1. Field of the Invention
The present invention relates generally to semiconductor packaging, and more particularly, to a semiconductor package with a wire bond arrangement to reduce cross talk between the wires.
2. Description of the Related Art
Advances in processing technology has allowed engineers to fabricate smaller and smaller transistors. The smaller transistors not only operate at faster speeds, but they also enable more and more transistors to be fabricated on a semiconductor die of a given size. This increased circuit density has enabled circuit designers to add greater functionality with each new generation of chips. The new functionality, however, increases the need for a greater number of signal inputs as well as power and ground inputs to the device. State of the art chip packages currently have hundreds and in some instances thousands of input-output pins. The increased number of input-output pins results in the bond pads on the die and the bond fingers or leads of the leadframe package to have a finer pitch. Consequently, wire bonds are spaced very close to one another on the packaged die. The closeness of the wires may create a problem. Namely, coupling noise and cross talk between the wires may cause false signal transitions on the signal input-output pins, causing the device to fail. The faster switching speeds of the transistors further exasperates this problem.
A number of approaches are known to reduce the coupling noise and cross talk problem with wire bonds of semiconductor packages. One conventional approach is to use wire bonds of different heights and loop profiles to reduce the cross talk and coupling noise between the wires. Another technique is to convert a significant number of signal bond pads into either ground (VSS) or power (VDD) pads. The spacing of either VSS or VDD pads between signal pads provides electrical shielding, isolating the adjacent signal and clock wires from coupling noise and cross talk. The problem with this approach is that it reduces the total number of usable signal input-output pins on the package.
Accordingly, there is a need for a semiconductor package with a wire bond arrangement to reduce cross talk between the wires.
The present invention relates to a semiconductor package for reducing signal cross talk between wire bonds of a semiconductor packages. The package includes a semiconductor die having a plurality of bond pads formed thereon. The bond pads are arranged in a first subset of bond pads and a second subset of bond pads. The package also includes a substrate having a plurality of contact points, the plurality of contact points are arranged in a first subset of contact points and a second subset of contact points. To reduce signal cross talk, the wire bonds are arranged such that a first subset of wire bonds are electrically coupled between the first subset of bond pads and the first subset of the contact points. The first subset of wire bonds have ball bonds formed on the first subset of bond pads and stitch bonds formed on the first subset of contact points respectively. A second subset of wire bonds are electrically coupled between the second subset of bond pads and the second subset of the contact points. The second subset of wire bonds have stitch bonds formed on the first subset of bond pads and ball bonds formed on the first subset of contact points respectively. The different height profiles of the first set and the second set of wire bonds tends to reduce signal cross talk between the wires.
The invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:
In the figures, like reference numbers refer to like components and elements.
Referring to
In accordance with the present invention, the wire bonds 26 are arranged in a first subset 26a and a second subset 26b.
As is evident in
Referring to
Although the foregoing invention has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. For example, the substrate 14 and described herein can be made of a number of different materials, such as ceramic or plastic. The substrate 14 can also be a lead frame made of a metal such as copper. In embodiments where the substrate 16 is a lead frame, the die 12 is attached to the die attach pad and the contact pads 22 are leads of the lead frame. Therefore, the described embodiments should be taken as illustrative and not restrictive, and the invention should not be limited to the details given herein but should be defined by the following claims and their full scope of equivalents.