JP4797777B2 - Pretreatment liquid for electroless nickel plating, pretreatment method for electroless nickel plating, electroless nickel plating method, and method for producing printed wiring board and semiconductor chip mounting substrate - Google Patents

Description

  The present invention relates to a pretreatment liquid for electroless nickel plating, a pretreatment method for electroless nickel plating, an electroless nickel plating method, and a method for manufacturing a printed wiring board and a substrate for mounting a semiconductor chip.

  The development of the information society in recent years has been remarkable, and consumer devices have been reduced in size, weight, performance, and functionality, such as personal computers and mobile phones. Industrial equipment includes wireless base stations, optical communication devices, and servers. In addition, there is a demand for improvement in functions in the same way regardless of whether it is large or small, such as routers and other network-related devices. In addition, with the increase in the amount of information transmitted, the frequency of signals handled tends to increase year by year, and high-speed processing and high-speed transmission technology are being developed. With regard to mounting relations, the development of system-on-chip (SoC), system-in-package (SiP), etc., as new high-density mounting technologies, as well as higher-speed and higher-performance LSIs such as CPUs, DSPs, and various types of memory are actively developed. Has been done.

  For this reason, build-up type multilayer wiring boards have come to be used for semiconductor chip mounting boards and motherboards in order to cope with high frequency, high density wiring, and high functionality. Electronic device manufacturers have been competing in high-density packaging to achieve smaller, thinner, and lighter products, and rapid technological progress has been made in narrowing the multi-pin pitch of packages. From QFP (Quad Flat Package) to BGA (Ball Grid Array) / CSP (Chip Size Package) mounting on the surface.

  By the way, the connection method between the semiconductor chip and the semiconductor mounting substrate is generally gold wire bonding, and the terminal on the wiring board side requires gold plating as an adhesive layer of the gold wire. Usually, gold plating is performed after nickel plating on copper wiring. Conventionally, electroplating has been applied as a method for forming a metal plating film on copper wiring. However, in recent years, the wiring on a substrate has become finer as the speed and integration of semiconductor chips has increased, leading to the supply of plating power. Line formation is difficult. Therefore, there is an increasing need for an electroless plating method that does not require lead wires.

  On the other hand, as an EU directive on the restriction of the use of specified hazardous substances for electrical and electronic equipment, the RoHS (Rose) Directive (Restriction of the use of certain Hazardous Substances in Electrical and Electronic Equipment) Since Japanese companies apply the directive to products that they export, each company is currently working on it. The RoHS Directive aims to minimize human health and environmental impact in the product life cycle from production to disposal and disposal. The target substances are six types: (1) lead (2) mercury (3) cadmium (4) hexavalent chromium (5) polybrominated biphenyl (6) polybrominated diphenyl ether. This directive will come into effect on July 1, 2006, and home appliances, personal computers, televisions, etc. that will be marketed in the EU after that are restricted from using six substances. Taking lead, the maximum allowable concentration in the proposed RoHS regulation is 0.1% by weight (1000 ppm) per homogeneous material. In the future, regulations will become even stricter, and it is predicted that the final goal will be to not contain them.

  Regarding the electroless plating method, an electroless nickel plating film and an electroless gold plating film are formed in this order on the surface of copper, such as a semiconductor chip connection terminal or a solder ball connection terminal (in order of copper / nickel / gold). Is a common method. And, for example, when performing electroless nickel plating on copper wiring, after performing activation treatment for depositing metallic palladium on copper wiring as a pretreatment step of electroless nickel plating, electroless nickel plating is performed. It is common. However, when the electroless nickel plating is applied to the copper wiring that has undergone such activation treatment, the electroless nickel plating may be deposited not only on the copper wiring portion but also on an insulating portion such as a resin around the copper wiring portion. . Such a phenomenon is called “bridge” and causes a short circuit of the wiring.

  Therefore, in order to prevent the above-mentioned “bridge”, a pretreatment method has been proposed in which a base material on which a copper pattern is formed is immersed in a solution containing thiosulfate immediately before the pretreatment step of electroless nickel plating. (For example, refer to Patent Document 1).

  As for electroless nickel plating, the solution is usually stabilized by adding about 1 ppm of lead ions as a stabilizer in the electroless nickel plating solution (see Non-Patent Document 1, for example). ). According to the study by the present researchers, when lead ions are contained in the plating solution at about 1 ppm, the lead content in the obtained electroless nickel plating film is 0.03 mass% (300 ppmm). This is not desirable from the standpoint of limiting the use of certain hazardous substances. However, recently, an electroless nickel plating solution not containing lead ions has been developed (see, for example, Patent Document 2). According to such a plating solution, it can be expected to respond to environmental regulations that will become stricter in the future.

“Electroless plating basics and applications”, Electroplating Study Group, p. 31, (1994) Japanese Patent No. 3387507 JP 2005-82883 A

  Recently, by using a wiring forming method such as a semi-additive method, for example, products having fine wiring of a wiring width / wiring interval (hereinafter referred to as “L / S”) = 35 μm / 35 μm level are mass-produced. .

  However, when electroless nickel plating is performed on such a fine wiring using an electroless nickel plating solution that does not contain lead ions, it is difficult to ensure sufficient insulation reliability between the wirings. It became clear by the examination. That is, it has been found that even when the pretreatment method described in Patent Document 1 is applied, electroless nickel plating is abnormally deposited on the insulating portion between the wirings, and a sufficient bridge suppression effect cannot be obtained.

  Therefore, the object of the present invention is to improve the above-mentioned problems of the prior art and sufficiently prevent the occurrence of bridging even when an electroless nickel plating solution containing no lead ions is used. An electroless nickel plating pretreatment solution, an electroless nickel plating pretreatment method, an electroless nickel plating method, and a printed wiring board and a method for manufacturing a semiconductor chip mounting substrate.

  As a result of intensive studies to achieve the above object, the present inventors have formed a copper wiring on the substrate before the substitution palladium plating treatment step, which is an activation treatment for providing an electroless nickel plating film. By immersing the wiring board in a pretreatment liquid containing specific amounts of specific sulfur compounds and organic solvents, the occurrence of bridging is sufficiently prevented in the wiring board obtained through subsequent activation treatment and electroless plating. As a result, the present invention has been completed.

That is, the pretreatment liquid for electroless nickel plating of the present invention is a wiring comprising a base material and a copper wiring to be subjected to a replacement palladium plating process for forming an electroless nickel plating film formed on the base material. A pretreatment liquid for electroless nickel plating to be brought into contact with the surface of a plate, an aliphatic thiol compound represented by the following general formula (1), an aliphatic thiol compound represented by the following general formula (2), and the following general In the pretreatment liquid, comprising at least one sulfur compound selected from the group consisting of an aliphatic thiol compound represented by the formula (3) and a disulfide compound represented by the following general formula (4), and an organic solvent: The total content of the above sulfur compounds is 0.0005 to 10 g / L, and the total content X (mL / L) of the organic solvent in the pretreatment liquid and the total content of the above sulfur compounds in the pretreatment liquid Amount Y (g L) the ratio of (X / Y) is characterized in that it is 80,000.
_{HS- (CH 2) a -COOH ...} (1)
In the formula (1), a represents any integer from 1 to 23.
_{HS- (CH 2) b -OH ...} (2)
In formula (2), b represents any integer from 5 to 23.
_{HS- (CH 2) c -NH 2} ... (3)
In formula (3), c represents any integer from 5 to 23.
^{_{R 1 - (CH 2) n}} - (R 3) p -S-S- (R 4) q - (CH 2) m -R 2 ... (4)
In formula (4), R ¹ and R ² each independently represent a hydroxyl group, a carboxyl group or an amino group, and R ³ and R ⁴ each independently represent a divalent organic group having a hydroxyl group, a carboxyl group or an amino group. N and m each independently represent any integer from 4 to 15, and p and q each independently represent 0 or 1.

  Here, the layer configuration of the wiring board is not particularly limited, and the wiring board may be one in which copper wiring is formed on a core substrate as a base material, and on a build-up layer as a base material. A multilayer wiring board having copper wiring formed thereon may be used.

  According to such a pretreatment liquid for electroless nickel plating, even when an electroless nickel plating liquid that does not contain lead ions is used, the occurrence of bridging can be sufficiently suppressed, and a copper wiring having a fine pattern can be prevented. In addition, electroless nickel plating can be performed while sufficiently preventing a short circuit of the wiring. Thereby, the lead content in the electroless nickel plating film can be sufficiently reduced, and a printed wiring board excellent in environmental regulations can be manufactured. Although it is not necessarily clear about the factor which obtains such an effect, the present inventors guess as follows.

