JP3443436B2 - Multilayer circuit board with built-in capacitance - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention corrects a temperature characteristic of a capacitance formed inside a capacitor, obtains a capacitance with low temperature dependency, and has a strong built-in capacitance. The present invention relates to a mold layer circuit board. 2. Description of the Related Art Conventionally, an insulating layer composed of an inorganic filler such as alumina and a glass component has been used at a low temperature (about 90 ° C.).
Multilayer circuit boards that can be fired (around 0 ° C.) have already been used. The low-temperature sinterable multilayer circuit board can use a low-resistance material such as gold, silver, or copper for the internal wiring pattern, and can realize an electronic circuit or a high-frequency circuit with a high signal propagation speed. Further, a capacitance generating pattern (insulation (dielectric)) is formed on such a multilayer circuit board together with an internal wiring pattern.
A multilayer circuit board with a built-in capacitor in which a pair of wiring patterns facing each other with a layer interposed therebetween is formed and a capacitor is built in is proposed. In this case, for example, an oscillator having a resonance circuit or the like in a multilayer circuit board with a built-in capacitor cannot be used without taking into account the dielectric constant temperature characteristics of the substrate composition material. This is because the glass component which is a material constituting the dielectric layer is, for example, borosilicate glass or aluminosilicate glass, and the inorganic filler is alumina, but these materials have a positive dielectric constant temperature characteristic, This is because the substrate body has a positive dielectric constant-temperature characteristic, and the capacitance value greatly fluctuates due to a temperature change. In order to correct the absolute value of the dielectric constant-temperature characteristic of such a substrate material to a small value, the use of titania together with alumina as an inorganic filler has already been proposed in JP-A-4-82297. However, titania has a dielectric constant temperature coefficient of -910 ppm / ° C., which is insufficient for correcting the dielectric constant temperature characteristics of the entire substrate material. This is because titania easily reacts with substrate materials such as alumina and glass components, wiring patterns, etc., especially with thick film resistors on the surface, etc., which lowers the strength of the substrate or changes the characteristics of especially thick film resistor films. This is because there is a possibility of causing the addition, and the addition amount is limited. As an inorganic filler added together with alumina for correcting the dielectric constant-temperature characteristics of a substrate material other than titania, a substance having a perovskite crystal structure and having a Curie point as high as room temperature, such as strontium stannate (dielectric) Rate-3720 ppm / ° C), strontium titanate (-3360 ppm / ° C), calcium titanate (-1620 ppm / ° C) and the like. [0007] However, when the above-mentioned substance having a perovskite crystal structure is used as an inorganic filler added together with alumina, the substance dissolves with a glass component during firing, and the crystal structure is broken. Conversely, there has been a problem that the above-described effect of correcting the dielectric constant-temperature characteristic is reduced. As a result of various experiments, the present inventors have found that the particle size of the inorganic filler of the substance having a perovskite crystal structure is controlled, for example, by increasing the particle size to reduce the contact area with the glass component. It has been found that the area in which a solid solution reaction occurs can be reduced. That is, it is possible to reduce the solid solution reaction and maintain a sufficient effect of correcting the dielectric constant-temperature characteristic. On the other hand, if the particle size is too large, the density of the fired substrate is inferior, and the strength and the moisture resistance reliability decrease. The present invention has been made based on the above findings, and an object of the present invention is to sufficiently correct the dielectric constant-temperature characteristics of a substrate by optimizing the particle size of an inorganic filler of a substance having a perovskite crystal structure. An object of the present invention is to provide a multi-layer circuit board with a built-in capacitor that can be manufactured and has high substrate strength. Means for Solving the Problems A plurality of dielectric layers composed of a glass component and an inorganic filler that can be fired at a relatively low temperature of 1000 ° C. or less are laminated, and a gold-based, silver-based, or copper-based conductor is provided inside. What is claimed is: 1. A multi-layer circuit board with a built-in capacitor comprising an internal wiring pattern made of a material and a capacitor generating pattern, wherein said inorganic filler comprises alumina powder, a perovskite crystal structure and a negative temperature characteristic of dielectric constant. And a strontium titanate powder of 3.9 