Patent Description:
Various kinds of thermal heads for printing devices such as facsimile machines and video printers have been proposed in the related art.

A connection structure in which solder for fixing an electronic component to a substrate has a fillet shape has been proposed.

<CIT> discloses a thermal print head that comprises: a semiconductor substrate; a resistor layer having a plurality of heat generating portions, supported on the semiconductor substrate and arranged in a main scanning direction, which generates heat by being electrified; and a wiring layer supported on the semiconductor substrate and included in a conductive passage for distributing power to the plurality of heat generating portions. The semiconductor substrate has a main surface and a back surface pointing to the opposite sides to each other in a thickness direction, and a protruding portion protruding in the thickness direction from the main surface and extending long in the main scanning direction. The plurality of heat generating portions overlap with the protruding portion when viewed from the thickness direction.

The present invention provides a thermal head according to claim <NUM> and a thermal printer according to claim <NUM>. Further embodiments of the present invention are disclosed in the dependent claims.

Embodiments of a thermal head and a thermal printer disclosed in the present application will be described below with reference to the accompanying drawings. Note that this invention is not limited to each of the embodiments that will be described below.

<FIG> is a perspective view schematically illustrating a thermal head according to an embodiment. In the embodiment, a thermal head X1 includes a heat dissipation body <NUM>, a head base <NUM>, and a flexible printed circuit board (FPC) <NUM> as illustrated in <FIG>. The head base <NUM> is located on the heat dissipation body <NUM>. The FPC <NUM> is electrically connected to the head base <NUM>. The head base <NUM> includes a substrate <NUM>, a heat generating part <NUM>, a drive IC <NUM>, and a covering member <NUM>.

The heat dissipation body <NUM> has a plate-like shape and has a rectangular shape in plan view. The heat dissipation body <NUM> has a function of dissipating the heat generated by the heat generating part <NUM> of the head base <NUM>, especially heat not contributing to printing. The head base <NUM> is bonded to an upper surface of the heat dissipation body <NUM> using a double-sided tape, an adhesive, or the like (not illustrated). The heat dissipation body <NUM> is made of, for example, a metal material such as copper, iron, or aluminum.

The head base <NUM> has a plate-like shape and has a rectangular shape in plan view. The head base <NUM> includes each member constituting the thermal head X1 located on the substrate <NUM>. The head base <NUM> performs printing on a recording medium P (see <FIG>) according to an electrical signal supplied from outside.

A plurality of drive ICs <NUM> are located on the substrate <NUM> and arranged in a main scanning direction. The drive ICs <NUM> are electronic components having a function of controlling a conductive state of the heat generating part <NUM>. A switching member including a plurality of switching elements inside, for example, may be used for the drive ICs <NUM>.

The drive IC <NUM> is covered by a covering member <NUM> made of a resin such as an epoxy resin or a silicone resin. The covering member <NUM> is located across the plurality of drive ICs <NUM>. The covering member <NUM> is an example of a sealing material.

The FPC <NUM> is electrically connected to the head base <NUM> at one end and is electrically connected to a connector <NUM> at the other end.

The FPC <NUM> is electrically connected to the head base <NUM> using an electrically conductive bonding material <NUM> (see <FIG>). An example of the electrically conductive bonding material <NUM> may include a solder material or an anisotropic conductive film (ACF) in which electrically conductive particles are mixed into an electrically insulating resin.

Hereinafter, each of the members constituting the head base <NUM> will be described using <FIG>. <FIG> is a cross-sectional view schematically illustrating the thermal head illustrated in <FIG>. <FIG> is a plan view schematically illustrating the head base illustrated in <FIG>.

