Q1 2026 Quarterly Report: Test Socket Revenue and AI/HBM Expansion

Quarterly Report (26th Term) Fiscal year: January 1, 2026 to March 31, 2026 Submitted to: Financial Services Commission, Korea Exchange Date: May 15, 2026 Filing entity type: Listed corporation Exemption reason: None Company name: ISC Co., Ltd. CEO: Kim Jeong-ryeol Head office: 26, Geumto-ro 40beon-gil, Sujeong-gu, Seongnam-si, Gyeonggi-do (Geumto-dong) Phone: 031-777-7675 Website: http://isc21.kr Responsible preparer: Lee Jae-seung, Finance Director I. Company Overview Sections 1-5 (company overview, history, capital changes, total shares, articles of incorporation): Per disclosure form preparation standards, these items are not included in the quarterly report. Refer to the 25th term annual report submitted on March 18, 2026. II. Business Content 1. Business Overview The company is a global semiconductor test components company consisting of four production and sales subsidiaries with ISC as headquarters. Our core business is semiconductor test sockets for testing semiconductor chips. We also operate an equipment/materials business supplying parts required for semiconductor test equipment and processes. We have internalized the entire production process for manufacturing, securing competitive advantage through production technology for stable quality and rapid delivery suited to the multi-product, short-lead-time characteristics of the test socket market. Overseas, in North America we operate through subsidiary ISC International for product distribution; in other regions we use direct sales to local buyers and distributor sales. Domestically we have built a strategic technical sales organization responding actively from early development through mass production. Detailed business content: (1) Test Sockets Test sockets are core components used in semiconductor development, mass production, and burn-in testing. Sockets are classified into pogo pin sockets using springs and elastomer sockets (silicone rubber sockets) using elastic materials. ISC produces and supplies both. (i) Elastomer Sockets (Silicone Rubber Sockets) First commercialized and mass-produced globally by ISC, elastomer sockets have been used for memory semiconductor test development and mass production. We entered the non-memory semiconductor test market in 2011. Elastomer sockets account for 80% of ISC's revenue, and ISC's share of the global elastomer socket market is estimated at approximately 90%. We entered the non-memory mass production market in 2023, and from 2024 began full-scale supply to global fabless customers' mass production markets. Currently we supply AI semiconductor test sockets applicable to various applications to global big-tech, fabless, OSAT, and ASIC companies. (ii) Pogo Pin Sockets The company entered the pogo pin business in 2014 and began market supply in 2018. Most are supplied for AP and SoC chip testing of global smartphone customers. (iii) Burn-In Test Sockets Burn-in testing operates semiconductor chips under high temperature and high voltage for a set period to screen for early failures. ISC commercialized the world's first silicone-material silicon burn-in socket in 2019, successfully entering memory customer mass production markets in 2020, and from H2 2023 entering non-memory customers with high evaluations. (2) Equipment/Materials Business In Q2 2025, the company acquired iSemi and Techdream, which operate semiconductor back-end test equipment and cleaning chemical materials for HBM and DRAM etching processes. This business is part of a test platform strategy targeting the AI/HBM semiconductor test market. Key items: (i) Module Tester: CPU/GPU compatibility and reliability test equipment for DRAM modules; memory module (LPCAMM, SOCAMM) test equipment (ii) High-Speed Burn-In Tester: Memory/non-memory performance evaluation in high and low temperature environments (iii) EFEM: Core automation modules for semiconductor manufacturing equipment (iv) Chemicals: Cleaning chemicals for etched DRAM and HBM (v) PCB: PCB substrates for test equipment and memory modules 2. Key Products and Services 1) Key Products: - Elastomer (silicone rubber) test sockets — memory/non-memory packaging test sockets (brand: iSC) - Burn-in test sockets — memory, non-memory (brand: iSB) - Pogo sockets — pogo pin packaging test sockets (brand: iSP) - Test solutions — server communication chip test temperature control (brand: iSTCU) - High-speed burn-in tester — high-spec burn-in equipment for high-performance semiconductor reliability testing - Module tester — AI accelerator/CPU and SOCAMM/DRAM compatibility test equipment - EFEM — automatic transfer device for test, inspection, etch/deposition equipment - Chemicals — DRAM/HBM cleaning chemicals - PCB — PCB intermediary business for memory modules 2) Revenue mix (KRW millions, %, consolidated): - Manufactured products (Test Sockets etc., iSC etc.): 56,951 (83.4%) - Merchandise (Test parts etc., iSC etc.): 10,641 (15.6%) - Services and other: 680 (1.0%) - Total: 68,272 (100.0%) 3) Price trends: Products typically command highest value at launch and decline over time, but most sales are made-to-order with pricing set per customer volume and spec, so price-decline risk is limited. 3. Raw Materials and Production Facilities 1) Key raw materials (KRW millions): Silicone, powder etc. — 23,848 (100%) used for product manufacturing. 2) Price trends: No material raw material price changes affecting profitability during the disclosure period, though international gold prices and supplier pricing changes could affect unit costs. 3) Production capacity: Varies with production days, personnel, and skill levels due to small-lot, multi-product made-to-order production. 4) Production results (thousand units): - Test Sockets etc. (Korea/Vietnam): Q1 26th term 1,313; 25th term 6,380; 24th term 7,772 - Pogo PIN: Q1 26th term 4,168; 25th term 9,036; 24th term 7,276 - Total: Q1 26th term 5,481; 25th term 15,416; 24th term 15,048 [Translation truncated]