Manufacturing method of laminated coil component

Abstract

To provide a manufacturing method of a laminated coil component that can suppress fading, cracking, and bleeding of conductive paste and can improve the adhesion of the conductive paste to green sheets.SOLUTION: A manufacturing method of a laminated coil component includes an insulator portion, a coil provided inside the insulator portion and electrically connected to a plurality of coil conductor layers, and an external electrode provided on the surface of the insulator portion and electrically connected to a lead-out portion of the coil, and includes forming a conductive paste layer from a conductive paste, forming an insulating paste layer from an insulating paste, forming a laminated molded body including the conductive paste layer and the insulating paste layer, and firing the laminated molded body, and the PVC of the conductive paste is 30% or more and 55% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a laminated coil component. [Background technology]

[0002] One example of a method for manufacturing a laminated coil component is disclosed in Patent Document 1 (Patent Document 1). A conductive paste that will become part of the coiled conductor is printed on each of a plurality of green sheets. Then, a plurality of non-magnetic sheets on which the conductive paste has been printed are stacked by compression bonding or the like. Then, the stacked plurality of green sheets are fired.

[0003] The green sheets are made of, for example, ferrite paste, which is formed by mixing a conductive material and a resin component in a predetermined ratio. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-109281 Summary of the Invention [Problem to be solved by the invention]

[0005] In a manufacturing method in which a conductive paste is printed on each of a plurality of green sheets and then the plurality of green sheets are laminated, the following problems occur when the PVC (pigment volume concentration) is too high or too low, where PVC is the concentration of the volume of the conductive material (typically silver powder) relative to the total volume of the conductive material and resin component in the conductive paste during preparation of the conductive paste.

[0006] The first problem caused by a PVC that is too high is that the high viscosity and hardness of the conductive paste can cause fading and cracks in the conductive paste when multiple green sheets are laminated.

[0007] A second problem caused by too high a PVC is that delamination may occur due to poor adhesion of the conductive paste to the green sheet.

[0008] A problem caused by a PVC that is too low is that the conductive paste may bleed when printed onto each of the plurality of green sheets due to the low viscosity of the conductive paste.

[0009] An object of the present disclosure is to provide a method for manufacturing a laminated coil component that can suppress smearing, cracking, and bleeding of the conductive paste and improve the adhesion of the conductive paste to the green sheet. [Means for solving the problem]

[0010] A method for manufacturing a laminated coil component according to one aspect of the present invention includes the steps of: an insulator portion; a coil provided inside the insulator portion, the coil having a plurality of coil conductor layers electrically connected to each other; an external electrode provided on a surface of the insulator portion and electrically connected to an extraction portion of the coil, forming a conductive paste layer using a conductive paste; forming an insulating paste layer using an insulating paste; forming a laminated compact including the conductive paste layer and the insulating paste layer; Firing the laminated molded body; The PVC content of the conductive paste is 30% or more and 55% or less. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a method for manufacturing a laminated coil component that can suppress smearing, cracking, and bleeding of the conductive paste and improve the adhesion of the conductive paste to the green sheet. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view schematically illustrating a laminated coil component 1 according to the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view showing a cut surface of the laminated coil component 1 shown in FIG. 1 taken along line xx. [Figure 3] FIG. 3 is a cross-sectional view showing a cut surface of the laminated coil component 1 shown in FIG. 1 taken along the line yy. [Figure 4] 4(a) to 4(e) are diagrams illustrating a method for manufacturing the laminated coil component 1 shown in FIG. [Figure 5] 5(a) to 5(d) are diagrams illustrating a method for manufacturing the laminated coil component 1 shown in FIG. [Figure 6] 6(a) to 6(d) are diagrams illustrating a method for manufacturing the laminated coil component 1 shown in FIG. [Figure 7] 7(a) to 7(e) are diagrams illustrating a method for manufacturing the laminated coil component 1 shown in FIG. [Figure 8] FIG. 1 is a diagram showing evaluations of bleeding, fading, and cracking in Examples and Comparative Examples. [Figure 9] 1 is a graph showing the line width ratio of a conductive paste to PVC. [Figure 10] 1 is a graph showing the crack occurrence rate of conductive paste relative to PVC. [Figure 11] FIG. 10 is a plan view showing an example of the spread of conductive paste on a ferrite sheet. [Figure 12] FIG. 10 is a plan view showing an example of a thin conductive paste on a ferrite sheet. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present disclosure will be described in detail below with reference to the drawings. However, the shapes and arrangements of the laminated coil component and the components of the present embodiment are not limited to the examples shown in the drawings.

[0014] A perspective view of a laminated coil component 1 of this embodiment is shown in Fig. 1, an xx cross-sectional view is shown in Fig. 2, and a yy cross-sectional view is shown in Fig. 3. However, the shapes and arrangements of the laminated coil components and the components of the following embodiments are not limited to the examples shown in the drawings.

