US20190330753A1

US20190330753A1 - Nickel (alloy) electroplating solution

Info

Publication number: US20190330753A1
Application number: US16/349,740
Authority: US
Inventors: Kazuya Shibata; Yuki Oohirabaru
Original assignee: Japan Pure Chemical Co Ltd
Current assignee: Japan Pure Chemical Co Ltd
Priority date: 2016-11-25
Filing date: 2017-11-22
Publication date: 2019-10-31
Also published as: CN109996907B; WO2018097184A1; TW201825461A; JPWO2018097184A1; KR102442997B1; TWI753971B; CN114262917A; KR20180059365A; KR20190082232A; JP7021781B2; CN109996907A

Abstract

The invention provides a nickel (alloy) electroplating solution which can fill minute holes or minute recesses 14 in the electronic circuit components 14 with the nickel or nickel alloy 18 without producing voids or seams, and can join two or more electronic components firmly together by filling minute gaps. The invention further provides a method of nickel or nickel alloy plating and filling using the aforesaid nickel (alloy) electroplating solution, a method of manufacturing a minute 3-dimensional structure, an electronic component assembly, and a method of manufacturing the same. The aforesaid problems in filling the minute holes or minute recesses 14 are overcome by using a nickel (alloy) electroplating solution containing a specific N-substituted pyridinium compound.

Description

FIELD OF THE INVENTION

The present invention relates to a nickel electroplating solution and nickel alloy electroplating solution (hereafter, these are referred to generally as “nickel (alloy) electroplating solution”. Besides, “nickel or nickel alloy”, which is deposited by using a “nickel (alloy) electroplating solution”, is referred to as “nickel (alloy)”.), and more specifically, to a nickel (alloy) electroplating solution suitable for filling minute holes or minute recesses in electronic components, or minute gaps between two or more electronic components which are superposed.
The present invention further relates to a method of filling minute holes or minute recesses using this nickel (alloy) electroplating solution, a method of manufacturing a minute three-dimensional structure, an electronic component assembly, and a method of manufacturing the same.

BACKGROUND OF THE INVENTION

Electronic circuit parts (hereafter referred to simply as “electronic components”) such as semiconductors and printed circuit boards have minute holes and minute recesses, such as via for forming wiring, throughholes, and trenches.
In the prior art, in the manufacture of a multilayer printed circuit board wherein a plurality of circuit boards are laminated together, a staggered via structure is usually formed wherein, after performing conformal copper plating of the wall surface of the vias, they are connected to other layers in a staggered arrangement.
However in recent years, with increasing miniaturization of electronic devices and more advanced features, it has become necessary to save space by forming a staggered via structure wherein the vias are filled with copper plating, and other layers are stacked thereupon to make interlayer connections.
The technique of filling by copper electro-plating is applied also to semiconductor manufacture, and techniques known as the damascene process and TSV (Through Silicon Via) have emerged. Thus, it is now possible to fill vias by copper electroplating, and to form three-dimensional wiring structures.
Although the copper electroplating solution contained two or more additives, and the vias were filled by controlling their optimal concentration balance, even if it were possible to fill so that there were no macrovoids of the order of several μm, a side effect of the additives was that microvoids of nm order remained.
Copper is a metal whereof the melting point is not very high (1083° C.), and it is well known that recrystallization occurs after copper electroplating even after standing at room temperature. Hence, there was a problem that, as a result of the condensation of microvoids of nm order in this recrystallization process, macroscopic voids were eventually formed.
For example, in non-patent document 1, it is reported that when polyethylene glycol (PEG) which is an additive is partly taken up by a copper film, microvoids of nm order are formed in the copper film, and in the copper recrystallization process, on standing at room temperature, large voids of diameter 70 nm are formed.
Therefore, the copper filling method which uses a copper electroplating solution has this potential problem, and there is a risk that as the wiring becomes still finer, due to growth of voids and movement of voids resulting from the condensation of microvoids, the reliability of the wiring may be compromised.
The inventor hypothesized that if a metal having high melting point in which room temperature recrystallization does not easily occur, and in particular nickel (melting point: 1455° C.) which is commonly used for base plating, could be used to fill minute holes and minute recesses, condensation of voids would not occur, and highly reliable wiring could be obtained.
Attempts to fill recesses by nickel electroplating have been considered.
In non-patent document 2, the ability to fill trenches when various additives were added to a nickel electroplating solution was considered, and it was stated that minute recesses (trenches) were filled by adding thiourea.
However, in further tests by the inventors (below-mentioned examples), it was clear that the filling properties of the nickel electroplating solution of non-patent document 2 were still insufficient, generation of voids could not be controlled, cracks were formed in the deposits, and the integrity of the structure was poor.
Thus, while the miniaturization of electronic circuitry is constantly advancing, the ability of known techniques to fill minute holes and minute recesses was insufficient. Consequently, a nickel filling method whereby defects such as voids, cracks, etc., did not occur, was desired.

PRIOR ART DOCUMENT

Non-Patent Documents

Non-patent document 1
Journal of the Surface Finishing Society of Japan, Vol. 52, No. 1, pp. 34-38 (2001)
Non-patent document 2
Journal of the Japan Institute of Electronics Packaging, Vol. 17, No. 2, pp. 143-148 (2014)

SUMMARY OF THE INVENTION

Problems which the Invention Aims to Solve

The present invention was conceived in view of the problems inherent in the aforesaid prior art, and aims to provide a nickel (alloy) electroplating solution which can fill minute holes and minute recesses in electronic circuit components without generating defects such as voids and seams, to provide a nickel or nickel alloy filling method using said nickel (alloy) electroplating solution, and a method of manufacturing a minute three-dimensional structure.
It further aims to provide a nickel (alloy) electroplating solution which can fill minute gaps formed when two or more electronic components are superposed and firmly join the electronic components together, as well as to provide an electronic component assembly using the same.

