Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Using radiant energy
Patent
1991-09-27
1993-03-16
Wieder, Kenneth A.
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Using radiant energy
324632, 324636, 324558, 324554, 340552, 73159, 73160, G01N 2200
Patent
active
051948150
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a detecting apparatus of conductive material such as metal contained in a stringy material such as glass fibers positioned in a cylindrical microwave cavity resonator.
BACKGROUND ART
With development of high density mounting technology, severer requirements such as high withstand voltage have been imposed on printed circuit boards on which electronic devices are mounted in a high density. These kind of printed circuit boards are formed by superposing a plurality of (e.g. seven) cloths, woven of glass fibers with paste, interposing epoxy resin between them.
If a high voltage is applied to printed circuit boards made of glass fibers containing minute metal pieces, discharges occur due to the minute metal pieces, so that it is impossible to get printed circuit boards with high withstand voltage if they use glass fibers containing minute metal pieces. Therefore it is necessary to use glass fibers without minute metal pieces for manufacturing high quality printed circuit boards. The development of technology to detect minute metal pieces contained in glass fibers has been a longstanding need in this technical field. The applicant of the present application already proposed in JP Pat. Kokai No. 63-145951 a microwave cavity resonator in which a protrusion is arranged in the center so that physical quantities of stringy materials can be precisely measured. As shown in FIGS. 5A and B, the cylindrical microwave cavity resonator 1 comprises protrusion 4 on its center and space 3 for passing stringy material 2 arranged on the center of protrusion 4 and the wall of the microwave cavity resonator opposed to the protrusion.
Such microwave cavity resonator 1 allows to measure metals contained in stringy materials such as glass fibers. To do so glass fibers without metal pieces are first placed at space 3 and then resonance characteristic for the glass fibers are measured with a measuring instrument of resonance characteristic by scanning the frequencies of microwave supplied to the microwave cavity resonator 1 from antenna 5, which frequencies are changed by changing the voltage of the voltage control oscillator. Next if glass fibers containing metal pieces are placed at space 3 for measuring resonance characteristics, the resonance characteristics will be different from that of the glass fibers without metal pieces. Measuring of shifted amount in resonant frequency and decreased amount in resonance peak voltage enables not only to detect metals contained but also to measure the accurate amount of contained metal.
The method of detecting metals by the change of resonance characteristics in this manner has an advantage to obtain accurate measurement results, but it has a disadvantage that the total system costs too much because it needs a voltage control oscillator and a measuring instrument of the resonance characteristics. In case of glass fibers by which printed circuit boards for high density assembling are manufactured, measuring the amount of contained metals is not necessary but only detection of contained metals is necessary. Furthermore in factories hundreds of, glass fibers are manufactured at the same time and a detecting apparatus for contained metals is needed for every glass fiber, so that the total cost of the detecting apparatus would be enormous. Therefore an acceptable detecting apparatus of contained metals in a stringy material must be inexpensive. In this sense the measuring apparatus for physical quantities disclosed in Pat. Kokai No. 63-145951 has some disadvantage when the introduction of the apparatus to factories of manufacturing glass fibers is considered.
On the other hand, in case of glass fibers used for high density printed circuit boards the only problem is whether or not metals are contained in the glass fibers. From this point of view, the detecting apparatus of physical quantities, as disclosed in Pat. Kokai No. 63-145951, which can measure not only the existence of metals but also accurately measure the amount of contained metals is an
REFERENCES:
patent: 3857091 (1974-12-01), Kalifon
patent: 4507605 (1985-03-01), Geisel
patent: 4580132 (1986-04-01), Kato
patent: 4890054 (1989-12-01), Maeno et al.
Dipole Electronics Co., Ltd.
Solis Jose M.
Wieder Kenneth A.
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