Solid-State Reactive Diffusion between Sn and Electroless Ni–P at 473 K

Abstract

Nickel-phosphorus alloys are electrolessly deposited onto Cu-base conductors to suppress formation of Cu-Sn compounds during soldering using Sn-base solders. However, a Ni-Sn compound is produced during soldering, and continuously grows during energization heating at solid-state temperatures. To examine influence of P on the growth behavior of the Ni-Sn compound during energization heating, the kinetics of the solid-state reactive diffusion between Sn and electroless Ni-P alloys was experimentally determined at 473 K in the present study. For the experiment, pure Cu sheets were electrolessly deposited with Ni-P alloys containing 4.6 at%, 18.5 at% and 20.4 at% of P, and then sandwiched between pure Sn plates. Such Sn/(Ni-P)/Cu/(Ni-P)/Sn diffusion couples were isothermally annealed at 473 K for various periods up to 1307 h. During annealing, a layer of Ni 3 Sn 4 is formed along the Sn/(Ni-P) interface in the diffusion couple. The annealing time dependence of the mean thickness of the Ni 3 Sn 4 layer is expressed by a parabolic relationship. The parabolic coefficient slightly increases with increasing P concentration in the Ni-P. Thus, P in the Ni-P lightly accelerates the growth of Ni 3 Sn 4 at the interconnection between the Ni-P and the Sn-base solder. Using the experimentally determined values of the parabolic coefficient, the interdiffusion coefficient in Ni 3 Sn 4 was analytically evaluated by a mathematical model. The acceleration effect of P on the growth of Ni 3 Sn 4 is quantitatively explained by the dependence of the interdiffusion coefficient on the P concentration in the Ni-P.

Influence of phosphorous content on microstructure development at the Ni-P Plating/SAC interface

“…The second intermetallic phase, possible to detect only in Ni-4.3P samples after reaction with solder, was described as (Ni,Cu) 3 Sn 4 . These results are in agreement with the examination of Yoon et al, [17] who identified the same intermetallics at the Sn-0.4Cu/ENIG interface and also observed similar morphology of large and faced scallops, but after 60 minutes of reaction time at 528 K. On the other 10-14 -225 ± 20 [14] 0 289 (Ea of self-diffusion in pure Ni) [14] hand, the second intermetallic phase (Ni,Cu) 3 Sn 4 formation was reported [2,18] during solid state reaction of plating and pure Sn solder. The presented here experimental results allow the conclusion that larger amount of phosphorous within the applied plating retarded the growth of (Cu,Ni) 6 Sn 5 and also the formation of Ni 3 Sn 4 intermetallic phases.…”

Effects of Under Bump Metallurgy (UBM) Materials on the Corrosion of Electroless Nickel Films

“…Table II lists the values of the lattice mismatch and the surface energy parameters of the Ni(P) film over various UBM materials using the material data found in the literature. [26,27] It can be seen that the utilized UBM materials fall into two distinct groups: noble metals Cu, Ag, and Au vs Ni and Co. The former substrates had relatively larger lattice mismatches with the Ni(P) film than the latter, and the former exhibited negative surface energy parameters, while the latter had significantly smaller lattice mismatches and positive energy parameters.…”

“…A qualitative understanding of the critical cluster size, in this case critical size of abnormally large nodules, can be constructed as follows in the manner of Tu et al [25] The free energy change of the The lattice parameters of the Ni(5P) film were deduced from Yamakami and Kajihara, [26] and the surface energies of metals reported by Skriver and Rosengard [27] were used. [27] exhibiting the regions of the three major growth modes.…”

Effect of Sodium Hypophosphite Content to the Deposition Rate, Structure and Magnetic Properties of Electroless Deposited Ni-P Alloy

“…It requires a combination of different characterization techniques. An illustration of this complexity are contradictory results, even obtained by using the best structure characterization techniques such as XRD and EXAFS -the dependence of the lattice parameter in the fcc phase of Ni-P on P content is opposite in alloys produced by different techniques [2], [11], [12]. In this regard, a more plausible approach at the initial stages of the research is to study the structure and properties of Ni-P coatings, depending on the basic parameter of electroless deposition i.e.…”