JPH07123092B2 - Manufacturing method of multilayer chip inductor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a laminated chip inductor which has a small loss due to distributed capacitance and has stable electric characteristic values.

[0002]

2. Description of the Related Art A chip inductor is used in combination with a chip capacitor to form an LC circuit, or is used alone as a circuit element. This chip inductor is
Due to the desire to make electronic devices lighter, thinner, shorter, and smaller, miniaturization is required, as is the case with other components such as chip capacitors, and this demand is gradually increasing. For this reason,
Multilayer chip inductors in which a coil-shaped conductor layer is incorporated in a magnetic material have been widely used.

A conventional method of manufacturing the above multilayer chip inductor is as follows. A binder or the like is added to the magnetic material powder and mixed to prepare a magnetic material slurry. This slurry is formed into a long sheet by a doctor blade method, a reverse coater method, or the like, cut into a predetermined size and shape, and a large number of magnetic material green sheet pieces 11, 11 ... A piece of green sheet of magnetic material as obtained by cutting is prepared. To each of some of these magnetic material green sheet pieces, each magnetic material green sheet piece 1,
1, through holes are formed at predetermined positions, and the conductor patterns 11a to 11e forming a part of the coil are formed so as to form a coil when these green sheets are stacked. Screen printing using a conductive material paste to connect to. At this time, the conductor patterns 11 of the green sheet pieces that are vertically stacked
Reference characters a and 11e are drawn out to opposite ends of each green sheet element and connected to external electrodes described later.

Next, the magnetic material green sheet pieces on which the conductor patterns are formed are laminated so that the conductor patterns are connected to each other through the through holes to form a coil, and on each of the upper and lower surfaces of the laminated body. The remaining green sheet pieces of magnetic material on which the conductor pattern is not formed are further laminated to form an unfired laminated body. The green sheet laminate is housed in a mold, pressed at a predetermined pressure and temperature, and pressure-bonded to form a pressure-bonded unfired laminate. This pressure-bonded unfired laminated body is cut into a grid pattern to prepare a large number of unfired laminated chips in which the green sheet pieces shown in FIG. 4 are laminated. These unfired laminated chips are once heated in the air for debinding, and then fired again in the air to obtain fired chips. Electrode material paste is applied by a dip method or the like to the opposite end faces of the fired chips that are pulled out to the ends of the conductor patterns and baked at a predetermined temperature to obtain a laminated chip inductor.

[0005]

In the conventional method for manufacturing a multilayer chip inductor according to any one of the above (1) to (3), since the conductor pattern is printed on the magnetic material green sheet piece by screen printing, the coated portion of the conductor pattern is higher than the periphery. When the green sheet pieces printed with these conductor patterns are overlapped with each other so that each conductor pattern forms a coil, the magnetic material green sheet pieces are layered one by one like the through hole portion of the conductor pattern and the corresponding portion. The overlapping portion and the conductor pattern overlap with each other through the magnetic material green sheet piece 1 layer, and then overlap with each other through the magnetic material green sheet piece 2 layer, and again overlap with each other through the magnetic material green sheet piece 1 layer, the conductor pattern 11b to 11d overlaps with each layer of the magnetic material green sheet, and the magnetic material is formed above and below it. The conductive pattern of each green sheet piece is different depending on the part, such as the overlapping portion of the green sheet pieces. The overlapping portions are not in close contact with each other and are separated from each other. When pressed in this state, the larger the number of overlapping portions of the conductor pattern through the magnetic material green sheet piece, the larger the pressure applied, and the conductor pattern adheres more strongly to the green sheet piece. If firing is performed in this state, the conductor pattern fired bodies will remain in close contact with the green sheet fired body as the number of overlaps increases, even if shrinkage occurs.

As described above, in the laminated chip inductor in which the conductor portion of the coil made of the fired body of the conductor pattern remains in close contact with the green sheet fired body, the distributed capacitance generated between the conductors sandwiching each green sheet fired body layer is Since it is also affected by the relative permittivity of the green sheet fired body, loss tan δ (= 1 when used at high frequencies.
There is a problem that / Q) becomes large and desired electrical characteristics as an inductor cannot be obtained. When the multilayer chip inductor manufactured by the conventional method as described above is used as an electronic component and operated, the coil mechanically expands and contracts, and when this is repeated, the conductor portion becomes a magnetic material green sheet fired body. Away from, the close contact is released. Therefore, a distributed capacitance is generated between the conductors of each layer through the air layer, and the electric characteristics at the initial stage and the electric characteristics after repeated use are different, which causes a problem that the electric characteristics are not stable.

An object of the present invention is to provide a laminated chip inductor having a small loss even when used at a high frequency and a stable coil electrical characteristic.

[0008]

In order to solve the above-mentioned problems, the present invention provides a plurality of magnetic material green sheets including a plurality of magnetic material green sheets printed with conductor patterns by laminating a plurality of magnetic material green sheets inside. A method of manufacturing a multilayer chip inductor comprising the steps of obtaining an unfired laminate for forming a coil, crimping the unfired laminate, and firing the crimped unfired laminate to obtain a fired body. Provided is a method for manufacturing a laminated chip inductor, characterized in that a polymer of an incompatible resin is used as a binder for each of a magnetic material green sheet and a conductor pattern.

