Manufacturing method of connection structure

Abstract

To connect a fine electronic component and a substrate using a conductive particle containing film.SOLUTION: A manufacturing method of a connection structure 40 in which a fine electronic component 1 having a length of a longest side of 600 μm or less or an area of each electrode of 1000 μm2 or less is electrically connected with a substrate 20 including an electrode 21 corresponding to an electrode 2 of the electronic component 1 includes: an overlapping step of overlapping the electronic component 1 and the substrate 20 via a conductive particle containing film 10 in which conductive particles 11 are held in an insulating resin layer 12; and a pressurizing and curing step of curing the insulating resin layer 12 of the conductive particle containing film while pressurizing the electronic component and the substrate which overlap via the conductive particle containing film. Regarding curing characteristics of the conductive particle containing film 10, in a case where the conductive particle containing film 10 is heated from 40°C to 80°C, a time from heating start to curing start of the insulating resin layer 12 is 10 minutes or more.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a connection structure that reliably electrically connects minute electronic components, which are difficult for humans to handle by hand, onto a substrate. [Background technology]

[0002] Miniature electronic components are being developed, for example, for display applications (Patent Documents 1 and 2). Such miniature electronic components are generally manufactured by separating them from wafers using dicing tools and then mounted on glass substrates on which driver circuits are formed by wire bonding or the like.

[0003] On the other hand, when connecting electronic components such as IC chips to a substrate, conductive particle-containing films are used, in which conductive particles are held in an insulating resin layer. When electronic components and substrates are connected via this conductive particle-containing film, the conductive particle-containing film exhibits conductivity only in the film thickness direction, and is therefore also called an anisotropic conductive film. In recent years, electronic components have become smaller, and in order to accommodate the miniaturization of electronic components, conductive particle-containing films have been modified to have a specific ratio between the thickness of the insulating resin layer and the particle diameter of the conductive particles, to arrange the conductive particles regularly, or to laminate a resin layer with high adhesion and low hardness to the resin layer containing conductive particles onto the resin layer containing conductive particles (Patent Documents 3 and 4). As a result, the electrode area in electrode rows such as bumps formed on electronic components can be 1000 μm². 2 Even tiny electronic components (e.g., approximately 100 x 10 μm) and even micro-sized semiconductor electrodes can be connected to a substrate using a conductive particle-containing film. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2017-521859 [Patent Document 2] Special Publication No. 2014-533890 [Patent Document 3] Japanese Patent Publication No. 2018-81906 [Patent Document 4] Patent No. 6688374 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The roles required of electronic components are diversifying. In addition to the minute semiconductor elements that were conventionally mounted using wire bonding, it is now necessary to connect even smaller electronic components to substrates using conductive particle-containing films, and this is creating new challenges.

[0006] For example, in conventional anisotropic conductive connections using conductive particle-containing films, it is required that the number of conductive particles trapped in a single electrode be 3 or more, preferably 10 or more, from the viewpoint of electrical stability. However, for example, if the area of ​​each electrode is 1000 μm² 2 When anisotropically conductively connecting minute electronic components, such as those described below or those with a longest side length of 600 μm or less, the electrodes themselves are miniaturized, which necessitates enabling solutions that cannot be met by conventional anisotropically conductive connection specifications, such as limiting the number of conductive particles captured per electrode to 1 to 3.

[0007] Furthermore, as electronic components become extremely small, the number of electronic components to be connected to the substrate also increases. This increases the difficulty of the connection process, which consists of the process of attaching the conductive particle-containing film to the substrate by adhesive, transfer, or laser lift-off (hereinafter also referred to as the temporary attachment process), the process of mounting electronic components onto the conductive particle-containing film attached to the substrate, and the curing process in which the electronic components are pressed onto the substrate via the conductive particle-containing film and the insulating resin layer of the conductive particle-containing film is cured by pressure curing or heat-pressure curing to complete the connection of the electronic components. This process requires a long time to perform the connection precisely, and there are concerns that the curing of the insulating resin layer may proceed unnecessarily before the connection is completed.

[0008] Therefore, the present invention relates to the area of ​​each electrode being 1000 μm² 2 The objective is to enable precise and reliable connection of the following or any other minute electronic components, or those with a longest side length of 600 μm or less, to a substrate using a conductive particle-containing film. [Means for solving the problem]

[0009] The inventors of the present invention have discovered that when a conductive particle-containing film is provided on a substrate, and fine electronic components and the substrate are superimposed on the conductive particle-containing film, and the superimposed electronic components and substrate are joined by curing the insulating resin layer of the conductive particle-containing film while applying pressure to them, if the insulating resin layer of the conductive particle-containing film is used, which takes more than 10 minutes from the start of heating to the start of curing even when heated to 40°C to 80°C, it is possible to prevent the insulating resin layer from unnecessarily starting to cure between temporary bonding and final connection, thereby enabling precise and reliable connection between the electronic components and the substrate, and have completed the present invention.

[0010] In other words, the present invention is a method for manufacturing a connection structure in which a minute electronic component and corresponding electrodes of a substrate having electrodes corresponding to the electrodes of the electronic component are electrically connected to each other. A superposition process in which electronic components and a substrate are superimposed via a conductive particle-containing film in which conductive particles are held in an insulating resin layer. A pressure curing process in which the insulating resin layer of the conductive particle-containing film is cured while applying pressure to the electronic components and substrate that are superimposed on each other via the conductive particle-containing film. It has, The curing characteristics of the conductive particle-containing film are such that the time from the start of heating to the start of curing of the insulating resin layer when the conductive particle-containing film is heated from 40°C to 80°C is 10 minutes or more. To provide a manufacturing method.

[0011] The present invention also provides a connection structure in which a fine electronic component and a substrate having electrodes corresponding to the electrodes of the electronic component are adhered with an insulating resin, and the corresponding electrodes of the electronic component and the substrate are electrically connected by one or more but less than three conductive particles sandwiched therebetween.

