JP3952743B2 - Manufacturing method of fine metal parts - Google Patents

Description

【図面の簡単な説明】
【図１】同図(a)〜(e)は、それぞれ本発明の製造方法によって微細金属部品を製造する工程の一例を示す断面図である。
【図２】同図(a)〜(d)は、微細金属部品の親金型から、上記製造工程に使用する型を形成する工程の一例を示す断面図である。
【符号の説明】
１ 導電膜
１′ 導電ペースト
２ 導電性基体
３ 型
３ａ 通孔パターン
４ 微細金属部品
ＥＭ 電鋳型[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a fine metal part having a predetermined three-dimensional shape.
[0002]
[Prior art]
Recently, metal parts having a fine three-dimensional shape with a thickness of over 100 μm and submicron accuracy have been put into practical use as functional parts for semiconductor chips such as LSIs or parts for micromachines. It's getting on.
A direct LIGA (Lithographie Galvanoformung Abformung) method is useful as a method for producing such fine metal parts.
[0003]
In this direct LIGA method, for example, a fine metal part having a high aspect ratio (height / width) can be manufactured or processed with a precision in the micron region, and a fine metal part having a height of several hundred μm can be manufactured. Can be easily manufactured, and is expected to be applied in a wide range of fields.
In order to manufacture a fine metal part by the direct LIGA method, first, a photosensitive resist structure is formed on a conductive substrate. The thickness of the resist structure is set to the height of the fine metal part to be manufactured.
[0004]
Next, the resist structure is irradiated with X-rays such as SR (Synchrotron Radiation) light through a mask having a predetermined pattern, and then developed using a resist-dedicated developer to form a resist structure. Then, a fine hole pattern reaching the surface of the conductive substrate corresponding to the shape of the fine metal part is formed.
Then, by selectively growing a plating film on the conductive substrate exposed at the portion of the through hole pattern by electroplating using the conductive substrate as an electrode, a fine metal component corresponding to the shape of the through hole pattern can be obtained. After the formation, the resist structure and the conductive substrate are removed to obtain a fine metal part.
[0005]
However, as described above, the direct LIGA method has a very high accuracy but is expensive to manufacture. The resist structure in which a through-hole pattern is formed by X-ray irradiation is used only once for the production of fine metal parts. Can not do it. For this reason, there is a limit to mass production of fine metal parts, and there is a problem that the manufacturing cost of individual fine metal parts is high. For example, when a wafer having a diameter of 4 inches is used as the conductive substrate, the number of fine metal parts that can be manufactured at one time is about several tens to several thousand.
[0006]
Although it is conceivable to use ultraviolet rays that are cheaper to irradiate than X-rays, ultraviolet rays have a longer wavelength than X-rays and are not directional. The edge portion of the hole pattern is rounded or light is diffused in the depth direction, so that the shape of the through hole pattern is easily deformed. For this reason, there exists a problem that the precision of the shape of a fine metal component falls.
In addition, although the wavelength of the electron beam is shorter than that of ultraviolet rays, the electron beam has a large interaction with the material forming the resist structure, and therefore cannot penetrate deeply in the thickness direction of the resist structure. For this reason, there is a limit to the thickness of the resist structure that can form a through-hole pattern, and the electron beam is not suitable for manufacturing a fine metal part having a particularly high aspect ratio.
[0007]
[Problems to be solved by the invention]
As a manufacturing method of fine metal parts instead of the direct LIGA method, the shape of the fine metal parts is formed by injection molding or reactive injection molding using a fine mold (parent mold) that is the basis of the fine metal parts. There is a method of manufacturing a fine metal part in the same manner as the direct LIGA method after forming a resin die having a corresponding fine hole pattern and then bonding the die to the surface of a conductive substrate. .
[0008]
In this method, for example, a resist mold is formed by forming a fine pattern by X-ray irradiation and development after irradiation (hereinafter referred to as “X-ray lithographic method”) and electroforming the fine pattern. By producing a large number of resin molds from one parent mold while maintaining high accuracy by the X-ray lithographic method, a larger amount of fine metal parts than before, And it becomes possible to manufacture at low cost.
[0009]
The resin mold needs to be fixed to the surface of the conductive substrate using an adhesive so as not to be displaced during electroplating.
However, the adhesive easily protrudes into the part of the through-hole pattern of the mold at the time of bonding, and if it is left as it is, it prevents the growth of the plating film during electroplating and cannot form a fine metal part having a predetermined shape. Cause.
Therefore, in order to remove the protruding adhesive, it is conceivable that the inside of the through-hole pattern before electroplating is washed with a solvent (wet etching) or dry-etched. The mold is likely to be damaged, and the shape of the through-hole pattern is likely to be deformed, particularly when the edge of the through-hole pattern is rounded or the side wall of the through-hole pattern is scraped off. For this reason, there exists a problem that the reproducibility of the shape of a fine metal component falls.
