JP5929321B2 - Multilayer coil parts - Google Patents

Description

  The present invention relates to a laminated coil component.

  As a conventional multilayer coil component, for example, one described in Patent Document 1 is known. In this laminated coil component, a coil conductor is formed on a glass ceramic sheet, the sheets are laminated, the coil conductors in each sheet are electrically connected, and the coil portion is placed inside by firing. The formed element body is formed. In addition, external electrode portions electrically connected to the end portions of the coil portions are formed on both end faces of the element body.

JP-A-11-297533

  Here, the multilayer coil component has a lower Q (quality factor) value than a wound coil wound with a wire due to reasons such as its structure and manufacturing method. However, with the recent demand for components that can cope with high frequencies in particular, high Q values are also required for laminated coil components. Conventional multilayer coil components have not been able to realize a high Q value until such a requirement is satisfied. Even if a high Q value is obtained, if the strength of the element body is weak, there is a problem that cracking or chipping occurs due to stress or impact.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a multilayer coil component that can obtain a high Q value and is resistant to stress.

  In order to increase the Q value of the coil, it is preferable to increase the smoothness of the surface of the coil conductor. The inventors of the present invention have found that it is effective to make the base ceramic amorphous so as to increase the smoothness of the surface of the coil conductor. When the element body is crystalline, the surface of the coil conductor in contact with the element body becomes uneven due to the influence of the unevenness on the surface of the element body, and the smoothness becomes low (see, for example, FIG. 3A). On the other hand, if the element body is amorphous, the surface of the coil conductor in contact with the element body becomes smooth due to the influence of the smooth surface of the element body, and the smoothness becomes high (see, for example, FIG. 3B). ).

  Here, the present inventors have found that when the element body is amorphous, the strength of the element body is weakened, and there is a problem that cracks and chips are generated due to external stress and impact. . Therefore, as a result of intensive studies, the present inventors have found a suitable configuration of a laminated coil component.

  That is, a multilayer coil component according to the present invention includes an element body formed by laminating a plurality of insulator layers, and a coil portion formed inside the element body by a plurality of coil conductors. The body includes an amorphous coil part arrangement layer made of glass ceramics, in which a coil part is arranged, a crystalline reinforcement layer made of glass ceramics that reinforces the coil part arrangement layer, and a coil part arrangement layer A stress relieving layer formed between the reinforcing layer and having a higher porosity than the other portions.

  In the multilayer coil component according to the present invention, the element body has a coil part arrangement layer in which the coil part is arranged, and a reinforcing layer that reinforces the coil part arrangement layer. Since the coil portion arrangement layer is an amorphous layer made of glass ceramics, it can improve the smoothness of the surface of the coil conductor arranged inside, thereby increasing the Q value of the multilayer coil component. Can do. Further, since the reinforcing layer is a crystalline layer made of glass ceramics, the amorphous coil portion arrangement layer can be reinforced. Furthermore, the element body includes a stress relaxation layer between the coil portion arrangement layer and the reinforcing layer. Since this stress relaxation layer has a higher porosity than other portions, it is possible to relieve stress acting on the element body between the coil portion arrangement layer and the reinforcing layer. As described above, the Q value of the multilayer coil component can be improved and can be strengthened against stress.

  In the multilayer coil component according to the present invention, the stress relaxation layer preferably has a porosity of 8 to 30%. By setting the porosity of the stress relaxation layer in this range, sufficient stress relaxation performance can be ensured. Moreover, when the porosity is too high, aging deterioration and strength due to moisture absorption are insufficient, but by setting the porosity of the stress relaxation layer to 30% or less, aging deterioration and insufficient strength can be suppressed.

In the multilayer coil component according to the present invention, the coil portion arrangement layer preferably contains 0.7 to 1.2% by weight of K ₂ O. Thereby, it can sinter at low temperature and a coil part arrangement | positioning layer can be made amorphous.

In the multilayer coil component according to the present invention, the K ₂ O content of the reinforcing layer is preferably smaller than the K ₂ O content of the coil portion arrangement layer. Thereby, when K diffuses from the coil part arrangement layer to the reinforcing layer, a stress relaxation layer can be formed in the vicinity of the boundary part in the coil part arrangement layer.

