With the development of high-density and high-precision products in the electronics industry, the same requirements are put forward for circuit boards. The most effective way to increase the density of PCB circuit boards is to reduce the number of through holes and accurately set blind hole boards (PCB circuit boards/circuit boards) and buried holes to achieve.
一、Definition of blind hole circuit board
a: Compared with through holes, through holes refer to holes drilled through all layers, and blind holes are non-drilled through holes. (Illustration of eight-layer boards as examples of blind holes and buried holes) b: Blind hole subdivision: blind hole (BLINDHOLE), buried hole BURIED HOLE (outer layer is invisible); c: Distinguish from the production process: blind hole Holes are drilled before lamination, while through holes are drilled after lamination.
二、Production method
1. Drill belt:
A: Select the reference point: Select the through hole (that is, a hole in the first drill belt) as the unit reference hole.
B: For each blind hole drilling strip, one hole needs to be selected, and its coordinates relative to the reference hole of the unit should be marked.
C: Pay attention to explain which drill belt corresponds to which layers: both the unit hole diagram and the drill nozzle table must be marked, and the names before and after must be consistent; there should be no situation where the hole diagram is represented by a b c and the front is represented by 1st, 2nd .
Note that when the laser hole is nested with the buried hole in the inner layer, that is, the holes of the two drill strips are at the same position, the customer needs to move the position of the laser hole to ensure the electrical connection.
2. Production of pnl board edge process holes:
Ordinary multi-layer circuit board: no drilling in the inner layer;
A: The rivets gh, aoigh, and et gh are all punched out after etching (beer out)
B: target hole (drilling gh) ccd: the outer layer needs to dig out the copper skin, x-ray machine: directly punch out, and note that the minimum length of the long side is 11inch.
All the tooling holes of the blind hole plate are drilled, pay attention to the rivet gh; beer out, to avoid alignment deviation. (aoi gh is also produced for beer), and the edge of the pnl board needs to be drilled to distinguish each board.
三、Film modification:
1. Indicate the positive film and negative film of the film:
General principles: board thickness greater than 8mil (without copper) go through the positive film process;
Plate thickness less than 8mil (without copper) go through the negative film process (thin plate);
When the line is thick and the line gap is large, the copper thickness at d/f should be considered, not the bottom copper thickness. Blind hole ring can be 5mil instead of 7mil.
The inner independent pad corresponding to the blind hole needs to be reserved. Blind holes cannot be made without rings.