The head base <NUM> further includes the substrate <NUM>, a common electrode <NUM>, an individual electrode <NUM>, a first electrode <NUM>, a second electrode <NUM>, a terminal <NUM>, a heat generating resistor <NUM>, a protective layer <NUM>, a covering layer <NUM>, a bonding material <NUM>, and an underfill material <NUM>. Note that, in <FIG>, the protective layer <NUM> and the covering layer <NUM> are omitted. <FIG> illustrates wiring of the head base <NUM> in a simplified manner, in which the protective layer <NUM>, the covering layer <NUM>, and the underfill material <NUM> are omitted. In <FIG>, a configuration of the second electrode <NUM> is illustrated in a simplified manner, and the alternate long and two short dashed lines indicate a schematic shape of the drive ICs <NUM> in plan view.

The substrate <NUM> has a rectangular shape in plan view. The substrate <NUM> has a first long side 7a that is one long side, a second long side 7b that is the other long side, a first short side 7c, and a second short side 7d. The substrate <NUM> is made of an electrically insulating material such as an alumina ceramic or a semiconductor material such as monocrystalline silicon.

The common electrode <NUM> is located on an upper surface of the substrate <NUM> as illustrated in <FIG>. The common electrode <NUM> is made of an electrically conductive material, and examples thereof include at least one metal selected from aluminum, gold, silver, and copper, or an alloy of these metals.

The common electrode <NUM> includes a first common electrode 17a, a second common electrode 17b, a third common electrode 17c, and the terminal <NUM> as illustrated in <FIG>. The common electrode <NUM> is electrically connected in common to the heat generating part <NUM> including a plurality of elements.

The first common electrode 17a is located between the first long side 7a of the substrate <NUM> and the heat generating part <NUM>, and extends in the main scanning direction. The plurality of second common electrodes 17b are located respectively along the first short side 7c and the second short side 7d of the substrate <NUM>. Each of the plurality of second common electrodes 17b connects the corresponding terminal <NUM> and the first common electrode 17a. Each of the third common electrodes 17c extends from the first common electrode 17a toward a corresponding element of the heat generating part <NUM>, and a part of the third common electrode 17c extends through the heat generating part <NUM> to the side opposite to the heat generating part <NUM>. The third common electrodes 17c are located at intervals in a second direction D2 (the main scanning direction).

The individual electrode <NUM> is located on the upper surface of the substrate <NUM>. The individual electrode <NUM> contains a metal component and thus has electrical conductivity. The individual electrode <NUM> is made of, for example, a metal such as aluminum, nickel, gold, silver, platinum, palladium, or copper, and an alloy of these metals. The individual electrode <NUM> made of gold has a high electrical conductivity. A plurality of individual electrodes <NUM> are located in the main scanning direction and each of them is located between adjacent third common electrodes 17c. As a result, in the thermal head X1, the third common electrodes 17c and the plurality of individual electrodes <NUM> are alternately arranged in the main scanning direction. Each individual electrode <NUM> is connected to an electrode pad <NUM> at a portion close to the second long side 7b of the substrate <NUM>. The electrode pad <NUM> is electrically connected to the drive ICs <NUM> via the bonding material <NUM> (see <FIG>). The electrode pad <NUM> may be made of the same material as the individual electrode <NUM>, for example.

The first electrode <NUM> is connected to the electrode pad <NUM>, and extends in a first direction D1 (a sub-scanning direction). The drive IC <NUM> is mounted on the electrode pad <NUM> as described above. The electrode pad <NUM> may be made of the same material as the first electrode <NUM>, for example.

The second electrode <NUM> extends in the main scanning direction and is located over a plurality of first electrodes <NUM>. The second electrode <NUM> is connected to the outside via the terminal <NUM>.

The terminal <NUM> is located on the second long side 7b side of the substrate <NUM>. The terminal <NUM> is connected to the FPC <NUM> via the electrically conductive bonding material <NUM> (see <FIG>). In this way, the head base <NUM> is electrically connected to the outside.

