JP5445818B2 - Electroless plating method and activation pretreatment method - Google Patents

Description

  The present invention relates to an electroless plating method and an activation pretreatment method.

  Metals have characteristics such as conductivity, rigidity, and heat conductivity, and are widely used in various fields such as automobiles, electronics, and semiconductors. In particular, in these fields where remarkable technological development is remarkable, not only metals having a single composition but also metals having a plurality of compositions in accordance with functions and characteristics such as alloys and resin-containing metals are used. In addition, these metal forms are used by processing into a plate-like or three-dimensional molded product by using processes such as stretching, pressing, and punching.

  On the other hand, in the printed wiring board and decoration fields, a metal layer is further formed on the surface of a resin or metal as a conductive layer or a corrosion prevention layer. As a method for forming a metal layer on the resin or forming (stacking) different metal layers on the metal surface in this way, an inexpensive and simple plating technique is used.

  Plating techniques include electroplating and electroless plating (chemical plating). Electroplating is a method in which an external power source and a metal electrode are connected and metal ions are reduced by electricity to deposit metal. On the other hand, electroless plating is generally called chemical plating and is a method of depositing metal using a chemical reaction, and there are a reduction type and a substitution type. Reduction type electroless plating is a method in which metal ions dissolved in a plating solution are reduced with a reducing agent and deposited. On the other hand, substitutional electroless plating can be used in the case of laminating a metal that is more precious than the underlying metal by utilizing the difference in ionization tendency of the metal. Both of them do not require the formation of a power source and energizing terminals as in electroplating, and are used in various fields as a cheaper and simpler plating method. (Hereinafter, reducing electroless plating is referred to as electroless plating, and substitutional electroless plating is referred to as displacement plating.)

  The use of electroless plating and displacement plating is expanding especially for printed wiring boards, which are remarkably low in price and high in definition. For example, in plating in a through hole after drilling, a palladium catalyst is first applied in the through hole, and electroless copper plating is performed to ensure conduction between layers. This is an example in which a copper conductive layer is formed on a resin by utilizing the feature that metal can be deposited on non-conductors such as plastics by electroless plating.

  On the other hand, electroless plating and displacement plating are also used when various kinds of metals are laminated on a metal that is a conductor. For example, in a printed wiring board for semiconductor mounting, as a terminal for wire bonding, replacement palladium plating is performed on a copper wiring as a barrier and a catalyst layer, electroless nickel plating is performed thereon, and a nickel layer is formed as a copper barrier layer Further, substitution gold plating is performed, and a gold layer is formed on the outermost layer to obtain a terminal having high bondability with a gold wire. In some cases, electroless gold plating is performed after displacement gold plating, and the gold layer is thickened (thick plating) to increase connection reliability.

  Displacement plating is simpler than electroless plating and can form a plating layer with good adhesion to the base metal, but it can be used only when laminating a noble metal than the base metal, and it is less basic than the base metal. When the metal is laminated, it cannot be used, and the selectivity of the metal to be laminated is low.

On the other hand, in electroless plating, if a catalyst is applied on a base metal, a uniform metal layer can be formed, and there are a wide range of metal options to be laminated. However, it is necessary to apply a catalyst, which is disadvantageous in that the process becomes long and the cost is high because noble metal is used for the catalyst. Therefore, it is required to laminate a metal by electroless plating on a base metal without using an expensive noble metal catalyst.

According to Patent Document 1, direct electroless nickel plating can be selectively performed only on copper without providing a catalyst. This is based on the fact that copper exhibits a catalytic action in the case of an electroless nickel system using a boron-based reducing agent. In this case, however, the plating process becomes unstable, and in order to stabilize plating. In addition to the reducing agent, it is necessary to add an additive, which limits the properties of the plating film. This cannot be achieved by a system using sodium hypophosphite as a reducing agent, which is generally widely used as electroless nickel plating.
Japanese Patent No. 3393190

  In this way, in electroless plating, the entire plating system including the metal to be laminated with the base metal and the reducing agent and pH must exhibit the precipitation (reduction) action of metal ions to be laminated, When attempting to stack metals without applying a catalyst such as a noble metal, the combination of the metals is very limited. For this reason, there has been a demand for an electroless plating method that uses electroless plating, does not use a noble metal catalyst, and loosely restricts the combination of metals to be laminated.

  The present invention solves the above-described problems, and provides an electroless plating method that does not use a precious metal catalyst and has a loose restriction on the combination of the metal to be laminated with the electroless plating system. Moreover, the method of laminating | stacking a metal by electroless plating on a base metal, without using noble metal catalysts, such as palladium and silver, is provided. Furthermore, the present invention provides a method of laminating a base metal by an electroless plating method without using a noble metal catalyst such as palladium or silver. Furthermore, using an electroless plating system that does not exert a catalytic action on the metal to be laminated, different metals are laminated on the underlying metal by an electroless plating method without using a noble metal catalyst such as palladium or silver. Provide a method. Furthermore, there is provided an activation pretreatment method for laminating a metal by electroless plating on a base metal without using a noble metal catalyst such as palladium.

