How Long Does Surface Preparation Last?

Surface preparation is a critical step in manufacturing applications, especially for critical industries like semiconductor packaging, electronics assembly, aerospace and medical devices. The effectiveness of surface preparation hinges on how long treatment benefits last before surface changes or recontamination occur.

Understanding the impact of surface contaminants, variables impacting preparation longevity, and methods for measuring and validating surface activation is essential for engineers seeking optimized processes and consistent results.

Coating Adhesion: The Science Behind Surface Preparation

Surface preparation is the process of cleaning, activating or modifying a surface to enhance coating, bonding, adhesion or other downstream processes. It directly impacts the longevity, reliability and quality of assembled products.

Proper surface preparation ensures a coating lasts and performs as expected. Poor preparation can allow contaminants like dirt, rust or oil to create a barrier between the surface and coating, preventing adhesion and leading to cracking, peeling and coating failure.

Surface preparation is rooted in surface chemistry, where even microscopic contaminants or surface irregularities can dramatically affect performance and adhesion. For instance, in semiconductor packaging, the surfaces of lead frames are often contaminated with organic residues, oxides or particulates from previous processing steps. Surface preparation using plasma treatment can remove these unwanted layers and increase surface energy to make the substrate more receptive to bonding. 

Ultimately, the effectiveness of surface preparation determines the success of downstream processes. Understanding and controlling surface chemistry allows engineers to create a consistent product quality while reducing the risk of defects and extending component operational life.

The Impact of Surface Contaminants on Duration

For applications where coating is necessary for enhancing protective properties, proper surface preparation is essential. Inadequate surface preparation can result in coating problems like:

• Peeling and flaking: Coating may not adhere to the surface and peel off in sheets. 
• Blistering: Trapped contaminants, air or moisture beneath the coating can create bubbles and lead to blistering.
• Rusting: Metal surfaces can experience rust or corrosion under coating, causing components to fail.
• Delaminating: Coating layers may separate from the substrate or other coating layers. 

After cleaning or activating a surface, the substrate becomes immediately vulnerable to recontamination. Depending on the environment, recontamination can occur within minutes or hours, and this process directly limits the activation window for a surface to remain in an optimal state for bonding, coating or assembly.

Common surface contaminants include grease, oils, dust, metal oxides and moisture. In manufacturing environments, airborne molecular contaminants can also settle on freshly prepared surfaces. For example, trace amounts of hydrocarbons from the air can absorb onto a plasma-treated wafer in semiconductor packaging. This process reduces surface energy and negates the benefits of the plasma treatment.

The length of time a surface remains in a high-adhesion state is highly variable. In a clean room, surfaces may retain activation for several hours, while standard production environments may offer mere minutes of activation for the same surface.

Other Factors Influencing Surface Preparation Longevity

While contaminants are often a primary concern for treatment longevity, several other factors influence preparation longevity, including:

• Substrate materials: The treated material has a significant impact on preparation longevity because each material can be subject to various processes. For example, metals are prone to rapid oxidation, and aluminum surfaces can form new oxide layers within minutes with air exposure.
• Environmental storage conditions: The treatment environment also impacts duration, as high humidity can accelerate water molecule absorption, which can neutralize or mask active surface sites. Elevated temperatures can increase contaminant mobility and promote unwanted species diffusion.
• Type of plasma treatment: Specific plasma treatment processes will also affect longevity. Processes relying on ionized gas can make surfaces more suitable for operations like bonding, coating and printing. These processes can improve adhesive properties and wettability, enhancing the quality and longevity of subsequent processes.

How Long Does Plasma Surface Treatment Last?

Plasma surface treatment length often varies by application, as various sectors have unique operating conditions. Common applications include:

• Semiconductor packaging: Plasma treatment is common in semiconductor packaging to clean and activate surfaces before processes like wire bonding, encapsulation or die attach. This field often has shorter activation windows in less controlled environments. For best results, teams should complete critical steps like adhesive application or bonding as soon as possible after treatment.
• Electronics assembly: In electronics assembly, plasma treatment can improve solderability, conformal coating adhesion or wire bonding. Treatment longevity is highly dependent on environmental cleanliness. In standard production environments, plasma activation benefits may only last for a few minutes before recontamination occurs. 
• Aerospace and automotive: The aerospace and automotive industries often use plasma treatment to prepare metal, composite or polymer surfaces for structural adhesive bonding or painting. In these applications, activation windows can last several hours to a few days if parts are stored in inert atmospheres. However, exposure to handling, air and humidity can rapidly diminish the treatment benefits.
• Medical devices and diagnostics: Medical device and diagnostics manufacturing demands strict control over surface properties. Material type and storage conditions can cause treatments to last between several minutes and several hours. Critical applications, such as catheter assembly, often rely on continuous processes for treatment and assembly to minimize recontamination risks.

Across sectors, teams can optimize the length of activation for plasma treatments by minimizing the time between treatment and subsequent processing.

Measuring and Validating the Duration of Plasma Treatment

Engineers must employ reliable methods to measure and validate treated surface properties. This process is essential for maintaining quality, optimizing process windows and meeting industry standards. Measurement and validation strategies include:

• Contact angle measurement involves placing a drop of liquid on the treated surface and measuring the formed angle between the surface and the droplet. Lower contact angles indicate higher surface energy and better adhesion. Measuring the contact angle at regular intervals can help engineers determine plasma treatment decay rates to optimize activation windows.
• Surface energy testing uses dyne test kits or pens with known surface tensions. Liquid or ink will bead on the surface if the surface energy is lower than the known value of the test liquid. In areas where the liquid does not bead, the surface energy is at least as high as the value of the liquid or pen.
• Adhesion testing can directly measure bond strength after plasma treatment. Performing mechanical tests, like peel tests or lap shear tests, at various time intervals post-treatment can help engineers establish practical durations.

Optimizing Manufacturing Processes With Surfx Technologies

Surfx Technologies provides atmospheric argon plasma systems for semiconductor manufacturing. Our plasmas offer unparalleled surface treatment, allowing engineering teams to boost efficiency and product quality. Working with us means transforming your operations with products suitable for manufacturing across applications.

Request a demo to learn more about our processes and products.