Method for manufacturing joined body, joined body, and conductive particle-containing hot melt adhesive sheet

Abstract

To provide a method for manufacturing a joined body which can obtain excellent adhesive strength and connection reliability, a joined body, and a conductive particle-containing hot-melt adhesive sheet.SOLUTION: A method for manufacturing a joined body includes thermally compressing a first electronic component 10 and a second electronic component 20 through a conductive particle-containing hot-melt adhesive sheet containing solder particles in a binder containing a crystalline polyamide resin having a carboxyl group, and connecting a conductive part 11 of the first electronic component 10 and a conductive part 21 of the second electronic component 20. A melting point of the solder particles is -30 to 0°C that is a thermal compression temperature. When melt viscosity of the conductive particle-containing hot-melt adhesive sheet is measured on the condition of a rate of temperature rise of 5°C / min, a ratio of melt viscosity at -40°C that is the thermal compression temperature to melt viscosity at -20°C that is the thermal compression temperature is 10 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present technology relates to a method for producing a bonded body using a hot melt adhesive sheet containing conductive particles, and to the bonded body. [Background technology]

[0002] Conventionally, connecting materials such as anisotropic conductive film (ACF) and anisotropic conductive paste (ACP) have been used as means for connecting electronic components. ACF is, for example, a film-like connecting material made by dispersing conductive particles in an insulating binder containing a thermosetting resin. ACP is, for example, a paste-like connecting material made by dispersing conductive particles in an insulating binder containing a thermosetting resin. The electrodes of electronic components to be anisotropically connected are thermocompression-bonded via ACF or ACP, thereby thermally curing the binder containing the thermosetting resin to achieve the connection. These ACFs and ACPs are examples of adhesive films or adhesives containing conductive particles.

[0003] In recent years, there has been a demand for low-temperature, low-pressure, and short-time connections between electronic components. Connections at low temperatures are required from the perspective of reducing thermal damage to electronic components, preventing variations in heating temperature during connection, and reducing the load on mounting equipment. Connections at low pressure are required from the perspective of preventing damage caused by the characteristics of the board (thinness, configuration, and material of the board). Connections in short times are required from the perspective of productivity, etc.

[0004] However, because conventional ACFs use thermosetting resins, if they are to be connected at low temperatures and in a short time, the storage period must be shortened because hardening occurs during storage, making them unsuitable for practical use. Also, from the perspective of productivity, storage stability of approximately 1 to 2 years at room temperature is sometimes required, but this is sometimes difficult to achieve with ACFs that use thermosetting resins.

[0005] Therefore, thermoplastic ACFs made of crystalline resins and amorphous resins have been proposed as ACFs that enable connections at low temperatures, low pressures, and in a short time while maintaining sufficient connection resistance (see, for example, Patent Document 1). Such ACFs and ACPs are used for anisotropic conductive connections between a first electronic component and a second electronic component, each of which has a plurality of opposing terminals, and are also used for anisotropic conductive connections when at least one of the first electronic component or the second electronic component has a full-surface electrode. Naturally, they can also be used for electrical connections in which both terminals are full-surface electrodes.

[0006] However, even with these ACFs, when the electrode surfaces of electronic components are OSP-treated (water-soluble preflux-treated), excellent adhesive strength and connection reliability may not be obtained. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 5964187 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-117468 Summary of the Invention [Problem to be solved by the invention]

[0008] The present technology has been proposed in view of the above-described conventional situation, and provides a method for manufacturing a bonded body that can achieve excellent adhesive strength and connection reliability, a bonded body, and a hot-melt adhesive sheet containing conductive particles. [Means for solving the problem]

[0009] The method for manufacturing a bonded body according to the present technology includes bonding a first electronic component and a second electronic component together using a conductive particle-containing hot melt adhesive, the conductive particle-containing hot melt adhesive including solder particles in a binder containing a crystalline polyamide resin having a carboxyl group and a crystalline polyester resin, and the proportion of the crystalline polyamide resin in the binder is 50 wt % or more. adhesive sheeta method for manufacturing a bonded body in which conductive parts of the first electronic component and conductive parts of the second electronic component are connected by thermocompression bonding via a conductive particle-containing hot melt adhesive sheet, wherein the melting point of the solder particles is −30 to 0°C of the thermocompression bonding temperature and is 130 to 160°C, and when the melt viscosity of the conductive particle-containing hot melt adhesive sheet is measured under conditions of a temperature rise rate of 5°C / min, the ratio of the melt viscosity at the thermocompression bonding temperature of −40°C to the melt viscosity at the thermocompression bonding temperature of −20°C is 10 or more.

[0010] The bonded structure according to the present technology includes a first electronic component, a second electronic component, and an adhesive layer that connects a conductive portion of the first electronic component to a conductive portion of the second electronic component, the adhesive layer being made of a crystalline polyamide resin having a carboxyl group. and a crystalline polyester resin. The solder particles have a melting point of 130 to 160°C in a binder containing the The proportion of the crystalline polyamide resin in the binder is 50 wt % or more, When the melt viscosity is measured at a temperature increase rate of 5°C / min, the ratio of the melt viscosity at 100°C to the melt viscosity at 120°C is 10 or more.

[0011] The conductive particle-containing hot melt adhesive sheet according to the present technology is made of a crystalline polyamide resin having a carboxyl group. and a crystalline polyester resin. The solder particles have a melting point of 130 to 160°C in a binder containing the The proportion of the crystalline polyamide resin in the binder is 50 wt % or more, When the melt viscosity is measured at a temperature increase rate of 5°C / min, the ratio of the melt viscosity at 100°C to the melt viscosity at 120°C is 10 or more. [Effects of the Invention]

[0012] According to the present technology, the carboxyl group-containing crystalline polyamide improves solder wettability, and excellent adhesive strength and connection reliability can be obtained. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an example of a bonded body according to the present embodiment. [Figure 2] FIG. 2 is a schematic perspective view showing an example of a smart card. [Figure 3] FIG. 3 is a top view showing an example of an IC chip area of ​​a card member. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present technology will be described in detail in the following order with reference to the drawings. 1.Zygote 2. Manufacturing method of the bonded body 3. Hot melt adhesive sheet containing conductive particles 4. Working Example

[0015] <1.Zygote> The bonded assembly according to this embodiment includes a first electronic component, a second electronic component, and an adhesive layer connecting the conductive parts of the first electronic component and the conductive parts of the second electronic component, the adhesive layer containing solder particles having a melting point of 130 to 160°C in a binder containing a crystalline polyamide resin having a carboxyl group, and when the melt viscosity is measured at a temperature rise rate of 5°C / min, the ratio of the melt viscosity at 100°C to the melt viscosity at 120°C is 10 or more. This improves solder wettability, and provides excellent adhesive strength and connection reliability.

