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Telecom equipment is subject to thermal cycles caused by both variations in temperature between day and night and variations in the telephone traffic. To simulate such thermal excursions, accelerated thermal cycle testing between — 10°C and 100°C has been established as a standard method within Ericsson Telecom. Thermal cycle tests have been carried out for frequencies ranging from one cycle per day to 30 cycles per hour in order to cover the different thermal excursions that occur in telecom equipment. It has been found that the life of a surface mounted PWB assembly can be predicted from the accelerated testing results using a frequency modified Coffin‐Manson relation. Factors which influence the fatigue life of solder joints such as solder material, compliant leads, compliant surface layers and mismatch between package and board are discussed. Based on results from accelerated testing it is suggested that the optimal PWB design for leadless ceramic chip carriers should be a moderate TCE matching combined with a compliant surface layer.

The choice of high pin count ASIC packages has a major impact on the total cost and performance of the whole packaging system. Six different types of ASIC packages have been compared with respect to production aspects, availability, reliability, thermal and electrical properties and cost. Recommendations for the proper choice of packages for different types of applications are given. All packages have been directly assembled to PWBs in order to study problems with handling, solder process, testing and repairability. Some of the assembled packages have been temperature cycled in order to test the solder joint reliability. The pin grid array packages are the most frequently used high pin count packages today. However, they are expensive and through‐hole mounting reduces the routing capability of the board. Pad area array packages are a hermetic alternative with a lower price for the package as well as very good thermal and electrical properties, but they need to be mounted on expensive PWBs. Another surface mountable package which is hermetic is the ceramic leaded chip carrier with fine lead pitch. This package is even more expensive than the pin grid array package and is difficult to handle. In the future, non‐hermetic alternatives will probably predominate. Plastic quad flat pack and TapePak can be used below 160–180 leads, while direct assembled TAB would be the best alternative for very high pin counts. Before one can use non‐hermetic packages in telecom products, a large qualification programme must be performed to evaluate the long‐term reliability.

Chips with 43 leads mounted on three layer tapes were outer lead bonded to different substrates. The substrate materials were ceramics with Cu thick film, glass fibre reinforced epoxy, Cu‐lnvar‐Cu with polyimide coating and ceramics with polyimide coating. The strengths of the inner and outer leads were measured before and after storage at elevated temperature, vibration test and temperature cycling. The initial pull strength distributions of the outer lead bonds on the different substrates were analysed. The bond strength on ceramic substrates with Cu thick film was slightly lower than on the other substrates. TAB devices on all substrates endured 750 cycles or more when tested between −55°C and 125°C. Owing to the rather large difference in the coefficient of thermal expansion between the ceramics and the Cu leads, failures occurred first on the ceramic substrate. Storage at 200°C for 2000 h resulted in a somewhat reduced inner lead bond strength. Two mechanisms were responsible for this. The most severe process was interdiffusion between Al and Au across the barrier metal (Ti/W). The second process was diffusion between Cu and Au with the subsequent formation of Kirkendall pores in the Cu leads.

Tape automated bonding (TAB) is a suitable technology for assembling ICs with a high number of l/Os. The gang bonding process usually applied requires increasing thermode forces for chips with high lead counts and narrow tolerances regarding thermode parallelism and planarity. Due to the high bonding pressure, TC bonding of Au bumps to Au‐plated tapes becomes critical for these applications. In order to avoid damage to the pad structure an inner lead bonding (ILB) process with reduced pressure is required. A tape metallisation of 0.5–1.0 µm Sn is not sufficient for a significant reduction of thermode pressure. As an alternative, the application of an eutectic Au‐Sn cushion which is deposited on top of the bumps is presented. A modified bumping process was developed for the deposition of the solder bumps. Soldering of the Au‐Sn bumps to a Au‐plated tape was performed successfully by two techniques: thermode gang bonding and laser soldering. Bond parameters and tin layer thickness were optimised. Reliability investigations by thermal ageing were performed. The special metallurgical aspects of the system were investigated with a microprobe.

A review of state‐of‐the‐art technology pertinent to tape automated bonding (for fine pitch, high I/O, high performance, high yield, high volume and high reliability) is presented. Emphasis is placed on a new understanding of the key elements (for example, tapes, bumps, inner lead bonding, testing and burn‐in on tape‐with‐chip, encapsulation, outer lead bonding, thermal management, reliability and rework) of this rapidly moving technology.

