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Subject:	PCB compliant to lead free
From:	Ofer Cohen <[log in to unmask]>
Reply To:	TechNet E-Mail Forum.
Date:	Sat, 24 Jan 2004 09:11:13 +0200
Content-Type:	text/plain
Parts/Attachments:	text/plain (23 lines)

Hi all,
There are many postings regarding components compliance to the LF requirements. I find some threatening problems in the PCB: first - PBB and PBDE should not be used as fire retardant aditives - I assume it's pretty easy, yet have to be verified. Second, the external coating - this is easy too - just specify the alternate coating according to your preferences (after all - like taste and smell it is also a question of preference - I don't like gold because of the Ni intolerability to press-fit). 

But there is another factor, that endengers the electrical performance: the exposure to extensive temperatures requires higher z-axis stability (especially in thicker PCB, because of the need of controlled impedances - 2.7 to 3.3 mm is typical here, and going to 6 mm for backplanes). This requires change of the laminates into another, which might have different electrical factors (Dk and dissipation factor, for example). This change may, in turn, require the change of the PCB routing and may be the stack-up, to ensure the geometries required for the controlled impedances. This means that we should call our designers and ask them to re-design and re-validate the products.

Any comments?

Regards
Ofer Cohen
Manager
Quality Assurance, Reliability and Production Technologies
SEABRIDGE Ltd. - A Siemens Company

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