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An investigation to evaluate the suitability of anodised aluminium as a substrate material has shown that the relatively high coefficient of thermal expansion of the aluminium caused the brittle cermet resistors to craze giving rise to unstable resistance values whereas PTF resistors appeared to suffer no ill effects. The work was implemented in conjunction with selection of low temperature thick film conductor and resistor inks to achieve the optimum combination of anodised aluminium substrate and ink system. These inks were then printed and fired on anodised aluminium, aluminium nitride and alumina substrates, and the physical and electrical properties of the inks and substrates compared. A combination of modest success, employing polymer resistors and cermet conductors, produced viable circuits with resistors of reasonable stability. A low power hybrid device, with surface mounted components, was employed to further validate the substrate/ink combinations in ongoing tests.

The purpose of this paper is to present the results of thermal analysis of cermet resistors made on alumina or LTCC substrate and polymer thick-film resistors embedded in FR-4 substrate.

The study was performed using a thermal imaging method. The research was carried out with an additional consideration of such factors as sheet resistance (which depended on the type of resistive paste), the size and topology of element and the kind of contact material (Cu, Ag or Ni/Au). A few key points on the element were specified for which a more thorough analysis was carried out. The results were approximated by physically acceptable function which allowed to determine the influence of different mechanisms of heat transfer and determine their time and thermal constants.

The effectiveness of heat dissipation from resistor is determined by the type of substrate material, width of conductive paths, and contact material. The best results were observed for elements with wider conductive paths made of Cu or Ni/Au. The LTCC substrate ensures the fastest achieving of stable temperature on the component. The changes of the temperature gradient in time can be described by a formula consisting of two or three exponent parts, each one presenting different mechanism of change.

These studies do not include more detailed determination of nature of found mechanisms of change. There has not also been established what form of the formula is more accurate physically description of the results for respective structure.

The results provide important data of the thermal properties of the chosen materials. This allows to determine their usability for specific applications where heat distribution plays an important role. The used analysis method is proven to provide reliable results and can be considered to be used for further studies in that subject.

The purpose of this paper is to present the properties of thick-film resistors made of novel pastes prepared from glass and graphite.

Graphite-based resistors were made of thick-film pastes with different graphite-to-glass mass fraction were prepared and examined. Sheet resistance, temperature coefficient of resistance, impact of humidity and short-term overload were investigated. The properties of the layers fired in atmospheres of air at 550°C and nitrogen at 875°C were compared.

Graphite-based resistors with various graphite-to-glass ratios made possible to obtain a wide range of sheet resistance from single O/square to few kO/square. These values were dependent on firing atmosphere, paste composition and the number of screen-printed layers. The samples made of paste with 1:1 graphite-to-glass ratio exhibited the temperature coefficient of resistance of about −1,000 ppm/°C, almost independently on the firing atmosphere and presence of a top coating. The resistors fired in the air after coating with overglaze, exhibited significantly lower sheet resistance, reduced impact of humidity and improved power capabilities.

In this paper, graphite-based resistors for applications in typical high-temperature cermet thick-film circuits were presented, whereas typical graphite-based resistors were fabricated in polymer thick-film technology. Owing to very low cost of the graphite, the material is suitable for low-power passive circuits, where components are not subjected into high temperature, above the typical temperature of operation of standard electronic components.

Polymer thick film circuits have been used in consumer appliances, a trend that is growing as one of the major technologies in Japan in this field. This paper discloses the state of the art of the processes involved along with the main features of the circuits. PTF has established a performance that equals that of the cermet type in some applications, which produces cost advantages for PTF circuits on polymer and/or ceramic substrates for wider applications.

The purpose of this paper is to characterize electrical properties of nickel-phosphorus (Ni-P) thin-film resistors made on FR-4 laminate in a wide range of temperature (from −180 to 20°C).