[0016] The viscosity of the adhesive layer at 100°C is preferably 8,000 to 800,000 Pa·s, more preferably 15,000 to 500,000 Pa·s, and even more preferably 20,000 to 300,000 Pa·s. The viscosity of the adhesive layer at 120°C is preferably 100 to 20,000 Pa·s, more preferably 500 to 15,000 Pa·s, and even more preferably 1,000 to 8,000 Pa·s. The melt viscosity of the adhesive layer can be measured, for example, using a rotational rheometer (manufactured by HAAKE) under the following conditions: gap 0.2 mm, temperature range 60 to 200°C, heating rate 5°C / min, measurement frequency 1 Hz, and measurement plate diameter 8 mm. The melt viscosity temperature can be set depending on various conditions, such as the characteristics of the substrates and the mass productivity of the connection, and may therefore be changed depending on the objects to be connected and the various conditions of the connection.

[0017] Fig. 1 is a cross-sectional view schematically illustrating an example of a bonded structure according to the present embodiment. As shown in Fig. 1, the bonded structure includes a first electronic component 10 having a first conductive portion 11, a second electronic component 20 having a second conductive portion 21, and an adhesive layer 30 made of a conductive particle-containing hot-melt adhesive sheet that connects the conductive portion 11 of the first electronic component 10 to the conductive portion 21 of the second electronic component 21. Here, the first conductive portion 11 and the second conductive portion 21 are not particularly limited and may be electrodes, wires, terminal arrays, or the like, and can be selected from a variety of forms.

[0018] Examples of the first electronic component 10 include a smart card member on which a second electronic component can be mounted, and a substrate (so-called printed wiring board: PWB) that can be broadly defined as a rigid substrate, a glass substrate, a flexible substrate (FPC: Flexible Printed Circuits), a ceramic substrate, a plastic substrate, and the like.

[0019] Examples of the second electronic component 20 include chips (elements) such as smart card IC chips, LEDs (Light Emitting Diodes), driver ICs (Integrated Circuits), flexible printed circuits (FPCs), and resin-molded components that are provided with wiring (conductive materials).

[0020] As described below, the adhesive layer 30 is a film of a conductive particle-containing hot melt adhesive sheet containing solder particles in a binder. The adhesive layer 30 solders the first conductive portion 11 of the first electronic component 10 and the second conductive portion 21 of the second electronic component 20 together at a solder joint 32, and also bonds the first electronic component 10 and the second electronic component together using a binder. When the first conductive portion 11 and the second conductive portion 21 face each other and are each composed of a set of individually independent electrodes, an anisotropic conductive connection is achieved, and the conductive particle-containing hot melt adhesive sheet according to the present technology can be used. The conductive particle-containing hot melt adhesive sheet according to the present technology can also be used for an (isotropic) conductive connection when the first conductive portion 11 and the second conductive portion 21 are each composed of an electrode covering the entire surface. Furthermore, the conductive particle-containing hot melt adhesive sheet according to the present technology can be used in a case where one conductive part is composed of a set of individually independent electrodes and the other conductive part is composed of a full-surface electrode. This is also true for known anisotropic conductive films. Needless to say, from a technical standpoint, "anisotropy" is more difficult to achieve in terms of conductivity.

[0021] The bonded structure according to the present embodiment includes a crystalline polyamide having carboxyl groups, and an adhesive layer containing solder particles having a predetermined melting point in a binder having a predetermined melt viscosity relationship. This improves solder wettability, enabling excellent adhesive strength and connection reliability to be achieved even when the electrode surfaces of the electronic components are OSP-treated (water-soluble preflux-treated). This is believed to be due to the flux effect of the carboxyl groups present in the crystalline polyamide. Furthermore, the bonded structure according to the present embodiment forms a metal bond between the conductive portions of the first electronic component and the second electronic component through the melting of the solder particles. This reduces swelling and elongation due to moisture absorption by the binder during a wet heat test, thereby achieving excellent connection reliability.

[0022] Next, as a specific example of a bonded assembly, a smart card using a card member as the first electronic component 10 and an IC chip as the second electronic component will be described. A smart card is a card incorporating an integrated circuit (IC) for recording and calculating information (data), and is also called an "integrated circuit card (IC card)" or "chip card." A smart card may also be a dual-interface card having two interfaces, contact and contactless, in a single IC chip, or a hybrid card equipped with a contact IC chip and a contactless IC chip. Unlike general IC chips used for displays, etc., the IC chip used in this smart card generally does not have multiple terminal rows. The IC chip described below will be an IC chip used in a smart card.

[0023] Fig. 2 is a schematic perspective view showing an example of a smart card, and Fig. 3 is a top view showing an example of an IC chip area of ​​a card member. The smart card comprises a card member 40 and an IC chip 50. The card member 40 is a laminate in which a first substrate, a second substrate having an antenna, and a third substrate are laminated in this order. The IC chip 50 has multiple contact terminals 51 on its front surface and electrodes on its back surface, for example, covering the entire surface.

[0024] The first substrate, the second substrate, and the third substrate are each formed, for example, by laminating multiple layers made of resin. Examples of resins that can be used to form each layer include recycled PVC (polyvinyl chloride), PET (polyethylene terephthalate), PET-G, and PC (polycarbonate), environmentally friendly biodegradable plastics (e.g., PLA (polylactic acid)), and ocean plastics, which are substrates made from plastic waste collected before it ends up in the ocean. By forming the substrate from multiple layers, it is possible to prevent the rigidity from becoming unnecessarily high compared to a substrate made from a single layer.