[0015] As shown in FIGS. 1 to 3 , the laminated coil component 1 of this embodiment is a laminated coil component having a substantially rectangular parallelepiped shape. In the laminated coil component 1, the surfaces perpendicular to the L axis in FIG. 1 are referred to as "end surfaces," the surfaces perpendicular to the W axis are referred to as "side surfaces," and the surfaces perpendicular to the T axis are referred to as "top surfaces" and "bottom surfaces." The laminated coil component 1 generally includes an element body 2 and external electrodes 4 and 5 provided on both end surfaces of the element body 2. The element body 2 includes an insulator section 6 and a coil 7 provided inside the insulator section 6. The insulator section 6 has a first insulator layer 11 and a second insulator layer 12. The coil 7 is configured by connecting coil conductor layers 15 in a coil shape by via conductors (not shown) that penetrate the first insulator layer 11. The coil 7 is connected to the external electrodes 4 and 5 at lead-out sections 18 provided on both ends of the coil 7. A gap 21 is provided between the insulator portion 6 and the main surface of the coil conductor layer 15 (the lower main surface in FIGS. 2 and 3), that is, between the first insulator layer 11 and the coil conductor layer 15.

[0016] A method for manufacturing the laminated coil component 1 of the present embodiment will be described below. In this embodiment, an example in which the insulator portions 6 are made of a ferrite material will be described.

[0017] (1) Preparation of ferrite paste

[0018] First, a ferrite material is prepared. The ferrite material contains Fe, Zn, and Ni as main components, and optionally further contains Cu. Typically, the main components of the ferrite material are substantially oxides of Fe, Zn, Ni, and Cu (ideally, Fe2O3, ZnO, NiO, and CuO).

[0019] The ferrite material is prepared by weighing out Fe2O3, ZnO, CuO, NiO, and, if necessary, additional components to obtain a predetermined composition, mixing them, and pulverizing them. The pulverized ferrite material is then dried and calcined at a temperature of, for example, 700-800°C to obtain calcined powder. A predetermined amount of solvent (such as a ketone-based solvent), resin (such as polyvinyl acetal), and plasticizer (such as an alkyd-based plasticizer) are added to this calcined powder, kneaded using a planetary mixer, and then dispersed using a three-roll mill to produce a ferrite paste.

[0020] (2) Preparation of ferrite sheets Next, the calcined powder of the ferrite material obtained in the same manner as above is mixed and pulverized with an organic binder such as polyvinyl butyral, and an organic solvent such as ethanol or toluene in a pot mill together with PSZ balls. The resulting mixture can be formed into a sheet of a predetermined thickness, size, and shape by a doctor blade method or the like to produce a ferrite sheet.

[0021] In the ferrite material, the Fe content, calculated as Fe2O3, is preferably 40.0 mol % or more and 49.5 mol % or less (based on the total of the main components, the same applies below), and more preferably 45.0 mol % or more and 49.5 mol % or less.

[0022] In the ferrite material, the Zn content, calculated as ZnO, is preferably 5.0 mol % or more and 35.0 mol % or less (based on the total of the main components, the same applies below), and more preferably 10.0 mol % or more and 30.0 mol % or less.

[0023] In the ferrite material, the Cu content, calculated as CuO, is preferably 4.0 mol % or more and 12.0 mol % or less (based on the total of the main components, the same applies below), and more preferably 7.0 mol % or more and 10.0 mol % or less.

[0024] In the ferrite material, the Ni content is not particularly limited, and can be the balance of the other main components Fe, Zn, and Cu.

[0025] In one embodiment, the ferrite material contains 40.0 mol % or more and 49.5 mol % or less of Fe calculated as Fe2O3, 5.0 mol % or more and 35.0 mol % or less of Zn calculated as ZnO, 4.0 mol % or more and 12.0 mol % or less of Cu calculated as CuO, and the balance being NiO.

[0026] In the present disclosure, the ferrite material may further contain additional components. Examples of additional components in the ferrite material include, but are not limited to, Mn, Co, Sn, Bi, and Si. The contents (addition amounts) of Mn, Co, Sn, Bi, and Si are preferably 0.1 to 1 part by weight, calculated as Mn3O4, Co3O4, SnO2, Bi2O3, and SiO2, respectively, per 100 parts by weight of the total of the main components (Fe (as Fe2O3), Zn (as ZnO), Cu (as CuO), and Ni (as NiO)). The ferrite material may further contain impurities that are unavoidable during manufacturing.

[0027] It is safe to assume that the Fe content (converted to Fe2O3), Mn content (converted to Mn2O3), Cu content (converted to CuO), Zn content (converted to ZnO), and Ni content (converted to NiO) in the sintered ferrite are substantially no different from the Fe content (converted to Fe2O3), Mn content (converted to Mn2O3), Cu content (converted to CuO), Zn content (converted to ZnO), and Ni content (converted to NiO) in the ferrite material before sintering.

[0028] (3) Preparation of conductive paste for coil conductor

[0029] First, a conductive material is prepared. Examples of conductive materials include Au, Ag, Cu, Pd, and Ni, with Ag or Cu being preferred, and Ag being more preferred. A predetermined amount of conductive material powder is weighed out and mixed with predetermined amounts of a solvent (e.g., eugenol), a resin (e.g., ethyl cellulose), and a dispersant using a planetary mixer or similar, and then dispersed using a three-roll mill or similar to produce a conductive paste for coil conductors.

