What is PCB Fabrication Process?
PCB fabrication process is the procedure of making the bare board, which will serve as the basic part for printed circuit board assembly. Everyone should select the PCB foundation contractor very carefully because a little carelessness can destroy the functioning of the entire board resulting in a useless product. Better interaction between the designer team and manufacturer is very important for making a completely functional PCB board. In this article, I am going to tell you all about the PCB fabrication process that you need to know.
PCB Fabrication Procedure
It is the process of fabricating a bare printed circuit board, which later is functional when components are assembled on them. The board needs to be printed and the earlier procedure is designing the board to direct the engineers where to place the components. The PCB fabrication process included the following steps:
- An entire engineering evaluation for circuitry
- Harmonize schematic and design databases
- Whole circuit prompt signal reliability and power reliability analysis
- Review PCB design rules and restrictions
- Bill for material and design used in manufacturing rules are reviewed
Initially, work starts on a printed circuit board which contains multiple layers, laser direct imaging (LDI) is used to print the areas which will be traces, Pads, and metal foundation of the printed circuit board. The following steps are involved:
- A dry film is used to be applied on the copper cover
- LDI is directly exposed to certain parts of the board to make the PCB pattern on them
- Any part which remains unexposed to LDI will develop off, leaving the residual film as an etch barrier
- The unexposed parts serve as an etch to form the copper circuitry
After doing the above steps, website developers perform an automated inspection to check the board for error detection. In case when they identify the errors in the board, they can correct them at this stage.
- Oxide and Lamination
A chemical treatment known as oxide is applied to the internal layers of the printed board to enhance the strength of the bond. After that, alternating layers of prepreg and copper are laminated together. This stage demands high concentration.
Holes must be drilled on the board to send signals from one layer of the board to another layer. Drilling may be different relying on the type of source being used. The result will be 5 mil larger as compared to the product.
- Electroless Copper Deposition and Dry Film Outer Layer
After drilling the holes, extra resin and debris are cleaned through a chemical and mechanical process. Then a thin copper coating is placed on the bare parts of the panel, making a metallic foundation for the process. After that, dry films are applied to the external layer of
Copper panel and exposed to the laser to direct imaging which leaves a pattern on the board.
- Electroplating, Stripping, and Etching
After printing the pattern on the panel, it is placed in a copper plating bath, which contains sulfuric acid and copper sulfate. The plate is removed and positioned into the tin plating bath to make an etch barrier. When the platting is finished, the dry film is removed. At this point, the board is ready for assembly.
- Surface Finish
Before going towards the PCB assembly stage, the circuit board will be protected with a mask called a solder mask using UV exposure. It gives a green color to the circuit board. A solder mask is a layer of polymer that safeguards the copper traces that are printed on the board from oxidation. It also avoids solder bridges when two conductors are connected mistakenly.
After printing the board and doing all the above steps, the board is ready for circuit assembly. In this stage, all the components and circuits are assembled on the board to make it functional.
How PCB fabrication process and PCB assembly process are different from each other?
PCB fabrication and assembly are two different processes in PCB manufacturing. PCB fabrication is the procedure of copying a circuit board layout on the physical structure of the board. On the other hand, PCB assembly is the procedure of assembling the electronic components on the board to make it work. PCB fabrication may be like the routing, paths, and zoning of a city while PCB assembly is the buildings, which enable the printed circuit boards to be functional.