  First, the present inventors consider as follows that the above-described conventional pretreatment liquid cannot sufficiently secure the insulation reliability between copper wirings after electroless nickel plating. That is, the conventional pretreatment liquid is considered to inactivate the catalyst remaining between the wirings in order to prevent the formation of a plating film between the wirings. However, when the distance between wirings becomes smaller, not only impurities such as catalyst remaining between the wirings, but also bridges caused by conductors (copper) remaining as etching residues around the copper wirings will cause short circuits. Conceivable. Therefore, in order to perform electroless nickel plating only on the copper wiring, it is important that only the copper wiring is selectively activated during the activation process of the copper wiring, and the conductor (copper) remaining as a residue is not activated. However, it is considered that such selective activation could not be sufficiently achieved with the conventional pretreatment liquid.

  On the other hand, according to the pretreatment liquid of the present invention, impurities such as a catalyst remaining between the wirings can be deactivated, and the conductor (copper) remaining as an etching residue is selectively deactivated so that only the copper wiring is obtained. It is considered that excellent bridging prevention property has been achieved because the substrate can be subjected to substitution palladium plating. This is because a conductor (copper) having a shape in which a sulfur compound remains as an etching residue by mixing the sulfur compound containing a specific number of methylene groups and polar groups in the molecule with an organic solvent in a well-balanced manner. This is thought to be due to the phenomenon that it is likely to remain adsorbed and hardly remain on a relatively smooth copper wiring.

  In addition, the bridge | bridging suppression effect is not fully acquired as the total content of the said sulfur compound is less than 0.0005 g / L. On the other hand, if it exceeds 10 g / L, it is considered that the amount of sulfur compounds remaining on the copper wiring increases and the activation of the copper wiring is inhibited, and problems such as non-deposition (skip) of electroless nickel plating occur. Resulting in. Moreover, even if the ratio (X / Y) exceeds 80000, the bridge suppressing effect cannot be sufficiently obtained.

  The pretreatment liquid for electroless nickel plating of the present invention is preferably brought into contact with the surface of the wiring board by dipping. That is, the pretreatment liquid for electroless nickel plating of the present invention is an electroless nickel plating in which a substrate having copper wiring is immersed before a replacement palladium plating treatment step which is an activation treatment for providing an electroless nickel plating film. A pretreatment liquid for use is preferable.

  Furthermore, the copper wiring is preferably formed by etching. As described above, according to the pretreatment liquid for electroless nickel plating of the present invention, it is considered that the activation treatment can be prevented from being applied to the conductor (copper) remaining as an etching residue on the base material. As a result, it is possible to more advantageously advance the miniaturization of the copper wiring subjected to electroless nickel plating.

In the pretreatment liquid for electroless nickel plating of the present invention, the total content X (mL / L) of the organic solvent in the pretreatment liquid, and the methylene group (—CH ₂ —) contained in the sulfur compound in the pretreatment liquid. ) (X / M) with respect to the total content M (mol / L) is preferably 9500 or more.

  By satisfying such a condition, it is possible to more reliably prevent non-deposition (skip) of electroless nickel plating while sufficiently preventing the occurrence of bridges. Thereby, the connection reliability of the connection terminal (copper wiring to which electroless nickel plating is given) of a wiring board can be raised to a higher level.

式（５）中、Ｓ_ｋは第ｋ番目の硫黄化合物のモル濃度（ｍｏｌ／Ｌ）を示し、Ｃ_ｋは第ｋ番目の硫黄化合物が有するメチレン基の数を示す。なお、ｋは１〜ｚの整数を示し、第ｋ番目の硫黄化合物とは、ｚ種類の硫黄化合物を１番目からｚ番目まで任意に順番をつけたときのｋ番目に対応する硫黄化合物を指す。 In addition, when the pretreatment liquid of the present invention contains z kinds of the above sulfur compounds, the total content M (mol / L) of methylene groups contained in the sulfur compounds in the pretreatment liquid is represented by the following formula (5). Means the desired value.

In the formula (5), S _k represents the molar concentration (mol / L) of the k-th sulfur compound, and C _k represents the number of methylene groups of the k-th sulfur compound. Note that k represents an integer of 1 to z, and the k-th sulfur compound refers to a sulfur compound corresponding to the k-th when z kinds of sulfur compounds are arbitrarily ordered from the first to the z-th. .

  The pretreatment liquid for electroless nickel plating of the present invention preferably further contains at least one compound selected from a complexing agent, a pH adjuster and a surfactant.

  Moreover, the pretreatment method of electroless nickel plating of the present invention includes any of the pretreatment liquids for electroless nickel plating of the present invention described above on the surface of a wiring board comprising a base material and copper wiring formed on the base material. And a second step of performing a substitution palladium plating process for forming an electroless nickel plating film on the copper wiring after the first step.

  According to such a pretreatment method for electroless nickel plating, the pretreatment liquid for electroless nickel plating of the present invention described above is brought into contact with the wiring board before being subjected to the activation treatment, and thereafter lead ions are contained. Even when an electroless nickel plating film is formed using a non-electroless nickel plating solution, generation of a bridge can be sufficiently prevented.

  In the pretreatment method for electroless nickel plating of the present invention, in the first step, the wiring board is preferably immersed in the pretreatment liquid for electroless nickel plating of the present invention. In the pretreatment method of electroless nickel plating according to the present invention, preferably, a substrate having a copper wiring is immersed in a solution before a replacement palladium plating treatment step which is an activation treatment for providing an electroless nickel plating film. In the pretreatment method for electroless nickel plating, the solution may be any of the pretreatment liquids for electroless nickel plating of the present invention.

  In the pretreatment method for electroless nickel plating according to the present invention, the base material includes an electrically insulating resin. Before the first step, the base material exposed at least between the copper wirings It is preferable to further include a step of removing the surface.

  In addition, it does not specifically limit about the shape and thickness of a base material, The base substrate may be a core board of a wiring board and may be a buildup layer in a multilayer wiring board.

  By having the above steps, etching residues and other foreign matters remaining on the base material between the copper wirings can be removed, and the amount of bridges generated can be further reduced.

  In addition, the above-mentioned step of removing the surface of the base material is performed by removing 0.005 μm to 5 μm in the thickness direction of the surface of the base material exposed between the copper wirings by a dry process, a wet process, or a process combining them. Preferably there is.

  If the amount to be removed is less than 0.005 μm, it is difficult to obtain the effect of further reducing the amount of generated bridges. On the other hand, if it exceeds 5 μm, it tends to be removed to the lower part of the copper wiring, and the wiring is peeled off. Is likely to occur.

  The electroless nickel plating method of the present invention is an electroless nickel plating step of forming an electroless nickel plating film on the surface of a copper wiring of a wiring board subjected to any of the pretreatment methods for electroless nickel plating of the present invention. It is characterized by having.

  According to the electroless nickel plating method of the present invention, even when an electroless nickel plating solution containing no lead ions is used, a short circuit between copper wires is sufficiently suppressed on a copper wire having a fine pattern. It is possible to form an electroless nickel plating film. And according to this method, the content of lead in the electroless nickel plating film can be sufficiently reduced, and a printed wiring board excellent in environmental regulations can be manufactured.

  In the method for producing a printed wiring board of the present invention, any of the pretreatment liquids for electroless nickel plating of the present invention is brought into contact with the surface of a wiring board comprising a base material and a copper wiring formed on the base material. It has the 1st process and the 2nd process which performs the substitution palladium plating process for forming an electroless nickel plating film | membrane on a copper wiring after a 1st process. According to such a method, by applying the pretreatment liquid for electroless nickel plating of the present invention, the electroless nickel plating in which the lead content is sufficiently reduced while sufficiently suppressing a short circuit between copper wirings having a fine pattern. Since it becomes possible to form a film satisfactorily, it is possible to produce a printed wiring board having high density, high connection reliability, and excellent environmental regulations.

  The method for producing a substrate for mounting a semiconductor chip according to the present invention comprises the step of pretreatment liquid for electroless nickel plating according to the present invention on the surface of a substrate for mounting a semiconductor chip comprising a base and a copper wiring formed on the base. It has the 1st process which contacts any, and the 2nd process which performs the substitution palladium plating process for forming an electroless nickel plating film | membrane on a copper wiring after a 1st process. According to such a method, by applying the pretreatment liquid for electroless nickel plating of the present invention, the electroless nickel plating in which the lead content is sufficiently reduced while sufficiently suppressing a short circuit between copper wirings having a fine pattern. Since it becomes possible to form a coating film satisfactorily, it is possible to manufacture a semiconductor chip mounting substrate that has high density, high connection reliability, and excellent environmental regulations.

