JP2013098350A - Lamination type inductor and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lamination type inductor which achieves high Q.SOLUTION: The method comprises the steps of: laminating a plurality of insulator sheets each prepared by applying, as an internal conductor material, one of Ag and Cu, or a metal including it as a primary component to an insulator layer by printing; and then baking the resultant laminate at a temperature of 875-920°C in a reducing atmosphere which includes hydrogen and/or nitrogen so that the length of diffusion of a metal component of the internal conductor material into a portion of the insulator layer around the internal conductor is between 10 μm and 20 μm inclusive. In the method, the insulator layer includes 35-75 mass% of borosilicate glass as a matrix, and 5-40 mass% of α-quartz and 5-60 mass% of zinc silicate, which are distributed in the matrix; in the borosilicate glass, the content percentages of SiOand BOare 70-90 mass% for SiO, and 10-30 mass% for BOrespectively.

Description

  The present invention relates to a multilayer electronic component, and more particularly to a multilayer inductor having a low dielectric constant of an insulator layer and good characteristics in a high frequency region used in mobile communication devices and the like.

  A multilayer electronic component 100 having an inductor portion typified by a multilayer inductor includes a plurality of laminated insulator layers and a spiral inner conductor formed in the insulator layer to constitute a laminate. . Lead electrodes are exposed on both end faces of the laminate, and external electrodes as shown in FIG. 1 are formed so as to be electrically connected to the lead electrodes. The external electrode is generally formed by applying a metal paste containing a metal component and glass frit to both ends of the laminate, drying and baking it to form a metal electrode film, and subsequently forming Ni on the metal electrode film. A plating film containing a main component is formed, and a plating film containing Sn as a main component is further formed thereon.

  Patent Document 1 describes that a borosilicate glass-based material is selected for an insulator layer of a high frequency multilayer inductor because low temperature firing is possible and high frequency characteristics are relatively excellent. Patent Documents 1 and 2 describe that Ag having a low specific resistivity is used as the internal conductor material, and the firing atmosphere is performed in the air because an Ag-based material is used for the internal conductor. .

  In recent years, multilayer inductors used for high-frequency circuit boards such as mobile communication devices have been rapidly miniaturized, but the trend of miniaturization in multilayer inductors has led to a decrease in Q value. In order to improve the Q factor (quality factor), which is an important characteristic of the multilayer inductor, in order to improve the Q factor, the internal conductor pattern shape is devised to increase the inner diameter of the coil. It is described to improve the value.

Japanese Patent Laid-Open No. 4-7809 JP 10-338545 A JP 2010-165975 A

  The multilayer electronic components described in Patent Documents 1, 2, and 3 have the following problems. In the internal conductor material fired in the air, the metal component of the internal conductor material may diffuse into the insulator layer around the internal conductor during the firing process. For this reason, the flux (magnetic flux) generated by the spiral inner conductor is hindered, and the Q value (quality factor) which is an important characteristic of the inductor is lowered.

  Such a problem is solved by configuring the multilayer inductor according to the present invention as follows. That is, the multilayer inductor according to the present invention is obtained by printing and applying an inner conductor material containing Ag or Cu as an inner conductor or a metal containing these as a main component to an insulator layer mainly composed of borosilicate glass. Laminating a plurality of body layers, then obtaining a laminate cut into individual pieces, and firing the laminate cut into individual pieces at a temperature of 875 ° C. to 920 ° C. in a reducing atmosphere containing hydrogen or nitrogen or both. Thus, the diffusion distance of the metal component of the inner conductor material to the insulator layer around the inner conductor is set to be 10 μm or more and 20 μm or less. By configuring the multilayer inductor as described above, the Q factor (quality factor), which is an important characteristic of the inductor, is improved.

  ADVANTAGE OF THE INVENTION According to this invention, the multilayer inductor which improved Q value (quality factor) which is an important characteristic of inductor components is provided.