Means for Solving the Problems

The inventor has intensively studied to solve the above-mentioned problems, and as a result, the inventor has found that by using a nickel electroplating solution containing a specific N-substituted pyridinium compound, minute holes or minute recesses could be filled with nickel without generating defects such as voids, and thereby arrived at the present invention.
That is, the present invention provides a nickel electroplating solution or nickel alloy electroplating solution containing a nickel salt, a pH buffer, and an N-substituted pyridinium compound represented by the following general formula (A):
In the general formula (A), —R¹is an alkyl group, alkylamino group or cyanoalkyl group, having 1-6 carbon atoms, an amino group (—NH₂) or a cyano group, —R²is a hydrogen atom, an alkyl group or hydroxyalkyl group having 1-6 carbon atoms, a vinyl group, a methoxycarbonyl group (—CO—O—CH₃), a carbamoyl group (—CO—NH₂), a dimethylcarbamoyloxy group (—O—CO—N(CH₂)₂), or an aldoxime group (—CH═NOH), and X⁻is an arbitrary anion.
The present invention further provides a nickel electroplating solution or nickel alloy electroplating solution containing a nickel salt, pH buffer, and an N-substituted pyridinium compound represented by the following general formula (B):
In the general formula (B), —R³is a hydrogen atom or a hydroxyl group (—OH), —R⁴is a hydrogen atom, an alkyl group having 1-6 carbon atoms, a vinyl group, or a carbamoyl group (—CO—NH₂), and m is 0, 1, or 2.
The present invention further provides a method of manufacturing a nickel deposit or a nickel alloy deposit by performing nickel electroplating using said nickel electroplating solution or nickel alloy electroplating solution.
The present invention further provides a method of manufacturing electronic components wherein minute holes or minute recesses are filled with a nickel deposit or nickel alloy deposit by performing electroplating using said nickel electroplating solution or nickel alloy electroplating solution.
The present invention further provides a method of manufacturing electronic components wherein, after first forming an electroplating seed layer on the surface of minute holes or minute recesses in the electronic components, said minute holes or minute recesses are filled with a nickel deposit or nickel alloy deposit by immersing the electronic components in said nickel electroplating solution or nickel alloy electroplating solution, and performing electroplating using an external power supply.
The present invention further provides a method of manufacturing a minute three-dimensional structure including a step of filling minute holes or minute recesses by plating using the aforesaid manufacturing method.
The present invention further provides a method of manufacturing an electronic component assembly wherein, when two or more electronic components are superposed and minute gaps are formed therebetween, the gaps are filled by immersing the two or more electronic components in said nickel electroplating solution or nickel alloy electroplating solution, and performing electroplating using an external power supply.
The present invention further provides an electronic component assembly wherein two or more electronic components are joined together by nickel or a nickel alloy, and a larger amount of nickel or nickel alloy is deposited in the vicinity of the minute gap formed between the electronic components than in other parts.
The present invention further provides a one-sided electronic component junction terminal formed of nickel or a nickel alloy, comprising a plug embedded in a material of thickness 1 mm or less in a substantially perpendicular direction relative to the material surface but not penetrating the material, and a cap having an outer diameter greater than the outer diameter of the plug such that it is in contact therewith, wherein the outer diameter of this cap is 200 μm or less, and the cap projects from the surface of the material.
The present invention further provides a two-sided electronic component junction terminal formed of nickel or a nickel alloy, comprising a plug embedded in a material of thickness 1 mm or less in a substantially perpendicular direction relative to the material surface and penetrating the material, and two caps having an outer diameter greater than the outer diameter of the plug such that they are respectively in contact therewith, wherein the outer diameter of each of the two caps is 200 μm or less, and the two caps project from the respective surfaces of the material.
The present invention further provides a one-sided electronic component junction terminal formed of nickel or a nickel alloy, comprising a plug embedded in a material of thickness 1 mm or less in a substantially perpendicular direction relative to the material surface but not penetrating the material, wherein the outer diameter of the plug is 100 μm or less.
The present invention further provides a two-sided electronic component junction terminal formed of nickel or a nickel alloy, comprising a plug embedded in a material of thickness 1 mm or less in a substantially perpendicular direction relative to the material surface and penetrating the material, wherein the outer diameter of the plug is 100 μm or less.

Effects of the Invention

According to the present invention, by using nickel plating or nickel alloy plating, minute holes or minute recesses in electronic circuit components can be filled without generating defects such as voids and seams.
According to the present invention, as minute holes and minute recesses can be filled with nickel, which has a high melting point and does not easily recrystallize at room temperature, defects due to condensation of voids do not easily occur even as wiring becomes finer, so this can be widely applied to forming three-dimensional wiring or three-dimensional MEMS (Micro Electro Mechanical Systems) parts which are becoming increasingly miniaturized.
Further, according to the present invention, as nickel can be deposited in minute parts, the nickel deposit amount in the minute gaps formed when electronic components are superposed can be increased, and the electronic components can be firmly joined together.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a cross section of the plating part periphery of a printed circuit board for evaluation used in the examples.

FIG. 2 is a photograph of a wiring pattern of the surface of the printed circuit board for evaluation used in the examples.

FIG. 3 is a schematic diagram showing a cross section before joining electronic components for evaluation (copper wire and copper plate) used in the examples.

FIG. 4 is a micrograph of a substrate cross section after plating and filling (Example 1).

FIG. 5 is a micrograph of a substrate cross section after plating and filling (Example 2).

FIG. 6 is a micrograph of a substrate cross section after plating and filling (Example 3).

FIG. 7 is a micrograph of a substrate cross section after plating and filling (Example 4).

FIG. 8 is a micrograph of a substrate cross section after plating and filling (Example 5).

FIG. 9 is a micrograph of a substrate cross section after plating and filling (Example 6).

FIG. 10 is a micrograph of a substrate cross section after plating and filling (Comparative Example 1).

FIG. 11 is a micrograph of a substrate cross section after plating and filling (Comparative Example 2).

FIG. 12 is a micrograph of a substrate cross section after plating and filling (Comparative Example 3).

FIG. 13 is a micrograph of cross sections of copper wire and copper plate after plating and filling (Example 7).

FIG. 14 is a micrograph of cross sections of copper wire and copper plate after plating and filling (Example 8).

FIG. 15 is a micrograph of cross sections of copper wire and copper plate after plating and filling (Comparative example 4).

FIG. 16 is a schematic diagram of a substrate cross section when minute holes or minute recesses are filled with nickel (alloy) deposits according to the method of the present invention.

FIG. 17 is a schematic diagram showing an example of a one-sided electronic component junction terminal according to the present invention.

FIG. 18 is a schematic diagram showing an example of a two-sided electronic-component junction terminal according to the present invention.

FIG. 19 is a schematic diagram showing an example of a one-sided electronic component junction terminal according to the present invention.

FIG. 20 is a schematic diagram showing an example of a two-sided electronic component junction terminal according to the present invention.

