Leadframe with power and ground planes

Abstract

A leadframe for use in an integrated circuit package is described. The leadframe comprises a plurality of electrically conductive leads, a die attach pad, and an electrically conductive ring or rings formed generally around the circumference of the die attach pad and between the die attach pad and leads. In one embodiment, at least one of the leads is formed integrally with each ring. The die attach pad may also be formed integrally with one or more leads. In another embodiment, the ring or rings are formed so that they are electrically isolated from the die attach pad, and the die attach pad, leads, and ring or rings are all formed in substantially the same plane. In some embodiments, the ring or rings are broken into electrically isolated sections. Each of the ring sections (and die attach pad, if appropriate) may be electrically connected to a voltage source outside the integrated circuit package (e.g., a power supply or ground). The leadframe is formed from a single sheet of material by, for instance, stamping or etching. The leadframe may be used in either ceramic or plastic packages. The leadframe reduces switching noise and crosstalk, allows more flexibility in placement of power and / or ground bond pads on the die, and allows provision of ground and power planes in an integrated circuit package that is thinner than previous integrated circuit packages containing both ground and power planes.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThis invention relates to integrated circuits and, in particular, to the provision of power and ground planes in an integrated circuit package.2. Related ArtThe presence of resistance, capacitance and inductance in the electrical conductors (e.g., bond wires, leads) within an integrated circuit package gives rise to noise (signal delays and signal distortions) in the electrical signals transmitted to and from the integrated circuit (a semiconductor die on which electrically conductive circuitry and bond pads are formed). Two sources of noise in an integrated circuit package are switching noise (.DELTA.I noise) and crosscoupling noise (crosstalk). Switching noise may be an inductive voltage spike that occurs on a conductive path as the result of rapid current switching in the conductive path. Crosstalk is the undesirable appearance of an electrical current in a conductive path as a result of mutual capacitance and inductance between...

AI Technical Summary

Benefits of technology

An integrated circuit package including the leadframe according to the invention has reduced effective inductance and crosstalk relative to existing integrated circuit packages.

In particular, provision of parallel current paths from power and / or ground planes inside the package to voltage sources outside the package minimizes the inductance and, thus, noise in power and ground paths. The leadframe according to the invention also provides off-chip power and ground bussing that allows more flexibility in layout of the circuitry on the die, thus allowing reduction of across-die voltage drops. Formation of the die attach pad, leads and ring in substantially one plane, as in some embodiments of the invention, allows provision of ground and power planes in an integrated circuit package that is thinner than previous integrated circuit packages containing both ground and power planes. The above improvements can be provided in an inexpensive and simple leadframe using conventional formation techniques and materials.

Problems solved by technology

The presence of resistance, capacitance and inductance in the electrical conductors (e.g., bond wires, leads) within an integrated circuit package gives rise to noise (signal delays and signal distortions) in the electrical signals transmitted to and from the integrated circuit (a semiconductor die on which electrically conductive circuitry and bond pads are formed).

Switching noise may be an inductive voltage spike that occurs on a conductive path as the result of rapid current switching in the conductive path.

Crosstalk is the undesirable appearance of an electrical current in a conductive path as a result of mutual capacitance and inductance between the conductive and other nearby conductive paths.

Such high speed operation exacerbates the problems of switching noise and crosstalk.

in power, ground and signal (i.e., other than power or ground) paths, and inductive coupling between adjacent current paths are particularly troublesome.

These vias and traces have an additional self-inductance that increases switching noise.

Additionally, the multilayer structure is more complex and expensive to produce since additional metal layers, dielectric layers, traces and vias must be formed.

This additional complexity can adversely affect the electrical and mechanical reliability of the integrated circuit package.

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