JPS5952073B2 - Diode matrix integrated thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head, and more particularly to a thermal head in which a diode array is integrally formed on the same substrate.

F. Conventional thermal heads are broadly classified into thick film heads using ruthenium oxide or the like as a resistor and thin film heads using tantalum nitride or the like as a resistor.

The former has the advantage of being easy to manufacture, suitable for mass production, and capable of producing relatively large heads.

However, it is difficult to form fine patterns and is unsuitable for high-density recording, and has drawbacks such as slow response. The latter has almost opposite advantages and disadvantages. By the way, the structure of such a thermal head is a so-called dot printer type in which minute heating resistor elements are arranged in a line on a heat-resistant insulating substrate, grouped into characters to be printed, and selectively energized. are widely used. In this type of head, a selection drive circuit including a backflow prevention diode is connected to each resistance element in order to drive the heating resistance element with an electrode common to each group.

In conventional thermal heads, the heating resistor and selection drive circuit were manufactured separately and integrated, but heads in which these were formed on the same substrate using integrated circuit technology have also been proposed (for example, in the 1970s). - Publication No. 80442). Heads with such an integrated structure require multilayer wiring for the lead wires of the selection drive circuit including the diode array, but when manufacturing heads with such a multilayer wiring structure using thin films, the following problems arise. arise. That is, in the case of multilayer wiring, for example, SiO is placed between the lower layer wiring and the upper layer wiring. An insulating layer such as a film is interposed, but when the insulating layer is formed by vapor deposition or sputtering, the presence of pinholes is unavoidable, and there is a drawback that upper and lower wirings are short-circuited through these pinholes. Furthermore, when connecting the upper and lower lead wires through through holes etched in the SiO2 film, there is a drawback that poor contact is likely to occur due to the difference in level. The probability of such a failure occurring increases as the number of resistor elements increases and the scale of the circuit increases, resulting in a decrease in manufacturing yield. The object of the present invention is to provide a thin film head that eliminates these drawbacks.

That is, in the head of the present invention, a group of thick film lead wires is formed on the surface of a heat-resistant insulating substrate, and the lead wire group is covered with a thick film glaze layer.

A heating resistor and lead wires are formed as thin films on the upper surface of this thick film glaze layer. According to the present invention, the lower lead wire group of the multilayer wiring part is made of a thick film, so even if a thick glaze layer is formed thereon, there will be no damage due to oxidation or the like during this heat treatment process. Since the glaze layer can also be made sufficiently thick, there is no fear of pinhole formation. In other words, if all the circuits are made of thin films as in the conventional example mentioned above, short circuits will occur due to pinholes in the glaze layer, and in order to prevent this, only the glaze layer is made of thick film. When baking the substrate at 900 to 1000[deg.] C. in the manufacturing process, damage such as oxidation and peeling of the previously formed thin film circuit occurred, making it impossible to realize. In this regard, the present invention solves the conventional problems by combining the so-called thick film and thin film circuits, in which the lower layer lead wire is made of a thick film and the upper layer circuit is made of a thin film. The present invention will be explained below with reference to Examples.

1 to 3 are top views showing the structure of the heat-sensitive head of the present invention according to the manufacturing process, and FIG. 4 is a sectional view taken along the dashed line AN in FIG. 3.

First, as shown in FIG. 1, a lower lead wire group 12 is formed on an alumina substrate 11 by a thick film method. That is, as the material for the lead wire, silver-palladium alloy (Ag-Pd) or gold (Au) is used, a powder paste of these is applied in a predetermined pattern by screen printing, and then 90%
Fire at 0-1000℃. Next, as shown in FIG. 2, a glaze layer 14 is formed on the entire surface of the substrate 11 by a thick film method, leaving the terminal lead-out portions 13 of the lower thick film lead wire group 12.

This glaze layer 14 is made of, for example, glass containing SiO2 as a main component. In the step of forming the glaze layer 14, through holes 15 are formed in predetermined portions of the lower lead wire group 12. This through hole 15 is formed by patterning during screen printing. After forming the glaze layer 14 on almost the entire surface of the substrate 11 using the thick film method, as shown in FIG.
Upper layer lead wire group] 7. The common electrode 18 is formed by a thin film method.

