Application of the photo-elastic method to measurement of dynamic stress distribution for NS-GT cut quartz crystal resonators
NS-GT cut quartz crystal resonators are widely used as a frequency standard element in consumer products and communication equipment. The vibration mode of the resonators was analyzed by the finite element method (FEM) because they have a complicated shape. As a result, an asymmetrical vibration mode at the main resonant frequency has been obtained by the FEM simulation. But, it is necessary to confirm the asymmetrical vibration mode experimentally because it is just a simulation. In this paper, stress distributions of the NS-GT cut quartz crystal resonators are measured experimentally by using a dynamic photo-elastic method when the resonators are vibrating in the resonant frequency; thereafter, vibration modes of the NS-GT cut resonators are estimated with the experimental data of the stress distributions. This experiment for the NS-GT cut quartz crystal resonators exposes the existence of a twisted asymmetrical vibration mode at the main resonant frequency, with the magnitude of the twisted vibration in proportion to thickness of the resonators.
Study on stress-optical coefficients for analyzing character of oscillating quartz crystal resonators
A dynamic photoelastic method (probe light beam modulation method) is a practical system for investigating quartz crystal resonators which are oscillating in the resonant frequency. This method has been applied to analyze the behavior of AT cut and NS-GT cut quartz crystal resonators in previous studies. When we analyze the character of an oscillating quartz crystal resonator by using optical methods we have to note that a quartz crystal has birefringence (double refraction). Then, if stress distributions of the resonator will be measured by the probe light beam modulation method, stress-optical coefficients C'(x, /spl Omega/) are very important factors. These coefficients are function of resonator's cut angles from an original quartz crystal and an incident angle of probe light beam to a surface of the quartz crystal resonator. A specific vibrating stress /spl sigma/'/sub b/ of the quartz crystal resonator can be detected separately, from unwanted spurious stresses and vice versa, when the incident angle of the probe light beam is chosen at an adequate direction.
Multilayer high density flex technology
The industrial trend of shrinking microelectronic devices while increasing the density of interconnections places great demands on the substrates upon which these devices are packaged. Multilayer flex circuits will provide the interconnection densities needed to meet these demands in a wide range of packaging and interconnection technologies. This paper discusses the development of ultra-high density flexible circuits. Processes and materials to fabricate fine line pitches from 12.5 /spl mu/m to 40 /spl mu/m are examined. Various microvia structures, through hole and blind via, are demonstrated. A test vehicle was designed and built for BGA packages to illustrate the density capability. A four-layer structure is demonstrated by using Z-connection to connect two layer pairs. Electrical, mechanical, and reliability test results are presented to show the selection of flex substrate material, Z-connection methodology and fabrication processes. A cost comparison of high-density flex to alternative substrates is discussed to identify potential.