A key precondition to a good solder joint is pre-tinning of all leads/pins
prior to assembly. For maximum reliability and consistency, the solder joints
should be made via automated processes:
(1) Wave solder for pin-in-hole connections
(2) Semi-automatic for surface mounting (e.g., flatpacks).
All solder joints should be inspectable; this requires that blind-hole
solder joints be restricted in the design.
For pin-in-hole solder joints, the solder should penetrate through the
barrel of a PTH. This applies also to wires, transformers, connectors, etc.,
and requires that the solder joint be made from the side of the PWB/MIB
opposite that on which the component is located.
Make all wire connections to a PWB/MIB only on the component side of the
PWB/MIB to simplify assembly, rework and repair, and to minimize handling
Flux must not become entrapped due to a blockage at one end of the PTH;
this has a high potential for causing a poor solder joint which will fail at a
Cavities are a natural place for moisture, foreign material, or solder to
get trapped and/or wedged, resulting in an electrical short to the frame. This
can be prevented by either:
(1) Designing the cavity out,
(2) Making the cavity sufficiently large so as to reduce the risk of
(3) Coating the area to prevent the short from occurring, or
(4) A combination of the latter two