A Thick Film Technology Study Based on RuO₂ Conductive Phase and Al₂O₃ Ceramic Substrate

This paper systematically analyzes the material composition, manufacturing process, and electrical performance of HVC's HVR series high voltage thick film resistors. This product series utilizes ruthenium oxide (RuO₂) as the conductive phase and 96% Al₂O₃ ceramic as the substrate material, manufactured through screen printing and high-temperature sintering processes. Experimental data demonstrates that the product achieves a Temperature Coefficient of Resistance (TCR) of ±15 ppm/°C and a Voltage Coefficient of Resistance (VCR) of 0.1 ppm/V, exhibiting excellent stability and reliability in high-voltage applications.

High voltage thick film resistors are critical passive components in power electronics, medical equipment, precision measurement, and other fields. With the trend towards device miniaturization and higher performance, there is an increasing demand for enhanced temperature stability, voltage linearity, and long-term reliability in high voltage resistors. This research addresses supply chain bottlenecks associated with traditional products like OHMITE, developing a fully compatible alternative solution.

2.1 Conductive Phase Material: RuO₂-based Thick Film Resistor Paste

RuO₂ (ruthenium dioxide) is a metallic oxide conductor with the following characteristics: - Resistivity: Approximately 35 μΩ·cm (at room temperature), adjustable by particle size and glass content. - Thermal Stability: Stable at 850°C sintering temperature, without phase transformation. - Chemical Stability: Resistant to acid and alkali corrosion, suitable for harsh environment applications. - Conduction Mechanism: Metallic conduction, with controllable temperature coefficient.

According to thick film resistor technical literature, the resistance value of RuO₂-based resistors can be approximately calculated using the following formula:

R = ρ × (L/W) × (1/t)

Where ρ is the sheet resistance (Ω/□), L is the resistor length, W is the width, and t is the film thickness.

Through laser trimming technology, ±1% precision control can be achieved.

2.2 Substrate Material: 96% Al₂O₃ Ceramic

Alumina ceramic is the most commonly used substrate material for thick film resistors. 96% pure Al₂O₃ exhibits the following performance parameters: - Dielectric Constant: εr ≈ 9.0 (at 1 MHz) - Dielectric Loss: tan δ < 0.

3.1 Screen Printing Technology

Using 200-325 mesh stainless steel screen, RuO₂ paste is printed on Al₂O₃ substrate.

Printing parameters: - Squeegee pressure: 20-30 N - Printing speed: 50-100 mm/s - Snap-off distance: 1-2 mm - Wet film thickness: 25-50 μm

3.2 Sintering Process

Sintering temperature profile: - Heating stage: Room temperature → 850°C, heating rate approximately 50°C/min - Holding stage: Hold at 850°C for 60-90 minutes - Cooling stage: Natural cooling to room temperature

During the sintering process, the glass phase melts and encapsulates RuO₂ particles, forming a three-dimensional conductive network.

The film thickness after sintering is approximately 40-50% of the wet film thickness.

4.1 Temperature Coefficient of Resistance (TCR) Testing

TCR is defined as the relative rate of change in resistance value with temperature:

TCR = (R₂ - R₁) / [R₁ × (T₂ - T₁)] × 10⁶ (ppm/°C)

Test conditions: Temperature range from -55°C to +155°C.

HVC's HVR series test results show TCR of ±15 ppm/°C, significantly superior to the industry standard of ±50 ppm/°C.

4.2 Voltage Coefficient of Resistance (VCR) Testing

VCR is defined as the relative rate of change in resistance value with applied voltage:

VCR = (ΔR/R) / V × 10⁶ (ppm/V)

Test results: VCR = 0.1 ppm/V, indicating that resistance value remains highly stable under high voltage applications.

4.3 Long-term Stability Testing

1000-hour load testing conducted according to MIL-STD-202 standard (rated power, +70°C ambient temperature).

Test results: - Resistance drift: < ±0.5% - Visual inspection: No cracks, bubbles, or discoloration - Voltage withstand test: Passed 1.5 times rated voltage test

Through comparative testing, the comparison of key parameters between HVC's HVR series and OHMITE Slim-Mox series is as follows:

Temperature coefficient: HVC: ±15 ppm/°C; OHMITE: ±50 ppm/°C

Voltage coefficient: HVC: 0.1 ppm/V; OHMITE: < 1 ppm/V

Resistance tolerance: HVC: ±1%; OHMITE: ±1%

Operating temperature: HVC: -55~+155°C; OHMITE: -55~+155°C

This study demonstrates that HVC's HVR series high voltage thick film resistors achieve excellent temperature stability and voltage linearity through optimized RuO₂ conductive phase formulation and sintering process.

Product performance meets or exceeds international brands such as OHMITE, while offering shorter lead times and more flexible customization services, providing a reliable alternative solution for high voltage resistor applications.

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B. Slim-Mox Series（）

：OHMITE Model（）| Power(W)（Power）| Voltage(kV)（Max）| A(mm)（）| B(mm)（）| C(mm)（）| (mm)（）| d(mm)（）| HVC Model（HVCProduct）

C. Ultra-Mox Series（Power）

：OHMITE Model（）| Power(W)（Power）| Voltage(kV)（Max）| A(mm)（）| B(mm)（）| C(mm)（）| HVC Model（HVCProduct）

D. ARC2 ResistorSeries

：OHMITE Model（）| Power(W)（Power）| Voltage(kV)（Max）| A(mm)（）| B(mm)（）| C(mm)（）| HVC Model（HVCProduct）

E. MOX ResistorSeries

：OHMITE Model（）| Power(W)（Power）| Voltage(kV)（Max）| A(mm)（）| B(mm)（）| C(mm)（）| HVC Model（HVCProduct）

7. OHMITE Model（100+）

OHMITE High VoltageThick FilmResistorStandardModel：

• ：Model OHMITE High VoltageThick FilmResistorStandardProduct。FE1%Tolerance，JE5%Tolerance。ModelParameters、HVC ， HVC ：sales@hv-caps.com*

6. HVC

HVR-[Series]-[Size]-[Resistance]-[]-[Power]-[Voltage]

: SLIM-MOX 102 → HVR-GFP-102-1M-F-0.5W-5kV

7. OHMITE Model

OHMITE Slim-Mox / Ultra-Mox SeriesModel（100）：