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The utilization of laser ablation of coating material on microelectronic parts.

Many scientists and engineers consider the creation of the first solid state transistor in 1947 by engineers at Bell Telephone Laboratories as the beginning of the microelectronics revolution. Winning the Nobel Prize in Physics, this small, low-power amplifier effectively replaced the bulky vacuum tube and opened the door to the fledgling computer industry. There have been continuous improvements in microelectronic technology and micromanufacturing capabilities ever since. It has resulted in microelectronic devices that are smaller, more reliable, and increasingly cost effective to produce on a large scale.

A 1972 article, published in the Journal of New Scientists, accurately predicted, “If microelectronics can make small computers as inexpensive as telephones, then people will buy them and eventually they will affect life to even a greater extent than the TV set . . . and the lack of bulk in microelectronics is reason enough to believe that in the future a micro-miniature TV camera, moving inside the body, is possible.”

But it was Jack Kilby, a newly hired engineer at Texas Instruments, and his 1958 invention of the monolithic integrated circuit, the microchip, that laid the conceptual and technical foundation for the entire field of modern microelectronics. His ingenious breakthrough allowed an entire circuit to be manufactured on the surface of a thin substrate of semiconductor material.

These advances and others in the field of microelectronics have been the foundation for today’s smart phones, driverless cars, iris security scanners, bionic body parts, 3D virtual reality gaming, 360° cameras, and even an electrochemical acidification carbon capture skid that turns sea water into fuel for U.S. Navy warships.

Within the medical category, as predicated back in 1972, microelectronics are now an essential technology in colonoscopy procedures where pills containing a micro-size camera travel through the intestine and provide up to eight hours of images for the doctor – all without anesthesia. Other medical applications include implantable devices and electroceuticals such as neuro stimulation devices, implantable RF transceivers, and cochlear implants that require advanced microelectronics.

Many components found in normal electronic design are available in a microelectronic equivalent and are in high demand. These include transistors, capacitors, inductors, resistors, diodes, insulators and conductors. In fact, the Semiconductor Industry Association (SIA), reports that for the third quarter of 2016 worldwide sales of semiconductors reached $88.3 billion, marking the industry’s highest-ever quarterly sales and an increase of 11.5 percent compared to the previous quarter.

Overcoming problematic issues facing microelectronic advances.

The increased demand for microelectronics is profitable news for manufacturers, but there is a potentially negative side engineers face. Their constant worry is due to the sheer nature of the small size of these parts and the fact that the delicate circuitry and componentry can be easily damaged if left unprotected.

Another engineering challenge is that applications for these parts are within harsh environments with extreme temperatures, dirt, water, pressure, acidity and altitudes that reach into space. This is why in part many microelectronics are designed and manufactured with protective coatings. These protective layers provide electrical insulation, cushion against mechanical shock and vibration, prevent abrasion and provide environmental protection. While the coating itself is beneficial, specific coating areas, which can be micro-sized and intricate, often need to be removed in the manufacturing process to create bonding surfaces, circuits or to make repairs.

Conventional processes for coating removal and the effects on microelectronic parts.

Coatings used for microelectronics range from acrylic, epoxy and silicone, to organic polymers such as polyimide, polyurethane, and parylene. There are many methods for removing these coatings on microelectronics with the use of chemical, thermal, mechanical, abrasion processes. While these coating removal options do have some useful applications, each one has limitations and can result in problematic if not catastrophic consequences to the actual microelectronic part.

Consider a microprocessor chip for example. Chemical removal or stripping of a coating using an emersion technique can cause extreme expansion or swelling of the base material. This can result in degrading the actual assembly integrity. This process also involves substantial lengths of emersion time and it’s difficult to prevent the harsh chemicals from seeping under the coating material, essentially removing area that should remain in place. There is also the adverse impact to the environment if the chemical is not properly used, maintained and disposed of post process.