EMBODIMENTS TO CARRY OUT THE INVENTION

In the following, the present invention is explained, but the present invention is not limited by the following specific embodiments, and can be optionally changed within the range of the technical thought of the present invention.
(Nickel (alloy) electroplating solution) The nickel (alloy) electroplating solution of the present invention (hereinafter, may be referred to simply as “the plating solution of the present invention”) contains a nickel salt, a pH buffer and an N-substituted pyridinium compound represented by the following general formula (A) or the following general formula (B).
In the general formula (A), —R¹is an alkyl group, alkylamino group or cyanoalkyl group, having 1-6 carbon atoms, an amino group (—NH₂) or a cyano group, —R²is a hydrogen atom, an alkyl group or hydroxyalkyl group having 1-6 carbon atoms, a vinyl group, a methoxy carbonyl group (—CO—O—CH₃), a carbamoyl group (—CO—NH₂), a dimethylcarbamoyloxy group (—O—CO—N(CH₃)₂), or an aldoxime group (—CH═NOH), and X⁻ is an arbitrary anion.
In the general formula (B), —R³is a hydrogen atom or a hydroxyl group (—OH), —R⁴is a hydrogen atom, an alkyl group having 1-6 carbon atoms, a vinyl group, or a carbamoyl group (—CO—NH₂), and m is 0, 1, or 2.
The nickel salt contained in the plating solution of the present invention may be, for example, nickel sulfate, nickel sulfamate, nickel chloride, nickel bromide, nickel carbonate, nickel nitrate, nickel formate, nickel acetate, nickel citrate or nickel fluoroboride from the viewpoints of water solubility and filling properties, but the nickel salt is not limited thereto.
These may be used alone, or two or more may be mixed and used together.
The sum total content of the nickel salt is preferably from 10 g/L to 180 g/L, but more preferably, from 50 g/L to 130 g/L, as nickel ions.
Within this range, the nickel deposition rate is sufficient, and minute holes or minute recesses can be filled without generating voids.
The pH buffer contained in the plating solution of the present invention may be, for example, boric acid, meta-boric acid, acetic acid, tartaric acid, citric acid, and salts thereof, but the pH buffer is not limited thereto.
These may be used alone, or two or more may be mixed and used together.
The sum total content of the pH buffer is preferably from 1 g/L to 100 g/L, but more preferably from 5 g/L to 50 g/L.
Within this range, the pH buffer is not likely to interfere with the action of the N-substituted pyridinium compound represented by the aforesaid general formula (A) or general formula (B) (hereafter, may be referred to as “specific N-substituted pyridinium compound”), and the advantageous effect of the invention is maintained.
The plating solution of the present invention contains a specific N-substituted pyridinium compound. Due to the action of the specific N-substituted pyridinium compound, the plating solution of the present invention can fill minute holes or minute recesses without generating voids.
Regarding R¹, R²and R⁴in the aforesaid general formula (A) and the aforesaid general formula (B), when R¹, R², R⁴is an alkyl group, alkylamino group, cyanoalkyl group, or hydroxyalkyl group having 1-6 carbon atoms, R¹, R², R⁴may be mutually different.
The number of carbon atoms in R¹, R², and R⁴is preferably 1-4, more preferably 1-3, but most preferably 1 or 2.
In the aforesaid general formula (A), as examples of R¹, —CH₃, —CH₂CH₃and —CH₂CN may be mentioned.
As examples of R², —H, —CH₃, —C₂H₅, —CH₂OH, —CH═CH₂, —CONH₂and —CH═NOH may be mentioned.
As examples of X⁻, halide ions (chloride ion, bromide ion, iodide ion) may be mentioned.
As examples of the N-substituted pyridinium compound represented by the aforesaid general formula (A), halide (chloride, bromide, iodide) of 1-methyl pyridinium, 1-ethyl pyridinium, 1-propylpyridinium, 1-butyl pyridinium, 1-pentyl pyridinium, 1-hexyl pyridinium, 1-ethyl-3-(hydroxymethyl) pyridinium, 1-ethyl 4-(methoxy carbonyl) pyridinium, 1-butyl-4-methyl pyridinium, 1-butyl-3-methyl pyridinium, 1-methyl pyridinium-2-aldoxime, 3-carbamoyl-1-methyl pyridinium, 3-(dimethylcarbamoyloxy)-1-methyl pyridinium (pyridostigmine), and 1-(cyanomethyl) pyridinium, may be mentioned.
In the aforesaid general formula (B), as specific examples of R⁴, those identical to R²may be mentioned.
As examples of the N-substituted pyridinium compound denoted by the aforesaid general formula (B), 1-(3-sulfonate propyl) pyridinium, 1-(2-sulfonate ethyl) pyridinium, 1-(4-sulfonate butyl) pyridinium, 2-vinyl 1-(3-sulfonate propyl) pyridinium, 3-vinyl 1-(3-sulfonate propyl) pyridinium, 4-vinyl 1-(3-sulfonate propyl) pyridinium, 2-methyl 1-(3-sulfonate propyl) pyridinium, 3-methyl 1-(3-sulfonate propyl) pyridinium, 4-methyl 1-(3-sulfonate propyl) pyridinium, 2-ethyl 1-(3-sulfonate propyl) pyridinium, 3-ethyl 1-(3-sulfonate propyl) pyridinium, 4-ethyl 1-(3-sulfonate propyl) pyridinium, 2-vinyl 1-(4-sulfonate butyl) pyridinium, 3-vinyl 1-(4-sulfonate butyl) pyridinium, 4-vinyl 1-(4-sulfonate butyl) pyridinium, 2-methyl 1-(4-sulfonate butyl) pyridinium, 3-methyl 1-(4-sulfonate butyl) pyridinium, 4-methyl 1-(4-sulfonate butyl) pyridinium, 2-ethyl 1-(4-sulfonate butyl) pyridinium, 3-ethyl 1-(4-sulfonate butyl) pyridinium, 4-ethyl 1-(4-sulfonate butyl) pyridinium, 4-tert-butyl-1-(3-sulfonate propyl) pyridinium, 2,6-dimethyl-1-(3-sulfonate propyl) pyridinium, 3-(amino carbonyl)-1-(3-sulfonate propyl) pyridinium, 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 2-vinyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 3-vinyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 4-vinyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 2-methyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 3-methyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 4-methyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 2-ethyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 3-ethyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium and 4-ethyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, may be mentioned.
In the general formula (B), “1-(3-sulfonate propyl) pyridinium” is a compound wherein —R³is a hydrogen atom, —R⁴is a hydrogen atom and m is 1, and it is also known by other names such as “1-(3-sulfopropyl) pyridinium hydroxide intramolecular salt”, “1-(3-sulfopropyl) pyridinium”, and “PPS”.
In the general formula (B), “2-vinyl 1-(3-sulfonate propyl) pyridinium” is a compound wherein —R³is a hydrogen atom, —R⁴is vinyl group attached in the ortho position, and m is 1, and it is also known by other names such as “1-(3-sulfopropyl)-2-vinyl pyridinium hydroxide intramolecular salt, “1-(3-sulfo propyl)-2-vinyl pyridinium betaine”, and “PPV”.
In the general formula (B), “1-(2-hydroxy-3-sulfonate propyl) pyridinium” is a compound wherein —R³is a hydroxyl group, —R⁴is a hydrogen atom, and m is 1, and it is also known by other names such as “1-(2-hydroxy-3-sulfonate propyl) pyridinium hydroxide intramolecular salt”, “1-(2-hydrox-3-sulfo propyl) pyridinium betaine”, and “PPSOH”.
One type of the specific N-substituted pyridinium compound may be used alone, or two or more may be mixed and used together.
The sum total content of the specific N-substituted pyridinium compound in the plating solution of the present invention is preferably from 0.01 g/L to 100 g/L, but more preferably from 0.1 g/L to 10 g/L.
In the above range, a large amount of nickel can be deposited to the exterior of minute holes or minute recesses, and minute holes and minute recesses can be filled without generating voids.
When the plating solution of the present invention is a nickel alloy electroplating solution, examples of metal ions that can be alloyed with nickel are tungsten, molybdenum, cobalt, manganese, iron, zinc, tin, copper, palladium and gold.
As sources of these metals, compounds known in the art can be used.
Although they are not metals, carbon, sulfur, nitrogen, phosphorus, boron, chlorine and bromine may be contained in the nickel or nickel alloy film.
In the plating solution of the present invention, if so required, a pit inhibitor, primary brightening agent, secondary brightening agent, surfactant or the like may be added within limits which do not impair the advantages of the present invention.
Although the plating solution of the present invention is particularly suitable for filling minute holes or filling minute recesses formed in electronic circuit components, it is applicable also to the manufacture of ordinary nickel (alloy) deposits. That is, the present invention relates also to a method of producing nickel deposits or nickel alloy deposits by performing electroplating using the aforesaid nickel electroplating solution or nickel alloy electroplating solution.
As shown by the following examples, when minute holes or minute recesses are filled by the plating solution of the present invention, the deposit amount inside the minute holes or minute recesses is larger than the deposit amount exterior to the minute holes or minute recesses, so nickel (or nickel alloy) can be thoroughly embedded in the minute holes or minute recesses.
Moreover, voids (holes) and seams (grooves) do not easily occur inside the minute holes or minute recesses. Consequently, also due to the high melting point of nickel, electronic circuit components wherein minute holes and minute recesses are filled with the plating solution of the present invention are expected to be highly reliable.

