Metal mask and manufacturing method

Abstract

To provide a metal mask excellent in stability as a structure while having a high through-hole ratio.SOLUTION: In the metal mask in which a plurality of through-holes are formed side by side in a thin film metal base material, the width x (μm) of a rib located between the through-holes is 90 μm or more and 180 μm or less, and x and the longitudinal dimension y (μm) of the through-hole satisfy the following formula: Y ≤ 0. 0321x3-14. 814x2 + 2324. 3x - 100503 SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a metal mask, more particularly to a metal mask suitable for forming components of a multilayer ceramic capacitor (MLCC). The present invention also relates to a method for manufacturing this metal mask. [Background technology]

[0002] MLCCs are chip-type capacitors with multiple layers of internal electrodes and dielectric layers. While MLCCs are becoming smaller, they still require capacitance as a capacitor. In order to increase capacitance without increasing size, it is necessary to reduce the thickness of the internal electrodes and increase the number of layers. Screen printing has traditionally been used to form the internal electrodes, but by using the sputtering method, it is possible to form thinner internal electrodes and increase the number of layers compared to conventional methods.

[0003] One method for producing metal masks used in sputtering, vapor deposition, etc. is to wet-etch a thin metal substrate (see, for example, Patent Document 1). Material flying from the target passes through through-holes formed by etching, and is deposited at a predetermined position with predetermined dimensions and shape. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5382259 Summary of the Invention [Problem to be solved by the invention]

[0005] In normal film formation, many through-holes are formed with shapes and dimensions corresponding to one product. By forming these through-holes with shapes and dimensions corresponding to multiple products and cutting out (singularizing) the multiple formed films into shapes and dimensions corresponding to one product, it is possible to produce more products from a substrate of the same area, improving production efficiency.

[0006] However, this method increases the area ratio of the through holes in the metal mask while decreasing the area ratio of the metal portion, which may reduce the stability of the structure. The inventors have investigated this issue from various angles and completed the present invention.

[0007] In view of the above circumstances, an object of the present invention is to provide a metal mask that has a high through-hole ratio and is also excellent in stability as a structure. [Means for solving the problem]

[0008] A first aspect of the present invention is a metal mask having a thin film metal substrate with a plurality of through holes arranged in a row. In this metal mask, the width x (μm) of the ribs located between the through holes is 90 μm or more and 180 μm or less, and x and the longitudinal dimension y (μm) of the through holes satisfy the following formula: y≦0.0321x 3 -14.814x 2 +2324.3x-100503

[0009] A second aspect of the present invention is a method for producing a metal mask having a thin film metal substrate with a plurality of through holes formed in an array. In this manufacturing method, the longitudinal dimension y (μm) of the through hole to be formed and the set width x (μm) of the rib located between the through holes are set so that x is 90 μm or more and 180 μm or less and satisfy the following formula, and etching is performed based on this setting to form the through hole. y≦0.0321x 3 -14.814x 2+2324.3x-100503 [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a metal mask that has a high through-hole ratio and is also excellent in stability as a structure. [Brief explanation of the drawings]

[0011] [Figure 1] 10A and 10B are diagrams illustrating through holes and ribs in a metal mask. [Figure 2] FIG. 1 is a schematic diagram showing an evaluation area in the study. [Figure 3] FIG. 10 is a schematic diagram showing twisting of a rib. [Figure 4] 10 is a table showing the measurement results of rib width. [Figure 5] 10 is a table showing the measurement results of rib width. [Figure 6] 10 is a table showing the measurement results of rib width. [Figure 7] 10 is a table showing the measurement results of rib width. [Figure 8] 10 is a table showing average twist range values ​​in the study. [Figure 9] 10 is a table showing average twist range values ​​in the study. [Figure 10] 10 is a graph showing the relationship between the twist range average value and the slit length for each rib width in the study. [Figure 11] 10 is a graph showing the relationship between the twist range average value and the slit length for each rib width in the study. [Figure 12] 10 is a graph showing the relationship between the twist range average value and the slit length for each rib width in the study. [Figure 13] 10 is a graph showing the relationship between the twist range average value and the slit length for each rib width in the study. [Figure 14] 1(a) and 1(b) are diagrams showing a process of a manufacturing procedure for an MLCC component using large-area deposition. [Figure 15]10 is a graph showing an example of the relationship between rib width and maximum slit length in a study. [Figure 16] 10 is a graph showing an example of the relationship between rib width and maximum slit length in a study. DETAILED DESCRIPTION OF THE INVENTION

[0012] An embodiment of the present invention will be described with reference to FIGS. As already explained, component manufacturing efficiency can be increased by simultaneously depositing thin films for multiple components using a metal mask. However, by laying out these through holes with as small an interval as possible, it becomes possible to further increase the number of components that can be produced using one metal mask, further improving manufacturing efficiency.

