Cement Coated Surface
Mount Wirewound Resistors
WA80Z Series
Marking
WA83Z and WA84Z resistors R10 and above are marked with
four colour bands in conformance with IEC62. Values
below R10 are marked with three bands (two digits and
tolerance); there is no multiplier band. WA85Z resistors are
legendmarked “WA85” plus resistance value and tolerance in
conformance with IEC62.
Welwyn Components
Solvent Resistance
The body protection and marking are resistant to all normal
industrial cleaning solvents suitable for printed circuits.
Flammability
The resistor coating will not burn under any condition of
applied temperature or component overload.
Performance Data
Maximum
Load at rated power: 1000hrs @ 25 or 70°C
Dry heat: 1000hrs @ 200°C
Short term overload
Derating from rated power @ 25°C
Climatic
Climatic category
TRC & Vibration
Robustness & solder heat
Long term damp heat
Temperature rise
Pulse handling
∆R%
∆R%
∆R%
5 +0.001Ω
5 +0.001Ω
5 +0.001Ω
See Graph 1
See Graph 2
∆R%
5 +0.001Ω
55/200/56
1
1
1
∆R%
∆R%
∆R%
5 +0.001Ω
5 +0.001Ω
5 +0.001Ω
Zero at 155˚C
2
Typical
3
3
1
Note: Testing was performed on FR4 test boards measuring 50mm x 50mm, with 1oz/ft
2
(300g/m
2
) copper pads. The track area
close to each pad was 120mm
2
. If a lower grade of PCB or less track area is used, derating of the power may be necessary.
Temperature Rise
Graph 1
260
240
220
200
180
160
WA80Z Thermal Performance
Temp Rise (K)
140
120
100
80
60
40
20
0
0
0.5
1
1.5
2
2.5
Power (W)
3
3.5
4
4.5
5
WA83Z Hot Spot
WA83Z Joint
WA84Z Hot Spot
WA84Z Joint
WA85Z Hot Spot
WA85Z Joint
© 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 G · 03.06
WELWYN [ WELWYN COMPONENTS LIMITED ]
