Extremely fast formation of Cu Sn intermetallic compounds in Cu/Sn/Cu system via a micro-resistance spot welding process

Cu6Sn5 crystal growth mechanisms during solidification of electronic interconnections

“…Figs. [1][2][3][4][5][6][7][8][9][10][11][12] and in solder joints on Cu substrates is that, in the latter case, there is a pre-existing Cu6Sn5 reaction layer in contact with the liquid at the peak temperature. Therefore, during cooling from the peak temperature, there is the possibility of growth of the pre-existing Cu6Sn5 layer into the liquid and/or the nucleation of new Cu6Sn5 grains in the liquid above the layer.…”

“…Hwang et al [18] observed dendritic Cu6Sn5 in Sn-6.9Cu-2.9Ag alloy cooled at ~17-500 K/s. Liu et al [6] reported Cu6Sn5 dendrites in Sn/Cu joints held at 426C for 80ms and 120ms before cooling at >800 K/s. For synchrotron radiography studies, direct observations showed that rod-like Cu6Sn5 formed in Sn-4Ag-0.5Cu cooled at 1 K/s [46] and Sn-0.7Cu/Cu cooled at ~0.33 K/s [22,23], and branched Cu6Sn5 formed in Sn-4Cu [7] and Sn-6.5Cu cooled at 0.05 K/s [9,47].…”

“…Cu6Sn5 is of particular interest because it is commonly found as primary crystals in the bulk solder and as the interfacial reaction layer in joints between Cu substrates and most Sn-rich solders. Thus, there has been increasing interest in methods to control the size and morphology of primary Cu6Sn5 [6][7][8][9].…”

“…Primary Cu6Sn5 has been reported to grow with various morphologies such as needles [10][11][12], hollow rods [11,13], X-shapes [9,14,15], Y-shapes [8,9], H-and M-shapes [16,17] and as dendrites [6,18]. Since many of these studies have been based on arbitrary 2D cross sections, it is not clear how many of these morphologies are separate growth forms in 3D.…”

Transient Liquid Phase Bonding of Copper Using Sn Coated Cu MWCNT Composite Powders for Power Electronics

“…During the joining process, as the temperature reaches 232°C, Sn coated on the Cu-MWCNT melts and reacts with copper to form Cu-Sn IMC. At the interface of Sn and Cu-MWCNT, Cu3Sn forms according to Equation (2), whereas in Sn rich regions (surface of Figure 5b [7,9,10,[25][26][27][28][29][30][31][32]. Microstructural aspects such as the type and dispersion of second phase particles play an important role in the mechanical property of the joint.…”