/ Blog / what are printed wiring boards?
Modern electronic assemblies are often quite complex, featuring a wide variety of parts that work together to establish functionality. Many of these various parts are often known by acronyms to simplify discussion, though this can cause issues when acronyms and parts are fairly similar to one another. An example of this is the printed wiring board (PWB), that of which may be conflated with a printed circuit board (PCB) as a result of their close names. Despite this, there is a difference between the two, making it important that one has a basic understanding of printed wiring boards, their design, and their use.
Like printed circuit boards, printed wiring boards may be considered one of the basic building blocks of modern electronic packaging, and they were first introduced to the commercial market in the early 1950s. In general, a printed wiring board is simply a bare-tempered board on which components are installed, eventually creating a printed circuit board. The main objective of a printed wiring board is to achieve the highest count of components per square inch, allowing for higher component density while ensuring optimal electrical, thermal, and signal integrity performance is upheld.
As stated before, printed writing boards can be used to create printed circuit boards, so one of the main differences is whether or not additional components are present and used. This means that the printed wiring board is simply just the substrate that is ready for electrical components, heat sinks, and other parts to be applied. With this, one may wonder why printed wiring boards are their own thing, rather than simply being considered a printed circuit board in progress. Despite being a term that is for the individual part itself, printed wiring boards also originally acted as connectors when electronics production was in its early days. Additionally, many manufacturers find the distinction important to discern between a semi-finished and fully-finished circuit board. Nevertheless, many will still utilize the term PCB during the entire manufacturing process.
When conducting operations with printed wiring boards, it is important to be aware of the various factors that may affect their performance. As wiring boards will utilize traces to conduct current from a power source to components, performance is dependent on the length of conductors and the time of flight. Generally, shorter conductors such as strip lines and micro-strips may be used to bolster performance. In regard to power consumption, it is important to understand that consumption increases with the amount of circuit gates that are implemented, and proper consideration of needs is necessary during the printed wiring board stage to avoid issues further down the line.
The final important factor to be aware of is thermal management, as printed wiring boards are quite inefficient at handling heat themselves with the substrate naturally absorbing heat. As such, various components that are used to bolster management, examples include heat sinks, heat vias, and conductive planes. The choice will typically come down to the application of the final PCB and the number of layers it has.
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