Stackpole Electronics has introduced the RMWA series of automotive‑grade wide termination thick film chip resistors designed for high power density and long‑term reliability in harsh environments.
The wide terminal thick film chip resistor series targets applications where thermal management, pulse handling and mechanical robustness are critical, such as automotive electronics, industrial controls and high‑reliability power supplies.
Key features and benefits
- Wide terminal design for better heat spreading
The long‑side terminations increase the effective contact area to the PCB, improving thermal conduction into the copper and reducing local hot spots on both the resistor and the board. - High power ratings up to 3 W in compact footprint
Selected high‑power versions like RMWA1225‑HP are rated up to 3 W, allowing designers to consolidate parallel resistors or downsize case formats while maintaining the same dissipation capability according to the manufacturer datasheet. - Automotive‑grade construction and AEC‑Q200 qualification
The series is qualified to AEC‑Q200 with verified stability under load life, temperature cycling, biased humidity and short‑time overload testing, supporting use in safety‑relevant and mission‑critical ECUs. - Improved thermal performance and extended system life
Better heat removal directly translates into lower operating temperatures, which typically extends resistor and PCB lifetime and helps maintain calibration and drift budgets over the product life. - Antisulfur materials for polluted environments
Antisulfur construction mitigates resistance drift or open‑circuit failures caused by sulfur‑rich atmospheres, which is important for under‑hood automotive, industrial and field‑installed equipment. - Defined pulse voltage and pulse power behavior
The RMWA family provides specified pulse characteristics, giving circuit designers clear design limits for transient and surge events rather than relying on generic derating assumptions. - Broad application reach across segments
The same platform serves automotive, industrial, power conversion and high‑reliability consumer electronics, simplifying qualification and vendor consolidation for multi‑market platforms.
Typical applications
The RMWA wide‑termination resistors are intended for circuits where a combination of power dissipation, pulse loading and environmental robustness is required.
- Automotive ECUs and modules
Suitable for power and signal conditioning stages in engine control, transmission, body electronics, ADAS and electrification systems where AEC‑Q200, thermal cycling and vibration robustness are mandatory. - High‑power gate drivers and switching stages
Gate resistors, snubbers or damping networks in IGBT, SiC and GaN driver circuits benefit from the defined pulse capability and the ability to handle repetitive switching surges. - Industrial controls and automation
PLCs, motor drives, inverters and power supplies operating in harsh or polluted industrial atmospheres can leverage the antisulfur design and wide thermal margins. - Power supplies and DC/DC converters
Bleeder, preload, inrush‑limiting, sharing and damping resistors in AC‑DC and DC‑DC power supplies gain from the higher power density to keep layouts compact. - High‑reliability consumer and prosumer equipment
Designs like high‑end appliances, tools and networking gear that require long operating life without field failures can use the automotive‑grade screening as an additional robustness margin.
Technical highlights
While individual ratings depend on size and value selection, the RMWA platform shares several common characteristics according to manufacturer documentation.
Construction and reliability
- Thick film chip resistor technology with wide, long‑side terminations.
- Automotive‑grade design with AEC‑Q200 qualification.
- Antisulfur construction for operation in corrosive or polluted atmospheres.
- Verified performance under:
- Load life testing.
- Temperature cycling.
- Biased humidity.
- Short‑time overload.
These tests simulate real‑world stress combinations such as power cycling, environmental humidity and transient over‑stress, which often drive long‑term drift and latent failures in conventional resistors.
Power and pulse capability
- Power ratings ranging from approximately 0.75 W up to 3 W depending on case size and high‑power options such as RMWA1225‑HP according to the manufacturer datasheet.
- Wide‑termination geometry that reduces PCB temperature rise for a given dissipation level.
- Defined pulse voltage and pulse power profiles to support design against transient and surge conditions.
Clearly specified pulse performance helps engineers size components for events like load dumps, inrush currents, short pulses in gate drivers or protective crowbar actions, instead of over‑dimensioning purely based on continuous power.
Example: wide‑termination vs. standard chip
The table below illustrates the design intent of wide‑termination thick film resistors like RMWA compared to conventional same‑size chips in typical use. Specific numeric values are indicative and actual ratings must be taken from the manufacturer datasheet.
| Aspect | Conventional chip (same size) | Wide‑termination RMWA‑type device |
|---|---|---|
| PCB contact area | Short‑side terminations, smaller copper interface | Long‑side terminations, larger copper interface |
| Thermal path into PCB | More localized heat flow, higher hot spot temperature | Improved heat spreading, lower local temperature |
| Achievable continuous power | Limited by local board heating | Higher possible power rating at same footprint |
| Mechanical robustness | More sensitive to board bending and flex | Improved solder joint robustness over wide edge |
| Pulse/surge definition | Often only generic overload guidance | Dedicated pulse voltage and pulse power curves |
Design‑in notes for engineers
When selecting and placing wide‑termination thick film resistors like the RMWA series, several practical points can help extract the full benefit of the technology.
- Use the PCB as a heat spreader
Maximize copper area connected to the wide terminations and, where possible, connect them to internal copper planes through vias to gain additional thermal mass and reduce temperature rise. - Respect derating curves and ambient conditions
Review the power derating versus temperature in the datasheet and ensure worst‑case ambient, self‑heating and enclosure conditions keep the resistor within safe limits. - Align pulse specification with real transients
Map system events such as load dump, inrush, repetitive gate pulses or clamping actions onto the defined pulse voltage and pulse power curves, including duration and duty cycle, to verify adequate margin. - Consider board flex and mechanical stress
Even with wide terminations, locate high‑power resistors away from areas with significant board flex, mounting holes or connectors to minimize mechanical strain on solder joints. - Account for antisulfur protection in environment choice
In applications prone to sulfur exposure (rubber, certain industrial processes, polluted air), antisulfur RMWA variants can significantly improve long‑term stability and reduce field failure risk. - Check AEC‑Q200 for automotive platforms
For automotive ECUs, verify that the chosen RMWA variant is listed as AEC‑Q200 compliant for the intended case size, resistance value and tolerance, and document this in the component approval file.
Layout and placement considerations
A few layout guidelines can further optimize performance:
- Place wide‑termination resistors so that their long edges align with the main heat‑spreading copper regions on the PCB.
- Avoid narrow thermal neck‑downs directly at the terminations; use gradual copper transitions to keep current and heat distribution uniform.
- In multi‑resistor networks handling significant power, distribute RMWA devices to avoid creating local hot clusters that can raise overall board temperature.
Source
This article is based on information from a Stackpole Electronics manufacturer press release and associated product documentation for the RMWA automotive‑grade wide termination thick film chip resistor series.