| 摘要 |
<p>PROBLEM TO BE SOLVED: To surely reduce invasion of plating liquid in a trimming trench by positioning a starting tip of the trimming trench at a part position outside a side surface edge of a resistance film and inside a side surface edge of an undercoat. SOLUTION: A resistance film 2, main electrodes 3 positioned at both ends of the film 2, and undercoat 4 which is composed of glass and covers the film 2 are formed on part positions of each insulating board 1. A laser ray is cast on the resistance film 2 on the upper surface of each of the insulating boards 1 from an upper part of a cover coat 6, and an L-shaped trimming trench 5 is notched. In a central control circuit, when a trimming trench is notched, a side surface edge 2a of the resistance film 2 is made reference, and a starting tip 5a of the trimming trench is fixed at a part position between the side surface edge 2a and a side surface edge 4a of the undercoat 4. The starting tip 5a of the trimming trench 5 is controlled so as to surely position at a part outside the side surface edge 2a of the resistance film 2 and inside the side surface edge 4a of the undercoat 4.</p> |
