1. When marking and making PCB sample slices, you should first know whether your slice is a transverse or longitudinal section of the hole, and where the problem lies. It must be marked with a colored oil pen or tape. Use an arrow to indicate the problem point

　　2. For circuit board sampling and gluing, if there are bubbles in the holes, the slice has lost its meaning. Therefore, gluing is the foundation of PCB sampling and slicing. The transparent glue used by everyone may be different, but it is only powder glue or blue and white glue There is always a component that is' rare ' Before gluing, please ensure that the sample is clean, otherwise there will definitely be bubbles generated. The method I use is to wipe and clean with a cotton swab dipped in acetone, or use ultrasonic cleaning Then wet it with a "dilute" solvent Or first dilute the glue and carefully fill the small hole with a toothpick Especially blind holes, carefully fill them with toothpicks, and then fill them with thick glue Drying should not be done too quickly, and the temperature should not be too high Otherwise, the outer layer is dry and the inner layer is soft, making it difficult to slice properly

　　3. Grind the slices and solidify them. Grinding is very important. Generally, you can prepare at least 240 #, 600 #, 800 #, 1200 #, 2400 # sandpaper at hand. Most factories have rotating grinding discs, so manual grinding is not introduced When grinding, attention should be paid to directionality, and the most taboo is to grind randomly without directionality Generally speaking, you first use coarse sandpaper to grind in one direction, and then use a finer sandpaper of one size to grind in a vertical direction. After knowing the fine grinding marks, completely polish the previous sandpaper's marks, then switch to a finer sandpaper for grinding in another direction Until near the problem point When grinding, it is best to place the slices close to the center of the original disc and avoid the edges as much as possible. You may want to use speed blocks, but it is difficult to make good slices that way If possible, after grinding at 2400 #, it would be even better to use a polishing step with alumina grinding solution for polishing. When holding the slice with your hands, do not exert force, otherwise it will deviate from balance. Gently hold and slowly place it, and find it steadily (flat)

　　4. Etching, etching is used to layer and display the metallic structure of copper. Generally, people use a system of hydrogen peroxide and acid. The key to etching is to control the timing This requires more practice from everyone to do well My own secret is to first add a large drop onto the slice, then quickly rinse it dry with water (pure water) or shake it dry, then use a cotton swab dipped in the medicine to wipe it carefully, and finally rinse it dry with water (pure water).