Ceramic substrate unit and manufacturing method therefor

Abstract

The present invention relates to a ceramic substrate unit and a manufacturing method therefor. The ceramic substrate unit comprises: a ceramic substrate having a metal layer formed on the upper surface of a ceramic base; a partial metal layer formed in one region of the metal layer; and a spacer formed by printing a conductive paste on the partial metal layer.

Description

Ceramic substrate unit and manufacturing method thereof

[0001] The present invention relates to a ceramic substrate unit and a manufacturing method thereof, and more particularly, to a ceramic substrate unit and a manufacturing method thereof (CERAMIC SUBSTRATE UNIT AND MANUFACTURING METHOD THEREOF) in which a partial plating layer is formed on a ceramic substrate to increase the reliability of bonding between the ceramic substrate and a spacer.

[0002] Recently, research on electric vehicles is being conducted due to environmental and energy-related issues. Power modules, a component of the power conversion device (inverter, converter) in the drive system of an electric vehicle, are equipped with semiconductor chips for power conversion. Due to the increasing demands for high-integration, high-frequency, and high-output semiconductor chips, semiconductor chips generate high temperatures due to high-voltage and high-current operation. For example, when using high-efficiency SiC chips, the operating temperature of the semiconductor chips can rise to approximately 250°C or higher. Therefore, power modules with dual-side cooling structures are being commercialized to enhance cooling efficiency. In these power modules, spacers can connect the upper and lower substrates, and can also be connected to the terminals of the semiconductor chips to serve as power transmission lines. To address cost issues and ensure precise thickness control, spacers can be formed by printing conductive paste on a ceramic substrate and then sintering it. At this time, there is a problem that warping or delamination occurs at the joint between the ceramic substrate and the spacer during the process of repeating printing and firing multiple times to form a spacer of the desired thickness, making it difficult to achieve reliable jointing between the ceramic substrate and the spacer.

[0003] The matters described in the background art above are intended to help understand the background of the invention and may include matters that are not publicly disclosed prior art.

[0004] The present invention has been made to solve the above-described problem, and the purpose of the present invention is to provide a ceramic substrate unit and a manufacturing method thereof that enable reliable bonding between a ceramic substrate and a spacer formed through a printing process through a partial metal layer formed in a portion of a metal layer of the ceramic substrate where a spacer is placed.

[0005] A method for manufacturing a ceramic substrate unit according to an embodiment of the present invention for achieving the above-described purpose may include a step of preparing a ceramic substrate having a metal layer formed on the upper surface of a ceramic substrate, a step of forming a partial metal layer in a part of the metal layer, and a step of forming a spacer by printing a conductive paste on the partial metal layer.

[0006] The step of forming a spacer may include a step of placing a screen mask having a conductive paste applied thereto on a ceramic substrate, passing the paste through an open pattern area of ​​the screen mask using a squeegee moving along one direction of the screen mask to print a paste layer on a partial metal layer, and a step of firing the paste layer.

[0007] The step of forming a spacer can form a spacer composed of a plurality of paste layers by repeatedly performing the step of printing a paste layer and the step of firing the paste layer.

[0008] The step of firing the paste layer can form a eutectic bonding layer by reacting the partial metal layer and the paste layer.

[0009] The partial metal layer may include Ag, and the paste layer may include Cu. Here, the eutectic bonding layer may be formed of an Ag-Cu alloy.

[0010] The step of forming a partial metal layer may include a step of forming a cover layer in which a pattern hole is formed in a shape corresponding to a portion of a metal layer of a ceramic substrate, a step of plating so that a partial metal layer is formed within the pattern hole, and a step of removing the cover layer.

[0011] The step of forming a cover layer may include a step of forming a photoresist layer on a metal layer, a step of placing a mask covering a portion except for a certain area on the photoresist layer and then exposing the mask, and a step of developing the exposed portion to form a pattern hole in the photoresist layer.

[0012] The step of forming a partial metal layer further includes a step of forming surface roughness in the partial metal layer, and the surface roughness may have an Ra value of 0.3 µm to 2.0 µm.

[0013] A ceramic substrate unit according to an embodiment of the present invention may include a ceramic substrate having a metal layer formed on an upper surface of a ceramic substrate, a partial metal layer formed in a portion of the metal layer, and a spacer formed by printing a conductive paste on the partial metal layer.

