JPS6225067A - Electrode forming method for thermal head - Google Patents

Abstract

PURPOSE:To narrow the area of a heat resistant substrate by forming patterned electrodes on the back surface through the side of a ceramic substrate, thereby effectively utilizing on the back surface. CONSTITUTION:Through holes 4 which penetrate from the front surface to the back surface along a line 6 are opened at a ceramic substrate 2 to form electrodes. Then, the substrate 2 is cut along the line 6 arranged with the holes 4. Further, the substrate is cut at the center along the longitudinal direction to form ceramic substrate 10 having heating resistance elements for one thermal head and electrodes. The substrate 10 is disposed on a supporting plate 12; the array of the resistance elements 18 and the electrodes connected with the elements are formed on the front surface, and a driving IC 22 for forming a driving circuit is bonded to the back surface to form a thermal head.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method of forming electrodes connected from the front surface of a heat-resistant substrate to the back surface via the side surface in a thermal head used for facsimiles and the like.

(Prior Art) In a conventional thermal head, a heating resistor element and an electrode connected to the heating resistor element are generally all formed on one surface of a heat-resistant substrate. Therefore, a large area is required for an expensive heat-resistant substrate such as a ceramic substrate, and the cost of the heat-resistant substrate increases the cost of the entire thermal head.

Therefore, a thermal head has been proposed in which a common electrode commonly connected to the heating resistor elements is formed through the side surface of the heat-resistant substrate to the back surface.

However, what is formed on the side surface of the heat-resistant substrate in this thermal head is a common electrode that is not patterned. No example of formation on the side surface of a substrate has been reported so far.

(Purpose) In order to reduce the area of the heat-resistant substrate and reduce the cost of the heat-resistant substrate, the present invention provides a heat-resistant substrate by forming patterned electrodes connected from the front surface to the back surface of the heat-resistant substrate on the side surface of the heat-resistant substrate. The purpose of this is to make it possible to effectively utilize the back side of the paper.

(Structure) In the present invention, the electrode that connects from the front surface of the heat-resistant substrate to the back surface via the side surface is formed by linearly arranging through holes penetrating the heat-resistant substrate from the front surface to the back surface, and the insides of these through holes are plated to conduct electricity. forming a heating resistor element, an electrode connecting the heating resistor element and the conductor layer of the through hole, and other necessary electrodes on the surface of the heat-resistant substrate;
It is formed by forming electrodes connected to the conductor layer of the through holes and other necessary electrodes on the back side of the heat resistant substrate, and then cutting the heat resistant substrate along the straight line in which the through holes are arranged.

An example will be specifically described below.

FIGS. 1 to 3 show one embodiment in the order of steps.

In FIG. 1, reference numeral 2 denotes a ceramic substrate as a heat-resistant substrate having a large area. The surface of this ceramic substrate 2 is covered with a glaze layer containing silicon oxide as a main component. First, a through hole 4 is formed in this ceramic substrate 2 along a straight line 6 from the front surface to the back surface. The through holes 4 are positions where electrodes on the side surfaces of the ceramic substrate will be formed later, and are formed at intervals of, for example, 1 mm.

Next, the walls of these through holes 4 are subjected to conductive treatment by plating. This conductive treatment can be performed, for example, by electroless copper plating.

Thereafter, a heating resistor element and electrodes are formed by a conventional method. The heating resistor elements are arranged in rows on one surface of the ceramic substrate 2, and electrodes are formed not only on the front surface but also on the back surface of the ceramic substrate 2. Some of the electrodes connect the through hole 4 and the heat generating resistor element, some electrodes connect only to the through hole 4 or the heat generating resistor element, or some electrodes connect to neither of them. When forming the heating resistor element and electrodes, etching is performed using photolithography, so the through holes 4
Through holes 4 are provided to prevent the conductive film from being etched.
Fill it with resist.

Next, the ceramic substrate 2 is cut along the straight line 6 along which the through holes 4 are arranged.

One such cut is shown in FIG. 2, and is in the area indicated by the symbol A in FIG. In the ceramic substrate shown in FIG. 2, concave portions 8 are formed by cutting the through holes 4 on both sides along the longitudinal direction, and the R conductive layer formed in these four portions 8 is formed on the side surfaces of the ceramic substrate. It becomes an electrode. Second
The heating resistor elements and electrodes of two thermal heads are formed on the ceramic substrate shown in the figure, so if this is cut at the center along the longitudinal direction, it will become 1 as shown in Figure 3.
A ceramic substrate 10 having heating resistor elements and electrodes of individual thermal heads is formed. After that, a wear-resistant layer is formed to protect the heating resistor elements, and the bonding parts of the N and poles are plated with gold. Ru.

An example of a thermal head using this ceramic substrate 10 having electrodes on its side surfaces is shown in FIGS. 4 and 5. FIG. 5 is a sectional view taken along the line AB in FIG. 4.

Reference numeral 12 denotes a support plate, on which a ceramic substrate 10, a plurality of diode arrays 14, and a printed wiring board 16 are bonded.

On the surface of the ceramic substrate 10, an array of heating resistor elements 18 and electrodes connected thereto are formed. The @pole 8 in the recess on the side surface of the ceramic substrate 10 serves as a selection electrode, and the electrode 20 between the electrode 8 and the heating resistor element 18 allows one @pole 8 to be connected to a plurality of heating resistors, such as eight, for example. is connected to the body element 18 .

As shown in FIG. 5, a driving IC 22 constituting a driving circuit is bonded to the back surface of the ceramic substrate 10, and an electrode 23 on the back surface connected to the electrode 8 on the side surface of the ceramic substrate 10 is attached to the driving IC 22. Wire bonding is performed between the drive IC 22 and the drive IC 22, and the drive IC 22 is also wire bonded to a conductor wiring 24 formed on the back surface of the ceramic substrate IO and connected to an input terminal.

The diode array 14 has diodes formed on a silicon substrate, for example, and is connected to individual electrodes 25 connected to the heating resistor elements 18 on the ceramic substrate 10 by wire bonding.

The printed wiring board 16 has a plurality of conductor wirings formed on a glass epoxy base, and connections are made between these conductor wirings and the diode array 14 by wire bonding.

The conductor wiring of the printed wiring board 16 is connected to the heating resistor element 1
8.

(Effects) According to the present invention, patterned electrodes can be formed on the back surface as well through the side surfaces of the ceramic substrate, so that the back surface can also be effectively utilized. Therefore, the area of the expensive heat-resistant substrate can be reduced, and the cost of the thermal head can be reduced.

[Brief explanation of the drawing]

1 to 3 are perspective views showing an embodiment of the present invention in the order of steps, FIG. 4 is a perspective view showing a thermal head using a ceramic substrate having electrodes formed according to the embodiment, and FIG. 5 4 is a sectional view taken along the line A-B in FIG. 4. 2...Ceramic substrate, 4...Through holes 6...Line line for arranging through holes, 8...
...Electrode on the side of the ceramic substrate.

Claims (1)

[Claims] (1) Through holes penetrating the heat-resistant substrate from the front surface to the back surface are arranged in a straight line, and the insides of these through-holes are conductive treated by plating, and heat-generating resistor elements and heat-generating elements are formed on the surface of the heat-resistant substrate. After forming an electrode that connects the resistor element and the conductor layer of the through hole and other necessary electrodes, and forming an electrode that connects to the conductor layer of the through hole and other necessary electrodes on the back surface of the heat-resistant substrate. . A method for forming electrodes on a heat-resistant substrate of a thermal head, characterized in that the heat-resistant substrate is cut along a straight line in which the through holes are arranged.