JP5287360B2 - Capacitor structure using conductive resin and manufacturing method thereof - Google Patents

Description

  The present invention relates to a capacitor structure using a conductive resin, in particular, a capacitor structure formed on a mother board, a semiconductor package substrate, and an LSI chip constituting an electronic device, and a method for manufacturing the same.

  Recent advances in functional and functional performance of electronic devices and functional modules and semiconductor packages constituting the electronic devices are supported by higher integration and higher performance of active components (semiconductor elements). Along with this, the number of passive elements constituting circuits such as capacitors, resistors, and filters constituting the circuit, particularly the number of capacitors and resistors that are mounted dramatically increases.

  Most capacitors and resistors are connected to and fixed to electrode portions on the surface of a mounted body such as a substrate in the shape of a chip-type component via solder. In addition, the size of chip-type parts has been steadily reduced with the demand for miniaturization of equipment, and at present, practical use has progressed to a minimum of 0402 type (JIS standard, 0.4 mm × 0.2 mm size). Yes. However, there has been a problem in the dramatic increase in the number of necessary passive elements, an increase in the mounting area of passive components even though the size is reduced, and the degree of freedom of placement of passive components for higher-speed operation.

  Against this background, research and development have been conducted on component-embedded substrates in which passive components are embedded in the substrate, and some have been put into practical use. The passive component built-in board supplies passive components in the form of chip-type components, and mounts and embeds them in a cavity-shaped substrate component, and creates passive elements in the substrate using a thin film process. The type (the latter) in which passive elements are formed by a thin film process is advantageous in terms of high integration due to miniaturization and thinning of parts and rationality due to batch formation of a plurality of elements.

  For example, Patent Document 1 discloses a technique for manufacturing a capacitor by forming an auxiliary electrode layer using a conductive paste containing gold, silver, or the like, and forming a conductive film using a conductive paste containing titanium as a main component. Has been. Patent Document 2 discloses a capacitor in which an electrode and an aluminum metal plate are bonded with a conductive paste in which conductive powder is mixed.

JP 2000-150301 A Japanese Patent Laid-Open No. 10-97952

  However, even in a thin film type capacitor, although it is reasonable in terms of being able to form a plurality of elements at once, the cost is still high, and its application range is practically limited to a high-end region with high added value. In other words, this thin film type capacitor is basically based on the photolithography technology, has a large number of process steps, and uses expensive equipment, leading to high cost. As an example, the electrode (conductor) layer forming step is shown as follows: “Conducting the entire surface of the conductor (copper foil bonding, etc.) → Full-surface application of photosensitive resin (photoresist) → Exposure → Development → Removal of excess photosensitive resin → Conductor Even roughly dividing “etching → etching resist removal”, it is necessary to take seven steps.

  In addition, the thin film type capacitor process may have a high environmental load. Specifically, in the photolithography process, many conductor materials, dielectric materials, and photosensitive resin materials are eventually discarded by etching, and chemicals used for the etching process must also be discarded. Reducing waste is a major issue as global environmental sustainability is attracting worldwide attention and regulations on environmentally hazardous substances are becoming active.

  The present invention has been made in view of the above circumstances, and in a capacitor of a type in which both sides of a dielectric layer are sandwiched between conductor layers, a capacitor structure that can improve or reduce at least one of manufacturing cost and environmental load, and It aims at providing the manufacturing process.

In one aspect , the method for manufacturing a capacitor structure according to the present invention includes a step of reducing the content of the conductive filler contained in one surface layer portion of the first conductive resin layer formed including the conductive filler. And then forming a second conductive resin layer containing a conductive filler on at least a part of the surface of the surface layer portion, and the conductivity contained in the second conductive resin layer The particle size distribution of the filler is distributed on a larger side than the particle size distribution of the conductive filler contained in the first conductive resin layer, and the step of reducing the conductive filler content is performed by chemical etching. , characterized in that.

  Thus, for example, by reducing the conductive filler on the surface layer of the first conductive resin layer, it functions as a dielectric layer, and apparently the lower electrode of the capacitor and the dielectric film are integrally formed. become. Therefore, it is possible to form the lower electrode film and the dielectric film at the same time by supplying the necessary amount of the conductive resin layer to the required location and heat-curing, and the lower electrode film and the dielectric film can be formed at the same time, leading to cost reduction. . In addition, as described above, the conductive resin electrode and the wiring are supplied in a necessary amount to a necessary place, and since there are very few waste materials, waste chemicals, etc., there is an advantage that the environmental load is very small.