The above-described third common electrode 17c, the individual electrode <NUM>, and the first electrode <NUM> can be made by forming a material layer constituting each of the electrodes on the substrate <NUM> using, for example, a screen printing method, a flexographic printing method, a gravure printing method, a gravure offset printing method, or the like. The above-described electrodes may be formed, for example, by sequentially layering the electrodes using a known thin film forming technique such as a sputtering method, and then processing the layered body into a predetermined pattern by using known photoetching, or the like. A thickness of each of the third common electrode 17c, the individual electrode <NUM>, and the first electrode <NUM> is, for example, approximately from <NUM> to <NUM>, and may be, for example, approximately from <NUM> to <NUM>.

The above-described first common electrode 17a, the second common electrode 17b, the second electrode <NUM>, and the terminal <NUM> can be made by forming a material layer constituting each of the electrodes on the substrate <NUM> using, for example, a screen printing method. A thickness of each of the first common electrode 17a, the second common electrode 17b, the second electrode <NUM>, and the terminal <NUM> is, for example, approximately from <NUM> to <NUM>. By forming the thick electrode in this manner, the wiring resistance of the head base <NUM> can be reduced. Note that the portion of the thick electrode is illustrated by dots in <FIG>, and this also applies to the following drawings.

The heat generating resistor <NUM> is located across the third common electrode 17c and the individual electrode <NUM> and spaced apart from the first long side 7a of the substrate <NUM>. A portion of the heat generating resistor <NUM> located between the third common electrode 17c and the individual electrode <NUM> functions as each element of the heat generating part <NUM>. Although each element of the heat generating part <NUM> is illustrated in a simplified manner in <FIG>, the elements are located at a density from, for example, <NUM> dpi to <NUM> dpi (dot per inch) or the like.

The heat generating resistor <NUM> may be formed, for example, by placing a material paste containing ruthenium oxide as a conductive component on the substrate <NUM> including the patterned various electrodes in a long strip-like shape elongated in the main scanning direction using a screen printing method or a dispensing device.

The protective layer <NUM> is located on the heat storage layer <NUM> formed on the upper surface of the substrate <NUM> to cover the heat generating part <NUM>. The protective layer <NUM> is located extending from the first long side 7a of the substrate <NUM> but separated from the electrode pad <NUM> and extending in the main scanning direction of the substrate <NUM>.

The protective layer <NUM> has an insulating property and protects the covered region from corrosion due to deposition of moisture and the like contained in the atmosphere, or from wear due to contact with the recording medium to be printed. The protective layer <NUM> can be made of, for example, glass using a thick film forming technique such as printing.

The protective layer <NUM> may be formed using SiN, SiO<NUM>, SiON, SiC, diamond-like carbon, or the like. Note that the protective layer <NUM> may be a single layer or be formed by layering a plurality of protective layers <NUM>. The protective layer <NUM> such as that described above can be formed using a thin film forming technique such as a sputtering method.

The covering layer <NUM> is located on the substrate <NUM> such that the covering layer partially covers the common electrode <NUM>, the individual electrode <NUM>, the first electrode <NUM>, and the second electrode <NUM>. The covering layer <NUM> protects the covered region from oxidation due to contact with the atmosphere or from corrosion due to deposition of moisture and the like contained in the atmosphere. The covering layer <NUM> can be made of a resin material such as an epoxy resin, a polyimide resin, or a silicone resin.

The bonding material <NUM> is located on the substrate <NUM>, and electrically connects the drive IC <NUM> and the individual electrode <NUM>. The bonding material <NUM> has electrical conductivity. The bonding material <NUM> may contain, for example, gold (Au) and tin (Sn). The bonding material <NUM> may contain a glass component. Note that bonding of the drive ICs <NUM> by the bonding material <NUM> will be described in detail later.

The underfill material <NUM> is located between the substrate <NUM> and the drive ICs <NUM>, and covers a part of the bonding material <NUM> and the drive ICs <NUM>. The underfill material <NUM> has insulating properties. The underfill material <NUM> can be made of, for example, a resin such as an epoxy resin. The underfill material <NUM> is an example of a sealing material.