  According to the present invention, a pretreatment liquid for electroless nickel plating that can sufficiently prevent the occurrence of bridging even when using an electroless nickel plating liquid that does not contain lead ions, a pretreatment method for electroless nickel plating, An electroless nickel plating method, and a printed wiring board and a method for manufacturing a semiconductor chip mounting substrate can be provided. As a result, an electroless nickel plating film can be formed on a copper wiring having an ultrafine pattern in which the interval between patterns is less than 50 μm while sufficiently suppressing a short circuit between the copper wirings. The lead content in the nickel plating film can be sufficiently reduced.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIG. A preferred electroless nickel plating method of the present invention is a wiring board preparation step S1 for preparing a wiring board having a base material and a copper wiring formed on the base material, and a pre-processing for pre-processing the wiring board. Step S2, a replacement palladium plating step S3 for performing a substitution palladium plating treatment for forming an electroless nickel plating film on the copper wiring of the pretreated wiring board, and a copper wiring having a substitution palladium plating treatment And an electroless nickel plating treatment step S4 for forming an electroless nickel plating film. In addition, the plating method of this embodiment is provided with solder resist formation process S15 which forms a solder resist on a base material in the middle of pre-processing process S2.

  In the electroless nickel plating method of the present embodiment, the pretreatment step S2 includes a substrate surface removal step S21 for removing the surface of the substrate between the copper wirings, a first degreasing treatment step S22, and a second degreasing treatment. It includes a step S23, a pretreatment step S24 in which the pretreatment liquid for electroless nickel plating of the present invention is brought into contact with the surface of the wiring board, and a soft etching treatment step S25. Furthermore, between each process, in order to remove the excess liquid remaining on the wiring board used in the previous process, a water washing process S5 for washing the wiring board with running water or the like is performed. Moreover, solder resist formation process S15 is performed between base-material surface removal process S21 and 1st degreasing process S22.

  In the electroless nickel plating method of the present embodiment, the electroless nickel plating is an electroless method using nickel alloys such as Ni—P, Ni—P—Cu, Ni—B, Ni—P—B—W, or pure Ni. As long as it contains nickel, the type of alloy is not particularly limited.

  Hereinafter, each process mentioned above is explained in full detail.

<Wiring board preparation process S1>
In the wiring board preparation step S1, a wiring board having copper wiring formed on the base material is prepared. As a method of obtaining such a wiring board, for example, a copper foil is formed as a metal layer on a core substrate surface or a build-up layer as a base material, and an unnecessary portion of the metal layer is removed by etching to form a copper wiring. Method (subtract method), a method of forming copper wiring by copper plating only on the core substrate surface or build-up layer where necessary (additive method), a thin metal layer (seed layer) on the core substrate surface or build-up layer ), And after forming necessary wiring by electrolytic copper plating, a thin metal layer is removed by etching (semi-additive method).

  The core substrate and the build-up layer as the base material are made of an insulating material, and an electrically insulating resin such as a thermosetting resin, a thermoplastic resin, or a mixed resin thereof can be used as the insulating material. Thermosetting resins include phenolic resin, urea resin, melamine resin, alkyd resin, acrylic resin, unsaturated polyester resin, diallyl phthalate resin, epoxy resin, polybenzimidazole resin, polyamide resin, polyamideimide resin, silicone resin, cyclohexane Resin synthesized from pentadiene, resin containing tris (2-hydroxyethyl) isocyanurate, resin synthesized from aromatic nitrile, trimerized aromatic dicyanamide resin, resin containing triallyl trimetallate, furan resin, ketone resin, A xylene resin, a thermosetting resin containing a condensed polycyclic aromatic, a benzocyclobutene resin, or the like can be used. Examples of the thermoplastic resin include polyimide resin, polyphenylene oxide resin, polyphenylene sulfide resin, aramid resin, and liquid crystal polymer. As the core substrate, for example, it is preferable to use a fiber sheet such as glass cloth impregnated with a thermosetting resin such as an epoxy resin. The build-up layer preferably contains a thermosetting organic insulating material as a main component.

  A filler may be added to the insulating material. Examples of the filler include silica, talc, aluminum hydroxide, aluminum borate, aluminum nitride, and alumina.

  As a method of forming a metal layer on the core substrate surface or buildup layer in the subtract method and a method of forming a thin metal layer (seed layer) on the core substrate surface or buildup layer in the semiadditive method, The method by vapor deposition or plating, the method of bonding metal foil, etc. are mentioned.

(Method by vapor deposition or plating)
As a method for forming a metal layer or a seed layer by vapor deposition on the core substrate surface or build-up layer, a method by sputtering can be mentioned. For example, when a base metal and a thin film copper layer are formed as a metal layer or a seed layer by sputtering, the sputtering apparatus used to form the thin film copper layer is two-pole sputtering, three-pole sputtering, four-pole sputtering, magnetron Sputtering, mirrortron sputtering, or the like can be used. A target used for sputtering is sputtered 5 to 50 nm using, for example, a metal such as Cr, Ni, Co, Pd, Zr, Ni / Cr, or Ni / Cu as a base metal in order to ensure adhesion. Thereafter, a metal layer or a seed layer can be formed by sputtering 200 to 500 nm using copper as a target. Moreover, as a method by plating, the method of forming by plating 0.5-3 micrometers electroless copper on the surface of a core board | substrate or a buildup layer is mentioned.

(Method of bonding metal foil)
When the core substrate or the build-up layer has an adhesive function, the metal layer or the seed layer can be formed by attaching a metal foil such as a copper foil by pressing or laminating.

  In addition, since it is very difficult to directly bond a thin metal layer, if necessary, a method in which a thick metal foil is pasted and then thinned by etching or the like, or a carrier layer after a metal foil with a carrier is pasted A peeling method or the like can be used. As the former method, for example, a method of removing carrier copper with an alkaline etching solution and nickel with a nickel etching solution using a three-layer copper foil of carrier copper / nickel / thin film copper, and the latter method, For example, a seed layer of 5 μm or less can be formed by using a peelable copper foil using aluminum, copper, insulating resin or the like as a carrier. Alternatively, after a copper foil having a thickness of 9 to 18 μm is pasted, the seed layer may be formed by uniformly thinning the copper foil by etching so that the thickness becomes 5 μm or less.

(Wiring formation by etching)
In the above subtractive method, for example, an etching resist is formed in a portion that becomes a wiring of a metal layer (copper foil in the present embodiment), and a chemical etching solution is sprayed and sprayed on a portion exposed from the etching resist. Wiring can be formed by etching away a metal layer (copper foil in this embodiment).

  When using copper foil as a metal layer like this embodiment, an etching resist can be formed using the etching resist material which can be used for a normal wiring board. For example, an etching resist can be formed by silk screen printing of a resist ink. Also, a negative photosensitive dry film for etching resist is laminated on a copper foil, and a photomask that transmits light is superimposed on the wiring shape on it, exposed to ultraviolet rays, and the unexposed areas are developed with a developer. The etching resist can be formed by removing.

  As the chemical etching solution, a chemical etching solution used for an ordinary wiring board, such as a solution of cupric chloride and hydrochloric acid, a ferric chloride solution, a solution of sulfuric acid and hydrogen peroxide, and an ammonium persulfate solution, can be used.

  In the semi-additive method, a plating resist is formed in a necessary pattern on the seed layer formed by the above method, and after forming a wiring by electrolytic copper plating through the seed layer, the plating resist is peeled off, Finally, the seed layer is removed by the above-described etching or the like, whereby a wiring can be formed.

(Wiring formation by plating)
In the additive method, as a method of forming a copper wiring by copper plating on the core substrate surface or the buildup layer, a wiring forming technique by normal plating can be used. For example, after depositing an electroless plating catalyst on the core substrate, a plating resist is formed on the surface portion where plating is not performed, and immersed in an electroless plating solution. Electrolytic plating can be performed to form wiring.

  Further, in the present embodiment, a wiring board in which a conductive paste containing copper or a copper compound is patterned on a base material by a printing method, a photolithography method, or the like, and a copper wiring is formed by a thermosetting process or a baking process. It can also be used.

<Pretreatment step (second step) S2>
(Substrate surface removal step S21)
In the base material surface removal step S21, in order to remove the residue existing between the copper wirings of the wiring board prepared as described above, a base material between the copper wirings (for example, an insulating layer made of an electrically insulating resin). Surface treatment is performed on Examples of the surface treatment method include a dry process, a wet process, and a physical polishing method, and a dry process anisotropic etching method is preferable. Moreover, it is also possible to perform processing by combining methods such as a dry process and a wet process. The depth of the base material surface between the copper wirings to be removed by a method such as dry process or wet process is preferably in the range of 0.005 μm to 5 μm, more preferably in the range of 0.01 μm to 4 μm, and 0.1 μm to 2 μm. A range is particularly preferred. When the depth is smaller than 0.005 μm, it is difficult to remove the metal residue on the base material between the wirings, and a bridge is likely to occur. On the other hand, if it is deeper than 5 μm, etching may occur up to the lower part of the copper wiring, and the wiring will be easily peeled off.

