文档介绍：THE EFFECTS OF SOLDER JOINT VOIDING
ON PLASTIC BALL GRID ARRAY RELIABILITY
Donald R. Banks, Terry E. te, Yeuk-Chow (Dennis) Cho,
William T. DeMarco, and Andrew J. Mawer
Motorola Semiconductor Products Sector
Austin, Texas
ABSTRACT [1]. This work attempts to address the question through
Solder joint voids are caused by solidification shrinkage, direct experimentation.
moisture, and flux volatilization, and mon in all
surface mount applications. Leaded devices, by their Voids in solder joints have many causes. Eutectic solder
nature, have flexibility pliance from the lead, and shrinks about four percent during solidification. The
solder voiding is seldom the cause of a reliability failure. interior of a joint would be expected to have a void simply
In plastic ball grid array (PBGA) packages, however, the because it is the last part of the joint to solidify. Outgassing
solder joint is the lead. All strain due to expansion of the printed circuit board or the PBGA substrate is
mismatch in the assembled package must be borne by the another possible void source. Moisture, plete
solder joint. The situation is worsened by the PBGA's joint laminate curing, or metallization contamination can supply
geometry--the flat package bottom surface directly above gases that may be entrapped in a solder joint [2].
the joint allows no path for trapped gases to migrate out of
t