(Method of Manufacturing Nickel (Alloy)-Filled Electronic Components, and Three-Dimensional Structure).

The invention further relates to a method of manufacturing electronic components wherein minute holes or minute recesses are filled with a nickel deposit or nickel alloy deposit by performing electroplating using said nickel electroplating solution or nickel alloy electroplating solution (That is, a method of filling nickel deposits or nickel alloy deposits).
The present invention is also a method of manufacturing electronic components wherein, after first forming an electroplating seed layer on the surface of the minute holes or minute recesses in the electronic components, the electronic components are immersed in the aforesaid nickel (alloy) electroplating solution, electroplating is performed using an external power supply, and the minute holes or minute recesses are filled with nickel deposits or nickel alloy deposits.
The present invention is also a method of manufacturing a minute three-dimensional structure including a step of filling minute holes or minute recesses by plating using the aforesaid manufacturing method.
“Minute holes or minute recesses” refer to minute hollow portions such as vias, through-holes and trenches formed in electronic circuit components such as semiconductors and printed circuit boards which, by filling them with metal by electro plating, function as wiring parts, and their configuration viewed from above is not limited.
Also, “minute holes” may be penetrating or non-penetrating.
In order to carry out the present invention, it is required to form minute holes and minute recesses on a substrate in electronic circuit components to be plated.
The substrate to be plated is not particularly limited, and as specific examples, glass epoxy, BT (Bismaleimide-Triazine) resin, polypropylene, polyimide, ceramics, silicon, metals and glass may be mentioned.
The method of forming minute holes and minute recesses in the plating substrate is not particularly limited, and methods known in the art may suitably be used.
For example, laser beam machining or ion etching may be mentioned, and a minute recess can be formed with an opening of 100 μm or less, and a depth with an aspect ratio of 0.5 or more.
Subsequently, if so required, a pattern is formed on the plating substrate surface by a photoresist or the like.
When the substrate to be plated in which the minute recess was formed is an insulation substrate, the electroplating seed layer is formed on the substrate surface and the inner surface of the minute recess. The method of forming the seed layer is not particularly limited, but as examples, metal deposition by sputtering and electroless plating may specifically be mentioned.
The metal which constitutes the seed layer is not particularly limited, but as examples, copper, nickel, or palladium may be mentioned.
After forming the electroplating seed layer, the substrate to be plated is immersed in the nickel (alloy) electroplating solution of the present invention, nickel (alloy) electroplating is performed using an external power supply, and minute holes and minute recesses are filled with nickel or a nickel alloy.
When the substrate to be plated is first dried after forming the seed layer, after degreasing and acid cleaning by the usual methods, electroplating using the plating solution of the present invention may be performed.
Herein, “filling” of minute holes or minute recesses means filling minute holes and minute recesses without forming large voids (holes).
However, the term “filling” is also understood to include the case when the minute holes or minute recesses are not completely filled (for example, as shown in FIG. 16(b), FIG. 19(c), etc., when, although nickel (alloy) is deposited inside the minute holes or minute recesses, there is also a hollow part, or when nickel or a nickel alloy is deposited even to the peripheral part outside the minute holes or minute recesses (as in the case of FIG. 16(a), etc.).
In the filling method of the present invention, when performing electroplating using an external power supply, the minimum plating cross section film thickness (X₂in FIG. 16) in a minute hole or minute recess 30 may be made larger than the maximum plating cross section film thickness (X₁in FIG. 16) of a peripheral part 31 outside the minute hole or minute recess 30.
That is, in the filling method of the present invention, it is possible to increase the nickel (alloy) deposit amount inside the minute hole or minute recess 30.
In the filling method of the present invention, when filling the inside of the minute hole or minute recess 30 with nickel (alloy), the minute hole or minute recess 30 may be completely filled with nickel (alloy) as shown in FIG. 16(a), or part thereof need not be filled as shown in FIG. 16(b) (i.e., it may have a reverse convex form).
Fine three-dimensional circuit wiring or a minute three-dimensional structure wherein minute holes and minute recesses are filled with nickel or a nickel alloy can be manufactured by including a step of plating and filling minute holes or minute recesses according to the nickel or nickel alloy filling and plating method of the present invention.
The plating temperature is preferably 30° C. or more, but more preferably 40° C. or more. Further, it preferably does not exceed 70° C., but more preferably does not exceed 60° C. Within this range, the ability to fill minute holes or minute recesses is superior, and it is also advantageous from the viewpoint of cost.
The current density for plating is preferably 0.1 A/dm²or more, but more preferably 1 A/dm²or more. Further, it preferably does not exceed 10 A/dm², but more preferably does not exceed 5 A/dm². Within this range, the ability to fill minute holes or minute recesses is superior, and it is also advantageous from the viewpoint of cost.
The current density during plating and filling may be constant, but need not be constant (for example, the initial current density may be low and then gradually increased; or pulsed current may be used; etc.).
If the current density is made constant during plating and filling (or constant for most of the time during plating and filling), filling can be performed easily without generating voids, and this is therefore preferred.
The plating time is preferably 5 minutes or more, but more preferably 10 minutes or more. Further, it preferably does not exceed 360 minutes, but more preferably does not exceed 60 minutes.
Within this range, the ability to fill minute holes or minute recesses is superior, and it is also advantageous from the viewpoint of cost.

