With the advancement of electronic products towards higher density and precision, similar demands are placed on circuit boards. The most efficient approach to enhancing PCB density is by minimizing the number of through-holes and implementing precise setups for blind and buried holes.
Knowledge of Blind and Buried Hole Fabrication in Circuit Boards:
A: In comparison to through-holes, which traverse all layers, blind holes are not drilled through the entire depth. For instance, in an eight-layer board (illustrated graphically as: HOLE, BLIND HOLE, BURIED HOLE), blind holes are segmented into BLIND HOLE and BURIED HOLE (externally invisible). From a production standpoint, blind holes are drilled before pressing, while through-holes are drilled after pressing.
A: Drill Belt:
(1): Selection of Reference Point: Through-holes (i.e., those in the initial drilling belt) are chosen as unit reference holes.
(2): Each blind hole drilling belt requires a designated hole, and its coordinates relative to the unit reference hole must be marked.
(3): Identification of Drill Belt Layers: The unit hole diagram and drill tip table should indicate which drill belt corresponds to which layers. Consistency in naming front and back is crucial; using A, B, and C to represent hole plots and subsequently employing 1st and 2nd to denote them is not acceptable.
Note that when laser holes coincide with buried holes in inner layers, necessitating the holes of both drill belts to occupy the same position, adjustments must be made to ensure electrical connectivity.
B: Production PNL Plate Edge Process Hole:
For common multilayer boards, inner layers remain unperforated.
(1): Rivet GH, AOI GH, ET GH are etched post-drilling (with beer out).
(2): Target Hole (Drilling GH) CCD: Outer layers should have copper cut, X-Ray machine: direct punching, ensuring a minimum length of 11 inches on the longer side.
Blind hole plates: All tooling holes are drilled out, with attention to rivet GH; beer-out is necessary to prevent positional deviation. (AOI GH also requires beer.) The PNL plate edge production necessitates hole drilling for board identification.
(1): Indication of Positive and Negative Films:
General Guidelines: For plates thicker than 8mil (without copper), positive film processing is preferred; for thinner plates, negative processing is used. Consideration should be given to the copper thickness at D/F, rather than at the bottom, when dealing with large line thicknesses and gap valleys. A 5mil ring suffices for blind hole applications, while 7mil is unnecessary. Independent pads corresponding to blind holes must be retained. Blind holes without ring holes are not permissible.
Knowledge of Blind and Buried Hole Fabrication in Circuit Boards:
A: In comparison to through-holes, which traverse all layers, blind holes are not drilled through the entire depth. For instance, in an eight-layer board (illustrated graphically as: HOLE, BLIND HOLE, BURIED HOLE), blind holes are segmented into BLIND HOLE and BURIED HOLE (externally invisible). From a production standpoint, blind holes are drilled before pressing, while through-holes are drilled after pressing.
A: Drill Belt:
(1): Selection of Reference Point: Through-holes (i.e., those in the initial drilling belt) are chosen as unit reference holes.
(2): Each blind hole drilling belt requires a designated hole, and its coordinates relative to the unit reference hole must be marked.
(3): Identification of Drill Belt Layers: The unit hole diagram and drill tip table should indicate which drill belt corresponds to which layers. Consistency in naming front and back is crucial; using A, B, and C to represent hole plots and subsequently employing 1st and 2nd to denote them is not acceptable.
Note that when laser holes coincide with buried holes in inner layers, necessitating the holes of both drill belts to occupy the same position, adjustments must be made to ensure electrical connectivity.
B: Production PNL Plate Edge Process Hole:
For common multilayer boards, inner layers remain unperforated.
(1): Rivet GH, AOI GH, ET GH are etched post-drilling (with beer out).
(2): Target Hole (Drilling GH) CCD: Outer layers should have copper cut, X-Ray machine: direct punching, ensuring a minimum length of 11 inches on the longer side.
Blind hole plates: All tooling holes are drilled out, with attention to rivet GH; beer-out is necessary to prevent positional deviation. (AOI GH also requires beer.) The PNL plate edge production necessitates hole drilling for board identification.
(1): Indication of Positive and Negative Films:
General Guidelines: For plates thicker than 8mil (without copper), positive film processing is preferred; for thinner plates, negative processing is used. Consideration should be given to the copper thickness at D/F, rather than at the bottom, when dealing with large line thicknesses and gap valleys. A 5mil ring suffices for blind hole applications, while 7mil is unnecessary. Independent pads corresponding to blind holes must be retained. Blind holes without ring holes are not permissible.
