JP2004071852A - Multilayer substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer substrate without deformation even after monolithic sintering. <P>SOLUTION: The multilayer substrate is adapted such that a plurality of ceramic green sheets each having a conductor pattern printed and formed thereon are laminated into a plate-shaped molding, and the conductor pattern and the ceramic green sheets are sintered in a monolithic manner. In the multilayer substrate, there are provided a plurality of first parting grooves in a principal surface of the multilayer substrate in parallel to each other, a plurality of second parting grooves perpendicular to the first parting grooves, internal circuit components on a plurality of individual laminates parted along the first and second parting grooves by making use of a conductor pattern, and a deformation suppressing conductor layer comprising the conductor pattern around an individual laminate formation region on the multilayer substrate. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laminated substrate formed by integrally sintering a dielectric or magnetic ceramic green sheet and a conductor pattern constituting a circuit element such as an inductor or a capacitor, and relates to suppression of warpage and deformation during sintering.
[0002]
[Prior art]
In recent years, there has been an increasing demand for miniaturization, thinning, and high functionality of various electronic devices and electronic devices. Accordingly, single-function surface mount components such as chip capacitors and chip inductors, needless to say. However, there is a similar demand for a composite laminated component in which a large number of the capacitors and inductors are composited and integrated.
A laminated substrate used for producing an individual laminated body (ceramic substrate piece) in the composite laminated component is obtained by the following production method. For example, an organic binder, a plasticizer, and an organic solvent are mixed with a ceramic dielectric material powder that can be fired at a low temperature by a ball mill, and after adjusting the viscosity, a ceramic green sheet is formed by a known sheet forming method such as a doctor blade or a pipe doctor. Next, on each green sheet, a conductor pattern forming an inductor, a capacitor, and a connection line connecting these is printed with a conductive paste such as Cu or Ag. Also, via holes for connecting conductive patterns between layers are formed in the green sheet. The obtained green sheets with a conductor pattern are appropriately laminated, and thermocompression-bonded at a temperature of 80 ° C. and a pressure of 12 MPa to form a plate-like molded body, and the main surface of the plate-like molded body is cut in two directions with a steel blade. It is manufactured by forming grooves, stacking them in a firing furnace, and sintering them at, for example, 900 ° C. to 1000 ° C. for 2 to 8 hours.
[0003]
[Problems to be solved by the invention]
By the way, since the ceramic layer and the conductor pattern of the laminated substrate have different shrinkage characteristics, the laminated substrate may be deformed during sintering. As described above, the conductor pattern is made of Ag, Cu, or the like, and the ceramic layer has, for example, Al ₂ O ₃ as a main component and at least one of SiO ₂ , SrO, CaO, PbO, Na ₂ O, and K ₂ O. A low-temperature sinterable dielectric material having multiple components. In another example, low-temperature sinterable dielectric material containing Al ₂ O ₃ as a main component and at least one of MgO, SiO ₂ and GdO as a multiple component. A dielectric material, and in another example, low temperature sinterable comprising at least one of Bi ₂ O ₃ , Y ₂ O ₃ , CaCO ₃ , Fe ₂ O ₃ , In ₂ O ₃ and V ₂ O ₅ It is a magnetic ceramic material, which is sintered at a low temperature by devising a ceramic component.
For this reason, the sintering shrinkage rates of each other are very large, and the shrinkage characteristics of each other are different. Generally, the conductor pattern starts to shrink quickly, but when the ceramic layer shrinks, the shrinkage of the conductor pattern portion has already ended. It is considered that the uniform shrinkage of the ceramic layer is hindered, thereby causing deformation of the laminated substrate.
In particular, when the arrangement of the conductor patterns in the laminated substrate is asymmetric in the laminating direction, the amount of deformation increases. This will be described below with reference to the cross-sectional views of the laminated substrate shown in FIGS. FIG. 5A shows a case where the conductor pattern 7 is formed symmetrically in the stacking direction. In this case, the amount of deformation can be reduced, but as shown in FIG. Are formed asymmetrically in the stacking direction, a difference occurs between the shrinkage on the side where the conductor pattern 7 is concentrated and the shrinkage on the side where the conductor pattern 7 is not concentrated, resulting in deformation.
The conductor pattern formed on the laminated board becomes complicated with the increase of the built-in circuit elements, and the stray capacitance and the electromagnetic coupling interference between the conductor patterns are eliminated as much as possible while maintaining the electrical characteristics. It is substantially difficult to arrange the laminated substrates symmetrically in the laminating direction to suppress the deformation.
[0004]
Also, when cutting grooves are cut in the form of a plate-shaped molded body and sintered, when cutting grooves are cut on only one main surface, the cutting grooves are cut on both main surfaces of the laminated substrate. The main surface on the side where the cutting groove is not provided has a tendency to shrink more than the main surface on the side where the cutting groove is carved, and there is a problem that the laminated substrate is deformed, or the case where the cutting groove is carved on both main surfaces. However, when the depths are different, there is a problem that the main surface having the shallow cut groove tends to shrink more than the other, and the laminated substrate is deformed.
