JPH1120216A - Thermal head, wire bonding method for thermal head, and manufacture of thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal head capable of achieving good printing density even when printing on a thick paper and of preventing variation of printing. SOLUTION: A thermal head comprises individual lead electrodes 5 which are connected to each of heating dots of heating resisters 4 arranged in a line on an insulation substrate 2 and have connecting terminals 5a, and a circuit board 3 on which a driving IC 9 for energizing each of the heating dots of heating resisters 4 is mounted. An output side connection terminal 9a of the driving IC 9 and a connection terminal 5a of the individual lead electrode are connected with a conductive wire 10 and an input side connection terminal 9b of the driving IC 9 and a connection terminal 3a of the circuit board are connected with a conductive wire 11. At that time, the height of the face of the connection terminal 5a is greater than that of each of the faces of the connection terminals 9a, 9b and the driving IC is sealed by a resin 13a. The height of the resin at the upper section of the input side connection terminal 9b is smaller than that of the resin at the upper section of the connection terminal 5a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal head,
The present invention relates to a wire bonding method for the thermal head and a method for manufacturing the thermal head.

[0002]

2. Description of the Related Art As shown in a plan view of FIG. 5, in a general structure of a thermal head, an insulating substrate 2 and a circuit substrate 3 are mounted on a support plate 1 made of aluminum or the like. On the insulating substrate 2, a heating resistor 4 is linearly arranged along one long side of the insulating substrate 2, and individual lead electrodes 5 individually connected to each dot of the heating resistor 4 are arranged. ing. Further, a common electrode 6 for passing a current commonly to each dot of the heating resistor 4 is arranged between one long side of the insulating substrate 2 and the heating resistor 4. Further, a protective film (not shown) is provided on the individual lead electrodes 5 and the common electrode 6, and both ends of the individual lead electrodes 5 and the common electrode 6 are orthogonal to the insulating substrate 2. The ends of the common electrodes provided along the short sides are exposed from the protective film to become individual lead electrode connection terminals 5a and common electrode connection terminals 6a, respectively.

The circuit board 3 has conductor wiring (not shown).
The connector 7 is attached as a means for connecting the conductor wiring to the outside. A drive IC 9 for driving each dot of the heating resistor 4 is mounted at a predetermined interval along a contact portion 8 where the circuit board 3 and the insulating substrate 2 are in contact with each other. 9a
The connection terminals 5a of the individual lead electrodes on the insulating substrate 2 are wire-bonded with the output wires 10. Similarly, the input connection terminals 9b of the drive IC 9 and the connection terminals 3a of the circuit board 3 are connected to the input wires. 11 is wire-bonded. Further, the common electrode connection terminal 6a
And the common electrode side connection terminal 3 b of the circuit board 3 are wire-bonded with the wire 12.

The drive IC 9 and the vicinity of the wire bonding are covered with a resin 13 and sealed. In the wire bonding, the connection terminals 9a and 9b of the drive IC 9 are bonded first (first bonding), and then the individual lead electrode connection terminals 5a of the insulating substrate 2 and the connection terminals 3a of the circuit board 3 are bonded (2nd bonding). ) Is done.

The problems of the thermal head are described below with reference to FIG.
The description will be made with reference to the plan view of FIG. FIG. 7 shows an AA ′ section of FIG. As shown in FIG. 7, a circuit board 3 having a slightly smaller thickness than the insulating board 2 placed on the support plate 1 is placed in contact with the contact portion 8, and is placed on the circuit board 3. The driving IC 9 is mounted. Then, the output side wire 1 from the drive IC 9 is output.
0, each connection terminal is connected by an input wire 11, and the upper portion thereof is covered with the resin 13 and sealed.

Here, the insulating substrate 2 is made of a ceramic plate and has a standard thickness of 1 mm. On the other hand, the circuit board 3 uses a glass epoxy plate and has a standard thickness of 0.1 mm.
There are various sizes in increments of 2 mm. In this case, a 0.8 mm glass epoxy plate slightly thinner than the insulating substrate 2 is used.

