Thermal heads and thermal printers

Abstract

A thermal head comprises a substrate (7), a bonding material (24), a conductive member (11b), and an aluminum electrode (19). The bonding material (24) is positioned above the substrate (7) and contains gold and tin. The conductive member (11b) is positioned on the bonding material (24). The aluminum electrode (19) is positioned on the substrate (7) and is electrically connected to the conductive member (11b) with the bonding material (24) therebetween.

Description

[Technical Field]

[0001] The disclosed embodiments relate to a thermal head and a thermal printer. [Background technology]

[0002] Various thermal heads have been proposed for use in printing devices such as facsimiles and video printers. For example, a known connection structure for electronic components is one in which aluminum wiring on a substrate is plated and then bonded using a bonding material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 61-244567 Summary of the Invention

[0004] A thermal head according to one aspect of the embodiment includes a substrate, a bonding material, a conductive member, and an aluminum electrode. The bonding material is located on the substrate and contains gold and tin. The conductive member is located on the bonding material. The aluminum electrode is located on the substrate and is electrically connected to the conductive member via the bonding material.

[0005] A thermal printer according to one aspect of the present disclosure includes the thermal head described above, a transport mechanism, and a platen roller. The transport mechanism transports a recording medium onto a heat generating portion located on a substrate. The platen roller presses the recording medium. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is an exploded perspective view showing an outline of a thermal head according to an embodiment. [Figure 2] FIG. 2 is a plan view showing an outline of the thermal head shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is an enlarged cross-sectional view of region A shown in FIG. [Figure 5] FIG. 5 is an enlarged cross-sectional view of region B shown in FIG. [Figure 6] FIG. 6 is a schematic diagram of a thermal printer according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] The conventional connection structure has room for improvement in durability.

[0008] Therefore, there is a need for a thermal head and a thermal printer that are highly durable.

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermal head and a thermal printer according to embodiments of the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments.

[0010] <Embodiment> Fig. 1 is an exploded perspective view showing an outline of a thermal head according to an embodiment. As shown in Fig. 1, the thermal head X1 according to an embodiment includes a head base 3, a connector 31, a sealing member 12, a heat sink 1, and an adhesive member 14. Note that the configuration of the thermal head X1 shown in Fig. 1 is merely an example, and for example, one or more of the connector 31, sealing member 12, heat sink 1, and adhesive member 14 may not necessarily be included.

[0011] The heat sink 1 dissipates excess heat from the head substrate 3. The head substrate 3 is placed on the heat sink 1 via an adhesive member 14. The head substrate 3 prints on a recording medium P (see Figure 6) when a voltage is applied from the outside. The adhesive member 14 bonds the head substrate 3 and the heat sink 1 together. The connector 31 electrically connects the head substrate 3 to the outside. The connector 31 has connector pins 8 and a housing 10. The sealing member 12 joins the connector 31 and the head substrate 3 together.

[0012] The heat sink 1 has a rectangular parallelepiped shape and is made of a metal material such as copper, iron, or aluminum, and dissipates heat generated in the heat generating portion 9 of the head base 3 that does not contribute to printing.

[0013] The head substrate 3 has a rectangular shape in a plan view, and the components that make up the thermal head X1 are arranged on a substrate 7. The head substrate 3 prints on a recording medium P (see FIG. 6) in accordance with an electrical signal supplied from the outside.

[0014] Next, the components constituting the thermal head X1 will be further described with reference to Figures 2 and 3. Figure 2 is a plan view showing an outline of the thermal head shown in Figure 1. Figure 3 is a cross-sectional view taken along line III-III in Figure 2. In Figure 2, the protective layer 25, the covering layer 27, and the sealing member 12 are indicated by dashed lines, and the covering member 29 is indicated by a broken line.

