Fig. 1 Schematic illustration of a synchrotron X-ray generation in a synchrotron storage ring [15] and b tube-generated X-ray beam [16]

Fig. 2 Schematic illustration of a absorption-contrast and b phase-contrast imaging with the corresponding images [21]

Fig. 3 Schematic diagram of X-ray computed tomography [24]

Fig. 4 A 3-D image of the packing structure in a 3-D IC reconstructed via synchrotron radiation tomography [25]

Fig. 5 a Synchrotron radiation images of a Sn/Cu joint during soldering at 350 oC. Note that Gi represents grown grains, while Di indicates dissolved and annexed grains [38]. b In situ images of a Sn/Cu interconnect during reflow soldering in different stages, including heating, dwelling, and cooling [40]

Fig. 6 In situ observations of L/S electromigration for a Cu/Sn-9Zn/Cu [51] and b Cu/Sn-Bi/Cu [52] interconnects under electromigration

Fig. 7 In situ images of a Cu/Sn/Cu solder joint during soldering under temperature gradient during the heating stage (0-51 s), heating preservation (259-2587 s), and cooling stage (3104-4910 s) [54]

Fig. 8 a X-ray tomography representations of electromigration-induced microstructural evolution in a Sn-0.7Cu/Cu couple under varying current density magnitude [59]; b 3-D reconstructions of Cu6Sn5 IMCs and voids under electromigration in pure bi-crystal Sn solder joints; Sn solder, voids, and IMCs are illustrated in transparent green, blue, and pink, respectively [61]

Fig. 9 In situ observations of Sn dendritic growth for a solidifying Sn-Bi alloy under a DC electric field [6]

Fig. 10 a Sequential images of the solidifying Sn-0.7Cu-0.5Ag alloy; b retrieved images showing the growth behavior of binary Sn-Ag3Sn eutectic and ternary Sn-Cu6Sn5-Ag3Sn eutectic [84]

Fig. 11 a Synchrotron radiography sequences of primary faceted and dendritic Cu6Sn5 in a Sn-Cu alloy [90]; b growth behaviors of primary Cu6Sn5 in Sn-Cu/Cu and Sn-Ag-Cu/Cu near interfacial IMCs layer during solidification [91]

Fig. 12 a Competitive growth of Ag3Sn during solidification in the Sn-Ag/Cu soldering reaction [103]; b in situ images of Cu/Sn-Ag/Cu interconnects during cooling [105]

Fig. 13 a In situ images of a single bubble at the Sn/Cu interface during heating at increasing times [109]; b 3-D morphologies of reflow porosities (red) and solder (yellow) under deformation from different strains [113]; c 3-D rendered images of the voids (purple) under electromigration [115]

Fig. 14 a Synchrotron radiation real-time images illustrating the microstructural evolution at the liquid Al/solid Fe interface during holding [123]; b 3-D images of tongue-like Fe2Al5 [124]

Fig. 15 a Synchrotron radiation real-time images showing the microstructural evolution at the Al-xSi(liquid)/Fe(solid) interface during holding [126]; b spatial distribution and 3-D morphologies of ternary Fe3Al3Si2 [124]

Fig. 16 a Real-time images of the growth behavior of FeAl3 IMC at the liquid Al/solid Fe interface during solidification [123]; b radiograph sequence showing growth of the primary FeAl3 crystal [127], c 3-D images of FeAl3 IMCs with various morphologies under different cooling rates [124]

Fig. 17 a Sequence of in situ radiographs showing the melting and solidification behavior of the Al/Cu bimetal [130]; b in situ images of the liquid Al/solid Cu interface under supersaturation during heating, holding, and cooling [131]; c schematic diagram showing the primary ε2 layer reaching its critical thickness followed by secondary γ1 IMC formation and the secondary γ1 IMC layer reaching its critical thickness followed by tertiary β IMC formation [131]

Fig. 18 3-D morphologies of Al2Cu IMCs in the Al-Cu alloy under a continuous cooling and b directional solidification [134]; c 3-D volume rendering of the Al2Cu phase in a recycled Al alloy [135]; d 3-D morphological evolution of primary Al2Cu IMCs upon increasing the cooling velocity [136]

Fig. 19 a In situ images of the microstructural evolution at the liquid Al/solid interface under supersaturation [140]; b in situ images of interfacial microstructures under unsaturation [141]; c real-time growth behavior of scallop-type Al3Ni [140]; d dynamic remelting and growth of columnar Al3Ni [142]

Fig. 20 a Dynamic growth of single-flake Al3Ni [143]; b in situ images showing the growth of variant-flake Al3Ni during solidification [143]; c dynamic growth behavior of hollowed Al3Ni crystals with regular and asymmetrical shapes [142]

Fig. 21 a 3-D morphology of microstructures in the Al/Ni interface [144]; b different intergrowth patterns of the two spatial Al3Ni crystals [145]; c complex morphology of dendritic proeutectic Al3Ni [146]; d specific surface area of Al3Ni dendrites as a function of volume: the inset represents 3-D morphologies of Al3Ni with high and normal SA values [146]