Advantages of the Invention

[0012] According to the present invention, as the conductive particle-containing film, a film in which the time from the start of heating to the start of curing of the insulating resin layer is 10 minutes or more when the conductive particle-containing film is heated from 40°C to 80°C is used. Thus, the conductive particle-containing film is provided on the substrate, a fine electronic article is overlaid on the substrate through the conductive particle-containing film, and the insulating resin layer is prevented from starting to cure unnecessarily while being pressure-cured. Therefore, even a fine electronic component with an area of each electrode of 1000 μm 2 or less or a length of the longest side of the electronic component of 600 μm or less can be accurately connected to the substrate.

Brief Description of the Drawings

[0013] [Figure 1] FIG. 1 is a cross-sectional view of a semiconductor component held on a film for semiconductor processing. [Figure 2A] FIG. 2A is a plan view showing the particle arrangement of a conductive particle-containing film. [Figure 2B] FIG. 2B is a cross-sectional view of a conductive particle-containing film. [Figure 3A] FIG. 3A is a cross-sectional view of a state where a release film is attached to a semiconductor component on a film for semiconductor processing. [Figure 3B] FIG. 3B is a cross-sectional view of a state where the film for semiconductor processing is peeled off from the semiconductor component. [Figure 4] FIG. 4 is a cross-sectional view of a state where a conductive particle-containing film arranged on a substrate is aligned with a semiconductor component attached to a release film. [Figure 5] FIG. 5 is a cross-sectional view of a state where a semiconductor component and a substrate are overlaid through a conductive particle-containing film and the release film is peeled off and removed. [Figure 6] Figure 6 is a cross-sectional view showing the semiconductor component and substrate, with the release film removed, being pressurized from the semiconductor component side using a pressure tool. [Figure 7] Figure 7 is a cross-sectional view showing the state in which conductive particles are sandwiched between the electrodes of the semiconductor component and the electrodes of the substrate by the first pressurization. [Figure 8] Figure 8 is a cross-sectional view showing the state in which the electrodes of the semiconductor component and the electrodes of the substrate are electrically connected by the second pressurization. [Modes for carrying out the invention]

[0014] The manufacturing method of the connecting structure of the present invention will be described in detail below with reference to the drawings. In each figure, the same reference numerals represent the same or equivalent components.

[0015] <Electronic Components> The electronic components connected by the method of the present invention, for example, have an individual electrode area of ​​1000 μm². 2 Below, 500μm 2 Below, and even 200 μm 2 The following are microscopic electronic components, or those with the longest side length of the electronic component being 600 μm or less, 300 μm or less, 150 μm or less, or even 50 μm or less. Examples of such electronic components include various ICs, including general driver ICs, optoelectronic elements, thermoelectric elements (Peltier elements), switching elements, and other semiconductor components, as well as piezoelectric elements and resistors. Among these, examples of optoelectronic elements include mini-LEDs with a chip side length of approximately 50 to 200 μm and μLEDs with a chip side length of less than 50 μm.

[0016] Figure 1 is a cross-sectional view showing an example of an electronic component 1 connected by the method of the present invention, in which multiple semiconductor components are held on a semiconductor processing film 3. The semiconductor processing film 3 includes known dicing tapes, die bonding tapes, release films, etc.

[0017] In the present invention, it is preferable that the multiple electrodes on the electrode formation surface of the electronic component 1 have the same height when connected to the electrodes of the substrate.

[0018] The electronic component 1 connected by the method of the present invention is fine. For example, the area of each electrode is 1000 μm 2 or less, 500 μm 2 or less, and further 200 μm 2 or less, or the length of the longest side of the electronic component 1 is 600 μm or less, 300 μm or less, 150 μm or less, and further 50 μm or less. The shortest side of the electronic component 1 needs to be of a size such that at least one conductive particle is surely sandwiched between each electrode. Therefore, it is preferable that the shortest side is a length obtained by adding a margin to the particle diameter of the conductive particle. Thus, the shortest side of the electronic component 1 connected by the method of the present invention is preferably 5 μm or more.

[0019] The preferable thickness of the electronic component 1 connected by the method of the present invention varies depending on the material, strength, height of the electrode, connection conditions, etc. of the electronic component 1. For example, when the area of each electrode of the electronic component is 1000 μm 2 or less or the length of the longest side of the electronic component is 600 μm or less, the thickness can be 200 μm or less, and further 50 μm or less. When the length of the longest side is 300 μm or less, the thickness can be 50 μm or less. When the length of the longest side is 150 μm or less, the thickness can be 30 μm or less. When the length of the longest side is 50 μm or less, the thickness can be 20 μm or less, and further 15 μm or less, particularly 10 μm or less. This is because if the ratio of the length of the longest side to the thickness of the electronic component approaches the value 1, there is a concern that lateral displacement may occur in the electronic component due to pushing during connection. In this case, the thickness does not include the height of the electrode used for electrical connection via the conductive particles.

[0020] The height of electrode 2 of electronic component 1 may be substantially zero, but in order to prevent pressure from being applied to areas other than the electrode during the pressure curing process and the pressure curing process performed as needed after the overlapping process, and to ensure that the conductive particles are efficiently pushed into the electrode by the pressure, it is preferable that the height of electrode 2 be greater than 1x the average particle diameter of the conductive particles. On the other hand, if the height of electrode 2 is excessively high, the amount of resin filled between the electrodes will be unnecessarily large, so it is preferable that the height of electrode 2 be 3x or less, and more preferably 2x or less, the average particle diameter of the conductive particles. Alternatively, it is preferable that it be 10 μm or less, and more preferably 6 μm or less.

[0021] Furthermore, although Figure 1 shows an example in which a semiconductor component 1 held in a semiconductor processing film 3 is used, in the method of the present invention, the electronic component used for connection to the substrate does not have to be held in a semiconductor processing film.

[0022] <Circuit board> In this invention, the substrate 20 to which the electronic component 1 is connected may be a transparent substrate such as a glass substrate or a plastic substrate, or it may be an opaque substrate. Furthermore, known electronic components such as ceramic substrates, rigid resin substrates, and FPCs can be used as the substrate 20.

[0023] <Conductive particle-containing film> Figure 2A is a plan view of an example of a conductive particle-containing film 10 used in the present invention, and Figure 2B is a cross-sectional view thereof. In the conductive particle-containing film 10, the conductive particles 11 are held in an insulating resin layer 12.

