WO2023281868A1 - Joint structure - Google Patents

Abstract

Provided is a joint structure in which an element member comprising a ceramic portion and an element electrode including a pair of inner electrodes and a pair of outer electrodes is electrically joined to a circuit board, the joint structure exhibiting stable electric characteristics under a high-humidity environment. A joint structure comprising: an element member in which a ceramic portion and an element electrode including a pair of inner electrodes and a pair of outer electrodes are formed on a first base material, wherein the ceramic portion is coated with a first protection layer, the pair of outer electrodes are exposed from the first protection layer, and the pair of inner electrodes are positioned inside the ceramic portion, the ceramic portion having a thickness of less than or equal to 40 μm; a circuit board having a pair of land electrodes formed on a second base material; and a joint portion electrically joining the pair of outer electrodes and the pair of land electrodes opposite each other, with the ceramic portion and the first protection layer disposed between the first base material and the second base material.

Description

junction structure

TECHNICAL FIELD The present disclosure relates to a bonded structure, and more particularly to a bonded structure in which an element member is electrically bonded (or mounted) to a circuit board via a bonding portion (also referred to as a “mounted structure”). .

Conventionally, there has been known a bonded structure in which an electronic component such as a chip component having a ceramic portion and a pair of external electrodes is bonded to a circuit board with a solder material (see Patent Documents 1 and 2).

Countermeasures against ion migration have become an important issue in such a bonded structure. In Patent Document 2, in order to prevent ion migration that may occur between a pair of external electrodes of the electronic component, of the four side surfaces of the substantially rectangular parallelepiped electronic component, the side surface facing the main surface of the circuit board is excluded. It discloses that three side surfaces (claim 1) or four side surfaces (claims 2 and 3) of a substantially rectangular parallelepiped electronic component are coated with a coating resin layer.

JP 2014-157951 A WO2017/110136 JP 2021-58894 A JP 2013-149774 A

Conventionally, chip parts and the like have been used as electronic parts that are electrically connected to circuit boards, but instead of chip parts, it is possible to use element members in which the element structure is formed on another substrate (base material). Conceivable.

In Patent Document 2, which relates to a joint structure in which a chip component is electrically joined to a circuit board, ion migration is defined as ionization of a metal component of one electrode between electrodes having a potential difference and migration toward the other electrode. It is a phenomenon in which the insulation between electrodes is reduced or the electrodes are short-circuited due to the metal that migrates and precipitates, and it is described that this phenomenon is likely to occur under high humidity conditions.

On the other hand, according to further research by the present inventors, an element member in which an element structure including a ceramic part and a pair of electrodes is formed on a substrate (base material) is electrically connected to a circuit board. In a structure, ion migration (hereinafter also simply referred to as “migration”) is the ionization of the metal component of one electrode between electrodes with a potential difference, moving toward the other electrode, and the deposited metal Insulation (in other words, resistance) between electrodes decreases, and in extreme cases short-circuiting occurs between the electrodes. It has been found that the resistance of the electrode increases, and in extreme cases, a phenomenon in which the one electrode is melted through (hereinafter referred to as "open") may occur. Migration occurs depending on the strength of the electric field, in other words, it occurs in proportion to the load voltage and in inverse proportion to the distance between the electrodes. According to the studies of the present inventors, when the element member includes an element electrode including a pair of internal electrodes and a pair of external electrodes, there is a problem that the electrodes are dissolved first by migration, resulting in a high resistance. There was found. Conventionally, in the case of general chip components, the problem of low resistance due to migration has been dealt with, but due to the thick electrodes, high resistance due to migration has not been a substantial problem.

In a high-humidity environment, it is not preferable for the resistance of the joint structure to become significantly lower or higher than the initial value due to ion migration, because in any case the electrical properties of the joint structure will be impaired.

An object of the present disclosure is to provide a junction structure in which an element member including a ceramic portion and an element electrode including a pair of internal electrodes and a pair of external electrodes is electrically bonded to a circuit board, and is used in a high-humidity environment. Another object of the present invention is to provide a joint structure exhibiting stable electrical characteristics.

[1]
An element member in which a ceramic part and element electrodes including a pair of internal electrodes and a pair of external electrodes are formed on a first substrate, the ceramic part being covered with a first protective layer, and the pair of external electrodes is exposed from the first protective layer, the pair of internal electrodes are located in the ceramic portion, and the thickness of the ceramic portion is 40 μm or less;
a circuit board having a pair of land electrodes formed on a second substrate;
electrically connecting the pair of external electrodes and the pair of land electrodes facing each other in a state in which the ceramic part and the first protective layer are arranged between the first base material and the second base material; A bonded structure comprising a bonding joint.

[2]
The surface of the first protective layer opposite to the first substrate protrudes toward the second substrate from the surfaces of the pair of external electrodes opposite to the first substrate. The joined structure according to [1] above.

[3]
The above [1] or [2], wherein the circuit board has a second protective layer disposed on the second base material, and the pair of land electrodes are exposed from the second protective layer. junction structure.

[4]
The surface of the second protective layer opposite to the second substrate protrudes toward the first substrate more than the surfaces of the pair of land electrodes opposite to the second substrate. The joined structure according to [3] above.

[5]
The joined structure according to any one of [1] to [4] above, wherein the first protective layer contains a first resin material.

[6]
The first resin material is polyimide resin, polyamideimide resin, epoxy resin, liquid crystal polymer, polyethylene resin, polypropylene resin, polystyrene resin, polyester resin, polyurethane resin, polyamide resin, polyetherimide. The joint structure according to [5] above, which contains at least one selected from the group consisting of acrylic resins and (meth)acrylic resins.

[7]
The joined structure according to [5] or [6] above, wherein the first protective layer further includes a first metal layer.

[8]
The joined structure according to any one of [1] to [7] above, wherein the first base material includes a second resin material and a second metal layer.

[9]
The joined structure according to any one of [1] to [8] above, wherein the second base material is a flexible substrate containing a third resin material.

[10]
The joint structure according to any one of [1] to [9] above, wherein the joint includes a solder material.

[11]
The junction structure according to [10] above, wherein the area of the junction regions of the pair of land electrodes is three times or less the area of the junction regions of the pair of external electrodes.

[12]
The bonded structure according to any one of [1] to [11] above, wherein the bonded portion is coated with a cured resin material as the fourth resin material.

[13]
The joint structure according to any one of [1] to [11] above, wherein the joint portion is coated with a thermoplastic resin material as the fifth resin material.

[14]
The joined structure according to any one of [1] to [9] above, wherein the joint contains an anisotropically conductive material.

[15]
The joint structure according to any one of [1] to [14] above, wherein the ceramic portion is formed between the pair of external electrodes.

[16]
The joint structure according to any one of [1] to [14] above, wherein the ceramic portion is formed adjacent to the pair of external electrodes.

[17]
The joint structure according to any one of [1] to [16] above, wherein the ceramic portion contains a thermistor material, and the joint structure is a temperature sensor.

According to the present disclosure, a junction structure in which an element member including a ceramic part and an element electrode including a pair of internal electrodes and a pair of external electrodes is electrically bonded to a circuit board, and Also provided is a bonded structure exhibiting stable electrical properties.

FIG. 1 is a schematic cross-sectional view showing a bonded structure according to one embodiment (Embodiment 1) of the present disclosure. 2A and 2B are diagrams for explaining the manufacturing method of the bonded structure in the embodiment of FIG. 1, and FIGS. 3A and 3B are diagrams for explaining the manufacturing method of the bonded structure in the embodiment of FIG. is a schematic cross-sectional view of the element member, and FIG. 3(b) is a schematic top view of the element member (FIG. 3(a) is a view taken along line AA in FIG. 3(b). It is a schematic schematic cross-sectional view at the time). 4A and 4B are diagrams for explaining a method for manufacturing a bonded structure in the embodiment of FIG. 1, FIG. 4A being a schematic cross-sectional view of a circuit board, FIG. 4A is a schematic top view (FIG. 4A is a schematic cross-sectional view taken along line BB in FIG. 4B). FIG. 5 is a schematic enlarged cross _- sectional view of the joint portion of the joint structure in the embodiment of FIG. ₁ , and FIG. , and FIG. 5(b) shows a case where L ₂ /L ₁ exceeds 3 (for example, 3.5) (L ₁ is the length of the junction region of the external electrode, L ₂ is 5 shows the external electrode 4a, the land electrode 14a and the joint portion 30a, but the external electrode 4b, the land electrode 14b and the joint portion 30b are the same). FIG. 6 is a schematic cross-sectional view showing a bonded structure according to another embodiment (embodiment 2) of the present disclosure. 7A and 7B are diagrams for explaining a method for manufacturing a bonded structure in the embodiment of FIG. 6, FIG. 7A being a schematic cross-sectional view of an element member, and FIG. FIG. 7A is a schematic top view (FIG. 7A is a schematic cross-sectional view taken along line AA in FIG. 7B). FIG. 8 is a schematic cross-sectional view showing a joined structure according to another embodiment (embodiment 3) of the present disclosure. FIG. 9 is a schematic cross-sectional view showing a bonded structure according to another embodiment (Embodiment 4) of the present disclosure. 10A and 10B are diagrams illustrating a method for manufacturing a bonded structure in the embodiment of FIG. 9, FIG. 10A being a schematic cross-sectional view of an element member, and FIG. FIG. 10(a) is a schematic top view (FIG. 10(a) is a schematic cross-sectional view taken along line AA in FIG. 10(b)). 11A and 11B are schematic schematic cross-sectional views showing a bonded structure according to another embodiment (embodiment 5) of the present disclosure, in which FIG. ) shows a cross section including a ceramic part (FIG. 11(a) is a schematic schematic cross-sectional view when viewed along the EE line in FIGS. 12(b) and 13(b), and FIG. 11(b) is a schematic cross-sectional view taken along line FF in FIGS. 12(b) and 13(b)). 12A and 12B are diagrams for explaining a method for manufacturing a bonded structure in the embodiment of FIG. 11, FIG. 12A being a schematic cross-sectional view of an element member, FIG. 12(a) is a schematic top view (FIG. 12(a) is a schematic cross-sectional view taken along line CC in FIG. 12(b)). 13A and 13B are diagrams for explaining a method for manufacturing a bonded structure according to the embodiment of FIG. 11, FIG. 13A being a schematic cross-sectional view of a circuit board, FIG. 13(a) is a schematic top view (FIG. 13(a) is a schematic cross-sectional view taken along line DD in FIG. 13(b)). FIG. 14 is a schematic cross-sectional view showing a comparative bonded structure in which a chip component is bonded to a circuit board.

