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Browse Prior Art Database

THE WASHING MACHINE TURBO-CULL

IP.com Disclosure Number: IPCOM000007887D
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2002-May-02
Document File: 1 page(s) / 61K

Publishing Venue

Motorola

Related People

Brian Webb: AUTHOR [+2]

Abstract

Semiconductor packages are being driven to be smaller lighter and thinner by our customers. One millimeter or less thick packages are common, resulting in requirements to fill the package thick- ness between the flag of the leadframe and the bot- tom of the package with defect free mold compound in order to insure environmental integrity, The thick- ness of this plastic may be from ,006 - ,008 inch thick. As the present thermoset molding compounds flow into the mold cavity they follow the path of least resistance, over the die to the vent, and finally filling the area under the flag. This ohen results in nit lines and voids under the flag, which are paths for moisture ingress. Thermally enhanced packages with heat spreaders are an even greater problem.

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Technical Developments

THE WASHING MACHINE TURBO-CULL

by Brian Webb and Jim Perkins

amount of thermal energy transferred to the com- pound. This increases the temperature of the com- pound resulting in lower viscosity and shorter reac- tion time to cross link and cure. These are two opposing reactions which must be optimized for each application.

HISTORY

  Semiconductor packages are being driven to be smaller lighter and thinner by our customers. One millimeter or less thick packages are common, resulting in requirements to fill the package thick- ness between the flag of the leadframe and the bot- tom of the package with defect free mold compound in order to insure environmental integrity, The thick- ness of this plastic may be from ,006 - ,008 inch thick. As the present thermoset molding compounds flow into the mold cavity they follow the path of least resistance, over the die to the vent, and finally filling the area under the flag. This ohen results in nit lines and voids under the flag, which are paths for moisture ingress. Thermally enhanced packages with heat spreaders are an even greater problem.

IMPROVEMENT AND APPLICATION

PRIOR ART

  U.S. patent No. 5,123,826 disclosed the turbo cull, which is presently being used successhtlly in many applications within motorola. Key to this pat- ent is a feature which protrudes from the mold base into the cull. This essentially increases the surface area of the passages that the mold compound must pass through on the way...