JPH0473871A - Terminal structure of ceramic substrate - Google Patents

Abstract

PURPOSE:To provide the resistance to heat and disturbance such as vibration and improve durability by thermally compressing and bonding a noble metal plated lead wire to an electrode layer, and covering the thermal compression bonding part with a protective layer mainly containing glass. CONSTITUTION:Patterns 42-47 are thick printed on a green sheet 40 by use of platinum paste, a green sheet 41 is laminated thereon and thermally compressed and bonded thereto, and the resulting ceramic substrate is sintered. Terminals 31-33 are integrally formed by etching a copper plate, and gold is plated thereon. The terminals 31-33 are disposed on electrodes 45-57, respectively, and thermally compressed and bonded thereto by heating a wedge 50 to 50O deg.C and pressing each terminal by the wedge, and the thermal compression bonding part is covered with a low melting point glass. Thus, a terminal structure resistant to heat and also disturbance such as vibration can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a terminal structure for a ceramic substrate.

[Prior art] Traditionally, electronic circuits have been made smaller and lighter by forming a pattern on a ceramic substrate with a noble metal paste mainly made of gold or platinum group noble metals and sintering the pattern. Things like this are being done.

Here, as a terminal structure for inputting and outputting signals on this type of ceramic substrate, for example, as shown in FIG.
A, 1b are formed and a normal lead wire 2 made of copper or the like is soldered A, or as shown in FIG. There is a device in which a lead wire made of a noble metal, for example, a platinum lead wire 5 is provided, a ceramic plate 6 is tightly attached thereon, and the platinum lead wire 5 is used as a terminal by being sintered together.

[Problems to be Solved by the Invention] By the way, when such a ceramic substrate is used as a substrate for various calibrators, for example, it can be attached to various combustion equipment and used as a gas sensor to detect gas components such as oxygen concentration in exhaust gas. In such cases, the former soldered terminal structure cannot be used because it is not heat resistant.
In addition, although the latter terminal structure using platinum lead wires has good heat resistance, platinum itself has low strength, so it is necessary to weld reinforcing lead wires, and platinum itself is expensive, so manufacturing costs are low. The problem is that it gets expensive.

Therefore, the present invention provides a terminal structure for a ceramic substrate that has heat resistance and can be produced at a relatively low cost, and also has a highly reliable terminal structure. The purpose is to make it sufficiently durable even when used in a detector installed in a place with high vibrations.

[Means for Solving the Problems] In other words, the present invention has been made to achieve the above object (a ceramic substrate, an electrode layer formed on the substrate and containing a noble metal as a main component, and a ceramic substrate bonded to the electrode layer by thermocompression). A terminal structure of a ceramic substrate having a noble metal plated lead wire, characterized in that the thermocompression bonded portion of the noble metal plated lead wire to the electrode layer is covered with a protective layer mainly composed of glass. This paper focuses on the terminal structure of ceramic substrates.

Here, the ceramic substrate may be a commonly used ceramic substrate, such as a fired ceramic substrate containing alumina, beryllia, mullite, steatite, etc. as a main component.

Next, as a lead wire for precious metal plated lead wire,
For example, lead wires whose main components are starch, iron, etc., or those plated with nickel, chromium, etc., are fine, and any normally used lead wires may be used, but from the viewpoint of processing costs, etc., copper or its alloys may be used. It is desirable to use lead wires of Further, as the noble metal plating in the noble metal plated lead wire, plating using platinum group metals such as platinum, palladium, indium, etc. or gold may be mentioned, but gold plating is particularly desirable from the viewpoint of bonding strength by thermocompression bonding.

As the electrode layer, an electrode layer mainly composed of gold or a platinum group metal can be used, similar to the above-mentioned precious metal plating.Platinum has a moderate electrical resistance, so it is often used as a resistor in electric circuits and as a heater. . Therefore, it is desirable to use platinum because the electric circuit can be used as an electrode as it is.

Also, in order to provide a durable electrode layer on the ceramic substrate, it is desirable to add an appropriate amount of ceramic powder.In this case, in order to increase the bonding strength with the ceramic substrate, the proportion of ceramic powder should be 4 to 20%. It is desirable to add it in

On the other hand, in order to increase the bonding strength with the noble metal plated lead wire, it is desirable that the proportion of ceramic powder added is small. Therefore, the electrode layer should be two layers, with 4 to 20% of ceramic powder added to the electrode layer on the ceramic substrate side, and a smaller proportion of ceramic powder added to the electrode layer on the noble metal plated lead wire side than the electrode layer on the ceramic substrate side. By doing so, it is possible to further improve the bonding strength between the ceramic substrate and the electrode layer, and between the electrode layer and the noble metal methoxylide wire.

In addition, when the electrode layer is made of two layers like this, it is better to use platinum for the ceramic substrate side electrode layer for the reasons mentioned above, and for the noble metal plating lead wire side electrode layer, platinum is used as described in the noble metal plating of the lead wire. Similarly, it is more effective to use gold.