The standard thickness of the drive IC 9 mounted on the circuit board 3 is 0.35 mm, and the height from the upper surface of the support plate 1 to the upper surface of the drive IC 9 is (0.8 mm + 0. 35 mm) = 1.15 mm.
Therefore, the difference in height between the upper surface of the drive IC 9 and the upper surface of the insulating substrate 2 is (1.15 mm-1.0 mm) = 0.
The upper surface of the drive IC 9 is higher by 15 mm.

Next, looking at the bonding portion of the common electrode 6, FIG. 8 shows a cross section taken along line BB 'of FIG. As shown in FIGS. 5 and 8, the common electrode connection terminal 6 a and the common electrode side connection terminal 3 b of the circuit board 3 are connected by wires 12.

Next, the problem of sealing with the resin 13 will be described with reference to FIG. In order to prevent corrosion of the mounting portion of the drive IC 9 and the wire bonding portion of the circuit board 3 due to moisture or the like, a resin 13 is applied and sealed. In this case, an epoxy resin is used as the resin 13, but this epoxy resin is adopted because the hardness of the cured resin layer is large and it is not necessary to separately provide a protective cover for protecting the inside from external force. I have.

In order to prevent moisture from intruding from the surface of the resin layer of the resin 13, it is necessary to apply the resin while securing a predetermined thickness from the upper surface of the drive IC 9 and the height of wire-bonded wires. The thickness of this resin is generally required to be 0.2 mm or more. Therefore, drive I
The coating is applied so that the resin thickness of the upper portions of the neck portions 10a and 11a of the wires 10 and 10 at the highest position near the mounting portion of C9 can be secured to 0.2 mm or more. Here, the neck portions 10a and 11a serve as pull-up portions of the wires 10 and 11 in the first bonding, and are required to be substantially vertically 0.15 mm or more. The reason is that when the wire is, for example, a gold wire, when this portion is subjected to wire bonding, the gold wire recrystallizes when a ball is formed by heating the tip of the wire, and becomes harder than the original gold wire height. This is because if the wire is connected in a bent shape at a portion, a problem such as breakage of the wire occurs.

Therefore, at the time of wire bonding, the wires 10 and 11 are firstly erected at the neck portions 10a and 11a by the first bonding, and the wires 10 and 11 are set up at approximately 0.15.
2nd as a shape that is gently bent around
It moves to the bonding side via the capillary of the wire bonding apparatus and the XY moving means, and is wire-bonded. After the completion of the wire bonding, the resin 8 is applied, and the cross-sectional shape of the applied resin 8 becomes a semi-cylindrical shape that is almost symmetric about the drive IC 9.

[0012]

With reference to FIG. 6, a description will be given of a state in which the problems of the thermal head thus configured are actually incorporated in a printer. As shown in FIG. 6, the center of the platen roller 14 is aligned with the heating resistor 4 of the thermal head, and the platen roller 14 is fixed by applying a constant pressing force to the heating resistor 4. Then, the paper 15 is inserted between the heating resistor 4 and the platen roller 14 from the circuit board 3 side, and the heating resistor 4 is energized while feeding the paper by the rotation of the platen roller 14 to perform printing.

At this time, the paper 15 is fed at the entrance angle α. However, if the paper 15 enters at an angle equal to or smaller than the entrance angle α, the paper 15 comes into contact with the resin 8 and the paper cannot be fed.
Since the thickness of the paper normally used is 100 μm or less and soft, the contact with the heating resistor 4 can sufficiently follow even if the angle of approach α to the platen roller 14 is large.
In the case of paper having a thickness of μm or more, for example, label paper, tag paper, film paper PET card, etc., if the paper is strong and the entrance angle α of the paper is large, the pressing force of the platen roller 14 is not sufficiently transmitted to the paper 15. As a result, the pressing force against the heating resistor 4 becomes weak, and as a result, the print density is reduced or the print density becomes uneven.

Therefore, in order to prevent this printing defect, the entrance angle α can be reduced by moving the place where the resin 8 is applied away from the heating resistor 4, but if this is done, the insulating The dimension from the heating resistor 4 to the connection terminal 5a of the individual lead electrode 5 becomes longer,
The insulating substrate itself has to be large, which does not lead to downsizing of the thermal head.

