Tadamichi Asai

Effect of inorganic binders on the properties of thick film copper conductor

Adhesion strength and solderability of a copper thick film on alumina substrate were studied. Films were prepared with three kinds of inorganic binders, i.e., glass frits, mixture of glass frits and metal oxides, and metal oxides. The effects of inorganic binders on the adhesion and solderability were examined by analyzing physical and chemical behavior of the inorganic binders in the copper thick film during firing. The films with an addition of glass frit or mixtures of glass frit and metal oxide did not provide good adhesion and solderability simultaneously. However, the copper thick film containing 10 wt.% bismuth oxide had excellent characteristics, i.e. high adhesion strength, good solderability, and low sheet resistivity. >

New thick-film copper paste for ultra-fine-line circuits

Key technologies for processing of a thick-film copper conductor applicable to photolithographic techniques are described. A flexo printer was used to obtain a film of less than 2- mu m thickness on a substrate. Using photolithographic techniques, fine-line circuits with 40- mu m-wide copper conductor lines were realized using copper pastes doped with chalcogens. Dense thin films and good adhesion to the substrate were achieved by doping chalcogens from 0.01 to 0.05 wt.%. Characteristics of these conductor films satisfied the standard requirements for hybrid ICs. >

Application of copper conductor and ruthenium containing oxides-glass resistor to high-frequency hybrid ICs for a portable cellular radio

An assessment of a copper-conductor and resistor system and its performance in a high-frequency hybrid application is presented. Resistance of the copper compatible resistor, containing RuO/sub 2/, increases after refiring over 600 degrees C and drastically increases as the firing temperature is raised. Scanning-electron-microscope and energy-dispersive microprobe analyses revealed the existence of a RuO/sub 2/-poor area in the resistor adjacent to the copper terminals. The resistivity in this area is higher than that in areas removed from the terminals, and it increased with the refiring temperature. These facts indicate that the resistance change is caused by the diffusion of Ru to the copper conductor. Various approaches were taken to minimize this phenomenon. The most effective was insertion of a conductor pad between the copper conductor and resistor. Resistors with this type of Ag-Pd conductor pad meet the various requirements for practical application of hybrid ICs. Based on these results, a prototype, high-frequency hybrid IC (voltage-controlled oscillator, VCO) was fabricated. >

Effect of conduction particle size on LaB6 thick film resistor

Abstract In order to obtain guidelines develop a thick film resistor (TFR) fireable in an N2 atmosphere and covering a wide practical range of sheet resistivities, i.e. 10–106 ω □ , the microstructures of TFRs were observed, the sintering behaviour of the conduction particles and glass was analysed and the particle size effect on the formation of the conduction path was simulated. Through these investigations, conductive material properties which influence the characteristics of the TFR have been found. (1) As conduction particles fireable in N2, LaB6 particles have suitable properties such as poor sinterability and good wettability with glass. (2) Particle size also has a large effect on the characteristics of the TFR, and it is necessary to use LaB6 ultrafine particles (UFPs) as conduction particles to cover a wide range of sheet resistivities. Using UFPs with specific surface areas of 8.9 and 83.0 m2 g−1, we found the possibility of developing TFRs fireable in N2 with resistivities of 10–106 ω □ in the LaB6-glass system.