Varistor Products Surface Mount Varistors > SM20 Series SM20 Varistor Series Description The Littelfuse 20mm SMD Series is a surface-mount metal oxide varistor device, for use in applications requiring hi-energy / transient current capability. The AC rated parts are designed to operate continuously across AC power lines. The DC rated parts are suitable for Automotive applications. The series comprises a Nylon molded package with folded tin plated metal leads for soldering to board. The SMD Series is based on radial 20mm internal varistor element with similar characteristics to the Littelfuse LA / ZA series of varistors. Agency Approvals Features Agency File Number E320116 • DC Voltage Rating 26VDC • AC Voltage Rating 175 - 320AC • No De-Rating up to 85°C ambient • Lead-Free, HalogenFree and RoHS Compliant • Low voltage devices specified for automotive load dump energy • Available in "waffle" tray packaging Absolute Maximum Ratings • For ratings of individual members of a series, see Device Ratings and Specifications chart Continuous SM20 Series Units 20 to 320 V 26 V up to 6500 A Steady State Applied Voltage: AC Voltage Range (VM(AC)RMS) DC Voltage Range (VM(DC)) Transients: Peak Pulse Current (ITM) 8/20μs Current Wave, Single Pulse Single Pulse Energy Capability (WTM) 10/1000μs Current Wave 165 J Load Dump Energy Capability (td>=30ms) 160 J Operating Ambient Temperature Range (TA) -40 to +85 O Storage Temperature Range (TSTG) -55 to +125 O C C Temperature Coefficient (aV) of Clamping Voltage (VC) at Specified Test Current <0.01 %/OC Hi-Pot Encapsulation (COATING Isolation Voltage Capability) (Dielectric must withstand indicated DC voltage for one minute per MIL-STD 202, Method 301) 2500 V COATING Insulation Resistance 1000 MΩ CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. ©2010 Littelfuse, Inc. Specifications are subject to change without notice. Please refer to www.littelfuse.com/series/sm20.html for current information. SM20 Series Varistor Revision: May 11, 2010 SM20 Series Agency Varistor Products Surface Mount Varistors > SM20 Series SM20 Series Ratings & Specifications Maximum Rating (85°C) Continuous Transient VRMS VDC VM(AC) VM(DC) (V) (V) Part Number Branding V26SM20 26SM20 20 26 V175SM20 V230SM20 V250SM20 V275SM20 V300SM20 V320SM20 175SM20 230SM20 250SM20 275SM20 300SM20 320SM20 175 230 250 275 300 320 225 300 330 369 405 420 Energy Peak Current 10 x 1000μs 8 x 20μs WTM ITM 1x pulse 1x pulse (J) 20 160 (note 1) 90 122 130 140 165 150 (A) Specifications (25°C) Maximum Varistor Voltage Clamping at 1mA DC Voltage Test Current 8 x 20 μs VNOM Min VNOM Max (V) 32 (10mA) 247 324 354 389 420 462 2000 6500 6500 6500 6500 6500 6500 (V) 40 (10mA) 303 396 429 473 517 540 Typical Capacitance f = 1MHz VC IPK C (V) (A) (pF) 63 20 12000 455 595 650 710 775 810 100 100 100 100 100 100 1400 1100 1000 900 800 750 1. Energy rating for impulse duration of 30ms minimum to one half of peak current (automotive load dump). Peak Current, Energy and Power Derating Curve Repetitive Surge Capability For applications exceeding 85ºC ambient temperature, the peak surge current and energy ratings must be reduced as shown below V175SM20 - V320SM20 10,000 1 5,000 SURGE CURRENT (A) 90 PERCENT OF RATED VALUE 10 2,000 100 80 70 60 50 40 30 1,000 500 MODEL SIZE 20mm V175SM20 - V320SM20 10 2 3 10 10 4 10 5 10 6 200 100 50 20 INDEFINITE 10 5 20 2 10 0 -55 2 1 50 60 70 80 90 100 110 120 130 140 150 AMBIENT TEMPERATURE ( oC) 20 100 1,000 IMPULSE DURATION (μs) 10,000 PERCENT OF PEAK VALUE Test Peak Pulse Current Test Waveform for Clamping Voltage O1 100 50 0 t TIM E t1 t 01 = Virtual Origin of Wave T = Time from 10% to 90% of Peak T1 = Rise Time = 1.25 x T T2 = Decay Time Example - For an 8/20 μs Current Waveform: 8μs = T1 = Rise Time 20μs = T2 = Decay Time ©2010 Littelfuse, Inc. SM20 Series Varistor Revision: May 11, 2010 Specifications are subject to change