The present invention proposes a thermal head that improves print density even when printing on thick paper, hardly causes print unevenness, and does not hinder miniaturization.

[0016]

According to the present invention, there is provided a thermal head which is individually connected to each heating dot of a heating resistor linearly arranged along one long side of an insulating substrate. An individual lead electrode having a connection terminal disposed along the other long side opposite to the side, a circuit board on which a drive IC for energizing each heating dot of the heating resistor is mounted, the insulating substrate and the circuit A supporting plate for supporting the substrate in contact with the substrate, between the output connection terminal of the drive IC and the connection terminal of the individual lead electrode;
In the thermal head in which the input side connection terminal of C and the connection terminal of the circuit board are respectively connected by conductive wires, the connection of the individual lead electrodes on the insulating substrate is more than the connection terminal surface of the drive IC. Increase the height of the terminal surface. Accordingly, the height of the resin above the connection terminals of the individual lead electrodes on the insulating substrate can be made lower than the height of the resin above the input-side connection terminals of the drive IC, and the drive IC can be sealed with the resin.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to a plan view of FIG. 5 and a sectional view of FIG. It should be noted that the plan view is the same as that of the related art, and therefore, FIG. As shown in FIGS. 1 and 5, an insulating substrate 2 and a circuit board 3 are mounted on a support plate 1. On the insulating substrate 2, a heating resistor 4 is linearly arranged along one long side of the insulating substrate 2, and individual lead electrodes 5 individually connected to each dot of the heating resistor 4 are provided. Are located. Further, a common electrode 6 for passing a current in common to each dot of the heating resistor 4 is arranged. Also, individual lead electrodes 5 and common electrodes 6
A protective film 16 (FIG. 1) is provided thereon, and the terminal portions of the individual lead electrodes 5 and the common electrode 6 are exposed from the protective film 13 to serve as connection terminals.

The circuit board 3 has conductor wiring (not shown).
The connector 7 (FIG. 5) is attached as a means for connecting the conductor wiring to the outside. Also,
A contact portion 8 where the circuit board 3 and the insulating substrate 2 are in contact with each other.
In the vicinity, a drive IC 9 for driving each dot of the heating resistor 4 along the contact portion 8 is mounted at a predetermined interval.
The output side connection terminal 9a of C9 and the connection terminal 5a of the individual lead electrode 5 on the insulating substrate 2 are wire-bonded with a wire 10, and the connection terminal 6a of the common electrode 6 and the circuit board 3 The connection terminal 3b is wire-bonded with a wire 12. The drive IC 9 and the vicinity where the wire bonding is performed are covered with a resin 8a and sealed with the resin 13a for protection.

The thermal head of the present invention will be described in detail with reference to the sectional view of FIG. 1. As shown in FIG. 1, the connection terminal surface of the drive IC 9 to be wire-bonded is positioned lower than the upper surface of the insulating substrate 2. Constitute. Here, as an example, the thickness of the insulating substrate 2 is selected to be a standard 1.0 mm, and the circuit substrate 3 is selected from a glass epoxy substrate having a standard thickness of 0.6 mm in increments of 0.2 mm. Further, the driving IC 9
For this, a general one having a height of 0.35 mm is selected. With this selection, the upper surface of the insulating substrate 2 and the drive I
The difference in height of the upper surface of C9 is 1.0- (0.6 + 0.3
5) = 0.05 mm, and the upper surface of the drive IC 9 can be made lower than before. That is, by making the connection terminal surface of the drive IC 9 lower than the upper surface of the insulating substrate 2,
As a result, the height of the resin 13a to be applied can be reduced.

On the insulating substrate 2, an individual lead electrode 5 is formed, on which a common electrode 6, a heating resistor 4, and a protective film 16 are further formed. The individual lead electrode 5
Is exposed in the vicinity of the side of the contact portion 8 between the insulating substrate 2 and the circuit board 3 to form a connection terminal 5a. As for the cross-sectional shape of the resin 13a applied after the wire bonding, it is necessary to secure the thickness from the upper surface of the drive IC 9 and the wires 10 and 11 to 0.2 mm or more in order to prevent moisture from entering from the resin surface.

