Resistive Products MELF Resistors - The World’s …

1 Document Number: 28802 For technical questions, contact: 18-Jun-101 vishay intertechnology , ProductsApplication NoteMELF Resistors - The World s Most Reliable andPredictable, High-Performing Film ResistorsAPPLICATION NOTEBy Udo Tribess, vishay Draloric/Beyschlag Resistors ABSTRACTFor more than 25 years, vishay s MELF Resistors havesuccessfully met the demanding requirements of theautomotive industry. They offer superior SMD resistorperformance in terms of accuracy, stability, reliability, andpulse load capability. The cylindrical construction of MELF devices provides an optimal power rating and pulse loadcapability related to the mounting space.

2 Continuousdevelopment has led to improved long-term stability andmoisture resistance, and allows high-temperature operationto + 175 paper explores why this resistor series has become sosuccessful, and why there is often no alternative to it todayin professional REQUIREMENTSThe continuously increasing requirements in professionalapplications call for electronic components that providesuperior properties regarding: High-reliability electronics Predictable behavior of components Zero-defect philosophy Harsh operating environments Environmental awarenessThe application areas with the most severe requirementsare: Automotive industry General industrial electronics Telecommunication infrastructureFor these applications , MELF Resistors have been thecustomers first choice for more than 25 years, meeting therequirements for: Long-term stability Moisture resistance Reliability Temperature cycling in lead (Pb)-free assembly processesMELF CONSTRUCTIONMELF Resistors consist of a homogeneous film of metalalloy deposited on a high-grade ceramic body.

3 Nickel-plated steel termination caps are pressed on the metalizedrods, before a special laser cuts a helical grove in theresistive layer to achieve the target resistance value. Theresistor elements are covered by a protective coating,designed for electrical, mechanical, and climatic terminations receive a pure tin plating for bestsolderability, either in lead (Pb)-free or lead-containingsoldering PERFORMANCE AND THERMAL MANAGEMENTThe Resistors cylindrical 0102, 0204, and 0207 case sizes -equivalent to flat chip sizes 0805, 1206, and 2512 - aresuitable for various application requirements. Operatingvoltages can be applied from 150 V (0102) up to 300 V(0207); rated power dissipation at + 70 C ambienttemperature ranges from W (0102) up to 1 W (0207).

4 Themaximum film temperature at the specified maximum powerrating is + 155 % Alumina Ceramic Rod(96 % for MMU)Metal Film Resistive LayerColor Code RingsProtective LacquerSteel Temination CapPlated Pure Tin on NickelMELF Resistors - The World s Most Reliable andPredictable, High-Performing Film Resistors technical questions, contact: Number: 288022 Revision: 18-Jun-10 Application NoteVishay intertechnology , NOTEThe ability to withstand these operating conditions isensured by the devices cylindrical construction. Comparedto chip Resistors of the same mounting space, the area of theeffective Resistive film is about three times greater, and thelarger volume of the ceramic body ensures sufficient COEFFICIENT, TOLERANCE, AND STABILITYThe Resistors dedicated metal alloy material, applied by asputtering process followed by thermal treatment, offersexcellent properties with respect to temperature coefficientand load-life stability.

5 The smooth helical laser, cuttingwithout damaging the ceramic body, enables very narrowtolerances and creates a current path of constant width fora uniform heat distribution. Consequently, resistortemperature coefficients down to 5 ppm/K are available,as well as tolerances down %. Long-term stabilityresults in a superior maximum resistance change ( R/R) % after 8000 h operation for high precision LOAD CAPABILITYA nother aspect of the Resistors is their reliability whenexposed to various overload conditions. The metal filmtechnology, together with the cylindrical construction of theMELF devices, provides an advantage compared tostandard thick and thin film chip Resistors in regard to pulseload capability.

6 As shown in the diagram below, thick filmflat chip Resistors fail at much lower pulse loads than thin filmflat chips, and both types are outperformed by thin filmMELF Resistors . Fig. 1 - Pulse load test - resistance change for different1 k Resistors of comparable body sizeRELIABILITYTens of billions of MELF Resistors have been deliveredto customers in the automotive, general industrial industriesand telecommunication infrastructure. The devices approved manufacturing process and certified qualitymanagement system are the base for the Resistors excellentobserved failure rate of FITOBSERVED x 10-9 s MELF Resistors are tested in accordance withseveral international standards, such as EN140401-803(superseding CECC40401-803).

7 Approval of conformity isindicated by the CECC logo on the package , the components meet the requirements ofAEC-Q200, which is the most important standard requestedby the automotive industry. Environmental aspects are alsorespected. All Products are completely lead (Pb)-free andcomply with the Global Automotive Declarable SubstancesList (GADSL), which includes full compliance with the APPLICATIONSF urther development of the existing MELF series hasenabled operation at ambient temperatures to + 175 C(MELF HT series). This improvement comes along with ahigher power rating capability ( from W to W forthe MMA 0204 HT).For the MELF HT series, three operation modes arespecified ( data for size 0204): Standard: W (derating from + 70 C) Power: W (derating from + 70 C) Advanced temperature: W (derating from + 70 C) Fig.

8 2 - Derating diagram for MMA 0204 HTThe maximum resistance change ( R/R) after 1000 h ofoperation is specified for the operation modes: Standard: % Power: % Advanced temperature: %This performance is unrivalled by thick film or even by mostthin film flat chips available on the market. With theirimprovements in stability and moisture resistance, and byachieving a higher operating temperature, MELF resistorscontinue to be the first choice for high-reliability 20100- 101100010010 Resistance Change (%)Pulse Load (W)Thick Film ChipThin Film ChipThin Film (W)Tamb ( C)High TemperaturePowerStandar