TSMC Asks Suppliers to Develop ~5µm HBM Microbumps: Halving Bump Height for Density Instead of Moving to Hybrid Bonding

According to materials-industry reports dated September 2, 2026, TSMC has asked materials and equipment partners to develop bonding and underfill solutions for ~5µm-class microbumps, rather than switching the HBM-to-interposer interface to copper hybrid bonding. Korean and Japanese supply chains have started development; volume-production timing is still uncertain, with estimates ranging from 2H2027 to 2H2028.

The decision is not a retreat on density but a choice to trade bump height for density: today's HBM4 bumps are around 10µm, and the goal is to halve their height while retaining the volume-proven solder, underfill, reflow and inspection flow, keeping total stack height within the JEDEC HBM4 limit of 775µm. For CMP materials and equipment, copper pad recess and surface roughness directly determine whether bumps make full contact during bonding, making them a key technical focus of this process and driving demand for higher-precision CMP planarization.

Source: NineScrolls (technical analysis) https://ninescrolls.com/news/tsmc-asks-suppliers-for-5-m-hbm-microbumps-halving-hbm4-s-bump-height-instead