Search results

The purpose of this paper is to provide a model for simulating contamination by ferromagnetic particles in sensors that use permanent magnets. This topic is especially important for automotive applications, where magnetic sensors are extensively used and where metallic particles are present, particularly because of friction between mechanical parts. The aim of the model is to predict the particle accumulation and its effect on the sensor performance.

Magnetostatic moment method is used to calculate particles' magnetization and magnetic field. Magnetic saturation is included and Newton–Raphson method is used to solve the non-linear system. Magnetic force on particles is calculated as a gradient of energy. Dynamic simulation provides the positions of agglomerated particles.

A simulation of magnetic park lock sensor shows a significant impact of ferromagnetic particles on sensor's accuracy. Moreover, gains on computational time because of model optimizations are reported.

Only magnetic force and gravity are taken into account for particle dynamics. Mechanical forces such as friction and particle interactions might be considered in future works.

This paper provides the possibility to evaluate and improve magnetic sensor design with respect to particles contamination.

The paper presents a novel simulation tool developed to answer the growing need for reliable and fast prediction of magnetic position sensors’ degradation in the presence of metallic particles.

In this paper, reproduced by permission of “Metal Finishing” (New Jersey), the author enumerates the required properties of electroplated gold coatings on printed circuit boards and wire to ensure satisfactory bonding by ultrasonic means. The gold plating procedures and process control methods which are necessary to produce coatings yielding consistently high bond strengths are described.

Over the past 20 years there has been a recurrent problem of a purple‐bluish stain appearing on the laminate materials of finished printed circuit boards between the gold‐plated fingers. The origin of this staining has been traced back to the PWB fabrication plant and it is generally accepted to be related to either the gold plating bath and/or the solder stripper chemistry. In this paper the authors report their investigation of this phenomenon and show that, far from being a benign, cosmetic defect, this purple stain poses a potentially serious metallic contamination to the laminate surface of the PWB. The purple colour arises from generation of a colloidal gold chromophore known as the ‘Purple of Cassius,’ which has been known since ancient times and has been in commercial use in the glass and ceramics industry for at least 300 years.

For many years the analysis of contaminant residues on PWB surfaces has been of major importance to the industry. While the identification of residues left on metallic surfaces has proven to be relatively straightforward, the analysis of organic contamination of similar composition to that of the underlying board surface has not been as successful. Through the use of modern XPS instrumentation, the non‐ionic component of water soluble flux has been identified and differentiated from the chemically similar FR‐4 and soldermask substrates. This paper presents the XPS results for a series of experiments aimed at determining the location and relative concentration of water soluble flux residues on standard surface insulation resistance (SIR) comb patterns. The data show that the water soluble flux residue is not present as a uniform coating on the board surface but appears in localised sites in high concentrations while being absent in other locations. Through more aggressive cleaning procedures the sites of high residue concentration can be significantly reduced.

It is not possible in an article of this size to deal with all aspects of the corrosion problems encountered in the handling and manufacture of food. Accordingly it is proposed to discuss only a few, namely, those special aspects which appear to make the food industry unique in the corrosion technologist's experience.

Criminal proceedings can only follow the commission of an offence, made so by statute. If an act is not unlawful, it matters little with what motives a person commits it or the consequences; he is outside the law, i.e. criminal law; civil law might have a remedy, but criminal law does not. Even when a criminal offence is committed, it may contain ingredients without which, what would otherwise be a punishable act, becomes guiltless. Most qualifications to guilt are of longstanding, used by parliamentary draftsmen in a wide range of statutes and have acquired reasonably precise judicial meaning. Most relate to intention—wilfully, intentionally, knowingly—and in a few, judicial extension of the popular meaning and usage of the term has occurred to prevent an innocent stance being simulated by a guilty party. “Knowledge” is such an example. The term has been deliberately widened to cover persons who “shut their eyes” to an offence; where a person deliberately refrains from making enquiries, the results of which he would not care to know, this amounts to having such knowledge— constructive knowledge.

In recent years, electronic devices have increasingly employed printed circuits produced using electrically conductive adhesives, commonly known as polymer thick films. This method is much more cost‐effective and efficient than other methods of wiring, including those using chemical etching or plating. In the past, the use of metal‐filled polymers as conductors in printed circuit fabrication has suffered from several limitations such as poor solderability, conductivity and adhesion. A new electrically conductive metal‐filled polymer formulation has been developed which overcomes these problems inherent in typical polymer thick film inks. This new product is based on transient liquid‐phase sintering wherein the metallic components of the formulation sinter at a relatively low temperature, resulting in a highly conductive continuous metal network. The sintering is achieved through the interaction of several metallic components with an adhesive‐flux component. The final product is highly conductive, solderable and exhibits excellent adhesion to a wide range of substrate materials. A new process for manufacturing fine‐line printed circuit boards using this ink technology is under investigation. It promises potentially simpler processing and lower cost than plating. In this new process, traces (in the form of troughs in the dielectric) are imaged using conventional photoimageable dielectrics. Exposure and developing conditions depend upon the polymer system used. The transient liquid phase sinterable conductive ink is applied to fill the photo‐exposed conductor pattern. Next, another layer of photoimageable dielectric is applied over the traces and imaged with vias for interconnections with subsequent layers. The dielectric is then cured and the ink applied to fill the vias. These steps may be repeated several times to produce low‐profile fine‐line multilayer printed circuits. This process for producing multilayer circuits using conductive inks simplifies the manufacturing of printed circuits, reduces profile, eliminates most waste in manufacturing, and reduces cost compared with plating.

Statements by Lord Denning, M.R., vividly describing the impact of European Community Legislation are increasingly being used by lawyers and others to express their concern for its effect not only on our legal system but on other sectors of our society, changes which all must accept and to which they must adapt. A popular saying of the noble Lord is “The Treaty is like an incoming tide. It flows into the estuaries and up the rivers. It cannot be held back”. The impact has more recently become impressive in food law but probably less so than in commerce or industry, with scarcely any sector left unmolested. Most of the EEC Directives have been implemented by regulations made under the appropriate sections of the Food and Drugs Act, 1955 and the 1956 Act for Scotland, but regulations proposed for Materials and Articles in Contact with Food (reviewed elsewhere in this issue) will be implemented by use of Section 2 (2) of the European Communities Act, 1972, which because it applies to the whole of the United Kingdom, will not require separate regulations for England and Wales, Scotland and Northern Ireland. This is the first time that a food regulation has been made under this statute. S.2 (2) authorises any designated Minister or Department to make regulations as well as Her Majesty Orders in Council for implementing any Community obligation, enabling any right by virtue of the Treaties (of Rome) to be excercised. The authority extends to all forms of subordinate legislation—orders, rules, regulations or other instruments and cannot fail to be of considerable importance in all fields including food law.

Talk around Britain's application to enter the European Economic Community goes on; it has never really ceased since the first occasion of the French veto, although in the last year or so, the airy promise of the first venture has given way to more sober thoughts on the obstacles to joining and the severe burdens to be carried not only by the British people but by many of our kith and kin beyond the seas if the country becomes a full member of the Community.