[0015] The head substrate 3 includes a substrate 7, a heating resistor 15, a common electrode 17, individual electrodes 19, a first connection electrode 21, a second connection electrode 26, a ground electrode 4, a connection terminal 2, a conductive member 23, a driving IC 11, a bonding material 24, a covering member 29, a protective layer 25, and a covering layer 27. The head substrate 3 does not necessarily have to include all of these members. The head substrate 3 may also include members other than these.

[0016] The substrate 7 is disposed on the heat sink 1 and is rectangular in plan view. The substrate 7 has a first surface 7f, a second surface 7g, and a side surface 7e. The first surface 7f has a first long side 7a, a second long side 7b, a first short side 7c, and a second short side 7d. The components that make up the head base 3 are disposed on the first surface 7f. The second surface 7g is located on the opposite side to the first surface 7f. The second surface 7g is located on the heat sink 1 side and is bonded to the heat sink 1 via an adhesive member 14. The side surface 7e connects the first surface 7f and the second surface 7g and is located on the second long side 7b side.

[0017] Substrate 7 is formed of, for example, an electrically insulating material such as alumina ceramics or a semiconductor material such as single crystal silicon. Hereinafter, for convenience of explanation, first surface 7f may be referred to as the "upper surface" and second surface 7g may be referred to as the "lower surface." Similarly, with side surface 7e as the reference, the first surface 7f side may be referred to as the "upper" or "upper side," and the second surface 7g side may be referred to as the "lower" or "lower" side.

[0018] The substrate 7 may have a heat storage layer 13 located on the first surface 7f. The heat storage layer 13 may have a base portion 13a and a raised portion 13b. The base portion 13a is located over the entire first surface 7f. The raised portion 13b rises from the base portion 13a in the thickness direction of the substrate 7. In other words, the raised portion 13b protrudes in a direction away from the first surface 7f.

[0019] The raised portion 13b is located adjacent to the first long side 7a of the substrate 7 and extends along the main scanning direction. The raised portion 13b may have a substantially semi-elliptical cross section. This allows the protective layer 25 located on the heat generating portion 9 to make good contact with the recording medium P (see FIG. 6) to be printed on. The height of the heat storage layer 13, including the base portion 13a and the raised portion 13b, from the first surface 7f of the substrate 7 can be, for example, 30 to 60 μm. The raised portion 13b is an example of a glaze.

[0020] The heat storage layer 13 is made of, for example, glass with low thermal conductivity, and temporarily stores some of the heat generated by the heat generating portion 9. This reduces the time required to increase the temperature of the heat generating portion 9, thereby improving the thermal response characteristics of the thermal head X1.

[0021] The heat storage layer 13 is formed, for example, by applying a predetermined glass paste obtained by mixing glass powder with an appropriate organic solvent to the first surface 7f by screen printing or the like, etching the paste if necessary, and then firing it.

[0022] The heating resistor 15 is located on the upper surface of the heat storage layer 13. A common electrode 17 and an individual electrode 19 are located on the heating resistor 15. An exposed region of the heating resistor 15 is located between the common electrode 17 and the individual electrode 19. As shown in FIG. 2 , the exposed regions of the heating resistor 15 are located in a row on the raised portion 13b of the heat storage layer 13, and each exposed region constitutes an element of the heating section 9.

[0023] The heating resistor 15 does not necessarily have to be located between the various electrodes and the heat storage layer 13. The heating resistor 15 may be located, for example, only between the common electrode 17 and the individual electrode 19 so as to electrically connect the common electrode 17 and the individual electrode 19. The heating resistor 15 may also be located between the first connection electrode 21 and the second connection electrode 26 and the heat storage layer 13, or between the ground electrode 4 and the heat storage layer 13.

[0024] The elements of the heating unit 9, which is made up of multiple heating resistors 15, are depicted in a simplified manner in Fig. 2 for ease of explanation, but are actually arranged at a density of, for example, 100 dpi to 2400 dpi (dots per inch). The heating resistors 15 are made of a material with relatively high electrical resistance, such as a TaN-based material, a TaSiO-based material, a TaSiNO-based material, a TiSiO-based material, a TiSiCO-based material, or a NbSiO-based material. Therefore, when a voltage is applied to the heating unit 9, the heating unit 9 generates heat due to Joule heating.

