Rev Date: 01/25/2012 1 www.seielect.com
This specification may be changed at any time without prior notice marketing@seielect.com
Please confirm technical specifications before you order and/or use.
WW/MWW/NWW Series
General Purpose and Precision Wirewound Resistor
Stackpole Electronics, Inc.
Resistive Product Solutions
Features:
• WWS offers miniature size at higher power rating
• High performance for low cost
• High power to size ratio
• MWW – completely molded construction with welded terminations
• Complete welded terminations
• Tinned copper leads
• Available in non-inductive styles
• High temperature silicone coating
• RoHS compliant
• Higher operating temperatures may be available. Contact factory.
Standard Non-Inductive
(N)WW12 - 500V 0.4W 0.1 - 2K 0.1 - 1K
(N)WW1 - 500V 1W 0.1 - 3K 0.1 - 1.5K
(N)WW1A RW-70 500V 1W 0.1 - 7K 0.1 - 3.5K
(N)WW2 RW-69 1,000V 1.5W 0.1 - 10K 0.1 - 5K
(N)WWS2 - 500V 2.5W 0.1 - 3K 0.1 - 1.5K
(N)WW2A - 1,000V 2.5W 0.1 - 15K 0.1 - 7.5K
(N)WW3 RW-79 1,000V 3W 0.1 - 22K 0.1 - 11K
(N)WWS3 RW-69 1,000V 3W 0.1 - 10K 0.1 - 5K
(N)WW3A - 1,000V 3W 0.1 - 30K 0.1 - 15K
(N)WW4 - 1,000V 4W 0.1 - 40K 0.1 - 20K
(N)WWS4 RW-79 1,000V 4W 0.1 - 22K 0.1 - 11K
(N)WW5 RW-67, RW-74 1,000V 5W 0.1 - 50K 0.1 - 25K
(N)WWS5 - 1,000V 5W 0.1 - 40K 0.1 - 20K
(N)WW7 - 1,000V 6.5W 0.1 - 70K 0.1 - 35K
(N)WWS7 RW-67, RW-74 1,000V 6.5W 0.1 - 50K 0.1 - 25K
(N)WW7B - 1,000V 7W 0.1 - 100K 0.1 - 50K
(N)WW10 RW-78 1,000V 10W 0.1 - 150K 0.1 - 75K
(N)WWS10 - 1,000V 10W 0.1 - 100K 0.1 - 50K
(N)MWW1 RW-70 1,000V 1W 0.1 - 2K -
(N)MWW3 RW-79 1,000V 3W 0.1 - 20K -
(N)MWW5 RW-67, RW-74 1,000V 5W 0.1 - 40K -
(N)MWW10 RW-68, RW-74 1,000V 10W 0.1 - 150K -
(1) Lesser of √PR or maximum working voltage
Ohmic Range(Ω) and Tolerance(1)
0.1%, 0.5%, 1% & 5%
Resitance Temperature
Coefficient
Type / Code
< 1Ω = ±90ppm/ºC
MIL-R-26 Ref.
Power Rating
(Watts)
@ 25ºC
>10Ω = ±20ppm/ºC
1Ω to 10Ω = ±50ppmºC
Dielectric
Strength
(V)
Electrical Specifications
Please refer to the High Power Resistor Application Note (page 4) for more information on designing and
implementing high power resistor types.
Rev Date: 01/25/2012 2 www.seielect.com
This specification may be changed at any time without prior notice marketing@seielect.com
Please confirm technical specifications before you order and/or use.
WW/MWW/NWW Series
General Purpose and Precision Wirewound Resistor
Stackpole Electronics, Inc.
