China's chip packagers ride AI demand, price hikes, but investment gains, capex cloud the profit picture

The Q4 price hikes and high utilization at China's OSAT houses are a pricing-power window driven by domestic substitution, not a structural upgrade in core manufacturing. Profit growth propped up by investment gains and tax credits reveals the fabrication side still lacks self-sustaining margins. Technology chain: AI chip demand is forcing a jump to 2.5D/3D packaging, but the real chokepoints sit upstream—ABF substrates remain dominated by Unimicron (Taiwan, China) and Ibiden, while hybrid bonding equipment is locked by BESI and ASM. Capex decoupled from domestic equipment localization will replay the 2019 memory overcapacity cycle. Risk: If local fiscal subsidies retreat or Washington adds wafer thinning and temporary bonding tools to export controls, depreciation on in-construction lines will devour already-thin gross margins. The structural vulnerability of "packaging autonomy, materials dependency" remains unresolved. Game theory: ASE and Amkor will likely accelerate CoWoS-class capacity in 2025 to lock in global AI customers. Once that window closes, standard packaging in China slides into price wars. The competitive axis has shifted from "grabbing customers" to "grabbing equipment lead times." Outlook: Within 18 months, advanced-packaging capex peaks and standard-packaging utilization drops below 70%. The industry bifurcates—top players tethered to domestic AI chip designers versus tail-end capacity becoming subsidized stranded assets. By 2026, China's advanced packaging reaches 70-80% of TSMC's capability, but yield consistency remains the hard ceiling.