glue

Abstract

To provide an adhesive with a sufficiently high permeability, with which it is simple and easy to handle during manufacture.SOLUTION: An adhesive 50 includes a bisphenol F resin 51, a curing agent 53 for the bisphenol F resin 51, and magnetic powder 52. The volume ratio of the magnetic powder 52 to the adhesive 50 is 35 vol.% or lower. The number average molecular weight of the bisphenol F resin 51 is 312 to 360 g / mol inclusive.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to adhesives. [Background technology]

[0002] The coil component described in Patent Document 1 includes a core. The core has a winding core portion and two flange portions. The winding core portion is rectangular prism-shaped. The two flange portions are connected to both sides of the winding core portion. Each flange portion protrudes outward from the winding core portion in a direction perpendicular to the central axis of the winding core portion. The core is made of a magnetic material. The coil component also includes a top plate. The top plate is a substantially rectangular plate. The top plate is connected to the core so as to bridge the two flange portions. The coil component includes an adhesive. The adhesive is interposed between the top plate and the core. The adhesive bonds the top plate and the core to each other. The adhesive also contains magnetic powder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-190633 Summary of the Invention [Problem to be solved by the invention]

[0004] The adhesive used in the coil component described in Patent Document 1 contains magnetic powder, which gives it a higher magnetic permeability than an adhesive without magnetic powder. On the other hand, the greater the proportion of magnetic powder in the adhesive, the higher the viscosity of the adhesive tends to be. If the adhesive's viscosity is excessively high, for example, when applying the adhesive to a top plate using a jig, a phenomenon such as the adhesive forming strings between the jig and the top plate occurs. In other words, the increased viscosity of the adhesive makes it difficult to handle during application. Therefore, there is a demand for an adhesive that ensures sufficient magnetic permeability while being easy to handle during manufacturing. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention provides an adhesive containing a bisphenol F type resin, a curing agent for the bisphenol F type resin, and a magnetic powder, wherein the volume ratio of the magnetic powder to the adhesive is 35 vol% or less, and the number average molecular weight of the bisphenol F type resin is 312 g / mol or more and 360 g / mol or less. [Effects of the Invention]

[0006] According to the above configuration, the adhesive can be easily handled during manufacturing while ensuring a sufficient magnetic permeability. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view of a coil component. [Figure 2] FIG. 2 is an exploded perspective view of the coil component. [Figure 3] FIG. 3 is a schematic diagram of the adhesive before hardening. [Figure 4] FIG. 4 is a graph showing the test results of the yarn breaking time. [Figure 5] FIG. 5 is a graph showing the test results of the yarn breaking time. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of a coil component including an adhesive will be described with reference to the drawings. Note that the drawings may show components enlarged for ease of understanding. The dimensional ratios of the components may differ from those in the actual product or from those in other drawings.

[0009] <About coil components> As shown in FIG. 1, the coil device 10 includes a drum core 10C as a first core and a top plate 10F as a second core.

[0010] The drum core 10C has a winding core 11. The winding core 11 is a quadrangular prism having a central axis 11C. The cross section of the winding core 11 perpendicular to the central axis 11C is rectangular. Note that the term "rectangular" as used here refers to a shape having four sides and an overall rectangular shape, and also includes shapes with chamfered corners. The material of the winding core 11 is, for example, alumina, Ni-Zn ferrite, synthetic resin, or a mixture thereof. In this embodiment, the material of the winding core 11 is Ni-Zn ferrite, which is a type of magnetic material.

[0011] Here, a specific axis perpendicular to the central axis 11C of the winding core 11 is defined as the first axis X. In this embodiment, the first axis X is parallel to the two short sides of the winding core 11 when viewed in the direction along the central axis 11C. An axis perpendicular to both the first axis X and the central axis 11C is defined as the second axis Y. In this embodiment, the second axis Y is parallel to the two long sides of the winding core 11 when viewed in the direction along the central axis 11C. An axis parallel to the central axis 11C is defined as the third axis Z. One of the directions along the first axis X is defined as the first positive direction X1, and the direction opposite to the first positive direction X1 is defined as the first negative direction X2. Similarly, one of the directions along the second axis Y is defined as the second positive direction Y1, and the direction opposite to the second positive direction Y1 is defined as the second negative direction Y2. One of the directions along the third axis Z is defined as a third positive direction Z1, and the direction opposite to the third positive direction Z1 is defined as a third negative direction Z2.

[0012] As shown in FIG. 1 , the drum core 10C has two flanges 20 connected to both ends of the winding core 11 in the direction along the central axis 11C. The two flanges 20 are specifically a first flange 21 and a second flange 22. The first flange 21 is connected to a first end, which is the end of the winding core 11 in the third positive direction Z1. The first flange 21 has a flat, approximately rectangular plate shape. The thickness direction of the first flange 21 is along the third axis Z. When viewed in the direction along the third axis Z, each side of the first flange 21 is approximately parallel to each side of the winding core 11. Furthermore, the first flange 21 protrudes outward from the outer surface of the winding core 11 in the directions along the first axis X and the second axis Y. That is, when viewed in a direction along the third axis Z, the first flange portion 21 protrudes from the outer surface of the winding core portion 11 over the entire periphery of 360 degrees.

[0013] The first flange 21 has a first recess 21A. The first recess 21A is recessed with respect to an end surface of the first flange 21 in the first positive direction X1. The first recess 21A is located at the center of the first flange 21 in the direction along the second axis Y. The first recess 21A is open to both sides of the first flange 21 in the direction along the third axis Z. As a result, the end surface of the first flange 21 on the first positive direction X1 side is divided into two parts with the first recess 21A in between.

