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HYBRID POWER MODULE INTERCONNECTION METHOD FOR STRAIN RELIEF USING S BEND AND C BEND STAMPED LEADS

IP.com Disclosure Number: IPCOM000007957D
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2002-May-08
Document File: 4 page(s) / 188K

Publishing Venue

Motorola

Related People

Martin Kalfus: AUTHOR

Abstract

The assembly of intelligent power modules with vertically integrated control logic requires numer- ous interconnections between the power stage or substrate and the control stage. In addition to the control function, a different set of connections is needed to provide power in and out terminations. Similarly, in dumb modules, it is necessary to bring to the outside world all the connections necessary to operate the semiconductors within. This is usually done with several sets of terminals and in some cases many different shapes and sizes may be need- ed. The cost of stamping tooling for several lead sets and complex fixtures for alignment has moti- vated the development of the following concepts.

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MOTOROLA Technical Developments

HYBRID POWER MODULE INTERCONNECTION METHOD FOR STRAIN RELIEF USING S BEND AND C BEND STAMPED LEADS

by Martin Kalfus

  The assembly of intelligent power modules with vertically integrated control logic requires numer- ous interconnections between the power stage or substrate and the control stage. In addition to the control function, a different set of connections is needed to provide power in and out terminations. Similarly, in dumb modules, it is necessary to bring to the outside world all the connections necessary to operate the semiconductors within. This is usually done with several sets of terminals and in some cases many different shapes and sizes may be need- ed. The cost of stamping tooling for several lead sets and complex fixtures for alignment has moti- vated the development of the following concepts.

  Complicating the above existing art configura- tions is the fact that many modules are potted using hard materials to provide both mechanical strength and environmental sealing of the exiting termina- tions. A soft encapsulant is often used inside the module to protect the Silicon ionically and the wire- bounds mechanically. When the terminals are mechanically constrained at each of their ends, the terminals or the package parts must be compliant enough to absorb the total expansion and or con- traction displacements that will occur over the entire operating temperature range. Without this compliance, delamination of the electrical conduc- tive paths may occur. Environmental sealing may also be compromised. Either of these conditions will ultimately lead to product failure.

  A method is described here that provides a sin- gle lead design that can be used to provide XYZ compliance, low and high current capability, flexi- bility in position, good planarity, and compatibility with efficient manufacturing practices.

  The major compliant feature of the terminal is the "S" bend shape which provides the necessary moment arms to allow compliance without fatigure. Finite Element Modeling has been utilized to help

understand the effects of strain/stress from package component heating and resistive heating effects within the terminal.

  The "S' bend is created by a stamping process rather than a metal bending operation. The work hardening effects are reduced and a softer "S" shape results. The stamped shape is easier to produce and store on a reel than a formed shape part. The reel becomes an integral part of a terminal insertion process. Along with the "S' shape, specific stamped features are easy to incorporate that facilitate the insertion equipment needs.

  A carrier system is added to contain all the leads as a single assembly part. The carr...