JPS5851830B2 - thermal head - Google Patents

Abstract

PURPOSE:To simplify an outer scanning circuit, reduce photo-etching on the substrate, and miniaturize the device by making a group of conductors coupled to a thermal element into an integral body, and making a print wiring per the integral body.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a thermal head that can be manufactured efficiently and is easy to repair and inspect.

A thermal head is a system in which minute resistance heating elements are arranged in a line or in a matrix, and a specific heating element is selected from among the plurality and energized to generate heat, causing the thermal paper in contact with it to develop color and transmit electrical information. It is something to visualize.

If a large number of heating elements are arranged in a row and each of them is to be electrically controlled, it is common to wire them as shown in FIG.

However, in order to simplify the external circuit, the resistor group R1,...
...shame is a group of certain numbers, usually 8, 16, 3
1 can be set to either N=2n such as 2 or 64.

By repeating this unit of N M more times, now N
=16, the circuit becomes as shown in FIG. 1, and the external circuit has N driver circuits for heating elements, and by switching them with M switching circuits, matrix control of MXN becomes possible.

However, in this case, the heating element resistance has no polarity, so a backflow prevention diode D is connected in series to each resistance.
1... must be placed.

Of course, this diode can also be replaced by a transistor.

As is clear from the wiring diagram in FIG. 1, the thermal head is roughly divided into three parts.

That is, the first part is a row of heating elements and corresponding electrodes, the second part is a backflow prevention diode array, and the third part is a multilayer wiring section for enabling matrix drive.

In the conventional case where all of these three parts are formed on the same substrate, the whole can be compactly integrated into one, but on the other hand, it is difficult to process each element and wiring in the process of forming large substrates. The problem of yield k and production cost is faced.

In other words, the main challenge for the heating element part, which is the first part, is to make it strong enough to withstand contact with paper and high temperatures. It is formed by vapor deposition and photoetching.

Specifically, this heat generating element portion is formed by vapor depositing nichrome or the like on a ceramic substrate or the like which has been subjected to high heat treatment in a vacuum, and then forming a fine pattern using a photoetching technique.

On the other hand, the backflow prevention diode array conductor wiring for energizing the heating resistor can be formed using the same technology as ordinary electronic circuit wiring, and these can be formed on ordinary printed circuit boards. .

In the past, parts with completely different functions and manufacturing methods were formed on the same substrate, which not only complicated the manufacturing process, but also required the entire board to withstand the heat treatment during the manufacturing of the heat generating parts. Therefore, the entire board had to be of high quality, which increased the product cost.

Furthermore, in recent years, when performing thermal printing with a thermal head, the resolution of heating elements has become particularly important, and it is necessary to have a minimum resolution of 4 lines per mm, that is, 4 heating elements per square inch. It has become necessary to drive.

Therefore, it is determined by the printing paper width, but in order to satisfy the necessary printing conditions, it is usually necessary to form several hundred or more heating elements, and all wiring and element formation is done by photo-etching to achieve that precision. However, since the physical size of the head itself is equal to the width of the thermal recording paper, its processing is not necessarily easy.

Therefore, the thermal resistance of the heating element tends to be low, but if the heating element becomes defective, not only the heating element but also the backflow prevention diode array and the multilayer wiring section are placed on the same board as the heating element. Since these are formed, they are also wasted, which is extremely inconvenient in terms of productivity and manufacturing costs.

The present invention aims to solve the above-mentioned technical problems and provide a thermal head that is mass-producible and highly reliable.

That is, in the thermal head of the present invention, the substrate is separated into a heat-resistant substrate and a wiring substrate, and a heat generating resistor element group is placed on the heat-resistant substrate, and a backflow prevention semiconductor element block is placed on the wiring substrate. At the same time, conductor wiring is formed, and the individually formed heating resistor element group and the backflow prevention semiconductor element block, and the backflow prevention semiconductor element block and the conductor wiring are electrically connected with precision using lead films. By adopting such a configuration, all of the problems peculiar to the thermal head described above can be eliminated.

Hereinafter, the components of the thermal head in the present invention will be explained as follows.
The configuration will be specifically explained with reference to FIGS.

2 and 3 show the structure of a heating resistor play used in the thermal head of the present invention, and FIG. 3 shows a cross section taken along line A-A' in FIG.

