KR20060122254A - Microwave sintering apparatus and method for manufacturing an embeded capacitor circuit board using the same - Google Patents

Abstract

A microwave sintering apparatus and a method for manufacturing a capacitor embedded circuit board using the same are provided to enhance a sintering density and a dielectric ratio by a self volume heat-emission of a ceramics by leading a hybrid rapid sintering. A method for manufacturing capacitor embedded circuit board includes the steps of: forming a first electrode by mounting a conductive metal at one side of an inner layer(S201); forming a thick film at the first electrode by using a thick film oxide material(S203); sintering the think film by a micro wave(S204); and forming a second electrode at the sintered thick film oxide(S205).

Description

Microwave sintering apparatus and method for manufacturing an embeded capacitor circuit board using the same}

1A is a cross-sectional view of a conventional sheet-type capacitor embedded circuit board;

1B is an enlarged cross-sectional view of the capacitor layer of FIG. 1A;

2 is a block diagram of a method for manufacturing a capacitor-embedded circuit board according to an exemplary embodiment of the present invention;

3A to 3E are schematic process diagrams of a method of manufacturing a circuit board of FIG. 2;

4a to 4c are views showing the microstructure of the sintered particles according to the microwave sintering temperature; And

5 is a schematic cross-sectional view of the microwave sintering apparatus used in the circuit board manufacturing method of FIG.

<Description of reference numerals for main parts of the drawings>

310: thick film oxide 500: microwave sintering apparatus

510: microwave generator 520: reaction chamber

522: substrate 523: side substrate

The present invention relates to a sintering apparatus and a method for manufacturing a circuit board using the same. More specifically, in order to increase the capacitance of a capacitor-embedded type on a circuit board, a thick film method, a spin coating, and a nano-nozzle which can produce a thin film compared to a conventional sheet type Microwave sintering device and capacitor using the same to form a thick film using various methods such as spraying method and apply microwave (2.45GHz) to induce hybrid rapid sintering that can be sintered in a short time to produce a capacitor having excellent electrical and mechanical properties. It relates to a method for manufacturing an embedded circuit board.

Capacitor is a device that stores energy in the form of electric charge. In case of DC power, electric charge is accumulated but no current flows. In the case of AC, electric charge is charged and discharged, and the electric current is proportional to the capacity of capacitor and the voltage change over time. It has the property of flowing.

The capacitor utilizes the characteristics described above for coupling and decoupling, filters, impedance matching, and signal matching in electrical and electronic circuits such as digital circuits, analog circuits, and high frequency circuits. ), An essential passive device used for various purposes such as charge pump and demodulation. Capacitors are also generally manufactured in various forms, such as chips and disks, and are mounted on the surface of circuit boards.

Capacitors in these electronic circuits are capacitors such as B (A) and F characteristics MLCC (Multilayer Ceramic Capacitor), which have low temperature stability but large capacity, and C characteristics, which have small capacity but stable capacity, according to their capacity and temperature stability. It can be classified into two types, such as a capacitor such as MLCC. The former is mainly used for the purpose of decoupling and bypass, and the latter is used for the purpose of signal matching and impedance matching.

Until now, such capacitors have been manufactured in various forms such as chips and disks, and have been used on the surface of circuit boards according to the purpose. However, according to the recent miniaturization and complexity of electronic devices, passive devices may be mounted on circuit boards. The smaller the area, the higher the frequency of electronic devices, the more parasitic impedances caused by various factors such as conductors and solders between passive devices and ICs. do. Therefore, in order to solve such a problem, various attempts to embed a capacitor inside a circuit board have been actively conducted by circuit board makers and electronic and electronic component makers.

However, current capacitor-embedded technology does not provide the various capacities required by the market, and in particular, the fluctuation of the capacity, that is, the tolerence, has not yet reached the component device. This is due to the fact that materials of various capacities and reliable prices are not supported, and development of various materials with long-term reliability is essential for active adoption of capacitor-embedded type in circuit boards.

A conventional commercially available material in the capacitor-embedded section consists of a glass-reinforced epoxy in a sheet state laminated between copper foil electrodes under Sanmina's trade name 'ZBC2000'. Therefore, it is possible to replace one layer of the multilayer circuit board with a capacitor material, and there is an advantage that the circuit forming process, which is an existing circuit board manufacturing process, can be used as it is, but has a disadvantage of low capacitance.

