JP4332795B2 - Electroless plating method - Google Patents

Description

  The present invention relates to an electroless plating method used for manufacturing printed wiring boards and the like.

  As a method for imparting conductivity or metallic luster to a resin material, electroless plating treatment is known. This electroless plating is a method in which metal ions in a solution are chemically reduced and deposited to form a metal film on the surface of the material. Unlike electrolytic plating in which electrolytic deposition is performed by electric power, metal such as resin is also applied to the insulator. A film can be formed. In addition, the resin material on which the metal coating is formed can be electroplated, and the application is expanded. For this reason, electroless plating is widely used as a method for imparting metallic luster or conductivity to resin materials used in fields such as automobile parts and home appliances.

  However, the plating film formed by the electroless plating process has a problem that it takes time until the film is formed or the adhesion of the film to the resin material is insufficient. For this reason, first, a chemical etching process is first performed on the resin material to roughen the surface, and then a process of electroless plating is generally performed.

  For example, Japanese Patent Laid-Open No. 01-092377 discloses a method in which a resin material is pretreated with ozone gas and then electroless plating is performed. According to the publication, the unsaturated bond of the resin material is cleaved by ozone gas to lower the molecular weight, and molecules having different chemical compositions are mixed on the surface, resulting in loss of smoothness and roughening. Therefore, it is described that the film formed by electroless plating firmly enters the rough surface and does not easily peel off.

  Japanese Patent Application Laid-Open No. 08-092752 describes a method in which polyolefin is used as a plating material, is roughened by etching, is contacted with ozone water, and is then treated with a cationic surfactant-containing solution. However, in the method of roughening by etching, it is necessary to use poisonous and deleterious substances such as chromic acid and sulfuric acid. Further, the problem that the surface smoothness of the plating material is low cannot be solved.

  By the way, in order to manufacture an electronic circuit board, a subtractive method is generally used in which a copper film is formed by plating on the entire surface of an insulating resin board such as an epoxy resin, and a predetermined circuit pattern is formed by etching the copper film. ing. However, in a circuit board such as LSI, the pattern may be damaged during etching because the pattern is fine.

  Also, an additive method that forms a pattern mainly on electroless copper plating on the surface of a resin substrate, a full additive method that forms a pattern with a plating resist after catalyzing the resin substrate, and then forms a conductor pattern by electroless copper plating, etc. Is also known. This full additive method is the simplest pattern forming method on a resin substrate, but since the plating resist is used as a solder resist as it is, it is necessary to use a highly reliable plating resist as the solder resist. The degree of freedom is low.

  In addition, in order to form a fine pattern having a width of about 10 μm on the resin substrate, the surface roughness of the resin substrate needs to be less than 1 μm. For this reason, a resin substrate is molded and then pressed to smooth the surface, and then a pattern is formed.

  However, when a plating film is formed on a smooth resin surface by electroless plating, there is a problem that the adhesion improving effect due to the anchoring effect cannot be obtained and the adhesion of the plating film is low. In particular, the finer the pattern, the lower the contact area with the resin substrate. Therefore, in the production of an electronic circuit board, improving the adhesion of the plating film is an important issue.

  Therefore, Japanese Patent Application Laid-Open No. 08-253869 or Japanese Patent Application Laid-Open No. 10-310873 discloses a method of performing electroless plating after irradiating the resin material surface with ultraviolet rays. According to this method, the resin surface is activated by irradiation with ultraviolet rays, and the polar groups on the activated resin surface are chemically bonded to the plating metal, so that the adhesion of the electroless plating film is improved.

Japanese Patent Application Laid-Open No. 2002-309377 describes that after a resin material is brought into contact with an ozone solution, it is treated with a solution containing a surfactant and an alkali component, and thereafter electroless plating is performed. According to this method, the double bond on the surface of the resin material is cut by oxidation with ozone, and a polar group is generated. Further, the brittle layer is removed by the alkali component, and the surfactant is adsorbed on the polar group. During the catalyst treatment prior to electroless plating, the catalyst is adsorbed to the surfactant adsorbed on the polar group, so that the metal easily binds to the polar group during electroless plating, improving the adhesion of the electroless plating film. To do.
Japanese Patent Laid-Open No. 01-092377 JP 08-092752 JP-A-10-310873 JP 2002-309377

  However, when forming a wiring pattern by an additive method or a full additive method using electroless plating, it is necessary to use a photoresist. Masking, resist coating, exposure, development, etching, resist stripping, etc. There are many man-hours.