without notice. Please refer to www.littelfuse.com/series/sm20.html for current information. Varistor Products Surface Mount Varistors > SM20 Series Lead (Pb) Soldering Recommendations The principal techniques used for the soldering of components in surface mount technology are IR Re-flow and Wave soldering. Typical profiles are shown on the right. Reflow Solder Profile 250 The terminals of SM20 series devices are tin plated copper, and the recommended solder is 62/36/2 (Sn/Pb/Ag), 60/40 (Sn/Pb) or 63/37 (Sn/Pb). Littelfuse also recommends an RMA solder flux. TEMPERATURE °C Wave soldering is the most strenuous of the processes. To avoid the possibility of generating stresses due to thermal shock, a preheat stage in the soldering process is recommended, and the peak temperature of the solder process should be rigidly controlled. 40-80 SECONDS ABOVE 183°C 150 RAMP RATE <2°C/s 100 PREHEAT DWELL 50 0 PREHEAT ZONE 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 TIME (MINUTES) Wave Solder Profile 300 Once the soldering process has been completed, it is still necessary to ensure that any further thermal shocks are avoided. One possible cause of thermal shock is hot printed circuit boards being removed from the solder process and subjected to cleaning solvents at room temperature. The boards must be allowed to cool gradually to less than 50ºC before cleaning. MAXIMUM WAVE 260°C TEMPERATURE °C 250 200 SM20 Series When using a reflow process, care should be taken to ensure that the SM20 chip is not subjected to a thermal gradient steeper than 4 degrees per second; the ideal gradient being 2 degrees per second. During the soldering process, preheating to within 100 degrees of the solder's peak temperature is essential to minimize thermal shock. MAXIMUM TEMPERATURE 230°C 200 150 SECOND PREHEAT 100 FIRST PREHEAT 50 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 TIME (MINUTES) 3.5 4.0 4.5 Lead–free (Pb-free) Soldering Recommendations Lead–free Re-flow Solder Profile The reflow profile must be constrained by the maximums in the Lead–free Reflow Profile. For Lead–free Wave soldering, the Wave Solder Profile still applies. Note: the Lead–free paste, flux and profile were used for evaluation purposes by Littelfuse, based upon industry standards and practices. There are multiple choices of all three available, it is advised that the customer explores the optimum combination for their process as processes vary considerably from site to site. ©2010 Littelfuse, Inc. Specifications are subject to change without notice. Please refer to www.littelfuse.com/series/sm20.html for current information. 300 MAXIMUM TEMPERATURE 250˚C, TIME WITHIN 5˚C OF PEAK 20 SECONDS MAXIMUM 250 TEMPERATURE °C The terminals of SM20 series devices are tin plated copper, and the recommended Lead-free solder is 96.5/3.0/0.5 (SnAgCu) with an RMA flux, though there is a wide selection of pastes and fluxes available that should be compatible. RAMP RATE <3˚C/s 200 60 - 150 SEC > 217˚C 150 100 PREHEAT ZONE 50 0 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 TIME (MINUTES) SM20 Series Varistor Revision: May 11, 2010 Varistor Products Surface Mount Varistors > SM20 Series Part Numbering System Product Dimensions ' Symbol Max --- 26 H1 --- 10.5 H2 1.0 -- t 0.50 0.70 S1 32.5 35 S2 3.0 4.5 W 6.2 6.6 D : (diameter) + + W 6 6 V 275 SM20 Millimeters Min For “VARISTOR” Max Voltage Rating (Two or three digits -- refer to ratings and specifications table) SM20 SERIES 6ROGHULQJ3DG/D\RXW Packaging Standard Packaging is in "Waffle" trays: Quantity per tray: 36 pieces Quantity per box: 108 pieces 192 mm 30 mm typical 8.4 mm typical 11.7 mm pocket depth 30 mm typical 192 mm Radius 30 mm typical ©2010 Littelfuse, Inc. SM20 Series Varistor Revision: May 11, 2010 Specifications are subject to change without notice. Please refer to www.littelfuse.com/series/sm20.html for current information.