(Electronic Component Assembly and Manufacturing Method for Same)

The present invention is also a method of manufacturing an electronic component assembly where two or more electronic components are superposed, and a minute gap is formed therebetween, wherein the two or more electronic components are immersed in the aforesaid nickel (alloy) electroplating solution, and electroplating is performed using an external power supply.
“Electronic components” means parts which are surface mounted on an electronic circuit.
“Electronic component assembly” means two or more electronic components joined together to form one structure.
When the surfaces of electronic components are plated and plural electronic components are joined together (when an electronic component assembly is manufactured), if the plating film is grown uniformly, the strength may be insufficient and faults may occur in the vicinity of the minute gaps between the electronic components.
When plating is performed using the nickel (alloy) electroplating solution of the present invention, the nickel or nickel alloy deposit amount is large in the vicinity of these minute gaps.
Specifically, according to the present invention, in the case of an electronic component assembly where two or more electronic components are joined together by nickel or a nickel alloy, an electronic component assembly wherein more nickel or nickel alloy is deposited in the vicinity of the minute gaps formed between the electronic components than in other parts, can be obtained.
In the electronic component assembly of the present invention, the nickel or nickel alloy deposit amount in the vicinity of the minute gaps is large, so sufficient strength is obtained in parts where the electronic components are joined together, and reliability is high.
According to the present invention, the plating temperature when the electronic component assembly is manufactured is preferably 30° C. or more, but more preferably 40° C. or more. Further, it preferably does not exceed 70° C., and more preferably does not exceed 60° C.
Within the above range, the nickel or nickel alloy deposit amount in the vicinity of the minute gaps is sufficient, and join strength easily improves.
According to the present invention, the current density when the electronic component assembly is manufactured is preferably 0.1 A/dm²or more, but more preferably 1 A/dm²or more. Further, it preferably does not exceed 10 A/dm², but more preferably does not exceed 5 A/dm².
Within the above range, the nickel or nickel alloy deposit amount in the vicinity of the minute gaps is sufficient, and join strength easily improves.
The current density during plating and filling may be constant, but need not be constant (for example, the initial current density may be set low and then gradually increased; or pulsed current may be used; etc.).
If the current density is made constant during plating and filling (or constant for most of the time during plating and filling), join strength easily improves, and this is therefore preferred.
The plating time is preferably 5 minutes or more, but more preferably 10 minutes or more.
Further, it preferably does not exceed 360 minutes, but more preferably does not exceed 60 minutes.
Within this range, the join strength is superior, and it is also advantageous from the viewpoint of cost.

(Terminal for Joining Electronic Components)

The present invention relates also to a terminal for joining electronic components with few voids (holes), embedded in a substantially perpendicular direction (60°-90° direction) relative to the surface of a substrate 11 in a substrate having minute holes and minute recesses.
A terminal 40 for joining electronic components according to the present invention comprises nickel or a nickel alloy.
The terminal for joining electronic components according to the present invention may be easily formed by using the aforesaid nickel (alloy) electroplating solution of the present invention.
The terminal 40 for joining electronic components according to the present invention is embedded in the substrate 11 having a thickness of 1 mm or less.
The terminal 40 for joining electronic components may be a one-sided terminal for joining electronic components (which does not penetrate the substrate 11) as shown in FIG. 17 or FIG. 19, or may be a two-sided terminal for joining electronic components (which does penetrate the substrate 11) as shown in FIG. 18 or FIG. 20.
The terminal shown in FIG. 17 is the one-sided terminal 40 for joining electronic components provided with a plug 41 embedded in a substantially perpendicular direction relative to the surface of the substrate 11 but not penetrating the substrate 11, and a cap 42 which is in contact with this plug.
The cap 42 projects from the surface of the substrate 11, its outer diameter is larger than the outer diameter of the plug 41, and is 200 μm or less.
Although a cross section parallel to the substrate surface of the plug 41 or cap 42 is usually circular, when it is not circular, “outer diameter” means the outer diameter of a circle of equivalent surface area (hereafter, the same for the terminal 40 for joining electronic components shown in FIGS. 18-20).
The terminal shown in FIG. 18 is the two-sided terminal 40 for joining electronic components provided with the plug 41 embedded in a substantially perpendicular direction relative to the surface of the substrate 11 and penetrating the substrate 11, and two caps 42 in contact with the ends of the plug 41.
The two caps 42 respectively project from the surface of the substrate 11, the outer diameters of the two caps 42 are larger than the outer diameter of the plug 41, and are 200 μm or less.
The terminal shown in FIG. 19 is the one-sided terminal 40 for joining electronic components comprising the plug 41 embedded in a substantially perpendicular direction relative to the surface of the substrate 11, but not penetrating the substrate 11. The outer diameter of the plug 41 is 100 μm or less.
The end of the plug 41 may project from the surface of the substrate 11 as shown in FIG. 19(a), may have the same height as the surface of the substrate 11 as shown in FIG. 19(b), or may be embedded relative to the surface of the substrate 11 as shown in FIG. 19(c).
The terminal shown in FIG. 20 is the two-sided terminal 40 for joining electronic components comprising a plug 41 embedded in a substantially perpendicular direction relative to the surface of the substrate 11, and penetrating the substrate 11. The outer diameter of the plug 41 is 100 μm or less.
The ends of the plug 41 may project from the surface of the substrate 11 as shown in FIG. 20(a), may have the same height as the surface of the substrate 11 as shown in FIG. 20(b), or may be embedded relative to the surface of the substrate 11 as shown in FIG. 20(c).
According to the prior art, it was not possible to manufacture a terminal for an electronic component junction of nickel (alloy) embedded in a substrate of thickness 1 mm or less, comprising the plug 41 having an outer diameter of 100 μm or less, and a cap 42 having an outer diameter of 200 μm or less.
By performing plating using the aforesaid nickel (alloy) electroplating solution of the present invention, generation of voids in the nickel (alloy) deposit is controlled, and a terminal for an electronic component junction of such size can be manufactured in sufficient yield.
When manufacturing the terminal for an electronic component junction using the nickel (alloy) electroplating solution of the present invention, the terminal can be easily embedded in a thin substrate of 0.8 mm or less, or thinner substrate of 0.5 mm or less.
It is also easy to manufacture a terminal for an electronic component junction comprising a plug having a smaller outer diameter of 70 μm or less or even smaller outer diameter of 50 μm or less, and a cap having a smaller outer diameter of 150 μm or less or even smaller outer diameter of 100 μm or less.
It is preferred that the plug 41 of the terminal 40 for an electronic component junction does not contain voids having a larger maximum width than 10 μm. By using the aforesaid nickel (alloy) electroplating solution of the present invention, a plug without such large voids can easily be formed.
The preferred conditions (plating temperature, current density, etc.) for manufacturing the aforesaid terminal for an electronic component junction by plating using the nickel (alloy) electroplating solution of the present invention, are substantially identical to the conditions described in the aforesaid section, (Method of manufacturing nickel (alloy)-filled electronic components, and three-dimensional structure).

