PC8240 View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

PC8240

Integrated Processor Family

Atmel Corporation 

Heat Sink Selection Example

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 fol-

lowing vendors:

Dow-Corning Corporation

Dow-Corning Electronic Materials

PO Box 0997

Midland, MI 48686-0997

800-248-2481

Internet: www.dow.com

Chomerics, Inc.

77 Dragon Court

Woburn, MA 01888-4014

Thermagon Inc.

3256 West 25th Street

Cleveland, OH 44109-1668

Loctite Corporation

1001 Trout Brook Crossing

Rocky Hill, CT 06067-3910

781-935-4850

Internet: www.chomerics.com

888-246-9050

Internet: www.thermagon.com

860-571-5100

Internet: www.loctite.com

For preliminary heat sink sizing, the die-junction temperature can be expressed as

follows:

TJ = TA + TR + (θJC + θINT + θSA) x 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.

θJC is the junction-to-case thermal resistance.

θINT is the adhesive or interface material thermal resistance.

θSA 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 specified in Table. 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 (θINT) is typically about 1°C/W.

Assuming a TA of 30°C, a TR of 5°C, a TBGA package θJC = 1.8, and a power consump-

tion (PD) of 5.0 watts, the following expression for TJ is obtained:

Die-junction temperature: TJ = 30°C + 5°C + (1.8°C/W + 1.0°C/W + θSA) x 5.0W

For preliminary heat sink sizing, the heat sink base-to-ambient thermal resistance is

needed from the heat sink manufacturer.

Though the die junction-to-ambient and the heat sink-to-ambient thermal resistances

are a common figure-of-merit used for comparing the thermal performance of various

microelectronic packaging technologies, one should exercise caution when only using

this metric in determining thermal management because no single parameter can ade-

quately describe three-dimensional heat flow.

14 PC8240

2149A–HIREL–05/02

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