# Need For Failure Analysis Techniques

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21-Dec-2014Category

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Failure Analysis (FA) is a process of collecting and analyzing data to determine the cause of failure. E.g. Failed components are taken for analysis and determine cause of the failure using a wide array of methods and techniques. Failure analysis engineers often play the lead role in this department Types of failures can be due to component, manufacturing or during production processing Failure analysis (FA) capability supports the development of semiconductor technology and packaging. Failure analysts need new techniques and advanced equipment to match the rate of Moore's Law so that problem solving can remain efficient and accurate. Moore's Law is the observation made in 1965 by Gordon Moore, co-founder of Intel, that the number of transistors per square inch on integrated circuits has doubled every year since the integrated circuit was invented.

### Transcript of Need For Failure Analysis Techniques

- 1. Power Point Presentation . NEED FOR FAILURE ANALYSIS TECHNIQUES Vinay Divakar CWB0912001, FT2012 M. Sc. (Engg.) in Electronic System Design Module Leader : Mr. Ugra Mohan Roy M.S.Ramaiah School of Advanced Studies 1
- 2. Overview Below are the topics to be discussed, they are as follows: . Introduction Importance of Failure Analysis Classification of Tests to Capture Failures Failure Rate (Bath Tub) Curve Estimating life of a system or Product Calculating the Failure Rate and Product Life (MTTF) Summary References M.S.Ramaiah School of Advanced Studies 2
- 3. Introduction Failure Analysis (FA) is a process of collecting and analyzing data to determine the cause of failure. E.g. Failed components are taken for analysis and determine cause of the failure using a wide array of methods and techniques. Failure analysis engineers often play the lead role in this department Types of failures can be due to component, manufacturing or during production processing Failure analysis (FA) capability supports the development of semiconductor technology and packaging. Failure analysts need new techniques and advanced equipment to match the rate of Moore's Law so that problem solving can remain efficient and accurate. Moore's Law is the observation made in 1965 by Gordon Moore, co-founder of Intel, that the number of transistors per square inch on integrated circuits has doubled every year since the integrated circuit was invented. M.S.Ramaiah School of Advanced Studies 3
- 4. Importance of Failure Analysis Electronic parts, why they fail? Preserve failure mechanism, dont loose (Carelessness) Failure of Critical applications e.g. Space satellite systems. Big loss due to chain reaction . M.S.Ramaiah School of Advanced Studies 4
- 5. Classification of Tests to capture failures Environmental Tests Temperature operating conditions, corrosion etc Mechanical Tests Packaging, Materials, insulation resistance etc Electrical Tests Electrical overstress, ground bounce etc Test Procedure, analysis and results Documentation of the overall results, analysis and the desired modifications (MIL-STD-883F 1996) M.S.Ramaiah School of Advanced Studies 5
- 6. Failure Analysis for Electrical Overstress (EoS) EOS- Thermal damage due to V or I beyond limit specification Trace VI curve for i/ps of each part part characterization Causes: a. b. c. d. Poor grounding EMI Uncontrolled supply latchup M.S.Ramaiah School of Advanced Studies 6
- 7. FAILURE RATE CURVE . M.S.Ramaiah School of Advanced Studies 7
- 8. Estimating Life of a Product Failure Rate () : Expressed in units of FIT Failure In Time (FIT): No of failures expected in 1 billion (109) device hours of operation Mean Time To Failure (MTTF): defines warranty period (Product life) and Reliability i.e. MTTF=1/ Acceleration factor (AF): Testing at two different temperature stresses. AF = exp [Ea/K (1/Tuse 1/Tstress)]--------1 Ea = Thermal Activation energy K = Boltsman Constant (1.380x10-23 J/K ) or (8.63x10-5 eV/K) Tuse = Use Temperature (oC + 273) Tstress = Life test stress temperature (oC + 273) M.S.Ramaiah School of Advanced Studies 8
- 9. CONTD Failure rate in FIT: = i=1 = [xi/(kj=1TDHj * AFij)]*(M*109/i=1 xi)-------- 2 = failure rate in FITs (Number fails in 109 device hours) = Number of distinct possible failure mechanisms k = Number of life tests being combined xi = Number of failures for a given failure mechanism i = 1, 2,... TDHj = Total device hours of test time for life test j, j = 1, 2,... k AFij = Acceleration factor for appropriate failure mechanism, i = 1, 2,... k M = Const associated with chi sq factor = chi square factor for 2r + 2 degrees of freedom r = total number of failures ( xi) M.S.Ramaiah School of Advanced Studies 9
- 10. CALCULATING THE FAILURE RATE AND PRODUCT LIFE (MTTF) Example : Assume that 600 parts where stressed at 150C ambient for 3000 hours with one failure at 2000 hours for a photoresist flaw (0.7eV) and one failure at 3000 hours for an oxide defect (0.3eV); the internal temperature rise (Tj) of the part is 20C and the product was tested at 1000, 2000 and 3000 hours. We want to find the FIT rate for the process at with M=6.3 (chi factor distribution for DOF = 2r+2 for r=2) at 55C.(William J. Vigrass 1997) Soln : Given Ea = 0.7eV and Eb = 0.3eV Tj = 20C Tuse = 55 + 20 + 273 = 348K Tstreee= 150 + 20 +273 = 443K r = 2 (total no of failures) M = 6.3 AF1 = exp[0.7/8.63*10-5(1/348 1/443)] = 148.2----3 (from eqn 1) AF2 = exp[0.3/8.63*10-5(1/348 1/443)] = 8.52---4 TDH = No of units * Hours under stress M.S.Ramaiah School of Advanced Studies 10
- 11. CONTD. TDH = 600 1000 + 599 1000 + 598 1000 = 1.797 10-6 hours Using equation 2, the failure rate (FIT) for the system tested for 3000 hours with a no of failures r = 2 and subjected to two different temperature stresses is calculated as follows: = [(1/1.797*106*148.2) + (1/1.797*106*8.52)]*(6.3*109/2) = 218 FITs Estimated life time of the product or system is MTTF = 1/ = 1/218 FITs = 4.59*106 Hours Note : 1 FIT = 1 failure in 109 device hours M.S.Ramaiah School of Advanced Studies 11
- 12. SUMMARY Moores problem FRACAS Classes of Testing for failure analysis EOS and its analysis Product Failure rate curve Equations for estimating the FIT and MTTF of a system or product based on some known data Example for finding failure rate and product life M.S.Ramaiah School of Advanced Studies 12
- 13. REFERENCES Walter Willing, Jonathan Fleisher & Michael Cascio (2012) ,Electronic Part Failure Analysis Tools and Techniques Northrop Grumman Corporation, USA. 2. ITEM Software, Inc (2007) ,Reliability Prediction Basics USA. 3. William J. Vigrass (1997), Calculation of Semiconductor Failure Rates Indianapolis,19-22 October. 4. DEPARTMENT OF DEFENSE TEST METHOD STANDARD MICROCIRCUITS (2004) ,MIL-STD-883F 31 December, USA. Rajeev Solomon, Peter Sandborn, and Michael Pecht (2000), Electronic Part Life Cycle Concepts and Obsolescence Forecasting University of Maryland, College Park, December, USA. Jim Glancey (2006), Failure Analysis Methods What, Why and How USA. 1. M.S.Ramaiah School of Advanced Studies 13
- 14. By- Vinay Divakar 14