JPS6245829B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a thermal head, and in particular, an object of the present invention is to provide an electrode having low electrode resistance and excellent bonding properties in a thin film type thermal head.

Generally, thin film type thermal heads have the disadvantage of high electrode resistance. In order to reduce this electrode resistance, it is possible to increase the thickness of the electrode by electroplating, but conventionally, a plating conductor is used to short-circuit all electrodes, and this plating conductor is used as the cathode of the electroplating device. Since the manufacturing method used was to etch off the plating conductor after connecting and electroplating each electrode of the head, there was a problem in that it was necessary to etch off the plating electrode, which had become thick as a result of plating, after plating. . Furthermore, due to the high temperature during the formation of the wear-resistant layer after plating, there was a problem in that the electrodes peeled off due to thermal distortion of the plating film.

Therefore, in order to solve this problem, an attempt was made to perform electroplating after forming the wear-resistant layer, but it was found that it was not practical because it became extremely difficult to etch off the plating electrode. The reason why it is difficult to etch off plating electrodes is that thermal head electrodes generally consist of two layers: an adhesive layer of Cr, etc., and a conductive layer of Au, Cu, etc. The layers form an alloy layer by interdiffusion reaction,
This is because it is very difficult to etch off this alloy layer.

That is, after etching off the plating film, if the interdiffusion reaction layer with Cr is reached during etching of Au, Cu, etc. of the thin film thin conductive layer, the etching rate decreases and the etching time becomes longer.

The present invention solves these conventional problems and provides a manufacturing method that does not require etching off the plating electrode. Hereinafter, a method of manufacturing a thermal head according to an embodiment of the present invention will be explained using the drawings of FIGS. 1 to 7.

Figure 1 shows the thermal head after the wear-resistant layer has been formed. In the figure, 1 is a glazed ceramic substrate, 2 is a Si--Ta based heating element with a resistance value of 300Ω/dot, and 3 is the heating element 2. A common electrode is connected to one end, and 4 is an individual electrode connected to the other end of the heating element 2. These electrodes are attached as an adhesive layer.
It has a two-layer structure with Cr and Au as the conductive layer. 5 was formed by sputtering technique so as to cover part of the heating element 2, the common electrode 3, and the individual electrodes 4.
It is a wear-resistant layer of SiC.

B4 version to explain the conventional electroplating method
Taking an 8dot/mm thermal head as an example, one common electrode has 32 heating elements and 125 individual electrodes.
It consists of 64 common electrodes arranged with a pitch of μm. It is these 64 common electrodes and 2048 individual electrodes that require electroplating. As can be seen from FIG. 1, the common electrode 3 and its individual electrodes 4 are electrically connected via the heating element 2, but the common electrodes are electrically insulated. 64
It is extremely difficult to bring the plating jig into contact with all of the common electrodes. For this reason, conventionally electroplating was performed in the following order. (1) When photo-etching the electrodes, each common electrode is not completely separated, but a conductor for plating is left in a part between adjacent common electrodes, so that the common electrodes are connected to each other. Etching process, (2) Abrasion resistant film formation process, (3) Plating insulating film formation process by printing or photolithography on an area slightly wider than the abrasion resistant film width (non-plated area), (4) 10 common electrodes (5) a step of electrically plating the common electrode and individual electrodes that are not covered with the insulating film for plating by contacting the plating jig at a rate of about one per plating device and connecting it to the cathode of the plating device; The process of peeling off the insulating film,
(6) a step of printing other parts than the plating conductor with an etching-resistant resist; (7) a step of etching off the plating conductor; and (8) a step of peeling off the etching-resistant resist. Although it requires a complicated process as described above,
According to the method of the present invention, each of the steps (3), (5), (6), (7), and (8) in the above steps is achieved by simultaneously utilizing the insulation and conductivity of the elastic connector. can be abolished.

Next, details of the present invention will be described using FIGS. 2 to 7.

