JP2011223025A - Ceramic core and manufacturing method thereof and chip-shaped electronic components using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasmall chip-shaped electronic component and a ceramic core used therein, which secures the necessary bonding strength of electrode terminals when mounted on a circuit board.SOLUTION: A ceramic core comprises a core part and a leg for holding the core part by both edges thereof, measuring 1.1 mm or less in the lengthwise direction and 0.6 mm or less in the breadthwise direction in a plan view. The edge of a protruding part of the leg in the breadthwise direction of the ceramic core has its corners and ridgelines curved at a radius of curvature of 5-25 μm.

Description

  The present invention relates to a particularly small chip-shaped electronic component having a size of 1005, 0603 mm or the like, and more specifically, a chip inductor in which a conductor is spirally formed on the outer periphery of a core core portion by winding or plating, and a ceramic as a member thereof Concerning the core.

  A large number of chip-shaped electronic components such as capacitors, CRs, and inductors are mounted on portable electronic devices, particularly cellular phones. As the above-mentioned devices become smaller and more functional, 1608 (plan view) The chip-like electronic components mounted with the long dimension of 1.6 mm, the short dimension of 0.8 mm, and so on to 1005, 0603, and 0402 are also rapidly miniaturizing. In particular, inductors are frequently used as circuit components for high-frequency noise removal, but high inductance is also required against the downsizing of the outer size, so it is currently difficult to secure an effective area for the coil formation part. It is.

  Although the chip-shaped electronic component is not illustrated, there is a chip-shaped electronic component 111 having a substantially H shape as shown in FIGS. 7A and 7B from a general rectangular shape. If the component 111 is a chip inductor, a conductor is wound around the core core portion 103 in a spiral manner by a winding 123 or a plating 124, and electrodes 122 are formed on the leg portions 102 at both ends sandwiching the core core portion 103. The electrode 122 is adhesively mounted on the conductor of the printed wiring board by solder reflow or the like.

  With the minimization of the longitudinal dimension L of the chip-shaped electronic component 111, for example, in the case of the chip inductor 121, the length X of the core core 103 is naturally shortened, and therefore the number of turns of the winding 123 or the plating 124 is reduced. There was a problem that an inductance value could not be obtained.

  In order to solve these problems, a ceramic core 101 shown in FIGS. 8A and 8B having a longitudinal dimension L of 0.6 mm and a core core 103 having a length X of 0.1 mm can be produced. Met. Specifically, it was possible to produce the ceramic core 101 having a width D of 0.25 mm of the leg portion 102 and a curvature radius R2 of the curved surface at the boundary between the core core portion 103 and the leg portion 102 of 0.06 mm.

  Further, in the manufacture of the ceramic core 101, a method for forming a portion that becomes a cross-sectional view of the core core 103 is shown in FIG. 9A, and a method for forming a portion that becomes a vertical cross-sectional view of the ceramic core 101 is shown. The powder molding apparatus 131 shown in 9 (b) was used. An outline of the operation is as follows. The ceramic powder filling hole 139 is filled with the ceramic powder 109, and then the upper punch 135 is lowered and pressed downward while being in contact with the first lower punch 136, thereby being fixed. The ceramic powder 109 filled by the second lower punch 137 is pressurized in a ceramic powder filling hole 139 surrounded by the upper punch 135 and the first lower punch 136, and the bottom surface 136a of the recess of the first lower punch 136 is formed. The ceramic molded body 110 that is lowered to the position of the projecting surface 137 a of the second lower punch 137 and becomes the ceramic core 101 was obtained. (See Patent Document 1)

JP-A-5-275256

  However, since the ceramic core 101 of Patent Document 1 has a remarkably large ratio 2D / L = 0.83 of the width D of the leg portion 102 with respect to the longitudinal dimension L, the length X of the core core portion 103 is reduced, and the ceramic core When 101 was used as the chip-shaped electronic component 111 or the chip inductor 121, the effective area for conductor formation was small. Furthermore, the curvature radius R2 of the curved surface at the boundary between the core core portion 103 and the leg portion 102 can be set to 60 μm. That is, the dimension of the cross section of the core core portion 103 is not substantially uniform in the longitudinal direction of the core core portion 103. Thus, when the ceramic core 101 is used as a chip inductor, there is a problem that the winding length of the winding 123 or the thickness of the plating 124 varies, and as a result, the inductance value varies.

