Overview of Laser Micro-Drilling

Laser Microhole DrillingOverview:

It is very common to make a small hole in a component. However, if hard materials are required, such as drilling small holes with diameters of up to 0.1 mm to several microns in cemented carbide, it is not easy to process with ordinary machining tools, and even if it is possible, the processing cost will be very high. The existing machining technology uses a small high-speed rotating drill with tens of thousands or hundreds of thousands of revolutions per minute to drill small holes in materials. This method can generally only process small holes with a hole diameter greater than 0.25 mm. Today's industrial production often requires processing holes with a diameter smaller than this. For example, in the production of electronic industry, the production of multi-layer printed circuit boards requires drilling thousands of holes with a diameter of about 0.1~0.3 mm on the board. Obviously, it is difficult to process with the drill bit mentioned above, the processing quality is difficult to guarantee, and the processing cost is not low. As early as the 1960s, scientists used lasers to open a small hole on a steel blade in the laboratory. After nearly 30 seconds of improvement and development, there was no small hole.

The principle of using laser to drill holes in materials is simple (Laser Drilling), and it is not complicated in practice.

The laser has good coherence and can be focused into a light spot with a very small diameter (less than 1 micron) using an optical system, which is equivalent to a "micro drill" for drilling holes. Second, the brightness of the laser is very high, and the laser energy density (the average energy per square centimeter) at the focus is very high. Generally, the energy generated by the laser output of a laser can reach 109 joules/cm2, which is enough to melt and vaporize the material, leaving a small hole in the material, just like drilling it with a drill.

How to use the laser "drill" well, laser scientists have also done a lot of research. Researchers have found that the quality of the small holes made by using multiple light pulses per second (commonly called high-repetition-rate laser pulses) as a "drill" is better than that of a single light pulse or a few light pulses per second. It may be like this: when drilling holes with one light pulse or a few pulses per second, the laser energy requirement for each light pulse is high, so that the material can be heated to melt before the hole is drilled. However, the molten material cannot be completely vaporized, but heats and vaporizes the nearby material, so the holes punched are not so neat in shape and size. If a high repetition rate laser output light pulse is used, the average energy of each light pulse is not high, but due to the narrow width of the light pulse, the power level is not low. Therefore, each laser pulse does not form much melt on the material, and mainly vaporization occurs. Because when the material near the small hole is heated, the molten material will not form a single pulse.

In order to improve the quality of drilling, it is also necessary to pay attention to the selection of the laser focus position. The principle of selecting the focus position is as follows: For thicker materials, the laser beam focus position should be inside the workpiece. If the material is thin, the focus of the laser beam should be placed above the surface of the workpiece. This arrangement will make the upper and lower sizes of the drilling basically consistent, and there will be no "barrel-shaped" holes.

Using laser grinding on the material not only has good grinding quality, but also can ensure that the size of multiple small holes is consistent, especially when grinding the same number of small holes, the grinding speed is fast, and the production efficiency is high. Therefore, in addition to the use of laser drilling in the production of the electronics industry, many other industrial production departments are also using laser drilling, such as the small holes on ordinary cigarette filters, the small holes on jet valves, and laser processing. Spray cans and bottlenecks have a method for controlling the flow of compressed substances (such as deodorants, oils or other liquids). The performance of the valve depends on this small hole on the sprayer. The diameter of this small hole is 10-40 microns, which is not well made by other mechanical processing methods. Laser processing can ensure both quality and speed.