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The purpose of this paper is to verify how solder joint properties correlate with soldering profile set-up. These characteristics act against each other. All observed properties may significantly affect the quality and reliability of solder joints. The purpose is also to design recommendations for manufacturers of electronic assemblies.

The samples for experiment were reflowed by using a laboratory reflow oven. A LEXT laser confocal microscope was used for wetting angle and intermetallic compound (IMC) thickness measurement. The ionic contamination was measured by using a contaminometer.

The appropriate choice of soldering profile is very important for the reliability of electronic assemblies. The higher temperatures or longer preheating and soldering times improve the wetting angle. Likewise, there is also the activation of all the fluxes. The result is low contamination with printed circuit boards (PCBs). On the other hand, we must not forget that higher temperatures and longer soldering time also affect the thickness of the IMC. The outer limits recommended by the manufacturer were selected for the soldering profile set-up. Even within these limits, it is possible to achieve an improvement in the wetting angle, an improvement in levels of PCB contamination and an increase in the thickness of the IMC. This paper presents the results achieved for solders Sn42Bi57.6Ag0.4, Sn96.5Ag3Cu0.5 and Sn97Ag3.

The gained knowledge on the correlation between IMC thickness, solderability of PCB and PCB contamination caused by different soldering profile set-ups can help to prevent reliability problems because each of the named effects has a significant influence on reliability.

The purpose of this paper is to increase the reliability of manufactured electronics and to reveal reliability significant factors. The experiments were focused especially on the influence of the reflow oven parameters presented by a heating factor.

The shear strength of the surface mount device (SMD) resistors and their joint resistance were analyzed. The resistors were assembled with two Sn/Ag/Cu-based and one Bi-based solder pastes, and the analysis was done for several values of the heating factor and before and after isothermal aging. The measurement of thickness of intermetallic compounds was conducted on the micro-sections of the solder joints.

The shear strength of solder joints based on the Sn/Ag/Cu-based solder alloy started to decline after the heating factor reached the value of 500 s · K, whereas the shear strength of the solder alloy based on the Bi alloy (in the measured range) always increased with an increase in the heating factor. Also, the Bi-based solder joints showed shear strength increase after isothermal aging in contrast to Sn/Ag/Cu-based solder joints, which showed shear strength decrease.

The interpretation of the results of such a comprehensive measurement leads to a better understanding of the mutual relation between reliability and other technological parameters such as solder alloy type, surface finish and parameters of the soldering process.