[0005]
Therefore, the present invention provides a method for integrally forming a conductive pattern formed in a plate-shaped molded body even when the conductive grooves are asymmetrical in the laminating direction, and when the cut grooves are not equally formed on both main surfaces of the plate-shaped molded body. An object of the present invention is to provide a laminated substrate that does not deform after sintering.
[0006]
[Means for Solving the Problems]
The present invention provides a plate-shaped molded body by laminating a plurality of ceramic green sheets on which a conductor pattern is printed and formed, and in a laminated substrate obtained by integrally sintering the conductor pattern and the ceramic green sheet, the main surface of the laminated substrate Has a plurality of first division grooves parallel to each other and a plurality of second division grooves orthogonal to the first division grooves, and a plurality of divisions formed along the first and second division grooves. An internal circuit element is formed in the individual laminate by the conductor pattern, and a deformation suppressing conductor layer formed of the conductor pattern is formed around an individual laminate formation region of the multilayer substrate.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
When the green sheet and the conductor pattern formed on the surface of the green sheet are integrally fired, first, the conductor constituting the conductor pattern such as Ag or Cu starts shrinking from the time when the glass transition point is reached. Subsequently, the ceramic of the green sheet starts shrinking when the glass transition point is reached.
As described above, the contraction generally precedes the conductor pattern. When the conductor suppresses the crystallization peak point, the contraction is almost completed. On the other hand, the ceramic has a crystallization peak point higher than that of the conductor, and thus contracts continuously.
The ceramic material used for the laminated substrate generally contains a component that easily becomes glass during sintering or a component that easily forms a liquid phase so that sintering can be performed at a relatively low temperature. In the later stage of high density, the ceramic material itself becomes soft, and deformation occurs due to uneven distribution of stress in the laminated substrate during sintering due to the difference in shrinkage characteristics between the ceramic and the conductor pattern.
Therefore, the present inventors have proposed to suppress deformation by forming a deformation suppressing conductor layer using the same conductor material as the conductor pattern around the individual laminated body forming region of the laminated substrate during the production of the laminated substrate. Was found.
FIG. 1 is an exploded perspective view of a laminated substrate according to one embodiment of the present invention.
The deformation suppressing conductor layer 4 is formed in the vicinity of the outer edge of the laminated substrate so as to surround the entire individual laminated body as a product, and the pattern in plan view, the number of layers, the formation position, and the like are the conductor patterns of the individual laminated body part 2. (Not shown) and the non-uniformity of the stress in the laminated substrate 1 due to the asymmetry of the ceramic layer. Since the deformation suppressing conductor layer 4 uses the same conductor as the conductor pattern forming the circuit element, both naturally exhibit the same shrinkage characteristics, and the deformation suppressing conductor layer 4 inhibits the contraction of the conductor pattern forming the circuit element. Nothing. Then, the conductor pattern that has been contracted earlier maintains a state where little deformation occurs even in a stage where densification progresses in the latter half of the sintering process, and as a result, it is possible to obtain a laminated substrate 1 with extremely small deformation. .
The area where the deformation suppressing conductor layer is formed is different from the individual laminated body part 2 and is generally a part which is not provided as a product but is discarded. There has never been a thought to form.
[0008]
Further, the unevenness of the stress caused by the cut grooves 3 cut in the laminated substrate can be eliminated by the deformation suppressing conductor layer 4, and a laminated substrate with extremely small deformation can be obtained.
[0009]
【Example】
An embodiment of the method for manufacturing a laminated substrate according to the present invention will be described.
First, a ceramic green sheet preparation step will be described. By doctor blade method, ceramic slurry consisting of dielectric ceramic powder, binder and plasticizer is applied on carrier film consisting of polyethylene terephthalate film with uniform thickness to form green sheet of several tens μm to several hundred μm. I do. Then, the dried green sheet is cut into a predetermined size with the carrier sheet attached.
Next, the conductor pattern forming step will be described. By a screen printing method or the like, a conductor pattern constituting a circuit element is formed by printing on a predetermined portion which is a product portion on the main surface of the green sheet opposite to the carrier sheet. The printing paste has an Ag metal powder acting as a circuit and an adhesive for fixing the metal powder to a printing surface.
As shown in FIG. 2, some of the green sheets surround the plurality of individual laminate portions 2 in the vicinity of the outer edge of the green sheet 5, and the deformation suppressing conductor layer 4 has a conductor pattern formed in a frame shape in plan view. Is formed. A grease sheet 5 for printing and forming a conductor pattern constituting a circuit element (not shown) together with the deformation suppressing conductor layer 4 and a grease sheet 5 on which only the deformation suppressing conductor layer 4 is formed are prepared.