to 10 μm. As described above, according to the present invention, since the material of the insulating (dielectric) layer is composed of a glass component and an inorganic filler, it can be used at a relatively low temperature (up to 1000 ° C.). Since sintering is possible, a metal material such as gold, silver, or copper having a small specific resistance can be used for the internal wiring pattern and the capacitance generation pattern. Further, as an inorganic filler used to correct the dielectric constant-temperature characteristic used together with the alumina filler, for example, a dielectric material having a perovskite crystal structure and a negative dielectric constant (hereinafter simply referred to as a negative temperature characteristic material) , The absolute value of the temperature characteristic of the entire dielectric constant of the dielectric layer can be corrected to a very small value, for example, ± 60 ppm / ° C., and a stable capacitance characteristic can be obtained even when a capacitance generation pattern is incorporated. Type multilayer circuit board. In the present invention, in particular, the particle diameter of the inorganic filler of the negative temperature characteristic material is set to 2 to 10 μm. That is, by setting the particle size to 2 μm or more, even when sintering at a low temperature (for example, 900 ° C.) together with alumina and a glass component, a solid solution reaction with the glass component can be suppressed during the sintering reaction, and the perovskite structure becomes Since it can be sufficiently maintained, the above-described correction action can be sufficiently maintained, and the dielectric constant temperature characteristic can be kept within ± 60 ppm as described above. Further, since the particle size is 10 μm or less, the entire substrate after firing can be densified, and the strength of the substrate can be maintained at a predetermined value or more. Here, the particle size is 10 μm.
If it exceeds m, the strength of the substrate will be remarkably deteriorated, and in the manufacturing process, when a slurry is formed with a solvent or the like together with the glass frit and the alumina filler, a settling phenomenon will occur and uniform dispersion cannot be achieved. Particularly, when strontium titanate is used as the negative temperature characteristic material, high substrate strength can be achieved. Furthermore, as compared with a substrate using titania, no titania component is deposited on the substrate surface, and even if a thick-film resistor film is formed on the surface, there is no significant change in its resistance characteristics. . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a multilayer circuit board with a built-in capacitor according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows a cross-sectional structure of a multilayer circuit board with a built-in capacitor according to the present invention. In the figure, 10 is a multilayer circuit board with a built-in capacitor, 1 is a plurality of dielectric layers 1a,
1b... Are laminated, and 2 is a dielectric layer 1
a, 1b... are predetermined internal wiring patterns formed between the dielectric layers 1a, 1b..., 4 are via-hole conductors,
Denotes a surface wiring pattern, and 6 denotes a thick resistor film. The substrate body 1 includes a plurality of dielectric layers 1a, 1b,.
a, 1b..., a predetermined internal wiring pattern 2 and a capacitance generating pattern 3 made of a gold-based, silver-based, or copper-based conductor and a via-hole conductor penetrating through the dielectric layers 1a, 1b. And 4. As a result, a part of a circuit having a predetermined capacitance is formed in the substrate body 1 by the capacitance generating patterns 3 opposed to each other across the dielectric layers, for example, 1c and 1d. On the main surface of the substrate main body 1, a predetermined surface wiring pattern 5 and a thick-film resistor film 6 made of a gold-based, silver-based, or copper-based conductor are formed. Is electrically connected to the internal wiring pattern 2 and the capacitance generating pattern 3, so that a predetermined circuit is achieved as a whole. Although not shown in the figure, a protective film is formed on the surface, and an IC chip, a chip electronic component, and the like are mounted as needed. Here, the capacitance formed inside the substrate main body 1 is generated, for example, between the capacitance generating patterns 3 having a predetermined facing area arranged so as to sandwich the dielectric layer 1c in the figure. Further, a predetermined capacitance is also generated between the capacitance generating patterns 3 arranged so as to sandwich the dielectric layer 1d. The dielectric layers 1a, 1b,... Are formed by sintering a glass component and an inorganic filler. The glass component is crystallized glass, amorphous glass, etc., the inorganic filler includes at least a powder of a negative temperature characteristic material,
Other examples include alumina powder. In addition, as inorganic filler negative temperature special materials, strontium titanate (−3360 ppm / ° C.), strontium stannate (−3720 ppm / ° C.), and calcium titanate (−1
620 ppm / ° C.). Examples of the glass component include low melting point glass such as borosilicate glass and aluminosilicate glass. The glass component constitutes 40 to 90% by weight.
