JP5807889B2 - Method for forming metal structure - Google Patents

Description

The present invention relates to a method for forming a metal structure in which a metal structure having a fine pattern is formed by an electroplating method, and in particular, a metal in which a metal structure having a fine pattern having a pattern area of the order of microns is formed by an electroplating method. It relates to the method of forming the structure.

  A method for forming a fine metal structure on a mounting wiring board is required in accordance with miniaturization and high functionality of electronic devices. Among these, there is a case where a method for forming a micron-order fine metal structure on the substrate, which is an extremely small area compared to the substrate area of a wiring substrate (hereinafter referred to as “substrate”), may be required.

  For example, in a flip chip connection method, which is one of the methods for connecting a silicon chip on which a semiconductor circuit is formed and a substrate, a fine metal structure called a bump is formed on the surface wiring of the non-conductive substrate such as FR4 and the silicon chip. Make electrical connections. A plurality of bumps are formed on the substrate, but even if the areas of all the bumps are combined, the ratio of the area occupied by the bumps to the total area of the substrate is extremely small.

  On the other hand, in a microelectromechanical system, that is, MEMS, the field, etc., there is a demand for a method for partially forming a very fine pattern on the order of microns on a substrate.

  Electroplating is widely used as a method for forming a fine metal structure on a substrate. In the method of forming a fine metal structure by electroplating, electroplating is performed after forming a plating mask film made of a photoresist having openings having a desired pattern shape on the surface of a conductive substrate.

  There are two types of electroplating methods: constant potential electroplating and constant current electroplating. The electroplating method using a constant voltage with a constant potential between the electrodes is very sensitive to the state of the substrate surface, and is particularly susceptible to contamination of the substrate surface. On the other hand, in the electroplating method with a constant current that makes it easy to control the amount of deposition, in a pattern with an opening area that is too small relative to the substrate area, the current is likely to leak to the connection cracks and resist cracks at the edges. In addition, since the overvoltage is extremely low, a sufficient current does not flow in a portion where a desired fine metal structure is to be formed.

  For this reason, for example, Japanese Patent Publication No. 56-36706 discloses a so-called frame plating method. In the frame plating method, after forming a film by electroplating on a conductive substrate on which a frame (frame) having a desired fine pattern shape is formed by a photoresist, an unnecessary plating film outside the frame is removed, This is a method for obtaining a desired fine pattern.

  In electroplating, it is widely used to arrange electrodes called external electrodes in order to achieve uniform film formation. For example, Japanese Patent No. 2870661 discloses the use of a donut-shaped auxiliary cathode for a circular substrate to be plated.

  As already described, in pattern plating, the surface of the conductive substrate is left with a desired pattern shape portion by a plating mask film such as a photoresist so that plating, that is, plating is not deposited.

However, as shown in FIG. 1, when the area of one opening is on the order of microns, that is, less than 1 mm ² , the same current density is obtained when the aperture ratio becomes smaller than 0.01% even if an external electrode is used. In spite of the fact that the film was deposited, we found that the amount of deposition decreased rapidly and almost no film was formed.

  Here, since the electroless plating method that does not pass current is a process that is essentially suitable for forming a fine metal structure, there is no problem even if the area of one opening is in the micron order. Conceivable. However, the electroless plating method is not easy to control compared to the electroplating method, and the pH and bath temperature are higher than the electroplating method, and damage to the substrate sometimes becomes a problem.

  Further, conventionally known external electrodes have been used to improve the film thickness distribution due to the current density distribution or to suppress so-called burns in the high current density portion. For this reason, the conventionally known external electrode is not a technique that can be applied to pattern plating that is difficult to deposit because the ratio of the area of the pattern to be formed to the total area of the substrate, the so-called pattern density, is extremely low.