<Removal of substrate surface between copper wirings by dry process>
The dry process used for removing the substrate surface between the copper wirings may be a plasma etching method, a reactive ion etching (RIE) method, a reactive ion beam etching (RIBE) method, or an atmospheric pressure plasma etching method. Examples of the apparatus used for the plasma etching method include a barrel type, a parallel plate type, and a down flow type apparatus, and are not particularly limited. The apparatus used for the reactive ion etching (RIE) method includes a parallel plate type, a magnetron type, a two-frequency type, an ECR type, a helicon type, and an ICP type apparatus, and is not particularly limited. Examples of the apparatus used for the reactive ion beam etching (RIBE) method include an ECR type, a Kaufman type, and an ICP type apparatus, and are not particularly limited. In any case, an etching gas can be appropriately selected, and any of an inorganic gas, an organic compound vapor, or a mixture thereof can be used. Examples of the inorganic gas include He, Ne, Ar, Kr, Xe, N ₂ , NO, N ₂ O, CO, CO ₂ , NH ₃ , SO ₂ , Cl ₂ , freon gas (CF ₄ , CH ₂ F ₂ , C ₄ F ₆ , C ₅ F ₈ , CHF ₃ , CH ₃ F, etc.), or a mixed gas thereof, and a mixed gas in which O ₂ or O ₃ is mixed into these gases. Among these, Ar is a more preferable gas because a stable resin surface can be obtained. Further, the organic compound vapor is not particularly limited, but for example, it is also preferable to mix an appropriate amount of organic compound vapor in the Ar gas so as to obtain an appropriate vapor pressure. Examples of the organic compound vapor include organic silicon compounds, unsaturated compounds such as acrylic acid, organic nitrogen compounds, organic fluorine compounds, and general organic solvents, but the organic compounds used in this embodiment are limited to these. It is not a thing. When the substrate surface between the copper wirings is removed by a dry process, it is more preferable to perform ultrasonic cleaning with water or an organic solvent, or a mixed solution thereof, or cleaning with an alkaline solution as a post-treatment.

<Removal of substrate surface between copper wirings by wet process>
As a wet process for removing the substrate surface between the copper wirings, there is a method of treating with an alkaline solution, a solution containing an oxidizing agent having a large oxidizing power, or a combination of them. Is not particularly limited as long as it is a treatment with a solution that etches 0.002 μm or more. As the alkaline solution, at least one compound containing an amino group such as alkali metal or alkaline earth metal hydroxide such as sodium hydroxide, potassium hydroxide or sodium carbonate, ethylenediamine, methylamine or 2-aminoethanol is used. A solution containing the above can be used, and a solution containing a complexing agent is preferable. As a solution containing an oxidizing agent having a large oxidizing power, it is possible to use a solution containing at least one permanganate, manganate, chromic acid, chromate, or dichromate. Moreover, as a commercial item, RESIST STRIPPER 9296 (Fuji Chemical Industry Co., Ltd. product name) containing 2-aminoethanol is mentioned.

<Removal of the substrate surface between copper wiring by physical polishing>
Examples of the physical polishing method for removing the substrate surface between the copper wirings include wet blasting (physical polishing by jet scrub or the like).

(Solder resist forming step S15)
In the present embodiment, the insulating layer forming step S15 is performed after the substrate surface removing step S21. In this step, an insulating layer having a predetermined opening is formed on the wiring board as a permanent resist for protecting wiring other than the copper wiring subjected to electroless plating.

  The solder resist can be formed, for example, by applying a known photosensitive resin composition and performing predetermined exposure and development.

(First degreasing treatment step S22)
In the first degreasing treatment step S22, the wiring board is immersed in an alkaline solution such as a potassium hydroxide solution in order to clean the wiring board obtained through the substrate surface removal step S21. In addition to the potassium hydroxide solution, at least one compound containing an alkali group such as sodium hydroxide or sodium carbonate or an alkaline earth metal hydroxide, or an amino group such as ethylenediamine, methylamine or 2-aminoethanol was included. A solution can be used, and a solution containing a complexing agent can also be used.

(Second degreasing step S23)
In the second degreasing step S23, the wiring board obtained through the first degreasing step S22 is immersed in a degreasing solution to mainly clean the copper wiring surface.

  It does not specifically limit as a degreasing liquid, For example, a solvent, acidic aqueous solution, or a commercially available degreasing liquid can be used.

(Pretreatment step S24 according to the present invention)
In the pretreatment step S24 according to the present invention, the pretreatment liquid for electroless nickel plating of the present invention is brought into contact with the surface of the wiring board obtained through the second degreasing treatment step S23. Examples of the contact method include a method of immersing the wiring board in the pretreatment liquid of the present invention, a method of spraying the pretreatment liquid of the present invention on the surface of the wiring board using a spray and the like. From the viewpoint of processing uniformity, a method of immersing the wiring board in the pretreatment liquid of the present invention is preferred.

  First, a preferred embodiment of the pretreatment liquid for electroless nickel plating of the present invention will be described.

The pretreatment liquid for electroless nickel plating of the present invention is an aliphatic thiol compound represented by the following general formula (1), an aliphatic thiol compound represented by the following general formula (2), and the following general formula (3). The total of sulfur compounds in the pretreatment liquid, including at least one sulfur compound selected from the group consisting of the aliphatic thiol compound represented by the formula and the disulfide compound represented by the following general formula (4) and an organic solvent The content is 0.0005 to 10 g / L, and the total content X (mL / L) of the organic solvent in the pretreatment liquid and the total content Y (g / L) of the sulfur compound in the pretreatment liquid ) (X / Y) is 80,000 or less.
_{HS- (CH 2) a -COOH ...} (1)
In the formula (1), a represents any integer from 1 to 23.
_{HS- (CH 2) b -OH ...} (2)
In formula (2), b represents any integer from 5 to 23.
_{HS- (CH 2) c -NH 2} ... (3)
In formula (3), c represents any integer from 5 to 23.
^{_{R 1 - (CH 2) n}} - (R 3) p -S-S- (R 4) q - (CH 2) m -R 2 ... (4)
In formula (4), R ¹ and R ² each independently represent a hydroxyl group, a carboxyl group or an amino group, and R ³ and R ⁴ each independently represent a divalent organic group having a hydroxyl group, a carboxyl group or an amino group. N and m each independently represent any integer from 4 to 15, and p and q each independently represent 0 or 1.

<Sulfur compound represented by the general formula (1)>
In the present embodiment, in the above formula (1), any compound in which a is an integer from 1 to 23 can be used, and of these, a is an integer from 4 to 15. It is preferable to use a compound. Moreover, the compound represented by the said General formula (1) can be contained in the pretreatment liquid for electroless nickel plating individually by 1 type or in combination of 2 or more types.

  In addition, when a in the general formula (1) exceeds 23, there is a problem called “skip (electroless nickel plating non-deposition)” in which the electroless nickel plating does not partially precipitate. It tends to be easy to do.

<Sulfur compound represented by the general formula (2)>
In the present embodiment, in the above formula (2), any of compounds in which b is an integer from 5 to 23 can be used. Among these, b is an integer from 8 to 15. It is preferable to use a compound. Moreover, the compound represented by the said General formula (2) can be contained in the pretreatment liquid for electroless nickel plating individually by 1 type or in combination of 2 or more types.

  In addition, in the said general formula (2), when b is less than 4, the effect which suppresses abnormal precipitation cannot fully be acquired, but the smell of a sulfur compound is strong and volatility becomes high, and it is unpreferable on a working environment. On the other hand, when a compound in which b in the formula exceeds 23, skip (electroless nickel plating undeposited) tends to occur.

<Sulfur compound represented by the general formula (3)>
In the present embodiment, in the above formula (3), any compound in which c is an integer from 5 to 23 can be used. Among these, c is an integer from 8 to 15. It is preferable to use a compound. Moreover, the compound represented by the said General formula (3) can be contained in the pretreatment liquid for electroless nickel plating individually by 1 type or in combination of 2 or more types.

  It should be noted that a compound in which c in the general formula (3) is less than 5 is not preferable in terms of working environment because the effect of suppressing abnormal precipitation cannot be sufficiently obtained and the odor of the sulfur compound is strong and volatile. On the other hand, when a compound in which c in the formula exceeds 23, skipping (electroless nickel plating undeposited) tends to occur.