  Here, the reason why only the length X of the core core 103 is reduced as a means for reducing the longitudinal dimension L of the ceramic core 101 is that the ceramic core 101 has a minimum dimension as shown in FIG. The die 132 for forming the sheet had to be minimized. However, since the concave shape of such a very small die 132 could not be processed accurately and sharply, when the ceramic powder is formed, the corner 102b and the ridgeline 102c of the protruding portion end surface 102a are curved surfaces having a radius of curvature R1 of at least about 45 μm. When the barrel treatment for removing deposits was performed after firing, the radius of curvature R1 was about 50 μm. That is, when the width D of the leg portion 102 is reduced, the straight portion 102d of the projecting portion end surface 102a of the leg portion 102 is reduced. Therefore, in order to secure the straight portion 102d, the width D of the leg portion 102 is 0.25 mm. It was necessary to make it large.

  On the other hand, when the width D of the leg portion 102 of the ceramic core 101 is 0.1 mm, the protruding portion end surface 102a of the leg portion 102 does not have the linear portion 102d or becomes slightly small. When an electrode is formed on the projecting portion end surface 102a to be an installation surface and bonded to the conductor of the substrate by solder reflow or the like, there is a problem that the adhesive strength is low.

  Further, the above-described upper punch 135 and first lower punch 136 are brought into contact with each other in the die 132 and lowered so that the second lower punch 137 comes to a predetermined position, thereby forming the ceramic core 101 to be formed. The manufacturing method of the molded body 110 has the following problems.

  FIG. 11 shows a perspective view of the second lower punch 137. With such a shape, the second lower punch that becomes the ridge line 102c of the leg 102 on the core core 103 side is processed by profile polishing. The corner portion 137a of 137 is a curved surface having a curvature radius R3 of 50 μm or more. Therefore, there is a problem that the radius of curvature R1 of the ridgeline 102c on the core core 103 side of the protruding end surface 102a of the leg portion 102 of the ceramic core 101 is 50 μm or more, and further, the upper punch 135, second shape of FIG. A clearance is required between the lower punch 137 and the die 132 to move up and down, and the ridgeline 102c on the outer edge 102a of the protruding portion 102a and the corner 102b of the leg portion 102 of the ceramic molded body 110 formed thereby are burrs. Will occur. The burr of the ceramic core 101 obtained by firing the ceramic molded body 110 exists as it is, and cannot be used as the chip-shaped electronic component 111. The burrs are removed by a known barrel process. As a result, the traces from which the burrs are removed become a chipping-shaped C surface or a curved surface, and in addition, the core core 103 of the projecting portion end surface 102a of the leg portion 102 is formed. There has been a problem of enlarging the curved surface of the side ridge line 102c.

On the other hand, when the corner 102b and the ridgeline 102c of the protruding end surface 102a of the leg portion 102 of the ceramic core 101 are formed as sharp edges having a curvature radius R1 that is substantially zero, the electrode 122 is formed in a U-shape. In this case, the thickness of the corners 102b and the ridge line 102c is reduced, and the lead line is disconnected at the edge of the ridge line 102c when the terminal line of the winding 123 is crimped to the electrode 122 (not shown). There was a problem to do.

  In order to solve the above-described problems, a ceramic core according to the present invention is provided with leg portions at both ends of a core core portion, and has a longitudinal dimension of 1.1 mm or less and a short dimension of 0.6 mm or less in plan view. And it is characterized by having a curved surface with a curvature radius of 5 to 25 μm at the corner and the ridgeline of the end face of the protruding portion of the leg portion.

  Furthermore, when the projecting portion end face width of the leg portion in plan view is D, it has a straight portion of at least D / 2 or more between the corners.

  Furthermore, when the longitudinal dimension of the ceramic core in plan view is L, 2D / L is 0.2 or more.

  The present invention also relates to a method for producing the ceramic core, wherein a ceramic powder molding apparatus comprising a die having a ceramic powder filling hole, and an upper punch and a lower punch for press-molding the ceramic powder is used. The die used in the molding step comprises a first die that constitutes an area outside the ceramic powder filling hole, and comprises the step of molding and the step of firing and barreling the obtained ceramic compact. A second die is disposed in a portion of the side surface of the powder filling hole corresponding to the end surface of the projecting portion of the ceramic core, the ceramic powder filling hole is filled with ceramic powder, the upper punch and the lower punch, And pressurizing the ceramic powder to form a ceramic compact.

  Further, of the side surfaces of the ceramic powder filling hole, both end portions of the side surface of the second die corresponding to the end surface of the projecting portion in the short direction of the ceramic core are brought into contact with the first die, and A ceramic powder molding apparatus having a clearance between the other side surface of the two dies and the first die is used.

  Furthermore, it includes a step of mixing at least water and the ceramic core and performing a centrifugal barrel treatment.

