Some Observations on the Accelerated Ageing of Thick-Film Resistors

Methods of accelerating the ageing of thick-film resistors (TFRs) have been explored, with encouraging results from experiments in which elevated temperature and damp heat were inflicted on TFRs. Consistent acceleration was obtained by increasing temperature, whether by storage or dissipation, the activation energies for thermal ageing of various resistor families lying in the range 0.5 eV-1.5 eV. Acceleration by humidity (RH) was also obtained, corresponding, for example, to a halving of life for a 20% increase of RH, some resistance changes being about an order of magnitude larger than those obtained at elevated temperature. The encapsulations played a dominant role in the degradation of resistors under both stress conditions. According to the theories of conduction, degradation could occur because of reactions at conductive sites, causing corresponding changes in the conductivity and resistance versus temperature (R(T)) characteristics. Progressive degradation certainly did occur, as evidenced by the conformity of the ageing behaviour to a diffusiontype (time) 1/2 dependence accompanied by shifts in the R(T) characteristics. Some interpretation of the degradation has been possible by referring to an empirical model of the temperature dependence of resistance, but conflicting changes can be reconciled with the model only by postulating competing degradation mechanisms. The report covers an early stage of the work

An integrated geophysical and GIS based approach improves estimation of peatland carbon stocks

Estimations of peatland carbon stocks often use generalised values for peat thickness and carbon content. Ground penetrating radar (GPR), a rapid technique for field data collection, has been increasingly demonstrated as an appropriate method of mapping peat thickness. Light Detection and Ranging (LiDAR) data as a method for understanding peatland surface elevation are also becoming more widely available. Reliable mapping and quantification of site-specific carbon stocks (e.g. upland raised bogs) is therefore, becoming increasingly feasible, providing a valuable contribution to regional, national and potentially global carbon stock assessments. This is particularly important because raised bogs, such as those found in South Wales are considerable carbon stores. They are, however, susceptible to climate warming owing to their southerly location within the UK. Accurate estimates of peatland carbon stocks has broader importance because world-wide peatland carbon stores are significant and threatened by climate change, posing a substantial challenge not only due to climate feedbacks if this stored carbon is released into the atmosphere, but also the impact on the other ecosystem services that they provide. Here, we assess the value of an integrated GPR, LiDAR and Geographic Information System (GIS) approach to improve estimation of regional carbon stocks. We apply the approach to three ombrotrophic raised bogs in South Wales, UK, selected for their conservation value and their topographically-confined raised bog form. GPR and LiDAR are found to be well suited, respectively, to mapping peat thickness at bog scale and surface elevation, thus allowing surface and basal topographies to be evaluated using GIS. In turn, this allows peat volumes to be estimated. For the first time, we record values between 55,200 m3 and 163,000 m3 for the sites considered here. The greater confidence in these peat volume estimates results from the ability to calibrate the GPR velocity using a depth-to-target calibration with peat cores extracted at locations encompassing the deepest bog area. Peat thickness is mapped at the bog scale with near centimetre precision, improving the robustness of subsequent volume calculations and our understanding of the contribution of these small but numerous sites to regional carbon stocks. Our evaluation shows that GPR corresponds well with conventional manual probing but is minimally invasive and therefore less disturbing of sensitive peatland sites, while also offering improved coverage and spatial resolution with less time and cost. In combination with measured bulk density and organic carbon contents, these peat volumes allow carbon stocks to be estimated with greater confidence compared to conventional approaches, having values between 2181 ± 122 tonnes carbon and 6305 ± 351 tonnes carbon at our three sites

Cheap multichip modules

The opportunity for mutual benefit across Europe to develop low-cost MCM technologies arose from recognition of the scientific skills and design and prototyping capabilities in organic and inorganic circuits in countries of Central Europe. As a results, the leading research institutions and small/medium-size enterprises of Hungary, Romania and Slovenia together with relevant institutions of the United Kingdom and Belgium proposed and received approval for an European Union INCO-COPERNICUS project (IC15-CT96-0743) "Establishment of Fast Prototyping Low Cost Multichip Module Technology Facilities in Eastern Europe for the Benefit of European Industry" (Cheap MultiChip Modules) to establish fast prototyping low cost multichip module (MCM) technology facilities. The project commenced in May 1997. MCM Technologies include the design, manufacturing, assembling and testing phases. The tasks of the Project are divided among the participants in accordance with these technological phases and conforming to their interest and capability in the field. Design is the task of the Rumanian Partners. They have installed CAD systems and developed circuit designs and simulations to determine the design rules and preferences for MCMs. Manufacturing is the task of the Hungarian and Slovenian Partners. They are focusing their laminate and ceramics capabilities towards MCM-L and MCM-C manufacturing and upgrading test technologies up to a level to fulfill the low cost, fast prototyping requirements of the participating Central European Countries (and later Europe-wide). The Hungarian Partner is also establishing mounting and bonding facilities for assembling MCMs in collaboration with the UK and Belgian Partners, exploiting their high level experience in the fields of microjoining and test technologies. The final test of demonstration modules is also the task of the Belgian Partner. The evaluation of the results in accordance with the manufacturing, application and economic aspects will be the task of all Partners with the leadership of the Hungarian Partner. The Project is carried out in close cc-operation of all Partners. In order to disseminate information for and about the Project, the Partnership participates in conferences, organizes seminars and training courses for themselves and for small and medium size enterprises who show interest in the prototyping technology of MCMs. Considerable progress has been made in the design facilities by the Rumanian Partner, and in the refinement of the printed circuit board (PCB) technology at Budapest, including laser patterning of MCM-Ls. Diffusion patterning and ceramics technology skills in Slovenia are enabling MCM-C prototyping to be demonstrated and further developed