In order to achieve the above object, the present invention provides (1) a method of forming an electroless nickel plating layer on a conductor that does not have a noble metal catalyst such as palladium, silver or platinum on the surface, and a) on the surface A step of preparing an aqueous solution in which a core, which is a powder having an average particle diameter of 10 nm or more and 1 mm or less having nickel or a nickel alloy, is dispersed by a continuous stirring operation using a stirring blade; and b) of gold, copper, nickel or a nickel alloy A step of immersing a conductor having any of the surfaces in the aqueous solution, and c) a step of adding an electroless nickel plating solution containing hypophosphite as a reducing agent to the aqueous solution at a constant flow rate, or Dividing the components of the electroless nickel plating solution into at least a nickel ion solution and a reducing agent solution, and adding each to the aqueous solution simultaneously and in parallel at a constant flow rate. The present invention relates to a method for electroless nickel plating on a conductive material.
Moreover, this invention relates to the electroless nickel plating method to the conductor as described in (1) whose (2) conductor is a conductor which has copper and gold on the surface.
The present invention is also (3) two or more conductors having at least different metal surfaces among conductors having one surface selected from gold, copper, nickel, or nickel alloy. It is related with the electroless nickel plating method to the conductor as described in (1).
The first feature of the present invention is characterized in that the core is dispersed in the electroless plating solution, and the core in which the conductive layer is deposited on the surface of the core is intermittently brought into contact with the conductor. The gist of the present invention is the electroless plating method for the conductor. In the first feature of the present invention, the nucleus on which the conductive layer is deposited by electroless plating is intermittently brought into contact with the conductor so that the potential on the surface of the conductor is the nucleus on which electroless plating is in progress. It becomes close to the potential of the body surface, an electroless plating reaction occurs on the conductor, and the conductive layer can be deposited. Furthermore, in the first feature of the present invention, since the nucleus is intermittently brought into contact with the conductor, the nucleus is not taken into the conductive layer on the conductor, and a smooth conductive layer can be formed on the conductor. Furthermore, in the first feature of the present invention, since the core is intermittently brought into contact with the conductor, the conductive layer deposited by the electroless plating reaction and the underlying conductor are different even if they have the same composition. However, a uniform conductive layer can be selectively formed without unevenness regardless of the underlying conductor.

  In addition, the second feature of the present invention is that in the plating solution in which nuclei are dispersed in the electroless plating solution, and the nuclei in which the conductive layer is deposited by electroless plating are dispersed on the surface of the nucleus. The gist of the present invention is an electroless plating method on a conductor characterized by immersing the conductor. According to this invention, the core body in which the conductive layer is being deposited can contact the conductor intermittently without unevenness.

  The third feature of the present invention is that the core is dispersed in the electroless plating solution, and the conductor is deposited in the liquid in which the core is deposited on the surface of the core by electroless plating. The subject matter of the present invention is a method of electroless plating on a conductor, characterized in that the conductor is immersed and the conductor is swung. According to this invention, the core body in which the conductive layer is being deposited can contact the conductor intermittently without unevenness.

  Further, the fourth feature of the present invention is that it is an electroless plating method characterized by not applying a precious metal catalyst to the conductor. According to this invention, since expensive noble metal catalysts such as palladium, gold, silver, and platinum are not used, the cost becomes easy. In addition, since there is no catalyst application step, there is an effect of shortening the step.

  Further, the fifth feature of the present invention is that it is an electroless plating method characterized in that the core is powdery or fibrous. According to the present invention, the size and shape of the core can be selected according to the shape of the conductor.

  The sixth feature of the present invention is an electroless plating method characterized in that the conductive layer deposited by electroless plating is nickel or nickel alloy, and the conductor is gold, copper, nickel or nickel alloy. Is the gist.

  A seventh feature of the present invention is that it is an electroless plating method characterized in that the average particle size of the core is 10 nm or more and 10 mm or less. According to the present invention, since the size of the nucleus can be arbitrarily selected, the size of the nucleus can be selected in accordance with the shape of the conductor and the electroless plating or activation pretreatment method system. .

  The eighth feature of the present invention is that it is an activation pretreatment method characterized in that the electroless plating method having any one of the first to seventh features is a pretreatment for plating. .

  Provide electroless plating with loose restrictions on the combination of electroless plating and base metal. Further, the metal can be deposited by electroless plating without performing catalyst treatment on the base metal.

  Embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic, and the number and length, the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in light of the following description. Further, these differ depending on the desired function and application, and should be appropriately determined. Moreover, it is a matter of course that the drawings include portions having different dimensional relationships and ratios.

  The conductive layer 1 according to the first embodiment of the present invention shown in FIG. 1 is a material that can be obtained by known electroless plating. The electroless plating of the present invention refers to a method of reducing and precipitating metal ions with the reducing power of a metal ion reducing agent. Specific materials that can be used as the conductive layer 1 include gold, platinum, silver, copper, lead, palladium, tin, nickel, iron, chromium, zinc, aluminum, and alloys thereof. Examples of other materials obtained by electroless plating include phosphorus-containing nickel, boron-containing nickel, and fluorine-containing nickel. From the viewpoint of corrosion resistance, metals such as gold, platinum, palladium, and nickel are preferable.

  In general electroless nickel plating using hypophosphorous acid as a reducing agent, phosphorus co-deposits in the nickel film. The phosphorus content ratio in nickel can be freely changed in the range of 1 to 14 weight percent depending on the liquid component of the reduction type electroless plating. Furthermore, since the phosphorus content affects various properties such as electric resistance, hardness, and magnetism of the nickel-phosphorus film, the phosphorus content may be adjusted according to the purpose. For example, when obtaining a nickel-phosphorus film having a low electric resistance, the phosphorus content is preferably 5% or less, and more preferably 3% or less. In order to further reduce the resistance, the phosphorus content is particularly preferably 1% or less.

  Since the hardness of the nickel film depends on the phosphorus content and annealing conditions, it is necessary to adjust the phosphorus content according to the desired state. In order to increase the hardness immediately after plating, a lower phosphorus content is better. Specifically, the phosphorus content is preferably 8% or less, and more preferably 5% or less. In order to further increase the hardness, the phosphorus content is more preferably 3% or less, and particularly preferably 1% or less.

  In addition, when annealing is performed at, for example, 500 ° C. or higher after plating, the crystal structure changes, so the hardness changes. In this case, in order to increase the hardness of the nickel-phosphorus film, a higher phosphorus content is better. Specifically, the phosphorus content is preferably 3% or more, and more preferably 5% or more. In order to further increase the hardness, the phosphorus content is more preferably 8% or more, and particularly preferably 10% or more.

  Further, the nickel-phosphorus film has an amorphous structure when the phosphorus content is about 8% or more, and the magnetism is lost. Therefore, when the nickel-phosphorus film is made magnetic, the phosphorus content is preferably 8% or less, and more preferably 3% or less. Furthermore, it is most preferable if the phosphorus content is zero.