  As described above, according to the ceramic core of the present invention, in the ceramic core having the leg portions at both ends of the core core portion and having a longitudinal dimension in a plan view of 1.1 mm or less and a short dimension of 0.6 mm or less, The protrusion end face has a curved surface with a radius of curvature of 5 to 25 μm at the corner and ridge line.

As described above, since the radius of curvature is 5 μm or more, even if the electrode part is formed in a U-shape on the end face of the leg part in the short direction of the ceramic core, the thickness variation of the electrode part is reduced. While being able to make it small, exposure of the ceramic core can be prevented at corners and ridge lines of the end face of the protrusion. Further, when the winding is wound around the core part of the ceramic core and the lead wire of the winding is attached to the end face of the projecting part across the ridge line of the projecting part end face of the leg part, the ridge line is Since it is a curved surface, it is possible to prevent disconnection of the lead wire. In addition, since the curved surface of the corner and the ridgeline of the protruding portion end surface of the leg portion has a curvature radius of 25 μm or less at the maximum, for example, in a very small ceramic core having a longitudinal dimension of 0.4 mm, at least the length of the core core is set to the longitudinal dimension. If the radius of curvature of the curved surface at the corner of the protruding portion end surface is 25 μm, the width of the protruding portion end surface of the leg portion in the short direction is at least 0. A straight line portion of 05 mm can be secured. As described above, when an electrode is formed on the end surface of the protruding portion and this surface is used as an installation surface and adhered to a printed wiring board, sufficient adhesive strength can be secured.

Further, when the end surface width of the projecting portion of the leg portion in plan view is D, at least D /
Since it has two or more straight portions, when it is used as a chip-shaped electronic component by providing an electrode on the end surface of the projecting portion of the ceramic core, it can be bonded to the printed wiring board with sufficient strength.

  Further, when the longitudinal dimension of the ceramic core in plan view is L, 2D / L is 0.2 or more, so that the core has a leg portion long enough to adhere to the printed wiring board, and the core Since the amount of conductor provided in the core portion can be increased, the effective value can be increased when used as an inductor or the like.

  According to the method for manufacturing a ceramic core of the present invention, the die of the ceramic powder molding apparatus is configured by disposing the second die at a portion corresponding to the end face of the projecting portion in the short side direction of the ceramic core, The area outside the die and the ceramic powder filling hole is constituted by the first die, and both ends of the side surface of the second die corresponding to the end face of the projecting portion of the ceramic core in the short direction are brought into contact with the first die. In addition, since the ceramic powder molding apparatus has a clearance between the other side surface of the second die and the first die, it is easy to form a straight portion in the projecting portion end face width of the leg portion, and the leg portion The radius of curvature of the end surface of the protrusion and the curved surface of the ridge line can be made extremely small.

  Further, after firing the ceramic molded body, when at least water and the ceramic core are mixed and subjected to a centrifugal barrel treatment, seizure is performed without significantly increasing the curvature radius of the curved surface at the corners and ridgelines of the protrusions of the legs. The kimono can be removed.

  Further, in the chip-shaped electronic component according to the present invention, when an electrode is formed in a U shape on the projecting portion end surface of the leg portion, the ceramic core projecting from the electrode is prevented from being exposed at the corner and the ridge line portion of the projecting portion end surface. In addition, when the electrode forming portion is mounted as an installation surface on the printed wiring board, sufficient adhesive strength with the printed wiring board can be secured.

  Moreover, when the chip-shaped electronic component of the present invention is used as an inductor, the amount of conductor provided in the core core portion can be increased. Further, when used as a winding type chip inductor, there is an effect that disconnection of the lead wire at the end of the winding can be prevented.

(A) is a perspective view which shows one Example of the ceramic core of this invention, (b) is a principal part side view, (c) is a perspective view which shows another Example. (A) is sectional drawing which shows the powder pressure molding apparatus used when manufacturing the ceramic core of this invention, (b) is a top view of the die | dye installed in the powder pressure molding apparatus. (A) is a top view which shows the other manufacturing method of the ceramic core of this invention, (b) is another Example of the ceramic core of this invention. (A) is a side view which shows one Example of the chip-shaped electronic component of this invention. (A) is sectional drawing which shows the manufacturing method of the conventional ceramic core, (b) is a top view. It is sectional drawing which shows the adhesive strength test of an electrode. (A), (b) is a side view of the conventional chip-shaped electronic component. (A) is a perspective view of the conventional ceramic core, (b) is a side view. (A) (b) is sectional drawing which shows the manufacturing method of the conventional ceramic core. It is a side view of the principal part of the conventional ceramic core. It is a perspective view which shows the manufacturing method of the conventional ceramic core.

