MIL-STD-1250 Corrosion Prevention And Deterioration Control In Electronic Components And Assemblies S/S By Mil-Hdbk-1250This standard establishes minimum requirements for procedures, materials and systems for protecting electronic components in DoD systems and assemblies from adverse environments. Protective measures shall be sufficient to maintain performance characteristics within specified limits both during and after exposure to moisture, high and low temperatures, corrosive gases, chemicals and microbial fungal attack.

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MIL-STD-1250A

4.    GENERAL REQUIREMENTS

4.1  Unacceptable designs.  Equipment design shall be considered unacceptable from a corrosion/deterioration prevention standpoint if any of the following conditions are included:

a.         Traps or crevices susceptible to moisture collection

b.        Unsealed permanent fasteners (install with wet primer of polysulfide sealant)

c.        Ineffective gasket and lid design and insufficient fasteners in moisture- tight housing design

d.        Untested adhesively bonded designs (qualify with stress and humidity testing)

e.         Metallic construction if nonmetallic is acceptable

f.          Printed circuit boards (PCBs) without conformal coating (use MIL-I-

46058)

g.         Unprotected galvanic couples as defined in table III

h.         Equipment requiring preventive maintenance for corrosion control i.          Non-hermetic design for sealing integrated circuits

J.          Graphite composite construction not insulated from structural metals k.         Conductive material or EMI gaskets without an environmental seal on

both sides of the contact area.

l.          Improper drain holes (size and location)

m.        Unsealed heat-shrinkable electrical connector boots n.         Surface metal coating susceptible to whisker growth

o.        Wooden containers or components housed in corrosive woods such as oak, chestnut, beech, douglas fir, cedar, birch or teak

p.         Desiccant design without visual indicators for periodic inspection

q.        Design that allows static potential build-up which could result in spark discharge

r.        Design that emits electromagnetic energy which could affect the operation of other equipment

s.         Copper alloys coupled to aluminum

t.          High residual stresses in formed metallic parts

u.         Electronic design located near and vented to vehicle exhaust gases

v.        Printed wiring assemblies (PWAs) mounted horizontally (mount PWAs vertically with the card edge connector on the vertical edges, not the bottom edge)

w.        Electrical connectors mounted vertically (mount connectors horizontally with the wires leading up to the connector back shells)

x.        Coaxial connectors with no sealant around the point where cable enters a connector (use a non-acid cure RTV-type sealant)

y.         Corrosion susceptible hinge mechanisms

z.        Wire rope and chain-type lanyard assemblies that are not corrosion resistant

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