Resistive Product Solutions
Test Test Condition Result
Moisture Resistance 1000 hours, 95% R.H., 40ºC 1% max
Load Life 1000 hours,
cycled power 1.5 hours ON, 0.5 hours OFF, 25ºC 1%
Temperature Cycling 5 cycles, -55ºC to 200ºC 0.5%
Short Time Overload 5 times rated power for 5 seconds 1%
0.31 ± 0.06 0.11 ± 0.03 0.03 ± 0.002 inches
7.92 ± 1.57 2.79 ± 0.79 0.64 ± 0.05 mm
0.38 ± 0.06 0.11 ± 0.03 0.03 ± 0.002 inches
9.53 ± 1.57 2.79 ± 0.79 0.64 ± 0.05 mm
0.42 ± 0.06 0.11 ± 0.03 0.03 ± 0.002 inches
10.67 ± 1.57 2.79 ± 0.79 0.64 ± 0.05 mm
0.37 ± 0.06 0.16 ± 0.03 0.03 ± 0.002 inches
9.40 ± 1.57 3.96 ± 0.79 0.81 ± 0.05 mm
0.55 ± 0.06 0.16 ± 0.03 0.03 ± 0.002 inches
13.97 ± 1.57 3.96 ± 0.79 0.81 ± 0.05 mm
0.56 ± 0.06 0.19 ± 0.03 0.03 ± 0.002 inches
14.22 ± 1.57 4.75 ± 0.79 0.81 ± 0.05 mm
0.50 ± 0.06 0.22 ± 0.03 0.03 ± 0.002 inches
12.70 ± 1.57 5.54 ± 0.79 0.81 ± 0.05 mm
0.70 ± 0.06 0.27 ± 0.03 0.04 ± 0.002 inches
17.78 ± 1.57 6.86 ± 0.79 0.91 ± 0.05 mm
0.88 ± 0.06 0.31 ± 0.03 0.04 ± 0.002 inches
22.23 ± 1.57 7.92 ± 0.79 0.91 ± 0.05 mm
1.00 ± 0.06 0.31 ± 0.03 0.04 ± 0.002 inches
25.40 ± 1.57 7.92 ± 0.79 0.91 ± 0.05 mm
1.20 ± 0.06 0.31 ± 0.03 0.04 ± 0.002 inches
30.48 ± 1.57 7.92 ± 0.79 0.91 ± 0.05 mm
1.78 ± 0.06 0.38 ± 0.03 0.04 ± 0.002 (1) inches
45.21 ± 1.57 9.53 ± 0.79 0.91 ± 0.05 (1) mm
0.39 ± 0.06 0.14 ± 0.03 0.03 ± 0.002 inches
9.78 ± 1.57 3.43 ± 0.79 0.81 ± 0.05 mm
0.56 ± 0.06 0.21 ± 0.03 0.03 ± 0.002 inches
14.22 ± 1.57 5.21 ± 0.79 0.81 ± 0.05 mm
0.93 ± 0.06 0.33 ± 0.03 0.04 ± 0.002 inches
23.50 ± 1.57 8.38 ± 0.79 0.91 ± 0.05 mm
1.97 ± 0.06 0.48 ± 0.03 0.04 ± 0.002 inches
49.91 ± 1.57 12.19 ± 0.79 1.02 ± 0.05 mm
(1) Available in 0.04mm / 0.0016"
(N)WW12
(N)WW3 / (N)WWS4
(N)WW3A
(N)WW4 / (N)WWS5
(N)WW1 / (N)WWS2
(N)WW1A
(N)WW2 / (N)WWS3
(N)WW2A
(N)MWW10
(N)WW5 / (N)WWS7
(N)WW7
(N)WW7B / (N)WWS10
(N)WW10
(N)MWW1
(N)MWW3
(N)MWW5
Type / Code A B C Unit
Mechanical Specifications
Performance Characteristics
Rev Date: 01/25/2012 3 www.seielect.com
This specification may be changed at any time without prior notice marketing@seielect.com
Please confirm technical specifications before you order and/or use.
WW/MWW/NWW Series
General Purpose and Precision Wirewound Resistor
Stackpole Electronics, Inc.
Resistive Product Solutions
Power Derating Curve:
20
80
60
40
100
120
350
Operating Temperature Range: -25ºC to +350ºC
Ambient Temperature (ºC)
25 325175 225 27575 125
Percent Rated Power (%)
How to Order
123456789
WW 1 F T 1 K 0 0
WW Code Quantity
WWS B
MWW D
NWW F
J
(N)MWW10
(N)WW10
(N)WWS10
(N)MWW1
(N)MWW3
(N)WW5
(N)WWS5
(N)WW7B
(N)MWW5
(N)WW1A
(N)WW3A
(N)WW4
(N)WWS4
Mini
Non-Inductive
Non-Inductive
NWWS 0.1 ohm = R100
2 Kohm = 2K00
Four characters
with the multiplier
used as the
decimal holder.