That is, first, etching-resistant tantalum pentoxide (Ta2O5) is applied to the surface of the glaze layer 14 (not shown).
For example, a tantalum titanide (Ta--N) resistive film is deposited thereon by high-frequency sputtering, and then, as a lead layer, for example, a chromium-gold (Cr--Au) film is deposited by sputtering or vacuum evaporation. Then, unnecessary portions of the Ta--N film and Cr--Au film thus deposited are removed by etching to form the upper layer lead wire group 17 and the common electrode 18 in a predetermined shape, pitch, and number. Thereafter, a portion of the lead wire group 17 configured as described above is removed by photoetching to expose the Ta--N film and form the resistor element array 16. As shown in FIG. 4, a wear-resistant protective film 19 such as Ta2O5 is provided on the surface of the resistive element array 6. As shown in FIG. A semiconductor chip 20 on which a diode array is formed is placed between the common electrode 18 and the upper layer lead wire group 17 and connected by a flip chip. Then, a moisture-resistant and heat-resistant sealing material 21 is applied and cured over the entire area of the electrode section including the semiconductor chip 20, thereby completing the process. Note that the connection between the lower layer lead wire group 12 and the upper layer lead wire group 17 is performed by sputtering a Cr--Au film through the through hole 15, and no special process is required.

FIG. 5 is an equivalent circuit diagram of the heat-sensitive head shown in FIG. 3.

The figures are numbered to correspond to those in FIG. According to the present invention described above, the following effects can be obtained.

(1) Since the lower lead wire group is formed from a heat-resistant thick film, it is possible to use a glaze layer using the thick film method as an insulating layer for multilayer wiring, so there are no pinholes and manufacturing defects such as short circuits and poor connections. Less is.

(2) Because the structure is such that a part of the lead wire is formed in the lower layer of the multilayer wiring, and a thin film circuit including a resistive element is formed in the upper layer, the glaze layer used to create unevenness on the board surface is also used as an insulating layer for the multilayer wiring. It has a simple structure and is easy to manufacture. (3) As a result of the above-mentioned multilayer wiring structure, the thin film circuit manufacturing process, which requires a relatively complicated manufacturing process, is carried out later, so manufacturing defects in the multilayer wiring process do not cause the entire head to be defective. This can be avoided and yields can be improved.

(4) Since the lower lead wire group and glaze layer are manufactured using the thick film method, through-holes for multilayer wiring can be formed by patterning during screen printing, and the etching process unlike the thin film method is unnecessary. .

In addition, in the thick film method, the glass flows through the through holes formed by screen printing and the edges are smoothed by the firing process, so that the upper layer lead wire group is completely attached and no connection failure occurs. This is a problem with through holes formed by etching. (5) Since the upper lead layer is attached by a thin film method, connection with the lower lead layer via through-holes can be made without requiring any special steps, and the manufacturing process is significantly simplified.

It goes without saying that the present invention is not limited to the above embodiments.

For example, materials other than those in the above embodiments may be used for the substrate, lead wires, resistor, and glaze layer.

Further, although the wiring shown in the equivalent circuit diagram of FIG. 5 is a special wiring in order to reduce the number of through holes, a circuit as shown in FIG. 6 may be used, for example.

[Brief explanation of the drawing]

1 to 3 are top views showing the structure of the thermal head of the present invention in the order of manufacturing steps, and FIG.
5 is an equivalent circuit diagram of this heat-sensitive head, and FIG. 6 is an equivalent circuit diagram of a heat-sensitive head showing another embodiment of the present invention. 11...Heat-resistant insulating substrate, 12...
(Lower layer) Thick film lead wire group, 14... Glaze layer 15... Through hole, 16... Resistance element array, 17... (Upper layer) Thin film Lead wire group, 18... Common electrode, 20... Diode array semiconductor chip.

Claims (1)

[Claims] 1 A group of thick film lead wires wired on a heat-resistant insulating substrate,
A thick film glaze layer formed to cover the substrate surface including the lead wire group, a thin film resistance element group arranged on this glaze layer, and a diode provided corresponding to the thin film resistance element group. an element group, a predetermined number of adjacent thin film resistive element groups are defined as a unit group, and the thick film lead wires are provided in a number equal to the predetermined number, and are located at symmetrical positions in the adjacent unit groups. The path shape of the thin film lead wire between the thin film resistance elements is approximately U-shaped, and the thin film lead wire having the approximately U-shaped path shape and the thick film lead wire group are connected to the through hole formed in the glaze layer. 1. A diode matrix integrated thermal head, characterized in that it has a means for interconnecting the diode matrix through the diode matrix.