JPH04319448A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain a thermal head capable of freely carrying a heat-sensitive medium to a heating resistor both in the forward direction and the opposite direction. CONSTITUTION:Electrode patterns 13, 16 connected to a heating resitor 14 are formed on each surface of the surface and rear of a substrate 11 respectively, a through-hole 18 for mutually connecting the electrode patterns 13, 16 on each surface of said surface and rear is formed to the substrate 11, and a driver circuit being connected to the electrode pattern 16 shaped on the rear of the substrate 11 and driving the heating resistor 14 is formed on the rear of the substrate 11.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head, and more particularly to a flat thermal head having a linear heating resistor.

0002

[Prior Art] A conventional planar thermal head is shown in FIG.
As shown in FIG. 5, a heat generating resistor 2 and a driver circuit 3 for driving the resistor are provided on the surface of the substrate (for example, Japanese Patent Application Laid-Open No. 151466/1983). As shown, a heating resistor is separately provided on the end surface of the base, and a driver circuit is separately provided on the side surface of the base. In FIGS. 4 and 5, reference numeral 4 indicates a protective cover for the driver circuit, respectively.

0003

[Problems to be Solved by the Invention] In the planar thermal head shown in FIG. 4, a driver circuit such as an IC is mounted on the surface of the substrate that has the heat-generating resistor, so this driver circuit gets in the way and heat-sensitive The heat-sensitive medium 4 such as a card or heat-sensitive sheet can only be conveyed from one direction relative to the heating resistor, from the left side in the figure, and in the edge-type thermal head shown in FIG. The feeding direction is
Either forward or reverse is possible, but since the heating resistor, which requires the finest pattern, is provided on the end face of the base, there is a problem that the photolithography process is difficult and the yield of the product is poor. .

0004

[Means for Solving the Problems] The present invention provides a thermal head having a linear heating resistor on the surface of a substrate, in which electrode patterns connected to the heating resistor are formed on each of the front and back surfaces of the substrate, A through hole is provided in the substrate to connect the electrode patterns on the front and back sides, and a driver circuit is connected to the electrode pattern formed on the back surface of the substrate to drive the heating resistor. It is characterized in that it is provided on the back surface of the substrate.

[0005]

[Function] The electrode patterns provided on the front and back sides of the board are connected to each other through the through holes of the board, the electrode pattern on the front side of the board is connected to the heating resistor, and the electrode pattern on the back side is connected to the driver circuit including the IC. are connected to each other. Since the driver circuit is provided on the back surface of the substrate, the heat-sensitive resistor is provided on the planar portion (not the end surface) of the substrate even though it is a planar thermal head, so there is no difficulty in the photolithography process.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 11 indicates a substrate of a thermal head. The substrate 11 is made of ceramic, and an underglaze layer 12 is provided on its surface, and an Au electrode 13 is formed on the glaze layer 12. A linear heating resistor 14 is provided at one end of the electrode 13 in a direction perpendicular to the plane of the paper, and the heating resistor 14 and the electrode 13 are covered with an overglaze layer 15.

On the back surface of the substrate 11 are an Au electrode 16 corresponding to the surface electrode 13, a printed circuit board 17, and this substrate 17.
An IC for driving the heating resistor mounted on the top is disposed. This driving IC causes a predetermined heating resistor to generate heat by passing a current through a predetermined electrode. Further, the printed circuit board 17 is provided with a circuit pattern connected to a control circuit for controlling the driving of the driving IC.

Through holes 18 corresponding to the number of dots are arranged in rows on the substrate 11 to connect the electrodes 13 and 16 provided on the front and back sides of the substrate 11, respectively. The IC is connected to the electrode 16 using Au wire 19 and to the printed circuit board 17 using Au wire 20 by wire bonding.

The electrodes 13 and 16 are formed by forming an Au film on the substrate 11, patterning it into a predetermined shape by photolithography, and then etching it. A heating resistor 14 is provided. A grace layer (not shown) is formed on the back surface of the substrate 11 except for the bonding pad 16dp (FIG. 2), and the IC and Au wires 19
, 20 are sealed with silicone resin to protect them.

The electrodes 13 and 16 are shown in FIGS. 3(a) and 3(b).
As shown in FIG. 2, the electrode groups 13a and 16a are composed of front electrode groups 13a, 13b, 13c, . . . and back electrode groups 16a, 16b, 16c, . . . arranged in a V shape. Electrode groups 13b and 16b; electrode group 13c
and 16c, each corresponding electrode group on the front and back is the substrate 1.
1 through through holes 18 arranged in a V-shape. That is, taking the electrode groups 13a and 16a as an example, the through holes 13a1 and 13 of each electrode of the electrode group 13a
a2...13an, 13an+1...13an
+x, and the corresponding through holes 16a1, 16a2, . . . 16an, of each electrode of the electrode group 16a,
16an+1 . . . 16an+x are connected to each other via through holes in the substrate 1.

Through holes 13a1, 13a2, . . .; 16a1, 16a2, .
By arranging the through holes in a V-shape, the distance between the through holes can be increased without the through holes expanding laterally. Further, the electrode group 16a on the back side of the electrode group 13a is formed to extend toward the tip side, that is, toward the heating element side,
By providing the bonding pad portion 16pd at the tip thereof, the IC can be mounted on the through-hole portion of the electrode group 16a, making it possible to reduce the size. In FIG. 1, a heat-sensitive medium 25 such as a heat-sensitive card or a heat-sensitive sheet is conveyed by a feed roller 26 in the direction of a solid line arrow or in the direction of a dotted line arrow, and information is recorded thereon.

0012

According to the present invention, since the mounting components constituting the driver circuit of the heat-generating resistor are not provided on the running surface of the heat-sensitive medium such as a card or sheet, the conveyance of the heat-sensitive medium to the heat-generating resistor is prevented. You can freely do it either forward or backward. Also, unlike edge-type thermal heads, since the Au electrode is patterned on a flat surface, it can be performed using a conventional photolithography process, and there is almost no need to modify manufacturing equipment, resulting in stable and high-precision electrodes. can be made.

[Brief explanation of drawings]

FIG. 1 is a side view of a thermal head showing an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a part of the thermal head.

FIG. 3 is a plan view showing electrode groups formed on the front and back sides of the substrate of the thermal head.

FIG. 4 is a side view showing an example of a conventional planar thermal head.

FIG. 5 is a side view showing an example of a conventional end-face type thermal head.

[Explanation of symbols]

11　　　　Substrate 13　　　　　Surface electrode 14 Heating resistor 16 Back electrode 17 Printed circuit board

Claims (1)

[Claims] 1. A thermal head having a linear heating resistor on the surface of a substrate, wherein electrode patterns connected to the heating resistor are formed on each of the front and back surfaces of the substrate, and the electrode patterns on each of the front and back surfaces are formed. A through hole for connecting the patterns to each other is provided on the substrate, and a driver circuit is provided on the back surface of the substrate to be connected to the electrode pattern formed on the back surface of the substrate and to drive the heating resistor. A thermal head characterized by: