As soon as the manufacturer gets the design file, they will check for issues that could affect the functionality or the PCB manufacturing process. This can eliminate problems and cut down on expenses. Once everything has been sorted, the manufacturing can begin. How is a PCB manufactured step by step? Read on to find out:
Step 1: Solder Paste Application
A thin metal stencil is placed over the PCB so that only the uncovered parts can get contact with the solder paste. The solder, mostly made of tin, with a bit of silver and copper, is melted and bonded to the surface.
Step 2: Pick and Place
A robotic arm picks the components and places them at precise locations on the PCB surface. In the past, workers would do this manually using tweezers but this was slow and prone to errors, especially once fatigue sets in. Automation improved consistency and accuracy despite long work periods.
Step 3: Reflow Soldering
In this step, the components are kept in place by solidifying the solder paste. The board is taken to a conveyor belt that moves through an oven with heaters that increase PCB temperature to melt the solder. It then passes through cooler heaters to gradually bring down the temperature. This ensures a permanent solder joint between the components and the PCB.
Step 4. Quality Control
Testing must ensue to check for functionality. Sometimes too much movement during reflow soldering results in bad connections and shorts. Misplaced components may touch areas that it should not be connected to. These errors may be found through manual checks such as in-person visual inspections. In large-scale manufacturing, it is more practical to implement automated optical inspection. This is much faster which reduces bottlenecks. For layered PCBs, it is possible to use X-ray inspection to check the interior and find hidden issues. Boards that fail the test reworked or scrapped completely.
Step 5: Component Insertion
Surface-mounted devices are not the only things that go into the PCB. Through-hole components may be needed as well. The holes enable them to pass signals from one side to another on the board. Since soldering paste is unsuited, manufacturers may use manual soldering to keep these components in place. Others rely on wave soldering to automate the process. In the case of two-sided boards, the unit may go back to step one until both sides are finished.
Step 6: Final Test
The PCB is ready for the final inspection. This will test its functionality to ensure that everything works as intended. Power is applied at the terminals and signals are simulated to check the electrical characteristics on the board. If acceptable fluctuations are found, then it passes the test. If current, voltage, or signal levels fall outside a specified range, then it fails. Failed boards may be scrapped or recycled.
Step 7: Cleaning
Boards can look filthy right after manufacturing. They need to be cleaned up to remove flux residue, oils, and dirt. Humans who touched them may leave fingerprints behind. Washing is necessary to remove all of these. High-pressure de-ionized water is used to get the job done without inflicting damage. The PCBs are dried using compressed air before packaging and shipment.