[0010]
The object of the present invention is to produce a fine metal part having a high aspect ratio with a sharp corner edge and excellent verticality in the height direction with good reproducibility and in a low cost and in a large number of steps. The object is to provide a method of manufacturing a fine metal part.
[0011]
[Means for Solving the Problems and Effects of the Invention]
The invention according to claim 1 is a fine metal powder having an average particle size of 400 nm or less. (Excluding chain-like ones) An electroforming mold in which a mold made of an insulating material having a fine through hole pattern corresponding to the shape of a fine metal part is fixed on a conductive substrate through a conductive film made of a conductive paste containing as a conductive component And a plating film selectively formed on the surface of the conductive film exposed at the hole pattern portion of the electroforming mold or on the surface of the conductive substrate and the conductive film by electroplating using these portions as electrodes. And a step of forming a fine metal part corresponding to the shape of the through-hole pattern.
[0012]
In order to solve the above-mentioned problem, the inventor examined using a conductive paste using metal powder as a conductive component instead of an adhesive. That is, with the resin mold fixed on a conductive substrate through a conductive film made of a conductive paste, the surface of the conductive film exposed at the hole pattern portion of the mold or the conductive paste is bonded to the conventional adhesive. A plating film is selectively formed by electroplating using these portions as electrodes on the surface of a conductive substrate made of conductive paste that is exposed at the portion of the through-hole pattern using the same as the agent and the conductive paste that protrudes there. It was thought that various problems associated with the protrusion and removal of the adhesive could be solved by growing the adhesive.
[0013]
However, when a conventional conductive paste is used in this method, the grain size of the metal crystal grains in the formed fine metal part changes discontinuously in the whole or part of the thickness direction. Therefore, it has been found that a fine metal part having a uniform crystal structure throughout and having good characteristics cannot be manufactured.
Further investigation of the cause revealed the following facts.
That is, the conventional conductive paste contains a metal powder having an average particle diameter of 1 μm or more as a conductive component, which is not so small as compared with a fine metal part.
[0014]
For this reason, when the surface of a conductive film formed using a conventional conductive paste is viewed microscopically at the level of the size of a fine metal part, the conductive part from which the metal powder is exposed and the insulating part between them are metal. According to the size of the powder, it is distributed in irregular spots, which is not electrically uniform.
Moreover, when the surface of the conductive film is similarly microscopically seen from the level of the size of the fine metal part, it has irregularities corresponding to the size of the metal powder and not so small compared to the size of the fine metal part. It is not flat.
[0015]
The crystal structure of the plating film formed by electroplating is easily affected by the base, and as described above, the surface of the plating film is not electrically uniform, and the growth is particularly difficult when the plating film is grown on a non-flat conductive film. The grain size of crystal grains generated at the initial stage of the film tends to be considerably larger than the original grain size obtained when, for example, a plating film is grown on a flat metal surface.
Then, when the growth of the film progresses and the surface approaches the flat metal surface, the crystal grains having the original grain size equivalent to the case of growing on the flat metal surface are generated, and then The film grows with this particle size.
[0016]
For this reason, the plating film grown on the conductive film does not have a uniform crystal structure throughout the thickness direction, and has a distribution in which the grain size of the metal crystal grains changes discontinuously in the thickness direction. It will be a thing.
Specifically, for example, when the conductive film is formed over the entire bottom surface of the through hole pattern on the conductive substrate, the fine metal part has a region in which the crystal grain size of the metal is larger than the original grain size. And a two-layer structure with a region having an original particle size on the top.
[0017]
In addition, when the conductive paste is used in the same manner as a conventional adhesive, the conductive substrate is basically exposed at the bottom of the through hole pattern, and in this region, the grain size of the metal crystal grains is from the beginning. A plated coating having an original particle size grows. However, in the portion where the conductive paste protrudes, on the conductive film made of the conductive paste, a region where the crystal grain size of the metal is larger than the original particle size is generated as described above.
Therefore, in any of the above cases, the manufactured fine metal part cannot exhibit the intended physical, mechanical, or electrical characteristics in the region where the grain size of the crystal grains is larger than the original.
[0018]
For this reason, when the fine metal part is viewed as a whole, there arises a problem that desired physical, mechanical or electrical characteristics cannot be obtained.
In addition, since the fine metal parts contain the parts with different physical and mechanical properties as described above, they may be distorted or damaged in some cases due to changes in external conditions such as temperature changes. There is also a fear.
