Cutting-Edge Plasma Treatment System Innovations from Nordson MARCH

Interview conducted by Alexander ChiltonJul 8 2015

David Seletak, Senior Business Development Manager at Nordson MARCH, talks to AZoM about their cutting-edge plasma treatment system innovations.

Could you provide our readers with a brief overview of the history of Nordson MARCH and explain how the company has grown over the last 25 years?

Nordson MARCH is a combination of two companies, Advanced Plasma Systems (est. 1981) and March Instruments (est. 1984), which were acquired by Nordson in 1996 and 1999, respectively.

March Instruments’ primary concentration was on plasma systems for the packaging of microelectronics – starting with tabletop and batch equipment, before transitioning to automated systems in 1998. Advanced Plasma Systems focused on customized large chamber plasma systems, using that experience to develop equipment for the printed circuit board (PCB) industry in the mid 1990s.

By 2002, Nordson MARCH had integrated the core competencies of both companies to build the foundation for the current compact, self-contained, and customizable plasma systems, allowing the company to expand beyond PCBs and microelectronics, into the life-science, hard disc, and electronics manufacturing and packaging industries.

In the years to come, Nordson MARCH plans to further expand on this core competency, targeting wafer-level packaging, automated PCB panel processing, and plasma enhanced conformal coating.

Could you explain what plasma treatment is and summarize the different types of plasma available?

Plasma treatment is simply the removal or addition of material/energy on any surface. There are five types of plasma, with four occurring in a low pressure (vacuum) environment and one at atmospheric conditions.

Each type of plasma has advantages and disadvantages, depending upon the process and material receiving treatment. Capacitively coupled plasma (CCP) places the material between the two electrodes generating the plasma. Inductively coupled plasma (CCP) is generated inside a tube, above the material requiring treatment.

Vacuum pull and bias help to draw the plasma towards the material. Unlike CCP and ICP, microwave plasma operates in the GHz range, not the MHz and KHz range. Like CCP, the material receiving plasma treatment can be placed directly in the area of plasma generation.

The last vacuum-based type of plasma is ion free plasma (IFP) or commonly known as downstream plasma, where ions are removed from the plasma to produce a highly reactive environment made of free radicals.

What are the advantages and disadvantages of the use of each different type of plasma?

If comparing between atmospheric and vacuum plasma, then the primary difference is surface treatment efficiency and longevity. Atmospheric plasma does not have the ionization energy to penetrate deeply into the surface, resulting in a shallower treatment and lower surface energy than vacuum plasma.

In contrast, atmospheric plasma is not limited by the size of a vacuum chamber, which enhances integration and utilization in fields such as automotive manufacturing, textile fabrication and food processing.

If comparing between the types of vacuum plasmas, then the advantages and disadvantages depend upon the application and device/substrate properties. When the device is sensitive to temperature, then CCP will have an advantage over ICP and microwave. If charge potential is a concern, then ion-free or microwave, which produces ions with a lower energy level, is preferable to ICP and CCP.

For UV sensitive components such as image sensors, then downstream plasma is preferable over direct plasma. Because of these varying differences between the plasma sources, it is always best to discuss the application with a plasma expert prior to selecting a system or platform.

MaxVIA Plasma Treatment System

When should plasma treatment be considered for implementation in the process flow? Is the treatment permanent or temporary? If it is temporary, what is the duration?

Plasma treatment should be considered for implementation in the process flow when there is a need to modify the surface property, resulting in an improvement to the final product. As noted in the previous discussion on the types of plasmas, consideration should be given to the device and material before selecting a type of plasma and process.

Not all plasma processes are permanent, so dwell time between the plasma treatment and the next process step can be critical. In the case of plasma treatment prior to wire-bonding, the duration is anywhere from 8 to 72 hours.

