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MIL-STD-690-SUP Failure Rate Sampling Plans and ProceduresThis standard provides procedures for failure rate FR qualification, sampling plans for establishing and maintaining FR levels at selected confidence levels, and lot conformance inspection procedures associated with FR testing for the purpose of direct reference in appropriate military electronic parts established reliability ER specifications. Figures and tables throughout this standard are based on exponential distribution. Weibull distribution will be acceptable in certain components such as capacitors. Use of Weibull distribution for any component must be approved by the qualifying activity. This standard also provides guidance to specification writers in the use of this standard see appendix A and references material for users of ER parts.

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MIL-STD-690D

TABLE IV. FRSP-10.

FR level

symbol

Quali-

fied FR

level 1/

Qualification

maintenance period

(in months)

Cumulative unit hours in millions

(c = number of failures permitted)

c=0

c=1

c=2

c=3

c=4

c=5

c=6

c=7

c=8

c=9

c=10

L M P R S

1.0

0.1

0.01

0.001

10.5 4/

.0532

.532

5.32

53.2

("M"

.110

1.10

11.0

110

row

.175

1.75

17.5

175

divided

.243

2.43

24.3

243

.315

3.15

31.5

315

"L")

.389

3.89

38.9

389

.467

4.67

46.7

467

.544

5.44

54.4

544

.623

6.23

62.3

623

.701

7.01

70.1

701

1/ Expressed in %/1,000 hours. For FR level expressed in terms other than %/1,000 hour, see 4.1c and 4.1d.

2/ Where a FR level greater than 1.0 percent is required, level "L" shall be specified and the cumulative unit hours computed as shown.

3/ Each lot.

4/ Applicable to FR level "S" only.

TABLE V. True failure rates for FRSP-10 (prepared for 1 percent per 1,000 hours FR level).

Number of failures permitted

True failure rate required to maintain qualification

19 times out of 20

True failure rate which would cause disqualification 9

times out of 10

( c )

(%/1,000 hrs)

0.49

0.67

0.74

0.78

0.81

0.83

0.84

0.85

0.86

0.87

0.88

(%/1,000 hrs)

21.8

7.3

4.8

3.8

3.3

2.9

2.7

2.5

2.4

2.3

2.2

NOTE: For other than M (1 percent) FR level, divide above FR values by

10 for P (0.1 percent) level; by 100 for R (0.01 percent); or by

1,000 for S (0.001 percent) level.