JP2507318Y2 - Thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a thermal head used in a thermal printer or the like.

(B) Conventional Technique In general, this type of thermal head is provided with a heating resistor array and a plurality of lead wires for supplying a drive current to the heating resistor array on a ceramic substrate. Since such a thermal head uses Joule heat when the resistor is energized, the smaller the resistance value of the lead wiring, the better.However, the pattern of the lead wiring portion is formed by the thick film technique or the thin film technique. Therefore, the resistance value of the lead wiring portion is determined by the film thickness and the pattern size. When the dot pitch of the heating resistor array is fine and the width of the lead wiring part must be reduced, the resistance value of the lead wiring becomes high. The drive circuit is being designed.

(C) Problems to be Solved by the Invention However, recently, thermal heads have come to be used also in printing units of portable copying machines and word processors. Since such a portable device is driven by a battery, the power consumption of the printing unit is naturally limited to a certain level or less. Particularly in the thermal head, it is extremely important to reduce the resistance value of the lead wiring portion described above in order to reduce the power consumption of the entire thermal head. As a method of reducing the resistance value of the lead wiring part, it is effective to increase the film thickness of each lead wiring and to reinforce it by laminating another conductor material on the upper part of the lead wiring. Since there is a problem of complication and the film thickness cannot be made too thick, there is a certain limit to the reduction of the resistance value.

An object of the present invention is to efficiently reduce the resistance value (wiring resistance) of a lead wire that supplies a drive current to a heating resistor, and to provide a thermal head with less power loss in the lead wire portion.

(D) Means for Solving the Problems In this invention, a conductor head is provided in a thermal head in which a plurality of heating resistors are provided on a substrate and wiring for supplying a driving current to each heating resistor is provided. A wiring board is provided, and the wiring for supplying the drive current and the conductor wiring are electrically connected in parallel.

(E) Action In the thermal head of the present invention, a plurality of heat generating resistors and wiring for supplying a drive current to each heat generating resistor are provided on the substrate. Further, the wiring board is only provided with conductor wiring. That is, since the conductor wiring is simply provided on the wiring board, for example, a copper foil is attached to a flexible substrate and the conductor foil is etched to form a conductor wiring having a low wiring resistance.
Here, by constructing a wiring board having such conductor wiring and electrically connecting the wiring for supplying the driving current and the conductor wiring in parallel, the driving current supplied to the heating resistor is It flows through the wiring for supplying the driving current and the conductor wiring provided on the substrate. That is, the wiring resistance in the thermal head can be significantly reduced.

(F) Embodiments FIGS. 1A and 1B show the structure of a thermal head according to an embodiment of the present invention.

FIG. 1A is a front view of the thermal head, and FIG. 1B is a left side view. In the figure, 10 is an insulating substrate such as ceramics, 11 is a heating resistor array, 12 is a common lead commonly connected to each heating resistor, and 12 'is a common lead connection terminal connected to the outside. is there. Reference numeral 13 is an individual lead drawn out for each heating resistor, and 5 is a driving IC for driving each heating resistor, which is wire-bonded to the individual lead 13 via a wire 15. Reference numeral 14 is a connection terminal for inputting a print signal from the outside, and the IC 5 is wire-bonded with a wire 16. Further, a resin 6 is molded on top of the IC5. 2 is a flexible cable which is an example of a wiring board according to the present invention, 20 is an insulating film such as polyimide that forms the base of the flexible cable, and 21 is a copper formed on the surface side of the film 20 that contacts the substrate 10. It is a conductor wiring of foil. As shown in FIG. 1 (A), the conductor wirings 21 are formed so as to have the same pitch as the individual leads 13, and the conductor wirings 21 and the individual leads 13 and the conductor wirings 21 are shown at the shaded portions in the drawing. The common lead 12 is electrically connected in parallel. (Two conductor wirings are connected in parallel to the common lead 12 as shown in the figure.) Therefore, the drive current output from the driving IC 5 or input to the IC 5 is the same as the individual lead 13 and the common. In addition to the leads 12, it also flows to the conductor wiring 21 of the flexible cable. Since the resistance value of the conductor wiring 21 is actually lower than that of the leads 12 and 13, most of the current flows through the conductor wiring side of the flexible cable.

The thermal head can be manufactured as follows.

