How Are Printed Circuit Boards Manufactured?

Printed Circuit Boards or PCBs form the backbone of all major electronics like computers, televisions, smartphones, digital cameras, calculators, digital electronics, etc. A PCB is responsible to direct electrical signals through electronics, which satisfies the device’s electrical and mechanical circuit requirements. In short, PCBs are the components that tell the electricity where to go, thus bringing your electronics to life. PCBs direct the current around their surface through a network of copper pathways, the complex system of which determines the unique role of each piece of the PCB.

To design a PCB, circuit designers and fabricators communicate with each other over the manufacturing demands, which reduces the risk of errors in the designing stage. There are various stages involved in the production of PCBs, which are mentioned in this blog. A leading manufacturer like Miracle Aerospace takes care that all these processes are precisely followed to provide clients with the best quality PCB assembly from India.

1)    A PCB design software is used to create a PCB layout. The most commonly used PCB design software include OrCAD, KiCad, Pads, Eagle, and Altium Designer. The designers are required to inform the contract manufacturer about the software version used, so that any issues caused by discrepancies are avoided. Once the design is approved, designers export the design into the format that the manufacturers support. The most frequently used program is extended Gerber. Different PCB design software calls for different Gerber file generation steps, encoding comprehensive vital information like copper tracking layers, apertures, drill drawing, component notations, etc. All the aspects are checked to ensure that no errors go undetected. After a thorough examination, the PCB files are forwarded to PC Board Houses for production, where design-for-manufacture checks are performed.

2)    A special printer known as the plotter is used to make photo films of the PCBs to print circuit boards. These films are used to image the PCBs using incredibly precise printing technology to provide a highly detailed film of the PCB design. The final product is a plastic sheet with a photo negative of the PCB in black ink. For the inner layers, the black ink represents the conductive copper parts of the PCB, and the clear portion denotes the areas of non-conductive material. On the other hand, for the outer layers, the black area refers to that of non-conductive material, and the clear areas denote the copper parts. The film is developed by the plotter, which is securely stored to prevent any unwanted contact. Each layer of PCB and solder mark receives such clear and black film sheet, thus mapping out the PCB alignment. To achieve perfect alignment, registration holes are punched through all films.

3)    Here, the actual PCB is constructed. It is a laminate board of epoxy resin and glass fiber. Copper is pre-bonded on both sides, which is whittled away to reveal the design from the films. The copper-sided laminate is cleaned, and passed into a decontaminated environment such that no dist particles settle on the surface, or else the circuit could be short or remained open. The clean panel then receives a layer of photo-sensitive film, which comprises of a layer of photo reactive chemicals that harden after exposure to UV light. This ensures an exact match, which are fit onto pins that hold them in place over the laminate panel. The UV light passes through the clear parts of the film, hardening the photo-sensitive film on the copper; the other areas slated for removal. The board is then washed with alkaline solution that removes any unhardened areas, and then dried.

4)    Next, a powerful chemical preparation is used on the board to remove any excess copper. In this way, the desired copper remains completely protected.

5)    With clean layers, alignment punches are required to line up all the layers. The registration holes align the inner layers to the outer layers, which are placed into a machine called optical punch for accurate punching.

6)    Now, the layers are fused together, where the outer layers are joined with the substrate through layering-up and bonding. The top and bottom of the original substrate are covered by a thin copper foil. All of this is then sandwiched together, such that any shifting is prevented during alignment. A bonding press computer is used to heat up the stack by applying pressure at the right places, and having it cooled at a controlled rate. The multi-layered PCB product are then unpacked.

7)    Then precision drill holes are bored into the stack board, with an X-ray locator identifying the proper drill target spots. The additional copper that lines the edges of the production panel then undergoes removal by a profiling tool.

8)    The next step is plating, where the different layers are fused together using chemical deposition. The panel then undergoes a series of chemical baths, which deposits a thin layer of copper over the surface of the panel.

9)    The photo-sensitive film is now reapplied to the panel, with the exception of the outer layers being imaged with the PCB design.

10)           The panel is then electroplated with a thin layer of copper, and then tin plated where the tin guards the section of the panel meant to remain covered with copper during the next etching stage to remove unwanted copper foil from the panel.

11)           The unwanted exposed copper again undergoes removal through application of chemical solution.

12)           The next stage is applying the solder mask to both sides of the board, before which the panels are cleaned and covered with an epoxy solder mask ink. The board is then passed into an oven to cure the solder mask.

13)           Next, the board is plated with gold and silver, and provided with hot air-leveled pads to result in uniform pads. The board is then provided with ink-jet writing that is used to indicate all vital information pertaining to the PCB. Finally, the PCB passes onto the last coating and curing stage.

14)           Finally, all possible electrical tests are performed on the PCB to check for errors; after which the boards are cut from the original panel.