Several embodiments of the present disclosure will be described in detail below with reference to the drawings, but the present disclosure is not limited to these embodiments. Similar members are denoted by similar reference numerals, and similar descriptions can be applied unless otherwise specified.

(Embodiment 1)
1 to 4, the joint structure 40 of this embodiment includes:
A pair of device electrodes 2a and 2b (hereinafter also referred to as device electrodes 2) including a pair of internal electrodes 3a and 3b and a pair of external electrodes 4a and 4b (hereinafter also referred to as device electrodes 2), a ceramic portion 5, and a first protective layer 6 are the first base material. an element member 10 formed on 1;
a circuit board 20 having a pair of land electrodes 14a and 14b formed on a second base material 11;
A pair of external electrodes 4a, 4b and a pair of land electrodes 14a, 14b facing each other are arranged in a state in which the ceramic part 5 and the first protective layer 6 are arranged between the first base material 1 and the second base material 11. and junctions 30a and 30b that electrically join the .

The ceramic portion 5 is covered with a first protective layer 6, the pair of external electrodes 4a and 4b are exposed from the first protective layer 6, and the pair of internal electrodes 3a and 3b are positioned within the ceramic portion 5 and The thickness t of 5 is 40 μm or less. According to this embodiment, such a configuration provides a joint structure that exhibits stable electrical characteristics even in a high-humidity environment.

Below, the joint structure 40 of the present embodiment will be described in detail through its manufacturing method. It should be noted that the description of each member and/or material can similarly apply to the joint structure 40 finally obtained unless otherwise specified.

Element Member As shown in FIG. 2( a ), the element electrodes 2 are formed on the surface of the first substrate 1 . (Hereinafter, the surface of the first base material 1 on which the element electrodes 2 are formed is also referred to as the "principal surface" of the first base material 1.)

The first base material 1 may be any appropriate base material (or substrate) as long as the surface portion on which the device electrodes 2 are formed is insulating. For example, the first base material 1 may be a flexible substrate (base layer). Although not particularly limited, the first base material 1 may contain any appropriate resin material (second resin material). The resin material (second resin material) used for the first base material 1 includes at least one selected from the group consisting of, for example, polyimide-based resin, polyester-based resin, glass-epoxy resin, liquid crystal polymer (LCP), and the like. can be anything. Even if the first substrate 1 is made of the above resin material, in some cases, in addition to the above resin material, other components may be added in a relatively small amount (for example, less than 50% by mass with respect to the entire first substrate 1, 30% by mass or less). The other component preferably has lower moisture permeability than the resin material. However, the present embodiment is not limited to this, and the first base material 1 may be a rigid substrate. The rigid substrate may be a conventional rigid substrate (which may consist of glass-epoxy resin, paper-phenolic resin, paper-epoxy resin, etc.).

The thickness of the first base material 1 can be selected as appropriate, and can be, for example, 10 μm or more and 5 mm or less. When the first substrate 1 is a flexible substrate, the thickness of the first substrate 1 may be relatively thin, for example 10 μm or more and 80 μm or less, particularly 60 μm or less, more particularly 50 μm or less.

The method of forming the element electrodes 2 on the surface of the first base material 1 is not particularly limited. For example, a metal foil (for example, Cu foil) is adhered to the first base material 1 with an adhesive, and the metal foil on the first base material 1 is patterned according to the shape of the device electrode 2 by photolithography, Appropriately, the element electrode 2 (in other words, the internal The electrodes 3a, 3b and the external electrodes 4a, 4b may be integrally formed (in this case, an adhesive layer may remain between the first substrate 1 and the element electrodes 2). According to such a method, the device electrode 2 having a fine structure can be formed with high accuracy. However, the present embodiment is not limited to this, and although it is less preferable, for example, a conductive paste is applied (for example, printed) on the first base material 1 in a pattern corresponding to the shape of the element electrode 2, The element electrodes 2 may be formed by appropriately heating. The heating may be performed simultaneously with the formation of the ceramic portion 5, which will be described later, or separately.

The device electrodes 2 are formed using any appropriate conductive material, and can be made of metal, for example. The Ag content in the device electrode 2 may be, for example, 20% by mass or less, particularly 10% by mass or less, and preferably substantially 0% by mass. Conventionally, in general chip parts, if a conductive paste containing Ag-containing particles (such as Ag particles or particles containing Ag and Pd) is used as the material for internal electrodes and/or external electrodes, the ceramic material is The internal and/or external electrodes often contained Ag, since the sintering can be co-sintered with the Ag-containing particles. However, when such a chip component is joined to a circuit board with a solder material, and while the joint structure thus obtained is used under high humidity conditions, Ag precipitates between the pair of external electrodes and dendrites grow. There is a danger that the resistance of the chip component will decrease and, in some cases, a short circuit will occur. On the other hand, in the present embodiment, the Ag content of the device electrode 2 is reduced as described above, preferably by substantially not containing Ag, so that the finally obtained junction structure 40 Even when the is used under high humidity conditions, there is a problem between the external electrodes 4a and 4b resulting from migration (compared to a bonded structure in which a chip component or a bonding member having a higher Ag content in the external electrode is bonded to a circuit board) This can reduce or prevent the growth of dendrites at the junction structure 40, and effectively reduce or prevent the resistance of the junction structure 40 from being lowered (short circuit in a significant case).

Although not limited to this embodiment, the device electrode 2 includes a base material made of at least one metal selected from the group consisting of Cu, Al, Ni, Sn, Ti, Zn, Fe, etc., and Ni, Au , Sn, Zn, Cr, W, Pd, Pt, Cu, etc., and a plated layer (which may be a single layer or multi-layer structure) made of at least one metal selected from the group consisting of.

The thickness of the element electrode 2 is not particularly limited as long as it is smaller than the thickness of the later-described ceramic portion 5. For example, it is 30 μm or less, particularly 20 μm or less. Such a relatively thin element electrode 2 would likely be susceptible to dissolution due to migration if it were not covered by joints 30a and 30b and the first protective layer 6, which will be described later.

The shape of the element electrode 2 (including the pair of internal electrodes 3a and 3b and the pair of external electrodes 4a and 4b) is determined according to the electrical characteristics and dimensions desired for the element member 10 and thus the junction structure 40. It can be selected as appropriate according to, for example.

Next, as shown in FIG. 2(b), ceramic portions 5 are formed on predetermined regions of the first substrate 1 and the element electrodes 2. Next, as shown in FIG.

The ceramic portion 5 can be formed using any appropriate ceramic material depending on the functions desired for the element member 10 . For example, in general, a raw material mixture containing particles of a predetermined metal oxide (ceramic material) is applied (e.g., printed) onto predetermined areas of the first substrate 1 and the element electrodes 2 by any suitable method. Then, the ceramic portion 5 can be formed by firing by heating, annealing and/or drying as appropriate. The heating (including firing) temperature can be set according to the ceramic material used, but it is preferable that the heating does not substantially cause deformation of the first substrate 1 .

