JP5877989B2 - Manufacturing method of thermal print head - Google Patents

Description

The present invention relates to a method for manufacturing a thermal printhead.

  In recent years, thermal print heads have attracted attention as output devices such as video printers, imagers, and seal printers. This thermal print head records on thermal paper, plate-making film photographic paper, media, etc. by generating heat from the heating resistors arranged on the substrate. Various developments have been made on thermal printing from the viewpoint of low noise and low running cost.

  The thermal print head has a support base in which a glaze layer is formed as a heat retaining layer on a ceramic substrate such as alumina. A heating resistor and a conductive layer serving as an electrode such as aluminum are laminated on the support substrate by a thin film forming method such as sputtering. Thereafter, a photoengraving process is performed to form a pattern in which pairs of heating resistors and individual electrodes connected in a straight line are arranged at intervals. Further, a protective coating layer covering the heating resistor and the electrode is formed by a thin film forming method such as sputtering, and the protective coating layer on the terminal portion of the individual electrode is removed.

JP 2009-137284 A

  In a thermal print head, if the protective coating layer is thick, it interferes with wire bonding between the terminal portion of the individual electrode and the circuit board, the bonding quality is lowered, and in some cases, bonding failure occurs. However, when the protective coating layer is thinned, the wear resistance is lowered.

  Therefore, an object of the present invention is to improve the bonding quality of wire bonding while maintaining the wear resistance of the thermal print head.

  In order to solve the above-described problem, the present invention provides a method for manufacturing a thermal print head, wherein a surface of a rectangular insulating substrate having a first long side and a second long side is formed along the first long side. A first step of forming resistors arranged at intervals and a wiring extending from the resistor to a terminal disposed at a position closer to the second long side than the resistor; and A second step of forming a whole surface protective coating layer covering the whole of the resistor, the wiring, the terminal and the insulating substrate later; and a positive resist layer covering the whole surface of the whole surface protective coating layer after the second step. A fourth step of exposing the terminal portion after the third step, a fifth step of forming a negative resist layer covering the entire positive resist layer after the fourth step, More than the terminal after the fifth step A sixth step of exposing a region extending along the second long side on the long side of the first region and the first long side; a seventh step of developing after the sixth step; After the seventh step, the method includes an eighth step of removing the positive resist layer, the negative resist layer, and the whole surface protective coating layer by etching, and a ninth step of peeling the positive resist layer. Features.

  According to the present invention, in the thermal print head, a rectangular insulating substrate having a first long side and a second long side, and a surface of the insulating substrate are spaced along the first long side. An array of resistors, wiring extending from the resistor to a terminal disposed at a position closer to the second long side than the resistor, and the terminal portion is open, and the first portion than the terminal A protective coating layer in which a portion thicker than the vicinity of the terminal is formed on the first long side than the boundary extending along the first long side on the side close to the long side. It is characterized by that.

  According to the present invention, it is possible to improve the bonding quality of wire bonding while maintaining the wear resistance of the thermal print head.

It is a flowchart which shows one Embodiment of the manufacturing method of the thermal print head concerning this invention with sectional drawing. It is sectional drawing of the thermal print head manufactured by one Embodiment of the manufacturing method of the thermal print head concerning this invention. It is a top view of the thermal print head manufactured with one embodiment of the manufacturing method of the thermal print head concerning the present invention. 1 is a partially enlarged plan view of a thermal print head manufactured by an embodiment of a method for manufacturing a thermal print head according to the present invention.

  An embodiment of a thermal print head according to the present invention will be described with reference to the drawings. Note that this embodiment is merely an example, and the present invention is not limited thereto.

  FIG. 2 is a cross-sectional view of a thermal print head manufactured by an embodiment of a method for manufacturing a thermal print head according to the present invention. FIG. 3 is a plan view of the thermal print head manufactured in the present embodiment. FIG. 4 is a partially enlarged plan view of the thermal print head manufactured in the present embodiment.

  The thermal print head 21 includes a heat radiating plate 10, a heating element plate 22, and a circuit board 11. The heat sink 10 is, for example, an aluminum plate.