The composition ratio of the inorganic filler composed of the alumina powder and the powder of the negative temperature characteristic material is 10 to 60% by weight.
When the amount of the inorganic filler is less than 10% by weight, materials that are effective for the strength of the substrate, such as alumina powder, are relatively reduced, so that the strength of the sintered substrate body 1 is reduced.
On the other hand, if it exceeds 60% by weight, a glass component is relatively insufficient in the sintered substrate body 1, so that a dense circuit board cannot be achieved. Preferably, the composition ratio of the glass component is 30.
To 50% by weight, with the balance being glass components. As described above, the particle diameter of the negative temperature characteristic material is 2 to 1
It is important to set it to 0 μm. Particle size 2-10μ
By setting m, even when the substrate material is made into a slurry state, a homogeneously mixed slurry can be obtained without causing a sedimentation phenomenon. Further, even when sintered at a temperature up to about 1050 ° C., a very stable perovskite crystal structure can be maintained, and a sufficient effect of correcting the dielectric constant temperature characteristic of the substrate 1 appears, and the temperature characteristic is kept within ± 60 ppm. be able to. As a result, even when the capacitance generating pattern 3 is formed, a stable capacitance component whose capacitance does not greatly depend on temperature can be easily formed. Furthermore, the relative permittivity can be set to 8.0 or more, and a sufficient capacitance value can be achieved even when the facing area of the capacitance generating pattern 3 is reduced. In particular, if strontium titanate is used as the above-mentioned dielectric material, the bending strength of the substrate is superior to other dielectric materials. Further, the characteristics of the conductor material forming the internal wiring pattern 2 and the capacitance generating pattern 3 formed between the dielectric layers 1a, 1b,... Are not affected. Further, when used together with the alumina powder of the inorganic filler, the strength of the substrate body 1 becomes a practical value. Incidentally, ruthenium oxide,
Even if the thick-film resistor film 6 made of lanthanum hexaboride, tin oxide, or the like is formed, no semiconductor conductivity is given to the thick-film resistor film 6 and the temperature characteristics are not shifted to the negative side at all. Among the above-mentioned negative temperature-sensitive materials, strontium titanate is preferable because, as described above, the strength of the substrate main body 1 is sufficiently obtained, the effect of compensating for the temperature characteristics appears remarkably, and the firing conditions are reduced. This is because it is relatively relaxed. For example, calcium titanate has a smaller ionic radius than strontium titanate.
The reaction with the glass component becomes remarkable, the crystal structure is easily broken, and the particle size is reduced to 10 μm in order to sufficiently obtain the effect of correcting the dielectric constant.
The value must be close to m. Further, strontium stannate is difficult to maintain a perovskite structure after sintering, and it is necessary to pay sufficient attention to the sintering conditions. The dielectric layers 1a, 1b,..., Besides the glass component, the alumina powder, and the powder of the negative temperature characteristic material,
An oxidizing agent or the like may be added as needed. Next, a description will be given of a method of manufacturing the multilayer circuit board with a built-in capacitor according to the present invention. First, the composition for the substrate (the dielectric layers 1a and 1b)
・ ・ ・) Or a crystallized or amorphous low melting point glass frit, alumina powder, a negative temperature characteristic material such as strontium titanate powder, an organic binder (for example, polymethacrylate resin), and a plasticizer (for example, dibutyl) (Phthalate), a solvent (for example, methyl ethyl ketone), and another additive (for example, an antifoaming agent) are mixed at a predetermined ratio, and the mixture is kneaded using a ball mill for about 24 to 72 hours to prepare a homogeneous slurry. After defoaming the slurry, the slurry is subjected to 50 to 30 by a known method such as a doctor blade method.