The thickness t (see FIGS. 1 and 3(a)) of the ceramic portion 5 should be 40 μm or less. The thickness t of the ceramic portion refers to the height from the surface (main surface) of the first substrate 1 to the surface of the ceramic portion 5 opposite to the main surface. The lower limit of the thickness of the ceramic portion 5 may be larger than the thickness of the element electrode 2, but may be larger than the thickness of the element electrode 2 by, for example, 2 μm or more, particularly 5 μm or more. Although the present embodiment is not bound by any theory, since the thickness t of the ceramic part 5 is so small, the bonding interface between the layers of the joint structure 40 finally obtained has less unevenness, resulting in sealing. When the joint structure 40 is used under high-humidity conditions, migration can be suppressed, and the resistance of the joint structure 40 is increased (open in extreme cases) and/or reduced. It is possible to effectively reduce or prevent (short circuit in a serious case).

After that, as shown in FIGS. 3(a) and 3(b), a first protective layer 6 covering the ceramic portion 5 is formed.

The first protective layer 6 may contain any appropriate material as long as the portions that contact the ceramic portion 5 and the element electrodes 2 are insulative. For example, the first protective layer 6 may be flexible. Typically, the first protective layer 6 may contain any suitable resin material (first resin material). The resin material (first resin material) used for the first protective layer 6 includes, for example, polyimide resin, polyamideimide resin, epoxy resin, liquid crystal polymer (LCP), polyethylene resin, polypropylene resin, polystyrene resin, It may contain at least one selected from the group consisting of polyester-based resins, polyurethane-based resins, polyamide-based resins (including nylon), polyetherimide-based resins, and (meth)acrylic-based resins. Among them, LCP is preferable because it has relatively low moisture permeability and is therefore more effective in suppressing migration. Even if the first protective layer 6 is made of the above resin material, in some cases, in addition to the above resin material, other components may be added in a relatively small amount (for example, less than 50% by mass with respect to the entire first protective layer 6, 30% by mass or less). The other component preferably has lower moisture permeability than the resin material.

The method of forming the first protective layer 6 covering the ceramic portion 5 is not particularly limited. For example, using a first protective layer 6 having an area sufficiently larger than that of the ceramic portion 5, the first protective layer 6 including an adhesive layer is formed on the ceramic portion 5 (or the first protective layer 6 is formed via an adhesive). ), followed by pressure bonding, the first protective layer 6 covering the ceramic part 5 can be formed. The adhesive may be one that can be adhered at room temperature or one that can be adhered by heating. Heating for forming may be performed simultaneously or separately.

The first protective layer 6 may be a single layer or multiple layers, and in the latter case may contain one or more adhesive layers as appropriate. The first protective layer 6 may or may not be a coverlay layer derived from a so-called coverlay. The surface of the first protective layer 6 may be water-repellent as it is, and/or may be subjected to water-repellent finishing as necessary.

The thickness of the first protective layer 6 can be appropriately selected according to the moisture permeability of the first protective layer 6, and can be, for example, 10 µm or more, particularly 15 µm or more, and more particularly 20 µm or more. Although the upper limit of the thickness of the first protective layer 6 is not particularly limited, the thickness can be, for example, 50 μm or less, particularly 40 μm or less, and more particularly 30 μm or less.

The first protective layer 6 can be formed on any appropriate region as long as it covers the ceramic portion 5 and exposes the pair of external electrodes 4a and 4b. The first protective layer 6 can be formed between the external electrodes 4a and 4b on the surface (main surface) of the first substrate 1, as shown in FIG. It can also be formed on the outer peripheral region of the surface (principal surface), and more preferably, it can be formed so as to surround each of the external electrodes 4a and 4b as shown in FIG. 3(b).

Of the element electrodes 2, the portions located within the ceramic portion 5 are internal electrodes 3a and 3b, and the portions exposed from the first protective layer 6 are external electrodes 4a and 4b. The element electrode 2 may further include a portion adjacent to the external electrodes 4a, 4b, which is located outside the ceramic portion 5 but is covered with the first protective layer 6, and these portions (particularly dissolution resulting from migration ) may be considered to be included in the internal electrodes 3a, 3b.

For example, the internal electrodes 3a and 3b may have a comb-like shape in which the tooth portions face each other, as shown in FIG. 3(b).

A ceramic portion 5 may be formed between the external electrodes 4a and 4b so as to be separated from each other as much as possible, as shown in FIG. The protective layer 6 is formed between the external electrodes 4a and 4b, and when a second protective layer 16, which will be described later, is present on the circuit board 20, the second protective layer 16 is formed between the land electrodes 14a and 14b). (Furthermore, for example, depending on the case, a ceramic portion 5 may be formed adjacent to the external electrodes 4a and 4b, as described in detail in Embodiment 5.)

However, the arrangement and/or shape of the internal electrodes 3a, 3b and the external electrodes 4a, 4b are not limited to this, and the electrical properties desired for the element member 10 and thus the junction structure 40 and the junction structure 40 are desired. It can be appropriately selected according to the dimensions and the like.

According to this embodiment, by covering the ceramic portion 5 with the first protective layer 6 and setting the thickness t (see FIGS. 1 and 3A) of the ceramic portion 5 to 40 μm or less, the final Even when the joint structure 40 obtained in 1 is used under high humidity conditions, the dissolution of the internal electrodes 3a and/or 3b (for example, near the external electrodes 4a and/or 4b) due to migration is reduced or prevented. As a result, it is possible to effectively reduce or prevent an increase in the resistance of the junction structure 40 (open in extreme cases).

The element member 10 can be manufactured as described above.

Circuit Board As shown in FIGS. 4(a) and 4(b), a pair of land electrodes 14a and 14b and lead wires 15a and 15b are formed on the surface of the second base material 11, respectively. (Hereinafter, the surface on which the land electrodes 14a and 14b of the second base material 1 are formed is also referred to as the "main surface" of the second base material 11.)

The second base material 11 may be any appropriate base material (or substrate) as long as the surface portions on which the land electrodes 14a, 14b and lead lines 15a, 15b are formed are insulating. For example, the second base material 11 may be a flexible substrate (base layer). Although not particularly limited, the second base material 11 may contain any appropriate resin material (third resin material). The resin material (third resin material) used for the second base material 11 may be the same as the resin material (second resin material) described above for the first base material 1 . Even if the second base material 11 is made of the above resin material, in some cases, in addition to the above resin material, other components may be added in a relatively small amount (for example, less than 50% by mass with respect to the entire second base material 11, 30% by mass or less). The other component preferably has lower moisture permeability than the resin material. However, the present embodiment is not limited to this, and the second base material 11 may be a rigid substrate. The rigid substrate may be similar to the rigid substrates described above for the first substrate 1 .

The thickness of the second base material 11 can be selected as appropriate, and can be, for example, 10 μm or more and 5 mm or less. When the second substrate 11 is a flexible substrate, the thickness of the second substrate 11 may be relatively thin, for example 10 μm or more and 80 μm or less, particularly 60 μm or less, more particularly 50 μm or less.

The method of forming the land electrodes 14a, 14b and the lead lines 15a, 15b is not particularly limited. For example, a metal foil (for example, Cu foil) is adhered to the second base material 11 with an adhesive, and the metal foil on the second base material 11 is photolithographically processed to form the land electrodes 14a, 14b and the lead lines 15a, 15b. A pattern is formed according to the shape, and the surface of the patterned metal (for example, a Cu base material) is appropriately plated electrolytically or electrolessly (for example, a plated layer containing Ni and/or Au) to form a land electrode. 14a, 14b and lead lines 15a, 15b may be integrally formed (in this case, adhesive layers remain between the second base material 11 and the land electrodes 14a, 14b and lead lines 15a, 15b). can be used). However, the present embodiment is not limited to this. For example, a conductive paste is applied (for example, printed) on the second base material 11 in a pattern corresponding to the shapes of the land electrodes 14a, 14b and the lead wires 15a, 15b. The land electrodes 14a, 14b and the lead wires 15a, 15b may be formed by appropriately heating.

The land electrodes 14a, 14b and lead lines 15a, 15b are formed using any appropriate conductive material, and can be made of metal, for example. The Ag content in the land electrodes 14a, 14b and lead wires 15a, 15b may be, for example, 20% by mass or less, particularly 10% by mass or less, and preferably substantially 0% by mass. In the present embodiment, the land electrodes 14a, 14b have a small Ag content as described above, and preferably contain substantially no Ag. Even when used under such conditions, the migration-induced migration between the land electrodes 14a, 14b (compared to a bonded structure in which a chip component or a bonding member is bonded to a circuit board having a higher Ag content in the land electrode) It is possible to reduce or prevent the growth of dendrites, and to effectively reduce or prevent a decrease in the resistance of the junction structure 40 (a short circuit in a significant case).

Although not limited to this embodiment, the land electrodes 14a, 14b and the lead wires 15a, 15b are made of at least one metal selected from the group consisting of Cu, Al, Ni, Sn, Ti, Zn, Fe, etc. and a plated layer (which can be a single layer or multi-layer structure) made of at least one metal selected from the group consisting of Ni, Au, Sn, Zn, Cr, W, Pd, Pt, Cu, etc. may be configured.

The thickness of the land electrodes 14a, 14b and the lead wires 15a, 15b is not particularly limited, but may be, for example, 30 μm or more, particularly 20 μm or more, and may be, for example, 50 μm or less, particularly 35 μm or less. Such relatively thin land electrodes 14a, 14b would be susceptible to dissolution due to migration if they were not covered by joints 30a, 30b (and second protective layer 16, if present), which will be described later. can be considered easy.

