Harsh Environments in Advanced Packaging: Just the Beginning
11/01/2007
BY KEREM DURDAG, Vectron International
Significant inroads to integrate surface-acoustic-wave- (SAW-) based electronics with sensors are producing more high-demand areas for packaging applications. Specifically, packaging techniques are being developed to expand the range of environments and lifespan of next-generation acoustic wave sensors.
The adoption of advanced acoustic wave sensors along with the demand for electronics that function in expanded operating-temperature ranges with better device lifecycles has increased the need for packaging and sealing techniques to support these applications. As a result of packaging technique advancements, doors have opened to new application areas previously thought impossible, such as instantaneous monitoring capabilities for a number of next-generation harsh-environment applications. For example, combining a sensing device and smart sensor electronics creates a real-time, in-line, threaded-body solid-state sensor that determines oil quality in mobile and fixed asset applications (Figure 1). High-temperature electronics, such as voltage-controlled crystal oscillators, demonstrate high performance and reliability in oil and gas down-hole tool applications. Standardization of these product innovations will make SAW-based sensor solutions available in harsh-environment application areas and generate solutions in disparate industries.
Packaging and manufacturing techniques developed to address these applications are being repurposed to answer growing demand for advances in a wide variety of other applications previously considered not applicable to the packaging market. The wireless sensor applications industry is one of the largest beneficiaries, as the melding of these sensors with new packaging techniques offers cost-effective solutions that combine a small footprint with a reliable and robust design requiring little power.
 Figure 1. Viscosity sensor for oil condition monitoring. |
Acoustic wave sensors function by generating an acoustic wave on a piezoelectric material when a bias is applied. As the acoustic wave propagates through or on the material surface, any changes to the characteristics of the propagation path affect the velocity and/or amplitude of the wave. Changes in velocity can be monitored by measuring the frequency or phase characteristics of the sensor, and can then be correlated to the corresponding physical quantity being measured. SAW-based sensors are optimal components to pair with advanced packaging techniques because they can operate without a battery, and can be connected wirelessly by a radio frequency (RF) link to a transceiver or reader unit. SAW sensors gain these properties from their ability to operate with a high level of electrical efficiency, low input signal levels, and solidified and hearty packaging techniques. Given these characteristics, the largest potential for growth is in the automotive industry, specifically in wireless tire pressure monitoring (TPM).
Demand for wireless TPM has recently soared as the U.S. government passed legislation requiring all new passenger vehicles as of September 1, 2007 to be equipped with tire pressure monitoring systems. Beyond this requirement, maintaining the correct tire pressure is crucial for maintaining optimal fuel economy. It’s been estimated that about one out of every four vehicles on the road is running on under-inflated tires, which costs drivers millions of dollars a year in gas, and significantly increases harmful emissions. Developers are stepping in to meet this new demand for TPM with wireless sensors equipped with rugged packaging, which adds to the sensor’s lifecycle by withstanding high-shock and high-pressure environments.
Wireless acoustic wave sensors are the best mechanisms to allow for affective, reliable, and accurate tire pressure monitoring. These sensors consume nominal energy; transmit data wirelessly; are reasonably priced; and can withstand time, pressure, and heat due to durable packaging.
Conclusion
While there is enormous potential for SAW-based sensors growth within the automotive industry, the previously-unheard-of attributes this new technology offers, in combination with advanced packaging techniques, indicates that initial products leveraging these technologies are the tip of the iceberg. There are many possible directions for SAW-based sensors to go, but directly on the horizon, new gas detection and biomedical applications will likely be developed with added advanced packaging know-how to meet other industry needs.
 |
KEREM DURDAG, director of business development, sensors & advanced packaging business unit, may be contacted at Vectron International, 267 Lowell Road, Hudson, NH, 03051; 207/856-6977; [email protected].