Hereinafter, embodiments of the present invention will be described. FIG. 1 (a) shows a ceramic core 1 of the present invention.
The perspective view which shows an example, (b) is the principal part sectional drawing, (c) has shown the perspective view of the other example of the ceramic core 1 of this invention. As shown in FIG. 1 (a), the ceramic core 1 is provided with leg portions 2 projecting in the short direction of the ceramic core 1 at both ends of the core core portion 3, and the core core portion 3 and the leg portion 2 are integrally formed. Has been. Further, as shown in FIG. 1 (b), the corner 2b of the projecting portion end surface 2a of the leg portion 2 of the ceramic core 1 and the ridge line 2c have a curved surface with a radius of curvature R1, and at both ends of the projecting portion end surface 2a. A straight line portion existing between the corners 2b is defined as a straight line portion 2d of the protrusion end surface 2a. Here, the material of the ceramic core 1 is preferably made of a ceramic such as alumina or ferrite.

  The ceramic core 1 of the present invention has a longitudinal dimension L in a plan view of 1.1 mm or less and a short dimension Y of 0.6 mm or less, and a corner of the projecting portion end surface 2 a of the leg portion 2 of the ceramic core 1. 2b and the ridgeline 2c have curved surfaces with a radius of curvature R1 of 5 to 25 μm.

Here, when the radius of curvature R1 is less than 5 μm, the corner 2b and the ridgeline 2c become sharp edges. Therefore, when the electrode is formed on the projecting portion end surface 2a, the electrode cannot be formed with high thickness accuracy, resulting in variations in the thickness of the electrode. Thus, the electrodes are peeled off at the corners 2b and the ceramic core 1 is easily exposed. If the radius of curvature R1 exceeds 25 μm, the corner 2 of the protrusion end face 2a is smaller when the ceramic core 1 has a minimum dimension such that the width D of the protrusion end face 2a of the leg 2 is less than 0.10 mm.
If the length of the straight portion 2d existing between b is less than 0.05 mm of the width D, and the ceramic core 1 is used as a chip-shaped electronic component, it causes a reduction in adhesive strength with the printed wiring board. That is, by setting the radius of curvature R1 to 5 to 25 μm, it is possible to prevent the ceramic core 1 from being exposed and to sufficiently provide the linear portion 2d of the projecting portion end surface 2a as shown in FIG. When the ceramic core 1 is used as a chip-shaped electronic component, it can have adhesive strength with a printed wiring board. The curvature radius R1 is preferably 5 to 10 μm in consideration of barrel processing time and the like.

  Furthermore, it is preferable that the linear part 2d of the protrusion part end surface 2a of the leg part 2 is 1/2 or more of the width D of the protrusion part 2a. This is because, when the linear portion 2d is less than ½ of the width D of the protruding portion 2a, there is a possibility that sufficient adhesive strength with the printed wiring board cannot be obtained when the ceramic core 1 is used as a chip-shaped electronic component. There is.

  Further, when the longitudinal dimension of the ceramic core 1 in plan view is L, 2D / L is preferably 0.2 or more. For example, when 2D / L is less than 0.2, for example, when the ceramic core 1 is used as an inductor, the core core portion 3 provided with the conductor is short, so that a desired effective value may not be obtained. is there. In addition, in order to obtain a desired effective value and to have sufficient adhesive strength with the printed wiring board, 2D / L is preferably 0.2 to 0.4.

  Next, the ceramic powder molding apparatus 31 used for manufacturing the ceramic core 1 of the present invention will be described.

  FIG. 2A is a schematic cross-sectional view of a ceramic powder forming apparatus 31 used for manufacturing the ceramic core of the present invention, and FIG. 2B is a plan view showing an embodiment of the die 32.

The ceramic powder molding apparatus 31 has a structure in which the ceramic powder body 9 is filled by filling the ceramic powder filling hole 37 surrounded by the die 32 and press-molding with the upper and lower punches 35 and 36 to form the ceramic molded body 10. It is made. As shown in FIG. 2B, the die 32 has a structure in which the second die 34 is arranged at a portion corresponding to the projecting portion end surface 2 a in the short side direction of the ceramic core 1 in the side surface of the ceramic powder filling hole 37. The first die 33 is configured outside the region of the second die 34 and the ceramic powder filling hole 37. Further, of the side surfaces of the ceramic powder filling hole 37, both end portions of the side surface 34 a of the second die 34 corresponding to the projecting end surface 2 a in the short direction of the ceramic core 1 are brought into contact with the first die 33. ing. On the other hand, it arrange | positions between the other side surfaces 34b, 34c, 34d of the 2nd die | dye 34, and the 1st die | dye 33 so that it may have the clearance g.