The arrangement and shape of the land electrodes 14a, 14b can be appropriately selected according to the arrangement and shape of the external electrodes 4a, 4b. The arrangement and shape of the lead wires 15a and 15b can be appropriately selected according to the desired dimensions and terminal positions of the joint structure 40 finally obtained.

Although not essential for this embodiment, the circuit board 20 may have a second protective layer 16 disposed on the second base material 11 . A pair of land electrodes 14 a and 14 b are exposed from the second protective layer 16 .

The second protective layer 16 can be formed on any appropriate area of the second substrate 11 as long as the pair of land electrodes 14a, 14b are exposed. The second protective layer 16 can be formed between the land electrodes 14a and 14b on the surface (main surface) of the second substrate 11, as shown in FIG. It can also be formed on the outer peripheral region of the surface (principal surface), and more preferably, it can be formed so as to surround each of the land electrodes 14a and 14b as shown in FIG. 4(b).

In addition, the above description of the first protective layer 6 can be applied to the second protective layer 16 as well. The second protective layer 16 may or may not be a coverlay layer derived from a so-called coverlay. The surface of the second protective layer 16 may be water-repellent as it is, and/or may be subjected to water-repellent finishing as necessary.

The circuit board 20 can be manufactured as described above.

・Joining part The element member 10 and the circuit board 20 produced above are arranged so that the ceramic part 5 and the first protective layer 6 are present between the first base material 1 and the second base material 11, and are opposed to each other. The pair of external electrodes 4a, 4b and the pair of land electrodes 14a, 14b are electrically joined at joints 30a, 30b.

The joints 30a, 30b are not particularly limited as long as they can electrically join the external electrodes 4a, 4b and the land electrodes 14a, 14b, but may contain a solder material, for example. The solder material may be lead-free solder material. The lead-free solder material may be, for example, Sn--Cu based, Sn--Ag based, Sn--Ag--Cu based, Sn--Zn based, Sn--Bi based, and the like. The Ag content in the solder material can be, for example, 20% by weight or less, in particular 10% by weight or less.

The method of forming the joints 30a and 30b is not particularly limited. Typically, a conductive paste containing particles of a solder material is applied (e.g., printed) onto land electrodes 14a, 14b, after which element member 10 and circuit board 20 are attached to ceramic portion 5 and first protective layer 6. It is arranged so as to exist between the first base material 1 and the second base material 11, and the pair of external electrodes 4a, 4b is placed on the conductive paste on the pair of land electrodes 14a, 14b facing thereto. By stacking them in such a manner and heating them in a reflow furnace or the like in such a stacked state, joint portions 30a and 30b for electrically joining the external electrodes 4a and 4b and the land electrodes 14a and 14b are formed. . The heating temperature can be set to be at or above the melting point of the solder material used, but the heating causes the first substrate 1, the second substrate 11, the first protective layer 6, and the second protective layer, if present, to melt. Preferably, substantially no deformation of 16 occurs.

The thickness of the conductive paste containing particles of solder material applied (for example, printed) on the land electrodes 14a, 14b is from the surface opposite to the surface (main surface) of the first substrate 1 of the external electrodes 4a, 4b. The maximum height h ₁ (see FIG. 1) to the surface of the first protective layer 6 opposite to the device electrode 2 and the surfaces of the land electrodes 14a and 14b opposite to the surface (principal surface) of the second substrate 11 to the land electrodes 14a, 14b of the second protective layer 16 and the surface of the second protective layer 16 opposite to the maximum height h ₂ (see FIG. 1). It can be set appropriately so that the solder material sufficiently wets and spreads on the exposed surfaces of the external electrodes 4a and 4b and the exposed surfaces of the land electrodes 14a and 14b when joined to 20 .

Conductive pastes containing particles of solder material may contain any suitable other ingredients in addition to particles of solder material as described above. Such other ingredients may be fluxes, viscosity modifiers, solvents, and the like. Flux is not particularly limited, and any known flux may be used. For example, the flux may use a flux composition containing rosin modifications, such as those described in US Pat. Such a flux composition is said to be able to coat particles of solder material and suppress migration. The modified rosin is composed of rosin or a rosin derivative and the following structural formula:
NH _3-n (R—OH) _n (n≦3)
It can be a rosin-modified product consisting of a reaction product with an alkanolamine represented by. Such modified rosin can be obtained by reacting rosin or a rosin derivative, an organic acid and an alkanolamine. More specifically, such modified rosin is an amide bond obtained by condensation of the COOH group of rosin or a rosin derivative and the NH _3-n group in the above structural formula (1), or the COOH group of rosin or a rosin derivative and It has an ester bond obtained by condensation with the OH group in the structural formula (1).

The solder material melts during the heating, wets and spreads on the exposed surfaces of the pair of external electrodes 4a and 4b and the pair of land electrodes 14a and 14b, and then solidifies as the temperature drops to form the joints. 30a and 30b are formed. In order to obtain sufficient conductivity and bonding strength, the area of the bonding regions of the land electrodes 14a, 14b should be substantially equal to or greater than the area of the bonding regions of the external electrodes 4a, 4b facing each other (i.e., 1 times or more). Also, the area of the bonding regions of the land electrodes 14a and 14b is preferably three times or less the area of the bonding regions of the external electrodes 4a and 4b facing each other.

The bonding region of the external electrodes 4a and 4b refers to the region of the surface of the external electrodes 4a and 4b on the side opposite to the first base material 1. The exposed surfaces of the external electrodes 4a, 4b refer to the joint regions of the external electrodes 4a, 4b and the side surfaces of the external electrodes 4a, 4b between the first substrate 1 and the joint regions. The bonding area of the land electrodes 14a and 14b refers to the area of the surface of the land electrodes 14a and 14b opposite to the second base material 11 . The exposed surfaces of the land electrodes 14a and 14b refer to the joint regions of the land electrodes 14a and 14b and the side surfaces of the land electrodes 14a and 14b between the second base material 11 and the joint regions.

When the ratio of the area of the bonding regions of the land electrodes 14a and 14b to the area of the bonding regions of the external electrodes 4a and 4b is 3 times or less, for example, the width of the bonding regions of the external electrodes 4a and 4b is reduced to the width of the land electrodes 14a and 14b. are the same, as _shown in _FIG . The ratio is 3 times or less (that is, L ₂ /L ₁ is 3 or less), so that when the element member 10 is joined to the circuit board 20, the solder material is applied to the exposed surfaces (bonding regions and side surfaces) of the external electrodes 4a and 4b. ) and the exposed surfaces (joint areas and side surfaces) of the land electrodes 14a and 14b. The joints 30a, 30b thus formed can sufficiently cover the external electrodes 4a, 4b and the land electrodes 14a, 14b (without substantially exposing them). According to the joints 30a and 30b obtained in this manner, even when the finally obtained joint structure 40 is used under high humidity conditions, it is caused by migration (exposed from the joints 30a and 30b). It is possible to reduce or prevent dissolution of the land electrodes 14a and/or 14b (at the portion where the connection is made), and effectively reduce or prevent the joining structure 40 from increasing in resistance (opening in a significant case). Although this embodiment is not bound by any theory, even if migration occurs due to the use of the joint structure 40 under high humidity conditions, the external electrodes 4a, 4b and the land electrodes 14a, 14b are (substantially exposed). ), the solder material of the joints 30a, 30b is selectively melted, and the electrical properties of the joint structure 40 are likely to be affected by the external electrodes 4a, 4b and/or Since the melting of the land electrodes 14a and 14b is reduced or prevented, stable electrical characteristics can be obtained.

On the other hand, when the ratio of the area of the bonding regions of the land electrodes 14a and 14b to the area of the bonding regions of the external electrodes 4a and 4b exceeds three times, for example, the width of the bonding regions of the external electrodes 4a and 4b is greater than the width of the land electrodes. When the widths of the bonding regions of 14a and _{14b are} the same, as shown in FIG. When bonding to the circuit board 20, the solder material does not sufficiently wet and spread on the exposed surfaces (bonding regions and side surfaces) of the external electrodes 4a and 4b and the exposed surfaces (bonding regions and side surfaces) of the land electrodes 14a and 14b. Portions of the electrodes 14a, 14b may remain uncovered by the joints 30a, 30b and remain exposed. (The exposed portions of the land electrodes 14a and 14b may be covered with a resin material, as described later in Embodiments 3 and 4, if necessary.)

As described above, the joint structure 40 of the present embodiment can be produced.