<Sulfur compound represented by the general formula (4)>
In the present embodiment, in the above formula (4), any of compounds in which n and m are each independently an integer of 4 to 15 can be used, and among these, n and m are each It is preferable to use a compound independently represented by an integer of 8 to 13. Moreover, the compound represented by the said General formula (4) can be contained in the pretreatment liquid for electroless nickel plating individually by 1 type or in combination of 2 or more types.

  In addition, when n or m in the general formula (4) is less than 4, an effect of suppressing abnormal precipitation cannot be obtained sufficiently, and the sulfur compound has a strong odor and high volatility, which is preferable in the working environment. Absent. On the other hand, when a compound in which n or m in the formula exceeds 15 is used, there is a tendency that skip (electroless nickel plating undeposited) tends to occur.

When p or q in the general formula (4) is 1, R ³ or R ⁴ is —CH (OH) —, —CH (COOH) —, —C _t H _2t CH (OH) — or —. C _u H _2u CH (COOH) — is preferred. Here, t and u are integers from 4 to 15.

The compound represented by the general formula (4) is preferably one in which p and q are 0 in that it can be easily obtained. That is, it is preferable that it is a sulfur compound represented by the following general formula (6).
^{_{R 5 - (CH 2) r}} -S-S- (CH 2) s -R 6 ... (6)
In formula (6), R ⁵ and R ⁶ each independently represent a hydroxyl group, a carboxyl group or an amino group, and r and s each independently represent any integer from 4 to 15. In the formula (6), it is preferable to use a compound in which r and s are each independently an integer of 8 to 13.

  Moreover, even if the pretreatment liquid for electroless nickel plating of the present invention includes one kind of the compounds represented by the above general formulas (1) to (4) alone or contains two or more kinds. Good.

<Organic solvent>
The type of the organic solvent contained in the pretreatment liquid for electroless nickel plating of the present invention is not particularly limited, but alcohols such as methanol, ethanol, n-propyl alcohol, n-butyl alcohol, di-n-propyl ether, Ethers such as di-n-butyl ether and diallyl ether, aliphatic hydrocarbons such as hexane, cyclohexane, heptane, octane and nonane, ketones such as benzene, acetone, methyl ethyl ketone and cyclohexane, dimethylformamide, dimethylacetamide, N Amide solvents such as methyl pyrrolidone, aromatic hydrocarbons such as toluene and phenol can be used. These solvents can be contained alone or in combination of two or more in the pretreatment liquid for electroless nickel plating. The solvent is preferably used by mixing with water. Furthermore, in this embodiment, it is preferable to use ethanol and acetone among the said solvent from a viewpoint that it can obtain easily.

  The pretreatment liquid for electroless nickel plating of the present invention requires that the total content of the above sulfur compounds in the pretreatment liquid is 0.0005 to 10 g / L, and such content is 0.0008 g / L. It is preferable that it is L-3g / L, and it is more preferable that it is 0.001g / L-0.05g / L. When the total content of the sulfur compounds is less than 0.0008 g / L, the effect of suppressing abnormal deposition of plating is weakened, and it is difficult to ensure sufficient insulation reliability between fine wirings. When the total content of the above sulfur compounds exceeds 3 g / L, depending on the content of the organic solvent, the amount of sulfur compounds remaining on the copper wiring surface increases. As a result, an electroless nickel plating non-deposition (skip) problem is likely to occur.

  In the pretreatment liquid for electroless nickel plating of the present invention, the total content X (mL / L) of the organic solvent in the pretreatment liquid and the total content Y (g of the sulfur compound in the pretreatment liquid). / L) (X / Y) is required to be 80,000 or less, but from the viewpoint of suppressing abnormal deposition of plating, the ratio is preferably 50000 or less, and preferably 20000 or less. More preferred.

Furthermore, in the pretreatment liquid for electroless nickel plating of the present invention, the total content X (mL / L) of the organic solvent in the pretreatment liquid and the methylene group (—CH) contained in the sulfur compound in the pretreatment liquid. ₂ - the total content M (mol / L) and the ratio of) (X / M) is preferably not 9500 or more. By satisfying such a condition, it is possible to more reliably prevent non-deposition (skip) of electroless nickel plating while sufficiently preventing the occurrence of bridges. Thereby, the connection reliability of the connection terminal (copper wiring to which electroless nickel plating is given) of a wiring board can be raised to a higher level.

  Further, from the viewpoint of suppressing both abnormal plating deposition and skipping (partial non-deposition of electroless nickel plating) at a high level, it is more preferable to set the above ratio (X / M) within the range of 9600 to 1600000. Preferably, it is still more preferable to set it within the range of 9600-500000.

  In the pretreatment liquid for electroless nickel plating of the present invention, in addition to the sulfur compounds represented by the general formulas (1) to (4), a heterocyclic compound containing sulfur in the molecule can be contained. Thereby, when the sulfur compound represented by the general formulas (1) to (4) includes a long-chain hydrocarbon group, the content of the organic solvent in the pretreatment liquid is suppressed while suppressing aggregation. It can be reduced, and the workability of the pretreatment can be improved.

  Examples of the heterocyclic compound containing sulfur in the molecule include 3-amino-5-mercapto-1,2,4-triazole, 2-amino-1,3,4-thiadiazole, 5-amino-1,3. , 4-thiadiazole-2-thiol, 6-amino-2-mercaptopentazothiazole, 2-mercapto-2-thiazoline, 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, 2-mercaptoimidazole, 6-mercaptopurine, 2-mercaptopyridine, 2-mercaptopyrimidine, 2-aminothiazole, 2-amino-2-thiazoline, 4-amino-2,1,3-benzothiazole, 5-amino-2-mercaptobenzimidazole, 4-amino- 6-mercaptopyrazole, 2,6-mercaptopurine, 2-mercaptobenzox Heterocyclic compounds having a mercapto group such as tetrazole and the like. These can be used alone or in combination of two or more in the pretreatment liquid for electroless nickel plating.

  Among the above compounds, 3-amino-5-mercapto-1,2,4-triazole, 2-amino-1,3,4-thiadiazole, 5-amino-1,3,4-thiadiazole-2-thiol, 6-amino-2-mercaptopentazothiazole, 2-mercapto-2-thiazoline, 2-mercaptobenzothiazole and 2-mercaptobenzoxazole are preferred.

  Moreover, it is preferable that the pretreatment liquid for electroless nickel plating of the present invention further contains one or more compounds selected from a complexing agent, a pH adjuster and a surfactant.

  Examples of complexing agents include ethylenediaminetetraacetic acid, sodium (1-, 2-, 3- and 4-sodium) salts of ethylenediaminetetraacetic acid, ethylenediaminetriacetic acid, nitrotetraacetic acid and alkali salts thereof, glyconic acid, tartaric acid, and gluconate. , Citric acid, gluconic acid, succinic acid, pyrophosphoric acid, glycolic acid, lactic acid, malic acid, malonic acid, triethanolamine glucono (γ) -lactone, etc., as long as it functions as a complexing agent. Well, it is not limited to these. These complexing agents may be used alone or in combination of two or more.

  Examples of acidic pH adjusters include compounds selected from, for example, iron compounds such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, formic acid, cupric chloride, ferric sulfate, alkali metal chlorides, ammonium persulfate, Alternatively, an aqueous solution in which these are combined, or an aqueous solution containing acidic hexavalent chromium such as chromic acid, chromic acid-sulfuric acid, chromic acid-hydrofluoric acid, dichromic acid, dichromic acid-borofluoric acid, and the like can be given. Further, as an alkaline pH adjuster, a compound containing an alkali group such as sodium hydroxide, potassium hydroxide or sodium carbonate or a hydroxide of an alkaline earth metal, an amino group such as ethylenediamine, methylamine or 2-aminoethanol A solution containing one or more of the above.

  As the surfactant, for example, any of a cationic surfactant, an anionic surfactant, an amphoteric surfactant, a nonionic surfactant, or a mixture thereof can be used.

  In the pretreatment step S24 according to the present invention, the above-described pretreatment liquid for electroless nickel plating of the present invention is brought into contact with the surface of the wiring board obtained through the degreasing treatment step S23, but the contact time is particularly limited. However, it is preferable to change appropriately according to the kind and concentration of the sulfur compound contained in the pretreatment liquid. Moreover, about the temperature of a pre-processing liquid, the range of 10 to 50 degreeC is preferable, the range of 15 to 40 degreeC is more preferable, and it is especially preferable that it is the range of 20 to 30 degreeC.

(Soft etching process S25)
In the soft etching treatment step S25, soft etching is performed by immersing the wiring board in an etching solution in order to smooth the copper wiring surface on the wiring board.

