Electronic digital logic circuitry – Multifunctional or programmable – Having details of setting or programming of interconnections...
Reexamination Certificate
2002-07-05
2004-02-03
Cho, James (Department: 2819)
Electronic digital logic circuitry
Multifunctional or programmable
Having details of setting or programming of interconnections...
C326S101000, C257S686000
Reexamination Certificate
active
06686768
ABSTRACT:
FEDERALLY SPONSORED RESEARCH
Not Applicable
SEQUENCE LISTING OR PROGRAM
Not Applicable
BACKGROUND
1. Field of Invention
The present invention relates to electrical devices. More specifically, the present invention relates to electrically-programmable interconnect architectures without active devices, capable of making user-defined connections between conductors to form desired networks. Certain aspects of the present invention relate to general-purpose electrically-programmable interconnect architectures which form sequential electrical connections between a master terminal and each of a plurality of slave terminals; such architectures may find widespread utility in a variety of applications. Other aspects of the present invention relate to structures and architectures useful primarily for interconnecting circuits in stacked arrays, especially integrated circuits (ICs) contained within stacked, mating programmable packages such as those described in my related U.S. Pat. No. 5,838,060. In particular, the present invention provides the programmable interconnect architectures necessary for such packages to be built and programmed easily and economically, thereby providing a new, powerful method of flexibly combining arrays of user-selected ICs, housed within packages containing said architectures, so that the arrays of configured packages contain the entire system schematic within their programmed connections.
BACKGROUND
2. Description of Prior Art
It has long been realized that electrical circuits can achieve higher densities, greater modularity, and higher speeds when they are stacked together in a three-dimensional array, rather than spread out over a comparatively large area in a two-dimensional pattern. Different stacked arrangements or circuits have been utilized for many years; in fact, even before the advent of the integrated circuit (IC) chip, stacked modules, each containing several electrical components, were sometimes used as “building blocks” in electrical systems designs. The most common use today of this circuit-stacking technique is the popular and powerful “stacked PC-board” concept (where printed circuit boards (PC-boards) are plugged into an array of parallel receptacles or “slots” in a motherboard). Almost all computers today take advantage of this useful arrangement.
This arrangement, as is currently used in personal computers, demonstrates the compactness and modularity of the stacking concept. A personal computer with several filled slots may have far more total PC-board area even than the footprint of the computer, and the add-on cards can be selected from thousands of available boards. However, since the stacking concept is used on a relatively large scale (stacked PC-boards populated with standard IC packages, each board as large as 10 cm×30 cm, separated by approximately 2 cm. between parallel boards), the circuit is still spread out over a large physical space; so the relative speed advantage inherent in a stacked arrangement is less apparent. In fact, in a standard personal computer today advertised to run at a given clock speed, at most only a small section of the motherboard actually runs at the specified speed; more commonly today, only a section of the CPU runs at the specified speed. In most personal computers today, the bus which connects the stacked PC-boards to the CPU runs much slower than the system clock speed; this speed ratio can be ten times or more. Clearly, although this stacked arrangement may in fact be somewhat faster than an equivalent but entirely two-dimensional arrangement, the inherent speed advantage of a stacked circuit arrangement is not apparent in this example case.
Yet stacked circuit arrangement at the PC-board level is by far the most prevalent application of the stacking concept today, in spite of the lack of significant speed advantages. This has come about for a variety of reasons, primarily having to do with cost and time-to-market. In order to understand why stacked PC-board applications are so overwhelmingly popular compared to other stacking methods, it is necessary to look at the methodology commonly used when building an electronic system.
ICs as they are produced today are inherently two-dimensional. They are produced by building up successive layers, each patterned using plate micro-photolithography, on a two-dimensional wafer substrate. Each wafer is subsequently diced into individual IC chips, each of which performs a required electrical function. IC chips are usually sold pre-packaged (in packages selected by the IC manufacturers) and pretested both at the wafer level and in packaged form. The packages used are generally made in technologies which bridge the microscopic world of the integrated circuit, where critical dimensions are currently measured in tenths of micrometers, to the macroscopic world of the PC-board, where critical dimensions are now measured in tenths of millimeters. Almost all chip packages are designed to be mounted directly onto a PC-board, so the package external contact points (pins, solder-bumps, etc.) are spaced at intervals compatible with PC-board dimensions. Because the external contact points are spread out compared to chip dimensions, most IC packages are significantly larger than their enclosed chip, yet smaller than a PC-board; yet since the design, substrate and fabrication costs per unit area are generally much less for package technologies than for IC technologies, the package cost is typically much less than the IC die cost. To make a system, designers connect different ICs together using PC-boards whose contacts and conductors are designed to mate with the external contact points of each IC package.
So when designing a new electronic system, systems designers can customize circuits at several levels. They can design new IC chips, custom packages, or custom PC-boards.
The costs and lead-time of developing a new IC are quite large, and are many times only justifiable where a large prospective market is anticipated for the new IC. Some custom ICs, also known as application-specific ICs (ASICs), use streamlined design techniques, to make a new IC design more cost-effective even for a smaller potential market; but these are still a relatively small sector of the total IC market. In general, systems designers use standard, relatively economical ICs as much as possible in their designs; customizing a particular system by designing new custom IC chips is almost never done.
Designing and building custom packages is also expensive, and the lead-time from the beginning of the package design cycle is quite long. Because of this, chip packages are generally considered as being relatively fixed, especially in terms of the package external form factor. Again, systems designers rely on standard packages as much as possible in their designs.
In contrast, building a new design using prior-art techniques always requires a custom PC-board design, in order to define the connectivity of the individual components and packaged chips, and thus define the entire circuit. The tooling costs and lead-times for custom PC-boards are both affordable, especially when compared with the costs of producing custom packages or ASICs for each chip in a design. Thus, as much as possible, systems designers use standard IC chips, in standard packages, mounted on custom PC-boards, in order to build their products.
With this currently prevalent methodology in mind, it is easy to see why circuit stacking is primarily used at the PC-board level. In any proposed stacking technology, a “pancake stack” of interconnected circuits requires that each “pancake” have its own custom interconnections, which mate with the connections on the pancakes above and below it in the stack. These custom interconnections now define the wiring connectivity of the components, and thus define the system. As discussed above, custom chips and custom packages are expensive and time-consuming to produce using standard techniques, while custom PC-boards are relatively cheaply and quickly fabricated; also, almost all systems today requir
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