[0030] In preparing the conductive paste, two types of conductive pastes (first and second conductive pastes) with different shrinkage rates upon firing are prepared by adjusting the PVC (pigment volume concentration), which is the volume concentration of the conductive material (typically silver powder) relative to the total volume of the conductive material and resin component in the conductive paste. That is, in this embodiment, the conductive paste is a silver paste.

[0031] The shrinkage rate of the first conductive paste due to firing is preferably 15% or more and 20% or less.

[0032] The shrinkage rate of the second conductive paste due to firing is smaller than the shrinkage rate of the first conductive paste due to firing, and is preferably 5% or more and 15% or less.

[0033] The PVC of the first conductive paste is preferably 30% or more and 55% or less. More preferably, the PVC of the first conductive paste is 35% or more. Also, more preferably, the PVC of the first conductive paste is 50% or less. The PVC of the first conductive paste may be 35% or more and 55% or less, 30% or more and 50% or less, or 35% or more and 50% or less.

[0034] The PVC of the second conductive paste is greater than that of the first conductive paste, preferably 40% to 55%, and more preferably 40% to 50%.

[0035] Here, the shrinkage rate can be determined by, for example, applying a conductive paste to a polyethylene terephthalate (PET) film, drying it, cutting it into a piece of about 5 mm x 5 mm, and then measuring the change in the sample dimensions using a thermomechanical analyzer (TMA).

[0036] The PVC can be determined by measuring the weight ratio of the conductive material to the resin component by thermogravimetry (TG) and calculating from the densities of the conductive material and the resin component.

[0037] (4) Preparation of resin paste

[0038] Prepare a resin paste for forming the voids in the laminated coil component 1. Such a resin paste can be produced by adding a resin (such as an acrylic resin) that disappears during firing to a solvent (such as isophorone).

[0039] (5) Fabrication of multilayer coil components

[0040] (5-1) Creating the base body First, a ferrite sheet 31 is prepared (FIG. 4(a)). Here, FIG. 4 is a plan view of the ferrite sheet as seen from above.

[0041] Next, the resin paste is printed on the area where the gap 21 is to be formed (that is, the area where the coil conductor layer is to be formed, excluding the lead-out area and the via formation area), to form a resin paste layer 32 (FIG. 4(b)).

[0042] Next, the second conductive paste is printed on the area where the lead portion is to be formed, to form a second conductive paste layer 33 (FIG. 4(c)).

[0043] Next, the first conductive paste is printed over the entire area where the coil conductor layer 15 is to be formed, to form a first conductive paste layer 34 (FIG. 4(d)).

[0044] Next, the ferrite paste is printed in the area where the first conductive paste layer 34 is not formed so as to have the same height as the first conductive paste layer 34, thereby forming a ferrite paste layer 35 (FIG. 4(e)). In other words, the ferrite paste is provided in the same layer as the layer where the first conductive paste is printed.

[0045] The above steps form a first pattern sheet.

[0046] Separately, a ferrite sheet 41 is prepared, and via holes 42 are formed in predetermined locations of the ferrite sheet 41 (FIG. 5(a)).

[0047] Next, the resin paste is printed on the area where the void 21 is to be formed, to form a resin paste layer 43 (FIG. 5(b)).

[0048] Next, the first conductive paste is printed over the entire area where the coil conductor layer is to be formed, to form a first conductive paste layer 44 (FIG. 5(c)).

[0049] Next, the ferrite paste is printed in the area where the first conductive paste layer 44 is not formed so as to be at the same height as the first conductive paste layer 44, thereby forming a ferrite paste layer 45 (FIG. 5(d)). That is, similar to the case of the first pattern sheet, a second ferrite paste different from the ferrite paste constituting the ferrite sheet 41 is provided in the same layer as the layer where the first conductive paste is printed.

[0050] The above process forms a second pattern sheet.

[0051] Separately, a ferrite sheet 51 is prepared, and in the same manner as the above pattern sheet, via holes 52, a resin paste layer 53, a first conductive paste layer 54, and a ferrite paste layer 55 are formed to obtain a third pattern sheet (Figures 6(a) to (d)).

[0052] Separately, a ferrite sheet 61 is prepared, and in the same manner as the above pattern sheet, via holes 62, a resin paste layer 63, a second conductive paste layer 64, a first conductive paste layer 65, and a ferrite paste layer 66 are formed to obtain a fourth pattern sheet (Figures 7(a) to (e)).

[0053] The first to fourth pattern sheets prepared as described above are stacked in order, blank ferrite sheets are placed above and below, and the sheets are thermocompressed to prepare a laminate block. This laminate block is then cut into individual pieces using a dicer or similar.

[0054] The obtained elements are subjected to barrel processing to remove the corners of the elements and form roundness. The barrel processing may be performed on an unfired laminate or on a fired laminate. The barrel processing may be either dry or wet. The barrel processing may be performed by rubbing elements together with media, or by barrel processing the elements together with media.

[0055] After the barrel treatment, the element is fired at a temperature of, for example, 880°C or higher and 920°C or lower to obtain the base body 2 of the multilayer coil component 1. The firing causes the resin paste layer to disappear, forming voids 21. The firing also causes the first conductive paste layer to shrink, creating pores inside the coil conductor. These pores relieve stress caused by the difference in shrinkage rate between the conductive paste and the ferrite sheet or ferrite paste, thereby suppressing defects such as cracks.

