Check PCB board
The following figure shows the aperture of the 300um hole in the FR4 circuit board and the 100um bolt hole in the PCB layer. Since the signal lines are arranged in the X direction and the Y direction, the pinhole must be arranged at the intersection of the X and Y directions so that the upper and lower lines can be turned on.
The arrangement of the bolt holes is arranged in a diagonal direction, and this type of slanting arrangement can reach the maximum number of bolt holes. General high density PCB circuit board density index is expressed in terms of pinhole density. The number of bolt holes per inch of square area can be expressed in VPSG units. Figure 6.1 FR4 circuit board pinhole density of only 4VPSG and PCB layer of circuit board pinhole density is as high as 20VPSG. In addition to increasing the circuit board plane line density is 37 times the general FR4 printed circuit board, because the insulation layer of the insulation layer thickness of only 40um than FR4 circuit board is thin, so the Z direction density is FR4 circuit board 2 times, So the entire increase in the circuit board circuit density can be more than 10 times the general FR4 circuit board. Since the density of the circuit board is much higher than that of the FR4 printed circuit board, the production yield of the increased circuit board will be significantly reduced if the precision required for the process can not be ensured.