  According to the present invention, the Q value of the multilayer coil component can be increased.

It is sectional drawing which shows the laminated coil component which concerns on embodiment of this invention. It is a schematic diagram which shows the relationship between the smoothness of the surface of a coil conductor, and surface resistance. It is a schematic diagram which shows the relationship between the state of an element body, and the smoothness of the surface of a coil conductor. It is the schematic diagram which shows a mode that a stress relaxation layer is formed, and the enlarged view which shows the mode of each layer.

  Hereinafter, a preferred embodiment of a multilayer coil component according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a laminated coil component according to an embodiment of the present invention. As shown in FIG. 1, the laminated coil component 1 includes an element body 2 formed by laminating a plurality of insulator layers, and a coil formed inside the element body 2 by a plurality of coil conductors 4 and 5. The part 3 and a pair of external electrodes 6 formed on both end faces of the element body 2 are provided.

  The element body 2 is a rectangular parallelepiped or cubic laminate made of a sintered body in which a plurality of ceramic green sheets are laminated. The size of the element body 2 is set to a length of about 0.3 to 1.7 mm, a width of 0.1 to 0.9 mm, and a height of about 0.1 to 0.9 mm. The element body 2 includes a coil part arrangement layer 2A in which the coil part 3 is arranged, a reinforcing layer 2B provided so as to sandwich the coil part arrangement layer 2A, and a coil part arrangement layer 2A and a reinforcement layer 2B. A stress relaxation layer 2C formed therebetween. The coil portion arrangement layer 2A is an amorphous layer made of glass ceramics. The thickness of the coil portion arrangement layer 2A is set to 0.1 mm or more. The reinforcing layer 2B is a crystalline layer made of glass ceramics. The reinforcing layer 2B has a function of reinforcing the strength of the amorphous coil portion arrangement layer 2A. The reinforcing layer 2B also has a function of maintaining the shape of the coil portion arrangement layer 2A during sintering. The thickness of the reinforcing layer 2B is set to 5 μm or more. The stress relaxation layer 2C is a layer made of ceramics having a large number of pores inside. The stress relaxation layer 2 </ b> C has a function of relaxing stress acting on the element body 2. The thickness of the stress relaxation layer 2C is set to about 10 to 25 μm. The reinforcing layer 2B is formed so as to cover the entire end face 2a and end face 2b facing each other in the stacking direction, among the end faces of the coil portion arrangement layer 2A. The stress relaxation layer 2C is formed so as to cover the entire end surface 2a and the end surface 2b between the coil portion arrangement layer 2A and the reinforcing layer 2B.

The coil portion arrangement layer 2A contains 35-60% by weight of a borosilicate glass component as a main component, 15-35% by weight of a quartz component, an amorphous silica component in the balance, and alumina as a subcomponent. The content of alumina is 0.5 to 2.5% by weight with respect to 100% by weight of the main component. And a coil portion disposed layer 2A is after sintering, SiO ₂ is from 86.7 to 92.5 _wt%, B 2 _{O 3} is 6.2 to 10.7 wt%, _{K 2} O is 0.7 to 1 .2 wt%, Al ₂ O ₃ has a composition of 0.5 to 2.4 wt%. Coil unit arrangement layer 2A is, by containing SiO ₂ of 86.7 to 92.5 wt%, it is possible to reduce the dielectric constant of the coil portion disposed layer 2A. The coil unit arrangement layer 2A is, by containing _Al 2 _{O 3} of 0.5 to 2.4 wt%, it is possible to prevent the crystal transition of the coil portion disposed layer 2A. Coil unit arrangement layer 2A is, by containing 0.7 to 1.2 wt% of _{K 2} O, is sintered at a low temperature (800 to 950 ° C.), the coil portion disposed layer 2A on the amorphous layer be able to. In addition, you may contain 1.0 weight% or less of MgO and CaO.

The reinforcing layer 2B contains 50 to 70% by weight of a glass component and 30 to 50% by weight of an alumina component as main components. And the reinforcing layer 2B is after sintering, SiO ₂ is 23 to 42 _wt%, B 2 _{O 3} is 0.25 to 3.5 wt%, _Al 2 _{O 3} is from 34.2 to 58.8 wt%, The alkaline earth metal oxide has a composition of 12.5 to 31.5% by weight, and is 60% by weight or more in the alkaline earth metal oxide (that is, 7.5 to 31.5% by weight of the entire reinforcing layer 2B). ) Is SrO.

