Knowledge Base

PCB Milling | A Comprehensive Guide

Do you know PCB milling? Whether you know it or not, read this article first. After reading it, you will definitely gain something.

PCB milling is a common and widely used process in electronic manufacturing, which is used to process precise circuit patterns on substrates. Compared with traditional chemical etching (PCB Etching), it does not rely on chemical solvents and etching liquids but removes materials through mechanical processing to form the required circuit pattern. This method can not only significantly improve the efficiency of circuit board production but also effectively save costs and reduce material waste, which also makes it one of the ideal choices in modern electronic manufacturing. The following is a comprehensive introduction to the PCB milling process, including definition, process flow, equipment and tools, as well as its advantages and specific applications in manufacturing.

What is PCB Milling?

PCB milling is a precise and efficient circuit board manufacturing process. In the PCB milling process, CNC equipment is used. This equipment will physically mill the PCB board mechanically according to the designed pattern to remove unnecessary materials, thereby forming precise circuit patterns and connections. The copper layer is removed by controlling the movement of the cutter to form the required conductive path in the milling process, so the control of the tool movement must be precise. In addition, PCB milling is particularly suitable for manufacturing environments with high environmental requirements because it does not rely on chemical solvents, and can also be flexibly used in small-batch production and prototype development, which makes this technology increasingly popular.

Key PCB Milling Process

Mechanism of PCB Milling

Unlike traditional chemical etching, PCB milling is a mechanical process where the milling cutter moves along the path defined in the PCB design file to remove material only in the required areas. This process has high requirements for processing accuracy and plate quality, so it requires precise parameter settings.

Design Parameters in PCB Milling

The success of PCB milling depends largely on its design parameters. Please see some key design parameters listed below:

1. Board quality

Carefully consider the hardness and thickness of the board, because the choice of material will affect the quality of milling (for example, thicker copper foil requires different milling speeds and feed rates, otherwise it may cause severe tool wear). If you want a material with good stability and durability, I recommend FR4 and other common composite materials (PCBasic will provide the best choice based on your needs). Also, consider the flatness of the board surface because this is very important for the "precise control of the tool" mentioned earlier.

2. Milling parameters

Milling parameters include tool diameter, cutting depth, feed rate and speed, cutting path, etc. The setting of these parameters plays a very critical role in PCB milling. If the set parameters are not suitable for the PCB to be produced, it will definitely produce undesirable results. For example, for harder materials or thicker copper layers, I set the feed rate and speed very high, then after a while, the tool must have severe wear and the cut pattern is not clear. The solution is to use lower feed rate and speed for hard materials or thicker copper layers, and higher speed for softer materials. So, set the appropriate milling parameters for milling PCB.

3. PCB Milling Methods

Process Method	Description	Applicable Scenarios
Laser Milling	Using high energy density laser beams to precisely remove material	High-precision and intricate circuit pattern machining
CNC Router Milling	Typically used for cutting PCB outlines and forming slots	Mass production and outline cutting
Carbide End Mills	Effectively cuts copper foil without damaging the substrate, typically used for detailed copper foil cutting or small structure machining	Small-batch production, detailed copper cutting, and small structure machining
Plated Slots	Creates plated slots on PCBs to connect multiple layers and enhance conductivity	Multi-layer boards and applications requiring electrical connections

4. Design for Manufacturing Manual for Milling

DFM guides manufacturers on how to optimize the design to reduce errors and costs in actual production, which is the key to successfully milling PCB.

PCB Milling vs. PCB Etching

Feature	PCB Milling	PCB Etching
Environmental Impact	High, no chemical waste	Low, produces chemical waste
Precision	High	Moderate
Processing Time	Short	Longer
Cost	Moderate to High	Lower
Suitable for	Small batches, complex designs	Large-scale production

Advantages and Applications of PCB Milling

The high manufacturing precision of PCB milling can ensure the quality of each PCB, and compared with etching, it produces less waste and does not involve chemicals. In addition, PCB milling is fast and efficient, which greatly shortens the product development cycle. It is more suitable for prototype design and small batch production that require high precision, and it can help companies bring them to market faster.

PCB milling is also widely used. Its high reliability and low failure rate make it particularly suitable for prototype design, military electronics, automotive electronics and other fields.

Common Problems and Solutions

Problems	Causes	Solutions
Edge Whitening	During PCB milling, if the milling force exceeds the bonding strength of the substrate, localized delamination occurs between resin and fiberglass, causing edge whitening.	① Adjust the milling force and use appropriate milling parameters and tools. ② Use high-quality substrates.
Tool Wear	One of the most common issues; Poor quality of tool material; high-quality machining requirements from the customer;	① Use higher hardness tool materials (e.g., carbide tools). ② Optimize the machining process to reduce tool wear. ③ Regularly maintain and replace worn tools in a timely manner.
Low Machining Accuracy	Incorrect machining process; improper milling parameter settings.	① Optimize the machining process, and set appropriate feed rate, rotation speed, and cutting depth parameters. ② Ensure the tool moves as perpendicularly as possible. ③ Use high-precision machines and tools for machining.
High Milling Temperature	Friction between the tool and workpiece easily raises cutting temperature, which reduces cutting efficiency and shortens tool life.	① Use cooling systems, such as coolant sprayers, to reduce tool surface temperature promptly. ② Choose appropriate tool materials and coatings.
Static Electricity	Friction during the milling process generates static electricity.	① Use anti-static devices or measures during milling, such as humidifiers or ion blowers. ② Use anti-static workbenches and fixture materials. ③ Maintain appropriate humidity levels in the processing environment.