1. Product Overview and Construction

The RK73H series consists of precision-grade flat chip thick film resistors. They feature a metal glaze thick film resistive layer for excellent heat and weather resistance. The electrodes have a triple-layer structure ensuring high stability and reliability. The resistors are small, lightweight, and compatible with various automatic mounting machines and soldering methods (flow and reflow). Lead-free terminations comply with EU RoHS, except for Pb-glass in electrodes and resistive elements, which are exempt.

Construction includes a ceramic alumina substrate, resistive film, inner electrode, nickel plating, solder plating, and protective coating. Coating colors vary by type: black or blue.

2. Features

• Small size and light weight.
• Metal glaze thick film for superior heat and weather resistance.
• Triple-layer electrode structure for enhanced stability and reliability.
• Compatible with automatic mounting and soldering processes.
• Lead-free terminations meeting EU RoHS standards.
• AEC-Q200 qualification for automotive applications (except 1F type).

3. Reference Standards

Compliance with IEC 60115-8, JIS C 5201-8, and EIAJ RC-2134C standards.

4. Type Designation and Dimensions

Types are designated by size codes (e.g., 1F, 1H, 1E, 1J, 2A, 2B, 2E, W2H, W3A) with detailed dimensions in millimeters and weights per 1000 pieces. Power ratings range from 0.03W (1F) up to 1W (W3A). Terminal surface materials include Sn (standard), Au (gold plated available for some types), and Sn/Pb (limited availability).

5. Electrical Ratings and Performance

*Consult manufacturer for values in parentheses.

6. Derating Curves

Power rating must be derated when operating above 70℃ ambient temperature or above specified terminal part temperatures. Derating curves are provided to guide reduction of rated power to ensure reliability under elevated temperature conditions.

7. Performance and Reliability Tests

• Resistance Accuracy: Within specified tolerance at 25℃.
• Temperature Coefficient of Resistance (T.C.R.): Within specified limits measured between +25℃/−55℃ and +25℃/+125℃.
• Overload (Short Time): Rated voltage ×2.5 (or ×2 for 1E and 2B) applied for 5 seconds.
• Solder Heat Resistance: 260℃ ±5℃ for 10 seconds.
• Rapid Temperature Change: 100 cycles between −55℃ and +125℃.
• Moisture Resistance: 1000 hours at 40℃, 90–95% RH with ON/OFF cycling.
• Endurance at 70℃: 1000 hours with ON/OFF cycling.
• High Temperature Exposure: 1000 hours at +125℃ (1F) or +155℃ (others).

8. Precautions for Use

• The alumina substrate has a different thermal expansion coefficient than mounting boards, which may cause solder joint cracks under repeated thermal cycling or load ON/OFF cycles, especially for larger W2H and W3A types.
• Design considerations should include pad size, solder volume, and board heat dissipation to minimize crack risk.
• RK73H1F type is sensitive to static electricity during assembly and may be damaged.
• When in doubt between rated ambient temperature and terminal part temperature for derating, prioritize terminal part temperature.
• Consult manufacturer before use in critical applications such as automotive, medical, or aerospace equipment due to potential risk of serious damage or loss of life.

9. Additional Notes

• Lead-free plating is standard; gold plating is available for certain types and resistance ranges.
• Packaging options include various taping formats and bulk packaging.
• Specifications are subject to change without notice; always confirm with latest datasheets before ordering or use.
• For jumper chip resistors, refer to RK73Z series.