In these figures, reference numeral 1 denotes a heat-resistant substrate having strength and insulating properties such as ceramic, and a glass layer 6 may be provided on the surface for smoothing the surface and keeping heat insulated.

3 is a heating resistor element formed in a line in a dot shape approximately in the center of a rectangular substrate, and is usually made of nichrome, silicon with a high impurity concentration, carbide, silicide, nitride resistor, etc. by vapor deposition or sputtering. It is formed into a thin film by a method such as

Buttons 4 and 2 are electrode terminals to the heating resistor element 3, and metal thin films such as nickel, gold, aluminum, etc. are used.

The electrode terminal 2 is an individual electrode on the separated electrode side, and the electrode terminal 4 is a common electrode on the common terminal side that electrically connects the heating resistor elements 3 in common for each specific number N (16 in this case). be.

Further, 5 is a wear-resistant layer for preventing wear caused by the element coming into contact with paper, and is made of a material such as silicon carbide, nitride, or oxide and has a thickness of about several microns.

A large number of rows of such heating elements can be manufactured by forming a large number of heating elements on a large substrate and then cutting or breaking the substrate, and this method is excellent in terms of productivity.

Further, in order to facilitate connection with a film lead formed by combining an insulating film and a conductor group as described later, the rows of separation terminals 2 have their tips gradually tapered with respect to the heat generating element group.

Figures 4 and 5 show the manufacturing method and structure of the wiring section in the thermal head of the present invention.
The figure shows a cross section taken along line A-A' in FIG.

The wiring for the N heating elements is made by photo-etching a thin copper plate bonded to a heat-resistant and flexible insulating film (usually a polyimide organic film), which is shown at 7 in Figure 4. conductor wires 8, 9 and 1
0 is formed, and its surface is plated with tin, solder, or the like.

Also, for reasons to be described later, the lower film portions of the conductor wires 8, 9 buttons and 10 were removed so that the tips of the conductor wires were exposed, and the film substrates were removed as shown at 12, 13 and 16. 1, opening 1 is provided with an opening.
3, a diode array block (semiconductor element block for backflow prevention) containing N diodes as shown in FIG. The diode array block is aligned one-to-one with the electrode protrusions, or bumps, formed on each diode terminal on the block, and the diode array block is connected to the middle part of the wiring by heat and pressure applied from above the fingers. be done.

As mentioned above, FIG. 5 is a diagram showing a cross section along the plane AA' with the diode array block 14 attached, based on FIG. 4, and shows the film openings 11, 12, 13.
This is where the electrode portion of the heat generating element is inserted, and also shows the state in which the fingers 9 and 10 are connected to the diode array flock 14 via bumps 15.

As will be described later, when the insulator 2 film 7 is used as wiring on the substrate of the thermal head, it is cut along the B-B' button and c-c' in FIG. Used in removed form.

FIG. 6 shows a metal fitting in which a heating element substrate 17 (namely, a heat-resistant substrate 1) and an insulating substrate 19 for wiring having N parallel conductors 18 are bonded onto a metal substrate 20, as shown in FIGS. 2 and 3. 2
1, and 22 is N wires for the common terminal of the heating element, which requires M wires.

FIG. 7 is a perspective view of a thermal head according to an embodiment of the invention constructed by combining the above-mentioned components.

In other words, one unit in which a diode is connected to the film lead in Figures 4 and 5 is replaced by 1 in Figure 6.
9 is shown mounted on the board shown in FIG.

In this state, the film was cut along lines BB' and C-C' shown in FIG. 4, and the excess film portion was removed.

Further, at this stage, the fingers 8 in FIG. 4 are separate terminals of the heating resistor.

The electrode terminal 2 shown in FIG. 2 is heat-pressed.

Furthermore, the fingers 8 shown in FIG. 4 are also heat-pressed to the common wiring section on the board 19 by pressing the button on the conductor 18 shown in FIGS. 3, forming a matrix of MXN as a whole.

That is, in the thermal head, as shown in FIG.
Both substrates 17 and 19 are arranged adjacent to each other on a metal substrate 20 so as to form one plane.

On the main surface of the heat-resistant substrate, one end side is formed by arranging a group of heating resistor elements in a row, which are electrically connected in common by a predetermined number (16 in this case) and divided into a plurality of groups by a common electrode. are doing.

