| 摘要 |
A first embodiment of a filter includes a circuit board, a metallic tube, and a metallic cap; the tube has an annular groove on outer side of first end, and a leak-stoppage ring fitted onto the groove; the board is held in the tube, and is secured to the tube by solder; the cap is tightly fitted around the first end of the tube such that the board is protected, and the leak-stoppage ring is sandwiched between the cap and the tube; in a second embodiment, annular groove is formed on outer side of a fitting end portion of the cap instead, and leak-stoppage ring is fitted onto the groove; the board is partially held in the cap, and is secured to the cap by solder; the tube is tightly fitted around the cap such that the board is protected, and the ring is sandwiched between the cap and the tube.
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