Wire and Film Technologies Division

Telephone: 361 992 7900 • Facsimile: 361 992 3377 • Website: www.irctt.com

February 2009 Issue Page 2 of 4

• 4222 South Staples Street • Corpus Christi Texas 78411 USA

OARS-3

Open Air Sense Resistors

Metal Alloy Strip

25

60

95

130

165

195

225

3.5

3.0

2.5

2.0

1.0

0.0

Ambient Temperature (°C)

Power Derating Curve

Environmental Data

Test Spec: AEC Q200

2m - 3m

4m - 15m

TCR +125 to -55°C

240ppm

40ppm

Thermal Shock

<0.75%

<0.75%

High Temperature Exposure 125°C

<1.75%

<0.5%

Temperature Cycling: -40 to +125°C

<1.0%

<1.0%

Operational Life

<2.0%

<1.0%

Baised Humidity

<0.75%

<0.5%

Mechanical Shock

<1.5%

<1.0%

Vibration

<1.0%

<1.0%

Moisture Resistance

<1.0

<2.5%

Terminal Strength

Meets JIS-C-6429

Solvent Resistance

Meets MIL-STD-202 Method 215

Solderability

Meets J-STD-002 Method B

Note:

The power derating curve is a guidance based on a con-

servative design model. The OARS is a solid metal alloy

construction that can withstand significantly greater operating

temperatures than conservative design models permit. The

resistive alloys can withstand temperatures in exess of 350°C.

Therefore, the system thermal design is a more significant

design parameter due to the heat limitations of solder joints

and/or circuit board substrate materials. Refer to additional

information below.

The thermal image (not a simulation) to the left is of an OARS

5 m

Ω running at 4 Watts, which exceeds the 1 Watt conserva-

tive model. Notice the hotpsot is nearly 230°C, but the solder

joint is approximately 110°C (FR4 is rated for 130°C). The

unique construction of the OARS isolates the hotspot from

the circuit board material preventing damage. Additionally,

the thermal energy is dissipated to the air instead of being

conducted into the circuit board potentially causing a nearby

power component to exceed its rating.

The standard test circuit board consists of a four layer FR4

material with 2 ounce outer layers and 1 ounce inner layers,

which is typical of many industry designs. Contact IRC for

more details or for other thermal image test data for specific

resistance values and power levels.

OARS R005 Thermal Image @ 4 Watts

Ambient conditions, No forced air.