Effect of Cu concentration on morphology of Sn-Ag-Cu solders by mechanical alloying

Abstract

The mechanical alloying (MA) process is considered an alternative approach to produce solder materials. In this study, the effect of Cu concentration in the ternary Sn-3.5Ag-xCu (x ϭ 0.2, 0.7, and 1) solder by MA was investigated. The (Cu,Sn) solid solution was precipitated as the Cu 6 Sn 5 intermetallic compound (IMC), which was distributed nonuniformly through the microstructure. The Cu 6 Sn 5 IMC, which was present in the SnAgCu solder with high Cu composition, causes the as-milled MA particle to fracture to a smaller size. Appreciable distinction on morphology of as-milled MA powders with different Cu content was revealed. When the Cu concentration was low (x ϭ 0.2), MA particle aggregated to a spherical ingot with large particle size. For higher Cu concentration (x ϭ 0.7 and x ϭ 1), the MA particle turned to flakes with smaller particle size. The distinction of the milling mechanism of Sn-3.5Ag-xCu (x ϭ 0.2, 0.7, and 1) solder by the MA process was discussed. An effective approach was developed to reduce the particle size of the SnAgCu solder from 1 mm down to 10-100 µm by doping the Cu 6 Sn 5 nanoparticle during the MA process. In addition, the differential scanning calorimetry (DSC) results also ensure the compatibility to apply the solder material for the reflow process.

Characterizing metallurgical reaction of Sn3.0Ag0.5Cu composite solder by mechanical alloying with electroless Ni-P/Cu under-bump metallization after various reflow cycles

“…The detailed fabrication process of Sn3.0Ag0.5Cu solder powders by the MA technique was described elsewhere. 14 The 130 mg Cu 6 Sn 5 nanopowders were added into 9.57 gS na nd 0.3 gA g and then mixed together to form 10 gSn3.0Ag0.5Cu solders. The RMA flux (TACFLUX, Indium Corporation of America, Utica, NY) was added directly into the solder powders at room temperature.…”

“…12,13 Recently, Sn-Ag-Cu composite solder alloy with doping nanosized Cu 6 Sn 5 was successfully produced by the MA process. 14 An electroless Ni-P under-bump metallization (UBM) is employed to provide adhesion and acts as ad iffusion barrier between solders and Si chips. Electroless Ni-P metallization has excellent uniformity, good corrosion resistance, strong adhesion to the substrate, and superior solderability.…”

Interfacial reactions and compound formation of Sn-Ag-Cu solders by mechanical alloying on electroless Ni-P/Cu under bump metallization

“…The detailed fabrication process of SnAgCu solder powders was described elsewhere. 9 The pH value of the plating solution was adjusted with a 50vol.%H 2 SO 4 solution and the working temperature was maintained at 85°C. After deposition for 15 min, the EN plated specimen was immediately immersed in DI water for 2 min and then dried with alcohol.…”

“…[5][6][7][8] Recently, mechanically alloyed SnAgCu solder alloy was successfully produced. 9 The SnAgCu solder paste was also produced by adding flux directly into mechanically alloyed powders. Recently, Ho et al reported that the small variation of Cu concentration would affect the type of IMC formed at the SnAgCu/Ni interface.…”

Wetting Properties and Interfacial Reactions of Mechanically Alloyed Cu5Zn8-Bearing Pb-Free Solders on a Copper Substrate

“…MA is a nonequilibrium process, and it is sometimes used to make Pb-free composite solder alloys with submicron homogeneity. [15][16][17] In this study, Cu 5 Zn 8 -bearing solders produced by MA are proposed to produce Zn-added solders without poor wetting properties. The wetting angles of the Cu 5 Zn 8 -bearing solders on a Cu substrate are compared with the wetting angles of bulk solder alloys with the same amount of Cu and Zn alloying elements.…”