A Review on Recent Advances in Transient Liquid Phase (TLP) Bonding for Thermoelectric Power Module

Abstract

In this study, the authors have reviewed recent advances on the transient liquid phase (TLP) bonding technology for various applications especially power module packaging in view of the recent increasing demand for the production of vehicles, smartphones, semiconductor devices etc. TLP bonding is one of the potential technologies from clean technology that can replace the Pb-base solder technology without causing any serious environmental issues. It is based on the concept of both brazing as well as diffusion bonding. During TLP bonding, the liquid phase is transiently formed at the bonding interface. At this point, the melting point of filler metal increases due to the diffusion of element which degrades the melting point from liquid phase to base metal. Subsequently, the bonding occurs by isothermal solidification at the bonding temperature of liquid phase. Here, after bonding, the melting temperature of the joint layer becomes higher than bonding temperature. This review introduces the various aspects of TLP bonding including its principle, materials, applications, advantages and properties in detail.

Recent Progress in Transient Liquid Phase and Wire Bonding Technologies for Power Electronics

“…Moreover, the joint strength depends upon the volume fraction of IMCs. The shear strength was increased at a smaller volume fraction of IMCs while the failure strain decreased steadily up to a higher volume fraction of IMCs [68].…”

“…The shear strength after bonding at 300 • C for 15 min (Sn + Cu 6 Sn 5 + Cu 3 Sn phases), 60 min (Cu 6 Sn 5 + Cu 3 Sn phases), and 120 min (Cu 3 Sn phase) were 11.7, 9.5, and 5.4 MPa, respectively. Reduced joint strength was correlated to the brittleness of IMCs and void production along the joint after Cu 3 Sn covered the whole joint [68]. Moreover, the joint strength depends upon the volume fraction of IMCs.…”

“…Most of the research activities are devoted to the use of various melting point reducing agents in the liquid metal for the isothermal solidification in TLP bonding [67]. Most widely used meting point depressants are pure C, B, or phosphorus as an interstitial element to reduce the isothermal solidification time [35,64,68]. Notable reduction in TLP bonding time has been obtained, to yield a very short 10 to 15 min, which covers the entire isothermal solidification and composition homogenization duration [35,[52][53][54][55][56][57][58][59][60][61][62][63][64].…”

“…Several researchers in the past [67,68] have used Sn foil as an interlayer to join Cu-Sn, Ni-Sn, or Sn-Ag via TLP bonding. Chu et al [69] studied and compared two sandwiched solder systems (Cu/Sn/Cu and Ni/Sn/Ni) for low-temperature wafer bonding at 255 • C for 5 min.…”

Interfacial Reactivity of the Filled Skutterudite Smy(FexNi1−x)4Sb12 in Contact with Liquid In-Based Alloys and Sn

“…The temperature of a joint process involving Sm y (Fe x Ni 1−x ) 4 Sb 12 has to be carefully chosen since it is restricted to a limited range by the operating temperature of the thermoelectric device (the studied skutterudite system shows the maximum ZT value at~700 K) and by the peritectic decomposition temperature of the material (~873 K [52]). Due to the lack of reliable soldering/brazing alloys in this temperature range, new methods had to be sought: the partial transient liquid phase bonding (PTLPB) applied to non-metallic materials allows to overcome the issue of producing a joint without affecting the skutterudite integrity as a consequence of high process temperatures [53][54][55]. This technique exploits metallic interlayers which melt, thus ensuring the contact and adhesion of the adjoining surfaces, and form new phases with higher melting temperatures by means of diffusion phenomena.…”