In the joint structure 40 of the present embodiment, the surface of the first protective layer 6 opposite to the first base material 1 (main surface) is the first base material 1 (main surface) of the pair of external electrodes 4a and 4b. ) in the direction of the second base material 11 . In this case, the path between the external electrodes 4a and 4b is no longer linear due to the protrusions located between them, and the larger the protrusions, the more difficult it is for water to enter. With such a configuration, even when the finally obtained bonded structure 40 is used under high humidity conditions, water intrusion is suppressed or inhibited (compared to the case where the protrusion is not present or the protrusion is smaller). It can reduce or prevent the growth of dendrites between the external electrodes 4a and 4b due to migration, and effectively reduce or prevent a decrease in the resistance of the junction structure 40 (a short circuit in a significant case). be able to. The size of the protrusion is, for example, 5 μm or more, particularly 10 μm or more, and the upper limit is the contact of the first protective layer 6 with the circuit board 20 (more specifically, the second protective layer 16 if present). can be defined.

In addition, in the joint structure 40 of the present embodiment, when the second protective layer 16 is present, the surface of the second protective layer 16 opposite to the second base material 11 (main surface) serves as a pair of land electrodes. It protrudes in the direction of the first substrate 1 from the surfaces of the 14a and 14b opposite to the second substrate 11 (main surface). In this case, the path between the land electrodes 14a and 14b is no longer linear due to the protrusions positioned between them, and the larger the protrusions, the more difficult it is for water to enter. With such a configuration, even when the finally obtained bonded structure 40 is used under high humidity conditions, water intrusion is suppressed or inhibited (compared to the case where the protrusion is not provided or the protrusion is smaller). It is possible to reduce or prevent the growth of dendrites between the land electrodes 14a and 14b due to migration, and to effectively reduce or prevent a decrease in the resistance of the junction structure 40 (short circuit in a significant case). can be done. The size of the protrusion is, for example, 5 μm or more, particularly 10 μm or more, and the upper limit can be defined by the contact of the second protective layer 16 with the element member 10 (more specifically, the first protective layer 6).

In addition, in the joint structure 40 of the present embodiment, unlike Patent Document 1, for example, it is not necessary to cover the entire element member 10 with a protective film made of a resin material from the surface of the element member 10 opposite to the circuit board 20. . With such a joint structure 40, it is easy to confirm whether the element member 10 is properly electrically joined to the circuit board 20, and the element member 10 can be replaced in the event of a failure. Further, when a plurality of element members 10 are joined to one circuit board 20, if a defect is found in a certain element member 10, only the element member 10 can be replaced.

As can be understood from the above description, according to the present embodiment, the joint structure 40 that exhibits stable electrical characteristics even in a high humidity environment is provided. The bonded structure 40 of the present embodiment can exhibit stable electrical characteristics and can have drip-proof or waterproof properties even when used in contact with a liquid containing ions (water, bodily fluids, etc.). .

In the joint structure 40 of this embodiment, the ceramic portion 5 may contain a thermistor material (for example, an NTC thermistor material). Such a joint structure 40 can be used as a moisture-resistant (or drip-proof or waterproof, hereinafter the same) temperature sensor, and is preferably a moisture-resistant thin and flexible temperature sensor (for example, an NTC thermistor). obtain. A thin and flexible temperature sensor having moisture resistance can be suitably used in, for example, in-vehicle applications and healthcare applications. If the temperature sensor is assumed to be used in a temperature range of -55°C to 150°C, for example, dew condensation occurs when the temperature changes from low to high. Also, in healthcare applications, it may be envisaged that the temperature sensor will come into direct contact with bodily fluids. The joint structure 40 of the present embodiment can exhibit stable electrical characteristics even when used as a temperature sensor exposed to such dew condensation and bodily fluids. The bonded structure 40 of the present embodiment has excellent sealing properties as described above, and the outer surface of the bonded structure 40 (more specifically, the surface opposite to the main surface of the first base material 1, Since there is no portion where the metal is exposed on both the main surface and the surface on the opposite side of the second base material 11, it exhibits high insulation against the external environment, and not only contacts with liquids, Even if the joint structure 40 comes into contact with a conductor such as a human body, electric shock, short circuit, noise, etc. can be prevented from occurring.

(Embodiment 2)
This embodiment is a modified example of Embodiment 1, and relates to an aspect in which one or both of the first protective layer and the first base material include a metal layer. In this embodiment, the points different from the above-described first embodiment will be mainly described, and unless otherwise specified, the same description as in the first embodiment can be applied.

In the bonded structure 41 of this embodiment, at least one of the first protective layer 6 and the first base material 1 includes a metal layer. 6 and 7, more specifically, the first protective layer 6 further includes a first metal layer 7 in addition to the first resin material described above in the first embodiment. The first base material 1 further includes a second metal layer 8 in addition to the second resin material described above in the first embodiment. The first metal layer 7 may be provided on the first protective layer 6 in any suitable manner as long as it does not come into direct contact with the ceramic portion 5 . The second metal layer 8 can be provided on the first substrate 1 in any suitable manner as long as it does not directly contact the device electrodes 2 (including the internal electrodes 3a, 3b and the external electrodes 4a, 4b). (Note that FIGS. 6 and 7 correspond to FIGS. 1 and 3 referred to in the first embodiment, respectively.)

The first metal layer 7 and the second metal layer 8 may comprise any suitable metal, for example may consist of metal. Such metals are not particularly limited, but may be, for example, at least one selected from the group consisting of Cu, Al, Ni, Au, and the like. The first metal layer 7 and the second metal layer 8 may consist of the same material (including metal) or different materials (including metal).

The thickness of the first metal layer 7 and the second metal layer 8 can be, for example, 1 μm or more and 30 μm or less. The first metal layer 7 and the second metal layer 8 can have the same or different thicknesses.

The method of manufacturing the first protective layer 6 and the first base material 1, which respectively include the first metal layer 7 and the second metal layer 8, is not particularly limited. For example, the first protective layer 6 can be formed by sandwiching a metal foil between two films made of a predetermined resin material (optionally with an adhesive interposed therebetween) and pressing them at room temperature or under heat. The first base material 1 can also be formed in the same manner.

　The metal layer has lower moisture permeability than the resin material. On the other hand, the resin material is excellent in workability, insulating properties, etc., and can be flexible. Therefore, by combining the metal layer and the resin material, the element structure 41 including the first protective layer 6 and the first base material 1 having low moisture permeability without adversely affecting the electrical properties and flexibility of the element structure 41. can be realized.

Therefore, according to this embodiment, migration can be further suppressed by the first protective layer 6 and the first base material 1 having low moisture permeability compared to the bonded structure of Embodiment 1, and migration can be further suppressed in a high-humidity environment. A junction structure 41 is provided that exhibits even more stable electrical characteristics.

In the embodiments shown in FIGS. 6 and 7, both the first protective layer 6 and the first base material 1 include metal layers, but the present embodiment is not limited to this and is less preferable. However, only one of the first protective layer 6 and the first substrate 1 may contain the metal layer.

(Embodiment 3)
This embodiment is a modified example of Embodiments 1 and 2, and relates to an aspect in which the joint portion is covered with a cured resin material. In this embodiment, the points different from the above-described first or second embodiment will be mainly described, and the description similar to that of the first or second embodiment can be applied unless otherwise specified.

As shown in FIG. 8, in the joint structure 42 of the present embodiment, joint portions 30a and 30b are covered with a cured resin material (cured resin material, fourth resin material) 31. As shown in FIG. (Note that FIG. 8 is a diagram corresponding to FIG. 6 referred to in the second embodiment.)

The cured resin material 31 may be any appropriate resin material (fourth resin material) cured by moisture, heat and/or radiation (including light, ultraviolet rays, etc.) as long as it has insulating properties. may be a cured product of a moisture-curable (so-called room-temperature-curable), radiation (eg, ultraviolet)-curable, and/or thermosetting resin material. Such cured resin materials may be, for example, silicone-based resins, acrylic-based resins, epoxy-based resins, and the like.

The cured resin material 31 covers at least part, preferably substantially all of the surfaces of the joints 30a, 30b that are not in contact with the external electrodes 4a, 4b and the land electrodes 14a, 14b. If there are portions of the external electrodes 4a, 4b and/or the land electrodes 14a, 14b that are not covered with the joints 30a, 30b, the cured resin material 31 can also cover such portions. The cured resin material 31 may or may not fill substantially the entire space between the element member 10 and the circuit board 20 except for the joints 30a and 30b.

The method of producing the cured resin material 31 covering the joints 30a and 30b is not particularly limited. For example, after producing the joint structure of Embodiment 1 or 2, an uncured resin material is applied around the joints 30a and 30b (preferably not in contact with the external electrodes 4a and 4b and the land electrodes 14a and 14b). It can be formed by applying the coating so as to cover substantially all of the surface) and then curing in a suitable manner depending on the uncured resin material used. The cured resin material 31, which is cured after supplying the uncured resin material, closely adheres to and covers the joints 30a and 30b (and preferably the external electrodes 4a and 4b and the land electrodes 14a and 14b) to seal them. can be stopped.

By covering the joints 30a and 30b (including the solder material) with the cured resin material 31, migration can also be suppressed in the joints 30a and 30b.

