Plasma-activated bonding is a technology-driven process that enhances the adhesion of an object's surface. The primary goal of plasma-activated bonding is to modify the surface of an object to allow for printing or bonding.
Several surfaces, such as highly glossy plastics, metals, or rubbers, are naturally resistant to adhesives such as paint, ink, or glue. The surfaces of such objects refuse to stick to one another, resulting in poor-quality finished products.
By employing plasma bonding, the surface of an object undergoes modifications to increase its wettability or hydrophilicity, making it easier for a liquid, such as paint, ink, or glue, to adhere to the object. As such, plasma bonding is an effective way to modify surfaces that would otherwise be challenging to bond with.
We will explore how this technique works, particularly for materials that are intrinsically resistant to adhesion, such as Polydimethylsiloxane (PDMS). Furthermore, we will examine the two types of plasma bonding, namely, low pressure and atmospheric pressure, and explain their respective applicability to varying needs.
In this article, we’ll teach you all you need to know about the plasma bonding process, so you will have a comprehensive understanding of the plasma bonding process and how it can benefit your professional endeavors.
What is Plasma-Activated Bonding?
Plasma-activated bonding — or simply “plasma bonding” — is the process in which we can increase the surface adhesion of an object through the usage of plasma technology. The purpose of plasma-activated bonding is to change the surface of an object so that it may be printed on or bonded with.
There are specific surfaces that are naturally resistant to items such as paint, ink, or glue. These can be highly glossy plastics, metals, or rubbers. The surfaces of these objects will refuse to stick to one another and will naturally resist paint.
If one were to print on a highly glossy surface, the ink will not stick to this space very effectively. It is possible that the finished product will look low quality. The use of plasma bonding will create modifications on the surface of an object to increase its wettability or cause it to be more hydrophilic. Simply meaning that a liquid, such as paint, ink, or glue, is more likely to stay on the object.
Through the process of plasma-activated bonding, the surface of the object will be entirely cleaned of any organic contaminations due to the nature of plasma technology. However, the surface of the object must be completely clear of micro debris before the process can be complete.
As a specific example, a silicone polymer called Polydimethylsiloxane (PDMS) is largely used in industries such as factory lubrication, medicine, cosmetics, contact lenses, stereolithography, and several other uses. Naturally, this object is highly hydrophobic — meaning any water-based liquids or glue will refuse to stick to it. Plasma bonding can be used on this object to increase how hydrophilic it can be.
The essential plasma process to promote bonding
If we take the PDMS plasma activation process, we need to consider that the PDMS will have on its surface organic aliphatic groups that are typically hydrophobic. This means that the PDMS surface will have poor bonding capabilities with hydrophilic substances; the objective of the plasma activation process is to modify the terminal groups to obtain hydrophilic groups.
This can be obtained by using an oxygen plasma; this plasma will remove all natural contaminants on the surface by utilizing highly reactive oxygen radicals. After the contamination removal, the plasma will convert the superficial hydrophobic groups of the PDMS into silanol (Si-OH) groups., These groups, being hydrophilic, will guarantee a stronger connective bond.
This plasma activation process is able to overcome the strong hydrophobic nature of the polydimethylsiloxane surface, allowing it to bond easily with other materials.
It is worth noting that plasma-activated bonding is a highly safe procedure since it does not alter the entire depth of an object. Instead, it only makes modifications minimally on the top few molecular layers. This way, the strength of the object overall is unchanged.
The process also avoids using any toxic chemicals which may be dangerous to humans or the environment.
The Two Types of Plasma Bonding
There are two basic types of plasma bonding, and either can be used depending on your needs.
1. Low Pressure
Low-pressure plasma-activated bonding happens within a vacuum plasma chamber. In the process, a low-pressure environment is required to complete this task.
This process is used when dealing with materials that are tough or difficult to process and have dimensions for which building a vacuum chamber does not become economically not sustainable.
The bigger the materials to treat, the bigger the vacuum plasma chamber become. This has an adverse economic effect as the means to maintain a certain productivity, i.e. the vacuum pumping systems, will become more and more expensive, driving up the cost of the overall system.
2. Atmospheric Pressure
Atmospheric pressure plasma bonding can be used on a production line when large surface substrates need to be treated with high productivity. This process does not require a vacuum chamber, and what it does differently is that it can create a plasma with a gas at atmospheric pressure.
The plasmas obtained with this technique are less performant than those created in a vacuum chamber as they need to be directed specifically on the surfaces to treat. They can’t access hidden spots and may cause overheating and damage to the products.
That said, the cost of these units is reduced compared to the vacuum plasma solution. Depending on the type of product to be treated, one technology is more appropriate than the other.
Is Plasma-Activated Bonding Right For Your Needs?
Whether one is interested in plasma treatment, plasma bonding, plasma cleaning, or other techniques, SCI Plasma has the professional knowledge and background to offer the best advice. SCI Plasma has expertly written guides in addition to its plasma bonding equipment. This way, one can brush up on even more knowledge when it comes to plasma bonding.
If you're interested in vacuum process technologies for the Semiconductor, Electronic, Automotive, Medical, and Life Science industries, there are various solutions available, such as Batch Plasma, Inline Plasma, or Strip Plasma. However, since these processes are highly specialized, it's advisable to consult industry-leading professionals who can provide customized solutions to meet your specific needs. These experts can help you identify the most suitable vacuum process technology for your application and guide you through the entire process, ensuring you achieve the desired results. So, if you want to ensure the success of your project, get in touch with us today.