Here, looking at the cross-sectional shape of the resin 13a, the output wire 10 is gradually inclined along the wire shape toward the connection terminal 5a of the individual lead electrode 5 on the insulating substrate 2 and the wire 10 and the resin cross-section. In this case, the thickness up to the surface layer is kept constant. On the other hand, the upper portion of the input side wire 11 has a resin thickness of 0.2 mm from the neck portion 11a and the connection terminal 3a on the circuit board 3 side.
It is applied toward. Therefore, the highest position in the cross-sectional shape of the resin 13a is above the neck 11a of the input-side wire 11 or in a range closer to the circuit board 3 than that.

Next, the bonding portion of the common electrode of the thermal head of the present invention will be described. As shown in FIGS. 4 and 5, the common electrode connection terminal 6 a on the insulating substrate 2 is wire-bonded with the wire 12. At this time, the circuit board 3
The side is bonded first (1st bonding), and then the insulating substrate 2 side is bonded (2nd bonding). This is because the order in which the bonding is performed is opposite to that in the related art, in order to reduce the height of the wires 12 passing over the insulating substrate 2 from the surface of the insulating substrate 2.

Thus, the resin 13a at the bonding portion of the common electrode 6 does not become higher than the output wire 10 connected to the drive IC 9, but follows the inclination of the output wire 10 of the drive IC 9 (FIG. 1). If the resin 13a is applied, the thickness from the wire 12 to the upper contour of the resin can be secured to 0.2 mm.

A state in which the thermal head thus constructed is actually assembled in a printer will be described with reference to FIG. As shown in FIG. 2, the center of the platen roller 14 is aligned with the heating resistor 4 and
Is fixed by applying a constant pressing force to the heating resistor 4. Then, the paper 15 is inserted between the heating resistor 4 and the platen roller 14 from the circuit board 3 side, and the heating resistor 4 is energized while feeding the paper by rotation of the platen roller 14 to perform printing.

As described above, in the thermal head of the present invention, the height of the resin 13a can be reduced as described above, and at the same time, the height of the resin 13a decreases toward the insulating substrate 2 side from the neck of the input side wire. Since the sheet is inclined, the entering angle α of the sheet can be made as small as possible. For this reason, even if the sheet is a special thick sheet, the sheet can be inserted between the heating resistor 4 and the platen roller 14 without largely bending the sheet under the platen roller.

Therefore, the pressing force of the platen roller 14 is sufficiently transmitted to the sheet regardless of the influence of the stiffness of the sheet, and it is possible to prevent problems such as a decrease in print density or an uneven print density. A thermal head capable of high quality printing can be realized.

Further, when the thermal head of the present invention is configured to be limited to the use of thin thermal paper, the printing position is not affected even if the paper entering angle is large. By moving from the body, the insulating substrate can be reduced in size. Therefore, the size of the insulating substrate can be reduced. As a result, the circuit board in contact with the insulating substrate also moves, and the mounting position of the driving IC is closer to the heating resistor.

On the other hand, in the conventional thermal head, the height of the resin 13 applied on the insulating substrate is high (FIG. 7). The stop resin contacts the platen roller to prevent the rotation of the platen roller, so that the size of the insulating substrate cannot be reduced, and it can be seen that the effect of the present invention is remarkable as compared with the conventional thermal head.

Next, another embodiment will be described with reference to FIG. In this embodiment, the thickness of the insulating substrate 2 is 1.
0 mm, the thickness of the circuit board 3 is also 1.0 mm, and the step 1 a is provided on the support plate 1, so that the connection terminal surface of the individual lead electrode on the insulating substrate 2 is larger than the connection terminal surface of the drive IC 9. Height can be increased. And
By sealing the drive IC 9 with the resin 13b, the same effect as in the above embodiment can be obtained.

[0030]

According to the present invention, it is possible to realize a high print quality thermal head in which the print density is not reduced even on thick paper and the print density unevenness does not occur. Further, it is possible to supply a thermal head capable of printing both thick and thin paper.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a thermal head according to the present invention.

FIG. 2 is a sectional view when a platen roller is installed on the thermal head of the present invention.

FIG. 3 is a sectional view of another embodiment of the thermal head of the present invention.

