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Method for interconnect bumping to improve the molding of die undergaps in microelectronic packages

IP.com Disclosure Number: IPCOM000009288D
Publication Date: 2002-Aug-14
Document File: 4 page(s) / 140K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for interconnect bumping to improve the molding of die undergaps in microelectronic packages. Benefits include improved reliability and improved performance.

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Method for interconnect bumping to improve the molding of die undergaps in microelectronic packages

Disclosed is a method for interconnect bumping to improve the molding of die undergaps in microelectronic packages. Benefits include improved reliability and improved performance.

Background

        � � � � � Void entrapment and formation of defects in the interconnect bumping area of a flip chip (FC) occur during the molding of molded matrix array packages (MMAP). (Figure 1)

        � � � � � Overmolded underfills (OMUFs) are a class of material that functions as both an underfill and a molding compound. A transfer molding process is used to encapsulate MMAPs with OMUF. During this process, the material is forced by the transfer pressure into the first-level interconnect area to underfill the undergap. OMUF technology involves a cheaper and single-step/single-material solution as compared to the conventional technology, which involves two materials (molding compound and underfill) and two processes (underfilling followed by transfer molding).

        � � � � � One of the key challenges with OMUF technology is to achieve void-free molding in the gap between the die and the substrate. Due to the narrow gap height, tight bump pitch, and high bump density, the resistance to flow of the OMUF material is significant in the undergap area. This situation leads to nonuniform flow fronts in the mold and entrapment of air pockets under the die. Entrapped air bubbles typically act as stress concentration points and increase the risk of failure rate during reliability stressing.

        � � � � � Utilizing a conventional vacuum MMAP molding process has many drawbacks, such as high tool/maintenance costs, lower process throughput, and frequent replacements of parts, such as vacuum gaskets and seals.

        � � � � � One conventional solution is drilling a vent-hole in the substrate. However, drilling a mechanical hole in the substrate uses valuable package electrical routing surface area.

General description

        � � � � � The disclosed method is a flip-chip interconnect bumping design that facilitates material flow in the die/substrate undergap area. The method reduces air entrapment and enables void-free molding of the packages.

        � � � � � The disclosed method is comprised of various bump pattern designs that facilitate material flow in the die/substrate undergap area.

        � � � � � The disclosed method provides the most advantages in the area of FC packages, and items requiring the molding of MMAP-type packages, such as flip-chip stacked chip scale packages (FCsCSPs) and FC/mixed technology stacked chip scale...