Therefore, the inventor further examined the conductive component included in the conductive paste, and as a result, the average particle size was 400nm or less It has been found that a sufficiently fine metal powder may be used as compared with a fine metal part. That is, the conductive film is electrically uniform even when viewed microscopically at the level of the size of the fine metal part because the fine metal powder is evenly dispersed. Further, the surface of the conductive film has only unevenness sufficiently smaller than the fine metal part corresponding to the size of the metal powder, and has high smoothness.
[0019]
Therefore, when a plating film is grown on the surface of the conductive film by electroplating, crystal grains having an original grain size equivalent to those grown on a flat metal surface from the initial stage of film formation are obtained. Generate.
Therefore, according to the structure of claim 1, a fine metal part having a single structure capable of exhibiting desired physical, mechanical, and electrical characteristics because the crystal grains have an original grain size is manufactured. The manufactured fine metal part has good characteristics.
[0020]
Invention of Claim 2 is a manufacturing method of the fine metal component of Claim 1 using the electrically conductive paste which contains a metal powder in the ratio of 5-95 weight% in solid content.
If the content ratio of the metal powder is less than 5% by weight, a conductive film having sufficient conductivity may not be formed. Then, crystal grains having an original grain size cannot be generated from the initial stage of film formation on the conductive film, and there is a possibility that a fine metal part having good characteristics cannot be obtained.
[0021]
Conversely, when the content ratio of the metal powder exceeds 95% by weight, the ratio of the binder is relatively insufficient, and the mold made of the insulating material by the binder is placed on the conductive substrate. The function of bonding and fixing becomes insufficient, and it is likely to cause mold displacement during electroplating, which may reduce the reproducibility of the shape of the fine metal part.
In order to achieve the effect of the invention according to claim 1 better, it is desirable that the average particle size of the metal powder is as small as possible even within the above range. 200nm It is preferable that:
[0022]
Therefore, the invention according to claim 3 has an average particle size of 200nm It is a manufacturing method of the fine metal component of Claim 1 using the metal powder which is the following.
In addition, in order to promote smoother crystal growth during electroplating and to manufacture fine metal parts having a better crystal structure, the metal lattice constant forming the metal powder and the metal lattice forming the plating film are used. It is desirable that the constant is as close as possible, and it is particularly preferable that the difference in lattice constant between the two metals is 5% or less.
[0023]
Therefore, the invention according to claim 4 is the method for producing a fine metal part according to claim 1, wherein a metal powder containing a metal having a lattice constant difference of 5% or less from the metal forming the plating film is used.
Although there are various combinations of metals that satisfy the above conditions, it is particularly preferable to use the same metal as the metal that forms the metal powder and the metal that forms the plating film. Thereby, the difference in the lattice constant between the two metals is set to 0%, and a fine metal part having better characteristics can be manufactured by smoother crystal growth.
[0024]
Therefore, the invention according to claim 5 is the method for producing a fine metal part according to claim 1 using metal powder containing the same metal as the metal forming the plating film.
Specific examples of such metals include one metal selected from the group consisting of Ni, Fe, Co, Ag, Au, Pt, Cu, In, Ir, Re, Rh, and Pd, or two or more metals. Alloy.
Therefore, the invention according to claim 6 is the one metal selected from the group consisting of Ni, Fe, Co, Ag, Au, Pt, Cu, In, Ir, Re, Rh, and Pd, or two or more metals. 2. The method for producing a fine metal part according to claim 1, wherein a metal powder formed of the alloy is used.
[0025]
Contract Claim 7 The invention described in the above is the method for producing a fine metal part according to claim 1, wherein the metal powder is formed by reacting a metal ion and a reducing agent in the liquid to precipitate in the liquid.
[0026]
Average particle size 400nm or less The fine metal powder can be produced by various methods such as a gas phase method and a liquid phase method. However, according to the above reduction precipitation method, it is possible to form a metal powder having a uniform particle size and a sharp particle size distribution. This is because the reduction reaction proceeds uniformly in the system.
So claims 7 According to the configuration, since the conductivity of the conductive film can be made more uniform, a fine metal part having even better characteristics can be manufactured.
[0027]
Claim 8 The invention described in claim 3 uses a trivalent titanium compound as a reducing agent. 7 It is a manufacturing method of the described fine metal component.
Various compounds can be considered as the reducing agent used in the reduction precipitation method. However, among these, when a trivalent titanium compound such as titanium trichloride is used, the solution after the metal powder is deposited and formed can be regenerated to a state usable for the production of the metal powder by repeating the electrolytic regeneration. There are advantages.
[0028]
Claim 9 The invention according to claim 1 is a method for producing a fine metal part according to claim 1, wherein Cu powder obtained by precipitating metal Cu into ultrafine particles by lowering the pH of a solution containing Cu (I) ammine complex ions is used. is there.