A green sheet having a thickness of about 0 μm is formed. Next, a hole to be a via-hole conductor 4 is punched on the surface of the obtained green sheet, and the filling of the via-hole conductor 4, the internal wiring pattern 2, and the capacitance generating pattern 3 are printed. The filling of the via-hole conductor 4 may be performed after the internal wiring pattern 2 and the capacitance generating pattern 3 are printed. Internal wiring pattern 2, capacitance generating pattern 3
As the conductive paste for use, a conductive paste mainly containing at least one metal selected from gold, silver, copper and alloys thereof is used. The green sheets on which the internal wiring patterns 2, the capacitance generating patterns 3, and the via hole conductors 4 are formed are sequentially laminated in consideration of the layer configuration of each of the dielectric layers 1a, 1b,. A laminate to be the substrate body 1 is formed. The laminate thus obtained is fired. First, in a first step, organic substances contained in the laminate are removed at a temperature lower than the softening point of the glass component, for example, at around 500 ° C. In the next stage, dielectric layers 1a, 1b,... Made of a glass component, alumina powder, strontium titanate,
Then, the internal wiring pattern 2, the capacitance generating pattern 3, and the via-hole conductor 4 are integrally sintered. This firing temperature depends on the glass components of the dielectric layers 1a, 1b,.
Is determined by the melting point of the conductive material such as
It is performed at a temperature of 1050 ° C. The firing atmosphere is determined by the conductor material of the internal wiring pattern 2. Thereby, a sintered substrate body 1 is achieved. A surface wiring pattern 5 and a thick resistor film 6 are formed on the obtained substrate main body 1. The thickness of the thick resistor film 6 is determined by the baking atmosphere of the surface wiring pattern 5 and the like. When baking is performed in a non-oxidizing atmosphere, the resistance is mainly composed of lanthanum hexaboride, tin oxide, or the like. It is formed using body paste.
When firing in an oxidizing atmosphere, the resistor paste is formed using a resistor paste containing ruthenium oxide as a main component. The surface wiring pattern 5 can be made of a silver-based conductor (silver or silver alloy) or a copper-based (copper or copper alloy), but is preferably a copper-based material in consideration of migration resistance and the like. . (Experimental example) As a glass frit, 51 mol% of silicon oxide, 19 mol% of aluminum oxide, 19 mol% of magnesium oxide, 8 mol% of zinc oxide, and 3 mol% of boron oxide (boric acid corresponding thereto) were mixed. After melting at about 1600 ° C., it was dropped into water and rapidly cooled to obtain a glass. The obtained glass was put in an alumina pot together with alumina balls, wet-pulverized and dried. Thereby, a crystallized glass frit having an average particle size of 2 to 3 μm was obtained. Next, crystallized glass frit, alumina powder having a particle size of 2 μm, and / or a particle size of 3.9 were prepared in the proportions shown in Table 1.
μm or strontium titanate powder having a particle size of 1.6 μm was mixed. The mixture was placed in an alumina pot together with alumina balls, mixed with a ball mill, and dried to obtain a composition for a multilayer circuit board with a built-in capacity. A slurry was prepared by adding 100 g of an acrylic resin, 70 g of a plasticizer and 400 g of toluene to 1000 g of the obtained composition for a substrate, and the slurry was subjected to a vacuum defoaming treatment. Next, a green sheet having a thickness of 200 μm was prepared from the slurry by a doctor blade method. Then, ten green sheets were laminated and hot-pressed, and the obtained laminate was fired at 870 ° C. for one hour to form a multilayer substrate body. A conductor film of indium-gallium was formed on both surfaces of the obtained substrate main body, and in accordance with JIS2141.
The dielectric constant was measured at 1 MHz with a Q meter. The evaluation in Table 1 shows that the dielectric constant-temperature characteristics are within ± 60 ppm in a practical temperature range of −30 to 80 ° C., and the flexural strength of the substrate is 15 kgf / cm ^2, which is a practical strength. The above was regarded as non-defective. [Table 1] In Experimental Examples 1 and 2 (adding strontium titanate having a particle size of 3.9 μm), the relative dielectric constant exceeded 8.0, and the dielectric constant-temperature characteristics were higher in forming a capacitor inside the substrate body 1. , A practical range of ± 60 ppm /
° C or less, and the transverse rupture strength can be secured to a strength suitable for practical use. In Comparative Example 1 (without addition of strontium titanate), the relative dielectric constant was as low as 6.5, and the dielectric constant-temperature characteristic was as large as 130 ppm / ° C. on the plus side. In Comparative Example 2 (adding strontium titanate having a particle size of 1.6 μm), the relative dielectric constant was 7.0, which was slightly improved as compared with Comparative Example 1. Of 78 to 90 ppm / ° C. is still large on the positive side. Here, the composition is the same as that of Example 1, but since the particle size of strontium titanate is less than 2.0 μm, a part of the perovskite crystal structure is collapsed during sintering. The effect of compensating for the temperature characteristic does not appear sufficiently. In Comparative Example 3 (without addition of alumina), the relative dielectric constant was 8.2, but the dielectric constant-temperature characteristic was 25.
