PC7410 Datasheet, PDF (15/57 Pages) ATMEL Corporation – PowerPC 7410 RISC Microprocessor Product Specification

PC7410
Figure 7-3.
Thermal Performance of Different Thermal Interface Materials
2
Silicone Sheet (0.006")
Bare Joint
Floroether Oil Sheet (0.007")
Graphite/Oil Sheet (0.005")
Synthetic Grease
1.5
1
0.5
7.3.1.1
0
0
10
20
30
40
50
60
70
80
Contact Pressure (psi)
Heat Sink Selection Example
For preliminary heat sink sizing, the die-junction temperature can be expressed as follows:
T_j = T_a + T_r + (θ_jc + θ_int + θ_sa) × P_d
where:
T_J = die-junction temperature
T_a = inlet cabinet ambient temperature
T_r = air temperature rise within the computer cabinet
θ_jc = junction-to-case thermal resistance
θ_int = adhesive or interface material thermal resistance
θ_sa = heat sink base-to-ambient thermal resistance
P_d = power dissipated by the device
During operation, the die-junction temperatures (T_J) should be maintained less than the value specified
in Table 6-3 on page 11. The temperature of the air cooling the component greatly depends upon the
ambient inlet air temperature and the air temperature rise within the electronic cabinet. An electronic
cabinet inlet-air temperature (T_a) may range from 30° C to 40° C. The air temperature rise within a cabi-
net (T_r) may be in the range of 5° C to 10° C. The thermal resistance of the thermal interface material
(θ_int) is typically about 1° C/W. Assuming a T_a of 30° C, a T_r of 5° C, a CBGA package θ_jc = 0.03, and a
power consumption (P_d) of 5.0 watts, the following expression for T_J is obtained:
T_j = 30° C + 5° C + (0,03° C ⁄ W + 1,0° C ⁄ W + θ_sa) × 5W
e2v semiconductors SAS 2007
15
0832F–HIREL–02/07