(A)-(d) is a whole perspective view which shows sequentially the capacitor preparation process of one Example of this invention. (A)-(d) is sectional drawing which shows sequentially the capacitor preparation process of one Example of this invention. It is a schematic cross section which shows the capacitor structure of one Example of this invention. It is a figure which shows an example of the particle size (particle size) distribution of the conductive filler contained in the conductive resin layer used for this invention. (A), (b) is a schematic cross section which shows the capacitor structure of the other Example of this invention. It is a figure which shows the image of the centrifugation in the capacitor manufacturing process of the other Example of this invention. (A), (b) is a schematic diagram which each shows the cross section before and behind centrifugation in the capacitor manufacturing process of the other Example of this invention.

  The conductive filler has a powdery or fibrous shape, simple substance of gold, silver, copper, nickel, carbon or a mixture thereof, the elements or alloys of the element and other elements, or other elements It is preferable that the filler surface is any one obtained by plating the element.

In the method for manufacturing a capacitor structure in one view point, the step of decreasing the conductive filler content is in the this to be performed by chemical etching, can be relatively easily and reliably remove the conductive filler in the vicinity of the surface, The region thickness to be removed can also be set thin. The ability to set the thickness of the region where the conductive filler is removed, that is, the portion functioning as the dielectric layer, leads to the realization of a larger capacitor capacity.

  In the case of a hybrid type in which at least the resin component of the first conductive resin includes both a thermosetting resin and a thermoplastic resin, the step of removing the conductive filler near the surface of the first conductive resin After that, it is preferable to further include a heating step. In the heating step, the thermoplastic resin component of the hybrid type resin is softened and the fluidity is increased, so that the surface of the partially exposed conductive filler can be covered and the insulation can be improved.

  Several exemplary embodiments of the invention will now be described in detail with reference to the drawings.

Example 1
A detailed structure of the first embodiment according to the present invention is shown in FIG. In Example 1, the first conductive resin layer 11 is formed on the substrate 10, and the vicinity of the outermost surface (surface layer portion) is a conductive filler-deficient layer (region having a low content of conductive filler) 13. The second conductive resin layer 12 is formed thereon. The conductive filler deficient layer 13 is obtained by etching away the conductive filler near the outermost surface of the first conductive resin layer. When the second conductive resin layer is subsequently supplied, at least a part of the holes formed by etching is filled with the resin component of the second conductive resin layer. In the first conductive resin layer and the second conductive resin layer, the particle size distribution of the conductive filler constituting the second conductive resin layer is a particle size distribution that has moved to the larger overall size. Yes. By doing so, it is possible to prevent the conductive filler contained in the second conductive resin layer from entering the hole portion formed by etching to form a conduction path, and to form the dielectric layer more reliably. It has become.

  The capacitor fabrication process of this example is shown in order as an overall perspective view in FIG. 1 and a sectional view in FIG. In addition, the symbol showing each process shown in FIG. 1 and FIG. 2 respond | corresponds. First, a substrate 10 is prepared as shown in FIGS. 1 (a) and 2 (a). Further, as shown in FIGS. 1B and 2B, the first conductive resin layer 11 is supplied by screen printing according to a predetermined pattern. The first conductive resin layer 11 is composed of a silver (Ag) filler, an epoxy thermosetting resin, a dispersant, and a solvent, and the particle size distribution of the Ag filler has a peak in the vicinity of 0.3 μm. The particle size distribution conforms to the definition described in JISZ8901. In this embodiment, the screen printing method is used for the method of supplying the first conductive resin layer 11 (and the second conductive resin layer 12 described later). However, the present invention is not limited to this method. Dispensing, intaglio printing method, relief printing method, offset printing method, etc. can also be used as appropriate, however, the physical properties required for printing materials differ depending on the supply method, and the resin type is used to adapt to the physical properties that suit the method. Needless to say, it is necessary to adjust the solvent type or the content thereof.

  Next, as shown in FIGS. 1C and 2C, a conductive filler deficient layer 13 is formed. Specifically, the substrate 10 was immersed in an alkaline etching solution having an Ag dissolving action. In this example, after immersing in an etching solution for about 3 minutes, a longitudinal section was prepared and the etched portion was observed in detail to confirm the thickness of the conductive filler-deficient layer 13 and found to be about 2 μm.

  In this embodiment, when the first conductive resin layer 11 is supplied, the lower electrode of the capacitor and the wiring are formed simultaneously. Accordingly, if the wiring is exposed at the time of etching, the Ag filler is also etched on the surface of the wiring. Moreover, since parts other than the 1st conductive resin layer 11 are also immersed in etching liquid, there exists a possibility of receiving a damage depending on compatibility with a substrate surface material etc. As such, if the immersion in the etching solution is inappropriate, a resist film or the like is formed in a place where etching is not desired or a place where the etching solution is likely to be damaged before the etching process. It is also possible to etch only the capacitor portion.

  In this embodiment, the substrate 10 has no large step, but other parts are already mounted, and the surface of the substrate 10 is so large that it is difficult to screen print. It is preferable to use a non-contact printing method such as inkjet.

