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Power electronics are usually soldered to Al₂‐O₃ direct‐bond‐copper (DBC) substrates to increase thermal diffusivity, while at the same time increasing electrical isolation. However, soldering gives rise to inherent residual stresses and out‐of‐plane deformation. The purpose of this paper is to look at the effect of soldering processes of Al₂‐O₃ DBC substrates to copper plates and power electronics, on their thermal fatigue life and warpage.

A numerical thermo‐mechanical finite element model, using the Chaboche material model, was developed to identify the thermal plastic strains evolved during soldering of DBC substrates to copper plates and power electronics. The plastic strains in conjunction with established extremely low cycle fatigue life prediction model for ductile material were used to predict the number of soldering cycles to failure. The predicted out‐of‐plane deformation and number of soldering cycles to failures was compared to realistic tests.

Soldering processes drastically reduce the thermal fatigue life of DBC substrates, giving rise to thermal cracking and premature failure. In this study the soldering process considered gave rise to out‐of‐plane deformations, consequently reducing heat dispersion in soldered DBC substrate assemblies. Furthermore, soldering gave rise to interface cracking and failed after three soldering cycles. Numerical finite element models were developed and are in good agreement with the experimental tests results.

The influence of soldering processes of DBC substrates to copper plates and electronics on the thermal fatigue life should be taken into consideration when establishing the design life of DBC substrates. Finite element models can be utilised to optimize soldering processes and optimize the design of DBC substrates.

The effect of soldering processes on DBC substrates was studied. A numerical finite element model used for the prediction of design life cycle and out‐of‐plane deformation is proposed.

Dibutyrylchitin (DBC) is an ester derivative of a natural polysaccharide – chitin. DBC is obtained by reaction of chitin with butyric anhydride in the presence of a catalyst. The production methods of DBC have been elaborated and optimized. DBC is easily soluble in common organic solvents and has film – and fibre forming properties. Such characteristics allow obtaining classical fibres from the polymer solutions. DBC is also a raw material for manufacturing yarn and for a broad range of textile dressing materials. Fibres with good mechanical properties are obtained by an optimized spinning process from the DBC solutions. The purpose of this paper is to present a further optimization of the mechanical properties of DBC‐fibres and yarns.

The excellent biomedical properties of the DBC are confirmed by different experimental results which prove that DBC is a biocompatible and biodegradable polymer and stimulates regeneration of damaged tissues. Tests of these DBC dressing materials under clinical conditions prove the excellent results of DBC‐based dressing materials for the ordered healing of tissues and wounds. The DBC dressing materials accelerate the healing of the wound and are biodegraded during the healing process. From the clinical tests, it can be clearly observed that the DBC dressing materials are absorbed into the fresh tissue formed during the healing process of the wounds.

The DBC and DBC‐based dressing materials are good bioactive textile materials for wound healing and for understanding the biological properties of chitin derivatives. The obtained results prove the importance of the O‐substitution of the hydroxyl groups present in chitin, not only for the solubility of the derivatives and the mechanical properties of the produced fibres, but still more important for the biological properties of these ester derivatives of chitin containing butyric acid. This development creates a link between textile products, based on material properties and human health, based on the biological properties of the basic material.

The mechanical properties of DBC are further optimized by blending it with poly(ε‐caprolactone). Good transparent and flexible products, such as films, with a high elongation to break are obtained by blending 10‐20 wt per cent of poly(ε‐caprolactone) with DBC. This creates new possible bioactive applications for DBC or poly(ε‐caprolactone).

The chapter provides a case study of the strategic-level employee involvement (EI) program at a high-performance company, Delta Air Lines. EI at Delta – probably the most extensive in breadth, depth, and representational structure for nonunion workers at an American company – extends from shop floor to board room. Attention here is on the board component: a group of five peer-selected employees called the Delta Board Council (DBC) which has a nonvoting seat on the board of directors and participates in a wide range of strategic decisions and roles. The chapter discusses why this kind of representational EI group, although widespread up to the 1930s, is now quite rare in the United States. The main part of the chapter focuses on the structure, purpose, and accomplishments of the DBC, presented through a question and answer (Q&A) interview with a founding DBC member. Provided are numerous EI “lessons-learned” and “do’s” and “don’ts” for managers.

This study extends the theoretical analyses of Duration-Based Costing (DBC), an alternative cost measurement system to Activity-Based Costing (ABC). DBC is simpler than ABC and uses the production cycle time to assign costs. This simplicity should allow DBC to be a better costing method for multiproduct firms that exhibit nonconstant returns to scale.

Data simulations for 1,000 cases and Data Envelopment Analysis (DEA) are used to analyze the production functions inside DBC and ABC models to determine their relative technical efficiency.

