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Electrically Conductive Adhesives Guide

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Electrically conductive adhesives combine strong, reliable adhesion with electrical conductivity. They consist of a polymer that is filled with metal, metallic, or metal-coated particles.

This guide explains what design engineers need to know about selecting electrically conductive adhesives, a category of products you'll find on Gluespec.

Gluespec’s comprehensive and quality-tested database of 35,000 adhesive materials includes the electrically conductive adhesives that design engineers need.

Along with technical data and key specifications, you’ll find best practices and comparable materials. You can also view test method information on dozens of material properties and data points.

Introduction

Types of Electrically Conductive Adhesives

Epoxy Adhesives

Silicone Adhesives

Heat Cure Adhesives

Two-Component Adhesives

Introduction

Adhesives are made of polymers, materials that are normally electrically insulating. By adding specialized fillers, however, an adhesive can become electrically conductive instead. Different types of fills are used.

Silver fills provide the greatest electrical conductivity; however, silver is relatively expensive. Nickel fills cost less, and nickel still provides good conductivity. Graphite is used for applications where a lower level of electrical conductivity is needed.

Electrically conductive adhesives can also provide shielding against electromagnetic interference (EMI) and radio frequency interference (RFI), or protection against electrostatic discharge (ESD). Silver-filled adhesives provide the highest levels of shielding, followed by nickel-filled products. Graphite fills provide the least EMI/RFI shielding, but they're also used for protection against ESD.

Applications for electrically conductive adhesives include electronics manufacturing for the defense, aerospace, medical, automotive, renewable energy, and consumer electronics industries. Often, these adhesive products are used at the printed circuit board (PCB) level. Some electrically conductive adhesives also container fillers that provide thermal conductivity for heat dissipation.

In these and other applications, the electrical connections and electronic enclosures sometimes use electrically conductive glues and tapes. You can also find these materials on Gluespec. Compared to tapes, glues provide higher structural strength.

Types of Electrically Conductive Adhesives

Gluespec divides electrically conductive adhesives into four categories and makes it easy to search for products online. These categories reflect the base material, the type of cure system, and/or the number of components.

Epoxy
Silicone
Heat Cure
Two-Component

Within each category, you can search for elecrically conductive adhesives based on specifications such as material form, supported substrates, and the amount of electrical conductivity.

The following sections describe the four categories of electrically conductive adhesives. They also provide information about material properties and performance, curing, and general advantages and disadvantages. You’ll also find links to technical resources with additional information, either in the Gluespec Knowledge Center or from other trusted resources.

Epoxy Electrically Conductive Adhesives

Epoxy elecrrically conductive adhesives form tough, high-strength bonds and combine good chemical resistance with excellent environmental resistance. They bond well to similar substrates and can be used with the metal, plastic, glass, and ceramic materials used in electronics.

Epoxies also have good void-filling capabilities and can resist creep under sustained loads. They usually cure at room temperature or with the addition of heat and are available in formulations with a range of cure times.

Unless they are modified, however, epoxy electrically conductive adhesives are hard and brittle after curing. Under stress, this can result in cracking.

One-part epoxies generally require heat to cure. Two-part epoxies began curing after the two materials (A+B) are mixed together. With the latter, optimal curing requires proper mix ratios for best results.

Epoxies that cure at room temperature won’t work well at operating temperatures over 120°C. Therefore, a heat-cured epoxy may be required within an electronic enclosure.

When searching for epoxy electrically conductive adhesives, design engineers can choose pastes or liquids, including solvent-free formulations and thixotropic materials. Consider all of the application conditions and, in the case of a high-temperature environment, the specific temperature range.

Today, 5G electronics are putting more numerous and higher-powered components into smaller spaces. Therefore, high-temperature resistance is becoming increasingly important. Epoxy adhesives have their advantages, but silicones may be needed for these and other high-temperature applications.

Applications

Applications for epoxy electrically conductive adhesives include:

Electrical connectors
Electronic modules
Radar and guidance systems
Satellite communications
Environments with harsh chemicals

Products

These are some of the epoxy elecrical conductive adhesives you'll find on Gluespec.

	Loctite Ablestik 56C w/ Cat 11 is a two-part, silver-filled epoxy paste that cures with heat and adheres to aluminum, ceramics, glass, metals, and plastic.
	FE7004A+B from H.B. Fuller is a two-part, liquid, electrically conductive epoxy that bonds to most metals and rigid plastics. It features high shear strength.
	SEC1233 from Resinlab is a silver-filled, two-part electrically conductive epoxy paste that cures at room temperature and is designed for electronics applications.

Explore Products

Tech Specs

Here are some of the technical specifications for epoxy electrically conductive adhesives.

Type	Spec	Definition
Cure	Cure Time (min)	The length of time needed for something to fully cure.
Bond Strength	General Bond Strength	The amount of adhesion between the bonded substrates. It is usually measured in pounds per square inch.
Hardness	Elongation %	The process of becoming or making something become longer and, often, thinner.
Conductivity	Electrical Conductivity (mhos/cm)	A property of materials that determines how well a given material will conduct electricity.

Resources

Here are some additional resources about epoxy electrically conductive adhesives.

Silicone Electrically Conductive Adhesives

Silicone electrically conductive adhesives resist higher temperatures than epoxy adhesives and provide long-lasting heat resistance without a significant loss in properties.

With their low modulus of elasticity, silicones can also absorb some of the stress that results from the material expansion and contraction that occurs at different rates when electronic substrates (such as glass and plastic) have different coefficients of thermal expansion (CTE). By contrast, epoxies have a higher modulus of elasticity and are less stress-relieving.

Electronics can fail for a variety of reasons, but moisture is one of the most common causes. Silicone adhesives have excellent hydrolytic stability and allow water vapor to pass through, which can help to limit corrosion.

Despite these advantages, silicone adhesives demonstrate poor adhesion to a variety of substrates. They are also less resistant to aggressive fluids than epoxy adhesives and cannot be painted or coated because of their low surface energy.

Silicone electrically conductive adhesives come in one- or two-part formulations and support the use of various curing methods. Evaporative drying occurs at room temperature and does not require the use of ovens; however, it can be time-consuming. Moisture curing uses the moisture in the air to initiate curing. Heat curing applies thermal energy to initiate or accelerate cross-linking. Ultraviolet curing requires irradiation at a specific wavelength and energy intensity. Instead of liquids, pastes, or gels, designers can choose tapes.