[0056] (5-2) Formation of external electrodes Next, an Ag paste containing Ag and glass for forming external electrodes is applied to the end faces of the element body 2 and baked to form base electrodes. Next, a Ni coating and an Sn coating are sequentially formed on the base electrodes by electrolytic plating to form the external electrodes, thereby obtaining the multilayer coil component 1 shown in Figure 1.

[0057] The present disclosure relates to the above manufacturing method, specifically an insulator portion; a coil provided inside the insulator portion, the coil having a plurality of coil conductor layers electrically connected to each other; an external electrode provided on a surface of the insulator portion and electrically connected to an lead-out portion of the coil, forming a conductive paste layer using a conductive paste; forming an insulating paste layer using an insulating paste; forming a laminated molded body including the conductive paste layer and the insulating paste layer; Firing the laminated molded body. wherein the PVC content of the conductive paste is 30% or more and 55% or less.

[0058] In a preferred aspect, the present disclosure provides a method for producing the above-mentioned laminated coil component, comprising: Preparing an insulating sheet; forming a resin paste layer on the insulating sheet using a resin paste; forming a conductive paste layer on the resin paste layer using a conductive paste; forming an insulating paste layer on the insulating sheet using an insulating paste so that at least a portion of an upper surface of the conductive paste layer is exposed; laminating a plurality of insulating sheets on which the resin paste layer, the conductive paste layer, and the insulating paste layer are formed to form a laminated molded body; The present invention provides the above-described manufacturing method, which includes firing the laminated molded body.

[0059] In a preferred aspect, the present disclosure provides a method for producing the above-mentioned laminated coil component, comprising: The present invention provides a method for producing the above laminated coil component, which includes providing a second insulating paste different from the insulating paste in the same layer as the layer on which the conductive paste is printed.

[0060] Although one embodiment of the present invention has been described above, this embodiment can be modified in various ways.

[0061] For example, in the above, a ferrite sheet corresponding to each insulating layer is prepared, printed on this sheet to form a coil pattern, and then these are pressed together to obtain an element, but the element may also be obtained by forming all layers by printing them sequentially.

[0062] The laminated coil component manufactured by the method of the present disclosure described above is less likely to suffer from defects such as cracks during manufacturing.

[0063] Therefore, the present disclosure also provides a laminated coil component obtained by the above-described manufacturing method.

[0064] Specifically, the present disclosure provides: an insulator portion; a coil provided inside the insulator portion, the coil having a plurality of coil conductor layers electrically connected to each other; an external electrode provided on the surface of the insulator portion and electrically connected to the lead-out portion of the coil; A laminated coil component comprising: The pore area ratio of the coil conductor layer is 5% or more and 15% or less. to provide.

[0065] In the laminated coil component 1 of this embodiment, the element body 2 is composed of an insulator portion 6 and a coil 7 .

[0066] The insulator portion 6 may include a first insulator layer 11 and a second insulator layer 12 .

[0067] The first insulator layers 11 are provided between the coil conductor layers 15 adjacent in the stacking direction, and between the coil conductor layers 15 and the upper or lower surface of the element body.

[0068] The second insulator layer 12 is provided around the coil conductor layer 15 so that the top surface (the upper main surface in FIGS. 2 and 3) of the coil conductor layer 15 is exposed. In other words, the second insulator layer 12 forms a layer at the same height in the stacking direction as the coil conductor layer 15. For example, in FIG. 2, the second insulator layer 12a is located at the same height in the stacking direction as the coil conductor layer 15a.

[0069] In one embodiment, the second insulator layer 12 may be provided so that a portion thereof overlaps the outer edge of the coil conductor layer 15. In other words, the second insulator layer 12 may be provided so as to cover the outer edge of the coil conductor layer 15. In other words, when one coil conductor layer 15 and the second insulator layer 12 are viewed in plan from the top, the second insulator layer 12 may extend further inward than the outer edge of the coil conductor layer 15.

[0070] The first insulator layer 11 and the second insulator layer 12 may be integrated in the element body 2. In this case, the second insulator layer 12 can be considered to be at the same height as the coil conductor layer 15.

[0071] The insulating portion 6 is preferably made of a magnetic material, more preferably made of sintered ferrite. The sintered ferrite contains at least Fe, Ni, and Zn as main components. The sintered ferrite may further contain Cu.

[0072] The first insulator layer 11 and the second insulator layer 12 may have the same composition or different compositions. In a preferred embodiment, the first insulator layer 11 and the second insulator layer 12 have the same composition.

[0073] In one embodiment, the sintered ferrite contains at least Fe, Ni, Zn, and Cu as main components.

[0074] In the sintered ferrite, the Fe content, calculated as Fe2O3, is preferably 40.0 mol % or more and 49.5 mol % or less (based on the total of the main components, the same applies below), and more preferably 45.0 mol % or more and 49.5 mol % or less.

[0075] In the sintered ferrite, the Zn content, calculated as ZnO, is preferably 5.0 mol % or more and 35.0 mol % or less (based on the total of the main components, the same applies below), and more preferably 10.0 mol % or more and 30.0 mol % or less.

[0076] In the sintered ferrite, the Cu content, calculated as CuO, is preferably 4.0 mol % or more and 12.0 mol % or less (based on the total of the main components, the same applies below), and more preferably 7.0 mol % or more and 10.0 mol % or less.

