JPH11240190A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expose a surface of an external connection gold-plated layer in a good state when an external wiring board is soldered by forming a belt-shaped gold-plated layer extending nearly parallel to a longitudinal direction of a driver IC at an area between an IC connection gold-plated layer and the external connection gold-plated layer. SOLUTION: A heat-generating element array of a plurality of heat-generating elements 2 and a rectangular driver IC5 arranged nearly parallel to the heat-generating element array are set at an upper face of an insulating substrate 1. An IC connection gold-plated layer 7 is formed at an upper face of one end of the insulating substrate 1 to be soldered to a terminal 5a of the driver IC5. An external connection gold-plated layer 8 is provided at the upper face of the other end to be soldered to a wiring of an external wiring board 11. A ground electrode wiring 6 connected to the heat- generating elements 2 via the driver IC5 or the like and a protecting resin 10 coating the driver IC5 are fitted. A belt-shaped gold-plated layer 9a extending nearly parallel to a longitudinal direction of the driver IC5 is formed at a surface of the ground electrode wiring 6 in a region between the IC connection gold-plated layer 7 and external connection gold-plated layer 8. An edge position of the protecting resin 10 is set by the plated layer 9a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head incorporated as a printer mechanism for a word processor, a facsimile or the like.

[0002]

2. Description of the Related Art Conventionally, a thermal head incorporated as a printer mechanism of a word processor or the like is, for example, as shown in FIG.
1, a heating element array in which a plurality of heating elements 22 are linearly arranged, a common electrode wiring 23 and an individual electrode wiring 24 connected to both ends of the heating element 22, and the heating element 2
2, a driver IC 25 for selectively generating heat based on external printing data, and an IC connection gold-plated layer 27 for soldering to a terminal 25a of the driver IC 25 on one end upper surface, and not shown on the other end upper surface. Gold plating layer for external connection 2 for soldering to wiring of external wiring board
8 and a ground electrode wiring 26 electrically connected to the heating element 22 via the driver IC 25 and the individual electrode wiring 24, respectively. , The driver I
Power is applied between the common electrode wiring 23 and the ground electrode wiring 26 by driving C25, and the heating elements 22 are individually and selectively heated, and the generated heat is transmitted to a heat-sensitive recording medium such as heat-sensitive paper. By forming a predetermined print on the thermosensitive recording medium, it functions as a thermal head.

The driver IC 25 of such a thermal head is protected by a protective resin 29 made of an epoxy resin or the like in order to protect it from corrosion due to contact with moisture or the like contained in the atmosphere, sliding contact with a thermosensitive recording medium, and the like. Coated. The protective resin 29 is formed by applying a liquid epoxy resin precursor to the region on the upper surface of the insulating substrate where the driver IC 25 is mounted using a dispenser or the like, and heating and curing the region at a high temperature. Is done.

[0004]

However, in this conventional thermal head, when the protective resin 29 is formed on the insulating substrate 21, the liquid precursor applied on the insulating substrate 21 faces both sides of the driver IC 25. In this case, the coating width sometimes undesirably expands. When a part of the liquid precursor thus spread flows to the vicinity of the external connection gold plating layer 28 provided at the other end of the ground electrode wiring 26, the precursor pool Z is formed in the vicinity thereof, and The connection gold plating layer 28 is buried in the precursor pool Z. Therefore, even if an attempt is made to solder the external wiring board to the ground electrode wiring 26, the above-mentioned precursor pool Z becomes an obstacle and cannot be soldered satisfactorily. The above-mentioned precursor pool Z had to be removed by etching or the like, which significantly reduced the productivity of the thermal head.

In the above-mentioned conventional thermal head, the driver IC 25 is face-down bonded onto the insulating substrate 21, and a slight distance of about 40 to 50 μm is provided between the upper surface of the insulating substrate 21 and the lower surface of the driver IC 25. A gap is formed. Therefore, the protective resin 29
The liquid precursor is used to form the driver IC 25
When the liquid precursor is applied to the mounting region, the liquid precursor cannot be flowed into the above-mentioned gap satisfactorily, and large bubbles remain in the gap. When heat for curing the precursor, heat for using the thermal head, or the like is applied to such bubbles, the thermal expansion of the bubbles causes a displacement of the driver IC 25 or a solder between the ground electrode wiring 26 and the driver IC 25. Breakage of the joint was induced, which also reduced the productivity and reliability of the thermal head.

