PCB Multilayer Circuit Board Production Process (1)

The purpose of blackening and browning:
A. Remove contaminants such as oil and impurities on the surface.
B. Enlarge the surface of the copper foil, thereby increasing the contact area with the resin, which is conducive to the full diffusion of the resin and the formation of greater bonding force.
C. Turn the non-polar copper surface into a polar CuO and Cu2O surface to increase the polar bond between the copper foil and the resin.
D. The oxidized surface is not affected by moisture at high temperatures, reducing the chance of delamination between the copper foil and the resin.
E. The internal circuit board must be blackened or browned before it can be laminated. It is to oxidize the copper surface of the inner board. Generally, Cu2O is red and CuO is black, so Cu2O in the oxide layer is mainly called browning, and CuO-based is called blackening.

1. Laminating is the process of bonding each layer of circuits into a whole with the help of B-stage prepreg. This kind of bonding is achieved through the mutual diffusion and penetration of macromolecules at the interface, and then interweaving.

2. Purpose: Press the discrete multi-layer board together with the bonding sheet into a multi-layer board with the required number of layers and thickness.
2.1 Typesetting copper foil, bonding sheet (prepreg), inner layer board, stainless steel, isolation board, kraft paper, outer layer steel plate and other materials according to the process requirements. If the board is more than six layers, pre-typesetting is required.
2.2 During the lamination process, the laminated circuit board is sent to a vacuum heat press, and the heat energy generated by the machine is used to melt the resin in the resin sheet, thereby bonding the substrate and filling the gap.
For the designer, the first consideration for lamination is symmetry, because the board will be affected by pressure and temperature during the lamination process, and there will be stress in the board after the lamination is completed. If the laminate is laminated The two sides of the board are not uniform, and the stress on the two sides is different, causing the board to bend to one side, which greatly affects the performance of the PCB.
In addition, even in the same plane, if the distribution of copper is not uniform, the resin flow speed at each point will be different, so that the thickness of the place with less copper will be slightly thinner, and the thickness of the place with more copper will be slightly thicker. In order to avoid these problems, various factors such as the uniformity of the copper distribution, the symmetry of the stack, the design and layout of the blind and buried holes, etc. must be considered in detail during the design.