[0077] In the sintered ferrite, the Ni content is not particularly limited, and can be the balance of the other main components Fe, Zn, and Cu.

[0078] In one embodiment, the sintered ferrite contains 40.0 mol % or more and 49.5 mol % or less of Fe calculated as Fe2O3, 5.0 mol % or more and 35.0 mol % or less of Zn calculated as ZnO, 4.0 mol % or more and 12.0 mol % or less of Cu calculated as CuO, and the remainder is NiO.

[0079] In the present disclosure, the sintered ferrite may further contain additional components. Examples of additional components in sintered ferrite include, but are not limited to, Mn, Co, Sn, Bi, and Si. The contents (addition amounts) of Mn, Co, Sn, Bi, and Si are preferably 0.1 to 1 part by weight, calculated as Mn3O4, Co3O4, SnO2, Bi2O3, and SiO2, respectively, per 100 parts by weight of the total of the main components (Fe (as Fe2O3), Zn (as ZnO), Cu (as CuO), and Ni (as NiO)). The sintered ferrite may further contain impurities that are unavoidable during manufacturing.

[0080] As described above, the coil 7 is formed by electrically connecting the coil conductor layers 15 to each other in a coil shape. The coil conductor layers 15 adjacent to each other in the stacking direction are connected by via conductors that penetrate the insulator portions 6.

[0081] The material constituting the coil conductor layer 15 is not particularly limited, but examples thereof include Au, Ag, Cu, Pd, and Ni. The material constituting the coil conductor layer 15 is preferably Ag or Cu, and more preferably Ag. The conductive material may be one type or two or more types.

[0082] The via conductors are provided so as to penetrate the first insulator layer 11. The material constituting the via conductors may be the same as the material constituting the coil conductor layer 15. The material constituting the via conductors may be the same as or different from the material constituting the coil conductor layer 15. In a preferred embodiment, the material constituting the via conductors is the same as the material constituting the coil conductor layer 15. In a preferred embodiment, the material constituting the via conductors is Ag.

[0083] The pore area ratio of the coil conductor layer is 5% or more and 15% or less, preferably 8% or more and 13% or less. By setting the pore area ratio of the coil conductor layer within the above range, internal stress can be alleviated and the occurrence of cracks, etc. can be suppressed.

[0084] The average pore diameter of the coil conductor layer is preferably 0.1 μm or more and 6.0 μm or less, more preferably 0.5 μm or more and 5.0 μm or less. By setting the average pore diameter of the coil conductor layer within the above range, internal stress can be alleviated and the occurrence of cracks, etc. can be suppressed.

[0085] The coil conductor layer is preferably formed from a material whose shrinkage rate upon firing is preferably 15% or more and 20% or less.

[0086] In a preferred embodiment, at least the winding portion of the coil conductor layer 15 (ie, the portion excluding the lead-out portion 18) has the above-mentioned pore area ratio and / or average pore diameter.

[0087] In the coil 7, the thickness of the coil conductor layer 15 in the lead-out portion 18 is greater than the thickness of the coil conductor layer 15 in the winding portion. By increasing the thickness of the coil conductor layer in the lead-out portion, the adhesion between the coil conductor layer and the insulator portion in the lead-out portion is improved.

[0088] In this embodiment, the coil conductor layer 15 of the lead-out portion of the coil 7 is formed by laminating a high pore area ratio layer 20 having the above-described pore area ratio and a low pore area ratio layer 19 having a smaller pore area ratio than the high pore area ratio layer 20. By laminating a low pore area ratio layer having a smaller pore area ratio in the lead-out portion, shrinkage during firing is suppressed, gaps are less likely to occur between the coil conductor layer of the lead-out portion and the insulator portion, and adhesion between the coil conductor layer of the lead-out portion and the insulator portion is improved.

[0089] On the other hand, the coil conductor layer 15 of the winding portion of the coil 7 can be a high pore area ratio layer that has a relatively large shrinkage rate during firing. By making the coil conductor layer 15 of the winding portion a high pore area ratio layer that has a relatively large shrinkage rate during firing, it is possible to alleviate the generation of internal stress during firing and also to more reliably form the voids 21 that are stress relaxation spaces.

[0090] The pore area ratio of the low pore area ratio layer 19 is 1.0% or more and 4.0% or less, preferably 2% or more and 3% or less. By setting the pore area ratio of the low pore area ratio layer 19 within the above range, it is possible to suppress the occurrence of gaps between the coil conductor layer and the insulator part of the lead-out part.

[0091] The average pore diameter of the low pore area ratio layer is preferably 0.1 μm or more and 5.0 μm or less, and more preferably 0.1 μm or more and 3.0 μm or less.

[0092] In one embodiment, the low pore area ratio layer 19 is formed from a material whose shrinkage rate upon firing is preferably 5% or more and 15% or less.

[0093] In the lead-out portion 18, the thickness ratio of the low pore area ratio layer 19 to the high pore area ratio layer 20 (low shrinkage layer / high shrinkage layer) may be preferably 0.2 or more and 1.8 or less, more preferably 0.2 or more and 0.8 or less.

[0094] The gap 21 functions as a so-called stress relaxation space.