[0013] On the other hand, when the spacing between the through holes becomes smaller, the ribs 2, which are the metal portions of the metal mask 1 that separate the through holes 10, become elongated, as shown in Figure 1. Although the metal mask 1 is made of metal, its thickness is quite thin, at 100 μm or less, and the inventors' investigations revealed that if the ribs 2 become too thin, problems will arise during film formation.

[0014] Specifically, since only both longitudinal ends of the rib 2 are supported by other metal parts, the stability of the unsupported middle longitudinal section depends solely on its own rigidity. Therefore, even a slight external force when installing the metal mask 1 in a film-forming apparatus for film formation can easily cause the rib to bend and displace in the width direction (hereinafter, this displacement may be referred to as "twist"), and the metal mask 1 may be installed in the film-forming apparatus in a state where the twist is not completely restored. That is, if the rib 2 becomes too thin in an attempt to further improve manufacturing efficiency, there is a high possibility that the shape of the film formed based on the through holes will not be as designed in parts, and the shape will change with each film forming process, making it unstable. As a result, defective products will be generated, making it difficult to improve manufacturing efficiency.

[0015] The phenomenon that causes the discrepancy between the through-hole design and the actual film shape is not limited to the displacement of the rib mentioned above, but also includes, for example, deviation of the rib width from the set width due to the accuracy of etching when forming the through-hole. However, because there are technical limits to this accuracy, it will be difficult to improve beyond the current situation unless a new breakthrough occurs. Therefore, the inventors have studied the range of the width of the rib 2 that allows for suitable film formation while improving manufacturing efficiency.

[0016] (Preparation of thin film metal substrate) A metal substrate made of SUS430 and having a thickness of 50 μm was prepared. Since the ease with which the ribs twist depends on the longitudinal dimension of the rib itself, multiple sets of ribs with different longitudinal dimensions and width dimensions were formed on the metal substrate, and the degree of twisting of the ribs during the standing operation was measured.

[0017] (Formation of through holes) Twelve through-holes (slits) of the same width were formed in a metal substrate by wet etching, and eleven ribs of the same width were fabricated between the through-holes. The following 12 types of slit length (Sl) and the following four types of rib width (Rw) were used. All measurements are in μm. Slit length: 35000, 30000, 25000, 21502, 18000, 16000, 13830, 9994, 7692, 5062, 3601, 1363 Rib width: 50, 65, 80, 90, 120, 150, 180, 210, 240, 270, 300, 400, 500, 1000 The slit width (Sw) was fixed at 1500 μm. As a result of the above, a total of 48 evaluation regions consisting of combinations of Sl and Rw were formed on the metal substrate, and metal masks for measurement were fabricated. Figure 2 shows the outline of the evaluation regions.

[0018] (Rib width measurement and rib width range calculation) The completed metal mask was placed on the stage of a measuring device (Nikon NEXIV series VMR-12072) and the actual width dimension of the rib in each measurement area was measured. The measurement points were the width of five consecutive ribs (Rw1 to Rw5 shown in Figure 2) including the center in the width direction within each evaluation area, and were set at the longitudinal center of the rib to match the measurement of the twist range average value described below. The difference (μm) between the maximum and minimum values ​​of the five dimensions obtained was taken as the "rib width range," which indicates the variation in rib width in each region.

[0019] (Measurement of rib twist amount and calculation of twist range average value) The metal mask was placed on the stage of the measuring device, and the widthwise dimensions of five consecutive slits (Sw1 to Sw5 shown in Figure 2), including the widthwise center, were measured among the 12 slits in each measurement area. Based on the assumption that the longitudinal center of the rib is the furthest from the support part and is therefore most susceptible to displacement, the measurement point was set to the longitudinal center of the slit, which reflects this. When twisting occurs in the rib, the width dimension of the slit on one side of the twisted rib becomes smaller, for example, as shown between points P and Q in Figure 3, while the width dimension on the other side becomes larger, as shown between points RS. The difference (μm) between the maximum and minimum values ​​of the five dimensions obtained was taken as the "twist range," which indicates the variation in rib width in each region. Because the twist pattern of each rib changed each time it was placed on the stage, after measurement the metal mask was lifted up and moved away from the stage, then placed back on the stage and the same measurement was carried out, for a total of five measurements. The arithmetic mean of the five twist range measurements obtained in each region was taken as the "average twist range" for each region.