  The stress relaxation layer 2C is a ceramic layer having a higher porosity than the coil portion arrangement layer 2A and the reinforcing layer 2B. The porosity of the stress relaxation layer 2C is preferably 8 to 30%, and more preferably 10 to 25%. By setting the porosity of the stress relaxation layer 2C within the range, sufficient stress relaxation performance can be ensured. In addition, when the porosity is too high, aging deterioration and strength due to moisture absorption are insufficient, but by setting the porosity of the stress relaxation layer 2C to 30% or less, more preferably 25% or less, aging deterioration and strength The shortage can be suppressed. The “porosity” refers to the ratio of the vacancy shown in the stress relaxation layer 2C in the observation visual field using the image analysis of the SEM image of the ceramic fracture surface after firing (the vacancy ratio relative to the entire area of the observation visual field. This is a value determined by calculating the area occupied by.

Specifically, the stress relaxation layer 2C is formed by an amorphous ceramic layer constituting the coil portion arrangement layer 2A having a large number of holes therein. When the ceramic green sheet of the coil portion arrangement layer 2A having the above composition and the ceramic green sheet of the reinforcing layer 2B having the above composition are laminated and fired, as shown in FIG. , Diffusion of K, B, etc. occurs. That is, components such as K and B (indicated by M in the drawing) of the coil portion arrangement layer 2A diffuse into the reinforcing layer 2B having fewer components than the coil portion arrangement layer 2A. As a result, the composition balance is lost due to a decrease in components such as K and B in the amorphous layer near the boundary, and the region is not sufficiently sintered. Since sufficient sintering does not occur in this way, grain growth in the region is not sufficiently performed, and as a result, voids H as shown in FIG. 4B are formed. The porosity of the stress relaxation layer 2C is adjusted by adjusting the components of the ceramic green sheet of the coil portion arrangement layer 2A and the ceramic green sheet of the reinforcing layer 2B at the boundary portion. By adjusting the components of both ceramic green sheets, components such as K and B are diffused from the reinforcing layer 2B to the coil portion arranging layer 2A, and the crystalline ceramic layer constituting the reinforcing layer 2B is empty. A hole may be formed to form the stress relaxation layer 2C. However, the K ₂ O content of the reinforcing layer 2B is made smaller than the K ₂ O content of the coil portion arrangement layer 2A, and the stress relaxation layer 2C is formed on the coil portion arrangement layer 2A side. preferable.

  In addition, as a method for forming the stress relaxation layer 2C, a method other than the method by adjusting the components of the ceramic green sheet of the coil portion arrangement layer 2A and the ceramic green sheet of the reinforcing layer 2B as described above may be employed. For example, a green sheet containing resin particles may be interposed between the ceramic green sheet of the coil portion arrangement layer 2A and the ceramic green sheet of the reinforcing layer 2B. In this green sheet, the resin particles are burned out by firing to form pores. Thereby, the portion of the green sheet becomes the stress relaxation layer 2C. In addition, the component of the green sheet at this time is not specifically limited. Alternatively, the resin amount of the ceramic green sheet (insulator paste) of the coil portion arrangement layer 2A and / or the ceramic green sheet (insulator paste) of the reinforcing layer 2B at the boundary portion may be increased. Thereby, since there is much resin in the said part, a void | hole is formed by baking and it becomes the stress relaxation layer 2C. In addition, when increasing the amount of resin and forming a void | hole, it is preferable that the amount of resin shall be 20-30 weight% with respect to the ceramic powder weight.

