Journal of Welding and Joining

1: J Weld Join. 2014;32(3):274-281. Published online June 30, 2014.
DOI: https://doi.org/10.5781/JWJ.2014.32.3.60; Effects of the Electroless Ni-P Thickness and Assembly Process on Solder Ball Joint Reliability; Ji-Hye Lee, Seok-Hwan Huh, Gi-Ho Jung, Suk-Jin Ham; Corresponding author: Seok-Hwan Huh ,Email: shhuh12@gmail.com

Abstract: The ability of electronic packages and assemblies to resist solder joint failure is becoming a growing concern. This paper reports on a study of high speed shear energy of Sn-4.0wt%Ag-0.5wt%Cu (SAC405) solder with different electroless Ni-P thickness, with HNO3 vapor’s status, and with various pre-conditions. A high speed shear testing of solder joints was conducted to find a relationship between the thickness of Ni-P deposit and the brittle fracture in electroless Ni-P deposit/SAC405 solder interconnection. A focused ion beam (FIB) was used to polish the cross sections to reveal details of the microstructure of the fractured pad surface with and without HNO3 vapor treatment. A scanning electron microscopy (SEM) and an energy dispersive x-ray analysis (EDS) confirmed that there were three intermetallic compound (IMC) layers at the SAC405 solder joint interface: (Ni,Cu)3Sn4 layer, (Ni,Cu)2SnP layer, and (Ni,Sn)3P layer. The high speed shear energy of SAC405 solder joint with 3μm Ni-P deposit was found to be lower in pre-condition level#2, compared to that of 6μm Ni-P deposit. Results of focused ion beam and energy dispersive x-ray analysis of the fractured pad surfaces support the suggestion that the brittle fracture of 3μm Ni-P deposit is the result of Ni corrosion in the pre-condition level#2 and the HNO3 vapor treatment.

Keywords :High speed shear energy, Electroless Ni-P, HNO3 vapor treatment, Ni corrosion