MLCC Solder Joint Property with Vacuum and Hot Air Reflow Soldering Processes

Abstract

After the joining of small 1005 and 0603 multilayer ceramic capacitor (MLCC) components for a semiconductor package using Type 4 (T4) and Type 7 (T7) Sn-3.0Ag-0.5Cu (SAC305), T4 Sn-1.0Ag-0.5Cu (SAC105), and T4 Sn-0.3Ag-0.7Cu (SAC0307) solder pastes, the differences between hot air reflow and vacuum soldering processes were compared in terms of void content, shear strength, and microstructure. Results showed that the hot air reflow soldering process exhibited a stable joint with a void content of 5% or less, and the vacuum soldering condition significantly reduced the void content of the solder joint as the soldering proceeded in a vacuum state. The shear strength of the SAC305 solder joint with the same powder particle size was measured to be greater for the shear strength of the vacuum soldered joint as compared to the reflow process. The vacuum soldering process was effective in removing voids during the void joining process and contributed to an improved joint strength of the solder joint by reducing the void content. When the same soldering process was applied using the 1005 MLCC chip component, the bonding strength of the T4 SAC305 solder was slightly higher than those of the SAC105 and SAC0307 solders. However, the overall initial bonding strengths were similar. The e ffects of Ag content within 0.3-3.0 wt% on the initial bonding strengths of the solders were judged to be the same. Diverse Cu6Sn5, Ag3Sn, (Ni,Cu,Pd)3Sn4, (Cu,Ni)6Sn5, NiP, and Ni3P intermetalli ccompounds (IMCs) were formed at the interfaces between the electroless nickel/electroless palladium/immersion gold finish substrate and SAC solder joint. The IMC types were constant regardless of Ag content and solder type, and the IMCs contributed to the initial solder joint strength.