General Note
IRC reserves the right to make changes in product specifi cation without notice or liability.
All information is subject to IRC’s own data and is considered accurate at time of going to print. A subsidiary of
TT electronics plc
• 4222 South Staples Street • Corpus Christi Texas 78411 USA
Wire and Film Technologies Division
Telephone: 361 992 7900 • Facsimile: 361 992 3377 • Website: www.irctt.com
Molded Surface Mount
Wirewound Resistor
WSM Series
• Flexible Terminations
• All welded construction
• Ideal for automatic pick and place
• Lead free, RoHS compliant construction only
• Contact factory for ohmic values above published ranges
*Note: 5% or 10% preferred below 0.1 ohms.
Electrical Data
IRC
Type
Power Rating
@ 70°C
(watts)
Resistance
Range
(ohms)
Maximum Working
Voltage
(volts)
TCR
(ppm/°C)
Resistance
Tolerance
(%)
Standard
Values
Ambient
Temperature
(°C)
WSM-1 1W 0.01 to 1K
√P x R 0.1Ω - <10Ω: 100
≥1Ω: 20 *1, 2, 5, 10 E24
Preferred -55 to 155
WSM-2 2W 0.01 to 2K
WSM-3 3W 0.01 to 3K
CONSTRUCTION
A high purity ceramic substrate is assembled with interference fi t end caps to which are welded the terminations.
The resistive element is wound on the substrate and welded to the caps. The unit is then molded.
FLAMMABILITY
The resistor coating is categorized as fl ame retardant epoxy under UL-94.
SOLVENT RESISTANCE
The body protection and marking are resistant to all normal industrial cleaning solvents suitable for printed
circuits.
MARKING
WSM resistors are legend marked with type, value and tolerance.
WSM Series Issue August 2009 Sheet 1 of 3
• 4222 South Staples Street • Corpus Christi Texas 78411 USA
Wire and Film Technologies Division
Telephone: 361 992 7900 • Facsimile: 361 992 3377 • Website: www.irctt.com
Physical Data
Recommended Pad Sizes
Dimensions (Inches & mm))
TypeABCD
WSM-1 0.115
(2.9)
0.100
(2.6)
0.189
(2.9)
0.389
(9.9)
WSM-2 0.134
(3.4)
0.158
(4.0)
0.237
(6.0)
0.552
(14.0)
WSM-3 0.134
(3.4)
0.178
(4.5)
0.434
(11.0)
0.788
(20.0)
Molded Surface Mount
Wirewound Resistor
L
l l
L
W W
H
W
H
W
Dimensions (Inches & mm))
Type L l W w H
WSM-1 0.310 max
(7.9 max)
0.100 nom
(2.54 nom)
0.275 max
(7.0 max)
0.165 max
(4.2 max)
0.155 max
(3.94 max)
WSM-2 0.473 max
(12 max)
0.122 nom
(3.1 nom)
0.413 max
(10.5 max)
0.260 max
(6.6 max)
0.217 max
(5.5 max)
WSM-3 0.709 max
(18 max)
0.122 nom
(3.1 nom)
0.630 max
(16 max)
0.276 max
(7 max)
0.256 max
(6.5 max)
B
C
A
B
WSM Series Issue August 2009 Sheet 2 of 3
• 4222 South Staples Street • Corpus Christi Texas 78411 USA
Wire and Film Technologies Division
Telephone: 361 992 7900 • Facsimile: 361 992 3377 • Website: www.irctt.com
Molded Surface Mount
Wirewound Resistor
*Note: The power ratings to be applied depend upon the board used and the ambient temperature.
Sample Part No.
IRC Type
(WSM1, WSM2, WSM3)
Resistance Value
(100Ω and greater - First 3 significant digits plus
4th digit multiplier) Example: 100Ω = 1000, 1000Ω = 1001,
150,000Ω = 1503 (Less than 100Ω - "R" is used to designate
decimal) Example: 51Ω = 51R0, 1Ω = 1R00, 0.25Ω = R250
Tolerance
(K = 10%, J = 5%, G = 2%, F = 1%)
Lead Free, RoHS Designator
Packaging Code
(TR = 13" Reel)
Ordering Data
WSM3 6801 F LF TR
Specify type, reference, etc. as indicated in this example of a
WSM3 6801 F resistor with tape and reel packaging.
Standard Quantities Per Package
Type Code WSM1 WSM2 WSM3
13" Reel
(330mm) R 1500 800 750
Packaging:
WSM2 resistors are supplied on .945 (24mm) wide
carrier tape.
WSM3 resistors are supplied on 1.26 (32mm) wide
carrier tape.
Both products are reeled onto 13.00 (330mm)
diameter reels.
*For packaging information, see Appendix "A".
Environmental Data
Characteristics WSM-1 WSM-2 WSM-1
Load at Rated Power: 1000 hours @ 70°C 2 ± 0.001Ω2 ± 0.001Ω3 ± 0.001Ω
Dry Heat: 1000 hours @ 155°C 2 ± 0.001Ω2 ± 0.001Ω3 ± 0.001Ω
Short Term Overload 2 ± 0.001Ω
Derating from Rated Power @ 70°C zero at 155°C
Moisture 1 ± 0.001Ω1 ± 0.001Ω1.5 ± 0.001Ω
Temperature Cycling 1 ± 0.001Ω
Resistance to Solder Heat 1 ± 0.001Ω
Isolation Voltage 1,000
Insulation Resistance >1000M
Substrate Bend 0.2 ± 0.001Ω
ΔR%
volts
ohms
ΔR%
ΔR%
ΔR%
ΔR%
ΔR%
ΔR%
Dimensions (Inches and (mm))
Ao Bo Ko W P T
WSM1 .165
(4.2)
.300
(7.62)
.165
(4.20)
.630
(16.0)
.315
(8.00)
.014
(0.36)
WSM2 .266
(6.75)
.470
(11.95)
.206
(5.22)
.945
(24.0)
.473
(12.0)
.014
(0.36)
WSM3 .288
(7.3)
.721
(18.3)
.264
(6.7)
1.26
(32.0)
.473
(12.0)
.016
(0.4)
A0P
B0W
K0
t
WSM Series Issue August 2009 Sheet 3 of 3
