Spot Defects Research Articles

Al-Zn合金における2次格子欠陥の直接観察

The secondary defects introduced by quenching of Al-Zn alloys were investigated by means of transmission electron microscopy, with particular attension to the effect of the quenching rates and the solute concentrations.Two different methods of quenching were employed in this experiments. One was a fast quenching at the quenching rate of 1×104 deg C/sec, and the other a slow quenching at the rate of 1×103 deg C/sec.The type, size and density of secondary defects were sensitive to the quenching rates and the solute concentrations. The types of secondary defects observed in quenched Al-Zn alloys were the Frank sessile loop, prismatic loop, helical dislocation and black spot defect. Frank sessile loops were observed only in pure Al by the fast quenching and in the alloys containing less than 1.9 at%Zn by the slow quenching. Helical dislocations were observed in the alloys containing above 7.0 at%Zn by the fast quenching but in alloys of more than 1.6 at%Zn by the slow quenching. Black spot defects were found in the alloys containing above 0.5 at%Zn by the fast quenching and in alloys of more than 7.0 at%Zn by the slow quenching. Judging from the various experimental results, the black spot defects found in the quenched Al-Zn alloys were thought to be the three dimensional vacancy clusters.The initial vacancy concentrations estimated roughly from the size and density of secondary defects in the quenched alloys were much larger than in pure Al. This may indicate that the presence of Zn in Al lowers the activation energy to form a vacancy.

Cost-size optima of monolithic integrated circuits

A generalized cost-size relationship is derived for a monolithic circuit consisting of N identical components, taking into account variations in component density, yield, and assembly costs with N. It is intended to reveal cost trends rather than give accurate results for specific cases and deals only with fabrication costs. A yield-area relationship is used which takes into account chip-to-chip variations in defect density. It is found that the ratio (circuit cost per component/cost of discrete transistor) is a minimum at a chip size which is determined primarily by the spot defect density on the device. This optimum chip size lies between approximately 20 and approximately 60 mils square for a wide range of parameter values. State-of-the-art parameter values indicate a potential order of magnitude cost saving in integrated circuits compared with discrete transistors. The minimum value for the cost ratio is in general inversely proportional to the maximum packing density of components on a semiconductor slice and has a limiting value approximately 1/8N, N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> being the number of components which can be packed on the chip size normally used for transistors. Arrays of identical logic gates fit the circuit model used quite closely, and the curves indicate that the cost per gate in reasonably densely packed arrays can be less than the cost of a discrete transistor. The results also indicate that when systems requirements make it desirable to include larger numbers of components in one package than the optimum for one monolith, wired-chip schemes are preferable to single monoliths, the optimum chip size being smaller than that for a simple monolith.

The failure of metallized-paper capacitors used with large series resistances

Although normally self-healing, metallized-paper capacitors sometimes become faulty when used in series with a high resistance. Accelerated life tests have shown that such faults may occur, for example, when 0.5μF capacitors are connected to an 80 V supply through a resistance of 1 MΩ or more.To calculate similar limiting conditions for other capacitances and supply voltages, the paper assumes that a rapid deterioration begins when a certain critical dissipation is reached at a defective spot, and that the fault will be cleared if the energy then stored in the capacitor is enough to evaporate the electrodes locally.In capacitors of various other kinds, not having metallized electrodes, no faults of this kind have occurred during life tests, or are thought likely.

New X-Ray Machine Helps Spot Defects in Children

New X-Ray Machine Helps Spot Defects in Children