Precision and Reliable Ultimate Thin Film Chip Resistor!

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Applications such as measurement, medical, aerospace and military frequently require resistors that are ultra accurate and ultra reliable. Engineers who design such systems have been choosing foil resistors, because they are known to be most precise as well as most reliable.

This short technical note challenges this notion and shows that Susumu’s RG VP series thin film chip resistors, with less than half the cost of foil resistors, can come extremely close to the performance of the foil resistors.

 

 

Resistance Tolerance

Resistance tolerance depends on the resistive material’s uniformity, thickness and the trimming technology utilized. The foil’s tolerance is listed as low as ±0.01% where RGVP’s is ±0.02%. The difference is inherent to the thinness of the thin film and the type of laser trimming technology used. If the requirement of the system is truly 0.01% accuracy or better, foil is still the answer but RGVP can replace any requirement as low as 0.02%.

 

 

Temperature Coefficient of Resistance (TCR)

Foil resistors boast stability against temperature change with TCR as low as 0.2ppm/ºC over the range of 25ºC to 125ºC. However, the TCR of foil is not linear to the temperature. The TCR at 25ºC can be near 0 but at 125ºC can be as high as 25ppm/ºC. RGVP’s TCR is ±5ppm but it is almost constant against temperature, that is, 5ppm at 25ºC and at 125ºC. Therefore, if the system is operating consistently at a higher temperature, RGVP has the advantage over foil resistors. See Figure 2.

 

 

Reliability

Some foil resistors' typical load life test drifts are as small as 0.005% after 2000 hours at 70ºC. The RGVP’s typical load life drift is 0.05% at 10,000 hours at 85ºC, as shown in Figure 1. If the temperature duration and difference are theoretically offset, RGVB is at least the same or better than foil.

 

High Frequency Performance

Foil, still being a bulk material, cannot avoid having the skin effect that limits the current flow to the surface area of the material at high frequency. RGVP does not have this problem because the resistive material is a thin film. Hence the RGVP’s resistant value stays consistent up to GHz range, while the foil’s R value remains the same only up to 1MHz.

 

Summary - RGVP vs. Foil Resistor

• Resistance value tolerance - RGVP ±0.02%, Foil ±0.01%
• TCR - RGVP has the advantage at higher and lower temperatures while foil has the advantage over a wider range of temperatures
• Reliability - Both are comparable to each other in load life and high temperature tolerance
• Noise - Both are comparable and much better than thick film in current noise
• High frequency performance - RGVP has the advantage with no change in resistance into the 1GHz range. Foil holds the resistance up to 1MHz.
• Thermal EMF - Both are comparable and almost negligible
• Size - RGBP is generally smaller than foil resistors for the same power and resistance requirements

As described above, even though foil may still have an advantage in the absolute tolerance and TCR, RGVP can be comparable to foil in overall performance with some characteristics that are better than foil. Moreover, RGVP has a significant advantage in cost. For example, using 2 RGVP in parallel, in place of 1 foil, cuts RGVP’s TCR in half and the cost is still better than using 1 foil resistor!

 

FEATURES Absolute resistive tolerance as low as ±0.02% TCR as low as 5ppm Operating temperature up to 155°C Moisture load life: maximum drift ±0.1% after 85/85 1000 hours Temperature cycle: maximum drift ±0.1% after –55°C/+125°C 1000 cycles High temperature exposure: maximum drift ±0.1% after 1000 hours at 155°C Load life test: maximum drift ±0.1%, rated voltage on/off 1000 cycles at 85°C (1000 hours) Various standard sizes: from 0402 to 1206 E-24, E-96 series ranging 10Ω to 1MΩ   ADVANTAGES Highly precise and maintains its tolerance for a long time period Tight resistant value distribution for matching application with multiple chips Robust against any harsh environment such as heat, chemical, dust etc. Thin film resistors have better general performance compared to thick film resistors in such areas as high frequency characteristics and low noise Completely RoHS-compliant

APPLICATIONS Any applications that require precision and/or environmental tolerance and long term reliability Power supplies Medical electronics Military/aerospace/aviation Automotive Automation/production equipment Measurement/testing

 

ML60

Because the standard reliability test methods are not severe enough to fail Susumu products, Susumu developed a more stringent patented reliability test method, ML60, where artificial sweat is applied over the products before they are exposed to a high temperature, high humidity environment. This test is so severe that Susumu’s conventional products that show far better moisture tolerance compared to competitors’ thin film chip resistors begin failing at about 250 hours. However during this test, the RG series does not begin to fail at least for 5000 hours.

 

 

Thin Film Resistors

Susumu’s typical resistive thin film is 20-200nm thick, whereas thick film resistors can be up to 50µm thick. Moreover, thin film is deposited using molecular processes such as sputtering and plasma enhanced chemical vapor deposition, whereas thick film is made of screen printed metal particles suspended in polymer. This fundamental difference results in the clear advantage of thin film resistors in performance. Thin film resistors have better high frequency characteristics (no skin effect: resistance change due to high frequency), low noise due to the evenness of the thin film and high resistance accuracy due to precise trimming of the thin film. The RG series combines the merit of such thin film performance with robustness and reliability that exceed thick film resistors.

 

 

To view all of Susumu’s RG products, click here.

 

 Featured Products

Part Number		Description	Data Sheet	App. Notes
RGxxxxVP Series		Thin Film Chip Resistor Series, Tol. ±0.02, TCR ±5ppm/ºC

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