In 1936, the first printed circuit board (PCB) was developed by Paul Eisle. However it was not until the 1950s when the U.S. Defense industry began integrating PCBs in their bomb detonator systems that printed circuit boards found wide application. Printed circuit boards are now utilized in almost all manufactured products including, automobiles, cellular telephones, computers, among others.
An Overview in the PCB Fabrication Processes – PCBs are initially fabricated with the aid of two kinds of software. Computer Aided Design (CAD) software is used to design the electronic schematic of the circuit to get produced. After the schematic is designed, Computer Aided Manufacturing (CAM) software is used by engineers to create the PCB prototype.
After the PCB prototype is designed, the initial step in the PCB production is always to select the material from the printed circuit board. There are various varieties of PCB materials available, but the popular ones, based on the application as well as a customer’s requirements, include: Alumina, Arlon, Bakelite, CEM1, CEM5, Ceramic, FR1, FR4, FR4 High Temperature, GeTek, Nelco, Polyimide and Rogers.The style requirement dictates the dimensions of the PCB (I.e., length, width and thickness).
After the material has been selected, the initial process is to use a coating of copper towards the entire board. The circuit layout will likely then be printed on the board by way of a photosensitive process. Then, a photo engraving process will be used so that all of the copper which is not portion of the circuit layout is going to be etched out or taken off the board. The resulting copper creates the traces or tracks in the PCB circuit. To connect the circuit traces, two processes are employed. A mechanical milling process will use CNC machines to eliminate the unnecessary copper from the board. Then, an etch-resistant, silk-screen, printing process is used to cover the regions where traces must exist.
At this time within the flexible pcb manufacturer, the PCB board contains copper traces without any circuit components. To mount the ingredients, holes must be drilled in the points where electrical and electronics parts are put on the board. The holes are drilled with either lasers or even a special type of drill bit made of Tungsten Carbide. Once the holes are drilled, hollow rivets are inserted into them or they are coated by an electroplating process, which creates the electrical link between the layers from the board. A masking material is then applied to coat the complete PCB with the exception of the pads as well as the holes. There are many types of masking material like, lead solder, lead free solder, OSP (Entek), deep/hard gold (electrolytic nickel gold), immersion gold (electroless nickel gold – ENIG), wire bondable gold (99.99% pure gold), immersion silver, flash gold, immersion tin (white tin), carbon ink, and SN 100CL, an alloy of tin, copper, and nickel. The last element of the PCB fabrication process would be to screen print the board so labels and the legend appear at their proper locations.
Testing the Quality of the PCB Board – Before placing the electrical and electronic components on the PCB, the board should be tested to ensure its functionality. In general, there are two types of malfunctions that can ysfurn a faulty PCB: a quick or even an open. A “short” is really a link between 2 or more circuit points that will not exist. An “open” is actually a point when a connection should exist but fails to. These faults should be corrected before the PCB is assembled. Unfortunately, some rigid flex circuit boards tend not to test their boards before they may be shipped, which can cause problems at the customer’s location. So, quality testing is a critical process of the PCB fabrication process. Testing ensures the PCB boards have been in proper working condition before component placement.