JPS6048338B2 - Thermal head manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a thermal head with good yield and high reliability.

A thermal head used for thermosensitive recording is composed of a large number of heat generating resistors and a drive circuit for driving these heat generating resistors, and these are usually arranged on the same substrate.

FIG. 1 schematically shows the mounting structure of such a thermal head, in which 1 is a ceramic substrate, 2 is a heating resistor section, and 3 is a drive circuit section. The heating resistor section 2 generally has a structure in which the heating resistor is disposed on a glaze layer serving as a thermal resistance layer in order to prevent the heat of the heating resistor from escaping to the substrate 1 side.

The glaze layer is formed by a printing and baking process.
On the other hand, the drive circuit section 3 uses a matrix drive method,
There is a parallel drive type, but in either case, it is configured to include a thick film circuit. For example, in the former case, thick film conductors and thick film insulators are used as conductors and interlayer insulators of multilayer wiring forming matrix wiring. These thick film circuits are also formed through printing and firing steps, similar to the glaze layer in the heating resistor section 2. However, the firing temperatures of the glaze layer in the heating resistor section 2 and the thick film circuit in the drive circuit section 3 are not necessarily the same, and the firing temperature of the latter is generally lower than that of the former.

Therefore, in the manufacturing process, it is necessary to first fire the cruise layer and then fire the thick film circuit. However, the glass in the glaze layer has a softening point at a temperature approximately 200 to 300°C lower than the firing temperature, so when the thick film circuit is fired, dust and paste deposited on the glaze layer and paste during printing of the thick film circuit are removed. etc., react with the glaze layer, causing unevenness in the glaze layer. For this reason, the heating resistor formed on the glaze layer is likely to have variations in resistance value or breakage, resulting in a decrease in yield and reliability. In order to avoid such inconveniences, it is possible to lower the firing temperature of the thick film circuit by about 500°C compared to that of the glaze layer. It is difficult to obtain materials that can be fired.

On the other hand, as shown in FIG. 2, the substrates include a substrate 1 on which a heating resistor section 2 is formed, and a substrate 1 on which a drive circuit section 3 is formed.

It is also possible to divide it into two parts. However, in this case, the divided substrates 1,,1. above. Electrical connection between a certain heating resistor section 2 and the drive circuit section 3 becomes difficult. For example, wire bonding or etched copper foil may be used for this connection, but if the density of heat generating resistors is 8/WgTt or more, all of them may be driven by such means. Correct connection to the circuit section 3 is very difficult and yields are significantly reduced. This invention was made in view of the above points, and its purpose is to avoid damaging the glaze layer on which the heating resistor is disposed, and to prevent the connection between the heating resistor Z body and the drive circuit section. An object of the present invention is to provide a method for manufacturing a thermal head that can be carried out reliably and easily.

This invention provides a first substrate in which a glaze I layer on which a heating resistor is disposed is formed by printing and baking, and a second substrate in which a thick film circuit in a drive circuit portion is formed by printing and baking. The first and second substrates are formed separately, and the first and second substrates are fired or hardened at a temperature lower than the firing temperature of each of the glaze layer and the first thick film circuit and lower than the softening point of the glaze layer. Alternatively, after joining and integrating at least the end faces with resin, a heating resistor is formed on the glaze layer, and then on the first and second substrates,
A conductor pattern is formed by vapor deposition or sputtering and etching to straddle the first and second substrates, the conductor pattern consisting of a thin film whose one end is connected to the heating resistor and whose other end is connected to the drive circuit section. do.

In this way, the glaze layer and the thick film circuit can be formed separately in advance, and since the firing or curing temperature of the glass or resin for bonding the first and second substrates is low, the thick film can be formed during the process. Not only the circuit but also the glaze layer will not be damaged in any way.

In addition, since the first and second substrates are equivalent to a single substrate by bonding their end faces together, they can be connected to the heat generating resistor using conductor patterns without using difficult methods such as wire bonding. Electrical connection with the circuit section can be made, and mass productivity is significantly improved. Examples of the present invention will be described below. FIG. 3 shows the steps of an embodiment of this invention. First, a first substrate 1, on which a glaze layer 11 is formed by printing and baking, and a thick film circuit 12 (
A second substrate 1 on which a thick film conductor or thick film insulator is formed by printing and firing. and are formed individually. board 11,
The material 12 is, for example, ceramic. In this case, the end surfaces of the substrates 1, 12 to be joined are tapered.
These first and second substrates 1, 1.

