28/7/2016 - an overview of the printed circuit board
An Overview of the Printed Circuit Board (PCB) Fabrication Process In 1936, the
first printed circuit board (PCB) was created by Paul Eisle. But it wasn't until
the 1950s when the . Defense industry began integrating PCBs in their bomb
detonator systems that printed circuit boards found wide application. PCBs are
now used in nearly all manufactured products such as, automobiles, cellular
telephones, personal computers, among others. A Summary of the PCB Fabrication
Processes PCBs are initially fabricated with the use of two types of software.
Computer Aided Design (CAD) software is used to design the electronic schematic
of the circuit to be produced. After the schematic is designed China PCB Prototype, Computer Aided
Manufacturing (CAM) software is used by engineers to produce the PCB prototype.
Once the PCB prototype is designed, the first step in the fabrication process is
to select the material of the printed circuit board. There are many different
types 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 design
requirement dictates the dimensions of the PCB (., length, width and thickness).
After the material has been selected, the first process is to apply a coating of
copper to the entire board. The circuit layout will then be printed on the board
by a photosensitive process. Then, a photo engraving process will be used so
that all the copper that is not part of the circuit layout will be etched out or
removed from the board. The resulting copper creates the traces or tracks of the
PCB circuit. To connect the circuit traces, two processes are used. A mechanical
milling process will use CNC machines to remove the unnecessary copper from the
board. Then, an etch-resistant, silk-screen, printing process is applied to
cover the regions where traces must exist. At this point in the PCB fabrication
process, the PCB board contains copper traces without any circuit components. To
mount the components, holes must be drilled at the points where the electrical
and electronics parts are placed on the board. The holes are drilled with either
lasers or a special kind 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 connection between the
layers of the board. A masking material is then applied to coat the entire PCB
with the exception of the pads and the holes. There are many types of masking
material such as, lead solder, lead free solder, OSP (Entek), deep/hard gold
(electrolytic nickel gold), immersion gold (electroless nickel gold - ENIG),
wire bondable gold ( pure gold), immersion silver, flash gold, immersion tin
(white tin), carbon ink, and SN 100CL, an alloy of tin, copper, and nickel. The
final step in 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 should be tested to verify its functionality. In general, there are two
types of malfunctions that can cause a faulty PCB: a short or an open Rigid flex PCB. A "short" is a
connection between two or more circuit points that should not exist. An "open"
is a point where a connection should exist but does not. These faults must be
corrected before the PCB is assembled. Unfortunately, some PCB manufacturers do
not test their boards before they are shipped, which can lead to problems at the
customer's location. So, quality testing is a critical process of the PCB
fabrication process. Testing ensures the PCB boards are in proper working
condition prior to component placement. Related Links
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A Propos
prototype pcb and rigid flex pcb is very good
Amis
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