Eliminating interfacial segregation and embrittlement of bismuth in SnBi/Cu joint by alloying Cu substrate

Microstructures and properties of Sn58Bi, Sn35Bi0.3Ag, Sn35Bi1.0Ag solder and solder joints

“…At the interface, the void can be observed obviously, which can be attributed to the volume shrink during Cu-Sn reaction. Moreover, Zou [10] found that the segregation of Bi at the SnBi/Cu interface dramatically decreased the mechanical properties, and the addition of Ag, Al, Sn and Zn elements into Cu substrate can eliminate the interfacial segregation and embrittlement of the SnBi/ Cu couple. However, in our experiments, no Bi segregation can be observed, this phenomenon may be affected by the reflow soldering processing.…”

Microstructure of lead-free solder bumps using laser reflow soldering

“…Sn-Bi eutectic solder has been considered a promising leadfree solder for low-temperature applications due to its low melting point (138°C). Several studies on Sn-Bi eutectic solder have been conducted to investigate the basic characteristics of the solder joint [5][6][7][8][9][10]. However, there is a lack information about laser reflow soldering for Sn-Bi eutectic solder.…”

Interfacial Microstructure and Growth Kinetics of Intermetallic Compound Layers in Sn-4 wt.%Ag/Cu-X (X = Zn, Ag, Sn) Couples

“…1 Based on the imminence of lead-free solders, many researchers have paid much attention to the interfacial reactions between Sn-based lead-free solders and Cu substrate. [1][2][3][4] It is well known that a layer of intermetallic compounds (IMCs) forms at the solder/ substrate interface when molten solder wets the substrate. [1][2][3][4] With prolonged aging time, not only does the thickness of the IMC layers increase but also a new phase, i.e., Cu 3 Sn, gradually forms on the Cu substrate.…”

“…[1][2][3][4] It is well known that a layer of intermetallic compounds (IMCs) forms at the solder/ substrate interface when molten solder wets the substrate. [1][2][3][4] With prolonged aging time, not only does the thickness of the IMC layers increase but also a new phase, i.e., Cu 3 Sn, gradually forms on the Cu substrate. Most previous results have reported that this phenomenon deteriorates the interfacial mechanical properties with increasing thickness of the IMC layers.…”

“…Recently, changing the solder composition to suppress the growth of the IMC layer and thereby optimize the mechanical properties of the solder joint has been one of the most popular methods; for example, it has been reported that addition of Ag or Zn can optimize the mechanical properties of the solders or solder joints. 3,4,8 However, for Sn-Bi/Cu solder, changing the solder composition cannot restrain the Bi segregation at the Cu 3 Sn/Cu interface. Recent experimental results have provided direct evidence that Cu alloys can effectively restrain the Bi segregation at the Sn-Bi/Cu interface and thus improve its mechanical properties, because Bi segregation at the Cu 3 Sn/Cu interface deteriorates the reliability of Sn-Bi/Cu joints.…”