JPS5854990B2 - netinserthead - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to thermal printing heads, and more particularly to a new thermal isolation structure.

Conventional Structure and Problems In a semiconductor planar type thermal printing head, since the semiconductor has good thermal conductivity, the method of thermal isolation between heating elements becomes a problem.

2. Description of the Related Art Conventionally, a thermal printing head is known which includes semiconductor mesas arranged on one surface of a substrate and a device for passing a current through a resistor provided in the mesas.

This type of thermal printing head has excellent thermal isolation because the mesas are completely insulated with air, but the process is complicated and mass production is difficult.

The first problem is that the semiconductor wafer after mesa formation is mechanically weak, so it is necessary to reinforce it by laminating a thick polysilicon layer, which causes warpage in the semiconductor wafer, so it is difficult to use a semiconductor wafer with a large diameter. could not be used.

The second problem is that after dicing the semiconductor wafer to predetermined dimensions and fixing the dies on the sides to the ceramic substrate, it is necessary to remove the polysilicon layer for mechanical reinforcement by etching. Not suitable. As described above, it is clear that the drawbacks of the conventional semiconductor planar type thermal printing head are due to the complete air insulation between the heating elements.

Purpose of the Invention In order to eliminate the above-mentioned drawbacks of the conventional technology, the present invention provides a structure in which heating elements are not completely insulated with air but connected in a narrow area, thereby achieving substantially sufficient thermal isolation and, moreover, being easy to manufacture. The object of the present invention is to provide a semiconductor planar thermal printing head that is easy to manufacture and has excellent mass productivity.

In other words, in the thermal printing head of the present invention, heating resistors formed on a semiconductor substrate by impurity diffusion are arranged in a predetermined shape to form each heating element, and the side of each heating element that contacts the thermal paper is forming a groove in the semiconductor substrate leaving a part of the periphery;
The invention is characterized in that a recess is formed in the semiconductor substrate on the side of each heating element that does not come into contact with the thermal paper.

DESCRIPTION OF EMBODIMENTS FIG. 1 is a perspective view of a thermal printing head according to an embodiment of the present invention.
2 is a semiconductor planar type thermal printing head made of silicon or the like; 3 is one heating element that includes a heating resistor therein.

In FIG. 1, four heating elements are shown.

4 and 5 are grooves formed leaving a part of the periphery of the heating element.

In this embodiment, the two connecting portions 6 and 7 do not have grooves, so the heating element 3 is connected to other parts of the thermal printing head 2 through these connecting portions 6 and 7.

However, grooves 4 and 5 are present in most of the periphery of the heating element 3.

Note that the space between the thermal printing head 2 and the insulating substrate 1 is filled with heat-resistant resin, and electrically connected by a flip chip method, a beam lead method, or the like.

Although the wiring is omitted in FIG. 1, the wiring will be explained in FIG. 2.

FIG. 2 shows a cross-sectional view taken along the cutting line AA passing through the heating element 3 in FIG. 1, and the wiring omitted in FIG. 1 is also illustrated.

A P-type diffusion layer 8, which acts as a heating resistor, is provided on the side that comes into contact with the thermal paper.

Furthermore, the wiring 10.11 is provided in a groove-free connection 6.7.

Further, 12 is a wear-resistant layer.

It is necessary to lead out the wiring 10.11 to the back side of the semiconductor wafer, but in order to do so, it is necessary to connect an insulating film to the side surface of the hole penetrating the front and back of the semiconductor wafer to ensure good throwability using CVD, sputtering, plating, etc. By forming a conductive layer using an excellent thin film formation method, the wirings 10 and 11 can be led out to the back surface.

One of the features of the isothermal printing head is that a recess 13 is provided on the surface that does not come into contact with the thermal paper.
3 and grooves 4 and 5, it is possible to use thick silicon and still provide the necessary thermal isolation.

In the thermal printing head of the present invention, the heat generating elements are surrounded by a groove leaving only a part of the connecting part, so the heat leakage is a little thicker than the conventional example in which each heat generating element is formed of a mesa, but the heat generating element density is When is 4 pieces/rIrIIL or more, there is almost no difference in print quality.

Figure 3 shows the print pattern of one heating element when printed with the thermal print head shown in Figure 1. Although microscopic observation shows that the print pattern smudges due to heat leaking through the connection without grooves, , the size of the blur is 0.05~0
．． Since it can be made as small as 1 rrvn or less, it is hardly noticeable to the naked eye.

Effects of the Invention Also, in the conventional method, the wiring passes through the groove of the mesa, resulting in a structure that is prone to disconnection, but with the thermal printing head of the present invention, as shown in Fig. 2, the wiring only needs to pass through the connecting part without a groove. Since a wear-resistant layer can be formed on this, there is no need to worry about wire breakage.

Furthermore, the thermal printing head of the present invention eliminates the need to use thin silicon (approximately 50 μm), which was the biggest drawback of conventional thermal printing heads with heating elements consisting of mesa.

That is, FIG. 2 shows this example, in which the depth of the groove 4.5 is 50 μm using silicon with a thickness of 200 μm, the depth of the recess 13 on the back surface is 150 μm, and the thickness of the heating element portion is 50 μm.
This is an example of μm.

Since the heat capacity of the heating element is almost the same as when using 50 ltm thick silicon, there is no difference in print quality.

Silicon having a thickness of 200 μm can be handled satisfactorily even in diameters of 2 inches or more without reinforcing mechanical strength with a thick polysilicon layer, and is excellent in mass production.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of the thermal printing head of the present invention;
The figure is a sectional view taken along the line A-A of the head, and FIG. 3 is an explanatory diagram showing the shape of printed dots produced by the head. 3... Heating element, 4, 5... Groove, 6,
7... Connecting portion, 8... Heat generating resistor, 13
・・・・・・Concavity.

Claims (1)

[Claims] 1. Each heating element is formed by arranging heating resistors formed by impurity diffusion on a semiconductor substrate in a predetermined shape, and a groove is formed in the semiconductor substrate leaving a part of the periphery of each heating element on the side that contacts the thermal paper. and a recessed portion is formed in the semiconductor substrate on a side of each of the heating elements that does not contact the thermal paper.