What does not constitute an acceptable solder connection?

An acceptable solder connection is critical for ensuring the reliability and functionality of electronic assemblies. An acceptable connection is typically characterized by good wetting, appropriate flow of solder around the joint, and minimal defects. Let's delve into why the presence of solder flux residue, voids in the solder joint, and poor wetting to tinned surfaces are all factors that would render a solder connection unacceptable.

The presence of solder flux residue can be problematic because it may lead to corrosion over time or potential electrical interference if not properly cleaned. While some flux residues can be benign, excessive or inappropriate residues can compromise the long-term reliability of the connection.

Voids in a solder joint are also concerning. These voids can create weak points in the joint that may lead to mechanical failure. They can trap air, moisture, or other contaminants that can degrade the performance of the solder connection. Voids also may reduce the effective cross-sectional area of the joint, affecting its electrical conductivity.

Poor wetting to tinned surfaces indicates that the solder is not properly adhering to the surfaces it is meant to bond with. This can result in poor electrical conductivity and mechanical dysfunction. If the solder does not flow adequately over the surfaces, it can create interfaces that are weak and thus prone to failure.