JP2000280508A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermal head wherein the damage of the connection part of an FPC-head substrate is effectively prevented and FPC can be stably supported by a support member and connection reliability is high. SOLUTION: In a thermal head consisting of a head substrate 1 wherein a heating element row 3 and a plurality of circuit conductors are mounted on a rectangular ceramic substrate so that the heating element row 3 is provided along one long side of the substrate and one ends of these circuit conductors are led out to the other long side of the upper surface of the ceramic substrate and a plurality of circuit terminals are provided to the led-out part side by side, an almost rectangular FPC 6 wherein one end parts are superposed on the ceramic substrate along the other long side thereof and a plurality of wiring terminals joined to the circuit terminals by soldering are provided to one end parts side by side and the support member supporting the head substrate and the FRCs 6, the support member has a large number of through-holes in the region just under the FPCs 6 and longitudinal stress is absorbed by the through- holes 13.

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 has been used as a printer mechanism such as a word processor.

[0003] Such a conventional thermal head, for example,
A long head substrate having a plurality of heating elements arranged in a straight line, and a long flexible wiring board for supplying external power and image data to the heating elements on the head substrate, driver ICs, and the like. (Hereinafter abbreviated as FPC)
And a support member on which the two substrates are mounted.

The head substrate employs a ceramic material such as alumina ceramic as a base, and the FPC employs a polyimide resin film as a base. Both of them use a solder terminal to connect circuit terminals on the head substrate and wiring terminals on the FPC. By joining, they are electrically and mechanically connected.

On the other hand, the support member supports the head substrate and the FPC on the upper surface thereof through an adhesive such as a double-sided tape, and absorbs a part of the heat of the head substrate to keep the head substrate in a good temperature state. For example, and is formed of a metal such as aluminum or SUS.

In such a thermal head, the heat generating elements on the head substrate are selectively and individually heated based on image data from the outside, and the generated heat is transmitted to a recording medium such as a thermal paper to generate a predetermined heat. It functions as a thermal head by forming a print.

[0007]

However, in this conventional thermal head, the thermal expansion coefficient (12.0.times.10.sup.- ⁶ / .degree. C.) of the FPC based on the polyimide resin is used.
Is larger than the thermal expansion coefficient (2.3 × 10 ⁻⁶ / ° C.) of a head substrate or the like based on a ceramic material. Therefore, when the temperature of each component becomes high due to the use of the thermal head or the like, a large thermal stress is applied to the connection portion between the FPC and the head substrate. A situation such as breakage occurs, and this has been one of the causes of reducing the reliability of the thermal head.

Further, F based on polyimide film
The PC is rich in flexibility and has properties that are incompatible with a highly rigid support member, and has a coefficient of thermal expansion of a support member made of aluminum or the like (thermal expansion coefficient: 23.0).
(× 10 ⁻⁶ / ° C.), and when a thermal stress is applied between the two due to the use of a thermal head or the like, the support member tends to stretch more than the FPC and
C has a drawback that a large tensile stress is applied to C, which also causes breakage of the connection portion, and makes it impossible to stably support the FPC with the support member.

Although various studies and proposals have been made on the problem of thermal stress generated when using a thermal head, most of them have been improved in flatness of a head substrate having a heating element array. However, few of them have taken the above-mentioned problem such as breakage of the connection portion between the FPC and the head substrate, and no effective solution to these problems has yet been found.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and a thermal head according to the present invention is provided on a rectangular ceramic substrate along a straight line along one long side of the substrate. A plurality of heating elements and a plurality of circuit conductors arranged in a shape are attached, and one end of each of the circuit conductors is led out to the other long side of the upper surface of the ceramic substrate, and a plurality of circuit terminals are provided at the lead portion. A substantially rectangular shape in which one end portion is overlapped along the other long side of the ceramic substrate and the plurality of wiring terminals to be soldered to the circuit terminal are arranged side by side at the one end portion. A flexible wiring board, and a support member for supporting the head substrate and the flexible wiring board,
The support member has a large number of through holes in a region directly below the flexible wiring board, and the through holes absorb longitudinal stress.