[0014] The spacer may include a plurality of paste layers, each of which may be formed by printing conductive paste and then firing the conductive paste.

[0015] The partial metal layer can react with the paste layer to form a eutectic bonding layer.

[0016] The partial metal layer may include Ag, and the paste layer may include Cu. Here, the eutectic bonding layer may be formed of an Ag-Cu alloy.

[0017] The surface roughness of the partial metal layer can have an Ra value of 0.3 ㎛ to 2.0 ㎛.

[0018] The area of ​​the partial metal layer can be formed to be larger than the area of ​​the spacer.

[0019] The gap between the side of the partial metal layer and the side of the spacer may be 0.01 μm or more.

[0020] According to the ceramic substrate unit of the present invention and its manufacturing method, when forming a spacer through a printing and firing process, by printing and firing the spacer on a partial metal layer formed on a ceramic substrate, eutectic bonding between the partial metal layer and the spacer can be induced, thereby greatly enhancing the bonding force.

[0021] In addition, according to the ceramic substrate unit of the present invention and the manufacturing method thereof, since the partial metal layer and the spacer are strongly bonded via the eutectic bonding layer, even if the spacer is formed by printing, no warping occurs at the bonding portion, thereby increasing reliability during electrical connection.

[0022] In addition, according to the ceramic substrate unit of the present invention and the manufacturing method thereof, there is no need to form the spacer itself with an expensive material having a low coefficient of thermal expansion to prevent warpage, and warpage or delamination can be effectively prevented while forming the spacer using relatively inexpensive Cu or the like.

[0023] In addition, according to the ceramic substrate unit of the present invention and the manufacturing method thereof, since a partial metal layer is formed in a portion of an area where a spacer is placed, the area exposed to air is minimized, thereby preventing oxidation and reducing the cost incurred in forming the partial metal layer.

[0024] FIG. 1 is a plan view showing a ceramic substrate unit according to an embodiment of the present invention.

[0025] Fig. 2 is a side view showing a ceramic substrate unit according to an embodiment of the present invention.

[0026] Figure 3 is a cross-sectional view taken along line A-A' of Figure 1.

[0027] Figure 4 is a flowchart for explaining a method for manufacturing a ceramic substrate unit according to an embodiment of the present invention.

[0028] FIG. 5 is a cross-sectional view illustrating a method for manufacturing a ceramic substrate unit according to an embodiment of the present invention.

[0029] FIG. 6 is a plan view showing a state in which a cover layer is removed after a partial metal layer is formed in a method for manufacturing a ceramic substrate unit according to an embodiment of the present invention.

[0030] Fig. 7 is a cross-sectional view showing a step of printing a paste layer in a method for manufacturing a ceramic substrate unit according to an embodiment of the present invention.

[0031] Figure 8 is a cross-sectional view showing a step of firing a paste layer in a method for manufacturing a ceramic substrate unit according to an embodiment of the present invention.

[0032] FIG. 9 is a cross-sectional view showing the repeated performance of the printing step and the firing step of the paste layer in a method for manufacturing a ceramic substrate unit according to an embodiment of the present invention.

[0033] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0034] These examples are provided to more fully illustrate the present invention to those skilled in the art. The following examples may be modified in various ways, and the scope of the present invention is not limited to the examples described below. Rather, these examples are provided to further faithfully and completely convey the spirit of the present invention.

[0035] The terms used herein are used to describe specific embodiments and are not intended to limit the present invention. Furthermore, the singular forms used herein may include the plural forms, unless the context clearly dictates otherwise.

[0036] In the description of the embodiments, when each layer (film), region, pattern or structure is described as being formed "on" or "under" the substrate, each layer (film), region, pad or pattern, "on" and "under" include both being formed "directly" or "indirectly" through another layer. In addition, the reference for above or below each layer is, in principle, based on the drawing.

[0037] The drawings are intended solely to facilitate understanding of the invention and should not be construed as limiting the scope of the invention. Furthermore, relative thicknesses, lengths, and sizes in the drawings may be exaggerated for convenience and clarity of explanation.

[0038] FIG. 1 is a plan view showing a ceramic substrate unit according to an embodiment of the present invention, FIG. 2 is a side view showing a ceramic substrate unit according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view taken along line A-A' of FIG. 1.

[0039] As shown in FIGS. 1 to 3, a ceramic substrate unit (1) according to an embodiment of the present invention may be configured to include a ceramic substrate (100), a partial metal layer (200), and a spacer (300).

