Acceleration Factor using norris landzberg equation


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Acceleration Factor using norris landzberg equation

  1. 1. Acceleration Factor Calculation Using Norris-Landzberg EquationUsing Accelerated Life Testing the specified Thermal Cycles can be reduced.Accelerated Tests are performed using stresses beyond normal life cycle or usageconditions. Accelerated tests are performed primarily to (a) identify or conform marginaldesign or manufacturing areas or (b) estimate product life. Prior to initiating acceleratedtesting, weak links should be investigated and potential failure modes eliminatedReference Qualification Test Plan for the Controller, the specified Durability ThermalCycles for the “Flight Lifetime” are 6242 and Durability Thermal Cycles for the “Maintenance Lifetime” are 6970The most widely used model is the modified Coffin-Manson (Norris-Landzberg)Equation. This can be used to determine a Acceleration Factor for the thermal testcondition and product environment. It uses: (1) an Arrhenius Term; (2) TemperatureCycling Frequency; (3) Maximum Temperature reached in a Cycle; (4) TemperatureRange during a Cycle.The modified Coffin-Manson (Norris-Landzberg) Equation and a worked example usingarbitrarily chosen values is shown in Page 2RecommendationUse appropriate Parameter (f1; f2; ∆T1; ∆T2; m; n; T1; T2; Ea ) Values for the modifiedCoffin-Manson (Norris-Landzberg) Equation to suit the Controller Design and DurabilityTest Requirements. Calculate Acceleration Factors for the Flight Lifetime andMaintenance Life Time and determine the Durability Flight & Maintenance CyclesBenefitDurability Thermal Cycles determined using the modified Coffin-Manson (Norris-Landzberg) Equation will be lower than using Coffin-Manson Equation, hence reductionin Test Time and a Cost SavingHilaire Ananda Perera Term Quality Assurance
  2. 2. Modified Coffin-Manson Equation for Acceleration Factor Calculations For solder joint failure under thermal fatigue (temperature and frequency are key factors), the most widely used model is the modified Coffin-Manson equation and is given in the following forms."1" represents test environment and the "2" represents the actual operating environment. m = 1/3, n = 1.9 ~ 2 Coffin-Manson Exponent (n) n = 1 to 3 for Ductile Metal (e.g. solder) n = 3 to 5 for Hard Metal Alloys / Intermetallics (e.g. Al-Au) n = 6 to 9 for Brittle Fracture (e.g. Si & Dielectrics: SiO 2 , Si 3 N4 ) 1 m n 2.5 f1 10 f2 4 ∆ T1 140 ∆ T2 125 T1 373 T2 344 3 Ea .7 Activation Energy (eV) for the failure mechanism 8.625 . 10 5 k Boltzmanns Constant (eV/deg.K) Ea . 1 1 m n Modified Coffin-Manson (Norris-Landzberg) Equation f2 ∆ T1 k T TAF . .e 2 1 f1 ∆ T2AF = 6.124 < -------- Acceleration Factor with Modified Coffin-Manson When -----> m 0 and Ea 0 Ea . 1 1 m n f2 ∆ T1 k T T AF . .e 2 1 f1 ∆ T2 AF = 1.328 < --------- Acceleration Factor with Coffin-Manson In the above equation; f = Temperature cycling frequency (In Cycles per 24 Hour Day) T = Maximum Temperature in Kelvins reached in a cycle ∆ T = Temperature range (in deg. C) during a cycle AP , 24Mar03 Hilaire Ananda Perera Long Term Quality Assurance