Accelerated Testing

4
Breakdown Times in Minutes of a Mylar-Polyurethane Insulating Structure (from Kalkanis and Rosso 1989)
Minutes
104 •••• 103 ••
• ••• •••
102
• ••• ••
• ••
•
Accelerated Testing Obtaining Reliability Information Quickly
William Q. Meeker Department of Statistics and Center for Nondestructive Evaluation
Iowa State University Ames, IA 50011
• Thus the 200◦C test was started later than the others.
11
New-Technology Integrated Circuit Device ALT Data
Hours
107 106 105 104 103 102
100
x
x
x
x
x
x
150
200
10
Interval ALT Data for a New-Technology IC Device
• Tests run at 150, 175, 200, 250, and 300◦C.
• Developers interested in estimating activation energy of the suspected failure mode and the long-life reliability.
• Use elevated temperature or humidity to increase rate of failure-causing chemical/physical process.
• Increase stress (e.g., voltage or pressure) to make degrading units fail more quickly. Use a physical/chemical (preferable) or empirical model relating degradation or lifetime at use conditions.
Proportion Failing
.99 .98
.95 .9
.8 .7 .6 .5 .4 .3 .2
.1 .05
.02 .01
0 10
219.0 157.1 122.4 100.3
1
2
3
10
10
10
Minutes
50 kV/mm
4
5
10
10
9
Plot of Inverse Power Relationship-Lognormal Model Fitted to the Mylar-Polyurethane Data (also Showing
the New-Technology IC Device.
Hours
107 106 105 104 103 102
100
x x x
150
200
250
Degrees C on Arrhenius scale
x x x 50%
10% 1%
300 350
15
Lognormal Probability Plot Showing the Arrhenius-Lognormal Model ML Estimation Results for
− tempU K temp K
• When temp > tempU , AF (temp, tempU , Ea) > 1.
13
Arrhenius Plot Showing ALT Data and the Arrhenius-Lognormal Model ML Estimation Results for
characteristics of the product or material being tested.
• The reaction rate Acceleration Factor is
AF (temp, tempU , Ea)
=
R(temp) R(tempU )
11605 11605
=
exp Ea
250 300 350
Degrees C
12
Elevated Temperature Acceleration of Chemical Reaction Rates
• The Arrhenius model Reaction Rate, R(temp), is
R(temp) = γ0 exp
−Ea kB(temp ◦C + 273.15)
the New-Technology IC Device with Given Ea = .8
Proportion Failing
.95 .9
.8 .7 .6 .5 .4 .3 .2
.1 .05
.02 .01 .005 .002
.0005
.0001
300 Deg C 250
2
3
10
10
200
175
150
361.4kV Data Omitted from the ML Estimation)
Minutes
105 104 103 102 101 100 10-1
50
•••• ••
•••••••
• •••••
•
• ••••
•
100
200
kV/mm
90%
•
•••••
50% 10%
•
500
8
Methods of Acceleration
• Failures had been found only at the two higher temperatures.
• After early failures at 250 and 300◦C, there was some concern that no failures would be observed at 175◦C before decision time.
1
What is Reliability?
• R(t) = 1 − F (t) • The probability that a system, vehicle, machine, device, and
so on, will perform its intended function under encountered operating conditions, for a specified period of time. • Quality over time • A powerful marketing tool • An engineering discipline requiring support from
• Implies increased need for up-front testing of materials, components and systems.
• Accelerated tests provide timely information for product design and development.
••
101
•
•
100Βιβλιοθήκη •• •••10-1
•
100
150
200
250 300 350 400
kV/mm
6
Inverse Power Relationship-Lognormal Model
The inverse power relationship-lognormal model is
where
Pr[T ≤ t; volt] = Φnor log(t) − µ σ
• µ = β0 + β1x, and • x = log(Voltage Stress).
• σ assumed to be constant.
7
Lognormal Probability Plot of the Inverse Power Relationship-Lognormal Model Fitted to the Mylar-Polyurethane Data
• Users must be aware of potential pitfalls
2
Overview
• Different kinds of accelerated tests • Example 1—Evaluation of an insulating structure • Example 2—New-technology microelectronic logic device • Accelerated Degradation Tests • Importance of physics of failure and physical/chemical mod-
level (HALT and STRIFE tests). • Screening (100% or audit) testing of manufactured product
(e.g. ESS and burn-in).
5
Accelerated Testing Background
• Today’s manufacturers face strong pressure to: Improve productivity, product field reliability, and overall quality using new technology. Develop newer, higher technology products in record time.