Using an abrasive process (such as micro-blasting) can be effective and damaging at the same time. As stated in a recent article in Circuits Assembly, “Micro abrasive blasters can generate static electricity as the high velocity air and particles impinge on the part surface. The voltage generated at the point of contact can cause damage to components and electrical circuits on an assembly.” This is definitely something every manufacturer wants to avoid.

Then there are mechanical coating removal methods. These typically involve cutting, picking, sanding or scraping a specific surface area of the coating to be removed. A mechanical process is not overly precise and is generally suited for spot removal of a coating where a high-quality end-product is not required. In addition, the mechanical coating removal is a very slow process often demands highly trained operators using incredible care and attention to the tiniest detail (not an easy proposition for anyone to successfully complete day in and day out) or the product could be irreparably damaged.

As the name implies, the thermal technique of microelectronics coating removal literally means burning the unwanted material off. This could involve tools such as a soldering iron and is a process that emits toxic fumes, is difficult for any operator to precisely manage and can easily damage coating material that is not intended for removal.

There is one microelectronic coating in particular that is nearly impossible to thoroughly remove using conventional processes: parylene. It can be applied and be instantly effective. It’s indestructible and is the primary coating choice for military and aerospace protection of printed circuit boards and assemblies.

According to VSi, a specialist in applying conformal coating on devices, “Parylene is essential to the protection of printed circuit boards and assemblies, and its mechanical, electrical, and thermal properties make it ideal for use in defense, military, and aerospace applications. Parylene is highly resistant to chemicals, gases, liquids, temperature and electrical exposure. But this does make removal and repair a challenge.”

One problematic consequence resulting from many of these coating removal processes, besides the inability to maintain uniformed precision for every part on a mass production scale, is the debris that can lodge within the microelectronic part. If this waste material is not removed, the microelectronic can fail due to shorts and cause part fatigue during usage.

Laser ablation: a better solution for microelectronic coating removal.

In technical terms, laser ablation is the precise removal of protective coatings and is very well suited for high production quantities where volume and quality must be maintained. With “selective” laser ablation, individual coating layers can be removed. The depth of material removal can be highly controlled, allowing for single micron depth of coating removal. Additionally, with laser ablation, the primary method of material removal is vaporization, resulting in minimal residue on the product.

Damage to under layers or substrates is typically not an issue using laser ablation since this proven micromanufacturing solution leaves the surfaces of conducting core material undamaged and without post process marks and defects (i.e.; cracks that result in material degradation, etc.). Another benefit to laser ablation is the precision coating removal to form spot, line shaped or two-dimensional geometry patterns.

Laser Light Technologies specializes in the ablation of a wide variety of microelectronic coating materials used in applications for electrostimulation devices, avionics, life sciences and countless other areas. This even includes parylene may be a challenge for other companies using traditional coating removal processes. With the precision thinking solutions at Laser Light, and our laser ablation capabilities and experience, we can deliver 100% parylene-free areas without underlying structure damage (even when ablating very small, precise and intricate shapes).

We have over 30 years of proven industry experience in all aspects of laser micromanufacturing and apply our knowledge base and experience daily to microelectronic coating removal (as well as micro cutting and drilling). These parts are on a micro scale in size and must be mass produced quickly and with unmatched precision (compared to other processes).

Our team of engineers work with each client to determine their exact laser ablation needs and requirements. From there we can determine the most advanced laser system technology to use at our facility. This consultative process ensures that each project uses the most effective laser wavelength, pulse energy, and number of pulses for optimal and efficient removal of the coating surface area – all without any detrimental impact to the properties of the underlying material.

At Laser Light, we are constantly implementing new micromanufacturing ablation process methods that are above and beyond conventional solutions in regards to precision, speed and production output. Plus, our laser-based coating removal is RoHS compliant since it avoids the use of acidic/caustic solutions which require extreme handling and disposal care that is typical with chemical processes.

That’s the Laser Light difference in the field of laser ablation for microelectronic coatings. Now imagine what we can do for the success of your project.