In fact, the four -layer board copy plate is to repeat two double panels, and the sixth floor is to repeat three double panels ... The reason why the multi -layer is daunting is because we cannot see the internal line. How can we see the inner layer of a precise multi -layer board? —— layered.

　　There are many methods on the problem of layered, including potions corroded, knife stripping, etc., but it is easy to divide the layer over the head and lose the information. Experience tells us that sandpaper polishing is the most accurate.

　　When we copy the top layer of the PCB, we usually use sandpaper to polish to grind the surface of the surface to display the inner layer; sandpaper is a common sandpaper sold by the hardware shop. Generally, PCB is paved, then pressing the sandpaper and rubbing on the PCB evenly on the PCB. (If the board is small, you can also lay sandpaper, and press PCB with a finger to rub on the sandpaper). The main point is to pave the flat, so as to grind evenly.

　　Silk printing and green oil generally fall off, and the copper line and copper skin should be wiped a few times. Generally speaking, the Bluetooth board can be wiped for a few minutes, and the memory bar is about ten minutes; of course, the strength is stronger, and the time will be a little less; the time of small strength will be a little bit more.

　　The grinding board is the most commonly used solution and the most economical. We can find a abandoned PCB to try it. In fact, the grinding board is not technically difficult, but it is a bit boring. It takes some effort. You do n’t have to worry about grinding the board to your fingers.