In 1936, the initial printed circuit board (PCB) was created by Paul Eisle. But 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 almost all manufactured products including, automobiles, cellular telephones, pcs, among others.
A Summary of the PCB Fabrication Processes – PCBs are initially fabricated by using two types of software. Computer Aided Design (CAD) software program is utilized to design the electronic schematic in the circuit to be produced. After the schematic was created, Computer Aided Manufacturing (CAM) software program is employed by engineers to produce the PCB prototype.
Once the PCB prototype was created, the initial step inside the pcb fabrication and assembly is to select the material from the printed circuit board. There are various kinds of PCB materials available, but the popular ones, based on the application and a customer’s requirements, include: Alumina, Arlon, Bakelite, CEM1, CEM5, Ceramic, FR1, FR4, FR4 High Temperature, GeTek, Nelco, Polyimide and Rogers.The design and style requirement dictates the size of the PCB (I.e., length, width and thickness).
Following the material continues to be selected, the very first process is to apply a coating of copper towards the entire board. The circuit layout will likely then be printed on the board with a photosensitive process. Then, a picture engraving process will likely be used so that all of the copper which is not part 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. For connecting the circuit traces, two processes are employed. A mechanical milling process uses CNC machines to eliminate the unnecessary copper through the board. Then, an etch-resistant, silk-screen, printing process is applied to cover the regions where traces must exist.
At this point within the flexible pcb, the PCB board contains copper traces without the circuit components. To mount the ingredients, holes has to be drilled in the points where the electrical and electronics parts are placed on the board. The holes are drilled with either lasers or even a special type of drill bit made of Tungsten Carbide. When the holes are drilled, hollow rivets are inserted into them or they are coated by an electroplating process, which produces the electrical connection between the layers in the board. A masking material will be applied to coat the whole PCB excluding the pads and also the holes. There are numerous kinds 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 final part of the PCB fabrication process is to screen print the board so labels and 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 ought to be tested to confirm its functionality. Generally speaking, there are two types of malfunctions that will ysfurn a faulty PCB: a brief or perhaps an open. A “short” is actually a connection between two or more circuit points that should not exist. An “open” is actually a point where a connection should exist but fails to. These faults should be corrected before the PCB is assembled. Unfortunately, some rigid flex printed circuit boards usually do not test their boards before they may be shipped, which can cause problems at the customer’s location. So, quality testing is a vital procedure of the PCB fabrication process. Testing ensures the PCB boards have been in proper working condition just before component placement.