In the frame plating method, the plating film deposited outside the frame after plating film formation must be removed. However, in the case where a base made of the same metal material as the plating film to be removed exists, the base is also affected when the plating film is removed, so that it is not easy to apply the frame plating method. Further, the process of removing the plating film is a costly process because the inside of the frame must be masked and then removed by an etching method or the like.
Japanese Patent Publication No. 56-36706 Japanese Patent No. 2870661

An object of this invention is to provide the formation method of the metal structure which forms the metal structure of a micron order stably by the electroplating method.

To achieve the above object, a method of forming the metal structure of the present invention, the mask layer formed on the surface of the substrate, forming a plating Makusu film each area is have a plurality of openings of less than 1 [mu] m ² or more 1 mm ² a step, the outer peripheral portion of the substrate, and the external electrode formation step of forming an external electrode which is simultaneously plated deposition and the substrate, electroplating the plated area of the opening and the external electrode of the substrate as a cathode in the electroplating step of forming a metal structure by law, method of forming a metallic structure having an area of the object to be plated region of the external electrode, or 3000 times the total area of the openings And the total area of the openings is 0.01% or less of the area of the substrate exposed at the inner periphery of the external electrode.

The present invention provides a method for forming a metal structure in which a metal structure in the order of microns is stably formed by electroplating.

  Hereinafter, a method for forming a metal structure according to an embodiment of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 2 is a partial perspective view for explaining the structure of the substrate and the metal structure used in the method of forming the metal structure of the present embodiment, and FIG. 3 is the method of forming the metal structure of the present embodiment. 4A and 4B are cross-sectional views for explaining the process of FIG. 4. FIG. 4A is a view of the metal structure forming method according to the present embodiment, and FIG. It is the IVB-IVB line sectional structure figure of (A). The drawings used in this specification are schematic diagrams for explaining the structure and the like. In particular, large openings in FIG. 4 and the like are shown for explanation and do not actually exist. .

  First, FIG. 2 is used to show the structure of the substrate 1 in a state where the bumps 11 that are the metal structures of the present embodiment are formed. A substrate 1 used in the method for forming a metal structure of the present embodiment has a copper wiring pattern 2 having a width of 25 μm and a thickness of 8 μm on a rectangular polyimide film 1A having a length of 38 mm, a width of 34 mm, and a thickness of 50 μm at a pitch of 45 μm. Two 229 wiring assemblies are formed. All the copper wiring patterns 2 are electrically connected at the outer periphery of the substrate 1.

The bump 11 which is a metal structure formed by the electroplating method is a metal structure having a 10 μm square and a height of 10 μm, ie, an area of 100 μm ² and made of nickel. In addition, an area of micron order means 1 μm ² or more and less than 1 mm ² .

  Next, a method for forming a metal structure according to the present embodiment will be described with reference to FIG.

<Board preparation step>
As shown in FIG. 3A, the substrate 1 is a wiring substrate in which a copper wiring pattern 2 is formed on a polyimide film 1A.

  First, as a base film (not shown), on the copper wiring pattern 2 of the substrate 1, a nickel film is 1.5 μm by a nickel plating method, a gold film is 0.7 μm by a displacement gold plating method and an electrogold plating method, Films are formed in order.

<Mask film forming step>
As shown in FIG. 3B, a photoresist film 3 (PMER-LA900PM manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied to the substrate 1 with a thickness of 13 μm using a spin coater.

  Then, as shown in FIG. 3C, by using a contact mask aligner, two 10 μm square resist pattern openings 3A each having an area of micron order on each copper wiring pattern 2, that is, a total of 458 A number of openings 3A are formed. That is, the plating max film 3B is formed.

<External electrode formation step>
As shown in FIGS. 3D and 4, external electrodes 6, which are members different from the substrate 1, are disposed on the outer periphery of the substrate 1 as shown in FIG. The external electrode 6 is a metal plate provided with an opening of 32 mm length and 27 mm width at the center of a 70 mm diameter metal plate made of stainless steel. The substrate 1 is installed in the opening of the external electrode 6, and the external electrode 6 and the copper wiring pattern 2 are electrically connected and connected to the lead portion 7. The substrate 1 and the external electrode 6 are pressed and fixed from both sides by a plastic cover 8 and a plastic cover 9 to constitute an object to be plated 10. The surface of the lead part 7 immersed in the plating solution is covered with a resin or the like so that no current flows.

