Th e board design er can ch oose between several types of th erm al in terfaces. Heat sin k
adh esive m aterials sh ou ld be selected based u pon h igh con du ctivity, yet adequ ate
m ech an ical stren gth to m eet equ ipm en t sh ock/ vibration requ irem en ts. Th ere are sev-
eral com m ercially-available th erm al in terfaces an d adh esive m aterials provided by th e
followin g ven dors:
Dow-Corn in g Corporat ion
Dow-Corn in g Electron ic Materials
P.O. Box 0997
517-496-4000
Midlan d, MI 48686-0997
Ch om erics, In c.
617-935-4850
216-741-7659
860-571-5100
609-882-2332
77 Dragon Cou rt
Wobu rn , MA 01888-4850
Th erm agon , In c.
3256 West 25th Street
Clevelan d, OH 44109-1668
Loct it e Corporat ion
1001 Trou t Brook Crossin g
Rocky Hill, CT 06067
AI Tech n ology (e.g. EG7 6 5 5 )
1425 Lower Ferry Road
Tren t, NJ 08618
Th e followin g section provides a h eat sin k selection exam ple u sin g on e of th e com m er-
cially available h eat sin ks.
7.8 Heat Sink Selection Example
For prelim in ary h eat sin k sizin g, th e die-ju n ction tem peratu re can be expressed as fol-
lows:
Tj = Ta + T + (θ + θ + θ ) * P
d
r
jc
int
sa
Wh ere:
Tj is th e die-ju n ction tem peratu re
Ta is th e in let cabin et am bien t tem peratu re
Tr is th e air tem peratu re rise with in th e system cabin et
θ is th e ju n ction -to-case th erm al resistan ce
jc
θ
θ
is th e th erm al resistan ce of th e th erm al in terface m aterial
is th e h eat sin k-to-am bien t th erm al resistan ce
int
sa
P is th e power dissipated by th e device
d
Typical die-ju n ction tem peratu res (Tj) sh ou ld be m ain tain ed less th an th e valu e speci-
fied in Table 3 . Th e tem peratu re of th e air coolin g th e com pon en t greatly depen ds
u pon th e am bien t in let air tem peratu re an d th e air tem peratu re rise with in th e com -
pu ter cabin et. An electron ic cabin et in let-air tem peratu re (Ta) m ay ran ge from 30 to 40
°C. Th e air tem peratu re rise with in a cabin et (Tr) m ay be in th e ran ge of 5 to 10 °C. Th e
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PPC740 and PPC750 Hardware Specifications
Preliminary and subject to change without notice
IBM [ IBM ]