[0014] The second flange 22 is connected to a second end of the winding core 11, which is the end on the third negative direction Z2 side. The second flange 22 has a shape that is plane-symmetrical to the first flange 21. That is, the second flange 22 is a substantially rectangular plate. The second flange 22 protrudes outward from the outer surface of the winding core 11 in the directions along the first axis X and the second axis Y. That is, the second flange 22 protrudes 360 degrees from the outer surface of the winding core 11 when viewed in the direction along the third axis Z. The second flange 22 has a second recess 22A that is similar to the first recess 21A of the first flange 21. The first flange 21 and the second flange 22 are made of the same Ni-Zn ferrite material as the winding core 11. That is, the drum core 10C is made of a magnetic material. The first flange 21 and the second flange 22 are integrally molded with the winding core 11.

[0015] The top plate 10F has a flat, rectangular plate shape. The thickness direction of the top plate 10F is along the first axis X. The long sides of the top plate 10F are parallel to the third axis Z. The short sides of the top plate 10F are parallel to the second axis Y. The top plate 10F is located on the first negative direction X2 side with respect to the drum core 10C. The top plate 10F is connected to both the surface of the first flange portion 21 facing the first negative direction X2 and the surface of the second flange portion 22 facing the first negative direction X2. In other words, the top plate 10F is connected to the drum core 10C so as to bridge between the first flange portion 21 and the second flange portion 22. The top plate 10F is made of the same material as the winding core portion 11. That is, the top plate 10F is made of Ni-Zn ferrite, a type of magnetic material. The top plate 10F forms a closed magnetic circuit together with the drum core 10C. In this embodiment, the top plate 10F, which is not directly wound with wires described later, and the flange 20 of the drum core 10C, which is not wound with wires, are also considered to be the core or part of the core.

[0016] The coil device 10 includes an adhesive 50. The adhesive 50 is interposed between the drum core 10C and the top plate 10F. That is, the adhesive 50 bonds the drum core 10C and the top plate 10F together. In this embodiment, the drum core 10C and the top plate 10F are in direct contact with the adhesive 50. In other words, the top plate 10F is connected to the two flanges 20 via the adhesive 50. Details of the adhesive 50 will be described later.

[0017] The coil device 10 includes four external electrodes 30. Specifically, the coil device 10 includes a first electrode 31, a second electrode 32, a third electrode 33, and a fourth electrode 34. The first electrode 31 is located on the end face of the outer surface of the first flange portion 21 on the first positive direction X1 side. The first electrode 31 is also located on the outer surface of the first flange portion 21 on the second positive direction Y1 side with respect to the central axis 11C. Specifically, the first electrode 31 is located on the second positive direction Y1 side with respect to the first recess 21A.

[0018] The second electrode 32 is located on the end face of the outer surface of the first flange 21 on the first positive direction X1 side. The second electrode 32 is also located on the outer surface of the first flange 21 on the second negative direction Y2 side with respect to the central axis 11C. Specifically, the second electrode 32 is located on the second negative direction Y2 side with respect to the first recess 21A.

[0019] The third electrode 33 is located on the end face of the outer surface of the second flange 22 on the first positive direction X1 side. The third electrode 33 is also located on the outer surface of the second flange 22 on the second positive direction Y1 side with respect to the central axis 11C. Specifically, the third electrode 33 is located on the second positive direction Y1 side with respect to the second recess 22A.

[0020] The fourth electrode 34 is located on the end face of the outer surface of the second flange 22 on the first positive direction X1 side. The fourth electrode 34 is also located on the outer surface of the second flange 22 on the second negative direction Y2 side with respect to the central axis 11C. Specifically, the fourth electrode 34 is located on the second negative direction Y2 side with respect to the second recess 22A.

[0021] Although not shown, the external electrode 30 has a metal layer and a plating layer. The material of the metal layer is silver. The metal layer is formed on the outer surfaces of the first flange portion 21 and the second flange portion 22. The plating layer consists of three layers. The plating layers are formed by stacking copper, nickel, and tin on the surface of the metal layer in this order. The end face of the coil component 10 on the first positive direction X1 side is the mounting surface that faces the substrate when the coil component 10 is mounted on the substrate.

[0022] 1, the coil device 10 includes a first wire 41 and a second wire 42. The first wire 41 and the second wire 42 are wound around the winding core portion 11 of the drum core 10C.

[0023] Although not shown, the first wire 41 includes a copper wire and an insulating coating. The insulating coating covers the outer surface of the copper wire. The first wire 41 has a substantially circular shape in a cross section perpendicular to the direction in which the first wire 41 extends. The second wire 42 has the same configuration as the first wire 41. That is, the second wire 42 includes a copper wire and an insulating coating. Note that in FIG. 1, the first wire 41 is colored with dots.

[0024] A first wire end 41A of the first wire 41 is connected to the first electrode 31. A second wire end 41B of the first wire 41 is connected to the third electrode 33. The first wire end 41A and the second wire end 41B are connected to the corresponding external electrodes 30 by thermocompression bonding.

[0025] In addition, the first wire 41 is wound around the winding core 11 so that, when viewed in the third negative direction Z2, it progresses clockwise as it travels from the first wire end 41A side to the second wire end 41B side.

[0026] A first end 42A of the second wire 42 is connected to the second electrode 32. A second end 42B of the second wire 42 is connected to the fourth electrode 34. The first end 42A and the second end 42B are connected to the corresponding electrodes by thermocompression bonding.