  The present invention has been made in view of the above circumstances, and an object thereof is to reduce the number of steps and to easily form a wiring pattern.

A feature of the electroless plating method of the present invention that solves the above problems is that a filler disposing step of forming a filler-containing resin body by disposing a filler member that is not activated and eroded by an ozone solution in a resin in a predetermined pattern, and a filler In the case where a polar group is formed in the filler member itself by the ozone treatment process in which the ozone solution is brought into contact with the containing resin body and the resin portion is selectively activated and etched to expose the surface of the filler member. A step of removing the surface portion of the filler member after the ozone treatment step , an electroless plating treatment step of electroless plating the filler-containing resin body, and forming an electroless plating film on a portion excluding the exposed surface of the filler member; It is to consist of.

  According to the electroless plating method of the present invention, an electroless plating film having excellent adhesion can be easily formed on the resin portion excluding the exposed surface of the filler member. Therefore, by arranging the filler members in a predetermined pattern in advance, a predetermined wiring pattern can be formed without using a photoresist, and the number of processes can be greatly reduced.

  Further, if a filler member that is not activated in the ozone treatment step is used, an electroless plating film is not formed on the surface, and therefore the number of steps can be further reduced.

  In the electroless plating method of the present invention, first, in the filler arranging step, filler members are arranged in a predetermined pattern in the resin to form a filler-containing resin body. The resin is not particularly limited as long as polar groups are generated on the surface by the ozone solution. ABS, AS, AAS, PS, EVA, PMMA, PBT, PET, PPS, PA, POM, PC, PP, PE, A polymer alloy containing elastomer and PP, a thermoplastic resin such as modified PPO, PTFE, or ETFE, or a thermosetting resin such as a phenol resin or an epoxy resin can be used. Its shape is not limited.

  Further, as the filler member, a material that is not eroded by the ozone solution is used, and an inorganic material such as ceramics or a fluororesin can be used. Further, if an extremely fine wire is used as the shape of the filler member and is arranged at a fine interval, a fine wiring pattern can be formed.

  Furthermore, if the electroless plating method according to the present invention is performed using a laminated substrate in which a general printed wiring board is laminated and a predetermined through hole is formed in the thickness direction as a material, each wiring is formed in the through hole. Since the substrate is etched with the ozone solution and the copper wiring pattern functions as a filler member, an electroless plating film that connects the wiring patterns in the thickness direction can be formed between the wiring substrates. Therefore, a three-dimensional wiring board can be easily formed.

  In order to arrange the filler member in the resin in a predetermined pattern, the filler member can be arranged by injecting a liquid resin in a state where the filler member is arranged in a mold and cooling and solidifying the reaction or solidifying the resin. The filler member may be exposed on the surface of the resin or may be arranged in an embedded state in the resin. The predetermined pattern is a negative pattern of a target wiring pattern.

  In the ozone treatment step, an ozone solution is brought into contact with the filler-containing resin body to selectively activate and etch the resin portion to expose the surface of the filler member. By bringing the resin and ozone solution into contact, the resin surface is activated, the solvent is activated with the activated groups on the resin surface to generate polar groups, and the resin is etched. Thus, when resin is present on the surface of the filler member, the resin is etched to expose the filler member, and polar groups are formed on the surface of the resin portion existing between the filler members.

  The ozone concentration in the ozone solution has a significant effect on the activation of the resin surface, and an activation effect is seen from about 10 ppm, but if it is 100 ppm or more, the activation effect and etching effect are dramatically increased, Shorter processing is possible. Further, since the deterioration is preceded when the concentration is low, the ozone concentration is preferably high.

  The ozone solution usually uses water as a solvent, but preferably uses an organic or inorganic polar solvent as a solvent. As a result, the processing time can be further shortened. Organic polar solvents include alcohols such as methanol, ethanol, isopropyl alcohol, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, hexamethylphosphoramide, formic acid, acetic acid, etc. Examples include organic acids, or a mixture of these with water or an alcohol solvent. Examples of the inorganic polar solvent include inorganic acids such as nitric acid, hydrochloric acid, and hydrofluoric acid.

  When contacting with the ozone solution, it is also preferable to irradiate ultraviolet rays simultaneously. In this way, high adhesiveness is manifested in a shorter processing time. In other words, in the state where the filler-containing resin body and the ozone solution are in contact with each other, by irradiating the filler-containing resin body with ultraviolet rays, the progress of the treatment is caused by the oxygen radicals generated by irradiating the ultraviolet rays to the oxygen generated from the solution. Is promoted. Moreover, the thermal damage given to a filler containing resin body can also be suppressed by releasing the excessive heat given to a filler containing resin body by ultraviolet irradiation to an ozone solution.

