From Concept to Creation: The PCB Manufacturing Process Explained
These days, it is rare to find yourself in a place where you are not completely surrounded by electronics. Whether it be phones and computers or household appliances and medical devices, we have come to rely on such items in many different facets of our lives.
Although there are many thousands of different electronic devices today in the modern world, and these products differ from one another in several ways, one element that many of them share is that they are manufactured with printed circuit boards (PCBs) at their core.
Most major electronics rely on PCBs to route electrical signals through them, thus satisfying their electrical and mechanical circuit requirements and bringing them to life.
What are the main steps of the PCB manufacturing process?
Before making their way into your electronic devices, PCBs must go through a multi-stage fabrication process, and each step of this process is crucial. In order to create an end product that is both functional and of high quality, a lot of time, planning, and consideration must go into each of these steps.
The following are the main stages in the PCB manufacturing process, as well as descriptions of the kind of work that must go into each of these steps:
1. Creating the design
As you might have imagined, the first stage in the PCB manufacturing process is the design stage, as it is always necessary to start with a plan. During this stage, the PCB’s designer (or designers) must create a blueprint for the PCB that meets all of its established requirements. PCB designers typically use some sort of design software to lay out this blueprint.
One of the most common types of design software in use is called Extended Gerber. Extended Gerber encodes all of the information the designer needs, like the number of solder masks or copper layers that are required. Then, all of the various components of the design can be thoroughly observed in search of errors.
2. Design review
Next, an engineer must review the design, thoroughly checking everything to see that there are no missing parts or structures that have been incorrectly placed or designed.
If some design errors are discovered, it might be necessary to go back to the drawing board. However, with a stamp of approval from an engineer, the PCB can then move on to the printing stage.
The third stage involves printing a transparent “film” of the PCB using a special device called a plotter printer. This film marks the inner and outer parts of the PCB with black and clear ink. For the inner elements of the design, the copper traces and circuits are marked in black ink, whereas the non-conductive parts are marked with clear ink. For the outer layers of the design, black ink shows areas where the copper will be removed, and clear ink denotes the copper pathways.
Once all of a PCB’s sheets have been printed, a registration hole is punched through them, which helps to align the sheets later on.
4. Copper printing
The manufacturer can now affix a copper foil layer or copper coating to the printed laminate film sheets from the previous step and pre-bond the copper to these sheets to form the PCBs’ structure. Since the copper covers up the earlier blueprint, it must be etched away after being attached.
The laminate panel must then be covered with a photo-sensitive film called the resist, which contains chemicals that harden upon exposure to ultraviolet (UV) light. When the PCB is blasted with UV light, it passes through and hardens the clear areas. However, the areas with black ink do not harden since they must be removed later on.
Finally, an alkaline solution helps remove leftover photoresists, followed by a pressure-washing process. After it dries, an engineer examines it once again.
5. Removing unneeded copper
Next, using chemicals, any unnecessary copper must be removed. At this point, if you are forming a multilayer printed circuit board, some additional steps will be required, which basically involve repeating earlier steps for each layer.
6. Alignment and inspection
Using the punched holes from earlier, the PCBs’ layers must be aligned by placing them on an optical punch machine, which drives a pin through the holes. Afterward, an AOI machine must inspect the PCB, seeking any defects by comparing it with the Extended Gerber design.
Now, the layers of the PCB have to be laminated. On the alignment base of a special press table, a technician must place a layer of pre-coated epoxy resin followed by a substrate layer, a copper foil layer, more pre-coated resin, and a final piece of copper.
Then, all the layers are pressed together with a mechanical press, and pins are punched through them before a laminating press is used to melt the epoxy and fuse the layers together.
8. Drilling and plating
Guiding holes are drilled first, followed by more specific holes that are made with a computer-powered drill. Then, the leftover copper must be filed off. Next, the PCB must be cleaned and bathed in chemicals that serve to coat the panel in a micron-thick copper layer.
9. Outer layer imaging and etching
A layer of photoresist must now be applied to the outer layer. Then, they must be plated in the same way as the previous step with the addition of a tin layer to guard the outer layer’s copper. Using a copper solvent, unwanted copper is removed once again.
10. Automated optical inspection
Similar to the inner layer, the outer layer needs an automated optical inspection (AOI) to ensure all necessary requirements have been met.
11. Applying solder masks, silkscreens, and surface finishing
After being cleaned again, the surface of each panel is covered in an ink epoxy and solder mask film. Ultraviolet light is used to indicate where solder mask removal is necessary.
After the removal of this mask, it is cured in an oven. Next, vital data, such as company ID numbers, warning labels, etc., must be printed directly on the board’s surface. Then, a surface finish is applied.
To finish the PCB, plating with various materials, including immersion silver, hard gold, lead-free HASL, immersion tin (ISn), etc., must occur. These finishes make it possible to mount electronic components.
13. Electrical reliability testing
Next, multiple electrical functionality tests must be applied to various areas of the PCB to ensure it complies with IPC-9252 standards. Through circuit continuity and isolation tests, any disconnections or shorts can be found.
14. Profiling, routing out, and final inspection
Fabrication engineers must identify the shape and size of the PCB. To separate boards easily, a CNC machine must do some scoring along the board’s edges. This is followed by one last inspection to verify several aspects of the board, such as hole sizes, board dimensions, cleanliness, etc.
How Circuits Central Can Help You Manufacture PCBs
As you can see, the PCB manufacturing process is a lengthy one that has many very specific steps. Without the proper expertise and specialized tools and equipment, it is easy to make errors along the way.
However, if you require PCB manufacturing in Toronto, a reliable third-party PCB manufacturer like Circuits Central can ensure that everything is done to the highest standard without you having to lift a finger.