The thermal head according to the present invention is characterized in that the plurality of through holes are each formed in a regular hexagonal shape, and are formed in a state of being close to a honeycomb shape.

Further, in the thermal head according to the present invention, the support member is formed by attaching a glass epoxy plate to a partial upper surface of a metal plate, and the plurality of through holes are formed only in the glass epoxy plate. It is characterized by the following.

Still further, the thermal head according to the present invention is characterized in that the total area of the opening areas of the through holes in the area where the through holes are formed is 30% to 70% of the area of the entire area. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 1 is a perspective view of a thermal head according to one embodiment of the present invention, FIG. 2 is an exploded perspective view of the thermal head of FIG. 1, and FIG. 3 is a cross-sectional view of the thermal head of FIG.
1 is a head substrate, 2 is a ceramic substrate, 3 is a heating element array, 4 is a circuit conductor, 5 is a circuit terminal, 6 is an FPC (flexible wiring board), 7 is a wiring conductor, 8 is a wiring terminal, 9 is a solder, 10 Is a support member.

The head substrate 1 has a heating element array 3 and a plurality of circuit conductors 4 arranged along one long side on a top surface of a rectangular ceramic substrate 2 in a predetermined pattern. In addition, one end of each of the circuit conductors 4 is led out to the other long side of the upper surface of the ceramic substrate, and a plurality of circuit terminals 5 are arranged in a row at the leading portion.

The ceramic substrate 2 is made of, for example, a ceramic material such as alumina ceramic, and has a heating element array 3, a circuit conductor 4, a driver IC (not shown)
It functions as a supporting base material for supporting the like.

When the ceramic substrate 2 is made of alumina ceramics, an appropriate organic solvent and solvent are added to and mixed with ceramic raw material powder such as alumina, silica, and magnesia to form a slurry. The ceramic green sheet is obtained by employing the doctor blade method, the calendar roll method, or the like, and is punched into a predetermined rectangular shape, and then fired at a high temperature.

The heating element array 3 is, for example, 300d
The heating element 3a is composed of a plurality of heating elements 3a arranged linearly at a dot density of pi.
Since it is made of an electric resistance material such as Ti-Si-O system or Ti-C-Si-O system, when electric power is supplied from the outside via the circuit conductor 4 or the FPC 6, Joule heat is generated individually. A predetermined temperature required for forming a print is obtained.

On the other hand, the circuit conductor 4 functions as a power supply wiring or a signal wiring for supplying external power, image data, and the like to the heating element 3a and the driver IC. One end is led out to the other long side of the upper surface of the ceramic substrate, and a plurality of circuit terminals 5 are juxtaposed at the lead-out portion.

The heating element 3a and the circuit conductor as described above
4 is deposited and formed in a predetermined pattern on the upper surface of the ceramic substrate 2 by employing a conventionally known thin film method, specifically, sputtering, photolithography, etching, or the like.

Next to the head substrate 1, substantially rectangular FPCs 6 are juxtaposed with one end thereof superposed along the other long side of the ceramic substrate 2.

The FPC 6 is formed by supporting a wiring conductor 7 made of a metal such as copper on a film 6a made of a polyimide resin, and leading one end of the wiring conductor 7 to the above-mentioned overlapping portion.
A plurality of wiring terminals 8 are arranged in a line in the lead-out portion.

In the FPC 6, a plurality of wiring terminals 8 arranged in parallel at one end thereof are individually soldered to corresponding circuit terminals 5 of the head substrate 1, whereby the head substrate 1 and the FPC 6 are connected to each other. Are electrically and mechanically connected.

The FPC 6 connects the head substrate 1 to the printer main body and supplies power, image data, and the like from the outside (the printer main body and the like) to the heating element 3 and the driver IC on the head substrate 1. At the rear end, a connector 14 for connecting the thermal head to the printer body is attached.

The soldering of the FPC 6 is performed by heating and melting the solder 9 interposed between the circuit terminal 5 and the wiring terminal 8 using a heater bar or the like.

