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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.
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M.S.Ramaiah School of Advanced Studies 1
Vinay Divakar CWB0912001, FT2012
M. Sc. (Engg.) in Electronic System Design
Module Leader : Mr. Ugra Mohan Roy
.
Power Point Presentation
NEED FOR FAILURE ANALYSIS
TECHNIQUES
M.S.Ramaiah School of Advanced Studies
Overview
.
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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
Introduction
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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.
M.S.Ramaiah School of Advanced Studies
Importance of Failure Analysis
•Electronic parts, why they fail?
•Preserve failure mechanism, don’t
loose (Carelessness)
•Failure of Critical applications e.g.
Space satellite systems.
•Big loss due to chain reaction
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.
M.S.Ramaiah School of Advanced Studies
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)
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M.S.Ramaiah School of Advanced Studies
Failure Analysis for Electrical Overstress (EoS)
• EOS- Thermal damage due to V or
I beyond limit specification
•Trace VI curve for i/p’s of each
part “ part characterization”
•Causes:
a. Poor grounding
b. EMI
c. Uncontrolled supply
d. latchup
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M.S.Ramaiah School of Advanced Studies
FAILURE RATE CURVE
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M.S.Ramaiah School of Advanced Studies
Estimating Life of a Product
Failure Rate (λ) : 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/ λ 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)
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M.S.Ramaiah School of Advanced Studies
CONTD…
Failure rate in FIT: λ = ∑β
i=1 = [xi/(∑k
j=1TDHj * AFij)]*(M*109/∑βi=1 xi)-------- 2
λ = failure rate in FITs (Number fails in 109 device hours) β = 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,... β 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 Χ = chi square factor for 2r + 2 degrees of freedom r = total number of failures (Σ xi)
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M.S.Ramaiah School of Advanced Studies
CALCULATING THE FAILURE RATE AND PRODUCT LIFE
(MTTF)
Example : Assume that 600 parts where stressed at 150°C 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 20°C 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 55°C.(William J. Vigrass 1997)
Soln : Given Ea = 0.7eV and Eb = 0.3eV Tj = 20°C 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
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M.S.Ramaiah School of Advanced Studies
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:
λ = [(1/1.797*106*148.2) + (1/1.797*106*8.52)]*(6.3*109/2) = 218 FIT’s Estimated life time of the product or system is MTTF = 1/ λ = 1/218 FIT’s = 4.59*106 Hours Note : 1 FIT = 1 failure in 109 device hours
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M.S.Ramaiah School of Advanced Studies
SUMMARY Moore’s 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
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M.S.Ramaiah School of Advanced Studies
REFERENCES 1. 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.
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By- Vinay Divakar
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