Abstract

This document provides a detailed technical analysis of HVC's high-voltage bolt terminal ceramic capacitor architecture, with in-depth performance benchmarking against the TDK UHV/FHV/FD series. Targeting demanding applications such as medical imaging, power transformers, industrial NDT, and laser power supplies, HVC delivers both a comprehensive performance upgrade and physically compatible drop-in replacement through N4700 Class 1 ceramic material, copper electrode technology, and dual-chip structure — offering engineers a high-reliability, short-lead-time alternative.

1. Technical Background & Design Challenges

High-voltage bolt terminal ceramic capacitors (commonly known as "doorknob capacitors") are widely used in high-frequency, high-voltage circuits. Their design faces three major challenges:

• Dielectric Selection: Under high-frequency high-voltage conditions, the ceramic dielectric must simultaneously deliver extremely low dissipation factor and good temperature stability. TDK uses Y5S/Z5T Class 2 ceramics which, while reaching Class 1 D.F. levels, are burdened by lead content and limited temperature stability.
• Electrode Migration: Under sustained high-voltage stress, silver ions in traditional silver-plated electrodes migrate across the ceramic surface, forming conductive paths that lead to insulation resistance degradation and eventual breakdown.
• Package Limitations: TDK employs a single-chip structure with a 60mm epoxy mold size ceiling, capping the highest specification at 50KV 2100pF. Higher voltage or larger capacitance requirements cannot be met with a single-chip design.

2. HVC Core Technology: Breakthrough from Materials to Structure

2.1 N4700 Class 1 Ceramic Material

HVC uses N4700 Class 1 ceramic across its entire product line, offering the following advantages over TDK's Y5S/Z5T/Y5P Class 2 ceramics:

• Lead-Free & Eco-Friendly: N4700 contains no lead, no RoHS exemption needed, ensuring long-term regulatory compliance.
• Lower Dissipation Factor: N4700 D.F. is typically < 0.002, resulting in less energy loss in high-frequency pulse applications.
• Excellent Temperature Characteristics: N4700 capacitance variation across -55℃ to +125℃ is far lower than Y5S/Z5T.
• Higher Insulation Resistance: N4700 volume resistivity is 1-2 orders of magnitude higher than Class 2 ceramics, minimizing leakage current under high voltage.

2.2 Copper Electrode Plating Technology

HVC uses advanced copper electrode plating in place of traditional silver electrodes:

• Migration Resistance: Copper ions have a far lower electrochemical migration rate than silver ions, significantly improving reliability under sustained HV stress.
• Current Handling: Copper's higher melting point and conductivity vs. silver enables greater surge current withstand capability.
• Long-Term Stability: Copper electrodes offer superior corrosion resistance in high-temperature, high-humidity environments, extending operational life.

2.3 Innovative Dual-Chip Structure

HVC breaks through single-chip package limits with its dual-chip design:

• Series Configuration: For 80KV, 100KV, 150KV ultra-high voltage products, far exceeding TDK's 50KV ceiling.
• Parallel Configuration: For 5000pF, 8000pF high-capacitance products, achieving unprecedented values within the N4700 material system.

3. Key Specification Benchmark

Parameter	HVC Spec (Typical)	TDK Baseline	Evaluation
Voltage Range	10KV ~ 150KV	UHV/FHV (20-50KV)	HVC covers wider range, up to 150KV
Max Capacitance (Standard)	8000pF (50KV)	2100pF (FHV-12AN)	HVC 3.8x higher
Ceramic Material	N4700 (Class 1, lead-free)	Y5S/Z5T (Class 2, leaded)	HVC lead-free, better stability
Electrode Process	Copper electrode plating	Silver plating	HVC superior HV/current handling
Internal Structure	Dual-chip series/parallel	Single chip	HVC breaks physical limits
Dissipation Factor	< 0.002 (N4700)	Y5S comparable to N4700	Equivalent; HVC better consistency
Standard Lead Time	4-6 weeks	12-16 weeks	HVC 3x faster

4. HVC HVCT8G Part Number Decoder

HVCT8G-[Voltage]-[Size Code]-[Capacitance Code]

Field	Meaning	Example
HVCT8G	Doorknob capacitor series prefix	HVCT8G-20KV-DL30-201K
Voltage	DC (e.g. 20KV/30KV/40KV/50KV) or AC (e.g. 10KVAC/20KVAC)	30KV
DL30-60	Body diameter code	DL40 = 40mm diameter
Capacitance Code	201=200pF, 102=1000pF, 702=7000pF	941K = 940pF ±10%
K	Tolerance ±10%	K

Ordering Example: Replace TDK UHV-4A 30KV 940pF → HVCT8G-30KV-DL40-941K

5. Complete Series Replacement Cross Reference

The following tables cover all standard models across TDK's UHV, FHV, TSF and FD series — 53 models with corresponding HVC replacement models. HVC uses N4700 Class 1 ceramic (lead-free, lower dissipation factor) to upgrade TDK's original Y5S/Z5T/Y5P Class 2 materials.

