Medical micromachining

Components are getting smaller and smaller, especially in the medical, automotive, and electronics markets. New micromachining technology, including advanced laser markers with superior beam quality offers similar results to traditional machining technologies, but they’re less expensive, faster, and more flexible. The fiber marker technology can be one-half to one-third the cost of standard technology.

High-volume manufacturers looking to meet miniaturization challenges while reducing costs can use the single-mode fiber marker to achieve excellent results on a range of materials, including steel, nickel, titanium, silicon, aluminum, and copper. The method should be considered by those thinking about updating or replacing electric discharge machining (EDM) equipment, as well as those who might otherwise turn to 532nm and 355nm lasers.
 

See result without seeing the details

Micromachining refers to making small features using standard machining operations such as drilling, cutting, scribing, and slotting on a smaller scale. There is no official scale for determining that an operation is micromachining, but a good benchmark is when the features cannot be seen without one’s glasses, or you are seeing results without seeing details. In other words, you might have no idea what was done to the material to get a particular effect. For example, if you drilled 50µm holes in a piece of copper you would see light, but would not be able to see how big or small the holes were that are letting light through.
 

The right tool for the job

In the hands of a skilled operator, recent advancements in the use of a fiber-laser marker for micromachining can create desired features not normally associated with this equipment. The major benefit of this approach is that fiber-laser markers are much less expensive than standard equipment used for micromachining.

Working successfully at such a small scale requires the right tool as well as knowledge of how to use it to achieve the desired results, in terms of both quality and speed of material removal.

For example, Miyachi Unitek recently introduced the LMF2000-SM single-mode fiber laser marker, which offers parameters and controls to enable micromachining of fine detail dimensionally and at excellent removal rates.

The laser marker features high beam quality, with an M-squared of less than 1.3, which produces a focused optical spot size down to 20µm, making it particularly suited for scribing and cutting a wide variety of materials, including alumina, silicon, copper, and aluminum foils. In addition, the use of selectable pulse-width waveforms with different peak power characteristics enables tuning of the removal rate and feature surface quality. This independent control of pulse width and peak power with pulse frequency offers control and process tunability advantages compared to traditional q-switched lasers.

The scan head that moves the laser is also a key part of the system, providing sufficient high-speed movements with suitable repeatability and accuracy.

Fiber laser micromachining technology can be used for a wide variety of applications, such as selective plating removal for solder barrier, solar cell scribing and hole drilling, hole drilling of stainless steels for medical hypo tubes and fluid flow control systems, and cutting of sub-0.02" thick metals for fast part prototyping.

Comparing technology

Single-mode fiber laser markers can be used as an alternative to more costly micromachining technologies, including sinker EDM equipment, or 532nm and 355nm Nd:YVO4 lasers.

For example, Figure 1 shows how the technology could be used as a replacement for sinker EDM machines. The picture on the left shows the drilling of a 150µm hole, ±10µm in 200µm thick steel, with no post processing. The minimal amount of debris and tight hole tolerance was achieved in 50% of the time taken by sinker EDM equipment.

In addition, because the laser marker offers a working X-Y area, multiple parts can be completed in a single loading operation, as opposed to one-up loading on sinker machines (unless an additional investment is made in motion equipment). This advantage makes the fiber laser marker return on investment even more compelling.

The fiber laser can also process difficult materials such as thin-sheet material and foils. Also in Figure 1 is a spiral with 100µm wide elements machined in 50µm thick copper foil.

Figure 2 shows a comparison of drilling silicon using a fiber laser marker (left) and a 355nm UV laser source (right). The UV laser provides better quality than the fiber laser, but the fiber laser results are good enough for this particular application. In addition, the fiber laser was 17 times faster than the UV laser and 50% of the cost. Note that the UV hole shows a roundness defect, due to a laser path program error.

Figure 3 compares the quality of holes drilled with a 20W single fiber laser (left) and 5W 355nm laser (right) in 0.008" stainless steel in the same processing time.

The finesse and machining control that is possible using the single-mode fiber laser, in which the fiber laser marker was used to machine a 25µm thick metal foil to a 13µm depth. The application was to provide a preferential failure point in a component. The channel width was 75µm and the depth variation over the entire area was ±1µm – equal to taking material that is one-fourth the width of a human hair and leaving only about one-tenth of it after micromachining.

Ceramic is another commonly used material in microelectronics, and a 355nm laser is typically used for scribing and drilling of ceramic materials. The fiber laser marker can avoid micro-cracking for a wide variety of features in ceramic materials.

There are many applications that can benefit from the laser’s capability to selectively remove platings or coatings on metals, ceramics, and even plastics. Fiber laser machining techniques have shown good results in micromachining solder barriers or solder dams, thin film resistor/capacitor trimming, and active layer removal in battery foils for welding purposes. This selective and tailored layer removal process is usually impossible during the component or part production process, because masking the area is simply not feasible.

The laser can select the exact resistance value for a circuit. It also can be used for resistance or capacitance trimming, as part of a dynamic iterative removal and measure tuning process in which removal areas may change from component to component.

Micromachining workstations

The single-mode fiber laser marker can be a cost-effective micromachining workstation for drilling, cutting, scribing, and ablation for a variety of applications. This desktop mini machining center provides the benefits of dual- or multi-purposing to maximize ROI.

It must be noted that, in addition to having the right tool for the job, it is important to know how to use the tool efficiently and effectively. Miyachi Unitek has developed a number of machining methods that enable the single-mode fiber laser to perform beyond its surface characteristics, while ensuring that the stability of the process is in line with volume production.

Miyachi Unitek
www.miyachiamerica.com

About the author: Dr. Geoff Shannon is the laser technology manager at Miyachi Unitek and can be reached at gshannon@miyachiamerica.com or 626.930.8448.