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Ingression-Resistant Process for Plastic Packages

IP.com Disclosure Number: IPCOM000040086D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Gons, S: AUTHOR

Abstract

A process for reducing exposure to corrosive chemical ingression through cracks or delaminated plastic lead frame interfaces of integrated circuit (IC) plastic packages is reported. Corrosive chemicals, i.e., lead preparation acids and solder fluxes, are used in the assembly and card attachment of integrated circuits (ICs) plastic packages. When corrosive chemicals invade a package through cracks and delaminated interfaces, failure rates are aggravated by the corrosion of device-bonding pads in the package. By filling these voids in the package prior to exposure to corrosive chemicals used in the final process steps, device integrity is preserved and the risk of corrosion is reduced.

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Ingression-Resistant Process for Plastic Packages

A process for reducing exposure to corrosive chemical ingression through cracks or delaminated plastic lead frame interfaces of integrated circuit (IC) plastic packages is reported. Corrosive chemicals, i.e., lead preparation acids and solder fluxes, are used in the assembly and card attachment of integrated circuits (ICs) plastic packages. When corrosive chemicals invade a package through cracks and delaminated interfaces, failure rates are aggravated by the corrosion of device-bonding pads in the package. By filling these voids in the package prior to exposure to corrosive chemicals used in the final process steps, device integrity is preserved and the risk of corrosion is reduced. Inert materials used to fill voids should 1) be chemically inert, 2) have a viscosity such as to allow the material to flow into

cracks and delaminated interfaces,

3) have a boiling temperature greater than 300 degrees C to

prevent vaporization during solder dip and card attach,

4) not leave a residue after evaporation,

5) be electrically insulating,

6) be non-soluable in water, and

7) be non-toxic. Fig. 1 shows a void between the semiconductor plastic encapsulant and lead frame caused by delamination. To fill the void, the product is placed in a container of preheated inert liquid, such as a flurochemical. The product container is placed in a chamber, and air is evacuated from the cracks and voids, as shown in Fig. 2. The chamber is...