Spalling of intermetallic compounds in a massive scale has been reported in the literature for several solder/substrate systems, including SnAgCu soldered on Ni substrate, SnZn on Cu, high-Pb PbSn on Cu, and high-Pb PbSn on Ni. In this work, a common mechanism based on thermodynamic arguments is proposed to explain this rather peculiar phenomenon that occurs across several systems. According to this mechanism, two necessary conditions must be met. This first is that the most reactive element must be present in a limited amount, and the second is that the soldering reaction must be very sensitive to the concentration of this element. With the growth of intermetallic, more and more of the most reactive elements are extracted out of the solder and incorporated into intermetallic. As the concentration of this element decreases, the local equilibrium phase at the interface changes. This changing of the equilibrium phases caused the non-equilibrium phase to spall.