
Thermal Specification of Microelectronic Packages 113
where T
j
and T
c
are junction and case temperatures and
is part of the heat that
ows from the die to the case of the package. The case is typically referred to
the external surface in the primary heat transfer path of the package. It is the top
surface for SOP, PGA, BGA, PLCC, and QFP packages with the die facing down
and the bottom surface for metal tabbed packages such as TO-220 and TO-263, and
QFP packages with the die facing up. The JEDEC standards use the notation θ
jcx
for junction-to-case thermal resistance where x is replaced by top or bot depending
on whether the ...