Note that, although the substrate <NUM> has been described as a single layer, the substrate may have a layered structure in which the heat storage layer is located on the upper surface thereof. The heat storage layer can be located over the entire region on the upper surface side of the substrate <NUM>. The heat storage layer is made of glass having low thermal conductivity, for example. The heat storage layer temporarily stores part of the heat generated by the heat generating part <NUM>, and thus the time required to increase the temperature of the heat generating part <NUM> can be shortened. This functions to enhance the thermal response properties of the thermal head X1.

The heat storage layer is made by, for example, applying a predetermined glass paste obtained by mixing glass powder with an appropriate organic solvent onto the upper surface of the substrate <NUM> using a known screen printing method or the like, and firing the upper surface.

Note that the heat storage layer may include an underlying portion and a raised portion. In this case, the underlying portion is located across the entire region on the upper surface side of the substrate <NUM>. The raised portion protrudes from the underlying portion in the thickness direction of the substrate <NUM>, and extends in a strip shape in the second direction D2 (the main scanning direction). In this case, the raised portion functions to favorably press the recording medium to be printed against the protective layer <NUM> formed on the heat generating part <NUM>. Note that the heat storage layer may include only the raised portion.

The main portion of the thermal head X1 according to an embodiment will be described in detail using <FIG> is an enlarged cross-sectional view of a region A illustrated in <FIG>.

The drive IC <NUM> includes an element portion 11a and a terminal portion 11b as illustrated in <FIG>. The element portion 11a is a main portion that achieves the above-described functions of the drive IC <NUM>. The terminal portion 11b is electrically connected to the element portion 11a. The terminal portion 11b has an end surface 11e facing the substrate <NUM>. In other words, the end surface 11e is a surface of 11b of the terminal portion on the substrate <NUM> side.

The terminal portion 11b is electrically connected to the electrode pad <NUM> located at an end portion of the individual electrode <NUM> via the bonding material <NUM> located on the substrate <NUM>. The terminal portion 11b is, for example, an electrically conductive metal member. The terminal portion 11b contains, for example, copper and nickel. The terminal portion 11b is an example of an electrically conductive member.

The bonding material <NUM> is located between the substrate <NUM> and the terminal portion 11b of the drive IC <NUM>, and fixes the drive IC <NUM> onto the substrate <NUM>.

The bonding material <NUM> is located on the substrate <NUM>, and is in contact with and adjacent to the individual electrode <NUM>. For this reason, the drive IC <NUM> and the individual electrode <NUM> are electrically connected via the bonding material <NUM>.

The bonding material <NUM> includes a protruding portion 24a located at an outer circumferential edge of the terminal portion 11b. The protruding portion 24a is located away from the substrate <NUM> and the terminal portion 11b. Since the bonding material <NUM> includes the protruding portion 24a as described above, durability is increased. This point will be described in comparison of <FIG> and <FIG>.

<FIG> and <FIG> are partial cross-sectional views to compare shapes of the bonding material. In the examples illustrated in <FIG> and <FIG>, the terminal portion 11b and the individual electrode <NUM> are electrically connected using a bonding material <NUM>, instead of the bonding material <NUM> illustrated in <FIG>.

In the example illustrated in <FIG>, the bonding material <NUM> includes a fillet portion 124a located at an outer circumferential edge of the terminal portion 11b. In the example illustrated in <FIG>, the bonding material <NUM> includes a raised portion 124b located at an outer circumferential edge of the terminal portion 11b.

In both <FIG> and <FIG>, the contact area between the underfill material <NUM> and the terminal portion 11b and the bonding material <NUM> is smaller than a case where the fillet portion 124a and the raised portion 124b are not included. In contrast, since the protruding portion 24a of the bonding material <NUM> is located away from the substrate <NUM> and the terminal portion 11b as illustrated in <FIG>, the contact area between the underfill material <NUM> and the terminal portion 11b and the bonding material <NUM> is larger than when the protruding portion 24a is not included. For this reason, peeling or breakage of the underfill material <NUM> is less likely to occur. As a result, in the embodiment, the thermal head X1 has improved durability.

