Takeshi Kawana

Wavelet transform based signal waveform identification: inspection of rotary compressor

This paper presents a new identification procedure of signal waveforms, based on wavelet theory, for the inspection of rotary compressors. The wavelet transform decomposes signals into time-frequency space, not into mere frequency space, limited by the uncertainty principle. This decomposition enables time-frequency analyses and provides a more flexible means of signal processing than before. To examine a rotary compressor pump, particular waves in the rotational load torque signals that correlate with failure modes are discriminated from one another and evaluated. To extract the focal waves, the signal is decomposed with wavelets and then only the particular waves, such as impulses, are reconstructed from a selected set of wavelet coefficients. This is called time-frequency space filtering. The wavelet local modulus maxims are used to open a time-frequency window through which only the focal waves can pass with high fidelity. The experimental results show the effectiveness of the maneuver.<<ETX>>

Quantitative estimation of conditions for solid-state bonding of Cu

This paper describes the conditions, especially for bonding time and temperature. Assuming that bonding of Cu depends on its recrystallization, the process can be estimated as follows. First, the temperature change of bonding parts is calculated by a simulation using F1-M. Conditions for the upper energy limit are given so the temperature does not exceed melting point. Then using Krupkowskis formula for recrystallization growth rate, constants are sought by the measurement of isothermal changes. From the formula and temperature change, the recrystallization change is calculated as the accumulation of growth in a short time. Conditions for lower energy limits are given as 90% of recrystallization rate. This hypothesis is verified by the fact that the conditions derived from the above calculation are in good agreement with the conditions of the experiment bonding Cu wires to Cu lands of printed circuit boards by parallel gap bonding, . As a result, it is now possible to choose a suitable bonding method and the conditions, not relying on experience OF trial and error.

Interconnection of Insulated Fine Wire for PCB

Summary High density assembly of PCB(Printed Circuit Board) is essential to small-size electronic devices. This paper reports on the interconnection of insulated fine wires of 20-100 micrometer diameters. Three new techniques are discussed: first, the thermal decomposition of high polymer is evaluated quantitatively; second, conditions for solid-state bonding of copper is studied using recrystallization growth rate equation and temperature simulation by FEM; lastly the current control unit for micro resistance bonding is developed. An interconnection machine has been developed, which decomposes high polymer insulation of wires by a CO2 laser and bond them without thermal damage of PCB.

Temperature distribution simulation of insulated wire at the time of ball forming for connection.

To keep pace with multipin semi-conductors or high-density circuit boards, the automated bonding technique for very fine insulated wires is required. One of the important subjects needed to be solved is to prevent the thermal damage of the insulation when a ball for bonding is formed. By computer simulation using the finite element method, we have found that cooling by heat conduction through a metal chuck held near the ball, or forming a ball in a short time is extremely effective.