th erm al resistan ce of th e in terface m aterial (θ ) is typically abou t 1 °C/ W. Assu m in g a
int
Ta of 30 °C, a Tr of 5 °C, a CBGA package θ = 0.03, an d a power dissipation (P ) of 5.0
jc
d
watts, th e followin g expression for Tj is obtain ed:
Die-junction temperature: Tj = 30 °C + 5 °C + (0.03 °C/W +1.0 °C/W + θ ) * 5 W
sa
For a Th erm alloy h eat sin k #2328B, th e h eat sin k-to-am bien t th erm al resistan ce (θ )
sa
versu s air flow velocity is sh own in Figu re 22 .
Thermalloy #2328B Pin-fin Heat Sink
(25 x 28 x 15 mm)
8
7
6
5
4
3
2
1
0
0.5
1
1.5
2
2.5
3
3.5
Approach Air Velocity (m/s)
Figure 22. . Thermalloy #2328B Pin-Fin Heat Sink-to-Ambient Thermal Resistance Versus Air flow
Velocity
Assu m in g an air velocity of 0.5 m / s, we h ave an effective θ of 7 °C/ W, th u s
sa
Tj = 30°C + 5°C + (2.2 °C/W +1.0°C/W + 7 °C/W) * 4.5 W,
resu ltin g in a ju n ction tem peratu re of approxim ately 81 °C wh ich is well with in th e
m axim u m operatin g tem peratu re of th e com pon en t.
Oth er h eat sin ks offered by Ch ip Coolers, IERC, Th erm alloy, Aavid, an d Wakefield
En gin eerin g offer differen t h eat sin k-to-am bien t th erm al resistan ces, an d m ay or m ay
n ot n eed air flow.
Th ou gh th e ju n ction -to-am bien t an d th e h eat sin k-to-am bien t th erm al resistan ces are
a com m on figu re-of-m erit u sed for com parin g th e th erm al perform an ce of variou s
m icroelectron ic packagin g tech n ologies, on e sh ou ld exercise cau tion wh en on ly u sin g
th is m etric in determ in in g th erm al m an agem en t becau se n o sin gle param eter can ade-
PPC740 and PPC750 Hardware Specifications
40 of 43
Preliminary and subject to change without notice
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