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

Resistance ratio accuracy (applicable to characteristics C, R, and V): Ratio accuracy is defined as the

percent difference between the nominal resistance ratio and the ratio determined from the actual resistance

measurement using the specified reference resistor from the applicable schematic (see 3.1). The ratio

accuracy required shall be as specified. The change in ratio for any test is defined as the percent change in

the actual ratio determined from resistance measurements before and after the test referred to the actual

ratio before the test. The resistance ratio is defined as follows:

RREF

Where:

Rr - Resistance of the element being measured

RREF - Resistance of the reference element.

4.8.6 Solderability (see 3.11). Networks shall be tested in accordance with method 208 of MIL-STD-202. The

following details and exceptions shall apply:

Application of flux. Flux, type A in accordance with J-STD-004 shall be used. Terminations shall be

immersed in the flux, which is at room temperature, to the minimum depth necessary to cover the surface to

be tested. The parts shall be attach to a dipping device and the flux terminations shall be immersed one

side at a time (gullwing devices) or the entire body of the part (LCC packages). The terminations to be

tested shall be immersed in flux for a period of 5 seconds to 10 seconds.

Solder dip. Molten solder shall be maintained at a uniform temperature of 245OC �5OC. The surface of the

molten solder shall be skimmed of dross and burned flux prior to immersing the terminations in the solder.

The part shall be attached to a dipping device and the flux terminations shall be immersed one side at a time

(for gullwing devices) or the entire body of the part may be immersed (LCC packages), in molten solder to

the depth and the terminations on the LCC shall be dipped at 30O to 45O from vertical. The immersion and

emersion rates shall be 1.000 inch �.250 inch (25.4 mm �6.35 mm) per second and the dwell time in the

solder bath shall be 5.0 seconds �0.5 second. During the solder dip time the part may be moved

horizontally in molten solder so that the withdrawal from the solder can be at a different location from the

immersion to avoid contamination of the fresh solder coating by the residual flux from the leads. After the

dipping process, the part shall be allowed to cool in air. Flux residue shall be removed from the terminations

by rinsing in a suitable solvent. If necessary, a soft cloth or cotton swab moistened with clean 91 percent

isopropyl alcohol or a suitable solvent shall be used to remove all remaining flux.

Examination of terminations. After each dip-coated termination has been thoroughly cleaned of flux, the

termination shall be examined using a magnification of 10X.

4.8.7 Resistance to solvents (see 3.12). Networks shall be tested in accordance with method 215 of

MIL-STD-202. The following details shall apply:

Mounting: Unmounted.

The marked portion of the network body shall be brushed.

The number of sample units shall be as specified in table XII or table XVI, as applicable.

Networks shall be inspected for mechanical damage and legibility of markings.