In 1936, the initial printed circuit board (PCB) was created by Paul Eisle. However it was not until the 1950s when the U.S. Defense industry began integrating Printed circuit boards in their bomb detonator systems that printed circuit boards found wide application. PCBs are now used in nearly all manufactured products like, automobiles, cellular telephones, personal computers, among others.
An Overview of the PCB Fabrication Processes – PCBs are initially fabricated by using two types of software. Computer Aided Design (CAD) software program is used to design the electronic schematic from the circuit to become produced. Following the schematic is made, Computer Aided Manufacturing (CAM) application is utilized by engineers to produce the PCB prototype.
After the PCB prototype is made, the first step within the pcb fabrication specifications is to pick the material of the printed circuit board. There are various varieties of PCB materials available, but the popular ones, based on the application along with a customer’s requirements, include: Alumina, Arlon, Bakelite, CEM1, CEM5, Ceramic, FR1, FR4, FR4 High Temperature, GeTek, Nelco, Polyimide and Rogers.The design requirement dictates the size of the PCB (I.e., length, width and thickness).
Following the material has been selected, the first process is to use a coating of copper towards the entire board. The circuit layout will be printed on the board by way of a photosensitive process. Then, a photo engraving process will be used to ensure that all the copper which is not portion of the circuit layout will likely be etched out or removed from the board. The resulting copper produces the traces or tracks from the PCB circuit. To connect the circuit traces, two processes are utilized. A mechanical milling process will use CNC machines to get rid of the unnecessary copper through the board. Then, an etch-resistant, silk-screen, printing process is applied to pay for the regions where traces must exist.
At this point within the flexible pcb, the PCB board contains copper traces without any circuit components. To mount the ingredients, holes must be drilled at the points where electrical and electronics parts are put on the board. The holes are drilled with either lasers or perhaps a special sort of drill bit made of Tungsten Carbide. Once the holes are drilled, hollow rivets are inserted into them or these are coated by an electroplating process, which produces the electrical connection between the layers in the board. A masking material is then placed on coat the entire PCB with the exception of the pads as well as the holes. There are many varieties of masking material including, 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 step in the PCB fabrication process is always to screen print the board so labels and also the legend appear at their proper locations.
Testing the Quality of the PCB Board – Prior to placing the electrical and electronic components on the PCB, the board should be tested to confirm its functionality. Generally speaking, there are 2 varieties of malfunctions that may ysfurn a faulty PCB: a quick or even an open. A “short” is a connection between several circuit points which should not exist. An “open” is really a point in which a connection should exist but does not. These faults should be corrected before the PCB is assembled. Unfortunately, some rigid flex printed circuit boards do not test their boards before they are shipped, which can lead to problems in the customer’s location. So, quality testing is a vital process of the PCB fabrication process. Testing ensures the PCB boards are in proper working condition prior to component placement.