JP7545828B2 - Thermal Printhead - Google Patents

Description

This disclosure relates to an IC chip mounting structure, a thermal printhead having the mounting structure, and a method for manufacturing a thermal printhead.

Patent Document 1 discloses an example of a conventional thermal printhead. The thermal printhead disclosed in the document includes a substrate, a glaze layer, an electrode layer (wiring layer), a heating resistor (resistance layer), and a driving IC (IC chip). The substrate is a plate-shaped member made of an insulating material, such as a ceramic such as alumina (Al ₂ O ₃ ). The glaze layer is formed on the surface of the substrate, such as glass. The wiring layer is formed on the glaze layer, and constitutes a current path for selectively passing a current to the resistance layer. The resistance layer has a plurality of heating parts arranged in the main scanning direction. The IC chip controls the current passed through each heating part.

In the thermal printhead disclosed in Patent Document 1, an IC chip is mounted on a substrate by flip-chip mounting. A plurality of conductive bonding materials, for example solder bumps, are provided on the mounting surface of the IC chip facing the substrate. A plurality of pads are provided on the wiring layer, and when mounting the IC chip on the substrate, the IC chip is placed on the wiring layer by a mounter, and the plurality of conductive bonding materials and the plurality of pads are temporarily attached. Then, the plurality of conductive bonding materials are melted by a reflow process to bond the plurality of pads to the plurality of conductive bonding materials. With this IC chip mounting structure, the plurality of conductive bonding materials of the IC chip can be bonded to the plurality of pads of the wiring layer at the same time. In addition, it is possible to narrow the pitch of the individual wiring leading to each of the plurality of pads, which is also suitable for fine wiring.

However, if the mounting position of the IC chip during flip-chip mounting is misaligned, the reflow process may cause the conductive bonding material to come into contact with or bond to pads or individual wiring that are not intended to be bonded. In this case, an unintended current path may be formed, causing an electrical short circuit.

JP 2014-87938 A

The present disclosure was conceived in light of the above circumstances, and its primary objective is to provide an IC chip mounting structure suitable for preventing defects during flip-chip mounting, and a thermal printhead equipped with said mounting structure.

The mounting structure of an IC chip provided by the first aspect of the present disclosure comprises a substrate having a main surface facing in one direction in the thickness direction, a support member having a wiring layer arranged on the main surface, an IC chip having a mounting surface, and a plurality of conductive bonding materials arranged on the mounting surface, and the IC chip is flip-chip mounted on the support member, the support member having a plurality of pad portions arranged corresponding to the plurality of conductive bonding materials and including at least two concave pad portions, the concave pad portion having a bottom surface and an inner wall surface facing the bottom surface when viewed in the thickness direction of the substrate, and the inner wall surface being constituted by the wiring layer.

The thermal printhead provided by the second aspect of the present disclosure has the IC chip mounting structure according to the first aspect of the present disclosure, and is provided with a resistor layer disposed on the main surface and including a plurality of heat generating portions arranged in the main scanning direction, the wiring layer is conductive to the resistor layer, and the IC chip controls the current flowing to each of the heat generating portions.

A method for manufacturing a thermal printhead provided by a third aspect of the present disclosure includes the steps of preparing a substrate, forming a wiring layer on the substrate to form a support member made of the substrate and the wiring layer, forming a resistor layer on the support member so as to overlap a portion of the wiring layer when viewed in the thickness direction of the substrate, and flip-chip mounting an IC chip having a mounting surface on which a plurality of conductive bonding materials are arranged, to the substrate, in which the step of forming the support member includes forming a plurality of pad portions corresponding to the plurality of conductive bonding materials, the pad portions including at least two concave pad portions having a bottom surface and an inner wall surface facing the bottom surface when viewed in the thickness direction of the substrate.

This disclosure improves positional misalignment during flip-chip mounting of IC chips, and is suitable for preventing defects caused by such misalignment.

Other features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

FIG. 1 is a plan view showing a thermal printhead according to a first embodiment of the present disclosure. 2 is a schematic cross-sectional view taken along line II-II in FIG. 1. FIG. 2 is an enlarged plan view of a main portion of the thermal printhead shown in FIG. FIG. 3 is a partially enlarged view of FIG. 2 . FIG. 4 is a partially enlarged cross-sectional view taken along line VV in FIG. FIG. 5 is a partially enlarged view of FIG. 4 . FIG. 2 is an enlarged plan view of a main portion of the thermal printhead shown in FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 7. 2 is a cross-sectional view showing a step of an example of a method for manufacturing the thermal printhead shown in FIG. 1. 10 is a cross-sectional view showing a process following FIG. 9 . FIG. 11 is a cross-sectional view showing a process following FIG. 10 . 12 is a cross-sectional view showing a process following FIG. 11 . 13 is a cross-sectional view showing a process following FIG. 12 . 14 is a cross-sectional view showing a process following FIG. 13. 15 is a cross-sectional view showing a process following FIG. 14 . 16 is a cross-sectional view showing a process following FIG. 15 . FIG. 17 is an enlarged cross-sectional view for explaining the step shown in FIG. 16 . FIG. 18 is a cross-sectional view similar to FIG. 17, illustrating a state after reflow processing. FIG. 17 is an enlarged cross-sectional view for explaining the step shown in FIG. 16 . FIG. 20 is a cross-sectional view similar to FIG. 19, illustrating a state after reflow processing. 8 is an enlarged plan view similar to FIG. 7 showing a main portion of a first modified example of the thermal printhead shown in FIG. 1. 8 is an enlarged plan view similar to FIG. 7 showing a main portion of a second modified example of the thermal printhead shown in FIG. 1. 23 is an enlarged cross-sectional view taken along line XXIII-XXIII in FIG. 22. 23 is an enlarged cross-sectional view taken along line XXIV-XXIV in FIG. 22. 1. FIG. 7 is a cross-sectional view similar to FIG. 6, showing a third modified example of the thermal printhead shown in FIG. 1. FIG. 9 is a cross-sectional view similar to FIG. 6, showing a fourth modified example of the thermal printhead shown in FIG. 1. FIG. 9 is a cross-sectional view similar to FIG. 6, showing a fifth modified example of the thermal printhead shown in FIG. FIG. 5 is a cross-sectional view similar to FIG. 4 showing a thermal printhead according to a second embodiment of the present disclosure. FIG. 29 is a partially enlarged view of FIG. 28 . 30 is a cross-sectional view similar to FIG. 29, showing a modified example of the thermal printhead shown in FIG. 28.

The preferred embodiment of this disclosure will be described in detail below with reference to the drawings.

In this disclosure, "a certain object A is formed on a certain object B" and "a certain object A is formed on a certain object B" include "a certain object A is formed directly on a certain object B" and "a certain object A is formed on a certain object B with another object interposed between the certain object A and the certain object B" unless otherwise specified. Similarly, "a certain object A is disposed on a certain object B" and "a certain object A is disposed on a certain object B" include "a certain object A is disposed directly on a certain object B" and "a certain object A is disposed on a certain object B with another object interposed between the certain object A and the certain object B" unless otherwise specified. Similarly, "a certain object A is located on a certain object B" includes "a certain object A is located on a certain object B in contact with a certain object B" and "a certain object A is located on a certain object B with another object interposed between the certain object A and the certain object B". Additionally, unless otherwise specified, "an object A overlaps an object B when viewed in a certain direction" includes "an object A overlaps the entirety of an object B" and "an object A overlaps a part of an object B."

First Embodiment
1 to 8 show a thermal printhead according to a first embodiment of the present disclosure. The thermal printhead A1 of this embodiment includes a substrate 1, a glaze layer 2, a wiring layer 3, a resistor layer 4, a protective layer 5, an IC chip 6, a protective resin 71, and a connector 72. The thermal printhead A1 includes a mounting structure in which the IC chip 6 is flip-chip mounted (the mounting structure of the IC chip according to the present disclosure). The thermal printhead A1 is incorporated into a printer that prints on a print medium 82 transported by a platen roller 81 (see FIG. 2). Examples of such print media 82 include thermal paper for producing barcode sheets and receipts.