Figures 2 and 3 are diagrams showing an elastic connector (product name) manufactured by Toray Industries, Inc. used as a part of an electroplating jig.
is silicone rubber, and 7 is a thin metal wire. This elastic connector 8 is a flexible connector in which a large number of thin metal wires 7 are embedded in silicone rubber 6 by penetrating it in the thickness direction. Further, the thin metal wire 7 is plated with gold, and both ends of the thin metal wire 7 protrude from both surfaces of the silicone rubber 6 to form an electrically conductive path between both surfaces of the silicone rubber 6. Thus, the elastic connector 8 serves to electrically connect the conductors arranged on both sides. Furthermore, the pitch at which the thin metal wires 7 are embedded in the silicone rubber 6 is smaller than the pitch at which the common electrode 3 of the head shown in FIG. 1 is embedded.

FIG. 4 is a diagram showing a plating jig using the elastic connector shown in FIGS. 2 and 3;
In the figure, reference numeral 9 denotes a metal plate such as an Au-plated Cu plate, which is bonded to the elastic connector 8 with an adhesive 10, and the thin metal wire 7 of the elastic connector 8 is electrically connected to the metal plate 9. 1
Reference numeral 1 denotes a base made of an insulating material such as vinyl chloride, which is adhered to a metal plate 9 via an adhesive 12.

Next, regarding the manufacturing method of the present invention when plating is performed using the plating jig 13 shown in FIG.
This will be explained using the drawings of FIGS. 5 to 7.

First, the head and the plating jig 13 are aligned so that the thin metal wire 7 of the plating jig 13 comes into contact with the common electrode 3 of the thermal head after the wear-resistant layer is formed as shown in FIG. At this time, as shown in FIG. 5, the thin metal wire 7 of the plating jig 13 contacts only the common electrode 3 and does not contact the individual electrodes 4. FIG. 6 is a cross-sectional view of part 7 of the thin metal wire in FIG.
The state shown is when pressed with a force of 1.5Kg/cm ² . The thin metal wire 7 of the plating jig 13 contacts the common electrode 3 and bends as shown in FIG. are electrically connected.

In this state, when the metal plate 9 is connected to the cathode of the electroplating device and electroplated in a plating solution, the silicone rubber 6 of the plating jig 13 is shown in FIG.
A plating film is formed on the common electrode 3 and the individual electrodes 4 in areas that are not covered. In addition, plating jig 1
3, only the common electrode 3 is directly connected to the cathode of the electroplating device, and the plating current flows through the individual electrodes 4 via the heating elements 2.

FIG. 7 is a diagram showing the thermal head after electroplating. In the figure, 31 is the electroplated part of the common electrode 3, 32 is the unplated part, and 41 is the part of the individual electrode 4 that is electroplated. The portion 42 is not plated. That is, the surface of the plating jig 13 in contact with the thermal head is made of flexible silicone rubber 6, and the plating jig 13 has a plating density of 1.5 kg/cm ^{2 .}
Since the plating liquid is pressed with the pressure of show.

As is clear from the above description, in the manufacturing method of the present invention, electroplating is performed by connecting only the common electrode 3 of the thermal head after forming the wear-resistant layer to the cathode of the electroplating device via the elastic connector 8. , it is not necessary to form an insulating film for a plating mask by printing or photolithography on the non-plated areas as in the past, and there is no need for conductors for plating and their etch-off, and since plating is performed after forming a wear-resistant layer, it is possible to As such, there is no exposure to high temperatures after plating, and there is no problem of electrode peeling due to thermal distortion of the plating film.
Since no interdiffusion reaction occurs between Cr and Au as the conductive layer, the surface becomes pure gold, resulting in good bonding properties.