[0025] The common electrode 17 includes main wiring portions 17a and 17d, a sub-wiring portion 17b, and a lead portion 17c. The common electrode 17 electrically connects the multiple elements constituting the heat-generating portion 9 to the connector 31. The main wiring portion 17a extends along the first long side 7a of the substrate 7. The sub-wiring portion 17b extends along each of the first short side 7c and the second short side 7d of the substrate 7. The lead portions 17c extend individually from the main wiring portion 17a toward each heat-generating portion 9. The main wiring portion 17d extends along the second long side 7b of the substrate 7.

[0026] The individual electrodes 19 electrically connect the heat generating section 9 and the driving IC 11. The multiple elements that make up the heat generating section 9 are divided into multiple groups. The individual electrodes 19 electrically connect each element of the heat generating section 9 that makes up each group to the driving IC 11 corresponding to that group. The individual electrodes 19 are electrically connected to the driving IC 11 by bonding material 24.

[0027] The first connection electrodes 21 electrically connect the driving IC 11 and the connector 31. The first connection electrodes 21 connected to each driving IC 11 are made up of a plurality of wires having different functions.

[0028] The second connection electrodes 26 electrically connect adjacent driving ICs 11. The second connection electrodes 26 are made up of a plurality of wirings having different functions.

[0029] The common electrode 17, the first connection electrode 21, and the second connection electrode 26 are formed of a conductive material. The material of the common electrode 17, the first connection electrode 21, and the second connection electrode 26 may be, for example, any one of aluminum, gold, silver, and copper, or an alloy thereof.

[0030] The individual electrodes 19 are so-called aluminum electrodes. The individual electrodes 19 contain, for example, aluminum or an aluminum alloy and are electrically conductive.

[0031] The ground electrode 4 is surrounded by the individual electrodes 19, the first connection electrode 21, and the main wiring portion 17d of the common electrode 17. The ground electrode 4 is maintained at a ground potential of 0 to 1V.

[0032] The thickness of the individual electrodes 19 is, for example, 0.5 μm or less, and may be, for example, about 0.1 μm to 0.5 μm. This makes it difficult for heat generated in the heat generating portion 9 to dissipate via the individual electrodes 19. Furthermore, by reducing the step with the substrate 7, for example, the protective layer 25 covering the heat generating portion 9 becomes less likely to peel off, improving the reliability of the thermal head X1.

[0033] The thickness of the various electrodes excluding the individual electrode 19 is, for example, about 0.1 μm to 10 μm, and may be, for example, about 0.3 μm to 5 μm. The thickness of the various electrodes excluding the individual electrode 19 may be the same as the thickness of the individual electrode 19.

[0034] The connection terminals 2 are located on the second long side 7b of the substrate 7, and connect the common electrode 17, the individual electrodes 19, the first connection electrode 21, and the ground electrode 4 to the connector 31. The connection terminals 2 are located to correspond to the connector pins 8, and when the connector 31 is connected, the connector pins 8 and the connection terminals 2 are connected so as to be electrically independent of each other.

[0035] 3, a conductive member 23 is positioned on each connection terminal 2. Examples of the conductive member 23 include solder and ACP (Anisotropic Conductive Paste). Note that a plating layer made of, for example, Ni, Au, or Pd may be positioned between the conductive member 23 and the connection terminal 2.

[0036] The various electrodes constituting the head substrate 3 can be formed by, for example, sequentially stacking metal material layers such as Al, Au, Ag, Cu, or Ni on the heat storage layer 13 using a thin-film forming technique such as sputtering, and then processing the stack into a predetermined pattern using photoetching or the like. The various electrodes constituting the head substrate 3 can be formed simultaneously in the same process. Alternatively, the various electrodes may be produced by, for example, screen printing, flexographic printing, gravure printing, or gravure offset printing.