  That is, in the present embodiment, the external electrode 6 which is a member different from the substrate 1 is brought into contact with the end portion of the copper wiring pattern 2 which is the conductive portion of the substrate 1 and fixed so as to be electrically connected. The substrate 1 and the external electrode 6 are energized from the power source. Of course, the substrate 1 and the external electrode 6 may not be electrically connected, and the respective power sources may be used for film formation.

In the present embodiment, the ratio of the area 2984 mm ² of the external electrode 6 to the total area of the opening 3A is 1: 1.5 × 10 ⁻⁵ , in other words, the area of the external electrode 6 is The total area of the opening 3A is 65000 times. Further, since the area of each opening 3A of the plating max film 3B is 100 μm ² and the total area of the 458 openings 3A is 45800 μm ² , the length is 32 mm and the width is 27 mm inside the external electrode of the substrate 1. Of the opening 3A to 864 mm ² , in other words, the opening ratio in which the total area of the openings 3A of the plating max film 3B is the ratio to the area of the substrate 1 is 0.0053%.

<Electroplating step>
First, the object 10 to be plated is immersed in a 10% by volume phosphoric acid aqueous solution containing 5% by weight of sodium chloride for 60 seconds, so that the inside of the opening 3A and the surface of the external electrode 6 are pretreated. And then washed with water. Further, the object to be plated 10 is subjected to an acid cleaning treatment by immersing it in a 10% by volume sulfuric acid aqueous solution for 60 seconds while being washed with water.

  Then, bumps 11 are formed by electroplating using an electroplating apparatus 20 as shown in FIG. As shown in FIG. 5, the electroplating apparatus 20 uses a soluble nickel plate as a counter electrode 23 at a position facing the plating surface of the object to be plated 10 and performs plating at a constant current using a power source 22. The composition of the plating solution 21 in the plating tank 24 and the plating conditions are shown below.

Nickel sulfate 280g
Nickel chloride 45g
40g boric acid
Additive A Appropriate amount
Additive B Appropriate amount
Surfactant appropriate amount
pH 4.05-4.07
Temperature room temperature
Current value 192mA
Time 180 seconds
As shown in FIG. 3E, by performing constant current electroplating, bumps 11 are formed at the openings 3A of the object to be plated 10 serving as the cathode, and plating films 11A are formed simultaneously on the external electrodes 6 serving as the cathode. The After the plating film formation, the plastic covers 8 and 9 and the external electrode 6 are removed from the substrate 1, and then the substrate 1 is washed with water and dried. Further, after removing the plating max film 3B by immersing the substrate 1 in acetone, the substrate 1 is subjected to a substitution process using ethanol and dried, so that the bump 11 which is a metal structure shown in FIG. A substrate 1 formed on the pattern 2 was obtained.

<Evaluation results>
As an evaluation of the substrate 1 on which the bumps 11 were formed, the appearance of the bumps 11 for one row of the three wiring substrates A1 to A3, that is, 229 bumps 11 was observed with an optical microscope. The results are shown below.

Sample A1: 2 undeposited, defective rate 0.87%
Sample A2: 2 undeposited, defective rate 0.87%
Sample A3: 1 undeposited, defective rate 0.44%
Average value: 5/3 undeposited, defective rate 0.73%
Next, the results of measuring the height of any five bumps 11 in one row of the three wiring boards A1 to A3 using a laser microscope are shown below. Note that the maximum variation is the difference between the minimum value and the maximum value, and the maximum error means the deviation rate of the measured value farthest from the average value with respect to the average value.

