PCB Tech - How to check PCB build-up circuit board

How to check PCB build-up circuit board

Printed Circuit Board Factory Editor: A comparison of the hole diameter of the 300um drilled pin hole in the general FR4 fiberglass board circuit board and the 100um pin hole in the PCB build-up circuit board. Because the signal lines are arranged along the X direction and the Y direction, a bolt hole must be arranged at the intersection of the X and Y direction wires to allow conduction between the upper and lower layers. The bolt holes are arranged in an oblique line direction, and 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 pin holes. The number of bolt holes that can be accommodated per inch square area is expressed in units of VPSG.

The pinhole density of FR4 circuit board is only 4VPSG, while the pinhole density of PCB build-up circuit board is as high as 20VPSG. In addition to the build-up circuit board plane circuit density is 3 times that of the general FR4 printed circuit board, since 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 manufacturing process cannot be ensured, the production yield of the build-up circuit board will be greatly reduced.

The glass fiber substrate of the traditional FR4 glass fiber board printed circuit board is laminated with a glass fiber cloth containing epoxy resin and a copper foil, and then mechanically drilled to form a perforation between the upper and lower layers, and photoetched Way to form a line. Therefore, part of the manufacturing process is mechanical processing, and part is chemical manufacturing.

PCB build-up circuit boards are basically completed by chemical processes except for a small part of the perforation process. Because the line density is much higher than the traditional FR4 fiberglass board circuit board inspection method for quality control. For the build-up circuit board, the control of the process error is very important. Therefore, how to select the process control parameters of the circuit board and the control process parameters is a very important work. However, since many circuit board process parameters cannot be directly inspected or observed directly, how to monitor these circuit board process parameters is one of the key points in determining whether the mass production technology of build-up circuit boards is mature or not.