Heat Transfer

Thermal Specification of Microelectronic Packages 113

where T

j

and T

c

are junction and case temperatures and



Q

jc

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 ...