[0024] (Conductive particles) Examples of conductive particles 11 held in the insulating resin layer 12 of the conductive particle-containing film 10 include metal particles such as nickel, cobalt, silver, copper, gold, and palladium; alloy particles such as solder; metal-coated resin particles; and metal-coated resin particles with insulating fine particles attached to their surface. Two or more types can be used in combination. Among these, metal-coated resin particles are preferred because, after connection, the resin particles repel each other, making it easier to maintain contact with the terminals and resulting in stable conductivity. Furthermore, the surface of the conductive particles may be subjected to an insulating treatment that does not impair the conductivity characteristics, using known techniques.

[0025] (Particle size of conductive particles) The particle diameter of the conductive particles 11 is set to less than 10 μm, preferably 4 μm or less, in order to ensure that at least one conductive particle is reliably captured by each electrode, even if the electrodes are minute. On the other hand, a diameter of 1 μm or more is preferable, and 2.5 μm or more is more preferable, in order to improve the accuracy of pressing the conductive particles 11 onto the electrodes. Here, particle diameter refers to the average particle diameter. The average particle diameter of the conductive particles 11 in the conductive particle-containing film 10 can be determined from a planar image or a cross-sectional image. The average particle diameter may also be determined by measuring the diameter of 200 or more particles under a microscope. Furthermore, the average particle diameter of the conductive particles as raw material particles before being incorporated into the conductive particle-containing film can be determined using a wet flow-type particle diameter and shape analyzer FPIA-3000 (Malvern). If insulating fine particles or other fine particles are attached to the conductive particles, the particle diameter should be the diameter excluding the fine particles.

[0026] (Arrangement of conductive particles) In order to ensure that one or more conductive particles are reliably captured at each electrode of a minute electronic component, it is preferable that the conductive particles 11 in the conductive particle-containing film 10 are arranged regularly, for example, in a grid pattern as described in Patent Document 3. In particular, when an electronic component 1 is obtained by dicing from a wafer, electrodes are formed along the edges of the electronic component 1, so it is desirable that the arrangement of the conductive particles 11 be a rectangular grid. In the conductive particle-containing film 10 shown in Figure 2A, the conductive particles 11 are arranged in a square grid pattern.

[0027] On the other hand, a conductive particle-containing film may be one in which the conductive particles are evenly and randomly dispersed.

[0028] The conductive particles 11 may be embedded in the insulating resin layer 12 or may be exposed. Preferably, the positions of each conductive particle 11 are aligned in the film thickness direction, and preferably, they are unevenly distributed on one side of the conductive particle-containing film. This uneven distribution on one side ensures that pressure is applied evenly and suppresses unexpected particle movement.

[0029] (Number density of conductive particles) There are no particular restrictions on the upper and lower limits of the number density of conductive particles, as these will vary depending on the object being connected. For example, the lower limit of the number density is 30 particles / mm². 2 or more, or 12,000 pieces / mm 2 Above, or 150,000 pieces / mm 2 The above can be used, and the upper limit of the number density is, for example, 500,000 pieces / mm 2 The following, or 350,000 pieces / mm 2 The following, or 300,000 pieces / mm 2 The following is possible:

[0030] (Layer structure of insulating resin layer) The insulating resin layer 12 constituting the conductive particle-containing film 10 may consist of a single insulating resin layer or a laminate of multiple insulating resin layers. For example, as shown in Figure 2B, the layer configuration of the conductive particle-containing film 10 is preferably such that the insulating resin layer 12 is a laminate of a high-viscosity resin layer 13 with a high minimum melt viscosity and a low-viscosity resin layer 14 with a low minimum melt viscosity, and the conductive particles 11 are held in the high-viscosity resin layer 13, in order to suppress the unwanted flow of the conductive particles 11. In this case, the minimum melt viscosity (A1) of the high-viscosity resin layer 13, the minimum melt viscosity (A2) of the low-viscosity resin layer 14, their ratio (A1 / A2), and their layer thicknesses can be the same as those of known anisotropic conductive films described in Japanese Patent No. 6187665, Japanese Patent Application Publication No. 2018-81906, etc.

[0031] (Thickness of the insulating resin layer) The thickness of the insulating resin layer 12 can be, at a lower limit, preferably 1.3 times or more the particle diameter of the conductive particles, or 3 μm or more. At an upper limit, it can be 2 times or less the particle diameter of the conductive particles, or 20 μm or less. If the insulating resin layer 12 is composed of a laminate of multiple insulating resin layers, it is preferable that the thickness of the laminate is within these ranges.

[0032] The thickness of the insulating resin layer 12 can be measured using a known micrometer or digital thickness gauge. In this case, for example, measurements can be taken at 10 or more locations, and the average value can be used as the layer thickness.

[0033] (Resin composition for insulating resin layer) The resin composition forming the insulating resin layer 12 is appropriately selected according to the type of electronic component 1 and substrate 20 connected by the conductive particle-containing film 10, and can be formed from a thermoplastic resin composition, a high-viscosity adhesive resin composition, or a curable resin composition. For example, a curable resin composition formed from a polymerizable compound and a polymerization initiator can be used, similar to the resin composition forming the insulating resin layer of the conductive particle-containing film described in Japanese Patent Publication No. 6187665. In this case, a thermal polymerization initiator may be used as the polymerization initiator, a photopolymerization initiator may be used, or both may be used in combination. For example, a cationic polymerization initiator may be used as the thermal polymerization initiator, and an epoxy resin as the thermal polymerizable compound, while a photoradical polymerization initiator may be used as the photopolymerization initiator, and an acrylate compound as the photopolymerizable compound. A thermal anionic polymerization initiator may also be used as the thermal polymerization initiator. As a thermal anionic polymerization initiator, it is preferable to use a microencapsulated latent curing agent having an imidazole modified material as a nucleus and its surface coated with polyurethane.

