Printed circuit boards began as electrical connection systems, first developed during the 1850s. Initially, rods or strips made of metal connected large electric components on wooden bases. Eventually, wires connected to screw terminals replaced the metal strips, and metal chasses replaced the wooden bases. Then, due to increased operating needs for products using these boards, the design size diminished.
Evolving Printed Circuit Board Assemblies
In 1925, a US patent was submitted, consisting of an electrical path on an insulated surface. For this, conductive inks and a stencil were used, thus leading to the name, “printed circuits.” Eighteen years later, another man patented an etching process for making circuits or a conductive pattern on top of a layer of copper foil-bonded glass fiber as the non-conductive base.
Although a popular technique, it was not until the 1950s, when the transistor was introduced specifically for commercial purposes, that the copper-backed process was widely accepted. After the transistor’s advent, components became extremely small, forcing manufactures to use printed circuit board assemblies as a means of reducing the overall size of the electronic component.
By 1961, Hazeltyne, a US firm, patented hole technology and its use in multi-layer printed circuit board assemblies. The result was that component density increased, and the newly close-spaced electrical paths changed the design of printed circuit board assemblies dramatically. During the 1970s, experts introduced integrated circuit chips, which were quickly added to the design and manufacturing process.
The Future of Printed Circuit Board Assemblies
Today, printed board circuit assemblies are sophisticated and used by multiple industries for various applications. For example, these boards play an intricate role in personal and business computers, as well as computers used in airplanes, automobiles, boats, and more. Virtually any type of computer system has one or more printed circuit board assembly.
For printed circuit board assemblies made and used today, there is no such thing as “standard.” The boards currently designed and manufactured have very specific functions, and companies that make them thereforerequire tremendous expertise.
The decreasing size of electronic components is what drives the manufacturing of printed circuit board assemblies. These boards are becoming smaller, but also more densely packed, while still providing increased electronic capabilities.
Design Process Behind Printed Circuit Board Assemblies
The PCB, or printed circuit board, is the central element in every electronic system. The board is the base on which the entire circuit is mounted, whether it is surface mounting or perforated board. These boards are meticulously designed to be efficient and compact, planned for every circuit individually.
The PCB Assembly Design Process
Different printed circuit board assemblies may contrast in certain nuances but the main PCB assembly design steps are common for all of them. The physical manufacturing part will involve laser cutting/drilling, CNC machining, etching, plating and optical inspection. Then there are testing methods for the PCB and its electrical components.
This is all preceded by the design part. Here are its stages.
Step One: Digitally Designing the PCB
In the old days before modern imaging/design software was available, the PCB architecture was simply drawn on paper. Modern PCB assembly design programs have a pre-made library of components used in printed circuit board assemblies which the designer puts in place.
Step Two: The PCB Assembly Film is Generated
The finalized circuit board diagram is taken and used by the software to produce a mask, or negative, of the design, which is then printed onto a clear plastic sheet. This resembles somewhat the old-fashioned slides, or x-ray prints. The value of this is having a tangible, real-size model of the PBC prior to actually manufacturing one.
Step Three: Material Selection
Most modern printed circuit board assemblies are made using fiberglass with copper foil bonded onto one or both of their sides. Some will be made of unbreakable glass or paper phenolic (which is mostly used in household electrical appliances).
Step Four: Drill Holes Preparation
Most PCBs will have pre-drilled holes for certain components, and those are made using carbide drills or similar machinery. The pattern, as well as other specifications (like drill bit sizes for example), are stored as part of the design in a file that get transferred to the machine which then executes it.
Step Five: Image Application
The image is printed on the PCB by different means, such as plotters, printers or hand applications. This, however, takes us beyond the design stage and into manufacturing, where the next steps are cutting, stripping, etching, and testing. Those we may discuss in future articles.
This concludes the description of PXB design steps. Hope this gave you a general idea of the process.
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