[0006]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned disadvantages, and a thermal head according to the present invention has a heating element array in which a plurality of heating elements are linearly arranged on an upper surface of an insulating substrate. A common electrode wiring connected to one end of the heating element, a plurality of individual electrode wirings connected to the other end of the heating element, and the heating element electrically connected to the individual electrode wiring. A rectangular driver IC arranged substantially in parallel with the row, an IC connection gold plating layer on one end upper surface for soldering to a terminal of the driver IC, and solder bonding to an external wiring board wiring on the other end upper surface. An external connection gold plating layer is applied, and a ground electrode wiring electrically connected to a heating element via the driver IC and the individual electrode wiring; and a protective resin covering the driver IC.
A thermal head for generating and driving the heating element by a power supply applied between the common electrode wiring and the ground electrode wiring, the thermal head being provided on the surface of the ground electrode wiring and for the IC connection. In a region between the gold plating layer and the external connection gold plating layer, a band-shaped gold plating layer extending substantially parallel to the length direction of the driver IC is formed, and the position of the edge of the protective resin is set by the band-shaped gold plating layer. It is a feature.

[0007] The thermal head of the present invention is characterized in that the IC
A plurality of connection gold plating layers are provided on a single ground electrode wiring, and these IC connection gold plating layers are arranged in a row or in a staggered manner along the length direction of the driver IC, and a part of the band-shaped gold plating layer is provided. Are extended toward the region between the adjacent gold layers for IC connection.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 1 is a plan view of a thermal head according to one embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line XX of FIG. 1, and FIG. 3 is an enlarged view of a main part showing patterns of various gold plating layers provided on the thermal head of FIG. FIG. 1 shows an insulating substrate, 2
Is a heating element, 3 is a common electrode wiring, 4 is an individual electrode wiring, 5
Denotes a driver IC, 6 denotes a ground electrode wiring, 7 denotes a gold plating layer for IC connection, 8 denotes a gold plating layer for external connection, 9a denotes a belt-shaped gold plating layer, and 10 denotes a protective resin.

The insulating substrate 1 is formed in a rectangular shape from an electrically insulating material such as alumina ceramics or glass, and has a heating element array, a common electrode wiring 3, a plurality of individual electrode wirings 4, It supports a plurality of driver ICs 5, a plurality of ground electrode wirings 6, a protective resin 10, and the like.

When the insulating substrate 1 is made of, for example, alumina ceramics, an appropriate organic solvent or an organic solvent is added to and mixed with a ceramic raw material powder of alumina, silica, magnesia or the like to form a slurry. The ceramic green sheet is obtained by adopting the doctor blade method, etc., and thereafter, the ceramic green sheet is subjected to a punching process to form a rectangular shape, which is fired at a high temperature (about 1600 ° C.). You.

On the upper surface of the insulating substrate 1, a row of heating elements is attached along the longitudinal direction of the substrate 1. The heating element row is configured by arranging a plurality of heating elements 2 in a linear shape, and these heating elements 2 are arranged at a line density of, for example, 600 dpi so as to correspond to pixels of one scanning line.

Each of the heating elements 2 is made of Ta-N
System, Ta-Si-O-based, Ti-Si-O-based, or other electric resistance material, so that power from an external power supply is applied via the common electrode wiring 3 and the individual electrode wiring 4 described later. Then, Joule heat is generated, and the temperature becomes necessary to form a print on a thermal recording medium such as thermal paper.

The heating element 2 is formed on the upper surface of the insulating substrate 1 by applying the above-mentioned electric resistance material to a predetermined thickness and a predetermined pattern by employing a conventionally known sputtering method and photolithography technique. You.

A common electrode wiring 3 and an individual electrode wiring 4 for applying power to the heating element 2 are electrically connected to both ends of the heating element 2. The common electrode wiring 3
Are connected in common to each end of the heating element 2, are patterned in a U-shape along one long side and two short sides of the insulating substrate 1, and are connected to an external wiring substrate 11 described later. Is electrically connected to a terminal on the positive (+) pole side of the external power supply via the power supply.

On the other hand, the individual electrode wirings 4
And switch means (not shown) such as a switching transistor provided inside a driver IC 5 to be described later and a ground electrode wiring 6.
And the like, it is electrically connected to a negative (−) pole side terminal of the external power supply.

