JPS61202857A - Thermal head - Google Patents

Abstract

PURPOSE:To reduce the effect of conductor corrosion upon a heating element and improve reliability by providing a common electrode for a thermal head at both ends of a chip and forming a feed pattern for plating on the common electrode line. CONSTITUTION:A common electrode line 9 has its end extending downward under a heating part 8 from one edge of a chip and connecting itself to a terminal 17 and the other end formed downward from the other edge of the chip encircling the heating part 8 and individual electrode lines 10a-10g. A plated feed pattern 16 is continuously formed from a common electrode line 9 formed at both edges even on both ends of a head chip. This pattern is counted to the common electrode line 9 of a contiguous head chip. Under this pattern formation, an electric current for electrolytic plating runs into each individual electrode line 10a-10g from one common electrode line 9 through the heating part 8. in the meantime, said current runs out to the common electric line of a contiguous head through the other common electrode line 9.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a thermal head, and more specifically, a plurality of heating resistor elements are linearly arranged on the same substrate, and the heating resistor elements are arranged in accordance with information. The present invention relates to a thermal head that generates heat by applying electricity to perform color recording on thermosensitive recording paper, or transfers and records onto plain paper via an ink ribbon.

[Prior art]

A conventional thermal head, for example, as shown in Fig. 2,
A thin glaze layer 2 is provided on an electrically insulating alumina substrate l. On top of that is a heating resistor layer 3 made of TatN or the like that generates heat and gives coloring energy to a thermal recording paper (not shown), etc., and Aj! connected to the heating resistor layer 3 to conduct current according to information. , Ni, etc. conductor JI4.
5 (see FIG. 4 for the conductor layer 5 made of Ni), and Si
An oxidation-resistant layer 6 made of Oz or the like to protect the heating resistor layer 3 from deterioration due to oxidation; and an oxidation-resistant layer 6 made of Ta, Os, etc. to protect the heating resistor layer 3 from wear due to contact with heat-sensitive recording paper.
It has a structure in which a conductive layer 4 and a wear-resistant layer 7 for protecting the oxidation-resistant layer 6 are sequentially laminated.

When a current is passed through the conductor layer 4.5, the conductor layer 4.
The heat generating part 8 is formed by removing a part of the
generates heat and provides color recording energy to thermal recording paper, etc. As shown in FIG. 3, the thermal head is provided with a common electrode line 9 and individual electrode lines 10a to 10g on both sides of the heat generating section 8. and common and individual electrode lines 9.10a-1
0g are the range of the lower terminal portion 11 defined by line B in the figure, and the solder layer 13 is pre-soldered covering the conductor layer 5 made of nickel as shown in FIG. There is.

This solder layer 13 is connected to an external circuit (not shown) by soldering. Upper head surface portion 1 other than the lower terminal portion 11 defined by middle line B in FIG. 3
2 is covered and protected by an oxidation-resistant layer 6 and a wear-resistant layer 7. Note that FIG. 2 is a sectional view taken along line AA' in FIG. 3.

[Conventional problems]

In such a conventional thermal head, the terminal portion 11
As shown in FIG. 4, a solder layer 13 is pre-soldered covering the conductor layer 5 made of nickel, and the pre-soldering can be done by, for example, dipping a thermal head directly into molten solder, or There are cases where solder cream is printed on the terminal portion ll and reflowed.

This builds up in a semi-cylindrical shape on the conductor layer 5, and its thickness and adhesion amount vary depending on the width of the terminal.

Generally, the gap between the terminals of a thermal head is as small as 0.2 mm or less, and if the solder layer 13 is formed on the thermal head by simply dipping the solder, the terminal 11 will have a flexible print that connects the terminal 11 electrically to an external circuit. When the circuit (FPC) is positioned, pressurized and heated to melt and weld both solders, the amount of solder is large and solder bridges occur between the terminals, resulting in frequent electrical short-circuit failures.

For this reason, in the terminal solder dipping process of the thermal head, for example, compressed air is blown from a nozzle to suppress the swelling due to surface tension, but the variation in the thickness of the solder attached to each terminal within the chip is approximately 10 to 10 mm. 20
In some cases, μm is also generated. As described above, forming the solder layer 13 of the terminal portion 11 by the solder dip method has an unavoidable drawback that the variation in thickness becomes fundamentally large.

For example, when welding an FPC (not shown) for external circuit connection with the solder layer 13 having large variations in thickness as shown in FIG. When a concentrated load is applied to the part where the solder layer 13 has increased in height, a large amount of the solder in that part melts and spreads, and the entire terminal is connected to the FPC, a solder bridge occurs between the terminals, causing an electrical short. Many defects occur.As a result, manufacturing control becomes difficult, and the product becomes completely defective in this final process, resulting in large losses.In order to improve these defects, conventional methods It has been proposed to replace the solder dip method with electric solder plating.