Further, the head substrate 1 and the FPC 6 soldered as described above are mounted and fixed on the upper surface of the support member 10.

The support member 10 includes a substantially rectangular metal plate 11.
And a substantially rectangular glass epoxy plate (glass cloth base epoxy resin substrate) 12 having a width smaller than that of the metal plate 11. It has a structure integrally attached by a system adhesive.

A glass epoxy plate among the support members 10
The FPC 6 is mounted and fixed in an area where the glass epoxy plate 12 is arranged, and the head substrate 1 is mounted and fixed in an area where the glass epoxy plate 12 is not arranged. Therefore, head substrate 1
Is on the upper surface of the metal plate 11, and FPC6 is a glass epoxy plate
It will be placed directly on the upper surface of each of the twelve.

The metal plate 11 constituting the supporting member 10 absorbs heat in the head substrate 1 and dissipates it into the atmosphere, thereby effectively preventing the head substrate 1 from being excessively heated. The glass epoxy plate 12 acts as a plate, and the glass epoxy plate 12 functions as a spacer to fill a step formed between the head substrate 1 and the FPC 6, and the connector 14 is inserted into and removed from the connector of the printer body when the thermal head is incorporated into the printer body. It also has a function as a reinforcing member for preventing the FPC 6 from being bent and damaged by an external force applied at that time.

The glass epoxy plate 12 disposed immediately below the FPC 6 has a large number of through-holes 13 formed in the central region in the longitudinal direction.

The large number of through holes 13 are formed in a regular hexagon having a diameter of each circumscribed circle of 8 mm to 14 mm, and are formed in a honeycomb-like state. Since a pair of opposite sides of the two sides are arranged substantially parallel (± 1 °) to the longitudinal direction of the FPC 6, the strength of the glass epoxy plate 12 is maintained high, and the elasticity in the longitudinal direction is enhanced. .

Therefore, when the temperature of the thermal head becomes high due to the use of the thermal head or the like, even if the constituent members of the thermal head try to thermally expand in accordance with the respective thermal expansion coefficients, the above-mentioned many through holes 13 are formed in FIG. By deforming and expanding and contracting the glass epoxy plate 12 in the longitudinal direction as shown in (1), the thermal stress in the longitudinal direction applied between the FPC 6 and the support member 10 and between the FPC 6 and the support member 10 is favorably absorbed and relaxed. be able to. Therefore, damage of the connection portion due to thermal stress applied between the FPC 6 and the head substrate 1 is effectively prevented, and the FPC 6
6 can be stably supported by the supporting member 10, and a thermal head with high connection reliability can be obtained.

Moreover, in this case, the through hole 13 is
The entire lower surface of the head substrate 1 is covered with the metal plate
Can be securely brought into contact with the upper surface of the
The heat dissipating action of 10 is not hindered. Therefore, when the thermal head is used, the head substrate 1 can be maintained at a favorable temperature.

The plurality of through-holes 13 are formed by setting the sum of the opening areas of the through-holes 13 in the drilling region within a range of 30% to 70% of the entire area of the drilling region.
It is possible to maintain appropriate stretchability and high mechanical strength.

If the plurality of through holes 13 are filled with a silicone resin, the mechanical strength can be kept high without impairing the stretchability even when the opening ratio of the through holes 13 is high. Can be.

The supporting member 10 is formed by punching a glass epoxy substrate formed by impregnating and polymerizing a predetermined glass cloth with a precursor of an epoxy resin to form a glass epoxy plate having a plurality of through holes 13. 12 is manufactured, and is bonded and fixed with an acrylic adhesive to the upper surface of a metal plate 11 formed one size larger than the glass epoxy plate 12 by a conventionally known metal working method.
When manufacturing the support member 10 by such a manufacturing method, a metal plate
As compared with the case where the through-holes 13 are formed by etching or the like in the step 11, the processing time is less, and the assembling workability and productivity of the thermal head can be improved.