The study was performed using resistors made of Ni-P foil with two different thicknesses (0.1 or 0.05 μm) and sheet resistances (100 or 250 Ω/sq), respectively. The resistance rectangular resistors had length and width from the range between 0.59 and 5.91 mm. The resistance versus temperature characteristics and their distribution as well as resistors ' durability to low-temperature thermal shocks were investigated.

The results showed almost linear temperature dependence of resistance with a negative temperature coefficient of resistance of about −95 ppm/°C for 250 Ω/sq layer and −55 ppm/°C for 100 Ω/sq layer. A very small dimensional effect was observed for sheet resistance as well as for R(T) characteristic. Thin-film resistors are also characterized by very high durability to low-temperature thermal shocks.

The results presented in this paper can be very useful for low-temperature applications of thin-film resistors made on printed circuit boards. They suggest possibility of wide applications of these components in a wide temperature range.

A weak change of resistivity caused by visible radiation both for commercial and for model thick‐film (cermet) resistors (TFRs) has been observed and studied in the temperature range 10–380 K. A possible origin of this photoelectric effect in terms of photoexcited electrons emitted from the metallic grain surface into the glassy region is discussed.

Electro‐Science Laboratories have recently introduced two new mixed‐bonded ternary conductors that form excellent cermet resistor terminations. Made of platinum, palladium, and silver (Pt/Pd/Ag), ESL 9565 and 9566 are more oxidation‐resistant during overglaze firing (500–525°C) than more commonly used palladium/silver (Pd/Ag) metallisations. Therefore they solder wet more easily after overglazing than with Pd/Ag.

Thermal ageing experiments on various thick film resistor systems have shown that resistance change is caused by a number of different mechanisms with different time dependences. Three distinct types of behaviour have been identified: corrosion due to ambient attack; diffusion through resistor interfaces with conductor terminations or through the resistor top surface; and stress relief within the bulk of the resistor. Wherever possible the dominant mechanism has been identified and the activation energy and time dependence of the ageing process have been determined.

Materials based on polymer films which are deposited by a screen printing process onto an inert substrate are finding innumerable applications in the fabrication of circuits in modern electronic assemblies. At one time the concept of ‘polymer thick film’ (PTF) technology might have been seen as an alternative to printed circuits on organic substrates or to thick film circuits on ceramic. The point is made here that, resulting from the very diverse range of materials now available, it is better to regard PTF as a supporting technology to be used in conjunction with other techniques from printed circuit or hybrid film technology. There are many examples where individual PTF materials have been selected and used in assisting or enabling roles with obvious technical advantages and significant commercial benefit.

The purpose of this paper is to study tuneable positive temperature coefficient (PTC) effect in polymer-wax-carbon composite resistors. The resistivity dependence on temperature of composite resistors made of carbon fillers dispersed in an organic matrix is known to be strongly affected by the matrix thermal expansion. High PTC effects, i.e. essentially switching from resistive to quasi-insulating behaviour, can be caused by phase changes in the matrix and the assorted volume expansion, a behaviour that has been previously shown with both simple organic waxes and semi-crystalline polymers. However, waxes become very liquid on melting, possibly resulting in carbon sedimentation, and tuneability of semi-crystalline polymers is limited.

The authors therefore study a ternary polymer-wax-conductor (ethylcellulose-octadecanol-graphite) composite resistor system, where polymer and wax fuse to a viscous liquid on heating, and re-solidify and separate by crystallisation of the wax on cooling.

It is shown that with appropriate formulation, the resulting resistors exhibit strong PTC effects, linked with the melting and crystallisation of the wax component. The behaviour somewhat depends on sample history, and notably cooling speed.

The phase equilibria and transformation kinetics of the polymer-wax system (including possible wax polymorphism), as well as the exact mechanism of the conductivity transition, remain to be investigated.

As many compatible polymer-wax systems with different melting/solidification behaviours are available, ternary polymer-wax-conductor composite PTC resistors allow a high tuneability of properties. Moreover, the high viscosity in the liquid state should largely avoid the sedimentation issues present with binary wax-conductor systems.