This wide range of time is a result of the plasma process time, the metal or alloy of the bond pad, the material of the lead-frame, the acceptable level of oxide re-growth, and the type of plasma. Not all cases are similar to plasma prior to wire bonding. For some medical applications, the temporary effects of plasma treatment can last as long as 6 months.

What are the types of equipment which are used for plasma treatment?

Typically, plasma treatment equipment falls into four categories – handheld, batch, standalone automated, and inline automated. Handheld is usually reserved for atmospheric plasma, since the plasma nozzle or jet can be used by hand or integrated into an assembly line or robot to plasma treat parts that would not conform or fit inside a vacuum chamber.

Batch plasma systems range in size from small tabletop units (R&D and lab experimentation) to large freezer-size models (high volume production). Loading and unloading of batch plasma systems is manually performed by the user or operator. Standalone automated systems are typically small plasma chambers that can process one or more components with each plasma cycle.

Loading and unloading of the plasma chamber is performed by a robot, which will pick and place components for treatment from their carrier – magazine or cassette. Inline automated plasma systems integrate directly into the assembly line.

Parts arrive at the system via a conveyor, where a robot will move the part into the chamber for plasma treatment before returning it to the conveyor, which will transport the part to the next equipment for further processing.

What are the factors which must be considered when choosing a plasma system? Can a plasma system be integrated into an automated production line?

The desired process and composition of the component or substrate are the key decision factors in choosing a plasma system and the type of plasma. As previously noted, each device mounted to the substrate undergoing plasma treatment needs to be considered when choosing the type of plasma – direct, CCP, ICP, microwave, IFP or downstream.

Once a plasma mode has been selected, the next factors to consider are the mechanical strength and physical property of the substrate. Can the substrate be handled by a robot? What are the keep-out regions that cannot be touched by a robot, gripper, pincher, roller, etc? Are there wires or leads on the substrate and what level of vibration can these wires handle during load/unload?

The first factor to consider on the process side is uniformity. A smaller chamber that processes one to 10 units at the same time will yield a more uniform treatment than a large batch system that processes 30 to 100 units.

The second factor to consider is process time. A small chamber will require less time to process a handful of components, but the overall throughput might not equate to a batch system that processes several hundred components with a single run that requires more time.

The third factor to consider is over-treatment, which could lead to changes in physical appearance of the product or damage to some devices mounted on the substrate. In a small chamber, the uniformity is high, so all parts receive the same rate of treatment. In a large batch system, the uniformity is low, so some parts will receive less treatment than other parts.

To insure that all parts receive adequate plasma treatment, the process time is dictated by the part that receives the least amount of plasma treatment. This translates into some parts receiving 2 or 3 times the desired plasma treatment.

Yes, a plasma system can be integrated into an automated production line. All of the previously mentioned factors need to be considered before planning the integration. Assuming the shape and size of the substrate fits inside the plasma chamber; the first integration factor is the method of delivery. How will the factory automation deliver the substrate – conveyor, overhead robot, shuttle, etc? Who will be responsible for the automation or hand-off at the plasma chamber – the equipment manufacturer or the factory?

The next integration factor is the communications protocol between the equipment and the factory. Is the factory using standard protocols such as SMEMA, SECS/GEM, or MES or something proprietary? The last integration factor to consider is the hand-off or transfer point. Will this be to the front, left or right of the plasma chamber? Does the customer want a pass-through system or drop-off and return?

Is a plasma system a ‘plug and play’ system? How critical is the need for application support and will any plasma system produce the same result?

Instead of answering this question, I will just give an example from one of our customers. This customer had plasma systems from Nordson MARCH and two of our competitors. Instead of asking for assistance with recipe development, the customer created a recipe and used the same recipe for all three plasma systems.

After three months of usage, the customer complained that the MARCH system was only achieving 98% yield, while the other systems were at 100%. A field application engineer was sent to check the system hardware for issues. He found nothing wrong, but noticed that the process recipe was not optimized for the application or system.

