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THERMAL APPLICATION NOTE FOR MICROPROCESSOR SYSTEMS USING STD/SERIES 7000 CARDS
SECTION 1 - INTRODUCTION
The failure rate of many electfical components is an
exponenti~l
function of
junction temperature.
Temperature rise from ambient to Junction temperature
depends on many factors such as power density i.e. watts/inch
3 ,
air velocity
over the high dissipating components, thermal ·resistance .(junction-to-case)
and dissipation of the component, and the thermal characteristics of the
cabinet which houses the system.
This application note is intended to aid the user in estimating and solving
his thermal problems.
Sample analyses of two Series
7000
Systems are included,
as well as suggestions for minimizing thermal effects.
Heat flow is analogous to current flow in an" electrical circuit.
The electrical
and thermal equivalent are presented in Figure 1.
AT
TH£R.nAL
CIRCuIT
= p,
I:l
V"~
I.
Ii
llT
-
'Re
THE~"1AL
EGuf-lTIONS
I
THERMAL
ELECTRICAL
!
SYMBOL
NAME
UNITS
/SYMBOL
NAME
UNITS
I
i
P
POWER (HEAT
WATTS
I
CURRENT
AMPS
FLOW)
T
TEMPERATURE
°c
DIFFERE;NCE
I
V
VOLTAGE
01
FF~:
VOL TSI
j
-
i
R'
THERMAL
°C/W
e
RESISTANCE
j
R
ELECTRICAL
OHMS!
I
RESISTANCE
i
~
I
r
FIGURE 1 - THERMAL AND ELI
16
o
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