In the case where the metal powder is Cu powder, by adopting the above method, Cu powder having higher purity and smaller particle diameter can be produced more safely. Claims 9 According to the configuration, the conductivity of the conductive film can be made more uniform, and the smoothness of the surface can be further improved, so that a fine metal part having better characteristics can be manufactured.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described below.
<Conductive paste>
The conductive paste that forms the conductive film has an average particle size as a conductive component. 400nm or less These metal powders are blended at a predetermined ratio together with a binder such as a resin and a solvent. Also ,liquid Atherosclerotic tree Fat The solvent may be omitted.
[0030]
(Metal powder)
As described above, the average particle size of the metal powder 4 A thing of 00 nm or less is used. The reason for this is as described above. In addition, considering the production of fine metal parts having better characteristics by making the conductivity of the conductive film more uniform and further improving the smoothness of the surface, the average particle size of the metal powder is Even within the above range, the thickness is particularly preferably 200 nm or less. In addition, in consideration of maintaining the uniformity of the conductive film by preventing aggregation of the metal powder in the conductive paste and uniformly dispersing the metal powder in the conductive paste, the average particle size of the metal powder is Even within the above range, it is particularly preferably 10 nm or more.
[0031]
The metal powder preferably contains a metal having a lattice constant difference of 5% or less from the metal forming the plating film. The reason for this is as described above. In addition, considering the production of fine metal parts having better characteristics by promoting smooth crystal growth, the difference in lattice constant is more preferably 3% or less. More preferably, the difference in lattice constant is set to 0% by using the same metal as the metal forming the metal powder and the metal forming the plating film.
[0032]
Note that the lengths of the three edges of the crystal unit cell are a, b, and c, and the angle between the a axis and the b axis is γ, and the angle between the b axis and the c axis is α, c axis When the angle formed with the a-axis is β, the six of a, b, c, α, β, and γ are called lattice constants. The difference in lattice constants in the present invention is 5% or less. This means that the difference is within 5% in all the six lattice constants corresponding to the metals to be compared.
[0033]
The metal powder satisfying such conditions is preferably made of a material usually used in fine metal parts, and as described above, Ni, Fe, Co, Ag, Au, Pt, Cu, In, Ir, Re It is preferable to use a metal powder formed from one metal selected from the group consisting of Rh, and Pd, or an alloy of two or more metals.
The metal powder is preferably formed by the reduction precipitation method as described above.
[0034]
In the reduction precipitation method, first, a reducing agent, for example, a trivalent titanium compound such as titanium trichloride and a solution in which, for example, trisodium citrate is dissolved (hereinafter referred to as “reducing agent solution”), ammonia water or the like. To adjust the pH to 9-10. As a result, trivalent titanium ions are combined with citric acid as a complexing agent to form a coordination compound, and the activation energy when oxidized from Ti (III) to Ti (IV) is reduced. The potential increases. Specifically, the potential difference between Ti (III) and Ti (IV) exceeds 1V. This value is significantly higher than the reduction potential from Ni (II) to Ni (0), the reduction potential from Fe (II) to Fe (0), and the like. Therefore, various metal ions having a reduction potential lower than that of these metals can be efficiently reduced to deposit and form metal powder.
[0035]
Next, a solution containing one or more metal ions is added to the reducing agent solution.
Then, when Ti (III) functions as a reducing agent and oxidizes itself to Ti (IV), metal ions are reduced and deposited in the liquid. That is, a metal powder made of the metal simple substance or alloy is deposited and formed in the liquid.
The formed metal powder has a uniform particle size and a sharp particle size distribution. This is because the reduction reaction proceeds uniformly in the system. Therefore, according to such a metal powder, the conductivity of the conductive film can be made more uniform, so that a fine metal part having better characteristics can be manufactured.
[0036]
The reducing agent solution after depositing the metal powder can be used for the production of the metal powder by the reduction deposition method by repeating the electrolytic regeneration as described above and repeatedly. That is, by reducing the Ti (IV) to Ti (III) by applying a voltage, for example, by putting the reducing agent solution after depositing the metal powder into an electrolytic cell, the reducing agent for electrolytic deposition again. Can be used as a solution. This is because titanium ions are hardly consumed during electrolytic deposition, that is, they are not deposited together with the metal to be deposited. The amount of titanium ions deposited is 100 ppm or less of the total amount of the metal powder.
[0037]
When the metal powder is Cu powder, such Cu powder is preferably formed by lowering the pH of a solution containing Cu (I) ammine complex ions to precipitate metal Cu into ultrafine particles.
In this method, a Cu (I) ammine complex that is stable when the solution is in a basic state is destabilized when the solution is in an acidic state, and Cu (I) ions (Cu ¹⁺ ) Cu (II) ion (Cu ²⁺ ) And metal Cu (Cu) are used as a result of disproportionation decomposition reaction, and metal Cu is precipitated in the solution.