It is the schematic block diagram which showed an example of the multilayer inductor which concerns on a prior art. 1 is a schematic configuration diagram illustrating an embodiment of a multilayer inductor according to an embodiment of the present invention. FIG. 3 is a schematic configuration diagram illustrating an embodiment of a method for manufacturing the multilayer inductor of FIG. 2. It is the schematic block diagram which showed one Example of the multilayer inductor before baking which concerns on embodiment of this invention. It is an EPMA analysis photograph which shows the diffusion state of the internal conductor material which concerns on embodiment of this invention. It is the graph which showed the frequency dependence of the Q characteristic of a multilayer type inductor.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected about the same or equivalent element, and the description is abbreviate | omitted when description overlaps.

  As an example of the multilayer electronic component according to the embodiment of the present invention, a multilayer inductor 1 is shown in FIG. FIG. 2A and FIG. 2B are views showing a perspective configuration of the multilayer inductor 1 from different angles. The multilayer inductor 1 shown in FIG. 2 has a substantially rectangular parallelepiped outer shape, and has a pair of end faces 1a and 1b facing in the longitudinal direction and a bottom face 1c facing a substrate (not shown) when mounted. The outer shape of the multilayer inductor 1 may be a substantially cubic shape. The multilayer inductor 1 has a pair of external electrodes 2 that are electrically connected to both ends of an internal electrode 3 provided therein. Each external electrode 2 is formed with a corner C formed by the end faces 1a and 1b and the bottom face 1c sandwiched between the bottom face 2a formed on the bottom face 1c and the end face 2b formed on the end faces 1a and 1b. It is composed. The bottom surface portion 2a and the end surface portion 2b of each external electrode 2 are formed continuously, so that each external electrode 2 has a portion of the end surfaces 1a, 1b adjacent to the bottom surface 1c across the corner portion C. The terminal has an L-shaped cross section that continuously covers a part of the bottom surface 1c. That is, each external electrode 2 is formed in an L shape.

  Next, a procedure for manufacturing the multilayer inductor 1 will be described. First, an insulator paste and a conductor paste are prepared.

The insulator paste is prepared by kneading an insulator material (nonmagnetic ceramic composition) and an organic vehicle. The insulator material is a non-magnetic ceramic composition in a matrix of 35 wt% (wt%) to 75 wt% (wt%) borosilicate glass powder, 5 wt% (wt%) to 40 wt% ( wt%) α-quartz powder and 5 mass% (wt%) to 60 mass% (wt%) zinc silicate powder are mixed and dispersed, and the borosilicate glass powder is composed of SiO ₂ and B _2. The content of O ₃ should be such that SiO ₂ is 70 mass% (wt%) to 90 mass% (wt%) and B ₂ O ₃ is 10 mass% (wt%) to 30 mass% (wt%). it can. As the insulator material, borosilicate glass is preferable because the dielectric constant can be reduced, but titanate complex oxide, zirconate complex oxide, or a mixture thereof is used because low temperature firing is possible. You can also. The average particle diameter of the insulator material (nonmagnetic ceramic composition) powder is not particularly limited, but is usually 0.1 μm to 5 μm, more preferably 0.5 μm to 3 μm. As the organic vehicle, for example, an organic binder dissolved in terpineol using ethyl cellulose as a solvent can be used. As the organic binder, other readily heat decomposable organic binders such as methacrylic acid ester polymer, acrylic acid ester-methacrylic acid ester copolymer, α-methylstyrene polymer, tetrafluoroethylene polymer can be used. is there. As the solvent, alcohol, toluene, acetone, methyl ethyl ketone, trichloroethylene, a mixture thereof, water, or the like can be used. The ratio of the organic binder and the solvent to the nonmagnetic ceramic composition of the insulator paste is not particularly limited, and the organic binder is 5 parts by mass to 15 parts by mass with respect to a normal ratio, for example, 100 parts by mass of the nonmagnetic ceramic composition. The solvent may be about 100 to 200 parts by mass. More specifically, for example, 10 parts by mass of ethyl cellulose as an organic binder and 140 parts by mass of terpineol as a solvent can be used with respect to 100 parts by mass of the nonmagnetic ceramic composition. This non-magnetic ceramic composition, an organic binder and a solvent are kneaded for 3 hours with a raikai machine to obtain an insulator paste.

