Phase characterisation and kinetic behaviour of diffusion soldered Cu/In/Cu interconnections

Abstract

The characterisation of diffusion soldered Cu/In/Cu interconnections is presented in this work. The main feature of this joining process is the production of a bond at a low fabrication temperature, which allows high service temperatures. The interconnection is formed entirely by intermetallic phases (IPs) which form isothermally rst by a liquid -solid reaction and then by a solid -solid reaction. The morphology and the growth kinetics of the IPs formed in the interconnection zone at temperatures in the range 180 -430°C were examined by electron probe microanalysis, X-ray diffraction and transmission electron diffraction analysis. In accordance with the phase diagram, the phases Cu 11 In 9 , Cu 2 In and Cu 7 In 3 (at T<310°C) and Cu 2 In and Cu 7 In 3 (at T>310°C) appeared in the interconnection zone. The thickness of the IPs formed during the solid -solid reaction obeyed a parabolic growth law. The growth rate constants were calculated for the Cu 2 In and Cu 7 In 3 phases. Using these values and the equilibrium concentration of the IPs, the integral interdiffusion coef cients were calculated through Wagner's approach.MST/5449

Kinetics of Ag3Sn growth in Ag–Sn–Ag system during transient liquid phase soldering process

“…14 for the present Ag-Sn-Ag system is different from the results reported for the interfacial reactions in the CuSn-Cu and Cu-InSn-Cu TLP systems with a time depen- dence of the form t 1/2 [15,24,25]. It is also different from the results reported for the coarsening kinetics of the Ni 3 Sn 4 scallops formed in the conventional Sn-based solder/Ni systems.…”

“…(15) can then be applied to the correlation length g 0 values in Fig. 11b and an initial value of 18.2 lm for the as-reflowed Ag-Sn-Ag sample to analyse the radial growth kinetics of Ag 3 Sn:…”

“…There are limited data available for the kinetic consumption of interlayers and growth of IMCs in other TLP systems, e.g. Cu-Sn-Cu and Cu-InSn-Cu systems, which were directed towards applications in electronic packaging and interconnects [15,24,25]. These kinetic data were all analysed and expressed using a time dependence of the form t 1/2 , in keeping with work reported on high-temperature TLP bonding processes used in the aerospace industry [1].…”

“…Since then, TLP bonding used to join base metals Ag, Au and Cu for electronic packaging and interconnects has been extensively investigated [2,[6][7][8][9][10][11][12][13][14][15][16][17], while that used to join base metals Ni, Pd, Pt and Zr was also reported [18][19][20]. In these efforts, TLP bonding has been be more appropriately termed TLP soldering [2].…”

Phase transformation and fracture behavior of Cu/In/Cu joints formed by solid–liquid interdiffusion bonding

“…For Ag-In interconnections bonded at 320°C for 280 min, Ag 9 In 4 firstly generated and transformed to Ag 3 In in 30 min. Sommadoosi [20] has found that Cu and In could react in different ways at different temperatures. Cu 11 In 9 firstly generates when the bonding temperature is below 310°C while Cu 2 In could generate firstly with higher temperature.…”