Hidehiko Karasaki

Concurrent in-line inspection system for CO2 laser drilling machine

We describe the concurrent in-line inspection system, which controls the CO2 laser drilling machine for printed wiring boards. The performance of a CO2 laser drilling process was improved drastically by the introduction of this inspection system. The principle of this inspection systems is based on the relationship between the exposed bottom area of the inner layer copper foil in via hole and the intensity of the reflected laser beam. The end of drilling process is detectable by the saturation of the reflected laser beam intensity generate at the copper foil surface of the blind via hole. We have carried out the drilling process for glass-cored epoxy substrate and have observed that the productivity of the drilling process i increased by 30 percent due to this inspection system.

New CO2 laser equipped with high-peak pulse power and high-speed drilling process

The new C02 laser has been developed for the high speed drilling and cutting process for sheet metals up to 16 mm thickness, with low operational costs.The new C02 laser is equipped with the newly developed acoustic filter and solid-state inverter power supply that have the fol lowing features: (1) To keep high quality glow-discharge under the laser gas flow, the acoustic filter has been newly applied to prevent the ripple of the laser gas pressure.Thus it is able to reduce fluctuations of the laser pulse power to within 10%. (2) The solid-state inverter power supply has been developed to make possible high response glow-discharge power.That creates a high peak pulse power, where the height of the laser pulse power is more than 4000w as well as twice cw laser power. The high speed drilling process using the high peak pulse power makes possible a driffing time of 5 secat 16 mm thickness and less than 0.5 sec at 9 mm thickness for mild steel.

Development of CO2 laser drilling system controlled by concurrent in-line inspection monitoring for printed wiring boards

The performance of a CO2 laser drilling system was improved by real-time process control with concurrent in-line inspection monitoring for printed wiring boards. The principle of the concurrent in-line inspection monitoring method was based on the relationship between the exposed bottom area of the inner layer copper foil in the via hole and the intensity of the reflected laser light. The end of the drilling process was detectable by the saturation of the reflected laser light intensity generated at the copper foil surface of the blind via hole.In this paper, the development of the CO2 laser drilling system for printed wiring boards, which is controlled by concurrent in-line inspection monitoring, is described. We carried out the drilling process for glass-cored epoxy substrate and observed that the productivity of the drilling process was increased by about 30 % due to control by concurrent in-line inspection monitoring.The performance of a CO2 laser drilling system was improved by real-time process control with concurrent in-line inspection monitoring for printed wiring boards. The principle of the concurrent in-line inspection monitoring method was based on the relationship between the exposed bottom area of the inner layer copper foil in the via hole and the intensity of the reflected laser light. The end of the drilling process was detectable by the saturation of the reflected laser light intensity generated at the copper foil surface of the blind via hole.In this paper, the development of the CO2 laser drilling system for printed wiring boards, which is controlled by concurrent in-line inspection monitoring, is described. We carried out the drilling process for glass-cored epoxy substrate and observed that the productivity of the drilling process was increased by about 30 % due to control by concurrent in-line inspection monitoring.

Development of beam-pointing compensating optical system for aspheric beam shaper of PWB laser drilling system

In a PWB laser drilling system, an aspheric beam shaper, which converts single-mode Gaussian beam into beam with uniform irradiance profile is widely used. This beam shaper is very sensitive to decentering of the input beam, which is caused by the instability of beam pointing. It degrades the irradiance profile uniformity of the output beam and the processing quality. To solve this problem, we develop a beam pointing compensation optical system. This system contains a newly designed collimator which have a function to project the origin of the pointing vector of the laser beam to the input surface of the shaper in addition to the conventional function to control the diameter and the wavefront curvature of the laser beam. We analyzed the performance of the collimator by simulation, and confirmed that the irradiance distribution of output beam was not degraded by the instability of the beam pointing. Also, we confirmed its effects by the optical experiments.

Analysis of laser drilling process for substrate by optical simulation rectified at the ablation rate

The shape of a processed hole is a key factor for laser drilling system. There are many studies to calculate the behavior of heat or the reaction of molecules in a substrate after laser irradiation. These simulations enable calculation of removed volume by laser power. However, there were some difficulties to estimate the shape of processed hole. To solve the problem, the shape of processed hole was calculated by optical simulation and the ablation rate. The laser intensity distribution on the substrate was calculated by optical simulation considered with diffraction of beam and the aberrations of optics. Furthermore the results of optical simulation were rectified by ablation rate. The calculated shape of the processed hole showed good agreement with actual. This simulation can be used to control the laser drilling process to realize high quality holes.

Development of a high-performance UV-DPSS laser drilling system for PWB

A high-performance UV-DPSS (Diode Pumped Solid State) laser drilling system (wavelength 355nm) for PWBs, which can drill a less than 50micrometers diameter via-hole, has been developed. This system has two main features as follows: 1. A vua-hole without smear is possible to be drilled for PWBs with the optimized irradiation conditions of UV laser. 2. High throughput was realized by using a high power UV-DPSS laser and a developed high-speed control method of galvanometric scanning. This paper describes the outline of the developed UV-DPSS laser drilling system. This system has the advantages which are required small via-holes formation less than 50micrometers in diameter, compares with a conventional CO2 laser system currently.

Development of the enhanced concurrent in-line inspection system for CO2 laser drilling machine

The performance of the concurrent in-line inspection system in CO2 laser drilling process has improved by the defect pattern estimation algorithm. The optical detection principle of the system is based on the relationship between the reflected laser intensity from the bottom copper foil in via-hole and the area size of the exposed copper surface. The principle and the advantage of the enhance concurrent inspection system was described. Using the improved concurrent inspection system, the etched hole diameter and defect of PWB can be examined. This function has a capability to substitute AOI function. As a result, reliability and throughput in PWB drilling process has been improved.