even phenolic has been used for RoHS compliant process compatible builds. Yes
FR4 may well survive in some applications, it all greatly depends on board size
and component mix. The final consideration is the reliability - if you don't
mind about reliability on a small and simple board then FR4 may be your
ecconomic choice.
There is no perscribed solution to any of these issues. They all have to be
considered on individual needs.
Chris
-----Original Message-----
From: [email protected] on behalf of Camille Good
Sent: Wed 02/02/2005 19:49
To: Scott Douglas; EMC-PSTC List
Cc:
Subject: Re: RoHS and FR-4
Scott,
There is a lead-free IPC listserver that I am also
signed up for and there is quite a bit of discussion
there about RoHS and meeting RoHS requirements.
(There is also a halogen-free listserver that IPC runs
as well, but it seems to be almost inactive, most
discussion takes place on the lead-free list.) I
recently posed a similar question about RoHS and FR-4,
I will post a summary of the replies below.
I would definitely agree with the comment about
needing documentation from your PCB vendor confirming
compliance with RoHS.
As for FR-4 surviving the lead-free process, I have
seen a lot of statements either way. Some sources
have said it can't survive lead-free solder
temperatures. Some sources say that it does fine.
Even the people who say FR-4 can survive lead-free
solder temperatures admit that it's a little bit
fragile at those temperatures. The process needs to
be watched VERY carefully to make sure IR reflow and
wave solder don't get too hot (which will also be a
concern for components as well). If the panel is
larger than 8 or 9 inches on a side, there needs to be
a center support or the panel is likely to warp.
Also, a speaker at one seminar I went to said rework
on any particular pad or hole can only be done about
two times after reflow & wave, if the FR-4 is heated
back up to lead-free soldering temperatures more than
two times lifting or cracking of the traces is very
likely.
Anyway, on to the discussion of RoHS & FR-4:
I posted a question on the IPC lead-free and
halogen-free lists in mid-January 2005 about
the use of halogenated flame retardants in FR-4
PCBs. My question was (essentially) that I had
heard some conflicting statements from various
sources but did not know a lot of specifics
about PCB laminate composition so I needed more
information. To briefly summarize the responses
I got:
1) Halogen-free is a separate concern from
RoHS. There are some halogenated materials
not restricted by RoHS.
2) FR-4 PCBs typically DO use halogenated flame
retardants, usually TBBPA (TetraBromoBisPhenol
-A). Halogen-free FR-4 PCBs are noticeably more
expensive than halogenated FR-4 PCBs.
3) HOWEVER, TBBPA is NOT one of the substances
banned per RoHS, so the use of TBBPA in PCBs
does not make them halogen-free but it does not
keep them from being RoHS-compliant.
Links
From posts on the Lead-Free list regarding use
of RoHS substances:
Joe Johnson of Microsoft put together a very
nice overview summary in his presentation at
the NEMI LF/RoHS Summit in Louisville, CO in
October:
ftp://nemi.org/webdownload/newsroom/Presentations/11.pdf
Also, check out the work of HDPUG to ID RoHS
chemicals in several electronic devices. This
presentation gives an overview of their work:
http://www.hdpug.org/public/4-papers/2003/dfe/4_dfe.pdf
I have checked out both links and they are good
presentations to read through, although they are
both more focused on personal computer / IT
equipment. The hdpug.org document is
particularly interesting in that it details the
amount of substances found in computer cables
and the breakdown of materials found in items
such as typical PC motherboards, CRT monitors,
cell phones, etc.
If you want to dig deeper into the actual chemistry
there is a lot there and I would recommend you look at
the IPC lead-free list archives for more detail from
the January discussion. One respondent said that TBBPA
is not as big of a concern as the PBBs
(poly-brominated bi-phenyls) and PBDEs
(poly-brominated di-phenyl ethers) that RoHS bans
because TBBPA cross-links with PCB laminates while the
PBBs and PBDEs tend to just mix in but don't actually
chemically link (or not as much) so TBBPA is not as
likely to migrate out of the PCB and into the rest of
the world as PBBs or PBDEs. I haven't had a chance to
do any more research on the chemistries of PCBs, so
that is about the extent of my knowledge.
One other thing about PCBs that I was warned about by
a local PCB house: some red & yellow silkscreens used
to be done with cadmium-based inks. Most US board
houses have gone away from the cadmium inks (or so I
was told), but that is something you may want to
specifically ask your PCB supplier about because it is
a concern they may not be aware of.
Hope that helps,
-Camille Good
Portland, Oregon
--- Scott Douglas <[email protected]> wrote:
> I am wanting to find out RoHS information for
> printed circuit boards
> (printed wiring boards in some places). We generally
> use FR-4 with
> flammability rating of 94V-0.
>
> How do I find out if the pcb material is RoHS
> compliant? I am not
> immediately concerned with the tinning of the etches
> at this point.
> Mostly just want to know if we are going to have to
> change to another
> material to replace the FR-4 base material.
>
> Any information to point me down a path will be
> greatly appreciated.
>
> Best regards,
>
> Scott Douglas
> [email protected]
>
>
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