[0025] The first substrate has an opening 41 corresponding to the shape of the IC chip 50, and the opening 41 exposes the second substrate, forming an IC chip area. The second substrate is disposed between the first substrate and the third substrate, and has an antenna pattern 42 that wraps around its outer periphery multiple times within a layer made of, for example, resin. The second substrate is also cut away in the IC chip area facing the opening 41 to form a recess corresponding to the back surface of the IC chip 50, for example, so that a portion of the embedded antenna pattern is exposed. That is, the recess in the second substrate corresponds to the shape of the opening 41, and a first exposed portion 42a and a second exposed portion 14b of the antenna pattern 42 are formed in the IC chip area. The metal wire of the antenna pattern 42 can be, for example, a copper wire.

[0026] The second base material preferably has a non-through hole such as a groove or a plurality of holes in the IC chip area. This allows the resin of the adhesive layer to flow into the grooves or holes, improving adhesion to the adhesive layer. The minimum length of the opening of the grooves or holes is preferably smaller than the average particle diameter of the solder particles. The lower limit of the minimum length of the opening of the grooves or holes is preferably 20% or more of the average particle diameter of the solder particles, more preferably 30% or more, and particularly preferably 40% or more. The upper limit of the minimum length of the opening of the holes is preferably 80% or less of the average particle diameter of the solder particles, more preferably 70% or less, and particularly preferably 60% or less. This makes it easier for the solder particles to fit into the grooves or holes, improving the solder particle capture and achieving excellent electrical connection with the IC chip.

[0027] The adhesive layer is interposed between the IC chip region of the opening 41 and the IC chip 50, and electrically connects the IC chip 50 to the first exposed portion 42a and the second exposed portion 42b of the antenna pattern 42. Note that the connection between the IC chip 50 and the antenna pattern 42 may not be anisotropic.

[0028] The smart card shown as an example includes an adhesive layer containing solder particles with a specific melting point in a binder with a specific melt viscosity relationship, which contains a crystalline polyamide with carboxyl groups. This improves solder wettability and provides excellent adhesive strength and connection reliability. This is believed to be due to the flux effect of the carboxyl groups present in the crystalline polyamide. Furthermore, the smart card shown as an example minimizes swelling and elongation due to moisture absorption of the binder during a wet heat test, thereby achieving excellent connection reliability. This technology can also be applied to general anisotropic connectors other than smart cards, such as FOBs consisting of a rigid substrate and an FPC, but details are omitted here. The scope of application of this technology is also similar to the manufacturing method of a bonded assembly.

[0029] <2. Method for manufacturing the bonded body> The method for manufacturing a bonded body according to this embodiment involves thermocompression bonding a first electronic component and a second electronic component together via a conductive particle-containing hot melt adhesive sheet containing solder particles in a binder containing a crystalline polyamide resin having carboxyl groups, thereby connecting the conductive portions of the first electronic component and the second electronic component. The melting point of the solder particles is between −30°C and 0°C of the thermocompression bonding temperature, and when the melt viscosity of the conductive particle-containing hot melt adhesive sheet is measured at a temperature rise rate of 5°C / min, the ratio of the melt viscosity at −40°C of the thermocompression bonding temperature to the melt viscosity at −20°C of the thermocompression bonding temperature is 10 or greater. This improves solder wettability, resulting in excellent adhesive strength and connection reliability. The temperature conditions for this viscosity can be varied depending on the manufacturing method for the bonded body.

[0030] Hereinafter, with reference to FIG. 1, the attachment process (A) of attaching a conductive particle-containing hot melt adhesive sheet to a second electronic component, the placement process (B) of placing the second electronic component on the first electronic component, and the pressure-bonding process (C) of thermocompression-bonding the first electronic component and the second electronic component will be described.

[0031] [Attachment process (A)] In the attachment step (A), a conductive particle-containing hot melt adhesive sheet is attached to the connection surface of the second electronic component 20. The attachment step (A) may be a lamination step in which the conductive particle-containing hot melt adhesive sheet is laminated onto the connection surface of the second electronic component, or may be a temporary attachment step in which the conductive particle-containing hot melt adhesive sheet is attached to the connection surface of the second electronic component 20 at a low temperature.

[0032] When the attachment process (A) is a lamination process, either a pressure laminator or a vacuum pressure laminator may be used. Because the attachment process (A) is a lamination process, a relatively large area can be mounted at once compared to a temporary attachment process. Furthermore, when the attachment process (A) is a temporary attachment process, only minimal changes, such as the installation or modification of tools, are required from the previous equipment, resulting in economic benefits.

[0033] In the attachment step (A), the temperature reached by the conductive particle-containing hot melt adhesive sheet is preferably equal to or higher than the temperature at which the binder flows and lower than the temperature at which the solder melts. The temperature at which the binder flows may be a temperature at which the melt viscosity of the conductive particle-containing hot melt adhesive sheet is 100 to 1,000,000 Pa·s, preferably 1,000 to 100,000 Pa·s. This allows the conductive particle-containing hot melt adhesive sheet to be attached to the connecting surface of the second electronic component 20 while maintaining the shape of the solder particles. The melt viscosity of the conductive particle-containing hot melt adhesive sheet can be measured, for example, using a rotational rheometer (manufactured by HAAKE) under the following conditions: gap 0.2 mm, temperature range 60 to 200°C, heating rate 5°C / min, measurement frequency 1 Hz, and measurement plate diameter 8 mm.

[0034] [Placement process (B)] In the placement process (B), the second electronic component 20 is picked up using, for example, a tool equipped with an adsorption mechanism, the first electronic component 10 and the second electronic component 20 are aligned, and the second electronic component 20 is placed via a hot-melt adhesive sheet containing conductive particles.

[0035] [Crimping process (C)] In the pressure-bonding step (C), a pressure-bonding device is used to thermocompression-bond the first electronic component 10 and the second electronic component 20. In the pressure-bonding step (C), the binder in the conductive particle-containing hot-melt adhesive sheet is sufficiently removed, and the conductive parts 11 of the first electronic component 10 and the conductive parts 21 of the second electronic component 20 are solder-bonded 32 by melting the solder particles 31.

