General Note
IRC reserves the right to make changes in product specification 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
Issue Preliminary
1205
• All welded construction
• Ideal for automatic pick and place
• Direct replacement for axial resistors
• Contact factory for ohmic values above published ranges
• Lead-Free, ROHS Conpliant Construction Available
SPECIFICATIONS:
Construction:
A high purity ceramic substrate is assembled with interference fit 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 flame 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.
WIREWOUND AND FILM TECHNOLOGIES DIVISION
736 Greenway Road • Boone, North Carolina 28607-1860 • Tel: 828-264-8861 • Fax: 828-264-8866 • www.irctt.com
Recommended Pad Sizes:
A
C
B
D
.134 .178 .434 .788
(3.4) (4.5) (11.0) (20.0)
.134 .158 .237 .552
(3.4) (4.0) (6.0) (14.0)
WSM1
WSM2
WSM3
in
(mm)
in
(mm)
in
(mm)
A B C D
.115 .100 .189 .389
(2.9) (2.6) (4.8) (9.9)
WSM2
2
0.01 to 2K
100
<1Ω : 100
< 1Ω : 20
WSM3
3
0.01 to 3K
100
< .03Ω : 700 < 0.1Ω :
200
*1, 2, 5, 10
E24 preferred
-55 to 155
Power rating at 70°C watts
Resistance range ohms
Limiting element voltage volts
TCR ppm/°C
Resistance tolerance %
Standard values
Ambient temperature °C
*Note: 5% or 10% preferred below 0.1 ohms.
WSM1
1
0.01 to 1K
100
<10Ω : 100
>10Ω : 20
Dimensions:
P/N
WSM-1
WSM -2
WSM-3
in
(mm)
in
(mm)
in
(mm)
L l W w
.310 max
(7.9 max)
.473 max
(12 max)
.709 max
(18 max)
.100 nom
(2.54 nom)
.122 nom
(3.1 nom)
.122 nom
(3.1 nom)
.275 max
(7.0 max)
.413 max
(10.5 max)
.630 max
(16 max)
.165 max
(4.2 max)
.260 max
(6.6 max)
.276 max
(7 max)
.155 max
(3.94 max)
.217 max
(5.5 max)
.256 max
(6.5 max)
L
W
l
L
Ww w
H H
l
MOLDED SURFACE MOUNT WIREWOUND RESISTOR
WSM SERIES
WSM PERFORMANCE DATA:
Note: The power ratings to be applied depend upon the board used and the ambient temperature.
WIREWOUND AND FILM TECHNOLOGIES DIVISION
736 Greenway Road • Boone, North Carolina 28607-1860 • Tel: 828-264-8861 • Fax: 828-264-8866 • www.irctt.com
WSM3 6K8 J R LF
Type
Value
Tolerance
(F=1%, G=2%, J=5%, K=10%
Packaging Code
Lead Free Construction
Ao B o K o W P T
WS M1
.165 .300 .165 .630 .315 .014
(4.2) (7.62) (4.20) (16.0) (8.00) (0.36)
WS M2
.266 .470 .206 .945 .473 .014
(6.75) (11.95) (5.22) (24.0) (12.0) (0.36)
WS M3
.288 .721 .264 1.26 .473 .016
(7.3) (18.3) (6.7) (32.0) (12.0) (0.4)
WSM1 WSM2 WSM3
Load at rated power: 1000 hrs. at 70°C
∆R% 2 ± 0.001Ω2 ± 0.001Ω3 ± 0.001Ω
Dry heat: 1000 hrs. @ 155°C
∆R% 2 ± 0.001Ω2 ± 0.001Ω3 ± 0.001Ω
Short term overload
∆R%
Derating from rated power @ 70°C
Moisture
∆R% 1 ± 0.001Ω1 ± 0.001Ω1.5 ± 0.001Ω
Temperature cycling
∆R%
Resistance to solder heat
∆R%
Isolation voltage V
Insulation resistance ohms
Substrate bend
∆R%
1,000
>1000M
0.2 ± 0.001Ω
2 ± 0.001Ω
zero at 155°C
1 ± 0.001Ω
1 ± 0.001Ω
STANDARD QUANTITIES PER PACKAGE:
Type Code WSM1 WSM2 WSM3
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.
13" Reel R 1500 800 750
(330mm)
*For packaging information, see Appendix "A".
HOW TO ORDER:
Specify type, reference, etc. as indicated in this example of a WSM3 6.8K ohms 5% resistor with tape and
reel packaging.