[0027] When viewed in the third negative direction Z2, the second wire 42 is wound around the winding core 11 so as to progress clockwise from the first wire end 42A to the second wire end 42B. That is, the second wire 42 is wound in the same direction as the first wire 41. The second wire 42 is wound around the winding core 11 from the outside of the first wire 41.

[0028] <About adhesives> As shown in FIG. 2, the adhesive 50 covers the entire surface of the first flange 21 facing the first negative direction X2. The adhesive 50 connects the first flange 21 and the top plate 10F without any gaps. Similarly, the adhesive 50 covers the entire surface of the second flange 22 facing the first negative direction X2. The adhesive 50 connects the second flange 22 and the top plate 10F without any gaps. In other words, the top plate 10F is connected to the two flanges 20.

[0029] As shown in Fig. 3, the adhesive 50 contains bisphenol F resin 51, magnetic powder 52, a curing agent 53, a curing accelerator 54, a silane coupling agent 55, and a dispersant 56. Note that Fig. 3 shows the adhesive 50 in a state before curing. In Fig. 3, only some of the magnetic powder 52, the curing agent 53, and the curing accelerator 54 are labeled with reference numerals.

[0030] Specifically, adhesive 50 was produced as follows: First, bisphenol F resin 51, curing agent 53, curing accelerator 54, silane coupling agent 55, dispersant 56, and magnetic powder 52 were mixed using a kneader (model number: Hibismix (registered trademark) 2P-03 (manufactured by Primix Corporation)) at a rotation speed of 30 rpm for 5 minutes. Then, using a disperser (model number: EXAKT 80E (manufactured by Nagase Screen Printing Research Institute)), the mixture was kneaded at a clearance of 6 μm and 230 rpm to produce pre-cured adhesive 50.

[0031] In this embodiment, the bisphenol F type resin 51 is a bisphenol F type epoxy resin. Specifically, the bisphenol F type resin 51 has CAS No. 9003-36-5. In this embodiment, the bisphenol F type resin 51 is collectively referred to as the bisphenol F type resin 51 regardless of whether it is a monomer or a polymer.

[0032] The number average molecular weight of the bisphenol F resin 51 is 312 g / mol. The number average molecular weight of the bisphenol F resin 51 may be 312 g / mol or more and 360 g / mol or less. The number average molecular weight can be measured using a GPC (model number: HLC-8120GPC (manufactured by Tosoh Technosystems)). GPC stands for gel permeation chromatography. In measurements using this device, the column temperature was 40°C. Tetrahydrofuran was used as the solvent in the measurements. The flow rate of the solution containing the solvent was 1.0 ml / min. The standard sample was monodisperse polystyrene.

[0033] In this embodiment, the volume ratio of the bisphenol F resin 51 to the adhesive 50 is 54.5 vol%. A more preferable volume ratio of the bisphenol F resin 51 to the adhesive 50 is 54.4 vol% or more and 68.7 vol% or less. The "volume ratio to the adhesive 50" refers to the volume ratio to the entire volume of the adhesive 50 before hardening, expressed as a percentage.

[0034] In this embodiment, the magnetic powder 52 is nickel powder. Specifically, the magnetic powder 52 has CAS No. 7440-02-0. The magnetic powder 52 includes particles having a particle size of 0.1 μm or more and 3.0 μm or less. The volume ratio of the magnetic powder 52 to the adhesive 50 is 35 vol% or less. In this embodiment, the volume ratio of the magnetic powder 52 to the adhesive 50 is 35 vol%. The volume ratio of the magnetic powder 52 to the adhesive 50 may be 35 vol% or less, and preferably 20 vol% or more.

[0035] In the particle size distribution of the magnetic powder 52, the median particle size (D50) is 0.8 μm or more and 2.5 μm or less. The median particle size (D50) of the magnetic powder 52 is calculated, for example, as follows. First, the magnetic powder 52 is sampled using a scanning electron microscope to obtain the particle size distribution. Next, in the particle size distribution, the frequency of each particle size is integrated from the smallest particle size to the largest particle size. The particle size at which this integrated value reaches 50% is defined as the median particle size (D50).

[0036] The curing agent 53 is a curing agent for the bisphenol F type resin 51. In this embodiment, the curing agent 53 is dicyandiamide. Specifically, the curing agent 53 has CAS No. 461-58-5. The volume ratio of the curing agent 53 to the adhesive 50 is 4.36 vol%. Note that the volume ratio of the curing agent 53 to the adhesive 50 is more preferably 4.36 vol% or more and 5.49 vol% or less.

[0037] The curing accelerator 54 is a curing accelerator for the bisphenol F type resin 51. In this embodiment, the curing accelerator 54 is an amine adduct. Specifically, the curing accelerator 54 has CAS No. 134091-75-1. The volume ratio of the curing accelerator 54 to the adhesive 50 is 2.73 vol%. Note that the volume ratio of the curing accelerator 54 to the adhesive 50 is more preferably 2.72 vol% or more and 3.43 vol% or less.

[0038] The dispersant 56 disperses the magnetic powder 52 within the adhesive 50. In this embodiment, the dispersant 56 is a modified carboxyl group-containing polymer. Specifically, it is a modified carboxyl group-containing polymer with an acid value of 55 mgKOH / g. The volume ratio of the dispersant 56 to the adhesive 50 is 3.1 vol%. A more preferable volume ratio of the dispersant 56 to the adhesive 50 is 2.18 vol% or more and 3.13 vol% or less.

[0039] In this embodiment, the silane coupling agent 55 is glycidoxypropyltrimethoxysilane. Specifically, the silane coupling agent 55 has CAS No. 253-83-8. The volume ratio of the silane coupling agent 55 to the adhesive 50 is 0.3 vol%. Note that the volume ratio of the silane coupling agent 55 to the adhesive 50 is more preferably 0.24 vol% or more and 0.35 vol% or less.