TSF & FD Series (AC Rated)

TDK Model	Spec (Voltage/Cap)	TDK Material	HVC Replacement	HVC Material (Upgrade)
TSF-40C	20KVAC, 1080pF	Z5T	HVCT8G-20KVAC-DL40-1081K	N4700
TSF-30	20KVAC, 400pF	Z5T	HVCT8G-20KVAC-DL30-401K	N4700
FD-9A	10KVAC, 100pF	Y5P	HVCT8G-10KVAC-DL30-101K	N4700
FD-10A / FD-10AU	10KVAC, 250pF	Y5P	HVCT8G-10KVAC-DL30-251K	N4700
FD-11A / FD-11AU	10KVAC, 500pF	Y5P	HVCT8G-10KVAC-DL30-501K	N4700
FD-12A / FD-12AU	10KVAC, 1000pF	Y5P	HVCT8G-10KVAC-DL40-102K	N4700
FD-16A / FD-16AU	13KVAC, 250pF	Y5P	HVCT8G-13KVAC-DL30-251K	N4700
FD-18A / FD-18AU	13KVAC, 500pF	Y5P	HVCT8G-13KVAC-DL30-501K	N4700
FD-20A	13KVAC, 1000pF	Y5P	HVCT8G-13KVAC-DL50-102K	N4700
FD-22A	20KVAC, 250pF	Y5P	HVCT8G-20KVAC-DL30-251K	N4700
FD-24A	20KVAC, 500pF	Y5P	HVCT8G-20KVAC-DL40-501K	N4700
FD-33A	25KVAC, 250pF	Y5P	HVCT8G-25KVAC-DL30-251K	N4700
FD-36A	25KVAC, 500pF	Y5P	HVCT8G-25KVAC-DL50-501K	N4700

FHV Series (DC Molded)

TDK Model	Spec (Voltage/Cap)	TDK Material	HVC Replacement	HVC Material (Upgrade)
FHV-153AN	15KVDC, 7000pF	Y5S	HVCT8G-15KV-DL60-702K	N4700
FHV-1AN	20KVDC, 1700pF	Y5S	HVCT8G-20KV-DL40-172K	N4700
FHV-2AN	20KVDC, 3000pF	Y5S	HVCT8G-20KV-DL50-302K	N4700
FHV-3AN	20KVDC, 5200pF	Y5S	HVCT8G-20KV-DL60-522K	N4700
FHV-4AN	30KVDC, 1200pF	Y5S	HVCT8G-30KV-DL40-122K	N4700
FHV-5AN	30KVDC, 2100pF	Y5S	HVCT8G-30KV-DL50-212K	N4700
FHV-6AN	30KVDC, 3500pF	Y5S	HVCT8G-30KV-DL60-352K	N4700
FHV-7AN	40KVDC, 850pF	Y5S	HVCT8G-40KV-DL40-851K	N4700
FHV-8AN	40KVDC, 1500pF	Y5S	HVCT8G-40KV-DL50-152K	N4700
FHV-9AN	40KVDC, 2600pF	Y5S	HVCT8G-40KV-DL60-262K	N4700
FHV-10AN	50KVDC, 700pF	Y5S	HVCT8G-50KV-DL40-701K	N4700
FHV-11AN	50KVDC, 1300pF	Y5S	HVCT8G-50KV-DL50-132K	N4700
FHV-12AN	50KVDC, 2100pF	Y5S	HVCT8G-50KV-DL60-212K	N4700

UHV Series (Ultra-High Voltage Bolt Terminal)