[0034] (Curing start time of insulating resin layer at 40-80°C) In the conductive particle-containing film 10, by selecting the type of curable resin composition that forms the insulating resin layer 12, adjusting the concentration of the polymerization initiator, etc., the time from the start of heating to the start of curing of the insulating resin layer 12 when the conductive particle-containing film 10 is heated from 40°C to 80°C is 10 minutes or more, 20 minutes or more, and even 25 minutes or more. This means that the time from when the insulating resin layer 12 of the conductive particle-containing film 10 is subjected to heating in the temperature range of 40°C to 80°C until the insulating resin layer 12 starts to cure is 10 minutes or more.

[0035] Furthermore, the time until curing begins refers to the time until curing begins for each insulating resin layer, if the insulating resin layer 12 is composed of multiple insulating resin layers. This ensures that even when a large number of fine electronic components are simultaneously aligned and stacked on the substrate after the conductive particle-containing film is placed on the substrate (after the temporary bonding process), and then heated and pressurized all at once to connect them, at least 10 minutes can be secured from the time the electronic components are first stacked on the substrate until the final stacking of the electronic components and the substrate is completed, and until each electronic component is heated and pressurized. This allows for precise and reliable connection between the electronic components and the substrate.

[0036] Generally, the overlapping process is performed on a stage of a pressurizing device heated to approximately 40°C. Even if the overlapping process is not performed on a heated stage, the film may be placed on a heated stage before the heating and pressurizing process. Therefore, if the curing start time of the resin composition when the conductive particle-containing film 10 is heated to 40 to 80°C is short, there is a risk that the resin composition will begin to cure before the overlapping process is completed. In contrast, by setting the curing start time at 40 to 80°C to 10 minutes or more, it becomes possible to complete the overlapping process before curing begins, even when the overlapping process is performed on a heated pressurizing device stage.

[0037] Furthermore, there is no particular limit on the upper limit of the time from the start of heating to the start of curing of the insulating resin layer when the conductive particle-containing film 10 is heated from 40°C to 80°C.

[0038] Furthermore, while it is preferable to set the time until curing begins according to the time required for the overlapping process, in order to ensure sufficient time for the process of setting the conductive particle-containing film on the substrate and the overlapping process, and to shorten the subsequent pressure curing process, setting this time to 10 minutes or more ensures that sufficient time is available for the overlapping process regardless of the application of the electronic component, such as smartphones, large televisions, public displays (digital signage), or wearable displays (smartwatches). In other words, generally, the process of overlapping electronic components such as IC chips (driver ICs) and substrates via a conductive particle-containing film requires several seconds to several tens of seconds, but if the electronic components to be overlapped are minute, this overlapping process becomes a precise operation. For example, if the area of ​​each electrode is 1000 μm² 2 For microscopic electronic components such as μLEDs, where the longest side length is 600 μm or less, it is preferable to allow a longer time for the superposition process compared to larger IC chips, etc. This is because, due to their small size, a larger number of components can be mounted. The time required for the superposition process varies depending on the mounting method and equipment conditions, but as an example, it can be 5 minutes or more, and in some cases 10 minutes or more.

[0039] Whether the curing start time of the insulating resin layer 12 of the conductive particle-containing film 10 at 40°C to 80°C is 10 minutes or more, or whether this curing start time is sufficiently long compared to the time required for the temporary bonding and overlapping process, can be confirmed, for example, by the following (i), (ii), and (iii).

[0040] (i) Peeling test of release film In a constant temperature and humidity chamber with a humidity of 40% RH and a temperature of 30°C, one side of a conductive particle-containing film, which has a pair of release films attached to both sides, is peeled off. This side is then attached to a glass plate, and the glass plate is placed on a hot plate set to 45°C. The conductive particle-containing film is then pressed from the other side. After a predetermined time corresponding to the time required for the overlapping process has elapsed, the laminate of the glass plate and conductive particle-containing film is cooled, and the release film attached to the conductive particle-containing film is lifted. The test checks whether the conductive particle-containing film peels off the glass plate. If the conductive particle-containing film peels off the glass plate, it indicates that hardening has not progressed within the predetermined time corresponding to the overlapping process. Therefore, high-precision alignment between the electronic component and the substrate becomes possible during this time.

[0041] (ii) Temperature measurement using differential scanning calorimeter The reaction start time may be measured from the peak temperature measured when the conductive particle-containing film 10 is heated using a differential scanning calorimeter (DSC). In this case, the temperature change may be measured with a DSC after processing under typical heating and pressing conditions in a typical overlapping process (so-called temporary bonding conditions, for example, 60-80°C, 1-2 seconds, 0.5-2 MPa).

[0042] More specific DSC measurement conditions include a heating rate of 10°C / min, preferably 5°C / min, and holding time after reaching 80°C. The target temperature can also be 60°C. In this case, the heating starts from room temperature (25°C ± 15°C). The target temperature may also be 40°C.

[0043] In the measurement procedure described above, it is preferable that a temperature peak (exothermic peak) indicating the start of curing does not occur between 40°C and 80°C for 10 minutes or more, and more preferably for 20 minutes or more. Note that "10 minutes or more" means 10 minutes or more from the time the temperature reaches 40°C if the temperature is raised from room temperature. For example, if the temperature is raised from 60°C, it means 10 minutes or more from the time the temperature rise starts at 60°C. If 80°C is reached within 10 minutes, the time at which the temperature is maintained at 80°C is included. A simplified test can also be performed by measuring the time the sample is left in a constant temperature bath set to 80°C.

[0044] On the other hand, if this time is excessively long, the latent properties of the polymerization initiator may be excessively high, and there is a risk that the target low temperature or short time required in the curing process by thermocompression bonding may not be achieved. Therefore, the temperature and time for curing the insulating resin layer 12 should be appropriately adjusted and determined according to the time required for the overlapping process of the electronic component and the substrate. It should be noted that the present invention prioritizes securing the time required for the preceding overlapping process rather than achieving a low temperature and short time for the curing process by thermocompression bonding, and in this respect, it differs from conventional methods for connecting electronic components using conductive particle-containing films.

[0045] (iii) Curing rate of the insulating resin layer The time from heating the conductive particle-containing film 10 to a temperature range of 40°C to 80°C until curing begins to be 10 minutes or more can be determined by the curing rate of the insulating resin layer 12 10 minutes after heating the conductive particle-containing film 10 to a temperature range of 40°C to 80°C being 25% or less, preferably 20% or less. Here, the curing rate can be determined by measuring the height of a specific peak in the FT-IR chart of the curable resin composition, measuring the exothermic peak area of ​​the DSC, etc.