The irradiated ultraviolet rays preferably have a wavelength of 310 nm or less, preferably 260 nm or less, and more preferably about 150 to 200 nm. The amount of ultraviolet irradiation is desirably 50 mJ / cm ² or more. As a light source capable of irradiating such ultraviolet rays, a low pressure mercury lamp, a high pressure mercury lamp, an excimer laser, a barrier discharge lamp, a microwave electrodeless discharge lamp, or the like can be used.

  In order to bring the filler-containing resin body into contact with the ozone solution, there are a method of showering the ozone solution on the surface of the filler-containing resin body, a method of immersing the filler-containing resin body in the ozone solution, and the like. The method of immersing the filler-containing resin body in the ozone solution is preferable because ozone is less likely to be detached from the ozone solution as compared to the contact by a shower. Moreover, in order to irradiate with ultraviolet rays, it is desirable to irradiate the filler-containing resin body in a state of being immersed in an ozone solution. In this way, deformation and deterioration of the filler-containing resin body due to heat from the ultraviolet light source can be suppressed, and problems such as poor adhesion of the plating film when ultraviolet light is irradiated for a long time can be prevented. You can also.

  In order to irradiate ultraviolet rays in a state where the filler-containing resin body is immersed in an ozone solution, irradiation may be performed with an ultraviolet light source placed in the ozone solution, or from the upper surface of the ozone solution. . Further, if the ozone solution container is made of an ultraviolet light transmissive material such as transparent quartz, it can be irradiated from the outside of the ozone solution container.

  Moreover, when irradiating an ultraviolet-ray after making a filler containing resin body contact with an ozone solution, it is desirable to irradiate an ultraviolet-ray within a short time within 1 minute after a contact with an ozone solution. If this time is long, it becomes difficult to produce synergistic effects by ozone and ultraviolet rays, and the adhesion of the plating film may be reduced by short-time treatment.

  In principle, the higher the treatment temperature in the ozone treatment step, the higher the reaction rate, but the higher the temperature, the lower the solubility of ozone in the ozone solution. When the resin layer on the surface of the filler member is etched, it is desirable that the temperature be 20 ° C. or higher, preferably about 80 ° C.

  The contact time between the ozone solution and the filler-containing resin body in the ozone treatment step varies depending on the resin type, but is preferably 10 minutes or more. If it is less than 10 minutes, the effect of ozone treatment becomes difficult even if the ozone concentration is 100 ppm.

  Moreover, when irradiating an ultraviolet-ray in an ozone treatment process, although the irradiation time changes with resin types, it is preferable to set it as 4 to 15 minutes. If it is less than 4 minutes, it is difficult to achieve the effect of ultraviolet irradiation. If it exceeds 15 minutes, the filler-containing resin body may be deteriorated by heat, or the adhesion strength of the plating film may be reduced.

  In the electroless plating method of the present invention, it is desirable to further perform an alkali treatment step of bringing the filler-containing resin body after the ozone treatment step into contact with an alkali solution containing an alkali component. The alkali component has a function of dissolving the surface of the resin at a molecular level, and can remove a brittle layer on the surface of the resin to express more functional groups. Therefore, the adhesion of the plating film is further improved.

  As an alkali component, what can melt | dissolve the resin surface in a molecular level and can remove an embrittlement layer can be used, and sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. can be used. The alkaline solution preferably further contains at least one of an anionic surfactant and a nonionic surfactant.

  It is considered that at least one functional group selected from C═O and C—OH is present on the surface of the resin by the ozone treatment process. Therefore, in this step, the surfactant is considered to adsorb the hydrophobic group to the functional group that is exposed. Further, the surfactant is also adsorbed to new functional groups that are exposed by removing the embrittlement layer by the alkali component. In the electroless plating treatment step, the filler-containing resin body on which the surfactant is adsorbed is brought into contact with the catalyst. Then, it is considered that the catalyst is adsorbed on the hydrophilic group of the surfactant adsorbed on the functional group. By applying electroless plating to the resin material that is sufficiently adsorbed by the catalyst, it is considered that the surfactant is removed from the functional group and the metal is bonded to the C—OH group and / or C═O group. Further, it is possible to form a plating film having further excellent adhesion.

