The solution for square sapphire windows that cannot be thrown through the four corners

This article discusses the solution to the situation where it is difficult to polish the four corners of the square (or non-circular) sapphire window during the double-sided grinding and polishing of sapphire.

The process of double-sided grinding and polishing is to place a star wheel between the upper and lower disks of the double-sided grinding and polishing machine. The star wheel has a hole of appropriate size. The sapphire piece is placed in the hole. The rotation of the star wheel drives the sapphire to rotate. The purpose of uniform grinding and polishing. Due to the rotation of the upper and lower disks, there is a linear velocity difference that gradually decreases from the edge to the center. Assuming that the star wheel does not rotate, due to the existence of this linear velocity difference, the thickness difference from the edge to the center after grinding (edge The upper is thin, the middle is thick).

If the sapphire sheet is a wafer, during grinding and polishing, when the high point of the sapphire touches the surface of the disk, due to the rotation of the star wheel, there will be a thrust to push the high point to the low point, that is, the wafer will adapt itself in the tooling position Rotate to keep the global thickness uniform.

However, if the sapphire sheet is not a positive wafer, due to the tooling, the sapphire sheet cannot be rotated during the grinding process, and can only be passively ground and polished, resulting in inconsistent thickness. Although this inconsistency is very small, it is polishing At this time, this difference will be extremely magnified, and the most obvious thing is that the edges cannot be thrown through for a long time.

First, carefully analyze the placement of the sapphire sheet. In order to ensure that the grinding disc is fully in contact with the sapphire sheet, we often have to place the edge of the sapphire sheet outside the grinding disc, so as to ensure that the grinding disc will not be deformed because there is no grinding material on the side. However, because the planetary wheel rotates during work, the sapphire sheet that exposes the grinding disc is often the corner area and the part with the fastest linear velocity. This will cause the corner area to be significantly thinner than other areas. This is the reason why the four corners cannot be polished through polishing.

For this situation, our solution is to turn over, that is, a normal grinding cycle is divided into at least two stages. After grinding to half of the set time, turn the sapphire sheet over, not just flip it upside down. It is also necessary to reverse the internal and external thickness, which can effectively reduce the thickness difference. If it can be turned over three to four times, it is better to basically completely solve the problem of the thickness difference. The impermeability of the polished corners is naturally alleviated or resolved. Taixing Hechen Crystal Technology Co., Ltd. focuses on the precision processing of sapphire windows. Welcome to contact us for guidance.