Sample A1: Average height 10.27 μm, maximum variation 0.87 μm, maximum error ± 4.2%
Sample A2: Average height 10.30 μm, maximum variation 0.89 μm, maximum error ± 4.4%
Sample A3: Average height 10.52 μm, maximum variation 0.63 μm, maximum error ± 3.0%
Average value: average height 10.33 μm, maximum variation 0.80 μm, maximum error ± 4.0%
As described above, the bumps 11 formed by the method for forming the bumps 11 according to the present embodiment have a small variation and a practically satisfactory level.

<Comparison form>
Hereinafter, a method for forming a metal structure according to a comparative embodiment of the present invention will be described. In addition, since the formation method of the metal structure of this comparative form is similar to the formation method of the metal structure of the first embodiment, the same components are denoted by the same reference numerals, Description is omitted.

In the method for forming a metal structure of this comparative embodiment, constant current plating film formation is performed without forming the external electrode 6 and at a current value of 18.32 μA, that is, a current density of 40 mA / cm ² in the electroplating step. went. The plating potential at this time was -0.64V. However, in the method for forming a metal structure of this comparative embodiment, no metal was deposited in the opening 3A, and the yield was 0%.

  As described above, in the method of forming the bump 11 according to the present embodiment, even when the opening that is the film forming portion is extremely small in the pattern plating method, the conductive material is electrically connected to the substrate. Electroplating is performed using an external electrode in which the potential is stable and a stable current flows during plating. For this reason, even if the opening corresponding to the area of the bump 11 is extremely small, a plating film is applied even when a current flowing to such an extent that no influence is exerted on the connecting portion or the scratched portion and the deposited surface is dirty. Control is performed so that the precipitation of the metal becomes a constant potential. For this reason, in the method for forming a metal structure of the present embodiment, a metal structure in the micron order can be stably formed by electroplating.

When the bump area described in the above embodiment, that is, the area of the opening of the resist film is large, a high yield can be obtained even by a known plating method. However, when the area of the opening is on the order of microns, that is, less than 1 mm ² , the effect of the metal structure forming method of the present embodiment appears, and when the area is 1000 μm ² or less, the effect is particularly remarkable. The lower limit of the area of the opening where the effect of the metal structure forming method of the present embodiment cannot be obtained has not been confirmed from the difficulty of forming the opening, but the effect is obtained up to 1 μm ^2. It has been confirmed. For this reason, the lower limit of the area of the opening is estimated to be nano-order, that is, less than 1 μm ² .

  Further, when the area ratio of the area of the external electrode 6 and the total area of the opening 3A is smaller than a predetermined ratio of 100, the effect of the metal structure forming method of the present embodiment can be obtained. Hateful. On the other hand, when the area ratio, the area of the external electrode 6 / the total area of the opening 3A is 3000 or more, the effect of the metal structure forming method of the present embodiment appears, and the area of the external electrode 6 / the total of the opening 3A The effect is particularly remarkable when the area is 10,000 or more and the area of the external electrode 6 / the total area of the opening 3A is 50000 or more. There is no particular upper limit of the ratio of the area of the entire opening 3A to the external electrode 6 and the area of the external electrode 6 / the area of the opening 3A, but the plating film deposited on the external electrode 6 is not used effectively, and is preferably 500000 or less, for example. .

<Modification of the first embodiment>
Hereinafter, a method for forming a metal structure according to a modification of the first embodiment of the present invention will be described. The method for forming the metal structure according to the present modification is similar to the method for forming the metal structure according to the first embodiment. Is omitted.

  In the first embodiment, a stainless steel metal plate is used as the external electrode 6, but in this modification, a titanium metal plate having the same shape as the external electrode 6 is used as the external electrode 6B. In the first embodiment, the nickel film and the gold film are formed on the copper wiring pattern 2 of the substrate 1 by the nickel plating method. However, in the present modification, only the nickel film is formed. Samples B1 to B4 having bump portions, which are metal structures, were obtained using the same processes as those in the first embodiment for other processes.

