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SEMI-PIERCE PLATE FOR ALIGNMENT OF SOLDER PREFORM AND DBC CERAMICS

IP.com Disclosure Number: IPCOM000008617D
Original Publication Date: 1998-Mar-01
Included in the Prior Art Database: 2002-Jun-27
Document File: 3 page(s) / 95K

Publishing Venue

Motorola

Related People

Pablo Rodriguez: AUTHOR

Abstract

The construction of power modules requires an isolation layer to a!low desired circuitry to be inte- grated directly in the module. While the layer may be required to maintain high voltage isolation, a highly thermally conductive path is crucial for the thermal management of the devices. In high power modules, such an isolation layer is typically constructed using direct bonded copper ceramics (DBC). A ceramic is directly sandwiched in copper layers; the top copper layer is etched to provide the desired circuitry while the bottom layer is used to subsequently solder the ceramic to a base plate.

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MOTOROLA Technical Developments

SEMI-PIERCE PLATE FOR ALIGNMENT OF SOLDER PREFORM AND DBC CERAMICS

by Pablo Rodriguez

  The construction of power modules requires an isolation layer to a!low desired circuitry to be inte- grated directly in the module. While the layer may be required to maintain high voltage isolation, a highly thermally conductive path is crucial for the thermal management of the devices. In high power modules, such an isolation layer is typically constructed using direct bonded copper ceramics (DBC). A ceramic is directly sandwiched in copper layers; the top copper layer is etched to provide the desired circuitry while the bottom layer is used to subsequently solder the ceramic to a base plate.

  Fabrication of power modules that use DBC ceramics is cumbersome, as alignment fixtures are required during ceramic attach. Procurement costs and management of these dedicated fixtures further

confirm the need for alternative methods of achieving the same goal.

  An alternate approach in providing alignment of the ceramic without alignment fixtures has been proposed using the semi-pierce approach. With this method, semi-pierce posts are stamped directly into the base plate, as illustrated in Figure 1. These posts, of controlled diameter and height, are intro- duced directly at the base plate stamping facility. Matching alignment holes are etched on the back side of the DBC ceramic, illustrated in Figure 2. Comparable features may also be required in the solder preform. The arrangement of features provides a built-...