Traditional PCBs have been widely in use in almost every electronic device ever since the 1940s. The electronics industry is full of experts on the designing, manufacturing, and assembling of PCBs. Miracle Electronics is one such expert who has the capabilities, skill, and expertise to manufacture the best quality μBGA and surface mount PCB Assembly from India.
There is another similar type of element, the flexible circuit board, which is not much common. While these flexible counterparts were introduced only a decade after the traditional PCBs, they haven’t gained much prominence. Yes, they do have their space in many consumer products like laptops, computers, and smartphones, but they make up only 15% of the worldwide market for printed circuits.
A flexible circuit is a vast array of conductors bonded to a thin dielectric film. They were originally designed as a replacement for traditional wire harnesses, and have been in use since the World War II took place. Ever since, they have been in use for certain applications, although very limited. However, the designing rules for flexible circuits are similar to the designing rules for traditional PCBs. They both share certain similarities in the manufacturing process too.
The only difference between traditional PCBs and flexible circuit boards is the flexibility that the latter possesses. Otherwise, the designing and manufacturing of both the types is generally the same. The materials used are different, to make the latter flexible, but the processes used are otherwise generally the same, at least up till a certain extent. The same printing and etching methods are used for both circuit board types. Both begin with full coverage of copper, with the unwanted areas being etched away from the pattern. Both utilize plating to create through holes and vias to allow multiple conductive layers. However, let us take a detailed look at how similar and dissimilar is the manufacturing process of flexible circuit boards with the manufacturing process of the traditional PCB.
Flexible circuit boards are made generally of copper clad polyimide, which is drilled, plated, photo-images, implanted, and imprinted just like traditional PCBs. The panels are then baked to remove any moisture from the wet processes, just like in the case of traditional PCBs. The processes used after this to manufacture flexible circuits are different from those used to manufacture traditional PCBs. While traditional PCBs are sent to the fuse mask station, flexible circuits are sent instead to the cover lay station, wherein the board is laminated to summarize and protect any peripheral circuitry of the circuit. This cover lay serves the same purpose as the solder mask, but with the added feature of flexibility. The thickness of this cover lay is generally 1 mil polyimide layered with 1 mil thick attached adhesive. However, there could be other thicknesses when certain precise design necessities need to be met. The attachment of the polyimide with the adhesive is done through force and heat; thus making a strong permanent bond! Due to the heat, any gaps among the traces and pads are filled in with the flow of adhesive, to stop the trapping of air between layers.