  Next, as shown in FIGS. 1D and 2D, the second conductive resin layer 12 was supplied by the screen printing method in the same manner as when the first conductive resin layer 11 was formed. In this case, it is necessary to form a film without absorbing the step by the thickness corresponding to the thickness of the first conductive resin layer 11, but the thickness of the first conductive resin layer 11 is 15 μm. Since the screen printing method uses offset printing in which the screen mask is printed while deflecting with a squeegee, the second conductive resin does not cause problems such as wiring breakage. The supply of layer 12 was possible.

  In this embodiment, the particle size distribution of the Ag filler of the second conductive resin layer 12 is adjusted to have a peak near 0.8 μm, and the overall particle size distribution is larger than the conductive filler diameter of the first conductive resin layer 11. To be bigger. FIG. 4 shows the concept for designing the filler diameter. The particle size of the powdered conductive filler has a certain particle size distribution. The shape of the particle size distribution becomes sharp or broad depending on the metal species, the method and conditions for producing the filler, the fineness of the selection after the powder is produced, and the like. In general, the more the powder having a sharp particle size distribution, that is, the diameter of the fillers, is increased, the process cost increases and the yield decreases, resulting in an expensive powder.

  FIG. 4 shows a particle size distribution image of the conductive filler contained in the first conductive resin layer 11 and the second conductive resin layer 12, and the portions where both overlap each other are both conductive resin layers. The particle size that can be present and the content ratio are shown. That is, this corresponds to the possibility that the conductive filler of the second conductive resin layer 12 may enter the pores on the surface of the first conductive resin layer formed by etching. It can be easily inferred that the overlapping portion is larger as the particle size distribution is similar, and smaller as the particle size distribution becomes sharper. Therefore, there is a risk that electrical leakage may occur through the pores by giving a difference in the particle size distribution of the conductive filler in the direction in which the conductive filler diameter of the second conductive resin layer 12 becomes larger. Efficiency can be reduced efficiently.

  Finally, the second conductive resin layer is heated and cured at 180 ° C. for 30 minutes to complete the capacitor fabrication (not shown).

  In Example 1, Ag filler was used as the conductive filler of the first conductive resin layer 11, but it is not limited to Ag, and other gold (Au), copper (Cu), nickel (Ni), a powder composed of any of carbon (C), or a mixture thereof, or the elements are plated with each other, an alloy of these elements with another element, or a filler surface composed of another element. Powder may be used.

  In the present embodiment, the first conductive resin layer 11 and the second conductive resin layer 12 use the same filler type (Ag), the same resin component, solvent, etc., although the particle size distribution of the conductive filler is different. However, the filler type and the resin type are not necessarily the same, and are appropriately selected individually. The adhesiveness and affinity of the second conductive resin layer with respect to the surface of the first conductive resin layer 11 after curing should be considered, but these are well known to those skilled in the art, and are detailed. Not to mention.

(Example 2)
FIG. 5A shows the configuration of the second embodiment according to the present invention. The schematic configuration of the second embodiment is the same as that of the first embodiment. The difference from the first embodiment is a method for forming a dielectric layer near the outermost surface of the first conductive resin layer 11. Specifically, in Example 1, the first conductive resin layer 11 was supplied, heat-cured, and then the conductive filler near the outermost surface was removed by etching. In Example 2, the first conductive resin layer 11 was removed. After supplying the conductive resin layer 11, the conductive filler is unevenly distributed by centrifugal treatment, and the resin layer 14 having very little or no conductive filler is formed near the outermost surface of the first conductive resin layer 11.

  Hereinafter, the process will be described in detail focusing on the formation portion of the resin layer 14 which is a difference process from the first embodiment.

  After supplying the first conductive resin layer 11 to the substrate 10 by screen printing, the entire substrate 21 supplied with the first conductive resin layer is set in the centrifugal separator 100 as shown in FIG. The substrate 21 supplied with the first conductive resin layer is set on the inner wall of the centrifuge with the printing surface inside. Then, it is rotated at about 1500 rpm for 1 minute. Then, the conductive filler that receives the force in the direction of the substrate due to the centrifugal force is mechanically settled, and is almost evenly conductive immediately after printing (FIG. 7A) as shown in the image of FIG. In the case where the filler has been distributed, the conductive filler sinks after centrifugation (FIG. 7B), and the resin layer 14 is formed in the vicinity of the outermost surface.

  Finally, the second conductive resin layer 12 is formed on the resin layer 14. In this case, as shown in FIG. 5A, the upper surface of the resin layer 14 apparently becomes a boundary 20 between the first conductive resin layer 11 and the second conductive resin layer 12. As an alternative, natural sedimentation by gravity may be used over a predetermined time instead of centrifugation.