  In the case of an Ag electrode as the conductive paste, Ag powder (average particle size: 1.0 μm to 2.5 μm) and an organic vehicle can be mixed at a mass ratio of 80:20 to 90:10 to obtain a conductive paste. . In the case of a Cu electrode, Cu powder (average particle size 0.2 μm to 0.5 μm) and an organic vehicle can be mixed at a mass ratio of 80:20 to 90:10 to obtain a conductor paste. Here, the average particle diameter of each of the Ag powder and the Cu powder was determined by using a commercially available laser diffraction particle size distribution measuring device and setting the cumulative 50% particle diameter as the average particle diameter.

As shown in FIG. 3A, an insulating paste is applied onto a PET (polyethylene terephthalate) film to form a sheet, and a plurality of insulating sheets 7 are prepared. Next, using the insulator sheet 7, insulator sheets 14, 15, 16, and 17 on which the internal conductor material is printed and applied are prepared. First, L-shaped through holes 8 and 9 are formed in the insulator sheet 7, and a conductor paste is printed and filled in these L-shaped through holes 8 and 9 to produce the insulator sheet 14. Next, L-shaped through holes 8 and 9 and through via holes 10 (a) are formed in another insulator sheet 7, and a conductor paste is applied to these L-shaped through holes 8 and 9 and through via holes 10 (a). In addition to printing and filling, the lead electrode pattern 11 is printed to form the insulator sheet 15. The through via hole 10 (a) is for connecting the coil pattern 12 between layers. Further, the L-shaped through holes 8 and 9 are formed in the other insulating sheet 7, and the L-shaped through holes 8 and 9 are printed and filled with a conductive paste, and the lead electrode pattern 13 is printed and formed. 16 is produced. Further, a through via hole 10 (b) is formed in the insulator sheet 14, and the through via hole 10 (b) is printed and filled with a conductive paste, and an insulating sheet 17 is formed by printing the coil pattern 12 thereon. As shown in the drawing, each insulator sheet 14, 15, 16, 17 has a plurality of L-shaped through holes, a plurality of through via holes, a plurality of lead electrode patterns, a plurality of coil patterns, and a plurality of laminated layers. A type inductor is formed at the same time.

  Next, as shown in FIG. 3B, the insulating sheets 7, 14, 15, 16, and 17 are appropriately laminated so that the coil pattern 12 and the extraction electrode patterns 11 and 13 are connected and pressed. Then, a green multilayer inductor substrate is manufactured. The green multilayer inductor substrate is obtained by cutting the green multilayer inductor substrate into individual pieces for each product.

  In addition, although the winding number of the coil by the internal conductor 3 shown by FIG. 2 is one time, it is good also as a structure which sets it as the number of turns of multiple turns according to an inductance value. Further, the coil pattern 12 formed on the insulator sheet is not limited to this. The positions of the through via holes 10 (a) and 10 (b) are not limited to the above as long as they are on the circumference of the coil pattern 12 according to the number of turns.

(Green multilayer inductor manufacturing method)
Below, the manufacturing method of each insulator sheet is demonstrated in detail.

  The above-described insulator sheet 7 used for manufacturing the multilayer inductor is first formed by applying an insulator paste on a PET film by a doctor blade method or the like, and drying to form an insulator sheet. The nonmagnetic ceramic composition of the insulator sheet 7 is composed of borosilicate glass glass. A plurality of insulator sheets 7 are formed with a thickness of about 5 μm to 40 μm. The insulator sheet 14 is formed with L-shaped through holes 8 and 9 for forming external electrodes in the insulator sheet 7 by laser processing or the like, and these L-shaped through holes 8 and 9 are filled with a conductive paste. And it is set as the insulator sheet 14 through a drying process.

  Insulator sheet 15 forms through via hole 10 (a) for coupling to coil pattern 12 in insulator sheet 14 by laser processing or the like, and is filled with a conductive paste. Then, through a drying process, a lead electrode pattern 11 for inputting and outputting the coil pattern 12 to the outside is formed. The lead electrode pattern 11 is made of a conductive paste by screen printing or the like, and the insulator sheet 15 is produced. The through via hole 10 (a) and the lead electrode pattern 11 are formed separately in the printing process, but they may be formed simultaneously by one printing.

