An Introduction To Conductive Epoxies

Electrically conductive epoxies are adhesive compounds that integrate the bonding capabilities and other properties of epoxy resins with electrical conductivity. Electrically conductive adhesives (ECAs) are formulated to provide reliable electrical pathways while ensuring effective adhesion to various substrates. These qualities render ECAs highly suitable for multiple aerospace, automotive, medical, telecom, and consumer device applications. Conductive epoxies offer a clean, lead-free solder alternative for component attachment in many electronic applications where the bonded components are temperature sensitive.

This article aims to help you understand conductive epoxies, covering their types, benefits, and applications.

Composition of Conductive Epoxies

A conductive epoxy resin system consists of epoxy resin mixed with a conductive filler. The epoxy resin provides the adhesive and mechanical strength properties to the design, and the conductive filler contributes electrical conductivity. There are a variety of conductive fillers of different sizes, shapes, and types, including metallic particles (such as silver, copper, or nickel) or non-metallic particles (such as carbon or graphite).

Why Should You Use a Conductive Epoxy?

Electrically conductive epoxy performs two key functions. It can mechanically bond two surfaces (substrates) with robust bonding strength and form an electrical interconnection between the two bonded substrates. Various formulations of epoxy resin systems can improve strength and conductivity and offer properties such as low thermal expansion, high thermal conductivity, and heat resistance.

Types of Conductive Epoxies

Several conductive epoxies are available, each with unique properties and suitable for particular applications. Understanding the following types can help you choose the most suitable one for your application. It is important to consult product technical datasheets and consider compatibility with the intended substrates in selecting a product for a particular application. Specific properties and performance of conductive epoxy resin systems vary depending on the conductive filler used in the design, the filler particle size, shape, and concentration, and other factors.

Silver-Filled Conductive Epoxies

Silver (Ag) is highly conductive, making epoxies with a silver filler ideal for applications that require excellent electrical conductivity. Silver-filled epoxies also offer strong and durable adhesion to various substrates, including metals, ceramics, plastics, and glass, with reliable bonding. They exhibit good thermal conductivity and are corrosion-resistant.

Nickel-Filled Conductive Epoxies

Nickel-filled conductive epoxy systems provide a balance between cost and performance. Nickel (Ni) is a highly conductive material and provides reliable electric conduction yet is more cost-effective than metals such as silver or copper. Nickel-filled conductive epoxy has corrosion-resistant qualities, high strength and durability, relatively good thermal conductivity, and strong adhesion to various substrates, such as metals, ceramics, plastics, and glass.

Copper-Filled Conductive Epoxies

Copper (Cu) imparts excellent electrical conductivity as it is one of the most conductive metals. These epoxies contain copper particles, offering high electrical and thermal conductivity. Copper balances performance and cost, as it is more cost-effective than metals such as silver. Copper-filled conductive epoxy is an excellent thermal conductor with high strength and durability, is inherently corrosion- resistant, and exhibits strong adhesion with reliable bonding. They suit applications requiring high electrical conductivity, resistance to corrosion, and efficient heat dissipation.

Aluminum-Filled Conductive Epoxies

Aluminum (Al) filler provides moderate electrical conductivity and good thermal conductivity, and is often used when weight reduction is a concern.

Graphite-Filled Conductive Epoxies

Graphite is an excellent conductor of electricity. It can withstand mechanical stresses, thermal cycling, and vibration to ensure long-term reliability. Graphite has natural lubricating properties. Adding graphite to an epoxy system improves wear resistance and reduces friction properties. Graphite is a lightweight material and can be used to reduce the overall weight of a product. Graphite-based conductive epoxies are often used in applications requiring lubricity, such as sliding or rotating electrical contacts or coating components that experience friction.

Carbon-Filled Conductive Epoxies

Carbon-filled epoxies strike a balance between electrical conductivity and cost-effectiveness. Carbon particles, such as carbon black, have excellent electrical conductivity. They are commonly used in applications that don’t require extremely high conductivity but still need reliable electrical paths. They are lightweight compared to conductive epoxy with metallic particles, possess good thermal conductivity, and are inherently corrosion-resistant. They are more cost-effective than conductive materials such as silver.

