New power supply heatsink construction patent for TDK

Designers of power supplies utilise a variety of components that dissipate heat, including leaded (through hole) and surface mount devices. These parts, however, require different cooling arrangements.

Surface mount power devices can be mounted on an insulated metal substrate (IMS) consisting of layers of copper traces and thermally conductive insulation bonded to a metal baseplate. This substrate is usually vertically mounted and electrically connected to the main circuit board with a lead-frame.

Although power semiconductors are available in surface mount packages, it is easier to transfer high currents to the main board with a leaded part. This alleviates the need for multiple low-current pins on the lead-frame, occupying valuable board area. Conversely leaded parts require fasteners and insulation to mount them to a heatsink. Surface mount I2PAK packages with leads to carry the high currents to the main board are available, but are expensive. Consequently, a combination of both surface mount and leaded components are generally required.

Martin Coates Senior Electrical Design Engineer, TDK-Lambda, explains: "Available space and electrical clearance was an issue. We needed a cost effective hybrid solution."

The heat-sink arrangement developed by TDK-Lambda utilises a traditional IMS board containing surface-mounted power components on one side. Leaded power semiconductors are attached to the other side with a double-sided adhesive tape with both insulating and thermally conductive properties. The completed space saving assembly does not use any mechanical fasteners and can be easily soldered to the main circuit board.

For more information about TDK-Lambda's AC-DC power supplies and the power supply heat-sink arrangement patent application, please visit the TDK-Lambda website at www.uk.tdk-lambda.com.