Next, thermocompression bonding involves heating and crimping the noble metal plated lead wire and the electrode layer, melting the bonded portion, and bonding.This method involves, for example, heating a heat-resistant wedge to a high temperature, This can be done by pressing from above the lead wire in the direction of the electrode layer.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

First, FIG. 1 is a partially sectional side view of an oxygen sensor for detecting the oxygen concentration in the exhaust gas of an internal combustion engine, to which the present invention is applied.

In the figure, 10 is a detection section for detecting oxygen concentration, which includes a detection element on a ceramic substrate, and 2 is a detection section 1.
a metal shell formed in a cylindrical shape for gripping the main body 12 and for attaching the sensor to an internal combustion engine; 13 a protector for protecting the tag detection unit 10; is an inner cylinder for gripping the detection part 0 together with the metal shell 12, and is gripped by the metal shell 12 and the inner cylinder 14 via the detection part 10 (spacer 15, filling powder 6 and glass seal) 7. Here, the filling powder 16 is a mixed powder of 1:] of talc and glass, and the glass seal 17 is made of low melting point glass and heated at 600'C.
This is to prevent the detection gas from leaking. Further, a threaded portion 12b for attaching an internal combustion engine is carved on the outer periphery of the metal shell 12, and a gasket 18 is provided at the portion that contacts the wall surface of the internal combustion engine to prevent exhaust gas from leaking.

] 9 is an outer cylinder attached to the metal shell 12 so as to cover the inner cylinder ] 4; 20 is a sealing material made of silicone rubber, which protrudes from the lead wires 21 to 24 and the glass seal 17 shown in FIG. This is for insulating and protecting the connection portions from the detecting section 10 to the terminals 31 to 33.

The connection between the lead wires 2] to 23 and the terminals 31 to 33 is established by applying a sealing material to the outer cylinder 19 in advance as shown in FIG.
0 and the lead wires 21 to 23, connect the crimping fittings 24 to 26 to the tips of the respective lead wires 21 to 23, and then crimping the crimping fittings 24 to 26 to the terminals 3] to 33. It will be done.

Next, the detection section] 0 is manufactured according to the steps (a), (b), and (glue) shown in FIG.

In the figure, 40 and 41 are A I20392% by weight, 5i0, with an average particle size of 1.5 [μm], as in the previous example.
12 parts by weight of butyral resin and 6 parts by weight of dibutyl phthalate (DBP) were added to 100 parts by weight of a mixed powder consisting of 24% by weight, 2% by weight of Ca, and 2% by weight of Mg, and mixed in an organic solvent to form a slurry. The green sheets are formed using a blade, and the green sheet 40 is formed to have a thickness of 1 [rrrn], and the green sheet 41 is formed to have a thickness of 0°2 [rrrn]. 42
Patterns 42 to 47 are thick-film printed with platinum paste containing 7% Al2O3 to Pt;
Reference numeral 3 indicates an electrode pattern serving as an electrode of the detection element 1]; 44 indicates a heating resistor pattern serving as a heater for heating the detection element 11; 45 to 47 apply power to the heating resistor pattern 44 or the detection element; These are electrodes for extracting detection signals, and are connected to terminals 3] to 33, respectively.

As shown in (a), the production of the main detection section O is first started by thick-film printing the patterns 42 to 47 on a green sheet 40 using platinum paste. As is clear from (b), an opening 49 is formed in the green sheet 41 by punching so that the tips of the electrode patterns 42 and 43 are exposed, and the electrode patterns 42 and 43 and the electrodes 45 to 47 in the green sheet 40 are removed. The green sheet 4] is laminated and thermocompressed onto the green sheet 40 so as to cover all the patterns. After that, this laminated thermocompression bonded green sheet 40.4]]500°C
The ceramic substrate is sintered by leaving it in the atmosphere for 2 hours. Next, as shown in (c), a detection element]] is provided in the opening 49, and this detection element 1] is composed of 100% Ti○2 powder with an average particle size of 1.2 [μm].
The opening 49 was filled with a TlO2 paste to which 1 mole part of platinum black was added, and 3% by weight of ethyl cellulose was added to the total powder, mixed in butyl calpitol, and the viscosity was adjusted to 3QO poise. And after printing a thick film so as to cover the tips of the electrode patterns 42 and 43,
It is baked by leaving it in the atmosphere at 1200°C for 1 hour.

Next, the electrodes 45 to 47 of the detection unit 10 and the terminals 31 to 33 are connected as shown in FIG. In addition, terminal 3
1 to 33 are 0. A 2.5mm thick copper plate is integrally formed by etching a 3mm thick copper plate.
[μm] gold plating is applied.

First, as shown in FIG. 5(a), each of the above terminals 31 to 3
3 are disposed on the electrodes 45 to 47, respectively. Then, by heating the 4950 shown in (b) to 500°C and pressing each terminal 31 to 33 with a force of 10 [kg], it is possible to bond the terminals by thermocompression, which is resistant to heat and vibration.

