PCB milling

Today we are going to talk about PCBs also known as Printed Circuit Board which are important when developing a device or when you are prototyping.

A PCB mechanically supports and electrically connects electronic components using conductive tracks, pads and other features etched from copper sheets laminated onto a non-conductive substrate. PCBs can be single sided (one copper layer), double sided (two copper layers) or multi-layer. Conductors on different layers are connected with plated-through holes called vias.

 

This is a picture of a etched PCB as you can see there are some details on the board with not etched copper.

 

Printed circuit boards are used in all but the simplest electronic products. PCBs require the additional design effort to lay out the circuit but manufacturing and assembly can be automated. Manufacturing circuits with PCBs is cheaper and faster than with other wiring methods as components are mounted and wired with one single part. Furthermore, operator wiring errors are eliminated.

In our vocational institute we make PCB with a mill because those board that we make are prototype, below I´ll explain quickly the process.

Printed circuit board milling (also known as isolation milling) is the process of removing areas of copper from a sheet of printed circuit board material to recreate the pads, signal traces and structures according to patterns from a digital circuit board plan known as a layout file. Similar to the more common and well known chemical PCB etch process, the PCB milling process is subtractive: material is removed to create the electrical isolation and ground planes required. However, unlike the chemical etch process, PCB milling is typically a non-chemical process and as such it can be completed in a typical office or lab environment without exposure to hazardous chemicals. High quality circuit boards can be produced using either process.

 

Pictures of Milled PCBs.

 

Milling them on a CNC is a quick way with a different set of pros and cons:

The good:

* Quick turnaround - don't have to wait days or weeks for it to ship.

* The mill does the drilling.

* No messy acid to deal with.

* Once you have good settings, the process is easily repeatable.

* Two sided boards are possibly slightly easier than with etched boards.

* Inexpensive - you're just paying for blank circuit boards which are a couple bucks each.

The not so good:

* Bits and end mills can be expensive and they wear out.

* Bits of copper clad fiberglass get all over the place.

* Milling a board can take a while.

* Board stock and mill bed flatness will present a challenge.

* Isolation size is a function of bit size and mill accuracy. Check your design carefully before you plan on using fancy SMT parts with densely packed pins.

 

 

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