JPS62262494A - Manufacture of multilayer circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Internal circuits such as conductor patterns and ground patterns that require large currents to pass through are made of thick films, and fine circuits such as the ICC indirect four circuits formed on the top are made of thin films. ,
A method for manufacturing a multilayer circuit board in which copper paste is used for internal conductor patterns, and gold paste is used for terminals and contact areas with thin film circuits.

[Industrial application field]

The present invention relates to a method for manufacturing a composite circuit using thick film ICs and thin film ICs.

2. Description of the Related Art In order to process a large amount of information at high speed, information processing devices are becoming more integrated and have a larger capacity, and thick film ICs and thin film ICs are used to form electronic circuits.

Here, thick film ICs do not require fine patterns and are used for applications where large currents flow, and thin film ICs are used for semi-donor ICs and L
It is often used for applications that require SI to process signals and fine patterns.

However, as the density of circuits increases and multilayer technology advances, composite circuits are now being formed using both thick film and thin film technologies.

The present invention relates to a method for manufacturing a composite circuit that can reduce costs.

[Conventional technology]

In forming multilayer circuits with thick film ICs and thin film ICs, power lines and ground lines are patterned on the substrate using thick film technology, and fine patterns are formed on the surface layer to connect the semiconductor IC and the circuit using thin film technology. things are being done.

In such applications, gold (Au) and silver-palladium alloy (AgPd) are used as conductor pattern forming materials for thick film ICs.
Alternatively, various conductor pastes mainly composed of copper (Cu, etc.) are commercially available, and these can be mixed with alumina (α-Aj2z
O: +) Screen printing is performed on a ceramic substrate and fired, and if multilayering is required, an insulating paste whose main component is glass is screen printed and fired, and then a conductor pattern is formed on top of this. ing.

Here, the conductor pattern needs to have as low a sheet resistance as possible, and from this point of view, it is suitable to use copper paste.

However, copper is easily oxidized and therefore needs to be fired in a nitrogen (N2) atmosphere, but glass contained in the paste tends to remain on the surface after firing.

Therefore, when forming a thin film circuit on this, phosphoric acid (
It is necessary to remove a thin layer of glass using, for example, H, POff).

Furthermore, even when fired in an inert atmosphere, the surface layer of copper is often oxidized, and in this case it is necessary to remove the oxidized layer.

In addition, when crimping a flexible printed board with an elastomer to a copper terminal for the purpose of connecting the circuit to the outside, good contact cannot be obtained, so surface treatment such as gold plating is required, which requires a complicated process. there was.

Next, the problem when using silver palladium paste is that the sheet resistance is as high as about 0.06Ω.

On the other hand, gold has a sheet resistance of about 0.02 Ω/mouth, and although it is a stable metal, it is expensive.

Therefore, conventionally, when copper paste is used, a method has been adopted in which contact portions and terminal portions are plated with gold, or a pattern is formed using gold paste.

[Problem that the invention seeks to solve]

When forming a multilayer circuit on a ceramic substrate, there is a problem with oxidation when using copper paste to form internal conductor patterns, silver-palladium paste cannot be used due to its high resistance, and gold paste is expensive. There is a problem that it is difficult to use.

Therefore, the challenge is to form a thick film circuit with excellent characteristics without increasing costs.

[Means for solving problems]

The problem mentioned above is that the process of forming a multilayer circuit on a ceramic substrate using a combination of thick film hybrid technology and thin film hybrid technology involves screen printing terminals and contact parts using gold paste on the substrate. a process of screen printing a copper paste for low-temperature firing to form a conductor pattern, connecting the circuit to the terminal part and contact part and firing it, and a process of screen printing an insulating paste on the copper conductor pattern. The present invention is solved by a method for manufacturing a multilayer circuit board, which comprises the steps of: baking and coating the substrate; and forming a thin film hybrid circuit on the substrate and connecting the circuit to the previously formed contact portion. be able to.

[Effect]

The present invention solves the above problem by using gold paste for the connection part with the external circuit and the contact part with the three-film conductor, and forming the other conductor patterns by screen printing copper paste. .

In this case, if the gold paste and copper paste are layered and fired, mutual diffusion will occur and the purpose will not be achieved.

In other words, the sheet resistance of the copper conductor pattern increases.

