Most adhesives are insulators — they bond substrates together while blocking both heat flow and electrical current. For the majority of assembly applications, this is exactly what is needed. But a growing range of electronics, power, and thermal management applications require an adhesive that does the opposite: one that forms a structural bond while also conducting electricity, heat, or both simultaneously. Thermally and electrically conductive adhesives fill this role, and understanding what distinguishes them from ordinary adhesives — and from each other — is the first step in specifying the right product for any application that demands conductivity alongside bonding.
How Conductive Adhesives Work
Standard epoxy adhesives are organic polymer networks with no inherent electrical or thermal conductivity. The polymer matrix alone has electrical resistivity above 10¹² Ω·cm and thermal conductivity of approximately 0.2 W/m·K — the properties of an insulator.
Conductive adhesives achieve conductivity by loading the epoxy matrix with conductive filler particles at high volume fractions. The filler particles — typically silver, copper, gold, or carbon-based materials for electrical conductivity, or silver, aluminum oxide, boron nitride, or aluminum for thermal conductivity — are incorporated at 60 to 85 percent by weight. At these loading levels, the filler particles are in close contact throughout the adhesive matrix, creating networks of particle-to-particle contacts that carry electrical current or thermal energy through the cured adhesive.
The particle loading and size distribution determine the conductivity achieved. A well-dispersed, high-loading silver-flake epoxy can reach bulk electrical conductivity of 10³ to 10⁴ S/cm — several orders of magnitude below pure silver (6 × 10⁵ S/cm), but adequate for many electrical interconnection applications. Thermal conductivity of filled adhesives reaches 1 to 5 W/m·K for thermally filled systems and up to 30 to 60 W/m·K for silver-filled electrically conductive systems — compared to 0.2 W/m·K for unfilled epoxy.
Thermally Conductive Adhesives: Applications and Use Cases
Thermally conductive adhesives are used wherever heat must be moved efficiently from a heat-generating component to a heat sink, spreader, or cooling structure, and an adhesive bond is the attachment method. They are not required to conduct electricity — thermal and electrical conductivity in adhesives are independently formulated properties, and many thermally conductive adhesives are also good electrical insulators.
Power electronics components bonded to heat sinks use thermally conductive adhesive at the component-to-heat-sink interface. The adhesive replaces thermal grease or phase change interface material in applications where the joint must be permanent rather than removable. IGBTs, power MOSFETs, and power diodes in motor drives, inverters, and switching power supplies dissipate significant power; reducing the thermal resistance at the mounting interface with a thermally conductive adhesive lowers junction temperature and extends component life.
LED assemblies use thermally conductive adhesive to mount LED packages, COB arrays, and thermal slugs to aluminum or copper PCBs and heat sinks. LED luminous efficacy and service life both decrease with increasing junction temperature; the thermal path from the LED junction to ambient air determines the operating temperature, and a thermally conductive adhesive minimizes the resistance in that path at the bond joint.
Ceramic substrates — alumina, aluminum nitride — bonded to metal heat spreaders in power modules use thermally conductive adhesive when the substrate cannot be soldered directly to the metal and braze processes are not available. Aluminum nitride’s thermal conductivity of 170 to 200 W/m·K makes it useful as a substrate, but that conductivity is only realized in the package if the substrate-to-heat-spreader interface has low thermal resistance.
Electrically Conductive Adhesives: Applications and Use Cases
Electrically conductive adhesives are used where an electrical connection must be made by bonding rather than soldering — because solder is incompatible with the substrate material, the assembly temperature is too low for solder processing, or the geometry makes solder application impractical.
Die attach — bonding semiconductor die to package substrates or lead frames — uses electrically conductive epoxy when the die must be grounded through its back side and the package design uses an adhesive bond rather than eutectic solder or braze. Silver-filled epoxy die attach materials are standard in many semiconductor packages where the die-to-substrate connection must carry both mechanical load and electrical current.
EMI shielding assembly uses electrically conductive adhesive to bond metal gaskets and shielding covers to PCB ground planes or chassis. The adhesive provides the structural retention of the shield while ensuring a continuous, low-resistance electrical connection around the shield perimeter that maintains the Faraday cage integrity required for electromagnetic interference containment.
Flex circuit repair and PCB trace repair use conductive adhesive to bridge broken conductors, attach replacement pads, or reroute signal traces when soldering would damage the substrate. The adhesive is applied in a thin bead over the break or at the attachment point and cured to restore electrical continuity.
Grounding connections on assemblies with mixed materials — ceramics, composites, and plastics that cannot be soldered — use conductive adhesive to attach ground straps, ground lugs, or ground planes to surfaces where solder cannot be used.
For conductive adhesive recommendations for your specific thermal or electrical application, Email Us — Incure can identify whether a thermally conductive, electrically conductive, or dual-function product is appropriate.
Dual-Function: Thermally and Electrically Conductive Together
Some applications require both high thermal conductivity and low electrical resistance from a single adhesive joint. Silver-filled epoxy systems optimized for die attach achieve both: silver has thermal conductivity of 429 W/m·K and electrical conductivity of 6 × 10⁵ S/cm, and silver-filled adhesives with high loading achieve the highest combined thermal and electrical conductivity of any organic adhesive system.
Power module die attach — bonding silicon or silicon carbide die to copper substrates in high-power inverters — is the application that places the most demanding simultaneous requirements on both properties. The die-to-substrate bond must carry the full source or drain current from the die back side to the package (electrical requirement) while also carrying the die power dissipation to the substrate (thermal requirement). Silver-sintered die attach has largely displaced silver-filled epoxy in the highest-power-density applications because of its higher conductivity and higher process temperature capability, but silver epoxy remains standard in cost-sensitive applications at moderate power density.
What Conductive Adhesives Cannot Do
Understanding the limitations of conductive adhesives prevents misapplication. Electrically conductive adhesives have contact resistance — the resistance at each particle-to-particle interface within the adhesive — that is higher than bulk metal. For current-carrying applications, the total resistance of the adhesive joint includes both the bulk resistivity of the adhesive and the contact resistance at the adhesive-substrate interfaces. Joints that must carry large currents with low power loss are constrained by this resistance, and solder or welded connections remain preferable for high-current power connections.
Thermally conductive adhesives, despite their improved conductivity relative to unfilled epoxy, have thermal conductivity of 1 to 5 W/m·K compared to 200 W/m·K for aluminum or 400 W/m·K for copper. At thin bondline thicknesses the thermal resistance is low and acceptable; at thicker bondlines or for very high heat flux, the adhesive remains a limiting thermal resistance in the stack.
Contact Our Team to discuss thermally conductive, electrically conductive, or dual-function adhesive selection for your specific assembly, service temperature, and conductivity requirements.
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