Failures Related to Castings

The information provided in this article is intended for those individuals who want to determine why a casting component failed to perform its intended purpose. It is also intended to provide insights for potential casting applications so that the likelihood of failure to perform the intended function is decreased. The article addresses factors that may cause failures in castings for each metal type, starting with gray iron and progressing to ductile iron, steel, aluminum, and copper-base alloys. It describes the general root causes of failure attributed to the casting material, production method, and/or design. The article also addresses conditions related to the casting process but not specific to any metal group, including misruns, pour shorts, broken cores, and foundry expertise. The discussion in each casting metal group includes factors concerning defects that can occur specific to the metal group and progress from melting to solidification, casting processing, and finally how the removal of the mold material can affect performance.

Special aspects of the use of laser coaxial melting of powder materials for creating objects from copper-base alloys

Among the methods of additive technologies, coaxial laser melting, i.e. direct metal deposition (DMD), is quite widespread. Essentially, this process is about creating objects by sequentially deposing layers of powder and melting them due to their simultaneous supply through a nozzle with focusing of laser radiation into the processing zone. Various powders are used as materials for this technology, the powders being selected depending on the tasks and final characteristics. One of the promising directions for implementation is the creation of complex structures from copper alloys for aircraft construction. Despite the fairly widespread use of this technology in relation to copper alloys, in particular bronzes, there is a small amount of data and research for this technology. The purpose of this study was to understand the process of forming the materials when grown by the DMD method. For this purpose, the fusion of bronzes with a steel substrate was investigated; special aspects were revealed, which made it possible to pose the second task - the study of fusion of bronzes with a copper substrate. As a result, the microstructure of the samples was considered and their micro-hardness was measured.

Semiconductor QFN Package with Advanced Interlocking Design

The mechanical interlocking structure for quad-flat no-lead (QFN) assembly for densified leadframe degrades as the package becomes thinner. Detractors such as package reliability and design requirement hinder further qualification of leadframes with increased number of input/output (I/O) pins. In this paper, a new and advanced design of leadframe is discussed and presented with improvement in mechanical interlocking structure of high stress areas such as lead and pad junction. The leadframe is re-designed having lead lines on the lead and pad that will be etched away after molding process replacing full copper base frame. Through application of the design, the effective mechanical interlocking is improved from 60% to 100% for mold-lead and mold-pad interface.