[0037] The driving IC 11 is located, for example, on the first surface 7f side of the substrate 7. The multiple driving ICs 11 are located along the arrangement direction of the heat generating portion 9 so as to correspond to each element of the heat generating portion 9, which is assigned to each driving IC 11. The driving ICs 11 are connected to the individual electrodes 19 and the first connection electrodes 21. The driving ICs 11 control the electrical state of the heat generating portion 9. The driving ICs 11 supply power to the heat generating portion 9 in accordance with an electrical signal supplied from the outside, causing each element of the heat generating portion 9 to individually generate heat. The driving ICs 11 can be, for example, a switching IC having multiple switching elements therein.

[0038] The bonding material 24 is located on the individual electrodes 19 and electrically connects the driving IC 11 and the individual electrodes 19. The bonding material 24 contains gold (Au) and tin (Sn) and is conductive. The bonding material 24 has high mechanical strength, for example, against shear stress, and is not easily peeled off from the individual electrodes 19, resulting in high durability. Details of the bonding between the individual electrodes 19 and the driving IC 11 by the bonding material 24 will be described later.

[0039] The protective layer 25 is located on the heat storage layer 13 located on the first surface 7f side of the substrate 7. The protective layer 25 covers the heating resistors 15 including the heating portions 9, the common electrode 17, and the individual electrodes 19. More specifically, the protective layer 25 covers the edges of the substrate 7, i.e., the first long side 7a, the first short side 7c, and the second short side 7d of the substrate 7, and parts of the individual electrodes 19. The protective layer 25 protects the covered areas from corrosion due to adhesion of moisture contained in the air, or abrasion due to contact with the recording medium P (see FIG. 6) to be printed. For example, SiN, SiON, SiO2, SiAlON, TiN, TiON, TiCrN, TiAlON, etc. can be used as the protective layer 25.

[0040] The covering layer 27 is located on the first surface 7f side of the substrate 7. The covering layer 27 partially covers the common electrode 17, the individual electrodes 19, the first connection electrode 21, and the second connection electrode 26. The covering layer 27 protects the covered area from oxidation due to contact with the atmosphere or corrosion due to adhesion of moisture contained in the atmosphere. The covering layer 27 can be made of a resin material such as an epoxy resin, a polyimide resin, or a silicone resin.

[0041] The covering member 29 seals the driving ICs 11 in a connected state with the individual electrodes 19, the second connection electrodes 26, and the first connection electrodes 21. The covering member 29 is arranged to extend in the main scanning direction, and integrally seals the multiple driving ICs 11. The covering member 29 can be made of a resin material such as an epoxy resin or a silicone resin.

[0042] The connector 31 has a plurality of connector pins 8 and a housing 10 that accommodates the plurality of connector pins 8. The connector pins 8 have a first end and a second end, and are electrically connected to various electrodes of the head base 3. The first end is exposed to the outside of the housing 10 and is electrically connected to the connection terminal 2 of the head base 3. The second end is housed inside the housing 10 and is drawn out to the outside.

[0043] The sealing member 12 has a first sealing member 12a and a second sealing member 12b. The first sealing member 12a is located on the first surface 7f of the substrate 7. The first sealing member 12a seals the connector pins 8 and the various electrodes. The second sealing member 12b is located on the second surface 7g of the substrate 7. The second sealing member 12b is located so as to seal the contact portions between the connector pins 8 and the substrate 7.

[0044] The sealing member 12 is positioned so that the connection terminals 2 and the connector pins 8 are not exposed to the outside. The sealing member 12 can be made of, for example, an epoxy-based thermosetting resin, an ultraviolet-curable resin, or a visible-light-curable resin. The first sealing member 12a and the second sealing member 12b may be made of the same material. Alternatively, the first sealing member 12a and the second sealing member 12b may be made of different materials.