Therefore, according to the present embodiment, as compared with the joint structures of Embodiments 1 and 2, an additional step for covering the joints 30a and 30b with the cured resin material 31 is required. , 30b (including a solder material) can further suppress migration by the cured resin material 31, thereby providing a joint structure 42 that exhibits more stable electrical characteristics even in a high-humidity environment.

In the aspect shown in FIG. 8, as a modified example of Embodiment 2, in the bonded structure 42 in which both the first protective layer 6 and the first base material 1 include metal layers, the bonded portions 30a and 30b are made of a cured resin. Although the one coated with the material 31 is shown, the present embodiment is not limited to this, and either the first protective layer 6 or the first base material 1 may include a metal layer. . Alternatively, as a modified example of Embodiment 1, in the bonded structure including the first protective layer 6 and the first base material 1 that do not contain a metal layer, the bonded portions 30a and 30b are coated with a cured resin material 31. may be

(Embodiment 4)
This embodiment is a modified example of Embodiments 1 and 2, and relates to an aspect in which the joint is covered with a thermoplastic resin material. In this embodiment, the points different from the above-described first or second embodiment will be mainly described, and the description similar to that of the first or second embodiment can be applied unless otherwise specified.

As shown in FIG. 9, in the joint structure 43 of the present embodiment, joint portions 30a and 30b are covered with a thermoplastic resin material (fifth resin material) 32. As shown in FIG. (Note that FIG. 9 is a diagram corresponding to FIG. 6 referred to in the second embodiment.)

The thermoplastic resin material 32 may be any suitable thermoplastic resin material (the thermoplastic resin material once heated and melted, the fifth resin material) as long as it has insulating properties. Such thermoplastic resin materials may be, for example, polyester-based resins, polyethylene-based resins, polypropylene-based resins, polystyrene-based resins, polyurethane-based resins, nylon-based resins, polyetherimide-based resins, and the like.

The thermoplastic resin material 32 covers at least part, preferably substantially all, of the surfaces of the joints 30a, 30b that are not in contact with the external electrodes 4a, 4b and the land electrodes 14a, 14b. If there are portions of the external electrodes 4a, 4b and/or the land electrodes 14a, 14b that are not covered with the joints 30a, 30b, the thermoplastic resin material 32 can also cover such portions. The thermoplastic resin material 32 may or may not fill substantially the entire space between the element member 10 and the circuit board 20 except for the joints 30a and 30b.

The method of manufacturing the thermoplastic resin material 32 covering the joints 30a and 30b is not particularly limited. For example, when producing the bonded structure of Embodiment 1 or 2, as shown in FIG. 10, after forming the first protective layer 6, the first protective layer 6 (and/or the first base material 1) A thermoplastic resin material 32' is applied (for example, printed) thereon so as to surround the external electrodes 4a and 4b, and the element member 10 is produced. (It should be noted that FIG. 10 is a diagram corresponding to FIG. 7 referred to in Embodiment 2.) After that, using such an element member 10, a joint portion is attached to a circuit board 20 in the same manner as in Embodiment 1 or 2. When joining with 30a and 30b (including the solder material), the thermoplastic resin material 32' is also heated and melted when the solder material is heated and melted. The thermoplastic resin material 32', which is formed by heating and melting the thermoplastic resin material 32' once, and then solidifying after being naturally deformed, forms the joint portions 30a and 30b (and preferably the external electrodes 4a and 4b and the land electrodes 14a and 14b). It is possible to seal them by coating them in close contact with each other.

By covering the joints 30a and 30b (including the solder material) with the thermoplastic resin material 32, migration can also be suppressed in the joints 30a and 30b.

Therefore, according to the present embodiment, compared to the joint structures of Embodiments 1 and 2, an additional step for covering the joints 30a and 30b with the thermoplastic resin material 32 is required. The thermoplastic resin material 32 covering 30a and 30b (including the solder material) can further suppress migration, thereby providing a joint structure 43 that exhibits more stable electrical characteristics even in a high humidity environment.

9 and 10, as a modified example of Embodiment 2, in the bonded structure 43 in which both the first protective layer 6 and the first base material 1 include metal layers, the bonded portions 30a and 30b are Although the one coated with the thermoplastic resin material 32 is shown, the present embodiment is not limited to this, and either one of the first protective layer 6 and the first substrate 1 includes a metal layer. may Alternatively, as a modified example of Embodiment 1, in a bonded structure including the first protective layer 6 and the first base material 1 that do not contain a metal layer, the bonded portions 30a and 30b are coated with a thermoplastic resin material 32. can be anything.

(Embodiment 5)
This embodiment is a modified example of Embodiments 1 and 2, and relates to a mode in which the joint includes an anisotropically conductive material. In this embodiment, the points different from the above-described first or second embodiment will be mainly described, and the description similar to that of the first or second embodiment can be applied unless otherwise specified.

As shown in FIGS. 11 to 13, particularly FIG. 11(a), in the joint structure 44 of the present embodiment, the joint 30' contains an anisotropically conductive material.

The anisotropically conductive material forming the joint portion 30′ is formed by dispersing a plurality of conductive particles 33 having at least a conductive surface in any suitable resin material (binder resin, sixth resin material) 34. obtain. Such a resin material (sixth resin material) may be a curable resin material, a thermoplastic resin material, or a mixture thereof, as long as it has insulating properties. It may be a cured product of a curable resin material (including light, ultraviolet rays, etc.).

The anisotropic conductive material forming the joint portion 30′ is not particularly limited, and any suitable anisotropic conductive material, such as a film-like or paste-like anisotropic conductive material (anisotropic conductive film (ACF) or Anisotropic Conductive Paste (ACP)).

The anisotropic conductive material as a raw material before forming the joint portion 30' is a composition containing the conductive particles 33 and a resin material (sixth resin material or its precursor), and optionally other components (for example, curing agents, fillers, solvents, etc.).

The resin material (sixth resin material or its precursor) constituting the composition is any suitable resin material curable by moisture, heat and/or radiation (including light, ultraviolet rays, etc.), or thermoplastic It may be a resin material, a mixture thereof, or the like. The resin material forming the composition may be, for example, a thermosetting and/or radiation-curable resin material, and may be cured by heating and/or radiation irradiation when forming the joint 30'. The resin material that constitutes the composition may typically be a thermosetting resin material, and is not particularly limited. It may contain one.

The conductive particles 33 are particles that exhibit conductivity when the joints 30′ are formed and that can electrically connect the external electrodes 4a′ and 4b′ and the land electrodes 14a′ and 14b′. good. Such conductive particles 33 may be, for example, particles made of a conductive material, or particles in which an insulating coating is formed on a core made of a conductive material, or a core made of any appropriate resin material. In addition, it may be a particle having a layer made of a conductive material and an insulating coating formed thereon. The average particle size of the conductive particles 33 may be, for example, 20 μm or less, particularly 15 μm or less, and the lower limit is not particularly limited, but may be, for example, 1 μm or more, particularly 5 μm or more. The average particle size means the median size, and can be measured using, for example, a laser diffraction particle size distribution analyzer.

The conductive substance that forms the conductive particles can be a metal or a metal-containing substance. If the resin material is a thermosetting resin material, the metal preferably does not melt at the heating temperature used to form the joint 30'. The metal may include, for example, at least one selected from the group consisting of Au, Ni, Pd and Cu, but is not limited thereto. If present, the thickness of the layer of electrically conductive material may be, for example, 0.1 μm or more, in particular 0.5 μm or more, more particularly 1 μm or more, the upper limit being defined by the particle size of the conductive particles.

The insulating coating, if present, may consist of any suitable resin material or the like. The thickness of the insulating coating is destroyed by pressure between the external electrodes 4a', 4b' and the land electrodes 14a', 14b' when forming the joint 30', and the electrical connection between them is broken. For example, it may be 50 μm or less, particularly 25 μm or less, and the lower limit may be set as appropriate, but may be, for example, 1 μm or more.

The anisotropic conductive material includes, for example, conductive particles having a metal having a melting point of 400 ° C. or higher on the conductive surface, a curable compound that can be cured by heating, and a thermosetting material, as described in Patent Document 4. It may be a composition containing an agent and a flux. Metals having a melting point of 400° C. or higher include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, cadmium, and alloys thereof. is mentioned. Alternatively, tin-doped indium oxide (ITO) may be used as the metal. Only one kind of the above metals may be used, or two or more kinds thereof may be used in combination. The conductive particles preferably have a nickel layer, a palladium layer, a copper layer or a gold layer on their outer surface. The curable compound is not particularly limited, and includes a curable compound having an unsaturated double bond, a curable compound having an epoxy group or a thiirane group, and the like, and includes a curable compound having a (meth)acryloyl group. is preferred. Examples of the heat curing agent include imidazole curing agents, amine curing agents, phenol curing agents, polythiol curing agents, acid anhydrides and thermal radical generators. The above flux is not particularly limited, but for example, zinc chloride, mixtures of zinc chloride and inorganic halides, mixtures of zinc chloride and inorganic acids, molten salts, phosphoric acid, derivatives of phosphoric acid, organic halides, hydrazine, Examples include organic acids and pine resin.