[0036] The thermocompression bonding temperature in the pressure-bonding step (C) is preferably set so that the temperature reached by the conductive particle-containing hot-melt adhesive sheet is equal to or higher than the melting point of the solder particles. The upper limit of the temperature reached by the conductive particle-containing hot-melt adhesive sheet is preferably 0 to +30°C above the melting point of the solder particles, more preferably 0 to +20°C above the melting point of the solder particles, and even more preferably 0 to +10°C above the melting point of the solder particles. Specifically, the temperature reached by the conductive particle-containing hot-melt adhesive sheet is preferably 120 to 180°C, more preferably 120 to 170°C, and even more preferably 130 to 160°C. This suppresses thermal shock to the first electronic component 10 and the second electronic component 20 and prevents deformation of the bonded assembly. Furthermore, in the pressure-bonding step (C), thermocompression bonding may be performed multiple times to sufficiently remove the binder from the conductive particle-containing hot-melt adhesive sheet and to melt the solder particles to form a metal bond.

[0037] The method for manufacturing a bonded body according to this embodiment uses a conductive particle-containing hot-melt adhesive sheet containing solder particles having a predetermined melting point in a binder containing a carboxyl-containing crystalline polyamide and having a predetermined melt viscosity relationship. This improves solder wettability and provides excellent adhesive strength and connection reliability, even when the electrode surface of an electronic component is OSP-treated (water-soluble preflux-treated). This is believed to be due to the flux effect of the carboxyl groups present in the crystalline polyamide. Furthermore, the method for manufacturing a bonded body according to this embodiment forms a metallurgical bond between the conductive parts of the first electronic component and the conductive parts of the second electronic component by melting the solder particles. This suppresses swelling and elongation due to moisture absorption by the binder during a wet heat test, thereby providing excellent connection reliability.

[0038] <3. Hot melt adhesive sheet containing conductive particles> The conductive particle-containing hot melt adhesive sheet according to this embodiment contains solder particles having a melting point of 130 to 160°C in a binder containing a crystalline polyamide resin having carboxyl groups, and when the melt viscosity is measured at a temperature increase rate of 5°C / min, the ratio of the melt viscosity at 100°C to the melt viscosity at 120°C is 10 or more. This improves solder wettability, and provides excellent adhesive strength and connection reliability. The temperature conditions at which this viscosity is exhibited can be changed depending on the manufacturing method of the bonded body.

[0039] The lower limit of the thickness of the conductive particle-containing hot melt adhesive sheet is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. The upper limit of the thickness of the conductive particle-containing hot melt adhesive sheet is preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 60 μm or less. This makes it suitable for use in the production of smart cards in which an IC chip is thermocompression bonded to a card member.

[0040] [binder] The binder contains at least a crystalline polyamide having a carboxyl group. The crystalline resin can be confirmed by, for example, observing an endothermic peak during the temperature rise process in differential scanning calorimetry.

[0041] The terminal carboxyl group concentration of the crystalline polyamide is preferably 0.5 mg KOH / g or more, more preferably 1.0 mg KOH / g or more, and even more preferably 2.0 mg KOH / g or more. The terminal carboxyl group concentration of the crystalline polyamide may be 50 mg KOH / g or less, 30 mg KOH / g or less, or 10 mg KOH / g or less. The terminal carboxyl group concentration of the crystalline polyamide can be evaluated, for example, in accordance with JIS K 0070-1992 or ISO 2114. Specific examples of commercially available crystalline polyamides having carboxyl groups include "HX2519" and "M1276" manufactured by Arkema Inc.

[0042] The carboxyl-containing crystalline polyamide is preferably a copolymer based on lauryllactam (PA12: polyamide 12 or nylon 21) or 11-aminoundecanoic acid (PA11: polyamide 11) as a monomer. Compared to polyamides based on dimer acid, such copolymers have higher crystallinity, higher melt viscosity, and higher rigidity, resulting in excellent connection reliability.

[0043] The lower limit of the melting point of the carboxyl-containing crystalline polyamide is preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 90°C or higher. The upper limit of the melting point of the carboxyl-containing crystalline polyamide is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. If the melting point of the carboxyl-containing crystalline polyamide is too high, the viscosity of the binder will not decrease sufficiently, resulting in insufficient resin removal and poor conductive properties. If the melting point of the carboxyl-containing crystalline polyamide is too low, the hardness during press-out will tend to be insufficient. The melting point can be measured, for example, by differential scanning calorimetry (DSC).

[0044] The lower limit of the weight-average molecular weight of the crystalline polyamide having carboxyl groups is preferably 5,000 or more, more preferably 8,000 or more, even more preferably 10,000 or more, and most preferably more than 10,000. The upper limit of the weight-average molecular weight of the crystalline polyamide having carboxyl groups is preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. If the weight-average molecular weight of the crystalline polyamide having carboxyl groups is too low, the binder may not cure sufficiently, resulting in problems such as increased resistance in connection reliability tests. The weight-average molecular weight Mw can be, for example, a value measured by gel permeation chromatography (GPC) and converted into a standard polystyrene molecular weight.

[0045] The crystalline polyamide having a carboxyl group preferably has a melt volume flow rate (MVR) of 2 to 50 cm when measured at a temperature of 160°C and a load of 2.16 kg. 3 / 10 min, preferably 3 to 30 cm 3 / 10 min, more preferably 5 to 10 cm 3 / 10 min. If the melt volume flow rate is too high, the hardness at press-out tends to be insufficient, and the connection reliability tends to decrease. The melt volume flow rate can be measured in accordance with the method for determining the melt flow rate of thermoplastic plastics specified in JIS K7210:1999.

[0046] By including at least a crystalline polyamide having a carboxyl group in the binder, solder wettability can be improved and excellent connection reliability can be obtained, which is thought to be due to the flux effect of the carboxyl group present in the crystalline polyamide.

