Published by: HVC Capacitor Technology Center Publication Date: July 2026 Document ID: WP-TDK-2026-07

1. The TDK Supply Challenge: Why OEMs Are Seeking Alternatives

TDK's UHV, FHV, and FD series screw-terminal (doorknob) high-voltage ceramic capacitors have been industry staples for decades, used in medical CT scanners, industrial X-ray NDT systems, high-power lasers, and power transformers across Asia and globally. However, since 2022, OEMs have faced mounting pressure:

• Extended lead times: TDK UHV/FHV standard lead times have stretched from 12-16 weeks to 30-40+ weeks for high-demand specifications
• End-of-life notices: Several FD series models have been quietly phased out, forcing last-time-buy decisions
• Material limitations: TDK primarily uses Class 2 ceramics (Y5S, Z5T, Y5P) which exhibit capacitance variation under DC bias and limited high-frequency performance
• Single-source risk: Many Asian OEMs have relied exclusively on TDK for screw-terminal caps, creating critical supply chain vulnerability

HVC Capacitor's HVCT8G series screw-terminal capacitors are designed as direct drop-in replacements for the full TDK UHV, FHV, and FD lineup, offering 4-6 week lead times and material upgrades across the board.

2. The Material Divide: Why Class 2 Ceramics Limit TDK's Performance

TDK's UHV and FHV series predominantly use Y5S and Z5T Class 2 dielectrics. While these materials offer high capacitance density, they have fundamental limitations that directly impact system reliability:

2.1 DC Bias Voltage Sensitivity

Class 2 ceramics (Y5S, Z5T, Y5P) exhibit significant capacitance reduction under applied DC voltage. A 20 kV-rated Y5S capacitor operating at 15 kV DC may lose 30-50% of its nominal capacitance. In a resonant circuit or voltage multiplier, this shift detunes the operating point and reduces system efficiency. HVC's N4700 Class 1 dielectric exhibits less than 2% capacitance change under the same conditions.

2.2 Dissipation Factor and Thermal Runaway

At 20-100 kHz operating frequencies typical in modern high-voltage generators, Y5S material can exhibit DF of 0.02-0.03 (2-3%). This generates significant internal heat through I²R losses. In an oil-filled or enclosed multiplier tank, this heat accumulation accelerates dielectric aging and can lead to thermal runaway. HVC's N4700 maintains DF below 0.002 (0.2%), reducing self-heating by 10-15x.

2.3 Partial Discharge and Long-Term Reliability

In high-voltage multiplier applications, partial discharge (PD) is the primary failure initiator. TDK's standard Y5S-based capacitors typically specify PD levels above 10 pC at rated voltage. HVC's N4700 capacitors undergo 100% PD screening at <5 pC at 1.5× rated voltage, ensuring treeing-free operation over the product lifetime.

3. Specification Benchmark: HVC vs TDK

4. Case Study: Medical CT OEM Replaces TDK UHV with HVC HVCT8G

A major Chinese medical imaging OEM producing CT scanners faced a critical supply gap when their primary TDK UHV-4A (30 kV, 940 pF) capacitor allocation was reduced. With CT production targets at risk, they evaluated HVC's HVCT8G-30KV-DL40-941K as a replacement.

Evaluation results:

• Mechanical fit: Identical M5 thread and 40mm diameter — zero PCB changes
• Capacitance: 941 pF (vs TDK 940 pF) — within 0.1%, no tuning adjustment needed
• DF measurement: HVCT8G @ 0.15% vs TDK @ 2.1% @ 1 kHz — 14x lower loss
• 500-hour accelerated life test @ 37.5 kV (1.25× rated) and 85°C: Zero failures
• Lead time: 5 weeks vs TDK's quoted 38 weeks

The OEM qualified HVC as an approved secondary supplier within 8 weeks, and subsequently converted three additional CT models to HVC capacitors, reducing their overall BOM cost by 22% on the capacitor line item.

5. Full Cross-Reference: TDK UHV / FHV / FD to HVC HVCT8G

The following table provides direct replacement mappings for all major TDK screw-terminal capacitor series. HVC replacements use N4700 Class 1 dielectric as the default upgrade, offering lower loss, higher voltage margin, and lead-free compliance.

6. Contact HVC for TDK Replacement Engineering Support

If you are experiencing TDK supply constraints, facing EOL notices, or designing new systems requiring screw-terminal HV capacitors, HVC's engineering team can help:

• Free samples for qualification testing — up to 5 pieces per model
• Cross-reference verification within 24 hours — confirm mechanical and electrical compatibility
• Custom specifications — non-standard voltage, capacitance, or terminal configurations
• Bulk delivery programs — 4-6 week lead times with inventory buffer options

Contact: sales@hv-caps.com | www.hv-caps.com

Request your free TDK-to-HVC Cross-Reference Guide — includes complete UHV / FHV / FD series mapping with mechanical drawings.