  The coil part 3 has a coil conductor 4 related to the winding part and a coil conductor 5 related to the lead part connected to the external electrode 6. The coil conductors 4 and 5 are formed of a conductor paste containing, for example, one of silver, copper, and nickel as a main component. The coil part 3 is arranged only inside the coil part arrangement layer 2A, and is not arranged in the reinforcing layer 2B and the stress relaxation layer 2C. Further, none of the coil conductors 4 and 5 of the coil portion 3 is in contact with the reinforcing layer 2B and the stress relaxation layer 2C. Both end portions of the coil portion 3 in the stacking direction are separated from the reinforcing layer 2B and the stress relaxation layer 2C, and the ceramic of the coil portion arrangement layer 2A is interposed between the coil portion 3, the reinforcement layer 2B, and the stress relaxation layer 2C. Is placed. The coil conductor 4 related to the winding portion is configured by forming a conductor pattern of a predetermined winding with a conductor paste on the ceramic green sheet forming the coil portion arrangement layer 2A. The conductor patterns of each layer are connected in the stacking direction by through-hole conductors. Further, the coil conductor 5 relating to the lead-out portion is configured by a conductor pattern that pulls the end of the winding pattern to the external electrode 6. In addition, the coil pattern of the winding part, the number of windings, the drawing position of the drawing part, etc. are not particularly limited.

  The pair of external electrodes 6 are formed so as to cover both end faces facing each other in the direction orthogonal to the stacking direction, among the end faces of the element body 2. Each external electrode 6 may be formed so as to cover the entire both end surfaces, and a part may wrap around from the both end surfaces to the other four surfaces. Each external electrode 6 is formed, for example, by screen-printing a conductor paste containing silver, copper, or nickel as a main component, or by using a dip method.

  Next, a method for manufacturing the multilayer coil component 1 having the above-described configuration will be described.

  First, a ceramic green sheet for forming the coil portion arrangement layer 2A and a ceramic green sheet for forming the reinforcing layer 2B are prepared. Each ceramic green sheet is prepared by adjusting a ceramic paste so as to have the above-described composition and molding the sheet by a doctor blade method or the like. The stress relaxation layer 2C may be adjusted with a separate composition only near the boundary between the ceramic green sheet of the coil portion arrangement layer 2A and the ceramic green sheet of the reinforcing layer 2B.

  Subsequently, a through hole is formed by laser processing or the like at a predetermined position of each ceramic green sheet serving as the coil portion arrangement layer 2A, that is, a position where a through hole electrode is to be formed. Next, each conductor pattern is formed on each ceramic green sheet to be the coil portion arrangement layer 2A. Here, each conductor pattern and each through-hole electrode are formed by screen printing using a conductive paste containing silver or nickel.

  Subsequently, each ceramic green sheet is laminated. At this time, the ceramic green sheet to be the coil portion arrangement layer 2A is stacked on the ceramic green sheet to be the reinforcing layer 2B, and the ceramic green sheet to be the reinforcing layer 2B is stacked thereon. The reinforcing layer 2B formed on the bottom and the top may be formed by a single ceramic green sheet, or may be formed by a plurality of ceramic green sheets. Next, pressure is applied in the stacking direction to pressure-bond each ceramic green sheet.

  Subsequently, the laminated body is fired at a predetermined temperature (for example, about 800 to 1150 ° C.) to form the element body 2. The firing temperature set at this time is set to be equal to or higher than the softening point of the coil portion arrangement layer 2A and lower than the softening point or melting point of the reinforcing layer 2B. At this time, the reinforcing layer 2B maintains the shape of the coil portion arrangement layer 2A. Further, during firing, in the region corresponding to the stress relaxation layer 2C, sufficient sintering does not occur as compared with other portions, and sufficient grain growth does not occur, thereby forming vacancies. As a result, an amorphous coil portion arrangement layer 2A, a crystalline reinforcing layer 2B, and a high porosity stress relaxation layer 2C are formed.

  Subsequently, the external electrode 6 is formed on the element body 2. Thereby, the laminated coil component 1 is formed. The external electrode 6 is applied with an electrode paste mainly composed of silver, nickel or copper on both end faces in the longitudinal direction of the element body 2 and baked at a predetermined temperature (for example, about 600 to 700 ° C.). It is formed by applying electroplating. For this electroplating, Cu, Ni, Sn, or the like can be used.

  Next, the operation and effect of the multilayer coil component 1 according to this embodiment will be described.