[0045] The adhesive member 14 is located on the heat sink 1. The adhesive member 14 joins the second surface 7g of the head substrate 3 to the heat sink 1. Examples of the adhesive member 14 include double-sided tape or a resin adhesive.

[0046] Next, the main parts of the thermal head X1 according to the embodiment will be described in detail with reference to Fig. 4. Fig. 4 is an enlarged cross-sectional view of area A shown in Fig. 3. Note that the covering member 29 is omitted in Fig. 4.

[0047] 4, the driving IC 11 has an element portion 11a and a terminal portion 11b. The element portion 11a is a main portion that realizes the above-mentioned functions of the driving IC 11. The element portion 11a is an example of an electronic component.

[0048] The terminal portion 11b is electrically connected to the element portion 11a. The terminal portion 11b is electrically connected to the individual electrode 19 via a bonding material 24 located on the substrate 7, more specifically on the base portion 13a. The terminal portion 11b is, for example, a conductive metal member. The terminal portion 11b contains, for example, copper and nickel. The terminal portion 11b is an example of a conductive member.

[0049] The terminal portion 11b may also have a first layer 111 and a second layer 112. The first layer 111 contains, for example, copper. The first layer 111 can increase the bonding strength between the driving IC 11 and the individual electrode 19 by, for example, mitigating thermal stress.

[0050] The second layer 112 is located closer to the substrate 7 than the first layer 111. The second layer 112 contains, for example, nickel. The second layer 112 can improve the durability of the driving IC 11 by, for example, making it difficult for gold atoms and tin atoms located in the bonding material 24 to diffuse toward the element portion 11a. The second layer 112 can improve the durability of the driving IC 11 by, for example, making it difficult for copper atoms contained in the first layer 111 to diffuse toward the bonding material 24.

[0051] In this way, the terminal portion 11b has the first layer 111 and the second layer 112, thereby improving the bonding reliability between the driving IC 11 and the individual electrode 19. Note that the terminal portion 11b may have, for example, only one of the first layer 111 and the second layer 112, or may have a further laminated structure in addition to the first layer 111 and the second layer 112.

[0052] The bonding material 24 is located between the individual electrode 19 and the terminal portion 11b of the driving IC 11. The bonding material 24 is conductive and electrically connects the individual electrode 19 and the driving IC 11. The portion of the individual electrode 19 located between the substrate 7 and the bonding material 24, i.e., the portion in contact with the bonding material 24, is referred to as the bonding region 20. Details of the bonding region 20 will be further described below with reference to FIG. 5.

[0053] Fig. 5 is an enlarged cross-sectional view of region B shown in Fig. 4. As shown in Fig. 5, the bonding region 20 may have a first portion 201 and a second portion 202.

[0054] The first portion 201 has a higher gold content than the individual electrode 19. Specifically, the first portion 201 may have, for example, a volume ratio of 65% to 75% Au atoms and 25% to 35% Al atoms. This improves the bonding strength between the first portion 201 and the bonding material 24 compared to the individual electrode 19, which is an aluminum electrode. The first portion 201 may also have a higher tin content than the individual electrode 19.

[0055] The second portion 202 has a higher aluminum content than the first portion 201. Specifically, the second portion 202 may have, for example, a volume ratio of 0% to 10% Au atoms and 90% to 100% Al atoms. This improves the bonding strength between the second portion 202 and the substrate 7 compared to the first portion 201.

[0056] In this way, the bonding area 20 has the first portion 201 and the second portion 202, which improves the adhesion between the bonding material 24 and the bonding area 20 and between the bonding area 20 and the substrate 7. This improves the bonding strength of the driving IC 11 and the durability of the thermal head X1.