For example, an example of this is shown in Figure 5.Although not shown, chips with the same pattern are formed on both sides of this head chip, and a predetermined number of chips are formed on one substrate. be. In FIG. 5, reference numeral 15 denotes a conductor pattern that connects the common electrode lines 9 of adjacent head chips.
Common electrode line 9 and individual electrode lines 10a to 1 shown in
A current for electric solder plating is applied to 0g.

When electrical solder plating is performed in this manner, the solder layer 14 has a uniform thickness, and the film thickness can be easily controlled. 6th
The figure is a cross-sectional view of the terminal portion 11, and the solder layer 14 can be formed with a uniform thickness on the conductor Ji5 made of Ni.

However, a head formed with such a pattern has 1
When separated into individual parts, the cross section of the conductor pattern for plating 15 is exposed, so if the conductor is made of Al or the like, it is likely to corrode, and the heat generating part 8 Because it is close to the cross section of the pattern, the heating element part 8 is the conductor Aj! The disadvantage was that it was extremely susceptible to corrosion.

[Object of the Invention] The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and its purpose is to change the position of the power supply conductor pattern for electroplating of the head terminal. ,
It is an object of the present invention to provide a highly reliable thermal head in which there is little variation in terminal solder thickness and in which the influence of conductor corrosion on a heating element is reduced.

[Structure of the invention]

In order to achieve the above objects, the present invention constitutes a head in which common electrode lines of a thermal head are provided on both sides of a chip, and a power supply pattern for plating is formed between the common electrode lines.

[Embodiments of the invention]

FIG. 1 is a plan view showing one embodiment of the present invention, in which 8 is a heat generating part, 9 is a common electrode line, 1
0a-10g are individual electrode lines. Here, the common electrode line 9 has one end extending below the heat generating section 8 and connected to the terminal section 17, and the other extending around the heat generating section 8 and the individual electrode lines 10a to Log on the chip. It is formed downward from the other end. In this way, the plated power supply pattern 16 is connected to the common electrode line 9 formed on both ends of the head chip, and is coupled to the common electrode line 9 of the adjacent head chip. .

By forming such a pattern, the current for forming electroplating flows from one common electrode line 9,
It flows through the heat generating part 8 to each individual electric bridge line 102 to 10g. Further, it flows out to the common electrode line of the adjacent head via the other common electrode line 9.

When the head of the present invention is divided into chips, the cross section of the conductor occurs at the part of the plated power supply pattern 16 connected to the common electrode line, but this part is the part farthest from the heat generating part 8. Even if corrosion were to start from the cross section, the effect on the heat generating section 8 would be reduced.

In addition, when an FPC is generally welded to the terminal part 17 of the head, the terminal part 17 is coated with a moisture-resistant resin, and the cross section of the conductor layer is coated in the vicinity of the terminal part 17. Even if there is, the probability of corrosion is very small.

【Effect of the invention〕

Therefore, in the present invention, the power supply pattern for electrical solder plating of the terminal part is provided on the common electrode line that is distant from the heat generating part, so compared to the conventional head in which the power supply pattern is formed near the heat generating part, conductor corrosion is less likely to occur. This has the advantage that a highly reliable thermal head can be constructed with less influence of heat. This effect is especially great when the conductor is made of a material that is prone to corrosion, such as An or Cu.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of the thermal head of the present invention, FIG. 2 is a sectional view showing a conventional thermal head taken along line AA' in FIG. 3, and FIGS. A plan view of a conventional thermal head, FIG. 4 is a sectional view showing a conventional terminal section, FIG. 5 is a plan view showing a pattern for electrical solder plating on a conventional terminal section, and FIG. FIG. 3 is a cross-sectional view showing a terminal portion formed by solder plating. l...Insulating substrate, 2...Glaze layer, 3...
...Heating resistor layer, 4, 5 conductor layer, 6... Oxidation resistant layer, 7... Wear resistant layer, 8... Heat generating part, 9...
Common electrode line, 10a-10g... Individual electrode line, 12... Head surface, 14... Solder layer, 16
...Power supply pattern for plating, 17...Terminal section. Figure 7 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In a thermal head formed on an insulating substrate and consisting of a heat generating part, a common electrode line, an individual electrode line, and a terminal part, a power supply pattern for forming electroplating on the terminal part is provided on the common electrode line. A thermal head characterized by being connected and formed at both ends of a terminal part.