JPH077724B2 - Method for manufacturing ceramic moisture-sensitive element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a humidity sensitive element that detects relative humidity as a change in surface electrical resistance.

[Conventional technology]

Generally, a humidity-sensitive element whose volume resistance change is detected is formed by press-molding a metal oxide powder or forming it into a sheet with a doctor blade or the like and punching it into a constant shape, and then baking the molded body. It is manufactured by printing RuO ₂ paste or the like on the front and back of the obtained sintered body, baking it to form an electrode, and connecting it to an external terminal. The connection between this electrode and the external terminal is made by a wire bonding method using a platinum wire. However, this method is not reliable because the platinum wire connection is unstable. Further, a jig for fixing the external electrode and the sintered body is required to manufacture a large number of elements, and the manufacturing process such as putting the sintered body and the external terminal in and out of the jig becomes extremely complicated. Further, since platinum wire is used, it is also disadvantageous from the economical point of view.

Next, a thick film type moisture sensitive element using surface resistance as a detection means is manufactured by printing a gold paste or the like on an alumina substrate and baking it. Furthermore, the humidity-sensitive element manufactured by this method generally has an extremely high resistance in the low humidity region, and is substantially 40%.
It is difficult to detect humidity below% RH. Further, in order to reduce the resistance, it is possible to increase the area of the comb-shaped electrode and reduce the interval between the combs, but in this case, the structure of the sensor becomes extremely large, and the place where it is used is limited. It Furthermore, it is extremely difficult to maintain the uniformity of performance.

In addition, when a comb-shaped electrode is baked on a porous moisture-sensitive element composition molded body without using an alumina substrate and an external terminal is soldered to this electrode, when soldered in a flux bath, the soldering deteriorates and There is a problem that the wet characteristic is also lost.

[Problems to be solved by the present invention] The electrodes of the sintered body and the external terminals are securely connected, and the reliability of electrical conduction between them is very high, and the humidity can be detected on the low humidity side. The manufacturing process is extremely simple, mass production is possible, and an extremely economical method of manufacturing a ceramic moisture-sensitive element is to be provided.

[Means for solving problems]

The present invention, a molded porous sintered body having a moisture-sensitive performance, after printing a comb-shaped electrode and baked, sandwich the end of the electrode with a lead frame coated with flux, after soldering, 300
A method for manufacturing a ceramic moisture-sensitive element, which is characterized by performing heat treatment at a temperature of not less than ° C.

The present invention is usually carried out as follows. First, a molded porous sintered body having a moisture-sensitive property is formed by mixing powders containing alumina, titania, zirconia, or a transition metal oxide as a main component, kneading, and molding to make the molded body porous. Thus obtained by firing. Molding is usually performed by a dry tableting method or punching of a sheet manufactured by a doctor blade method, but the method is not particularly limited. Further, it is preferable that the shape of the molded body is a plate-like shape in which the lead frame can be easily sandwiched and the directionality of the comb-shaped electrode can be clearly confirmed. Next, a conductive paste is printed on one surface of the sintered body in a comb shape and baked. Next, the pad portions at both ends of the comb-shaped electrode are sandwiched by a lead frame coated with flux, dipped in a solder bath for a predetermined time, and soldered. Then 300
Heat treatment is performed at a temperature of ℃ or more. As a result, a humidity sensitive element having excellent characteristics can be obtained.

Hereinafter, examples will be described.

〔Example〕

Titanium oxide and sodium selenite (Na ₂ S ₂ O ₃ ) were weighed so that the mol% was 96.5% and 3.5%, and 1 was measured with a pot mill.
Mixed wet for 6 hours. The obtained mixture was dried at 140 ° C. for 4 hours, granulated, and a raw material powder was prepared. This raw material powder was pressure-molded under the condition of 500 kg / cm ² , and the diameter was 7 mm and the thickness was 0.8 mm.
A disk-shaped molded body of

This compact was sintered at 900 ° C. for 3 hours, and then gold / platinum / palladium paste was screen-printed in a comb shape on one surface of the sintered body and baked at about 850 ° C. Furthermore, the comb-shaped pad on both ends was sandwiched by the flux-applied lead frame normally used for hybrid ICs and usually used for hybrid ICs.

Next, the sandwiched portion was dipped in a solder bath for 3 seconds for soldering. Further, this element was heat-treated at 350 ° C. for 5 minutes. Although 1000 humidity-sensitive elements were manufactured by this method, all the elements showed the same pattern of humidity-sensitive characteristics, and there were no broken elements. The moisture sensitivity characteristics of the obtained element are as follows, and the resistance value in the low humidity range is lower than that of the thick film type moisture sensitivity characteristic, and it is an element that can accurately measure in the low humidity range. It was

[Effects of the Invention] According to the present invention, it is possible to reliably connect the electrode of the sintered body and the external terminal, and to make the reliability of electrical conduction between them extremely high. Further, the ceramic moisture sensitive element obtained by the present invention can measure humidity on the low humidity side. INDUSTRIAL APPLICABILITY The present invention is a method in which the manufacturing process is extremely simple and mass production is possible, and a ceramic moisture-sensitive element can be manufactured extremely economically.

[Brief description of drawings]

FIG. 1 is a front view showing the form of a moisture sensitive element manufactured by the manufacturing method of the present invention. The numbers in the figure are as follows. 1 ... Sintered body, 2 ... Comb type electrode, 3 ... Comb type electrode pad 4 ... Lead frame, 5 ... Solder

Claims (1)

[Claims] 1. A comb-shaped electrode is printed on a molded porous sintered body having a moisture-sensitive property and baked, and the end of the electrode is sandwiched by a lead frame coated with flux. After soldering, 30
Manufacturing method of ceramic moisture-sensitive element characterized by performing heat treatment at 0 ° C. or higher