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A thick film resistor is a type of fixed resistor manufactured by screen-printing a resistive paste (typically a cermet—ceramic-metal composite) onto a ceramic substrate and then firing it at high temperatures. This process creates a durable, stable resistive element that can be precisely trimmed to achieve tight tolerances. Unlike wirewound resistors, thick film technology offers low inductance, high power density, and excellent high-frequency performance, making it the preferred choice for switching power supplies, snubber circuits, power amplifiers, and voltage regulation applications.
At RST Electric, we specialize in manufacturing high-reliability thick film power resistors in industry-standard TO220 and TO247 packages. Our PRT35, PRT50, and PRT100 series deliver power ratings from 35W to 100W (heatsink mounted) with resistance values from 0.1Ω to 1MΩ. With over 10 years of thick film engineering expertise and ISO 9001 certified facilities, we provide components that combine precision, thermal efficiency, and long-term stability for the most demanding industrial, automotive, and consumer applications.
Selecting the optimal thick film resistor requires careful consideration of several key parameters:
·Power Rating & Thermal Management: Determine the continuous or intermittent power the resistor must dissipate. Our PRT35 (35W), PRT50 (50W), and PRT100 (100W) series are rated with a heatsink; without a heatsink, they handle 2.5W–3.5W. Proper thermal interface material (grease or pad) and heatsink sizing are critical for achieving full power.
·Resistance Value & Tolerance: Choose from 0.1Ω to 1MΩ with tolerances of ±1%, ±5%, or ±10%. Tight tolerances ensure precision in feedback networks, voltage dividers, and current sensing circuits.
·Temperature Coefficient (TCR): For stable performance across temperature, select TCR as low as ±50 ppm/°C (for values >10Ω) to ±300 ppm/°C (for low ohmic or high-resistance ranges). Our TCR options are optimized for each resistance band.
·Package Style:
TO220 (PRT35/PRT50) – Compact, single-screw mounting, ideal for space-constrained PCBs and heatsinks.
TO247 (PRT100) – Larger footprint with higher power handling, suitable for industrial drives and high-power supplies.
·Voltage Rating: Verify that the maximum working voltage (up to 700V) and dielectric withstand (1800VAC) meet your circuit requirements.
·Operating Environment: Consider temperature range (-65°C to +175°C), humidity resistance, and insulation requirements (>10GΩ). Our resistors are designed for harsh industrial and automotive environments.
By evaluating these parameters, you can ensure that your thick film resistor delivers reliable, stable performance in its intended application.
The PRT35 series offers a compact, versatile solution for applications requiring up to 35W of power dissipation with proper heatsink mounting. Housed in a standard TO220 package, it features a molded plastic case with high insulation resistance (>10GΩ) and 1800VAC dielectric strength. Resistance values span 0.1Ω to 1MΩ, with TCR as low as ±50 ppm/°C for precision ranges. Ideal for switching power supplies, snubber circuits, and voltage regulation.
Building on the same TO220 footprint, the PRT50 series increases power handling to 50W with heatsink mounting (3W without heatsink). It shares the same wide resistance range, tight tolerances, and robust construction as the PRT35, making it suitable for higher-power applications such as motor drives, power amplifiers, and industrial controls.
For applications demanding maximum power density, the PRT100 series utilizes the larger TO247 package to deliver 100W with heatsink mounting (3.5W without heatsink). With a maximum working voltage of 700V and an extended operating temperature range of -65°C to +175°C, it is designed for high-power switching supplies, pulse loading circuits, and renewable energy inverters. Resistance values range from 0.2Ω to 1MΩ with TCR options from ±50 to ±300 ppm/°C.
·Non-Inductive Construction: Thick film technology inherently provides ultra-low inductance, ideal for high-frequency switching applications.
·Single-Screw Mounting: Easy attachment to heatsinks or chassis with M3 screws (max torque 0.9 Nm).
·Precision Tolerances: Available in ±1%, ±5%, and ±10% to meet both high-accuracy and general-purpose requirements.
