Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – With separate tie bar element or plural tie bars
Reexamination Certificate
2000-01-25
2001-10-16
Clark, Jhihan B. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
With separate tie bar element or plural tie bars
C257S666000, C257S669000, C257S674000
Reexamination Certificate
active
06303984
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to fabrication technology used in the assembly of integrated circuit packages and, more particularly, to the design of a lead frame for an encapsulated integrated circuit.
According to conventional integrated circuit manufacture, the lead frame, and, in particular, the tie bars of the lead frame, often bows or becomes distorted during the die attachment and encapsulation process. The result is an improper spatial relationship of the die attach pad relative to the integrated circuit package. Such displacement causes mechanical and electrical failure within the integrated circuit package and results in loss of system integrity and quality.
Accordingly, a need exists for a lead frame design that effectively reduces bowing and distortion of the lead frame during integrated circuit packaging operations.
BRIEF SUMMARY OF THE INVENTION
This need is met by the present invention wherein a lead frame is provided and includes an angle iron tie bar with lateral reinforcement portions.
In accordance with one embodiment of the present invention, a lead frame is provided comprising a die mounting portion and at least one tie bar mechanically coupled to the die mounting portion. The tie bar includes a longitudinal reinforcement crease defined along at least a portion of the fie bar and a tie bar flap formed along the reinforcement crease. The lead frame may further comprise electrically conductive leads mechanically coupled to the tie bar. The tie bar may further comprises a tie bar span defined by the longitudinal reinforcement crease. The tie bar flap may be substantially planar. The tie bar flap and the fie bar span are preferably offset by an angle selected so as to enable closely packed lead frame stacking, e.g., less than 90°. The die mounting portion and the tie bar preferably form a one-piece, integrally constructed, lead frame.
In accordance with another embodiment of the present invention, a lead frame is provided comprising a die paddle and an angle iron tie bar mechanically coupled to the die paddle. The angle iron tie bar is preferably characterized by a bend angle of less than 90°. The angle iron tie bar preferably includes an extension portion, a tie bar span defined by a longitudinal reinforcement crease, and a tie bar flap formed along the reinforcement crease. The tie bar span may be mechanically coupled to the die paddle via the extension portion.
In accordance with yet another embodiment of the present invention, a lead frame is provided comprising a die mounting portion and at least one tie bar. The tie bar includes a tie bar span mechanically coupled to the die mounting portion and a substantially planar tie bar flap connected to the tie bar span. The tie bar span and the tie bar flap may lie in intersecting planes. The angle iron tie bar may include an extension portion and the tie bar span may be mechanically coupled to the die paddle via the extension portion. The tie bar flap and the tie bar span may be connected along a longitudinal reinforcement crease formed by a bend in the lead frame.
In accordance with yet another embodiment of the present invention, a lead frame is provided comprising a die mounting portion and at least one tie bar mechanically coupled to the die mounting portion. The tie bar includes a longitudinal reinforcement crease defined along at least a portion of the tie bar. The tie bar includes a tie bar span and a tie bar flap and the reinforcement crease is formed by bending the tie bar flap relative to the tie bar span.
In accordance with yet another embodiment of the present invention, a lead frame is provided comprising a die mounting portion and at least one tie bar mechanically coupled to the die mounting portion. The at least one tie bar includes a longitudinal reinforcement crease defined along at least a portion of the tie bar, a tie bar flap formed along the reinforcement crease, and a lateral reinforcement portion extending from the tie bar to the die mounting portion. The lateral reinforcement portion extends in a direction perpendicular to a direction of the longitudinal reinforcement crease and may comprise a chamfered span.
In accordance with yet another embodiment of the present invention, a method of forming a lead frame is provided comprising the steps of: providing a die mounting portion and at least one tie bar, wherein the tie bar includes a fie bar span mechanically coupled to the die mounting portion; and bending a portion of the tie bar span along a longitudinal reinforcement crease defined along at least a portion of the tie bar so as to form a tie bar flap connected to the tie bar span along the reinforcement crease.
In accordance with yet another embodiment of the present invention, a method of forming a lead frame is provided comprising the steps of: providing a die mounting portion and at least one tie bar, wherein the tie bar is mechanically coupled to the die mounting portion; and forming a longitudinal reinforcement crease along at least a portion of the tie bar.
In accordance with yet another embodiment of the present invention, a method of forming a lead frame is provided comprising the steps of: providing a die mounting portion and at least one tie bar, wherein the tie bar includes a longitudinal tie bar span mechanically coupled to the die mounting portion; and connecting a tie bar flap to the tie bar span.
In accordance with yet another embodiment of the present invention, a mounted die arrangement is provided comprising a lead frame and an integrated circuit die. The lead frame includes a lead frame body including a plurality of electrically conductive leads, a die mounting portion, and at least one tie bar extending from the lead frame body to the die mounting portion, wherein the at least one tie bar includes a longitudinal reinforcement crease defined along at least a portion of the tie bar and a tie bar flap formed along the reinforcement crease. The integrated circuit die is mounted on the die mounting portion and includes electrical connections conductively coupled to the electrically conductive leads. The integrated circuit die may be characterized by physical characteristics indicative of formation from a wafer including a plurality of similar integrated circuit dies.
In accordance with yet another embodiment of the present invention, an encapsulated integrated circuit is provided comprising: a plurality of electrically conductive leads; a die mounting portion; an integrated circuit die, at least one tie bar, and an encapsulating material. The integrated circuit die is mounted on the die mounting portion and includes electrical connections conductively coupled to the electrically conductive leads. The tie bar is mechanically coupled to the die mounting portion and includes a longitudinal reinforcement crease defined along at least a portion of the tie bar and a tie bar flap formed along the reinforcement crease. The encapsulating material surrounds the tie bar, the integrated circuit die, and portions of the electrically conductive leads to form a solid state encapsulated integrated circuit.
In accordance with yet another embodiment of the present invention, a method of encapsulating an integrated circuit is provided comprising the steps of: providing a plurality of electrically conductive leads, a die mounting portion, and at least one tie bar mechanically coupled to the die mounting portion; mounting an integrated circuit die on the die mounting portion, the integrated circuit die including electrical connections; conductively coupling the electrically conductive leads to the electrical connection; reinforcing the tie bar by forming a longitudinal reinforcement crease along at least a portion of the tie bar; and encapsulating the integrated circuit die, at least a portion of the tie bar, and portions of the electrically conductive leads. The tie bar may include a tie bar flap and a tie bar span and the longitudinal reinforcement crease may be formed by bending a tie bar flap relative to a tie bar span along the longitudinal reinforcement creas
Clark Jhihan B.
Killworth, Gottman Hagan & Schaeff LLP
Micro)n Technology, Inc.
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