Thus, the above-described thermal head supplies electric power from the outside to the heating element 3 via the FPC 6 and the circuit conductor 4 of the head substrate 1, and selectively supplies the heating element 3 individually based on external image data. Joule heat is generated, and the generated heat is conducted to a recording medium such as thermal paper to form a predetermined print, thereby functioning 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 embodiment, the support member 10 is constituted by the metal plate 11 and the glass epoxy plate 12, but the support member 10 may be constituted by only the metal plate 11 instead. In this case, the through hole 13 is formed in the metal plate 11, and in order to impart appropriate elasticity to the metal plate 11, when the metal plate 11 is made of aluminum, the thickness is 0.5 mm to
It is preferable to set it to 2.0 mm.

In the above embodiment, the shape of the through hole 13 is a regular hexagon, but the shape of the through hole 13 may be circular, elliptical, or rhombic instead. In this case, although the elasticity of the support member 10 is inferior to the above-described embodiment, there is an advantage that the workability of drilling is improved.

[0041]

According to the thermal head of the present invention, FP
Since a large number of through-holes are formed in the support member located in the area directly below C, when the temperature of the thermal head becomes high due to the use of the thermal head or the like, the components of the thermal head have respective thermal expansion coefficients. Accordingly, even if the thermal expansion is attempted, the through hole of the support member is deformed and expands and contracts in the longitudinal direction, so
Longitudinal thermal stress applied between the connection portion between C and the head substrate or between the FPC and the support member can be favorably absorbed and reduced. Therefore, it is possible to obtain a thermal head with high connection reliability, in which damage to the connection portion of the FPC-head substrate can be effectively prevented, and the FPC can be stably supported by the support member.

According to the thermal head of the present invention, each of the plurality of through-holes is formed in a regular hexagonal shape and is formed in a honeycomb-like manner so that the strength of the supporting member is maintained at a high level. In addition, the above-mentioned expansion and contraction action can be exhibited extremely favorably.

Further, according to the thermal head of the present invention, the support member is composed of a metal plate and a glass epoxy plate, and the through hole is formed only in the glass epoxy plate, so that the thermal head can be easily assembled. Thus, a thermal head with high productivity can be obtained.

Further, according to the thermal head of the present invention, the sum of the opening areas of the through holes in the through holes is set within a range of 30% to 70% of the total area of the through holes. Thereby, a suitable stretch property and high mechanical strength can be maintained.

[Brief description of the drawings]

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

FIG. 2 is an exploded perspective view of the thermal head of FIG.

FIG. 3 is a cross-sectional view of the thermal head of FIG.

FIG. 4 is a plan view for explaining the effect of absorbing and relaxing thermal stress.

[Explanation of symbols]

1 ... head substrate, 2 ... ceramic substrate, 3 ...
Heating element row, 4 ... circuit conductor, 5 ... circuit terminal,
6 ... flexible wiring board (FPC), 7 ... wiring conductor, 8 ... wiring terminal, 9 ... solder, 10 ... support member, 11 ... metal plate, 12 ... glass Epoxy board

Claims (4)

[Claims] 1. A plurality of heating elements and a plurality of circuit conductors arranged linearly along one long side of a rectangular ceramic substrate are provided on a rectangular ceramic substrate. One end of the ceramic substrate is led out to the other long side of the upper surface of the ceramic substrate, and a plurality of circuit terminals are juxtaposed on the head part, and one end is overlapped along the other long side of the ceramic substrate. A substantially rectangular flexible wiring board in which a plurality of wiring terminals to be solder-bonded to the circuit terminals are provided at one end thereof; and a support member for supporting the head substrate and the flexible wiring board. The support member has a large number of through holes in a region directly below the flexible wiring board, and the through holes absorb longitudinal stress. De. 2. The thermal head according to claim 1, wherein each of the plurality of through holes has a regular hexagonal shape and is formed in a state of being close to a honeycomb shape. 3. The support member according to claim 1, wherein a glass epoxy plate is attached to a part of the upper surface of the metal plate, and the plurality of through holes are formed only in the glass epoxy plate. 2. The thermal head according to 1. 4. The thermal head according to claim 1, wherein the total area of the openings of the through holes in the through holes is 30% to 70% of the total area of the through holes.