[0020] The measurement results of the rib width are shown in Figures 4 to 7. The rib width range was roughly 2 to 4 μm in all areas, regardless of the dimensions of the slits and ribs. This indicates the dimensional accuracy of etching at the current technological level, and means that even if twisting of the ribs could be completely eliminated, this variation in the dimensions of the deposited film would be unavoidable.

[0021] Next, the average twist range values ​​are shown in Figures 8 and 9. For all rib widths, the amount of twist tended to increase as the slit length increased, and there were also areas where the average twist range was more than 10 times the rib width range. Figures 10 to 13 are graphs showing the relationship between the average twist range and slit length for each rib width in this study. As the rib width decreases, the twist range increases, and when the rib width falls below 100 μm, this increase tends to become more pronounced.

[0022] In a metal mask, the upper limit of the twist range average value for performing proper film formation varies depending on the application of the formed structure, but in any case, the difference obtained by subtracting the rib width range from the maximum allowable variation is the upper limit of the twist range average value. Below, we will explain the concept and the upper limit of the twist range average value using an example where the metal mask according to this embodiment is used to produce an internal electrode component of an MLCC.

[0023] 14(a), a large-area film 50 is cut into a plurality of components 60 of the same shape and size as shown in FIG. 14(b). Each component 60 has a rectangular shape in plan view, with a metal thin film 62 made of a nickel alloy or the like formed on a substrate 61 such as a ceramic green sheet, and has a margin 63 along one side in plan view where the metal thin film 62 is not formed. The internal electrode structure of an MLCC can be formed by stacking and integrating multiple components 60 so that the sides with margins 63 are staggered. In an MLCC, external electrodes are disposed at both ends in the direction in which the margins 63 are located, but in this case, the sides with the margins 63 must be electrically disconnected from the external electrodes. Therefore, if the film 50 overflows excessively into the areas that should be the margins 63 due to variations in film formation, the component 60 cannot be used stably.

[0024] The width of the margin 63 depends on the dimensions of the MLCC to be manufactured, but is at least about 10 μm. In this case, if the variation in the planar dimensions of the formed film is 10 μm or more, at least a part of the margin will disappear across the width, potentially resulting in electrical continuity with the external electrode. Based on this, in this embodiment, the upper limit of the twist range average value is set to 6 μm, which is obtained by subtracting the rib width range of 4 μm from 10 μm.

[0025] Based on Figs. 10 to 13, the slit length at which the twist range average value is 6 µm was determined for each set rib width, and the results were as follows. Setting width 50μm: 4073μm Setting width 65μm:5996μm Setting width 80μm: 9967μm Setting width 90μm: 12069μm Setting width 120μm: 20511μm Setting width 150μm: 23072μm Setting width 180μm: 24948μm Setting width 210μm: 27343μm Setting width 240μm: 30357μm Setting width 270μm: 43896μm Setting width 300μm: 53312μm Setting width 400μm: 54922μm Setting width 500μm: 70591μm Setting width 1000μm: 126662μm Of the above, four points with set widths from 90 μm to 180 μm were plotted as shown in Figure 15. However, since it was difficult to conceive of a straight line passing through all four points, a curve passing through all four points was calculated, as shown in Figure 8. It was found that the value of the rib width x at which the average twist range value is 6 μm for a certain slit length y can be expressed by the following formula (A). y=0.0321x 3 -14.814x 2 +2324.3x-100503 …(A)

[0026] Therefore, when the rib width x is 90 μm or more and 180 μm or less, if the rib width x and the slit length y satisfy the relationship shown in the following formula (1) based on the above formula (A), the metal mask can generally be used without problem for manufacturing internal electrode components of MLCCs, and the inventors' studies have revealed that safety can be further ensured if the relationship satisfies formula (1a) obtained by multiplying this by a safety factor. y≦0.0321x 3 -14.814x 2 +2324.3x-100503 …(1) y≦(0.0321x 3 -14.814x 2 +2324.3x-100503)×0.95…(1a)

[0027] From Figure 15, it can be seen that when the rib width is in the range of 120 μm or more and 180 μm or less, increasing the rib width does not significantly increase the slit length. Furthermore, it can be seen that when the rib width is less than 120 μm, twisting of the rib becomes more likely to occur. This finding was first discovered by the inventors.

