Malcolm,
Interesting question. Since the text reads "halide-free" not "halogen-free"
it would seem to me that the original writers were speaking only of ionic
members of Group VII (Whether that is Group VIIa or VIIb depends on whether
you follow IUPAC conventions). Also, the spot tests and electrical tests
(fluoride ion, copper mirror, halide ion, SIR, electromigration) would not
normally detect covalent group VII atoms. Examples would be carbon
tetrachloride, Freons (CFC's) and perfluorocarbons (like your own flux
resist). For instance, the latter passed all Bellcore mandated testing.
So now the question remains, what is zero percent? Is it really zero, or
0.05% as you ask, or 0.1% or 0.001%? I seem to recall that someone has
actually determined the limits of detection of the chromate paper, but I
can't remember what that value was. This is probably the "zero" of the
standard. However, I have also been told that at least one flux
manufacturer has been known to add masking agents to their material so their
products would pass the halide spot test, although they had "high" values.
I don't really think that it too much of a concern, because the real tests
are the electrical ones. The spot tests are just that, filtering agents so
we don't tie up humidity chambers with things that for sure will not pass.
I know I haven't provided a complete answer to your question, but hopefully
this is a start. Jump in everyone!
regards,
Bev Christian
Nortel
> ----------
> From: Malcolm Warwick[SMTP:[log in to unmask]]
> Sent: Thursday, August 06, 1998 6:32 AM
> To: [log in to unmask]
> Subject: [TN] ANSI/J-STD 004 Interpretation
>
> Rereading this document recently, a question arose about the
> interpretation
> of "halide free" for flux classification and I wonder if anyone know the
> intent behind the specification. There are minor anomolies in relation to
> which tests have to be carried out (if it passes chromate paper, is a
> quantitative test needed or not?), but the real question concerns the
> maximum value of total ionic halie which changes the classification from
> L0
> to L1. According to Table 2, the halide must be 0.0% for L0. The analyst
> in
> me says that this means <0.05%. Is this interpretation correct? Some users
> will of course specify other test methods and limits of detection, so what
> is halide free by J-STD004 need not be halide free by other criteria.
> A supplementary question is, how is the product classified if the user
> specifies (as he is allowed) an analytical method which detects covalent
> halide? If the product is L0 by the standard test method but has more than
> 0.05% halide including covalent material, what should it be listed as?
> Thanks in advance for your help.
> Malcolm
>
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