0.5%
1%
Tol
(N)WW3
(N)WWS3
0.1%
T
(N)WW12
(N)WW1
(N)WW2
(N)WWS2
(N)WW7
(N)WWS7
Type/Code
Standard
5%
(N)MWW10
(N)WW10
(N)WW2
(N)WWS3
(N)WW2A
(N)WW3
Product Series
Description Size
Resistance ValueTolerance
Code
Packaging
Mini
Molded
10W
1W
3W
5W
10W
(N)WWS4
(N)WW2A
2,500
(N)WW12
(N)WW1
(N)WWS2
(N)WW1A
(N)MWW1
(N)MWW3
6.5W
7W
10W
(N)WW3A
(N)WW4
(N)WWS5
(N)WW5
(N)WWS7
(N)WW7
(N)WW7B
(N)MWW5
(N)WWS10
11" Tape and Reel
Power Rating
3W
3W
3W
4W
4W
5W
5W
6.5W
2,000
500
250
@ 25ºC
0.4W
1W
1W
1.5W
2.5W
2.5W
Legacy Part Number (before January 3, 2011):
Nominal
Code Resistance Tolerance
1 10K 1%
T
y
pe Description Tolerance T
y
pes Qt
y
Description Code
WW Standard 0.1% (N)WW12, (N)WW1, (N)WWS2, (N)WW1A, (N)MWW1 2,500
WWS Mini 0.5%
MWW Molded 1%
NWW Non-Inductive 5% (N)WW3A, (N)WW4, (N)WWS5, (N)WW5,
(N)WW10, (N)MWW10 250
500
(N)WWS7, (N)WW7, (N)WW7B,
(N)WWS10, (N)MWW5
2,000
Mini
Non-Inductive
NWWS
SEI Type Packaging
WW R
11" reel
tape R
(N)WW2, (N)WWS3, (N)WW2A, (N)WW3,
(N)WWS4, (N)MWW3
Rev Date: 01/25/2012 4 www.seielect.com
This specification may be changed at any time without prior notice marketing@seielect.com
Please confirm technical specifications before you order and/or use.
WW/MWW/NWW Series
General Purpose and Precision Wirewound Resistor
Stackpole Electronics, Inc.
Resistive Product Solutions
High Power Chip Resistors and Thermal Management
Stackpole has developed several surface mount resistor series in addition to our current sense resistors,
which have had higher power ratings than standard resistor chips. This has caused some uncertainty and
even confusion by users as to how to reliably use these resistors at the higher power ratings in their designs.
The data sheets for the RHC, RMCP, RNCP, CSR, CSRN, CSRF, CSS, and CSSH state that the rated
power assumes an ambient temperature of no more than 100 degrees C for the CSS / CSSH series and 70
degrees C for all other high power resistor series. In addition, IPC and UL best practices dictate that the
combined temperature on any resistor due to power dissipated and ambient air shall be no more than 105C.
At first glance this wouldn’t seem too difficult, however the graph below shows typical heat rise for the CSR
½ 100 milliohm at full rated power. The heat rise for the RMCP and RNCP would be similar. The RHC with
its unique materials, design, and processes would have less heat rise and therefore would be easier to
implement for any given customer.
The 102 degrees C heat rise shown here would indicate there will be additional thermal reduction techniques
needed to keep this part under 105C total hot spot temperature if this part is to be used at 0.75 watts of
power. However, this same part at the usual power rating for this size would have a heat rise of around 72
degrees C. This additional heat rise may be dealt with using wider conductor traces, larger solder pads and
land patterns under the solder mask, heavier copper in the conductors, vias through PCB, air movement, and
heat sinks, among many other techniques. Because of the variety of methods customers can use to lower
the effective heat rise of the circuit, resistor manufacturers simply specify power ratings with the limitations
on ambient air temperature and total hot spot temperatures and leave the details of how to best accomplish
this to the design engineers. Design guidelines for products in various market segments can vary widely so it
would be unnecessarily constraining for a resistor manufacturer to recommend the use of any of these
methods over another.
Note: The final resistance value can be affected by the board layout and assembly process, especially the size of the
mounting pads and the amount of solder used. This is especially notable for resistance values ≤ 50 mΩ.
This should be taken into account when designing.
