Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2002-10-31
2004-11-30
Pham, Long (Department: 2814)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C257S734000, C257S735000, C257S736000
Reexamination Certificate
active
06825108
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to the field of integrated circuit (IC) device packaging technology and, more particularly, to techniques for providing support to a ball grid array (BGA) packages during assembly processes.
2. Background Art
Integrated circuit (IC) dies are typically mounted in or on a package that facilitates attachment to a printed circuit board (PCB). One such type of IC die package is a ball grid array (BGA) package. BGA packages provide for smaller footprints than many other package solutions available today. A BGA package has an array of solder balls located on a bottom external surface of a package substrate. The solder balls are reflowed to attach the package to the PCB. In one type of BGA package, the IC die is mounted to a top surface of the package substrate. Wire bonds typically couple signals in the IC die to the substrate. The substrate has internal routing which electrically couples the IC die signals to the solder balls on the bottom substrate surface.
A number of BGA package substrate types exist, including ceramic, plastic, and tape (also known as “flex”). In some BGA package types, a stiffener may be attached to the substrate to supply planarity and rigidity to the package. In such packages, the IC die may be mounted to the stiffener instead of the substrate. Openings in the stiffener may be used to allow the IC die to be wire-bonded to the substrate.
Die-up and die-down BGA package configurations exist. In die-up BGA packages, the IC die is mounted on a top surface of the package, opposite of the side to which the solder balls are attached. In die-down BGA packages, the IC die is mounted on a bottom surface of the package, on the same side as which the solder balls are attached.
Various assembly process steps for the BGA package may cause harmful stresses and shocks to the IC die. These process steps include attachment of the IC die to the BGA package, attachment of wire bonds, encapsulation of the IC die and wire bonds for environmental protection, attachment of solder balls to the BGA package, and other steps. As a result of the stress occurring during these processes, the package stiffener may become deformed. The deformation of the stiffener may lead to the formation of cracks in the IC die, potentially rendering the IC die inoperable. Hence, costs in terms of lost money and time may be incurred for repairing and replacing damaged IC dies and BGA packages, among other costs.
Hence, what is needed are improved BGA package assembly processes that reduce stresses and shocks that may harm the BGA package.
BRIEF SUMMARY OF THE INVENTION
Ball grid array (BGA) packages having enhanced electrical, thermal, and mechanical characteristics are described herein. In particular, improved assembly processes and structures are described. In an aspect of the present invention, a system and method of assembling a BGA package with integrated circuit (IC) die support are described. A stiffener is attached to a substrate that includes a centrally located opening with an IC die support structure removably held therein. An IC die is mounted to a central region of the stiffener. The IC die support structure is subsequently removed from the centrally located opening.
In a further aspect, additional assembly process steps in addition to mounting the IC die are performed before removing the IC die support structure. Such additional steps include, for example, connecting a bond pad of the IC die to a contact pad on the substrate with a wire bond. In another aspect, the IC die is encapsulated on the stiffener. The IC die support structure supports the stiffener during one or more of these assembly process steps to reduce deformation of the stiffener and damage to the IC die.
In an aspect of the present invention, the IC die support structure is attached to the substrate by an adhesive tape. The adhesive tape to which the IC die support structure is attached removably holds the IC die support structure within the centrally located opening. The applied adhesive tape is detached from the substrate to remove the IC die support structure from the centrally located opening.
In another aspect of the present invention, the IC die support structure is formed in the opening as a portion of the substrate. The IC die support structure portion of the substrate remains removably held in the opening by one or more substrate tabs. The one or more substrate tabs are broken to release the IC die support structure from the centrally located opening.
In another aspect of the present invention, a system and method of assembling a plurality of BGA packages is described. A substrate strip that includes a plurality of substrates that each include a centrally located opening with an IC die support structure removably held therein is formed. A stiffener strip that includes a plurality of stiffeners is attached to the substrate strip such that a first surface of each stiffener of the plurality of stiffeners is attached to a first surface of a corresponding substrate of the plurality of substrates. An IC die is mounted to a central region of a second surface of each stiffener of the plurality of stiffeners. A bond pad of the IC die mounted to each stiffener of the plurality of stiffeners is connected to a contact pad on the first surface of the corresponding substrate of the plurality of substrates with a wire bond. The IC die and the wire bond are encapsulated on the second surface of each stiffener of the plurality of stiffeners. The IC die support structure is subsequently removed from the centrally located opening of each substrate of the plurality of substrates.
Further aspects, features, and advantages of the present invention, as well as the structure and operation of the various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.
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Khan Reza-ur Rahman
Zhao Sam Ziqun
Broadcom Corporation
Ha Nathan W.
Pham Long
Sterne Kessler Goldstein & Fox PLLC
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