JP3112640B2 - Thermal print head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal print head equipped with a driving circuit. 2. Description of the Related Art Generally, a direct drive type thermal print head (hereinafter, referred to as a DD type thermal print head) equipped with a driving integrated circuit (hereinafter, referred to as an IC).
Is an IC in which a plurality of heating resistors, individual electrodes for supplying current to these heating resistors, logic circuits such as shift registers, latches and gates, and an independent transistor driver for each heating resistor are integrated. And this IC
And a drive electrode for transmitting image signals, control signals, etc. supplied from outside to the thermal print head body, which is formed on a ceramic substrate, and electrically connects the thermal print head body to an external circuit. And an interface section made of a flexible circuit board or the like. The above-mentioned DD type thermal print head has the following problems. First, pressure connection is used to electrically connect the flexible circuit board and the drive electrodes of the thermal print head body. Usually, it is difficult to secure reliability unless gold (Au) is used for this pressure welding. However, the use of this gold increases the price of the thermal print head, which is against the trend of the era of price reduction. In addition, at the time of pressure welding, a contact failure between the flexible circuit board and the driving electrode may occur due to a temperature change or the like, and it is difficult to ensure high reliability. Second, since an IC is mounted on a ceramic substrate (usually using an alumina ceramic substrate), the area occupied by an expensive alumina ceramic substrate increases, which leads to an increase in cost. The workability when performing is reduced. Third, when mounting an IC on a ceramic substrate, a multi-layer wiring is used because the wiring density is high, so an insulating film is formed on the driving electrodes of the ceramic substrate. However, forming this insulating film requires
This leads to complicating the process of manufacturing the thermal print head, which may damage the insulating film at the time of replacement of a defective IC, and in a significant case, may damage the drive electrode below the insulating film. Therefore, there is a split type thermal print head which solves the second and third problems. This thermal print head includes a substrate on which a heating resistor is mounted, and an IC.
Is formed on a separate substrate. According to this thermal print head, the area of the substrate on which the heating resistor for performing the batch processing is mounted can be reduced, and there is an advantage that a large number of substrates can be processed at the same time. However, a substrate on which an IC is mounted usually requires a thick film wiring composed of a matrix wiring. In order to make reliable electrical connection between the board on which the IC is mounted and an external circuit, it is necessary to press-connect a flexible circuit board provided with connection means such as a connector. Therefore, the first problem still cannot be solved. A technique for solving the above-mentioned problem is disclosed in Japanese Utility Model Laid-Open Publication No. 57-108.
No. 949. The basic configuration of the thermal print head disclosed in this publication is such that a common signal input lead wire is provided on a glass epoxy substrate, and a set of drive electrodes connected to electronic components mounted on one tape carrier and adjacent drive electrodes are provided. The common electrode is connected to a signal input lead and a common signal input lead on an epoxy substrate via one tape carrier. The following effects can be obtained by using this thermal print head. That is, since the glass epoxy substrate is superior in mechanical workability, it is possible to easily install a means for connecting to an external circuit such as a connector. Therefore, an inexpensive thermal print head can be obtained. However, when the present inventor trial-produced this thermal print head and conducted experiments, it was found that the following problems were encountered. First, since the tape carrier is used for connecting the IC, the area of the connecting portion is increased as compared with the wire bonding, and the size becomes large, which is contrary to the trend of the technology which is being sought for miniaturization. Second, when replacing a defective IC after mounting it on the thermal print head, the tape carrier is peeled off. In this case, there is a risk that the wiring layer on the substrate is also peeled off together with the tape carrier. Third, metallization such as Au-Sn or solder-solder is generally used to perform connection using a tape carrier. However, since the temperature of the wiring layer increases near the heating resistor, soldering or metallization is required. A low melting point metal such as Sn cannot be used. In order to avoid this problem, the present inventors have considered two methods for metallizing a wiring layer for supplying a current to a heating resistor. (1) The whole is made of Au, and the tape carrier and Au-S
A method of connecting by n-eutectic. (2) The whole is made of a metal having a relatively high melting point such as Al,
A method in which an Sn or solder layer is formed at a connection portion with a tape carrier and the tape carrier is connected to the tape carrier by Sn-Au or solder-solder. However, the first method not only increases the cost because metallization is performed on the entire substrate with expensive Au, but also uses wet etching for the etching process. For this reason, it is difficult to accurately form the lead wire and the heating resistor due to over-etching or the like. I do not endure. In the second method, an inexpensive dry-etchable metal such as Al can be used, and the shape and dimensions of the heating resistor can be accurately formed. However, Sn or solder must be partially adhered as a connection layer with the tape carrier, which complicates the process, lowers productivity, increases costs, and is suitable for actual thermal printhead production. Absent. The present invention has been made in view of the above problems, and has as its object to provide a reliable thermal print head. In order to achieve the above object, a thermal print head according to the present invention comprises a plurality of thermal print heads.
Thermal resistor and individual electrodes electrically connected to the thermal resistor
And the plurality of heating resistors electrically connected in common.
A high-resistance base on which the conductive electrodes are arranged, and the heating resistor.
Multiple driving integrated circuits that open and close according to supplied image signals
If, image signal, a control signal input from the external driving circuits, electrostatic