[0040] <About adhesive properties> The cured adhesive 50 had a glass transition temperature of 125°C or higher. The glass transition temperature of the adhesive 50 was measured as follows. First, bisphenol F resin 51, curing agent 53, curing accelerator 54, silane coupling agent 55, dispersant 56, and magnetic powder 52 were mixed and then baked in a 150°C atmosphere for 3 hours to prepare a cured adhesive test piece. The dimensions of the adhesive test piece were 20 mm in length, 10 mm in width, and 1.5 mm in thickness. Then, both short sides of the adhesive test piece were fixed to a viscoelasticity measuring device (model number: DMS7100 (manufactured by Hitachi High-Technologies Corporation)), and the elastic modulus was measured. During the measurement, the test atmosphere was heated while a sinusoidal wave force with a frequency of 1 Hz was applied to the adhesive test piece. The heating rate was 5°C / min, and the temperature range was 25°C to 280°C. The change in the modulus of elasticity of the adhesive test piece relative to the temperature increase was measured, and the inflection point was taken as the glass transition temperature.

[0041] The adhesive strength of the adhesive 50 after curing is 10 MPa or more. The adhesive strength of the adhesive 50 was measured as follows. First, a bisphenol F-type resin 51, a curing agent 53, a curing accelerator 54, a dispersant 56, a silane coupling agent 55, and a magnetic powder 52 were mixed to obtain the pre-cured adhesive 50. The adhesive 50 was then applied between two alumina substrates in a 5 mm square area. Therefore, this measurement allows the measurement of the adhesive strength per 25 square millimeters. Then, the two alumina substrates coated with the pre-cured adhesive 50 were baked in an atmosphere at 150°C for 3 hours to prepare a cured adhesive test piece. Then, one alumina substrate and the other alumina substrate were fixed to an autograph (model number: AG XD Plus, manufactured by Shimadzu Corporation) and a tensile test was performed. That is, in this embodiment, the tensile adhesive strength was measured as the adhesive strength. In the test, the tensile speed was 20 mm / min. The load at which the adhesion test piece broke was taken as the adhesive strength of the adhesive 50. The temperature of the test environment was 23°C, and the relative humidity was 50%.

[0042] <Continuous printing of adhesive> Four samples of adhesive 50 with different number-average molecular weights of bisphenol F resin 51 were prepared, and the thread breakage time for each sample was measured. All four samples were identical except for the number-average molecular weight of bisphenol F resin 51. The volume ratio of magnetic powder 52 in each of the four samples was 35 vol%. Note that the volume ratio here refers to the volume ratio in the adhesive 50 before curing. The thread breakage time is the time from when the uncured adhesive 50 is applied to a substrate with a squeegee using a screen printer, and then when the squeegee is removed from the substrate, until the adhesive 50 stretched between the squeegee and the substrate breaks. The screen printing conditions for measuring the thread breakage time were a printing speed of 60 mm / s, printing pressure of 0.2 MPa, back pressure of 0.125 MPa, and clearance of 1 mm. Under these conditions, 100 consecutive prints were performed, and the thread breakage times were measured for the first, 25th, 50th, and 100th prints, and the average value was used as the representative thread breakage time.

[0043] The number average molecular weight of the bisphenol F resin 51 in the first sample was 312 g / mol, the same as in the above embodiment. The number average molecular weight of the bisphenol F resin 51 in the second sample was 340 g / mol. The number average molecular weight of the bisphenol F resin 51 in the third sample was 360 g / mol. The number average molecular weight of the bisphenol F resin 51 in the fourth sample was 380 g / mol. These four types of samples are Examples 1, 2, and 3 and Comparative Example 1 listed in Table 1 below.

[0044] As shown in FIG. 4 , the thread-breaking time for the first sample was 11 seconds. The thread-breaking time for the second sample was 12 seconds. The thread-breaking time for the third sample was 20 seconds. The thread-breaking time for the fourth sample was 80 seconds. Thus, it was found that the thread-breaking time increases as the number-average molecular weight of the bisphenol F resin 51 in the adhesive 50 increases. Furthermore, it was found that the thread-breaking time increases sharply when the number-average molecular weight of the bisphenol F resin 51 exceeds 360 g / mol. In other words, it was found that the inflection point of the thread-breaking time relative to the increase in number-average molecular weight is approximately 360 g / mol. When applying the adhesive 50 using a screen printing machine, the longer the thread-breaking time, the longer the waiting time with the squeegee separated from the substrate, which deteriorates continuous printing performance. From this perspective, it can be said that, from the standpoint of handling the adhesive 50, it is preferable that the number-average molecular weight of the bisphenol F resin 51 in the adhesive 50 be 360 ​​g / mol or less.

[0045] Five samples of the adhesive 50 were prepared, each with a different volume ratio of the magnetic powder 52, and the breakage time for each sample was measured. All five samples were identical except for the volume ratio of the magnetic powder 52. The number-average molecular weight of the bisphenol F resin 51 for each of the five samples was 340 g / mol. The definition of the breakage time was the same as described above. The volume ratio of the magnetic powder 52 for the first sample was 20 vol%. The volume ratio of the magnetic powder 52 for the second sample was 25 vol%. The volume ratio of the magnetic powder 52 for the third sample was 30 vol%. The volume ratio of the magnetic powder 52 for the fourth sample was 35 vol%. The volume ratio for the magnetic powder 52 for the fifth sample was 40 vol%. The volume ratios here are the volume ratios in the adhesive 50 before curing. These five samples are Examples 4, 5, 6, and 2, and Comparative Example 2, as listed in Table 1 below.