  The core 3 according to the first embodiment of the present invention refers to a body to be plated on which the conductive layer 1 is deposited by electroless plating and a body to be plated having the conductive layer 1 on the surface. The size and shape of the core 3 are defined as an initial state in which the conductive layer 1 is deposited on the surface by electroless plating of the present invention.

  The size and shape of the core 3 are preferably fine powder. The shape of the core 3 is not particularly limited, but specifically, as shown in FIGS. 2A to 2E, it is fibrous, powdery, spherical, elliptical, porous, polygonal, or these shapes These composites and aggregates are included. Further, the surface of the core 3 is preferably less uneven because it is easy to obtain a uniform plating film by electroless plating.

  When the shape of the core 3 is fibrous, the length direction is preferably 10 mm or less and more preferably 1 mm or less in order to ensure entanglement in the liquid and uniform dispersibility. Furthermore, the maximum length of the cross section is preferably 50 μm or less, and more preferably 10 μm or less. Further, the core 3 is preferably powder rather than fibrous because the core 3 is less dispersible in liquid and less adherent to a container or the like, or the solid-liquid is easily separated. The size of the core 3 is preferably an average particle size of 10 nm or more and 10 mm or less.

  When it is necessary to perform solid-liquid separation between the core 3 and the plating solution, the core 3 is preferably larger. Specifically, the average particle diameter is more preferably from 100 nm to 10 mm, and particularly preferably from 1 μm to 10 mm.

  In addition, when the core 3 is uniformly stirred and dispersed, the size of the core 3 is preferably smaller although it depends on the size of the plating tank. Specifically, an average particle size of 10 nm to 1 mm is more preferable, and an average particle size of 10 nm to 100 μm is particularly preferable.

  In addition, the average particle diameter described in the present invention refers to the median diameter. Moreover, although the particle size distribution is not limited, it is more preferable to be uniform when solid-liquid separation using filtration is assumed. Specifically, the value obtained by dividing the absolute value of the difference between D50 (median diameter) and D10 or D90 by D50 and multiplying by 100 is preferably within 200, and more preferably within 100. Furthermore, 50 or less is more preferable, and 10 or less is particularly preferable. Of course, the apparent size and shape change as the deposition of the conductive layer 1 on the surface of the core 3 proceeds by electroless plating.

  The material of the core 3 related to the first embodiment of the present invention is not particularly limited. 3A to 3E show cross sections of the core 3 on which the conductive layer 1 is deposited on the surface.

  As shown in FIG. 3A, the core 3 may be entirely composed of the same composition as the conductive layer 1 formed on the surface. In this case, the metal or alloy described as the conductive layer 1 described above is formed. Can be used. These are highly versatile because various metals and alloys of various sizes are on the market and can be easily obtained.

  On the other hand, as shown in FIG. 3B, the core 3 may be made of a material different from that of the conductive layer 1 on the surface. For example, a metal or alloy other than the surface conductive layer 1 of the core 3, plastic, ceramic, organic matter, etc. can be used. Specifically, metals such as gold, platinum, silver, copper, lead, palladium, tin, nickel, iron, chromium, zinc, aluminum, and alloys thereof, polyvinyl chloride resin (PVC), polyvinylidene chloride resin, poly Vinyl acetate resin, polyvinyl alcohol resin (PVA), polystyrene resin (PS), styrene / acrylonitrile / butadiene copolymer (ABS), polyethylene resin (PE), ethylene / vinyl acetate copolymer (EVA), polypropylene resin (PP ), Poly-4-methylpentene (TPX), polymethyl methacrylate (PMMA), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), cellulose acetate, tetrafluoride Ethylene resin (PTFE), tetrafluoride, 6 Propylene fluoride resin (FEP), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / ethylene copolymer (ETFE), trifluoroethylene chloride (PCTFE), vinylidene fluoride (PVDF) ), Polyethylene terephthalate resin (PET), polyamide resin (nylon), polyacetal (POM), polyphenylene terephthalate (PPO), polycarbonate resin (PC), polyurethane resin, polyester elastomer, polyolefin resin, silicone resin, polyimide resin, etc. And inorganic materials such as glass, quartz, carbon, silica, and aluminum hydroxide. Furthermore, as a material of the core body 3, an organic substance such as cellulose can be used.

  As shown in FIG. 3B, the core 3 may have a multi-layer structure as described above. Moreover, those aggregates may be sufficient. Further, as shown in FIGS. 3C and 3D, a layer may be formed on the surface of the aggregate. In particular, in order to uniformly disperse the core 3 in the plating solution, it is desirable that the core 3 has a low volume density. Therefore, it is preferable to use a plastic for the core 3, and a plastic material having a lighter specific gravity is preferable. .

  Furthermore, as shown in FIG. 3B, when the core 3 has a layer structure and a metal is formed on the surface of the plastic, the volume density of the entire core 3 is reduced if the metal is thinner. Is preferable, and the volume density is lighter. Specifically, the thickness of the surface conductive layer 1 is preferably 50 percent or less, more preferably 30 percent or less of the average particle diameter of the core 3. Furthermore, 10 percent or less is more preferable, and 5 percent or less is particularly preferable. For example, nickel having an average particle diameter of 10 μm (phosphorus content 1% or less) has a volume density of 8.9, but nickel (conductive layer 1) has a thickness of 0.1 μm on the surface of polystyrene particles having an average particle diameter of 10 μm. The core 3 formed with (one percent of the average particle size) has a volume density of about 1.5. Therefore, the latter polystyrene and nickel core 3 is more highly dispersed in water (plating solution) by weak stirring than the former nickel single core 3.

  Furthermore, it is preferable that the surface of the core 3 is a material having a hydrophilic functional group because dispersibility in the plating solution is increased. Examples of the hydrophilic functional group include a hydroxy group, an amino group, and a sulfone group.

