Steve, can't comment on this directly, but have always said that we have
been conditioned over the last 10 years to expect electronics of the
portable kind that you can treat like absolute cr*p and still expect it to
work.

Lead free joints do not compare well to tin lead on surviving a drop test. I
would expect all portable products to be less reliable.

The cell phone manufacturers have gotten around this to some extent by under
filling micro BGA's and CSP etc, but I am not sure how wide spread this is
outside of the mobile market.

John

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Monday, October 16, 2006 10:23 AM
To: [log in to unmask]
Subject: [TN] [LF] [TN] One of the First Lead Free Casualties?

Hi All!

I get the Circuitnet email newsletter everyday and today's newsletter
had a interesting link about all the laptop battery recalls as of late.

http://www.digitimes.com/bits_chips/a20061012A4013.html

************************************************************************
*****

What lies behind the Sony battery recall? Cracked MLCCs or the absence
of an NTC resistor?
Nuying Huang, Taipei; Esther Lam, DigiTimes.com [Thursday 12 October
2006]



Although the major cause of the recent Sony battery recall has not been
revealed, passive component makers suspect that cracking of the
multi-layer ceramic capacitors (MLCCs) or the inappropriate use of
negative temperature coefficient (NTC) resistors caused the batteries to
overheat.

Sources at US-based passive component makers commented that overheating
may have originated in the electrical insulation of the batteries and
that MLCC and other passive components should not be the major cause of
the incident.

Some Taiwan-based makers, on the other hand, suspect that the adopted
MLCCs had been cracked by printed circuit board (PCB) assembly, and that
this may have caused an unstable flow of current, leading eventually to
overheating.

Most of the MLCCs that had been found to be cracked had been made using
X7R material, and X7R-based MLCCs are widely employed in applications
that require a relatively high current.

In order to avoid cracking, some makers introduce a so-called "open mode
design," which adjusts the design of the MLCC electrode. The US-based
Kemet and Taiwan-based Walsin Technology have both introduced this kind
of design.

Some industry players add organic materials to MLCCs, to avoid cracking.
They usually term this type of supplementation of organic materials,
"soft termination"or "polymer termination." Industry players that
include the UK-based Syfer and Avx/Kyocera have introduced this type of
solution.

The inappropriate adoption or lack of NTC resistors may also lead to
overheating problems, said some Taiwan players. Since NTC resistors play
a critical role in terminating the power supply, when overheating is
detected, the inappropriate use or lack of NTC resistors may also have
the effect of causing overheating.

************************************************************************
***

I may be wrong about this, but aren't lead free solders more rigid or
stiff in comparison to standard tin lead solders? Could the less
compliant lead-free solder joints be contributing the higher incidences
of MLCC cracking? Just a thought....

-Steve Gregory-

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