  As the surfactant, one having a hydrophobic group easily adsorbed to at least one functional group consisting of C═O and C—OH is used, and at least one of an anionic surfactant and a nonionic surfactant is used. Is used. With a cationic surfactant and a neutral surfactant, it is impossible to form a plating film or it is difficult to achieve the effect. Examples of the anionic surfactant include sodium lauryl sulfate, potassium lauryl sulfate, sodium stearyl sulfate, and potassium stearyl sulfate. Examples of the nonionic surfactant include polyoxyethylene dodecyl ether and polyethylene glycol dodecyl ether.

  As the solvent of the alkaline solution, it is desirable to use a polar solvent, and water can be used as a representative, but an alcohol solvent or a water-alcohol mixed solvent may be used in some cases. Moreover, in order to make an alkaline solution contact with the filler containing resin body after an ozone treatment process, the method of immersing a filler containing resin body in an alkaline solution, the method of apply | coating an alkaline solution to the filler containing resin body surface, the filler containing resin body surface The method can be performed by spraying or showering with an alkaline solution.

  The concentration of the surfactant in the alkaline solution is preferably in the range of 0.01 to 10 g / L. When the concentration of the surfactant is lower than 0.01 g / L, the adhesion of the plating film is lowered. When the surfactant concentration is higher than 10 g / L, the surfactant is brought into an association state on the surface of the filler-containing resin body, and the excess surfactant is present. Since it remains as an impurity, the adhesion of the plating film is lowered. In this case, after the alkali solution treatment, the filler-containing resin body may be washed with water to remove excess surfactant.

  The concentration of the alkali component in the alkaline solution is preferably 12 or more in terms of pH value. The effect can be obtained even if the pH value is less than 12, but the amount of the functional group to be exposed is small, so that the time for forming the plating film by a predetermined film thickness becomes long.

  The contact time between the alkaline solution and the filler-containing resin body is not particularly limited, but is preferably 1 minute or longer at room temperature. If the contact time is too short, the amount of surfactant adsorbed on the functional group may be insufficient, and the adhesion of the plating film may be reduced. However, if the contact time is too long, the layer in which at least one functional group selected from C═O and C—OH is exposed may be dissolved and electroless plating may be difficult. About 1 to 5 minutes is sufficient. A higher temperature is desirable, and the higher the temperature, the shorter the contact time can be. However, room temperature to about 60 ° C. is sufficient.

  In the alkali treatment, the surfactant may be adsorbed after treatment with an aqueous solution containing only an alkali component, but an embrittlement layer may be formed again until the surfactant is adsorbed. It is desirable to carry out the reaction in a state where at least one of an anionic surfactant and a nonionic surfactant and an alkali component coexist in the alkaline solution.

  Moreover, although it is preferable to perform an alkali treatment after an ozone treatment process, depending on the case, it is also possible to perform an ozone treatment process and an alkali treatment simultaneously. In this case, a mixed solution of an ozone solution and an alkaline solution is prepared, and the filler-containing resin body is immersed in the mixed solution, or the mixed solution is sprayed on the surface of the filler-containing resin body. In this case, since the reaction between ozone and the surface of the filler-containing resin body becomes rate-determining, the treatment time is determined according to the ozone concentration in the mixed solution.

  In addition, you may perform the process of washing with water and removing an alkaline component after an alkali treatment. Since the surfactant is strongly adsorbed to the functional group, it is known that the adsorbed state is maintained without being removed by washing with water. Therefore, the treated filler-containing resin body does not lose its effect even if time elapses before the electroless plating step.

In the electroless plating treatment step, the surface of the ozone-treated filler-containing resin body is subjected to electroless plating to deposit an electroless plating film. In this step, first, the catalyst is adsorbed on the resin surface on which polar groups are formed by ozone treatment. As this catalyst, a catalyst used in conventional electroless plating treatment such as Pd ²⁺ can be used. In order to adsorb the catalyst, a solution in which catalyst ions are dissolved may be brought into contact with the resin surface. Moreover, conditions, such as contact time and temperature, may be the same as before.

  Thereafter, an electroless plating process is performed as in the conventional case. The conditions of the electroless plating treatment, the metal species to be deposited, etc. are not particularly limited, such as Ni, Cu, Zn, Co, Cr, Sn, Au, Ag, and can be performed in the same manner as the conventional electroless plating treatment.

  Thereafter, it is desirable to further perform an electrolytic copper plating treatment and form an electrolytic plating film on the surface of the formed electroless plating film. Thereby, a plating film can be formed thickly.

