JPS5941281A - Thermal head - Google Patents

Abstract

PURPOSE:To contrive to enhance density of heating resistor elements and to enhance resolution, by placing tape carriers in a partially overlapping manner. CONSTITUTION:The tape carriers 3 each of which is obtained by adhering a copper foil on a surface of a polyimide sheet or the like and providing electrodes in a predetermined pattern are placed in a partially overlapping manner. Each of the tape carriers 3 is inner-bonded to driving circuit elements 2, and is outer-bonded to electrodes 4 for the heating resistor elements 1 provided on a glazed ceramic substrate 6 (which is provided with the resistor elements 1, the electrodes 4, a protective layer for the elements 1 and the like on a surface thereof) and to wiring 7 provided on a printed wiring plate 5. Accordingly, the density of the heating resistor elements 1 can be enhanced, and a thermal head having a high resoloing power be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head used in printers, facsimile machines, etc., which converts electrical signals into characters and images on thermal paper, and which is equipped with a drive circuit element using a tape carrier method.

Tape carrier method is film carrier method or TAB
It has the advantage that both the inner bonding between the mounted drive circuit element and the tape carrier, and the outer bonding between the tape carrier and the thermal head electrodes and wires can be performed with high precision and only partially by bonding. are doing.

For this reason, it has become common practice to mount drive circuit elements in thermal heads using a tape carrier method.

In a conventional thermal head, a tape carrier on which drive circuit elements are mounted one by one is arranged along an array of heating resistor elements so as not to overlap each other. Therefore, the resolution of printed information, that is, the heating resistor element density, is limited by the width of the tape carrier and the number of heating resistor elements driven by each drive circuit element. For example, if the width of the tape carrier is 8wn,
Assuming that 32 heat generating resistor elements are driven by one drive circuit element, the upper limit of resolution is 4 dots/r in a type in which the tape carrier is placed on one side of the heat generating resistor element array.
In a type in which tape carriers are arranged on both sides of the heating resistor element array, the number of dots is 8 dots/min.

An object of the present invention is to provide a high-resolution thermal head in which a drive circuit element is mounted using a tape carrier method. The aim is to achieve the above objectives.

Examples will be described below.

FIG. 1 shows a part of one side of a thermal head according to a first embodiment of the present invention, in which driving circuit elements 2 are mounted on both sides of an array of heating resistor elements 1 by tape carriers 3. . The tape carriers 3 are arranged so as to partially overlap each other, each tape carrier 3 is inner bonded to the drive circuit element 2, and the heating resistor element 1 is bonded to the drive circuit element 2.
Outer bonding is performed between the electrode 4 and the wiring 6 on the printed wiring board 5. 7 is a glazed ceramic substrate having a heating resistor element 11, an electrode 4, a protective film for the heating resistor 1, etc. on its surface. Although only two tape carriers 3 are shown in the figure, a plurality of tape carriers 3 are similarly arranged so as to partially overlap each other.

The drive circuit elements mounted in the present invention include ICs (integrated circuits such as 551, MSI, and LSI) equipped with a register, a latch, and a driver in order to achieve high-speed printing operations, as well as other circuit configurations. For example, an IC1 or a diode array having the following characteristics can be mentioned.

The tape carrier 3 is made by pasting copper foil on the surface of a tape base material made of resin (mainly bolywood), forming electrodes in a predetermined pattern using photolithography and etching techniques, and then applying tin or solder onto the copper electrodes. Since the tape carrier 3 has layers attached to it, the electrodes are exposed on the surface of the tape carrier 3. Therefore, if the conductors come into contact with each other, short circuits are likely to occur, especially when tape carriers are stacked on top of each other. In addition, when the drive circuit element 2 is mounted, the drive circuit element 2 protrudes from the tape carrier 3, so when the tape carriers 3 are largely overlapped, the inner bonding portion between the inner lead of the tape carrier 3 and the drive circuit element 2 Defects may occur. In particular, a so-called finger touch failure in which the inner lead comes into contact with the edge of the drive circuit element 2 is likely to occur.

Therefore, in the second embodiment of the present invention, the electrodes on the tape carrier 3 are insulated.

The insulation treatment can be performed by coating the tape carrier 3 with an insulating agent such as a general insulating resin. Such insulation treatment prevents short circuits and defects at the inner bonding portion.

FIG. 2 is a diagram showing a third embodiment, and shows a cross section of the tape carrier 3 and the drive circuit element 2 at a position corresponding to line AB in FIG. 1. On the tape carrier 3-1, the drive circuit element 2-1 is mounted with its pad surface facing downward, the so-called face-down method, and on the next tape carrier 3-2, the drive circuit element 2-2 is mounted with its pad surface facing downward. In the next tape carrier 3-3, the drive circuit element 2-3 is mounted face-down again, and so on, and so on. Carriers and face-down type tape carriers are alternately arranged. In this case, the electrodes of the tape carrier 3 may be located either above or below the tape carrier.

According to this embodiment, tape carriers 3-1.3-2.・
Even if the degree of mutual overlapping of the drive circuit elements 2-1, 2-2. . . . The tape carrier is no longer strongly pressed by the adjacent tape carrier, which is effective in preventing the occurrence of defects in the inner bonding between the drive circuit element and the tape carrier.

FIG. 3 is a diagram showing the fourth embodiment, and shows a cross section at the same position as FIG. 2. The tape carriers 3 are arranged so as to partially overlap each other as shown in FIG. Each tape carrier 3 is raised by an appropriate angle θ using the bonding portion with 6 as a fulcrum. The angle θ is 5
degree or more, preferably 10 degrees or more.

In this embodiment, even if the tape carriers 3 are arranged so as to overlap each other, they can be prevented from coming into contact with each other, which is effective in preventing the occurrence of defects such as short circuits and finger touches.

In the embodiments shown in FIGS. 2 and 3 as well, if the surface of the tape carrier is insulated as in the second embodiment, it will be more effective in preventing short circuits and finger touches.

As described above, in the present invention, since the tape carriers are arranged at least partially overlapping each other, it is possible to realize a thermal head with a high density of heating resistor elements 1.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing a part of one embodiment of the present invention, and FIGS. 2 and 3 are sectional views showing the arrangement of tape carriers in other embodiments. l...Heating resistor element, 2.2-1.2-2.2-3
...Drive circuit element, 3.3-1.3-2.3-3...
・Tape carrier. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] (1) In a thermal head in which a substrate having a heat generating resistor element etc. on its surface is fixed to a support plate, and a drive circuit element for the heat generating resistor element is mounted on a tape carrier, the tape carriers are connected to each other at least A thermal head characterized by being arranged partially overlapping each other.