Paper presented at 2012 RAMS about considerations and decisions related to the design of an ongoing reliability test

1. Establishing Effective ORT
Requirements
Fred Schenkelberg, Consultant
Monday, January 23rd, 2012
RAMS 2012 Jan 23 to 26
Session 1D

2. The best post production testing
is the testing that
does not have to occur.

3. Material & process changes,
and transit damage occurs
along the entire supply chain

4. Variation
Happens
Find it before
the customer does

5. Cost Effective
Timely
Detect Failures
Accurate
Sensitive

6. Current practice
3 samples
Light stress
Limited duration

7. Failures are bad
Lack of detection
Inaccurate
Insensitive
ineffective

8. Consider each day’s production goes somewhere.

9. Cost of Failures vs. Time to Detect by Failure Rate Percent
4000000
3500000
Production 18k per day @ $25/unit
Distribution Center 250k units @ $30/unit
3000000
Retailers 500k units @$50/unit
Customers 1m units @ $100/unit
2500000
Cost, dollars
1%
2000000 2%
3%
4%
1500000 5%
1000000
500000
0
0 10 20 30 40 50 60 70
Time, days

10. An Example
Suppose
Coating to avoid rust
-new process
-small window
-THB for 12 days
= 1 year use

11. Success Run Sample Size
10000
1000
Number of Samples
100
Confidence
10
60%
80%
90%
1
0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1
Reliability

12. 50 Sample
Capacity
Detects:
4.5% in 12 days
Or
1.2% in 24 days

14. Wrap up
Do the math
Fit within constraints
Meet budget
Provide protection
Questions?