As shown in FIG. 11(a), in the joint structure 44 of the present embodiment, the conductive particles 33 are formed between the external electrodes 4a' and 4b' and the land electrodes 14a' and 14b' in the joint portion 30'. By being sandwiched between them, they are electrically connected, and the resin material (sixth resin material) 34 includes the conductive particles 33, the external electrodes 4a' and 4b', and the land electrodes 14a' and 14b'. to cover.

In the joint structure 44 of the present embodiment shown in FIGS. 11 to 13, referring to FIG. 12, the pair of internal electrodes 14' and 14b', the ceramic portion 5' and a first protective layer 6' are formed.

The method of manufacturing the joint 30' is not particularly limited. For example, an element member 10' shown in FIG. 12 and a circuit board 20' shown in FIG. A pair of external electrodes 4a', 4b' and a pair of land electrodes 14a', 14b' arranged to exist between the material 1' and the second base material 11' and facing each other are anisotropic. By sandwiching the conductive material and applying pressure while heating appropriately, it is possible to electrically join them at the joining portion 30'.

By including the anisotropic conductive material in the joint portion 30', the external electrodes 4a', 4b', the land electrodes 14a, '14b', and all of the conductive particles 33 therebetween are all at once by the resin material 34. Migration can be suppressed.

Therefore, according to this embodiment, as compared with the bonded structures of Embodiments 1 and 2, a pressurizing process for forming the bonding portion 30' is required, but the resin material 34 of the bonding portion 30' A joint structure 44 that can suppress migration at once and exhibits stable electrical characteristics even in a high-humidity environment is provided.

11 to 13, as a modified example of Embodiment 2, in the bonded structure 44 in which both the first protective layer 6' and the first base material 1' include metal layers, the bonded portion 30' is , contains an anisotropic conductive material, but the present embodiment is not limited to this, and either one of the first protective layer 6' and the first substrate 1' contains a metal layer. may Alternatively, as a modified example of Embodiment 1, in the bonded structure including the first protective layer 6' and the first base material 11' that do not contain a metal layer, the bonded portion 30' contains an anisotropic conductive material. There may be.

(Example 1)
Example 1 relates to the joint structure described above in the first embodiment.

・Element material (thermistor sample)
10% by mass of manganese acetylacetonate (total mass of metal oxide particles ), ethanol was added as a solvent, and mixed for 16 hours to obtain a raw material mixture in the form of a slurry. A Cu layer with a thickness of 12 μm is patterned into a predetermined shape by photolithography on a first substrate (base layer) that is a polyimide film with a thickness of 25 μm. A plated layer and an Au plated layer were sequentially formed electrolessly. The total thickness of these plating layers was 3 μm. As a result, the Cu/Ni/Au element electrodes (thickness 15 μm) were used as portions corresponding to the pair of internal electrodes, and a pair of comb-shaped counter electrodes were arranged with a comb-teeth electrode spacing of 1.0 mm (d, FIG. 2 ( a), and on both sides of the pair of comb-shaped counter electrodes, a portion corresponding to the pair of external electrodes has a width (W ₁ ) of 0.4 mm and a length (L ₁ ) of 0.2 mm. It was made in a rectangular shape. A precursor laminate was obtained by supplying the raw material mixture obtained above in the form of a sheet having a thickness of 20 μm onto the device electrode and the exposed surface of the first substrate by a doctor blade method. After drying this precursor laminate at 100° C. for 10 hours, it is heated at 270° C. for 30 minutes under a pressure of 100 MPa using a heating press, and then heated to 250° C. to remove unnecessary organic matter that may remain. was annealed for 10 hours to form a ceramic portion having a thickness (t) of 20 μm. A 25 μm-thick coverlay (epoxy resin (EP) adhesive layer and polyimide resin (PI) cover layer) were pressed together. After that, it was cut with a dicing saw to obtain a thermistor sample (NTC thermistor) having a width of 0.8 mm, a length of 1.6 mm and a total thickness of about 50 μm as an element member.

Circuit board A 12 μm thick Cu layer is patterned into a predetermined shape by photolithography on a second base material (base layer) that is a 25 μm thick polyimide film, and then the surface of the patterned Cu base material. Then, a Ni plating layer and an Au plating layer were sequentially formed electrolessly. The total thickness of these plating layers was 3 μm. As a result, a pair of rectangular land electrodes made of Cu/Ni/Au (thickness 15 μm) with a width (W ₂ ) of 0.4 mm and a length (L ₂ ) of 0.2 mm were produced together with a pair of lead wires. . On the region including between the pair of land electrodes of the second substrate (including the portion near the land electrodes of the pair of lead wires) so as to expose the pair of obtained land electrodes and cover the other surface, As the second protective layer, a 25 μm-thick coverlay (consisting of an adhesive layer of epoxy resin (EP) and a cover layer of polyimide resin (PI)) was press-bonded. A circuit board having a total thickness of about 50 μm was thus obtained.

・Junction On the pair of land electrodes of the circuit board, a conductive paste mainly composed of SnAgCu-based solder material (consisting of 3% by mass of Ag, 0.5% by mass of Cu, and the balance of Sn) is printed with a thickness of 60 μm. Then, the thermistor sample prepared above as an element member was placed on a circuit board so that the pair of land electrodes and the pair of external electrodes faced each other, and subjected to reflow at 240° C. for 10 seconds to form a circuit. A thermistor sample was mounted on the board. Thus, a joined structure of Example 1 was obtained.

(Examples 2-3 and Comparative Example 1)
Examples 2 and 3 relate to the bonded structure described above in the first embodiment.

Same as Example 1 except that the thickness (t) of the ceramic portion was set to 30 μm (Example 2), 40 μm (Example 3), and 50 μm (Comparative Example 1) (the total thickness of the thermistor sample was about 50 μm). Then, a bonded structure was obtained.

(Example 4)
Example 4 relates to an aspect (that is, a modified example of Embodiment 1) in which the first protective layer and the first base material do not contain a metal film in the bonded structure described above in Embodiment 3.

After forming the joints, between the element member (thermistor sample) and the circuit board, a room temperature curing silicone resin is supplied around the pair of joints, left to stand for an appropriate time, and the joints A bonded structure was obtained in the same manner as in Example 1, except that the space around and in the vicinity of was filled with the cured silicone resin.

(Example 5)
Example 5 relates to an aspect (that is, a modified example of Embodiment 1) in which the first protective layer and the first base material do not contain a metal film in the bonded structure described above in Embodiment 3.

(i) a 25 μm thick liquid crystal polymer (LCP) film was placed as the first protective layer instead of a 25 μm thick coverlay (total thickness of the thermistor sample about 50 μm), and (ii) After forming the joints, between the element member (thermistor sample) and the circuit board, a room temperature curing silicone resin is supplied around the pair of joints, left to stand for an appropriate time, and the joints A bonded structure was obtained in the same manner as in Example 1, except that the space around and in the vicinity of was filled with the cured silicone resin.

(Example 6)
Example 6 relates to a mode in which the first protective layer and the first base material in the bonded structure described above in Embodiment 3 contain a metal film (that is, a modified example of Embodiment 2).

(i) As a first substrate, a Cu foil (thickness 12 μm) having the same dimensions as the ceramic part is placed on the lower surface side (the surface opposite to the main surface) of a polyimide film (base layer) having a thickness of 25 μm. (ii) as a first protective layer, a 25 μm thick liquid crystal polymer (LCP) film was placed on top of which a ceramic placing a Cu foil (12 μm thick) of the same dimensions as the part, on top of which a 12 μm thick liquid crystal polymer (LCP) film was placed (total thickness of the thermistor sample about 100 μm), and (iii ) After forming the joints, between the element member (thermistor sample) and the circuit board, a room temperature curing silicone resin is supplied around the pair of joints, left to stand for an appropriate time, and joined A bonded structure was obtained in the same manner as in Example 1, except that the space around and in the vicinity of the part was filled with the cured silicone resin.

(Example 7)
Example 7 relates to a mode in which the first protective layer and the first base material include a metal film in the bonded structure described above in Embodiment 4 (that is, a modified example of Embodiment 2).

(i) As a first substrate, a Cu foil (thickness 12 μm) having the same dimensions as the ceramic part is placed on the lower surface side (the surface opposite to the main surface) of a polyimide film (base layer) having a thickness of 25 μm. (ii) as a first protective layer a 25 μm thick liquid crystal polymer (LCP) film was used, on top of which a ceramic A Cu foil (12 μm thick) of the same dimensions as the part was placed, and a 12 μm thick liquid crystal polymer (LCP) film was placed on top of it (total thickness of the thermistor sample was about 100 μm), and (iii ) A bonded structure was obtained in the same manner as in Example 1, except that a polyethylene (PE) film was pressure-bonded around the pair of land electrodes before the conductive paste was printed. Note that PE is a thermoplastic resin, which once melted during heating (reflow) during bonding with a solder material, naturally deformed, and then solidified to cover the periphery of the bonded portion.

