JPS5851832B2 - thermal recording head - Google Patents

Abstract

PURPOSE:To compose a multi-layer wiring part on an insulator sheet containing plural openings with plural pieces of upper layer wiring provided in parallel to the heat generating resistance row and the lower wiring containing L-shaped electrode terminal connected to the heat generating resistor. In this way, the production can be facilitated with enhanced quality.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal recording head used in an information recording device such as a facsimile.

At present, the recording methods of information recording devices such as Hook Jimiri include electrically sensitive recording methods such as current thermal recording, discharge breakdown recording, and electrostatic recording, as well as thermosensitive recording methods. It is expected that the thermal recording method will be used considerably in the future, since it is necessary to make the device very compact.

Therefore, a conventional example of the thermal recording method will be explained.

Thermal recording method is a thermal recording head in which minute resistance heating elements are arranged in a row or in a matrix, and a thermal paper that develops color when heated is brought into contact with the head, and specific heating resistors of the head are selected and energized to generate heat. Electrical information is visualized by heating and coloring specific parts of the paper.

A matrix control method is generally used to control thermal recording heads, and a specific circuit configuration will be explained below with reference to the drawings.

In FIG. 1A, 2 is a heating resistor, 3 is a directional element such as a diode or transistor for preventing the backflow of current flowing through the heating resistor 2, and 1 is a heating resistor 2.
4 is a multilayer wire portion connecting the conductor from the image signal terminal portion 5 and the conductor from the heating resistor 2.

If N 1 heat generating resistors 2 are stored in the past and divided into M sections, there will be 0 electrode terminals 1, and the other terminal will be connected to the N image signal terminals 5, with conductors from other sections. connected in common.

One image signal terminal per housing is connected to M heating resistors.

The external circuit has N driver circuits for heating resistors, and by switching them using M switching circuits, matrix control of MXN is possible.

Alternatively, as shown in FIG. 1B, the positions of the directional element 3 and the heating resistor 2 may be interchanged.

As mentioned above, the thermal recording head has a very simple circuit structure.

However, actually producing it is not always easy.

This is because, with the spread of facsimile, a resolution of at least four lines per unit has become required for recording information, and it has become necessary to form and drive four heating elements per l mvt.

For this reason, thin film formation by photoetching is the only method, and moreover, usually several hundred sides or more must be arranged.

Therefore, quite advanced technology is required.

Generally, when a circuit configured as shown in FIG. 1 is formed into a thin film and controlled in a matrix, multilayer wiring is required.

However, one of the upper and lower conductor layers of the multilayer wiring reaches a length comparable to the total length of the thermal recording head, so a thin film has a high resistance value, and this resistance is in series with the heating resistor. A voltage drop occurs within the conductor, making it difficult to cause the heating resistor to generate heat normally, making it impossible to obtain the necessary recording quality.

Here, gold is used for the thin film conductor for its reliability against corrosion and ease of adhesion, but if the gold is made thicker to lower the resistance value, it will not only be difficult to etch but also be expensive. The sheet resistance value of the thin film conductor is 10
It is difficult to reduce the number of layers to less than 2 m, which has a considerable effect on image quality.

In addition, the thin insulating layer has many short circuits between the upper and lower conductors due to pinholes, resulting in extremely low yield.

The present invention has been made in view of the practicality of the thermal recording method and the above-mentioned conventional technology.
To provide a thermal recording head having a structure that provides recording with sufficient quality, is easy to manufacture, and can improve production efficiency.

Hereinafter, one embodiment of the present invention will be explained in detail.

FIG. 2 is an enlarged plan view of the thermal recording head of the present invention.

13 is a heat generating resistor; 14 is a unidirectional element such as a diode or transistor for preventing the current flowing through the heat generating resistor from flowing backward; 12 is an electrode terminal in which a specific number of heat generating resistors 13 are connected; 6 is an alumina substrate.

7 is a brace surface with excellent smoothness, which is printed and fired on the entire surface of the aluminum substrate except for the peripheral area, and has a surface roughness of 250A or less, and is generally obtained by firing at a temperature of 1100℃ or higher. .

8 is an insulating sheet made of polyamide or polyester film having slits 10, and 9 is a copper foil conductor with a thickness of 35 μm bonded onto the insulating sheet 8.

15 is a multilayer wiring section. It consists of an L-shaped lower layer wiring 11 and an upper layer wiring 9 made of a copper foil conductor.

FIG. 3 is a plan view and a side cross-sectional view of a film lead that becomes the upper layer wiring of the multilayer wiring part.

8 is an insulating sheet, 9 is a copper foil conductor, 10 is a slit, 16
are holes for fixing and positioning during assembly.

Braced ceramic substrate 6I/c in FIG.
After forming a heating resistor 13 such as silicon (Si) or tantalum (Ta) and a conductor such as chromium (Cr) or gold (Au) using thin film technology, the common terminal portion 12 is formed using photoetching technology.
Thin film lower wiring 1 of heating resistor section 13 and multilayer wiring section 4
Form 1.

At this time, the lower layer wiring 11 is made into an L-shape, and the inter-electrode pitch and electrode width of the portion parallel to the arrangement of the five heating resistors 13 are made large to match the upper layer wiring.

Next, silicon carbide (SiC) or the like is formed as a wear-resistant film near the heating resistor section 13 by a method such as sputtering, and then a chip containing KN diodes (6 in the case of Fig. 2) per chip is assembled into a minimod. The directional element portion 14 is formed by bonding using a method such as the above.

Next, the multilayer wiring section, which is a feature of the present invention, will be explained.

