Hi folks - this is one of those cases where everyone is a little bit
correct but we are all thinking of different situations. The issue with
soft error from solder comes into play for components that utilize flip
chips instead of a wire bonded die. As several folks have detailed, alpha
particles don't have much "umphf" for penetration so normally the package
is well protected from an alpha event but for a flip chip, you have solder
bumps in very close proximity to the active die surface so it is
vulnerable. Here is a good paper by Xilinx detailing the issue:
http://www.xilinx.com/support/documentation/white_papers/wp208.pdf
Dave
Guy Ramsey <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
03/07/2012 02:23 AM
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Re: [TN] Fw: Help. Is this true-- SOFT ERRORS FROM SOLDER??
Gosh Pat,
Confirming Karen's comment. I am certain I remember a program that
required
traceability of the Pb in solder back to the mine. I am fairly certain it
was because an FA determined that unpredictable performance was related to
emissions from the Pb in solder.
As to the possibility that Sn may contribute . . . I don't know.
Guy
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Goodyear, Patrick
Sent: Tuesday, March 06, 2012 4:50 PM
To: [log in to unmask]
Subject: Re: [TN] Fw: Help. Is this true-- SOFT ERRORS FROM SOLDER??
I looked it up on my tables and approximately 16% of natural tin are
isotopes that are radioactive, out of 10 total, and decay via isometric
transistion or gamma decay, max half life is 300 days, so these are
considered stable isotopes since only the radioactive portions of the 2
are
produced as the result of fission fragments. The other 8 Sn isotopes are
considered stable.
Pb has a similar makeup with only 4 natural isotopes and only 2 that are
radioactive to a slight amount, mostly half lives of less than 2 hours,
and
therefore are considered stable, decay again by isometric transition and
gamma, there are no alpha emmitters considered naturally occuring. There
are 32 isotopes that occur thru decay chains but are NOT natrually
occurring
with half lives on the order of a few seconds to about 4 hours max. Pb
202,
205, and 210 are long lived radioactive isotopes but are not naturally
occuring and none alpha emit they either electron capture or beta emit.
Information is from the 16th edition of chart of the nuclides by Knolls
Atomic Power Laboratory.
So with that said I would look for some other contaminant in the process.
pat
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Karen Tellefsen
Sent: Tuesday, March 06, 2012 10:33 AM
To: [log in to unmask]
Subject: Re: [TN] Fw: Help. Is this true-- SOFT ERRORS FROM SOLDER??
This is much more of a problem with tin-lead solder than SAC solder,
because
naturally occurring lead emits a tiny amount of alpha particles.
It's mostly an issue with BGA spheres,some of which are high lead alloys,
and are often close to IC chips where the alpha emissions are most likely
to
cause damage.,
Karen Tellefsen - Electrical Testing
[log in to unmask]
908-791-3069
[TN] Fw: Help. Is this true-- SOFT ERRORS FROM SOLDER??
harvey
to:
TechNet
03/06/2012 11:58
AM
Sent by:
TechNet <[log in to unmask]>
Please respond to TechNet E-Mail Forum, harvey
Could this be true only of 63-37 or would lead-free SAC alloys also be
potentially guilty of causing soft errors?
----- Forwarded Message ----
From: "Gandhi, Mahendra S (AS)" <[log in to unmask]>
To: "[log in to unmask]" <[log in to unmask]>;
"[log in to unmask]" <[log in to unmask]>;
"[log in to unmask]" <[log in to unmask]>
Sent: Tue, March 6, 2012 8:38:40 AM
Subject: Help. Is this true??
Evidently regular solder has decaying Uranium in it, or somehow generates
alpha particles, which are being blamed for upsets. Some chips are moving
to a special "low alpha" solder internally to avoid this problem on
bump-grid-arrays in flipchip parts.
Mahendra Gandhi
SME - PWB Technologies
Aerospace Engineering
One Space Park, M5/1085A
Redondo Beach, Ca. 90278/*[log in to unmask]
(Office: 310.813.6857 Fax: 310.812.8630
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