Advancing Precision and Reliability in Semiconductor Bonding: LG Chem’s Ag/Cu Paste R&D Team
2026. 08. 28
As the electric vehicle, AI data center, renewable energy, and ESS (Energy Storage System) markets continue to grow, power semiconductors are required to operate under increasingly higher voltages, currents, and temperatures. Accordingly, packaging technologies that enable and sustain semiconductor performance are becoming increasingly important.
The performance and lifespan of semiconductors depend not only on the chips themselves, but also on how securely the chips are bonded to substrates and how effectively the heat they generate is dissipated. Ag (silver) Paste and Cu (copper) Paste are representative materials that form these bond layers and create pathways for electrical current and heat.
What strengths and technical challenges does each material present? We spoke with LG Chem’s Ag/Cu Paste R&D teams to learn about the roles these materials play in semiconductor packages and the development process, from material design and reliability validation to mass-production implementation.
Hello! Could you introduce the teams and your current responsibilities?
We develop bonding materials for power semiconductor and automotive electronics packages. Ag Paste development is handled by the Electronics Materials Business Unit of the Advanced Materials Company, while Cu Paste development is led by LG Chem’s CTO Platform Technology R&D organization.
The Ag Paste R&D team oversees the entire product development process, from material design and process optimization to product reliability validation and technical support for customers. Its primary role is to translate research-stage materials into commercial products for customer applications.
The Cu Paste R&D team is conducting advanced development of a next-generation bonding material that builds on Ag Paste. Its responsibilities span Cu Paste formulation and process development, reliability validation, and the development of technologies required for mass-production implementation.
What are Ag Paste and Cu Paste, and what roles do they play in semiconductor packages?
Ag Paste and Cu Paste are conductive bonding materials based on silver (Ag) and copper (Cu), respectively. Applied between power semiconductor chips and substrates, they create strong bonds and provide efficient pathways for the transfer of electrical current and heat.
Ag Paste is used as a high-reliability bonding solution in today’s market based on its excellent electrical conductivity, thermal conductivity, and bonding reliability. Cu Paste, by contrast, is being developed as a next-generation bonding material designed to deliver comparable performance with greater cost competitiveness. Because copper oxidizes easily during processing, it is essential to control the structure and surface of copper particles and to prevent oxidation or reduce oxidized copper.
The quality of the bond layers formed by these materials directly affects the electrical performance, thermal management, and long-term reliability of power semiconductor packages.
Cu Paste is often described as a next-generation technology rather than a replacement for Ag Paste. What distinguishes the two materials, and what strengths does each offer?
Rather than viewing Cu Paste as a simple replacement for Ag Paste, it is more appropriate to see it as a new technology platform developed to address the evolving demands of next-generation power semiconductor packaging. The two materials complement each other by offering distinct strengths.
Ag Paste offers excellent electrical and thermal conductivity and sintering performance, together with proven reliability in automotive and industrial power semiconductor applications. Its ability to maintain stable bonding performance under high-temperature and high-power conditions makes it well suited for high-specification power semiconductor packages based on *SiC (silicon carbide) and *GaN (gallium nitride). It is widely recognized as a bonding material for power semiconductor applications requiring high reliability.
*SiC (silicon carbide): A power semiconductor material that operates reliably at higher voltages and temperatures than conventional silicon
*GaN (gallium nitride): A next-generation power semiconductor material offering high power efficiency and fast switching performance
Leveraging copper’s excellent electrical and thermal properties as well as its cost efficiency, Cu Paste is a next-generation material capable of addressing markets that require both performance and cost competitiveness. Once oxidation-control and sintering technologies are fully established, Cu Paste has the potential to become a powerful game changer in applications that use large volumes of bonding material, including electric vehicles.
Ultimately, Ag Paste offers advantages in applications where high performance and proven reliability take priority, while the potential for Cu Paste is expected to grow in areas where balancing performance and cost efficiency is critical. LG Chem plans to address diverse packaging requirements through a portfolio built around these two materials.
As power semiconductors and advanced packaging technologies continue to evolve, how are requirements for conductive bonding materials changing?
Bonding materials are evolving beyond “supporting materials” that physically connect chips and substrates into “critical functional materials” that determine the performance and reliability of the entire package.
Accordingly, evaluation criteria are moving away from a focus on any single property toward a comprehensive assessment of electrical performance, thermal management, mechanical reliability, and process compatibility. Optimizing each property individually is no longer sufficient; these attributes must be balanced within customers’ package structures and manufacturing processes.
In electric vehicles, AI servers, and renewable energy systems in particular, the heat dissipation and long-term stability of bond layers directly affect the efficiency and lifespan of the overall system. The competitiveness of conductive bonding materials therefore depends on balancing technical performance, manufacturability, and cost competitiveness for actual application environments.
Why is Ag Paste attracting attention in semiconductor packaging?
Ag Paste is attracting attention primarily because it simultaneously delivers high-temperature reliability, excellent thermal conductivity, low electrical resistance, and strong *thermal cycling durability that are difficult to achieve with conventional bonding materials such as *solder.
As the market grows for next-generation SiC- and GaN-based power semiconductors that operate under high-voltage and high-temperature conditions, Ag Paste has emerged as a preferred premium solution that rapidly dissipates intense heat generated by chips and maintains bond integrity through repeated temperature changes over extended periods.