  The material of the upper and lower punches 35 and 36 and the dies 32, 33, and 34 is a cemented carbide made of Wc, Wc-Co, etc., and the dies 32, 33, and 34 are preferably made of ultrafine particles. Further, the abutment and fixing of the both end portions 34a of the second die 34 and the first die 33 are fixed by inserting a lock pin 38 or the like from the first die 33 to the second die 34 as shown in FIG. You can do it. Further, the side surface 34a of the second die 34 is disposed in contact with the first die 33, but the other side surfaces 34b and 34d may have a clearance g between the first dies 33, or one side may be the first side. It may be in contact with one die 33. In the structure as shown in FIG. 2B, it is sufficient that the clearance g exists between at least the side surface 34 c and the first die 33.

  Here, a second die 34 is arranged in a portion corresponding to the projecting portion end surface 2a in the short side direction of the ceramic core 1 in the side surface of the ceramic powder filling hole 37. The projecting portion end surface 37a of the ceramic powder filling hole 37 forming the corner 2b of the projecting portion end surface 2a of the leg portion 2 of the ceramic core 1 by constituting and arranging the first die 33 outside the region of the powder filling hole 37. The corner 37b can be formed as a sharp edge.

  For example, in the case of the die 32 in which the first die 33 and the second die 34 are integrally configured, a curved surface with a radius of curvature of about 45 μm is formed even if it is performed by wire electric discharge machining with a thin wire 0.7 mmφ. Since it is unavoidable that it is formed, the curved surface of the end face of the obtained product has a large curvature radius of about 45 μm.

  Further, when the clearance g is provided between the first die 33 and the second die 34, the lock pin 38 and the like are fitted and fixed to the first die 33 and the second die 34, so that when the die 32 is assembled, The protrusion of the first die 33 corresponding to the corner 37b of the protrusion end surface 37a of the ceramic powder filling hole 37 can be prevented from being crushed. Furthermore, since the contact means is not shrink fit, crimping, brazing, etc., the influence on the dimensional accuracy of the die 32 can be minimized, so that the dimensional accuracy required for the ceramic powder molding apparatus 31 of the micro ceramic core 1 is achieved. It can satisfy ± 5 μm or less. On the other hand, when either the first die 33 or the second die 34 needs to be replaced due to wear or the like, only the minimum parts need be replaced, and the maintenance can be simplified. Here, the clearance g is not particularly limited as long as it is 2 μm or more. Further, it is reasonable to mold a plurality of ceramic molded bodies 10 at the same time, and the number of the ceramic molded bodies 10 may be appropriately selected.

  FIG. 3A shows a plan view of a die 32 of a ceramic powder forming apparatus 31 which is another embodiment of the present invention. This is because the second die 34 is brought into contact with either the left or right pair of projecting portion end surfaces 37a with respect to the axis a direction of the ceramic powder filling hole 37 corresponding to the projecting portion end surfaces 2a at both ends to be the leg portions 2 of the ceramic core 1. It is in contact. As shown in FIG. 3B, the ceramic core 1 thus obtained is only required to form the electrodes 12 on the projecting portion end faces 2a of the pair of leg portions 2 formed by the second die 34. While positioning the electrode 12 is easy, it is only necessary to install two second dies 34, and there is an advantage that the ceramic powder molding apparatus 31 can be made inexpensive.

  Next, the manufacturing method of the ceramic core of this invention using the above-mentioned ceramic powder shaping | molding apparatus 31 is demonstrated.

The ceramic powder filling hole 37 is filled with ceramic powder 9 such as alumina, and press-molded by the upper punch 35 and the lower punch 36 to obtain the ceramic molded body 10. After firing the ceramic molded body 10 at a predetermined firing temperature, barrel processing is performed to produce a desired ceramic core 1. Here, it is preferable that the barrel treatment is carried out by mixing at least water and the ceramic core 1 as a product and introducing it into a centrifugal barrel device for barrel treatment. In some cases, when an abrasive is added to water and the ceramic core 1 and barrel treatment is performed, large curved surfaces are formed at the corners 2b and the ridgeline 2c. That is, since the ceramic core 1 of the present invention has a minimum dimension of 1.1 mm or less in the longitudinal dimension and 0.6 mm or less in the short dimension, the effect of the abrasive used in the normal barrel processing is reduced. It is to have it in itself. Therefore, by performing barrel treatment without using the abrasive, it is easy to control the surface of the ceramic core 1 to an appropriate curved surface as well as removing the deposits. In addition, in the barrel processing, in order to shorten the barrel processing time by applying an appropriate stirring force to the fluid, media that do not affect the curved surface formation may be added.

