A New Method of Metallization for Silicon Solar Cells

A low cost ohmic contact on silicon solar cells based on molybdenum-tin metal systems was developed. The approach is based on the formulation of a screenable ink composed from molybdenum oxide and tin mixture. The reduction of Mo03 into Mo and the establishment of Mo 03:Sn ratio is studied. Both tasks were done in an experimental station constructed for this purpose. The results show that molybdenum was formed from its oxide at 800 C. and improved in bonding to silicon at 900 C. A 20% Mo03-80%Sn mixture was converted into metallic coating within this temperature range

Investigation of nickel-silicon metallization process

The metallization of silicon solar cells passivated with silicon nitride coating was investigated by using commercial Ni pastes #5517 from Thick Film Systems, #7028-5 from Cermalloy, experimental formulation # X-A by Sollos, Inc. and evaporated Ti-Ni film. Comparative and reference tests were done with the Dupont Ag paste #7095 and with a mixture of Ni paste #5517 with Ag paste #7095 in the respective ratio of 9 to 1 by weight. The evaluation criteria for the metallization was the mechanical bond strength of the contact, solderability, copper plating ability and electrical characteristics in terms of Voc, Isc values and shape of the V-I curve. The results revealed that the Dupont Ag paste #7095 mt all required criteria, while the quality of the cells metalized with the commercial Ni paste #5517 from Thick Film Systems, #7028-5 from Cermalloy as well as the experimental paste # X-A from Sollos, Inc. was below the acceptable standards. A significant improvement was obtained with the mixture of Ni paste #5517 from Thick Film Systems with 10% addition of Dupont paste # 7095

The European Perspective on Women\u27s Leadership

The perspective of women in leadership positions is of particular impor- tance in Europe. It is a main subject in the areas of research and science. For example: At the University of Augsburg we conducted several studies of women\u27s leadership and the female academic career in view of gender is- sues such as gender within the family and in socialization. Furthermore we accomplished two gender mainstreaming studies with the focus on equity in several universities in Germany (Gender mainstreaming is a European law of 1997 and a political strategy of diversity management). In this article we want to show the perspective on women\u27s leadership in Europe. Therefore we want to present the European data on the educational status of girls and women at schools and universities and in academic ca- reers. Data for Germany is presented as an example to provide evidence of some details. First, we want to point out four contradictions for women in the education system and concerning leadership positions. Second, data is discussed and some results of research explaining the data are given. Fi- nally, we present a European Program for the educational system to give women more chances: The so called Gender Mainstreaming Program

Willingness to Pay for Voluntary Health Insurance in Tanzania

To assess how willing people would be to join a voluntary health insurance scheme and to see how they respond to changes in the benefit package. We also examined willingness to cross-subsidise the poor. Cross-sectional study. Two thousand two hundread and twenty four households comprising of 1,163 uninsured household heads asked about their willingness to pay for insurance in seven districts/councils (three urban and four rural) and 1,061 insured households were asked about their willingness to pay for insurance premiums for the poor in their community. Uninsured respondents were presented with two scenarios, the first reflected the current design of the Community Health Fund/Tiba Kwa Kadi (CHF/TIKA), the second offered expanded benefits, and included inpatient care in public facilities and transport. Only 30 % of uninsured rural households were willing to pay more than Tsh 5,000 the current premium level, their average amount was Tsh 10,741, while in urban areas one percent of households were willing to pay more than Tsh 5,000. There was very limited willingness to pay more than 5,000 Tsh, even with an expanded package in rural areas. Household from rural areas were more willing to cross-subsidise the poor, but contribution levels were higher in urban areas. Communities need to be sensitised about the existence of the CHF/TIKA to encourage enrollment. Expanding the benefit package would further increase enrollment. However, few people would be willing to pay more than the current premium.\u

High reliability bond program using small diameter aluminum wire

The program was undertaken to characterize the performance of small diameter aluminum wire ultrasonically bonded to conductors commonly encountered in hybrid assemblies, and to recommend guidelines for improving this performance. Wire, 25.4, 38.1 and 50.8 um (1, 1.5 and 2 mil), was used with bonding metallization consisting of thick film gold, thin film gold and aluminum as well as conventional aluminum pads on semiconductor chips. The chief tool for evaluating the performance was the double bond pull test in conjunction with a 72 hour - 150 C heat soak and -65 C to +150 C thermal cycling. In practice the thermal cycling was found to have relatively little effect compared to the heat soak. Pull strength will decrease after heat soak as a result of annealing of the aluminum wire; when bonded to thick film gold, the pull strength decreased by about 50% (weakening of the bond interface was the major cause of the reduction). Bonds to thin film gold lost about 30 - 40% of their initial pull strenth; weakening of the wire itself at the bond heel was the predominant cause. Bonds to aluminum substrate metallization lost only about 22%. Bonds between thick and thin film gold substrate metallization and semiconductor chips substantiated the previous conclusions but also showed that in about 20 to 25% of the cases, bond interface failure occurred at the semiconductor chip

Heat addition to a subsonic boundary layer: A preliminary analytical study

A preliminary analytical study of the effects of heat addition to the subsonic boundary layer flow over a typical airfoil shape is presented. This phenomenon becomes of interest in the space shuttle mission since heat absorbed by the wing structure during re-entry will be rejected to the boundary layer during the subsequent low speed maneuvering and landing phase. A survey of existing literature and analytical solutions for both laminar and turbulent flow indicate that a heated surface generally destabilizes the boundary layer. Specifically, the boundary layer thickness is increased, the skin friction at the surface is decreased and the point of flow separation is moved forward. In addition, limited analytical results predict that the angle of attack at which a heated airfoil will stall is significantly less than the stall angle of an unheated wing. These effects could adversely affect the lift and drag, and thus the maneuvering capabilities of booster and orbiter shuttle vehicles