For the multilayer wiring section 15, a thermal recording head is formed by separately preparing a film lead as shown in FIG. 3 and attaching it to the thin film lower layer wiring section of the ceramic substrate.

For the film lead, slits 10 are formed at regular intervals on a polyimide film 8 with a thickness of 50μ, a copper foil with a thickness of 35μ is adhered, N striped electrodes are formed using photoetching technology, and the portions exposed by the slits 10 are formed. Apply tin or solder plating to the surface.

It is difficult to reduce the inter-electrode pitch of such copper foil striped electrodes having a thickness of about 35 μm as in the case of thin film technology.

Therefore, the thin film lower layer wiring should be L-shaped, and the upper layer copper foil wiring @
In addition, the pitch between the electrodes and the width of the electrodes are widened accordingly.

Now, position the film lead on the 7-inch board with the copper foil electrode facing upward, that is, with the polyimide film as an electrical insulator sandwiched between the thin film lower layer electrode on the ceramic and the copper foil upper layer electrode. put.

For positioning and fixing, an assembly jig with pins is used using the holes 16 on the insulating sheet.

That is, the holes 16 on the insulating sheet are fitted into the pins of the assembly jig, and the insulating sheet is stretched.

A ceramic substrate with thin-film lower layer wiring is inserted under the insulating sheet.

At this time, the thin film lower layer wiring on the ceramic substrate and the copper foil upper layer wiring on the insulating sheet are in a state where they are floating at the slit 10 portion by 50 μm, which is the thickness of the insulating sheet.

However, as shown in the third sectional view B, the copper foil 9 may be dented at the slit 10 portion.

In this state, a tool that fits into the slit 10 is used to press the copper foil upper layer wiring in the slit 10 portion with the casing that is in contact with the thin film lower layer wiring, and a pulse current is passed through the tool to heat it.

Now, if the copper surface of the copper foil upper layer wiring is plated with chromium as the thin film lower layer wiring and tin is applied to the entire structure, then by heating the tool to about 500 degrees Celsius.

Alloying of gold and tin occurs, and the copper foil upper layer wiring and thin film lower layer wiring are connected.

In this case, N wires (six wires in FIG. 2) crossing the slit are bonded at the same time.

Such bonding is repeated for the number of slits, that is, M times, to complete the connection of the multilayer wiring.

This connection provides N image signal terminals.

For the N picture signal terminals, the multilayer wiring film shown in Figure 2 may be extended as is, but the multilayer wiring film should be cut off on the ceramic board, and another flexible flat cable should be connected to the edge of the ceramic board. It may also be connected to thin film lower layer wiring.

As explained above, in the thermal recording head of the present invention,
The multilayer wiring part is formed by having a plurality of upper layer wirings provided on an insulating sheet having a plurality of slits, parallel to the heating resistor row and across the slits, and an L-shaped electrode terminal connected to the heating resistor. The electrode section parallel to the heating resistor array of the lower layer wiring is connected to the upper layer wiring through the opening of the insulating sheet, and the structure of the multilayer wiring section is extremely easy to manufacture.

In other words, if the number of common terminal sections is M = 24 and the number of image signal terminal sections is N-32, bonding would normally have to be done at 24 x 32 = 768 locations, but with the thermal recording head of the present invention, bonding can be performed only once. It all ends with 24 bondings.

In addition, since a polyimide film or polyester film with a thickness of about 50 μm is used as the insulator between the thin film lower layer wiring and the copper foil upper layer wiring, insulation defects due to pinholes, which often occur with thin film insulators, are almost eliminated. Yield deterioration due to poor insulation is almost eliminated.

Furthermore, for wiring that requires a length equal to or longer than the length of the row of heat-generating resistors, the electrical resistance of the wiring portion becomes a problem, but as in the present invention, that portion has a thickness of 35 μm and a width of 160 μm.
If the wiring is done using μ copper foil, the electrical resistance of that part can be ignored compared to the resistance value of the heating resistor.

Therefore, sufficient voltage can be applied to the heating resistor,
The necessary recording quality can be obtained.

[Brief explanation of the drawing]

1A and 1B are wiring diagrams of a thermal recording head in which heating resistors are arranged in a row, FIG. 2 is a plan view showing an embodiment of the thermal recording head of the present invention, and FIGS. 3A and 3B are respectively FIG. 3 is a plan view and a cross-sectional view of a film lead for upper layer wiring of a multilayer wiring section. 1.12... Electrode terminal, 2,13...
heating resistor, 3, 14... directional semiconductor element,
4, 15...Multilayer wiring section, 6...Alumina substrate, 7...Glaze layer, 8...
Insulating sheet, 9... Copper foil upper layer wiring, 10...
...Opening (Surin)), 16...Hole for fixing and positioning during assembly.

Claims (1)

[Scope of Claims] 1. A plurality of heating resistor groups arranged in a row on an insulating substrate, a unidirectional semiconductor element group connected to the heating resistors, and the heating resistors divided into several groups. A common terminal portion in which one terminal of the heating resistor is commonly connected for each group, an L-shaped conducting wire of different lengths connected to the other end of the unidirectional semiconductor element, and this L-shaped conducting wire. a wiring section connected in a matrix, the wiring section being constituted by a plurality of matrix wiring conductors provided on an insulating sheet having a plurality of openings in parallel with the heating resistor rows, and the insulating 1. A thermal recording head, wherein the cross-shaped conductive wire and the matrix wiring conductor are connected at an opening in the sheet. 2. The thermal recording head according to claim 1, wherein each of the matrix wiring conductors is formed continuously on an insulating sheet even when a button is placed in the opening. 3. A thermal recording head according to claim 1 or 2, wherein the insulating sheet is a polyester film or a polyimide film.