  The insulator sheet 16 forms a lead electrode pattern 13 for inputting and outputting a coil pattern to the outside on the insulator sheet 14. The lead electrode pattern 13 can be obtained by forming a conductive paste by screen printing or the like.

  At this time, the L-shaped through hole 8 filled with the conductive paste for the external electrode and the lead electrode pattern 11 are electrically connected. Further, the L-shaped through hole 9 filled with the conductive paste for the external electrode and the lead electrode pattern 13 are electrically connected.

  The through via holes 10 (a) and 10 (b) filled with the conductive paste, the lead electrode patterns 11 and 13, and the coil pattern 12 may be formed simultaneously in one step in each insulator sheet. Alternatively, it may be formed in a plurality of steps. In addition, the thicknesses of the extraction electrode patterns 11 and 13 and the coil pattern 12 of this embodiment are about 12 μm.

  As a method of forming the L-shaped through holes 8 and 9 and the through via holes 10 (a) and 10 (b), an optimum method such as drilling and mechanical punching may be used in addition to laser processing. As the conductive material of the conductive paste, Ag or Cu is used in the present embodiment, but any metal other than these may be used, and an alloy including one or more of them may be mentioned as an example. However, the present invention is not limited to this.

  Further, the widths of the L-shaped through holes 8 and 9 filled with the conductive paste are not particularly limited, and are not particularly limited as long as the width appropriately corresponds to the outer diameter size of the coil pattern 12.

  The insulating sheet 17 is a through-hole for connecting the coil pattern 12 to the insulating sheet 7 by L-shaped through holes 8 and 9 and laser processing instead of processing the insulating sheet 14 as described above. A via hole 10 (b) is formed. These through via holes 10 (b) are filled with a conductive paste. Next, the coil pattern 12 is printed to form the insulator sheet 17. The coil pattern 12 is composed of one or more types and can be appropriately changed depending on the number of turns of the coil (inductance value). Accordingly, the position of the through via hole 10 (b) is appropriately changed on the circumference of the coil pattern 12 according to the number of turns. The coil pattern 12 may be formed by printing simultaneously when filling the L-shaped through holes 8 and 9 and the through via hole 10 (b) with a conductor paste.

Each insulator sheet 7, 14, 15, 16, 17 prepared as described above is peeled off from the PET film, and is laminated by a peeling laminating method or a thermocompression laminating method with a configuration as shown in FIG. Through a uniaxial pressing process (for example, 40 ° C., 100 N / mm ² , holding for 30 seconds), a green multilayer inductor substrate is formed. The green multilayer inductor board is cut into individual pieces for each product by a dicing saw or a press cutting machine so that the conductor material filled in the L-shaped through holes 8 and 9 is exposed on the cut surface. A type inductor is obtained (see FIG. 4). The external electrode 2 of the green multilayer inductor has a structure embedded in the multilayer body, and is exposed on the multilayer body surface as a structure having an L-shaped cross section.

  The green multilayer inductor is chamfered after solidification drying (110 ° C. to 150 ° C.). For example, barrel polishing is performed to form a curved surface R with a radius of curvature r at the corner of the laminate. For barrel polishing, the green multilayer inductor 1 can be polished by putting the green multilayer inductor 1, polishing media, polishing liquid, etc. into a barrel cage and causing relative movement by rotation, vibration, or the like. It is not always necessary to put the polishing media, and the polishing liquid is not particularly limited, but water or the like that is hardly soluble in the binder contained in the green multilayer inductor may be used.

