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The paper gives design guidelines for polymer thick‐film technology (PTF). After an introduction reviewing the main PTF properties, materials and processes, detailed PTF design rules are presented. They are conservative, to achieve high production yield. The design rules are based on the considerable experience in the companies of the authors and of the persons mentioned in the acknowledgements, as well as on information from the open literature and from materials suppliers. The design guidelines are intended primarily for designers, but they are also important for production personnel, to facilitate a close coupling between design and production, and thus provide optimum use of PTF and obtain high production yield.

The properties and constituents of PTF inks are outlined. Surface resistivity in relation to PTF inks is defined. Applications of PTF inks are discussed with emphasis on potential design and cost benefits for SMT applications, including crossovers, polymer multilayer, printing through holes, printed resistors, carbon key pads, moulded and three‐dimensional circuits.

The paper describes the results obtained by the integration of Polymer Thick Film and Printed Circuit Technologies. Polymer Thick Film (PTF) Technology, applied to PCB manufacturing, helps the designer's task considerably and offers an interesting way to achieve time and cost reduction. The use of conductive and dielectric materials to generate cross‐overs and low interconnection density multilayers on epoxy‐glass substrates is shown and basic design rules are discussed. The performances of PTF conductive materials from two different suppliers are investigated in terms of conductivity, current carrying capacity and contact resistance with the copper‐clad layer. Surface and bulk insulation resistance, capacitance, loss factor and breakdown voltage are studied for dielectric materials from two different suppliers. The effects of environmental tests, i.e., thermal shocks, high temperature storage and temperature‐humidity‐bias test, on the performances of dielectric and conductive PTF are investigated by means of suitable test patterns. Application examples of Transmission System boards are discussed in terms of design and manufacturing times and costs.

The results of a characterisation carried out on thick film resistors (TFRs) with dimensions reduced below the usual limits are reported in this paper. The test vehicle was a purpose‐designed test pattern with resistors whose dimensions reached a limit of 0·3 mm in length and 0·4 mm in width. The proposed aim of the work was to look for dimensional limits where TFRs could still give acceptable performances, though, if possible, keeping unchanged the materials system and the process conditions which are used in the authors' thick film hybrids facility.

The square resistance of thick film resistors on dielectric layers can show a very complex behaviour. From resistance measurements of a test pattern three suitable paste parameters Q(L), M(L) and A(L) can be calculated as numerical functions of the resistor length L. All formulae needed for establishing an accurate resistor layout by means of the parameters are presented in this paper. The three‐dimensional surface of the square resistance as a function of length L and width W can also easily be calculated.

A new model for thick film resistor calculation accounts for the physical effects which make variations in local sheet resistivity and local volume resistivity: geometry and terminal diffusion effects. Taking the criterion of homogeneity in the observations of local resistivity, a resistor is transformed geometrically and electrically into equivalent modular parts. Comparing the resistor transformed by equivalent geometrical and electrical transformation (EGET) with an ideal resistor a new semi‐empirical formula for thick film resistor calculation was evaluated. This model takes into account the technological process which makes possible more accurate resistor projection compared with other models.

ISHM (UK) presented a technical meeting on this topic on the 23rd October 1982 at the Cunard International Hotel, London. The meeting was attended by some 50 engineers, both those involved in the field of hybrids and potential users. It was generally felt that this was a useful meeting but more especially that it would have appealed to many potential users of hybrids, had the right people been able to be contacted.

A new method of studying the accelerated ageing of interconnection materials is applied to a high‐stability thick film resistor system (the Du Pont HS‐80 system). The new method, referred to hereafter as the in‐situ method, allows measurement of the electrical resistance of a thick film resistor to a resolution of a few ppm during accelerated ageing. With the in‐situ technique, the electrical resistance measurements are performed at the elevated ageing temperature during the ageing treatment, whereas with the conventional ageing method the resistance measurements are carried out at room temperature, between subsequent annealing steps. The measuring resolution obtainable with the in‐situ method is orders of magnitude better than with the conventional method. The ageing kinetics can therefore be studied on a shorter time scale and in greater detail than with the conventional method. In this paper, the authors use the in‐situ method to study the accelerated ageing of the Du Pont HS‐80 thick film resistor system, encapsulated with a proper glaze. It will be shown that kinetics of the resistance drift observed in this system cannot be described by an Arrhenius‐type equation. The ageing data can only be interpreted in terms of a kinetic model incorporating a spectrum of activation energies for the ageing process. Such a model is given, and is shown to provide a good explanation of the observed ageing behaviour. The physical process that causes the observed ageing is most probably diffusion of silver from the contacting terminals into the amorphous matrix of the thick film resistor.

For thick film resistor materials with low sheet resistivity (less than 10 ohm/□) sheet resistivity increases with decreasing resistor length, when terminated with Pd alloy based conductors. This is due to the reaction of palladium from the thick film conductor and bismuth ruthenate (Bi2Ru2O7), which is the active phase in thick film resistor material. The experimental results indicate the formation of Pd/Bi solid solution on the interface between the conductor and resistor. Because of its higher specific resistivity, this layer functions as an additional source of resistivity.

The purpose of this study was to determine the effects of chickpea (Cicer arietinum) protein hydrolysates prepared at two degrees of hydrolysis (DH) on lipoprotein profile and on oxidant status in cholesterol-fed rats.

Eighteen male Wistar rats (220 ± 10 g) were divided into three groups and fed for 30 days a diet containing 20 per cent casein supplemented with 1 per cent cholesterol and 0.5 per cent cholic acid. During the experimentation, the first and the second groups received daily by gavage 250 mg of chickpea protein hydrolysates/rat at DH = 8 per cent (CPH8) and DH = 17 per cent (CPH17), respectively. The third group, named control group (CG), received water under the same conditions.

Serum total cholesterol concentrations were reduced in CPH8 (p < 0.0073) and CPH17 (p < 0.0004) groups versus CG. This reduction corresponded to a lower very-low-density lipoprotein (VLDL)-cholesterol (p < 0,0019). CPH17 reduced low-density lipoprotein- and high-density lipoprotein (HDL)-cholesterol (p < 0.0001) but increased apolipoprotein A4 (p < 0.002) concentrations and lecithin-cholesterol acyltransferase activity (p < 0.0001). APOA1 remained unchanged in the treated groups. Liver total and esterified cholesterol contents were twofold lower in both treated groups versus CG. CPH8 increased triacylglycerols and phospholipids (p < 0.0001) contents, while CPH17 decreased those of unesterified cholesterol (p < 0.0016). Compared with CG, CPH8 and CPH17 reduced serum (p < 0.0001) and lipoprotein hydroperoxides by stimulating paraoxonase activity (p < 0.0001). However, only CPH17 treatment reduced serum, VLDL- and HDL-malondialdehyde contents and improved glutathione peroxidase activity (p < 0.061).

Thus, chickpea protein hydrolysates and especially hydrolysed at DH = 17 per cent may have a great potential for use as a nutraceutical to reduce hypercholesterolaemia and, by consequence, oxidative stress. Therefore, the degree of enzymatic hydrolysis has a significant influence on the production of potent bioactive peptides.