[0095] The thickness of the void portion 21 is preferably 1 μm or more and 30 μm or less, and more preferably 5 μm or more and 15 μm or less.

[0096] The width and thickness of the void can be measured as follows.

[0097] The chip is polished with the LT surface facing the polishing paper, and polishing is stopped at the center of the W dimension of the coil conductor layer. After that, the chip is observed under a microscope. The width and thickness of the gap located at the center of the L dimension of the coil conductor layer are measured using the measurement function attached to the microscope.

[0098] In a preferred embodiment, in a cross section perpendicular to the winding direction of the coil, one surface of the void portion contacts the insulator portion, and the other surface contacts the coil conductor layer. That is, as shown in Fig. 2, one surface of the void portion 21 contacts the first insulator layer 11, and the other surface contacts the coil conductor layer 15. In other words, the void portion 21 on the first insulator layer 11 is covered by the coil conductor layer 15.

[0099] External electrodes 4 and 5 are provided to cover both end faces of element body 2. The external electrodes are made of a conductive material, preferably one or more metal materials selected from Au, Ag, Pd, Ni, Sn, and Cu.

[0100] The external electrode may be a single layer or a multilayer. In one embodiment, the external electrode may be a multilayer, preferably two to four layers, for example, three layers.

[0101] In one embodiment, the external electrodes are multilayered and may include a layer containing Ag or Pd, a layer containing Ni, or a layer containing Sn. In a preferred embodiment, the external electrodes are composed of a layer containing Ag or Pd, a layer containing Ni, and a layer containing Sn. Preferably, the layers are provided in the following order from the coil conductor layer side: a layer containing Ag or Pd (preferably Ag), a layer containing Ni, and a layer containing Sn. Preferably, the layer containing Ag or Pd is a layer formed by baking an Ag paste or a Pd paste, and the layer containing Ni and the layer containing Sn may be plated layers.

[0102] The laminated coil component of the present disclosure preferably has a length of 0.4 mm or more and 3.2 mm or less, a width of 0.2 mm or more and 2.5 mm or less, and a height of 0.2 mm or more and 2.0 mm or less, and more preferably has a length of 0.6 mm or more and 2.0 mm or less, a width of 0.3 mm or more and 1.3 mm or less, and a height of 0.3 mm or more and 1.0 mm or less. [Example]

[0103] Example Ferrite paste preparation Fe2O3, ZnO, CuO, and NiO powders were weighed out to account for 49.0 mol%, 25.0 mol%, 8.0 mol%, and the remainder, respectively, of the total. These powders were placed in a ball mill along with PSZ media, pure water, and a dispersant, wet mixed and pulverized, dried, and calcined at 700°C to obtain calcined powder. The calcined powder was then mixed with the specified amounts of ketone solvent, polyvinyl acetal, and alkyd plasticizer, kneaded in a planetary mixer, and further dispersed in a three-roll mill to produce a ferrite paste.

[0104] Preparation of ferrite sheets The ferrite material was weighed to have the same composition as the ferrite paste. The weighed material was placed in a ball mill along with PSZ media, pure water, and a dispersant, wet mixed and pulverized, then dried and calcined at 700°C to obtain calcined powder. The calcined powder was then mixed with a polyvinyl butyral organic binder, ethanol, and toluene in a pot mill along with PSZ balls and mixed and pulverized. The resulting mixture was formed into a sheet using a doctor blade method to produce a ferrite sheet.

[0105] Preparation of conductive paste for coil conductors A predetermined amount of silver powder was prepared as the conductive material, and then mixed with eugenol, ethyl cellulose, and a dispersant in a planetary mixer. The mixture was then dispersed in a three-roll mill to produce a conductive paste for coil conductors. The average particle size D50 of the silver powder used as the conductive powder in the conductive paste for coil conductors is 1.0 μm. The decomposition temperature of the binder (eugenol, ethyl cellulose) in the coil conductor paste is 280°C.

[0106] In the preparation of the conductive paste described above, six types of conductive paste with different PVCs were prepared, with the PVCs of the six types of conductive pastes being 30%, 35%, 40%, 45%, 50%, and 55%, respectively.

[0107] Preparation of resin paste A resin paste was prepared by mixing isophorone with an acrylic resin.

[0108] - Fabrication of multilayer coil components Using the above ferrite sheet, ferrite paste, first conductive paste, second conductive paste and resin paste, pattern sheets were produced according to the procedures shown in Figures 4 to 7, and these were then pressed together to obtain an assembly of a laminate block.

[0109] Next, the laminate block was cut using a dicer or the like to separate into individual elements. The resulting elements were then subjected to barrel processing to remove the corners of the elements and form rounded edges. After barrel processing, the elements were fired at a temperature of 920°C to obtain an element body.

[0110] Next, an Ag paste containing Ag and glass for forming external electrodes was applied to the end surfaces of the element body and baked to form base electrodes. Next, a Ni coating and an Sn coating were sequentially formed on the base electrodes by electrolytic plating to form external electrodes, thereby obtaining laminated coil components of the examples. Hereinafter, a laminated coil component in which the PVC content of the conductive paste is 30% will be referred to as Example (A). A laminated coil component in which the PVC content of the conductive paste is 35% will be referred to as Example (B). A laminated coil component in which the PVC content of the conductive paste is 40% will be referred to as Example (C). A laminated coil component in which the PVC content of the conductive paste is 45% will be referred to as Example (D). A laminated coil component in which the PVC content of the conductive paste is 50% will be referred to as Example (E). A laminated coil component in which the PVC content of the conductive paste is 55% will be referred to as Example (F).