FIG. 4 is a sectional view of a main part for describing the thermal head of the present invention.

FIG. 5 is a plan view for explaining a thermal head of the present invention and a general thermal head.

FIG. 6 is a cross-sectional view when a platen roller is installed on a conventional thermal head.

FIG. 7 is a sectional view of a conventional thermal head.

FIG. 8 is a sectional view of a main part for explaining a conventional thermal head.

[Explanation of symbols]

1. Support plate 2. Insulating substrate 3. Circuit board 4.
-Heating resistor 5-Individual lead electrode 6-Common electrode 9-Drive I
C 10, 11 .... Conductive wires 13a, 13b ...
resin

Claims (5)

[Claims] 1. An insulating substrate, a heating resistor linearly arranged along one long side of the insulating substrate, and one end individually connected to each heating dot of the heating resistor and the insulating substrate. An individual lead electrode having a connection terminal disposed along the other long side opposite to the one long side, and a circuit board on which a drive IC for energizing each heating dot of the heating resistor is mounted. Between the output connection terminal of the drive IC and the connection terminal of the individual lead electrode;
In a thermal head in which a connection terminal between the input side connection terminal of C and the connection terminal of the circuit board is connected by a conductive wire, a connection terminal of the individual lead electrode on the insulating substrate rather than a connection terminal surface of the drive IC. A thermal head characterized by a higher surface height. 2. The drive IC is sealed with a resin, and the height of the resin above the connection terminals of the individual lead electrodes on the insulating substrate is lower than the height of the resin above the input connection terminals of the drive IC. The thermal head according to claim 1, wherein 3. The thermal head according to claim 1, wherein a connector for making an electrical connection with the outside is provided on the circuit board. 4. An insulating substrate, a heating resistor linearly arranged along one long side of the insulating substrate, and one end individually connected to each heating dot of the heating resistor and the insulating substrate. An individual lead electrode having a connection terminal disposed along the other long side of the heating resistor, a circuit board on which a drive IC for energizing each dot of the heating resistor is mounted, and An individual lead electrode on the insulating substrate rather than a connection terminal surface of the drive IC of the thermal head having the heating resistor and a common electrode disposed between one long side of the insulating substrate and substantially parallel to the body; The height of the connection terminal surface is increased, and the height between the output side connection terminal of the drive IC and the connection terminal of the individual lead electrode and between the input side terminal of the drive IC and the connection terminal of the circuit board are increased. Connect each with a conductive wire, and Wire bonding of a thermal head in which a common electrode connection terminal disposed orthogonal to the common electrode along both short sides of the insulating substrate and a common electrode side connection terminal of the circuit board are connected by conductive wires. A method, wherein one end of a conductive wire is first wire-bonded to a common electrode-side connection terminal of the circuit board, and then the other end of the conductive wire is wire-bonded to a common electrode-side connection terminal on the insulating substrate. A wire bonding method for a thermal head. 5. An insulating substrate, a heating resistor linearly arranged along one long side of the insulating substrate, one end of which is individually connected to each heating dot of the heating resistor and the insulating substrate. An individual lead electrode having a connection terminal disposed along the other long side of the heating resistor, a circuit board on which a drive IC for energizing each dot of the heating resistor is mounted, and An individual lead electrode on the insulating substrate rather than a connection terminal surface of the drive IC of the thermal head having the heating resistor and a common electrode disposed between one long side of the insulating substrate and substantially parallel to the body; The height of the connection terminal surface is increased, and the height between the output side connection terminal of the drive IC and the connection terminal of the individual lead electrode and between the input side terminal of the drive IC and the connection terminal of the circuit board are increased. Connect each with a conductive wire, and A method of manufacturing a thermal head, comprising connecting a common electrode connection terminal disposed orthogonally to the common electrode along both short sides of the insulating substrate and a common electrode side connection terminal of the circuit board with a conductive wire. When sealing the drive IC with resin, the height of the resin on the connection terminals of the individual lead electrodes on the insulating substrate is lower than the height of the resin on the input connection terminals of the drive IC. A method for manufacturing a thermal head, comprising applying a resin to the substrate.