Introduction to the production of blind hole plates

With the development of electronic products to high density and high precision, the same requirements are put forward for circuit boards accordingly. The most effective way to increase PCB density is to reduce the number of through holes, and accurately set blind holes and buried holes. With the development of electronic products to high density and high precision, the same requirements are put forward on circuit boards accordingly. The most effective way to increase PCB density is to reduce the number of through holes, and accurately set blind holes and buried holes. 1. Blind hole definition a: In contrast to through holes, through holes refer to holes drilled through each layer, and blind holes are non-drilled through holes. b: Blind hole subdivision: blind hole (BLIND HOLE), buried hole BURIED HOLE (outer layer is not visible); c: distinguish from the production process: (mechanical) blind holes are drilled before pressing, and through holes are Drill holes after pressing. 2. Production method: a: drill belt: (1): select reference point: select the through hole (that is, a hole in the first drill belt) as the unit reference hole. (2): Each blind hole drilling belt needs to select a hole and mark its coordinates relative to the unit reference hole. (3): Pay attention to which drill belt corresponds to which layers: the unit sub-hole diagram and drill bit table must be marked, and the names of the front and back must be consistent; the sub-hole diagram cannot appear with abc, and the front is 1st, 2nd Indicates the situation. ***Note that when the laser hole is sleeved with the inner buried hole, that is, the holes of the two drill belts are in the same position, you need to ask the customer to move the position of the laser hole to ensure the electrical connection. B: Production pnl board edge process hole: Ordinary multi-layer board: Directly use the negative film to align, then the inner layer will not be drilled; use CCD to drill the alignment hole and other tool holes, such as rivet holes, test holes, AOI holes, etc. ….. (1): When not drilling, the rivet hole is directly punched out with a punching machine. (2): The target hole is punched directly by the x-ray machine. Mechanical blind hole plate: All tooling holes are drilled. Note that the rivets are best made by punching to avoid misalignment. 3. Film modification: (1): Indicate that the film produces positive and negative films: General principles: board thickness greater than 8mil (without copper) follow the positive film process; board thickness less than 8mil (without copper) follow the negative film process (thin board); thick line When the gap is large, the copper thickness at d/f needs to be considered, not the bottom copper thickness. The blind hole ring can be made 5mil, no need to make 7mil. The inner independent pad corresponding to the blind hole needs to be retained. Blind holes cannot be made without ring holes. 4. Process: The buried-hole plate is the same as the ordinary double-sided board. Mechanical blind hole board, that is, one side is the outer layer: Positive film process: Single-sided circuit is required. When D/Ff exposure, the polished copper surface is covered with black tape to prevent light transmission. Because the blind hole board is made more than twice, the thickness of the finished product is very easy to be too thick. Therefore, the thickness of the board should be controlled and the copper thickness and the range of the board thickness should be indicated after the etching. After pressing the board, use the x-ray machine to punch out the target holes for the multilayer board. Negative film process: For thin boards (<12mil> due to process conditions, such as the positive film process, the single-sided copper thickness is often too thick, causing etching difficulties, thin lines and other abnormalities, so this type of board needs to use the negative film process. And the outer circuit In the case of two electroplating, the surface copper will be thicker, and usually the copper reduction process must be supplemented. 5. The drilling sequence of through holes and blind holes is different, and the deviation during production is inconsistent; blind holes are more prone to deformation, It is difficult to open the horizontal and straight material to the multi-layer board alignment and the control of the tube distance, so only open the horizontal material or only the straight material when opening the material. 6. Laser drill: LASER DRILL is a kind of blind hole, with its own characteristics: Aperture size: 4-6 mil pp thickness must be