[0046] As shown in FIG. 5, the thread cutting time for the first sample was 10 seconds. The thread cutting time for the second sample was 10 seconds. The thread cutting time for the third sample was 11 seconds. The thread cutting time for the fourth sample was 12 seconds. The thread cutting time for the fifth sample was 80 seconds. In other words, it was found that when the volume ratio of magnetic powder 52 in adhesive 50 exceeds 35 vol%, the thread cutting time increases sharply. In other words, it was found that the inflection point of the thread cutting time relative to the increase in the volume ratio of magnetic powder 52 is approximately 35 vol%. From this, it can be said that from the perspective of handling of adhesive 50, it is preferable that the volume ratio of magnetic powder 52 in adhesive 50 be 35 vol% or less.

[0047] <About the comparative test> The adhesives of Examples 1 to 9 and Comparative Examples 1 and 2 shown in Tables 1 and 2 below were prepared. The adhesives of these Examples and Comparative Examples were tested for their properties before and after curing. In the adhesives of Examples 1 to 9 and Comparative Examples 1 and 2, the synthetic resin was a bisphenol F epoxy resin. In the adhesives of Examples 1 to 6 and Comparative Examples 1 and 2, the median particle size (D50) of the magnetic powder 52 was 0.8 μm. The adhesives of Examples 1 to 9 and Comparative Examples 1 and 2 each contained magnetic powder 52, curing agent 53, curing accelerator 54, silane coupling agent 55, and dispersant 56.

[0048] <Regarding Examples 1 to 6> The results of the comparative test of the adhesives of Examples 1 to 6 and Comparative Examples 1 and 2 will be explained below.

[0049] [Table 1]

[0050] As shown in Table 1, in the adhesive of Example 1, the number average molecular weight of the bisphenol F type resin 51 is 312 g / mol. In the adhesive of Example 1, the volume ratio of the magnetic powder 52 is 35 vol%. In the adhesive of Example 1, the viscosity is 1833 Pa·s before curing. In the adhesive of Example 1, the magnetic permeability is 2.5 after curing. In the adhesive of Example 1, the glass transition temperature is 125°C after curing. In the adhesive of Example 1, the adhesive strength is 14 MPa after curing.

[0051] The viscosity was measured using a rotational rheometer (model number: MCR302 (manufactured by Anton Paar)). In the measurement using this device, a Φ25 mm cone plate was used. In addition, in the measurement, the rotation mode was set to flow curve, and the shear rate was set to 0.01 s -1 The temperature of the test environment was 25°C.

[0052] The magnetic permeability was measured as follows. First, bisphenol F resin 51, curing agent 53, curing accelerator 54, dispersant 56, silane coupling agent 55, and magnetic powder 52 were mixed to obtain an uncured adhesive 50. The adhesive 50 was then baked for one hour in an 85°C atmosphere to obtain a semi-cured adhesive 50. The semi-cured adhesive 50 was then filled into a mold with an outer diameter of 16 mm and an inner diameter of 10 mm. A small heat press (model number: H300-15, manufactured by AS ONE Corporation) was used to apply pressure at 4 MPa and a heating temperature of 150°C for 15 minutes to obtain a toroidal core. The real magnetic permeability of the toroidal core was measured using an impedance analyzer (model number: E4991A, manufactured by Keysight Technologies) at 10 MHz. The temperature of the test environment was 25°C.

[0053] In the adhesive of Example 2, the number average molecular weight of the bisphenol F type resin 51 is 340 g / mol. In the adhesive of Example 2, the volume ratio of the magnetic powder 52 is 35 vol%. In the adhesive of Example 2, the viscosity is 2528 Pa·s before curing. In the adhesive of Example 2, the magnetic permeability is 2.5 after curing. In the adhesive of Example 2, the glass transition temperature is 125°C after curing. In the adhesive of Example 2, the adhesive strength is 14 MPa after curing.

[0054] In the adhesive of Example 3, the number average molecular weight of the bisphenol F type resin 51 is 360 g / mol. In the adhesive of Example 3, the volume ratio of the magnetic powder 52 is 35 vol%. In the adhesive of Example 3, the viscosity is 3223 Pa·s before curing. In the adhesive of Example 3, the magnetic permeability is 2.5 after curing. In the adhesive of Example 3, the glass transition temperature is 125°C after curing. In the adhesive of Example 3, the adhesive strength is 14 MPa after curing.

[0055] In the adhesive of Example 4, the number average molecular weight of the bisphenol F type resin 51 is 340 g / mol. In the adhesive of Example 4, the volume ratio of the magnetic powder 52 is 20 vol%. In the adhesive of Example 4, the viscosity is 283 Pa·s before curing. In the adhesive of Example 4, the magnetic permeability is 1.7 after curing. In the adhesive of Example 4, the glass transition temperature is 125°C after curing. In the adhesive of Example 4, the adhesive strength is 14 MPa after curing.

[0056] In the adhesive of Example 5, the number average molecular weight of the bisphenol F type resin 51 is 340 g / mol. In the adhesive of Example 5, the volume ratio of the magnetic powder 52 is 25 vol%. In the adhesive of Example 5, the viscosity is 567 Pa·s before curing. In the adhesive of Example 5, the magnetic permeability is 2.0 after curing. In the adhesive of Example 5, the glass transition temperature is 125°C after curing. In the adhesive of Example 5, the adhesive strength is 14 MPa after curing.