·Comprehensive Safety: Withstands 1800VAC dielectric strength with insulation resistance >10GΩ, ensuring safe operation in high-voltage circuits.
| Industry | Specific Application | Recommended Series |
| Switching Power Supplies | Output load resistors, snubber circuits, pre-charge networks | PRT35, PRT50 |
| Motor Drives & VFDs | Dynamic braking, snubber circuits | PRT100, PRT50 |
| Power Amplifiers | Emitter degeneration, Zobel networks | PRT35, PRT50 |
| Voltage Regulation | Feedback networks, bleeder resistors | PRT35, PRT100 |
| Pulse Circuits | Pulse loading, inrush current limiting | PRT100 |
| Industrial Controls | Motor drive snubbers, braking circuits | PRT50, PRT100 |
| Automotive Electronics | DC-DC converters, LED lighting drivers | PRT35, PRT50 |
| Renewable Energy | Solar inverter snubbers, wind turbine controls | PRT100 |
| Test & Measurement | Electronic loads, calibration standards | PRT35, PRT50, PRT100 |
As a certified manufacturer based in China, we maintain full control over thick film deposition, laser trimming, assembly, and testing. Our factory-direct pricing ensures competitive costs without compromising quality.
Our 7,000+ square meter facility is equipped with automated screen-printing lines, high-temperature firing furnaces, and laser trimming systems. Every thick film resistor undergoes:
·100% resistance and tolerance verification
·Dielectric withstand and insulation resistance testing
·TCR sampling per IEC 60115
·Sample testing for temperature cycling, load life, and humidity
We specialize in custom configurations to match your exact specifications:
·Power ratings: 35W, 50W, 100W (custom available)
·Resistance values: 0.1Ω to 1MΩ (special values available)
·Tolerances: ±1%, ±5%, ±10% (custom down to ±0.5%)
·TCR: ±50 to ±300 ppm/°C (custom available)
·Packaging: Bulk tubes, tape & reel, custom
·Lead forming: Straight, cut and formed, custom
·Special screening: High-temperature aging, thermal cycling, burn-in
With exports to over 40 countries, including the United States, Germany, Japan, and South Korea, we have earned a reputation for reliability. Our multilingual technical support team provides pre-sales consultation, application engineering, and after-sales service.
Q: What is the difference between thick film and thin film resistors?
A: Thick film resistors use screen-printed cermet paste, offering lower cost and wider resistance range (0.1Ω–1MΩ) with moderate precision. Thin film resistors use sputtered metal layers, providing tighter tolerances (±0.1%) and lower TCR (±25 ppm/°C) at higher cost. Thick film is preferred for power applications; thin film for precision instrumentation.
Q: How do I mount a TO220/TO247 resistor for maximum power dissipation?
A: Use a suitable heatsink with thermal grease (or thermal pad) between the resistor tab and heatsink. Tighten the mounting screw to 0.9 Nm maximum. Ensure the heatsink surface is flat and clean. Without a heatsink, power must be derated to 2.5W–3.5W.
Q: Can I use a thick film resistor for high-frequency switching circuits?
A: Yes. Thick film resistors have inherently low inductance, making them suitable for snubber circuits, gate drive resistors, and high-frequency power converters. For extremely critical applications, our PRT series offers non-inductive performance.
Q: What is the typical lifespan of a thick film resistor?
A: With proper derating and adequate cooling, thick film resistors can operate for decades. Our endurance testing simulates 1000 hours at rated power with minimal resistance drift.
Q: How do I select the correct TCR for my application?
A: For precision circuits (e.g., voltage references, feedback networks), choose low TCR (≤±50 ppm/°C). For general-purpose applications, TCR up to ±300 ppm/°C is acceptable. Our data sheet provides TCR ranges by resistance value.
To learn more about our specific thick film resistor offerings, please explore the following product categories:
·PRT35 Series (TO220, 35W) – Compact, versatile thick film resistor for power supplies and amplifiers.
·PRT50 Series (TO220, 50W) – Higher power in the same TO220 footprint for industrial applications.
·PRT100 Series (TO247, 100W) – High-power thick film resistor for inverters, motor drives, and renewable energy systems.
Whether you need a standard thick film resistor for a new power supply design or a custom-engineered solution for a specialized industrial application, our team is ready to assist. Contact us today for a detailed proposal, technical consultation, or factory tour.
