Flash (manufacturing)

Abstract: A molded package having reduced unintentional and undesirable mold flash or bleed around an exposed heat sink is provided through the use of a compression structure within the package. The compression structure may be integral with a heat sink, die bond flag, if one is present, or may be a separate structure, which extends from a die support surface of the heat sink to the opposite side of the mold. During molding, the compression structure presses a heat dissipation surface of the heat sink against the mold surface forming a tight seal to prevent the mold compound from creeping around between the mold and the heat dissipation surface to form flash. The heat sink may also be provided with adhesion promotion features along its side to improve the physical bond or attachment between the heat sink and the plastic body of the package.

Abstract: During flash sintering, ceramic materials can sinter to high density in a matter of seconds while subjected to electric field and elevated temperature. This process, which occurs at lower furnace temperatures and in shorter times than both conventional ceramic sintering and field-assisted methods such as spark plasma sintering, has the potential to radically reduce the power consumption required for the densification of ceramic materials. This paper reviews the experimental work on flash sintering methods carried out to date, and compares the properties of the materials obtained to those produced by conventional sintering. The flash sintering process is described for oxides of zirconium, yttrium, aluminium, tin, zinc, and titanium; silicon and boron carbide, zirconium diboride, materials for solid oxide fuel applications, ferroelectric materials, and composite materials. While experimental observations have been made on a wide range of materials, understanding of the underlying mechanisms responsible for the onset and latter stages of flash sintering is still elusive. Elements of the proposed theories to explain the observed behaviour include extensive Joule heating throughout the material causing thermal runaway, arrested by the current limitation in the power supply, and the formation of defect avalanches which rapidly and dramatically increase the sample conductivity. Undoubtedly, the flash sintering process is affected by the electric field strength, furnace temperature and current density limit, but also by microstructural features such as the presence of second phase particles or dopants and the particle size in the starting material. While further experimental work and modelling is still required to attain a full understanding capable of predicting the success of the flash sintering process in different materials, the technique non-etheless holds great potential for exceptional control of the ceramic sintering process.

Abstract: A lead from 10 carries an integrated circuit on a die support pad 14. The lead frame has a dam bar including a transverse portion that extends between adjacent leads (20) for limiting mold flash. The dam bar transverse portion 26 is entirely severed from the adjacent leads for final removal by a metal punch 33 along with the supporting web 16.

Abstract: System and methods for flash heating of materials deposited using atomic layer deposition techniques are disclosed. By flash heating the surface of the deposited material after each or every few deposition cycles, contaminants such as un-reacted precursors and byproducts can be released from the deposited material. A higher quality material is deposited by reducing the incorporation of impurities. A flash heating source is capable of quickly raising the temperature of the surface of a deposited material without substantially raising the temperature of the bulk of the substrate on which the material is being deposited. Because the temperature of the bulk of the substrate is not significantly raised, the bulk acts like a heat sink to aid in cooling the surface after flash heating. In this manner, processing times are not significantly increased in order to allow the surface temperature to reach a suitably low temperature for deposition.