[0038]
According to this method, Cu powder can be produced more safely without using hydrazine or a hydrazine compound, which is a dangerous substance, used as a reducing agent in the reduction precipitation method. Therefore, production facilities and storage facilities with strict safety management are not required.
The solution containing Cu (I) ammine complex ions is prepared by adding metal Cu to a solution containing Cu (II) sulfate, ammonia and ammonia sulfate, for example, and reacting them under oxygen-free conditions. The solution containing Cu (II) ions after depositing metal Cu to obtain Cu powder can be reused as a starting material when preparing a solution containing Cu (I) ammine complex ions again. That is, the solution can be used almost semipermanently.
[0039]
Therefore, the production cost of Cu powder can be further reduced than before.
Moreover, in all the processes from the preparation process of the solution containing the Cu (I) ammine complex ion described above to the process of depositing Cu metal to produce Cu powder, there is a risk of eutectoid with Cu such as phosphate. It is not necessary to add a component containing certain elements. In addition, as the disproportionation decomposition reaction conditions are adjusted to increase the deposition rate of metal Cu, the amount of impurities mixed in can be reduced.
[0040]
Therefore, the purity of Cu powder can be maintained at a high purity even when a low-purity and inexpensive metal Cu such as recycled Cu is used for preparing a solution containing, for example, a Cu (I) ammine complex ion. It becomes.
In addition, by performing the above disproportionation decomposition reaction under stirring, for example, the precipitation of metal Cu can be progressed almost uniformly in the solution, so that the generated Cu powder has a particle size between a plurality of particles. It will be almost complete.
[0041]
Moreover, when the disproportionation decomposition reaction is carried out under stirring, it is possible to prevent the metal Cu from selectively precipitating only in specific parts of the individual particles and to average the growth of the particles in all directions. The produced Cu powder has a substantially spherical shape.
Therefore, when the Cu powder is used, the conductivity of the conductive film can be made more uniform, and the smoothness of the surface can be further improved, so that a fine metal part having better characteristics can be manufactured.
[0042]
(Binder)
As the binder for forming the conductive paste together with the metal powder, any of various conventionally known compounds can be used as the binder for the conductive paste. Examples of such a binder include thermoplastic resins, curable resins, and liquid curable resins. Particularly preferred are acrylic resins, fluorine resins, phenol resins and the like.
[0043]
(Conductive paste)
The conductive paste is prepared by blending a metal powder and a binder together with an appropriate solvent at a predetermined ratio. Also, as mentioned above, liquid curable resin Fat The solvent may be omitted.
According to such a conductive paste, the function of the metal powder having a small average particle diameter as described above can form a conductive film having more uniform conductivity than before and having excellent surface smoothness. Fine metal parts having good characteristics can be produced.
[0044]
The blending ratio of each component is not particularly limited, but the solid content, that is, the ratio of the metal powder in the total amount of the metal powder and the binder is preferably 5 to 95% by weight. The reason for this is as described above.
<Production of electroforming mold>
In the manufacturing method of the present invention, as shown in FIG. 1 (b), first, through a conductive film 1 made of the above-described conductive paste, a fine passage corresponding to the shape of a fine metal part is formed on a conductive substrate 2. An electroforming mold EM having a hole pattern 3a and having a shape fixed with a mold 3 made of an insulating material is produced.
[0045]
As a specific process, first, as shown in FIG. 1 (a), a conductive paste 1 'is applied to the entire surface of a conductive substrate 2 such as a metal plate, and then, as shown in FIG. 1 (b). Overlay mold 3 as shown. Then, the conductive paste 1 ′ is dried, and when the binder is a curable resin, the conductive paste 1 ′ is cured to form the conductive film 1, and the mold 3 is fixed on the conductive substrate 2. In the electroforming mold EM shown in the figure produced by such a process, the entire bottom surface of the through-hole pattern 3a is covered with the conductive film 1 having excellent characteristics as described above. There are no problems involved.
[0046]
Although not shown, the electroforming mold EM can also be manufactured using a conductive paste in the same manner as a conventional adhesive. That is, after the conductive paste is applied to the lower surface of the mold 3 and then superimposed on the conductive substrate 2, the conductive paste is dried, and when the binder is a curable resin, it is cured. The mold 3 may be fixed on the conductive substrate 2 to produce the electroforming mold EM. In this case, as described above, basically, the conductive substrate 2 is exposed at the bottom of the through-hole pattern 3a, and the conductive substrate 2 is particularly formed in a part around the through-hole pattern 3a. Although the conductive film is formed, the conductive film has excellent characteristics as described above, and thus does not need to be removed. Therefore, in this case as well, there is no problem associated with the removal of the adhesive.
