On Sun, 18 Jul 2010 20:32:22 -0400, Phil Hobbs
wrote:

wrote:
On Sun, 18 Jul 2010 19:47:15 -0400, Phil Hobbs
wrote:

William Sommerwerck wrote:
Correct. The original writer was probably confused by the
fact that the materials ceramic ICs are made of can contain
radioactive materials that can cause errors.
No, the alphas from lead are a real problem. Ten years ago, there were
folks going round to churches with lead roofs, offering them a new lead
roof in exchange for their old--and now low-alpha--lead ones.
But where is the lead /within/ ICs? (The wires are bonded, not soldered.)
Alpha particles have poor penetrating power.


Only a problem with flip-chip (C4) bonding. At one point I worked in
the packaging research group at IBM Yorktown lab (no, I'm not a
packaging guy--it's a long story).

The C4 balls were lead-indium, IIRC.


Lead-tin eutectic in my era (1987-2008), followed by gold-tin currently,
IIRC.

The last time I dealt with any of this was in the mid '70s. Before TCMs, even
(LEMs). I'm pretty sure they were lead-indium, but there may have been tin in
there too. There was also an issue of polonium contamination causing
uncorrectable L1 errors, but that's a completely different issue.