| 摘要 |
A method for forming through holes, which has laser beam as the light source to project the laser beam to the work object using an optical system through a photomask for the formation of through holes on the work object by ablation processing, comprises the steps of increasing the concentration of the optical processing energy contributing to the process using the reflected beam created from the work object in the laser ablation processing; and forming each of through holes having the configuration enabling the narrower end to be changed to the wider end in the incident direction of laser beam. With the structure thus arranged, it becomes possible to increase the energy concentration that contributes to the process as compared with the usual ablation processing, because the reflected beam created in the ablation processing can be utilized again for the optical processing. Then, each of the through holes can be formed easily in the configuration in which the narrower end changes to the wider end in the incident direction of laser beam, which cannot be easily processed by the application of the usual ablation processing.
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