[0111] Comparative Example A laminated coil component of a comparative example was obtained in the same manner as the above-described example, except that two types of conductive paste with different PVCs were used. The PVCs of the two types of conductive paste were 25% and 60%, respectively. Hereinafter, the laminated coil component in which the PVC of the conductive paste was 25% will be referred to as comparative example (G). Furthermore, the laminated coil component in which the PVC of the conductive paste was 60% will be referred to as comparative example (H).

[0112] The samples (laminated coil components) in the examples and comparative examples all had a length (L) of 1.0 mm, a width (W) of 0.5 mm, and a height (T) of 0.5 mm.

[0113] evaluation For each 100 laminated coil components of the obtained examples and comparative examples, the presence or absence of bleeding, blurring, and cracks was evaluated. The results are shown in FIGS. 8 to 10. The presence or absence of bleeding, blurring, and cracks was confirmed by polishing the LT surface, stopping the polishing at the approximate center, and observing the polished surface using a digital microscope.

[0114] Bleeding is a phenomenon in which the printed conductive paste becomes wider than the preset printed line width. An example of bleeding is shown in FIG. 11.

[0115] Regarding bleeding, in this evaluation, if the line width ratio r = W1 / W2 of the line width W1 of the printed conductive paste to the preset printed line width W2 is 1.0 <= r < 1.1, it was evaluated as "OK1". Also, if 1.1 <= r < 1.5, it was evaluated as "OK2". Also, if 1.5 <= r, it was evaluated as "NG". In this evaluation, the line width ratio r is the average value of the measured values at 10 locations.

[0116] Blurring is a phenomenon in which the printed conductive paste becomes narrower than the set printed line width. An example of blurring is shown in FIG. 12.

[0117] Regarding blurring, in this evaluation, if 0.9 < r <= 1.0, it was evaluated as "OK1". Also, if 0.5 < r <= 0.9, it was evaluated as "OK2". Also, if r <= 0.5, it was evaluated as "NG".

[0118] From the above, in this evaluation, if 0.9 < r < 1.1, it was evaluated as "OK1", if 0.5 < r <= 0.9 or 1.1 <= r < 1.5, it was evaluated as "OK2", and if r <= 0.5 or 1.5 <= r, it was evaluated as "NG".

[0119] As shown in Figures 8 and 9, Examples (B) to (E) were rated "OK1", with almost no bleeding or fading. Example (A) was rated "OK2" due to bleeding. Example (F) was rated "OK2" due to fading. Comparative Example (G) was rated "NG" due to bleeding. Comparative Example (H) was rated "NG" due to fading.

[0120] As shown in Fig. 8 and Fig. 10, the evaluation of cracks in the conductive paste is expressed as the crack occurrence rate. That is, the number of cracks was counted for 100 pieces of each of the laminated coil components of the example and the comparative example. No cracks were observed in Examples (A) to (E) and Comparative Example (G). In Example (F), cracks were observed in 25 out of 100 pieces. In Comparative Example (H), cracks were observed in all 100 pieces.

[0121] The method for manufacturing the laminated coil component described above can achieve the following effects.

[0122] According to this method, the PVC concentration of the conductive paste is not too high, at 55% or less. This prevents the conductive paste from becoming too viscous or hard. As a result, it is possible to prevent blurring during printing and cracks in the conductive paste when the laminate is pressed. In addition, it is possible to prevent poor adhesion between the green sheet and the conductive paste due to a high binder content, thereby reducing the possibility of delamination.

[0123] This method ensures that the PVC concentration of the conductive paste is not too low, at 30% or more. This prevents the viscosity of the conductive paste from becoming too low. As a result, bleeding of the conductive paste can be prevented when printing the conductive paste onto each of the multiple green sheets.

[0124] According to this method, the resin paste layer disappears when the laminated molded body is fired, and a void portion that functions as a stress relaxation space can be formed between the conductive paste layer and the green sheet (insulating layer).

[0125] When multiple green sheets are stacked to form a laminated compact, the conductive paste layer may stretch in a direction intersecting the stacking direction due to the action of pressure from the stacking direction. The stretching of the conductive paste layer in a direction intersecting the stacking direction may cause cracks to occur in the conductive paste. According to this method, the second insulating paste (ferrite paste) provided in the same layer as the layer on which the conductive paste is printed can prevent the conductive paste from stretching in a direction intersecting the stacking direction. As a result, the possibility of cracks occurring in the conductive paste can be reduced.

[0126] According to this method, the PVC of the conductive paste is 35% or more. Therefore, the viscosity of the conductive paste can be made higher than when the PVC of the conductive paste is 30% or more but less than 35%. As a result, when printing the conductive paste onto each of the multiple green sheets, bleeding of the conductive paste can be suppressed more than when the PVC of the conductive paste is 30% or more but less than 35%.