  In addition, the first conductive resin layer 11 is heated and cured without allowing the conductive filler to settle, and then the second conductive resin layer 12 is supplied and then the conductive filler is forcibly distributed by centrifugation. It is valid. A detailed cross-sectional image in this case is shown in FIG. 5B, and the image of centrifugation is the same as in FIG. 6 (the substrate 22 supplied with the first and second conductive resin layers is disposed). However, when the second conductive resin layer 12 is subjected to centrifugation, the conductive filler is unevenly distributed to the outermost surface side, so that the direction in which the centrifugal force is applied is reversed. Therefore, it is necessary to attach the substrate 22 so that the second conductive resin layer 12 is on the outside. In this case, as shown in FIG. 5B, the lower surface of the resin layer 14 becomes a boundary 20 between the first conductive resin layer 11 and the second conductive resin layer 12.

  In addition, in the metal used for the conductive filler and the resin component, the specific gravity of the metal is more than 5 times larger, and when mixed, it will naturally separate from the difference in specific gravity, but the normal conductive resin layer is In order to achieve uniform dispersion of the conductive filler, it is designed to suppress sedimentation as much as possible by adjusting the resin or adding a dispersant. However, this embodiment is intended to promote sedimentation of the conductive filler, and there is a problem in that the filler sedimentation occurs before printing of the conductive resin layer in terms of stable material supply. Therefore, it is possible to more easily realize layer separation by adjusting the dispersant and adjusting the change in viscosity with respect to the resin temperature so that sedimentation occurs by heating to a temperature lower than the main curing temperature of the resin. .

  The conductive resin layer may contain an appropriate amount of a filler having a perovskite structure and a high dielectric constant such as barium titanate (BaTiO3) and strontium titanate (SrTiO3). By doing so, the apparent dielectric constant of the resin film portion is improved, which leads to an improvement in capacitance.

(Example 3)
The schematic configuration of the third embodiment is the same as that of the first embodiment. The difference from the first embodiment is that the resin component of the first conductive resin layer is a hybrid type of a thermosetting resin and a thermoplastic resin. Yes, the process is changed accordingly (not shown).

  Specifically, a hybrid type of an epoxy thermosetting resin and a thermoplastic resin is adopted as the resin component of the first conductive resin layer, and the contents of the thermosetting resin and the thermoplastic resin are set to be approximately equal. .

  As a process, after forming the first conductive resin layer and removing the conductive filler on the surface layer portion by etching, preheating treatment is performed at 100 ° C. for 10 minutes, followed by main heating at 180 ° C. for 30 minutes. Example 1 is the same as in Example 1. This is because the thermoplastic resin is softened by reheating even after being cured and has fluidity, and it is 100 against the danger of exposure of the conductive filler inside the pores generated by etching. An effect of covering the conductive filler portion where the thermoplastic resin component having improved fluidity by heating at 0 ° C. is exposed and maintaining insulation can be expected.

  Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention can be changed even if there is a design change or the like without departing from the gist of the present invention. include. In other words, the conductive filler material, conductive filler particle size distribution, method of adding centrifugal force to the sample, hybrid type conductive resin material, preheating conditions, etc. shown in the examples are merely examples, and the purpose, application, etc. It can be changed as appropriate according to the situation. In the embodiment, capacitor fabrication on a substrate is illustrated, but the application range is not limited thereto, and it can be applied to formation of a capacitor on a silicon chip or glass. It is also possible to manufacture a multilayer substrate with a built-in capacitor using the method proposed in the present invention.

DESCRIPTION OF SYMBOLS 10 Board | substrate 11 1st conductive resin layer 12 2nd conductive resin layer 13 Conductive filler deficiency layer 14 Resin layer 20 Boundary of 1st conductive resin layer and 2nd conductive resin layer 21 1st conductivity Conductive resin layer supply substrate 22 First and second conductive resin layer supply substrate 100 Centrifuge

Claims (3)

Reducing the content of the conductive filler contained in one surface layer portion of the first conductive resin layer formed including the conductive filler; and
Next, forming a second conductive resin layer containing a conductive filler on at least a part of the surface of the surface layer portion, and
The particle size distribution of the conductive filler contained in the second conductive resin layer is distributed on a larger side than the particle size distribution of the conductive filler contained in the first conductive resin layer ,
The method of manufacturing a capacitor structure, wherein the step of reducing the conductive filler content is performed by chemical etching . The conductive filler has a powdery or fibrous shape, simple substance of gold, silver, copper, nickel, carbon or a mixture thereof, an alloy of the elements or an alloy of the element and another element, or another element 2. The method of manufacturing a capacitor structure according to claim 1, wherein the surface of the filler is any one obtained by plating the element. After the step of decreasing the conductive filler content, which further comprises a heating step, The process according to claim 1 or 2.

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