Browse Prior Art Database

AN ALTERNATE EXTERNAL LEAD-TO-HEATSINK GROUNDING METHOD

IP.com Disclosure Number: IPCOM000006105D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2001-Dec-04
Document File: 2 page(s) / 124K

Publishing Venue

Motorola

Related People

Ted Golubic: AUTHOR [+2]

Abstract

The basic IC power circuit, packaged in a single in-line package (SIP) or other similar package, requires silicon-to-heatsink and heatsink-to-external lead interconnection for efficient circuit design. The silicon-to-heatsink connections are typically accomplished through wire bonds from the circuit bonding pads to the heatsink, hereinafter termed "down-bonds".

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 50% of the total text.

Page 1 of 2

0 M

MOTOROLA INC. Technical Developments Volume 12 April 1991

AN ALTERNATE EXTERNAL LEAD-TO-HEATSINK

GROUNDING METHOD

by Ted Golubic and Tim Olson

   The basic IC power circuit, packaged in a single in-line package (SIP) or other similar package, requires silicon-to-heatsink and heatsink-to-external lead interconnection for efficient circuit design. The silicon-to-heatsink connections are typically accomplished through wire bonds from the circuit bonding pads to the heatsink, hereinafter termed "down-bonds".

  In the prior art, connection of the heatsink to an external package lead is typically accomplished by one of the following two means:

  1. Wire bonds from the leadframe bonding surface to the heatsink, also hereinafter termed "down- bonds". (Figure 1)

2. Mechanical connection of the lead to the heatsink by such means as "staking". (Figure 3)

  Both the wire "down-bonds" and "staking" connection means have proven to be marginally reliable in accelerated life testing and in actual field performance.

  An improved method has been developed by the authors which replaces the mechanical staking or down-bonds with an extruded heatsink pedestal and corresponding metallurgical weld for the external lead-to-heatsink connection.

  In addition, the authors have filed for U.S. and foreign patents on an improved method for accomplishing wire down-bonds. The improved

down-bond method may be used for either circuit-to- heatsink or external lead-to-heatsink electrical connection, however, the herein described "alternate eternal lead-to-heatsink grounding method" is preferred for the lead-to-heatsink portion of the electrical path.

In the improved design, the heatsink pedestal is

0 Motorola, 1°C. ,991

created during the normal heatsink stamping process through a special tool design. The pedestal is created by an upward extrusion of heatsink metal. The pedestal is elevated to the correct height to come in contact with the underside of any one or more of the package external leads. The pedestal and lead(s) are then metallurgically welded to guarantee a low resistance, highly reliable bond.

  The alternate circuit-to-heatsink grounding method, developed by the authors, boasts several strong advantages over the prior art outlined previously. These advantages include, but are not limited to:

  1. Su...