Figure 1 is a plan view showing the thermal printhead A1. Figure 2 is a schematic cross-sectional view taken along line II-II in Figure 1. Figure 3 is an enlarged plan view of the thermal printhead A1. Figure 4 is a cross-sectional view showing an enlarged portion of Figure 2. Figure 5 is a partially enlarged cross-sectional view taken along line V-V in Figure 3. Figure 6 is a cross-sectional view showing an enlarged portion of Figure 4. Figure 7 is an enlarged plan view of the thermal printhead A1, showing a portion of the IC chip. Figure 8 is a cross-sectional view taken along line VIII-VIII in Figure 7. For ease of understanding, the protective layer 5 is omitted in Figures 1 and 3. The connector 73 is omitted in Figure 4. The protective resin 71 is omitted in Figure 7. In these figures, the longitudinal direction (main scanning direction) of the substrate 1 is the x-direction, the lateral direction (sub-scanning direction) is the y-direction, and the thickness direction is the z-direction. In addition, with regard to the y direction, the lower side in Figures 1 and 3 (the left side in Figures 2 and 4) is the "upstream" side where the print medium is fed, and the upper side in Figures 1 and 3 (the right side in Figures 2 and 4) is the "downstream" side where the print medium is discharged. In addition, with regard to the z direction, the upper side in Figures 2 and 4 (the direction indicated by the arrow showing the z direction) is the "upper" side, and the opposite direction is the "lower" side. The same applies to the following figures.

The substrate 1 is made of a ceramic such as _Al2O3 , and has a thickness of, for example _, about 0.6 to 1.0 mm. As shown in Fig. 1, the substrate 1 has an elongated rectangular shape extending long in the x direction. The glaze layer 2, the wiring layer 3, the resistor layer 4, the protective layer 5, the IC chip 6, and the protective resin 71 are disposed on the substrate 1. The connector 72 is for connecting to an external device, and is provided, for example, at the lower end of the substrate 1 in the y direction in Fig. 1.

The glaze layer 2 is disposed on the substrate 1 and is made of a glass material such as amorphous glass. In this embodiment, the glaze layer 2 is formed to have a constant thickness and has a substantially flat main surface 21 facing upward in the z direction. The thickness of the glaze layer 2 is, for example, 50 to 200 μm.

The thermal printhead A1 has a so-called thick-film configuration and is manufactured using thick-film printing. The glaze layer 2 is formed by printing a thick film of glass paste on the substrate 1 and then firing it. In other words, the glaze layer 2 is formed by thick-film formation technology.

The wiring layer 3 is for forming a path for passing electricity through the resistor layer 4, and is disposed on the main surface 21 of the glaze layer 2. The wiring layer 3 is formed so as to have a resistivity value smaller than that of the resistor layer 4. The wiring layer 3 of this embodiment has a first metal portion 3a and a second metal portion 3b made of a metal different from that of the first metal portion 3a. Specifically, the first metal portion 3a is made of a conductor mainly composed of gold (Au), and the second metal portion 3b is made of a conductor mainly composed of silver (Ag). The first metal portion 3a is made of resinate Au to which rhodium, vanadium, bismuth, silicon, etc. are added as additive elements, for example. From the viewpoint of electrical conductivity, it is possible to obtain superior properties by forming only the first metal portion 3a, but considering the cost issue, it is desirable to use the cheaper second metal portion 3b in combination.

As shown in Figures 3 to 8, the wiring layer 3 has a common electrode 33, multiple individual electrodes 34, multiple signal wiring sections 37, and multiple pad sections 38.

The common electrode 33 has a common portion 331 and multiple common electrode strip portions 332. Specifically, the common portion 331 is disposed downstream in the y direction relative to the resistor layer 4, and extends along the x direction. The multiple common electrode strip portions 332 each extend upstream in the y direction from the common portion 331, and are arranged at equal pitches in the x direction.

The multiple individual electrodes 34 are for partially passing electricity through the resistor layer 4, and are portions that have the opposite polarity to the common electrode 33. The individual electrodes 34 extend from the resistor layer 4 toward the IC chip 6. The multiple individual electrodes 34 are arranged in the x direction, and each has an individual electrode strip portion 35 and a connecting portion 36.

Each individual electrode strip portion 35 is a strip portion extending in the y direction and is located between two adjacent common electrode strip portions 332 of the common electrode 33. The connecting portion 36 is a portion extending from the individual electrode strip portion 35 toward the IC chip 6, and most of it has a portion along the y direction and a portion inclined with respect to the y direction. The connecting portions 36 are arranged at relatively narrow intervals in the x direction on the upstream side in the y direction. The interval between adjacent connecting portions 36 on the upstream side in the y direction is, for example, about 20 μm or less. As shown in FIG. 7, the upstream end of each connecting portion 36 in the y direction overlaps with the IC chip 6 when viewed in the z direction.

The multiple signal wiring sections 37 form a wiring pattern connected to the connector 72 and the IC chip 6. As shown in FIG. 7, the multiple signal wiring sections 37 are arranged in the x direction near the IC chip 6 and each extends in the y direction. The downstream end of each signal wiring section 37 in the y direction overlaps with the IC chip 6 when viewed in the z direction. The IC chip 6 used in the thermal printhead A1 typically has a rectangular planar shape (see FIG. 1). The long side of the IC chip 6 is aligned with the x direction (main scanning direction), which is the direction in which the resistor layer 4 extends.

In this embodiment, as shown in Figures 3 and 5, the first metal portion 3a includes a common portion 331 and multiple common electrode strip portions 332 of the common electrode 33, and individual electrode strip portions 35 of the multiple individual electrodes 34. The first metal portion 3a is connected to the resistor layer 4 (multiple heat generating portions 41 described below). The second metal portion 3b is disposed in a region upstream in the y direction from the first metal portion 3a. The second metal portion 3b includes connecting portions 36 of the multiple individual electrodes 34 and multiple signal wiring portions 37.

As shown in Figures 6 and 8, the multiple pad portions 38 are connected to the flip-chip mounted IC chip 6 via multiple conductive bonding materials 62. The multiple pad portions 38 are arranged in groups in the x and y directions. As shown in Figure 7, the multiple pad portions 38 are connected to the upstream end in the y direction of any of the multiple connecting portions 36 (individual electrodes 34) or the downstream end in the y direction of any of the multiple signal wiring portions 37. In this embodiment, the multiple pad portions 38 are formed in two rows in the y direction.

A plurality of conductive bonding materials 62 are arranged on the mounting surface 61 (the surface facing the substrate 1) of the IC chip 6. The conductive bonding materials 62 are, for example, solder bumps. The plurality of pad portions 38 are arranged corresponding to the plurality of conductive bonding materials 62.

The pad sections 38 are arranged in large numbers in the x direction to correspond to the multiple connecting sections 36 (individual electrodes 34) and the multiple signal wiring sections 37. The distance L1 between adjacent pad sections 38 in the x direction is relatively small, for example, about 10 to 20 μm. On the other hand, the distance L2 between pad sections 38 in the y direction is relatively large, for example, about 100 to 200 μm.

The multiple pad portions 38 include at least two concave pad portions 381. In this embodiment, all of the multiple pad portions 38 are concave pad portions 381. The term pad portion 38 includes both the concave pad portion 381 and a pad portion that is not concave (a pad portion whose entire area is flat when viewed along the thickness direction).

In this embodiment, the wiring layer 3 (second metal portion 3b) is configured to include a first layer 31 and a second layer 32, and the concave pad portion 381 is configured by the first layer 31 and the second layer 32. Specifically, the first layer 31 is disposed on the main surface 21 of the glaze layer 2. The first layer 31 has a flat surface 311 facing upward. The thickness of the first layer 31 is, for example, about 2 to 5 μm. The second layer 32 is disposed on the surface 311 of the first layer 31. The second layer 32 is disposed on a portion of the first layer 31. The second layer 32 is formed in a plurality of regions corresponding to the plurality of pad portions 38 (concave pad portions 381). Each region of the second layer 32 is formed in a rectangular ring shape when viewed in the z direction, and has a top surface 321. The top surface 321 is the upper end surface of the second layer 32 in the z direction. The thickness of the second layer 32 (the dimension in the z direction from the surface 311 to the top surface 321) is, for example, about 2 to 5 μm.

