With the development of high-density and high-precision electronic products, the same requirements are put forward for circuit boards, which makes circuit boards gradually develop in the direction of HDI. The most effective way to increase PCB density is to reduce the number of through holes, and to accurately set blind holes and buried holes.
1. Definition of HDI blind hole plate
a: In contrast to through holes, through holes refer to holes drilled through each layer, and HDI blind holes are non-drilled through holes.
b: HDI blind hole subdivision: blind hole (BLINHOLE), buried hole BURIEDHOLE (outer layer is not visible);
c: Distinguish from the HDI circuit board manufacturing process: blind holes are drilled before pressing, while through holes are drilled after pressing.
2. How to make a circuit board
A: Drill belt:
(1): Select the reference point: select the through hole (that is, a hole in the first drill strip) as the unit 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 is nested with the inner buried hole, that is, the holes of the two drill strips are in the same position. B: Production pnl board edge process hole:
Ordinary PCB multilayer circuit board: the inner layer is not drilled;
(1): Rivets gh, aoigh, etgh are all punched out after etching the plate (beer out)
(2) : target hole (drilling gh) ccd: the outer layer needs to be cut out of copper, x-ray machine: direct punch, and pay attention to the minimum length of 11 inches.
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: HDI circuit board thickness is greater than 8mil (without copper) and take the positive film process;
The thickness of the circuit board is less than 8mil (without copper) and the negative film process (thin board);
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.
Blind holes cannot be ring-free holes.