[0040] The ceramic substrate (100) may be configured to include a ceramic substrate (110), an upper metal layer (120) formed on the upper surface of the ceramic substrate (110), and a lower metal layer (130) formed on the lower surface of the ceramic substrate (110).

[0041] The ceramic substrate (110) may be formed of an insulating ceramic material having high thermal conductivity and excellent flexural strength. For example, the ceramic substrate (110) may be formed of any one of Al2O3, AlN, Si3N4, and ZTA (Zirconia Toughened Alumina).

[0042] A ceramic substrate (110) may have a metal foil brazed on both sides to form an upper metal layer (120) and a lower metal layer (130). The upper metal layer (120) and the lower metal layer (130) may be formed into a circuit pattern capable of electrically connecting a semiconductor chip (not shown) by etching or mechanical processing. The upper metal layer (120) and the lower metal layer (130) may be Cu metal layers. Brazing bonding may use a brazing bonding layer made of an alloy material including at least one of Ag, AgCu, and AgCuTi. Heat treatment for brazing may be performed at 780°C to 900°C. In this way, the ceramic substrate (100) may be an AMB (Active Metal Brazing) substrate, and the AMB substrate has excellent durability and heat dissipation performance. The embodiment describes an AMB substrate as an example, but the ceramic substrate (100) may also be a DBC (Direct Bonding Copper) substrate. In the ceramic substrate (100), the thickness of the ceramic base material (110) may be formed to be 0.25 mm or more, and the thicknesses of the upper metal layer (120) and the lower metal layer (130) may be formed to be 0.127 mm or more.

[0043] The partial metal layer (200) may be formed on at least one of the upper metal layer (120) and the lower metal layer (130) of the ceramic substrate (100). The partial metal layer (200) is formed to improve the bonding strength between the ceramic substrate (100) and the spacer (300), and may be formed in a portion of an area where the spacer (300) is placed. As will be described later, the partial metal layer (200) is formed for the purpose of inducing eutectic bonding between the spacers (300) to improve the bonding strength between the ceramic substrate (100) and the spacer (300), and may be formed of a material that reacts with the spacer (300) to form a eutectic bonding layer (reference numeral 400 in FIG. 8). For example, the partial metal layer (200) may be any one of Ag, an Ag alloy, Cu, and a Cu alloy. Preferably, when the spacer (300) includes Cu, the partial metal layer (200) can be formed to include Ag or an Ag alloy, and the eutectic bonding layer (400) can be made of an Ag-Cu alloy. The partial metal layer (200) can be formed by electrolytic plating or electroless plating, and can also be formed by various processes such as a physical vapor deposition method, a screen printing method, and a medium-temperature sintering printing method. Here, the medium-temperature sintering printing method forms the partial metal layer (200) using a medium-temperature sintering paste, and the medium-temperature sintering paste can be solidified by being fired at a temperature of 350°C or higher and 480°C or lower after printing to form the partial metal layer (200).

[0044] The spacer (300) is formed on the partial metal layer (200) of the ceramic substrate (100) and can serve as an electrical signal or a power transfer line for power conversion. Although not shown, the spacer (300) can be arranged to be connected to the source terminal, the drain terminal, and the gate terminal of a semiconductor chip such as Si, SiC, or GaN, so that the semiconductor chip can be mounted on the ceramic substrate (100) in a form similar to a flip chip. In this way, when the semiconductor chip is bonded to the ceramic substrate (100) using the spacer (300), the power transfer path can be shortened, thereby improving electrical loss and load due to resistance on the power transfer path. In addition, the spacer (300) can serve as an electrical signal and a power transfer line for power conversion instead of conventional wire bonding. In this way, by omitting wire bonding, the inductance value can be minimized, miniaturization can be achieved, and heat dissipation performance can be improved. The spacer (300) can be formed of any one of Cu, Ag, and CuMo materials having electrical and thermal conductivity, and preferably, can be formed of Cu material.

[0045] In addition, in a power module with a double-sided cooling structure, the spacer (300) may have its lower surface bonded to the metal layer of the ceramic substrate (100) and its upper surface bonded to the metal layer of another ceramic substrate (100) placed above or below the ceramic substrate (100). This spacer (300) may increase heat dissipation efficiency by spacing the upper ceramic substrate (100) and the lower ceramic substrate (100), and may also function as a heat dissipation electrode that electrically connects circuit patterns formed on the metal layers of the upper and lower ceramic substrates (100).

