Which of the following is an acceptable solder joint configuration for through-hole components?

An acceptable solder joint configuration for through-hole components is characterized by a concave fillet with sufficient wetting. This configuration indicates that the solder has effectively flowed and adhered to both the component lead and the pad on the circuit board. The concave shape of the solder joint is the result of the proper amount of heated solder that has been applied, ensuring full coverage and a sound mechanical and electrical connection.

Sufficient wetting is crucial because it enhances the reliability of the solder joint, ensuring that it can withstand thermal and mechanical stresses. This wetting also facilitates the electrical conductivity required for the joint's functional performance.

In contrast, a gap between the solder and the component lead would lead to a weak joint, as it signifies poor adhesion or a lack of solder fill. A flat solder surface alone does not guarantee a reliable joint; it may indicate insufficient solder or poor wetting, which can compromise the joint's integrity. Excess solder not adhering suggests that the solder has not formed a proper connection with the lead or pad, jeopardizing the mechanical strength and electrical conductivity of the joint. Therefore, the configuration that describes a concave fillet with sufficient wetting is essential for meeting quality standards in soldering for electronic assemblies.