Taiwanese chip substrate maker Unimicron is sliding again, and this time the pressure is coming from its biggest customer — bad news for holders of IC substrate stocks.

• Broadcom told investors it will switch on its own substrate capacity in Singapore starting in its 2027 fiscal year.
• That would ease the supply bottleneck the whole sector has been cashing in on, so the shortage may stop widening and price hikes could be capped.
• Unimicron dropped more than 5% in early trade, breaking below the low it hit during the earlier "country-of-origin relabelling" controversy.
• Foreign and local institutions still say that controversy involved ordinary circuit boards, not the high-end ABF substrates that drive the stock, and they remain positive on it.
• Even so, domestic funds have been dumping shares, selling heavily for three straight sessions.

Outlook: Expect more weakness in substrate stocks until investors can judge how much capacity Broadcom will really bring in-house.