[0047] The binder may also contain other components as necessary. The other components may be selected appropriately depending on the purpose, such as a crystalline resin or an amorphous resin. The crystalline resin is not particularly limited as long as it has a crystalline region, and examples thereof include polyester resin, polyolefin resin, and polyurethane resin. Examples of polyester resins include polyethylene terephthalate resin and polybutylene terephthalate resin, and examples of polyolefin resins include polyethylene resin, polypropylene resin, and polybutylene resin. Examples of amorphous resins include those exemplified in the description of the crystalline resin. Among these, it is preferable to include a crystalline polyester resin as the other component from the viewpoint of adhesion at low temperature and in a short time.

[0048] Furthermore, the proportion of the crystalline polyamide having carboxyl groups in the binder is preferably 10 to 100 wt%, more preferably 30 to 100 wt%, and even more preferably 50 to 100 wt%. This allows the flux effect to be exerted even in low-temperature compression bonding at 160°C or less, improving solder wettability and achieving excellent connection reliability. Note that in the case of low-temperature, short-time compression bonding, such as for card applications, if the proportion of the crystalline polyamide having carboxyl groups in the binder is 10 wt% or less, it becomes difficult to obtain a sufficient flux effect.

[0049] The binder may further contain a flux compound. Examples of flux compounds include carboxylic acids such as levulinic acid, maleic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and sebacic acid. The content of the flux compound is preferably 1 to 15 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 1 to 5 parts by mass, per 100 parts by mass of the binder. This allows for good solder joints to be obtained.

[0050] The binder preferably has a melt volume flow rate (MVR) measured at a temperature of 160°C under a load of 2.16 kg, which is the same as that of the crystalline polyamide having a carboxyl group. That is, the melt volume flow rate (MVR) is preferably 2 to 50 cm 3 / 10 min, preferably 3 to 30 cm 3 / 10 min, more preferably 5 to 10 cm 3 If the melt volume flow rate is too large, the hardness at the time of press-out becomes insufficient, and the connection reliability tends to decrease.

[0051] [Solder particles] The solder particles are not particularly limited as long as they are non-eutectic alloys, but are preferably alloys containing two or more elements selected from the group consisting of Sn, Bi, Ag, In, Cu, Sb, Pb, and Zn. Examples of solder particles include Sn-Pb, Pb-Sn-Sb, Sn-Sb, Sn-Pb-Bi, Bi-Sn, Sn-Bi-Cu, Sn-Cu, Sn-Pb-Cu, Sn-In, Sn-Ag, Sn-Pb-Ag, and Pb-Ag, as defined in JIS Z 3282-2017 (corresponding international standard: ISO 9453:2014). These solder particles can be appropriately selected depending on the electrode material and connection conditions. Non-eutectic alloy solder particles remain semi-molten for a longer period of time during thermocompression bonding than eutectic alloy solder particles, allowing for sufficient removal of resin and achieving excellent connection reliability. In this specification, the term "non-eutectic alloy" refers to an alloy that does not have a eutectic point.

[0052] The lower limit of the solidus temperature (melting point) of the solder particles is preferably 120°C or higher, more preferably 130°C or higher, and even more preferably 135°C or higher. The upper limit of the liquidus temperature of the solder particles may be 210°C or lower, preferably 200°C or lower, more preferably 195°C or lower, and even more preferably 190°C or lower. Here, the liquidus is a curve showing the relationship between the temperature (melting point) of the liquid phase in equilibrium with the solid phase and the composition of the liquid phase. The upper limit of the solidus temperature of the solder particles may be 155°C or lower, preferably 150°C or lower, more preferably 145°C or lower, and even more preferably 140°C or lower. Furthermore, a flux compound may be directly bonded to the surface of the solder particles for the purpose of surface activation. Activating the surface can promote metallic bonding with metal wires or electrodes.

[0053] The solder particles preferably have a solidus temperature (melting point) of 155°C or lower, preferably 150°C or lower, and are one or more selected from the group consisting of Sn-Bi-Cu alloy, Sn-Bi-Ag alloy, Sn-Bi alloy, Sn-Pb-Bi alloy, and Sn-In alloy. Specific examples of solder particles include Sn30Bi0.5Cu, Sn30Bi, Sn40Bi, Sn50Bi, Sn58Bi, Sn40Bi0.1Cu, Sn43Pb14Bi, and Sn20In. This allows for excellent connection reliability.

[0054] The lower limit of the mass ratio range of the amount of solder particles to be blended is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 80 parts by mass or more, per 100 parts by weight of binder, and the upper limit of the mass ratio range of the amount of solder particles to be blended is preferably 500 parts by mass or less, more preferably 400 parts by mass or less, and even more preferably 300 parts by mass or less, per 100 parts by weight of binder. The amount of conductive particles to be blended can also be expressed in terms of volume.

[0055] If the amount of solder particles is too small, excellent conductivity will not be obtained, and if the amount is too large, sufficient adhesive strength will not be obtained, making it difficult to achieve excellent conductivity reliability. When the solder particles are present in the binder, the volume ratio may be used, and when producing a conductive particle-containing hot melt adhesive sheet (before the solder particles are present in the binder), the mass ratio may be used. The mass ratio can be converted to a volume ratio based on the specific gravity and compounding ratio of the components.

[0056] The solder particles may be kneaded and dispersed in the resin of the conductive particle-containing hot melt adhesive sheet, or may be arranged in a spaced apart state. This arrangement may be regular. Examples of regular arrangement include lattice arrangements such as a square lattice, a hexagonal lattice, an oblique lattice, and a rectangular lattice. The solder particles may also be arranged as aggregates in which multiple particles are aggregated. In this case, the arrangement of the aggregates in the plan view of the conductive particle-containing hot melt adhesive sheet may be regular or random, similar to the arrangement of the solder particles described above.

[0057] The average particle size of the solder particles is preferably 70% or more, more preferably 80% or more, and even more preferably 95% or more of the thickness of the conductive particle-containing hot melt adhesive sheet, which allows the solder particles to be easily melted and metallically bonded between the conductive parts of the first electronic component and the second electronic component during thermocompression bonding.