[0046] Regarding the time until curing begins in the temperature range of 40°C to 80°C as described above, when a conductive particle-containing film is transferred to the electrodes of an electronic component or a substrate by laser lift-off, pre-fragmented to match the size and arrangement of the μLEDs, it is preferable that the reaction rate of the curable resin composition constituting the insulating resin layer of the conductive particle-containing film after transfer be preferably 25% or less, more preferably 20% or less, and even more preferably 15% or less. It is preferable to select the type of resin in the curable resin composition, adjust the concentration of the polymerization initiator, etc., to satisfy this condition. If the fragments are small, the reaction rate may be measured from the remaining portion of the original film from which the fragments were obtained (e.g., the edges near the processed area).

[0047] Furthermore, when the reaction rate (curing rate) of the curable resin composition after 10 minutes of heating the conductive particle-containing film transfer by the laser lift-off method to 40°C to 80°C is preferably 25% or less, more preferably 20% or less, and even more preferably 15% or less, it is possible to obtain sufficient time to place and connect a large number of micro-components, thereby relaxing the manufacturing conditions and contributing to stable productivity.

[0048] The reaction rate of the conductive particle-containing film after transfer can be determined, for example, using FT-IR, by comparing the reaction rate of the epoxy group (914cm) before and after laser irradiation in the laser lift-off method. -1 (Near), (meth)acryloyl group (1635 cm) -1 Peak heights of reactive groups such as (near) A,a and methyl group (2930cm) -1 The peak heights B and b of the control (in the vicinity) are measured, and the rate of decrease of the reactive group can be calculated using the following formula.

[0049] Response rate (%) = {1 - (a / b) / (A / B)} × 100 In the formula, A is the peak height of the reactive group before laser irradiation, B is the peak height of the control before laser irradiation, a is the peak height of the reactive group after laser irradiation, and b is the peak height of the control after laser irradiation.

[0050] For FT-IR measurements, it is preferable to use a small sample with a film thickness of 10 μm or less, sandwiched between diamond cells, and set in the IR detector. Furthermore, to improve detection sensitivity, it is preferable to pre-cool the IR detector with liquid nitrogen for about 30 minutes. The FT-IR measurement conditions are, for example, as follows: Measurement method: Transmission method Measurement temperature: 25℃ Measured humidity: 60% or less Measurement time: 12 seconds Detector spectral range: 4000-700 cm² -1

[0051] If other peaks overlap with the peak of the reactive group, the peak height of the reactive group in the fully cured (100% reaction rate) sample should be set to 0%.

[0052] Furthermore, if the peak height of the reactive group is small, or if the curable resin composition contains alicyclic epoxy groups or oxetanyl groups, the reaction rate may be calculated using HPLC (High Performance Liquid Chromatography) according to the following formula.

[0053] Response rate (%) = {1 - c / C} × 100 In the formula, C is the peak height or area of ​​the reactive component before laser irradiation, and c is the peak height or area of ​​the reactive component after laser irradiation.

[0054] In HPLC measurements, it is preferable to extract the sample with a solvent such as acetonitrile and perform gradient elution, continuously changing the eluent from X (water / acetonitrile = 9:1) to Y (acetonitrile).

[0055] By suppressing the reaction rate after transferring the conductive particle-containing film in fragments to the electrodes of an electronic component or a substrate, as described above, it becomes possible to thermocompression-bond the electrodes of other electronic components or substrates to the fragmented conductive particle-containing film after transfer. Fragmentation may be performed by laser ablation, laser lift-off (laser lift method), or other known methods.

[0056] (Adhesion of conductive particle-containing film) As shown in Figure 1, when an electronic component 1 to be connected to a substrate is attached to a semiconductor processing film 3, it is preferable to make the adhesive force of the conductive particle-containing film 10 to the electronic component 1 greater than the adhesive force of the semiconductor processing film 3 to the electronic component 1, so that even when the electronic component 1 is attached to the semiconductor processing film 3, temporary bonding between the electronic component 1 and the substrate 20 via the conductive particle-containing film 10 is possible (Figures 4 to 6).

[0057] The adhesive strength of the conductive particle-containing film 10 can be measured, for example, by performing a peel test in which a small piece of the conductive particle-containing film (e.g., 0.3 to 1.0 mm wide and 2 cm long) with a release film on one side is attached to a glass substrate, and the edge of the release film is picked up with tweezers and removed. In this peel test, if the case in which the conductive particle-containing film remains attached to the glass is considered a success, then it is preferable that the number of tests (n) is 20 or more, preferably 30 or more, and the success rate is 75% or more, more preferably 80% or more, even more preferably 90% or more, and particularly preferably 95% or more. By maintaining the adhesive strength with high precision, the surface of the conductive particle-containing film maintains the holding force necessary for mounting minute electronic components.

[0058] It is preferable that this adhesive strength be maintained during the temporary bonding and overlapping processes.

[0059] Furthermore, the adhesive strength can be measured in accordance with JIS Z 0237, as described in Japanese Patent Publication No. 2019-214714, or it can be measured as tack force by the probe method in accordance with JIS Z 3284-3 or ASTM D 2979-01.

[0060] Whether the conductive particle-containing film 10 has a high-viscosity resin layer 13 and a low-viscosity resin layer 14 as an insulating resin layer 12, or a single layer of insulating resin, the tack force of each side of the conductive particle-containing film measured by the probe method is, for example, measured at a probe pressing speed of 30 mm / min, a pressing force of 196.25 gf, a pressing time of 1.0 sec, a peeling speed of 120 mm / min, and a measurement temperature of 23°C ± 5°C, with at least one of the front and back surfaces measuring 1.0 kPa (0.1 N / cm²). 2 It can be set to 1.5 kPa (0.15 N / cm²) or higher. 2 It is preferable to set it to 3 kPa (0.3 N / cm²) or higher, 2 It is preferable that it be higher than ).