  In addition, as shown in FIG. 3B, when the core 3 has a layer structure, the surface thereof is the same material as the conductive layer 1 formed by the electroless plating of the present invention. The conductive layer 1 is easy to deposit due to its catalytic property, which is preferable. Furthermore, even if the surface of the core 3 is not made of the same material as that of the conductive layer 1 formed by electroless plating according to the present invention, a metal having a catalytic action for electroless plating can be used. For example, when electroless nickel or copper plating is performed, as shown in FIG. 3B, when palladium or silver is formed on the surface of the plastic particles, the nickel or copper conductive layer 1 is formed on the surface of the core 3. Is preferable.

  As shown in FIG. 3 (a), when the entire nuclear body 3 has the same composition, the constituent material is formed. On the other hand, as shown in FIGS. 3 (b), (c), and (d), In the case of a layer structure, it is preferable that the surface material contains a noble metal or a noble metal because the core 3 can be used repeatedly as described later.

  When the core 3 is layered as shown in FIGS. 3B, 3C, and 3D, the surface may not be a continuous shape (layer). Specifically, FIG. As shown in (), a form in which a granular object adheres to the surface may be used.

  As the material of the conductor 2 shown in FIG. 1, a conductive material such as a metal, an alloy, or an organic component or an inorganic component-containing metal can be used. Specific examples of the material of the conductor 2 include metals such as gold, platinum, silver, copper, lead, palladium, tin, nickel, iron, chromium, zinc, and aluminum, and alloys thereof. Examples of other materials obtained by electroless plating include phosphorus-containing nickel, boron-containing nickel, and fluorine-containing nickel. Further, the shape is not particularly limited, but a plate shape, a sphere, a rod shape, and the like may be raised, and the surface may be smooth, uneven, or a mixed state thereof.

  The catalyst related to the first embodiment refers to a substance that exhibits a catalytic action with respect to the electroless plating when the electroless plating for forming the conductive layer 1 is performed. The catalyst varies depending on the combination of the conductive layer 1 and the conductor 2 to be deposited by electroless plating and the electroless plating system used. Specifically, when the conductor 2 is copper and the conductive layer 1 is nickel or a nickel alloy formed by electroless nickel plating using sodium hypophosphite as a reducing agent, a palladium catalyst, a silver catalyst, a platinum catalyst, etc. Is mentioned. Conventionally, when the conductive layer 1 to be deposited by electroless plating is a base material than the conductor 2, substitution plating using a difference in metal ionization tendency is impossible, so the electroless plating on the conductor 2 is not possible. However, in the present invention, it is not necessary to apply a catalyst to the conductor 2. Therefore, in FIG. 1, which is a state when the present invention is implemented, no catalyst exists at the interface between the conductor 2 and the conductive layer 1.

  According to the present invention, the conductive layer 1 can be formed by electroless plating without performing the catalyst application treatment on the conductor 2, but at the same time, the electroless plating proceeds to the core 3. For example, when electroless nickel plating is performed on the conductor 2, if the core 3 or the surface of the core 3 is made of gold, palladium, platinum or the like having high stability, In this form, a nickel layer is formed. When nickel precipitated on the surface of the core 3 is dissolved with dilute nitric acid or the like, the core 3, the gold, palladium, platinum, etc. on the surface of the core 3 remain undissolved, and the core 3 can be reused. . Palladium, platinum, and the like have a catalytic action on electroless copper plating and electroless nickel plating, and are therefore more preferable when used as the material of the core 3.

  The first embodiment of the present invention is a method of electrolessly plating a conductive layer 1 on the conductor 2 by intermittently contacting the core 3 on which the conductive layer 1 is being deposited with the conductor 2. is there. As a method for intermittently contacting the core 3 on which the conductive layer 1 is deposited, the conductor 2 and the core 3 are immersed in a liquid, and a magnetic stirrer, stirrer (three-one motor BL600 type, Shinto Scientific Co., Ltd.) It is achieved by stirring and dispersing by air shaking, vibration, application of ultrasonic waves, etc. Further, when the conductor 2 is held by a fixture such as a rack or a cable, and the core 3 is immersed in the stirred and dispersed liquid by the method described above, the conductor 2 is pulled up in a desired time. It is preferable because the core 3 and the conductor 2 can be easily separated. Further, there is a method in which the core 3 is intermittently brought into contact with the conductor 2 by immersing the conductor 2 in the liquid and swinging the conductor 2. In this case, the conductor 2 serves as a stirring blade, and the core 3 is stirred and dispersed in the liquid.

  As the electroless plating method for depositing the conductive layer 1 on the core 3 according to the first embodiment of the present invention, a conventional electroless plating method can be used. For example, a method of laying a plating solution, dispersing the core 3 and electroless plating (JP 2003-157717 A, JP 2007-184115 A), into an aqueous solution in which the core 3 is immersed, Examples include a sequential addition method (Japanese Patent No. 2093116 and Japanese Patent No. 2602495) in which plating is performed while dropping a plating solution component.

  Specifically, water containing the complexing agent and the core 3 subjected to the catalyst application treatment are dispersed, and at least the metal ions, the reducing agent, and the alkali are divided among the electroless plating solution components. This is a method in which aqueous solutions are dropped individually and simultaneously in parallel. However, the reducing agent and alkali may be mixed. In addition, electroless plating components other than metal ions, reducing agents, and alkalis, for example, additives, complexing agents, etc., may be contained in any of the aqueous solution and dropping solution in which the core 3 is divided. Also good. For example, when the dropping is advanced in the sequential addition method, the plating solution in which the core 3 is dispersed increases, and the concentration of the complexing agent in the initial suspension aqueous solution in which the initial complexing agent and the core 3 are built is lowered. Therefore, by adding a complexing agent or additive to the dropping solution appropriately in advance, the concentration of the complexing agent or additive in the entire bath does not change even when the dropping proceeds, and the deposited conductive layer 1 is uniform and preferable. FIG. 4 schematically shows changes over time in which the conductive layer 1 deposited by electroless plating is formed on the conductor 2 according to the present invention. Note that the elapsed time shown in FIG. 4 and the ratio of the thickness and other sizes of the conductive layer 1 are different from actual ones.

