JP3170205B2 - Thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head for a printer, and more particularly to a thermal head for a printer which is suitable for miniaturizing and simplifying a printing section of the printer.

[0002]

2. Description of the Related Art FIGS. 4A to 4C show an example of a thermal head conventionally used in a printing section of a printer. FIG.
In FIG. 1A, a heat-generating substrate 2 made of an insulating material such as alumina and a circuit board 3 made of an insulating material such as glass epoxy are mounted on a heat sink 1 made of a good conductor such as aluminum. Further, a heating resistor (heating element) 4 and a driving IC 5 for driving the heating element 4 are mounted on the heating element substrate 2, and wiring (not shown) is provided on the circuit board 3. The driving IC 5 is connected to the wiring on the heating element 4 side and the wiring on the circuit board side by bonding wires 6. The driving IC 5
Is protected by a protective layer 7 made of a thermosetting resin and a metal cover 8. Reference numeral 9 denotes a connector for connecting the wiring of the circuit board 3 to the outside.

FIG. 4B is an enlarged view of a main part of a thermal head showing an example in which a driving IC 5 is connected to wirings on a heating element 4 side and a circuit board 3 side by flip chip on bonding. In the flip-chip on bonding, a bump 10 provided in advance on a surface of the driving IC 5 facing the heating element substrate 2, that is, a lower surface of the driving IC 5, is provided.
Heating element 4 side and circuit board 3 by solder reflow method or the like
The driving IC 5 is connected to the wiring on the side.

FIG. 4C is an enlarged view of a main part of a thermal head showing an example in which a driving IC 5 is connected to wires on the side of the heating element 4 and the circuit board 3 by tape automated bonding (TAB method). is there. In the TAB method, the driving IC 5 and the heating element 4 side and the circuit board 3 are mounted on a copper foil tape 11 provided with solder plating or bumps (not shown) at the ends.
Connect to the side wiring.

Further, in order to easily press a hard, that is, hardly bendable printing medium against the heating element 4, the width of the thermal head, that is, the dimension in the feeding direction of the printing medium (see FIG.
In order to reduce the size of the printing unit by reducing the code W), FIG.
Instead of the flat type described above, an end face type shown below is also considered. FIG. 5 is a side view showing an example of an end face type thermal head, and the same reference numerals as those in FIG. 4 indicate the same or equivalent parts.
In the drawing, a heating element 4 is provided at an end of a curved surface of a heating element substrate 2, and wirings of the heating element 4 and the circuit board 3 are connected to a driving IC 5 by a wire bonding method. This connection method can be based on the TAB method or flip chip on-bonding as described with reference to FIG.

The above-mentioned end-face type thermal head can reduce the dimension W, and can also set the driving I
Since there is no protrusion such as C5 and metal cover 8, there is an advantage that the running property of a hard print medium such as a plastic card can be improved. However, this end-face type thermal head has a problem that the manufacturing process is complicated, and therefore, it lacks mass productivity and is difficult to cope with multi-product production. That is, in the end face type, there is a possibility that productivity may be deteriorated due to difficulty in forming a film on the curved surface portion of the heating element substrate 2 and an increase in the number of photo-etching operations during film processing.

To solve this problem, the following thermal head has been proposed (JP-A-5-50633). In the thermal head shown in FIG. 6, a heating element substrate 2 and a circuit board 3a made of a flexible film are provided on one end surface of a heat sink 1, and a driving IC 5 is mounted on the circuit board 3a side. And
The circuit board 3a is bent along the heat sink 1 and is adhered to another surface (side surface) of the heat sink 1.
A connector 9 is provided at an end of the circuit board 3a.

In this thermal head, since the heating element 4 and the driving IC 5 are arranged on the same surface of the heat sink 1, the dimension W is larger than that of the end face type described with reference to FIG. However, by bending the circuit board, FIG.
Dimension W can be made smaller than that of
In addition, the manufacturing process such as film formation is improved, and the same productivity as that of the planar type can be maintained.