The external power supply is adapted to hold, for example, a positive (+) pole side terminal at a potential of 24 V and a negative (-) pole side terminal at a 0 V potential. A 24V potential difference is provided between the common electrode wiring 3 and the ground electrode wiring 6, and a voltage corresponding to this potential difference is applied to the heating element 2 to generate and drive the heating element 2.

The common electrode wiring 3 and the individual electrode wiring 4 are made of a metal such as aluminum by using a conventionally well-known sputtering method and photolithography technique or the like to have a predetermined thickness and a predetermined pattern. Formed on the upper surface of the substrate.

Further, a gold plating layer 7 for IC connection is applied to a part of the upper surface of the individual electrode wiring 4 and is electrically connected to the output terminal 5a of the driver IC 5 via the gold plating layer 7 for IC connection. . The driver ICs 5 each have a rectangular shape, and are arranged in a row with the length direction arranged substantially parallel to the heating element row. The driver IC5
Is a switch means such as a switching transistor, a latch for holding print data from outside,
A shift register for serially transferring the print data of one line in synchronization with a clock signal, and the like, and an operation of selectively heating the heating elements 2 individually; While the signal is being supplied, an operation of individually controlling the on / off of the power applied to the heating element 2 is performed based on the print data stored in the latch.

The plurality of driver ICs 5 employ a conventionally known face-down bonding method, and a plurality of terminals 5a and 5b provided on the lower surface thereof are connected to individual electrode wirings 4 via an IC connection gold plating layer 7 described later. And is soldered to the ground electrode wiring 6 and the like, and is attached and mounted on the upper surface of the insulating substrate 1. In this case, between the upper surface of the insulating substrate 1 and the lower surface of the driver IC 5, 40 to 5
A gap of about 0 μm is formed.

On the upper surface of the insulating substrate 1, a ground electrode wiring 6 electrically connected to a ground terminal 5b of the driver IC 5 is attached. The ground electrode wiring 6 has an IC connection gold plating layer 7 for soldering to the ground terminal 5b of the driver IC 5 on one end upper surface, and soldering to a wiring (not shown) of the external wiring board 11 on the other end upper surface. An external connection gold plating layer 8 for bonding is respectively attached, and the driver I
It is electrically connected to the heating element 2 via C5 and the individual electrode wiring 4, and is electrically connected at the other end to a terminal on the minus (-) pole side of the power supply via an external wiring board 11 described later.

Further, the I provided on the ground electrode wiring 6
The gold plating layer 7 for C connection and the gold plating layer 8 for external connection
When soldering the ground electrode wiring 6 to the ground terminal 5b of the driver IC 5 and the wiring of the external wiring board 11, this is for improving the solder wettability, and these gold plating layers 7, 8 are applied. The ground electrode wiring 6 is soldered to the terminal 5a of the driver IC 5 or the wiring of the external wiring board 11 only at the position where the wiring is provided. As shown in FIG. 3, a plurality of the gold plating layers 7 for IC connection are provided in a row on the individual ground electrode wirings 6 along the length direction of the driver IC 5.

The ground electrode wiring 6, like the common electrode wiring 3 and the individual electrode wiring 4, is made of a metal such as aluminum by a conventionally known sputtering method and photolithography technique, and has a predetermined thickness and a predetermined thickness. It is formed on the upper surface of the insulating substrate 1 by being attached to a pattern.

The gold plating layer 7 for IC connection and the gold plating layer 8 for external connection are adhered to the ground electrode wiring 6 to a thickness of 2.0 to 5.0 μm by using a conventionally known electroplating method or the like. Are formed at the same time.

On the surface of the ground electrode wiring 6 and in the region between the gold plating layer 7 for IC connection and the gold plating layer 8 for external connection, a band-like gold plating extending substantially parallel to the length direction of the driver IC 5 is provided. The layer 9a is formed.

The band-shaped gold plating layer 9a is formed by the above-described IC.
Gold (Au) of the same thickness (2.0-5.0 μm) as the connection gold plating layer 7 and the external connection gold plating layer 8 and of the same quality
Thus, a wall is formed between the plurality of gold plating layers 7 for IC connection and the gold plating layer 8 for external connection,
A part thereof extends toward a region between the adjacent gold plating layers 7-7 for IC connection.

