| 简介 |
A ring shaped body includes a top flat region, a ring inner side and a ring outer side. The ring inner side comprises an approximately vertical wall. A conformal protective layer is disposed on at least the top flat region, the ring inner side and the ring outer side of the ring shaped body. The protective layer has a first thickness of less than 300 μm on the top flat region and a second thickness on the vertical wall of the ring inner side, where the second thickness is 45-70% of the first thickness. |
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