Check PCB buildup circuit board
Comparison of the hole diameter of 300um drilled holes in general FR4 circuit boards and 100um holes in PCB build-up circuit boards. Because the signal lines are arranged along the X direction and the Y direction, bolt holes must be arranged at the intersections of the X and Y direction wires so that the upper and lower lines can be conducted. The configuration of the bolt holes is arranged in an oblique direction. This oblique line arrangement can reach the maximum number of bolt holes. Generally, the density index of high-density PCB circuit boards is expressed by the density of bolt holes. The number of bolt holes that can be accommodated in the area per inch is expressed in units of VPSG. The bolt hole density of FR4 circuit board is only 4VPSG, while the PCB hole density of PCB build-up circuit board is as high as 20VPSG. Except that the planar circuit density of the build-up circuit board is three times that of the ordinary FR4 printed circuit board, because the insulation layer thickness of the build-up circuit board is only 40um and thinner than the FR4 circuit board, the density in the Z direction is also twice that of the FR4 circuit board Therefore, the circuit density of the entire build-up circuit board can exceed 10 times that of the general FR4 circuit board. Since the circuit density of the build-up circuit board is much higher than that of the FR4 printed circuit board, if the precision required for the process cannot be ensured, the production yield of the build-up circuit board will be greatly reduced.
The glass fiber substrate of the conventional FR4 printed circuit board is formed by laminating a glass fiber cloth containing epoxy resin and copper foil, and using mechanical drilling to form a through hole between the upper and lower layers, and forming it by photo etching line. Therefore, part of the process is mechanical processing, and part of it is chemical processing.
In addition to a small part of the perforation process, the PCB build-up circuit board is basically completed by a chemical process. Because the circuit density is much higher than the traditional FR4 circuit board inspection method for quality control. For the layered circuit board, the control of process errors is very important, so how to select the process control parameters and control the process parameters is a very important task. However, because many process parameters cannot be directly inspected or directly observed, how to monitor these process parameters is one of the key points in determining whether the production technology of the layer-added circuit board is mature.