Benefits of Conductive Epoxies

Conductive epoxies offer the following advantages, making them sought-after across diverse industries and applications:

Electrical Conductivity

The top quality of conductive epoxy resin is its ability to conduct electricity. Conductive epoxies act as efficient pathways for electrical signals, ensuring smooth and uninterrupted transmission. This characteristic is crucial in applications with vital electrical connections, such as electronic circuits or sensitive components. Electrical conductivity varies depending on the type and concentration of the conductive filler used in the system. A higher proportion of conductive filler results in higher conductivity but may weaken the bond strength by displacing the adhesive.

Strong Adhesion

Conductive epoxies excel in their adhesion properties, exhibiting excellent adhesion to a wide range of substrates. Whether metals, ceramics, plastics, or glass, they create secure connections that withstand various environmental factors.

Efficient Heat Dissipation

Conductive epoxies help prevent overheating and ensure optimal performance by efficiently dissipating heat generated by electronic components. This is particularly beneficial in high-power applications or devices with critical thermal management.

Mechanical Strength

Conductive epoxies offer excellent mechanical strength with their ability to withstand various stresses, including mechanical loads and thermal cycling.

Chemical Resistance

Conductive epoxies offer impressive resistance to chemicals, solvents, and environmental factors, safeguarding bonded components in harsh environments or against corrosive substances. This chemical resilience ensures the longevity and functionality of the epoxy’s electrical and adhesive properties, even in challenging conditions.

Thermal Stability

Many conductive epoxies exhibit good thermal stability and tolerate high temperatures without significant degradation. Conductive epoxies offer efficient thermal dissipation, thereby improving the reliability of electronic systems by cooling the component.

Versatility

Conductive epoxies can be tailored to deliver optimal application performance through formulation adjustments and targeted selection of conductive fillers.

Durability

The durability of conductive epoxy resin ensures long-term performance and reliability, reducing the need for frequent repairs or replacements. As a result, industries can rely on the enduring properties of conductive epoxies in applications where consistent and sustained performance is vital.

Ease of Application

The user-friendly nature of epoxy resin systems streamlines manufacturing and assembly processes, saving time and increasing productivity. As a result, smoother operations and faster turnaround times are enjoyed with the efficient application of conductive epoxies.

Common Applications of Conductive Epoxies

Here are some common applications where conductive epoxies are employed:

• Electronics:

  electronic component assembly, such as electrical bonding components (e.g., electronic chips and printed circuit boards), die attach processes and solderless interconnections, wire bonding, component renovation, display interconnections, and heat dissipation

• Aerospace and defense:

  enclosures, gaskets, and seals to provide electromagnetic interference (EMI) or radio-frequency shielding, grounding, and conductive sealing (e.g., aircraft electronics)

• Automotive:

  bonding sensors (e.g., for engine management systems), electronic control units, electrical grounding applications, cameras, ADAs, radars, and LiDARs

• Medical devices: medical electronics, electrode fabrication, and implantable device production (e.g., pacemakers)

• Energy and renewable sources:

  assembling fuel cells, solar panels, sensors, and batteries (e.g., for renewable energy systems or electrochemical applications)

• Telecommunications:

  bonding antennas, connectors, and electronic modules (e.g., for wireless communication devices)

• Consumer electronics:

  bonding touchscreens, display assemblies, and PCBs (e.g., for smartphones, tablets)

• Industrial equipment:

  bonding electronic modules, sensors, and control systems (e.g., for manufacturing machinery)

• Research and development:

  prototyping, circuit design, and experimental setups (e.g., in laboratories)

• Wearable Technology:

  bonding flexible electronics, sensors, and smart textiles (e.g., fitness trackers, smartwatches)

• Robotics:

  electrical connections, and circuit board assembly (e.g., for robotic arms, drones)

• Optoelectronics:

  bonding LEDs, optical sensors, and fiber optics (e.g., for lighting systems, visual communications)

• Instrumentation:

  bonding sensors, control systems, and data acquisition devices (e.g., for scientific instruments)

United Resin: Powering Connectivity With Superior Conductive Epoxies

United Resin has your solution for superior conductive epoxy resin. We have a legacy of over 50 years of experience with epoxy resin systems and have consistently met our valued customers’ epoxy resin needs. Our unwavering commitment is to excellence and quality.

