MC68020 Motorola, MC68020 Datasheet - Page 276

• Manufacturer Part Number: MC68020
• Description: (MC68020 / MC68EC020) MICROPROCESSORS USERS MANUAL
• Manufacturer: Motorola

Solving Equations (10-1) and (10-2) for K gives:
where K is a constant pertaining to the particular part. K can be determined from equation
(10-3) by measuring P
values of P
any value of T
The total thermal resistance of a package ( q
q
package (case) surface, and q
ambient air. These terms are related by the equation:
q
dependent and can be minimized by such thermal management techniques as heat sinks,
forced air cooling, and use of thermal convection to increase air flow over the device.
Thus, good thermal design on the part of the user can significantly reduce q
approximately equals q
semiconductor junction temperature.
10.2.1 MC68020 Thermal Characteristics and
MC68020 Thermal Resistance (°C/W)
The following table provides thermal resistance characteristics for junction to ambient and
junction to case for the MC68020 packages with natural convection and no heatsink.
MC68020 CQFP Package
Table 10-1 provides typical and worst case thermal characteristics for the MC68020
CQFP package both with and without a heatsink. The heatsink used is black anodized
aluminum alloy, 0.72"x0.75"x0.6" high with an omnidirectional 5x6 array of fins.
Attachment was made using Epolite 6400 one part epoxy.
10-2
JC
JC
and q
is device related and cannot be influenced by the user. However, q
Resistance is to bottom center (pin side) of case for PGA and PPGA packages, top center of case
for CQFP and PQFP packages.
Thermal Resistance
DC Electrical Characteristics
PGA Package (RC Suffix)
PPGA Package (RP Suffix)
CQFP Package (FE Suffix)
PQFP Package (FC Suffix)
CA
D
. q
CharacteristicÑNatural Convection and No Heatsink
and T
A
JC
.
represents the barrier to heat flow from the semiconductor junction to the
J
can be obtained by solving equations (10-1) and (10-2) iteratively for
D
JC
(at thermal equilibrium) for a known T
. Substitution of q
K = P
CA
M68020 USERÕS MANUAL
represents the barrier to heat flow from the case to the
D
¥ (T
q
JA
A
=q
+ 273°C) + q
JC
JC
JA
+ q
for q
) can be separated into two components,
CA
JA
in equation (10-1) results in a lower
JA
¥P
D 2
A
. Using this value of K, the
q
26
32
46
42
JA
q
CA
10
15
20
JC
3
CA
so that q
MOTOROLA
is user
(10-3)
(10-4)
JA