[0047]
The mold 3 can be formed by various methods. In particular, the mold 3 is formed by injection molding or reactive injection molding using the parent mold prepared by the X-ray lithography method and electroforming as described above. Is preferred.
That is, first, using X-ray lithographic method and electroforming, as shown in FIG. 2 (a), a parent mold IM1 as a base of a fine metal part is formed and fixed to the substrate IM2. Thus, by the injection molding or the reactive injection molding, the precursor 3 ′ of the mold 3 having the fine concave portions 3b corresponding to the shape of the parent mold IM1 and having the through-hole pattern 3a is obtained [FIG. ) (c)].
[0048]
Then, when this precursor 3 'is polished to a predetermined thickness, that is, a thickness corresponding to the height of the fine metal part and penetrated through the recess 3b, the shape of the parent mold IM1 is obtained as shown in FIG. A mold 3 having a corresponding hole pattern 3a is formed.
According to this method, a large amount of the mold 3 can be formed by using the single parent mold IM1 any number of times, and as a result, the manufacturing cost of the fine metal parts can be greatly reduced as compared with the past.
[0049]
As another method for producing the electroforming mold EM, the precursor 3 'shown in FIG. 2 (c) is bonded and fixed on the conductive substrate 2 via a conductive paste with the concave portion 3b on the lower side, and then a fine metal. There is also a method of passing through the recess 3b by polishing to a thickness corresponding to the height of the component. When the electroforming mold EM is manufactured by any one of the above methods, the coating thickness of the conductive paste is preferably 0.5 to 70 μm. If the coating thickness is less than 0.5 μm, the effect of fixing the mold 3 on the conductive substrate 2 by the conductive paste cannot be sufficiently obtained, and the mold is liable to be displaced at the time of electroplating. The reproducibility of the image may be reduced. On the other hand, when the thickness exceeds 70 μm, when the mold 3 is overlaid on the conductive substrate 2, the excessive conductive paste pushed out by the stress at the time of stacking, the weight of the mold 3, etc. As a result, the plating start surface is deformed and a plating film having a uniform crystal structure cannot be formed, or the conductive paste swells, resulting in the plating film being swelled. There is a possibility that it becomes thin and it becomes impossible to manufacture a fine metal part having a predetermined thickness.
[0050]
As the conductive substrate 2, a conductive layer is formed by sputtering or the like on a metal or alloy substrate such as stainless steel, aluminum or copper, or a non-conductive substrate such as Si, glass, ceramics or plastic. Examples include composites formed by stacking. In addition, a conductive layer made of a different kind of metal can be formed on the metal or alloy base by sputtering or the like, if necessary.
[0051]
As the insulating material for forming the mold 3, a resin capable of injection molding, reactive injection molding, or the like as described above is preferably used. Examples of such a resin include polymethyl methacrylate, polypropylene, polycarbonate, and epoxy resin.
<Manufacture of fine metal parts>
Next, the surface of the conductive film 1 exposed at the portion of the through hole pattern 3a as shown in FIG. 1B of the electroforming mold EM manufactured by any of the above methods, or though not shown, the through hole A plating film is selectively grown on the surface of the conductive substrate 2 exposed at the pattern 3a and the surface of the conductive film 1 made of a conductive paste protruding from the pattern 3a by electroplating using these portions as electrodes. That is, the conductive film 1 or the conductive substrate 2 is used as a cathode, the metal to be plated or platinum or the like is used as an anode, and the plating film is grown by applying a voltage by immersing it in an electroplating bath. A fine metal part 4 having a uniform crystal structure throughout and corresponding to the shape of the through-hole pattern 3a is formed [FIG. 1 (c)].
[0052]
Next, after the front end surface of the formed fine metal component 4 is polished or ground to a predetermined height, the mold 3 is removed [FIG. 1 (d)]. As a method for removing the mold 3, in order not to deform the fine metal part 4 by applying excessive stress, non-contact such as ashing using oxygen plasma or decomposition by irradiation with X-rays or ultraviolet rays is used. The method which can be performed by is preferable.
Finally, when the conductive film 1 and the conductive substrate 2 are removed, a fine metal part is completed [FIG. 1 (e)].
[0053]
As a method of removing the conductive film 1 and the conductive substrate 2, a method of dissolving the conductive film 1 using an appropriate solvent or decomposing and removing it by dry etching or the like is preferable. Thus, after the conductive film 1 is extinguished, the remaining conductive substrate 2 may be removed.
As described above, according to the manufacturing method of the present invention, although not limited to this, for example, the corner edge is sharp and the vertical direction in the height direction is excellent, the width is several μm to several hundred μm, and the height is Fine metal parts having a high aspect ratio of more than several hundred μm can be manufactured with good reproducibility and at low cost and in large quantities with fewer processes. In addition, since fine metal parts having complicated shapes can be integrally formed, particularly in a plane direction perpendicular to the height direction, there is an advantage that an assembling work of fine parts is not required.