[0046] As described above, since the spacer (300) is connected to the terminal of the semiconductor chip or the circuit pattern of the ceramic substrate (100), it is most important in terms of electrical characteristics to improve the bonding strength with the ceramic substrate (100). The spacer (300) can be formed by printing a conductive paste and then sintering it to precisely control the cost and thickness. The spacer (300) can be formed by printing a paste containing at least one of Cu, Ag, CuMo, and AgCu, and preferably, it can be formed by printing a Cu paste having excellent electrical and thermal conductivity.

[0047] When printing the spacer (300), it is formed by the screen printing method. However, since the thickness of the spacer (300) that can be formed through a single screen printing is approximately 20 μm or less, if the desired thickness is thicker than this, multiple printing and firing steps must be performed. For example, if the thickness of the spacer (300) is to be formed as 100 μm, a first paste layer (310) with a thickness of approximately 20 μm is formed through screen printing with a conductive paste, and then the first paste layer (310) is fired. After that, the screen printing process is repeated again to form a second paste layer (320) with a thickness of approximately 20 μm, and then fired. By continuously repeating the screen printing and firing processes a total of 5 times, a spacer (300) with a thickness of 200 μm can be manufactured. In this way, forming the spacer (300) through multiple printing and firing processes is called TPC (Thick Printing Coppe). In this embodiment, a spacer (300) including first to fifth paste layers (350) formed through five screen printing and firing processes is disclosed, but the present invention is not limited thereto, and the total number of paste layers may be less or more depending on the thickness of the spacer (300). For example, if the thickness of the spacer (300) is 200 μm, the spacer (300) may be formed in a form in which the first to tenth paste layers are laminated.

[0048] In this way, when the spacer (300) is formed by directly screen printing on the metal layer of the ceramic substrate (100), a problem occurs in that the spacer (300) is easily separated from the ceramic substrate (100). The metal layer of the ceramic substrate (100) is mainly formed of bare copper with a purity of 99.9% or more without impurities. On the other hand, in the case of the paste used when printing the spacer (300), since it includes components such as a binder component and a vehicle, the spacer (300) formed with the paste contains about 85% copper. Accordingly, the metal layer of the ceramic substrate (100) formed of pure copper and the spacer (300) have different coefficients of thermal expansion, and in the process of repeating printing and firing multiple times to a desired thickness, a difference in the degree of deformation (contraction or expansion) due to temperature change occurs, causing the joint to warp or a so-called delamination phenomenon in which peeling occurs between the ceramic substrate (100) and the spacer (300), resulting in a deterioration of electrical and heat dissipation characteristics.

[0049] In order to solve this problem, the ceramic substrate unit (1) according to the embodiment of the present invention is characterized in that, when printing the paste layer (310) of the spacer (300), it is not printed directly on the metal layer of the ceramic substrate (100), but is printed on the partial metal layer (200). This partial metal layer (200) can react with the paste layer (310) during the process of firing the paste layer (310) to form a eutectic bonding layer (400). For example, when the partial metal layer (200) includes Ag and the paste layer includes Cu and the paste layer (310) is heated to a temperature of about 780° C. for firing, the interface region of the partial metal layer (200) and the paste layer (310) can be eutectically bonded to form a eutectic bonding layer (400). Here, eutectic bonding is a method of bonding between metals by heating the metals to the eutectic temperature and then hardening them at a temperature below the eutectic temperature to form a eutectic bonding layer (400), and has the advantage of being able to form a strong and highly reliable bond.

[0050] In this way, since the ceramic substrate unit (1) according to the embodiment of the present invention forms a eutectic bonding layer (400) by a eutectic reaction between the partial metal layer (200) formed on the ceramic substrate (100) and the paste layer (310) of the spacer (300) at the interface area, the ceramic substrate (100) and the spacer (300) can be strongly bonded together through the eutectic bonding layer (400). That is, the eutectic bonding layer (400) can serve as a bonding filler that bonds the ceramic substrate (100) and the spacer (300) together, and can significantly improve the bonding strength. Even if the spacer (300) is formed by printing on the ceramic substrate (100) by the eutectic bonding layer (400), warping or delamination of the bonding portion is prevented, thereby improving reliability during electrical connection, and electrical resistance or thermal resistance can be eliminated.