  The heating element plate 22 includes a ceramic substrate 23, a heat retaining layer 24, a resistor layer 25, an electrode layer 26, and a protective coating layer 27. The ceramic substrate 23 is a rectangular plate having a first long side 31 and a second long side 32, and is made of alumina, for example. The heat insulating layer 24 is a layer made of, for example, glass formed on the surface of the ceramic substrate 23. The resistor layer 25 and the electrode layer 26 are stacked on the surface of the heat retaining layer 24.

  The resistor layer 25 and the electrode layer 26 extend linearly in the short side direction of the ceramic substrate 23. The resistor layer 25 and the electrode layer 26 extending in a straight line are arranged at intervals along the first long side 31 of the ceramic substrate 23. There is a void in which the electrode layer 26 is not formed on a part of the surface of the resistor layer 25, and the resistor layer 25 in the void portion becomes a resistance heating portion 28. The resistance heating portions 28 are arranged linearly along the first long side 31 of the ceramic substrate 23. An electrode terminal 29 is disposed at the end of the electrode layer 26 that extends in a straight line on the opposite side of the resistance heating portion 28. In other words, between the resistance heating part 28 arranged at intervals along the first long side 31 and the electrode terminal 29 arranged closer to the second long side 32 than the resistance heating part 28. The wiring formed in the electrode layer 26 extends.

  The heat insulating layer 24, the resistor layer 25, and the electrode layer 26 are covered with a protective coating layer 27 except for the electrode terminals 29. The protective coating layer 27 is made of, for example, SiON.

  The thickness of the protective coating layer 27 is different at a boundary 33 extending along the first long side 31 at a position closer to the first long side 31 than the electrode terminal 29. The thickness of the protective coating layer 27 in the region between the boundary 33 and the resistance heating portion 28, that is, the region between the boundary 33 and the first long side 31, is greater than the boundary 33 on the electrode terminal 29 side, that is, the boundary 33 and the second side. It is thicker than the thickness of the protective coating layer 27 in the region between the long side 32 of the two. Therefore, a step of the protective coating layer 27 is formed at the boundary 33. The height of the step is 0.2 μm to 10 μm.

  The circuit board 11 is an epoxy board on which a printed circuit is formed, for example. A driver IC (Integrated Circuit) 12 is mounted on the circuit board 11.

  The heat generating plate 22 and the circuit board 11 are placed on the same surface of the heat radiating plate 10. The heat generating plate 22 and the circuit board 11 are fixed to the heat radiating plate 10 with a double-sided tape 15, for example.

  A bonding wire 13 is bridged between the driver IC 12 and the electrode terminal 29. A bonding wire 13 is also bridged between the driver IC and a terminal formed on the circuit board 11. The driver IC 12, the bonding wire 13, and the electrode terminal 29 are sealed with a sealing resin 14. The height of the topmost part of the sealing resin 14 is, for example, 500 μm.

  Due to the level difference at the boundary 33 portion of the protective coating layer 27, the sealing resin 14 does not flow into the resistance heating portion 28 side from the boundary 33 but exists only on the electrode terminal 29 side from the boundary 33.

  Next, a method for manufacturing the thermal print head will be described.

  FIG. 1 is a flowchart showing a method of manufacturing a thermal print head in the present embodiment together with a cross-sectional view.

  First, a glass paste is printed on the surface of the ceramic substrate 23 in a predetermined pattern and fired to obtain the insulating substrate 50 in which the heat insulating layer 24 is formed on the surface of the ceramic substrate 23.

  Next, the resistor layer 25 and the electrode layer 26 are laminated on the surface of the heat insulating layer 24 by a thin film forming method such as a sputtering method. A part of the resistor layer 25 and the electrode layer 26 is removed by a photoengraving process to obtain a predetermined pattern. As a result, the resistance heating section 28 and the resistance arranged on the surface of the rectangular insulating substrate 50 having the first long side 31 and the second long side 32 at intervals along the first long side 31. A wiring layer 51 including the wiring extending from the resistance heating portion 28 is formed to the electrode terminal 29 arranged at a position closer to the second long side 32 than the heating portion 28 (first step).