The tapered end surfaces of the glass are butted together, glass paste is printed in the gap between the butts, and then fired. FIG. 3a shows the first and second substrates 1, .
The tapered end faces of 12 are bonded using glass 13 as an adhesive layer, and the first and second substrates 1, 12 are shown integrated. The reason why the end surfaces of the first and second substrates 11 and 12 to be joined are tapered is to increase the joining area and the joining strength. Here, the firing temperature of the glaze layer 11 is IIOOOC) and the softening point is 900.
If the firing temperature of the thick film circuit 12 is 900°C, the glass 13 used has a firing temperature of about 500'C.

If the thick film circuit 12 is printed and fired after printing and firing the glaze layer 11 as in the conventional method, the glaze layer 11 will be softened during firing of the thick film circuit 12, and if there is any deposit on the glaze layer 11, the surface will be damaged. As mentioned above, unevenness is caused. In contrast, according to the present invention, printing and firing of the thick film circuit 12 is performed in advance on the second substrate 12 that is separate from the first substrate 11 on which the glaze layer 11 is formed, so that the glaze layer 12 is 11 will not be damaged by causing unevenness or the like. . Also, when firing the glass 13, the firing temperature of the glass 13 is lower than the firing temperature and softening point of the glaze layer 11, and also the firing temperature of the thick film circuit 12, which may damage the glaze layer 11 and the thick film circuit 12. There's no fear. Next, as shown in FIG. 3b, a heating resistor 14 is formed on the glaze layer 11 by, for example, thin film circuit technology, and a thin film is further formed to connect the heating resistor 14 and the drive circuit section 3. A conductor pattern 15 is formed.

In this case, the conductor pattern 15 can be easily formed with high density and high yield by a process such as vapor deposition, sputtering, or etching. As described above, according to the present invention, yield can be further improved and reliability can be improved compared to conventional methods.

Next, another embodiment of the invention will be described. Figure 4 shows the first
This is an example in which the back surfaces of the second substrates 11 and 12 are bonded to the third substrate 17 using glass 16 to increase the overall mechanical strength. Note that it is desirable that the heat transferred from the heating resistor 14 to the first substrate 1 be dissipated quickly, but in FIG. Because heat is transferred, heat dissipation is not very good.

The embodiment shown in FIG. 5 improves this point by making the lower part of the glaze layer 11 of the first substrate 1 thicker than the other parts, and applying the second composite substrate 12 to the surface of the thinly extended part. The back surface is bonded with glass 16. The embodiment shown in FIG. 6 includes substrates 1, 1.

The end faces of the first and second substrates 1, 12 are tapered in a direction opposite to that shown in FIGS. 3 to 5.
The glass 13 is printed from the back side of the glaze layer 11. In the above explanation, glass is used for bonding between the substrates, but resins such as epoxy and polyimide may also be used, and the softening temperature of the resin is the same as that of the glaze layer 11. Similar effects can be obtained as long as the firing temperature and softening point are lower than the firing temperature of the thick film circuit 12.

[Brief explanation of the drawing]

FIGS. 1 and 2 are diagrams schematically showing the mounting structure of a thermal head, FIGS. 3A and 3B are sectional views showing the steps of an embodiment of the present invention, and FIGS. 4 to 6 are diagrams showing the present invention. FIG. 3 is a sectional view for explaining another embodiment of the invention. 1,...first substrate, 12...second substrate, 2.
...Heating resistor section, 3...Drive circuit section, 11...
Glaze layer, 12...Thick film circuit, 13, 16...Glass, 14...Heating resistor, 15...Conductor pattern, 17...Third substrate.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a thermal head having a heat generating resistor, a glaze layer on which the heat generating resistor is disposed, and a drive circuit including a thick film circuit for driving the heat generating resistor. A first substrate on which a glaze layer is formed by printing and baking, and a second substrate on which the thick film circuit is formed by printing and baking are formed separately, and these first and second substrates are bonded to the glaze layer. and after joining and integrating at least the end faces with glass or resin that is fired or hardened at a temperature lower than the firing temperature of each of the thick film circuits and lower than the softening point of the glaze layer, the glaze layer the heating resistor is formed on the first
, a conductor pattern made of a thin film, one end of which is connected to the heating resistor and the other end of which is connected to the drive circuit section, is formed on the second substrate by vapor deposition or sputtering and etching, and the conductor pattern is formed on the first and second substrates. A method for manufacturing a thermal head, characterized by forming the head so as to straddle the two. 2. The method of manufacturing a thermal head according to claim 1, wherein the end surfaces of the first and second substrates to be joined are tapered. 3. The method of manufacturing a thermal head according to claim 1 or 2, wherein the back surfaces of the first and second substrates are bonded onto a common substrate. 4. The thermal device according to claim 1 or 2, wherein the back surface of one of the first and second substrates and the front surface of the other substrate are bonded by glass or resin. Head manufacturing method.