WSM_C.qxd 29/4/03 10:38 am Page 1 Moulded Surface Mount Wirewound Resistors Welwyn Components WSM Series • Ideal for automatic pick and place • Direct replacement for Axial resistors • All welded construction Electrical Data WSM1 WSM2 Power rating at 70°C watts 1 2 3 Resistance range ohms 0R01 to 1K 0R01 to 2K 0R01 to 3K < 1 Ω : 100 < 1 Ω : 100 ≥ 1 Ω : 20 ≥ 1 Ω : 20 Limiting element voltage volts TCR ppm/°C Resistance tolerance WSM3 100 % ≤.03 Ω 700 ≤0.1 Ω : 200 ≤10R 100 >10R 20 *1, 2, 5, 10 Standard values E24 preferred Ambient temperature range °C -55 to 155 *Note 5% or 10% preferred below 0.1 ohms Physical Data Dimensions (mm) Type L max I Nom W Max w Max H Max WSM1 7.9 2.54 7 4.2 3.94 WSM2 12 3.1 10.5 6.6 5.5 WSM3 18 3.1 16 7 6.5 L W w I H Recommended Pad Sizes Type A B C D WSM1 2.9 2.6 2.8 8.1 WSM2 3.4 4.0 6 14 WSM3 3.4 4.5 11 20 B C A D Construction Marking 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. 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. The body protection and marking are resistant to all normal industrial cleaning solvents suitable for printed circuits. 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. © Welwyn Components Limited · Bedlington, Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: [email protected] · Website: www.welwyn-tt.com A subsidiary of TT electronics plc Issue C · 04.03 45 WSM_C.qxd 29/4/03 10:38 am Page 2 Moulded Surface Mount Wirewound Resistors Welwyn Components WSM Series Physical Data Dimensions (mm) Ao Bo Ko W P t Po WSM1 4.2 7.62 4.2 16 8 0.36 4 ± 0.1 WSM2 6.75 11.95 5.22 24 12 0.36 4 ± 0.1 WSM3 7.3 18.3 6.7 32 12 0.4 4 ± 0.1 All other dimensions as per EIA481 standard Performance Data WSM1 WSM2 WSM3 Load at rated power: 1000 hrs @ 70°C ∆R% 2 ± 0.001Ω 2 ± 0.001Ω 3 ± 0.001Ω Dry heat ∆R% 2 ± 0.001Ω 2 ± 0.001Ω 3 ± 0.001Ω 1000 hrs @ 155°C Short term overload ∆R% 2 ± 0.001Ω Derating from rated power @ 70°C zero at 155°C Moisture ∆R% Temperature cycling ∆R% 1 ± 0.001Ω Resistance to solder heat ∆R% 1 ± 0.001Ω Isolation voltage 1 ± 0.001Ω 1 ± 0.001Ω V 1.5 ± 0.001Ω 1,000 Insulation resistance ohms >1000M Substrate bend ∆R% 0.2 ± 0.001Ω Note: The power ratings to be applied depend upon the board used and the ambient temperature. © Welwyn Components Limited Bedlington, Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 · Facsimile: +44 (0) 1670 829465 · Email: [email protected] · Website: www.welwyn-tt.com 46 Issue C · 04.02