The most effective way to increase the density of PCB is to reduce the number of through holes, and to accurately set blind holes and buried holes.

　　1. Blind hole definition

　　a: In contrast to through holes, through holes refer to holes drilled through all layers, while blind holes are non-drilled through holes.

　　b: Blind hole subdivision: Blind hole (BLINHOLE), buried hole BURIEDHOLE (outer layer is not visible); c: Distinguish from the production process: Blind holes are drilled before pressing, while through holes are drilled after pressing .

　　2. Circuit board production method of Shenzhen circuit board factory

　　A: Drill belt:

　　(1): Select the reference point: select the through hole (that is, a hole in the first drill strip) as the element reference hole.

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

　　(3): Pay attention to indicating which drill belt corresponds to which layers: the unit sub-hole diagram and drill nozzle table must be marked, and the names before and after must be the same; the sub-hole diagram cannot be represented by abc, and the front is used 1st, 2nd indicated situation.

　　Note that when the laser hole and the inner buried hole are nested together, that is, the holes of the two drill strips are in the same position, the customer needs to move the position of the laser hole to ensure the electrical connection.

　　B: Shenzhen circuit board factory is producing pnl board edge process hole: ordinary PCB multilayer circuit board: inner layer is not drilled;

　　(1): The rivets gh, aoigh and etgh are all made after etching the plate

　　(2): target hole (drilling gh) ccd: copper skin needs to be cut out for the outer layer, x-ray machine: direct punching, and pay attention to the minimum length of 11 inches.

　　Blind and buried via board (circuit board) PCB multilayer circuit board

　　Blind and buried via board (circuit board) PCB multilayer circuit board

　　Blind hole plate:

　　All tooling holes are drilled, pay attention to the rivets; they need to be drilled to avoid alignment deviation.

　　(aoigh is also beer), the edge of the pnl board needs to be drilled to distinguish each board.

　　3. Film modification:

　　(1): indicate that the film is a positive film and a negative film:

　　General principle: the plate thickness is greater than 8mil (without copper), and the positive film process; the plate thickness is less than 8mil (without copper), and the negative film process (thin plate);

　　When the line thickness and the gap valley are large, the copper thickness at d/f should be considered, not the bottom copper thickness. The blind hole ring can be made 5mil, not 7mil. The inner layer independent pad corresponding to the blind hole needs to be reserved. Holes cannot be made without ring holes.

　　4. The process of Shenzhen circuit board factory:

　　The buried via board is the same as the common double-sided circuit board.

　　Blind hole plate, that is, one side is the outer layer:

　　Positive film process: need to do single-sided d/f, be careful not to roll the wrong side (when the double-sided bottom copper is inconsistent); when d/f is exposed, the light copper surface is covered with black tape to prevent light transmission. Because the blind hole board is used for more than two times, the finished product is very easy to be too thick, so the drawing should pay attention to the control of the thickness of the board and the copper thickness, and indicate the range of the thickness of the copper thick plate after etching. After pressing the board, use an x-ray machine to punch out target holes for multi-layer circuit boards.

　　Negative film process: For the thin plate (<12mil with copper), it must be produced in water metal drawing because it cannot be produced in the drawing, and the water gold drawing cannot apply current in different sides, so it is impossible to do single-sided non-current or punching according to the requirements of mi. Small current. If the positive film process is used, the copper thickness on one side is often too thick, resulting in difficult etching and thin lines. Therefore, this type of board uses the negative film process.

　　5. The drilling sequence of through holes and blind holes is different, and the deviation is inconsistent during production

　　The blind hole plate is easy to be deformed, and it is difficult to control the alignment of the multi-layer board and the tube position distance when opening the horizontal and straight materials. Therefore, only the horizontal material or only the straight material is opened when the material is opened.

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