SK keyfoundry to run at 100% as Vishay doubles down on AI power chips

SK keyfoundry will push its production line utilization to 100% from about 90% as Vishay Intertechnology ramps outsourced output of power semiconductors for AI server power supplies. Industry sources confirmed the expansion on the 12th, and the volumes run at the Cheongju fab, currently the Korean foundry's only production site.

Vishay, a U.S. chipmaker, began outsourcing MOSFET production to SK keyfoundry in August and started shipments last month. MOSFETs are power semiconductors that switch current flows on and off. The plan: double Vishay's AI-related revenue by expanding foundry volumes through the first half of next year.

Why 8-inch fabs win this work

The 80-volt MOSFETs Vishay produces at SK keyfoundry go mainly into the 48-volt power supply sections of AI servers. Power semiconductors must withstand high voltages, so performance depends less on shrinking circuit line widths than on device structures that improve resistance characteristics. That makes 8-inch (200-millimeter) fabs running mature, several-hundred-nanometer processes well suited to power chip production.

Eight-inch lines lag 12-inch lines in process technology. But they cost less to run, because they use fully depreciated existing equipment. That cost structure is now meeting a demand spike.

What does this change for the AI supply chain?

AI servers consume enormous amounts of electricity, which sharply raises the number of power semiconductors each one needs. The industry estimates power consumption per graphics processing unit (GPU) will climb from 2 kilowatts to as much as 4 kilowatts. Onsemi, another U.S. power semiconductor maker, expects the value of power chips supplied for a single AI server rack to rise from about $15,000 now to as much as eight times that figure in next-generation racks.

SK keyfoundry prepared early. Earlier this year it unveiled a BCD process — a combined bipolar, CMOS and DMOS manufacturing technology — for AI data center power semiconductors that withstands up to 200 volts. The process runs at Cheongju, which has capacity of around 100,000 wafers a month.

Samsung's exit reshapes the 8-inch market

Samsung Electronics will halt operations at its 8-inch foundry plant by 2030, and the related volumes are expected to shift to SK keyfoundry and DB HiTek. Samsung is estimated to account for 7% of global 8-inch foundry capacity this year; SK keyfoundry holds 3% and DB HiTek 5%.

Samsung has run 8-inch foundry equipment at Line 6 of its Giheung campus. It plans to convert the site into an advanced foundry fab for 2-nanometer and 4-nanometer chips under its "Kairos Project," phasing out the 8-inch production facilities.

A second anchor customer

Monolithic Power Systems (MPS), another U.S. power semiconductor maker, is also a key SK keyfoundry customer. The relationship dates back to the foundry division of Magnachip Semiconductor, SK keyfoundry's predecessor. MPS outsources several-hundred-nanometer power management integrated circuits (PMICs), chips that regulate voltage, to SK keyfoundry. It is also increasing orders with Taiwan's UMC as it moves product requirements to the 40-nanometer level.

Supply remains tight across the segment. An industry official said: "With power semiconductor demand surging, lead times from order to delivery exceed 40 weeks, so SK keyfoundry will benefit for some time."