The development of the printed circuit board is an important advancement in the field of electronics. Its application in the assembly of integrated circuits has great impact on machines today. It allowed for the reduction of the size, increased functional reliability, and even decreased energy consumption.
Manufacturing printed circuit boards is easier and costs less compared to making any other form of wiring technology. Although extra effort is needed in designing the board, most of the processes involved in manufacturing printed circuit boards can be done by computer-guided instruments. Nevertheless, producing printed circuit boards can also be done manually.
In producing a printed circuit board
The things needed are board/laminate, thin sheet of copper (copper foil), chemical for etching (ferric chloride), drilling machine, annular rings, pads, and soldering equipment. In a large-scale production, important computer software must also be prepared for some advanced processes such as photo lithography, testing, drilling, etc.
The board is made of non-conducting materials. A good board or base metal (substrate) is made of glass fiber (FR4). Other less expensive but less rigid alternatives are plastic (Kapton) and cotton paper.
The first step is to laminate the thin copper sheet on one or both sides of the substrate. It is done by applying heat and pressure on top of copper-covered board for a few minutes. Once the copper sheet is firmly pressed on the substrate, the next step is to draw the required pattern for the copper tracks. The pattern is generated by Computer Aided Manufacturing (CAM) software. There are many open-source CAMs out there so it shouldn’t be hard to get one.
There are many complicated methods to imprint the pattern on the copper sheet.
One is through the use of laser ink. For large-scale production of printed circuit boards, copper printing is done using machines dedicated for this purpose. In making simple printed circuit boards, the following process is applied. First, print the pattern using laser ink on a glossy piece of paper. Place the printed (glossy) side of the paper against the top of the board. Use an iron and press it against the board for a few minutes depending on the type of paper used. Submerge the board and the paper in hot water for 10 minutes. Remove the glossy paper and the pattern will be left printed on the board. Soak it again if some part of paper is hard to peel off.
Another method is by using a UV insulating chamber/machine and a photosensitive board.
The process is essentially the same as the previous one. Instead of glossy paper though, a transparent sheet is used. The pattern is printed using laser ink on the transparent sheet. The printed transparent sheet is then placed on top of the board. Afterwards, the board is put inside the UV radiating machine for 10 to 20 minutes. After getting the board out of the machine, all that needs to be done is remove the transparent sheet and clean the copper coated side.
The next step after the pattern is printed on the copper sheet is to submerge the board in the chemical etchant. Ferric chloride is commonly used for etching away unwanted copper. It can etch away the copper not covered by the laser-ink printed pattern. In the case of UV radiated board, the UV radiated copper is etched away while the one covered by the pattern from the UV light will remain.
The board should be left submerged for 3 to 5 minutes. Once that’s done, the etchant must be washed away with water. For the laser-ink patterned copper, just remove the ink using special solvents. Using sandpaper is also an alternative.
Drilling can be done, manually or using machines, once the unwanted copper is etched away. Annular rings and pads can then be inserted and installed. Layering the solder mask and adding the silkscreen label can then be done.
Simply put, there are several ways to make PCBs, although the most popular ones seem to be based on the same concept or procedure – the main difference lies in the materials used.
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