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August 2002

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Wed, 14 Aug 2002 15:41:37 +0300
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Joyce

If I may be cynical, the EU don't STUDY anything, they just enact
restrictions (examples: lead-free solder, trichloroethylene etc. to the
power of hundreds).

Brian

joyce wrote:
>
> BRIAN,
> are they going to take them back after use? (like the leadfree group
> proposed for the lead containing solder).  Does EU got a task group study
> this? wow!  I thought just the fire insurance goes up as side effect (as the
> otherside argue about the health insurance goes down)...
>
> jk
>
> >-----Original Message-----
> >From: TechNet [mailto:[log in to unmask]]On Behalf Of b_ellis
> >Sent: Wednesday, August 14, 2002 2:16 AM
> >To: [log in to unmask]
> >Subject: Re: [TN] Bromine
> >
> >
> >Joyce,
> >
> >Not to mention that the new stuffs (nitrogen- and phosphorus- organics)
> >may leach just as much ... or more!
> >
> >Brian
> >
> >joyce wrote:
> >>
> >> Dave,
> >> agree with you on the toxins... the engineering method is to
> >determine what
> >> is probability of burning at what temp. produce what kind of
> >result.  Most
> >> of the Flame retardant product is UL 94-0 rating... as long as
> >you replace
> >> something with the same performance: corrosion, UL, material
> >compatibility
> >> etc.etc. and low cost...I am sure everybody would be happy.
> >However, few of
> >> the traps some of us went into are the "flashy" stuff, promise a lot,
> >> implemented at the product level without sufficient test in real
> >life data.
> >> To replace a deficient product with an "unknown" is very scary.  Costly
> >> lesson to learn.
> >> ...my 2.cents.
> >>                                                       jk
> >>
> >> >-----Original Message-----
> >> >From: TechNet [mailto:[log in to unmask]]On Behalf Of David Fish
> >> >Sent: Tuesday, August 13, 2002 1:05 PM
> >> >To: [log in to unmask]
> >> >Subject: Re: [TN] Bromine
> >> >
> >> >
> >> >Brian
> >> >
> >> >Bromine always seemed like such a 'nice' chemical, didn't it?
> >> >
> >> >Let me take you in a different direction.  Brominated flame retardant
> >> >incineration produces toxins:
> >> >* polybrominated biphenyl ether (PBBE)
> >> >* polybrominated biphenyl oxide (PBBO)
> >> >
> >> >Dave Fish
> >> >
> >> >----- Original Message -----
> >> >From: "b_ellis" <[log in to unmask]>
> >> >To: <[log in to unmask]>
> >> >Sent: Tuesday, August 13, 2002 5:14 AM
> >> >Subject: [TN] Bromine
> >> >
> >> >
> >> >> Yet once again, bromine has raised its head in a couple of recent
> >> >> threads on this list. I'm beginning to question whether
> >brominated fire
> >> >> retardants are as bad as they are made out to be or whether they are
> >> >> just painted bad. Unfortunately, my knowledge of polymer chemistry is
> >> >> insufficient to form a judgement. Here is what I'm thinking:
> >> >>
> >> >> The basic manufacture of epoxy resins is in two stages, the
> >> >> prepolymerisation and the crosslinking. I won't go into more than the
> >> >> basics, as I know that the subject is very complex. The epoxy group is
> >> >> provided by epichlorohydrin which is reacted with bisphenol A (BPA) in
> >> >> the presence of an alkali (NaOH), the latter serving to
> >react with the
> >> >> liberated chlorine atom to form NaCl, during the
> >prepolymerisation. Most
> >> >> of the latter is removed for electrical grade resins, but some remains
> >> >> (hence the high dielectric constant and poor power factors).
> >> >>
> >> >> The epoxy groups are subsequently reacted with cross linking
> >agents for
> >> >> the final polymerisation (curing) of the resin. Theoretically, if all
> >> >> the components are stoichiometric, the resultant cured resin is
> >> >> perfectly homogeneous with uniformly-sized molecules. In
> >practice, this
> >> >> is never perfect.
> >> >>
> >> >> The bromine comes in with FR-4 by using tetrabromobisphenol A
> >(TBBPA) in
> >> >> place of some of the BPA. This has the characteristic of releasing HBr
> >> >> and Br2 when heated to combustion temperature, this, being heavy,
> >> >> blankets the burning resin and excludes oxygen, thereby extinguishing
> >> >> the flame. TBBPA is identical to BPA other than that 4 of the H atoms
> >> >> are replaced by Br atoms, which are therefore covalently bonded to two
> >> >> of the non-cyclic carbon atoms. There is therefore no question of any
> >> >> ionic bromide being present in FR-4. Why then do bromide ions
> >leach out
> >> >> of FR-4, as has been proved time and time again? (Let's
> >discount bromide
> >> >> activated fluxes from this equation.)
> >> >>
> >> >> I have several thoughts on the matter:
> >> >> a) could it be that the TBBPA is supplied with excess free Br atoms or
> >> >> with brominated impurities that are less stable?
> >> >> b) could it be that pressing temperatures already start a breakdown of
> >> >> the TBBPA, allowing free HBr to float around the resin
> >matrix? (This may
> >> >> explain why FR-4 is marginally poorer electrically than G-10)
> >> >> c) could it be that the NaOH is capturing some Br from the
> >TBBPA during
> >> >> prepolymerisation?
> >> >> d) could it be that the TBBPA is astoichiometrically in excess,
> >> >> providing an easily attacked molecule?
> >> >> e) could it be that there are no free bromide ions at all, until our
> >> >> extraction fluid hydrolyses some organobromine compound? (If
> >this is so,
> >> >> then our ion extraction/ion chromatography tests become less
> >meaningful,
> >> >> as providing a means of a reaction!)
> >> >>
> >> >> I think we need the thoughts of a specialist polymer chemist
> >to obtain a
> >> >> much better understanding of what is happening and its
> >influence on the
> >> >> reliability of our FR-4 substrated assemblies.
> >> >>
> >> >> Anyone any ideas????
> >> >>
> >> >> Brian
> >> >>
> >> >>
> >>
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