[0058] The lower limit of the average particle diameter of the solder particles is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. The upper limit of the average particle diameter of the solder particles is preferably 50 μm or less, more preferably 45 μm or less, and even more preferably 40 μm or less. The maximum diameter of the solder particles can be 200% or less of the average particle diameter, preferably 150% or less of the average particle diameter, and more preferably 120% or less of the average particle diameter. By having the maximum diameter of the solder particles within the above range, the solder particles can be sandwiched (positioned) between the conductive parts of the first electronic component and the conductive parts of the second electronic component, and the conductive parts can be metallically bonded by melting the solder particles.

[0059] The solder particles may also be in the form of aggregates of a plurality of solder particles. In the case of an aggregate of a plurality of solder particles, the size of the aggregate may be set to be equal to the average particle size of the solder particles. The size of the aggregate can be determined by observation with an electron microscope or an optical microscope.

[0060] Here, the average particle size refers to the average major axis diameter of particles measured, for example, at N=20 or more, preferably N=50 or more, and more preferably N=200 or more, in observation images using a metallurgical microscope, optical microscope, or electron microscope such as a scanning electron microscope (SEM). In the case of spherical particles, it refers to the average diameter of the particles. The observed images may also be measured using known image analysis software (such as "WinROOF" from Mitani Corporation or "Azo-kun (registered trademark)" from Asahi Kasei Engineering Corporation) or may be measured (N=1000 or more) using an image-based particle size analyzer (e.g., FPIA-3000 (Malvern Instruments)). The average particle size determined from the observed images or an image-based particle size analyzer may be the average maximum length of the particles. When producing a hot melt adhesive sheet containing conductive particles, it is possible to simply use manufacturer values ​​such as the particle size (D50) at which the cumulative frequency in the particle size distribution determined by laser diffraction / scattering method is 50%, and the arithmetic mean diameter (preferably on a volume basis).

[0061] [Other additives] In addition to the binder and solder particles described above, various additives can be blended into the conductive particle-containing hot melt adhesive sheet as long as they do not impair the effects of the present technology. For example, nano-sized silica (primary particle diameter of 1 nm or more but less than 1000 nm) can be dispersed to improve gas barrier properties and elastic modulus. Furthermore, resin particles, rubber particles, silicone rubber particles, silica, etc. of a specified size can be dispersed as spacer particles to maintain a constant height of the solder particles after compression bonding. Furthermore, for example, thermosetting resins and curing agents can be added as long as they do not impair the effects of the present technology.

[0062] The conductive particle-containing hot melt adhesive sheet according to this embodiment contains a crystalline polyamide having carboxyl groups, and solder particles having a predetermined melting point are contained in a binder having a predetermined melt viscosity relationship. Therefore, even when the electrode surface of an electronic component is OSP-treated (water-soluble preflux-treated), the sheet improves solder wettability and provides excellent adhesive strength and connection reliability. This is believed to be due to the flux effect of the carboxyl groups present in the crystalline polyamide. Furthermore, the method for manufacturing a bonded assembly according to this embodiment forms a metal bond between the conductive parts of a first electronic component and the conductive parts of a second electronic component by melting the solder particles, thereby suppressing swelling and elongation due to moisture absorption of the binder during a wet heat test and providing excellent connection reliability.

[0063] [Method for producing a conductive particle-containing hot melt adhesive sheet] The method for producing a conductive particle-containing hot melt adhesive sheet includes a varnish preparation step in which each resin component of the binder is dissolved in a solvent to prepare a varnish, a conductive particle-containing resin composition preparation step in which solder particles are added to obtain a conductive particle-containing resin composition, and a drying step in which the conductive particle-containing resin composition is applied to a release substrate to a predetermined thickness and dried. Note that when the conductive particles in the conductive particle-containing hot melt adhesive sheet are arranged at intervals or in a regular pattern, the sheet can be prepared without adding conductive particles, and the conductive particles can be arranged separately by a known method.

[0064] The solvent used for each resin component is not particularly limited and can be selected appropriately depending on the purpose. For example, a mixed solvent of methyl ethyl ketone:toluene:cyclohexanone in a ratio of 50:40:10 (by mass), or a mixed solvent of toluene:ethyl acetate in a ratio of 50:50 (by mass), can be used.

[0065] Furthermore, examples of the releasable substrate include those having a contact angle with water of 80° or more, and specific examples of the releasable substrate include silicone-based films, fluorine-based films, silicone-based films, PET, PEN, glassine paper, etc. that have been treated with a release agent such as a fluorine-based release agent. The thickness of the releasable substrate is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 20 μm to 120 μm.

[0066] The conductive particle-containing hot melt adhesive sheet may also be supplied as a film wound body formed into a tape and wound around a core. The diameter of the core is not particularly limited and can be selected appropriately depending on the purpose, but is preferably 50 to 1000 mm. There is also no particular limit to the film length, but a length of 5 m or more allows for trial production using manufacturing equipment, and a length of 1000 m or less does not impose excessive burdens on workability and handling. [Example]

[0067] <4. Example> In this example, a conductive particle-containing hot melt adhesive sheet containing solder particles was prepared, and a bonded assembly was produced using this sheet. The bonded assembly was then evaluated for connection reliability, insulation resistance, initial adhesive strength, and conduction resistance after a water immersion test. However, this example is not limited to these.