3A to 3F show other examples of the deformation suppressing conductor layer. Here, the plan view pattern of the deformation suppressing conductor layer is shown in an enlarged manner. As illustrated, a non-continuous pattern may be formed, and the formation position in the stacking direction may be formed over the entire stacking direction, or may be formed only near the upper and lower surfaces of the stacked substrate. Due to the formation conditions such as the depth of the conductor pattern and the cut groove to be formed, the shrinkage characteristics and the physical properties of the ceramic layer, etc., unless limited to the technical idea of the present invention, the materials are not limited to those illustrated in FIGS. It can be configured freely without any.
[0010]
Next, the green sheets are laminated and pressed in a predetermined order to obtain a flat molded body having a thickness of approximately 0.8 mm. Via holes are formed in the green sheet, and conductor patterns between ceramic layers are appropriately connected to each other so as to function as circuit elements.
Then, the plurality of first division grooves parallel to each other and the plurality of second division grooves orthogonal to the first division groove on the main surface of the flat molded body are each formed to have a depth of approximately 0.1 mm. Carved with a steel blade. Thereafter, the flat molded body was degreased and sintered to obtain a laminated substrate of 80 mm × 75 mm × 0.8 mm.
The depth of the division groove is appropriately set in the range of 50 μm to 300 μm from the viewpoint of ease of division and ease of handling.
[0011]
In addition, a laminated substrate having undergone the same process as in the above-described embodiment except that it did not have the deformation suppressing conductor layer was used as a sample of the comparative example.
[0012]
Ten laminated substrates selected as described above are prepared, placed on a work table of a three-dimensional measuring device, and a displacement amount in a laminating direction (Z-axis direction of the three-dimensional measuring device) is measured by a laser displacement meter. For example, by repeating at a pitch of 2 mm, the displacement of the entire main surface of the laminated substrate is obtained, the inclination when the laminated substrate is arranged on the work table is corrected by computer processing, and the maximum measured value and the minimum measured value obtained are corrected. The difference was defined as the amount of deformation and evaluated. As a result, while the average value of the deformation amount in the comparative example was 361 μm, the deformation amount in the example was 40 μm, and the deformation amount was significantly suppressed.
[0013]
In addition, when the deformation suppressing conductor layer is formed over a plurality of layers at a portion overlapping the cutting groove in the laminating direction, when dividing into individual laminations, it may hinder the progress of cracks. In such a case, for example, as shown in FIG. 2A, the deformation suppressing conductor layer is made discontinuous, and the conductor layer is not formed at a portion overlapping the cut groove of the deformation suppressing conductor layer in the laminating direction. You can do it.
Further, when the deformation suppressing conductor layer is formed over a plurality of layers, the crimpability may be deteriorated due to a difference in deformability of the conductor pattern and the green sheet with respect to pressure, but the conductor pattern of the deformation suppressing conductor layer may be appropriately changed. It may be formed so that the deformation suppressing conductor layers 4 formed on the adjacent ceramic layers 5 do not overlap in the laminating direction as much as possible, as shown in the cross-sectional view of the laminated substrate shown in FIG.
[0014]
【The invention's effect】
According to the present invention, in a laminated substrate having a conductor pattern constituting a plurality of circuit elements therein, even if the conductor pattern structure is asymmetric in the lamination direction or a structure that is easily deformed by a cut groove, It can suppress deformation of the substrate and improve the quality of the laminated substrate.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a laminated substrate according to one embodiment of the present invention.
FIG. 2 is a plan view of a ceramic green sheet on which a deformation suppressing conductor layer used in one embodiment of the present invention is formed.
3 (a) to 3 (f) are enlarged views of formation patterns of a deformation suppressing conductor layer according to another embodiment of the present invention.
FIG. 4 is a cross-sectional view of a deformation suppressing conductor layer portion of the laminated substrate according to one embodiment of the present invention.
FIGS. 5A and 5B are cross-sectional views of a conventional laminated substrate.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 laminated substrate 2 individual laminated body 3 divided groove 4 deformation suppressing conductor layer 5 ceramic green sheet 6 ceramic layer 7 conductor pattern

Claims (1)

A conductor pattern is formed by laminating a plurality of ceramic green sheets printed and formed into a plate-shaped molded body, and the conductor pattern and the ceramic green sheet are integrally sintered in a laminated substrate.
The main surface of the laminated substrate has a plurality of first division grooves parallel to each other and a plurality of second division grooves orthogonal to the first division grooves,
An internal circuit element is formed by the conductor pattern on the plurality of individual laminates divided along the first and second division grooves,
A laminate substrate, wherein a deformation suppressing conductor layer made of the conductor pattern is formed around an individual laminate body forming region of the laminate substrate.

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