[0061] The adhesive strength of the conductive particle-containing film 10 can also be determined in accordance with the adhesive strength test described in Japanese Patent Publication No. 2017-48358. In this adhesive strength test, for example, when the conductive particle-containing film is sandwiched between two glass plates, one glass plate is fixed, and the other glass plate is peeled off at a peeling speed of 10 mm / min and a test temperature of 50°C, by strengthening the adhesion between the fixed glass plate and the conductive particle-containing film, it becomes possible to measure the adhesive strength between the peeling glass plate and the surface of the conductive particle-containing film that is bonded to that glass plate. The adhesive strength measured in this way is preferably 10 kPa (1 N / cm²). 2 ) or more, more preferably 100 kPa (10 N / cm²) 2 ) can be set to 2 or more.

[0062] Because the conductive particle-containing film 10 has the adhesive strength described above, the electronic component 1 to be heat-pressed can, for example, have a longest side length of 600 μm or less, or the area of ​​each electrode can be 1000 μm or less, which is smaller than a typical IC chip. 2 Even with the following electronic components, the problem of misalignment during temporary crimping in the overlapping process can be minimized.

[0063] The conductive particle-containing film 10 is not particularly limited in terms of its own manufacturing method, and can be obtained, for example, by the method described in Japanese Patent Publication No. 6187665.

[0064] <Connecting electronic components to a circuit board> The manufacturing method of the present invention generally includes a temporary bonding step of attaching a conductive particle-containing film 10 to a substrate 20, a step of overlapping an electrode 2 of a fine electronic component 1 and a substrate 20 having an electrode corresponding to the electrode 2 of the electronic component 1 via the conductive particle-containing film 10 (overlapping step), and a step of curing the insulating resin of the conductive particle-containing film 10 while applying pressure to the electronic component 1 and the substrate 20 that are overlapped via the conductive particle-containing film 10 (pressure curing step). In the connection structure obtained by this manufacturing method, the number of electrodes of the electronic component 1 may be one or more. This can be appropriately determined depending on the application of the connection structure.

[0065] Furthermore, between the overlapping process and the pressure curing process, a pre-pressure step may be provided as needed, in which the electronic component 1 and the substrate 20, which are overlapped via the conductive particle-containing film 10, are pressed with a pressure smaller than the pressure applied in the pressure curing process, thereby sandwiching the conductive particles between the electrodes of the electronic component 1 and the electrodes of the substrate 20. Hereinafter, the pressure applied in the pre-pressure step will be referred to as the first pressure, and the pressure applied in the pressure curing process will be referred to as the second pressure.

[0066] Furthermore, the manufacturing method of the present invention may include preliminary or additional steps as needed.

[0067] The following describes a manufacturing method of one embodiment of the present invention, which includes a temporary bonding step, an overlapping step, a pre-pressure step, and a pressure curing step, when connecting a semiconductor component attached to a dicing tape 3 as an electronic component 1 to a substrate 20, based on Figures 3A to 8. The dicing tape 3 may be replaced with a transfer stamp material, an adhesive film, an adhesive-coated substrate film, etc.

[0068] (1) Alignment process and preparation process therefor In the method of the present invention, multiple electronic components can be connected at once, and as described later, the first and second pressurization can be performed using a pressurizing device. However, it is preferable to adjust the number of electronic components connected at once so as not to exceed the thrust limit of the pressurizing device and to align the electronic components.

[0069] To align the electrode 2 of the electronic component 1 with the electrode 21 of the substrate 20, first, as shown in Figure 3A, an adhesive release film 4 is attached to the electronic component 1 held by the dicing tape 3, and then the dicing tape 3 is peeled off from the electronic component 1 to expose the electrode 2 of the electronic component 1, as shown in Figure 3B. It is preferable to use a release film 4 whose adhesive force to the electronic component 1 is less than the adhesive force of the conductive particle-containing film 10 to the electronic component 1.

[0070] In this embodiment, an example is shown in which multiple electronic components 1 are connected to the substrate 20 simultaneously. However, in the present invention, when connecting multiple electronic components 1 to the substrate 20, it is not necessary to connect all of them at the same time. They may be connected individually, multiple components may be selectively connected within the whole, or all of them may be connected at once.

[0071] On the other hand, as shown in Figure 4, a conductive particle-containing film 10 is placed on the electrode 21 formation surface of the substrate 20 on the stage 31 and temporarily attached. In this embodiment, the conductive particle-containing film 10 uses an insulating resin layer 12 which has a two-layer structure consisting of a thermosetting high-viscosity resin layer 13 in which conductive particles 11 are held and a low-viscosity resin layer 14 laminated on the high-viscosity resin layer 13. In the conductive particle-containing film 10 shown in the figure, the conductive particles 11 are present at the interface between the high-viscosity resin layer 13 and the low-viscosity resin layer 14, and the conductive particles 11 protrude from the interface towards both the low-viscosity resin layer 14 and the high-viscosity resin layer 13. However, the amount of protrusion on the low-viscosity resin layer 14 side is smaller than the amount of protrusion on the high-viscosity resin layer 13 side, and the conductive particles 11 are substantially held by the high-viscosity resin layer 13.

[0072] When arranging the conductive particle-containing film 10 on the substrate 20, the description in Japanese Patent Application Publication No. 2017-098126 may be applied to selectively arrange the good portion of the conductive particle-containing film 10 on the substrate 20.

[0073] After placing the conductive particle-containing film 10 on the substrate 20 and temporarily attaching it, the electrodes 2 of the electronic component 1 and the electrodes 21 of the substrate 20 are aligned. Known techniques can be used for the alignment method, and there are no particular limitations. In this invention, since the insulating resin layer 12 does not begin to harden before the alignment is completed, precise alignment becomes possible.