United Resin’s conductive epoxy resin systems include the following featured products:

United Resin Conductive Epoxy with Hardener 601

Our most popular system, with very low resistivity and good lap shear strength. Approved and listed under NSN 8040-01-518-7921.

United Resin Silver-filled Epoxy with Hardener 601

Military-grade material meets Mil-Spec MMM-A-1931 TYPE II.

United Resin NCE Paste Adhesive with Hardener 205

For those electrically conductive applications exposed to salt water. Approved and listed under NSN 8040-01-231-2399.

United Resin Conductive Epoxy with Hardener 143

Designed to make electrical connections where soldering is impractical and for RF shielding applications. Approved and listed under NSN 8040-00-450-7259.

All United Resin epoxy systems are non-hazardous and REACH/RoHS compliant.

Contact us today to explore our high-quality epoxy resin systems, including conductive epoxy resin systems. You can also request a quote to get started.

The information presented in this blog is intended for general background and informational purposes only and not as advice about any product, application, or process. We encourage you to contact us for information concerning your specific needs and requirements and to discover how United Resin may assist you.

Key Considerations in Choosing Epoxies

Epoxies are two-part thermosetting polymers that consist of a resin and a hardener. Polymerization (curing) is initiated when the resin is mixed with a hardener (sometimes referred to as a catalyst). Epoxy resins form cross-links during this process, creating a three-dimensional polymer of great mechanical strength.

Epoxy resins are known for their excellent adhesion, chemical resistance, and mechanical properties. They are typically sold in kits that contain the two components in separate containers, although some formulations are one-component systems. When mixed, the resin and hardener react to form a rigid, durable material. As a result, they can be used as adhesives, coatings, and encapsulants in a wide range of applications.  Some epoxy systems are specifically designed for particular applications, so it is important at the outset to consider the requirements of the intended use and select an epoxy that suits that application.

Choosing the right epoxy for a project can be complex, as different epoxy systems have varying physical and chemical properties. Epoxy resin systems are highly versatile because a wide range of processing, cure, and property characteristics can be achieved. Epoxy systems can be modified to enhance specific properties.  For example, where fire safety is a factor, epoxy systems can incorporate fire retardant additives to enhance the fire resistance or fire retardance of the system.

Here are the key considerations you should keep in mind when selecting an epoxy:

1. Physical Properties

The following are some of the key physical properties to consider:

Adhesion

The core quality of epoxy is its exceptional strength and adhesive properties, with its ability to form bonds of great strength and durability.  It’s crucial, however, to consider the surface (substrate) to which the epoxy will be applied to ensure good adhesion. Epoxy is compatible with various materials, including metal, wood, concrete, and many plastics. Some items are unsuitable for bonding with epoxy resin.

Tensile Strength

Tensile strength measures the maximum tension a material can withstand before breaking and failing. Epoxies with high tensile strength are suitable for applications where the material will be subject to pressure or pulling forces. Higher tensile strength is important for applications subject to great stresses and strains and where structural integrity is critical.

Flexural Strength

Flexural strength is a critical mechanical property that measures the ability of the epoxy to resist bending, flexing, or twisting forces without breaking and failure. It’s crucial to consider flexural strength for applications where the material will be subject to warping or twisting, such as in construction, aerospace, automotive, and marine applications. High flexural strength generally indicates a material that can withstand greater bending and flexing stresses.

Compressive Strength

It is important to consider the compressive strength of epoxy, where the application must withstand heavy loads or pressure without cracks or failure. There are epoxies with high compressive strength to ensure the stability, safety, and durability of those applications where structural integrity is critical. A higher compressive strength generally indicates a material that can withstand greater compressive or crushing forces and is important to ensure the structural integrity of the final product.

Hardness

Epoxies are available in soft or harder systems.  If an abrasion resistant system is required, choosing an epoxy with high hardness is recommended.

Impact Resistance

Selecting an epoxy with high-impact resistance is ideal for projects requiring encapsulants or composite materials. This property ensures that the material can withstand sudden impact or shock. A related consideration is vibration dampening, where vibration may create undesired noise or lead to breaking and failure.