On the other hand, on the main surface of the wiring board 19, the backflow prevention semiconductor element block 14 is disposed along the other end side of the heating resistor element group (that is, the side opposite to the common electrode formed on the heating resistor). They are placed corresponding to each heating resistor element group.

Further, on the main surface of the wiring board 19, a plurality of conductor wirings 18 are formed for supplying current to the heating resistor element through each semiconductor element of the backflow prevention semiconductor element block 14.

Further, each of the heating resistor elements is electrically connected to a bump on one side of the backflow prevention semiconductor element block 14 by a film lead, and a bump on the other side of the semiconductor element block 14 and a parallel conductor 18 are connected to each other. Electrically connected by film leads.

In the thermal head of the present invention as described above, (1) the heating resistor element group forming the heating section is formed separately from the wiring section consisting of the backflow prevention semiconductor element block and the conductor wiring section; Because it is a heat-resistant substrate, it can be manufactured independently, making it possible to mass-produce heat-generating parts by forming the heat-generating parts for multiple thermal heads at once on a large heat-resistant substrate, and then dividing the heat-resistant substrate. Not only that, but the heat-resistant substrate required for one thermal head is miniaturized, and product and production costs are significantly reduced.

(2) Since each component is made into blocks and can be manufactured independently in this way, it is possible to take out only good products from each component and assemble them, and defective products are not discovered once the product is completed. This eliminates the conventional inconveniences, and is extremely advantageous in terms of productivity and yield.

(3) Since blocks of unidirectional semiconductor elements such as diodes are grouped into blocks, replacement in the event of failure is extremely convenient.

(4) As the ends of the conductive wires of the insulating sheet protrude as film leads, it is not only easy to connect, but also because the heating elements are extremely small, it is difficult to wire when forming M x N heating elements. Since the pitch error can be corrected by modifying the shape of the insulating sheet unit, manufacturing is easy.

(5) Furthermore, (when changing the overall length of the head (increasing or decreasing the number of heat generating elements), the number of insulating sheets can be increased or decreased, so it can be handled immediately without major design changes.

(6) Also, since the high-density wiring etc. are unitized, repairs and inspections are extremely easy.

As described above, since each component of the thermal head of the present invention is skillfully formed into blocks, the overall processing cost can be reduced and mass productivity can be improved, making it extremely useful industrially.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram of a thermal head arranged in one row, Fig. 2 is a perspective view of a heating element for a thermal head according to an embodiment of the present invention, and Fig. 3 is a cross section taken along the line A-A' in Fig. 2. Figure, 4th
7 to 7 relate to a thermal head according to an embodiment of the present invention, FIG. 4 is a perspective view of an insulating sheet provided with a conductor group, and FIG. 5 is a cross-sectional view of a diode block attached to the insulating sheet. 6 is an assembled view showing the insulating substrate and the heat-sensitive element section attached to the substrate, and FIG. 7 is a perspective view showing the insulating sheet and diode block attached to FIG. 6. 1...Heat-resistant substrate, 7...Insulating film, 8,9°10...Conductor part, 13...
Opening, 14...Diode block, 15.
...Bump, 16...Opening, 17...
...Heating element board, 18...Common conductor part,
19...Insulating substrate, 20...Metallic substrate.

Claims (1)

[Claims] 1. A heat-resistant substrate and a wiring board are arranged adjacently so that their main surfaces form almost the same plane, and one end of the heat-resistant substrate is electrically connected by a common electrode at intervals of a predetermined number. Heat generating resistor elements connected in common and divided into a plurality of groups are arranged in a row, and on the main surface of the wiring board, a backflow prevention semiconductor is arranged along the other end side of the heat generating resistor element group. An element block is placed corresponding to each heat generating resistor element group, and also on the main surface of the wiring board, for supplying current to the heat generating resistor element through each semiconductor element of the backflow prevention semiconductor element block. A group of conductors formed on an insulating sheet with both ends protruding from the edge of the insulating sheet connects the other end side of the heating resistor element group and the backflow protection semiconductor. One side terminal of the element block is electrically connected, and the other side terminal of the backflow prevention semiconductor element block and the conductor wiring are electrically connected by another conductor group having an insulating sheet formed in the same manner as the conductor group. A thermal head connected to