[0028] Figure 16 shows a graph plotting the entire range of all set widths. From each plot, it was inferred that the relationship between the rib width x and the slit length y changes depending on the value of x, and it was thought that there were roughly four types as follows. This was the first discovery made by the inventors. First range (Sec1 in FIG. 16): x≦90 μm Second range (Sec2 in FIG. 16): 90 μm≦x≦180 μm Third range (Sec3 in FIG. 16): 180 μm≦x≦300 μm Fourth range (Sec4 in FIG. 16): 300 μm≦x Of the above, the second range has already been explained, but for the other three ranges, it was estimated that linear approximation was possible from the plots to which they belong, so linear approximation was attempted for each. As a result, in the first range, if the rib width x and the slit length y satisfy the relationship shown in the following formula (2), twisting of the rib can be suppressed and good film formation can be achieved, and it was considered more preferable if the relationship satisfied formula (2a) obtained by multiplying this by a safety factor. y≦206.2354x-6668.0204…(2) y≦(206.2354x-6668.0204)×0.95 …(2a) In the third range, if the rib width x and the slit length y satisfy the relationship shown in the following formula (3), twisting of the rib can be suppressed and good film formation can be achieved, and it was considered more preferable if the relationship satisfied formula (3a) obtained by multiplying this by a safety factor. y≦244.27x+22653.6 …(3) y≦(244.27x+22653.6)×0.95 …(3a) In the fourth range, if the rib width x and the slit length y satisfy the relationship shown in the following formula (4), twisting of the rib can be suppressed and good film formation can be achieved, and it was considered more preferable if the relationship satisfied formula (4a) obtained by multiplying this by a safety factor. y≦110.0071x-15867.8621…(4) y≦(110.0071x-15867.8621)×0.95 …(4a)

[0029] In the metal mask according to the present embodiment, which is based on the above findings, the relationship between the width of the ribs arranged between the plurality of through holes and the length of the through holes is set to satisfy at least one of the above formulas (1) to (4a), so that the metal mask has a high through hole ratio in a planar view and excellent structural stability. As a result, when formula (1) or (1a) is satisfied, the arrangement efficiency of large-area through holes equivalent to the number of components of an MLCC can be maximized in the mask, which can contribute to the efficient manufacture of components of an MLCC. When the value of x is one of the range boundaries of 90 μm, 180 μm, and 300 μm, either of the range formulas may be applied.

[0030] Furthermore, in the method for manufacturing a metal mask according to this embodiment, which takes into account the above findings, a step of substituting the longitudinal dimension of the through hole to be formed into one of equations (1) to (4) is performed, whereby the longitudinal dimension y (μm) of the through hole to be formed and the set width x (μm) of the rib located between the through holes are set so as to satisfy the used equation. Then, a step of forming the through hole by etching based on the set x and y is performed, whereby the appropriate and minimum rib width can be easily achieved. As a result, the effort of fabricating multiple prototypes to verify the degree of rib twist can be significantly reduced, and a metal mask with high film formation efficiency and minimal rib twist can be produced extremely easily.

[0031] As an example of the film deposition 50, by setting the slit width to 1000 μm, film deposition for 0402 size MLCC can be performed on two surfaces. By setting the slit width to 2500 μm, film deposition for 1005 size MLCC can be performed on two surfaces. By setting the slit width to 500 μm, film deposition for 0201 size MLCC can be performed on two surfaces. When the film 50 is used for an 0402 size MLCC, the slit width is set to 1500 μm, and by dividing it into individual pieces as described above, a component 60 suitable for a 402 size with a long side dimension of the metal thin film 62 of approximately 600 μm can be obtained. The short side dimension of the component 60 is determined by factors such as the size of the MLCC, but the longer the slit length, the more components 60 can be manufactured from one substrate. As described above, the present invention makes it possible to determine the maximum slit length for metal masks that allows for highly accurate film formation 50, thereby contributing to maximizing the efficiency of two-sided mounting. Furthermore, even in metal masks used for forming elongated films with larger or smaller areas, the present invention can significantly contribute to maximizing manufacturing efficiency by optimizing the rib width and slit length.

