American Dynamics PMC-4U-CACI user manual Construction and Reliability, Thermal Considerations

Construction and Reliability

PMC Modules were conceived and engineered for rugged industrial environments. The PMC-4U is constructed out of 0.062 inch thick FR4 material.

Through hole and surface mounting of components are used. IC sockets use gold plated screw machine pins. High insertion and removal forces are required, which assists in the retention of components. If the application requires unusually high reliability or is in an environment subject to high vibration, the user may solder the corner pins of each socketed IC into the socket, using a grounded soldering iron.

The PMC connectors are rated at 1 Amp per pin, 100 insertion cycles minimum. These connectors make consistent, correct insertion easy and reliable.

The PMC secured against the carrier with four screws attached to the 2 stand-offs and 2 locations on the front panel. The four screws provide significant protection against shock, vibration, and incomplete insertion.

The PMC Module provides a low temperature coefficient of 2.17 W/oC for uniform heat. This is based upon the temperature coefficient of the base

FR4 material of 0.31 W/m-oC, and taking into account the thickness and area of the PMC. The coefficient means that if 2.17 Watts are applied uniformly on the component side, then the temperature difference between the component side and solder side is one degree Celsius.

Thermal Considerations

The PMC-4U design consists of CMOS circuits. The power dissipation due to internal circuitry is very low. It is possible to create a higher power dissipation with the externally connected logic. If more than one Watt is required to be dissipated due to external loading then forced air cooling is recommended. With the one degree differential temperature to the solder side of the board external cooling is easily accomplished.

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