Steps in PCB Circuit Board Manufacturing
Printed circuit boards are fascinating things. Every day, you allow us to fabricate your printed circuit boards that go into everything from personal electronics to airplanes, and robots to research projects. It's our responsibility to deliver top quality products for these important projects. There are several unique steps in the PCB manufacturing process. This circuit board manufacturing tutorial will walk you through our PCB manufacturing process step-by-step for a double sided PCB.
Step 1: Film Generation
Films for all of the copper and soldermask layers are made from photographically exposed mylar. We generate these films from your design files, creating an exact (1:1) film representation of your design. When Gerber files are submitted, each individual Gerber file represents one layer of the PCB.
Step 2: Select Raw Material
Industry standard 0.059" thick FR-4 laminate copper clad on two sides. Panels will be sized to accommodate many boards.
Step 3: Drill Holes
Through holes required for your PCB design are created from your submitted files, using NC drill machines and carbide drill bits.
Step 4: Electroless Copper
In order for the through holes to electrically connect to different layers of the PCB, a thin layer of copper is chemically deposited into the through holes. This copper will later be thickened through electrolytic copper plating (step 6).
Step 5: Apply Photo-resist and Image
To transfer the PCB design from the electronic CAD data to the physical circuit board, we start by applying photosensitive photo-resist to the panel,covering the entire board area. Then the copper layer film image (step 1) is placed over the board, a high intensity UV light source exposes the uncovered portion of the photo-resist. Then we chemically develop the board (remove the unexposed photo-resist from the panel) creating the pads and traces.
Step 6: Pattern Plate
This step is an electrochemical process which builds copper thickness into the holes and onto the surface of the PCB. Once the copper thickness is built up on the circuitry and in the holes, we plate and additional layer of tin to the exposed surface. This tin will protect the plated copper during the etching process (step 7) and be later removed.
Step 7: Strip & Etch
This process takes place in multiple steps. The first is to chemically remove (strip) the photo-resist from the panel. Then the newly exposed copper is chemically removed (etched) from the panel. The tin applied in step 6 protects the desired copper circuitry from being etched. At this point, the fundamental circuitry of the PCB is defined. Finally, the protective layer of tin is chemically removed (stripped) to expose the copper circuitry.
Step 8: Soldermask
Next we coat the entire panel with a liquid soldermask layer. Using films and high intensity UV light (similar to step 5) we expose the solderable areas of the PCB. The main function of the soldermask is to protect the majority of the copper circuitry from oxidation, damage and corrosion as well as maintain isolation of the circuits during assembly.
Step 9: Nomenclature (silkscreen)
Next we print the reference designators, logos, and other information contained in the electronic files onto the panel. This process is very similar to an inkjet printing process, but designed specifically for PCBs.
Step 10: Surface Finish Applied
The final surface finish is then applied to the panels. This surface finish (tin / lead solder or immersion silver) is used to protect the copper (solderable surfaces) from oxidation as well as act as a site for soldering of components to the PCB.
Step 11: Fabrication
Last, but not least, we route the perimeter of the PCB from the larger panel using NC equipment. The PCB is now complete, and is quickly shipped off to you — our happy customer!