Laser scribing is used for forming kerfs, for rated break points for separating brittle materials, or for opening up channels in a variety of materials. Depending on the material, a maximum scribing speed of several meters per second can be achieved. Applications are found in the electronics, solar/photovoltaics, semiconductor, medical and packaging industries.
Laser cutting is a laser based technology used to cut a variety of materials for industrial manufacturing, medical, and other various applications. Laser cutting works by directing the output of a high-power laser through delivery optics that manipulate the beam and deliver to the work piece. The laser beam is typically focused by a lens to a small spot size (<100um) for fine cutting, and to a larger diameter (>100um) or thicker materials. Often times gas, or forced air is delivered directly about the laser focus spot to keep the optics clean and remove the cut material from the surface. Depending on the customer’s requirements, and materials, gas assist can be used to improve the cutting quality and speed. A variety of different laser sources can be used for laser cutting, both pulsed and CW. Some of the main criteria for selecting the appropriate laser source are material type, material thickness, desired speed/throughput and quality needed. Nanosecond and longer pulsed lasers are often used for cutting thicker materials, where as picosecond or femtosecond lasers are typically used to cut thinner materials. In the case of the nanosecond and longer pulsed lasers, the wavelength that is used has to be matched to the material type due to the fact that in that pulse regime, materials absorb some wavelengths better than others. For example in the glass we’ve found that often the visible wavelength absorbs better with a nanosecond pulse. For ultrafast lasers, such as picosecond laser and femtosecond lasers, matching the material type to the wavelength is not nearly as critical, as the means of removal is not dependent on the wavelength absorption.
Laser drilling is a process in which lasers are used to make holes, instead of conventional mechanical drilling. Laser drilling is one of the few techniques for producing high-aspect-ratio holes. Laser-drilled high-aspect-ratio holes are used in a variety of applications, including the automotive, solar, industrial, aerospace and medical industries. By selecting the proper laser source and beam delivery optics the user can accurately control the feature size and shape of the hole being drilled.
Lasers make it possible to machine very small, blind, unusually shaped high aspect ratio and precisely tapered holes into all types of materials. Lasers can be used to drill holes at steep angles and process otherwise difficult-to-machine materials. Laser drilling is a non-contact process, so there is no tool wear or breakage and minimal material distortion. By selecting the proper laser source and parameters users can control how much heat is induced into the material. Laser drilling can lead to an increase in throughput with less setup time for switching out tooling, and an increase in quality and process versatility.
A variety of solid state lasers can be used to mark, etch, and process products in just about every industry. Plastic, metal, glass, and ceramic materials can be laser marked with various identifiers including corporate logos, product labels, barcodes, lot and date codes, or any other desired feature. Fiber lasers or free space lasers can be used for this process. Often times fiber lasers are used for their ease of integration. Free space pulsed and CW lasers are used where materials require higher peak powers than what are available in fiber lasers, or where harmonics are needed for better material absorption.
Laser welding is a welding technique that utilizes a focused laser beam to thermally join materials. Most laser welding is done on metals, but there are laser applications for laser welding plastic, and even laser welding glass. Laser welding relies on the high power density of a laser beam to apply localized heat in a focused spot to join materials together. Typical power densities seen for laser welding are on the order of 1MW/cm². The average power used is proportional to the penetration depth achieved in most materials. The higher the average power, the further the laser weld penetrates into the material. High power CW lasers are often used for laser welding thick materials, as millisecond pulsed high energy lasers cater to thin metals, such as razor blades or jewelry. When choosing a laser source for laser welding, the absorption wavelength of the material must be considered. The most common laser sources used for laser welding are solid state lasers and gas lasers.