[0057] Here, a central portion 20A and an end portion 20B of the bonding region 20 are defined. The central portion 20A is a portion located in the center along the width direction of the bonding material 24. The width direction of the bonding material 24 is the direction connecting both end surfaces 241 of the bonding material 24 shown in FIG. 5. The end portion 20B is a portion located at an end along the width direction of the bonding material 24, and includes a portion that contacts both end surfaces 241 of the bonding material 24.

[0058] In this case, the second portion 202 may be located at the end 20B of the bonding region 20. By having the second portion 202 located at the end 20B, the adhesion between the bonding region 20 and the substrate 7 is further increased, making them less likely to peel off.

[0059] Furthermore, the area ratio of the second portion 202 may be greater at the end portion 20B than at the central portion 20A of the bonding region 20 along the width direction of the bonding material 24. Here, the area ratio of the second portion 202 refers to the area ratio of the second portion 202 in the bonding region 20 in a cross-sectional view. By making the area ratio of the second portion 202 at the end portion 20B greater than that at the central portion 20A, the adhesion between the bonding region 20 and the substrate 7 is further improved, making it less likely to peel off.

[0060] Furthermore, the first portion 201 may be thicker at the center than at the end portions thereof, so that the thickness of the first portion 201 is smaller at the end portions along the width direction of the bonding material 24 where stress tends to concentrate, thereby improving the adhesion between the bonding region 20 and the substrate 7.

[0061] The positions, shapes, and area ratio of the first portion 201 and the second portion 202 can be determined visually or by other means based on a scanning electron microscope (SEM) image of a cross section of the individual electrode 19 including the bonding region 20. Alternatively, they can also be determined by observing the diffusion state of Au, Al, or Sn with an electron probe micro analyzer (EPMA).

[0062] Although not shown, the ground electrode 4, the first connection electrode 21, and the second connection electrode 26 may be connected to the driving IC 11 in the same manner as the individual electrodes 19 described above.

[0063] Next, a thermal printer Z1 having a thermal head X1 will be described with reference to Fig. 6. Fig. 6 is a schematic diagram of a thermal printer according to an embodiment.

[0064] The thermal printer Z1 according to the embodiment includes the thermal head X1, a transport mechanism 40, a platen roller 50, a power supply unit 60, and a control unit 70. The thermal head X1 is attached to a mounting surface 80a of a mounting member 80 disposed in a housing (not shown) of the thermal printer Z1. The thermal head X1 is attached to the mounting member 80 so as to be aligned along the main scanning direction, which is a direction perpendicular to the transport direction S.

[0065] The transport mechanism 40 includes a drive unit (not shown) and transport rollers 43, 45, 47, and 49. The transport mechanism 40 transports a recording medium P, such as thermal paper or image receiving paper onto which ink is transferred, along a transport direction S indicated by an arrow onto a protective layer 25 located above the heat generating elements 9 of the thermal head X1. The drive unit drives the transport rollers 43, 45, 47, and 49, and may be, for example, a motor. The transport rollers 43, 45, 47, and 49 may each have a cylindrical shaft 43a, 45a, 47a, and 49a made of a metal such as stainless steel, covered with elastic members 43b, 45b, 47b, and 49b made of a material such as butadiene rubber. When the recording medium P is an image receiving paper onto which ink is transferred, an ink film (not shown) is transported between the recording medium P and the heat generating elements 9 of the thermal head X1 along with the recording medium P.

[0066] The platen roller 50 has the function of pressing the recording medium P onto the protective layer 25 located above the heat generating portion 9 of the thermal head X1. The platen roller 50 is arranged to extend in a direction perpendicular to the transport direction S, and both ends are supported and fixed so that it can rotate while pressing the recording medium P onto the heat generating portion 9. The platen roller 50 can be configured, for example, by covering a cylindrical shaft 50a made of a metal such as stainless steel with an elastic member 50b made of butadiene rubber or the like.

[0067] As described above, the power supply device 60 has a function of supplying current for generating heat in the heat generating portion 9 of the thermal head X1 and current for operating the driving IC 11. The control device 70 has a function of supplying a control signal to the driving IC 11 for controlling the operation of the driving IC 11 in order to selectively generate heat in the heat generating portion 9 of the thermal head X1.