Example 1
[Conductor adjustment]
As the conductor 2, a 10 mm × 10 mm copper plate (Hull cell test copper plate, Yamamoto plating tester) was prepared and suspended from a glass rod using a covered wire. Furthermore, as a comparative sample, an acrylic plate, a polystyrene plate, and a slide glass of 10 mm × 10 mm were prepared, and each was similarly suspended from the glass rod provided with the copper plate. Thus, 3 sets (sample A1, B1, C1) of the glass rod from which the copper plate, the acrylic plate, the polystyrene plate, and the slide glass were suspended were prepared. The copper plate was washed with dilute sulfuric acid, the others were washed with an aqueous sodium hydroxide solution for 10 seconds, and immediately washed with pure water before use.

[Electroless plating on conductors]
In a 1000 ml beaker, 600 ml of water and 16 g of sodium tartrate as a complexing agent were added and warmed to 80 ° C. 4 g (specific gravity: 2.0, average particle size 3 μm) of spherical core 3 whose surface is covered with nickel is added here, and stirred with a stirrer (three-one motor BL600 type, manufactured by Shinto Kagaku Co., Ltd.). (Fluorine 4 blades, 300 rpm) to disperse the particles. At this time, the dispersion was in a gray suspension state. Sample A1 was put into this suspension. Next, the plating solutions X and Y shown in Table 1 were simultaneously dropped into this beaker at a rate of 3.2 ml / min using a metering pump. Bubble generation was confirmed from the suspension 30 seconds after the start of dropping, and nickel plating on the core 3 started. Further, Sample B1 was put into the suspension 10 minutes after the dropping. Samples A1 and B1 were pulled up 20 minutes after the start of dripping, and sufficient running water was washed.

  When the surface of Sample A1 and Sample B1 was observed with incident light from an optical microscope, the acrylic plate, polystyrene plate, and slide glass were not changed, but the copper plate surface was light gray. The copper plate had a smooth surface with no foreign matter such as irregularities and particles attached to the surface.

  When the copper plates of Samples A1, B1, and C1 were dissolved in aqua regia and atomic absorption measurement (deflection Zeeman atomic absorption photometer, Z-2300 type, manufactured by Hitachi, Ltd.) was performed, samples A and B were both nickel. However, only copper was detected from C1, and nickel was not detected. From this, it was confirmed that nickel was deposited as the conductive layer 1 on the copper plate surfaces of Samples A1 and B1. In addition, palladium, gold | metal | money, and lead were not detected from any of the copper plate of sample A1, B1, C1. Further, when the surfaces of the samples A1 and B1 were analyzed using EDX (manufactured by Horiba, Ltd., EDX EX-300), the deposited nickel contained 2.5 weight percent phosphorus. The nickel deposited on the copper plate was found to be lead-free and low phosphorus.

  In this way, using sodium hypophosphite-based electroless nickel plating, nickel, which is a base metal rather than copper, is deposited by an electroless plating method on a copper plate not subjected to catalytic treatment such as palladium. I was able to.

  In addition, when the core 3 after plating was sufficiently dried and the weight was measured, it was about 4.1 g heavier than before plating. Further, 20 mg of the core 3 before and after plating was weighed, dissolved in about 1 ml of aqua regia, diluted to 20 ml with a volumetric flask, and then diluted 100 times. When this was subjected to atomic absorption measurement (deflection Zeeman atomic absorption photometer, Z-2300 type, manufactured by Hitachi, Ltd.), nickel was detected, 3.2 ppm before use of plating, and 6.8 ppm after use of plating. It was done. Copper was not detected. From this, it was found that the core 3 was subjected to electroless nickel plating.

  Table 1 shows the dropping solution for nickel plating.

(Example 2)
[Conductor adjustment]
A gold wire 5 cm (manufactured by Niraco Co., Ltd.) having a diameter of 0.30 mm was wound around a glass rod having a diameter of 5 mm to form a spiral shape. The gold wire was washed in dilute sulfuric acid for 10 seconds and immediately washed with running water.

[Electroless plating on conductors]
In a 1000 ml beaker, 600 ml of water and 16 g of sodium tartrate as a complexing agent were added and warmed to 80 ° C. 4 g of core 3 having a nickel layer on the surface (specific gravity: 2.0, average particle size of 3 μm) was added here, and stirred with a stirrer (three-one motor BL600 type, manufactured by Shinto Kagaku Co., Ltd.) (made of fluorine) 4 blades, 300 rpm) to disperse the particles. At this time, the dispersion was in a gray suspension state. The plating solutions X and Y shown in Table 1 were simultaneously dropped at a rate of 0.5 ml / min. When the gold wire was pulled up 20 minutes after the start of dropping, the gold wire was gray and a nickel film was formed. The surface of the wire was observed with incident light using an optical microscope, but the entire surface was covered with a nickel film, the surface was smooth, and there was no adhesion of particles.

  This gold wire was dissolved in aqua regia, and this stock solution was subjected to atomic absorption measurement (deflection Zeeman atomic absorption photometer, Z-2300 type, manufactured by Hitachi, Ltd.), but palladium was not detected.

(Example 3)
An electroless nickel plating solution (ICP Nicolon U, manufactured by Okuno Pharmaceutical Co., Ltd.) was erected at 85 ° C., and air agitation was performed.

  Samples A3 and B3 were obtained in the same procedure as in Example 1. The copper plate was washed in dilute nitric acid for 10 seconds, and the other samples were washed in an alkaline aqueous solution for 10 seconds. Further, the gold wire treated in Example 2 was washed in dilute nitric acid solution for 10 seconds and immediately washed with running water.

  These samples were put into the electroless nickel plating solution bathed above. After 30 minutes, it was pulled up and washed with running water.

