10 Apr
2010
10 Apr
'10
5:16 p.m.
On 10 Apr 2010 at 17:57, William Donzelli wrote:
The little solder ball blob (the B in BGA) is there
specifically to
act as a cantilever to absorb stresses. IBM figured this out when they
pioneered the technology in the 1960s. Without the tiny amount of give
that the ball gives, failures would be so frequent that the devices
would be useless, especially in today's world of relatively high
power, small outline devices that are constantly going to sleep and
waking up.
Well, yes and no. The web (and IEEE's transactions on semicondutor
packaging) is littered with papers comparing eutectic Sn-Pb solder
with RoHS lead free and the results seem to be in favor of leaded
solder. In particular, Pb-free solder seems to exhibit some
brittleness that Pb solders do not. For example, here's a paper
comparing shock (drop) tests:
http://www.europeanleadfree.net/SiTE/UPLOAD/DOCUMENT/Projects/Drop_Tes
t_Failure_Analysis_of_BgA_Packages.pdf
It's not as if we can compare 70's era IBM BGAs with today's
material, either. Today's BGAs tend to be larger and dissipate more
power.
When done badly, as in the Xbox "Red Ring of Death", failure results.
When done well with careful design, RoHS BGA work is probably quite
durable.
--Chuck