The end surface 11e of the terminal portion 11b facing the bonding material <NUM> includes a first end surface <NUM> and a second end surface <NUM> as illustrated in <FIG>. The second end surface <NUM> is located closer to the substrate <NUM> than the first end surface <NUM>, and surrounds the first end surface <NUM> in plan view. The first end surface <NUM> and the second end surface <NUM> are included in this manner, and thus the contact area between the terminal portion 11b and the bonding material <NUM> increases. Therefore, the terminal portion 11b is less likely to detach from the bonding material <NUM>. As a result, in the embodiment, the thermal head X1 has improved durability.

The end portion of the protruding portion 24a may be located farther from the substrate <NUM> than the first end surface <NUM>. Specifically, a dimension h2 from the substrate <NUM> to the end portion of the protruding portion 24a may be greater than a dimension h1 from the substrate <NUM> to the first end surface <NUM> as illustrated in <FIG>. The contact area between the underfill material <NUM> and the bonding material <NUM> is increased by locating the protruding portion 24a in this manner. Therefore, peeling of the underfill material <NUM> from the bonding material <NUM> is less likely to occur. As a result, in the embodiment, the thermal head X1 has improved durability.

The underfill material <NUM> has a portion located between the protruding portion 24a and the terminal portion 11b. In other words, a part of the underfill material <NUM> enters between the protruding portion 24a and the terminal portion 11b. With such a configuration, the contact area between the underfill material <NUM> and the bonding material <NUM> is further increased. Therefore, peeling of the underfill material <NUM> from the bonding material <NUM> is even less likely to occur.

Note that, although not illustrated, the connection of the drive IC <NUM> to the electrode pad <NUM> located at the first electrodes <NUM> can also be the same as and/or similar to the connection of the drive IC <NUM> to the electrode pad <NUM> located the end portions of the individual electrode <NUM> described above.

A thermal printer Z1 with the thermal head X1 will be described with reference to <FIG> is a schematic view of a thermal printer according to an embodiment.

In the present embodiment, the thermal printer Z1 includes the above-described thermal head X1, a transport mechanism <NUM>, a platen roller <NUM>, a power supply device <NUM>, and a control device <NUM>. The thermal head X1 is attached to a mounting surface 80a of a mounting member <NUM> disposed in a housing (not illustrated) of the thermal printer Z1. Note that the thermal head X1 is attached to the mounting member <NUM> such that the thermal head is aligned in the main scanning direction orthogonal to a transport direction S.

The transport mechanism <NUM> includes a drive unit (not illustrated) and transport rollers <NUM>, <NUM>, <NUM>, and <NUM>. The transport mechanism <NUM> transports a recording medium P, such as heat-sensitive paper or image-receiving paper to which ink is to be transferred, on the protective layer <NUM> located on a plurality of heat generating parts <NUM> of the thermal head X1 in the transport direction S indicated by an arrow. The drive unit has a function of driving the transport rollers <NUM>, <NUM>, <NUM>, and <NUM>, and a motor can be used for the drive unit, for example. The transport rollers <NUM>, <NUM>, <NUM>, and <NUM> may be configured by, for example, covering cylindrical shaft bodies 43a, 45a, 47a, and 49a made of a metal such as stainless steel, with elastic members 43b, 45b, 47b, and 49b made of butadiene rubber or the like. Note that, if the recording medium P is an image-receiving paper or the like to which ink is to be transferred, an ink film (not illustrated) is transported between the recording medium P and the heat generating part <NUM> of the thermal head X1 together with the recording medium P.

The platen roller <NUM> has a function of pressing the recording medium P onto the protective layer <NUM> located on the heat generating part <NUM> of the thermal head X1. The platen roller <NUM> is disposed extending in a direction orthogonal to the transport direction S, and both end portions thereof are supported and fixed such that the platen roller <NUM> is rotatable while pressing the recording medium P onto the heat generating part <NUM>. The platen roller <NUM> includes a cylindrical shaft body 50a made of a metal such as stainless steel and an elastic member 50b made of butadiene rubber or the like. The shaft body 50a is covered with the elastic member 50b.

