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

5.20 Conformal coatings. Unless otherwise specified, conformal coatings for

moisture resistance, debris isolation and protection, and insulation shall be in accordance with MIL-I-46058, or as approved by the procuring activity. Coatings shall be selected for insulating and protective qualities. They shall not affect electrical properties nor physically damage fragile components being coated. Where practical, the desired total coating thickness shall be obtained by applying several thinner coats. Coatings shall be fully cured before next assembly in accordance with the applicable application instructions.

5.21 Insulators, insulating and dielectric materials. Insulators, insulating and dielectric materials shall be in accordance with MIL-STD-454.

5.21.1 Ceramic and glass materials. Unless otherwise specified, ceramic materials shall be glazed. Surfaces shall be smooth, uniform and free from porosity. Glass bonded mica shall not be used except with prior approval of the procuring activity.

5.22 Packaging and preservation. Packaging and preservation of electronic components and assemblies shall be in accordance with MIL-P-116 or as directed by the procuring activity. Desiccants, when used, shall be in accordance with paragraph 5.2(c).

5.22.1 Incompatible packaging materials. In addition to avoiding the incompatible materials listed in table IX, special care shall be taken to avoid enclosing incompatible materials within a package or compartment. Attention is called to the following:

a. Wood (sometimes used for shelves and boxes) emits harmful gases. Oak, cedar, chestnut, and some plywoods are especially bad.

b. Cushioning materials often give off sulfurous or acidic vapors, attacking silver, cadmium and other metals.

c. Acidic and ammonia vapors attack cadmium.

d. Vapors from paper and cardboard not specifically designed for packaging electronic hardware may tarnish silver and copper.

e. Copper, iron and manganese promote cracking of rubber.

f. Uncured or partially cured organic materials outgas, corroding nearby surfaces.

5.22.2 Volatile corrosion inhibitors. Volatile corrosion inhibitors shall be used to protect metals against corrosion in accordance with MIL-I-8574. Volatile corrosion inhibitors may be used as crystals, in oil or grease, or impregnated in paper or other materials.