[0009]

The thermal head shown in FIG. 6 has been improved in productivity and dimensions W, but has the following problems which have not been solved. That is, in order to make the entire circuit board 3a flexible, for example, a base film (intermediate layer) made of polyimide, copper electrodes arranged on both sides of the base film, and the copper electrodes are respectively covered. May be composed of a surface layer made of polyimide. As described above, the circuit board 3a is composed of multilayer electrodes and films, and thus has a large thickness. Moreover, since expensive polyimide is used in multiple layers, there is a problem that the cost of the circuit board 3a is increased.

Further, when the circuit board 3a is bent and bonded, the thickness is large, so that the circuit board 3a tends to return to a linear shape against the bending and the heat distortion due to the manufacturing process involving heat. The circuit board 3a may float from the heat sink 1. When such a floating state occurs, the position of the portion on which the driving IC 5 is mounted is deviated from a predetermined position, which may hinder the automatic wire bonding of the circuit board 3a.

In the case of a small-sized printer for labels and cards having a small size, there is a technical background in which an increase in the size of each component is suppressed to further reduce the size of the entire printer. However, there is a demand to reduce the size as much as possible. However, since the flexible substrate 3a has a weak adhesive force with the heat sink 1, if the bending radius of the substrate 3a is small, a floating state occurs due to the influence of the moment and thermal strain. I have to make it big. Then, since the dimension W increases, there has been a problem that the demand cannot be sufficiently satisfied.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has been made to reduce the size W of the thermal head in the feed direction of the print medium, to improve the workability of the bonding operation, and to improve the circuit performance. An object of the present invention is to provide a thermal head capable of reducing the cost of a substrate.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and achieve the object, the present invention provides a heating resistor substrate provided on a heat sink, a heating resistor substrate provided on the heat sink,
A circuit board on which a driving IC for supplying electricity to the heating resistor on the heating resistor is mounted, wherein the circuit board includes:
A first non-flexible portion, a second non-flexible portion, and a flexible portion provided between the first and second non-flexible portions, at least the first non-flexible portion is adjacent to the heating resistor substrate. The first feature is that the first heat sink is arranged on the heat sink.

[0014] The present invention also relates to a second aspect of the present invention, wherein the second inflexible portion of the circuit board is connected to another surface of the heat sink adjacent to the surface of the heat sink to which the first inflexible portion is joined. Wherein the circuit board comprises a flexible layer and a non-flexible layer disposed on at least one side of the flexible layer, and removes a part of the non-flexible layer except for the flexible layer. There is a third feature in that the flexible portion is thus formed.

According to the first to third features, an inflexible portion, that is, a portion having good dimensional stability, of the circuit board can be securely joined to the heat sink, so that the driving IC mounted on the circuit board can be connected to the heating resistor. It is easy to standardize the work of connecting to the body and the circuit on the circuit board, which leads to an improvement in production efficiency. In addition, since at least one of the inflexible portions can be freely changed in angle around the flexible portion, for example, when a connector is connected to the inflexible portion in which the angle can be changed, the degree of freedom of the position of the other party connected to the connector increases.

According to the present invention having the second feature, the circuit board is bent at the flexible portion, and the first unflexible portion and the second non-flexible portion of the circuit board are closely attached to the two surfaces of the heat sink, respectively. it can. In particular, since the bending radius at the flexible portion can be reduced, the protruding portion of the circuit board can be reduced, and the size of the thermal head can be reduced as a whole.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a perspective view of a thermal head showing one embodiment according to the present invention, and FIG. 2 is a side view thereof. Unless otherwise indicated, the same reference numerals as those in FIG. 6 denote the same or equivalent parts. 1 and 2, a heating element substrate 20 provided on one end surface of the heat sink 1 has a mountain-shaped cross section, and a heating element 4 is provided on the top thereof. The heating elements 4 are provided in a large number in the length direction of the heating element substrate 20.
, A current is supplied from the driving IC 5.