(Baking and electrode plating treatment)
Next, the barrel-polished green multilayer inductor is fired in a reducing atmosphere. For example, it is inserted into a φ100 mm tubular furnace, and nitrogen gas is introduced as a reducing atmosphere at a flow rate of 2 liters / minute and hydrogen gas at a flow rate of 0.2 liters / minute. The firing profile is maintained at a firing temperature of 2 hours at a firing rate of 2.0 ° C./min from a normal temperature to 400 ° C., 3.3 ° C./min from 400 ° C. to the firing temperature. The firing temperature is preferably in the range of 875 ° C to 920 ° C. After firing, for example, a multilayer inductor having a shape of 1.0 mm in length, 0.5 mm in width, and 0.5 mm in thickness (hereinafter referred to as 1005 shape) is obtained. In order to confirm the lower limit of the firing temperature in the embodiment, a multilayer inductor fired at a firing temperature of 870 ° C. and 860 ° C. is also produced. In order to confirm the upper limit of the firing temperature in the embodiment, a multilayer inductor fired at 930 ° C. as the firing temperature is also produced. For comparison of firing atmospheres, a green multilayer inductor having an inner conductor made of an Ag conductor was fired in a temperature range of 860 ° C. to 900 ° C. in an air atmosphere in a φ100 mm tubular furnace to obtain the multilayer inductor 1. obtain.

  Further, the fired multilayer inductor 1 is subjected to electroless plating or electroplating at the end. For example, a Cu plating layer having a thickness of 5 μm is formed on the external electrode 2. Further, a 2 μm Ni plating layer is formed on the Cu plating layer to prevent solder erosion, and then a 4 μm Sn plating layer is formed to improve solderability.

  In the above description, an example in which the external electrode 2 is formed in an L-shaped terminal shape is exemplified as the multilayer inductor 1, but by using the L-shaped terminal as an external electrode, the multilayer inductor is mounted on the mounting substrate. In doing so, it becomes possible to mount the laminated inductor with the bottom surface or the top surface thereof facing the mounting substrate, and the degree of freedom of element mounting during mounting is improved. Configuration (mounting) in which the coil axis of the inner conductor described above is parallel to the mounting surface and perpendicular to the opposing direction of the pair of external electrodes formed on the opposing end surfaces of the multilayer body. (See FIG. 2). For example, as shown in FIG. 1, a multilayer inductor having an external electrode that is a five-sided terminal, that is, the external electrode wraps around two end faces facing each other and ends of four faces adjacent to each end face. The present invention can also be applied to the formed multilayer inductor, and the same effect can be obtained.

The non-magnetic ceramic composition of the insulator paste includes, as borosilicate glass, SiO ₂ : 80 mass% (wt%), B ₂ O ₃ : 18 mass% (wt%), K ₂ O: 2 mass% (wt %) Containing powder 65 mass% (wt%), Zn ₂ SiO ₄ (zinc silicate) powder 15 mass% (wt%), α-quartz powder 20 mass% (wt%). Each powder used had an average particle size of borosilicate glass: 1.2 μm, Zn ₂ SiO ₄ (zinc silicate): 0.5 μm, and α-quartz: 0.7 μm. As the conductor paste, in the case of an Ag electrode, Ag powder (average particle size 2.0 μm) and an organic vehicle are mixed at a mass ratio of 85:15 to obtain a conductor paste. In the case of a Cu electrode, Cu powder (average particle size) 0.3 μm) and an organic vehicle were mixed at a mass ratio of 80:20 to form a conductor paste, and a green multilayer inductor was prepared according to the manufacturing method described in the above embodiment.

(Evaluation method)
The Q value and the diffusion distance of the metal component of the inner conductor material were measured for each firing temperature, inner conductor material, and firing atmosphere of the green multilayer inductor. The Q value was evaluated using an impedance analyzer, and a Q value at 1 GHz of 40 or more was judged as “◯”, and a value smaller than 40 was judged as “X”. Since an inductor capable of handling high frequencies often requires characteristics having a Q value of 40 or more at 1 GHz, the Q value of 40 is used as a criterion. The criteria for evaluating the sinterability were “◯” when the shrinkage rate due to sintering was 15% or more, and “X” when the shrinkage rate due to sintering was less than 15%. The measurement of the diffusion distance of the metal component of the inner conductor material was performed as follows. A cross section was obtained by cutting parallel to the central axis of the coil formed by the spiral inner conductor of the multilayer inductor (perpendicular to the insulator sheet). This cross section was analyzed with an electron beam microanalyzer (EPMA) under the conditions of electron beam irradiation per 1 μm with an acceleration voltage of 15.0 kV, an irradiation current of 0.1 μA, and a measurement time of 30 msec. An analysis example of Example 3 is shown in FIG. At this time, the distance from the interface between the inner conductor and the insulator in the region where the metal component concentration of the inner conductor material was 1% by mass (wt%) or more was measured. These measurement results are shown in Table 1 as average values obtained by measuring five cross-sections for each of the five pieces.