  The etching solution is not particularly limited as long as it is used for ordinary soft etching treatment. For example, an ammonium persulfate aqueous solution, a sodium persulfate aqueous solution, a sulfuric acid-hydrogen peroxide aqueous solution, or a commercially available soft etching solution may be used. it can.

  In the soft etching treatment step S25, subsequent to the soft etching, in order to remove the oxide film formed on the copper wiring, the wiring board is immersed in dilute acid for a relatively short time to perform acid cleaning. The dilute acid is not particularly limited, and for example, dilute sulfuric acid, dilute hydrochloric acid, dilute nitric acid and the like can be used.

<Substitutional palladium plating process S3>
In the replacement palladium plating treatment step S3, a metal serving as a catalyst is immersed on the surface of the copper wiring by immersing the wiring board obtained through the pretreatment step S2 including the pretreatment step S24 according to the present invention described above in a palladium compound-containing aqueous solution. Palladium (Pd) is selectively formed.

The palladium compound-containing aqueous solution is not particularly limited as long as it can replace copper on the copper wiring surface with Pd, and may be used for pretreatment of conventional Ni plating. Any palladium compound may be used as long as it contains palladium ions (Pd ²⁺ ). Examples thereof include palladium fluoride, palladium chloride, palladium bromide, palladium iodide, palladium nitrate, palladium sulfate, palladium oxide, and palladium sulfide. It is done.

<Electroless nickel plating treatment S4>
In the electroless nickel plating treatment S4, the wiring board obtained through the substitution palladium plating treatment step S3 is immersed in an electroless nickel plating solution to selectively form an electroless nickel plating film only on the copper wiring.

  Conventionally used electroless nickel plating solutions can be used. For example, in addition to nickel ion sources such as nickel chloride or nickel sulfate and reducing agents such as hypophosphites or amine boron compounds, complexing agents such as organic acids such as citric acid, malonic acid or tartaric acid or salts thereof, Or, various other commonly used additives such as other pH adjusting agents may be contained in appropriate amounts.

  The temperature of the electroless nickel plating solution during immersion of the wiring board and the immersion time of the wiring board in the plating solution can be appropriately set so that a nickel plating film having a desired film thickness can be obtained.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, in the electroless nickel plating method of the present invention, the pretreatment step S2 only needs to include at least a pretreatment step S24 in which the pretreatment liquid for electroless nickel plating of the present invention is brought into contact with the surface of the wiring board. Other processing steps (base surface removal step S21, first degreasing step S22, second degreasing step S23, soft etching step S25) may be omitted or changed.

  Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited thereto. Hereinafter, the concentration is mass% unless otherwise specified.

  FIG. 2 is a schematic view showing an example of a completed printed wiring board referred to for explaining the steps of the embodiment. A semiconductor chip mounting substrate 10 shown in FIG. 2 includes a gold wire bonding connection terminal 1 and a solder resist 3 provided on the substrate so as to have an opening 2 through which the gold wire bonding connection terminal 1 is exposed. It is configured with. The process until the electroless plating was performed on the gold wire bonding connection terminal 1 of the semiconductor chip mounting substrate 10 was performed, and the state of the formed plating was evaluated.

(Example 1)

(Process a) (Wiring formation)
An etching resist is formed on “MCL-E-679F” (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a copper-clad laminate, and unnecessary copper is etched using a ferric chloride etchant, A copper wiring pattern having the shape shown in FIG. 2 was formed as a gold wire bonding connection terminal 1 in a part. The formed connection terminals had a terminal width: 50 μm, a terminal length: 200 μm, a space between terminals: 30 μm, and a terminal conductor thickness: 18 μm.

(Process b) (Solder resist formation)
Next, a solder resist 3 having an opening 2 was formed on the wiring board provided with the copper wiring by the following procedure so that the gold wire bonding connection terminal 1 was exposed. That is, a photosensitive solder resist “PSR-4000 AUS5” (trade name, manufactured by Taiyo Ink Manufacturing Co., Ltd.) was applied with a roll coater so that the thickness after curing was 40 μm. Subsequently, a solder resist 3 having an opening 2 at a desired location was formed by exposure and development.

(Process c) (Pretreatment 1)
The wiring board provided with the insulating resin layer was immersed in a 30 g / L potassium hydroxide solution at 50 ° C. for 3 minutes, washed with hot water for 1 minute, and then washed with water for 5 minutes.

(Process d) (Pretreatment 2)
Next, the wiring board was immersed in a degreasing solution “Z-200” (trade name, manufactured by World Metal Co., Ltd.) at 50 ° C. for 3 minutes and washed with water for 2 minutes.

(Step e) (Pretreatment 3 (Pretreatment with pretreatment liquid for electroless nickel plating))
Next, the wiring board was immersed in a 5 mL / L aqueous ethanol solution adjusted so that the concentration of mercaptoacetic acid as an aliphatic thiol compound was 0.02 g / L at 25 ° C. for 3 minutes, and hot water was added at 50 ° C. for 1 minute. After washing, it was washed with water for 1 minute.

(Process f) (Pretreatment 4)
Next, the wiring board was immersed in a 100 g / L ammonium persulfate solution for 1 minute and washed with water for 2 minutes. Subsequently, the wiring board was immersed in 10% sulfuric acid for 1 minute and washed with water for 2 minutes.

(Step g) (Substituted palladium plating treatment)
Next, the wiring board was immersed for 5 minutes at 25 ° C. in “SA-100” (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a plating activation treatment solution, and washed with water for 2 minutes.

(Process h) (Electroless nickel plating treatment)
Next, the wiring board is immersed in an electroless nickel plating solution containing no lead having the following composition at 85 ° C. for 10 minutes to form an electroless nickel plating film having a thickness of about 2.5 μm on the connection terminal. Formed. Then, this was washed with water for 1 minute, and the 1st wiring board by which the electroless nickel plating was given on the connection terminal was obtained. On the other hand, the wiring board obtained through the process g was immersed in the same electroless nickel plating solution at 85 ° C. for 20 minutes to form an electroless nickel plating film having a thickness of about 5 μm on the connection terminal. . Then, this was washed with water for 1 minute, and the 2nd wiring board by which the electroless nickel plating was given on the connection terminal was obtained.
Nickel sulfate hexahydrate 22.5g / L
Sodium hypophosphite 20.0g / L
Malic acid 10.0 g / L
Succinic acid 10.0 g / L
Glycine 0.5g / L
Thiodiglycolic acid 5mg / L
Hexaammine chromium (II) chloride 50mg / L
pH: 4.6 (adjusted with sodium hydroxide)

  About the 1st wiring board and 2nd wiring board which were obtained above, the abnormal precipitation of plating was evaluated on the following reference | standard. Furthermore, for a wiring board in which 350 connection terminals (terminal width: 50 μm, terminal length: 200 μm, inter-terminal space: 30 μm) are formed at 350 locations, the same processing method as for the first wiring board and the second wiring board Then, electroless nickel plating was performed, and the occurrence of skip was evaluated for each wiring board according to the following criteria. The results are shown in Table 11. In Table 11, the total content X (mL / L) of the organic solvent in the pretreatment liquid and the total content Y of the sulfur compounds represented by the above formulas (1) to (4) in the pretreatment liquid (G / L) ratio (X / Y), and the total content X (mL / L) of the organic solvent in the pretreatment liquid, and the above formulas (1) to (4) in the pretreatment liquid The ratio (X / M) with the total content M (mol / L) of the methylene group contained in the indicated sulfur compound is shown. Further, Table 16 shows the names of the sulfur compounds used in Example 1, their chemical formulas and molecular weights, and the number of methylene groups contained in the sulfur compounds.

<Evaluation of abnormal deposition of plating>
A: The plating film is satisfactorily formed on the connection terminal without abnormal precipitation. (See Figure 4)
B: Plating partially protrudes from the outer periphery of the connection terminal. (See Figure 5)
C: Plating protrudes and deposits on the entire outer periphery of the connection terminal, and plating also deposits on a part of the substrate surface between the terminals. (See Figure 6)
D: Plating protrudes and deposits on the entire outer periphery of the connection terminal, plating also deposits on a part of the substrate surface between the terminals, and is partially short-circuited. (See Figure 7)
E: Plating protrudes and deposits on the entire outer periphery of the connection terminal, and plating also deposits on a part of the substrate surface between the terminals, thereby completely short-circuiting. (See Figure 8)

<Skip evaluation>
A: A plating film is satisfactorily formed on all of the 350 connection terminals.
B: There are 1 or more and 3 or less connection terminals on which the plating film is not well formed.
C: There are 4 or more and 34 or less connection terminals on which the plating film is not satisfactorily formed.
D: There are 35 or more connection terminals where the plating film is not formed well.