First, a glaze layer is formed on the surface of the end portion of the substrate 10 on which the heating resistor array 11 is to be formed. This is because the vicinity 4 of the heating resistor array 11 is projected to make good contact with the thermal transfer ribbon and the paper. Next, a resistor layer and a conductor layer are formed on the entire surface of the substrate, and the two layers are patterned by a photolithography process to form the common leads 12 and the individual leads 13 and expose the heating resistor array 11. Further, a protective film is formed in a region other than the hatched portion and the mounting portion of the driving IC 5 shown in FIG. 1 (A) to enhance the wear resistance near the heating resistor array, and this film is used later in the flexible cable. The solder resist film is used when soldering.

On the other hand, the flexible cable 2 is formed by laminating a copper foil having a thickness of about 35 μm on one surface of an insulating film such as polyimide, forming an etching resist film by photolithography or by screen printing, and performing etching. Individual lead as shown in (A)
Pattern conductor wiring that matches lead pits such as 13. Further, an insulating film is coated on a portion of the copper foil forming surface other than the soldering area, and the flexible cable is formed by cutting it to a predetermined size shown in FIG. 1 (A).

When soldering the above flexible cable onto the board, a solder film is formed on the exposed portion of the copper foil of the flexible cable by electroplating, and the common lead 12 and individual lead
A solder film is formed on the soldering portion 13 by solder dipping, and soldering is performed by heating and pressurizing the solder forming surfaces of the two so as to face each other. At this time, the solder film thickness after joining is 5 to 6 μm.

Since the copper foil having a thickness of about 35 μm is used as the conductor wiring as described above, the reinforcing effect is 5 to 6 times as large as that of the conventional reinforcing method in which the film thickness of the common leads or the individual leads on the substrate is increased.

As shown in FIG. 1 (B), the thermal head manufactured as described above is bonded to the metal plate 3 which also serves as heat dissipation and incorporated in a thermal printer or the like.

In the above embodiment, the common lead 12 and the individual lead on the board
Although the conductor wiring of the flexible cable is electrically connected in parallel to the wiring 13, the drive current may be supplied only by the conductor wiring of the wiring board as described below.

FIG. 2 is a plan view showing the structure of the thermal head in that case. The difference from the thermal head shown in FIG. 1 (A) is that each lead drawn from the heating resistor array 11 is
That is, no conductor pattern is formed between the leads on the connection terminal side and the driving IC side. That is, the second
In the figure, 12a and 12b are common leads, and 13a and 1b
Although all 3b are individual leads, no pattern is formed in the central portion of the substrate, and the leads are electrically connected by soldering with the conductor wiring 21 of the flexible cable 2. In this case, all the driving current is supplied through the conductor wiring 21 of the flexible cable, but its resistance value is low, and the problem of voltage drop due to wiring resistance is solved.

In the two embodiments described above, since the flexible cable is used as the wiring board, the thickness of the entire thermal head is suppressed, and the thermal transfer ribbon and the paper are not disturbed. In addition, since soldering is performed in a relatively small area at both ends of the flexible cable, solder touch can be prevented even if the wiring pitch is fine.

(G) Effect of the Invention As described above, according to this invention, the drive current for the heating resistor is also supplied by the conductor wiring formed on another wiring board. Therefore, even if the shape of the substrate forming the thermal head must be lengthened, the wiring resistance can be significantly reduced, there is no power loss in the wiring, and the overall power consumption of the thermal head can be reduced. . Therefore, for example, it can contribute to the reduction of the power consumption of the entire battery-driven device. Further, since the wiring resistance is reduced, the fluctuation of the voltage applied to the heating resistor is suppressed, and high printing quality is maintained.

[Brief description of drawings]

1A and 1B are views showing the structure of a thermal head according to an embodiment of the present invention, and FIG. 2 is a view showing the structure of a thermal head according to another embodiment. 2-Circuit board, 10-board, 11-heating resistor array, 12-common lead, 13-individual lead, 21-conductor wiring.

Claims (1)

(57) [Scope of utility model registration request] 1. A thermal head having a plurality of heating resistors on a substrate and wiring for supplying a driving current to each heating resistor, wherein a wiring substrate having conductor wiring is provided and the driving current is supplied. The thermal head is characterized in that the wiring and the conductor wiring are electrically connected in parallel.