[0068] The thermal printer Z1 performs a predetermined print on the recording medium P by pressing the recording medium P onto the heat generating portion 9 of the thermal head X1 with the platen roller 50, while transporting the recording medium P onto the heat generating portion 9 with the transport mechanism 40, and selectively causing the heat generating portion 9 to generate heat with the power supply unit 60 and the control unit 70. Note that if the recording medium P is receiver paper or the like, printing on the recording medium P is performed by thermally transferring ink from an ink film (not shown) transported together with the recording medium P onto the recording medium P.

[0069] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments and various modifications are possible without departing from the spirit of the present disclosure. For example, although a planar head in which the heat generating portion 9 is located on the main surface of the substrate 7 has been described as an example, an edge head in which the heat generating portion 9 is located on the edge surface of the substrate 7 may also be used.

[0070] In addition, although the heating resistor 15 has been described as being formed by sputtering, which is called a thin film head, the present invention is not limited to a thin film head, and may be a thick film head, in which the heating resistor 15 is formed by printing or the like.

[0071] Furthermore, the portion covering the bonding material 24 and the terminal portion 11b may be covered with an underfill material instead of the covering member 29. Such an underfill material may be made of, for example, an insulating resin such as an epoxy resin.

[0072] Alternatively, the common electrode 17 and the individual electrodes 19 may be formed on the heat storage layer 13, and the heating resistor 15 may be formed only in the region between the common electrode 17 and the individual electrodes 19, thereby forming the heating section 9.

[0073] Furthermore, although an example in which the connector 31 is directly connected to the substrate 7 has been shown, a flexible printed circuit (FPC) may be connected to the substrate 7.

[0074] Although the thermal head X1 has been exemplified as having the covering layer 27, the covering layer 27 is not necessarily provided. In that case, the protective layer 25 may be positioned up to the area where the covering layer 27 was provided. The covering layer 27 may also be provided in an area other than that shown in the figure.

[0075] Further advantages and modifications will readily occur to those skilled in the art. Therefore, the disclosure in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. [Explanation of symbols]

[0076] X1 thermal head Z1 Thermal Printer 1 Heat sink 3 Head base 4 Ground electrode 7. Circuit Board 9 Heat generating part 11 Driver IC 15 Heating resistor 17 Common electrode 19 Individual electrodes 20 Joint area 21 First connection electrode 24 Bonding material 25 Protective layer 26 Second connection electrode 27 Covering layer 29 Covering materials

Claims

1. A substrate; a bonding material containing gold and tin located on the substrate; a conductive member located on the bonding material; an aluminum electrode located on the substrate and electrically connected to the bonding material; Equipped with the aluminum electrode has a bonding region located between the substrate and the bonding material, The bonding region has a first portion having a higher gold content than the aluminum electrode and a second portion having a higher aluminum content than the first portion. Thermal head.

2. The conductive member has a first layer containing copper and a second layer containing nickel, the second layer being located between the first layer and the bonding material. The thermal head according to claim 1 .

3. The thickness of the aluminum electrode is 0.5 μm or less. The thermal head according to claim 1 .

4. The bonding material is in contact with the aluminum electrode. The thermal head according to claim 1 .

5. The second portion is located at an end of the bonding area along the width direction of the bonding material. The thermal head according to claim 1 .

6. The area ratio of the second portion is larger at the end portion of the bonding region than at the center portion along the width direction.

6. The thermal head according to claim 5.

7. The first portion has a thickness greater at a center portion of the bonding region along the width direction of the bonding material than at an end portion. The thermal head according to claim 1 .

8. A thermal head according to any one of claims 1 to 7; a transport mechanism that transports a recording medium onto a heat generating portion located on the substrate; a platen roller that presses the recording medium onto the heat generating portion; A thermal printer comprising:

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