PCB laser engraving: laser engraving machine for circuit boards

Lasers can engrave on copper surfaces. Traditionally, this is done by chemical etching to produce complex conductive paths. And a new process application is PCB laser engraving on thin copper sheets, improving quality and efficiency.

Laser engraving is often confused with laser marking, but they are actually two different processes.laserpecker 2 laser engraver Engraving is generally accompanied by a process of physical removal of the material, which produces a change in the contour of the substrate being processed.

Engraving is used in a wide variety of applications,laser pecker 4 from steel engraving to stone engraving, and touches every aspect of daily life. When you sit in your car and run your hands over the dashboard and interior trim, you will feel that these faux leather materials have nothing to do with animal fur. These interiors are processed, usually by first carving floral patterns on steel molds with nanosecond pulsed fiber optic excitation, and then using these abrasives to create the faux leather material. The manufacture of coin and medal molds also falls into the field of laser engraving. Laser engraving of precious metals is also becoming more common in the jewelry industry. The traditional way of craftsmen engraving patterns with punches and hammers is slowly disappearing. Today, everything can be done with laser processing.

While ultrafast lasers and continuous (CW) lasers can also be used for engraving applications,laser pecker pro it is the nanosecond pulsed fiber laser that is used the most. Nanosecond laser pulses are short and have high peak power, making them particularly suitable for PCB laser engraving. The design of the Master Oscillation Power Amplification (MOPA) allows the user to freely select the pulse width and the repetition frequency is up to 4 MHz. e.g. SPI Laser's PulseTune technology, which allows the pulse width to be adjustable in the range of 3ns~2µs, gives the user the opportunity to optimize the pulse performance, thus improving the quality or efficiency of the laser engraving.

New Process Improves PCB Laser Engraving Productivity, Ensures Quality

Lasers are capable of engraving on copper surfaces. A new process application (nanosecond pulsed lasers) is the engraving of printed circuit boards (PCBs) on thin sheets of copper, whereas traditionally complex conductive paths are created by chemical etching. The copper layer is relatively thin, typically 40 to 100µm thick, but the metal layer can be easily removed by the engraving technique to expose the FR4 substrate. As with the VIN marking example, varying the laser parameters can remove any remaining debris from the FR4 substrate. In addition, the laser can also cut thin copper sheets to the desired size. While laser engraved circuit boards are not well suited for mass production, they can be used for rapid PCB prototyping.

Laser engraving is essentially material removal, and a laser process removes only a few tens of micrometers in depth. The material removal process is therefore relatively slow, with currently achieved removal rates measured in cubic millimeters per minute and removal efficiencies determined by average power. The key to achieving both high quality laser engraving and efficient material removal is the use of optimized processing solutions. Since raster scanning typically creates furrows, there are problems with low removal depth and residual roughness, so this process is generally not recommended unless the engraving requirements are not high.

The principle of PCB laser engraving is relatively simple. The laser pulse acting on the material causes the material to melt, forming a molten pool. After a certain amount of heat is reached, the surface of the material vaporizes and recoil pressure is generated on the melt, resulting in melt ejection, which is the main mechanism of removing material by laser engraving. There may be some misconceptions about laser engraving, for example, that the higher the pulse energy, the more material is removed; the higher the peak power and the shorter the pulse width, the better the quality of laser engraving. In fact, the laser engraving process is extremely complex, and there is no fixed processing solution that can guarantee the quality of engraving. Since engraving quality and material removal rate are mutually dependent, it is important for the user to optimize the pulse characteristics, optics and processing/scanning parameters in order to ensure a good balance between quality and efficiency.

Alternatively, if only lines and simple text need to be engraved, laser dithering can be used. This technology is ideally suited for Vehicle Identification Number (VIN) marking, where the engraved VIN remains visible even after painting and is difficult to rub off, making it safer. In addition, thanks to the powerful functional selectivity of the laser system, oxides and surface spatters generated during the laser engraving process can be effectively removed by simply changing the laser parameters, e.g., by shortening the pulse width and cranking up the repetition frequency.

However, for large areas and complex shapes of laser engraving, if a certain fixed direction of laser scanning is continuously maintained, the uneven effect will be gradually superimposed, so it is necessary to change the direction of laser scanning as well as take a layer-by-layer removal of the processing method, so as to make the processing effect more uniform. For example, from the perspective of reducing Moore's interference fringes using multiple laser scanning each time the scanning angle is different can make the engraving quality greatly improved. This technique has been used in the printing industry for many years to ensure uniform print quality and is now well suited for laser engraving.

Laser engraving quality depends on pulse parameters

As mentioned above, process optimization is a long but useful process that in some cases can double the material removal rate or halve the residual roughness. In addition to the pulse parameters, laser engraving also takes into account the pulse overlap and scan line spacing. These optimizations can to some extent be structured and semi-automated by marking samples to show the interdependence of the selected parameters.

For example, when laser engraving pcb's on brass, keeping the average power the same (pulse overlap and scan line spacing are kept constant) and the pulse energy at the highest level and pulse width at the shortest level, the peak power is the highest while the material removal rate is very low. However, the new process of nanosecond pulsed lasers by increasing the repetition frequency to reduce the pulse energy and peak power and increasing the pulse width can significantly increase the material removal rate - up to 40% in some cases.

Interestingly, the same test parameters are applied to different materials with different results, which is not surprising since key physical properties such as conductivity, specific heat capacity, melting point, and fluid viscosity vary from material to material, and these physical properties are also related to the process. Therefore, the optimal laser engraving parameters for aluminum and steel are very different and need to be tested repeatedly.

Although various processing models and simulation methods have been proposed for laser engraving, there is no single model that covers all available process parameters and material types, so it is clear that laser engraving is indeed a very complex process.

One of the biggest challenges in laser engraving is to increase the material removal rate while still maintaining high engraving quality. The thermal effects present in laser engraving limit the amount of laser power that can be used. When the laser power of 50 ~ 100W when the heat accumulation began to appear resulting in engraving quality and consistency of the decline of course, there are also high-power laser successfully used for large-area engraving of block materials such as printing rolls of engraving, but these applications are more limited.

Thermal effects in laser engraving of pcb can be reduced by different techniques one of the more effective techniques is interlacing which can be done in one or more rows the blank area is filled in by subsequent interlacing compared to sequential scanning when using a 100W laser for interlaced engraving on aluminum and brass surfaces the material removal rate and residual surface roughness is significantly improved however when using interlacing on stainless steel the material removal rate and residual surface roughness is significantly improved. However, when using the interlaced technique on stainless steel there was no significant improvement in the material removal rate but the surface roughness was improved. The interlaced technique is currently being trialed with a 200W laser power and good results are expected.