In this embodiment, the concave pad portion 381 has a bottom surface 312 and an inner wall surface 322. The bottom surface 312 is formed by the area of the surface 311 of the first layer 31 that is surrounded by the second layer 32 when viewed in the z direction. The inner wall surface 322 is formed by the surface of each area of the second layer 32 that faces the bottom surface 312 when viewed in the z direction. In this embodiment, the inner wall surface 322 is a rectangular ring that surrounds the bottom surface 312 when viewed in the z direction. As shown in Figures 6 and 8, each of the multiple conductive bonding materials 62 is bonded to the concave pad portion 381 (the first layer 31 to the second layer 32 of the wiring layer 3) while a portion of the conductive bonding material 62 is accommodated in the inner space of the concave pad portion 381.

The resistor layer 4 is made of a material having a higher resistivity than the material constituting the wiring layer 3, such as ruthenium oxide, and is formed in a strip shape extending in the x direction. As shown in FIG. 3, the resistor layer 4 intersects with the common electrode strip portions 332 of the common electrode 33 and the individual electrode strip portions 35 of the individual electrodes 34. Furthermore, the resistor layer 4 is laminated on the opposite side of the substrate 1 to the common electrode strip portions 332 of the common electrode 33 and the individual electrode strip portions 35 of the individual electrodes 34. The portions of the resistor layer 4 sandwiched between each common electrode strip portion 332 and each individual electrode strip portion 35 are heat generating portions 41 that generate heat by being partially energized by the wiring layer 3. One print dot is formed by the heat generated by two adjacent heat generating portions 41 sandwiching one individual electrode strip portion 35. The thickness of the resistor layer 4 is, for example, about 3 to 10 μm.

The protective layer 5 is for protecting the wiring layer 3 and the resistor layer 4. The protective layer 5 is made of, for example, amorphous glass. However, the protective layer 5 exposes an area including a plurality of recessed pad portions 381 (pad portions 38).

The IC chip 6 selectively energizes the individual electrodes 34 to partially heat the resistor layer 4. As shown in FIG. 1 and FIG. 4, the IC chip 6 is disposed upstream in the y direction with respect to the resistor layer 4 (the heating portions 41). In this embodiment, the IC chips 6 are disposed on the glaze layer 2 by flip-chip mounting. As described above, the mounting surface 61 of the IC chip 6 is provided with a plurality of conductive bonding materials 62, which are bonded to the plurality of concave pad portions 381. As shown in FIG. 2, FIG. 4, and FIG. 6, the IC chip 6 is covered with a protective resin 71. The protective resin 71 is made of, for example, a black soft resin. The IC chip 6 and the connector 72 are connected by the plurality of signal wiring portions 37. The IC chip 6 is supplied with a print signal, a control signal, and a voltage supplied to the heating portions 41 from the outside via the connector 72. The heating portions 41 are selectively heated by being individually energized according to the print signal and the control signal.

In the above configuration, the substrate 1 and the glaze layer 2 disposed on the substrate 1 constitute the "base material" in this disclosure. In addition, the substrate 1, the glaze layer 2 (base material), and the wiring layer 3 disposed on the main surface 21 of the glaze layer 2 constitute the "support member" in this disclosure.

Next, we will briefly explain an example of how to use the thermal printhead A1.

The thermal print head A1 is used in a state where it is incorporated in a printer. As shown in FIG. 2, in the printer, each heat generating portion 41 of the thermal print head A1 faces a platen roller 81. When the printer is in use, the platen roller 81 rotates to feed a print medium 82 such as thermal paper between the platen roller 81 and each heat generating portion 41 at a constant speed along the y direction. The print medium 82 is pressed against the portion of the protective layer 5 that covers each heat generating portion 41 by the platen roller 81. Meanwhile, a potential is selectively applied to each individual electrode 34 shown in FIG. 3 by the IC chip 6. As a result, a voltage is applied between the common electrode 33 and each of the multiple individual electrodes 34. Then, a current selectively flows through the multiple heat generating portions 41, generating heat. Then, the heat generated in each heat generating portion 41 is transmitted to the print medium 82 via the protective layer 5. Then, multiple dots are printed in a line area that extends linearly in the x direction on the print medium 82. In addition, the heat generated by each heat generating portion 41 is also transmitted to the glaze layer 2 and stored there.

Next, an example of a method for manufacturing the thermal printhead A1 will be described below with reference to Figures 9 to 20. Note that Figures 9 to 16 are cross-sectional views showing a step in the method for manufacturing the thermal printhead A1, and correspond to the partially enlarged cross-sectional view shown in Figure 4.

First, a substrate 1 is prepared as shown in Fig. 9. The substrate 1 is a plate material made of _ceramic such as _Al2O3 , and has a predetermined thickness.

Next, as shown in FIG. 10, the glaze layer 2 is formed. The glaze layer 2 is formed by printing a thick film of glass paste on the substrate 1 and then firing it. The glaze layer 2 covers the entire surface of the substrate 1. The glaze layer 2 has a main surface 21. The main surface 21 is substantially flat and faces upward in the z direction. The steps shown in FIG. 9 and FIG. 10 correspond to the "step of preparing a substrate" of this disclosure.

Next, as shown in FIG. 11, the first metal portion 3a of the wiring layer 3 is formed. Here, a paste of resinate Au is first thick-film printed on the main surface 21 of the glaze layer 2, and then the paste is fired to form a metal film. Next, the metal film is patterned, for example by etching, to form the first metal portion 3a of a predetermined shape.

Next, as shown in FIG. 12, the first layer 31 of the wiring layer 3 (second metal portion 3b) is formed (first layer formation process). Here, first, a negative type photosensitive Ag paste is placed on the main surface 21 of the glaze layer 2 by screen printing and dried. Next, the photosensitive Ag paste on the main surface 21 is partially exposed to ultraviolet light using, for example, a photomask. The exposed portion of the photosensitive Ag paste is the portion that is to become the first layer 31. Next, the photosensitive Ag paste other than the exposed portion is removed using a developer. Next, the photosensitive Ag paste remaining on the main surface 21 is fired to form a film. This forms the first layer 31. The photosensitive Ag paste used to form the first layer 31 corresponds to the "first photosensitive metal paste" in this disclosure.

Next, as shown in FIG. 13, the second layer 32 of the wiring layer 3 (second metal portion 3b) is formed. Here, first, a negative photosensitive Ag paste is placed on the surface 311 of the first layer 31 by screen printing and dried. Next, for example, a photomask is used to partially expose the photosensitive Ag paste on the first layer 31 to ultraviolet light. The exposed portion of the photosensitive Ag paste is the portion that is to become the second layer 32. Next, a developer is used to remove the photosensitive Ag paste other than the exposed portion. Next, the photosensitive Ag paste remaining on the first layer 31 is baked to form a film. This forms the second layer 32. Here, the second layer 32 is formed in a plurality of regions corresponding to the ends of the plurality of connecting portions 36 and the ends of the plurality of signal wiring portions 37, and each region of the second layer 32 is formed in a rectangular ring shape when viewed in the z direction. By forming the second layer 32, each area of the surface 311 of the first layer 31 that is surrounded by the second layer 32 when viewed in the z direction becomes the bottom surface 312. In each area of the second layer 32, the surface facing the bottom surface 312 when viewed in the z direction becomes the inner wall surface 322. In this manner, in this process, a plurality of concave pad portions 381 are formed, each of which has a bottom surface 312 and an inner wall surface 322. The photosensitive Ag paste used to form the second layer 32 corresponds to the "second photosensitive metal paste" in this disclosure.

Next, as shown in FIG. 14, the resistor layer 4 is formed. The resistor layer 4 is formed by thick-film printing a resistor paste containing a resistor such as ruthenium oxide, and then firing it.

