Browse Prior Art Database

HOT AIR NOZZLE ENCAPSULANT DISPERSER

IP.com Disclosure Number: IPCOM000006089D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2001-Dec-03
Document File: 1 page(s) / 60K

Publishing Venue

Motorola

Related People

Glenn Gold: AUTHOR [+3]

Abstract

Glob top encapsulation is used to afford protection to integrated circuits (I&). This process involves dispensing of a viscous glob top material over an IC and then curing, or hardening, the encapsulant in a convection oven. The most desirable glob top encapsulants have a high viscosity at room temperature, and below. Complete encapsulation of an IC requires full spreading of the glob top over the desired surface area. Incomplete encapsulation, or voiding, leads to accelerated failure of the device. Due to the high viscosity of the glob top at room temperature, spreading must be induced by raising the temperature of the glob top prior to dispense,, raising the temperature of the IC and the underlying substrate, or both. Initially, heating the glob top in the syringe lowers its viscosity but, ultimately, it initiates the curing of material in the syringe. In addition, heating of the syringe also makes dispense-to-dispense volume repeatability difficult to achieve because material tends to ball up at the tip of the dispense needle. Heating of the underlying substrate, again, prematurely initiates curing of the encapsulant.

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ti0r0~0LA INC. Technical Developments Volume 12 April 1991

HOT AIR NOZZLE ENCAPSULANT DISPERSER

by Glenn Gold, Frank Juskey and Bruce Freyman

  Glob top encapsulation is used to afford protection to integrated circuits (I&). This process involves dispensing of a viscous glob top material over an IC and then curing, or hardening, the encapsulant in a convection oven. The most desirable glob top encapsulants have a high viscosity at room temperature, and below. Complete encapsulation of an IC requires full spreading of the glob top over the desired surface area. Incomplete encapsulation, or voiding, leads to accelerated failure of the device. Due to the high viscosity of the glob top at room temperature, spreading must be induced by raising the temperature of the glob top prior to dispense,, raising the temperature of the IC and the underlying substrate, or both. Initially, heating the glob top in the syringe lowers its viscosity but, ultimately, it initiates the curing of material in the syringe. In addition, heating of the syringe also makes dispense-to-dispense volume repeatability difficult to achieve because material tends to ball up at the tip of the dispense needle. Heating of the underlying substrate, again, prematurely initiates curing of the encapsulant.

  This invention incorporates a hot air nozzle which directs a heated gas onto glob topped IC devices. Heated airlnitrogenihelium is blown through a metal tube directed at the point where the glob top enc...