[0051] In the present invention, since the spacer (300) is formed by printing a conductive paste, a bonding filler formed in a liquid state, similar to the paste, cannot be used when bonding the ceramic substrate (100) and the spacer (300). In addition, when the Cu spacer (300) is formed by directly printing it on the Cu metal layer of the ceramic substrate (100), heating must be performed at a high temperature of 1000°C or higher. On the other hand, in the present invention, since the partial metal layer (200) is in a solidified state, the spacer (300) can be formed by printing a paste on the partial metal layer (200), and since the bonding strength between the partial metal layer (200) and the spacer (300) is increased by forming a eutectic bonding layer (400), there is no need to use a liquid bonding filler. In addition, since the eutectic reaction occurs at the firing temperature of the paste layer (310), there is an advantage in that the bonding strength can be increased by forming the eutectic bonding layer (400) at a relatively low temperature. In addition, to prevent warping, there is no need to form the spacer (300) itself with an expensive material such as CPC with a low coefficient of thermal expansion, and warping or delamination can be effectively prevented while forming the spacer (300) using a relatively inexpensive material such as Cu.

[0052] Referring to FIG. 3, the area of ​​the partial metal layer (200) may be formed to be larger than the area of ​​the spacer (300). At this time, the distance (s) between the side surface of the partial metal layer (200) and the side surface of the spacer (300) may be 0.1 mm or more. Since the spacer (300) is formed to be very small when connected to the terminals of the semiconductor chip, if the area of ​​the partial metal layer (200) and the area of ​​the spacer (300) are the same, it is difficult to accurately print the paste layer (310) on the upper surface of the partial metal layer (200). Therefore, by forming the area of ​​the partial metal layer (200) to be larger than the area of ​​the spacer (300), the process of printing the paste layer (310) on the upper surface of the partial metal layer (200) can be performed more smoothly.

[0053] Meanwhile, although not shown, the partial metal layer (200) may be provided with surface roughness on the surface where the spacer (300) is formed before the spacer (300) is formed. The surface roughness refers to the degree of unevenness formed on the surface of the partial metal layer (200), and the units include centerline surface roughness (Ra), maximum height (Rmax), and average roughness at 10 points (Rz). A preferable example of the surface roughness in the partial metal layer (200) may be an Ra value of 0.3 µm to 2.0 µm. Since the partial metal layer (200) has unevenness formed on the surface and thus increases the specific surface area, the bonding strength with the spacer (300) formed by printing the conductive paste may be improved. If the surface roughness (Ra) of the partial metal layer (200) is less than 0.3 ㎛, there is a problem that the surface of the partial metal layer (200) is smooth and the adhesion with the spacer (300) deteriorates. In addition, if the surface roughness (Ra) of the partial metal layer (200) exceeds 2.0 ㎛, the surface of the partial metal layer (200) becomes too rough and the spacer (300) may not be attached locally. Therefore, in the present invention, it is preferable to provide the surface roughness (Ra) of the partial metal layer (200) to be 0.3 ㎛ to 2.0 ㎛ in order to improve the adhesion with the spacer (300). When the surface roughness of the partial metal layer (200) is 0.3 ㎛ to 2.0 ㎛ as the Ra value, the Rz value may be 3 ㎛ to 8 ㎛, and the Rmax value may be 5 ㎛ to 15 ㎛.

[0054] In addition, it is preferable that the partial metal layer (200) be formed with a thickness of 0.1 µm to 1.0 µm. If the thickness of the partial metal layer (200) is formed to be less than 0.1 µm, it is difficult to provide surface roughness, and if the thickness of the partial metal layer (200) is formed to exceed 1.0 µm, the process time for forming the partial metal layer (200) becomes longer, which may reduce mass productivity.

[0055] If the partial metal layer (200) is formed on the entire surface of the metal layer (120) rather than on some areas, the surface of the metal layer in the remaining areas except for the areas where the spacers (300) are formed may be exposed to air and thus may be deteriorated due to oxidation. In addition, since the price of silver is high, as the area of ​​the plating layer increases, the amount of silver used increases, which increases the production cost and reduces economic feasibility. On the other hand, if the partial metal layer (200) is formed on some areas of the metal layer (120) where the spacers (300) are arranged, the surface of the partial metal layer (200) can be prevented from oxidation because the spacers (300) are formed and are not exposed to the air, and the amount of silver plated is reduced, which can reduce costs. This partial metal layer (200) enables reliable bonding between the ceramic substrate (100) and the spacers (300), and is also effective in preventing silver diffusion and dissipating heat.