That is, the sheet type of the conventional capacitor-embedded material has a composite structure of dielectric constant filler and polymer of ceramic powder, so it is suitable to be applied to the circuit board method, but the dielectric capacitance value is large to replace the role of the chip capacitor. Lack. In general, with the same oxide material, the capacitance value increases as the thickness becomes thinner and the area becomes larger. At present, in the case of the capacitor-embedded sheet type 101 as shown in FIG. 1A, the thickness of the sheet 101 is more than several tens of micrometers, and as shown in FIG. (103) has a component structure of about 10 to 20%. However, the component structure has a limitation in filling the ceramic filler, which makes it difficult to reduce the thickness and increase the dielectric capacity. In order to increase the dielectric capacity, the related art is solved by sintering.

However, in the case of sintering by conventional sintering method, for example, bulk piezoceramic PbZrTiO3 (PZT) is volatile at high temperature, so a small amount of PbO powder is added to the sample and then sintered to compensate for the volatilization of PbO generated during sintering. At this time, pores due to volatilization of PbO are present in the microstructure of the sintered compact, and thus there is a problem in that electrical characteristics are deteriorated.

The present invention has been made to solve the above-mentioned problems of the prior art, in order to increase the capacitance of the capacitor embedded in the circuit board to form a thick film using a variety of methods, such as thick film method, spin coating and nano-nozzle spray method The present invention provides a method for manufacturing a capacitor-embedded circuit board in which the capacitance is increased by making the thickness of the capacitor thinner within several tens of nm to several μm.

In addition, another object of the present invention, by applying a microwave (2.45GHz) to induce a hybrid rapid sintering that can be sintered in a short time can improve the sintering density and dielectric constant by the self-volume heating of the ceramics and improve the sintering time Since it can be reduced as much as possible, not only can greatly reduce the process time and energy, but also it can be sintered evenly on the entire surface of the sintered part by using microwaves compared to the conventional heat sintering method, thereby providing a method for manufacturing a capacitor-embedded circuit board with increased yield. will be.

Further, another object of the present invention is to provide a microwave sintering apparatus in which manufacturing cost and production capacity are improved by simultaneously sintering a plurality of substrates using microwaves.

In order to achieve the above object of the present invention, the present invention comprises the steps of forming a lower electrode by mounting a conductive metal on one side of the inner layer, forming a thick film using a thick film oxide material on the copper plate, the thick film by microwave It provides a method for manufacturing a capacitor-embedded circuit board comprising the step of sintering, and forming an upper electrode on the sintered thick film oxide.

In another aspect, the present invention provides a microwave sintering apparatus comprising a micro-generator, a reaction chamber, a thermometer, a source gas and a vacuum pump for adjusting the pressure of the source gas.

Hereinafter, a method for manufacturing a capacitor-embedded circuit board and a microwave sintering apparatus according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a flow chart of a method for manufacturing a capacitor-embedded multilayer flip chip package substrate according to an embodiment of the present invention.

As shown in FIG. 2, the substrate manufacturing method includes forming a conductive metal layer in which a circuit pattern is formed first, and then sequentially forming an inner layer of one layer in the order of an insulator (S100), and stacking a conductive metal layer on the insulator. Forming a lower electrode (S201), applying a conductive paste while surface treating the lower electrode (S203), forming a thick film oxide on the lower electrode (S203), and using microwave on the thick film oxide Sintering (S204), stacking a conductive metal layer on the sintered thick film oxide (S205), and forming a circuit layer in a multi-layer after step (S205) (S300 and / or S400). It includes.

Next, a process for manufacturing the capacitor layer of FIG. 2 will be described in detail with reference to FIGS. 3A to 3G.

First, as shown in FIG. 3A, in forming the lower electrode, a circuit pattern is formed after the formation of the conductive metal laminate formed by mounting the conductive metal 302 on the insulating layer 301.

It is preferable to use an electrolytic copper foil as a conductive metal. In order to increase the adhesive force with the resin, the copper foil is chemically reacted with the resin during the formation of the copper foil, and is made to penetrate about 5 μm toward the resin. Although the thickness of copper foil is about 18 micrometers-70 micrometers normally, it is preferable that the thickness of copper foil is very thin to 1/2 or less of conventional ones, such as 5 micrometers, 7 micrometers, and 15 micrometers with refinement | miniaturization of a wiring pattern.

