JPS6194773A - Thin film thermal printing head - Google Patents

Abstract

PURPOSE:To obtain the titled head satisfying simultaneously different perform ances such as soldering performance and wire bonding performance, wherein either a part or the entire part of each of a common electrode and individual electrodes is formed in a four-layer structure of chromium, aluminum, chromium and copper. CONSTITUTION:Either a part or the entire part of each of the common electrode 16 and the individual electrodes 15a, 15b... is formed in a four-layer structure of chromium, aluminum, chromium and copper, in the order of from lower to upper layers. The structure is etched sequentially from the upper side so as to leave the individual metals at required parts, whereby an inexpensive thin film thermal printing head can be obtained which simultaneously satisfies different performances such as soldering and bonding.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] This invention relates to a membrane layer thermal printing head, and more particularly to improvements in the common electrode and individual electrodes thereof.

[Background of the tomb and its problems]

Generally, thermal print heads are used in facsimile machines, printers, and the like as means for recording information such as data and graphics. Various types of thermal printheads have been proposed and put into practical use, but there is a strong demand for high speed and high resolution, and thin film thermal printheads, which are superior in these respects, are becoming mainstream. There are two types: a diode matrix type, which combines a backflow prevention diode and matrix wiring, and a direct drive type, which is equipped with a driving integrated circuit. Since the diode matrix type is time-divisionally driven, the recording time is no more than IQ ms/1ine even when driven at high speed, but with the direct drive type, the recording time is 2ms.
/1ine printing is also possible. Furthermore, from the system side, the drive circuit required in the diode matrix type is no longer necessary, and the device can be further downsized.

For the above reasons, direct drive type thin film thermal printheads are increasingly used in the market.

Now, in a conventional general thin film thermal print head, an integrated circuit is formed on one of two divided insulating substrates, a plurality of heating resistors are formed on the other, and a common electrode is attached to one end of the heating resistor. Individual electrodes are connected to the other ends, and these individual electrodes are further connected to the integrated circuit.

The thin film thermal print head described above is also called a split type because the insulating substrate provided with the integrated circuit and the insulated substrate provided with the heating resistor are separate. In this split type, the common electrode requires soldering and the individual electrodes require wire binding. The metal that can be soldered is Au.
gAgsN'gCueSn, p
There are metals such as b-3n, and metals to which wires can be bonded include Au1A1 and the like.

Au is the only metal that satisfies both of these functions, and therefore four Au bodies have been commonly used in the past. In this case, adhesive strength cannot be obtained with only %An, so C
'#U, It is used in a structure sandwiched by metal such as Cr. In addition to Cr, Tt and Nt can be used as adhesive metals.
, NiCr, etc. are well known, and any material may be selected from these.

However, Au is a very expensive metal.

Even if the amount of gold used as a conductor is small, if a film is formed by evaporation or the like, a large amount of Au is required as an evaporation source. Therefore, using Au as a conductor inevitably increases the price. On the other hand, in order to lower the price, people uI2 should be replaced with metal f
When used as a conductor, wire binding of individual electrodes is possible, but direct soldering is not possible. When used as a Cu f conductor, soldering is possible but wire binding is not possible. In addition, Ni does not work well for the same reason as Cu.

[Purpose of the invention]

The purpose of this invention is to eliminate the above-mentioned conventional drawbacks,
It is an object of the present invention to provide a low-cost thin film 8mm print head.

[Summary of the invention]

This invention provides that all or part of the common electrode and the individual electrodes are made of chromium (hereinafter referred to as r), aluminum (hereinafter referred to as AI), chromium @ (hereinafter referred to as Cu).
This is an N-film thermal print head composed of a layered structure. [Embodiment of the Invention] The thin-film thermal print head of the present invention is constructed as shown in FIG. is an insulating substrate 11.13 made of alumina and divided into two parts.
is installed. On this one insulating substrate 13,
Driving integrated circuits 22a, 22b, . . . are formed. Also, on the other insulating substrate 13 1/(Fi glaze plate 14
A plurality of ps resistors 2oa, 2ob, . . . are formed at predetermined positions on the glaze Br3. A common electrode 16 is connected to one end of the heating resistors 20a, 20b, . . . , and individual electrodes 15m, 5b, . . . are formed at the other end. These heating resistors 20a
, 20b..., common electrode 16°, individual electrodes 15a, 1
5b... are formed using a film forming method such as vapor deposition or suction/mother ivy. In this case, the common electrode 16, the individual electrode g
% I 6 a, I 5 b All or at least a portion of the common electrode 16 and the individual electrodes 15a, 15b... from the lower layer thereof is Cr.