The band-shaped gold plating layer 9a has a poor wettability with an epoxy resin (liquid precursor) for forming the protective resin 10, which will be described later. The position of the edge of the protective resin 10 can be set by blocking the flow well, and it is effective that the liquid precursor tries to spread toward the solder joint with the external wiring board 11 beyond the band-shaped gold plating layer 9a. Can be prevented. As a result, the surface of the external connection gold plating layer 8 can be exposed in a good state when soldering the external wiring board 11, and the productivity of the thermal head is improved.

Since a part of the band-shaped gold plating layer 9a extends toward the region between the adjacent IC connection gold plating layers 7-7, the protective resin 10 is formed on the insulating substrate 1. At this time, a part of the liquid precursor is poured into the region between the adjacent gold plating layers 7-7 for IC connection along the extending portion A, and a part of the protective resin 10 is partially removed from the upper surface of the insulating substrate 1 and the lower surface of the driver IC5. Can be satisfactorily filled in the gaps between them. Thereby, the insulating substrate 1 and the driver IC 5
Almost no air bubbles exist between them, and even when heat for curing the liquid precursor or heat for using the thermal head is applied, the driver IC 5 can be attached and mounted well, This also increases the thermal head productivity,
In addition, the reliability can be greatly improved.

Further, the band-shaped gold plating layer 9a is made of an IC.
Since it is formed of the same material (plated gold) as the connection gold plating layer 7 and the external connection gold plating layer 8, etc., these gold plating layers 7, 8, 9a can all be formed simultaneously in the same process. This also keeps the productivity of the thermal head high.

Further, as shown in FIG. 2 and FIG. 3, if a gold plating layer 9b is individually applied to a part of the upper surface of the individual electrode wiring 4 as well, when the protective resin 10 is formed on the insulating substrate 1, The flow of the liquid precursor can be satisfactorily blocked on the heating element 2 side as well, so that the amount of the liquid precursor used to form the protective resin 10 can be minimized. Therefore, it is preferable that the gold plating layer 9b is also individually applied to the upper surface of a part of the individual electrode wiring 4.

Furthermore, by forming the band-shaped gold-plated layer 9a and the gold-plated layer 9b on the individual electrode wiring 4 at a position separated from the gold-plated layer 7 for IC connection by 200 to 400 μm, the individual gold-plated layers 7, 9a and 9b can be more accurately patterned. Therefore, the band-shaped gold plating layer 9a and the gold plating layer 9b are used as the gold plating layers 7 for IC connection.
Is preferably formed at a position 200 to 400 μm away from the substrate.

The band-shaped gold plating layer 9a is connected to the ground electrode wiring 6 with a thickness of 2.0 to 5.0 μm by using a conventionally known electrolytic plating method or the like, as described above. It is formed simultaneously with the gold plating layer 7 for external use and the gold plating layer 8 for external connection.

The plurality of driver ICs described above
5 is commonly covered with a protective resin 10. The protective resin 10 is made of an epoxy resin or the like, and in addition to protecting the plurality of driver ICs 5 from corrosion due to contact with moisture or the like contained in the air, sliding contact with the thermosensitive recording medium, and the like,
By supporting a heat-sensitive recording medium such as heat-sensitive paper on its surface during printing, it also functions as a guide member for guiding the heat-sensitive recording medium onto the heating element 2.

When the protective resin 10 is made of, for example, an epoxy resin, a plurality of driver ICs 5 are formed by using a liquid epoxy resin precursor by using a dispenser or the like.
A plurality of driver ICs 5 are applied in a strip shape on the upper side and heated and cured at a temperature of 100 to 200 ° C.
Are formed so as to cover the common.

Further, on the rear end side of the insulating substrate 1, an external wiring substrate 11 is soldered. The external wiring board 11 is made of a flexible printed wiring board (FPC) or the like, and is connected to an external electric circuit such as a printer body via a connector 12 attached to one end of the external wiring board. 2 and the driver IC 5 are supplied with signals such as electric power and print data from the printer main body.

Thus, the above-described thermal head of the present invention is driven by the driver IC 5 to drive the common electrode wiring 3
The heat generating elements 2 are selectively and individually heated by the power supply power applied between the individual electrode wirings 4, and the generated heat is transmitted to a heat-sensitive recording medium such as a heat-sensitive paper, so that the heat-sensitive recording medium corresponds to print data. By forming a predetermined printed image, it functions as a thermal head.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention.

For example, in the above-described embodiment, the plurality of gold plating layers 7 for IC connection applied on the upper surface of the ground electrode wiring 6 are arranged in a line, but they may be arranged in a zigzag instead. .