67 ppm / ° C. and slightly larger at to 80 ° C., further becomes the bending strength falls below the practical strength 15 kgf / cm ^2. Also in this case, the particle size of strontium titanate is 2
Since the perovskite crystal structure is partially collapsed because the particle diameter is smaller than μm, the temperature characteristic is ± 60 ppm / ° C. without adding alumina powder having a positive temperature characteristic.
Can not be within. As can be seen from the above experimental results, as shown in Examples 1 and 2, a dielectric material having a perovskite crystal structure having a particle diameter of 2 μm or more and having a negative temperature characteristic was used.
By using as an inorganic filler together with the alumina powder, the temperature characteristics of the dielectric constant of the dielectric layers 1a, 1b.
Since the capacitance is 60 ppm / ° C., even when the capacitance generating pattern 3 is formed inside the substrate body to obtain a predetermined capacitance,
The capacitance can maintain a stable capacitance against a change in ambient temperature. Further, since the relative permittivity can be increased more than before, a sufficient value of capacitance can be obtained even if the area of the capacitance generating pattern 3 is reduced, for example.
Further, the microstrip line pattern 7 shown in FIG.
Is formed inside the substrate main body 1, a miniaturized line pattern 7 is achieved, and by controlling the compounding amount of the dielectric material according to the wavelength shortening rate, a further microstrip line can be minimized. Can be done. Further, the negative temperature characteristic material has no adverse effect on the internal wiring pattern 2, the capacitance generating pattern 3, the via hole conductor 4 and the surface wiring pattern 5, the thick resistive film 6, etc. of the substrate body 1. For example, the resistance-temperature characteristics of the thick-film resistor film 6 on the surface of the substrate body 1 do not change at all. In the above-described embodiment, the substrate body 1 in which the capacitance generating pattern 3 and the microstrip line pattern 7 are formed is exemplified. However, a coil pattern may be additionally provided inside the substrate body 1 or the substrate body. 1 and can be widely used in various circuit networks, such as forming an LC resonance circuit together with a capacitance component formed inside. As described above, according to the present invention, low-temperature baking is performed, and the internal wiring pattern and the capacitance generating pattern are
A multi-layer circuit board with a built-in capacitor comprising a metal material such as gold, silver, or copper having a small specific resistance, wherein a dielectric layer constituting the substrate body is composed of a glass component, an alumina component, and a particle size of 2 to 2.
It is configured to include a negative temperature characteristic material of 10 μm, and the temperature characteristics of the substrate main body can be within ± 60 ppm. Therefore, a capacitance generating pattern can be formed in the substrate main body to form a stable capacitance. . Further, since the above-mentioned negative temperature characteristic material can maintain a stable crystal structure even after sintering, the dielectric constant-temperature characteristic of the substrate can be corrected well, and the thickness of the thick resistor film on the substrate surface can be improved. It does not affect the resistance temperature characteristics. In particular, when strontium titanate is used as a dielectric material, it is effective for maintaining a perovskite crystal structure, and the particle size can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a cross-sectional structure of a multilayer circuit board with a built-in capacitor according to the present invention. [Description of Signs] 10 ... Capacitance built-in multilayer circuit board 1 ... Board bodies 1a, 1b ... Dielectric layer 2 ... Inner wiring pattern 3 ... ..Capacitance generating pattern 4 Via-hole conductor 5 Surface wiring pattern 6 Thick film 7 Microstrip line pattern

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Claims (1)

(57) [Claim 1] A plurality of dielectric layers composed of a glass component and an inorganic filler which can be fired at a relatively low temperature of 1000 ° C. or less, and a plurality of dielectric layers each including gold, silver, or copper therein. A multilayer circuit board with a built-in capacitor comprising an internal wiring pattern and a capacitance generating pattern made of a system conductor material, wherein the inorganic filler has an alumina powder , a perovskite crystal structure, and a negative temperature characteristic of a dielectric constant. particle size 3.9 ~10μ
m. strontium titanate powder .