Steps in Flex PCB Fabrication
When a designer creates a design for a flexible circuit board, they have to consider how it will flex and mount into its enclosure. The design needs to be optimized for production and adhere to smaller design rules than regular PCBs.
After the design is ready, the manufacturing files are generated and sent to the fabricator for the fabrication process. These files include Gerber and drill files. The Gerber file is a set of instructions that guides the fabrication machinery to perform all the necessary steps for creating a flex PCB.
The first step in flex pcb fabrication is to lay down the base material. This is typically FR-4, a glass fiber epoxy laminate. Other materials, such as aluminum, can be used for specific applications.
Once the base material is in place, copper foil is applied to the surface. This is the material that will carry all the electrical signals through the finished rigid-flex PCB. The copper foil is deposited on the base material using photo imaging technology. This is a process that requires precise alignment to ensure the foil is positioned correctly.
Next, the circuit pattern on the copper laminate is etched. This is done by either dipping the laminate in an etching solution or spraying the pattern with an etchant. This is a crucial step that must be performed accurately to avoid damaging the flex circuit board.
Essential Steps in Flex PCB Fabrication
Once the etching process is complete, the flex circuit board must be cut to size. There are several different techniques for cutting the flex circuit board, but hydraulic punching is the most preferred method. It allows for precision cutting and produces very little waste. This method also allows for fast and efficient production, which is important for a manufacturer.
Finally, the flex circuit board must be laminated between the rigid sections of the board. This is a process that involves heat, pressure, and adhesives. This step is necessary to ensure that the flex circuit boards are properly aligned and connected with each other. It is also important to use high-quality adhesives for this step.
After the flex-rigid assembly is complete, it must undergo inspection and cleaning. This is a crucial step that ensures the rigid-flex PCB meets its minimum design specifications. It also enables the technician to see any areas that need to be repaired or replaced.
Once the flex-rigid assembly has passed inspection and cleaning, it is ready for the final stage of fabrication. This is the process of plating the copper traces and pads on both sides of the board. This process is very similar to the one that is used for standard PCBs. However, a special type of copper coating is required for flex-rigid circuits to withstand dynamic bending. This coating is known as HASL (High-Temperature Air-Location System). This special material helps the flex circuit board maintain its performance under temperature fluctuations. This is especially important for devices like disk drives that are designed to flex hundreds of times per day.