At this time, it is preferable that the polymers of the incompatible resin have a difference in solubility parameter value of 2 or more.

Next, the present invention will be described in detail. In the present invention, a polymer of an incompatible resin is a polymer of a resin which is difficult to mix, and when it is expressed by a solubility parameter (solvability parameter, SP), the larger the difference, the more difficult it is to mix. Therefore, the difference is preferably 2 or more. As will be described later, it is difficult for the polymer of the resin having a large difference in SP value to adhere the one coating film surface to the other coating film. Table 1 shows the SP value of the polymer of the resin. The official data is "Adhesives and Adhesives" (Kanamaru Akira, 1971 Dai Nippon Book Publishing Co., No. 31-
It is described in the table on page 32 and can also be used.

[0011]

[Table 1]

A polymer of a resin dissolves better as its SP value has a smaller difference from the SP value of a solvent. Therefore, when preparing a resin solution, it is preferable to reduce the difference in SP value. When the coating material containing is applied on a coating film using another resin as a binder, S of the coating film on the coating side is applied.
The wettability at the time of applying the coating material is determined by the difference from the P value. If this wetting is poor, the adhesion between the applied coating film and the applied coating film will be poor, and the two will easily separate. From this, not only the SP value of the polymer of the resin but also the SP value of the solvent of the coating material to be applied is the SP of the resin of the coating film to be applied.
It is preferable that the difference from the value is large. Table 2 shows the SP value of the solvent
For example. The SP value of the mixed solvent, the mixed resin, etc. can be determined from the SP value of each solvent, resin, etc.

[0013]

[Table 2]

[0014]

In general, the enthalpy change ΔH of the mixture of substances can be approximated by the following equation. ΔH = A (δ1−δ2) ² (square of difference between δ1 and δ2) (wherein, δ1 and δ2 are SP values of substances to be mixed, and A is a coefficient). In, the solubility is good when ΔH is small, and the solubility is poor as ΔH is large. Regarding the adhesion of two substances, the larger ΔH is, the more difficult it is for the two substances to adhere. That is, the less compatible the resin is, the less compatible the resin is, and the more easily the resin is separated.

From the above, by using resins having a large SP value difference between the magnetic material green sheet and the conductor pattern coating film, the adhesion between the two is poor when the pressure-bonded unfired laminate is prepared. , Because it becomes easy to separate, in the multilayer chip inductor obtained by firing this pressure-bonded unfired laminated body, a gap is created between the conductor pattern fired body and the magnetic material green sheet fired body, and both are connected via the air gap. Will be done. As a result, the distributed capacitance can be reduced and the loss thereof can be reduced, and since the connection state does not change even after the operation of the laminated chip inductor, its electric characteristics can be stably maintained.

In addition, the resin and the solvent having a large difference in SP value make it difficult for the latter to wet the coating film of the former, so that the coating material using this solvent does not wet well and the adhesion of the coating film also deteriorates.

[0017]

EXAMPLES Examples of the present invention will be described below. Example 1 (1) Preparation of multilayer chip inductor 48 mol% iron sesquioxide (Fe ₂ O ₃ ), ZnO 2
4 mol%, NiO 18 mol%, and CuO 10 mol% were weighed at the respective ratios, charged into a ball mill as raw materials, and wet-mixed for 15 hours. The mixture obtained is dried and then ground, and the powder obtained is calcined at 750 ° C. for 1 hour. The obtained calcined powder is wet-milled for 15 hours in a ball mill, dried and then crushed to obtain a ferrite powder.

Polyvinyl butyral resin (SP value 9.4) as a binder for this ferrite powder
10% by weight, 20% by weight of toluene (SP value 8.9), 20% by weight of ethanol (SP value 12.8) and 40% by weight of butanol (11.1) were added, and the mixture was mixed with a ball mill at 15% by weight.
Perform time mixing. The obtained slurry is used to form a long ferrite green sheet having a film thickness of 80 μm by using a doctor blade method. The obtained ferrite green sheet is cut into a predetermined size to obtain a ferrite green sheet piece obtained by cutting a plurality of ferrite sheet pieces 1, 1 ... As shown in FIG. Some of these ferrite green green sheet pieces include the respective ferrite sheet pieces 1, 1, ...
..To form a conductor pattern for the internal coil corresponding to, through holes are drilled at predetermined positions, 10 parts by weight of Ag powder as a conductive material, and phenol resin (SP value 11.5) as a binder 1 Parts by weight, n-
A conductor material paste consisting of 4 parts by weight of propanol (SP value 12.1) and 0.1 part by weight of oleic acid as a dispersant is applied in a predetermined pattern by a screen printing method, heated and dried to apply a conductor pattern having a thickness of 18 μm. Layers 21-2
9 is formed. Of these, the conductor pattern coating layer 21,
Numeral 29 is a conductor pattern coating layer for leading / extracting electrodes up to the opposite ends of the respective ferrite sheet pieces.

