An Apple patent (number 20100213958) systems and methods for providing a system-on-substrate has appeared at the US Patent & Trademark Offices. It involves shrinking the size of a system's circuitry by providing all of the components of the system on the same microchip -- such as the A4 processor used in the iPad.

The patent relates to systems and methods for providing a system-on-a-substrate. In some embodiments, the necessary components for an entire system (e.g., a processor, memory, accelerometers, I/O circuitry, or any other suitable components) can be fabricated on a single microchip in “bare die” form. The die can, for example, be coupled to suitable flash memory through a substrate and flexible printed circuit board (“flex”). In some embodiments, the flex can extend past the substrate, die, or both, to allow additional, relatively large components to be coupled to the flex.

In some embodiments, the die can be coupled to the flash memory through the flex and without a substrate. In some embodiments, component test points can be placed on the flash memory side of the substrate.The inventors are Gloria Lin, Bryson Gardner Jr., Joseph Fisher, Dave Goh, Barry Corlett, Dennis Pyper and Amir Salehi.

Here's Apple's background and summary of the invention: "Systems, such as systems for an electronic device, are often created from multiple components. For example, the components of a system can include one or more of a processor, memory (e.g., RAM, SDRAM, DDR RAM, or ROM), CODEC circuitry, Input/Output (“I/O”) circuitry, communication circuitry, accelerometers, capacitors, inductors, or any other suitable components. Traditionally, each of these components are a distinct 'entity' and can be created on a separate microchip or can be included in a separate package.

"To create the circuitry for the entire system, the separate components (e.g., separate microchips) are typically coupled together through a printed circuit board (“PCB”) or other suitable medium. The PCB can be fabricated with the appropriate wiring or routing to suitably connect all of the separate components.

"This relates to systems and methods for providing a system-on-a-substrate. For example, rather than including the components of a system as discrete entities (e.g., as discrete microchips or as discrete parts), the components of a system can be formed together in 'bare die' form. In other words, the components can be formed together on a single substrate, such as a silicon die or a die of other suitable material. In this manner, the components of an entire system can be densely and efficiently packed together, thus allowing the system to achieve a smaller size than a system using components that are discrete entities.

"The components can include, for example, one or more of a processor, memory (e.g., RAM, SDRAM, DDR RAM, ROM), CODEC circuitry, Input/Output ('I/O') circuitry, communication circuitry, accelerometers, capacitors, or any other suitable components. A system utilizing these components can be included in any suitable electronic device such as, for example, a cellular telephone, a personal data assistant ('PDA'), a digital media player (e.g., an iPod available from Apple Inc. of Cupertino, Calif.), a computer, or any other suitable electronic device.

"In some embodiments, a die including the components of a system can be coupled to a substrate. The substrate, in turn, can be coupled to a flexible printed circuit board ('flex'). The substrate and the flex can include any suitable wiring and routing to electrically couple the die to other parts of the system such as, for example, a flash memory. In some embodiments, the flex can be coupled to a different surface of the substrate than the die. In some embodiments, the flex can be coupled to the same surface of the substrate as the die.

"In some embodiments, the flex can include a ledge to which one or more components can be coupled. In some embodiments, a system can be created which does not include a substrate. In this case, all necessary wiring can be provided through the flex. In some embodiments, test points can be provided for a component of a die. For example, the test points can be included in a portion of the flex located substantially below the component to be tested.

"In some embodiments, rather than being included together in a single die, the components of a system can be included as discrete entities. The discrete entities can be coupled to a substrate rather than being coupled to a printed circuit board ('PCB'). As a substrate can have more stringent design rules than a PCB, coupling the discrete entities to the substrate can allow for a system that is smaller and more compact in size. For example, the wiring for the system can be created using less layers and can be formed more densely in a substrate than in a PCB."