[0057] In the adhesive of Example 6, the number average molecular weight of the bisphenol F type resin 51 is 340 g / mol. In the adhesive of Example 6, the volume ratio of the magnetic powder 52 is 30 vol%. In the adhesive of Example 6, the viscosity is 1143 Pa·s before curing. In the adhesive of Example 5, the magnetic permeability is 2.2 after curing. In the adhesive of Example 6, the glass transition temperature is 125°C after curing. In the adhesive of Example 6, the adhesive strength is 14 MPa after curing.

[0058] In the adhesive of Comparative Example 1, the number average molecular weight of the bisphenol F resin 51 is 380 g / mol. In the adhesive of Comparative Example 1, the volume ratio of the magnetic powder 52 is 35 vol%. In the adhesive of Comparative Example 1, the viscosity is 3760 Pa·s before curing. In the adhesive of Comparative Example 1, the magnetic permeability is 2.5 after curing. In the adhesive of Comparative Example 1, the glass transition temperature is 125°C after curing. In the adhesive of Comparative Example 1, the adhesive strength is 14 MPa after curing.

[0059] In the adhesive of Comparative Example 2, the number average molecular weight of the bisphenol F type resin 51 is 340 g / mol. In the adhesive of Comparative Example 2, the volume ratio of the magnetic powder 52 is 40 vol%. In the adhesive of Comparative Example 2, the viscosity is 4507 Pa·s before curing. In the adhesive of Comparative Example 2, the magnetic permeability is 2.9 after curing. In the adhesive of Comparative Example 2, the glass transition temperature is 125°C after curing. In the adhesive of Comparative Example 2, the adhesive strength is 14 MPa after curing.

[0060] As a result of the comparison test of thread cutting time, the thread cutting time of the adhesive of Example 1 was 11 seconds. The thread cutting time of the adhesive of Example 2 was 12 seconds. The thread cutting time of the adhesive of Example 3 was 20 seconds. The thread cutting time of the adhesive of Example 4 was 10 seconds. The thread cutting time of the adhesive of Example 5 was 10 seconds. The thread cutting time of the adhesive of Example 6 was 11 seconds. The thread cutting time of the adhesive of Comparative Example 1 was 80 seconds. The thread cutting time of the adhesive of Comparative Example 2 was 80 seconds.

[0061] In the "Judgment" column of "Properties (before curing)" in Tables 1 and 2, ○ indicates that the thread breakage time is 20 seconds or less, and × indicates that the thread breakage time is longer than 20 seconds. The above judgment value was determined as the boundary for whether or not there is a risk that adhesive 50 dripping from the squeegee will adhere to something other than the printing target.

[0062] The test results of Examples 1 to 6 and Comparative Example 1 showed that the thread breakage time tended to increase when the number average molecular weight of bisphenol F resin 51 was large. That is, as with the measurement results of thread breakage time using the above-mentioned four types of samples, the rate of increase in thread breakage time became rapidly larger when the number average molecular weight of bisphenol F resin 51 was greater than 360 g / mol. In other words, it can be said that the number average molecular weight of bisphenol F resin 51 is preferably 360 g / mol or less.

[0063] The test results of Examples 1 to 6 and Comparative Example 2 showed that the thread cutting time tended to be longer when the volume ratio of magnetic powder 52 was large. That is, as with the measurement results of thread cutting time using the above-mentioned five types of samples, the rate of increase in thread cutting time became rapidly large when the volume ratio of magnetic powder 52 exceeded 35 vol%. In other words, it can be said that the volume ratio of magnetic powder 52 is preferably 35 vol% or less.

[0064] Furthermore, in the case of Example 3, where the adhesive had a viscosity of 3223 Pa·s, the thread breaking time was 20 seconds. On the other hand, in the case of Comparative Example 1, where the adhesive had a viscosity of 3760 Pa·s, the thread breaking time was 80 seconds. From this, it is predicted that the inflection point in the transition of thread breaking time with increasing viscosity will be between 3223 Pa·s and 3760 Pa·s, i.e., approximately 3500 Pa·s. Therefore, it can be said that the viscosity of the adhesive is preferably, for example, 3500 Pa·s or less.

[0065] The adhesives of Examples 1 to 6 all had a magnetic permeability of greater than 1.7 after hardening. Thus, if the magnetic permeability exceeds 1.7, the adhesive is practically usable as adhesive 50 for bonding drum core 10C and top plate 10F of coil device 10. In other words, the adhesives of Examples 1 to 6 have a sufficient magnetic permeability value for adhesive 50 for coil device 10.

[0066] <Regarding Examples 2, 3, 7 to 9> The results of the comparative test of the adhesives of Examples 2, 3, and 7 to 9 will be explained below.

[0067] [Table 2]

[0068] As shown in Table 2, the adhesive of Example 2 is the adhesive of Example 2 described above. That is, in this adhesive, the median particle size (D50) of the magnetic powder 52 is 0.8 μm. The adhesive of Example 3 is the adhesive of Example 3 described above. That is, in this adhesive, the median particle size (D50) of the magnetic powder 52 is 0.8 μm.

[0069] In the adhesive of Example 7, the number average molecular weight of the bisphenol F resin 51 is 340 g / mol. In the adhesive of Example 7, the volume ratio of the magnetic powder 52 is 35 vol%. In the adhesive of Example 7, the median particle size (D50) of the magnetic powder 52 is 0.5 μm. In the adhesive of Example 7, the viscosity before curing is 2911 Pa s.

[0070] In the adhesive of Example 8, the number average molecular weight of the bisphenol F resin 51 is 360 g / mol. In the adhesive of Example 8, the volume ratio of the magnetic powder 52 is 35 vol%. In the adhesive of Example 8, the median particle size (D50) of the magnetic powder 52 is 1.5 μm. In the adhesive of Example 8, the viscosity before curing is 1820 Pa s.

