here...
> >
> > Kevin Glidden
> > Manufacturing Engineer
> > Astronics Luminescent Systems Inc.
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Bloomquist, Ken
> > Sent: Thursday, November 30, 2006 3:45 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Question about J-STD-001 cleanliness designator C-22
> >
> > Along the same lines, sort of. If you use COTS magnetics and the
supplier
> > changes to no-clean and after assembly you put that in your ROSE tester
> the
> > readings can go through the roof.
> >
> > If you are satisfied that the mag manufacturer is doing everything right
> and
> > you can live with no-clean flux on the mag, how do you perform a ROSE
test
> > on the assembly and trust the reading?
> >
> > Thanks,
> >
> > KennyB
> >
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