And a driving electrode for transmitting a source to the driving integrated circuit.
And a driving circuit substrate, wherein the driving circuit substrate
An electrode for supplying a current to the common electrode forms the driving integrated circuit.
The individual electrode and the driving electrode
The integrated circuit and the electrode and the electrode extending toward the electrode;
Electrically connected to common electrode by wire bonding
It is characterized by being. By adopting the above-described structure, the thermal print head of the present invention does not need to use a tape carrier or the like, so that reliability is deteriorated such as peeling of a wiring layer or the like which occurs when a defective IC or the like is replaced. Nothing. DETAILED DESCRIPTION OF THE INVENTION Hereinafter, an embodiment of a thermal printing head of the present invention with reference to FIGS. Figure
2 In (a) and (b), an alumina ceramic substrate (2) is fixed to one end of a surface of a support plate (1) made of iron via an adhesive member (not shown). A drive circuit board (11) having a glass-epoxy laminate as a base material is fixed to the other end of the support plate (1) via an adhesive member (not shown). This alumina ceramic substrate (2)
A plurality of heating resistors (3) and individual electrodes (4) for supplying a current to these heating resistors (3) are formed thereon. An IC (6) for opening and closing the current supplied to the heating resistor according to the image signal and the control signal is mounted on the drive circuit board (11) via an adhesive member (not shown). I have. This IC (6) has a connector (1) for connection.
A drive electrode (5) for transmitting an image signal, a control signal, and a current input from an external circuit through the drive circuit (0) is formed on the drive circuit board (11). This individual electrode (4) and I
It is electrically connected to C (6) using an electrical connection means, for example, wire bonding (12). The thermal print head shown in FIG .
Since a flexible circuit used for connecting a conventional thermal print head to an external circuit is not required, the number of components can be reduced. In addition, A required for the pressure contact part
Since the metallization of u is not required, it is possible to reduce material costs and man-hours, and to provide a low-cost thermal print head. Furthermore, since a contact failure of the press contact portion due to a temperature change does not occur, a very reliable thermal print head can be provided. Further, there is no need to install the IC on the ceramic substrate. As a result, the area of one expensive alumina ceramic substrate per thermal print head can be significantly reduced, and the number of products per batch (such as sputtering of a heating resistor from one alumina ceramic plate) during batch processing Can increase the number of alumina ceramic substrates having a heat generating portion used in the thermal print head formed in step (1), thereby improving productivity and workability and reducing material costs. Further, the IC is directly mounted on the glass-epoxy substrate.
By mounting the IC, a structure in which productivity and workability do not decrease even if the IC mounting location is not necessarily located at the lower portion of the driving electrode is adopted, so that an insulating film on the driving electrode becomes unnecessary. This not only simplifies the process, but also eliminates the risk of damaging the drive electrodes below the IC when replacing a defective IC. In addition, in this embodiment, since wire bonding is used for all the electrical connection means, the area required for connection can be reduced, and the substrate of the individual electrode can be dry-etched, for example, like Al. Possible and inexpensive metals can be used. Thus, accurate heating resistor shapes and dimensions can be formed without using a complicated metal configuration. Therefore, according to the thermal print head of the present invention, recording can be performed with a uniform and accurate pixel size. In addition to the glass-epoxy substrate described above, in the thermal print head of the present invention, an IC may be mounted on a metal or resin film.
Further, it goes without saying that the same effect as that of the thermal print head shown in FIG . In FIG . 1 , if a part of the driving electrode (5) is used as an external take-out terminal (21), there is an effect that the thermal print head can be directly connected to an external circuit. (22) indicates a common electrode, (23) indicates an electrode for supplying a current to the common electrode (22), and (24) indicates a cover for protecting the IC (6). Note that FIG.
The same reference numerals are given to the same parts and the same members. By adopting the above configuration, the thermal print head of the present invention prevents the risk of the drive electrode peeling off due to replacement of a defective IC or the like, for example, when the tape carrier is no longer used. High reliability can be obtained very easily.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially cutaway schematic perspective view showing an embodiment of a thermal printhead of the present invention. Examples of the thermal printing head of the present invention; FIG Display
It is a cross section and a simplified plane view . [Description of Signs] 2 Alumina ceramic substrate 3 Heating resistor 4 Individual electrode 5 Driving electrode 6 Driving integrated circuit 11 Glass-epoxy substrate 12 Wire bonding

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazuo Kobayashi 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Horikawa-cho Plant (56) References JP-A-60-2381 (JP, A) JP-A-60 −97871 (JP, A) Actually open sho 59-164176 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) B41J 2/345

Claims (1)

(57) [Claims] The plurality of heating resistors, the individual electrodes electrically connected to the heating resistors, and the plurality of heating resistors are electrically connected to each other.
And a high-resistance substrate having disposed a common electrode connected in common, double that open and close in response to the image signal supplied to the heating resistor
A driving integrated circuit number, image signals input from the external drive circuit, a control signal, and a drive circuit substrate arranged a driving electrode that transmits the driving integrated circuit power, to the drive circuit substrate Is a power supply for supplying a current to the common electrode.
A pole is formed at an outer peripheral position surrounding the driving integrated circuit,
The individual electrode, the driving integrated circuit, and the electrode and the electrode
A thermal printhead , wherein the common electrode extending toward the first substrate is electrically connected to the common electrode by wire bonding.