[0071] In the adhesive of Example 9, the number average molecular weight of the bisphenol F resin 51 is 340 g / mol. In the adhesive of Example 9, the volume ratio of the magnetic powder 52 is 25 vol%. In the adhesive of Example 9, the median particle size (D50) of the magnetic powder 52 is 2.5 μm. In the adhesive of Example 9, the viscosity before curing is 1137 Pa s.

[0072] As a result of the comparison test of thread breakage time, the thread breakage time of the adhesive of Example 7 was 16 seconds, the thread breakage time of the adhesive of Example 8 was 11 seconds, and the thread breakage time of the adhesive of Example 9 was 11 seconds.

[0073] The test results for Examples 2, 3, and 7 to 9 showed that when the median particle size (D50) of the magnetic powder 52 was within the range of 0.8 μm or more and 2.5 μm or less, the thread breakage time was 20 seconds or less. The test results also showed that the smaller the median particle size (D50) of the magnetic powder 52 in the adhesive 50, the greater the viscosity. For this reason, it can be said that it is preferable that the median particle size (D50) of the magnetic powder 52 be 0.8 μm or more.

[0074] <Effects of this embodiment> (1) According to the above embodiment, the adhesive 50 contains magnetic powder 52, and therefore has better magnetic permeability than an adhesive without magnetic powder 52. Meanwhile, the viscosity of the adhesive 50 tends to increase as the number-average molecular weight of the bisphenol F resin 51 in the adhesive 50 increases. Here, commercially available bisphenol F epoxy resins are known to have number-average molecular weights of approximately 3,300 g / mol and approximately 5,500 g / mol. Meanwhile, the number-average molecular weight of the bisphenol F resin 51 in the above embodiment is 312 g / mol or more and 360 g / mol or less, which is significantly smaller than the number-average molecular weight of typical bisphenol F resins. By deliberately using a bisphenol F resin 51 within this number-average molecular weight range, the viscosity of the adhesive 50 can be prevented from increasing.

[0075] Similarly, the greater the volume ratio of the magnetic powder 52 in the adhesive 50, the higher the viscosity of the adhesive 50 tends to be. In the above embodiment, the volume ratio of the magnetic powder 52 in the adhesive 50 is 35 vol% or less. With such a volume ratio of the magnetic powder 52, it is possible to prevent the viscosity of the adhesive 50 from becoming high.

[0076] As described above, the above configurations ensure the desired magnetic permeability of the adhesive 50 for the coil component 10, while simplifying handling during manufacturing. In particular, the adhesive 50 of the above embodiment can reduce thread breakage time when applying the uncured adhesive 50 to the top plate 10F of the coil component 10 using a screen printer. In other words, the adhesive 50 is also preferable from the viewpoint of continuous printability.

[0077] (2) According to the above embodiment, the volume ratio of the magnetic powder 52 in the adhesive 50 is 20 vol % or more. With such a volume ratio of the magnetic powder 52, the adhesive 50 applied to the coil component 10 can obtain a preferable magnetic permeability.

[0078] (3) According to the above embodiment, the adhesive 50 contains a silane coupling agent 55. This configuration can improve the adhesive strength of the adhesive 50. In particular, in the above embodiment, the adhesive 50 is interposed between the drum core 10C and the top plate 10F. The silane coupling agent 55 is useful for bonding with such inorganic substances.

[0079] (4) According to the above embodiment, the adhesive 50 contains the dispersant 56. With this configuration, the dispersant 56 can suppress aggregation of the magnetic powder 52. Therefore, even if the volume ratio of the magnetic powder 52 is relatively high, for example, aggregation of the magnetic powder 52 can be suppressed.

[0080] (5) According to the above embodiment, the glass transition temperature of the adhesive 50 is 125°C or higher. That is, this configuration improves the heat resistance of the adhesive 50. Therefore, even if the coil component 10 is used in a high-temperature environment, for example, it is possible to prevent a decrease in the reliability of the coil component 10.

[0081] (6) In the above embodiment, the median particle size (D50) of the magnetic powder 52 is 0.8 μm or more. The smaller the median particle size (D50) of the magnetic powder 52 in the adhesive 50, the greater the viscosity tends to be. The results of the above-mentioned comparative test show that if the median particle size (D50) of the magnetic powder 52 is 0.8 μm or more, the breakage time of the adhesive 50 can be prevented from becoming long.

[0082] (7) In the above embodiment, the median particle size (D50) of the magnetic powder 52 is 2.5 μm or less. The larger the median particle size (D50) of the magnetic powder 52, the more likely it is that the magnetic powder 52 will collide with each other within the adhesive 50. In other words, depending on the shape of the area to which the adhesive 50 is applied, the magnetic powder 52 may not conform to the shape of the area to which the adhesive 50 is applied and may become unevenly distributed within the adhesive 50. If the median particle size (D50) of the magnetic powder 52 is within the above range, these problems are unlikely to occur.

[0083] (8) In the above embodiment, the adhesive strength of the adhesive 50 to alumina per 25 square millimeters is 10 MPa or more. By using adhesive 50 with such adhesive strength, a preferable adhesive strength can be obtained in the coil component 10.

[0084] (9) In the above embodiment, the coil device 10 has a closed magnetic circuit made up of the flange 20 and the top plate 10F. In this way, using the adhesive 50 of the above embodiment as the adhesive 50 for bonding the flange 20 and the top plate 10F that form the closed magnetic circuit is particularly advantageous in terms of improving the characteristics of the coil device 10 as a whole.