  Next, the chip-shaped electron of the present invention in which the ceramic core 1 of the present invention is used in FIG. 4 and the electrodes 12 are formed on the projecting portion end surfaces 2a of the pair of short legs 2 serving as the installation surfaces of the ceramic core 1 is shown. A side view of the part 11 is shown. As described above, when the electrode 12 is formed in a U-shape on the projecting portion end surface 2a of the leg portion 2 of the ceramic core 1, the curvature radius R1 of the corner 2b is small, so that the thickness t of the electrode 12 is also less varied. And since the linear part 2d of the protrusion part end surface 2a is fully ensured, when it mounts on a board | substrate conductor surface as an installation surface, sufficient adhesive strength is securable. Furthermore, even if the length X of the core core portion 3 is a very small ceramic core 1, it is sufficiently large, so that the circuit formation effective region 3a can be made large. Furthermore, since the circuit can be formed in a direction perpendicular to the substrate surface, the circuit integration density can be improved.

  Moreover, if the chip-shaped electronic component 11 is used as a chip inductor, the radius of curvature R2 at the boundary between the core core portion 3 and the leg portion 2 is small, so that the dimensional accuracy of the cross section of the core core portion 3 is high. When the wire is wound, the length variation is small, and even when the plating 24 is formed and etched with a laser or the like to form a coil shape, the variation in the thickness of the plating 24 can be suppressed, resulting in a variation in inductance value. It can be made smaller. Further, in the winding method, the terminal lead wire is attached to the electrode 12 on the projecting portion end surface 2a of the leg portion 2, but the ridge line 2c of the projecting portion end surface 2a of the leg portion 2 of the ceramic core 1 is excessively sharp. Since it is not an edge, the problem that the lead wire is disconnected can be prevented.

  The ceramic core of the present invention was prepared by the following method.

  First, as shown in FIG. 2, the ceramic powder molding apparatus 31 used when producing the ceramic core of the present invention has an upper punch 35 above and below the ceramic powder filling hole 37 provided in the die 32, respectively. The lower punch 36 is installed, and the upper punch 35 and the lower punch 36 are relatively interlocked to press-mold the ceramic powder filled in the ceramic powder filling hole 37. The die 32 is composed of two dies. Of the side surfaces of the ceramic powder filling hole 37 provided in the die 32, a portion corresponding to the projecting portion end surface 2 a in the short side direction of the ceramic core 1 to be molded. The second die 34 is disposed in the first die 33 outside the area of the second die 34 and the ceramic powder filling hole 37. The materials of the first die 33, the second die 34, the upper punch 35, and the lower punch 36 are all WC cemented carbides having an ultrafine particle diameter.

Next, a ceramic powder molding device in which ceramic powder 9 in which resin binder is further mixed with a sintering aid composed of 96 mass% Al ₂ O ₃ alumina and the balance being SiO ₂ , MgO, and CaO is set in a press device. The ceramic powder hole 37 provided in the die 32 of 31 is filled, and the ceramic powder 9 is pressure-formed at about 120 to 130 MPa by the upper punch 35 and the lower punch 36.

  The ceramic molded body obtained above was fired at 1600 ° C., then the fired ceramic core 1 and water were put into a pot, the pot was placed in the centrifugal barrel device, and the rotational speed was 60 rpm. By performing the time processing, as shown in FIG. 1 (a), the longitudinal dimension L = about 0.5 mm, the short dimension Y = about 0.3 mm, and the width D of the protrusion tip 2a of the leg 2 = about 0.1 mm. An H-shaped ceramic core 1 of the present invention was produced.

Example 1
About the ceramic core 1 of this invention obtained by said manufacturing method, the corner | angular 2b, the curvature radius R1 of the ridgeline 2c, and the length of the linear part 2d were verified. The ceramic core 1 of the present invention was produced so that the radius of curvature R1 of the corner 2b and the ridgeline 2c was about 15 μm by setting the barrel conditions.

  In addition, as a comparative example, a ceramic core was manufactured using a ceramic powder molding apparatus 131 including a die 132 manufactured by 0.7 mmφ thin wire electric discharge machining as shown in FIGS. 5 (a) and 5 (b). In addition, the material of the die 132, the upper punch 135, and the lower punch 136 is WC cemented carbide. The die 132 used was precisely machined so that the corner 102b of the protruding end surface 102a of the ceramic core to be molded and the curvature radius R1 of the ridgeline 102c were minimized. The material of the ceramic powder, the firing condition of the ceramic molded body, and the barrel condition after firing are the same as those of the embodiment of the present invention, and the longitudinal dimension L, the lateral dimension Y of the ceramic core, and the width of the protrusion tip 2a D and the shape were made to be equivalent to those of the example of the present invention.

