MIL-STD-981C
5.5.10 Soldering. Soldering and preparation of soldering shall conform to NASA-STD-8739.3. Use of any other soldering standard in lieu of or in addition to NASA-STD-8739.3 shall require the approval of the procuring activity. When several solder compositions are combined to complete a solder joint (e.g.the terminal is pre-plated, low temperature solder is used to wick magnet wire insulation, and the joint is made with a third solder) care shall be taken to assure that the combined materials have the desired melting point.
5.5.11 Soldering equipment and tools. Shall conform to NASA-STD-8739.3 . Use of any other soldering standard in lieu of or in addition to NASA-STD-8739.3 shall require the approval of the procuring activity.
5.5.12 Prepot visual inspection.
5.5.12.1 Examination. The device examination shall include, but not be limited to, inspection for conformance to the construction and workmanship criteria specified below.
5.5.12.2 Solder joints. All solder joints shall be well formed and positioned and shall not show any of the following characteristics when inspected under 10X minimum to 30X maximum magnification.
a. Sharp solder joints (tips, peaks).
b. Excessive solder which obscurers the connection configuration, except connections of AWG 38 or smaller magnet wires.
c. Swelling of stranded leads due to excessive wicking.
d. Loose wire (except stress relief wraps), leads and core bands (if applicable). e. Foreign or extraneous material embedded in the solder.
f. Fractures, cracks, or pinholes.
g. Bare conductor or dewetting within the solder joint area.
h. Protrusion of the bare wire end of strand out of solder joint. i. Necking down of the magnet wire at the joint.
j. Pitting or voids in corona free ball connections.
5.5.12.3 Lead wires. Lead wires shall have stress relief of at least three times the insulated wire diameter whenever practical. Stress relief loops shall not interfere with other conductive paths. For any bend, the radius of the bend shall not be less than three times the insulated wire diameter. In addition, the magnet wire shall also have adequate stress relief at the solder joint, and shall be anchored to the coil. A device that displays a sharp bend of any lead wire (solid or stranded) at the solder joint, or peeling out
from the solder fillet, shall be rejected, even if the solder joint otherwise appears to be well formed.
NOTE: Due to space limitations, stress relief of magnet wire for cylindrical parts is not practical, in the absence of space limitations, for Families 04, 13, 14, 50, 51 and 52.
5.5.12.4 Coils. Coils of "C" cores and laminations shall be wound either on bobbins or core tubes of appropriate material size.
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