PCB manufacturing is a complex procedure with various challenges to overcome using multiple contingency steps. Beginning with the design, proceeding through the production of the boards, and concluding the process with packaging & delivery. Generally, computer-guided and automated machinery is used by several printed circuit board companies to ensure accuracy and efficiency in the PCB fabrication process. With stringent quality checks in place, the standard helps the PCB manufacturing sector keep up with the qualitative aspects of the consignments.
The types of machinery being used when it comes to PCB fabrication India are many and to get a better understanding of how it functions let’s move ahead with breaking it down procedure by procedure.
The PCB manufacturing process begins with the designing initiative, the schematic layout has to be made from scratch which will further guide the fabrication process. This schematic is a plan containing all the intended design requirements, for which the designers normally use computers with PCB design software. OrCAD, Altium Designer, KiCAD, Eagle and PADS are PCB manufacturers’ most generic PCB design software. This software produces design output in the standard formats commonly known as Gerber, these formats encode vital information regarding the design for any Indian PCB manufacturer.
Once the manufacturer receives the Gerber file, they perform checks like DFM (Design for Manufacturing), which ensures the design fulfils the basic requirements for executing the manufacturing process.
Once the design checks are complete and the layout is confirmed, the printed circuit board companies move ahead with printing the design files. A specialized printer known as a plotter is used for this task. The output is a film that showcases all the details and layers of the board as a photo negative. Copper conductive traces and pads appear as black opaque areas, while the non-conductive regions remain clear.
After printing, the operator aligns the films and, using a punching machine, creates a registration hole through them. This hole serves as a guide for aligning the films in the subsequent processes.
Indian PCB manufacturers nominally use a copper-clad laminate with copper foil that will be attached to both sides of the dielectric substrate to create a layer pair. A photosensitive film known as the resist is applied to the copper foils, which contains photo-reactive chemicals like ferric chloride or hydrochloric acid. These chemicals harden when exposed to UV rays which come under the UV light blasting procedure.
Then the manufacturer places the corresponding layer films onto the resist which has to be aligned with the copper-clad laminate. Further moving onto the UV light blasting procedure in which the whole setup is exposed to ultraviolet rays allowing the light to pass through the clear areas and reach the resist. Whereas, the black opaque parts of the film block the UV rays.
The exposed areas of the photoresist are hardened by the UV light, leaving the unexposed areas unchanged. Then the board is cleaned with an alkaline solution and pressurized water, removing the excess, unaffected photoresist from the copper surface.
Unwanted exposed copper from the board is removed by the manufacturer using a chemical solution that dissolves the exposed copper on the board. This procedure cleans the board seamlessly leaving intact the copper portion covered by the solidified photoresist.
Once this is executed, all the hardened resist is removed or stripped from the copper surfaces to form the circuit of the inner layer pair. The Indian PCB manufacturer also performs a visual inspection of the board to inspect the circuit on the layers with a backlighted magnifying glass.
The professionals at the printed circuit board companies then align the layer pair with a computer-controlled optical punch machine, using the registration hole as a guiding scope. This machine punches the vias and other required holes, other than this laser drilling machines may also be utilized for further creating blind, buried or micro vias.
After which the manufacturer then employs an automated optical inspection (AOI) technique to examine all inner layer pairs, which is done by a video camera connected to a computer. This device detects defects in the copper circuit pattern on the board layers marking out the corrections to be done. This procedure helps in cleaning the board completely leaving intact the copper portion covered by solidified photoresist.
The multiple-layer pairs are aligned by stacking with a layer of pre-coated epoxy resin known as prepreg. This prepreg is added between each pair along with another sheet of prepreg on both sides of each layer, followed by other layer pairs. This process is repeated after which a press plate is placed on the top and the stack is sent to a lamination press.
The laminating press then applies heat and pressure, causing the epoxy in the prepreg to melt and fuse all the layers into a composite circuit board. Once fused, the press plates are removed by the experts at several printed circuit board companies, and the board is prepared for drilling.
Two outermost layers are added which are single-sided copper clads, that form the top and bottom layers on the boards. Then the Indian PCB manufacturer subjects the entire board to heat and pressure, causing the epoxy to resist melting and bond the layers.
After which the circuit is printed on these external layers using the same process as for the inner layers and are exposed to UV light. Then the manufacturer aligns the circuit board for further drilling as per the registration holes using an X-ray machine to locate the drilling spots. Then as per the Gerber design, the computer-guided drilling machines drill through the complete stack, creating thorough holes, vias, non-plated holes and mounting holes for mechanical components.
Indian PCB manufacturers first strip the hardened photoresist from the board and chemically etch away the excess copper. Then, the protecting tin is added after the plating is removed, finalizing the primary fabrication of the circuit board.
Next, an automated optical inspection (AOI) is performed on the two outermost layers, similar to the inner layers. This inspection ensures that the outer layers conform to the design specifications and do not have any extra or missing copper on the surface.
After thoroughly cleaning the board, a machine applies ink epoxy to both sides and aligns a solder mask film. The board is then exposed to UV light, which sets the solder mask pattern and is subsequently baked in an oven to cure the mask. Further, an inkjet printer is used to apply necessary details, including part numbers, warning labels, manufacturer logos and ID numbers.
The last step of manufacturing PCBs involves covering the exposed copper on the board’s surface with conductive materials. This surface finish protects the copper pads before soldering and ensures a reliable connection between the PCB and electronic components. Indian PCB manufacturers must use Pb-free surface finishes to comply with RoHS and WEEE regulations.
Various tests are conducted by Indian PCB manufacturers in order to check the electrical conductivity of a PCB according to IPC-9252 standards. Tests like circuit continuity, shorts and opens, using mainly two machines; the In-Circuit Tester and the Flying Probe Tester.
PCB fabrication in India involves a detailed process from design to delivery. Drawing out the schematics, printing, etching, testing and adherence to accredited standards like RoHS and WEEE, all sums up the efficient way of manufacturing PCBs. Several printed circuit board companies follow the exact procedures mentioned above or go ahead with any in-house manufacturing technique that suits them, but more or less it remains the same.
At CircuitWala, we utilize automated machinery for PCB manufacturing due to their superior reproducibility, accuracy and reliability. Given the numerous intricate steps involved in PCB production, human error can quickly compromise the complete fabrication process. As an authorized Indian PCB manufacturer, we are inclined towards employing automated means of production. This enables us to confidently handle bulk consignments and quicker response for prototype orders, upholding the highest quality. Check out our online ordering mode to experience the ease of purchasing PCBs!
