With the development of electronic products towards high density and precision, the same requirements have been put forward for circuit boards. The most effective way to increase PCB density is to reduce the number of through holes and precisely set blind holes and buried holes to achieve this.

　　1. Definition of blind holes

　　a: Compared to through holes, through holes refer to holes that are drilled through each layer, while blind holes are non drilled through holes. (Illustrated, eight layer board examples: through hole, blind hole, buried hole) b: blind hole subdivision: BLIND HOLE, buried hole Buried HOLE (outer layer not visible); c: Distinguish from the production process: blind holes are drilled before pressing, while through holes are drilled after pressing.

　　2. Production method

　　A: Diamond belt:

　　(1) : Select reference point: Select a through hole (i.e. a hole in the first drilling strip) as the unit reference hole.

　　(2) Each blind hole drill belt needs to select a hole and label its relative coordinates to the reference hole of the unit.

　　(3) : Please note which drilling strip corresponds to which layers: The unit drilling diagram and drilling nozzle table should be indicated, and the names before and after should be consistent; It is not possible to use a, b, and c to represent the hole diagram, while using 1st and 2nd to represent it earlier.

　　Note that when the laser hole is nested with the inner buried hole, that is, the holes of the two drilling belts are in the same position, it is necessary to ask the customer to move the position of the laser hole to ensure electrical connection.

　　B: Production of PNL board edge process holes:

　　Ordinary multi-layer board: the inner layer is not drilled;

　　(1) Rivets gh, aoi gh, et gh are all produced after etching the plate (with a draft)

　　(2) Target hole (drilling gh) CCD: outer layer needs to be made of copper sheet, X-ray machine: directly drill, and note that the minimum length of the long side is 11 inches.