[0068] [Preparation of solder particles] The metal materials were placed in a heated container in a predetermined compounding ratio, melted, and then cooled to obtain a solder alloy. Powder was produced from the solder alloy by atomization, and the powder was classified to have a particle size in the range of 20 to 38 μm, obtaining solder powder with the following composition. Sn-40Bi-0.1Cu (solid phase melting point 139℃) Sn-58Bi (solid phase melting point 138℃) Sn-57Bi-0.4Ag (solid phase melting point 136℃) Sn-50In (solid phase melting point 120℃) Sn-3Ag-0.5Cu (solid phase melting point 217℃)

[0069] [Preparation of conductive particle-containing hot melt adhesive sheet] The following resins were prepared: M1276 (Arkema, crystalline polyamide, terminal carboxyl group concentration 6.56 mg KOH / g, melting point 109°C, MVR 8 cm 3 / 10 min, weight average molecular weight 12000) →Solution with solids / ethanol / toluene = 30 / 35 / 35 PES111EE (Toagosei, crystalline polyester) →Solution with solids / cyclohexanone = 25 / 75

[0070] As shown in Tables 1 and 2, the above resins were mixed and stirred to the specified solid content (parts by mass) to obtain a mixed varnish. Subsequently, a specified amount of solder particles per 100 parts by mass of the mixed varnish solids was added to the resulting mixed varnish to obtain a conductive particle-containing resin composition. The resulting conductive particle-containing resin composition was applied to a 50 μm-thick PET film so that the average thickness after drying would be 40 μm, and the film was dried at 70°C for 5 minutes and then at 120°C for 5 minutes to produce a conductive particle-containing hot-melt adhesive sheet.

[0071] [Preparation of junction] As the first electronic component, a printed wiring board (0.4 mm pitch (line / space = 0.2 / 0.2 mm), glass epoxy substrate thickness 1.0 mm, copper pattern thickness 35 μm, surface OSP treatment) was used.

[0072] As the second electronic component, a flexible printed circuit board (0.4 mm pitch (line / space = 0.2 / 0.2 mm), polyimide substrate thickness 50 μm, copper pattern thickness 12 μm, nickel / gold plating treatment) was used.

[0073] A conductive particle-containing hot-melt adhesive sheet was cut to a width of 2.0 mm and temporarily pressure-bonded to the conductive portion of the first electronic component at 120°C, 1 MPa, and 1 second. A second electronic component was then placed on the conductive particle-containing hot-melt adhesive sheet. The second electronic component was then heated and pressed with a heating tool (2.0 mm wide) at 140°C, 3 MPa, and 5 seconds, via a buffer material (silicone rubber, 0.2 mm thick), to obtain a bonded assembly.

[0074] [Melt viscosity measurement] An 8 mm diameter sensor and plate were attached to a MARS3 rheometer (manufactured by HAAKE), and a conductive particle-containing hot melt adhesive sheet was set on it. The melt viscosity was measured under conditions of a gap of 0.2 mm, a heating rate of 5°C / min, a frequency of 1 Hz, and a measurement temperature range of 60 to 200°C. The 100°C viscosity (V1) and the 120°C viscosity (V2) were read, and the ratio (V1 / V2) was calculated. The viscosity (V1) at 100°C for the Examples and Comparative Examples was 20,000 to 300,000 Pa·s, and the viscosity (V2) at 120°C for the Examples and Comparative Examples was 1,000 to 8,000 Pa·s.

[0075] [Evaluation of connection reliability] After a high-temperature, high-humidity test (500 hours at 60°C, 95% RH) and a heat cycle test (500 cycles at -40°C for 30 minutes and 100°C for 30 minutes), the resistance of the bonded body was measured using a digital multimeter with a four-terminal method at a current of 1 mA. The resistance was measured for 30 channels, and the maximum resistance was evaluated according to the following criteria. AA: Resistance less than 0.1Ω A: Resistance is 0.1Ω or more and less than 0.2Ω B: Resistance is 0.2Ω or more and less than 0.5Ω C: Resistance is 0.5Ω or more

[0076] [Insulation resistance evaluation] The initial insulation resistance of the bonded body was measured and evaluated using the following method. A digital multimeter was used to measure the insulation resistance when a voltage of 20 V was applied between adjacent conductive parts. Resistance was measured for 15 channels, and the maximum resistance was evaluated according to the following criteria. A: Resistance value is 10 9 Ω or more B: Resistance value is 10 8 Ω or more, 10 9 Less than Ω C: Resistance value is 10 8 Less than Ω

[0077] [Evaluation of adhesive strength] A 90° peel test (JIS K6854-1) was conducted in which the flexible printed circuit board was peeled from the printed wiring board at a 90° angle. In the peel test, the adhesive strength was measured using a test piece cut to a width of 1 cm, and the adhesive strength was evaluated according to the following criteria. A: Adhesive strength is 12N / cm or more B: Adhesive strength is 7N / cm or more and less than 12N / cm C: Adhesion strength is less than 7N / cm

[0078] [Evaluation of conduction resistance after water immersion test] After measuring the initial resistance of the bonded body, the bonded body was immersed in water at room temperature, and after 24 hours, it was taken out and the conduction resistance was measured. Evaluation was made according to the following criteria. A: The ratio of resistance after immersion to initial resistance is less than 2. C: The ratio of resistance after immersion to initial resistance is 2 or more.

[0079] Table 1 shows the formulations of the conductive particle-containing hot melt adhesive sheets of Examples 1 to 5, as well as evaluations of the connection reliability of the joined bodies, insulation resistance, adhesive strength, and conduction resistance after a water immersion test. Table 2 also shows the formulations of the conductive particle-containing hot melt adhesive sheets of Examples 6 to 8 and Comparative Examples 1 to 3, as well as evaluations of the connection reliability of the joined bodies, insulation resistance, adhesive strength, and conduction resistance after a water immersion test. In practice, it is preferable that all parameters be B or higher.

[0080] [Table 1]

[0081] [Table 2]

[0082] In Comparative Example 1, the melting point of the solder particles was too low at 120°C, so good connection was not obtained, and the conduction resistance values ​​after the high-temperature, high-humidity test and the water immersion test were evaluated as C. In Comparative Example 2, the melting point of the solder particles was too high at 217°C, so good connection was not obtained, and the conduction resistance values ​​after the high-temperature, high-humidity test and the water immersion test were evaluated as C. In Comparative Example 3, because it did not contain a crystalline polyamide resin, good connection was not obtained, and the conduction resistance values ​​after the high-temperature, high-humidity test and the water immersion test were evaluated as C.