Next, as shown in FIG. 15, protective layer 5 is formed. Protective layer 5 is formed, for example, by applying glass paste by thick-film printing to the area where protective layer 5 is to be formed, and then baking it. Substrate 1 is then cut into a lattice shape along the x and y directions, and divided into a plurality of individual pieces. The process of dividing into the individual pieces is performed, for example, by laser irradiation. Each individual piece corresponds to substrate 1 of thermal printhead A1.

Next, as shown in FIG. 16, the IC chip 6 is mounted on the glaze layer 2 by flip-chip mounting. Here, first, for example, flux (not shown) is applied to the plurality of conductive bonding materials 62, and the conductive bonding materials 62 are placed on the plurality of electrodes (not shown) formed on the mounting surface 61 of the IC chip 6. As an alternative method, the conductive bonding materials 62 may be placed on each electrode after applying flux (not shown) to the plurality of electrodes (not shown). When mounting the IC chip 6, the IC chip 6 is placed on the wiring layer 3 while aligning the plurality of conductive bonding materials 62 and the plurality of pad portions 38 (concave pad portions 381) with a mounter (not shown), and the plurality of conductive bonding materials 62 and the plurality of pad portions 38 (concave pad portions 381) are temporarily attached with the above-mentioned flux. Next, the plurality of conductive bonding materials 62 are melted by a reflow process to bond the plurality of pad portions 38 (concave pad portions 381) and the plurality of conductive bonding materials 62.

Before the reflow process, when the IC chip 6 is placed on the wiring layer 3 as described above and the multiple conductive bonding materials 62 and the multiple pads 38 (recessed pads 381) are temporarily attached, the mounting position of the IC chip 6 may be shifted due to mechanical variations. In this case, as shown in Figures 17 and 19, for example, the positions of the multiple conductive bonding materials 62 are shifted relative to the multiple pads 38 (recessed pads 381). Figure 17 shows the state of positional shift of the multiple conductive bonding materials 62 (IC chips 6) in the y direction, and Figure 19 shows the state of positional shift of the multiple conductive bonding materials 62 (IC chips 6) in the x direction.

In the embodiment shown in Figures 17 and 19, as the conductive bonding material 62 melts during the reflow process, the conductive bonding material 62 is guided to fall into the concave shape of the concave pad portion 381 (the space surrounded by the bottom surface 312 and the inner wall surface 322). As a result, as shown in Figures 18 and 20, the conductive bonding material 62 is accommodated in the concave pad portion 381, and the misalignment of the conductive bonding material 62 and the IC chip 6 is improved.

After flip-chip mounting of the IC chip 6, the thermal printhead A1 is obtained by forming the protective resin 71 and attaching the connector 72.

Next, we will explain the function of thermal print head A1.

A plurality of conductive bonding materials 62 are arranged on the mounting surface 61 of the flip-chip mounted IC chip 6. The wiring layer 3 (support member) has a plurality of pads 38 arranged corresponding to the plurality of conductive bonding materials 62, and the plurality of pads 38 include at least two concave pads 381. With this configuration, even if some misalignment occurs when the IC chip 6 is mounted, when the conductive bonding material 62 is bonded to the wiring layer 3 (support member) (during reflow processing), the conductive bonding material 62 is guided to fall into the concave pads 381 (the space surrounded by the bottom surface 312 and the inner wall surface 322 facing the bottom surface 312). This improves the misalignment of the conductive bonding material 62 and the IC chip 6, making it suitable for preventing problems caused by misalignment when the IC chip 6 is flip-chip mounted.

The wiring layer 3 includes a first layer 31 and a second layer 32. The first layer 31 is disposed on the main surface 21 of the glaze layer 2, and the second layer 32 is disposed on a part of the first layer 31. The bottom surface 312 of the concave pad portion 381 is constituted by the first layer 31, and the inner wall surface 322 of the concave pad portion 381 is constituted by the second layer 32. According to this configuration, the conductive bonding material 62 contained in the concave pad portion 381 is bonded across the bottom surface 312 and the inner wall surface 322 (the first layer 31 and the second layer 32), so that the bonding area is large, which is suitable for increasing the bonding strength of the conductive bonding material 62. In addition, in this embodiment, the bonding area between the conductive bonding material 62 and the wiring layer 3 (the first layer 31 and the second layer 32) is large, so that the reliability of the conductive bonding between the conductive bonding material 62 and the wiring layer 3 is improved.

In this embodiment, the inner wall surface 322 constituting the recessed pad portion 381 forms a rectangular ring (annular) shape surrounding the bottom surface 312 when viewed in the z direction. With this configuration, even if misalignment occurs in both the x and y directions when the IC chip 6 is mounted, misalignment of the conductive bonding material 62 and the IC chip 6 in both the x and y directions is improved.

In this embodiment, all of the pads 38 are recessed pads 381. This configuration more reliably reduces misalignment during flip-chip mounting of the IC chip 6.

<Modification of the First Embodiment>
21 to 24 show modified examples of the thermal printhead A1 according to the first embodiment described above. In the figures following Fig. 21, elements that are the same as or similar to those of the thermal printhead A1 of the above embodiment are given the same reference numerals as in the above embodiment, and descriptions thereof will be omitted as appropriate.

<First Modification of First Embodiment>
21 shows a first modified example of the first embodiment. In the thermal printhead A11 of this modified example, some of the pad portions 38 are configured as concave pad portions 381, which differs from the thermal printhead A1 in that all of the pad portions 38 are configured as concave pad portions 381.

In the thermal printhead A11 illustrated in FIG. 21, the pads 38 are arranged in the x and y directions, and the pads 38 located at the four corners in the x and y directions are configured as concave pads 381. The specific configuration of each concave pad 381 is the same as that of the thermal printhead A1. Therefore, each region of the second layer 32 that configures the concave pad 381 is rectangular and annular when viewed in the z direction. The concave pad 381 has a bottom surface 312 configured by the first layer 31, and an inner wall surface 322 configured by the second layer 32 and having a rectangular annular shape that surrounds the bottom surface 312 when viewed in the z direction. In this modified example, the configuration other than the arrangement of the concave pads 381 is the same as that of the thermal printhead A1.

Although detailed illustrations are omitted, a plurality of conductive bonding materials 62 are arranged on the mounting surface 61 of the flip-chip mounted IC chip 6. In this modified example, the wiring layer 3 (support member) also has a plurality of pad portions 38 arranged corresponding to the plurality of conductive bonding materials 62, and the plurality of pad portions 38 include a plurality (four) of concave pad portions 381. With this configuration, even if some misalignment occurs when the IC chip 6 is mounted, when the conductive bonding material 62 is bonded to the wiring layer 3 (support member) (during reflow processing), the conductive bonding material 62 is guided to fall into the concave pad portion 381 (the space surrounded by the bottom surface 312 and the inner wall surface 322 facing the bottom surface 312). This improves the misalignment of the conductive bonding material 62 and the IC chip 6, making it suitable for preventing problems caused by misalignment when the IC chip 6 is flip-chip mounted. Instead of the four concave pad portions 381 shown in FIG. 21, one concave pad portion 381 may be placed at each of the two diagonal corners of the IC chip 6. In this case, two concave pad portions 381 are placed on one IC chip 6. In addition to the two concave pad portions 381 described above, three concave pad portions 381 may be used, including a concave pad portion 381 located at another corner. In this case, problems caused by misalignment during flip-chip mounting of the IC chip 6 can also be prevented.

The wiring layer 3 includes a first layer 31 and a second layer 32. The first layer 31 is disposed on the main surface 21 of the glaze layer 2, and the second layer 32 is disposed on a part of the first layer 31. The bottom surface 312 of the concave pad portion 381 is constituted by the first layer 31, and the inner wall surface 322 of the concave pad portion 381 is constituted by the second layer 32. According to this configuration, the conductive bonding material 62 contained in the concave pad portion 381 is bonded across the bottom surface 312 and the inner wall surface 322 (the first layer 31 and the second layer 32), so that the bonding area is large, which is suitable for increasing the bonding strength of the conductive bonding material 62. In addition, in this embodiment, the bonding area between the conductive bonding material 62 and the wiring layer 3 (the first layer 31 and the second layer 32) is large, so that the reliability of the conductive bonding between the conductive bonding material 62 and the wiring layer 3 is improved.

