JP2013016688A - Manufacturing method of laminate type inductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a laminate type inductor element which realizes stress relaxation without adding additive agents and changing the composition.SOLUTION: First through holes are formed on each ceramic green sheet, and the first through holes are filled with a resin paste. Next, second through holes, each of which has a diameter smaller than that of the first through hole, are formed in the first through holes filled with the resin paste, and the second through holes are filled with a conductive paste. Then, the ceramic green sheets are laminated to be tentatively crimped and burned. Since the resin paste in the first through holes is burned out by burning, a cavity is formed around a silver paste in each first through hole. Alternatively, even if the resin paste is not burned out, the resin functions as a stress relaxation agent and thus the stress is relaxed.

Description

  The present invention relates to a method for manufacturing a multilayer inductor element in which an inductor is formed by forming a coil pattern inside a multilayer body formed by laminating a plurality of ceramic green sheets.

  Conventionally, in a ceramic laminate in which via holes are formed to make interlayer connections, the laminate may crack due to stress generated in response to thermal shrinkage during firing, and electrical connection may not be achieved due to disconnection or short circuit. It was.

  Therefore, for example, measures as disclosed in Patent Document 1 and Patent Document 2 are taken. Patent Document 1 describes that stress relaxation is performed by adding an inorganic pore forming material such as tungsten. Patent Document 2 describes that a region having a reduced void ratio is provided by increasing the boron content of the ceramic in the region near the via hole.

JP 2002-176236 A JP 2009-32935 A

  Conventional stress relaxation measures are methods of adding a stress relaxation agent to the conductive paste or changing the composition of the ceramic.

  Therefore, an object of the present invention is to provide a method for manufacturing a multilayer inductor element that realizes stress relaxation without adding an additive or changing a composition.

  The multilayer inductor element of the present invention is an element in which a coil pattern is formed and laminated on a ceramic green sheet containing a magnetic material, and is manufactured by the following steps.

(1) Step of forming a first through hole in the ceramic green sheet (2) Step of filling the first through hole with the first paste (3) After filling the first paste, the first paste Forming a second through-hole having a diameter smaller than that of the first through-hole at a location filled with the first paste. (4) Filling the second through-hole with a conductive second paste. Step (5) forming a coil pattern electrically connected to the second through hole on the ceramic green sheet;
(6) Laminating the ceramic green sheets, electrically connecting one end of the coil pattern to the second paste to make an interlayer connection, and creating a laminate having an inductor formed therein (7) ) Step of firing the laminated body Thus, after filling the first through hole with the first paste (for example, resin paste) and further filling the first paste, the diameter is larger than that of the first through hole. By forming a second through hole having a small diameter and filling a second paste (for example, silver paste), the resin is filled outside the first through hole, and the silver paste is filled inside. Become. Then, when the ceramic green sheets are laminated and fired, the resin paste is burned out, so that the periphery of the silver paste in the first through hole becomes a cavity. Alternatively, even if the resin paste is not completely burned out, the resin paste functions as a stress relaxation agent. Therefore, the stress due to the difference in thermal shrinkage during firing is eliminated or alleviated, there is no possibility that the laminate will crack, and there is no possibility that the electrical connection is broken.

  In particular, the multilayer inductor element of the present invention is a mode in which through holes are formed for each green sheet of magnetic material, resin paste is filled on the outside, silver paste is filled on the inside, and then laminated and fired. It is suitable when manufacturing a ceramic green sheet containing a hard magnetic material (ferrite).

  It is to be noted that a resin paste is applied to the inner wall of the first through hole, and the entire inside of the first through hole is not filled with the resin paste, but a hole (second through hole) remains in the central portion. However, a structure similar to the above can be realized.

  Moreover, it is desirable that the thermal contraction rate of the second paste is intermediate between the thermal contraction rate of the ceramic green sheet and the thermal contraction rate of the first paste.

  In the multilayer inductor element of the present invention, it is desirable to impregnate the multilayer body after firing the multilayer body. In this case, the portion where the first paste is burned out and becomes a cavity is filled again with resin, and the strength is improved.

  According to this invention, stress relaxation can be realized without adding an additive or changing the composition.

FIG. 1A is a view showing the top surface of a part of the ceramic green sheet constituting the multilayer inductor element, and FIG. 1B is a partial longitudinal sectional view of the multilayer inductor element. It is a figure which shows the manufacturing process of a multilayer inductor element. It is a figure which shows the manufacturing process of a multilayer inductor element. It is a figure which shows the manufacturing process of the multilayer inductor element in the case of impregnating resin. It is a figure which shows the manufacturing process of the multilayer inductor element in the case of impregnating resin.

  FIG. 1 (A) is a view showing the top surface of a part of the ceramic green sheets 2 constituting the multilayer inductor element 1 according to the embodiment of the present invention. FIG. 1B is a partial longitudinal sectional view of the multilayer inductor element 1. In the longitudinal cross-sectional view of FIG. 1B, the upper side of the paper is the upper surface side of the multilayer inductor element 1, and the lower side of the paper is the lower surface side of the multilayer inductor element 1.