The detection unit 10 manufactured in this manner is to be gripped by the inner cylinder 4 as described above and detects the oxygen concentration in the exhaust of an internal combustion engine. The detection element 11 is heated by applying a heating power source to the terminals 33 and 33, and the oxygen concentration in the exhaust gas can be obtained by detecting a change in the resistance value between the terminals 32 and 33.

As explained above, in the oxygen sensor of this example,
The electrodes and terminals of the ceramic substrate on which the detection element for detecting oxygen concentration is formed are connected by thermocompression bonding using a heated wedge, and since the thermocompression bonding part is covered with low melting point glass, it is possible to The oxygen sensor has a terminal structure that is resistant to external disturbances such as vibrations.

In the above example, when manufacturing the detection part O, the electrode layer is formed by printing a thick film of platinum paste containing 7% ceramic (alumina) powder on a green sheet that will serve as a ceramic substrate. As for this electrode layer, by adjusting the amount of ceramic powder added, the bonding between the substrate and the electrode layer and between the electrode layer and the terminal can be made stronger, and the electrode layer can be made into two layers. It can be seen that the bonding strength can be further improved by adjusting the amount of ceramic powder added to each layer. That is, as shown in FIG. After producing the green sheet, as the electrode layer 11, a paste made by adding alumina (or glass) to platinum (or gold) in the ratio shown in the table below is printed as a thick film on the green sheet, and the paste is heated at atmospheric temperature. 150
A ceramic substrate 1 having an electrode layer 11 is produced by firing under the conditions of 0° C. and a holding time of 2 hours, and further has a diameter of 0. The lead wire 111, which is a 3 [mm] copper lead wire plated with 2.5 [μm] gold, is connected to the electrode layer 11 by pressing a wedge heated to 500° C. with a force of 10 [kgl]. Line 111 was thermocompressed and the broken line B is shown in the figure.
As shown in the table below, the lead wire 111 was pulled in a direction perpendicular to the ceramic substrate 1, and the peel strength between the substrate and the electrode or between the electrode and the lead was measured. In this case, the electrode layer containing 10% alumina has the highest bonding strength, and when the electrode layer 11 is made of two layers, the bonding strength can be made larger than that of a single layer. If the second layer (electrode layer on the lead wire 111 side) is made of an electrode layer mainly made of gold,
It has been found that greater bonding strength can be obtained than when the second layer is an electrode layer mainly composed of platinum.

In addition, NO4 and NO5 in the following table have one electrode layer, with platinum as the main component and the proportion of alumina varied as shown in the table, NO6 and NO7 have two electrode layers, and NO6 has one layer. The second layer, the precious metal plated lead wire side, is fired with 98% platinum and 2% alumina.For NO7, the first layer is 80% platinum and 20% alumina. %, alumina 20%, and the second layer was fired with 95% gold and 5% glass. Further, the mark * in No. 1 indicates that the ceramic substrate and the electrode layer were peeled off, and for the other samples, the electrode layer and the lead wire were peeled off.

[Effects of the Invention] As detailed above, in the present invention, an electrode layer containing a noble metal as a main component is formed on a ceramic substrate, and a terminal is formed by thermocompression bonding a noble metal plated lead wire to this electrode layer. Furthermore, this thermocompression bonded portion is covered with a protective layer mainly composed of glass. This results in a durable terminal structure that is resistant to heat and disturbances such as vibration. In addition, after firing the ceramic board, the precious metal plated lead wires can be thermocompressed, making it easy to connect the terminals.Furthermore, there is no need to use precious metals themselves, as you can simply plate the terminals with precious metals. It can be manufactured at a relatively low cost.

[Brief explanation of the drawing]

1 to 3 are partial cross-sectional views showing the structure of an oxygen sensor according to an embodiment of the present invention, and FIG. 4 is a front view and a cross-sectional view taken along line A-A showing the assembly process of the detection section of the oxygen sensor. FIG. 5 is a front view and a sectional view taken along the line B-B showing the terminal structure of the detection section, FIG. 6 is an explanatory diagram illustrating a measurement test of the bonding strength of the substrate-electrode layer-lead wire, and FIG. 7 and the eighth
The figure is a perspective view showing the terminal structure of a conventional ceramic substrate. 10...Detection part]7...Glass seal 31.32.33...Terminal 40...Green sheet 45, 46. 47... Electrode 50... Model 1.
... Ceramic substrate 11 ... Electrode layer 111 ...
·Lead

Claims (1)

[Claims] A terminal structure of a ceramic substrate comprising a ceramic substrate, an electrode layer formed on the substrate and containing a noble metal as a main component, and a noble metal plated lead wire thermocompressed to the electrode layer, the terminal structure comprising: the noble metal plating. A terminal structure for a ceramic substrate characterized in that the thermocompression bonded portion of the lead wire to the electrode layer is covered with a protective layer mainly composed of glass.