[0054]
【Example】
Hereinafter, the present invention will be described based on examples and comparative examples.
Example 1
<Preparation of conductive paste>
As the metal powder, Ag powder having an average particle diameter of 200 nm was used.
Then, 15 parts by weight of this Ag powder and 85 parts by weight of a liquid epoxy resin as a binder were mixed to prepare a conductive paste.
[0055]
<Production of electroforming mold>
An Ni-based mold IM1 that is a 50 μm wide and 100 μm high fine metal part produced by X-ray lithography and electroforming is bonded to a stainless steel substrate IM2 with an epoxy resin. By using the one pasted with the agent, the through-hole pattern 3a corresponding to the shape of the parent mold IM1 is obtained by the steps of FIGS. 2 (a) to (d) including the reactive injection molding. A mold 3 made of polymethylmethacrylate was formed.
[0056]
The conductive paste 1 ′ was applied to the entire surface of one side of a stainless steel plate as the conductive substrate 2 using a roll coater, and then the mold 3 was stacked. Then, by heating at 100 ° C. for 4 hours to cure the epoxy resin in the conductive paste 1 ′, the conductive film 1 is formed, and the mold 3 is fixed on the conductive substrate 2, and FIG. The electromold shown was made. The coating thickness of the conductive paste 1 ′ was 5 μm.
<Manufacture of fine metal parts>
A conductive terminal is attached to the electroconductive substrate 2 of the electroforming mold to form a power feeding part, which is immersed in a nickel plating bath having the following formulation, and a current density of 50 mA / cm. ² Then, electroplating was performed at a liquid temperature of 50 ° C.
[0057]
Nickel plating bath (pH 4.0)
(Component) (Concentration)
Nickel sulfamate 450g / L
Boric acid 30g / L
When the electroplating was performed for 4 hours, the hole pattern 3a of the electroforming mold was filled with the nickel coating. Therefore, after removing the electroforming mold from the plating bath and thoroughly washing with water, the tip surface of the nickel coating was polished to a predetermined level. Aligned to the height of. Then, after ashing with oxygen plasma to decompose and remove the mold 3, the conductive film 1 is dissolved and removed by wet etching to remove the conductive substrate 2, and the width of 50 μm corresponding to the shape of the parent mold IM1 is high. A fine metal part 4 having a thickness of 50 μm was produced.
[0058]
The cross section of the obtained fine metal part was observed with a metallographic microscope, and the size of the crystal grains was measured at positions of 5% above and below in the thickness direction. And the crystal grain size φ on the conductive film side ₁ And crystal grain size φ on the coating surface side ₂ And from equation (1):
Rφ = φ ₁ / Φ ₂ (1)
The crystal grain size ratio Rφ was found to be 1.1, and there was almost no variation in the crystal grain size, and the fine metal part had a uniform crystal structure throughout the thickness direction. confirmed.
[0059]
Further, the hardness of the surface of the fine metal part on the conductive film 1 side is measured by using a micro Vickers hardness tester (MVK-ELS manufactured by Akashi Seisakusho Co., Ltd.), a micro hardness test method defined in Japanese Industrial Standard JIS Z2251. As a result, it was confirmed that a plating film having the original hardness of nickel was formed from the initial stage of plating.
From these facts, it was confirmed that fine metal parts having a sharp corner edge and excellent verticality in the height direction and having a high aspect ratio can be manufactured with good reproducibility and at a low cost and in a large number of steps.
[0060]
Example 2
<Formation of Cu powder>
Copper (II) sulfate, ammonia, and ammonium sulfate were added to pure water to prepare a solution containing each component at the following concentrations.
(Component) (Concentration)
Copper (II) sulfate 0.5M
Ammonia 5.0M
Ammonium sulfate 1.0M
Next, an excess amount (about 10 g) of copper wire (diameter 2 mm) was immersed in 1 liter of this solution, and nitrogen was bubbled to remove dissolved oxygen.
[0061]
Next, this solution was reacted for 24 hours at 25 ° C. with stirring in a highly airtight container so that oxygen was not mixed to produce a solution containing Cu (I) ammine complex ions.
Next, while stirring the liquid temperature of this solution at 25 ° C., 100 mL of a 20% sulfuric acid solution is added to cause disproportionation decomposition reaction to precipitate metallic copper in the solution. Generated. At this time, the rate of decrease ΔpH / sec per unit time of the pH of the solution was 0.25.
[0062]
Next, the produced Cu powder was separated from the solution, washed with pure water, and dried.
