The Various Steps of the PCB Manufacturing Process
The pcb manufacturing process includes several steps, from design to assembly. During the manufacturing process, all critical elements are reviewed and strictly controlled to guarantee quality results.
Local PCB contract manufacturers often cultivate relationships with fabricators that offer quick turnaround times for bare boards. These fabricators will work with the CM to provide Design for Manufacturability guidelines that help the original equipment manufacturer create designs that are compatible with their fabrication process.
The Design Process
The design process for PCBs involves creating a product concept, schematic entry and layout design. The output files are then converted into a physical board on which components can be placed and soldered. The manufacturing and inspection processes may vary slightly between manufacturers, but the general steps are similar.
Once the design is finalized, the contract manufacturer receives a bill of materials and begins sourcing the necessary components. During this phase, the CM will also review pcb manufacturing the design for manufacturability. This includes reviewing the component placement and critical nets routing to ensure that the design can be manufactured at a reasonable cost.
Next, the design is transferred to a piece of laminate material. A copper foil layer or coating is pre-bonded to this laminate, which functions as the structure for the circuit board. This layer is then etched away, revealing the earlier discussed design blueprint. Finally, the photo-sensitive film known as resist is applied to the exposed area of the laminate and hardened by exposure to ultraviolet light.
Then, a machine compares the digital image to the original Gerber file to confirm that there are no errors in the layers. The outer layers of the laminate are then aligned using the holes that were punched in earlier. Lastly, the drilled layer is inspected by another machine to confirm that the copper is free of defects and that the laminates are free of errors.
The Fabrication Process
The fabrication process is where the PCB’s actual structure begins to take shape. It involves several critical steps that are carried out with computer-guided tools and automated machinery to guarantee speed, efficiency, and high-performing standard PCBs. This stage encompasses a variety of important tasks that range from preparing the laminate for drilling to testing the finished product.
The first step in the process involves pre-bonding the copper foil layer to the laminate. After that, NextPCB uses a photo-sensitive film to cover the laminate panel with photo-reactive chemicals that harden under ultraviolet light. Then, the panel is etched to reveal the previously discussed design blueprint. Finally, the exposed copper is plated with tin to protect it from corrosion and damage.
This step is vital to the manufacturing process as it ensures that the PCB will be made according to the manufacturer’s specifications. It also allows the engineer to check for any potential errors that can be corrected before the board is assembled and soldered.
Once the virtual schematic diagram is ready, the next step in the process is component placement. This is a crucial part of the process that helps to determine how many layers are needed, as well as other technical specifications. The OEM and CM must communicate closely during this step to prevent any confusion in file formats.
The Inspection Process
There are always a number of mistakes that can happen to a PCB – even when the proper design and fabrication processes are in place. This is where inspection and testing come in. Identifying and resolving these issues before the PCB is produced and delivered to a customer is critical to quality control.
After the Gerber Extended software has successfully encoded the blueprint for a board, the fabricator performs an additional check called a Design For Manufacture (DFM) inspection to see if all elements meet requirements. This includes verifying that the layout complies with requirements for track width, board edge and trace spacing, and hole size.
At this stage, a technician inspects each layer of the board for defects. A PCB Manufacturing Supplier multi-layer board requires a total of four clear and black film sheets, while a simple two-layer board skips this step. Each sheet must match up perfectly with the copper areas that will emerge once the board is etched and exposed to the solder mask. This is an important inspection step that can help to avoid rework costs down the road if it is not done correctly.
This is also where the components reference designators and other documentation are silkscreened onto the board. If this process isn’t properly inspected and documented, it can lead to mismatched parts, which can cause problems in the assembly process later on down the line. This is why a first article inspection process is important, which involves inspecting a random sample of the first production run of a PCB. This process can detect errors that would have otherwise gone undetected – which could cost thousands of dollars in rework and other costs down the road for customers.
The Testing Process
The next phase of the pcb manufacturing process involves testing the boards for defects. This is a crucial step because if there are any errors found at this stage, they’ll be impossible to fix later in production. This testing can include DFT (Design for Test) tests that run checks against the Gerber files, E-testing that uses electrical probes to verify the conductivity of each unpopulated circuit board, and ICT and flying probes that are more detailed tests.
For ICT testing, fixed probes that are arranged according to the PCB’s layout are used to test each solder connection for its integrity. This can be a good alternative to more expensive flying probe or Bed of Nails tests.
This method compares the digital image of each layer with its corresponding Gerber file, then flags any inconsistencies to the technician. This helps to prevent human error and ensures that the finished product is as expected.
This step is necessary for ensuring that the layers are properly aligned for copper insertion. It follows a similar procedure to inner layer imaging, with the design printing on a plotter printer and the solder mask being printed out as well. A machine then drills registration holes in the two films to help with alignment when they’re added together and infused with copper. This is the final step in the manufacturing plan and gives a go/no-go decision on whether the product will power up as expected.