TDK Model	Spec (Voltage/Cap)	TDK Material	HVC Replacement	HVC Material (Upgrade)
20KV Grade
UHV-221A	20KVDC, 200pF	Z5T	HVCT8G-20KV-DL30-201K	N4700
UHV-222A	20KVDC, 400pF	Z5T	HVCT8G-20KV-DL30-401K	N4700
UHV-223A	20KVDC, 700pF	Z5T	HVCT8G-20KV-DL30-701K	N4700
UHV-224A	20KVDC, 1000pF	Z5T	HVCT8G-20KV-DL30-102K	N4700
UHV-1A	20KVDC, 1400pF	Z5T	HVCT8G-20KV-DL40-142K	N4700
UHV-2A	20KVDC, 2500pF	Z5T	HVCT8G-20KV-DL50-252K	N4700
UHV-3A	20KVDC, 4000pF	Z5T	HVCT8G-20KV-DL60-402K	N4700
30KV Grade
UHV-231A	30KVDC, 200pF	Z5T	HVCT8G-30KV-DL30-201K	N4700
UHV-232A	30KVDC, 400pF	Z5T	HVCT8G-30KV-DL30-401K	N4700
UHV-233A	30KVDC, 700pF	Z5T	HVCT8G-30KV-DL30-701K	N4700
UHV-4A	30KVDC, 940pF	Z5T	HVCT8G-30KV-DL40-941K	N4700
UHV-5A	30KVDC, 1700pF	Z5T	HVCT8G-30KV-DL50-172K	N4700
UHV-6A	30KVDC, 2700pF	Z5T	HVCT8G-30KV-DL60-272K	N4700
40KV Grade
UHV-241A	40KVDC, 100pF	Z5T	HVCT8G-40KV-DL30-101K	N4700
UHV-242A	40KVDC, 200pF	Z5T	HVCT8G-40KV-DL30-201K	N4700
UHV-243A	40KVDC, 400pF	Z5T	HVCT8G-40KV-DL30-401K	N4700
UHV-7A	40KVDC, 700pF	Z5T	HVCT8G-40KV-DL40-701K	N4700
UHV-8A	40KVDC, 1300pF	Z5T	HVCT8G-40KV-DL50-132K	N4700
UHV-9A	40KVDC, 2000pF	Z5T	HVCT8G-40KV-DL60-202K	N4700
50KV Grade
UHV-251A	50KVDC, 100pF	Z5T	HVCT8G-50KV-DL30-101K	N4700
UHV-252A	50KVDC, 200pF	Z5T	HVCT8G-50KV-DL30-201K	N4700
UHV-253A	50KVDC, 400pF	Z5T	HVCT8G-50KV-DL40-401K	N4700
UHV-10A	50KVDC, 560pF	Z5T	HVCT8G-50KV-DL40-561K	N4700
UHV-11A	50KVDC, 1000pF	Z5T	HVCT8G-50KV-DL50-102K	N4700
UHV-12A	50KVDC, 1700pF	Z5T	HVCT8G-50KV-DL60-172K	N4700

6. Microstructure & Material Engineering

HVC's high performance is built on sustained investment in ceramic materials science:

• N4700 Grain Control: Precise control of the sintering process keeps N4700 dielectric grain size within 1-3µm, achieving over 98% theoretical density and effectively reducing partial discharge risk.
• Copper Electrode Interface Optimization: Multi-layer co-firing creates a metallurgical bond between the copper electrode and ceramic substrate, improving interface bond strength by 40% over traditional silver electrodes and eliminating electrode delamination.
• Dual-Chip Voltage Balancing: In series configurations, a voltage-balancing buffer layer between chips ensures uniform voltage distribution, preventing excessive stress on any single chip.

7. Typical Replacement Cases

TDK P/N	HVC Replacement	Key Technology Upgrade
UHV-4A 30KV 940pF	HVCT8G-30KV-DL40-941K	Copper electrode replaces silver, N4700 replaces Z5T
FHV-3AN 20KV 5200pF	HVCT8G-20KV-DL60-522K	Y5S(leaded) → N4700(lead-free), full RoHS compliance
FD-12A 10KVAC 1000pF	HVCT8G-10KVAC-DL40-102K	N4700 delivers more stable HF characteristics under AC conditions
UHV-12A 50KV 1700pF	HVCT8G-50KV-DL60-172K	Dual-chip design breaks single-chip package limits

8. Verification Test Data

Reliability is the core of any replacement. HVC's lab conducted rigorous testing per IEC 60384 standards:

• Dielectric Withstanding Voltage: 1.5x rated voltage applied for 60 seconds — no flashover or breakdown.
• Life Aging Test: 1000 hours at rated voltage and +85℃; capacitance change ΔC/C < ±5% (exceeding the standard ±10% requirement).
• Temperature Cycling: 100 cycles from -55℃ to +125℃ — no mechanical damage or electrical performance degradation.

9. Engineering Application Recommendations

1. Mechanical Compatibility: HVC HVCT8G screw terminal spacing and mounting dimensions are fully equivalent to TDK UHV/FHV series — drop-in replacement, no PCB or bracket modification needed.
2. Derating: For extended lifetime, limit continuous operating voltage to 80% of rated voltage.
3. Cleaning & Protection: Keep HV capacitor surfaces clean and dry; apply HV silicone grease after installation to reduce surface leakage.

10. Market Track Record & Customer Recognition

HVC high-voltage ceramic capacitors have been qualified by globally recognized companies:

• Nikon / Konica Minolta — Precision optical equipment
• GE Healthcare — CT / X-ray medical imaging equipment
• Johnson & Johnson — Medical devices
• Baker Hughes — Oil exploration equipment

Since Murata's discontinuation of HV bolt capacitors in 2018, HVC has provided N4700 1:1 precision replacements for dozens of former Murata customers, accumulating deep replacement experience and technical support capabilities.

© HVC Capacitor Manufacturing Co., Ltd. TDK® is a registered trademark of TDK Corporation. This document is for technical comparison purposes only and does not imply affiliation with or endorsement by the trademark holder.