  The multilayer inductor element 1 according to the present embodiment is configured by forming a coil pattern 11 in a multilayer body in which a plurality of ceramic green sheets 2 are laminated and connecting them in the lamination direction. If an IC or a capacitor is connected to the multilayer inductor element 1, a DC-DC converter can be realized by using the inductor 1 as a choke coil.

  A multilayer inductor element 1 shown in FIGS. 1 (A) and 1 (B) shows a mother multilayer body before breaking. The mother laminate is broken into chips of a predetermined size at the shipping destination. In FIGS. 1A and 1B, the mother stacked body before breaking is shown for four adjacent chips, but in reality, a larger number of chips are arranged.

  As shown in FIG. 1A, a coil pattern 11 is formed on part of the ceramic green sheets 2 constituting the laminate. The coil pattern 11 is formed by applying a silver paste in a loop shape. One end of the coil pattern 11 is electrically connected to the other end (hereinafter referred to as an end portion 12) of the coil pattern 11 on the ceramic green sheet 2 of the other layer through the via hole 21. Therefore, the coil pattern 11 of each ceramic green sheet 2 is spirally connected with the stacking direction of the stacked body as an axis to form an inductor.

  The via hole 21 is formed by the following process. FIG. 2 is a diagram showing a process of mainly forming the via hole 21 in the manufacturing process of the multilayer inductor. First, as shown in FIG. 2A, a first through hole is formed by laser for each ceramic green sheet. The shape of the first through hole is not limited to the circle in the figure, and may be other shapes such as a rectangle or a semicircle.

  As a manufacturing process of the multilayer inductor element, first, a ceramic green sheet is prepared, a coil pattern 11 is formed for each ceramic green sheet, and then a first through hole forming process of FIG. Is called. A 1st through-hole is formed from the lower surface side in the location (location where the above-mentioned coil pattern 11 exists) where the coil pattern 11 on each ceramic green sheet is formed. Since the first through hole is formed by a laser, the metal layer of the coil pattern 11 remains. The coil pattern 11 may be formed after the via hole 21 is formed. When the coil pattern 11 is formed later, the first through hole can be formed from the lower surface side or the upper surface side.

  Next, as shown in FIG. 2B, the first through hole is filled with a resin paste. The resin is made of a phenol resin, an epoxy resin, a silicon resin, a urea resin, a polymethacrylate resin, or a composite thereof. The thermal contraction rate of the resin paste is preferably intermediate between the thermal contraction rate of the ceramic green sheet 2 and the thermal contraction rate of the conductive paste (silver paste) serving as the via electrode.

  Next, as shown in FIG. 2C, a second through hole having a diameter smaller than that of the first through hole is formed inside the first through hole filled with the resin paste. The second through hole is also formed by a laser. The second through hole is not limited to the circular shape in the drawing, but may be another shape such as a rectangle or a semicircle.

  Then, as shown in FIG. 2D, the second through hole is filled with a conductive paste (silver paste). The coil pattern 11 is formed after the filling process of the conductive paste. As a result, the resin inside is filled inside the first through hole, and the silver paste is filled inside.

  Thereafter, as shown in FIG. 2E, the ceramic green sheets are laminated and temporarily pressed. At this time, the conductive paste is laminated so as to be in contact with and electrically connected to the end portions 12 of the coil patterns 11 of each layer, whereby interlayer connection (electric conduction) in the via hole 21 is performed. As described above, a mother laminate (raw laminate) before firing is formed.

  Finally, as shown in FIG. 2 (F), the mother laminate is fired. At this time, since the resin paste in the first through hole is burned off by firing, the periphery of the silver paste in the first through hole becomes a cavity. Therefore, the ceramic and the silver paste are not brought into contact with each other, and stress due to the difference in the thermal shrinkage rate during the thermal firing is not generated.

  Alternatively, even if the resin paste does not burn out, the resin paste functions as a stress relaxation agent when the thermal shrinkage rate of the resin paste is intermediate between the thermal shrinkage rate of the ceramic and the thermal shrinkage rate of the silver paste serving as the via electrode. Therefore, stress is relieved.

  Therefore, in the multilayer inductor element of the present embodiment, there is no possibility that the multilayer body is cracked during firing, and there is no possibility that the electrical connection between the via hole 21 and the coil pattern 11 is broken.

  In particular, in the manufacturing method as described above, a through-hole is formed for each ceramic green sheet, a resin paste is filled outside, a silver paste is filled inside, and then laminated and fired. It is suitable for an element manufactured by processing a ceramic green sheet of very hard magnetic material (ferrite).

