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January 2005

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(Leadfree Electronics Assembly Forum)
Date:
Thu, 13 Jan 2005 21:14:27 +0100
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Dear Brian,

thank you for clarification! I apologize for spreading myths myself instead
of asking proper questions. Your chemical explanation really stifles me,
because now I have to ask myself "why is there a drive for halogen free
concurrently with the drive for leadfree"? Excuse me if I let out this
question here in the leadfree forum, but I feel now the discussion is once
more on the edge of "is there any use behind this", after first politics
drive us into economically (and ecologically) insane procedures, and now
industry themself seems to do the same (maybe DDave knows a thread in
halogen free where this has been discussed before?). Last question - how's
it with recycling of FR4 do you see problems due to the TBBA content in the
epoxy?

Schön' Gruß
Thomas Ahrens, Boostedt

----- Original Message -----
From: "Brian Ellis" <[log in to unmask]>
To: "(Leadfree Electronics Assembly Forum)" <[log in to unmask]>; "Thomi"
<[log in to unmask]>
Sent: Thursday, January 13, 2005 10:00 AM
Subject: Re: [LF] Halogen free alert


> I think one should be less alarmist about the products resulting from
> the incineration of FR-4. What do you mean by dioxin? Strictly speaking,
> dioxin is formed by two benzene rings joined by, as the name implies, by
> two oxygen atoms. None of the three unsaturated cyclic compounds is a
> very dangerous or persistent chemical. However, the name dioxin has been
> loosely applied to a dioxin derivative,
> 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD)which has been blamed
> for all sorts of ills, including the poisoning of the new Ukrainian
> president. This is a very persistent chemical but is dangerous only in
> relatively high doses. The only usual symptom of exposure is chloracne.
> It is very undesirable, though, due to its long residence time. Since
> the Seveso disaster, its toxicity and epidemiology has become well
> known. There are a number of isomers of 2,3,7,8-TCDD but these do not
> have the persistence of 2,3,7,8, nor do the analogue substances
> containing fewer chlorine atoms.
>
> It is conceivable to have a bromine analogue,
> 2,3,7,8-tetrabromodibenzo-p-dioxin. It is possible that this may be
> slightly more toxic than 2,3,7,8-TCDD, because the looser covalent bonds
> to the bromine may be the cause of a more rapid metabolisation. However,
> by the same token, it would have a much lower persistence in nature.
>
> Is it possible for 2,3,7,8-TBDD (or -TCDD) to be formed during
> incineration? Let's discount the TCDD (the substance usually loosely
> called 'dioxin') straight away: all the chlorine atoms in FR-4 resins
> are ionically bonded. Let's examine how heat affects TBBPA in
> cross-linked resins. The substance is stable until it reaches
> temperatures exceeding 350°C. Decomposition occurs by the release of
> bromine gas (which is what gives the flame-retardant properties). At
> higher temperatures, a whole host of other reactions may occur and most
> of the remaining bromine would be driven off as hydrogen bromide and
> bromomethanes, which would rapidly decompose to hydrogen bromide and
> carbonyl bromide (all nasty compounds, but easily removed by scrubbing).
> It is true that TBBPA has two benzene rings, but they are separated by a
> methyl group and there is insufficient oxygen in the resin to make it
> likely that they would would form a dioxin bond together, let alone for
> a 2,3,7,8-TBDD molecule to form. I therefore believe it to be a myth
> that incinerating FR-4 will form dioxin and, if perchance it did, it
> would neither be a dangerous one nor in any significant quantity. In
> other words, the danger is within the emotive frame of the word 'dioxin'
> and not in the incineration.
>
> Brian
> Thomi wrote:
> > Please keep in mind that "RoHS compliant" is not synonym with "Halogen
> > free".
> > The already RoHS compliant available FR4 materials (nowadays standard
> > materials) and polymer package compounds contain chemically bound TBBA
> > (tetrabrombisphenol A) flame retardants, which are not forbidden by
RoHS.
> > Halogen free is way beyond RoHS scope, but (of course) better in terms
of
> > "green electronics" due to the fact that they do not form dioxines
during
> > carcination, and are better suited for recycling.
> >
> > Schön' Gruß
> > Thomas Ahrens, Boostedt
> >
> > ----- Original Message -----
> > From: "Lee Parker" <[log in to unmask]>
> > To: <[log in to unmask]>
> > Sent: Tuesday, January 11, 2005 5:29 PM
> > Subject: Re: [LF] Halogen free alert
> >
> >
> >
> >>Ofer
> >>
> >>Isola has a very good web page on their materials showing their degree
> >>of compliance.
> >>
> >>While you are at it, you may also want to contact the soldermask
> >>suppliers. I understand not all soldermask are compliant.
> >>
> >>Lee
> >>
> >>-----Original Message-----
> >>From: Leadfree [mailto:[log in to unmask]] On Behalf Of Ofer Cohen
> >>Sent: Tuesday, January 11, 2005 3:56 AM
> >>To: [log in to unmask]
> >>Subject: [LF] Halogen free alert
> >>
> >>Hi all,
> >>Finally we've received a customer's requirement for halogen-Free
> >>product. I've already looked at the PCB laminates issue. Does anyone
> >>have any clue about the components availability? Any general idea for
> >>the price tag?
> >>
> >>Regards
> >>Ofer Cohen
> >>Manager
> >>Quality Assurance, Reliability and Production Technologies
> >>SEABRIDGE Ltd. - A Siemens Company
> >>
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