In recent years, interest has grown rapidly in developing pulsed ultrafast laser sources in the picosecond and femtosecond regime with high output powers. Such sources are starting to make a big impact on a variety of micromachining applications. At sufficient energy densities, when using a picosecond or femtosecond laser, electrons are stripped from the atoms inside the material and the positively charged atoms undergo a Coulomb explosion. The Coulomb explosion removes, via “cold ablation”, a material layer on the order of 10-100nm per pulse. Since the cold ablation process is material unspecific, ultrafast lasers provide a universal micromachining tool for virtually any material, unlike nanosecond lasers which partially rely on wavelength specific absorption to heat the material and ablate by evaporation. An ultrafast laser should be used anytime the user is looking to limit the amount of HAZ (Heat Affected Zone) on a given material. HAZ is almost always present when using longer pulsed nano or microsecond laser sources. Common features of HAZ are microcracks, darkening of the material along the laser cut and slag. Brittle materials, such as those used in the display and solar industry, benefit from the use of these ultrafast, picosecond and femtosecond laser sources. One example would be the solar industry that offers long term warranties on their solar panels. In that instance, microcracks and other HAZ related features can greatly reduce the lifetime and efficiency of the processed materials. Overtime microcracks could propagate through the material and lead to either a complete failure of the panel or a significant reduction in the solar panel’s efficiency. The medical industry also looks to picosecond laser and femtosecond lasers for their abilities to delivery superb quality when machining a variety of materials used for implantable devices.
Thin Film Removal
Laser thin film removal is the process of selectively ablating a very thin layer of material from a substrate. This process is used in a variety of application areas, with the primary applications being in the semiconductor and electronic fields. Common materials used for substrates and thin films include silicon, glass, ceramics, plastics and metals. Pulsed lasers are ideal for thin film removal as they offer control of pulse characteristics and the ability to operate at high repetition rates to allow for sufficient pulse overlap at high processing speeds. One of the most common means of thin film removal is via chemical etching that utilizes a masking technique and chemicals to remove films and create the desired pattern. This process, known as lithography, requires a significant investment with multiple steps that utilize environmentally hazardous chemicals that require proper disposal. Laser thin film removal is a low cost, low maintenance alternative to lithography with ease of use and no tool wear or hazardous materials to be dealt with.
Indium Tin Oxide (ITO) is a solid mixture of Indium oxide and tin oxide that is used to make transparent conductive coatings for the display industry, solar industry, LED industry and others, often created using a vapor deposition process. The conventional way of removing ITO has been via a wet etch process. An alternative to this wet etch process is laser ablation with either a pulsed UV nanosecond source, or a picosecond or femtosecond laser source.
Edge Deletion, LFC, Via Drilling, EWT, MWT,
Edge Deletion is a thin film removal application that is used in a variety of applications including solar and consumer electronics. Edge deletion is often utilized to electrically isolate the edge of the substrate so that it can be mounted into a frame or other support structure. Edge deletion is also used in the glass industry to remove coatings that have a negative effect on the adhesion properties of glass sealants. A wide variety of lasers can be utilized for this process. The composition of the material, and the quality and throughput requirements are the major factors when deciding on the appropriate laser configuration.
Laser Fired Contacts
Laser Fired Contacts is a c-Si solar application that creates a conductive path between the silicon wafer and the rear sided aluminum electrode. The light of the laser is focused onto the electrode which causes it to heat and melt through a non-conductive passivation layer, which is coated on the rear of the silicon, and bond directly to the Silicon.
A “VIA” in the electronics industry, is a hole through a material that creates an electrical path between two or more conductive layers. There are two types of VIAs, “through VIAs” and “blind VIAs”. A “through via” will go completely through the material, from one side to the other; as a blind via will stop at one of the layers inside of the material. The drilling of VIAs is often times a mechanical process, but as the size of the holes decrease, mechanical drilling is no longer a viable solution. So as the consumer market continues to push for smaller, more advanced electronics, the laser via drilling market continues to grow.
Emitter Wrap Through (EWT) is a form of laser drilling utilized in the solar industry that allows for the complete elimination of solar cell’s front side metal conductive grid which results in higher efficiency cells.
Metal Wrap Through (MWT) is a solar application that was developed to eliminate the bus bars on the front side of a solar cell.