MIL-PRF-914 Resistor Networks, Fixed, Film, Surface Mount, Nonestablished Reliability, And Established Reliability, General Specification ForThis specification covers the general requirements for nonestablished reliability \(non-ER\) and established reliability \(ER\), hermetically sealed \(see 3.27\) and nonhermetically sealed networks \(see 3.27.1\). These networks consist entirely of fixed, film resistors. They are primarily intended for use in surface mount applications where space is a major concern. ER resistors covered by this specification will have life failure rates \(FR\) ranging from 1 percent to 0.001 percent per 1,000 hours \(see 1.2.1.7\). The ER FR are established at a minimum 60-percent confidence level on the basis of life tests. Designers are CAUTIONED on using these resistors in pulse applications \(see 6.4.4\).

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MIL-PRF-914C

4.7.1 Sampling plan. If more than 1,000 resistor networks of any style or style grouping are produced over the

maintenance period, the group C tests shall be performed as specified. If the production rate is less than 1,000

resistor networks for any style or style grouping over the maintenance period, then the monthly, quarterly, or

semi-annual group C inspection may be postponed until at least 1,000 resistor networks of that style or style grouping

are produced (except for the monthly life test). In any case, the monthly tests shall be performed at least once every

3 months. The quarterly tests shall be performed at least every 6 months and the semi-annual tests shall be

performed at least once every year. This requirement is waived if the manufacturer has obtained a reduced

inspection status through the qualifying activity.

All qualified styles may be grouped together in a sample. This can be accomplished by proportion based on

manufacturing percentages by styles, equally divided by style, or by establishing an alternating style sequence. In

order to incorporate a style sampling grouping, a written description must be presented and approved by the

qualifying activity. This plan must assure that the grouping only combines styles of the same basic design,

encapsulation material, and the same element type.

4.7.2 Monthly.

4.7.2.1 Subgroup 1. Ten sample units of any resistance value between the critical values and low values shall be

inspected every month. If none of these values are produced during the month, networks of the lowest resistance

value produced shall be inspected, with one defective unit allowed.

4.7.2.2 Subgroup 2 (not applicable to gullwing packages). Eight sample units of any value shall be inspected

every month, with one defective unit allowed.

4.7.3 Quarterly.

4.7.3.1 Subgroup 1, subgroup 3 and subgroup 4. Ten sample units from the highest resistance decade produced

shall be subjected to the tests of subgroup 1 (one defective unit shall be allowed), 10 sample units of the value

produced closest to the critical value shall be subjected to the test of subgroup 3 (one defective unit allowed), 10

sample units from the highest resistance decade shall be subjected to the test of subgroup 4 (one defective unit

allowed).

4.7.3.2 Subgroup 2. Test samples shall be selected from each inspection lot produced during a 1-month period.

These samples shall be accumulated and placed on the life test as specified in 4.8.19, once a month, for the full

10,000-hour life test period. The test sample size shall be determined by the manufacturer so that the unit hours

generated meet the requirements specified for the qualified FRL (see 4.4.4). In any event, a minimum of five

samples shall be selected from each lot. As far as practical, the resistance values tested during a maintenance

period shall be representative of all resistance decades produced during this period. The accumulated data shall be

used for maintenance and extension of FR qualification.

4.7.4 Semiannually. Ten sample units of any resistance value shall be inspected semiannually. One defective

unit shall be allowed.

4.7.5 Disposition of samples. Sample units that have been subjected to group C inspection shall not be delivered

on the contract.