The circuit board 30 is formed in a layered form, a flexible layer is disposed on an intermediate layer, and an inflexible layer is disposed on both sides thereof. The inflexible layer is partially removed, and the intermediate layer is formed so that the flexible layer is exposed in that portion. The circuit board 30 includes a portion (flexible portion) 30c where the flexible layer is exposed and two inflexible portions 30 on both sides thereof.
a and 30b. That is, the circuit board 3 is a hard member having good dimensional stability as a whole,
Only a part thereof is made of a soft member so that it can be bent. Here, the inflexible portion does not mean that it is not deformed at all, but means that it is less likely to be deformed than the flexible portion, and the easiness of bending of both portions is relative.

The one inflexible portion 30a is mounted on and bonded to the heat sink 1 on the same side as the side on which the heating element substrate 20 is provided. The inflexible portion 30a has a driving I
C5 is mounted. The other inflexible portion 30b may be bent at the flexible portion 30c and adhered to the heat sink 1 on a vertical surface adjacent to the surface to which the inflexible portion 30a is adhered, The inflexible portion 30b may be rotatable using the portion 30c as a hinge portion.

That is, in the present embodiment, a flexible portion 30c is provided between the non-flexible portions 30a and 30b, unlike the conventional circuit board of FIG. 6 in which the entire circuit board 3a is made flexible. Therefore, even if the bending angle is changed by rotating the flexible portion 30c, the inflexible portion 30a is securely joined to the heat sink 1, so that bending distortion is transmitted to the inflexible portion 30a and the inflexible portion 30a is deformed. I never do. As a result, the inflexible portion 30a can be maintained in a tightly adhered and adhered state on the heat sink 1 while the flexible portion 30c is bent with a small bending radius. In FIG. 1, the protective layer 7 is not shown. Further, on the protective layer 7, FIG.
The metal cover 8 shown in FIG.

In FIG. 2, the position of the non-flexible portion 30b when the circuit board 30 is linear is shown by imaginary lines. As described above, since the angle of the inflexible portion 30b can be freely changed as indicated by the arrow A, an optimum angle can be selected and used according to the position of the mating side connected to the connector 9, and the dimension W can be reduced. When used, the flexible portion 30c can be bent so that the inflexible portion 30b is brought into close contact with the heat sink 1.

Next, a specific example of the circuit board 30 will be described. FIG. 3 is an enlarged sectional view of a main part showing a specific example of the circuit board 30. First, in FIG. 3A, a flexible layer F is disposed on an intermediate layer of the circuit board 30, and non-flexible layers R1 and R2 are disposed on both surfaces thereof. Inflexible layers R1 and R2
Is partially removed to expose the flexible layer F, and the flexible portion 30c
Is formed. An electrode 13 and a polyimide film 14 as a base material are disposed on the core of the flexible layer F, and an insulating layer (coverlay) 15 is disposed on one surface of the electrode 13. The coverlay 15 can be formed of a polyimide film.

Further, an adhesive layer 17 is disposed on the lowermost layer of the non-flexible layer R1, and a glass epoxy substrate 18 is disposed thereon as an insulating layer. Further, an electrode 19 is arranged on the upper layer, and a solder resist layer 20 is formed on the uppermost layer. Since the inflexible layer R2 is the same as the inflexible layer R1, the reference numerals and descriptions are omitted. In this first example, since the polyimide film 14 is used as the base material, FIG.
Since the flexibility is the best among the examples, the rigid member 3
It is suitable for applications where rotation of 0b is frequently expected.

