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Low-Temperature Cofired Ceramics Fuel Growth Of High-Frequency Designs
Driven into the mainstream by wireless applications, LTCCs extend the benefits of integration, thermal performance, and durability to automotive and other applications.
Date Posted: October 02, 2000 12:00 AM
Another approach to testing sintered materials, the "whispering-gallery" mode, provides highly accurate measurements of dielectric loss. In this method, a disk-shaped LTCC sample rests on a dielectric rod. The sample is driven into resonance with coupling loops. Because of its high accuracy, this method helps reduce conductor losses.
Although measuring sintered materials with metals attached is the primary challenge, there is still a need to gather information on unsintered materials. The split-post resonator method now in development offers both simplicity and accuracy. It lets designers measure the dielectric constant within ±0.5% and read the loss tangent with 1 × 10−5 accuracy. In this approach, a thin sample of material is placed between two fixed dielectric resonators. Selected for their low dielectric constant and low loss, these resonators are driven using loop coupling. Changes in resonance and Q of the fixed resonators with and without the sample in place can be used to calculate the sample's dielectric properties. This method works for frequencies ranging from 1.5 to 12 GHz.
As the industry refines and standardizes its test methodologies, LTCC designers and manufacturers will benefit. Better test data will help LTCC material developers and foundries improve their processes, reduce costs, and extend the limits of high-frequency performance. At the same time, designers will find it easier to compare different material systems in their applications.
For further reading:
- "Current and Future Applications for Thick-Film and Low-Temperature Cofired Ceramic Technology in the Automotive Industry," Samuel J. Horowitz, DuPont Microcircuit Materials, Summer 2000 MMRC meeting, Dearborn, MI. Go to www.dupont.com/mcm/automotive/mmrc.html.
- "Frequently Asked Questions for LTCC Vendors" and "Design Rules for Physical Layout of Low Temperature Cofired Ceramic Modules," Revision 8.1, Jan. 5, 2000, National Semiconductor. Go to www.national.com/appinfo/wireless/0,1822,357,00.htm.
- "Ferro LTCC System for Wireless Packaging Applications," Liang Chai and Simon Turvey, Ferro Corp. Go to www.ferro.com/content/product_render.asp?use_case=EM2&Phase=products&FamilyId=18&DivisionId=3.