A Study on the End Shape of the Sealed Parts of the Bulb Side in the Super High Pressure Discharge Lamps to Improve the Lamp Strength under Internal Pressure

Abstract

Super high pressure mercury discharge lamps have been used as a UV and visible light sources for photolithography exposure process, such as patterning LCDs, PCBs and semiconductors. This study examines their rupture characteristics and discuss a guideline for designing a part of lamp between the end of bulb and the end of the sealed part under internal pressure. Finite-Element method (FEM) was employed to investigate the maximum principal stress σ1 distribution near the end of the sealed part. Furthermore, static water pressure tests were conducted to examine the strength characteristic of the bulbs. As the results, the rupture characteristics near the end of the sealed parts can be elucidated and the guideline for designing the end of the sealed parts were drawn up. Moreover, the relationships among the rupture pressure and the outer diameter D2 of the glass parts in the sealed parts and the length L1 near the end of the sealed parts were obtained for increasing the bulb strength. It was found that the strength near the end of the bulb was increased as the diameter D2 was decreased and the length L1 was increased. The rupture characteristics obtained by the numerical results were in fairly good agreements with those by the experiments.