[0032] Although the present invention has been described above, the specific configuration is not limited to this embodiment, and modifications and combinations of the configuration within the scope of the gist of the present invention are also included.

[0033] For example, the thin-film metal substrate according to the present invention is not limited to stainless steel such as SUS430 used in the above-mentioned study. Therefore, the manufacturing method according to the present invention can be suitably applied to the case where a metal mask is produced using a thin-film metal substrate made of Invar, Super Invar, or the like. If the thin-film metal substrate is made of a magnetic metal material such as those described above, there is an advantage in that it can be fixed to the film-forming apparatus using magnetic force.

[0034] Furthermore, the thickness of the thin-film metal substrate is not limited to 50 μm as in the above study. As the thickness of the thin-film metal substrate increases, the rigidity of the rib increases, so thicknesses of 50 μm or more can also be used without any problems.

[0035] The use of the metal mask according to the present invention is not limited to the internal electrodes of MLCCs described in the embodiments, but can be widely applied to various uses that require the formation of films in elongated shapes. [Explanation of symbols]

[0036] 1 Metal Mask 2. Ribs 10 through holes

Claims

1. A metal mask having a plurality of through holes arranged in a thin film metal substrate, The width x (μm) of the rib located between the through holes is 90 μm or more and 180 μm or less, and x and the longitudinal dimension y (μm) of the through hole satisfy the following formula: Metal mask. y≦0.0321x ３ -14.814x ２ +2324.3x-100503

2. A metal mask having a plurality of through holes arranged in a thin film metal substrate, The width x (μm) of the rib located between the through holes is 180 μm or more and 300 μm or less, and x and the longitudinal dimension y (μm) of the through hole satisfy the following formula: y≦244.27x+22653.6 Metal mask.

3. A metal mask having a plurality of through holes arranged in a thin film metal substrate, The width x (μm) of the rib located between the through holes is 300 μm or more, and x and the longitudinal dimension y (μm) of the through hole satisfy the following formula: y≦110.0071x-15867.8621 Metal mask.

4. A metal mask having a plurality of through holes arranged in a thin film metal substrate, The width x (μm) of the rib located between the through holes is 90 μm or less, and x and the longitudinal dimension y (μm) of the through hole satisfy the following formula: y≦206.2354x-6668.0204 Metal mask.

5. The thin film metal substrate is made of a magnetic metal material. The metal mask according to claim 1 .

6. The magnetic metal material is any one of SUS430, Invar, and Super Invar. The metal mask according to claim 5 .

7. The thickness of the thin film metal substrate is 50 μm or more. The metal mask according to claim 1 .

8. A method for manufacturing a metal mask having a plurality of through holes arranged in a thin film metal substrate, comprising: The longitudinal dimension y (μm) of the through hole to be formed and the set width x (μm) of the rib located between the through holes are set so that y and x satisfy the following formula while x is 90 μm or more and 180 μm or less: performing etching based on the setting to form the through-hole; A method for manufacturing metal masks. y≦0.0321x ３ -14.814x ２ +2324.3x-100503

9. A method for manufacturing a metal mask having a plurality of through holes arranged in a thin film metal substrate, comprising: The longitudinal dimension y (μm) of the through hole to be formed and the set width x (μm) of the rib located between the through holes are set so that y and x satisfy the following formula, with x being 180 μm or more and 300 μm or less: performing etching based on the setting to form the through-hole; A method for manufacturing metal masks. y≦244.27x+22653.6

10. A method for manufacturing a metal mask having a plurality of through holes arranged in a thin film metal substrate, comprising: The longitudinal dimension y (μm) of the through hole to be formed and the set width x (μm) of the rib located between the through holes are set so that y and x satisfy the following formula while x is 300 μm or more: performing etching based on the setting to form the through-hole; A method for manufacturing metal masks. y≦110.0071x-15867.8621

11. A method for manufacturing a metal mask having a plurality of through holes arranged in a thin film metal substrate, comprising: The longitudinal dimension y (μm) of the through hole to be formed and the set width x (μm) of the rib located between the through holes are set so that y and x satisfy the following formula while x is 90 μm or less: performing etching based on the setting to form the through-hole; A method for manufacturing metal masks. y≦206.2354x-6668.0204

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