It has a four-layer structure of Al, Cr, and Cu.

At this time, during manufacturing, a photoresist is applied using a spinner, a roller coater, or the like. Thereafter, exposure and development are performed using a photomask to form holes and turns, and etching is performed. And soldering place 18
The top layer of Cu is left behind, and the rest is removed by etching.

At this time, use an etching solution that does not affect the underlying Alvc! ! - Select and use. For example, ammonium persulfate or the like may be used. Next, a pattern of a normal head in which heating resistors are individually formed is formed. The second Cr from the top is left on the kl electrode that is to be formed on the protective film 21, and is used to further strengthen the adhesion between the protective film and the electrode. Note that this Cr is removed from the portion corresponding to the dending pad 19.

Now, the above individual electrodes 15a, 15b...
The integrated circuit 22a,
22b... 19 in the figure is a denting pad of the individual electrodes 15a, 15b..., and 2
3 is an integrated circuit 22a.

22b... is a bonding pad. Further, the heating resistors 20a and 20b- are covered with a protective trowel film,
The individual electrodes 15a, 15b, . . . and the integrated circuits 22a, 22b, . . . are covered with a cover 25, and covered with the Passpar 17Fi paper guide.

〔Effect of the invention〕

According to this invention, the common electrode 16, the individual electrodes 15a, 1
5b... are all or partially from the lower layer"s
Since it is composed of a four-layer structure of AlgCrsCu, if you perform etching from the top so that the metal remains where it is needed, it can be used at a low cost and satisfies different performances such as soldering and wire bonding at the same time. A thin film thermal print head can be provided.

[Modified example of the invention]

FIG. 2 shows a modification of the present invention, which provides the same effects as the above embodiment. That is, in the above embodiment, a line type head having a width of A4 or 34 size paper in which a large number of heating resistors are arranged in a row is described, but in this invention, the head itself is movable using heating resistors of about 10 to 30 dots. It can also be applied to a serial type head that prints.

This serial type head is constructed as shown in FIG.
A driving integrated circuit 35 and a plurality of heating resistors 3 are installed at predetermined locations on the insulating substrate 3Q covered with a glaze layer (not shown).
2a, 32b... are formed. One end of the heating resistors 32a, 32b... is connected to the common electrode 31, and the other end is connected to the individual electrodes 33m, 33b.... A bonding pad 34 located at the tip of each of the individual electrodes 33m, 33b, . . . is connected to the integrated circuit 35 by a binding wire 36.

This integrated circuit 35 is connected to input/output signal lines 378, 37b, . The hatched portions) are connected to flexible tape (not shown) or the like by soldering.

Also in the case of this modification, the common electrode 3 and the individual electrodes 33a
, 33b... are all or partially "*Al
g It is composed of a four-layer structure IIC of Cr and Cu. During film formation, leave Cu on the diagonal line part of the common electrode 3 so that it can be attached to the individual electrode 33a.
, 33b... are made of Al'
Leave it in. Although not shown in this modification,
Heat generating resistor 32a.

There is a protective film on the top of 32b, as in the above embodiment.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a thin film thermal printing head according to an embodiment of the invention, and FIG. 2 is a plan view showing a modification of the invention. 11.13--Insulating substrate, 15 a 15 b- Individual electrode, 16... Common electrode, 20a, 20b... Heating resistor, zzx, z2b... Integrated circuit.

Claims (1)

[Claims] At least an integrated circuit and a plurality of heat generating resistors formed at predetermined positions on an insulating substrate, and a common electrode and individual electrodes respectively connected to both ends of the heat generating resistor, the individual electrodes and the integrated circuit being connected. 1. A thin film thermal print head characterized in that all or part of each of the common electrode and the individual electrodes has a four-layer structure of chromium, aluminum, chromium, and copper.