  The multilayer inductor element of the present embodiment can be modified as follows. FIG. 3 is a diagram mainly showing a process of forming the via hole 21 in the manufacturing process of the multilayer inductor according to the modification. First, as shown in FIG. 3A, a first through hole is formed by laser for each ceramic green sheet. Also in this case, the shape of the first through hole is not limited to the circle in the figure, and may be another shape such as a rectangle or a semicircle. Also in this modified example, first, a ceramic green sheet is prepared, the coil pattern 11 is formed for each ceramic green sheet, and then the first through-hole forming step of FIG. A 1st through-hole is formed from the lower surface side in the location (location where the above-mentioned coil pattern 11 exists) where the coil pattern 11 on each ceramic green sheet is formed. Since the first through hole is formed by a laser, the metal layer of the coil pattern 11 remains. The coil pattern 11 may be formed after the via hole 21 is formed. When the coil pattern 11 is formed later, the first through hole can be formed from the lower surface side or the upper surface side.

  Then, as shown in FIG. 3B, a resin is applied to the inner wall of the first through hole, and the entire inside of the first through hole is not filled with the resin, but a hole (second through hole) is formed in the center portion. Make holes). Therefore, the first through hole according to the modified example has a diameter (for example, a diameter of 500 μm or more) enough to leave a hole in the central portion. The shape of the hole remaining in the center is not limited to the circular shape in the figure.

  Thereafter, as shown in FIG. 3 (C), the central hole (second through hole) is filled with silver paste, and each ceramic green sheet is laminated as shown in FIG. Is done. In addition, you may form the coil pattern 11 after filling of the silver paste of FIG.3 (C). Finally, as shown in FIG. 3 (E), the mother laminate is fired. Also in this modification, since the resin is filled outside the first through hole and the silver paste is filled inside, the periphery of the silver paste inside the first through hole becomes a cavity. Alternatively, even if the resin paste does not burn out, if the resin heat shrinkage is intermediate between the ceramic heat shrinkage and the silver paste heat shrinkage that will be the via electrode, the resin functions as a stress relaxation agent, Stress is relieved.

  Next, FIGS. 4 and 5 are diagrams mainly showing a process of forming the via hole 21 in the manufacturing process of the multilayer inductor according to the application example. The process from FIG. 4A to FIG. 4F is the same as the process from FIG. 2A to FIG. 2F, and the process from FIG. 5A to FIG. Since it is the same as the steps from FIG. 3A to FIG. 3E, description thereof will be omitted.

  As shown in FIGS. 4G and 5F, in the multilayer inductor element according to the application example, after firing the multilayer body, the multilayer body is impregnated with resin. As a result, the resin paste is filled again in the portion where the resin paste is burned out and becomes a cavity, and the strength is improved.

  In the present embodiment, the resin paste is shown as the first paste. However, the resin paste is burned down by firing, or the thermal contraction rate is intermediate between the thermal contraction rate of the ceramic and the thermal contraction rate of the silver paste that becomes the via electrode. Any thing can be used.

DESCRIPTION OF SYMBOLS 1 ... Multilayer inductor element 2 ... Ceramic green sheet 11 ... Coil pattern 12 ... End part 21 ... Via hole

Claims (6)

A method for manufacturing a multilayer inductor element in which a coil pattern is formed and laminated on a ceramic green sheet containing a magnetic material,
Forming a first through hole in the ceramic green sheet;
Filling the first through hole with the first paste;
After filling the first paste, forming a second through hole having a diameter smaller than that of the first through hole at a place filled with the first paste;
Filling the second through hole with a conductive second paste;
Forming a coil pattern electrically connected to the second through hole on the ceramic green sheet;
Laminating the ceramic green sheets, making an interlayer connection by electrically connecting one end of the coil pattern with the second paste, and creating a laminate in which an inductor is formed;
Firing the laminate;
A method for manufacturing a multilayer inductor element, comprising: A method for manufacturing a multilayer inductor element in which a coil pattern is formed and laminated on a ceramic green sheet containing a magnetic material,
Forming a first through hole in the ceramic green sheet;
Applying a first paste to the inner wall of the first through-hole, and leaving a second through-hole having a smaller diameter than the first through-hole at the center of the first through-hole;
Filling the second through hole with a conductive second paste;
Forming a coil pattern electrically connected to the second through hole on the ceramic green sheet;
Laminating the ceramic green sheets, making an interlayer connection by electrically connecting one end of the coil pattern with the second paste, and creating a laminate in which an inductor is formed;
Firing the laminate;
A method for manufacturing a multilayer inductor element, comprising:   The method for manufacturing a multilayer inductor element according to claim 1, wherein the first paste contains a resin. When the thermal shrinkage rate of the ceramic green sheet is A, the thermal shrinkage rate of the first paste is B, and the thermal shrinkage rate of the second paste is C,
A <B <C
Or C <B <A
The method for manufacturing a multilayer inductor element according to claim 1, wherein:   The method for manufacturing a multilayer inductor element according to claim 1, wherein the second paste contains silver.   6. The method for manufacturing a multilayer inductor element according to claim 1, wherein the multilayer body is impregnated with a resin after the multilayer body is fired.

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