  When these samples A3 and B3 were subjected to surface observation with incident light from an optical microscope, the acrylic plate, polystyrene plate, and slide glass did not change, but the two copper plate surfaces had a gray surface overall, A nickel film was formed. The surface of the nickel film was smooth without foreign matter such as irregularities and particles. Further, the surface of the gold wire was also gray, and a smooth nickel film was formed without adhesion of foreign matters such as irregularities and particles.

  When a part of samples A3 and B3 was cast using an epoxy resin and then polished, and a cross section of the copper wiring was observed using SEM, the nickel film on the copper wiring was about 4 μm. Peeling and voids were not observed at the interface between the copper wiring and nickel, and good adhesion was obtained.

  Furthermore, when the copper plate and gold wire of samples A3 and B3 were dissolved in aqua regia and atomic absorption measurement (deflection Zeeman atomic absorption photometer, Z-2300 type, manufactured by Hitachi, Ltd.) was performed, from the copper plate and the gold wire Nickel was detected, but no palladium was detected in any of them.

  As described above, in Example 3, the sample obtained by performing the operations of Examples 1 and 2 according to the present invention is further dipped (immersed) in a normal electroless nickel plating bath, thereby nickel plating on copper or gold. It was shown that a film can be formed. Therefore, the operations of Examples 1 and 2 according to the present invention bring about the same effect as the pretreatment of the electroless plating method by general dipping (immersion), for example, activation treatment such as precious metal catalyst treatment and displacement plating treatment. It can be used as a pretreatment.

  In the hypophosphorous acid electroless nickel plating, it is difficult to deposit nickel directly on the copper plate, and it is necessary to perform a precious metal catalyst treatment (activation treatment) such as palladium or silver on the copper plate in advance.

Example 4
In a beaker, put a reference electrode (RE-1C saturated KCl / silver / silver chloride, manufactured by BAS Co., Ltd.) and a gold wire, and both are potentiostat (HA-151 type, manufactured by Hokuto Denko Co., Ltd.) The operation was performed in the same procedure as in Example 2 except that the connection was made. A gold wire was connected to the working electrode.

  When the dropping of the plating solutions X and Y was started, the potentiostat changed from −520 mV to −600 mV. Thereafter, the value of the potentiostat became a constant value in the range of -520 mV to -600 mV.

  After dripping for 20 minutes, the gold wire was pulled up and sufficiently washed with running water. A gray nickel film was formed on the surface of the gold wire. The wire was stretched and the surface of the wire was observed with incident light using an optical microscope, but the entire surface was covered with a nickel coating, the surface was smooth, and no particles adhered.

  When the core 3 in which nickel deposition is in progress contacts the gold wire surface, the potential of the gold wire surface is changed to the potential of the surface of the core 3, that is, the nickel reduction potential. A large number of cores 3 dispersed in a beaker are intermittently brought into contact with the gold wire by stirring, so that the potential of the entire gold wire approximates the potential of the surface of the core 3, and even if there is no catalyst, the surface of the gold wire It is thought that the nickel layer was deposited on the surface. Similarly in Example 1, it is considered that the infinite number of nuclei 3 contacted the copper plate intermittently and continuously, so that the potential of the copper plate became close to the potential of the surface of the nuclei 3 and nickel precipitation occurred.

(Example 5)
[Conductor adjustment]
The following samples were prepared as the conductor 2, and the weight was measured.
Copper, 25mm x 22mm (Hull cell test copper plate, Yamamoto plating tester)
Nickel, 20 mm x 20 mm (Nickel plated on the copper surface of the copper-clad laminate) *
Gold, 20mm x 20mm (copper-clad laminate with nickel / gold plated on copper surface) *
* Copper-clad epoxy laminate: MCL-E-679 (manufactured by Hitachi Chemical Co., Ltd., trade name)

  These were suspended from a glass rod using a coated wire, and three sets (samples A5, B5, C5) were prepared. The copper plate was washed with dilute sulfuric acid, the others were washed with dilute hydrochloric acid for 10 seconds, and immediately washed with pure water before use.

[Electroless plating on conductors]
In a 1000 ml beaker, 600 ml of water and 16 g of sodium tartrate as a complexing agent were added and warmed to 80 ° C. Here, 28 g of nickel particles (specific gravity: 8.9, average particle size of 10 μm) are introduced as the core 3 and a stirrer (three-one motor BL600 type, manufactured by Shinto Kagaku Co., Ltd.) (using four fluorine blades) The particles were dispersed by stirring (400 rpm). At this time, the dispersion was in a gray suspension state. Plating solutions X and Y shown in Table 1 were simultaneously dropped into this beaker at a rate of 6.0 ml / min using a metering pump. Bubble generation was confirmed from the suspension 30 seconds after the start of dropping, and nickel plating on the core 3 started. After dropwise addition for 5 minutes, there was no unevenness in the generation of bubbles, and after the reaction in the beaker was sufficiently uniform, Samples A5 and B5 were put into the suspension. Ten minutes after the start of dropping, Samples A5 and B5 were pulled up and washed with running water sufficiently.

  An electroless nickel plating solution (ICP Nicolon U, manufactured by Okuno Pharmaceutical Co., Ltd.) was placed at 85 ° C. and stirred with air. Here, samples B5 and C5 were immersed, and plating was performed for 30 minutes while the sample was rocked. The sample was pulled up from the plating solution, washed with running water and dried.

  Table 2 shows the weight measurement results and appearance observation results of Samples A5, B5, and C5 after electroless plating.

  In Table 2, the nickel thickness of the sample was calculated according to the following calculation formula.

また、表２において、ニッケルの析出（外観）は、析出有りを〇、析出無しを×とした。

In Table 2, the nickel precipitation (appearance) was marked with ◯ when there was precipitation and x when there was no precipitation.

  From the results in Table 2, it was confirmed that the samples A5 and B5 subjected to the electroless plating method according to the present invention had nickel deposited on the surfaces of the Au plate, Ni plate, and Cu plate. On the other hand, in the sample C5 subjected only to the electroless plating process by normal dipping, no nickel deposition was confirmed on the surfaces of the Au plate and the Cu plate, and nickel was deposited only on the surface of the Ni plate due to the change in weight. This is probably because nickel has autocatalytic properties.

