The continuous advancement of electronic technology has made flexible circuit boards increasingly important across various fields, whether in consumer electronics, the automotive industry, or robotics manufacturing. In the field of circuit board processing, UV lasers are gradually gaining prominence; their efficiency, precision, and low thermal stress make them the tool of choice.
A Comparison of Ultraviolet Lasers and Traditional Methods
In the manufacturing and processing of printed circuit boards, traditional methods such as milling and mechanical cutting have gradually been replaced by UV lasers. Operating at low power, UV lasers employ a process known as “cold ablation,” in which the heat-affected zone generated by the beam is small, minimizing thermal stresses such as edge chipping and carbonization—problems that often accompany the use of high-power lasers.
Ultraviolet lasers have short wavelengths that are invisible to the naked eye, but this characteristic allows them to focus more precisely, thereby maintaining extremely high accuracy while processing circuit boards and creating exceptionally fine circuit features.
In addition, the high-energy photons of UV lasers make them suitable for a wide range of materials, including standard materials such as FR4, high-frequency ceramic composites, and flexible PCB materials such as polyimide. While the absorption rates of UV lasers vary among different materials, overall, UV lasers perform exceptionally well in numerous PCB material applications.
Absorption Rates of Ultraviolet Lasers in Different Materials
Figure 1 shows the absorption rates of three common PCB materials at different laser wavelengths. These include an excimer laser (wavelength of 248 nm), an infrared laser (wavelength of 1064 nm), and two CO₂ lasers (wavelengths of 9.4 μm and 10.6 μm, respectively). In contrast, the ultraviolet laser (Nd:YAG, wavelength 355 nm) exhibits a relatively consistent absorption rate across these three materials.
Ultraviolet lasers exhibit extremely high absorption rates when processing resins and copper, while also offering adequate absorption rates when processing glass. Only the expensive excimer laser (wavelength 248 nm) can achieve better overall absorption when processing these primary materials. These material-specific differences make UV lasers the optimal choice for a wide range of PCB material applications across numerous industrial sectors—whether in the manufacture of basic circuit boards, circuit routing, or the production of embedded chips in advanced processes.
A seamless process from design to manufacturing
UV laser systems are capable of processing printed circuit boards directly from computer-aided design data, without any intermediate steps. This feature makes the PCB manufacturing process more efficient and precise. Furthermore, the precise focusing capability of UV light enables the implementation of high-precision designs and allows for easy repeatable positioning.
Application 1: Surface Etching and Circuit Board Manufacturing
UV lasers operate quickly during the production of circuit boards, etching surface patterns onto the boards in just a few minutes. This makes UV lasers one of the fastest methods for producing PCB prototypes. An increasing number of prototyping labs are also equipping themselves with in-house UV laser systems to speed up the prototyping process.
The beam size of an ultraviolet laser can reach 10–20 μm, making it ideal for producing flexible circuit traces. The application examples in Figure 2 demonstrate the significant advantages of ultraviolet light in producing circuit traces that are so small they can only be seen under a microscope. This circuit board measures 0.75 inches by 0.5 inches and consists of a sintered ceramic substrate with a tungsten/nickel/copper surface. The laser can produce circuit traces 2 mils wide with a spacing of 1 mil, resulting in an overall spacing of just 3 mils.
Although laser beam processing of circuits is one of the fastest methods for producing PCB prototypes, chemical processes are still the best choice for large-scale surface etching applications.
Application 2: PCB Disassembly
Cutting with ultraviolet lasers is an optimal choice for both large-scale and small-scale production, especially during the PCB de-paneling process. De-paneling refers to the removal of individual circuit boards from a panel, and as the variety of materials continues to increase, this process has become increasingly challenging. Traditional V-groove cutting and automated PCB cutting methods are prone to damaging thin, sensitive substrates, and these issues become even more pronounced when de-paneling flexible and rigid-flex circuit boards.
Cutting with a UV laser eliminates the effects of mechanical stress on the disassembly process and, compared to other lasers such as CO₂ lasers, also reduces the impact of thermal stress. Figure 3 illustrates the results of cutting the same flexible substrate (polyimide) using a CO₂ laser and an ultraviolet laser. It can be seen that the high-temperature CO₂ laser caused greater charring and burr formation, whereas the ultraviolet laser demonstrated advantages in cold ablation.
Reducing the ”cutting buffer” saves more space, allowing components to be placed closer to the edge of the circuit, enabling each circuit board to accommodate more circuits, thereby improving efficiency and pushing the limits of flexible circuit applications.
Application 3: Drilling
The small beam size and low-stress characteristics of ultraviolet lasers also make them ideal for drilling applications, including through-holes, microholes, and blind holes. Ultraviolet laser systems perform drilling by precisely focusing a vertical beam; depending on the material being processed, they can drill holes as small as 10 μm.
UV lasers are particularly useful for drilling multilayer PCBs. Multilayer PCBs consist of multiple materials thermally bonded together, which tend to delaminate when processed with high-temperature lasers. However, the low-stress characteristics of UV lasers solve this problem. Figure 4 shows the drilling of a multilayer board on a flexible copper-clad polyimide substrate, with no delamination observed between the layers. Furthermore, the low-stress nature of UV lasers helps improve the yield—that is, the percentage of usable circuit boards removed from a single panel.
Application 4: Deep Engraving
Another common application of ultraviolet lasers is depth engraving, which takes many forms. Using software to control the laser system, operators can perform controlled depth ablation, cutting materials to the desired depth as needed, and then pause, resume, or complete the process. Applications involving depth control include small-scale production of embedded chips and surface grinding to remove organic materials from metal surfaces.
UV lasers can also perform multiple steps on the same substrate—for example, creating a 2-mil groove in polyethylene, followed by an 8-mil groove, and finally a 10-mil groove. This highlights the comprehensive user control capabilities offered by UV laser systems.
Ultraviolet lasers are capable of handling a wide range of printed circuit board processing applications, which means there is no longer a need to use different equipment, processes, or methods to complete various applications; a single processing step is all that is required to produce a finished part.
This streamlined production process helps eliminate quality control issues that arise when circuit boards are transferred between different processes. In addition, the debris-free ablation properties of UV light eliminate the need for post-processing cleaning, thereby improving production efficiency.
Frequently Asked Questions
1. What are the advantages of UV lasers in circuit board processing?
Ultraviolet lasers offer advantages such as high precision, low thermal stress, and compatibility with a wide range of materials, making them suitable for a variety of printed circuit board processing applications.
2. What is the difference between an ultraviolet laser and a CO₂ laser?
Ultraviolet lasers have shorter wavelengths and provide precise focusing, making them suitable for a wide range of materials, whereas CO₂ lasers have longer wavelengths and typically generate more heat.
3. In which applications do ultraviolet lasers excel?
Ultraviolet lasers perform exceptionally well in applications such as surface etching, circuit board manufacturing, PCB disassembly, drilling, and deep engraving.
4. Are special safety measures required for UV laser processing?
Yes, the laser beam from a UV laser poses a potential hazard to the eyes and skin, so operators must take appropriate safety precautions.
5. What is the cost of an ultraviolet laser?
The cost of UV lasers varies depending on the model and features; generally, higher-power UV lasers are more expensive, but they are a worthwhile investment for certain advanced applications.
In the field of printed circuit board manufacturing, ultraviolet lasers have demonstrated their exceptional performance and versatility, providing strong support for the further development of electronic technology. Whether it is to improve production efficiency or achieve high-precision processing, ultraviolet lasers are indispensable tools.
