Defense electronics boosts advanced packaging: recent events have helped to increase the need for advanced packaging technology in military applications.

The Government Electronics and Information Technology Association (GEIA, Arlington, VA) estimates that the electronics content of the 2002 fiscal year U.S. defense budget will be $63.1 billion. While the use of advanced electronic systems in fighter jets, battleships, nuclear submarines, satellites and communications equipment, missiles and radar systems has been common for decades, complex electronic systems are increasingly found in tanks, bombs and other military equipment. In addition, the contract for the new F-22 fighter is expected to generate the use of additional advanced electronics. Current military actions have dramatically increased the demand for defense electronics and, while business is slow for much of the electronics industry, this segment has seen a burst of new activity. What may be a surprise to many is that defense electronics, formerly known as military electronics, is a growing market for advanced packaging and more economical solutions.

With the push for lower cost electronics, many programs have turned to commercial off-the-shelf (COTS) solutions for semiconductor packaging needs. COTS approaches include chip-scale packages (CSPs), ball grid arrays (BGAs), multichip packages (MCPs) and chip on board (COB). Ceramic, laminate and flex circuit technology is currently used for many defense electronics applications. While wire bond has been the dominant interconnect, flip chip is also seeing growth in this sector.

Operating Environment and Driving Forces

Major driving forces for package selection in defense electronics have some remarkable similarities to consumer products (volume and weight), with one exception--reliability. Military and aerospace electronic systems cover a wide range of functions, including communications, guidance and navigation, event avoidance, countermeasures, sensors and data recorders. Systems in these environments operate at up to multi-GHz frequencies, have high heat dissipation, must function over a wide range of temperature extremes and are subjected to a variety of severe environmental conditions such as vibration, shock, humidity, radiation and atmospheric pressure.

Package Testing

Specific testing was developed for packages used in defense electronics called military standard (MIL STD 883) test methods. Driven by reliability concerns in the Minuteman Missile Program, MIL STD tests were first developed in the 1960s in response to the need for quality packages to meet the demands of the harsh environments of military applications. Extensive test methods were developed to weed out infant mortality of the packaged devices so they did not fail when incorporated into military systems. Test methods were also developed to provide environmental screening. Specific methods were developed for such procedures as temperature cycles and burn-in. The series of standard test methods provided assurance that packaged devices from different suppliers would meet the same reliability standards. The specifications have grown from a few pages to a volume and have been adopted by other industries. Rome Labs (Rome, NY) remains the focal point for the specification (1). While MIL STD testing has not been relaxed for off-the-shelf component packages, occasional modifications have been required to ruggedize some packages.

Advanced Packaging Research and Production

Advanced packaging research for defense electronics is not new, but the actual use of advanced packages such as BGAs and CSPs is a recent development. Beginning in 1993, the Defense Advanced Research Projects Agency (DARPA, Arlington, VA) funded various multichip module substrate development activities. While many of these research activities did not result in commercial success, the basic concept of multiple chips inside a package has been put into practice for a variety of defense and aerospace systems.

Contract assembly houses, such as Amkor Technology (West Chester, PA), assemble CSPs for use in defense applications and a variety of companies specialize in military electronics assembly. White Electronic Designs Corp. (Phoenix, AZ) is building a PowerPC-based MCP including a 128K x 72 of L2 SyncSRAM cache. The PowerPC is flip chip attached to a ceramic (alumina) substrate (Figure 1). This MCP is found in air-to-air missiles, Apache helicopter upgrades, nuclear submarines and M1A2 tank upgrades. Figure 2 shows an MCP for a family of synchronous dynamic random access memory (SDRAMs) packaged in a high glass transition temperature plastic BGA. Applications for this package include the Apache helicopter, F-18 and F-16 fighter plane upgrades and other systems.

[FIGURE 2 OMITTED]

Defense Electronics of the Future

Defense systems are expected to become increasingly complex over the next 10 years. New demands for command and control functions, land, sea and air battle operation, communications and sensors, for a variety of new threats, will drive the continued development of new electronic systems. While the defense electronics market is much smaller than the commercial electronics business market, it is a critically important one.

Reference:

(1.) Circuits Assembly, September 1997, p.24.

E. Jan Vardaman is president of TechSearch International, Austin, TX; e-mail: jan@TechSearchInc. com