  When the surface of Sample A5 was observed with incident light from an optical microscope, the surfaces of all the plates were light gray. These surfaces were smooth surfaces with no foreign matter such as irregularities or particles attached thereto. Moreover, since the thickness of the nickel was about 0.2 μm for all of the Au plate, Ni plate, and Cu plate, the amount of nickel deposited does not depend on the underlying metal.

  Thus, the conductive layer 1 could be formed on the conductor 2 by electroless plating without using a catalyst such as a noble metal. In addition, the formed conductive layer 1 had no unevenness on the surface of the conductor 2, and the thickness thereof was a submicron level and a very small amount, and a very thin conductive layer 1 could be uniformly formed. Furthermore, the conductive layer 1 is an electroless plating method in which the metal layer to be laminated is loosely restricted because the conductive layer 1 can be formed with substantially the same thickness without depending on the conductor 2. Furthermore, different conductors 2 can be placed in the same plating bath, and at the same time, almost the same amount of nickel can be deposited by electroless plating, which has the effect of shortening the plating process and limits the plating system. Is a loose electroless plating method. As a result, a wide variety of objects to be plated (conductors 2) can be processed simultaneously.

  Furthermore, when the surface of the Au plate, Ni plate, and Cu plate of sample B5 was observed with incident light from an optical microscope, the surfaces of all the plates were gray with no unevenness. These surfaces were smooth surfaces with no foreign matter such as irregularities or particles attached thereto. The deposited nickel had a thickness of 4.4 to 5.0 μm, and the thickness did not depend on the base metal. In this way, electroless plating by ordinary dipping was possible without performing catalyst application treatment on the base metal. Moreover, it was possible to form a nickel layer having a uniform thickness by electroless plating by ordinary dipping regardless of the base metal. Thus, it has been shown that it can be used as a pretreatment method for activation of the object to be plated, which replaces the precious metal catalyst application step performed by electroless plating by ordinary dipping.

  Nickel is a base metal than copper and gold. In order to deposit nickel on gold or copper by a normal electroless plating method, it is necessary to apply a noble metal on the gold or copper. It was. In particular, in electroless nickel plating using a hypophosphorous acid-based reducing agent, since copper does not exert a catalytic action on nickel, nickel does not precipitate without a noble metal catalyst. In the electroless plating method according to the present invention, a base metal can be laminated by an electroless plating method without using a noble metal catalyst such as palladium or silver. Furthermore, using an electroless plating system that does not exert a catalytic action on the metal to be laminated, a different metal is laminated on the underlying metal by an electroless plating method without using a noble metal catalyst such as palladium or silver. did it.

(Example 6)
[Conductor adjustment]
A copper plate (25 mm × 22 mm, Hull cell test copper plate, Yamamoto plating tester) was prepared as the conductor 2, suspended from a glass rod using a coated wire, and three sets (samples A6, B6, C6) were prepared. Each sample was protected with polyimide tape for about half the area of the plate, washed with dilute sulfuric acid for 10 seconds, and immediately washed with pure water. Immediately after washing with water, displacement gold plating (HGS-500, manufactured by Hitachi Chemical Co., Ltd., displacement gold plating solution, 90 ° C.) and electroless gold plating (HGS-5400, manufactured by Hitachi Chemical Co., Ltd., electroless gold plating solution, 65 ° C.) and about 1 μm of gold plating was applied. The polyimide tape was removed to obtain a sample in which half of gold and half of copper were exposed.

[Electroless plating on conductors]
Each sample was subjected to electroless nickel plating in the same procedure as in (Example 5). When the surface of Sample A6 was observed with incident light from an optical microscope, the copper surface and the gold surface were all light gray, and nickel was deposited. Moreover, there was no adhesion of foreign matters such as irregularities and particles on the surface, and the surface was smooth, and there was no difference between the gold and copper bases.

  Next, when the surface of Sample B6 was observed with incident light from an optical microscope, the entire copper surface and gold surface were gray. In addition, there was no adhesion of foreign matters such as irregularities and particles on the surface, and the surface was smooth, and there was no difference between the gold and copper bases. However, sample C6 had no change, and the copper surface was oxidized and discolored.

  When sample B6 was cast using an epoxy resin and then polished, and a cross section of the copper wiring was observed using SEM, the nickel film on copper and the nickel film on gold were both about 4 μm. . Peeling and voids were not observed at the interface between the base metal and nickel, and good adhesion was obtained.

  Thus, even if the conductor 2 was formed of different metals and was a continuous (conductive) surface, a uniform nickel film could be formed regardless of the difference of the metals.

(Example 7)
[Conductor adjustment]
The following plate samples were prepared and weighed.
Copper, 25mm x 22mm (Hull cell test copper plate, Yamamoto plating tester)
Nickel, 20 mm x 20 mm (Nickel plated on the copper surface of the copper-clad laminate) *
Gold, 20mm x 20mm (copper-clad laminate with nickel / gold plated on copper surface) *
Polystyrene, 20mm x 20mm
* Copper-clad epoxy laminate: MCL-E-679 (manufactured by Hitachi Chemical Co., Ltd., trade name)

  Each of these was firmly fixed to the blade portion of a fluorine stirring blade (diameter 3.5 cm, 4 blades) one by one. This was fixed to a stirrer (three-one motor BL600 type, manufactured by Shinto Kagaku Co., Ltd.). Immediately before use, the sample portion was immersed in a 300 ml beaker containing dilute sulfuric acid, washed for 10 seconds, and immediately washed with pure water using a washing bottle.