  In order to increase the quality factor (Q) value of the coil, it is preferable to increase the smoothness of the surface of the coil conductor. The higher the frequency, the shallower the skin depth. In the case of a high frequency, the smoothness of the surface of the coil conductor affects the Q value. For example, as shown in FIG. 2B, when the surface of the coil conductor has low smoothness and unevenness is formed, the surface resistance of the coil conductor increases and the Q value of the coil decreases. On the other hand, if the smoothness of the surface of the coil conductor is high as shown in FIG. 2A, the surface resistance of the coil conductor is lowered, and the Q value of the coil can be increased.

  In order to increase the smoothness of the surface of the coil conductor, it is effective to make the ceramic of the element body amorphous. As shown in FIG. 3A, when the element body is crystalline, the unevenness of the surface of the coil conductor in contact therewith increases due to the influence of the unevenness of the surface of the element body, and the smoothness becomes low. On the other hand, as shown in FIG. 3B, when the element body is amorphous, the surface of the coil conductor in contact with the element body becomes smooth due to the influence of the smooth surface of the element body, and the smoothness increases. .

  Here, the present inventors have found that when the element body is amorphous, the strength of the element body is weakened, and there is a problem that cracks and chips are generated due to external stress and impact. . Therefore, as a result of intensive studies, the present inventors have found a suitable configuration of the multilayer coil component 1.

  That is, in the multilayer coil component 1 according to the present embodiment, the element body 2 includes a coil part arrangement layer 2A in which the coil part 3 is arranged, and a reinforcing layer 2B that reinforces the coil part arrangement layer 2A. Have. Since the coil portion arrangement layer 2A is an amorphous layer made of glass ceramics, the smoothness of the surfaces of the coil conductors 4 and 5 arranged inside can be improved. Q value can be increased. Further, since the reinforcing layer 2B is a crystalline layer, the amorphous coil portion arrangement layer 2A can be reinforced. Furthermore, the element body 2 includes a stress relaxation layer 2C between the coil portion arrangement layer 2A and the reinforcing layer 2B. Since this stress relaxation layer 2C has a higher porosity than the other portions, the stress acting on the element body 2 can be relaxed between the coil portion arrangement layer 2A and the reinforcing layer 2B. As described above, the Q value of the multilayer coil component 1 can be improved and can be made strong against stress.

  In the present embodiment, the coil portion arrangement layer 2A is not completely amorphous and contains a small amount of the alumina component (0.5 to 2.5% by weight). Since the amount is extremely small, a smooth surface as shown in FIG. As described above, the term “amorphous” as used herein corresponds to a part containing a crystalline substance in a small amount.

  The present invention is not limited to the embodiment described above.

  For example, in the above-described embodiment, the laminated coil component having one coil part is illustrated, but for example, it may have a plurality of coil parts in an array.

  In the above-described embodiment, the coil portion arrangement layer 2A is sandwiched between the pair of reinforcement layers 2B and the stress relaxation layer 2C from both sides in the stacking direction. However, the reinforcement layer 2B and the stress relaxation layer 2C are provided only on one of them. It may be formed. Alternatively, the pair of reinforcing layers 2B is formed on both sides in the stacking direction, while the stress relaxation layer 2C may be formed in only one of the stacking directions.

  DESCRIPTION OF SYMBOLS 1 ... Multilayer coil component, 2 ... Element body, 2A ... Coil part arrangement | positioning layer, 2B ... Reinforcement layer, 2C ... Stress relaxation layer, 3 ... Coil part, 4, 5 ... Coil conductor, 6 ... External conductor.

Claims (3)

An element body formed by laminating a plurality of insulator layers;
A coil portion formed inside the element body by a plurality of coil conductors,
The prime field is
An amorphous coil part arrangement layer made of glass ceramics, in which the coil part is arranged;
A crystalline reinforcing layer made of glass ceramics that reinforces the coil portion arrangement layer;
A stress relaxation layer formed between the coil portion arrangement layer and the reinforcing layer and having a higher porosity than other portions ;
The K _{2 O} content of the reinforcing layer laminated coil component, wherein the smaller this than the content of K _{2 O} of the coil part arranged layer.   The multilayer coil component according to claim 1, wherein the stress relaxation layer has a porosity of 8 to 30%. The coil unit arrangement layer laminated coil component according to claim 1 or 2, wherein the containing 0.7-1.2 wt% of K _{2 O.}

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