PCB Milling Guide, Meaning , Facts, Information and Description
PCB Milling basics
Printed Circuit Board Milling is the process of removing areas of copper from a sheet of printed circuit board material to recreate the pads, traces and structures found in the PC board's layout file data. Like the more common and well known chemical PCB etching 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 chemical free process and as such it can be used in a typical office or lab environment without worry. High quality boards can be produced using either process. In the chemical etch process the quality of a board is governed by the accuracy/ quality of the photo masking and the state of the etching chemicals, both of which are the board designers control. In the case of PCB milling the quality of a board is chiefly determined by the system's true, or weighted, milling accuracy and control as well as the condition (sharpness, temper) of the milling bits and their respective feed/ rotational speeds all of which are directly under user control.
The common operations supported on most machines are milling, drilling and routing, in some cases other operations such as solder paste application, board digitizing, and measurement are provided, but these are not required for the actual production of a board. Milling is the act of cutting an isolation path through the copper cladding to create the required electrical isolation around board features. Milling is also used to remove large areas of copper; this is often referred to as rubout. Drilling is, as the name applies, the creation of holes in the board for through hole components and vias, while routing is the milling of mechanical features like board outlines or large mounting holes. The intent in routing is to separate the circuit board by fully piercing the board material. Some PCB Milling machines do allow for limited 3D routing and contouring. Hardware
Generally speaking a PCB milling system is a single machine solution on which all actions required for the creation of a prototype board - with the exception of vias and through hole plating - can be handled. For most machines only a standard 120 VAC outlet as well as a shop type vacuum are required for operation, vacuum and setup are covered later in this document.