Search results

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.

Using visual materials to understand a social object requires the researcher to know that object's purpose, and this is true whether the object is an artifact, a restricted event, a small social world, or something as massive as the modern city. I argue that the purpose of the city as a settlement is driven by the need to safely sleep in peace at night while satisfying other basic biophysical needs during the day as conveniently as possible. An examination of these needs identifies 10 functional prerequisites for human settlement, entangling its inhabitants in involuntary community with entities and events other than themselves, whether they like it or not. In addition, the rise of the modern city exacerbates the challenge of living in a reluctant community and pressures its inhabitants to come to terms with the consequences for how these relationships affect daily life. I highlight nine challenges posed as questions that have been particularly salient in American urban history since the mid-nineteenth century. How these challenges have been addressed indicates not only what it takes to make a modern city a settlement suitable for satisfying human needs, but also just how deeply invested its residents are in making the city work. Finally, the 10 functional prerequisites and nine moral challenges not only provide a framework for researching the city, but also suggest a coherent outline for imagining a “shooting script” or guide for conducting visual research.