As described above, the power supply device <NUM> has a function of supplying a current for causing the heat generating part <NUM> of the thermal head X1 to generate heat and a current for operating the drive IC <NUM>. The control device <NUM> has a function of supplying a control signal for controlling operation of the drive IC <NUM>, to the drive IC <NUM> in order to selectively cause the heat generating parts <NUM> of the thermal head X1 to generate heat as described above.

The thermal printer Z1 performs predetermined printing on the recording medium P by selectively causing the heat generating parts <NUM> to generate heat with the power supply device <NUM> and the control device <NUM>, while the platen roller <NUM> presses the recording medium P onto the heat generating parts <NUM> of the thermal head X1 and the transport mechanism <NUM> transports the recording medium P on the heat generating parts <NUM>. Note that, if the recording medium P is image-receiving paper or the like, printing is performed onto the recording medium P by thermally transferring, to the recording medium P, an ink of the ink film (not illustrated) transported together with the recording medium P.

Thermal heads X1 according to a first variation to a fifth variation of the embodiment will be described with reference to <FIG>.

<FIG> is a cross-sectional view illustrating the main portion of the thermal head according to the first variation of the embodiment. An outer circumferential surface 11c is located such that the terminal portion 11b of the drive IC <NUM> has a constant cross-sectional area along the end surface 11e in the embodiment described above. In contrast, the outer circumferential surface 11c may be located such that the terminal portion 11b has a cross-sectional area along the end surface 11e that becomes smaller as the terminal portion 11b gets closer to the substrate <NUM> as illustrated in <FIG>. The outer circumferential surface 11c of the terminal portion 11b is located in this manner, and thus the area of the end surface 11e becomes smaller, and pressure applied to the bonding material <NUM> by the end surface 11e increases. With this configuration, the overhang of the bonding material <NUM> (the protruding portion 24a) increases, and the contact area between the bonding material <NUM> and the underfill material <NUM> increases accordingly. Therefore, peeling of the underfill material <NUM> from the bonding material <NUM> is less likely to occur. As a result, the thermal head X1 according to the present variation has improved durability.

<FIG> is a cross-sectional view illustrating the main portion of the thermal head according to the second variation of the embodiment. The outer circumferential surface 11c may be located such that the terminal portion 11b has a cross-sectional area along the end surface 11e that becomes smaller as the terminal portion 11b becomes away from the substrate <NUM> as illustrated in <FIG>. The outer circumferential surface 11c of the terminal portion 11b is located in this manner, and thus the protruding portion 24a of the bonding material <NUM> is likely to be located away from the terminal portion 11b. For this reason, the underfill material <NUM> enters the gap between the protruding portion 24a and the terminal portion 11b, and thus the underfill material <NUM> is less likely to be peeled from the bonding material <NUM>. As a result, the thermal head X1 according to the present variation has improved durability.

<FIG> is a cross-sectional view illustrating the main portion of the thermal head according to the third variation of the embodiment. In the above-described embodiment illustrated in <FIG>, the outer circumferential surface 11c is located such that the protruding portion 24a of the bonding material <NUM> surrounds the outer circumferential edge of the terminal portion 11b. In contrast, the protruding portion 24a may be located at a part of the outer circumferential edge of the terminal portion 11b as illustrated in <FIG>.

The terminal portion 11b may include an exposed region <NUM> in which no bonding material <NUM> is located on the outer circumferential surface 11c in the direction intersecting the end surface 11e as illustrated in <FIG>. Metal atoms, for example, Au atoms, contained in the individual electrode <NUM> which is electrode may partially diffuse to the bonding material <NUM> side. When only a covered region <NUM> in which the bonding material <NUM> is located is provided, without the exposed region <NUM> on the outer circumferential surface 11c, the diffusion of Au atoms as an example of metal atoms may progress, and thus the individual electrode <NUM> may be disconnected. In contrast, when the exposed region <NUM> is provided on the outer circumferential surface 11c of the terminal portion 11b, diffusion of Au atoms is curbed, and a disconnection of the individual electrode <NUM> is less likely to occur. As a result, the thermal head X1 according to the present variation has improved durability.

