**Eight-Layer Circuit Board Manufacturing Process**
1. High-precision eight-layer circuit boards have become one of the most common products in the printed circuit board (PCB) industry. Their wiring density significantly exceeds that of single-sided PCBs, and they allow for components to be installed on both sides, optimizing the structure of electronic products. As a result, these boards quickly replaced single-sided PCBs and became the foundational product for the development of multi-layer PCB technology. The technology is both mature and complex, enabling eight-layer PCBs to deliver high-performance, high-quality solutions for single-sided and double-sided PCBs, as well as high-precision eight-layer circuit boards.
2. **Eight-Layer Circuit Board Wiring Method**:
Generally, an eight-layer PCB consists of a top layer, a bottom layer, and two internal layers. The top and bottom layers are used for signal lines. The internal layers are created by using the command DESIGN/LAYERSTACKMANAGER to add INTERNALPLANE1 and INTERNALPLANE2, which serve as power planes such as VCC (power) and GND (ground). These internal planes are linked with the corresponding network labels. (Be cautious not to use ADDLAYER, as this will create additional layers.) This process will add two middle layers (PLANE1 and PLANE2), which are primarily used to connect the power (VCC) and ground (GND) planes and are key for routing multi-layer signal lines.
1. If the copper foil is not properly laid flat, it can crease. The thinner the copper foil used in a PCB multilayer board, the higher the likelihood of creasing. Thicker copper foils tend to have a self-flattening effect, reducing the chance of creasing. Once it is confirmed that the copper foil is flat during processing, the next factor to consider is whether it is in a blank area of the substrate. If the film experiences excessive flow during the melting process, the copper foil may lack sufficient support and slip. For this reason, most circuit board manufacturers carefully control the inner substrate layout and aim to avoid overly large blank areas. Creases are more likely to occur in areas with significant line density differences, particularly where there is a large copper surface next to an empty area in the design.
2. In addition, the combination method of the film (PP) and the hot pressing parameters plays a critical role. If the film overlaps or moves improperly, or if the adhesive flow is not controlled correctly, the copper foil may shift on the molten resin surface, causing creases. To prevent such issues, the carrier plate used in the pressing process is a key consideration. Most industry designs for carrier plates now use elastic and highly adjustable sliding block mechanisms. This design effectively prevents the steel plate from slipping during the pressing process, thereby eliminating the risk of creases.
3. When selecting the film, it is advisable to avoid using types with excessive adhesive content and to choose lower pressing and heating rates, as long as the filling process is completed. If a PCB has wrinkles, and the product specifications are flexible, one option is to remove the surface copper and re-press the board. While this will increase the board’s thickness slightly, it can still be remedied if the customer’s specifications allow for it.
4. The editor of Shenzhen Circuit Board Factory shares the processing flow for high-precision eight-layer circuit boards:
– Eight-layer copper-clad board blanking
– Drilling of reference holes
– CNC drilling of via holes
– Inspection
– Deburring and brushing
– Electroless plating (through-hole metallization)
– Electroplating of thin copper across the entire board
– Inspection, brushing, and screen printing of negative circuit patterns
– Curing (dry film or wet film, exposure, development)
– Inspection, repairs, and circuit pattern plating
– Tin electroplating (anti-corrosion nickel/gold)
– Removing the printed photosensitive film
– Copper etching and tin stripping
– Cleaning and brushing
– Screen printing of solder resist graphics (applying photosensitive dry or wet film, exposure, development, thermal curing, typically using photosensitive green solder mask)
– Cleaning, drying, and screen printing of marking characters
– Curing, shaping, cleaning, drying
– Electrical communication break inspection
– Spraying tin or applying organic solder mask
– Final inspection, packaging, and shipment of the finished product.
5. The eight-layer PCB may include vias and blind vias. Vias are holes that run from the top layer to the bottom layer. Blind vias are visible only from one of the outer layers (top or bottom), and are not visible from the opposite side; the hole is drilled from the surface but does not go through all layers. There is also the concept of buried vias, which are holes located within the inner layers, making them invisible from both the top and bottom layers. The advantage of using buried and blind vias is that they help to increase available routing space.