(Examples 2 to 58)
Instead of the pretreatment liquid for electroless nickel plating in step e (pretreatment 3: pretreatment liquid for electroless nickel plating) in Example 1, the sulfur compounds and solvents shown in Tables 1 to 4 are listed in Table 1. The first wiring board and the second wiring board of Examples 2 to 58 are the same as Example 1 except that the pretreatment liquid for electroless nickel plating including the contents shown in -4 is used. Obtained. About the obtained 1st wiring board and 2nd wiring board of Examples 2-58, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Tables 11 and 12. In Tables 11 and 12, the total content X (mL / L) of the organic solvent in the pretreatment liquid and the total content of the sulfur compounds represented by the above formulas (1) to (4) in the pretreatment liquid The ratio (X / Y) with the amount Y (g / L), the total content X (mL / L) of the organic solvent in the pretreatment liquid, and the above formulas (1) to (4) in the pretreatment liquid The ratio (X / M) with the total content M (mol / L) of the methylene group contained in the sulfur compound shown by this is shown. Furthermore, Table 16 shows the names of the sulfur compounds used in Examples 2 to 58, their chemical formulas and molecular weights, and the number of methylene groups contained in the sulfur compounds.

(Example 59)
A first wiring board and a second wiring board of Example 59 were obtained in the same manner as in Example 1 except that the following dry process 1 was carried out as a process a ′ after the process a in Example 1. . About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 13.

(Dry process 1)
By the reactive ion etching (RIE) method, the surface of the insulating resin between the copper circuits was removed under the following conditions, and the surface of the insulating resin was removed by 0.5 μm.
Device name: Plasma cleaning device (SPC-100B, manufactured by Sanyo High Technology)
Power: 600W
Gas and flow rate: Ar, 5SCCM
Processing time: 3 min

(Example 60)
A first wiring board and a second wiring board of Example 60 were obtained in the same manner as in Example 1 except that the following wet process 1 was carried out as a process a ′ after the process a in Example 1. . About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 13.

(Wet process 1)
The wiring board that has undergone step a is dipped in a 10 mL / L aqueous solution of “ethylenediamine monohydrate” (trade name, manufactured by Kanto Chemical Co., Ltd.) at 50 ° C. for 30 minutes, and then washed with hot water at 50 ° C. for 5 minutes. The insulating resin surface was removed by 0.5 μm etching.

(Example 61)
A first wiring board and a second wiring board of Example 61 were obtained in the same manner as in Example 1 except that the following wet process 2 was performed as the process a ′ after the process a in the example 1. . About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 13.

(Wet process 2)
The wiring board that has undergone step a is immersed in a 10 mL / L aqueous solution of “40% methylamine aqueous solution” (trade name, manufactured by Kanto Chemical Co., Ltd.) at 50 ° C. for 30 minutes, and then washed with hot water at 50 ° C. for 5 minutes. The insulating resin surface was removed by 0.5 μm etching.

(Example 62)
A first wiring board and a second wiring board of Example 62 were obtained in the same manner as in Example 1 except that the following wet process 3 was carried out as a process a ′ after the process a in Example 1. . About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 13.

(Wet process 3)
The wiring board that has undergone step a is dipped in a 10 mL / L aqueous solution of “RESIST STRIPPER 9296” (trade name, manufactured by Fuji Chemical Industry Co., Ltd.) at 90 ° C. for 3 minutes, and then rinsed in water at 50 ° C. for 5 minutes and for 3 minutes. The surface of the insulating resin was removed by 0.5 μm by washing with water.

(Example 63)
A first wiring board and a second wiring board of Example 63 were obtained in the same manner as in Example 1 except that the following wet process 4 was carried out as a process a ′ after the process a in Example 1. . About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 13.

(Wet process 4)
The insulating board surface between the copper circuits was removed from the wiring board having undergone step a with a solution containing permanganate as an oxidizing agent having a high oxidizing power. For the treatment, a desmear treatment system (trade name: Circoposit 200MLB, manufactured by Shipley Far East Co., Ltd.) was used. Specifically, the wiring board is made into a mixed aqueous solution of the circuposit MLB conditioner 211 and the circuposit Z (water: 70 vol%, conditioner 211: 20 vol%, circuposit Z: 10 vol%) as a swelling treatment. Immersion treatment was carried out at 3 ° C for 3 minutes. Next, the wiring board was added to a mixed aqueous solution of circuposit MLB promoter 213A and circuposit MLB promoter 213B (water: 75 vol%, promoter 213A: 10 vol%, promoter 213B: 15 vol%) at 70 ° C as a removal process. Immersion treatment was performed for a minute. Next, the wiring board was immersed in Circposit MLB Neutralizer 216-4 (water: 80% by volume, Neutralizer 216-4: 20% by volume) for 5 minutes as a neutralization treatment, and further washed with water for 3 minutes. did. By these treatments, the insulating resin surface was removed by 0.5 μm.

(Example 64)
After the step a in Example 1, the first wiring board and the second wiring board of Example 64 were obtained in the same manner as in Example 1 except that the following physical polishing 1 was performed as the process a ′. It was. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 13.

(Physical polishing 1)
The surface of the insulating resin between the copper circuits was removed by wet blasting (physical polishing with jet scrub or the like) under the following conditions, and the insulating resin surface was etched away by 0.5 μm.
Device name: PFE-3000T (Mako Co., Ltd.)
Pressure: 0.2MPa
Fine particles: Alumina # 2000 (center particle size: about 6.7 μm)
Conveyance speed: 0.5m / min

(Example 65)
In Example 30 (Example using an ethanol solution containing 8-amino-1-octanethiol 0.1 (g / L) instead of the pretreatment liquid for electroless nickel plating in Step e of Example 1) A first wiring board and a second wiring board of Example 65 were obtained in the same manner as in Example 30 except that the dry process 1 was performed as the process a ′ after the process a. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 13.

Example 66
In Example 30 (Example using an ethanol solution containing 8-amino-1-octanethiol 0.1 (g / L) instead of the pretreatment liquid for electroless nickel plating in Step e of Example 1) A first wiring board and a second wiring board of Example 66 were obtained in the same manner as in Example 30 except that the above-described wet process 1 was performed as the process a ′ after the process a. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 13.

(Example 67)
In Example 30 (Example using an ethanol solution containing 8-amino-1-octanethiol 0.1 (g / L) instead of the pretreatment liquid for electroless nickel plating in Step e of Example 1) After step a, a first wiring board and a second wiring board of Example 67 were obtained in the same manner as in Example 30 except that the above wet process 2 was performed as step a ′. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 13.

Example 68
In Example 30 (Example using an ethanol solution containing 8-amino-1-octanethiol 0.1 (g / L) instead of the pretreatment liquid for electroless nickel plating in Step e of Example 1) After step a, a first wiring board and a second wiring board of Example 68 were obtained in the same manner as in Example 30 except that the above wet process 3 was performed as Step a ′. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 13.

(Example 69)
In Example 30 (Example using an ethanol solution containing 8-amino-1-octanethiol 0.1 (g / L) instead of the pretreatment liquid for electroless nickel plating in Step e of Example 1) After step a, a first wiring board and a second wiring board of Example 69 were obtained in the same manner as in Example 30 except that the wet process 4 was performed as step a ′. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 13.

  In Table 13, the total content X (mL / L) of the organic solvent in the pretreatment liquid and the total content Y of the sulfur compounds represented by the above formulas (1) to (4) in the pretreatment liquid (G / L) ratio (X / Y), and the total content X (mL / L) of the organic solvent in the pretreatment liquid, and the above formulas (1) to (4) in the pretreatment liquid The ratio (X / M) with the total content M (mol / L) of the methylene group contained in the indicated sulfur compound is shown. Table 16 shows the names of the sulfur compounds used in Examples 59 to 69, their chemical formulas and molecular weights, and the number of methylene groups contained in the sulfur compounds.

(Comparative Example 1)
Except that the step e (pretreatment 3: pretreatment with a pretreatment solution for electroless nickel plating) shown in Example 1 was not performed, the same steps as in Example 1 were performed, and the first of Comparative Example 1 was performed. A wiring board and a second wiring board were obtained. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 14.

(Comparative Examples 2-35)
Instead of the pretreatment solution for electroless nickel plating in step e of Example 1 (pretreatment 3: pretreatment with pretreatment solution for electroless nickel plating), the sulfur compounds and solvents shown in Tables 7 to 9 are used in Table 7. The first wiring board and the second wiring board of Comparative Examples 2 to 35 are the same as in Example 1 except that the pretreatment liquid for electroless nickel plating including the contents shown in FIGS. Obtained. About the obtained 1st wiring board and 2nd wiring board of Comparative Examples 2-35, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Tables 14 and 15.