<Evaluation results>
As the evaluation of the substrate 1 on which the bumps 11 were formed, the appearance of the bumps 11 for one row of the four wiring substrates B1 to B4, that is, 229 bumps 11 was observed with an optical microscope. The results are shown below.

Sample B1: 1 undeposited, defective rate 0.44%
Sample B2: 0 undeposited, defective rate 0%
Sample B3: 1 undeposited, defective rate 0.44%
Sample B4: 0 undeposited, 0% defect rate
Average value: 2/4 undeposited, defective rate 0.22%
Next, the results of measuring the height of any five bumps 11 in one row of each of the four wiring boards B1 to B4 using a laser microscope are shown below. The maximum variation is the difference between the minimum value and the maximum value, and the maximum error rate is the deviation rate of the measured value farthest from the average value with respect to the average value.

Sample B1: Average height 9.05 μm, maximum variation 0.66 μm, maximum error ± 3.7%
Sample B2: Average height 8.81 μm, maximum variation 1.15 μm, maximum error ± 6.4%
Sample B3: average height 8.10 μm, maximum variation 0.56 μm, maximum error ± 3.4%
Sample B4: Average height of 8.42 μm, maximum variation of 1.09 μm, maximum error of ± 6.4%
Average value: average height 8.60 μm, maximum variation 0.87 μm, maximum error ± 4.0%
As described above, the bumps 11 formed by the method of forming the bumps 11 according to this modification have a small variation and a practically satisfactory level.

  When a metal is used as the external electrode 6, a metal having low contact resistance is preferable, and examples thereof include gold, copper, and brass. In order to use the external electrode 6 repeatedly, the metal deposited on the surface of the external electrode 6 needs to be chemically dissolved and removed, or physically removed by peeling or the like. The material is preferably a chemically stable metal. As a material for the external electrode, for example, gold, stainless steel, titanium, or the like can be used.

<Second Embodiment>
Hereinafter, a method for forming a metal structure according to the second embodiment of the present invention will be described with reference to FIG. FIGS. 6A and 6B are (A) a diagram viewed from the front of the object to be plated 10B and (B) a sectional view taken along the line VIB-VIB in FIG. 6 (A), which is used in the method for forming a metal structure of the present embodiment. It is. In addition, since the formation method of the metal structure of this Embodiment is similar to the formation method of the metal structure of 1st Embodiment, the same code | symbol is attached | subjected to the same component and the same process etc. Description is omitted.

  In the first embodiment, a metal plate made of stainless steel, which is a member different from the substrate 1, is used as the external electrode 6. However, in the present embodiment, a member different from the substrate 1 is used in the external electrode forming step. The conductive copper tape is affixed to the outer periphery of the circular substrate 1B to form the external electrode together with the conductive substrate 5. That is, the conductive tape fixes the substrate 1B to the conductive substrate 5 and at the same time forms the external electrode 4 to obtain the object to be plated 10B. In FIG. 6, the lead portion is not shown. Further, the back surface or the like of the conductive substrate 5 may be masked with a resin or the like so as not to form a plating film.

  The substrate 1B on which the bumps 11 are formed in the electroplating step using the object to be plated 10B shows a high yield as in the first embodiment and the substrate 1.

  In addition, as a conductive tape for forming the external electrode 4, a metallic conductive tape such as a carbon tape or a copper tape can be used. However, a tape that does not cause unnecessary components to melt from the tape during plating is desirable.

  Further, the external electrode 4 can be formed using a conductive paste instead of the conductive tape. An example of the conductive paste is a silver paste. However, it is necessary to sufficiently perform heat treatment or the like before plating so that unnecessary components do not dissolve from the paste during plating.

  The conductive substrate 5 may be any conductive substrate that does not dissolve when immersed in a plating solution, and a copper plate or a stainless steel plate can be preferably used. In addition, it is preferable to use a substrate in which copper or gold is formed on a silicon wafer by a vacuum deposition method or the like as the conductive substrate 5 because the smoothness is high as the external electrode.

