11
TSPC603R
2125A–12/01
Thermal
Characteristics
The data found in this section concerns 603r’s packaged in the 255-lead 21 mm multi-layer
ceramic (MLC), ceramic BGA package. Data is shown for the case of using the Thermalloy
#2328B heat sink.
The internal thermal resistance for this package is negligible due to the exposed die design. A
thermal interface material is recommended at the package lid-to-heat sink interface to mini-
mize the thermal contact resistance.
Additionally, the CBGA package offers an excellent thermal connection to the card and power
planes. Heat generated at the chip is dissipated through the package, the heat sink (when
used) and the card. The parallel heat flow paths result in the lowest overall thermal resistance
as well as offer significantly better power dissipation capability if a heat sink is not used.
The thermal characteristics for the flip-chip CBGA and CI-CGA packages are as follows:
Thermal resistance (junction-to-case) = R
jc
or
θ
jc
= 0.095
°
C/Watt for the 2 packages.
Thermal resistance (junction-to-ball) = R
jb
or
θ
jb
= 3.5
°
C/Watt for the CBGA package.
Thermal resistance (junction-to-bottom SCI) = R
js
or
θ
js
= 3.7
°
C/Watt for the CI-CGA package.
The junction temperature can be calculated from the junction to ambient thermal resistance,
as follow:
Junction temperature:
T
j =
T
a
+(R
jc
+R
cs
+ R
sa
) * P
T
a
is the ambient temperature in the vicinity
of the device
R
jc
is the die junction-to-case thermal
resistance of the device
R
cs
is the case-to-heat sink thermal
resistance of the interface material
R
sa
is the heat sink-to-ambient
thermal resistance
P is the power dissipated by the device
Where:
During operation, the die-junction temperatures (T
j
) should be maintained less than the value
specified in Table 5.
The thermal resistance of the thermal interface material (R
cs
) is typically about 1
°
C/Watt.
Assuming a T
a
of 85
°
C and a consumption (P) of 3.6 Watts, the junction temperature of the
device would be as follow:
T
j =
85
°
C + (0.095
°
C/Watt + 1
°
C/Watt +R
sa
) * 3.5 Watts.
For the Thermalloy heat sink #2328B, the heat sink-to-ambient thermal resistance (R
sa
)versus
airflow velocity is shown in Figure 4.