[0056] FIG. 4 is a flowchart for explaining a method for manufacturing a ceramic substrate unit according to an embodiment of the present invention, and FIG. 5 is a cross-sectional view for explaining a method for manufacturing a ceramic substrate unit according to an embodiment of the present invention.

[0057] As illustrated in FIG. 4, a method for manufacturing a ceramic substrate (100) according to an embodiment of the present invention may include a step (S100) of preparing a ceramic substrate (100) having a metal layer (120) formed on the upper surface of a ceramic substrate (110), a step (S200) of forming a partial metal layer (200) in a portion of the metal layer (120) of the ceramic substrate (100), and a step (S300) of forming a spacer (300) by printing a conductive paste on the partial metal layer (200).

[0058] In the step (S100) of preparing a ceramic substrate (100), a metal foil may be brazed to both sides of a ceramic substrate (110) to form an upper metal layer (120) and a lower metal layer (130). The ceramic substrate (110) may be formed of any one of Al2O3, AlN, Si3N4, and ZTA (Zirconia Toughened Alumina). The upper metal layer (120) and the lower metal layer (130) may be Cu metal layers. In the ceramic substrate (100), the thickness of the ceramic substrate (110) may be formed to be 0.25 mm or more, and the thicknesses of the upper metal layer (120) and the lower metal layer (130) may be formed to be 0.127 mm or more.

[0059] In the step (S200) of forming a partial metal layer (200), the partial metal layer (200) can be formed in a portion of the metal layer of the ceramic substrate (100) where the spacer (300) is placed. The partial metal layer can be formed by various processes such as electrolytic plating, electroless plating, physical vapor deposition, screen printing, and medium-temperature sintering printing. In this embodiment, the formation of the partial metal layer (200) by electrolytic plating or electroless plating will be described in order to implement a constant thickness along the surface.

[0060] Referring to FIG. 5, the step (S200) of forming a partial metal layer (200) may include a step (S210) of forming a cover layer in which a pattern hole (h) is formed in a shape corresponding to a portion of an area where a spacer (300) is placed on an upper metal layer (120), a step (S220) of plating so that a partial metal layer (200) is formed within the pattern hole (h), and a step (S230) of removing the cover layer.

[0061] The step (S210) of forming a cover layer may include a step (S211) of forming a photoresist layer (P) on the upper metal layer (120), a step (S212) of placing a mask (M) covering the remaining portion except for a portion where a spacer (300) is placed on the photoresist layer (P) and then exposing it, and a step (S213) of developing the exposed portion to form a pattern hole (h) in the photoresist layer (P). In the present embodiment, the cover layer may be a photoresist layer (P) patterned by a photolithography process.

[0062] In the step (S211) of forming a photoresist layer (P), the photoresist layer (P) may be formed by applying a dry film or a photoresist liquid on the upper metal layer (120). Here, the dry film has the advantage of being able to simplify the manufacturing process because it has a uniform thickness and does not require a separate drying process.

[0063] In the exposing step (S212), a mask (M) covering the remaining portion except for a portion where the spacer (300) is placed is placed on the photoresist layer (P), and then a light source such as UV (Ultra violet) is irradiated thereon. In this way, by irradiating the light source through the mask (M), the pattern of the mask (M) can be transferred to the photoresist layer (P). Here, the type in which only the portion exposed by the light source is developed is the positive type, and the type in which only the portion not exposed is developed is the negative type. In this embodiment, an example in which a positive type photoresist layer (P) is used is described, but the negative type can also be used.

[0064] In the step (S213) of forming a pattern hole (h), when the photoresist layer (P) is developed after exposure, some areas where the spacer (300) is placed are removed, so that a pattern hole (h) can be formed.

[0065] Thereafter, the plating step (S220) may be electrolytically or electrolessly plated so that a partial metal layer (200) is formed within the pattern hole (h). That is, the plating step (S220) may form a partial metal layer (200) in a portion of the pattern hole (h) where the spacer (300) is placed, using the photoresist layer (P) as a barrier.

[0066] Afterwards, in the step of removing the cover layer (S230), when the photoresist layer (P) is removed and cleaned, the remaining portion except for the region where the partial metal layer (200) is formed in the upper metal layer (120) can be exposed, as shown in FIG. 6.