[0074] Furthermore, as a method for placing the conductive particle-containing film 10 on the electrodes 21 of the substrate 20, and a method for aligning and placing the electrodes 2 of the electronic component 1 on the conductive particle-containing film 10 placed on the electrodes 21 of the substrate 20, for example, a known laser lift-off method (e.g., Japanese Patent Application Publication No. 2017-157724) or a similar method may be used to irradiate the conductive particle-containing film 10 with laser light, detach individual pieces of film corresponding to the area of ​​the electrodes 21 from the conductive particle-containing film 10, and land them on the electrodes 21. Alternatively, laser light may be irradiated onto the electronic component 1 formed vertically and horizontally on a translucent substrate, and the electronic component 1 may be landed on the conductive particle-containing film on the electrodes 21 of the substrate 20 while aligning it. The laser lift-off method can be performed using a commercially available laser lift-off device (e.g., a laser lift-off device from Shin-Etsu Chemical Co., Ltd., product name "Invisi LUM-XTR").

[0075] Alternatively, the conductive particle-containing film 10 may be transferred to the electrode 2 of the electronic component 1 or the electrode 21 of the substrate 20 by a transfer method using a known stamping material (for example, Japanese Patent Application Publication No. 2021-141160).

[0076] (2) Overlay process The aligned electronic component 1 and substrate 20 are placed on top of each other via a conductive particle-containing film 10, as shown in Figure 5, according to a known method, and temporary pressing is performed as needed. If necessary, the release film 4 is peeled off and removed. The conductive particle-containing film 10 may be pre-cut into individual pieces.

[0077] Furthermore, although not shown in detail, the individual pieces of the conductive particle-containing film may be landed on the substrate using the laser lift-off method described above, or the μLEDs may be landed on the conductive particle-containing film. In this case, the size of the individual pieces of the conductive particle-containing film is determined appropriately according to the size of the μLEDs and electrodes, and there may be one piece per μLED, one piece per electrode, or multiple μLEDs may be connected by a single piece.

[0078] Furthermore, when electronic components such as μLEDs are projected onto the conductive particle-containing film 10 using the laser lift-off method, the substrate may have, for example, a silicone rubber layer to suppress deformation, destruction, and displacement of the projectile position of the electronic components. The conductive particle-containing film may be in the form of individual pieces, and the silicone rubber layer may be polydimethylsiloxane (PDMS).

[0079] By using the laser lift-off method, conductive particle-containing films and electronic components such as μLEDs can be attached or arranged on a silicone sheet such as a polydimethylsiloxane (PDMS) sheet, and then transferred to a substrate. In other words, by transferring the state in which the conductive particle-containing film and electronic components are attached to the silicone sheet to the substrate, the electronic components and the substrate can be superimposed. To put it another way, whether the conductive particle-containing film is attached or arranged on a substrate using a silicone sheet such as a polydimethylsiloxane (PDMS) sheet by the laser lift-off method, or whether electronic components such as μLEDs are attached or arranged on a conductive particle-containing film using a silicone sheet by the laser lift-off method, the electronic components such as μLEDs or the fragmented conductive particle-containing film on the silicone sheet can be transferred. In other words, by transferring the state in which the electronic components or fragmented conductive particle-containing film are attached to the silicone sheet to the substrate, the electronic components and the substrate can be superimposed. The conductive particle-containing film may be fragmented. The laser lift-off method can be used in various forms when performing the superimposition process.

[0080] In addition, the insulating resin layer 12 constituting the conductive particle-containing film 10 is preferably configured to have a rubber hardness of 20-40, more preferably 20-35, and even more preferably 20-30, as measured by durometer A (according to JIS K 6253), by incorporating cushioning rubber materials, silica, talc, titanium dioxide, calcium carbonate, magnesium oxide, and other inorganic fillers, and the storage modulus of elasticity measured by dynamic viscoelasticity testing using an indentation device at a temperature of 30°C and a frequency of 200Hz is preferably 60 MPa or less. This is because if the storage modulus of elasticity is too high, the insulating resin layer of the conductive particle-containing film cannot absorb the impact of electronic components ejected at high speed by laser irradiation, and the transfer rate of electronic components tends to decrease.

[0081] On the other hand, the storage modulus of the insulating resin layer after laser irradiation is preferably 100 MPa or higher, and more preferably 2000 MPa or higher, at a temperature of 30°C and a frequency of 200 Hz. If this storage modulus is too low, good conductivity cannot be obtained, and connection reliability tends to decrease. The storage modulus at 30°C can be measured in tensile mode using a viscoelasticity tester (Vibron, A&D Co., Ltd.) in accordance with JIS K7244, for example, under measurement conditions of a frequency of 11 Hz and a heating rate of 3°C / min.

[0082] (3) Pre-pressurization process (first pressurization) In the pre-pressurization process, as shown in Figure 6, pressure is applied from the electronic component 1 side to the electronic component 1 and substrate 20, which are stacked on top of each other via the conductive particle-containing film 10, using a pressurization tool 30. This first pressurization is carried out until the conductive particles 11 contained in the conductive particle-containing film 10 are sandwiched between the electrode 2 of the electronic component 1 and the electrode 21 of the substrate 20, as shown in Figure 7. In other words, the first pressurization holds the conductive particles between the electrodes so that they do not move unnecessarily. It is preferable that the distance between the electrode 2 of the electronic component 1 and the electrode 21 of the substrate 20 is set to 70% to 100% of the original particle diameter of the conductive particles 11 sandwiched between them by the first pressurization.

[0083] The pressure applied in the first pressurization can be, for example, 0.5 to 15 MPa, preferably 2 to 8 MPa. This can be adjusted as appropriate depending on the size of the conductive particles, compressibility (hardness), repulsive force, thickness of the resin layer, etc.

[0084] The temperature during the first pressurization may be heated if necessary, but it is preferable to keep it below the curing reaction start temperature of the conductive particle-containing film 10, usually 80°C or lower, preferably 55°C or lower, and more preferably 40°C or lower. There is no particular lower limit, and pressure may be applied only at room temperature (25°C ± 15°C). In other words, the temperature during the first pressurization can be the ambient temperature. This pre-pressurization step (first pressurization) may be omitted in some cases.

[0085] (4) Pressure curing process (second pressure) In the pressure curing process, a second pressure is applied at a higher pressure than the first pressure without reducing the pressure from the first pressure. The pressure at this time can be 30 to 120 MPa, preferably 60 to 80 MPa. This pressure is adjusted according to the size of the conductive particles, compressibility (hardness), repulsive force, thickness of the resin layer, etc. As a result, as shown in Figure 8, the conductive particles 11 sandwiched between the electrode 2 of the electronic component 1 and the electrode 21 of the substrate 20 are pressed and flattened, ensuring reliable electrical connection between these electrodes 2 and 21.

