COOLS to Present Bonding-Cycle Technology at ISMP 2026, Calling Heat the Bottleneck in HBM Back-End Packaging

COOLS (쿨스), headed by chief executive Cho Jin-hyun, said on Oct. 13 that it will give an oral presentation at the International Symposium on Microelectronics and Packaging (ISMP 2026), to be held on Nov. 4 at the Paradise Hotel in Busan. The presentation covers a "selective energy coupling" platform that applies both to thermocompression bonding of high-bandwidth memory (HBM) and to bonding for co-packaged optics (CPO). The method delivers the heat needed for bonding only to the bonding interface, and only at the moment it is required, rather than to the whole package, raising process speed while reducing the heat exposure of surrounding structures.

HBM supply is now determined by back-end processing capacity: SK hynix is spending 19 trillion won on P&T7, an advanced packaging fab in Cheongju, and both Samsung Electronics and SK hynix are giving HBM priority on their in-house back-end lines. What limits that capacity is heat. Each time a layer of HBM is stacked, the joint must be heated and then cooled, and that cooling time sets how much a bonding tool can process. Repeated heating and cooling also build up thermal history and stress in the lower layers.

COOLS approached both problems — processing speed and thermal damage — through a single principle. The presentation, titled "Thermal Clutch and Optical Clutch: A Selective Energy Coupling Platform for HBM Bonding and Co-Packaged Optics," was accepted as an oral presentation after abstract review.

The Thermal Clutch, intended for HBM thermocompression bonding, brings a high-conductivity aluminium nitride heat acceptor into contact with the heater immediately after bonding to draw heat out by solid conduction, then regenerates the acceptor while the next chip is being aligned, removing cooling time from the process cycle. In tests using a modified production thermocompression bonding heater, COOLS cut the bonding cycle for an 11×11mm HBM3E chip from 7.0 seconds to 3.4 seconds, a 51% reduction. The figure comes from 10 repeated measurements with no change to the heater structure.

The Optical Clutch, for CPO bonding, applies the same principle using light. Light at wavelengths of 1.45 to 1.60 micrometres passes through the silicon photonic integrated circuit and is absorbed only in the metal layer at the bonding interface, so heating is complete before heat spreads to the surrounding area.

"What bonding requires is heat at the interface, not heat across the entire package," Cho said. "Competition in back-end packaging is a fight over how much you can bond with the same equipment, and with less damage."

COOLS is a semiconductor packaging technology company founded in April this year and has filed 2,713 patent applications. Cho holds bachelor's and master's degrees in mechanical engineering from Seoul National University and a doctorate in heat transfer engineering from the University of Michigan, and worked for 28 years at Samsung Electronics' Visual Display Business as a master engineer.