Testing the Differences: Laser Marking Results on Different Types of PCBs

The experiment compared the results of laser marking on three common types of PCBs: FR-4, metal, and ceramic. The results were analyzed in terms of character clarity, heat-affected zone, and processing efficiency.The guide provides specific suggestions for setting parameters, helping engineers and production staff select the right PCB materials according to actual needs, and improving product quality and production efficiency.

Why does the material of the PCB affect the marking?

Last year, while helping a friend adjust a production line, I discovered that using the same fiber laser on ordinary FR-4 boards produced clear white markings, but when the same laser was used on aluminum boards, the markings always had blurred edges.This experience made me realize that the material of the PCB has a greater effect on the laser marking results than I had imagined.In the following, we will use real-world examples to discuss how the thermal conductivity of different materials and surface treatment processes affect laser energy absorption.

A comparison of the three main types of material.

We prepared three 1.6-mm-thick samples: an ordinary FR-4 fiberglass board, a 5052 aluminum alloy board, and a 96 % alumina ceramic board.Five sets of experiments were conducted in the same environmental conditions using a 20-watt fiber laser.

FR-4 glass fiber board.

At 85 % power and 600mm / s speed, the characters come out razor sharp.However, the epoxy resin layer is easily carbonized, and when the power exceeds 90 %, a yellow halo forms around the characters.This is especially true when the pattern requires high precision, such as a 2D barcode.

The challenge of metal substrates

The reflective nature of aluminum-based boards caused some problems at the beginning.Later it was discovered that by setting the frequency to 80 kHz and using black anodized surfaces, it was finally possible to produce high-contrast white markings on a dark gray background.However, metals dissipate heat more quickly than FR-4, so it takes about 30 % more power to achieve the same depth.

Special handling for ceramic boards.

The laser treatment creates micro-cracks in the surface of the ceramic, creating a matte finish.The results of testing showed that a Q-switch frequency of 50kHz and a power of 60 % can form a mark on a dark gray surface with a texture similar to that of stone carvings.But care must be taken to control the heat-affected zone so as to avoid affecting the performance of surrounding circuits.

Practical advice for choosing materials.

Based on six months of practical experience, here are some tips on how to use the system.

- For ordinary electronic equipment, FR-4 is the most economical. Pay attention to controlling carbonization.

- When using metal substrates in heat dissipation applications such as LED lighting, remember to do surface treatment in advance.

If ceramic is used for high-frequency circuits, it is suggested that a prototype be tested for thermal deformation.

Tips for setting parameters.

The author also shares some practical tips on debugging.

1. First use scrap to test the power of the furnace, and find the critical point for carbonization.

2. Applying a small amount of matte paint to a metal plate before marking it can reduce glare interference by over 80 %.

3. When encountering a multi-layer board, it is recommended that the frequency be lowered to avoid delamination.