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MIL-STD-690 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

w/ CHANGE 1

5.1.2.1 True failure rates for FRSP-60 and FRSP-90. Table III gives two points on each of the operating characteristic curves for FRSP-60 and FRSP-90, as follows:

a. The true failures rates required of the product so that process will qualify 19 times out of 20; and b. The true failure rates of a product whose process will fail to qualify 9 times out of 10.

TABLE III. True failure rates for FRSP-60 and FRSP-90 (prepared for 1%/1,000 hr FR level).

Number of

failures permitted

True product failure rate required to

qualify a process 19 times out of 20 (%/1,000 hour)

True product failure rate which would fail

to qualify a process 9 times out of 10 (%/1,000 hours)

( c )

FRSP-60

0.06

0.18

0.26

0.33

0.38

0.42

0.45

0.47

0.50

0.52

0.54

FRSP-90

0.02

0.09

0.15

0.20

0.25

0.28

0.31

0.34

0.36

0.38

0.40

FRSP-60

2.51

1.92

1.71

1.60

1.53

1.47

1.43

1.41

1.38

1.36

1.34

FRSP-90

1.0

* NOTE: For other than "M" (1%) FR level; divide above FR values by 10 for "P" (0.1%)

level; by 100 for "R" or "U" (0.01%) level; by 1,000 for "S" or "V" (0.001%)

level (see 4.1a).

5.1.3 Failure FR test. All sample units subjected to the specified qualification test shall be maintained on test for the total time specified for the extended FR test.

5.1.4 Failure to qualify. When the number of failures permitted is exceeded; the manufacturer shall discontinue the FR test and shall notify the qualifying activity. The manufacturer may request approval to reinstitute qualification testing on a new set of sample units provided the failures have been analyzed and the cause of failure has been corrected as specified in MIL-STD-790 .

5.1.5 Details to be specified. The following details are to be specified in the ER specification:

a. Initial FR level symbol and FRSP-60 or FRSP-90, as applicable (see 5.1.2).

b. Duration of ER test (specify rated, and where applicable, accelerated conditions) (see 5.1).

c. Number of sample units to be inspected and number of failures permitted for FR test (see 5.1).

d. Duration of extended ER test (specify rated and, where applicable, accelerated conditions) (see 5.1.3).

e. Number of samples to be continued on FR test (specify rated and, where applicable, accelerated conditions

(see 5.1.3).

f. Failure criteria (see 4.2).