What could cause a tendon area in the solder joint?

A tendon area in a solder joint typically refers to a weak or undesirable area that can occur when the fit between two components is not ideal, either due to a loose fitting or insufficient solder application. When there is a gap between the components, it can lead to inadequate filling of the joint, resulting in a weaker connection. If the fitting is too loose or if there isn’t enough solder used to effectively fill the joint, the solder cannot properly bond with both metals. This lack of proper contact and sufficient solder can create a tendon area, compromising the mechanical strength of the joint and potentially leading to failure under stress.

Using the correct amount of solder and ensuring a tight fit between the components play critical roles in achieving a strong solder joint. The effectiveness of the solder joint is dependent on complete coverage and proper bonding, which is why addressing the fit and the quantity of solder is so crucial in soldering practices.