Therefore, the present invention uses gold paste 9 to screen-print terminals and contact areas, and then fires at a high temperature of 800 to 950°C, and then screen-prints a conductor pattern using a copper paste for low-temperature firing. By firing at a low temperature of 750°C, significant interdiffusion can be eliminated.

In addition, at this time, the overlapped part of the gold paste and copper paste is 5
It is economical to limit the thickness to about 00 μm.

By doing this, a conductor pattern with low resistance can be formed, and since the terminal portion and the contact portion are formed of a thick gold film, contact failure will not occur.

〔Example〕

FIG. 1 is a circuit diagram of a thermal head to which the present invention is applied, and FIG. 2 is a perspective view thereof.

That is, the thermal head has a structure in which a large number of heating resistors 1 for printing are patterned in a horizontal row on an alumina substrate, and ICs 2 for driving the resistors 1 are similarly mounted in a horizontal row.

On the board, a common conductor 3 that supplies current to a large number of heat generating resistors 1, a power supply line that drives a large number of ICs 2, a ground, etc. are thick films, and the heat generating resistor 1 is connected to a common conductor 3 and an IC.
A conductor pattern for circuit connection to IC 2 and a signal line of IC 2 are formed using a thin film.

Here, the multilayer circuit of thick film and thin film is formed in the dashed area 4 in FIG. 1, and in the elongated rectangular area 5 in FIG.

Examples of the present invention are as follows.

On the alumina substrate 6, only the area where the heating resistor 1 is formed is partially glazed, but the contact area (through hole area) between the terminal area 7 on the alumina substrate 6 and the thin film pattern has a thickness of approximately 5 μm. The thickness was screen printed with gold paste and fired in air at a temperature of 870°C.

Next, screen print copper paste for low temperature firing to make all thick film conductor patterns including common conductor 3.
It was formed by firing at 00°C.

Next, an insulating paste mainly composed of glass was screen printed on the conductor pattern and baked at 650° C. to form a protective layer.

3 is a cross-sectional view taken along the line x-x" in FIG. 2, and FIG. The formed terminal portion 7 and contact layer 9 of the contact portion 8 and the conductor pattern 10 formed by printing and firing the copper paste are printed with a slight overlap of about 500 μm, and the conductor pattern 10 is printed with a slight overlap of about 500 μm. Each of them is covered with a protective layer 11.

If the gold layer and copper layer are formed by partially overlapping each other by changing the firing temperature using the thick film method as described above, mutual diffusion will be slight, so the resistance value of the connection part will not increase, and the contact between the terminal part 7 and the copper layer will not increase. Since layer 9 is made of gold, its contact resistance is low.

Next, on the substrate, tantalum nitride (TatN) is sputtered and patterned to form a heating resistor 1, and aluminum (A 6 ) is sputtered and patterned to form a heating resistor 1 on a common conductor 3. A conductor pattern for circuit connection to the IC 2 and an upper conductor pattern 12 on the elongated rectangular region 5 having a multilayer structure were formed.

By doing this, it is possible to significantly reduce the cost compared to the conventional method of forming all conductor patterns using gold paste or screen printing copper paste and applying gold plating after firing, and also provides low resistance. conductor patterns can be created.

〔Effect of the invention〕

As described above, by carrying out the present invention, a multilayer board with low resistance and low contact resistance with an external circuit can be manufactured at a lower cost than in the past.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a thermal head to which the present invention is applied, Fig. 2 is a perspective view of a thermal head to which the present invention is applied, Fig. 3 is a sectional view taken along line xx' in Fig. 2, and Fig. 4 2 is a cross-sectional view of the contact portion taken along line YY' in FIG. 2. FIG. In the figure, 1 is a heating resistor, 2 is an ICl, 3 is a common conductor, 7 is a terminal part, 8 is a contact part, 9 is a contact layer, 10 is a conductor pattern,
11 is a protective layer, and 12 is an upper conductor pattern.

Claims (1)

[Claims] The process of forming a multilayer circuit on a ceramic substrate using a combination of thick film hybrid technology and thin film hybrid technology includes screen printing terminal parts and contact parts on the substrate using gold paste. The conductor pattern is formed by screen-printing copper paste for low-temperature firing.
a step of connecting a circuit to the terminal portion and the contact portion and firing it; a step of screen printing an insulating paste on the copper conductor pattern and baking it to cover it; and a step of forming a thin film hybrid circuit on the substrate and first A method for manufacturing a multilayer circuit board, comprising the step of connecting the formed contact portion to a circuit.