<Third Embodiment>
Hereinafter, a method for forming a metal structure according to the third embodiment of the present invention will be described with reference to FIG. 7A is a cross-sectional view taken along the line VIIB-VIIB of FIG. 7A used in the method for forming a metal structure of the present embodiment. .
In addition, since the formation method of the metal structure of this Embodiment is similar to the formation method of the metal structure of 1st Embodiment, the same code | symbol is attached | subjected to the same component and the same process etc. Description is omitted.

  In the first embodiment, a metal plate made of stainless steel, which is a member different from the substrate 1, is used as the external electrode 6, but in this embodiment, as shown in FIG. 7, the outer peripheral portion 1 </ b> C <b> 1 of the substrate 1 </ b> C. Are used as external electrodes. That is, in the present embodiment, the external electrode 6 is the same member as the substrate 1.

  For this reason, in this embodiment, when forming the plating mask film 3B having the opening 3A from the photoresist film 3, simultaneously removing the resist film on the outer peripheral portion of the substrate 1C corresponds to an external electrode forming step. To do.

  The substrate 1C is enlarged as an external electrode to form the external electrode in the same substrate, and after plating, the outer peripheral portion 1C1 is cut off.

  The substrate 1 </ b> C on which the bumps 11 are formed in the electroplating step using the object to be plated 10 </ b> C shows a high yield as in the first embodiment and the substrate 1.

<Additional notes>
As a substrate to be prepared in the substrate preparation step, not only a wiring substrate but also a substrate in which a metal film is formed on a non-conductive substrate can be used. The material of the non-conductive substrate and the metal to be formed are appropriately determined depending on the purpose of use. Examples of the material of the non-conductive substrate include ceramics such as glass, silicon wafers, and organic resins such as FR4. As a material for the non-conductive substrate, not only a rigid substrate but also a flexible film-like material such as a polyimide film can be used. Examples of the metal to be deposited include gold, copper and nickel, and these metals are deposited by a known method such as electroless plating, vacuum deposition or sputtering. When an organic resin is used as the material for the non-conductive substrate, a metal foil such as copper can be adhered to the non-conductive substrate. Since the metal layer of these substrates is used as an electrode for electroplating, the film thickness is generally about 100 nm to 20 μm in order to make the sheet resistance lower than a predetermined value.

  As shown in the embodiment, a wiring board in which a metal film is formed over a non-conductive substrate and a wiring or the like is formed by patterning the metal film can be used. However, a metal structure can be formed only on a metal pattern, and a metal structure cannot be formed on an isolated metal pattern.

  For the opening pattern formation by the mask film, a screen printing method or a photolithography method can be used. In particular, a resist opening pattern by a photolithography method using a photoresist is desirable because it is necessary to form a fine pattern.

  The thickness of the resist is appropriately determined according to the thickness of the metal structure to be formed, in other words, the height, but is approximately 1 to 20 μm.

  As the pretreatment for the electroplating film formation, a known pretreatment is performed. Examples of the pretreatment include immersion treatment in a 10% sulfuric acid solution. In particular, in a substrate on which a mask film having a fine opening pattern is formed, bubbles are often attached to the openings, and it is necessary to sufficiently perform bubble removal processing. Examples of the removal of bubbles include a treatment with a solution containing a surface activity and a knocking method in which a substrate or a jig holding the substrate is physically hit to remove it.

  The metal structure can be formed of various types of metals that can be formed by electroplating. For example, the metal structure can be formed of a metal such as gold, silver, copper, platinum, cobalt, iron, nickel, chromium, or zinc, or an alloy material such as cobalt-iron, nickel-iron, or nickel phosphorus. Depending on the type of metal or alloy formed by the electroplating method, the plating bath to be used is determined as appropriate, but it is necessary to select a plating bath that takes into account the characteristics of the materials that are actually required. To do. Note that other plating conditions such as bath temperature and pH, excluding current density and potential during film formation, are appropriately determined depending on the plating bath.

