
MOTOROLA
EC603e Microprocessor Hardware Specifications (PID7t), Rev. 2.0
25
The board designer can choose between several types of thermal interface. Heat sink adhesive materials
should be selected based upon high conductivity, yet adequate mechanical strength to meet equipment
shock/vibration requirements. There are several commercially-available thermal interfaces and adhesive
materials provided by the following vendors:
Dow-Corning Corporation
517-496-4000
Dow-Corning Electronic Materials
PO Box 0997
Midland, MI 48686-0997
Chomerics, Inc.
617-935-4850
77 Dragon Court
Woburn, MA 01888-4850
Thermagon Inc.
216-741-7659
3256 West 25th Street
Cleveland, OH 44109-1668
Loctite Corporation
860-571-5100
1001 Trout Brook Crossing
Rocky Hill, CT 06067
AI Technology (e.g., EG7655)
609-882-2332
1425 Lower Ferry Rd.
Trent, NJ 08618
The following section provides a heat sink selection example using one of the commercially available heat
sinks.
1.8.6.3 Heat Sink Selection Example
For preliminary heat sink sizing, the die-junction temperature can be expressed as follows:
Tj = Ta + Tr + (qjc + qint + qsa) * Pd
Where:
Tj is the die-junction temperature
Ta is the inlet cabinet ambient temperature
Tr is the air temperature rise within the computer cabinet
qjc is the die junction-to-case thermal resistance
qint is the adhesive or interface material thermal resistance
qsa is the heat sink base-to-ambient thermal resistance
Pd is the power dissipated by the device
During operation the die-junction temperatures (Tj) should be maintained less than the value specied in
Table 2. 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 (Ta) may range from 30 to 40 C. The air temperature rise within a cabinet (Tr) may be in the
range of 5 to 10 C. The thermal resistance of the thermal interface material (
qint) is typically about 1 C/
W. Assuming a Ta of 30 C, a Tr of 5 C a CBGA package qjc = 0.095, and a power consumption (Pd) of 3.0
Watts, the following expression for Tj is obtained:
Die-junction temperature: Tj = 30 C + 5 C + (0.095 C/W + 1.0 C/W + Rsa) * 3.0 W