Manufacturers use computer-controlled drilling machine to produce circuit boards based on the specifications indicated in the standard design format that the computer can also understand. The printed circuit boards industry has developed different ways of exporting designs of PCBs: photo-resist, silkscreen, and milling. Each of these have their own advantage and disadvantages that designers must consider in choosing a method that would suit their needs. Let’s briefly discuss these printing methods one by one:
Photo-resist. Photo-resist boards are glass boards composed of several layers: the plastic film, the photosensitive coating, and the PCB mask. When you peel off the thin sheet of plastic film, the sensitive layer of the board will be revealed. This layer is made of copper that reacts to light. With the photo-resist board and the PCB mask attached together, it will be transferred to the UV light box. Now, this stage works in a very same way as how you develop a photo from traditional cameras that uses films. After not more than three minutes of being exposed to light, the photo-resist board and the PCB mask will be soaked in a container filled with developer. Developer is a liquid type that dissolves the covering that was exposed to light. Remember that it shall only stay in the developer for only ten seconds. After that, the board must be washed with clean water. The board is then transferred in an etchant where it is heated. In this stage, the etchant dissolves the unwanted copper layer so the tracks will be revealed cleanly. After making sure that no copper tracks are damaged, the circuit board is now ready for drilling.
Silkscreen. While photo-resist boards are made in a similar way photographers develop films, silkscreen works the same way professionals prints your t-shirts. Silk-screening is a printing technique that involves a cloth pulled tight over the frame. This cloth is the attached piece called the silk-screen stencil where the design of your circuit is printed. The silkscreen stencil forms open areas of the cloth that transfer ink onto a substrate. The ink is pressed through the cloth using a fill blade moved across the screen stencil. This ink resists the etchant which then dissolves the copper of the board. This entire process is usually done with a machine. A silk cloth is used in this type of processes because it has very small holes avoiding unnecessary inks to be transferred in the finished printed circuit boards.
Milling. Unlike the two above mentioned methods of printing circuit board designs, milling does not involve any chemical in the process. A machine called, PCB milling system, does all the work where a controller drills the circuit board to produce the desired design. The mill removes the copper around the wires with directions that follows an X, Y and Z angles principles. This subtractive way of the machine leaves the board with accurate traces of electric paths. This method is also called, “isolation milling”. This is probably the cheapest method but is also not recommended for mass production.
While there are a lot of manufacturers that produces printed circuit boards, beginners and hobbyist may also opt to test their design using do-it-yourself or DIY methods. Perhaps, you are an electrical engineering student working on a project instead of a professional working for a company. Good news is, the methods above can be performed in an alternative way that you can do in the comfort of your own home. So instead of mass-producing your printed circuit boards, you can just gather your materials and kits available on hardware shops and work on your own.
The printed circuit board is the base of most electronics including computer components. Circuit boards are composed of a specified number of copper conductive layers.