High-performance lead-free negative temperature coefficient temperature-sensitive thick film and preparation method thereof

Abstract

The invention discloses a high-performance lead-free negative temperature coefficient temperature-sensitive thick film and a preparation method thereof. Major composite components are combined in two combination modes. In an inorganic phase I combination mode, (1-t)Ba1-yMyFe1-xSnxO3+tBaCo<II>zCo<III>2zBi1-3zO3, wherein t is more than or equal to 0.4 and less than or equal to 0.95 and is a molar ratio; and in an inorganic phase II combination mode, (1-m-1)Ba1-yMyFe1-xSnxO3+mBaCo<II>zCo<III>2zBi1-3zO3+1 / 2Ag2O, wherein m is more than or equal to 0.3 and less than or equal to 0.65; l is more than or equal to 0.05 and less than or equal to 0.3; m and l are molar ratios; and the composite components are uniformly mixed with an organic carrier in the mass ratio of 75:25 so as to form thick film resistance paste. The preparation method comprises the following steps of: printing the paste on a substrate by a screen printing process; flattening, baking, pre-sintering and repeatedly printing so as to obtain a thick film biscuit with a required thickness; and sintering the biscuit at the temperature of between 750 and 850 DEG C and preserving heat for 40 to 80 minutes so as to obtain the lead-free negative temperature coefficient temperature-sensitive thick film. The thick film has a simple preparation process and a low film forming temperature, the film thickness is between 10 and 100 mu m, the temperature sensitive constant value is between 2,500 and 5,500 K, the room temperature resistivity is between 150 ohm.cm and 10 M ohm.cm and the aging resistant time is over 800 hours.

Description

technical field [0001] The invention relates to the preparation of a thermistor, in particular to a high-performance lead-free negative temperature coefficient thermosensitive thick film and a preparation method thereof. Background technique [0002] Negative Temperature Coefficient Thermistors (Negative Temperature Coefficient Thermistors, abbreviated as "NTCR") refer to a type of electronic information material device whose resistance decreases exponentially with the increase of temperature. These NTC thermosensitive devices are generally composed of bulk materials based on spinel and perovskite structures. Among them, the spinel-type NTCR mainly contains elements such as Fe, Mn, Cu, Ru, Ni, Cd, Sb, W, and rare earth; and the perovskite structure can be YFe x mn 1-x o 3 、BaBiO 3 or BaBiO 3 / BaTiO 3 Composite materials, etc. Thermistors made of these traditional NTC thermal materials can basically meet the needs of the traditional electronics industry. However, wit...

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Problems solved by technology

However, the performance of film-type NTC thermistors prepared from traditional spinel NTC thermistor ceramic materials is far inferior to that of bulk NTC thermistors. The two most difficult key points are: (1) room temperature The resistivity is too high (usually above 1MΩ??cm); (2) the thermal constant is low (the thermal constant above 1 MΩ??cm is usually lower than 3500K, for such a high room temperature resistivity of bulk ceramic materials The corresponding thermal constant is generally above 4500K)

In addition, an important problem usually encountered in film resistance devices is: In the preparation process of thick film resistance devices, it is usually necessary to add inorganic binders to increase the density, conductivity and improve the stability of the combination with the substrate. This inorganic binder is used The most frequent is the toxic PbO, and the content is usually more than 50%

These two systems both contain expensive ruthenium, and the thermal constant does not exceed 3500 K. The linearity of the relationship between resistivity and temperature reciprocal is poor, and the performance is far from the requirements of bulk NTC thermistors. They are only suitable for low sensitivity occasion use

In addition, since these two systems do not use glass additives, the film-forming properties are relatively poor

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