In the above embodiment, nickel (Ni) is applied between the ground electrode wiring 6 and the various gold plating layers 7, 8, 9a, 9b in order to maintain a high adhesion between them.
A plating layer, a palladium (Pd) layer, or the like may be interposed.

Further, in the above-described embodiment, the extending portion A of the band-shaped gold plating layer 9a is formed in a triangular shape. Alternatively, the extending portion A of the band-shaped gold plating layer 9a may be formed in a rectangular shape.

Further, in the above embodiment, the gold plating layer for IC connection is formed in a square shape. Alternatively, the gold plating layer for IC connection may be made circular.

Further, in the above-described embodiment, the heating element 2 and the like on the insulating substrate 1 are replaced with the protective film 1 made of silicon nitride, glass or the like.
3 may of course be applied.

[0042]

According to the thermal head of the present invention, the driver I is provided on the surface of the ground electrode wiring and in the region between the gold plating layer for IC connection and the gold plating layer for external connection.
Since the band-shaped gold plating layer extending substantially in parallel with the length direction of C is formed, when the protective resin is formed on the insulating substrate, the flow of the liquid precursor serving as the protective resin causes the band-shaped gold plating having poor wettability of the precursor. The layer can provide good damping and the position of the edge of the protective resin can be set. Therefore, when the external wiring board is soldered, the surface of the external connection gold plating layer can be exposed in a favorable state, and the productivity of the thermal head can be improved.

According to the thermal head of the present invention, a plurality of the gold plating layers for IC connection are provided, and the gold plating layers for IC connection are arranged in a row or in a staggered manner along the length direction of the driver IC. By forming a part of the strip-shaped gold plating layer toward an area between the adjacent gold plating layers for IC connection, when the protective resin is formed on the insulating substrate, a part of the liquid precursor is extended by this extension. It flows into the gap between the driver IC and the insulating substrate along the portion, and a part of the protective resin can be filled well. Therefore, almost no air bubbles exist between the insulating substrate and the driver IC, and even if heat for curing the liquid precursor or heat for using the thermal head is applied, the driver IC is not used.
Can be satisfactorily attached and mounted, which also greatly improves the productivity and reliability of the thermal head.

Further, according to the thermal head of the present invention, since the band-shaped gold plating layer is formed by the same gold plating as the gold plating layer for IC connection and the gold plating layer for external connection, all of these gold plating layers are simultaneously formed in the same step. And the productivity of the thermal head is kept high.

[Brief description of the drawings]

FIG. 1 is a plan view of a thermal head according to one embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is an enlarged view of a main part showing patterns of various gold plating layers provided on the thermal head of FIG. 1;

FIG. 4 is a sectional view of a conventional thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating board 2 ... Heating element 3 ... Common electrode wiring 4 ... Individual electrode wiring 5 ... Driver IC 5b ... Terminal 6 ... Ground electrode wiring 7 ... IC connection Gold plating layer 8 ... Gold plating layer for external connection 9a ... Belt-shaped gold plating layer 10 ... Protective resin

Claims (2)

[Claims] 1. A heating element array in which a plurality of heating elements are linearly arranged on an upper surface of an insulating substrate; a common electrode wiring connected to one end of each of the heating elements; A plurality of individual electrode wirings to be connected; a rectangular driver IC electrically connected to the individual electrode wirings and arranged substantially in parallel with the heating element row; A gold-plated layer for IC connection for solder bonding, and a gold-plated layer for external connection for solder bonding to wiring of an external wiring board are attached on the upper surface of the other end side, and a heating element is provided via the driver IC and the individual electrode wiring. And a protection resin for covering the driver IC. The heating element is turned on by power supplied between the common electrode wiring and the ground electrode wiring. A thermal head to be heated and driven, comprising: a band extending substantially parallel to the length direction of the driver IC on a surface of the ground electrode wiring and in a region between the gold plating layer for IC connection and the gold plating layer for external connection. A thermal head, wherein a gold plating layer is formed, and the position of the edge of the protective resin is set by the band-shaped gold plating layer. 2. A plurality of gold plating layers for IC connection are provided on a single ground electrode wiring, and the gold plating layers for IC connection are arranged in a row or in a staggered manner along the length direction of the driver IC. 2. The thermal head according to claim 1, wherein a part of the band-shaped gold plating layer extends toward a region between the adjacent gold plating layers for IC connection.