| 摘要 |
A back metal plate comprising a plurality of substantially spheric surfaced dimples each having a portion adjoined to a portion of another dimple, the dimples being formed at least on either a front or a back surface of the back metal plate, flat portions having the upper end surface surrounded by the dimples constituting the same plain as the plate surface, and boundary portions which are lower than the flat portion and higher than the bottom portion of the dimples formed to the adjoined portion of the dimples, and a method of manufacturing the back metal plate includes forming the dimples by cold-working the plate material through coining.
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