  From the results of Example 2 and Comparative Example 2 (firing temperature 880 ° C., inner conductor material Ag), in the case of a 1005-shaped multilayer inductor, the metal component diffusion distance of the inner conductor material is shorter in reducing atmosphere firing than in air atmosphere firing. It can be seen that the Q value is high. The frequency characteristic of the Q value at this time is shown in FIG. As shown in Comparative Example 5, also in the reducing atmosphere firing, when the firing temperature becomes 930 ° C. or higher, the metal component diffusion distance of the internal conductor material becomes longer and the Q characteristic is also lowered. Also, as shown in Comparative Example 4, in reducing atmosphere firing, when the firing temperature is 870 ° C. or lower, the metal component diffusion distance of the inner conductor material is shortened, which is preferable in this respect, but the sinterability of the inner conductor material is poor. Sufficient and poor connectivity (low conductivity). For this reason, the DC superposition resistance Rdc increases and the Q value decreases. In addition, since the insulator material is in an unsintered state, it causes insufficient bending strength of the inductor and ingress of the plating solution. From these, it can be seen that the firing temperature in the reducing atmosphere is preferably in the range of 875 ° C. to 920 ° C.

  Next, as shown in Example 5, when the internal conductor material is made of Cu, it can be confirmed that the Q value is high by firing in a reducing atmosphere, and the metal component diffusion distance of the internal conductor material is short. It was. In addition, since Cu is very easily oxidized, there is a problem that if the firing process is performed in an oxidizing atmosphere during production, Cu oxide is generated, the volume expands, and cracks are generated.

As described above, the inner conductor of the multilayer inductor manufactured in this embodiment can suppress the diffusion of the metal component of the inner conductor material electrode toward the insulator during firing in a reducing atmosphere. More specifically, by firing so that the metal component diffusion distance of the inner conductor material into the insulator is 10 μm to 20 μm, a multilayer inductor having a high Q value and a good sintered state can be provided. By setting the metal component diffusion distance of the inner conductor material into the insulator within this range, it is possible to suppress the inhibition of the flux (magnetic flux) generated by the spiral inner conductor, thereby improving the Q characteristic.

Since the inhibition of the flux generated by the spiral inner conductor can be suppressed, it can be used in multilayer electronic components such as a multilayer LC filter having a spiral inner conductor in the multilayer body.

DESCRIPTION OF SYMBOLS 1 ... Multilayer inductor, 1a, 1b ... End face, 1c ... Bottom face, 1d ... Top face, 2 ... External electrode, 2a ... Bottom face part, 2b ... End face part, 3 ... Internal conductor, 7 ... Insulator sheet, 8, 9 ... L-shaped through holes, 14, 15, 16, 17 ... Insulator sheet

Claims (3)

  A multilayer inductor, wherein an inner conductor is spirally laminated in an insulator mainly composed of borosilicate glass, and a metal component diffusion distance of the inner conductor material into the insulator is 10 μm to 20 μm. .   2. The multilayer inductor according to claim 1, wherein the inner conductor material is Ag or Cu or a metal mainly composed of these.   A green multilayer inductor in which an internal conductor made of Ag or Cu or a metal mainly composed of Ag or Cu is spirally laminated in an insulator mainly composed of borosilicate glass is reduced with hydrogen or nitrogen or both. A method of manufacturing a multilayer inductor, comprising firing in a temperature range of 875 ° C. to 920 ° C. in an atmosphere.