[0083] On the other hand, in Examples 1 to 7, good results were obtained in all items. Furthermore, in Example 8, in which glutaric acid was added, good results were obtained in all items. In particular, in the evaluation of the conduction resistance value after the high-temperature, high-humidity test, an improvement was observed compared to the case in which glutaric acid was not added. This is thought to be due to the flux effect of glutaric acid, which forms a metallic bond between the electrodes of the OSP-treated substrate and the solder particles. [Explanation of symbols]

[0084] 10 First electronic component, 11 First conductive portion, 20 Second electronic component, 21 Second conductive portion, 30 Adhesive layer, 31 Solder particle, 32 Solder joint, 40 Card member, 41 Opening, 42 Antenna pattern, 42a First exposed portion, 42b Second exposed portion, 50 IC chip, 51 Contact terminal

Claims

1. A method for manufacturing a bonded body, comprising thermocompression bonding a first electronic component and a second electronic component via a conductive particle-containing hot-melt adhesive sheet, the conductive particle-containing hot-melt adhesive sheet containing solder particles in a binder containing a crystalline polyamide resin having a carboxyl group and a crystalline polyester resin, the proportion of the crystalline polyamide resin in the binder being 50 wt % or more, and connecting a conductive part of the first electronic component with a conductive part of the second electronic component, The melting point of the solder particles is −30 to 0° C. of the thermocompression bonding temperature and is 130 to 160° C., When the melt viscosity of the conductive particle-containing hot melt adhesive sheet is measured at a temperature increase rate of 5°C / min, the ratio of the melt viscosity at a temperature of -40°C (the thermocompression bonding temperature) to the melt viscosity at a temperature of -20°C (the thermocompression bonding temperature) is 10 or more.

2. 2. The method for producing a bonded body according to claim 1, wherein the ratio of the melt viscosity of the conductive particle-containing hot melt adhesive sheet at 100°C to the melt viscosity at 120°C is 10 or more when the melt viscosity is measured at a temperature increase rate of 5°C / min.

3. 3. The method for producing a bonded body according to claim 1, wherein the crystalline polyamide has a terminal carboxyl group concentration of 0.5 mgKOH / g or more.

4. 4. The method for producing a bonded body according to claim 1, wherein the crystalline polyamide resin accounts for 70 wt % or more of the binder.

5. The method for producing a bonded body according to any one of claims 1 to 4, wherein the conductive particle-containing hot melt adhesive sheet further contains a flux compound.

6. the fluxing compound is a carboxylic acid; 6. The method for producing a bonded body according to claim 5, wherein the content of the carboxylic acid is 1 to 10 parts by mass with respect to 100 parts by mass of the binder.

7. 7. The method for manufacturing a joined body according to claim 1, wherein the solder particles are one or more selected from the group consisting of a Sn—Bi—Cu alloy, a Sn—Bi—Ag alloy, a Sn—Bi alloy, a Sn—Pb—Bi alloy, and a Sn—In alloy.

8. 8. The method for manufacturing a bonded body according to claim 1, wherein the content of the solder particles is 40 to 320 parts by weight per 100 parts by weight of the binder.

9. 9. The method for producing a joint body according to claim 1, wherein the average particle diameter of the solder particles is 70% or more of the thickness of the conductive particle-containing hot melt adhesive sheet.

10. 10. The method for manufacturing a bonded body according to claim 1, wherein the conductive portion of at least one of the first electronic component and the second electronic component is treated with a water-soluble preflux.

11. The method for producing a bonded body according to any one of claims 1 to 10, wherein the temperature for the thermocompression bonding is 120 to 180°C.

12. a first electronic component, a second electronic component, and an adhesive layer connecting a conductive portion of the first electronic component and a conductive portion of the second electronic component; The adhesive layer contains solder particles having a melting point of 130 to 160°C in a binder containing a crystalline polyamide resin having a carboxyl group and a crystalline polyester resin, the proportion of the crystalline polyamide resin in the binder is 50 wt% or more, and when the melt viscosity is measured under the condition of a temperature rise rate of 5°C / min, the ratio of the melt viscosity at 100°C to the melt viscosity at 120°C is 10 or more.

13. 13. The bonded body according to claim 12, wherein the conductive portion of at least one of the first electronic component and the second electronic component is treated with a water-soluble preflux.

14. A conductive particle-containing hot melt adhesive sheet comprising solder particles having a melting point of 130 to 160°C contained in a binder comprising a crystalline polyamide resin having a carboxyl group and a crystalline polyester resin, wherein the proportion of the crystalline polyamide resin in the binder is 50 wt% or more, and when the melt viscosity is measured under conditions of a temperature rise rate of 5°C / min, the ratio of the melt viscosity at 100°C to the melt viscosity at 120°C is 10 or more.

15. 15. The conductive particle-containing hot melt adhesive sheet according to claim 14, wherein the ratio of the melt viscosity at 100°C to the melt viscosity at 120°C is 10 or more when the melt viscosity is measured at a temperature rise rate of 5°C / min.

16. 16. The conductive particle-containing hot melt adhesive sheet according to claim 14, wherein the crystalline polyamide has a terminal carboxyl group concentration of 0.5 mg KOH / g or more.

17. 17. The conductive particle-containing hot melt adhesive sheet according to claim 14, wherein the proportion of the crystalline polyamide resin in the binder is 70 wt % or more.

18. The conductive particle-containing hot melt adhesive sheet according to any one of claims 14 to 17, further comprising a flux compound.

19. the fluxing compound is a carboxylic acid; 19. The conductive particle-containing hot melt adhesive sheet according to claim 18, wherein the content of the carboxylic acid is 1 to 10 parts by mass per 100 parts by mass of the binder.

20. The conductive particle-containing hot melt adhesive sheet according to any one of claims 14 to 19, wherein the solder particles are one or more selected from the group consisting of Sn-Bi-Cu alloy, Sn-Bi-Ag alloy, Sn-Bi alloy, Sn-Pb-Bi alloy, and Sn-In alloy.

21. 21. The conductive particle-containing hot melt adhesive sheet according to claim 14, wherein the content of the solder particles is 40 to 320 parts by weight per 100 parts by weight of the binder.

22. 22. The conductive particle-containing hot melt adhesive sheet according to claim 14, wherein the average particle diameter of the solder particles is 70% or more of the thickness of the conductive particle-containing hot melt adhesive sheet.

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