Resin is used as a base material of the copper clad laminate. Resins have excellent electrical properties, but have the disadvantage that mechanical strength is insufficient and the dimensional change (thermal expansion coefficient) due to temperature is about 10 times larger than that of metal. To compensate for these drawbacks, paper, glass cloth, and glass nonwoven fabrics are used as reinforcing materials. By using the reinforcing base material, the strength of the resin in the longitudinal and transverse directions (X and Y directions) increases, and the dimensional change due to temperature also decreases.

According to the use of such reinforcing materials, it is divided into glass epoxy copper clad laminate, heat resistant resin copper clad laminate, paper / phenol copper clad laminate, high frequency copper clad laminate, flexible copper clad laminate, and any one of the copper clad laminates listed according to the intended use can be used. Can be.

Next, as shown in FIG. 3B, the surface treatment 303 and the conductive paste 304 are applied to the lower electrode on which the wiring pattern is formed to increase the adhesive strength with the thick film.

The surface treatment 303 provides a roughness to the surface of the copper foil and is intended to increase the adhesion to the thick film during formation of the thick film oxide described later. The surface treatment 303 may be performed using a plasma, an ion beam, a chemical method, a mechanical method, or a mixed method. Among them, a surface treatment using a mixed method etching will be described.

The mixed surface treatment method is a mixture of mechanical and chemical methods. The surface treatment is divided into a soft etching method after a brush, a brush method after a line soft etching, and a brush method after a line acid treatment.

Of these, the present invention preferably uses a brush method after the acid treatment. After the linear acid treatment, the brush method is the most widely used method, which performs acid treatment to remove oxides, fingerprints, oils, and the like, and gives roughness to the front surface of the brush.

In addition, the conductive paste 304 is used in the same manner as the surface treatment 303 in order to increase adhesion to the thick film when forming the thick film oxide to be described later.

Next, as shown in FIG. 3C, a thick film oxide 310 is formed on the lower electrode on which the surface treatment 303 and the conductive paste 304 are applied, and then sintered by applying microwave.

At this time, the thick film oxide 310 is made of a ceramic material, strontium titanate (SrTiO3), barium titanate (BaTiO3), strontium barium titanate ((Ba, Sr) TiO3), lead zirconate (PbZrO3), lead titanate (PbTiO3) Any one of these can be used.

As a method of forming the thick film oxide 310, a thick film method, a spin coating method, a nano nozzle spray method, or the like may be used.

The sheet-type capacitor built-in type replaces the conventional decoupling capacitor, which has a low capacitance (about 15 mA / in2), which makes it difficult to replace the capacitor. However, by using the above-described thick film method, the thickness of the capacitor is tens of times compared to the sheet-type capacitor built-in type. The capacitance value can be increased by thinning the thickness from nm to several micrometers.

Next, as shown in FIG. 3D, an upper electrode 305 is formed on the sintered thick film oxide layer 310.

The upper electrode 305 is preferably formed of electroless plating and electroplating. In order to increase the bonding strength between the upper electrode and the thick film oxide layer, the surface of the thick film oxide may be implemented using chemical, mechanical, plasma, ion beam, or a combination thereof. In addition, the thickness of the upper electrode is very thin, preferably less than 1/2 of the conventional, such as 5㎛, 7㎛, 15㎛.

In addition, as a method of forming an upper electrode, a method of forming a thin seed layer (100 Cu to 5000 Å) of Ru, Cu, Ni, Cr, Mo, or a combination thereof using a sputter, and screen printing on the thick oxide layer ( It is also possible to apply a conductive paste such as Ru, Cu, Ni, Cr, Mo, or a combination thereof as a conductive nano metal, and then dry at a predetermined temperature to form a metal layer (10 to 50 µm).

Finally, as shown in FIG. 3E, multilayer printing is performed on the upper electrode 305 by build-up in multiple layers to form a multilayer substrate.

In the above-described manufacturing method, the change in the microstructure of the sintered particles, which appear in the initial stage, the middle stage and the final stage, which are generally three stages in the sintering process of FIG. 3C, will be described in detail with reference to FIGS. 4A to 4C.

 Sintering is a phenomenon in which a non-metal or metal powder is press-formed and heat-treated at a temperature below the melting point, and a bond is formed between the powders to harden into a molded shape. It is important for manufacturing ceramic products, ceramics, powder metallurgy, cermet, etc. It's a trick. The driving force of sintering is the extra surface energy of the powder. In other words, when the powder is simply collected, the sum of the surface energies is not the minimum and is thermodynamically unbalanced. The heat treatment causes the particles to move in the direction of reducing the surface energy, that is, the direction of the surface area, to bond the particles together.