[0127] According to this method, the PVC of the conductive paste is 50% or less. Therefore, the viscosity and hardness of the conductive paste can be lower than when the PVC of the conductive paste is 55% or less but more than 50%. As a result, the occurrence of fading and cracking of the conductive paste during the formation and firing of the laminated compact can be suppressed compared to when the PVC of the conductive paste is 55% or less but more than 50%. Furthermore, the adhesion of the conductive paste to the green sheet can be suppressed from decreasing compared to when the PVC of the conductive paste is 55% or less but more than 50%. Therefore, the possibility of delamination can be reduced compared to when the PVC of the conductive paste is 55% or less but more than 50%.

[0128] The method for manufacturing the laminated coil component described above can also be expressed as follows.

[0129] (1) A method for manufacturing a laminated coil component according to one aspect of the present disclosure includes: an insulator portion; a coil provided inside the insulator portion, the coil having a plurality of coil conductor layers electrically connected to each other; an external electrode provided on a surface of the insulator portion and electrically connected to an extraction portion of the coil, forming a conductive paste layer using a conductive paste; forming an insulating paste layer using an insulating paste; forming a laminated compact including the conductive paste layer and the insulating paste layer; Firing the laminated molded body; The PVC content of the conductive paste is 30% or more and 55% or less.

[0130] (2) In the method for manufacturing a laminated coil component according to (1), Preparing an insulating sheet; forming a resin paste layer on the insulating sheet using a resin paste; forming a conductive paste layer on the resin paste layer using a conductive paste; forming an insulating paste layer on the insulating sheet using an insulating paste so that at least a portion of an upper surface of the conductive paste layer is exposed; laminating a plurality of insulating sheets on which the resin paste layer, the conductive paste layer, and the insulating paste layer are formed to form a laminated molded body; sintering the laminated compact.

[0131] (3) In the method for producing a laminated coil component according to (1) or (2), The method may include providing a second insulating paste different from the insulating paste in the same layer as the layer on which the conductive paste is printed.

[0132] (4) In the method for manufacturing a laminated coil component according to any one of (1) to (3), The conductive paste may be a silver paste.

[0133] (5) In the method for manufacturing a laminated coil component according to any one of (1) to (4), The PVC of the conductive paste may be 35% or more and 55% or less.

[0134] (6) In the method for manufacturing a laminated coil component according to any one of (1) to (5), The PVC content of the conductive paste may be 30% or more and 50% or less.

[0135] Any of the various embodiments described above may be combined appropriately to achieve the effects of each of them.

[0136] While the present invention has been fully described in connection with preferred embodiments, with appropriate reference to the drawings, various changes and modifications will become apparent to those skilled in the art, and it is to be understood that such changes and modifications are included within the scope of the present invention as defined by the appended claims unless they depart therefrom. [Industrial Applicability]

[0137] The laminated coil component according to the present disclosure can be used in a wide variety of applications, such as as an inductor. [Explanation of symbols]

[0138] 1. Multilayer coil components 2 Base 4,5 External electrode 6 Insulator part 7 coils 11 First insulating layer 12 Second insulating layer 15 Coil conductor layer 18 Drawer section 19 Low pore area ratio layer 20 High pore area ratio layer 21 Cavity 31 Ferrite sheet 32 Resin paste layer 33 Second conductive paste layer 34 First conductive paste layer 35 Ferrite paste layer 41 Ferrite sheet 42 Beer Hall 43 Resin paste layer 44 First conductive paste layer 45 Ferrite paste layer 51 Ferrite sheet 52 Beer Hall 53 Resin paste layer 54 First conductive paste layer 55 Ferrite paste layer 61 Ferrite sheet 62 Beer Hall 63 Resin paste layer 64 Second conductive paste layer 65 First conductive paste layer 66 Ferrite paste layer

Claims

1. an insulator portion; a coil provided inside the insulator portion, the coil having a plurality of coil conductor layers electrically connected to each other; an external electrode provided on a surface of the insulator portion and electrically connected to an extraction portion of the coil, forming a conductive paste layer using a conductive paste; forming an insulating paste layer using an insulating paste; forming a laminated compact including the conductive paste layer and the insulating paste layer; Firing the laminated compact; wherein the PVC of the conductive paste is 30% or more and 55% or less.

2. Preparing an insulating sheet; forming a resin paste layer on the insulating sheet using a resin paste; forming a conductive paste layer on the resin paste layer using a conductive paste; forming an insulating paste layer on the insulating sheet using an insulating paste so that at least a portion of an upper surface of the conductive paste layer is exposed; laminating a plurality of insulating sheets on which the resin paste layer, the conductive paste layer, and the insulating paste layer are formed to form a laminated molded body; The method for producing a laminated coil component according to claim 1 , further comprising firing the laminated compact.

3. 3. The method for producing a laminated coil component according to claim 1, further comprising providing a second insulating paste different from the insulating paste in the same layer as the layer on which the conductive paste is printed.

4. 3. The method for producing a laminated coil component according to claim 1, wherein the conductive paste is a silver paste.

5. 3. The method for producing a laminated coil component according to claim 1, wherein the PVC of the conductive paste is 35% or more and 55% or less.

6. 3. The method for producing a laminated coil component according to claim 1, wherein the PVC of the conductive paste is 30% or more and 50% or less.

Images