[0067] Although not illustrated, the step (S200) of forming a partial metal layer (200) may further include a step of forming surface roughness on the partial metal layer (200). In the step of forming the surface roughness, the surface roughness of the partial metal layer (200) may be formed to have an Ra value in the range of 0.3 µm to 2.0 µm. The surface roughness of the partial metal layer (200) may be formed by etching, machining, or the like.

[0068] FIG. 7 is a cross-sectional view showing a step of printing a paste layer in a method for manufacturing a ceramic substrate unit according to an embodiment of the present invention, FIG. 8 is a cross-sectional view showing a step of firing a paste layer in a method for manufacturing a ceramic substrate unit according to an embodiment of the present invention, and FIG. 9 is a cross-sectional view showing repeating the printing step and firing step of a paste layer in a method for manufacturing a ceramic substrate unit according to an embodiment of the present invention.

[0069] As illustrated in FIGS. 7 to 9, the step (S300) of forming a spacer (300) may include a step (S310) of placing a screen mask (11) on which a conductive paste (not shown) is applied on a ceramic substrate (100), and printing a paste layer (310) on a partial metal layer (200) by passing the paste through an open pattern area of ​​the screen mask (11) using a squeegee (20) that moves along one direction of the screen mask (11), and a step (S320) of firing the paste layer (310).

[0070] Referring to Fig. 7, the step (S310) of printing the paste layer (310) may use a screen printing device (10) configured such that a screen mask (11) is supported by a frame (12). Here, the screen printing device (10) is shown in a smaller size than the actual size for convenience, with the remaining components omitted to emphasize the configuration of the screen mask (11) and the frame (12). In the screen printing device (10), the frame (12) may support a screen mask (11) having a certain shape, for example, a mesh shape having a square shape, and position it spaced apart from the screen mask (11) on a ceramic substrate (100). At this time, the conductive paste may be uniformly applied to one surface of the screen mask (11).

[0071] In the step (S310) of printing the paste layer (310), the conductive paste applied to the screen mask (11) is pressed by a squeegee (20) moving in one direction (the direction of the arrow in FIG. 7) and is discharged onto the upper surface of the partial metal layer (200) through the open pattern area of ​​the screen mask (11), thereby forming the paste layer (310). At this time, the conductive paste may not pass through a portion covered by the emulsion pattern formed on the screen mask (11), but may be discharged through a gap of the screen mask (11) that is not covered by the emulsion pattern. Although not shown, the emulsion pattern of the screen mask (11) may be formed so that the paste does not pass through the remaining areas except for some areas where the spacers (300) are arranged.

[0072] Referring to FIG. 8, the step (S320) of firing the paste layer (310) can form a eutectic bonding layer (400) by reacting the partial metal layer (200) and the paste layer (310). The firing process can be performed in a reducing atmosphere, and firing can be performed at a temperature of 780°C to 850°C. When the partial metal layer (200) includes Ag and the paste layer (310) includes Cu, when heating to a temperature of about 780°C for firing the paste layer (310), the interface region of the partial metal layer (200) and the paste layer (310) can undergo a eutectic reaction to form the eutectic bonding layer (400). In this way, the method for manufacturing a ceramic substrate unit according to an embodiment of the present invention can strongly bond a ceramic substrate (100) and a spacer (300) via a eutectic bonding layer (400) without a separate bonding filler, thereby preventing bending or delamination of the bonding portion, thereby increasing reliability during electrical connection.

[0073] Although not illustrated in detail, the thickness of the paste layer (310) after firing may be reduced compared to the thickness of the paste layer (310) before firing. For example, if the thickness of the paste layer (310) before firing is about 36 μm, the thickness may be reduced to about 20 μm after firing as the binder, etc. included in the paste layer (310) evaporates. Therefore, the step (S310) of printing the paste layer (310) is preferably formed by taking into account that the thickness of the paste layer (310) will be reduced after the firing step (S320).