In the initial stage, as shown in Fig. 4a, coalescence occurs between particles, and the area of this portion gradually increases. This change is called neck growth. At this stage, the relative density (ratio of sintered body density to theoretical density) is about 0.5 to 0.6 and the shrinkage is about 4 to 5%.

Next, as shown in Figure 4b, in the medium-term stage the gap of the channel shape is gradually narrowed, the relative density is increased to 0.6 ~ 0.95, the shrinkage rate is close to 5 ~ 20%. In general, the growth of particles occurs distinctly.

Next, as shown in FIG. 4C, in the final stage, the relative density becomes 0.95 or more, leaving only the edges of the polyhedralized particles or the voids (called pores) in the particles. The pores that communicate with the outside air are called open pores, and the pores that do not pass through the closed pore. In this late stage, densification occurs by the disappearance of the pores. The mechanisms of sintering are largely divided into evaporation-condensation mechanisms, diffusion mechanisms, dissolution-precipitation mechanisms, and flow mechanisms due to differences in mass transport modes. Which of these mechanisms prevails is mainly determined by analysis using the rate expression or shrinkage rate formula of cervical growth at the stage of initial sintering. In practice, sintering is often caused by a mixture of several mechanisms.

In the sintering described above, the present embodiment is preferably sintered by applying microwaves instead of sintering by applying high temperature heat. For example, when PZT is used for thick film, since PbO is volatile at high temperature, PbO is volatile at a high temperature, and a small amount of PbO powder is added to the sample and then sintered to compensate for volatilization of PbO generated during sintering. However, at this time, pores due to volatilization of PbO are present in the microstructure of the sintered compact, and thus electrical properties may be degraded. In this problem, the present invention using microwaves can rapidly reduce the sintering process time to several minutes (for example, about 20 minutes) by rapidly heating PZT, and greatly reduce the process time and energy, and volatilize PbO with a short sintering process time. There is an effect that can be suppressed as much as possible.

In addition, there may be a yield problem, such as uneven heat distribution during the conventional heat sintering, so that a certain level of sintering cannot be carried out over the sintering site, but defects may occur. It can be effective.

5 is a schematic cross-sectional view of a microwave sintering apparatus used to manufacture the circuit board described above.

As shown in FIG. 5, the microwave sintering apparatus 500 includes a microwave shielding case 560, a microwave generator 510, a reaction chamber 520, a firebrick 521, a thermometer 540, and the like. , A gas source 531 and a vacuum pump 532 for adjusting the pressure of the source gas.

The microwave shielding case 560 is formed of a shielding structure to minimize the loss of microwaves to the outside when microwave is applied, and stainless steel or iron plate is used to reflect the microwaves. (Not shown) and an outlet (not shown) from which the sintered substrate sample is drawn.

The microwave generator 510 is located on one side of the inner surface of the microwave shielding case 560 and generates microwaves when power is applied. Up to two microwave generators can be mounted, depending on the area of the substrate. The microwave generated at this time preferably uses a wavelength of 2.45 GHz. Unlike the conventional sintering method by heating by sintering by microwave, several substrate samples 550 can be sintered at once by the characteristic of microwave having high penetration ability. Therefore, it is possible to improve manufacturing cost and production capacity. have.

The reaction chamber 520 is composed of high-temperature heat insulating materials 524a and 524b, a substrate 522, and a side substrate 523. In order to position the substrate sample 550 to be sintered in the cavity, The brick 521 is positioned at the center of the base surface of the microwave shielding case 560, and a high temperature insulating material 524a is mounted on one side of the firebrick 521, and the substrate 522 is placed thereon, and then the substrate sample is placed thereon. The side substrate 523 is positioned on the left and right sides of the substrate sample 550 so that the 550 can be placed thereon. In this case, the substrate 522 and the side substrate 523 may preferably use either silicon carbide (SiC) or zirconia (ZrO 2) having high microwave absorption capability. By using either silicon carbide or zirconia there is an advantage that can maximize the efficiency during microwave application.

