Root Causes and Prevention Measures of Excessive Solder on PCB Solder Joints

Causes of Excessive Solder:

Low soldering temperature leading to increased viscosity of the molten solder.
Low preheating of the PCB, causing heat absorption by components and the PCB, resulting in a decrease in actual soldering temperature.
Poor activity or insufficient proportion of flux, causing solder to concentrate in one area without spreading.
Poor solderability of pads, plated through-holes, or pins, preventing sufficient wetting and trapping air bubbles in the solder joint.
Reduction in the proportion of tin or increase in copper content in the solder alloy, leading to increased viscosity and decreased fluidity of the solder.
Excessive solder dross leading to solder alloy encapsulating dross residue, which accumulates at the solder joint, causing it to enlarge.

Improvement Measures for Excessive Solder:

Adjusting and selecting appropriate peak soldering temperature and soldering time.
Setting preheating temperature based on PCB size, number of layers, quantity of components, presence of surface-mounted components, etc.
Changing flux or adjusting its proportion appropriately.
Improving the processing quality of PCBs, implementing a first-in-first-out component handling policy, and avoiding storage in humid environments.
Adjusting the alloy composition of solder.
Cleaning solder dross at the end of each shift.