EXAMPLES

Hereafter, the present invention will be described in further detail referring to examples and comparative examples, but the present invention should not be construed as being limited thereto unless otherwise stated.

[Filling of Minute Recesses]

Examples 1-6, comparative examples 1-3 As a model of minute recesses, the printed circuit boards for evaluation (made by Japan Circuit Co. Ltd.) of 12 mm angle having laser vias of aspect ratio 0.88 (Ø45 μm×40 μm D) were used.
FIG. 1 shows a cross-sectional view of a plating part periphery 10.
After sticking a copper foil 13 of thickness 12 μm on the via hole forming part of a substrate 11 of BT (Bismaleimide-Triazine) having a thickness of 0.4 mm, and laminating a prepreg type buildup resin 12 of thickness 60 μm, a blind via hole (hereafter, may be referred to simply as “via hole” or “via”) 14 having Ø45 μm×40 μm D was made by a laser, and a seed layer 15 was formed to a thickness of approx. 1 μm by non-electrolytic copper plating on the substrate outer surface (surface of the buildup resin 12) and the inner wall of the via 14.
A circuit pattern shown in FIG. 2 was then formed by a dry film resist (DFR) 16 of thickness 25 μm, and a pad (opening) 17
(Ø190 μm) having the via 14 was formed therein to make the printed circuit board 1 for evaluation.
In FIG. 2, the white parts are copper plating parts, and the black parts are dry film resist parts. Among the white parts, the circular part with the largest size to which wiring is connected is equivalent to the circular pad 17 (Ø190 μm) of FIG. 1.
The via hole 14 which is the minute recess shown in FIG. 1 was formed in all the circular pads 17.

(Manufacture of Nickel Electroplating Solution)

Nickel sulfamate at 600 g/L, nickel chloride at 10 g/L and boric acid at 30 g/L were dissolved in deionized water to prepare a nickel electroplating solution.
To the aforesaid nickel electroplating solution, the additives shown in Table 1 were added in the amounts shown in Table 1, and dissolved.
Next, a suitable amount of an aqueous solution containing 100 g/L of sulfamic acid was added to adjust the pH to 3.6, to thereby prepare the nickel electroplating solution of the present invention.

TABLE 1

			Addition
		General	amount
	Additive	formula	(g/L)

Example 1	1-propyl pyridinium	(A)	0.5
	chloride
Example 2	1-(cyanomethyl) pyridinium	(A)	0.1
	chloride
Example 3	3-carbamoyl-1-methyl	(A)	0.5
	pyridinium chloride
Example 4	1-methyl	(A)	0.5
	pyridinium-2-aldoxime
	chloride
Example 5	1-(3-sulfonate propyl)	(B)	0.5
	pyridinium
Example 6	2-vinyl-1-(3-sulfonatee	(B)	0.5
	propyl) pyridinium
Comparative	None	—	—
Example 1
Comparative	Thiourea	—	0.2
Example 2
Comparative	Thiourea	—	0.1
Example 3	Dodecyltrimethylammonium	—	0.65
	Chloride

(Filling of Via by Nickel Electroplating)

Nickel electroplating was performed to the aforesaid printed circuit board 1 for evaluation in a step shown in Table 2.
In the nickel electroplating step, the current density was adjusted to 1.0 A/dm²using an external power supply.
The plating area was calculated as the surface area including the sides of the via 14.

TABLE 2

Step	Reagent	Temp. (° C.)	Time

Degreasing	Acid immersion	50° C.	5	min
	and degreasing
	solution
	PAC-200
	(Murata Co.
	Ltd.)

Water rinse

—

	Acid rinse	10 vol %	Room		30	sec
		sulfuric acid	temperature

Water rinse

—

Nickel	Nickel	50° C.	60	min
electroplating	electroplating
	solutions in
	the Examples
	and
	Comparative
	Examples

(Plating and Filling Evaluation Test)

After plating, the substrate was embedded and fixed in a polishing resin, its cross section was polished, and the filling condition of the via was observed with a metallurgical microscope.
As regards filling properties, when there was more deposit amount inside the via hole than the deposit amount outside the via hole, the case where no voids (holes) or seams (grooves) were observed inside the via hole was marked “O”, and other cases were marked “X”.
It was also observed whether there were any cracks in the via hole exterior.
When the filling properties were “O” and there was no crack, the result was judged as “good”, otherwise it was judged as “defective”.
FIGS. 4-12 show micrographs of the substrate cross section after plating and filling.
Table 3 shows the evaluation results.

TABLE 3

		Filling		Evaluation
	Additive	properties	Cracks	result

Example 1	1-propyl pyridinium	◯	No	Good
	chloride
Example 2	1-(cyanomethyl)	◯	No	Good
	pyridinium chloride
Example 3	3-carbamoyl-1-methyl	◯	No	Good
	pyridinium chloride
Example 4	1-methyl	◯	No	Good
	pyridinium-2-aldoxime
	chloride
Example 5	1-(3-sulfonate propyl)	◯	No	Good
	pyridinium
Example 6	2-vinyl-1-(3-sulfonate	◯	No	Good
	propyl) pyridinium
Comparative	None	X	No	Defective
Example 1
Comparative	Thiourea	X	No	Defective
Example 2
Comparative	Thiourea	◯	Yes	Defective
Example 3	Dodecyltrimethyl

	ammonium Chloride

In Examples 1-6, the amount of deposited nickel 18 was larger inside the via holes which are minute recesses than outside the via holes, and the filling was good without voids or seams.
No cracks were observed outside the via holes.
In Comparative Example 1, the plating was conformal plating with approximately the same amount of deposited nickel 18 inside and outside the via holes, and filling was poor.
In Comparative Example 2, the inside of the vias had voids V of maximum width 14 μm, and filling was poor.
In Comparative Example 3, although there were no voids inside the vias and filling was good, the deposited part was very weak, cracks had occurred, and remarkable exfoliation of deposited nickel 18 was seen in the upper part of the via after polishing.
Therefore, as a minute three-dimensional structure, it was poor.
From the results of Examples 1-6 and Comparative Examples 1-3, by performing electroplating with the nickel electroplating solution containing a N-substituted pyridinium compound represented by the general formula (A) or general formula (B), minute holes formed in the electronic components could be filled with nickel well, and it was possible to manufacture a minute three-dimensional structure.