In this modified example, among the multiple pad portions 38, those located at the four corners in the x and y directions are configured as concave pad portions 381. With this configuration, the effect of improving the positional deviation during flip-chip mounting of the IC chip 6 can be appropriately obtained.

<Second Modification of First Embodiment>
22 to 24 show a second modified example of the first embodiment. A thermal printhead A12 of this modified example differs from the thermal printhead A1 of the above embodiment in the specific configuration of the concave pad portion 381.

In the thermal printhead A12 illustrated in Figures 22 to 24, the shape of each region of the second layer 32 constituting the concave pad portion 381 is different from that of the thermal printhead A1. Each region of the second layer 32 constituting the concave pad portion 381 is composed of a pair of standing walls that are spaced apart from each other in the x direction and each extend in the y direction. The portion of the surface 311 of the first layer 31 that is sandwiched between the pair of standing walls when viewed in the z direction is the bottom surface 312 of the concave pad portion 381. The pair of standing walls has a pair of inner wall surfaces 322 that face each other, and the pair of inner wall surfaces 322 face one side in the x direction and the other side in the x direction, which correspond to the longitudinal direction of the IC chip 6.

In the thermal printhead A12 of this modified example, a plurality of conductive bonding materials 62 are arranged on the mounting surface 61 of the flip-chip mounted IC chip 6. In this modified example, the wiring layer 3 (support member) also has a plurality of pads 38 arranged corresponding to the plurality of conductive bonding materials 62, and the plurality of pads 38 include a plurality of concave pads 381. With this configuration, even if some misalignment occurs in the x direction when the IC chip 6 is mounted, the conductive bonding material 62 is guided to fall into the concave pads 381 (the space surrounded by the bottom surface 312 and the inner wall surface 322 facing the bottom surface 312) when the conductive bonding material 62 is bonded to the wiring layer 3 (support member) (during reflow processing). This improves the misalignment of the conductive bonding material 62 and the IC chip 6, making it suitable for preventing problems caused by misalignment when the IC chip 6 is flip-chip mounted.

The wiring layer 3 includes a first layer 31 and a second layer 32. The first layer 31 is disposed on the main surface 21 of the glaze layer 2, and the second layer 32 is disposed on a part of the first layer 31. The bottom surface 312 of the concave pad portion 381 is constituted by the first layer 31, and the inner wall surface 322 of the concave pad portion 381 is constituted by the second layer 32. According to this configuration, the conductive bonding material 62 contained in the concave pad portion 381 is bonded across the bottom surface 312 and the inner wall surface 322 (the first layer 31 and the second layer 32), so that the bonding area is large, which is suitable for increasing the bonding strength of the conductive bonding material 62. In addition, in this embodiment, the bonding area between the conductive bonding material 62 and the wiring layer 3 (the first layer 31 and the second layer 32) is large, so that the reliability of the conductive bonding between the conductive bonding material 62 and the wiring layer 3 is improved.

In this modified example, the inner wall surface 322 is formed by the second layer 32. The concave pad portion 381 has a pair of inner wall surfaces 322 facing one side in the x direction and the other side in the x direction, facing each other. With this configuration, misalignment in the x direction, which corresponds to the longitudinal direction of the IC chip 6, can be appropriately improved when the IC chip 6 is flip-chip mounted. Furthermore, the distance L1 between adjacent pad portions 38 in the x direction is smaller than the distance L2 between pad portions 38 in the y direction. With this configuration, the effect of improving the misalignment of the IC chip 6 can be efficiently obtained while reducing the formation area of the second layer 32.

<Third Modification of First Embodiment>
25 shows a third modified example of the first embodiment. In a thermal printhead A13 of this modified example, the wiring layer 3 does not have a second layer 32 and is made of a single layer, and therefore the configuration of the concave pad portion 381 differs from that of the thermal printhead A1.

In the thermal print head A13 illustrated in FIG. 25, all of the pads 38 are recessed pads 381, and each recessed pad 381 is configured such that the wiring layer 3 is partially recessed from the surface 311. The recessed pad 381 has a bottom surface 313 and an inner wall surface 314. The bottom surface 313 is configured by a portion of the wiring layer 3 that is relatively thin. The inner wall surface 322 forms a ring surrounding the bottom surface 313 when viewed in the z direction. The wiring layer 3 having such a recessed pad 381 is formed on the main surface 21 of the glaze layer 2, and is made of a conductor containing, for example, Ag as a main component. In forming the wiring layer 3, first, Ag paste is thick-film printed on the main surface 21, and then the paste is fired to form a metal film. Next, the metal film is patterned using a method such as etching to form the wiring layer 3 having a plurality of individual electrodes 34 and a plurality of signal wiring portions 37, etc. Next, the wiring layer 3 is patterned using a technique such as half etching to form a concave pad portion 381 having a bottom surface 313 and an inner wall surface 314.

In the thermal printhead A13 of this modified example, a plurality of conductive bonding materials 62 are arranged on the mounting surface 61 of the flip-chip mounted IC chip 6. In this modified example, the wiring layer 3 (support member) also has a plurality of pad portions 38 arranged corresponding to the plurality of conductive bonding materials 62, and the plurality of pad portions 38 include a plurality of concave pad portions 381. With this configuration, even if some misalignment occurs when the IC chip 6 is mounted, when the conductive bonding material 62 is bonded to the wiring layer 3 (support member) (during reflow processing), the conductive bonding material 62 is guided to fall into the concave pad portion 381 (the space surrounded by the bottom surface 313 and the inner wall surface 314 facing the bottom surface 313). This improves the misalignment of the conductive bonding material 62 and the IC chip 6, making it suitable for preventing problems caused by misalignment when the IC chip 6 is flip-chip mounted.

The concave pad portion 381 is formed in the wiring layer 3 and has a bottom surface 313 and an inner wall surface 314. The bottom surface 313 is formed by a portion of the wiring layer 3 that is relatively thin, and the inner wall surface 322 forms a ring surrounding the bottom surface 313 when viewed in the z direction. With this configuration, the conductive bonding material 62 contained in the concave pad portion 381 is bonded across the bottom surface 312 and the inner wall surface 322, so that the bonding area with the wiring layer 3 is large, which is suitable for increasing the bonding strength of the conductive bonding material 62. In addition, with the configuration in which the inner wall surface 322 forms a ring surrounding the bottom surface 313 when viewed in the z direction, even if a positional deviation occurs in both the x direction and the y direction when the IC chip 6 is mounted, the positional deviation of the conductive bonding material 62 and the IC chip 6 in both the x direction and the y direction is improved.

In this modified example, all of the pads 38 are recessed pads 381. This configuration more reliably reduces misalignment during flip-chip mounting of the IC chip 6.

<Fourth Modification of First Embodiment>
26 shows a fourth modification of the first embodiment. In a thermal printhead A14 of this modification, the wiring layer 3 is made of a single layer, and therefore the configuration of the concave pad portion 381 differs from that of the thermal printhead A1.

In the thermal printhead A14 illustrated in FIG. 26, all of the pad portions 38 are concave pad portions 381, and each concave pad portion 381 is configured such that the wiring layer 3 partially penetrates to the glaze layer 2. The concave pad portion 381 has a bottom surface 211 and an inner wall surface 315. The bottom surface 211 is configured by a portion of the main surface 21 of the glaze layer 2 that is exposed from the wiring layer 3. The inner wall surface 315 is annular and surrounds the bottom surface 211 when viewed in the z direction, and is configured by the inner surface of the penetration portion of the wiring layer 3. In this modified example, the concave pad portion 381 is configured by the glaze layer 2 and the wiring layer 3.

The wiring layer 3 in this modified example is formed on the main surface 21 of the glaze layer 2, and is made of a conductor containing, for example, Ag as a main component. In forming the wiring layer 3, Ag paste is first thick-film printed on the main surface 21, and then fired to form a metal film. Next, the metal film is patterned using a method such as etching to form the wiring layer 3 having a plurality of individual electrodes 34 and a plurality of signal wiring portions 37, etc., and at the same time, a plurality of concave pad portions 381, each of which has a bottom surface 211 and an inner wall surface 315, are formed.