  After forming the wiring layer 51 with a predetermined pattern on the surface of the insulating substrate, the entire surface protective coating layer 41 covering the entire substrate is formed (second step). That is, as shown in FIG. 1, the entire surface of the heat insulating layer 24 that is not covered with the resistance heating portion 28, the electrode layer 26, the electrode terminal 29, and these wirings is covered with the entire protective coating layer 41.

  After the second step, as shown in FIG. 1, a positive resist layer 42 that covers the entire surface of the entire protective coating layer 41 is formed (third step). The thickness of the positive resist layer 42 is about 2 μm to 10 μm.

  After the third step, the electrode terminal 29 is exposed with the mask 44 covered (fourth step). The mask 44 has an opening at a portion corresponding to the electrode terminal 29. As a result, the positive resist layer 42 in the portion 43 in contact with the opposite side to the electrode terminal 29 of the entire protective coating layer 41 is exposed.

  After the fourth step, a negative resist layer 46 covering the entire positive resist layer 42 including the exposed portion 43 is formed (fifth step). After the fifth step, exposure is performed with the mask 45 covered (sixth step). The mask 45 has an edge at the boundary 33 where the step of the protective coating layer 27 is formed after completion, and covers the electrode terminal 29 side from the boundary. As a result, the region between the boundary 33 extending along the second long side 32 on the first long side 31 side with respect to the electrode terminal 29 and the first long side 31 is exposed. As a result, the region 47 between the boundary 33 extending along the second long side 32 on the first long side 31 side of the electrode terminal 29 and the second long side 32 is not exposed to light.

  Next, the positive resist layer 42 and the negative resist layer 46 are developed (seventh step). As a result, the exposed portion 43 of the positive resist layer 42 and the unexposed region 47 of the negative resist layer 46 are removed.

  After the seventh step, etching is performed by, for example, a dry etching method (eighth step). In this etching, first, a portion where the positive resist layer 42 of the whole surface protective coating layer 41 is not formed, that is, the exposed portion 43 of the positive resist layer 42 is removed and the exposed portion is removed with time. At this time, the portion of the positive resist layer 42 not covered with the negative resist layer 46 is also removed. When the portion of the positive resist layer 42 not covered with the negative resist layer 46 disappears, the entire surface of the protective coating layer 41 is also removed over time at that portion. This etching is performed until the entire protective coating layer 41 on the surface of the electrode terminal 29 disappears.

  As a result, the protective coating layers 27 having different thicknesses are formed at the boundary 33 extending along the second long side 32 on the first long side 31 side of the electrode terminal 29. The material and thickness of the positive resist layer 42, the etching gas, and the like are selected so that a predetermined step is formed at the boundary 33 portion by etching until the entire surface of the electrode terminal 29 is free of the protective coating layer 41.

  Thus, after forming the protective coating layer 27, the remaining negative resist layer 46 and the positive resist layer 42 covered with the negative resist layer 46 are peeled off (9th process). Thereby, the heat generating body plate 22 is completed.

  Thereafter, the heating plate 22 and the separately manufactured circuit board 11 are placed on the heat sink 10 and fixed. Next, wire bonding is performed between the heating element plate 22 fixed to the heat radiating plate 10 and the driver IC 12 on the circuit board 11. Further, the driver IC and the bonding wire 13 are sealed with the sealing resin 14 to complete the thermal print head 21.

  The protective coating layer 27 in the vicinity of the electrode terminal 28 is thicker than the protective coating layer 27 in the vicinity of the resistance heating portion 28. For this reason, the possibility that the protective coating layer 27 interferes with the wire bonding is small. As a result, the bonding quality of wire bonding is improved. In addition, since the surface of the thin protective coating layer 27 in the vicinity of the electrode terminal 29 is protected by the sealing resin 14, the possibility that the soundness is impaired is small. On the other hand, in the vicinity of the resistance heating portion 28 that comes into contact with the printing medium, the protective coating layer 27 is thickened, so that predetermined wear resistance performance can be ensured.

