PCB milling – the advantages

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You may be more familiar with the more well known process of chemical PCB etching rather than PCB milling – so what’s the difference, as either method is capable of producing high quality printed circuit boards?

PCB milling is a subtractive process which means it involves the removal of areas of copper from a sheet of PCB material in order to recreate pads, signal traces and structures based on supplied patterns on a digital circuit board plan or ‘layout file’. When the copper is removed it facilitates electric isolation and creates the necessary ground planes.

With the milling method, the circuit board’s quality will be determines by the accuracy of the PCB milling system. Other factors include the control and the sharpness and overall condition of the bits and also the system’s feed and speed of rotation.

With the chemical PCB etch process, the quality is dependent on the quality and accuracy of the photomasking and also the quality of the chemicals used in the etching.

As the above is a chemical process, this means it should be carried out in a laboratory environment and may incur exposure to dangerous chemicals. So an initial advantage of PCB milling is that it could feasibly be carried in a non-hazardous environment, in fact even an office.

There are however many more advantages, both in prototyping but also when used to produce specialist PCB designs.
PCB prototyping has a quick turnaround and this type of circuit board production process doesn’t require wet processing. And if a CNC mill is being used for drilling already, that one machine is capable of carrying out both parts of the process.

PCB milling is particularly suitable for those that might take a lot of drilling or profiling of the outline. In order to ensure that tracks accurately follow the shape of the board, you can again use the one CNC mill with both as this minimises any potential scaling and registration errors.

In fact, many PCBs that are easy to produce in the milling process could potentially be extremely difficult to do by wet etching followed by manual drilling.

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