In general, the ceramic dielectric material does not absorb the microwave sufficiently at room temperature, so the critical transition temperature, which is a temperature at which the ceramics self-heats indirectly by using silicon carbide or zirconia having a large microwave absorption capacity (tan δ) at room temperature. It can be heated up to) and above the critical transition temperature, the ceramics can reach the sintering temperature by heat generation and can be sintered within minutes. Due to such rapid heating, the densification proceeds rapidly with shortening of processing time and low activation energy. Gas flows from the gas source 531 according to the sintering atmosphere required. The gas is regulated by a vacuum pump 532 that regulates the pressure of the source gas.

At this time, the gas used above is preferably an inert gas, for example nitrogen gas.

The temperature measurement of the surface of the substrate sample 550, i.e., the specimen, is carried out in the thermometer 540 through a small hole 501 processed in a refractory positioned on one side of the microwave apparatus 500, preferably located above the microwave apparatus 500. Measure with

The thermometer 540 may use either an optical thermometer or a non-contact infrared temperature sensor close to the surface of the substrate sample.

According to the method and apparatus for manufacturing a capacitor-embedded circuit board of the present invention, in order to increase the capacitance of a capacitor-embedded circuit board, a thick film method, a spin coating method, and a nano-nozzle spray method, which can produce a thin film, compared to a conventional sheet type, etc. By forming a thick film using a variety of techniques to manufacture a thinner capacitor thickness of several tens nm to several micrometers compared to the sheet-type capacitor built-in replace the conventional decoupling capacitor can improve the capacitance value.

In addition, according to the method and apparatus for manufacturing a capacitor-embedded circuit board of the present invention, by applying a new energy source (microwave (2.45 GHz)) to induce hybrid rapid sintering that can be sintered within a short time, the sintered density due to self-volume heating of ceramics Improves the dielectric constant, improves the dielectric constant, and reduces the sintering time as much as possible, thereby greatly reducing the process time and energy.

In addition, according to the method and apparatus for manufacturing a capacitor-embedded circuit board according to the present invention, there may be a yield problem such as a failure due to uneven heat distribution during the conventional heat sintering and a certain level of sintering cannot be performed over the sintering site. The yield can be improved by sintering evenly on the whole sintered site by using.

In addition, according to the method and apparatus for manufacturing a capacitor-embedded circuit board of the present invention, unlike the conventional sintering method of heating by sintering by microwave, several substrate samples can be sintered at the same time by the characteristic of microwave having high penetration ability. Therefore, manufacturing cost and production capacity can be improved.

Claims (12)

(a) mounting a conductive metal on one side of the inner layer to form a first electrode; (b) forming a thick film on the lower electrode by using a thick film oxide material; (c) sintering the thick film with microwaves; And (d) forming a second electrode on the sintered thick film oxide. The method of claim 1, The manufacturing method further comprises the step of surface-treating the first electrode after the step (a).  The method of claim 2, The surface treatment is a capacitor embedded circuit board manufacturing method, characterized in that the surface treatment using at least one of plasma, ion beam, chemical etching. The method of claim 1, The thick film oxide material is a capacitor embedded circuit board manufacturing method, characterized in that the ceramic material. The method of claim 1, The conductive metal is a copper foil embedded circuit board manufacturing method, characterized in that the copper foil. The method according to any one of claims 1 to 5, The manufacturing method further comprises the step of forming a multi-layer by building up the external substrate after the step (d). A microwave shielding case for reducing microwave loss to the outside when microwave is applied; A microwave generator disposed on one side of an inner surface of the microwave shielding case and radiating microwaves to the inside; And And a reaction chamber positioned inside the microwave shielding case so as to place a substrate sample for embedding a device made of a thick film oxide thereon and sintering the substrate sample with microwaves. The method of claim 7, wherein The reaction chamber is located in the center of the bottom surface of the microwave shielding case, the refractory brick is mounted on one side of the refractory brick, the high-temperature insulating material, and after placing the substrate on it again, the side substrates on the left and right of the substrate sample, characterized in that Microwave sintering device. 9. The microwave sintering apparatus according to claim 8, wherein the substrate is any one of silicon carbide or zirconia. 10. The microwave sintering apparatus according to claim 9, wherein the side substrate is one of silicon carbide or zirconia. 11. The microwave sintering apparatus according to claim 10, further comprising a thermometer exposing a measurement unit inside the shielding case to measure an internal temperature of the shielding case. 12. The microwave sintering apparatus according to claim 11, wherein the thermometer is any one of an optical thermometer and a non-contact infrared temperature sensor.

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