(Comparative Example 36)
After step a in Example 1, the above-described dry process 1 is performed as step a ′, and step e (pretreatment 3: pretreatment with a pretreatment liquid for electroless nickel plating) is not performed. Except for this, the same steps as in Example 1 were performed to obtain the first wiring board and the second wiring board of Comparative Example 36. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 15.

(Comparative Example 37)
After step a in Example 1, the above-described wet process 1 is performed as step a ′, and step e (pretreatment 3: pretreatment with a pretreatment solution for electroless nickel plating) is not performed. Except for this, the same steps as in Example 1 were performed to obtain the first wiring board and the second wiring board of Comparative Example 37. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 15.

(Comparative Example 38)
After step a in Example 1, the above-described wet process 2 is performed as step a ′, and step e (pretreatment 3: pretreatment with a pretreatment liquid for electroless nickel plating) is not performed. Except for this, the same steps as in Example 1 were performed to obtain the first wiring board and the second wiring board of Comparative Example 38. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 15.

(Comparative Example 39)
After step a in Example 1, the above wet process 3 is performed as step a ′, and step e (pretreatment 3: pretreatment with a pretreatment liquid for electroless nickel plating) is not performed. Except for this, the same steps as in Example 1 were performed to obtain the first wiring board and the second wiring board of Comparative Example 39. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 15.

(Comparative Example 40)
After step a in Example 1, the above-described wet process 4 is performed as step a ′, and step e (pretreatment 3: pretreatment with a pretreatment liquid for electroless nickel plating) is not performed. Except for this, the same steps as in Example 1 were performed to obtain the first wiring board and the second wiring board of Comparative Example 40. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 15.

(Comparative Example 41)
After step a in Example 1, the above-described physical polishing 1 is performed as step a ′, and step e shown in Example 1 (pretreatment 3: pretreatment with a pretreatment solution for electroless nickel plating) is performed. A process similar to that of Example 1 was performed except that there was not, and a first wiring board and a second wiring board of Comparative Example 41 were obtained. About the obtained 1st wiring board and 2nd wiring board, it carried out similarly to Example 1, and evaluated abnormal precipitation of plating, respectively. Further, the occurrence of skip was also evaluated in the same manner as in Example 1. The results are shown in Table 15.

  Also in Table 15, the total content X (mL / L) of the organic solvent in the pretreatment liquid and the total content Y (g of the sulfur compounds represented by the above formulas (1) to (4) in the pretreatment liquid / L) (X / Y), the total content X (mL / L) of the organic solvent in the pretreatment liquid, and the above formulas (1) to (4) in the pretreatment liquid. The ratio (X / M) to the total content M (mol / L) of methylene groups contained in the sulfur compound is shown. In addition, when the pretreatment liquid did not contain the sulfur compound represented by the above formulas (1) to (4), “-” was marked as having no corresponding value.

As is clear from the results of Examples 1 to 69, according to the present invention, even when an electroless nickel plating solution that does not contain lead ions is used, the occurrence of bridging between wirings can be sufficiently prevented. Therefore, it is possible to realize electroless plating with excellent insulation reliability for a wiring board having fine wiring. Further, the total content X (mL / L) of the organic solvent in the pretreatment liquid and the total content M (mol / L) of the methylene group (—CH ₂ —) contained in the sulfur compound in the pretreatment liquid In an example in which the ratio (X / M) was 9500 or more, it was confirmed that non-precipitation (skip) of electroless nickel plating can be more reliably prevented while sufficiently preventing the occurrence of bridges.

It is a flowchart of suitable embodiment of the electroless nickel plating method of this invention. It is a schematic diagram which shows an example of the board | substrate for semiconductor chip mounting. It is a schematic diagram which shows the shape of the connection terminal for gold | metal | money wire bonding in which electroless nickel plating is given. It is a schematic diagram which shows the connection terminal for gold | metal wire bonding in which the abnormal precipitation of plating did not generate | occur | produce and electroless nickel plating was formed favorably. It is a schematic diagram which shows an example of the wiring board in which abnormal precipitation of plating has generate | occur | produced the circumference | surroundings of the connection terminal for gold wire bonding, and between terminals. It is a schematic diagram which shows the other example of the wiring board in which the abnormal precipitation of plating has generate | occur | produced the circumference | surroundings of the connection terminal for gold wire bonding, and between terminals. It is a schematic diagram which shows the other example of the wiring board in which the abnormal precipitation of plating has generate | occur | produced the circumference | surroundings of the connection terminal for gold wire bonding, and between terminals. It is a schematic diagram which shows the other example of the wiring board in which the abnormal precipitation of plating has generate | occur | produced the circumference | surroundings of the connection terminal for gold wire bonding, and between terminals.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Gold wire bonding connection terminal, 2 ... Opening part, 3 ... Insulating resin layer, 4 ... Gold wire bonding connection terminal in which electroless nickel plating was well formed, 5 ... Substrate, 6 ... Around the connection terminal Deposited plating, 7 ... Plating deposited on the substrate between the terminals, 10 ... Semiconductor chip mounting substrate, 12 ... Pad, 14 ... Lead wire.

Claims (8)

A pretreatment for electroless nickel plating, which is brought into contact with the surface of a wiring board, comprising: a base material; and copper wiring to be subjected to substitution palladium plating processing for forming an electroless nickel plating film formed on the base material. Liquid,
An aliphatic thiol compound represented by the following general formula (1), an aliphatic thiol compound represented by the following general formula (2), an aliphatic thiol compound represented by the following general formula (3), and the following general formula (4) And at least one sulfur compound selected from the group consisting of disulfide compounds represented by formula (I) and an organic solvent,
The total content of the sulfur compound in the pretreatment liquid is 0.0005 to 10 g / L, and the total content X (mL / L) of the organic solvent in the pretreatment liquid and the pretreatment liquid A pretreatment solution for electroless nickel plating, wherein the ratio (X / Y) of the total content Y (g / L) of sulfur compounds is 80000 or less.
_{HS- (CH 2) a -COOH ...} (1)
[In Formula (1), a shows the integer in any one of 1-23. ]
_{HS- (CH 2) b -OH ...} (2)
[In the formula (2), b represents any integer from 5 to 23. ]
_{HS- (CH 2) c -NH 2} ... (3)
[In the formula (3), c represents any integer from 5 to 23. ]
^{_{R 1 - (CH 2) n}} - (R 3) p -S-S- (R 4) q - (CH 2) m -R 2 ... (4)
[In Formula (4), R ¹ and R ² each independently represent a hydroxyl group, a carboxyl group or an amino group, and R ³ and R ⁴ each independently represent a divalent organic group having a hydroxyl group, a carboxyl group or an amino group. A group, n and m each independently represent any integer from 4 to 15, and p and q each independently represent 0 or 1; ]   Ratio (X / M) of the total content X (mL / L) of the organic solvent in the pretreatment liquid and the total content M (mol / L) of methylene groups contained in the sulfur compound in the pretreatment liquid The pretreatment liquid for electroless nickel plating according to claim 1, wherein:   The pretreatment liquid for electroless nickel plating according to claim 1 or 2, further comprising at least one compound selected from a complexing agent, a pH adjusting agent and a surfactant. The 1st process of making the pretreatment liquid for electroless nickel plating according to any one of claims 1 to 3 contact the surface of a wiring board provided with a substrate and copper wiring formed on the substrate. ,
A second step of performing a substitution palladium plating treatment for forming an electroless nickel plating film on the copper wiring after the first step;
A pretreatment method for electroless nickel plating, comprising: The base material includes an electrically insulating resin,
5. The pretreatment method for electroless nickel plating according to claim 4, further comprising a step of removing at least the surface of the base material exposed between the copper wirings before the first step.   An electroless nickel plating step of forming an electroless nickel plating film on the surface of the copper wiring of the wiring board subjected to the pretreatment method for electroless nickel plating according to claim 4 or 5. Electroless nickel plating method. The 1st process of making the pretreatment liquid for electroless nickel plating according to any one of claims 1 to 3 contact the surface of a wiring board provided with a substrate and copper wiring formed on the substrate. ,
A second step of performing a substitution palladium plating treatment for forming an electroless nickel plating film on the copper wiring after the first step;
A method for producing a printed wiring board, comprising: 4. A first treatment liquid for electroless nickel plating according to claim 1, which is in contact with a surface of a semiconductor chip mounting substrate comprising a base material and a copper wiring formed on the base material. 1 process,
A second step of performing a substitution palladium plating treatment for forming an electroless nickel plating film on the copper wiring after the first step;
A method of manufacturing a semiconductor chip mounting substrate, comprising:

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