The results show that, for a given set of simulations, DBC shows more nonconstant returns to scale than does ABC. This corroborates prior research and suggests that a more complex costing system, such as ABC, may not always match the production technology of a multiproduct firm. Thus, DBC may have a higher level of accuracy than does ABC for firms that exhibit nonconstant returns to scale.

Since DBC has only recently been theoretically developed, this study is the first to analyze the relative technical efficiency of DBC compared to ABC.

This study should bring some further awareness of the implications of alternative costing methods. The limitation of DBC is that it does not capture other factors not driven by the production cycle time that could be necessary for management decision making. However, DBC is better for multiproduct firms than a more complicated costing system and does help decision makers determine whether the production process is operating efficiently. It is imperative that firms choose which costing methods fit the firm’s needs and economic structure.

The study explores the role of dialogic public communication and information quality (IQ) in evaluating the operational performance of donation-based crowdfunding (DBC) tasks. These tasks are primarily used to support disaster relief operations. The authors also test the influence of cognitive trust and swift trust as moderating variables in explaining the relationship between both IQ and dialogic communication with operational performance.

The authors used a primary survey to test the hypotheses. A total of 203 responses were collected from multiple crowdfunding platforms. The authors used archival data from task creators on donation-based crowdfunding platforms, and a structured questionnaire is also used to collect responses. Data are analyzed using Warp PLS 6.0. Warp PLS 6.0 works on the principle of partial least square (PLS) structured equation modeling (SEM) and has been used widely to test path analytical models.

The authors found out that the operational performance is explained significantly by the quality of information and its association with dialogic public communication. The results support the arguments offered by dialogic public communication theory and trust transfer theory in assessing the operational success of DBC. The study also confirms that cognitive trust positively moderates the relationship between IQ and organizational public dialogic communication and operational performance. It is also revealed that the duration of the DBC task has no significant control over dialogic public communication.

The study lays practical foundations for task creators on DBC platforms and website designers as it sets the importance of both IQ and dialogic communication channels. The communication made by the task creator and/or the DBC platforms with the donors and potential donors in the form of timely and appropriate information forms the key to the success of any DBC task. The study also helps task creators choose a suitable platform to improve performance.

The authors propose a unique framework by integrating two theoretical perspectives: dialogic public relation theory and trust transfer theory in understanding the operational performance of donation-based crowdfunding tasks. The authors address DBC tasks catering to disaster relief operations by collecting responses from task creators on DBC platforms. The study uniquely positions itself in the area of information and communication.

Direct‐bond‐copper (DBC) substrates crack after about 15 thermal cycles from −55 to 250°C. The purpose of this paper is to study the phenomenology of thermal‐cracking to determine the suitability of DBC for high‐temperature packaging.

The thermal plastic strain distribution at the edge of the DBC substrate was analyzed by using a finite element method with the Chaboche model for copper. The parameters of the Chaboche model were verified by comparing with the three‐point bending test results of DBC substrate. The thermal analyses involving different edge tail lengths indicated that susceptibility to cracking was influenced by the edge geometry of the DBC substrate.

Interface cracking was observed to initiate at the short edge of the bonded copper and propagated into the ceramic layer. The interface crack was caused by the accumulation of thermal plastic strain near the short edge. The edge tail can decrease the thermal strain along the short edge of the DBC substrate. Thermal cycling lifetime was improved greatly for the DBC substrate with 0.5 mm edge tail length compared with that without edge tail.

The thermal cracking of DBC substrates should be studied at the microstructure level in the future.

Thermal cycling induced failure of DBC was analyzed. A method of alleviating the thermal plastic strain distribution on the weakest site and improving the thermal fatigue lifetime of DBC substrates under thermal cycling was proposed.

Prior research has used computer-generated data to illustrate the benefits of the recently developed duration-based costing (DBC) and its affiliate modified duration-based costing (MDBC). The purpose of this paper is to use data from a Fortune 500 corporation to compare its traditional, or functional-based, cost allocation method with that of the recently developed DBC and MDBC models.

A Fortune 500 company provided one month of production data for a particular, key machine within its manufacturing process. The data were used to apply DBC and MDBC.

Variations arising from differences in the models’ cost allocation reveal the advantages of using time-based cost allocation over the traditional, mostly non-time-based allocation to estimate profit.

By using actual data, this case study enhances prior theoretical research concerning the benefits of utilizing DBC and MDBC over the traditional costing method.

This case study is of benefit to practitioners who use traditional costing since it will encourage them to explore DBC and/or MDBC that tend to be more accurate in situations where the old adage of “time is money” applies. Implementing DBC and MDBC was not difficult to do for the Fortune 500 company as all of the components to run the models were readily available.

This is the first study to utilize actual company data to illustrate DBC and MDBC, and thus, adding to the literature concerning DBC and MDBC.