[0086] Furthermore, the pressure curing process cures the insulating resin layer 12, fixing the conductive particles 11 sandwiched between the electrode 2 of the electronic component 1 and the electrode 21 of the substrate 20, thereby obtaining the connection structure 40 of the present invention. Therefore, if the insulating resin layer 12 is formed of a thermosetting resin, the temperature is increased in the pressure curing process. In this case, it is preferable to heat it for a short time using a pulse heater or the like. The heating rate is appropriately determined according to the curing characteristics of the insulating resin layer 12, but for example, the target temperature is set to 100°C or higher, preferably 120°C or higher, more preferably 150°C or higher, and the time until press-out is 4 seconds or more, preferably 7 seconds or more, more preferably 10 seconds or more. Note that if the conductive particles are solder, the pressure curing process can be replaced with a reflow process.

[0087] The resulting connection structure 40, shown in Figure 8, for example, has an area of ​​1000 μm² for each electrode. 2 A fine electronic component 1, or one with a longest side length of 600 μm or less, and a substrate 20 having electrodes 21 corresponding to the electrodes 2 of the electronic component 1 are bonded together by a cured insulating resin layer 12 of a conductive particle-containing film 10, and the electrodes 2 of the electronic component 1 and the electrodes 21 of the substrate 20 are electrically connected by conductive particles 11 sandwiched between them.

[0088] In this invention, the number of conductive particles 11 sandwiched between the electrode 2 of the electronic component 1 and the electrode 21 of the substrate 20 may be 3 or more per pair of opposing electrodes 2 and 21, as in a typical anisotropic connection. However, it may be less than 3, or even 1, as long as the conductive particles 11 located on the opposing pair of electrodes 2 and 21 reliably contribute to conductivity. Therefore, the number density of conductive particles 11 in the conductive particle-containing film 10 is preferably 3 or more conductive particles 11 per pair of opposing electrodes 2 and 12. However, as long as the particles are reliably captured and there are no short circuits, it is practically usable with fewer than 3 or more particles.

[0089] In the above example, the conductive particle-containing film 10 was first placed on the substrate 20 during the alignment process, but in the present invention, the conductive particle-containing film 10 may be first placed on the electronic component 1.

[0090] The above describes an embodiment in which a semiconductor component is connected to a substrate as electronic component 1, based on the drawings. However, the present invention can be applied when connecting various miniature electronic components 1 to a substrate. [Explanation of symbols]

[0091] 1. Semiconductor components, electronic components 2. Electrodes of electronic components 3. Films and dicing tapes for semiconductor processing. 4. Release film 10. Conductive particle-containing film 11 Conductive particles 12. Insulating resin layer 13 High viscosity resin layer 14 Low viscosity resin layer 20 circuit boards 21 Electrodes of the substrate 30 Pressure Tools 31 stages 40 Connection Structures

Claims

1. A method for manufacturing a connection structure in which corresponding electrodes of a fine electronic component and a substrate having electrodes corresponding to the electrodes of the electronic component are electrically connected, A superposition step of superposing the electronic component and the substrate via a conductive particle-containing film in which conductive particles are held in an insulating resin layer, A pressure-curing step of curing the insulating resin layer of the conductive particle-containing film while pressurizing the electronic component and the substrate superposed via the conductive particle-containing film, having, The curing characteristics of the conductive particle-containing film are such that the time from the start of heating to the start of curing of the insulating resin layer when the conductive particle-containing film is heated from 40°C to 80°C is 10 minutes or more manufacturing method.

2. The manufacturing method according to claim 1, further comprising a pre-pressurization step of sandwiching the conductive particles between the electrodes of the electronic component and the electrodes of the substrate by pressurizing the electronic component and the substrate superposed via the conductive particle-containing film with a pressure smaller than the pressure applied in the pressure-curing step, between the superposition step and the pressure-curing step.

3. The manufacturing method according to claim 1 or 2, wherein the conductive particle-containing film is held on the electronic component or the substrate by a laser lift-off method.

4. The manufacturing method according to claim 1 or 2, wherein the electronic component is superposed on the substrate by a laser lift-off method.

5. The manufacturing method according to claim 1 or 2, wherein the time from the start of heating to the start of curing of the insulating resin layer when the conductive particle-containing film is heated from 40°C to 80°C is adjusted according to the time required for the superposition step of the electronic component and the substrate, etc.

6. The manufacturing method according to claim 1 or 2, wherein the conductive particles in the conductive particle-containing film are regularly arranged.

7. The manufacturing method according to claim 1 or 2, wherein the conductive particles in the conductive particle-containing film have a particle density such that one or more and less than three conductive particles are captured at each electrode. Claim 8 The manufacturing method according to claim 1 or 2, wherein the insulating resin layer is formed of a laminate of two insulating resin layers having different minimum melt viscosities. Claim 9 The manufacturing method according to claim 1 or 2, wherein the electronic component is a semiconductor component. Claim 10 The manufacturing method according to claim 9, wherein the semiconductor component to be superposed on the substrate via the conductive particle-containing film is adhered to a semiconductor processing film. Claim 11 The manufacturing method according to claim 10, wherein the adhesive force of the conductive particle-containing film to the semiconductor component is greater than the adhesive force of the semiconductor processing film to the semiconductor component. Claim 12 The manufacturing method according to claim 1, wherein an electronic component having a length of the longest side of 300 μm or less is used as the electronic component. Claim 13 An electronic component having a length of the longest side of 600 μm or less or an area of an individual electrode of 1000 μm 2 The following electronic component and a substrate having an electrode corresponding to the electrode of the electronic component are adhered with an insulating resin, and the corresponding electrodes of the electronic component and the substrate are electrically connected by one or more and less than three conductive particles sandwiched therebetween. Connection structure. Claim 14 The connection structure according to claim 13, wherein the length of the longest side of the electronic component is 300 μm or less.

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