[Junction of Electronic Components]

Examples 7-8, Comparative Example 4

As a model for joined electronic components, copper wire (Ø0.9 mm) and copper plate (20 mm×20 mm×0.3 mmt) whereof the back surface was masked, were used.
As shown in FIG. 3, two copper plates 22 whereof the back side was masked with a masking material 22 a were prepared, a copper wire 21 was inserted between the surfaces of the two copper plates 22 which were not masked, and fixed by a jig 23 so as to form minute gaps 24 between the copper wire 21 and copper plate 22.

(Preparation of Nickel Electroplating Solution)

Nickel sulfamate at 600 g/L, nickel chloride at 10 g/L and boric acid at 30 g/L were dissolved in deionized water to prepare a nickel electroplating solution.
To the aforesaid nickel electroplating solution, the additives shown in Table 4 were added in the amounts shown in Table 4, and dissolved.
Next, a suitable amount of an aqueous solution containing 100 g/L of sulfamic acid was added to adjust the pH to 3.6, to thereby prepare the nickel electroplating solution of the present invention.

TABLE 4

			Addition
		General	amount
	Additive	formula	(g/L)

Example 7	1-propyl pyridinium	(A)	0.5
	chloride
Example 8	2-(vinyl)-1-(3-sulfonate	(B)	0.5
	propyl) pyridinium
Comparative	None	—	—
Example 4

(Joining of Copper Wire and Copper Plate by Nickel Electroplating)

The aforesaid electronic component sample was immersed in the aforesaid nickel electroplating solution so that the linear directions of the copper wire 21 and the plating surface were substantially perpendicular, and nickel electroplating was performed in the step shown in Table 5. The nickel anode was made to face the outside of the masking material 22 a every one sheet. The current density was adjusted to 1.0 A/dm²in a nickel electroplating step using an external power supply.
The plating area was taken as the surface area of only the copper plate 22.

TABLE 5

Step	Reagent	Temp. (° C.)	Time

Water rinse

—

	Acid rinse	10 vol %	Room		30	sec
		sulfuric acid	temperature

Water rinse

—

Nickel	Nickel	50° C.	120	min
electroplating	electroplating
	solutions in
	the examples
	and
	comparative
	examples

(Join Properties Evaluation Test)

After plating, the electronic component sample (assembly) was embedded and fixed in a polishing resin, its cross section was polished, and the join between the copper wire 21 and copper plate 22 was observed with a metallurgical microscope.
As regards join properties, when the nickel plating thickness of the minute gaps 24 in contact with the copper wire 21 and copper plate 22 was thicker than in other parts, it was marked “O”, otherwise it was marked “X”.
FIGS. 13-15 show micrographs of a cross section of the electronic components sample (assembly) after plating and filling.
Table 6 shows the evaluation results.

TABLE 6

		Join
	Additive	properties

Example 7	1-propyl pyridinium chloride	◯
Example 8	2-(vinyl)-1-(3-sulfonate
	propyl) pyridinium	◯
Comparative	None	X
Example 4

According to Examples 7-8, the amount of deposited nickel 18 in the minute gaps 24 where the copper wire 21 and copper plate 22 were in contact was larger than in other places, and they were joined more firmly together.
In Comparative Example 4, the plating was of substantially uniform thickness in all places, and the join properties were poor.
As shown by the results for Examples 7-8 and Comparative Example 4, by performing electroplating using the nickel electroplating solution containing a N-substituted pyridinium compound represented by the general formula (A) or the general formula (B), joins between minute components could be plated more thickly with nickel, and they could be joined more firmly together.

INDUSTRIAL APPLICABILITY

The nickel (alloy) electroplating solution containing an N-substituted pyridinium compound according to the present invention can fill minute holes or minute recesses in electronic circuit components reliably, and as the electronic components can be firmly joined together, the wiring can be made even finer, so the solution has wide application in forming 3-dimensional wiring or 3-dimensional MEMS components.

DESCRIPTION OF REFERENCE SIGNS

1 Printed circuit for evaluation
10 Periphery of plated part
11 Substrate
12 Buildup resin
13 Copper foil
14 Blind via hole
15 Seed layer
16 Dry film resist
17 Pad
18 Deposited nickel (alloy)
V Void
20 Electronic component sample
21 Copper wire
22 Copper plate
22 a Masking material
23 Jig
24 Minute gap
30 Minute hole/minute recess
31 Peripheral area
40 Terminal for joining electronic components
41 Plug
42 Cap

Claims

1-21. (canceled)

22. A nickel electroplating solution or nickel alloy electroplating solution containing a nickel salt, a pH buffer and an N-substituted pyridinium compound represented by the following general formula (A) or (B):

In the general formula (A), —R¹is an alkyl group, alkylamino group or cyanoalkyl group, having 1-6 carbon atoms, an amino group (—NH₂) or a cyano group, —R²is a hydrogen atom, an alkyl group or hydroxyalkyl group having 1-6 carbon atoms, a vinyl group, a methoxycarbonyl group (—CO—O—CH₃), a carbamoyl group (—CO—NH₂), a dimethylcarbamoyloxy group (—O—CO—N(CH₃)₂), or an aldoxime group (—CH═NOH), and X⁻is an arbitrary anion

In the general formula (B), —R³is a hydrogen atom or a hydroxyl group (—OH), —R⁴is a hydrogen atom, an alkyl group having 1-6 carbon atoms, a vinyl group, or a carbamoyl group (—CO—NH₂), and m is 0, 1, or 2.

23. The nickel electroplating solution or nickel alloy electroplating solution according to claim 22 where X⁻is a halide ion.

24. The nickel electroplating solution or nickel alloy electroplating solution according to claim 22 wherein said nickel salt is one or more selected from the group consisting of nickel sulfate, nickel sulfamate, nickel chloride, nickel bromide, nickel carbonate, nickel nitrate, nickel formate, nickel acetate, nickel citrate, and nickel fluoroboride.

25. The nickel electroplating solution or nickel alloy electroplating solution according to any of claim 22, wherein said pH buffer is one or more selected from the group consisting of boric acid, meta-boric acid, acetic acid, tartaric acid, citric acid, and salts thereof.

26. The nickel electroplating solution or nickel alloy electroplating solution according to claim 22, wherein the N-substituted pyridinium compound represented by the general formula (A) is one or more compounds selected from the group consisting of halide of 1-methyl pyridinium, halide of 1-ethyl pyridinium, halide of 1-propyl pyridinium, halide of 1-butyl pyridinium, halide of 1-pentyl pyridinium, halide of 1-hexyl pyridinium, halide of 1-ethyl-3-(hydroxymethyl) pyridinium, halide of 1-ethyl 4-(methoxy carbonyl) pyridinium, halide of 1-butyl-4-methyl pyridinium, halide of 1-butyl-3-methyl pyridinium, halide of 1-methyl pyridinium 2-aldoxime, halide of 3-carbamoyl-1-methyl pyridinium, halide of 3-(dimethylcarbamoyloxy)-1-methyl pyridinium, and halide of 1-(cyanomethyl) pyridinium.

