3.3 Grinding: The sample is ground to the center of the hole using the cutting force of sandpaper in order to observe the cross-section of the hole wall. A rapid grinding method is often used with a fast turntable to save time and for mass production. The sandpaper can be fixed with adhesive backing on the surface of the disk, or with a gauze paper fixed by an edge turn-shaped fixer, or with sandpaper with a center hole inserted into the rotating shaft. When wet and rotating at high speed, the sandpaper will be flat on the disk and can grind the sample. Some simple cut samples can be smoothed on ordinary sandpaper by hand, and the turntable can be omitted. The appropriate sandpaper numbers to be used are as follows:
3.3.1 Use No. 220 sandpaper for rough grinding until two parallel lines of the hole wall fault appear, and pay attention to spraying water or other liquids to reduce heat.
3.3.2 Use No. 400 sandpaper and regrind until the indication line of the center of the hole appears.
3.3.3 Use fine sandpaper above 600 to lightly grind a few times to correct non-parallel oblique grinding.
3.4 Polishing: Careful polishing must be done to remove scratches from the sandpaper in order to clearly see the truth of the slice. When a large amount is used, a rotary felt with alumina suspension as an auxiliary agent is used for micro-contact polishing. The direction of the cutting sample should be frequently changed during polishing to achieve a more uniform effect until the sand marks completely disappear. A small amount of cutting can be changed to a general cloth head and rubbed with copper ointment. The polishing pressure should be lighter with more reciprocations for a better effect. Oil-based polishing can provide a better truth of the copper surface than water-based polishing.
3.5 Microetch: After the polished surface is washed with water or dilute alcohol and dried, micro-etching can be performed to find out the respective layers of the metal and the crystallization condition. The micro-etching solution consists of 10 cc ammonia, 10 cc pure water, and 2-3 drops of hydrogen peroxide. The surface of the slice should be gently wiped with the liquid using a cotton swab for about 2 seconds, and then immediately rinsed off with water and dried with toilet paper.
3.6 Photographs: Photography is the best method for record and communication, although it can be expensive. It is important to have a picture for reference. The most difficult part of taking pictures is the alignment of the focal length. The visual focal length is not the same as the photographic focal length. The amount of light required for exposure is calculated by multiplying light intensity by time, and a good photo should try to extend the time and reduce the light intensity. After adding various filters, different effects can be achieved. The surface of the image must be flat, otherwise there will be local clear and local blurring when the multiple is large.