Tape Automated Bonding (TAB) is a modern technology which meets the requirements for micro‐connecting VLSI circuits. The limitations for gang bonding chips with high lead counts and reduced pitches are increased bond forces and induced mechanical stress. Laser soldering is an alternative for such contacts. Because microjoining of surfaces occurs via thermal energy from the laser beam, no mechanical pressure is necessary. Due to the optical properties of the laser beam and the possibility to reduce the laser spot, soldering of small pitches is possible. The results of TAB inner lead bonding with a pulsed Nd:YAG laser are presented. Tapes with three metallisations (Sn, Ni‐Sn and Au) were laser soldered to bumps consisting of gold and gold‐tin. The pull strength of laser soldered TAB‐contacts was optimised by variation of laser power and reliability investigations were performed. The metallurgy of laser soldering is different and more critical to long term reliability than that of gang bonded ILB‐contacts, even if identical tape and bump materials are applied. An accumulation of eutectic 80/20 Au‐Sn solder in the bonded interface results in a strong degradation due to Kirkendall pore formation in the ternary Cu‐Sn‐Au system. The application of a tape with a diffusion barrier of Ni inhibits this effect. But during thermal ageing these contacts show a strong degradation of pull forces which is attributed to the formation of brittle intermetallic compounds of the elements Ni, Sn and Au in the contact area. Laser soldering of Au‐plated tapes to Au‐Sn solder bumps is possible. The contacts show optimal pull forces and a minimal degradation after thermal ageing. This is attributed to the formation of an intermetallic compound with a high stability. The Zeta phase acts as a diffusion barrier between the copper lead and the eutectic Au‐Sn solder.

In this paper an overview of the issues underlying surface mount solder joint long‐term reliability is presented. The paper gives state‐of‐the‐art solutions for ‘Design for Reliability’ in simple design tool form, discusses the important accelerated reliability test issues, and provides the equations to estimate the reliability of SM product in use as well as the expected cyclic life in accelerated tests.

The purpose of this paper is to expand understandings of how logistics can reduce food waste in food supply chains (FSCs).

Using a research framework that associates causes of food waste with logistics solutions, a multiple-case study was conducted in three Swedish FSCs of meat, fruit and vegetables, and ambient products, respectively, and involving industrial producers, wholesalers, and retailers. Data were collected during 19 semistructured interviews and four site visits, and logistics solutions were analysed according to logistics activities, actors involved and their stages in the FSC, and coordination mechanisms.

A joint analysis of nine logistics solutions revealed that to efficiently reduce food waste in FSCs, solutions have been implemented at three stages of FSCs, as well as that those solutions differ in their integration of six logistics activities and four coordination mechanisms. The findings moreover indicate that the solutions are interlinked, thereby implying that coordination is necessary both within solutions as well as among them.

The chief limitation is that the potential of the identified logistics solutions is not quantified.

The paper makes recommendations for reducing food waste in FSCs by developing new solutions and modifying existing ones.

The paper suggests ways to reduce significant environmental impacts of food waste.

By building upon previous research explaining causes of food waste, this paper focusses on logistics solutions for reducing such waste.

For the proposed coupling transformer, a magnetic bypass based on the virtual air gap principle is realized by inserting auxiliary windings in a return leg added to a standard transformer. With such a setup, it is able to act as a voltage regulator as well as protect the power electronics of the dynamic voltage restorer from electrical grid fault currents. This paper focuses on the electrical design part of the coupling transformer. It aims to explain how the behavior of the auxiliary windings electrical circuit of the magnetic bypass impacts the performances of the device.

The influence of the electrical auxiliary windings circuit configurations on the operation of the coupling transformer is studied by finite element analyses with nonlinear and isotropic magnetic materials.

A configuration for the realization of the electrical circuit of the auxiliary windings is determined according to the finite element simulation results to achieve the design of the coupling transformer whose magnetic core was previously designed.

By studying the operation of a special coupling transformer with nonlinear saturation phenomenon by finite element analyses, a to-do list of the electrical circuit parameters is described to design this device well.