27. The nickel electroplating solution or nickel alloy electroplating solution according to claim 22, wherein the N-substituted pyridinium compound represented by the general formula (B) is one or more compounds selected from the group consisting of 1-(3-sulfonate propyl) pyridinium, 1-(2-sulfonate ethyl) pyridinium, 1-(4-sulfonate butyl) pyridinium, 2-vinyl 1-(3-sulfonate propyl) pyridinium, 3-vinyl 1-(3-sulfonate propyl) pyridinium, 4-vinyl 1-(3-sulfonate propyl) pyridinium, 2-methyl 1-(3-sulfonate propyl) pyridinium, 3-methyl 1-(3-sulfonate propyl) pyridinium, 4-methyl 1-(3-sulfonate propyl) pyridinium, 2-ethyl 1-(3-sulfonate propyl) pyridinium, 3-ethyl 1-(3-sulfonate propyl) pyridinium, 4-ethyl 1-(3-sulfonate propyl) pyridinium, 2-vinyl 1-(4-sulfonate butyl) pyridinium, 3-vinyl 1-(4-sulfonate butyl) pyridinium, 4-vinyl 1-(4-sulfonate butyl) pyridinium, 2-methyl 1-(4-sulfonate butyl) pyridinium, 3-methyl 1-(4-sulfonate butyl) pyridinium, 4-methyl 1-(4-sulfonate butyl) pyridinium, 2-ethyl 1-(4-sulfonate butyl) pyridinium, 3-ethyl 1-(4-sulfonate butyl) pyridinium, 4-ethyl 1-(4-sulfonate butyl) pyridinium, 4-tert-butyl-1-(3-sulfonate propyl) pyridinium, 2,6-dimethyl-1-(3-sulfonate propyl) pyridinium, 3-(amino carbonyl)-1-(3-sulfonate propyl) pyridinium, 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 3-vinyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 4-vinyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 2-methyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 3-methyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 4-methyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 2-ethyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, 3-ethyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium, and 4-ethyl 1-(2-hydroxy-3-sulfonate propyl) pyridinium.

28. The nickel electroplating solution or nickel alloy electroplating solution according to any of claim 22, used for filling a minute hole or a minute recess in an electronic component, or a minute gap formed when electronic components are superposed on one another.

29. A method of manufacturing a nickel deposit or a nickel alloy deposit, wherein electroplating is performed using the nickel electroplating solution or nickel alloy electroplating solution according to claim 22.

30. A method of manufacturing an electronic component in which a minute hole or minute recess is filled with a nickel deposit or a nickel alloy deposit, wherein electroplating is performed using the nickel electroplating solution or nickel alloy electroplating solution according to claim 22.

31. A method of manufacturing an electronic component in which a minute hole or minute recess is filled with a nickel deposit or a nickel alloy deposit, wherein, after first performing electroplating on the surface of the minute hole or minute recess, said electronic component is immersed in a nickel electroplating solution or nickel alloy electroplating solution according to claim 22, and electroplating is performed using an external power supply.

32. The method of manufacturing an electronic component in which the minute hole or minute recess is filled with a nickel deposit or a nickel alloy deposit according to claim 31, wherein when electroplating is performed using an external power supply the minimum plating cross section film thickness X₂in the minute hole or minute recess is made to be larger than the maximum plating cross section film thickness X₁of the peripheral part outside the minute hole or minute recess.

33. A method of manufacturing a minute three-dimensional structure, comprising a step wherein a minute hole or a minute recess is electroplated and filled by the manufacturing method according to claim 30.

34. A method of manufacturing a minute three-dimensional structure, comprising a step wherein a minute hole or a minute recess is electroplated and filled by the manufacturing method according to claim 31.

35. A method of manufacturing an electronic component assembly, wherein, when two or more electronic components are superposed and a minute gap is formed therebetween, said two or more electronic components are immersed in a nickel electroplating solution or nickel alloy electroplating solution according to claim 22, and electroplating is performed using an external power supply.

36. An electronic component assembly wherein two or more electronic components are joined together by nickel or a nickel alloy, and a larger amount of nickel or nickel alloy is deposited in the vicinity of the minute gap formed between the electronic components than in other parts.

37. A one-sided electronic component assembly terminal formed of nickel or a nickel alloy, comprising a plug embedded in a material of thickness 1 mm or less in a substantially perpendicular direction relative to the material surface but not penetrating said material, and a cap having an outer diameter greater than the outer diameter of said plug such that it is in contact with said plug, wherein the outer diameter of said cap is 200 μm or less, and said cap projects from the surface of said material.

38. A two-sided electronic component assembly terminal formed of nickel or a nickel alloy, comprising a plug embedded in a material of thickness 1 mm or less in a substantially perpendicular direction relative to the material surface and penetrating said material, and two caps having an outer diameter greater than the outer diameter of said plug such that they are respectively in contact with said plug, wherein the outer diameter of each of said two caps is 200 μm or less, and said two caps project from the respective surfaces of said material.

39. A one-sided electronic component assembly terminal formed of nickel or a nickel alloy, comprising a plug embedded in a material of thickness 1 mm or less in a substantially perpendicular direction relative to the material surface but not penetrating said material, wherein the outer diameter of said plug is 100 μm or less.

40. A two-sided electronic component assembly terminal formed of nickel or a nickel alloy, comprising a plug embedded in a material of thickness 1 mm or less in a substantially perpendicular direction relative to the material surface and penetrating said material, wherein the outer diameter of said plug is 100 μm or less.

41. An electronic component assembly terminal according to any of claim 37, wherein there is no void in said plug having a maximum width greater than 10 μm.

42. An electronic component assembly terminal according to any of claim 38, wherein there is no void in said plug having a maximum width greater than 10 μm.

43. An electronic component assembly terminal according to any of claim 39, wherein there is no void in said plug having a maximum width greater than 10 μm.

44. An electronic component assembly terminal according to any of claim 40, wherein there is no void in said plug having a maximum width greater than 10 μm.

45. An electronic component assembly terminal according to claim 37, formed using a nickel electroplating solution or nickel alloy electroplating solution.

46. An electronic component assembly terminal according to claim 38, formed using a nickel electroplating solution or nickel alloy electroplating solution.

47. An electronic component assembly terminal according to claim 39, formed using a nickel electroplating solution or nickel alloy electroplating solution.

48. An electronic component assembly terminal according to claim 40, formed using a nickel electroplating solution or nickel alloy electroplating solution.