In the thermal printhead A14 of this modification, a plurality of conductive bonding materials 62 are arranged on the mounting surface 61 of the flip-chip mounted IC chip 6. In this modification, the glaze layer 2 or the wiring layer 3 (support member) also has a plurality of pad portions 38 arranged corresponding to the plurality of conductive bonding materials 62, and the plurality of pad portions 38 include a plurality of concave pad portions 381. With this configuration, even if some misalignment occurs when the IC chip 6 is mounted, when the conductive bonding material 62 is bonded to the wiring layer 3 (support member) (during reflow processing), the conductive bonding material 62 is guided to fall into the concave pad portion 381 (the space surrounded by the bottom surface 211 and the inner wall surface 315 facing the bottom surface 211). This improves the misalignment of the conductive bonding material 62 and the IC chip 6, and is suitable for preventing problems caused by misalignment when the IC chip 6 is flip-chip mounted.

The bottom surface 211 of the concave pad portion 381 is formed by a portion of the main surface 21 of the glaze layer 2 that is exposed from the wiring layer 3. The inner wall surface 315 is formed by the wiring layer 3 and is annular in shape surrounding the bottom surface 211 when viewed in the z direction. With this configuration, even if misalignment occurs in both the x and y directions when the IC chip 6 is mounted, misalignment of the conductive bonding material 62 and the IC chip 6 in both the x and y directions is improved.

In this modified example, all of the pads 38 are recessed pads 381. This configuration more reliably reduces misalignment during flip-chip mounting of the IC chip 6.

Fifth Modification of First Embodiment
27 shows a fifth modification of the first embodiment. In a thermal printhead A15 of this modification, the wiring layer 3 is made of a single layer, and therefore the configuration of the concave pad portion 381 differs from that of the thermal printhead A1.

In the thermal printhead A15 illustrated in FIG. 27, all of the pads 38 are concave pads 381. Each concave pad 381 is formed by a combination of a configuration in which the surface 311 is partially recessed and the wiring layer 3 partially penetrates the glaze layer 2. The concave pad 381 has a bottom surface 212, an intermediate surface 316, an inner wall surface 317, and an inner wall surface 318. The bottom surface 212 is formed by a portion exposed from the wiring layer 3 on the main surface 21 of the glaze layer 2. The inner wall surface 318 is annular and surrounds the bottom surface 212 when viewed in the z direction, and is formed by the inner surface of the penetration portion of the wiring layer 3. The intermediate surface 316 is formed by a portion of the wiring layer 3 that is relatively thin. The inner wall surface 317 is annular and surrounds the bottom surface 212 and the intermediate surface 316 when viewed in the z direction. In this modified example, the concave pad portion 381 is composed of a glaze layer 2 and a wiring layer 3.

The wiring layer 3 in this modified example is formed on the main surface 21 of the glaze layer 2, and is made of a conductor containing, for example, Ag as a main component. In forming the wiring layer 3, first, Ag paste is thick-film printed on the main surface 21, and then this is fired to form a metal film. Next, the metal film is patterned using a method such as etching to form the wiring layer 3 having a plurality of individual electrodes 34 and a plurality of signal wiring portions 37, etc. Next, the wiring layer 3 is patterned using a method such as half etching to form the intermediate surface 316 and the inner wall surface 317. Next, the wiring layer 3 is patterned using a method such as etching to form a plurality of concave pad portions 381, each of which has a bottom surface 212, an intermediate surface 316, an inner wall surface 317, and an inner wall surface 318.

In the thermal printhead A15 of this modification, a plurality of conductive bonding materials 62 are arranged on the mounting surface 61 of the flip-chip mounted IC chip 6. In this modification, the glaze layer 2 or the wiring layer 3 (support member) also has a plurality of pad portions 38 arranged corresponding to the plurality of conductive bonding materials 62, and the plurality of pad portions 38 include a plurality of concave pad portions 381. With this configuration, even if some misalignment occurs when the IC chip 6 is mounted, when the conductive bonding material 62 is bonded to the wiring layer 3 (support member) (during reflow processing), the conductive bonding material 62 is guided to fall into the concave pad portion 381 (the space surrounded by the bottom surface 212 and the inner wall surfaces 317, 318 facing the bottom surface 212). This improves the misalignment of the conductive bonding material 62 and the IC chip 6, and is suitable for preventing problems caused by misalignment when the IC chip 6 is flip-chip mounted.

The bottom surface 211 of the concave pad portion 381 is formed by a portion of the main surface 21 of the glaze layer 2 that is exposed from the wiring layer 3. The inner wall surface 317 is formed by the wiring layer 3 and is annular in shape surrounding the bottom surface 211 when viewed in the z direction. With this configuration, even if misalignment occurs in both the x and y directions when the IC chip 6 is mounted, misalignment of the conductive bonding material 62 and the IC chip 6 in both the x and y directions is improved.

The inner wall surface 318 forms a ring shape surrounding the bottom surface 212 when viewed in the z direction. The intermediate surface 316 is formed by a portion of the wiring layer 3 that is relatively thin, and the inner wall surface 317 forms a ring shape surrounding the bottom surface 212 and the intermediate surface 316 when viewed in the z direction. With this configuration, the conductive bonding material 62 contained in the concave pad portion 381 is bonded across the inner wall surface 318, the intermediate surface 316, and the inner wall surface 317, so that the bonding area with the wiring layer 3 is large, which is suitable for increasing the bonding strength of the conductive bonding material 62.

In this modified example, all of the pads 38 are recessed pads 381. This configuration more reliably reduces misalignment during flip-chip mounting of the IC chip 6.

Second Embodiment
28 and 29 show a thermal printhead according to a second embodiment of the present disclosure. A thermal printhead A2 of this embodiment differs from the thermal printhead A11 of the above embodiment in the configuration of the glaze layer 2 and the configuration of the wiring layer 3. Accordingly, the configuration of the concave pad portion 381 differs from that of the thermal printhead A1.

In the thermal printhead A11 shown in FIG. 28, the glaze layer 2 has a heater glaze portion 22 and a glass layer 23. The heater glaze portion 22 has a cross-sectional shape perpendicular to the x direction that bulges in the z direction, and is a z-directional band extending long in the x direction. The glass layer 23 is formed adjacent to the heater glaze portion 22, and has a flat upper surface (main surface 231). The glass layer 23 overlaps a part of the heater glaze portion 22. The resistor layer 4 (multiple heat generating portions 41) is disposed on the heater glaze portion 22, and overlaps with the heater glaze portion 22 when viewed in the z direction. When forming the glaze layer 2 having such a heater glaze portion 22 and glass layer 23, a thick film of glass paste is printed on the substrate 1, and then the glass paste is fired, which is repeated multiple times.

As shown in FIG. 29, the wiring layer 3 has a base layer 3c and a plating layer 3d. The base layer 3c occupies the majority of the wiring layer 3, and the common electrode 33, the multiple individual electrodes 34, and the multiple signal wiring sections 37 are made up of the base layer 3c. An example of a material that makes up the base layer 3c is Al. The base layer 3c is formed by a thin film formation technique such as sputtering. The thickness of the base layer 3c is, for example, about 0.5 to 2.0 μm.

The plating layer 3d is provided to form a plurality of pad portions 38 (recessed pad portions 381), and is laminated on a portion of the base layer 3c. The plating layer 3d is laminated near the upstream end in the y direction of the connecting portion 36 of the plurality of individual electrodes 34, and near the downstream end in the y direction of the plurality of signal wiring portions 37. The plating layer 3d is, for example, an electroless plating made of Ni. The thickness of the plating layer 3d is, for example, about 1 to 2 μm.

In the thermal printhead A2 of this embodiment, all of the multiple pad portions 38 are concave pad portions 381. Each concave pad portion 381 is configured such that the wiring layer 3 (base layer 3c and plating layer 3d) partially penetrates to the glaze layer 2 (glass layer 23). The concave pad portion 381 has a bottom surface 232 and an inner wall surface 303. The bottom surface 232 is configured by a portion exposed from the wiring layer 3 on the main surface 231 of the glass layer 23. The inner wall surface 303 is annular and surrounds the bottom surface 232 when viewed in the z direction, and is configured by the inner surface of the penetration portion of the plating layer 3d. In this modified example, the concave pad portion 381 is configured by the glaze layer 2 (glass layer 23) and the wiring layer 3 (plating layer 3d).