[0085] <Example of change> The above-described embodiment and the following modified examples can be implemented in combination with each other to the extent that no technical contradiction occurs.

[0086] <Examples of changes to coil components> The shape of the winding core 11 is not limited to the example in the above embodiment. For example, the shape of the winding core 11 may be a cylinder or a polygonal prism other than a quadrangular prism.

[0087] The configuration of the drum core 10C is not limited to the example of the above embodiment. For example, the drum core 10C may not have the first recess 21A and the second recess 22A. In this case, it is sufficient that the first electrode 31 and the second electrode 32 are spaced apart from each other and the third electrode 33 and the fourth electrode 34 are spaced apart from each other.

[0088] The material and shape of the external electrode 30 are not limited to those described in the above embodiment. For example, the material of the plating layer of the external electrode 30 may be an alloy of tin or nickel. The external electrode 30 may not have a plating layer. In this case, the exposed portion of the conductive metal layer may be used as the external electrode 30.

[0089] The coil device 10 may include at least one wire. When the number of wires is one, one external electrode 30 may be provided on the first flange 21 and one external electrode 30 may be provided on the second flange 22.

[0090] The coil device 10 is not limited to a configuration including a drum core 10C and a top plate 10F. The coil device 10 may have a first core around which a wire is wound and a second core connected to the first core via an adhesive 50. The first core and the second core may be bonded together by the adhesive 50.

[0091] <Examples of changes to adhesives> The adhesive 50 is not limited to being applied to the coil component 10. The adhesive 50 is preferably applied to an electronic component having a core made of a magnetic material.

[0092] The type of the curing agent 53 in the adhesive 50 is not limited to the example in the above embodiment. Any curing agent compatible with the bisphenol F type resin 51 may be used. The volume ratio of the magnetic powder 52 in the adhesive 50 may be 35 vol% or less. In other words, the volume ratio of the magnetic powder 52 in the adhesive 50 may be less than 20 vol%. The volume ratio of the magnetic powder 52 may be set so as to obtain a desired magnetic permeability in the coil component 10 to be used.

[0093] The number average molecular weight of the bisphenol F resin 51 in the adhesive 50 may be in the range of 312 g / mol or more and 360 g / mol or less. The adhesive 50 does not necessarily contain the silane coupling agent 55, the dispersant 56, and the curing accelerator 54. In addition, the types of the silane coupling agent 55, the dispersant 56, and the curing accelerator 54 are not limited to those in the above embodiment.

[0094] The glass transition temperature of the adhesive 50 after curing may be less than 125° C. The glass transition temperature may be any suitable temperature depending on the intended use of the adhesive 50. The median particle size (D50) of the magnetic powder 52 in the adhesive 50 may be less than 0.8 μm or greater than 2.5 μm. The median particle size (D50) of the magnetic powder 52 may be any value that allows the adhesive 50 to be handled in a preferable manner.

[0095] After hardening, the adhesive strength of the adhesive 50 to alumina per 25 square millimeters may be less than 10 MPa. The adhesive strength of the adhesive 50 is preferably in a range that allows the top plate 10F and the drum core 10C to be sufficiently bonded together.

[0096] <Additional Notes> The technical concepts that can be derived from the above-described embodiments and modifications will be described below. [1] An adhesive containing a bisphenol F type resin, a curing agent for the bisphenol F type resin, and a magnetic powder, wherein the volume ratio of the magnetic powder to the adhesive is 35 vol% or less, and the number average molecular weight of the bisphenol F type resin is 312 g / mol or more and 360 g / mol or less.

[0097] [2] The adhesive according to [1], wherein the volume ratio of the magnetic powder in the adhesive is 20 vol% or more. [3] The adhesive according to [1] or [2], further containing a silane coupling agent.

[0098] [4] The adhesive according to any one of [1] to [3], further comprising a dispersant for dispersing the magnetic powder. [5] The adhesive according to any one of [1] to [4], wherein the magnetic powder has a median particle size (D50) of 0.8 μm or more.

[0099] [6] The adhesive according to any one of [1] to [5], wherein the magnetic powder has a median particle size (D50) of 2.5 μm or less. [7] The adhesive according to any one of [1] to [6], which has a glass transition temperature of 125°C or higher after curing.

[0100] [8] The adhesive according to any one of [1] to [7], wherein after curing, the adhesive has an adhesive strength to alumina of 10 MPa or more per 25 square millimeters. [Explanation of symbols]

[0101] 10...Coil parts 10C...Drum core 10F...top 11...Core 20...Flange 30...External electrode 41...First wire 42...Second wire 50...adhesive 51...Bisphenol F resin 52...Magnetic powder 53...hardener 54...Curing accelerator 55...Silane coupling agent 56...Dispersant

Claims

1. An adhesive containing a bisphenol F resin, a curing agent for the bisphenol F resin, and a magnetic powder, a volume ratio of the magnetic powder to the adhesive is 20 vol% or more and 35 vol% or less, The number average molecular weight of the bisphenol F resin is 312 g / mol or more and 360 g / mol or less. glue.

2. Further contains a silane coupling agent The adhesive of claim 1 .

3. Further contains a dispersant for dispersing the magnetic powder. The adhesive of claim 1 .

4. The magnetic powder has a median particle size (D50) of 0.8 μm or more. The adhesive of claim 1 .

5. The magnetic powder has a median particle size (D50) of 2.5 μm or less. The adhesive of claim 1 .

6. After curing, the glass transition temperature is 125°C or higher The adhesive of claim 1 .

7. After curing, the adhesive has an adhesive strength of 10 MPa or more per 25 square millimeters to alumina. The adhesive of claim 1 .

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