About 0.670 mm, the wafer must be thinned, otherwise it will cause great loss to the cutting knife and scrape it twice. We do DIP packaging, and the 4-inch wafer should be as thin as 0.300mm；; A 6-inch wafer should be as thin as about 0.320 mm with an error of 0.020 mm. ..
The thickness of the measuring instrument is measured by micrometer, and the film thickness is generally measured by thermal wave instrument. By measuring the thickness of different points, the average film thickness is obtained, which generally reflects the uniformity of the film at the same time, and the simulated contour line can be seen.