In forming the concave pad portion 381, the base layer 3c is patterned using a method such as etching to form a plurality of individual electrodes 34 and a plurality of signal wiring portions 37, and holes 302 penetrating from the surface 301 of the base layer 3c to the glass layer 23 are formed. As a result, a portion of the main surface 231 of the glass layer 23 is exposed from the wiring layer 3, becoming the bottom surface 232. Next, a plating layer 3d is formed to cover a portion of the surface 301 of the base layer 3c and the hole 302. As a result, an inner wall surface 303 facing the bottom surface 232 when viewed in the z direction is formed in the plating layer 3d. In this way, a plurality of concave pad portions 381, each having a bottom surface 232 and an inner wall surface 303, are formed.

In the thermal printhead A2 of this embodiment, a plurality of conductive bonding materials 62 are arranged on the mounting surface 61 of the flip-chip mounted IC chip 6. In this embodiment, the glaze layer 2 or the wiring layer 3 (support member) also has a plurality of pad portions 38 arranged corresponding to the plurality of conductive bonding materials 62, and the plurality of pad portions 38 include a plurality of concave pad portions 381. With this configuration, even if some misalignment occurs when the IC chip 6 is mounted, when the conductive bonding material 62 is bonded to the wiring layer 3 (support member) (during reflow processing), the conductive bonding material 62 is guided to fall into the concave pad portion 381 (the space surrounded by the bottom surface 232 and the inner wall surface 303 facing the bottom surface 232). This improves the misalignment of the conductive bonding material 62 and the IC chip 6, and is suitable for preventing problems caused by misalignment when the IC chip 6 is flip-chip mounted.

The bottom surface 232 of the concave pad portion 381 is formed by a portion of the main surface 231 of the glass layer 23 (glaze layer 2) that is exposed from the wiring layer 3. The inner wall surface 315 is formed by the wiring layer 3 and is annular in shape surrounding the bottom surface 211 when viewed in the z direction. With this configuration, even if misalignment occurs in both the x and y directions when the IC chip 6 is mounted, misalignment of the conductive bonding material 62 and the IC chip 6 in both the x and y directions is improved.

In this embodiment, all of the pads 38 are recessed pads 381. This configuration more reliably reduces misalignment during flip-chip mounting of the IC chip 6.

<Modification of the second embodiment>
30 shows a modification of the second embodiment. A thermal printhead A21 of this modification differs from the thermal printhead A2 of the above embodiment in the configurations of the base layer 3c and plating layer 3d of the wiring layer 3. Accordingly, the configuration of the concave pad portion 381 differs from that of the thermal printhead A2.

In the thermal printhead A21 of this modified example, all of the multiple pad portions 38 are concave pad portions 381. Each concave pad portion 381 is configured such that the wiring layer 3 is partially concave. The concave pad portion 381 has a bottom surface 306 and an inner wall surface 307. The bottom surface 306 is configured from a portion of the wiring layer 3 that is relatively thin. The inner wall surface 307 forms a ring shape surrounding the bottom surface 306 when viewed in the z direction. The bottom surface 306 and the inner wall surface 307 are configured from the plating layer 3d (wiring layer 3).

In forming the concave pad portion 381, first, the base layer 3c is patterned using a method such as etching to form multiple individual electrodes 34 and multiple signal wiring portions 37. Next, a concave surface 304 recessed from the surface 301 of the base layer 3c is formed using a method such as half etching. Next, a plating layer 3d is formed to cover part of the surface 301 of the base layer 3c and the concave surface 304. As a result, in the plating layer 3d, a bottom surface 306 recessed from the upper surface 305 and an inner wall surface 307 facing the bottom surface 306 when viewed in the z direction are formed. In this way, multiple concave pad portions 381, each having a bottom surface 306 and an inner wall surface 307, are formed.

In the thermal printhead A21 of this modified example, a plurality of conductive bonding materials 62 are arranged on the mounting surface 61 of the flip-chip mounted IC chip 6. In this embodiment, the wiring layer 3 (support member) also has a plurality of pad portions 38 arranged corresponding to the plurality of conductive bonding materials 62, and the plurality of pad portions 38 include a plurality of concave pad portions 381. With this configuration, even if some misalignment occurs when the IC chip 6 is mounted, when the conductive bonding material 62 is bonded to the wiring layer 3 (support member) (during reflow processing), the conductive bonding material 62 is guided to fall into the concave pad portion 381 (the space surrounded by the bottom surface 306 and the inner wall surface 307 facing the bottom surface 306). This improves the misalignment of the conductive bonding material 62 and the IC chip 6, making it suitable for preventing problems caused by misalignment when the IC chip 6 is flip-chip mounted.

The concave pad portion 381 is formed in the plating layer 3d (wiring layer 3) and has a bottom surface 306 and an inner wall surface 307. The bottom surface 306 is formed by a portion of the wiring layer 3 that is relatively thin, and the inner wall surface 307 forms a ring surrounding the bottom surface 306 when viewed in the z direction. With this configuration, the conductive bonding material 62 contained in the concave pad portion 381 is bonded across the bottom surface 306 and the inner wall surface 307, so that the bonding area with the wiring layer 3 is large, which is suitable for increasing the bonding strength of the conductive bonding material 62. In addition, with the configuration in which the inner wall surface 307 forms a ring surrounding the bottom surface 306 when viewed in the z direction, even if a positional deviation occurs in both the x direction and the y direction when the IC chip 6 is mounted, the positional deviation of the conductive bonding material 62 and the IC chip 6 in both the x direction and the y direction is improved.

In this modified example, all of the pads 38 are recessed pads 381. This configuration more reliably reduces misalignment during flip-chip mounting of the IC chip 6.

In the second embodiment, a glaze layer 2 including a heater glaze portion 22 and a glass layer 23 is disposed on a substrate 1, and various layers are formed on the glaze layer 2 by a thin film formation technique. Alternatively, various layers may be formed on the glaze layer 2 by a thick film formation technique.

In the second embodiment, the substrate 1 is made of a ceramic such as _Al2O3 , but instead of this _, the substrate 1 may be made of a semiconductor substrate such as a silicon substrate. In the case of the substrate 1 made of a semiconductor substrate, a plurality of thermal printheads are manufactured from the semiconductor substrate by dividing the semiconductor substrate into a plurality of individual pieces.

The thermal printhead according to the present disclosure is not limited to the above-described embodiment. The specific configuration of each part of the thermal printhead according to the present disclosure can be freely designed in various ways.

In the above embodiment, the IC chip mounting structure according to the present disclosure has been described as being applied to a thermal printhead, but the IC chip mounting structure according to the present disclosure may also be applied to other electronic devices. In the IC chip mounting structure according to the present disclosure, it is preferable that no insulating film is provided on the main surface of the substrate on which the IC chip is flip-chip mounted. Examples of such insulating films include resist films such as solder resist in printed circuit boards, and resin films such as polyimide films in flexible circuit boards.