  In the electroplating step in the method for forming a metal structure of the present invention, the deposition rate of the plating film itself is often different from the conventionally expected rate, so that the coating is performed using the actually used substrate, resist pattern, and external electrode. A plated body is formed, and the deposition rate is preliminarily measured. That is, in constant-current electroplating, although the deposition rate is constant, the deposition rate is often different from the expected value, so the substrate to be actually used and the resist pattern, using the external electrode, the object to be plated is formed, Measure the deposition rate.

  In the electroplating step of the present invention, it is possible to perform plating by either constant potential electroplating or constant current electroplating. For example, by adjusting the current value so that the plating potential is always -1.8 V with respect to the silver-silver chloride electrode at a distance of 1 cm from the plating surface, the potential is -1800 mV (vs Ag / AgCL). It is also possible to perform constant potential plating film formation. However, the constant current electroplating method is preferable to the constant potential electroplating method because it stabilizes the amount of current and makes the deposition rate constant.

  In the case where the characteristics of the plating film depend on the deposition rate, the current amount is adjusted appropriately to measure the current amount so as to obtain a desired deposition rate, and then the plating film is formed.

  The present invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the scope of the present invention.

It is a figure which shows the relationship between an aperture ratio and the precipitation amount. It is a fragmentary perspective view for demonstrating the structure of the board | substrate used in the formation method of the metal structure of 1st Embodiment, and a metal structure. It is sectional drawing for demonstrating the process of the formation method of the metal structure of 1st Embodiment. 5A is a cross-sectional view taken along the line IVB-IVB in FIG. 4A, which is used in the method for forming a metal structure of the first embodiment. It is a schematic diagram of the plating apparatus used in the formation method of the metal structure of a 1st embodiment. (A) The figure seen from the front of a to-be-plated body used in the formation method of the metal structure of 2nd Embodiment, and (B) VIB-VIB sectional view taken on the line of FIG. 6 (A). (A) The figure seen from the front of a to-be-plated body used in the formation method of the metal structure of 3rd Embodiment, and (B) The VIIB-VIIIB line sectional structure figure of FIG. 7 (A).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate 1A ... Polyimide film 1B ... Substrate 1C ... Substrate 1C1 ... Outer peripheral part 2 ... Copper wiring pattern 3 ... Photoresist film 3A ... Opening 3B ... Max film 4 ... External electrode 5 ... Conductive substrate 6 ... External electrode 6B ... External electrode 7 ... Lead part 8 ... Plastic cover 9 ... Plastic cover 10 ... Substance to be plated 10B ... Substance to be plated 10C ... Substance to be plated 11 ... Bump 11A ... Plating film 20 ... Plating apparatus 21 ... Plating solution 22 ... Power source 23 ... Counter electrode

Claims (5)

A mask film forming step of forming a plating max film having a plurality of openings each having an area of 1 μm ² or more and less than 1 mm ^{2 on} the surface of the substrate;
An external electrode forming step of forming an external electrode that is formed on the outer periphery of the substrate simultaneously with the substrate;
An electroplating step of forming a metal structure by electroplating using the opening of the substrate and the plating area of the external electrode as a cathode, and a method of forming a metal structure,
The area of the plating area of the external electrode is 3000 times or more the total area of the openings, and
The metal structure forming method, wherein a total area of the openings is 0.01% or less of an area of the substrate exposed at an inner peripheral portion of the external electrode.   2. The method of forming a metal structure according to claim 1, wherein an area of the plated region of the external electrode is not less than 50000 times and not more than 500000 times the total area of the openings. The board is a wiring board on which a large number of wirings are formed,
The method for forming a metal structure according to claim 1, wherein the metal structure is a bump on the wiring. The said electroplating method is a constant current plating method, The formation method of the metal structure of any one of Claim 1 to 3 characterized by the above-mentioned.   The method for forming a metal structure according to any one of claims 1 to 4, wherein the external electrode is a member different from the substrate.

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