Although much of the communications industry remains in the doldrums, the wireless sector seems to be picking up momentum. Cellular phone shipments are growing, and the wireless LAN market is exploding. Within wireless products, the packaging of radio frequency integrated circuits (RFICs) presents a number of challenges. The RF section of wireless products typically includes:
Wireless Packaging RFIC packages can be found in numerous forms, including leadframe packages, array packages, modules, chip carriers and specialty packages. As with the overall IC population, leadframe packages are the package of choice for RFIC devices. The packages are inexpensive and easy to assemble, have an established infrastructure and are adequate for most RF applications. Leadframe CSPs are popular packages for RFICs, as this package has a short and flat trace, resulting in low inductance and capacitance. The electron flows from the die through the leadframe to the PWB-a fairly simple path with few layers of material to add inductance to the equation.
Flip-chip versions of this package, such as those offered by Amkor and Carsem, eliminate the wire bonds, which are an additional lengthy layer, smoothing, shortening and thus improving the dynamics of this package. The fact that the leadframe is encased within the molding also lowers the inductance. An array-style package, in contrast, has solder balls and a substrate, each adding inductance to the package. The low-I/O nature of the leadframe CSP is acceptable, as RFICs tend to have less than 10 I/O. Modules for RFIC are often referred to as an example of System-in-Package (SiP). Resistors and capacitors are combined with an IC within a single module, so that these parts are in very close proximity to interact at very high rates of speed. Since many of the functions performed by the module are contained within the module itself, the external I/O count to the PWB is relatively low. Being a somewhat sophisticated package with low volumes, the price per I/O is relatively high for RF modules. Specialty packages are custom in nature, and can take any number of forms. They are not covered within JEDEC specifications, and may use non-conventional substrate materials. Applications Key applications for RFICs include cellular telephones and wireless LANs. New applications are coming down the pike, while others are just a dream. And wireless home entertainment is viewed as a huge potential market. The plan is for home electronics-video and audio-to interface with a "master" PC via a wireless gateway. Remote personal health monitoring of heart rate and vital statistics is an interesting topic in the wake of 9/11. Field commanders of firefighting units, for instance, can monitor the health of the men and women in the field. Based on that information, they can know when to order a person to retreat from the scene, or when to send in reinforcements to help an ailing comrade. Motorola has developed a prototype of this technology. Applied Digital Solutions manufactures a tiny wireless ID chip that can be implanted in humans for medical, security and related applications. CITRIS is a consortium pertaining to medical monitoring in the home. iSense Corporation recently received a grant from the National Medical Technology Testbed, Inc. to develop telemetry (wireless) and telemedicine systems to be used with its current continuous glucose monitoring system.
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