High-precision eight-layer circuit board is now one of the mainstream finished products in printed circuit boards, because its wiring density is much higher than that of single-sided PCB circuit boards, and electronic components can be installed on both sides; the structure of electronic products is more reasonable. When it appeared, it quickly replaced the single-sided circuit board, and became the basic unit product for the development of PCB multilayer boards. The process is mature and the technology is relatively complicated. The eight-layer PCB circuit board can provide high-efficiency and high-quality single-sided PCB circuit boards, double-sided circuit boards, and high-precision eight-layer circuit board production manufacturers.
Eight-layer circuit board wiring method:
Generally speaking, an eight-layer PCB circuit board can be divided into a top layer, a bottom layer, and two middle layers. The top layer and the bottom layer go through the signal line, and the middle layer first passes the command
DESIGN/LAYERSTACKMANAGER uses ADDPLANE to add INTERNALPLANE1 and NTERNALPLANE2 respectively as the most used power supply layer such as VCC and ground layer such as GND (that is, connect to the corresponding network label. (Be careful not to use ADDLAVER, which will increase MIDPLAYER, which is mainly used for multiple Layer signal line placement) such that PLNNE1 and
PLANE2 is two layers of copper connected to the power supply VCC and ground GND.
If the copper skin is not laid flat, it will definitely wrinkle. The thinner the copper skin is, the higher the final folding chance will be for the PCB multilayer board. The thicker copper skin will produce a flattening effect under pressure and reduce the final folding chance. If it has been confirmed that the copper skin is flat during the operation, it depends on whether it is a problem with the blank area of the substrate. If the film produces a large star flow during the melting process, there will be a possibility that the copper skin will have poor support and slip. Therefore, most circuit board manufacturers will pay attention to the layout of the inner substrate circuit and try to avoid making the empty area too obvious. Most copper skin flame breaks will occur in areas with large differences in line density, especially where one side is designed to have a large copper surface but a large empty area appears.
In addition, the film (PP) combination method and hot pressing parameters are also very important. If the film is superimposed and moved or the flow of glue is not proper, the copper skin will drift on the surface of the molten resin and folds will inevitably occur. To prevent such problems from happening, the carrier plate used for the pressing plate is the focus of the work. At present, most of the plate designs used by the industry have adopted the anti-slip design with elastic height control. This design can completely prevent the steel plate from slipping during the pressing process, so that the resulting snap-off will not occur.
In terms of film selection, try not to use the type with too high glue content within the possible range, and take a lower level in the pressing and heating rate, as long as it can achieve complete filling. If the produced PCB circuit board has wrinkles, it can be considered to remove the surface copper and re-make the lamination when the product specification is loose. Although the plate thickness will be slightly higher; but if the customer specification is acceptable, it can still be remedied.
Let me share with you the processing flow of the high-precision eight-layer circuit board:
Cutting of eight-layer CCL—drilling of reference holes—NC drilling of via holes—inspection, deburring—brushing—electroless plating (metallization of via holes)—full plate thin copper plating—inspection and brushing—screen printing of negative circuit graphics, Curing (dry film or wet film, exposure, development)—inspection, board repair—circuit pattern electroplating—tinning (anti-corrosion nickel/gold)—removing printing material (photosensitive film)—etching copper—removing tin—cleaning and scrubbing—netting Printing solder resist graphics (pasting photosensitive dry film or wet film, exposure, development, thermal curing, commonly used photosensitive thermal curing green oil) ~ cleaning, drying - screen printing mark character graphics, curing - shape processing, cleaning, drying - electrical connection Continuous detection, spray tin or organic solder film inspection, packaging, and finished product delivery.
More than eight layers are divided into vias and blind holes. Vias are opened from the top layer to the bottom layer, and blind holes can only be seen on one of the top or bottom layers, and the other layer cannot be seen, that is to say, blind holes Drills from the surface but does not drill through all layers. There is also a kind of buried hole, which refers to the via hole in the inner layer, and the bottom layer of the surface cannot be seen. The advantage of making buried and blind holes is that it can increase the wiring space.
