Various Stages of PCB Manufacturing
PCB manufacturing has different stages. PCB manufacturing starts with designing. The design is made with different computer software like CAD system. Every design system has its own data formats. The standardized data required for the manufacturer. This problem is solved by Extended Gerber. The Gerber files define copper paths, solder masks and components notations. After designing the file is printed in with special printer called plotter which makes photo films of PCBs.
This printer is a laser printer with high precision printing technology which detailed make a detailed film of PCB. After printing the film resulted in a plastic sheet with a photo of PCB in black ink which indicates the copper parts of the PCB. Next step is to print the figure on the copper foil. The core material is a mixture of epoxy resin and glass fibre. This laminate is for receiving the copper structure of the PCB. This laminate provides sturdy and dust-resistant structure for PCB. The copper is pre-bonded on both sides and provides whittling away the copper for the design. The cleanness is most important in PCB manufacturing.
If a small dust particle is on the PCB and PCB is damaged. The panel receives a layer of photo-sensitive film and a layer of photo reactive chemicals and hardens after take it to the UV light. The black ink prevents the UV lights that not to harden. When the board is made it is washed with an alkaline solution which removes unhardened photo-resistant. After this, the board is dried up for the next process. The board is examining by a technician and give approval on it for next process. In this process, the unwanted copper is removed with alkaline solutions. The copper solvent removes access to copper and remains the hardened layer. Layer alignment process aligns the two layers and punched them. After them, it is impossible to correct any defect. Another machine inspects optically for confirming that the board is defectless.
The two-layer boards consist of fibre glass sheet with epoxy resin and this mixture called prepreg. There is thin copper foil covers the top and bottom. The bonding process happens at a steel table with metal clamps. The prepregs need to fit the pins of the table to be aligned. An aluminium foil and copper press complete the board and are ready for pressing. The whole process is controlled and done by computer. With the layers are moulded together the PCB is ready for drill and other processes.
The holes are the drill with very preciously. The holes are drilled to a diameter of 100 microns which is less than the diameter of a hair. After drilling the board goes for plating. The board is under goes with a bath of different chemicals which makes one-micron thick copper layer on it and covered all drilled holes with it. The whole process is controlled by computer and does precisely of dipping, removal and procession. The plating process has tin plating for removing excess copper on the board. The final etching process removes the unwanted copper from the board and tin saves the required copper. Before the solder mask applied the board is cleaned and covered with epoxy solder mask ink. Then the board is taking the UV light and cover portion is unhardened. The board is placed in an oven to cure the solder mask. The final electrical test is performed on PCB to ensure that customer get the best product.
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