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Electronic PCB Thermal Breakdown - Case Study

Decades of electronic printed circuit board (PCB) repair have uncovered some common but elusive conditions.

Electronic Components soldered onto PCBs develop thermally induced intermittent operation.

This occurs as these components age and are subjected to constant thermal stresses (expansion and contraction) applied
during normal operation. Over time, thermal interactions by dissimilar metal compositions have the tendency of either fusing
together with the other metals or repelling dissimilar metals creating a "barrier" (air gaps, fissures, films, membranes,
residues and the like) between these components (read Notes).

Obviously then, this creates intermittent operation. Some examples are:

Flat screen monitors that slightly fade in and out during normal operation.
Power supplies that become erratic.
Hard Drives that skip Read/Write cycles.
Video Card that become unstable.
Peripheral input devices that become erratic.
Backplanes that disrupt the flow of input/output data.
Ribbon Cables that become intermittent at the board connection level.
Mechanical or Electronic Relays that cease to toggle ON/OFF.
NOTES:

Some metallic chemical properties are altered as well due to thermal decomposition.
Poor assembly workmanship is exacerbated as thermal breakdown progresses.
Mechanical components also undergo chemical alterations due to thermal decomposition.
Cold Solder Joints
Between 40 to 60 % of these issues can be resolved by reworking the electronics.

By "reworking", I am referring to:

Submersion into a solvent based ultra-sonic cleaner to dislodge debris, dissolve barriers and remove residues.
Apply fresh premium grade electronic solder flowed with premium grade Rosin Flux.
Examine and Inspect the workmanship per industry or military standards of practice.
Stereo Microscope Examination and Quality Inspection