[Electroless plating on conductors]
In a 1000 ml beaker, 600 ml of water and 20 g of sodium lactate as a complexing agent were added and warmed to 80 ° C. Here, 6 g (specific gravity: 2.0, average particle size 5 μm) of the core 3 having a nickel layer on the surface was charged. The particles were dispersed by stirring with a stirrer (three-one motor BL600 type, manufactured by Shinto Kagaku Co., Ltd.) in which the sample was fixed to the blades. The stirrer was operated at 150 rpm, 5 seconds forward / 5 seconds reverse. The dispersion became gray suspension by this operation, and the core 3 was dispersed. Plating solutions X and Y shown in Table 2 were simultaneously dropped into this beaker at a rate of 6.0 ml / min using a metering pump. Bubble generation was confirmed from the suspension 30 seconds after the start of dropping, and nickel plating on the core 3 started. After 10 minutes from the start of dropping, the sample was quickly lifted from the plating solution and washed thoroughly with running water.

  When this sample was removed from the stirring blade and the weight was measured, the weight of the gold, copper, and nickel samples was increased by several mg, but the polystyrene was not changed. Furthermore, when the surface was observed with incident light of an optical microscope, the entire surface of copper and gold was light gray, and it was confirmed that nickel was deposited. Further, the surface was smooth without any foreign matter such as irregularities or particles adhering to the surface. Thus, by swinging the conductor 2 in the liquid, the core 3 in which the conductive layer 1 is being deposited and the conductor 2 were in contact with each other, and electroless nickel plating could be performed on the conductor 2. Since the core 3 is likely to adhere to the surface of the conductor 2 due to bubbles (hydrogen) generated by electroless plating, the core 3 needs to be sufficiently dispersed and stirred. When the conductor 2 was swung, the core 3 was not taken into the nickel layer on the surface of the conductor 2 even with stirring at a low rotational speed, and a nickel layer could be formed.

  Next, this sample was suspended from a glass rod using a coated wire. The electroless nickel plating solution was erected at 85 ° C. and stirred with air. (ICP Nicolon U, manufactured by Okuno Pharmaceutical Co., Ltd.) The sample was washed with dilute sulfuric acid for 10 seconds, then washed with running water for 10 seconds, immediately immersed in a plating solution, and then plated for 30 minutes while shaking the sample. . The sample was pulled up from the plating solution, washed with running water and dried.

  When each weight of the sample was measured, the weight of the gold, copper and nickel samples was increased by 30 to 40 mg, but the polystyrene was not changed. Nickel was deposited on gold, copper and nickel by electroless plating. Further, when the surface of the sample was observed with incident light of an optical microscope, the entire surface of gold, copper and nickel was gray. In addition, the surface has a smooth surface with no foreign matter such as irregularities and particles, and after casting a sample of gold, copper, or nickel using an epoxy resin, polishing is performed, and a cross section is observed using an SEM. As a result, both nickel films were about 4 μm. Peeling and voids were not observed at the interface between the base metal and nickel, and good adhesion was obtained.

(Comparative Example 1)
The same procedure as in Example 1 was performed, except that acrylic globular particles: 8 g (specific gravity: 1.0, average particle size: 3 μm) were used for the core 3. A conductor 2 and a 10 mm × 10 mm copper plate (Hull cell test copper plate, Yamamoto plating tester), an acrylic plate, a polystyrene plate, and a slide glass were prepared as samples for comparison and suspended from a glass rod using a coated wire A11 was prepared.

In accordance with the procedure of Example 1, sample A11 was put into the liquid in which core 3 was dispersed, and plating solutions X and Y shown in Table 1 were simultaneously used at a rate of 3.2 ml / min using a metering pump. It was dripped. However, no change occurred even after 5 minutes. When the dropping was continued as it was, bubbles suddenly formed from the beaker and black precipitates were generated. The plating solution was decomposed and nickel was abnormally deposited and precipitated. Sample A11 was pulled up, washed with running water, and observed, but no change was observed in any of the plates. In particular, copper was oxidized and discolored, but nickel was not deposited.

  Moreover, the acrylic core 3 was taken into the abnormally precipitated nickel lump, or was found to have no change. However, since the nickel layer considered to have been continuously deposited by electroless plating was not formed on the surface of the core 3, the electroless plating had not progressed to the core 3. all right.

  Thus, even when the core 3 on which no metal deposition occurred by electroless plating was brought into contact with the conductor 2, electroless plating on the conductor 2 did not occur.

FIG. 4 is a cross-sectional view of a conductive layer formed by electroless plating and a conductive layer formed by intermittently contacting a core in which a conductive layer is being deposited by electroless plating according to the first embodiment of the present invention. It is a bird's-eye view of the nuclear body which concerns on embodiment of this invention. It is sectional drawing of the nucleus which concerns on embodiment of this invention. In the cross-sectional view of the core body, the conductor, and the conductive layer according to the embodiment of the present invention, the core body on which the conductive layer is deposited by electroless plating intermittently contacts the conductor, It is the figure which represented the process in which a conductive layer precipitates in time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Conductive layer 2 ... Conductor 3 ... Nucleus

Claims (3)

A method of forming an electroless nickel plating layer on a conductor that does not have a noble metal catalyst such as palladium, silver, or platinum on its surface,
a) a step of preparing an aqueous solution in which a core, which is a powder having an average particle diameter of 10 nm or more and 1 mm or less having nickel or a nickel alloy on its surface, is dispersed by a continuous stirring operation with a stirring blade;
b) a step of immersing a conductor having any of gold, copper, nickel or nickel alloy on the surface thereof in the aqueous solution;
c) a step of adding an electroless nickel plating solution containing hypophosphite as a reducing agent to the aqueous solution at a constant flow rate, or at least a nickel ion solution and a reducing agent solution among the components of the electroless nickel plating solution divided, electroless nickel plating method and adding a constant flow rate simultaneously and in parallel respectively into the aqueous solution, the to including electrical conductors.   The electroless nickel plating method for a conductor according to claim 1, wherein the conductor is a conductor having copper and gold on the surface.   The conductor according to claim 1, wherein the conductor is at least two conductors having at least different metal surfaces among conductors having one metal selected from gold, copper, nickel, or nickel alloy on the surface. Electroless nickel plating method.

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