Flexible circuit boards are an important aspect of the modern slim and compact electronic products. As a circuit board, it has the same functionality and arrangements but has a different support substrate for the components and the copper trace. So, manufacturing such flexible circuits takes some special steps. The overall process of flex board manufacturing includes few additional processes than the actual circuit board manufacturing process.
The manufacturing process starts with the CAD design as usual but the designer must take some extra steps to place key components and fragile circuitry away from the stress points.
The flex board design must align the components parallel to the direction of the intended bending position to minimize the stress on the solder joint and copper strip beneath it.
Flex Board Laminate Preparation
After the CAD design, the flex pcb manufacturing heads to copper laminates for the flex board. A thin layer of heat resistant polymer of similar material is prepared and cut to the desired shape and size.
The sheet if heat resistant base is coated with a heat-induced adhesive on of sides.
A thin layer of copper sheet is placed over the adhesive layer and heat pressed for several hours to bond them together.
A second protective layer is usually added to the flex board manufacturing to strengthen the surface and to bear the temperature and stress placed on the board.
Circuit Etching Process
The PCB design is converted to a graphical image and imposed on the flex board laminate with UV curable masking paste and a computerized UV exposed. This step marks the copper for the circuit connection and leaves the unwanted copper exposed.
The sheet is carefully transferred to the chemical treatment bath for etching the excess copper way. A powerful industrial solvent is used to etch the copper. The flex board manufacturing includes the number of washes to ensure the elimination of chemical and flux residue.
For the solder mask, unlike traditional methods, the flex pcb manufacturing process covers the entire copper trace with a thin layer of the laminate sheet in which the required holes are pre-pressed.
Assembly and Testing in Flex Board Manufacturing
The next step in the flex board manufacturing is the silkscreen layer printing. This marks the component’s outline and alignment marks.
As these flex boards are usually tiny the assembly is mostly done by high-resolution robots. Some of the complex components are soldered by hand.
The flex pcb manufacturing tests the board in each layer for defects and misalignments.