Integrated circuits (IC's) are typically assembled into packages by physically and electrically coupling them to a substrate made of organic or ceramic material. One or more IC packages can be physically and electrically coupled to a printed circuit board (PCB) to form an “electronic assembly”. The “electronic assembly” can be part of an “electronic system”. An “electronic system” is broadly defined herein as any product comprising an “electronic assembly”. Examples of electronic systems include computers (e.g., desktop, laptop, hand-held, server, etc.), wireless communications devices (e.g., cellular phones, cordless phones, pagers, etc.), computer-related peripherals (e.g., printers, scanners, monitors, etc.), entertainment devices (e.g., televisions, radios, stereos, tape and compact disc players, video cassette recorders, MP3 (Motion Picture Experts Group, Audio Layer 3) players, etc.), and the like.
In the field of electronic systems there is an incessant competitive pressure among manufacturers to drive the performance of their equipment up while driving down production costs. This is particularly true regarding forming electronic devices such as transistors in IC's, where each new generation of IC must provide increased performance, particularly in terms of an increased number of devices and higher clock frequencies, while generally being smaller or more compact in size. As the density and clock frequency of IC's increase, they accordingly generate a greater amount of heat. However, the performance and reliability of IC's are known to diminish as the temperature to which they are subjected increases, so it becomes increasingly important to adequately dissipate heat from IC environments.
An IC is fabricated on a substrate that may comprise a number of metal layers selectively patterned to provide metal interconnect lines (referred to herein as “traces”), and one or more electronic devices attached in or on one or more surfaces of the substrate. The electronic device or devices are functionally connected to other elements of an electronic system through a hierarchy of electrically conductive paths that include the substrate traces. The substrate traces typically carry signals that are transmitted between the electronic devices, such as transistors, of the IC. Some IC's have a relatively large number of input/output (I/O) terminals (also called “lands”), as well as a large number of power and ground terminals or lands.
As the internal circuitry of IC's, such as processors, operates at higher and higher clock frequencies, and as IC's operate at higher and higher power levels, the amount of heat generated by such IC's can increase their operating temperature to unacceptable levels. Thermal management of IC's refers to the ability to keep temperature-sensitive elements in an IC within a prescribed operating temperature. Thermal management has evolved to address the increased temperatures created within such electronic devices as a result of increased processing speed/power of the electronic devices.
With the advent of high performance processors, electronic devices have required more innovative thermal management. For example, in the last several years processing speeds of computer systems have climbed from 25 MHZ to over 1000 MHZ. Each of these increases in processing speed and power generally carry with it a “cost” of increased heat that must be dissipated. Corresponding improvements in thermal management such as improved heat sinks or heat pipes have accompanied such technological improvements. Further improvements in thermal management are needed to keep pace with ever increasing processor speeds and the desire to reduce manufacturing costs.