  Under the above conditions, 5 samples were prepared for each of the examples and comparative examples of the present invention, the sample numbers of the examples of the present invention were 1 to 5, and the sample numbers of the comparative examples were 6 to 10, respectively. L, the width D of the protrusion end surface of the leg, the straight line lengths 2d and 102d, the corners, and the curvature radius R1 of the ridgeline were measured. The results are as shown in Table 1.

  As can be seen from Table 1, the ceramic core according to the comparative example was prepared by setting the ceramic powder forming apparatus 131 so that the curvature radius R1 of the corner 102b and the ridgeline 102c of the protruding portion end surface 102a was minimized. The radius of curvature R1 at the corner 102b of 101 is as large as 49 μm on average, and as a result, the straight portion 102d existing between the corners 102b of the protrusion end surface 102a has an average value of 0.001 mm and is substantially provided with a straight portion 102d. I couldn't.

On the other hand, in the ceramic core 1 according to the embodiment of the present invention, the corner radius 2b of the projecting portion end surface 2a and the curvature radius R1 of the ridge line 2c can be made close to the set values, and the projecting portion end surface 2a of the leg portion 2 can be obtained. The straight portion 2d between the corners 2b was 0.067 mm on average, and the straight portion 2d of the leg 2 was sufficiently secured.

(Example 2)
The electrode 12 is formed on the projecting portion end surface 2a of the leg portion 2 of the ceramic core 1 on the ceramic core having various radii of curvature R1 at the corners and ridgelines of the projecting portion end surface produced by the manufacturing method described above. Along with the appearance inspection of the chip-shaped electronic component, a test for confirming the adhesive strength of the electrode 12 to the substrate was performed. Furthermore, the winding wire 123 was wound around the core core part 3, and the confirmation test of the disconnection incidence rate in the ridgeline 2c of the protrusion part end surface 2a of the leg part 2 of the lead wire was performed.

  Here, the ceramic core 1 forming the chip-shaped electronic component was manufactured by the same manufacturing method as the ceramic core of the present invention of Example 1. In addition, the corner 2b of the protrusion part end surface 2a of the ceramic core 1 and the curvature radius R1 of the ridgeline 2c were finely adjusted in the range of 2 to 14 hours in the barrel treatment.

  In addition, a sample in which the curvature radius R1 of the corner 2b and the ridgeline 2c exceeds 40 μm was manufactured by the same manufacturing method as the ceramic core 101 which is a comparative example of Example 1.

  As shown in FIG. 5, a U-shaped electrode 12 is formed on the projecting portion end surface 2 a of the leg portion 2 of the ceramic core 1 manufactured by the above-described manufacturing method, and the core core portion 3 is formed of 20 μmφ Cu wire. After the winding wire 23 was formed by a winding machine, the lead electronic wire was drawn out so as to cross the ridge line 2c of the protruding portion end surface 2a of the leg portion 2, and the chip electronic component 11 was manufactured. Here, the electrode 12 was formed by forming 20 μm of Cu as a base electrode material by dipping, forming 2 μm of Ni on the Cu, and further forming Sn of 5 μm on the Ni.

  A confirmation test performed on the chip-shaped electronic component produced above was performed as follows.

  In the appearance inspection of the chip-shaped electronic component, the presence or absence of exposure of the ceramic core protruding from the electrode 12 was inspected with respect to the corner 2b and the ridgeline 2c of the protruding portion end surface 2a where the electrode was formed on the chip-shaped electronic component.

In addition, as shown in FIG. 6, a test for confirming the adhesive strength of the chip-shaped electronic component to the substrate is performed by providing a pore 41a in a 96% by mass alumina substrate 41 in which a Cu layer 42 is formed to a thickness of 35 μm. A chip-like electronic component is placed so as to straddle the pore 41a, the electrode 12 is soldered to the alumina substrate 41 by Sn-Pb solder reflow, and the pressure jig 43 is passed through the pore 41a from the back side of the chip-like electronic component placement surface. Was pressed against the chip-shaped electronic component. The speed is about 1 mm / sec. When the pressure load reaches 5N, 10 sec. After a collision test with contact and holding, whether or not there was any peeling between the electrode 12 of the chip-shaped electronic component and the Cu layer 42 of the alumina substrate 41 was observed with a microscope.