Next, in the circuit board 30 shown in FIG. 3B, the flexible layer F is composed of a base material made of a relatively thin glass epoxy substrate 21 and the electrodes 13. An insulating layer (coverlay) 15 is disposed on one side of the electrode 13. Here, the glass epoxy substrate 2
It is preferable that 1 is made as thin as about 60 μm to have flexibility. The inflexible layers R1 and R2 have the same configuration as in FIG. In the second example, although the flexibility is inferior to that of the first example, the glass epoxy substrate 2
With 1, the dimensional stability is high. Further, since the glass epoxy substrate 21 which is less expensive than a polyimide film can be used, it is suitable for the case where the above-mentioned inflexible member 30b is bonded to the heat sink 1 and used.

In the circuit board 30 shown in FIG. 3C, the flexible layer F is composed of a base material made of a relatively thin glass epoxy substrate 21 and the electrodes 13 as in the second example. are doing. The difference from the second example is that insulating layers (coverlays) 15 and 16 are arranged on both surfaces. In the third example, the insulating layers (coverlays) 15 and 16 on both sides can be used a plurality of times while the glass epoxy substrate 21 maintains high dimensional stability.

As described above, when the flexible portion 30c is frequently bent, it is preferable to use a polyimide film as the base material of the flexible layer F and to provide a high wiring density (for example, 0 mm). In such a case, it is preferable to use a glass epoxy substrate having stable dimensions, that is, a small variation, as a base material from the viewpoint of workability of wire bonding. In the above three examples, the inflexible layers are provided on both sides of the flexible layer F. However, the inflexible layers may be provided only on one side of the flexible layer F.

When the circuit board 30 having the flexible portion 30c shown in FIG. 3A is used, the bending radius of the flexible portion 30c is 1.5 mm with a bending moment (f) of about 500 g / cm. I was able to: On the other hand, the bonding state of the heat sink 1 was also stabilized by setting the mounting portion of the driving IC 5 to the inflexible portion 30a. As a result, the width dimension of the non-flexible portion 30a could be suppressed to 4 mm or less. In the conventional thermal head shown in FIG. 6, it was difficult to suppress the width corresponding to the above to 8 mm or less.

[0028]

As is clear from the above description, according to the first to third aspects of the present invention, the circuit board can be bent with a small bending radius, so that the dimension W can be reduced, and the printer can be made smaller. The size of the printing mechanism can be reduced. Further, since the circuit board can be securely fixed to the heat sink, the dimensional stability is increased, and the wire bonding method with high productivity and low cost can be stably used for connecting the driving IC and the board. Further, since the bending angle of the circuit board can be freely selected, the degree of freedom of the layout of the thermal head in the printing mechanism increases, and the applicability to printers for various uses is expanded.

[Brief description of the drawings]

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

FIG. 2 is a side view of the thermal head according to one embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a circuit board according to one embodiment of the present invention.

FIG. 4 is a side view of a conventional flat thermal head.

FIG. 5 is a side view of a conventional end face type thermal head.

FIG. 6 is a side view of a conventional improved thermal head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat sink, 2, 20 ... Heating element board, 3, 3
0: circuit board, 4 heating element, 5: driving IC, 6
... bonding wire, 7 ... protective layer, 9 ... connector, 30a, 30b ... inflexible part, 30c ... flexible part

Claims (3)

(57) [Claims] 1. A heat sink, a heating resistor substrate provided on the heat sink and having a heating resistor formed thereon, and a driving IC provided on the heat sink and energizing the heating resistor are mounted. And a circuit board, wherein the circuit board comprises a first unflexible portion, a second unflexible portion, and a flexible portion provided between the first and second unflexible portions. A thermal head, wherein a non-flexible portion is arranged adjacent to the heat-generating resistor substrate and joined to the heat sink. 2. The heat sink according to claim 1, wherein the second inflexible portion of the circuit board is joined to another surface of the heat sink adjacent to the surface of the heat sink to which the first inflexible portion is joined. The described thermal head. 3. The circuit board comprises a flexible layer and a non-flexible layer disposed on at least one side of the flexible layer, and a part of the non-flexible layer is removed except for the flexible layer. 3. The thermal head according to claim 1, wherein the flexible portion is formed.