Browse Prior Art Database

X-PATTERNED GOLD DIE CAVITY

IP.com Disclosure Number: IPCOM000009868D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2002-Sep-25
Document File: 2 page(s) / 99K

Publishing Venue

Motorola

Related People

Eliatamby Nadarajah: AUTHOR

Abstract

A Pin Grid Array hermetic package (PGA) is used to house many different devices, including the 68000 series microprocessors, digital signal processors and RJSC. This type of PGA is a ceramic package with a gold only internal die cavity area which uses silver glass paste as the die attach material.

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MOTOROLA

Technical Developments

X-PATTERNED GOLD DIE CAVITY

by Eliatamby Nadarajah

BACKGROUND

A Pin Grid Array hermetic package (PGA) is used to house many different devices, including the 68000 series microprocessors, digital signal processors and RJSC. This type of PGA is a ceramic package with a gold only internal die cavity area which uses silver glass paste as the die attach material.

Typically, after a we is placed on a deposit of silver glass paste in the cavity, the paste is cured by applying heat. During curing the silver glass melts to form a bond between the we and the paste and between the cavity and the paste. The gold only cavity is required for physical connection between the die and other laminate layers of the PGA package through via holes. These connections are mainly for providing a good grounwng.

THE PROBLEM

After the die-bonded package has been cured, the strength of adhesion between the die and the cavity area needs to be monitored in-house. This is to ensure that there are no reliability issues later when the packages are shipped to customers. The pull force required to displace the we from the package determines the strength of adhesion. The normal pull force for the PGA package was very good, typically about 200 - 300% above specification. A problem surfaced when there was a deterioration in the pull force to such an extent that some units were as low as 0 lbs.

When this phenomenon was observed the SUppliers of the ceramic package and the paste claimed that there were no changes made to their products.

As an interim measure a heat cnre process was added to the process flow prior to the die bond process. This interim process caused nickel to migrate to the surface and a layer of nickel oxide is formed due to the dry air in the furnace. The oxide

Motorola. Inc. 2000

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