He ran some experiments with the customer and developed a new recipe that used less gas flows, lower RF power and shorter process time. In the end, the MARCH system was able to achieve a 100% yield, but with a higher throughput than the competitive plasma systems.

What are the key application areas which benefit from plasma treatment?

In the semiconductor packaging industry, plasma treatment has been shown to improve wire-bonding, flip-chip underfill, molding, wafer bumping and package marking. After the semiconductor devices are mounted on PCB boards, plasma improves conformal coating or even be used as a method to deliver ultra-thin coatings. At the electronics assembly level, plasma has been shown to improve adhesion between non-compatible components in camera modules, mobile phones and wearable devices.

For life-science apparatuses and devices, plasma has improved the compatibility of implanted electronics with the human body. In addition, plasma has made soft-contact lenses more resistant to bacterial growth, comfortable to wear and breathable.

Outside of packaging, plasma treatment is a core process in the manufacturing of PCBs. Plasma is used to remove smear from blind and through vias after mechanical or laser drilling. In addition, plasma is used to enhance the adhesion between the various layers that compose a PCB panel.

Why is plasma treatment particularly important in nanotechnology application areas?

In nanotechnology fabrication, the deposition and removal of thin films is typically in the nanometer to micrometer thickness range. By using plasma, it is possible to control the reaction rate and uniformity of the process.

With plasma, treatment is performed at the atomic level, which minimizes the overall height and size of the completed device. After fabrication, plasma continues to play a role in the packaging and assembly of the device. With the usage of plasma, it is possible to achieve better adhesion between surfaces, while minimizing the thickness of the adhesive or protective layer.

Due to more stringent reliability standards today in the automotive industry and the consequences of failures in the medical and aerospace industries, the use of plasma treatment has recently become more critical. Could you provide our readers with an overview of these recent developments in industry?

As more and more electronics become a part of our daily lives, the reliability of automotive, medical and aerospace electronics needs to live well beyond the normal life expectancy of consumer electronics, which can be anywhere from 1 to 5 years.

This push or initiative for greater reliability is not driven by one or more government bodies or laws, but more from protection against liabilities and lawsuits. If you recall the airbag sensors and ignition switch issues that plagued GM between 2003 and 2012, then you know the cause of the 303 deaths were attributed to the failure of the electronic devices in those modules.

To mitigate potential risks to both the company and end users, manufacturers are enhancing reliability by improving the assembly and packaging process to withstand harsher elements and environmental conditions.

For example, the aerospace industry implements plasma treatment prior to wire-bonding to minimize early failures and shorts, before conformal coating to strengthen adhesion and protect the circuit against harsh conditions, and ahead of hermetical molding to eliminate contaminants that could outgas or cause package separation.  

How do you see the plasma treatment industry progressing over the next five years?

Plasma has been around for a long time and the progression of the technology is more about cost/value than capability. A good example is plasma dicing. At present, the average price for a plasma dicer ranges from 1 to 1.2 million USD. This is 1.5 to 5x more than a comparable laser dicer or blade dicer, respectively.

Within the next five years, the scribe lines between dies and wafer thicknesses will decrease, pushing the dicing market from blade towards laser and ultimately plasma.

This doesn’t mean that blade and laser dicing will completely disappear, but it just means more acceptance and usage of plasma dicing for the higher valued devices, where yield is paramount.

Beyond dicing, plasma treatment is already making headway in emerging applications such as wafer-level fan-out packaging and thin wafer destress.

About David Seletak

David has been with Nordson Corporation since 1980. His current responsibilities for Nordson ASYMTEK and Nordson MARCH are to develop business opportunities that involve technologies from both businesses, such as conformal coating and plasma treatment.

In previous positions within Nordson, David has worked in direct sales for both ASYMTEK and MARCH, and for several other Nordson product lines in several technology and manufacturing industries.

He has a BS in Accounting/Finance from Baldwin-Wallace University, Berea, Ohio.