Janusz Pstrus

Thermophysical properties and wetting behavior on Cu of selected SAC alloys

Purpose – The purpose of this paper is to study the effect of copper concentration in near‐eutectic liquid SAC solders on their thermophysical properties: viscosity, surface tension, density; as well as wetting behavior on copper substrates at 523 K.Design/methodology/approach – Viscosity, surface tension, and density were studied over a broad range of temperatures with the recently developed Roach‐Henein method. The obtained results were compared with the data from modified capillary, maximum bubble pressure, wetting balance and dilatometric measurements. Wetting angles measured with wetting balance method were compared with the results of sessile drop measurements.Findings – The results obtained indicate that increasing concentration of copper in the alloy results in higher density, surface tension and viscosity, but differences resulting from copper concentration on wettability are relatively small. At 523 K, the density is: 7.097, 7.186, 7.232 g cm−3, the surface tension is: 538.1, 553.5, 556.7 m Nm−1...

Densities of solid aluminum-lithium (Al-Li) alloys

Densities of solid Al and Al-Li alloys were measured by the dilatometric method for six compositions of mole fractions of lithium: 0.05,0.1,0.125,0.15,0.20, and 0.25. A curvilinear dependence of density on temperature (room temperature up to 923 K) was observed for all investigated alloys. Results could be described by parabolic equations. The molar volumes of Al-Li alloys were calculated from the density measurements. It has been found that the densities of solid Al-Li alloys initially show slightly negative deviations from linearity that reverse to positive above 0.075 mole fraction of Li. Molar volume exhibits negative deviation from linear dependence for all samples in the experimental concentration range. Power series were used to fit the dependences of density on temperature and concentration. Coefficients of volume expansion were calculated and discussed. The density of the β phase along the (α + β)/β boundary was calculated and described by a temperature-dependent polynomial.

Investigation of the wetting of PCBs with SnCu (HASL) and Snimm finishes by SnZnBiIn solders

Purpose – The purpose of this article is to establish why the wetting on PCBs with SnCu (HASL) and Snimm finishes in the presence of a flux is better than the wetting of those on a copper substrate. The practical aspect of the obtained results is the main goal of these investigations.Design/methodology/approach – The authors applied the wetting balance method for the wetting measurements at 230 and 250°C, in nitrogen atmosphere, in the presence of the ORM0 type flux. The PCBs with the SnCu (HASL) and Snimm finishes were investigated in the state “as received”. To establish the wetting properties of the SnCu (HASL) and Snimm finishes on the PCBs, wetted by the investigated SnZnBiIn alloys, the SEM and EDX analyses were performed.Findings – The authors obtained very good wetting results of the PCBs with the SnCu and Snimm finishes, wetted by the SnZn7Bi3In4 alloys. By applying the SEM and EDX methods, it was possible to establish that the barrier layer which was created during the HASL process between the c...

Interfacial reactions of Sn–Zn–Ag–Cu alloy on soldered Al/Cu and Al/Al joints

ABSTRACT This work shows the effect on the soldering process of the addition of Ag and Cu to Sn–Zn alloys. Soldering of Al/Cu and Al/Al joints was performed for a time of 3 min, at a temperature of 250°C, with the use of flux. Aging was carried out at 170°C for Al/Cu and Al/Al joints for 1 and 10 days. During the aging process, intermetallic layers grew at the interface of the Al/Cu joint at the Cu substrate. Intermetallic layers were not observed during wetting of Al/Al joints. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed. The experiment was designed to demonstrate the effect of Ag and Cu addition on the dissolution of Al substrate during the soldering and aging processes. In the solder alloys, small precipitates of AgZn3 and Cu5Zn8 were observed.