Furthermore, in the present invention, although the thin metal wire of the elastic connector does not come into contact with the individual electrodes 4,
The plating thickness of the individual electrodes 4 is thicker than that of the common electrode 3. For example, when the plating thickness of the common electrode 3 is 4μ, the plating thickness of the individual electrodes 4 is about 5μ. The reason for this is that the individual electrodes 4 are connected to the common electrode 3 via the heating element 2, and as a result, the individual electrodes 4 are electrically connected to the cathode of the plating device. Moreover, since the individual electrodes 4 are connected to the semiconductor element, the pitch at the tip end is finer than the pitch at the heating element, and the electrode width is narrower, so current concentration occurs and the plating thickness becomes thicker. Moreover, because of the structure shown in Figure 4, the plating jig is installed perpendicularly to the thermal head surface, dividing the plating solution into two areas: the common electrode area and the individual electrode areas.
This has the effect of separating the anode plates facing the thermal head into separate ones for the common electrode and for the individual electrodes.
Since the distance to the thermal head can be adjusted independently, it is easy to make the plating thickness of the individual electrodes thicker than that of the common electrode. That is, as a result, the common electrode 3 may be thin because the lead wires are soldered, but the individual electrodes 4 are made of Au-
Since bonding is performed using the Sn eutectic reaction, the thicker the film is, the better. Considering this, the manufacturing method of the present invention is a method that is highly effective in improving bonding properties.

Further, in the manufacturing method of the present invention, when conductive rubber is used as a plating jig instead of the elastic connector 8, electrolytic etching occurs at the boundary between the plated part and the unplated part, and the lower electrode film is damaged. Not only was there a phenomenon where Cr was exposed, but when the conductive rubber was pressed against the head with the Au plating solution attached to it and plated, Au was deposited on the surface where it was not desired to be plated, causing stains. However, when the elastic connector 8 was used as in the above embodiment, such a problem did not occur at all.

Furthermore, in the manufacturing method of the present invention, if there is an abnormality in the resistance value distribution of the heating element 2, the current flowing through the individual electrode 4 connected to the heating element 2 during plating will be different compared to that in the vicinity. By comparing the thickness with the thickness in the vicinity, the difference can be seen at a glance, and an abnormality in the resistance value distribution can be detected by visual inspection without actually measuring the resistance value.

In addition, if the embedded pitch of the thin metal wires 7 of the elastic connector 8 of the plating jig 13 is made sufficiently smaller than the pitch of the common electrode 3 of the thermal head, even if there is a thin metal wire 7 with poor contact, , at least one thin metal wire 7 connects each common electrode 3
This makes it possible to plate all electrodes.

As described above, according to the method for manufacturing a thermal head of the present invention, there is no need to form an insulating film for a plating mask by printing or photolithography on the non-plated parts as in the conventional method, and there is no need for conductors for plating or etching. A thermal head having electrodes with low electrode resistance and excellent bonding properties can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the state of a thermal head before electroplating according to the method of manufacturing a thermal head of the present invention, FIG. 2 is a plan view showing an elastic connector used in the method of manufacturing a thermal head of the present invention, and FIG. 2 is a sectional view taken along the line A-A', FIG. 4 is a sectional view showing a plating jig using the elastic connector shown in FIGS. 2 and 3, and FIGS. 5 and 6 are FIG. 7 is a plan view and a sectional view showing the plating jig pressed against the thermal head shown in FIG. 1, respectively, and FIG. 7 is a plan view showing the thermal head after being plated by the manufacturing method of the present invention. 2...Heating element, 3...Common electrode, 4...Individual electrode, 5...Abrasion resistant layer, 6...Silicone rubber,
7... Fine metal wire, 13... Plating jig, 31, 4
1... Electroplated part, 32, 42... Unplated part.

Claims (1)

[Scope of Claims] 1. After forming a wear-resistant layer covering a plurality of heat generating elements having one end connected to a common electrode and the other end connected to an individual electrode, and then forming a wear-resistant layer covering the heat generating elements, A method for manufacturing a thermal head for electroplating, characterized in that during electroplating, only the common electrode is connected to the cathode of an electroplating device via a plating jig, and electroplating is performed on the common electrode and the individual electrodes. A method of manufacturing a thermal head. 2. Claim 1, characterized in that the plating jig is a silicone rubber in which a large number of fine metal wires are embedded in the thickness direction so that both ends protrude from both surfaces. A method of manufacturing a thermal head. 3. The method of manufacturing a thermal head according to claim 2, wherein the pitch of embedding the thin metal wires in the silicone rubber is smaller than the pitch of the common electrode.