Who KYEC is
King Yuan Electronics (2449.TW) is a pure-play semiconductor test house: wafer probing, final test, burn-in, and backend support. Testing is about 98% of sales. It is the largest dedicated test specialist globally by that cut. It does not run CoWoS, FOCoS or any 2.5D line. It tests the AI GPU and ASIC that come off those packages.
It is not on NVIDIA's published 800 VDC list. It belongs here because CoWoS-class AI parts need long, hot, high-power test loops, and because KYEC's own call dated Rubin, CSP ASIC and that longer test time.
Business mix
From the Q4 2025 investor-update deck used on the 19 March 2026 call:
- Final test (FT) — 58.7% of 2025 sales, including system-level test (SLT).
- Chip probing (CP) — 30.6%.
- Burn-in — 7.7%. Self-made high-power ovens are the AI-GPU claim.
- Other — equipment, tools, lease, miscellaneous.
Customers are mostly fabless. The growth argument on the call is mix, not a new service line: AI GPU (Blackwell into Rubin) plus CSP ASIC (Google TPU, AWS Trainium and others), with test time and ASP up as TDP and complexity rise.
Where it sits in the NVIDIA 800 VDC stack
Downstream of the package, upstream of the rack. A CoWoS GPU still has to be probed, burned in and final-tested before an ODM can ship a cabinet. The March 2026 call never named 800 V or HVDC.
What it did say about the AI package:
- Next-generation AI chips take more than 70% longer to test than the prior generation. KYEC bills time.
- 2026 capex on that call was NT$393.72bn, described as customer-driven for NVIDIA Rubin and CSP-ASIC test specs the existing fleet cannot cover. A later April 2026 board raised the same budget to NT$500bn; that figure is not in the March note.
- AI test capacity was full. Further growth waits on cleanroom.
Do not read KYEC as a CoWoS foundry or as a named NVIDIA 800V vendor. It is the test slot on a CoWoS-class part.
Coverage note
One note, Q4 / FY 2025 (19 March 2026). Dual-tagged on the CoWoS hub. The 1Q 2026 investor-update slides (May 2026) and the 28 August 2026 event are not written here: May is a slide deck without a completed Q&A dump in this archive, and 28 August had not been held when this note was written.