<FIG> is a plan view illustrating the main portion of the thermal head according to the fourth variation of the embodiment. The bonding material <NUM> may include a plurality of protruding portions 24a located in different directions in plan view as illustrated in <FIG>. Specifically, for example, when the outer circumferential surface 11c of the terminal portion 11b includes surfaces 11c1 to 11c4 and has a rectangular shape in plan view, the protruding portion 24a may be located on the surfaces 11c1 and 11c2 side. The plurality of protruding portions 24a are provided as described above, peeling of the underfill material <NUM> from the bonding material <NUM> is less likely to occur. As a result, the thermal head X1 according to the present variation has further improved durability.

<FIG> is a plan view illustrating the main portion of the thermal head according to the fifth variation of the embodiment. When a plurality of terminal portions 11b adjacent to each other are provided, the bonding materials <NUM> of the plurality of terminal portions 11b may include protruding portions 24a located in the same direction in plan view as illustrated in <FIG>. Specifically, for example, when the outer circumferential surface 11c of the terminal portion 11b includes surfaces 11c1 to 11c4 and has a rectangular shape in plan view, the protruding portion 24a may be located on the surface 11c2 side of each terminal portion 11b. Due to the protruding portions 24a provided in this manner, the protruding portions 24a located in the bonding materials <NUM> adjacent to each other come into contact with each other, and thus a failure such as short-circuiting is reduced. As a result, the thermal head X1 according to the present variation has further improved durability.

Although the embodiments and variations of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above, and various modifications can be made without departing from the spirit thereof. For example, although a planar head in which the heat generating part <NUM> is located on the main surface of the substrate <NUM> has been described, an end-surface head in which the heat generating part <NUM> is located on an end surface of the substrate <NUM> may be employed.

Although description has been made using a so-called thick film head including the heat generating resistor <NUM> formed by printing, the present disclosure is not limited to a thick film head. A thin film head including the heat generating resistor <NUM> formed by sputtering may be used.

A material of the underfill material <NUM> covering the bonding material <NUM> and the terminal portion 11b may be the same material as the covering member <NUM> covering the drive ICs <NUM>.

The connector <NUM> may be electrically connected to the head base <NUM> directly without providing the FPC <NUM>. In this case, a connector pin (not illustrated) of the connector <NUM> may be electrically connected to the electrode pad <NUM>.

Although the thermal head X1 including the covering layer <NUM> is exemplified, the covering layer <NUM> may not be necessarily provided. In this case, the protective layer <NUM> may extend to the region in which the covering layer <NUM> could be provided.

Claim 1:
A thermal head (X1) comprising:
a substrate (<NUM>);
an electrode (<NUM>) located on the substrate (<NUM>);
a bonding material (<NUM>) located on the substrate (<NUM>) or the electrode (<NUM>);
an electrically conductive member (11b) located on the bonding material (<NUM>) and electrically connected to the electrode (<NUM>) via the bonding material (<NUM>); and
a sealing material (<NUM>) located on the substrate (<NUM>), the sealing material (<NUM>) covering the bonding material (<NUM>) and the electrically conductive member (11b),
wherein the bonding material (<NUM>) includes a protruding portion (24a) located at an outer circumferential edge of the electrically conductive member (11b), the bonding material (<NUM>) being away from the substrate (<NUM>) and the electrically conductive member (11b), and
characterised in that
the electrically conductive member (11b) includes a first end surface (<NUM>) facing the bonding material (<NUM>) and a second end surface (<NUM>) located closer to the substrate (<NUM>) side than the first end surface (<NUM>) and surrounding the first end surface (<NUM>) in a plan view.