The purpose of this paper is to study the phenomenology of Al₂O₃-DBC substrate thermal-cracking under different high temperature cyclic loadings. The extremely low cycle fatigue (ELCF) life prediction model for ductile materials was used to describe the thermal fatigue life of Al₂O₃-DBC substrates.

Four groups of thermal cycling tests using Al₂O₃-DBC substrates with 0.65 mm thick copper were conducted using different peak temperatures. The failure samples were observed by optical microscope. The thermal plastic strain distribution in the Al₂O₃-DBC substrates was analyzed using a finite element method with the Chaboche model for describing plastic deformation of copper. The ELCF life prediction model was used to predict the life of Al₂O₃-DBC substrates under high temperature cyclic loadings.

Interface cracking was observed to initiate at the short edge of the bonded copper and deviated into the ceramic layer when the crack grew beyond the critical length of 0.1-0.8 mm. The interface crack deviated into the ceramic layer at different thickness and grew parallel to the interface layer between the ceramic layer and copper layer. The crack propagation stopped after certain cycles. The copper layer with 10-20 μm thick alumina inside was not split away totally from the ceramic layer. The ELCF life prediction model could predict the life of Al₂O₃-DBC substrates well under high temperature cyclic loading. The material constants in the extremely low fatigue life prediction model were obtained using thermal fatigue tests results.

The influence of copper layer thickness and ceramic layer thickness on thermal cracking characteristics of DBC substrate should be studied in the future. Failure models should also be further investigated.

The failure model of Al₂O₃-DBC substrates under high temperature cyclic loading was studied. A method for predicting the life of the substrate samples under high temperature cyclic loading was proposed.

This paper aims to investigate the sintering and solid liquid interdiffusion bonding (SLID) techniques to attach AlGaN/GaN-on-Si chips to direct bond copper (DBC) substrate. The influence of metal layers deposited on the backside of AlGaN/GaN-on-Si dies on the assembly process is also investigated.

The authors assumed the value of the shear strength to be a basic parameter for evaluation of mechanical properties. Additionally, the surface condition after shearing was assessed by SEM photographs and the shear surface was studied by X-ray diffraction method. The SLID requires Sn-plated DBC substrate and can be carried out at temperature slightly higher than 250°C and pressure reduced to 4 MPa, while the sintering requires process temperature of 350°C and the pressure at least 7.5 MPa.

Ag-, Au-backside covered high electron mobility transistor (HEMT) chips can be assembled on Sn-plated DBC substrates by SLID technology. In case of sintering technology, Cu- or Ag-backside covered HEMT chips can be assembled on Ag- or Ni/Au-plated DBC substrates. The SLID process can be realized at lower temperature and decreased pressure than sintering process.

For SLID technology, the adhesion between Cu-backside covered HEMT die and DBC with Sn layer loses its operational properties after short-term ageing in air at temperature of 300°C.

In the SLID process, Sn-Cu and Sn-Ag intermetallic compounds and alloys are responsible for creation of the joint between Sn-plated DBC and micropowder Ag layer, while the sintered joint between the chip and Ag-based micropowder is formed in diffusion process.

This paper aims to present certain issues in direct bonded copper (DBC) technology towards the manufacture of Al2O3 or AlN ceramic substrates with one or both sides clad with a copper (Cu) layer.

As part of the experimental work, attempts were made to produce patterns printed onto DBC substrates based on four substantially different technologies: precise cutting with a diamond saw, photolithography, the use of a milling cutter (LPKF ProtoMat 93s) and laser ablation with differential chemical etching of the Cu layer.

The use of photolithography and etching technology in the case of boards clad with a 0.2-mm-thick Cu layer, can produce conductive paths with a width of 0.4 mm while maintaining a distance of 0.4 mm between the paths, and in the case of boards clad with a 0.3-mm-thick copper layer, conductive paths with a width of 0.5 mm while maintaining a distance of 0.5 mm between paths. The application of laser ablation at the final step of removing the unnecessary copper layer, can radically increase the resolution of printed pattern even to 0.1/0.1 mm. The quality of the printed pattern is also much better.

Etching process optimization and the development of the fundamentals of technology and design of power electronic systems based on DBC substrates should be done in the future. A limiting factor for further research and its implementation may be the relatively high price of DBC substrates in comparison with typical PCB printed circuits.

Several examples of practical implementations using DBC technology are presented, such as full- and half-bridge connections, full-wave rectifier with an output voltage of 48 V and an output current of 50 A, and part of a battery discharger controller and light-emitting diode illuminator soldered to a copper heat sink.

The paper presents a comparison of different technologies used for the realization of precise patterns on DBC substrates. The combination of etching and laser ablation technologies radically improves the quality of DBC-printed patterns.