PCB Manufacturer Handle Multi-Layer Designs
Multi-layer designs are common in PCBs used in professional and commercial electronic devices. They provide increased functionality and capacity in a compact size that is easier to fit into tight spaces than single-layer boards. However, the process for making a multi-layer board is complex and requires high-precision. How does a pcb manufactures handle these intricate and delicate processes?
In multi-layer printed circuit boards (PCBs), thin layers of different prepreg and copper foil sheets are layered together to form the PCB. The stack is then put into a press and subjected to high heat and pressure. The resulting lamination bonds the copper layers and dielectric layers into one solid unit. The PCB is then etched to remove the copper and prepare it for layer registration, inner layer automated optical inspection, and oxide application.
First comes the substrate, a piece of laminate material that serves as the pcb manufactures foundation and provides strength and flexibility. Next is the copper layer, which can either be a copper foil or a full-on copper coating. Either way, its purpose is to carry electrical signals within the PCB, much like your nervous system carries messages from your brain to your muscles. After the layers are etched, they are ready for a computer-guided machine called an optical punch to punch holes through them and align them. The punching also ensures the alignment of the outer and inner layers. Once the layers are aligned, they are sent to a machine that performs inner layer automated optical inspection (AOI). This inspects for complete patterns and fuses the copper to the surrounding epoxy resins.
How Does a PCB Manufacturer Handle Multi-Layer Designs?
If the AOI passes, the inner layers are prepared for oxide application. Oxide is applied to the inside surface of the inner layers, which improves bonding between the copper foil and insulating epoxy resin layers that make up the core of the multi-layer PCB. This step also enables the multi-layer PCB to be drilled more easily.
After the layers are prepped, they are bonded together using prepreg materials and then cured under extreme heat and pressure. The resulting multi-layer PCB is then ready for assembly and testing.
During the assembly phase, the PCB is inspected for defects and compared to the Extended Gerber design that served as the manufacturer’s model. The manufacturer can then correct any errors that may have been caused during the manufacturing process, and the multi-layer PCB is ready to go into production.
The multi-layer PCB fabrication process is complicated, and it takes longer than a single-layer board. The extra steps of layer registration, inner layer fabrication, and lamination add up to a longer production time than with a single-layer board. The complexity of the internal signal layers, power planes, and blind/buried vias also increases the production time.
The fabricator and the OEM must have a close relationship to ensure that the PCB is fabricated according to the original design specifications. In addition, the two groups must communicate well to ensure that the correct files are used when sharing information. This can be difficult if the fabricator uses a different file format than the original designer did. To reduce the risk of error, both parties should use the same file format throughout the entire design and fabrication process.