When the particle size and particle shape of the obtained Cu powder were observed with a scanning electron microscope, it was confirmed that the particle size was substantially uniform and the particle shape was also substantially spherical. Moreover, it was 30 nm when the average particle diameter of Cu powder reflected on the photograph was measured.
Moreover, it was 99.96% when the purity of the obtained Cu powder was measured by ICP mass spectrometry.
[0063]
<Preparation of conductive paste>
A conductive paste was prepared in the same manner as in Example 1 except that the same amount of the Cu powder formed above was used as the metal powder.
<Production of electroforming mold and production of fine metal parts>
Except for using the above-mentioned conductive paste, the same shape of the electroforming mold was prepared as in Example 1, and the same shape of the fine metal part was used under the same conditions as in Example 1 except that this electroforming mold was used. Manufactured.
[0064]
The cross section of the obtained fine metal part was observed with a metallographic microscope, and the ratio Rφ of the crystal grain size was found by the above formula (1). However, it was confirmed that the fine metal part has a uniform crystal structure throughout the thickness direction.
Further, the hardness of the surface of the conductive film 1 side of the fine metal part was measured according to the microhardness test method defined in Japanese Industrial Standard JIS Z2251 using the micro Vickers hardness meter, and was 220 Hv, From the initial stage of plating, it was confirmed that a plating film having the original hardness of nickel was formed.
[0065]
Comparative Example 1
A conductive paste was prepared in the same manner as in Example 1 except that the same amount of Ag powder having an average particle diameter of 2 μm was used as the metal powder.
<Production of electroforming mold and production of fine metal parts>
Except for using the above-mentioned conductive paste, the same shape of the electroforming mold was prepared as in Example 1, and the same shape of the fine metal part was used under the same conditions as in Example 1 except that this electroforming mold was used. Manufactured.
[0066]
The cross section of the obtained fine metal part was observed with a metallographic microscope, and the crystal grain size ratio Rφ was determined by the above formula (1). Thus, it was confirmed that the fine metal part has a two-layer structure of a large region and a small region of metal crystal grains.
Moreover, when the hardness of the surface of the conductive metal 1 side of the fine metal part was measured in accordance with the microhardness test method defined in Japanese Industrial Standard JIS Z2251 using the micro Vickers hardness meter, it was 170 Hv, It was confirmed that the plating film having the original hardness of nickel was not formed at the initial stage of plating.
[0067]
The above results are summarized in Table 1.
[0068]
[Table 1]

[Brief description of the drawings]
FIGS. 1A to 1E are cross-sectional views showing an example of a process for producing a fine metal part by the production method of the present invention.
FIGS. 2A to 2D are cross-sectional views showing an example of a process for forming a mold used in the manufacturing process from a parent mold of a fine metal part.
[Explanation of symbols]
1 Conductive film
1 'conductive paste
2 Conductive substrate
Type 3
3a Hole pattern
4 Fine metal parts
EM electric mold

Claims (9)

Corresponding to the shape of fine metal parts on a conductive substrate through a conductive film made of a conductive paste containing a fine metal powder (excluding chain-like ones) having an average particle size of 400 nm or less as a conductive component A step of preparing an electroforming mold having a fine through hole pattern in which a mold made of an insulating material is fixed, and the surface of the conductive film exposed at the through pattern portion of the electroforming mold or the conductive substrate and the conductive substrate. Forming a fine metal part corresponding to the shape of the through-hole pattern by selectively growing a plating film on the surface of the film by electroplating using these portions as electrodes. Manufacturing method of fine metal parts.   The manufacturing method of the fine metal component of Claim 1 using the electrically conductive paste which contains a metal powder in the ratio of 5-95 weight% in solid content.   The method for producing a fine metal part according to claim 1, wherein metal powder having an average particle diameter of 200 nm or less is used.   The manufacturing method of the fine metal component of Claim 1 using the metal powder containing the metal whose lattice constant difference with the metal which forms a plating film is 5% or less.   The manufacturing method of the fine metal component of Claim 1 using the metal powder containing the same metal as the metal which forms a plating film.   A metal powder formed of one metal selected from the group consisting of Ni, Fe, Co, Ag, Au, Pt, Cu, In, Ir, Re, Rh, and Pd or an alloy of two or more metals. The method for producing a fine metal part according to claim 1 to be used.   The manufacturing method of the fine metal component of Claim 1 using the metal powder formed by making it react in a liquid by making a metal ion and a reducing agent react.   The method for producing a fine metal part according to claim 7, wherein a trivalent titanium compound is used as the reducing agent.   The method for producing a fine metal part according to claim 1, wherein Cu powder obtained by precipitating metal Cu into ultrafine particles by lowering the pH of a solution containing Cu (I) ammine complex ions is used.

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