Thanks all, you are all already telling that cutting fluids may not be harmless. Will now try to get specific information.
/Ingemar

-----Original Message-----
From: Leo Roos [mailto:[log in to unmask]]
Sent: den 8 oktober 2003 19:00
To: TechNet E-Mail Forum.; Ingemar Hernefjord (KC/EMW)
Subject: Re: [TN] Anti-tarnish on copper


Strange as it may seem, cutting fluids are problems in other areas. For
stability they contain sulfur compounds that can react with metals to form
stable complexes. One reason they are used. If there are any parts in the
MCM that react with S it may be a problem

Leo Roos
----- Original Message -----
From: "Ingemar Hernefjord (KC/EMW)" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, October 08, 2003 6:09 AM
Subject: Re: [TN] Anti-tarnish on copper


> Wow, this cybercypruscopperdoctorellis has knowhow as high as Mont Blanc.
May I swap a side question while He is on line? What are cutting fluids made
of? If I happen to get some microdrops of such a fluid on inside of a
hermetic MCM, what harm would they do? Odd q? Yes, sometimes we make odd
things..
>
> Ingemar Hernefjord
> Ericsson Microwave Systems
>
> -----Original Message-----
> From: Brian Ellis [mailto:[log in to unmask]]
> Sent: den 3 oktober 2003 09:46
> To: [log in to unmask]
> Subject: Re: [TN] Anti-tarnish on copper
>
>
> This may appear facetious, but you would be surprised at how many
> different organic compounds there are on the surface of a laminate after
> pressing. No doubt they contribute to reducing the oxidation rate.
>
> Firstly, let us look at the prepreg. The glass cloth is impregnated with
> the epoxy soup in a solvent. The soup consists of all sorts of
> chemicals, such as the basic prepolymer and various additives. The
> solvent is often a volatile ketone. Most of this is evaporated in the
> treater dryer, but the rest remains in the roll, where it cannot readily
> evaporate.
>
> Then there is the copper, which is a largely epitaxial growth with
> distinctly bonded crystals and many micrometre-sized and smaller gaps
> between them (this is why ED foil is slightly less dense than rolled
> copper from the ingot). These gaps are actually pores which traverse, in
> many cases, the copper thickness.
>
> Put the two together in the laminating press and what happens? The
> vapour pressure of the solvent residues increases and seeks ways to
> escape, such as through the microfilter of the copper. However, it is
> not just the solvent that reaches the outer copper layer, but also some
> of the chemicals dissolved in it, often in astoichiometric ratios. So
> you will get probably low MW bleeding of epoxy chemicals reaching the
> surface and remaining there.
>
> But it doesn't stop there. What is the copper in contact with in the
> press? A very thin release film largely composed of polyvinyl fluoride
> aka Tedlar (R). Now this shrinks about 1% during pressing, so there is a
> friction between the film and the copper which may help to spread the
> exudates. But is PVF resistant to the solvents at pressing temperatures?
> The answer is no. It is not inconceivable that the lower MW molecules in
> the film may be slightly softened and even transferred to the copper.
>
> Are other chemicals used in the process? Let's ignore the stainless caul
> plates, even though they may have had indeterminate cleaning chemicals
> applied at some time in their working life, which could diffuse across
> the porous PVF film. I'm thinking of the Kraft padding, of very
> indeterminate chemical composition.
>
> I published a paper in 1969 relating to these contaminants and abrasive
> particles on single sided circuits being a major cause of solder
dewetting.
>
> Brian
>
> Steve Kelly wrote:
> > Does anyone know what is in anti-tarnish? Is there a specification on
> > thickness or composition? Thanks .
> >
> >
> >
> > Steve Kelly
> >
> >
> >
> > PFC Flexible Circuits Limited
> >
> > Ph: (416) 750-8433
> >
> > Fax: (416) 750-0016
> >
> > Cell: (416) 577-8433
> >
> > E-Mail: [log in to unmask]
> >
> >
> >
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