[0074] Referring to FIG. 9, the step (S300) of forming a spacer (300) can form a spacer (300) composed of a plurality of paste layers (310, 320, 330) by repeatedly performing the step (S310) of printing a paste layer (310) and the step (S320) of firing the paste layer (310). That is, after performing the printing step (S310) and the firing step (S320) to form a first paste layer (310), the printing step (S310) and the firing step (S320) are performed again to form a second paste layer (320) on the first paste layer (310), and the printing step (S310) and the firing step (S320) are repeated once more to form a third paste layer (330) on the second paste layer (320). If a paste layer with a thickness of about 20 μm can be formed by performing a single printing step (S310) and firing step (S320), a spacer (300) with a thickness of 60 μm can be manufactured by stacking the first to third paste layers (310, 320, 330) through three screen printing and firing processes. In this way, the method for manufacturing a ceramic substrate unit of the present invention can form the spacer (300) as thick as desired through multiple screen printing and firing processes.

[0075] The above description is merely an illustrative illustration of the technical idea of ​​the present invention, and those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the technical idea of ​​the present invention, and the scope of the technical idea of ​​the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of the rights of the present invention.

Claims

1. A step of preparing a ceramic substrate having a metal layer formed on the upper surface of the ceramic substrate; A step of forming a partial metal layer in some area of ​​the above metal layer; and A method for manufacturing a ceramic substrate unit, comprising the step of forming a spacer by printing a conductive paste on the above partial metal layer.

2. In paragraph 1, The step of forming the above spacer is: A step of placing a screen mask with a conductive paste applied thereto on the ceramic substrate, and printing a paste layer on the partial metal layer by passing the paste through an open pattern area of ​​the screen mask using a squeegee moving along one direction of the screen mask; and A method for manufacturing a ceramic substrate unit, comprising a step of firing the above paste layer.

3. In paragraph 2, The step of forming the above spacer is: A method for manufacturing a ceramic substrate unit, wherein a spacer composed of a plurality of paste layers is formed by repeatedly performing the steps of printing the paste layer and firing the paste layer.

4. In paragraph 2, The step of firing the above paste layer is: A method for manufacturing a ceramic substrate unit by reacting the above-mentioned partial metal layer and the above-mentioned paste layer to form a eutectic bonding layer.

5. In paragraph 4, A method for manufacturing a ceramic substrate unit, wherein the partial metal layer comprises Ag and the paste layer comprises Cu.

6. In paragraph 5, A method for manufacturing a ceramic substrate unit in which the above eutectic bonding layer is made of an Ag-Cu alloy.

7. In paragraph 1, The step of forming the above partial metal layer is: A step of forming a cover layer having a pattern hole formed in a shape corresponding to the partial area on the metal layer of the ceramic substrate; A step of plating so that a partial metal layer is formed within the pattern hole; and A method for manufacturing a ceramic substrate unit, comprising the step of removing the above cover layer.

8. In paragraph 7, The step of forming the above cover layer is: A step of forming a photoresist layer on the metal layer; A step of placing a mask covering the remaining portion except for the above-mentioned part on the photoresist layer and then exposing it; and A method for manufacturing a ceramic substrate unit, comprising a step of developing an exposed portion to form a pattern hole in the photoresist layer.

9. In paragraph 7, The step of forming the above partial metal layer is: Further comprising a step of forming surface roughness on the above partial metal layer, A method for manufacturing a ceramic substrate unit having a surface roughness Ra value of 0.3 ㎛ to 2.0 ㎛.

10. A ceramic substrate having a metal layer formed on the upper surface of the ceramic substrate; a partial metal layer formed in some area of ​​the above metal layer; and A ceramic substrate unit including a spacer formed by printing a conductive paste on the above partial metal layer.

11. In paragraph 10, The above spacer comprises a plurality of paste layers, A ceramic substrate unit in which each of the plurality of paste layers is fired after the conductive paste is printed.

12. In paragraph 11, A ceramic substrate unit in which the above partial metal layer reacts with the above paste layer to form a eutectic bonding layer.

13. In paragraph 12, A ceramic substrate unit wherein the partial metal layer comprises Ag and the paste layer comprises Cu.

14. In paragraph 13, The above eutectic bonding layer is a ceramic substrate unit made of an Ag-Cu alloy.

15. In paragraph 10, A ceramic substrate unit having a surface roughness of the above partial metal layer having an Ra value of 0.3 ㎛ to 2.0 ㎛.

16. In paragraph 10, A ceramic substrate unit formed such that the area of ​​the above partial metal layer is larger than the area of ​​the above spacer.

17. In paragraph 16, A ceramic substrate unit in which the distance between the side surface of the above-mentioned partial metal layer and the side surface of the above-mentioned spacer is 0.01㎛ or more.

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