Moulded Surface Mount
Wirewound Resistors
WSM Series
Welwyn Components
•
Ideal for automatic pick and place
•
Direct replacement for Axial resistors
•
All welded construction
Electrical Data
WSM1
Power rating at 70°C
Resistance range
Limiting element voltage
TCR
Resistance tolerance
Standard values
Ambient temperature range
*Note 5% or 10% preferred below 0.1 ohms
°C
watts
ohms
volts
ppm/°C
%
< 1
Ω
: 100
≥
1
Ω
: 20
1
0R01 to 1K
WSM2
2
0R01 to 2K
100
< 1
Ω
: 100
≥
1
Ω
: 20
*1, 2, 5, 10
E24 preferred
-55 to 155
≤.03 Ω
700
≤0.1 Ω
: 200
≤10R
100
>10R 20
WSM3
3
0R01 to 3K
Physical Data
Dimensions (mm)
Type
WSM1
WSM2
WSM3
L max
7.9
12
18
I Nom
2.54
3.1
3.1
W Max
7
10.5
16
w Max
4.2
6.6
7
H Max
3.94
5.5
6.5
I
H
L
W
w
Recommended Pad Sizes
Type
WSM1
WSM2
WSM3
A
2.9
3.4
3.4
B
2.6
4.0
4.5
C
2.8
6
11
D
8.1
14
20
A
D
B
C
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 moulded.
Marking
WSM resistors are legend marked with type value and
tolerance.
WSM1 Resistors are marked with value and tolerance.
Solvent Resistance
Flammability
The resistor coating is a flame retardant epoxy to UL 94.
General Note
Welwyn Components reserves the right to make changes in product specification without notice or liability.
All information is subject to Welwyn’s own data and is considered accurate at time of going to print.
A subsidiary of
TT electronics plc
Issue C · 04.03
The body protection and marking are resistant to all normal
industrial cleaning solvents suitable for printed circuits.
© Welwyn Components Limited
· Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com
45
Moulded Surface Mount
Wirewound Resistors
WSM Series
Welwyn Components
Physical Data
Dimensions (mm)
Ao
WSM1
WSM2
WSM3
4.2
6.75
7.3
Bo
7.62
11.95
18.3
Ko
4.2
5.22
6.7
W
16
24
32
P
8
12
12
t
0.36
0.36
0.4
Po
4 ± 0.1
4 ± 0.1
4 ± 0.1
All other dimensions as per EIA481 standard
Performance Data
WSM1
Load at rated power: 1000 hrs @ 70°C
Dry heat
Short term overload
Derating from rated power @ 70°C
Moisture
Temperature cycling
Resistance to solder heat
Isolation voltage
Insulation resistance
Substrate bend
∆R%
∆
R%
∆
R%
V
ohms
∆
R%
1 ± 0.001Ω
1000 hrs @ 155°C
∆R%
∆R%
∆
R%
2 ± 0.001Ω
2 ± 0.001Ω
WSM2
2 ± 0.001Ω
2 ± 0.001Ω
2 ± 0.001
Ω
zero at 155°C
1 ± 0.001Ω
1 ± 0.001
Ω
1 ± 0.001
Ω
1,000
>1000M
0.2 ± 0.001
Ω
1.5 ± 0.001Ω
WSM3
3 ± 0.001Ω
3 ± 0.001Ω
Note: The power ratings to be applied depend upon the board used and the ambient temperature.
Ordering Procedure
Example: WSM2 at 4.7 ohms and 5% tolerance on a reel of 800 pieces
–
WSM2
–
4R7J
I
Type
Value (use IEC62 code)
Tolerance (use IEC62 code)
F
G
1%
2%
J
K
5%
10%
Packing
I
Tape
WSM1
WSM2
WSM3
1500/reel
800/reel
750/reel
Standard
© Welwyn Components Limited
Bedlington, Northumberland NE22 7AA, UK
Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: info@welwyn-tt.com · Website: www.welwyn-tt.com
Issue C · 04.02
46
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