This disclosure includes the following configurations:

[Appendix 1]
A support member having a base material having a main surface facing in one direction of the thickness and a wiring layer disposed on the main surface;
an IC chip having a mounting surface;
a plurality of conductive bonding materials arranged on the mounting surface, and the IC chip is flip-chip mounted on the support member,
the support member has a plurality of pad portions including at least two concave pad portions arranged corresponding to the plurality of conductive bonding materials,
The concave pad portion has a bottom surface and an inner wall surface facing the bottom surface when viewed in a thickness direction of the base material,
The inner wall surface is formed by the wiring layer, thus forming an IC chip mounting structure.
[Appendix 2]
2. The IC chip mounting structure according to claim 1, wherein an insulating film is not provided on the main surface of the substrate.
[Appendix 3]
a resistor layer disposed on the main surface and including a plurality of heat generating portions arranged in a main scanning direction;
the wiring layer is electrically connected to the resistor layer,
3. A thermal printhead having the mounting structure described in claim 2, wherein the IC chip controls a current flowing to each of the heat generating parts.
[Appendix 4]
the wiring layer includes a first layer disposed on the main surface and a second layer disposed on a portion of the first layer;
The inner wall surface is constituted by the second layer,
4. The thermal printhead of claim 3, wherein the bottom surface is formed by the first layer.
[Appendix 5]
5. The thermal printhead according to claim 4, wherein the concave pad portion has a pair of inner wall surfaces facing one side in the main scanning direction and the other side in the main scanning direction and opposing each other.
[Appendix 6]
5. The thermal printhead of claim 4, wherein the inner wall surface is annular and surrounds the bottom surface when viewed in the thickness direction of the base material.
[Appendix 7]
the bottom surface is formed by a portion of the wiring layer that has a relatively small thickness,
4. The thermal printhead of claim 3, wherein the inner wall surface is annular and surrounds the bottom surface when viewed in the thickness direction of the base material.
[Appendix 8]
the bottom surface is formed by a portion of the main surface that is exposed from the wiring layer,
4. The thermal printhead of claim 3, wherein the inner wall surface is annular and surrounds the bottom surface when viewed in the thickness direction of the base material.
[Appendix 9]
The pad portions are arranged in a plurality of rows in the main scanning direction and in the sub-scanning direction,
9. The thermal printhead according to claim 3, wherein among the plurality of pad portions, those located at four corners in the main scanning direction and the sub-scanning direction are the concave pad portions.
[Appendix 10]
9. The thermal printhead according to claim 3, wherein all of the plurality of pad portions are the concave pad portions.
[Appendix 11]
11. The thermal printhead according to claim 3, wherein the conductive bonding material is a solder bump.
[Appendix 12]
12. The thermal printhead according to claim 3, wherein at least a portion of the wiring layer is made of a material containing Ag.
[Appendix 13]
the IC chip is disposed upstream of the heat generating portions in a sub-scanning direction,
A thermal printhead described in any of Appendix 3 to 11, wherein the wiring layer includes a first metal portion connected to the multiple heat generating portions, and a second metal portion arranged in a region upstream of the first metal portion in the sub-scanning direction and connected to the multiple conductive bonding materials.
[Appendix 14]
14. The thermal printhead of claim 13, wherein the first metal portion is made of a material containing Au, and the second metal portion is made of a material containing Ag.
[Appendix 15]
15. A thermal printhead as described in any one of claims 3 to 14, wherein the base material includes a substrate and a glaze layer disposed on the substrate and having the main surface.
[Appendix 16]
16. The thermal printhead of claim 15, wherein the substrate is made of ceramic.
[Appendix 17]
Providing a substrate;
forming a wiring layer on the base material to form a support member including the base material and the wiring layer;
forming a resistor layer on the support member so as to overlap a portion of the wiring layer when viewed in a thickness direction of the base material;
and flip-chip mounting an IC chip having a mounting surface on which a plurality of conductive bonding materials are arranged on the substrate,
In the step of forming the support member, a plurality of pad portions including at least two concave pad portions and corresponding to the plurality of conductive bonding materials are formed,
A method for manufacturing a thermal printhead, wherein the concave pad portion has a bottom surface and an inner wall surface facing the bottom surface when viewed in the thickness direction of the base material.
[Appendix 18]
The method for manufacturing a thermal printhead described in Appendix 17, wherein the step of forming the support member includes a first layer formation step of forming a first layer on the base material, and a second layer formation step of forming a second layer that constitutes the inner wall surface on the first layer.
[Appendix 19]
The first layer forming step includes a step of printing a negative type first photosensitive metal paste on the base material, a step of partially exposing the first photosensitive metal paste, a step of removing a portion of the first photosensitive metal paste other than the exposed portion, and a step of firing the first photosensitive metal paste,
The method for manufacturing a thermal printhead described in Appendix 18, wherein the second layer formation process includes the steps of printing a negative-type second photosensitive metal paste on the substrate, partially exposing the second photosensitive metal paste, removing the second photosensitive metal paste except for the exposed portion, and firing the second photosensitive metal paste.
[Appendix 20]
20. The method for manufacturing a thermal printhead described in claim 19, wherein at least the second photosensitive metal paste of the first photosensitive metal paste and the second photosensitive metal paste contains Ag.

A1, A11, A12, A13, A14, A15, A2, A21: Thermal print head 1: Substrate 2: Glaze layer 21: Main surface 211: Bottom surface 212: Bottom surface 22: Heater glaze portion 23: Glass layer 231: Main surface 232: Bottom surface 3: Wiring layer 3a: First metal portion 3b: Second metal portion 3c: Base layer 3d: Plating layer 301: Surface 302: Hole 303: Inner wall surface 304: Concave surface 305: Top surface 306: Bottom surface 307: Inner wall surface 31: First layer 311: Surface 312: Bottom surface 313: Bottom surface 314: Inner wall surface 315: Inner wall surface 316: Intermediate surface 317: Inner wall surface 318: Inner wall surface 32 : second layer 321 : top surface 322 : inner wall surface 33 : common electrode 331 : common portion 332 : common electrode strip portion 34 : individual electrode 35 : individual electrode strip portion 36 : connecting portion 37 : signal wiring portion 38 : pad portion 4 : resistor layer 41 : heat generating portion 5 : protective layer 6 : IC chip 61 : mounting surface 62 : conductive bonding material 71 : protective resin 72 : connector 81 : platen roller 82 : printing medium

Claims (10)

A support member having a base material having a main surface facing in one direction of the thickness and a wiring layer disposed on the main surface;
an IC chip having a mounting surface;
A plurality of conductive bonding materials arranged on the mounting surface;
a resistor layer disposed on the main surface and including a plurality of heat generating portions arranged in a main scanning direction , and the IC chip is flip-chip mounted on the support member,
No insulating film is provided on the main surface of the base material,
the wiring layer is electrically connected to the resistor layer,
The IC chip controls a current flowing through each of the heat generating parts,
the support member has a plurality of pad portions including at least two concave pad portions arranged corresponding to the plurality of conductive bonding materials,
The pads are arranged in a main scanning direction.
The concave pad portion has a bottom surface and an inner wall surface facing the bottom surface when viewed in a thickness direction of the base material,
the inner wall surface is formed by the wiring layer ,
the concave pad portion includes a pair of upright walls spaced apart from each other in the main scanning direction and each extending in the sub-scanning direction,
The pair of upright walls faces one side in a main scanning direction and the other side in the main scanning direction, and has a pair of inner wall surfaces facing each other. the wiring layer includes a first layer disposed on the main surface and a second layer disposed on a portion of the first layer;
The inner wall surface is constituted by the second layer,
The thermal printhead of claim 1 , wherein the bottom surface is constituted by the first layer. The pad portions are arranged in a plurality of rows in the main scanning direction and in the sub-scanning direction,
3. The thermal printhead according to claim 1, wherein among said plurality of pad portions, those located at four corners in the main scanning direction and the sub-scanning direction are said concave pad portions. 3. The thermal printhead according to claim 1 , wherein all of said plurality of pad portions are said concave pad portions. 5. The thermal printhead according to claim 1 , wherein the conductive bonding material is a solder bump. 6. The thermal printhead according to claim 1, wherein at least a part of the wiring layer is made of a material containing Ag. the IC chip is disposed upstream of the heat generating portions in a sub-scanning direction,
A thermal printhead as described in any one of claims 1 to 6, wherein the wiring layer includes a first metal portion connected to the plurality of heat generating portions, and a second metal portion arranged in a region upstream of the first metal portion in the sub-scanning direction and connected to the plurality of conductive bonding materials. The thermal printhead according to claim 7 , wherein the first metal portion is made of a material containing Au, and the second metal portion is made of a material containing Ag. 9. The thermal printhead of claim 1 , wherein the base material includes a substrate and a glaze layer disposed on the substrate and having the main surface. The thermal printhead of claim 9 , wherein the substrate is made of ceramic.

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