  Further, the confirmation test of the disconnection rate of the lead wire of the chip-like electronic component is performed by pulling the lead wire 2c at a right angle when the lead wire is drawn so as to cross the ridge line 2c of the protruding portion end surface 2a. When the lead wire was pulled and stretched with such a strength that no looseness occurred in the winding 23 of the core 3 part, the disconnection rate of the winding 23 was determined per 100 repetitions of the lead wire breakage. The results are as shown in Table 2.

As can be seen from Table 2, the electrode 12 of the chip-like electronic component 11 and the Cu layer 4 of the alumina substrate 41
The results of the test for confirming the adhesive strength with No. 2 are as follows: Sample Nos. 16 and 17, which are comparative examples in which the radius of curvature R1 of the corner 2b of the projecting portion end surface 2a of the leg 2 exceeds 25 μm, are between the Cu layer 42 and the electrode 12 Peeling was confirmed.

  Further, in the test of the occurrence rate of breakage of the ridge line 2c, the winding wire 23 is wound around the core core part 3, and the lead line is pulled out by extending the ridge line 2c horizontally on the protruding end surface 2a of the leg part 2 of the ceramic core 1. In Sample No. 11, which is a comparative example in which the curvature radius R1 is less than 5 μm, the lead wire was disconnected at a rate of 2%.

  From the above results, in the extremely small ceramic core, the straight portion 2d of the protrusion end face is at least D / 2 with respect to the width D of the leg with the corner radius of the protrusion and the curvature radius of the ridge line of 5-25 μm. When the above is ensured, when an electrode is formed on the leg portion of the ceramic core and that portion is used as the installation surface and adhered to the substrate, sufficient adhesion strength is obtained, and at least the curvature and the corners and ridge lines of the end surface of the protruding portion are obtained. Since it has a curved surface with a radius of 5 μm or more, the occurrence of disconnection can be prevented even if a lead wire or the like crosses the corner or ridge line.

  The present invention is suitable as an extremely small chip-shaped electronic component having a leg portion with a size of 1005 mm or less.

DESCRIPTION OF SYMBOLS 1,101: Ceramic core 2.102: Leg part 2a, 102a: Protruding part end surface 2b, 102b: Corner | angular 2c, 102c: Ridge line 3, 103: Core core part 3a, 103a: Circuit formation effective area 9: Ceramic powder 10 : Ceramic molded body 11, 111: Chip-shaped electronic component 12, 122: Electrode 23, 123: Winding 124: Plating 31, 131: Ceramic powder molding apparatus 32, 132: Die 33: First die 34: Second die 35 : Upper punch 36: Lower punch 136: First lower punch 137: Second lower punch 37: Ceramic powder filling hole 38: Lock pin 41: Alumina substrate 42: Cu layer 43: Pressure jig

Claims (8)

A ceramic core having legs at both ends of the core core and having a longitudinal dimension of 1.1 mm or less and a short dimension of 0.6 mm or less in plan view. A ceramic core having a curved surface with a radius of 5 to 25 μm. 2. The ceramic core according to claim 1, wherein when the end surface width of the protruding portion of the leg portion in plan view is D, the ceramic core has a straight portion of at least D / 2 between the corners. 2. The ceramic core according to claim 1, wherein 2D / L is 0.2 or more, where L is a longitudinal dimension of the ceramic core in plan view. 4. A method for producing a ceramic core according to claim 1, wherein the ceramic powder comprises a die having a ceramic powder filling hole, an upper punch for pressing the ceramic powder, and a lower punch. The die used in the forming step comprises a step of forming using a forming device and a step of firing and barreling the obtained ceramic formed body. A second die is disposed at a portion of the side surface of the ceramic powder filling hole corresponding to the end surface of the projecting portion of the ceramic core, the ceramic powder filling hole is filled with the ceramic powder, and the upper punch And the lower punch pressurizing the ceramic powder to form a ceramic molded body. The die used in the forming step is such that, of the side surfaces of the ceramic powder filling hole, both end portions of the side surface of the second die corresponding to the end surface of the projecting portion in the short direction of the ceramic core are applied to the first die. 5. The method of manufacturing a ceramic core according to claim 4, wherein a clearance is provided between the other side surface of the second die and the first die. 5. The method for producing a ceramic core according to claim 4, further comprising a step of mixing at least water and the ceramic core and performing a centrifugal barrel treatment. 4. A chip-shaped electronic component comprising: a ceramic core according to claim 1, wherein an electrode is formed at least on a projecting portion end surface of a pair of short-side leg portions serving as an installation surface. 8. A chip-shaped electronic component according to claim 7, wherein a conductor is provided on the core core and the conductor is spirally wound by winding or plating.

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