*Solder: A low-melting-point alloy-based material used to join metals
*Thermal cycling: A material’s durability against thermal stress caused by repeated expansion and contraction under alternating high- and low-temperature conditions
How does LG Chem achieve the key performance attributes of Ag Paste?
LG Chem develops Ag Paste based on silver particle design, control of sintering behavior, microstructure optimization, and rheological property control.
During sintering, silver particles are designed to bond with one another and form a dense metallic network, securing electrical and thermal conductivity as well as bonding stability. LG Chem also precisely controls flow behavior, or rheological properties, so that Ag Paste flows consistently during printing and dispensing while retaining its intended shape.
From the early stages of development, the team incorporates customers’ package structures and process conditions and conducts a range of evaluations and validations to meet the stringent reliability standards required for automotive semiconductors. Through these technologies and validation processes, LG Chem can improve product performance and system efficiency while delivering greater design flexibility and long-term reliability.
*Sintering: A process in which metal particles bond together below their melting point to form a dense structure
What led LG Chem to focus on Cu Paste amid these market changes?
As the power semiconductor market expands and material use increases rapidly, maintaining high package performance while lowering manufacturing costs has become a key industry challenge. In particular, as the number of semiconductor devices used in each electric vehicle rises, material unit costs have a greater impact on overall manufacturing costs. Copper (Cu) is considered the most promising alternative because it is more cost-effective than silver (Ag) while offering excellent electrical and thermal conductivity.
However, copper has a critical limitation: it oxidizes easily during processing, which interferes with particle-to-particle sintering. This can reduce the electrical and thermal performance and long-term reliability of bond layers.
To address this challenge, LG Chem has applied the nanostructure and surface-control technologies of its CTO R&D organization. Its proprietary technologies minimize oxidation of copper particles from the outset while reducing copper oxides that have already formed, enabling stable sintering and supporting progress toward commercialization.
What are the most important technical challenges in developing Ag Paste and Cu Paste?
The most important challenge is achieving the right balance between electrical and thermal performance, mechanical reliability, and process compatibility.
High-performance power semiconductors must handle extremely high power densities and operating temperatures. Bonding materials therefore need to do more than simply hold chips in place; they must serve as essential pathways for electrical current and heat. This requires minimizing micro-voids within the bond layer to increase sintered density and interface stability, while relieving stress caused by differences in thermal expansion among materials.
Ultimately, the final—and most important—challenge is optimizing all of these core technologies for customers’ actual package structures and mass-production process conditions.
How is LG Chem applying its Ag Paste business experience and technological capabilities to Cu Paste development?
From the Cu Paste design stage, LG Chem fully incorporates its understanding of customer requirements and package design, as well as its reliability evaluation expertise accumulated through its Ag Paste business.
From a technical perspective, LG Chem combines its proven capabilities in microstructure design and sintering analysis from Ag Paste development with oxidation-prevention and reduction technologies tailored to copper, securing stable bonding performance. This process is supported by close collaboration: the business unit defines market needs and process conditions, while the CTO R&D organization develops the core technologies required to address them.
Through this approach, LG Chem is developing Cu Paste not as a simple cost-saving substitute, but as a proprietary next-generation technology platform that delivers both performance and cost efficiency.
How do you expect the conductive paste market to evolve, and how is LG Chem preparing for the future?
The conductive paste market is expected to become a key arena for innovation in semiconductor thermal management.
Multifunctional materials offering not only electrical and thermal performance but also environmental sustainability and compatibility with fine-pitch packaging processes will lead the market. In response, LG Chem continues to enhance the reliability of its premium Ag Paste portfolio while accelerating the commercialization of next-generation Cu Paste technologies.
The ultimate goal is to build a robust portfolio spanning both materials and move beyond supplying individual products to provide a Total Interconnection & Thermal Management Solution optimized for customers’ package structures and thermal management requirements.
Although Ag Paste and Cu Paste are rarely visible inside a package, they create pathways for electrical current and heat while maintaining a stable bond between chips and substrates. As power semiconductor output and operating temperatures rise, it becomes even more important for these thin bond layers to deliver electrical performance, heat dissipation, durability, and processability at the same time.
LG Chem is connecting the customer and mass-production experience accumulated through its Ag Paste business with the core technologies of its CTO R&D organization to prepare for both today’s premium market and tomorrow’s next-generation market. We will continue developing bonding and thermal management solutions that balance performance, reliability, and cost efficiency for each customer’s package structure and operating environment.
[Explore More from LG Chem’s Advanced Materials R&D Interview Series👉]
1) CCL R&D Team: Driving Semiconductor Performance in the AI Era: An Interview with LG Chem’s CCL R&D Team
2) DAF R&D Team: The Hidden Enabler of Advanced Semiconductor Packaging: LG Chem’s DAF(Die Attach Film) R&D Team
3) PID R&D Team: Pushing the Boundaries of Next-Generation Semiconductor Packaging: LG Chem’s PID (Photo Imageable Dielectric) R&D Team
4) BUF R&D Team: Designing the Core Layer of High-Performance Packages: LG Chem’s BUF (Build-Up Film) R&D Team
5) Stripper R&D Team: A Supporting Force Enhancing Advanced Displays and Semiconductors: LG Chem’s Stripper R&D Team
There are no comments yet! Be the first to let us know your thoughts!