(Examples 8-10)
Examples 8-10 relate to the bonded structure described above in Embodiment 1.

(i) The dimensions of the pair of external electrodes of the element member (thermistor sample) were rectangular with a width (W ₁ ) of 0.4 mm and a length (L ₁ ) of 0.1 mm, and (ii) a pair of circuit boards. The dimensions of the land electrodes of are rectangular with a width (W ₂ ) of 0.4 mm and a length (L ₂ ) of 0.2 mm (Example 8), 0.3 mm (Example 9), and 0.35 mm (Example 10). A bonded structure was obtained in the same manner as in Example 1, except for the above.

(Example 11)
Example 11 relates to a mode in which the first protective layer and the first base material in the bonded structure described above in Embodiment 5 include a metal film (that is, a modified example of Embodiment 2).

(i) As a first substrate, a Cu foil (thickness 12 μm) having the same dimensions as the ceramic part is placed on the lower surface side (the surface opposite to the main surface) of a polyimide film (base layer) having a thickness of 25 μm. (ii) forming a ceramic part adjacent to a pair of external electrodes; (iii) as the first protective layer, the thickness A liquid crystal polymer (LCP) film with a thickness of 25 μm is placed, a Cu foil (thickness of 12 μm) having the same dimensions as the ceramic part is placed thereon, and a liquid crystal polymer (LCP) film with a thickness of 12 μm is further placed thereon. (iii) the element member and the circuit board were placed (total thickness of the thermistor sample: about 100 μm); A bonded structure was obtained in the same manner as in Example 1, except that an anisotropic conductive film (ACF) with a thickness of 25 μm contained in was used for (crimping) bonding.

(Comparative example 2)
Comparative Example 2 relates to a bonded structure in which a conventional general chip component is bonded to a circuit board.

Instead of element members, commercially available chip parts (NTC thermistor manufactured by Murata Manufacturing Co., Ltd., see chip part 50 shown in FIG. 14. A pair of internal electrodes 43a and 43b and a pair of external electrodes 44a and 44b are made of Ag—Pd, the thickness (t) of the ceramic portion 45 is 0.8 mm, the overall length is 1.6 mm and the overall width is 0.8 mm, and the dimensions of the bonding area of the external electrodes are the width ( A bonded structure (see FIG. 14) was obtained in the same manner as in Example 1 except that W ₁ was 0.4 mm and length (L ₁ ) was 0.2 mm.

(Comparative Example 3)
Comparative Example 3 relates to a bonded structure in which a conventional general chip component is bonded to a circuit board.

After forming the joints, a room-temperature curing silicone resin is supplied around the pair of joints between the chip component and the circuit board, left to stand for an appropriate period of time, and the surroundings of the joints and therebetween. A bonded structure was obtained in the same manner as in Comparative Example 2, except that the adjacent space was filled with the cured silicone resin.

(evaluation)
The joint structures produced in Examples 1 to 11 and Comparative Examples 1 to 3 were subjected to an immersion test in water to examine changes in resistance value (average time until migration occurred) and evaluate their stability.

For each example and comparative example, three bonded structures were prepared in the same manner, and a voltage of 5 V was applied to them (without being immersed in pure water). A voltage of 5 V was applied to the samples while they were immersed in pure water, and the average time until the resistance value changed by 3% or more from the initial value was measured. If the resistance value changes by 3% or more, it can be considered that migration has occurred. When the resistance value did not change by 3% or more even after 500 hours from the start of immersion and voltage application, it was examined whether the resistance value changed by 3% or more at 1000 hours after 500 hours. Table 1 shows the results. (In Table 1, ">500hr" means that the resistance value did not change by 3% or more at the time of 500 hours, but the resistance value changed by 3% or more at the time of 1000 hours. means that the resistance value changed by 3% or more even after 1000 hours.)

* 1st base material: LCP+Cu+PI about 50μm
** chip parts

For the bonded structure in which migration occurred, visual observation and elemental analysis by EDX were performed together.
In all of Examples 1 to 3 and Comparative Example 1, migration occurred due to dissolution of the internal electrode in the vicinity of the external electrode, resulting in high resistance. In particular, in Comparative Example 1, clear areas where the adhesion of the first protective layer was insufficient were observed. However, in Examples 1 to 3, compared to Comparative Example 1, it was confirmed that the time until migration occurred was longer, and higher resistance value stability was exhibited.
In Example 4, Cu dendrites were observed after 500 hours and the resistance decreased, and in Examples 5 and 6, no change of 3% or more in resistance value was observed even after 1000 hours. From these results, it is preferable to coat the solder joints with silicone resin rather than as they are. However, it was confirmed that LCP is preferable.
In Examples 8 and 9, the solder joints were able to cover the external electrodes and the land electrodes, but in Example 10, the solder joints could not sufficiently cover the land electrodes, resulting in high resistance due to dissolution of the land electrodes. bottom.
In Example 11, migration resistance of 1000 hours or longer, similar to Examples 5 to 7, was confirmed.
In Comparative Examples 2 and 3, Ag dendrites were observed and the resistance was lowered.

The joint structure of the present disclosure is suitably used in electronic devices that can be used in high humidity environments, but is not limited to such uses.

This application claims priority based on Japanese Patent Application No. 2021-114406 filed in Japan on July 9, 2021, the entire contents of which are incorporated herein by reference.

1, 1' first substrate 2, 2a, 2b element electrodes 3a, 3b, 3a', 3b' internal electrodes 4a, 4b, 4a', 4b' external electrodes 5, 5' ceramic portions 6, 6' first protection Layers 7, 7' First metal layers 8, 8' Second metal layers 10, 10' Element members 11, 11' Second substrates 14a, 14b, 14a', 14b' Land electrodes 15a, 15b, 15a', 15b 'Leader lines 16, 16' Second protective layers 20, 20' Circuit boards 30a, 30b Joints (solder material)
30' junction (anisotropic conductive material)
31 cured resin material 32, 32' thermoplastic resin material 33 conductive particles 34 resin material 40, 41, 42, 43, 44 joint structure 43a, 43b internal electrode 44a, 44b external electrode 45 ceramic part 50 chip component 60 joint structure body

Claims (17)

1. An element member in which a ceramic part and element electrodes including a pair of internal electrodes and a pair of external electrodes are formed on a first substrate, the ceramic part being covered with a first protective layer, and the pair of external electrodes is exposed from the first protective layer, the pair of internal electrodes are located in the ceramic portion, and the thickness of the ceramic portion is 40 μm or less;
   a circuit board having a pair of land electrodes formed on a second substrate;
   electrically connecting the pair of external electrodes and the pair of land electrodes facing each other in a state in which the ceramic part and the first protective layer are arranged between the first base material and the second base material; A bonded structure comprising a bonding joint.
2. The surface of the first protective layer opposite to the first substrate protrudes toward the second substrate from the surfaces of the pair of external electrodes opposite to the first substrate. The bonded structure of claim 1, wherein
3. 3. The joining structure according to claim 1, wherein the circuit board has a second protective layer disposed on the second base material, and the pair of land electrodes are exposed from the second protective layer. body.
4. The surface of the second protective layer opposite to the second substrate protrudes toward the first substrate more than the surfaces of the pair of land electrodes opposite to the second substrate. 4. The bonded structure of claim 3, wherein:
5. The bonded structure according to any one of claims 1 to 4, wherein the first protective layer contains a first resin material.
6. The first resin material is polyimide resin, polyamideimide resin, epoxy resin, liquid crystal polymer, polyethylene resin, polypropylene resin, polystyrene resin, polyester resin, polyurethane resin, polyamide resin, polyetherimide. The joint structure according to claim 5, comprising at least one selected from the group consisting of acrylic resins and (meth)acrylic resins.
7. The bonded structure according to claim 5 or 6, wherein the first protective layer further includes a first metal layer.
8. The bonded structure according to any one of claims 1 to 7, wherein the first base material includes a second resin material and a second metal layer.
9. The bonded structure according to any one of claims 1 to 8, wherein the second base material is a flexible substrate containing a third resin material.
10. The joint structure according to any one of claims 1 to 9, wherein the joint contains a solder material.
11. 11. The junction structure according to claim 10, wherein the area of the junction regions of the pair of land electrodes is three times or less the area of the junction regions of the pair of external electrodes.
12. The joint structure according to any one of claims 1 to 11, wherein the joint portion is coated with a cured resin material as a fourth resin material.
13. The joint structure according to any one of claims 1 to 11, wherein the joint portion is coated with a thermoplastic resin material as the fifth resin material.
14. The joint structure according to any one of claims 1 to 9, wherein the joint contains an anisotropically conductive material.
15. The joint structure according to any one of claims 1 to 14, wherein the ceramic portion is formed between the pair of external electrodes.
16. The joint structure according to any one of claims 1 to 14, wherein the ceramic portion is formed adjacent to the pair of external electrodes.
17. The joint structure according to any one of claims 1 to 16, wherein the ceramic part contains a thermistor material, and the joint structure is a temperature sensor.

Images