1. High-precision eight-layer circuit boards have become one of the most common products in the printed circuit board (PCB) industry. Their wiring density significantly exceeds that of single-sided PCBs, and they allow for components to be installed on both sides, optimizing the structure of electronic products. As a result, these boards quickly replaced single-sided PCBs and became the foundational product for the development of multi-layer PCB technology. The technology is both mature and complex, enabling eight-layer PCBs to deliver high-performance, high-quality solutions for single-sided and double-sided PCBs, as well as high-precision eight-layer circuit boards.
2. **Eight-Layer Circuit Board Wiring Method**:
Generally, an eight-layer PCB consists of a top layer, a bottom layer, and two internal layers. The top and bottom layers are used for signal lines. The internal layers are created by using the command DESIGN/LAYERSTACKMANAGER to add INTERNALPLANE1 and INTERNALPLANE2, which serve as power planes such as VCC (power) and GND (ground). These internal planes are linked with the corresponding network labels. (Be cautious not to use ADDLAYER, as this will create additional layers.) This process will add two middle layers (PLANE1 and PLANE2), which are primarily used to connect the power (VCC) and ground (GND) planes and are key for routing multi-layer signal lines.
1. If the copper foil is not properly laid flat, it can crease. The thinner the copper foil used in a PCB multilayer board, the higher the likelihood of creasing. Thicker copper foils tend to have a self-flattening effect, reducing the chance of creasing. Once it is confirmed that the copper foil is flat during processing, the next factor to consider is whether it is in a blank area of the substrate. If the film experiences excessive flow during the melting process, the copper foil may lack sufficient support and slip. For this reason, most circuit board manufacturers carefully control the inner substrate layout and aim to avoid overly large blank areas. Creases are more likely to occur in areas with significant line density differences, particularly where there is a large copper surface next to an empty area in the design.
2. In addition, the combination method of the film (PP) and the hot pressing parameters plays a critical role. If the film overlaps or moves improperly, or if the adhesive flow is not controlled correctly, the copper foil may shift on the molten resin surface, causing creases. To prevent such issues, the carrier plate used in the pressing process is a key consideration. Most industry designs for carrier plates now use elastic and highly adjustable sliding block mechanisms. This design effectively prevents the steel plate from slipping during the pressing process, thereby eliminating the risk of creases.
3. When selecting the film, it is advisable to avoid using types with excessive adhesive content and to choose lower pressing and heating rates, as long as the filling process is completed. If a PCB has wrinkles, and the product specifications are flexible, one option is to remove the surface copper and re-press the board. While this will increase the board’s thickness slightly, it can still be remedied if the customer’s specifications allow for it.
4. The editor of Shenzhen Circuit Board Factory shares the processing flow for high-precision eight-layer circuit boards:
– Eight-layer copper-clad board blanking
– Drilling of reference holes
– CNC drilling of via holes
– Inspection
– Deburring and brushing
– Electroless plating (through-hole metallization)
– Electroplating of thin copper across the entire board
– Inspection, brushing, and screen printing of negative circuit patterns
– Curing (dry film or wet film, exposure, development)
– Inspection, repairs, and circuit pattern plating
– Tin electroplating (anti-corrosion nickel/gold)
– Removing the printed photosensitive film
– Copper etching and tin stripping
– Cleaning and brushing
– Screen printing of solder resist graphics (applying photosensitive dry or wet film, exposure, development, thermal curing, typically using photosensitive green solder mask)
– Cleaning, drying, and screen printing of marking characters
– Curing, shaping, cleaning, drying
– Electrical communication break inspection
– Spraying tin or applying organic solder mask
– Final inspection, packaging, and shipment of the finished product.
5. The eight-layer PCB may include vias and blind vias. Vias are holes that run from the top layer to the bottom layer. Blind vias are visible only from one of the outer layers (top or bottom), and are not visible from the opposite side; the hole is drilled from the surface but does not go through all layers. There is also the concept of buried vias, which are holes located within the inner layers, making them invisible from both the top and bottom layers. The advantage of using buried and blind vias is that they help to increase available routing space.
