Decision to Maintain Patent for Liquid Encapsulant Used in Semiconductor Packages for Generative AI

Resonac Corporation (President and CEO: Hideto Takahashi, hereinafter "the Company") announced that the Japan Patent Office has recognized the validity of its Japanese patent related to liquid encapsulants (Patent No. 7687499), following a third-party challenge to its enforceability. The decision, issued on March 11, 2026, confirms the patent's maintenance. This patented technology is critical for addressing reliability issues—such as stress and crack formation due to differences in thermal expansion—in 2.5D semiconductor packages for generative AI, where demand is expected to grow significantly.

With the rapid advancement of generative AI, there is increasing demand for AI semiconductors capable of high-speed processing of large data volumes and low power consumption. To meet these requirements, development of 2.5D semiconductor packaging—enabling high-density integration of multiple semiconductor chips—is accelerating, and the market for such packages is projected to expand further. *1

In 2.5D semiconductor packages, chips and interposer substrates*2 are connected to the package substrate via small bump-shaped electrode terminals, leaving gaps between them. Liquid encapsulants fill these gaps, protecting the semiconductor package from temperature, humidity, and mechanical stress.

As semiconductor packages become more advanced, constituent components such as semiconductors, interposers, and printed circuit boards are becoming larger and more complex. This has led to challenges in reliability tests such as reflow processes*3 and thermal cycling, where differences in thermal expansion coefficients and elastic moduli between materials can induce stress, resulting in cracks in substrates or encapsulants.

By improving the resins and additives used in liquid encapsulants, the Company developed a material with controlled thermal expansion and elasticity within specific ranges. It obtained a patent for this invention in May 2025. In November 2025, a third party filed an opposition, but the Company submitted a rebuttal to the Patent Office arguing the novelty and inventive step of the technology. After examination, patentability was confirmed, leading to the current decision to maintain the patent.

Regarding its patents on liquid encapsulants for AI semiconductors, the Company has faced eight oppositions to date, all of which have resulted in decisions upholding the patents. Resonac continues to actively acquire and leverage intellectual property in next-generation semiconductor materials to secure technological superiority and contribute to accelerating the development of advanced devices as a leading semiconductor materials company.

*1 Market growth forecast: 2.5D packaging is expected to grow at a CAGR of 18.8% from 2025 to 2031 (Source: Fuji Chimera Research, "2026 Electronics Packaging New Materials Directory," survey period: October 2025 – January 2026).

*2 An intermediate substrate used to connect chips with different functions via wiring and mount them onto a package substrate (refer to diagram below).

*3 A process in which soldering under high temperature connects electrode terminals (bumps), enabling electrical signal transmission.