Multilayer PCB Production Process
The production of multilayer PCBs involves several steps, from design and fabrication to assembly and testing. Here is an overview of the typical production process:
Design
The design process involves creating the schematic and layout of the PCB using specialized PCB design software. The design includes defining the layer stack-up, trace routing, component placement, and signal integrity considerations.
CAM Processing
Once the PCB design is complete, it undergoes CAM processing. CAM software converts the design data into manufacturing instructions, including generating Gerber files, drill files, and layer-specific information required for fabrication.
Material Preparation
The PCB fabrication process begins with material preparation. The core material, typically FR-4 fiberglass epoxy, is cut into appropriate panel sizes. Copper foil sheets are also prepared in the required thicknesses for the inner and outer layers.
Inner Layer Processing
- Cleaning: The copper foil is cleaned to remove any contaminants
- Lamination: The copper foil is laminated to the core material using heat and pressure
- Imaging: A photosensitive layer called the photoresist is applied to the panel
- Etching: The panel is etched to remove the unwanted copper
- Drilling: Precision holes are drilled in the panel to create vias and component mounting holes
Outer Layer Processing
The outer layer processing involves similar steps as the inner layer, including cleaning, lamination, imaging, etching, and drilling. The outer layer processing also includes the application of soldermask and silkscreen layers.
Multilayer Lamination
Once the inner and outer layers are processed, they are stacked together with layers of prepreg material. The stack is then placed in a hydraulic press and subjected to heat and pressure to bond the layers together.
Plating and Surface Finish
The plated-through holes (vias) are electroplated with copper to ensure electrical connectivity between the layers. The exposed copper surfaces are then treated with a surface finish.
Routing and V-Cut
After the multilayer lamination, the PCB panel is routed to separate individual PCBs. V-cut or scoring techniques may also be used to create perforation lines.
Assembly
The assembled components and soldering take place on the multilayer PCB. This involves the placement of electronic components onto the PCB and soldering them to the copper pads.
Testing and Inspection
Once the assembly is complete, the PCBs undergo various testing and inspection procedures to ensure functionality, electrical continuity, and quality.
Packaging and Shipping
The final step involves packaging the PCBs to protect them during transportation and shipping them to the desired destination.