Cause Analysis and Improvement of Solder Wetting on LTCC Substrates During Reflow Soldering

Low temperature co-fired ceramic (LTCC) technology plays a significant role in the field of electronic packaging due to its high-frequency properties, high integration capabilities, and fine wiring capacity. The quality of surface component assembly on LTCC has always been a focus of the industry, with particular attention to the solder wetting issue in gold layers of non-soldering areas. Solder wetting phenomenon in gold layers of non-soldering areas is primarily caused by solder splashing during the reflow process, with specific causes including solder moisture absorption, an unreasonable reflow profile, and poor solder sphere performance. Therefore, the mechanism of solder wetting after LTCC reflow soldering and its impact on assembly quality are deeply investigated through theoretical analysis and experimental verification, and corresponding improvement measures are proposed in this paper. Experimental results indicate that the longer the solder is exposed to air, the higher the risk of moisture absorption, leading to an increase in solder splashing and solder wetting ratios. By strictly controlling workshop temperature and humidity, optimizing the production mode to single-piece flow, and controlling the cycle time within 127 seconds, the solder wicking ratio in gold layers of non-soldering areas is successfully reduced from the original 2.00‰ to 1.19‰～1.36‰ in this paper, achieving a significant improvement.