  The positive resist layer 42 is more suitable for fine patterning than the negative resist layer 46. Therefore, by using the positive resist layer 42, it is possible to form a plurality of openings smaller than a region covered with the negative resist layer 46 that forms a step in the protective coating layer 27.

  Further, after exposing the positive resist layer 42 of the portion 43 to be removed of the entire protective coating layer 41, a negative resist layer 46 is formed on the surface thereof. The negative resist layer 46 may be formed by exposing a region 47 to be left after development. For this reason, even if light passes through the negative resist layer 46 and the positive resist layer 42 on the back surface of the negative resist layer 46 is exposed, the exposed portion is covered with the negative resist layer 46 and is removed during etching. It will never be. Therefore, the electrode terminal 29 can be exposed by a single etching process, and the step of the protective coating layer 27 can be formed at the boundary 33.

  Thus, according to the present embodiment, it is possible to improve the bonding quality of the wire bonding while maintaining the wear resistance of the thermal print head.

  Further, due to the step at the boundary 33 portion of the protective coating layer 27, the sealing resin 14 does not flow into the resistance heating portion 28 side from the boundary 33, and exists only on the electrode terminal 29 side from the boundary 33. For this reason, even if the resistance heating part 28 and the electrode terminal 29 are brought close to each other, it is not necessary to consider the flow of the sealing resin 14 to the vicinity of the resistance heating part 28 during manufacturing. The size can be reduced in the short side direction.

  Here, the case where one thermal print head 21 is manufactured from one ceramic substrate 23 has been described, but a portion to be a plurality of thermal print heads 21 is formed on one ceramic substrate 23 and then divided. Thus, a plurality of thermal print heads 21 may be manufactured. Although the driver IC 12 is mounted on the circuit board 11, the driver IC 12 is mounted on the heating element plate 22 side, and the bonding wire 13 is bridged from the driver IC 12 to the circuit board 11 side. Good.

DESCRIPTION OF SYMBOLS 10 ... Heat sink, 11 ... Circuit board, 12 ... Driver IC, 13 ... Bonding wire, 14 ... Sealing resin, 15 ... Double-sided tape, 21 ... Thermal print head, 22 ... Heat generating body plate, 23 ... Ceramic substrate, 24 ... Thermal insulation layer, 25 ... resistor layer, 26 ... electrode layer, 27 ... protective coating layer, 28 ... resistance heating part, 29 ... electrode terminal, 31 ... first long side, 32 ... second long side, 33 ... boundary , 41 ... Entire protective coating layer, 42 ... Positive resist layer, 44 ... Mask, 45 ... Mask, 46 ... Negative resist layer, 50 ... Insulating substrate, 51 ... Wiring layer

Claims (2)

Resistors arranged on the surface of a rectangular insulating substrate having a first long side and a second long side at intervals along the first long side, and the second length longer than the resistor Forming a wiring extending from the resistor to a terminal disposed at a position close to the side;
A second step of forming an overall protective coating layer covering the resistor, the wiring, the terminal, and the insulating substrate after the first step;
A third step of forming a positive resist layer covering the entire surface of the whole surface protective coating layer after the second step;
A fourth step of exposing the terminal portion after the third step;
A fifth step of forming a negative resist layer covering the entire positive resist layer after the fourth step;
A sixth step of exposing a region between the first long side and a boundary extending along the second long side on the first long side of the terminal after the fifth step;
A seventh step of developing after the sixth step;
An eighth step of etching and removing the positive resist layer, the negative resist layer, and the entire protective coating layer after the seventh step;
A ninth step of removing the positive resist layer;
A method of manufacturing a thermal print head, comprising: A bonding step of connecting the drive element for driving the resistor and the terminal with a wire after the ninth step;
After the bonding step, a sealing step of sealing the drive element and the wire by applying a resin on the second long side from the boundary;
The manufacturing method of the thermal print head of Claim 1 characterized by the above-mentioned.

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