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This paper aims to investigate the creep behaviour of the recently developed Sn–8Zn–3Bi–xSb (x = 0, 0.5, 1.0 and 1.5) low temperature lead-free solder alloys.

An in-house compressive test rig was developed to perform creep tests under stresses of 20–40 MPa and temperature range 25°C–75 °C. Dorn power law and Garofalo hyperbolic sine law were used to model the secondary creep rate.

High coefficient of determination R² of 0.99 is achieved for both the models. It was found that the activation energy of Sn–8Zn–3Bi solder alloy can be significantly increased with addition of Sb, by 60% to 90 kJ/mol approximately, whereas the secondary creep exponent falls in the range 3–7. Improved creep resistance is attributed to solid solution strengthening introduced by micro-alloying. Creep mechanisms that govern the deformation of these newly developed lead-free solder alloys have also been proposed.

The findings are expected to fill the gap of knowledge on creep behaviour of these newly developed solder alloys, which are possible alternatives as lead-free interconnecting material in low temperature electronic assembly.

The purpose of this paper is to assess the long‐term reliability of lead‐free Sn96.5Ag3.0Cu0.5 (SAC305) under accelerated temperature cycling (ATC) conditions. Test vehicles consisted of commercial 2512 ceramic chip resistors soldered to printed circuit boards (PCBs) using three different Pb‐free surface finishes: organic solderability preservative (OSP), immersion silver (IAg) and electroless nickel immersion gold (ENIG).

Two populations of solder joints were monitored continuously during a thermal cycle of 0°C to 100°C with a ramp rate of 10°C/min and a 30 min dwell at the temperature extremes. One population was cycled to 2,500 cycles, the other population was cycled to 8,250 cycles. Failures were defined in accordance with the IPC‐9701A industry test guidelines and failure data are reported as characteristic life, η. Microstructural evolution was characterised using metallographic techniques and back‐scattered scanning electron microscopy (SEM). Fractography was performed on post‐cycled resistors to determine failure mechanisms.

The results showed that the lifetime of the chip resistors could be ranked as follows: OSP>ENIG>IAg after 8,250 thermal cycles, when>73 per cent of the population had failed. It was found that the relative performance of OSP finishes improved with longer periods of cycling. This was attributed to diffusion of copper into the bulk solder and which subsequently, over time, acted as a dispersion strengthening mechanism. The relatively poor performance of IAg finishes was attributed to void formation.

The paper provides new and valuable information to end‐users about the long‐term reliability of lead‐free solder on three commonly used lead‐free surface finishes. The performance of each surface finish is explained in terms of microstructural evolution and void formation.

A survey of these records shows that while in a number of the larger factories work has been carried out under conditions likely to insure the production of sound and wholesome materials, in many others of this class the opposite has been the case. In a very large number of the smaller factories and food preparing places the conditions found were unsatisfactory in the extreme.

The purpose of the present work is to study the impacts of rapid cooling and Tb rare-earth additions on the structural, thermal and mechanical behavior of Bi–0.5Ag lead-free solder for high-temperature applications.

Effect of rapid solidification processing on structural, thermal and mechanical properties of Bi-Ag lead-free solder reinforced Tb rare-earth element.

The obtained results indicated that the microstructure consists of rhombohedral Bi-rich phase and Ag99.5Bi0.5 intermetallic compound (IMC). The addition of Tb could effectively reduce the onset and melting point. The elastic modulus of Tb-containing solders was enhanced to about 90% at 0.5 Tb. The higher elastic modulus may be attributed to solid solution strengthening effect, solubility extension, microstructure refinement and precipitation hardening of uniform distribution Ag99.5Bi0.5 IMC particles which can reasonably modify the microstructure, as well as inhibit the segregation and hinder the motion of dislocations.

It is recommended that the lead-free Bi-0.5Ag-0.5Tb solder be a candidate instead of common solder alloy (Sn-37Pb) for high temperature and high performance applications.

THE past month has brought no dramatic change in the general situation, great as have been the events that have been passing. So far as librarians are concerned, the remarkable fact has been that in most towns the demands made upon them have exceeded anything in their record. We do not know if this is the universal experience; it certainly is a well‐spread one. Our difficulties are not eased by the continuous call‐up of women assistants and the replacements which ensue. Some towns are unable to offer salaries to new comers which enables them to obtain competent assistants. Many of the temporary workers are doing well, however. Another progressively disturbing matter is the paucity of books, new or reprinted, and the small return for money spent on such as we do get. The only good thing about the “war‐time economy” book is its slenderness; we can get a hundred on a shelf where previously only thirty could be housed. The times do not lack small interests of this sort.

.Counter Competition. SUPERMARKETS and private shopkeepers battle for business in every High Street. In all shopping centres the private trader competes for the customer's cash with chain and departmental stores. He finds life increasingly difficult in face of rising overheads and shrinking profit margins.

THE serious and intractable housing problem persists to plague governments and embitter citizens. Why this is so can be gleaned from a few statistics.

Last month saw two major developments for the future of the Careers Service. An all‐party Expenditure Committee published their views on the Youth Employment Service and almost simultaneously Mr Maurice Macmillan, Secretary of State for Employment, presented his Employment and Training Bill to Parliament for its second reading.