9 pieces of ferrite green sheet pieces obtained by cutting the ferrite sheet pieces 1, 1 ... Forming the conductor pattern coating layers 21 to 29 are stacked so that these conductor pattern coating layers form a coil. , 8 pieces of ferrite green sheet pieces having no conductor pattern coating layer on each of the upper surface and the lower surface of this stack
Stack the sheets. Then, the obtained unsintered laminate is 0.5
Pressure-bonding is performed at a pressure of t / cm ² (0.5 ton per square centimeter) to obtain a pressure-bonded unfired laminate. This pressure-bonded unfired laminated body is cut into a predetermined size and shape to obtain individual laminated chip inductor unfired bodies in which the ferrite sheet pieces shown in FIG. 2 are laminated. (10) After heating the obtained multilayer chip injector unfired body 4 at 500 ° C. for 1 hour to remove the binder,
Bake at 880 ° C. for 1 hour.

(11) An Ag electrode material paste is applied to the end surface of the fired body where the extraction electrode is exposed, by an immersion method, dried at 150 ° C. for 15 minutes, and then at 600 ° C. for 10 minutes.
The coating film is baked for a minute, and the conductor pattern tof layer 2 in FIG.
Ferrite sheet pieces 1, 1 ...
A multilayer chip inductor installed in the fired body is obtained. Figure 1
A sectional view of the laminated chip inductor is shown in FIG. In the figure, 24a, 25a, 26a and 27a are coil conductors 1a, 1a. ． ． Are magnetic layers which are fired bodies of ferrite sheet pieces, and 2 and 2 are external electrodes having upper and lower internal conductor patterns as extraction electrodes. Here, the coil conductor is hardly adhered to the magnetic layer, and a void is formed.

(2) Evaluation test The following inspection / test was performed on the obtained multilayer chip inductor.
Appearance inspection and measurement of electrical characteristics were performed by the test method, and the results are shown in Table 3.

Test method Measurement of distributed capacity YHP4195A (manufactured by Yokogawa Hewlett-Packard Company)
Is used to measure Cp (parallel mode capacitance) in impedance mode. At this time, the frequency has a peak of capacitance on the higher frequency side than the resonance point.

Measurement of tan δ (= 1 / Q) YHP4194A (manufactured by Yokogawa Hewlett-Packard Company)
To use the Ls-Q mode in the impedance mode. The obtained result is shown by the dotted line in FIG. The frequencies of Q listed in Table 1 are shown in FIG.

The measurement is performed in the same manner as the measurement of the inductance value L.

Comparative Example In Example 1, in the above step, that is, the step of applying the conductor material paste, ethyl cellulose resin (SP value 9.4), n-
A multilayer chip inductor was prepared in the same manner except that the same conductive material paste was used except that butyl carbitol acetate (BCA) was used instead of propanol.
The results of the same evaluation test as in Example 1 are shown in Table 3 and FIG. 3 by solid lines.

[0026]

[Table 3]

From the results of FIG. 3, the Q f characteristic curve of the multilayer chip inductor of Example 1 shifts to a higher frequency side than the Q f characteristic curve of the multilayer chip inductor of the comparative example. Further, it can be seen that the resonance frequency fo (Ls) also shifts to the high frequency side due to the decrease in the capacitance Cp.

[0028]

According to the present invention, since an incompatible resin is used as the resin used for the binder of the conductor pattern coating film and the binder of the magnetic material green sheet, the conductor pattern of the obtained fired body has the magnetic properties sandwiching the conductive pattern. Material It is easy to separate from the green sheet fired body, and since it is connected through a gap, it is possible to reduce the distributed capacitance when it is used as a laminated chip inductor, and the loss of the laminated chip inductor even when used at high frequencies, that is, It is possible to reduce tan δ. Further, since the connection state of the conductor pattern and the fired magnetic material green sheet sandwiching the conductor pattern is not changed by the repeated operation of the laminated chip inductor, the electrical characteristics can be stably maintained.

[Brief description of drawings]

FIG. 1 is a sectional view of a multilayer chip inductor according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a first manufacturing process of the above embodiment.

FIG. 3 is a measurement graph of Q (1 / tan δ) of the above-mentioned example and comparative example.

FIG. 4 is a perspective view showing one manufacturing process of a conventional multilayer chip inductor.

[Explanation of reference numerals] 1, 1, ... Magnetic material green sheets 21 to 29 Conductor pattern coating layer

Claims (2)

[Claims] 1. A step of obtaining an unfired laminate in which a coil having a conductor pattern is formed by laminating a plurality of magnetic material green sheets including a plurality of magnetic material green sheets having conductor patterns printed thereon, and the laminate. In the method for manufacturing a laminated chip inductor, which comprises a step of crimping and a step of firing the crimped laminate to obtain a fired body,
A method of manufacturing a laminated chip inductor, wherein a polymer of an incompatible resin is used as a binder for each of the magnetic material green sheet and the conductor pattern. 2. The method for manufacturing a multilayer chip inductor according to claim 1, wherein the polymers of the incompatible resin have a difference in solubility parameter value of 2 or more.