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Although PCB is already well-known, it can even be said that we deal with it every day.
So, what exactly is it?
How is it produced?
How many production processes are there?
Let’s walk into the PCB manufacturing factory in Shenzhen, China for some exploration!
1. What is PCB?
Now that you have come to the PCB manufacturing factory, you must first understand what a PCB is.
PCB (Printed Circuit Board) is a printed circuit board, abbreviated as a printed circuit board, which is an important electronic component and a support for electronic components, and it is also a carrier for electrical connection of electronic components.
Nowadays, almost every kind of electronic equipment ranges from electronic watches and mice to computers and large-scale communication equipment. As long as the electronic components of the integrated circuit can be used, the PCB board will be used.
PCB may seem very complicated, but it is actually relatively simple.
It is actually a lot of small copper wires sandwiched between multiple layers of glass fibers. The copper wires can effectively connect each integrated circuit to form a new electronic circuit.
2. The production process of PCB
2.1 Design board receiving and inspection
The engineering department of the factory accepts and checks the design board file sent by the customer.
The contents of the inspection include: whether the design document is appropriate, whether the layer is missing, ensuring that there is a border on the file, whether the drilling file exists, etc.
If the design is flawed, the engineering department will inform the designer to modify it. If there is no design problem, mass production can be carried out according to the design.
2.2 Print the design into transparencies
Print the checked design documents into transparencies.
The light is projected onto these films, and the photoresist is exposed on the circuit board in a way similar to exposing photos. The design of the circuit boards is like a movie, lifelike and particularly vivid.
2.3 Cutting and edge polishing of glass fiber
The glass fiber is selected and cut and polished.
Select FR-4 type glass fiber with copper plated on the top and bottom layers, and then cut the designed size on the cutting machine. Because the edge of the glass fiber is too rough, we need to polish its edge.
2.4 Inner layer production
The top and bottom layers of glass fiber are covered with plastic dry film and are hardened under UV exposure.
After the two sides of the glass fiber are hardened with dry film, the machine is used to press them together, which can effectively prevent the copper from being dissolved by the alkaline liquid in the subsequent process.
2.5 Etching process
The purpose of the entire etching process is to remove excess copper and photoresist from the copper plate, and complete the prototype of the PCB after a series of processes.
Remove excess copper and photoresist from the laminated glass fiber, complete the etching process through the baptism of alkaline solution, and finally complete the entire etching process through the combination of film removal, washing, drying, and drying.
2.6 Automatic optical inspection (AOI) and editing vacuum (PP)
The purpose of automatic optical inspection is to check the etching of the inner layer to ensure that the etching of the inner layer is normal.
Attach a yellow patch similar to epoxy to both sides of the board to increase the bonding force.
2.7 High temperature and high pressure treatment
After 200 degrees Celsius and 27 kilograms of pressure, the epoxy resin in the melted prepreg glues the PCB board on both sides to complete the lamination.
2.8 Drilling technology
Drilling is to use a machine that automatically replaces the drill bit to drill out the required holes according to the design.
There are three types of holes on the PCB board: through holes, blind buried holes, and mechanical holes.
In this step of drilling, holes can be punched out as needed to facilitate subsequent operations such as welding of components.
2.9 Electroplating process
Electroplating requires a very complete chemical process to be completed.
After drilling, the areas without copper are plated with copper, so that the PCB can be turned on, and then the copper in the hole is thickened again, because the plating is not thick at one time and requires multiple operations.
2.10 Solder mask and drying
The electroplated PCB board needs another automatic optical inspection (AOI) before it can be painted with a green liquid solder mask and then dried.
When it comes to the color of the PCB board, everyone’s first reaction is definitely green, so how did it come from?
The secret lies in the solder mask.
2.11 Welding mask removal, washing and screen
After the removal, the solder mask needs to be cured. After keeping the original shape, we need to wash off the unnecessary things, remove the pads of the circuit board, and finally paste the silk screen for the customers in need.
2.12 Hot air treatment (HASL)
Hot air processing involves immersing the circuit board in liquid solder, and after pulling it out, blow off the excess with a hot air sheet.
2.13 PCB cutting
Since there are many different small pieces on each large PCB, they come from many different customers.
Therefore, we need to cut it.
2.14 Short circuit and open circuit test
Do you think this is over?
NO! NO! NO!
There is also the most important link. We need to perform short-circuit and open-circuit tests on the circuit boards to ensure that each circuit board can conduct normally.
The miniature robotic arm quickly verifies the electrical connection between the two pads, one after the other, which is really incredible.
2.15 Packaging and shipping
PCB packaging and transportation are also very particular. After a series of processes such as sorting, packaging, and labeling are completed, they can be shipped to customers.
Generally, customers can complete the order within 24 hours after placing an order. For domestic orders, it can be delivered within 1-2 days, and for international orders, it takes about a week.
3. Summary
After reading the above sharing, you must have discovered that the factory production of PCB boards has a total of about 15 processes, whether it feels particularly complicated.
In fact, with the development of science and technology, many jobs that require manpower are slowly being replaced, and the industrial system and industrial technology are constantly being improved and updated. I believe that in the near future, the PCB industry will also have many new innovations.
The PCB board has been made, so how are the miniature components soldered to the circuit board?
We will announce the next issue, so stay tuned!