Heat Resistance

Epoxies with high heat resistance can withstand exposure to high temperatures, making them suitable for extreme heat applications. An epoxy system must be selected to handle the temperature range to which the application will be exposed, including high and low temperatures.

Chemical Resistance

Epoxies with high chemical resistance can resist degradation and damage when exposed to harsh chemicals or solvents. An epoxy system must withstand the particular chemicals to which it will be exposed.

Electrical Properties

In addition to the other physical properties of epoxy, epoxy is widely used in the electronics industry for its excellent electrical properties. Epoxy has high dielectric strength, making it ideal for insulating electrical components. It has a low dielectric constant, a factor in determining the capacitance of electrical parts, a low dissipation factor, high volume resistivity, and high surface resistivity, which are important measures for effective electrical insulation.

It also has low thermal conductivity, making it an excellent thermal insulator. The significance of these properties to a particular application should be considered in evaluating and selecting a suitable epoxy system.

Water Resistance

Epoxies with high water resistance are ideal for marine coatings, flooring, and other applications where water contact or moisture is expected.

Viscosity

A viscosity appropriate for the specific application is important. Viscosity can impact ease and manner of use and application.

Aesthetics

Epoxy can benefit a project by improving its aesthetics. If important to the project, an epoxy that meets your needs for both finish and color (even clarity) should be considered. Epoxy also can improve application aesthetics by eliminating the need for metal fasteners in some bonding applications.

2. Mixing Ratio and Curing Time

It is imperative to accurately measure and completely mix the resin and hardener in the prescribed ratio to achieve the desired performance characteristics. Proper curing is essential for achieving optimal properties and longevity of the cured material. Following the manufacturer’s recommendations on curing time and environmental conditions is crucial to ensure the best results. The curing time will impact the production time of the application. An epoxy system may have a long or very short curing time, and a system may be formulated to fine-tune the desired working time.  The curing time determines the length of time to work with the material before it starts to harden.

3. Application Method

The method of application may be selected to best suit your needs and can also affect the performance of the epoxy. Application methods can be semi-automated or manual. Some methods are more suitable for certain applications than others and the selection of the appropriate method depends on the requirements of the project, its size and scope, and the desired outcome.  The following are some common methods of application:

Brush, Roller, Cartridge Gun, Syringe, or Bottle

Brush, roller, cartridge gun, syringe or bottle application are simple and cost-effective methods of applying epoxy. They are suitable for small to medium-sized projects and can be used for coatings and adhesives.

Spray

This fast and efficient method of applying epoxy is suitable for large projects and can be used for coatings, adhesives, and encapsulants.

Pour or Injection

Epoxy resin systems may be poured, via semi-automated or manual methods. The injection is a specialized method of applying epoxy that involves injecting the material into a cavity. It is commonly used for concrete repair and can be used for encapsulants and adhesives.  Dispensing machines are frequently used in potting or encapsulation applications, as they accurately mix and dispense the material in a controlled manner.

4. Precautions

It is important to follow all manufacturer’s instructions for use and precautions. Reviewing the safety data sheet (SDS) and taking the necessary precautions — such as wearing appropriate protective equipment and working in a well-ventilated area — are important.

5. Cost

The cost of epoxies can vary widely depending on factors such as quality, quantity, and application method. Because epoxy offers durability, reliability, low maintenance, versatility and reduced waste, among other factors, it can be the most effective cost solution to your application needs. The price must be evaluated in the context of these factors, as well as the performance requirements of the project.

Trust United Resin for Your Epoxy Resin Needs

United Resin is your trusted partner for your epoxy resin needs. With our wide portfolio of established epoxy resin systems and our continual focus on innovations to serve our customers, we are committed to providing high-quality and reliable solutions for various industries. In addition, we understand that a project may be unique and require specific properties, so we also offer custom formulation services to meet your particular needs.

Contact us today to explore our high-quality epoxy resin systems, including structural adhesive solutions. You can also request a quote to get started!

The information presented in this blog is intended for general background and informational purposes only and not as advice pertaining to any product, application, or process. We encourage you to contact us for information concerning your specific needs and requirements and to discover how United Resin may assist you.