Synthesis and Characterization of Lead-Free Solders with Sn-3.5Ag-xCu (x=0.2, 0.5, 1.0) Alloy Nanoparticles by the Chemical Reduction Method

Abstract

Due to the concerns of human health and the natural environment, the investigation of an alternative Pb-free solder is necessary. Currently, near-eutectic SnAgCu alloys are being developed as a lead-free solder. In this study, lead-free solders with Sn-3.5 Ag-xCu ͑x = 0.2, 0.5, 1.0͒ nanoparticles were synthesized by chemical precipitation with NaBH 4. The X-ray diffraction ͑XRD͒ patterns revealed that the Ag 3 Sn was formed due to the alloying process. From the XRD patterns, only Cu 6 Sn 5 was formed when Cu concentration was as high as 1.0 wt % in the derived nanopowders. The formation of Ag 3 Sn and Cu 6 Sn 5 gave strong evidence that the nanoparticles were mixed homogeneously. From transmission electron microscopy observation, the isolated particles were close to spherical shape and the particle sizes of powders were about 5 nm. The field emission scanning electron microscopy morphology of SnAgCu nanoparticles indicates that the major particle size of SnAgCu nanoparticles is in the range of 40 nm. It was evidenced from the differential scanning calorimetry profile that the SnAgCu nanoparticles could be melted successfully. In the wettability test, good metallurgical bonding was revealed between solders and substrates after reflow. Thus, the nanoparticles derived by the chemical reduction method in this study can be used as appropriate solder powders in electronic packaging.

Nanoparticles of the Lead-free Solder Alloy Sn-3.0Ag-0.5Cu with Large Melting Temperature Depression

“…The Ag 3 Sn phase (2h = 39.24 deg and 74.76 deg) was also found in the XRD pattern, indicating successful alloying between Sn and Ag during the manufacturing of the particles. 11,12 No major oxide peaks were observed from the XRD patterns, indicating that both studied protection coolant media used helped to reduce the oxidation of the nanoparticles.…”

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

“…[1][2][3][4][5] The mechanical alloying (MA) technique is one of the used methods to produce new solder alloys. [6][7][8][9][10] Mechanical alloying is ac onvenient technique producing particles with submicron homogeneity by repeated welding, fracturing, and rewelding of powder particles in ahigh-energy ball mill. 11 Recently, metals or intermetallic compounds have been introduced into solders and the composite solders are derived.…”

Pulse Electrodeposition of Lead-Free Tin-Based Composites for Microelectronic Packaging

“…[18,20] Various processing routes like melting and casting, powder metallurgy, high-energy ball milling/mechanical alloying, physical vapor deposition, sol-gel, plasma sprayed deposition, chemical methods, and electroplating have been employed to produce solder materials. [9][10][26][27][28][29][30][31] Powder metallurgy and mixing methods have been often used to fabricate the lead-free solders reinforced with nanoparticles: Cu, SiC, ZrO 2, Al 2 O 3 , SnO 2 , Y 2 O 3, TiB 2 , carbon nanotube (CNT), rare earth. [9, 21-22, 25, 32-36] There is also a limit on the amount of nanoreinforcement addition in the solder matrix; otherwise, it will deteriorate the solderability and strength.…”