  In the resin body formed by the electroless plating method of the present invention, the filler member is exposed on the surface, and an electroless plating film having excellent adhesion is formed on the surface of the resin portion between the filler members. Therefore, by forming the electroless plating film from a conductor such as copper, electrolytic plating becomes possible, and the electrolytic plating film can be formed only on the surface of the electroless plating film. And since the formed plating film is divided by the filler member, a wiring pattern can be formed with a plating film by making a filler member into an insulator. As a result, a wiring pattern can be formed without the need for a photoresist process or an etching process, and the number of steps can be significantly reduced.

  In addition, if the resin body is a block-like resin body having holes, the inside of the holes can be etched by impregnating the holes with an ozone solution to expose the filler members, and are exposed between the filler members. A plating film having excellent adhesion can be formed on the surface of the resin portion. Accordingly, a three-dimensional wiring pattern can be easily formed.

  Hereinafter, the present invention will be described specifically by way of examples.

Example 1
First, the glass fiber reinforced epoxy resin was cured in the mold 1 to form a resin plate 2. As shown in FIG. 1, a slit member 3 having a plurality of metal plates 30 arranged in parallel and having a large number of slits 31 is arranged on the surface, and SiO ₂ in a molten state is less than the height of the metal plate 30. The filler member 4 was formed as shown in FIG. Thereafter, the slit member 3 was removed as shown in FIG. The filler member 4 is integrally joined to the resin plate 2, and a plurality of slits 40 formed by the metal plate 30 and opened on the upper surface are arranged in parallel at intervals.

  A glass fiber reinforced epoxy resin was further injected therein and cured while pressing with an upper mold (not shown) to form a resin portion 5 filling the slit 40 as shown in FIG. Thereby, the resin plate 2 made of glass fiber reinforced epoxy resin and the resin portion 5 made of glass fiber reinforced epoxy resin are integrally joined, and the filler member 4 is embedded integrally with the resin plate 2 and the resin portion 5 inside. A bonded substrate 6 was prepared.

  Next, as shown in FIG. 5, a shower treatment was performed for 30 minutes from the surface side of the resin portion 5 of the substrate 6 using ozone water in which 150 ppm of ozone was dissolved and heated to 80 ° C. Thereby, the resin part 5 is etched and the front-end | tip of the filler member 4 is exposed. However, since the filler member 4 is not etched by ozone water, the resin portion 5 has a height equal to or lower than the height of the slit 40 as shown in FIG. A large number of polar groups are present on the surface of the resin part 5 in the slit 40 by ozone water treatment.

  This was subjected to a cleaner / conditioner treatment in which it was immersed in an aminopolycarboxylic acid solution for 6 minutes, and then subjected to a soft etching treatment in which it was immersed in a sodium persulfate / sulfuric acid solution for 1 minute. Next, a pre-penetration treatment was carried out by washing with a sodium chloride solution, and 0.1% by weight of palladium chloride and 5% by weight of tin chloride were dissolved in a 3N hydrochloric acid aqueous solution and immersed in a catalyst solution heated to 30 ° C. for 5 minutes. Subsequently, in order to activate palladium, it was immersed in 1.5N hydrochloric acid aqueous solution for 5 minutes, and thereby the catalyst was adsorbed. Thereafter, it was immersed in a copper sulfate plating bath kept at 40 ° C., and as shown in FIG. 7, an electroless plating film 7 having a thickness of 0.5 μm was formed on the surface of the resin part 5 in the slit 40.

  The electroless plating film 7 was not formed on the surface of the filler member 4. If the electroless plating film 7 is formed on the surface of the filler member 4, it is necessary to remove the electroless plating film 7 on the surface of the filler member 4 by mechanical polishing or chemical treatment.

  Next, copper sulfate-based electrolytic copper plating was performed using the electroless plating film 7 as a negative electrode. As shown in FIG. 8, a copper plating film 8 having a thickness of 20 μm or more was formed only on the surface of the electroless plating film 7 in the slit 40.

  In the obtained substrate 6, as shown in FIG. 9, the copper plating film 8 is formed in a stripe shape on the surface, and the filler member 4 is interposed between the copper plating films 8. A short circuit between the copper plating films 8 is reliably prevented.

  Therefore, according to the electroless plating method of the present embodiment, it is not necessary to use a photoresist, and a wiring pattern can be formed without the need for steps such as masking, resist coating, exposure, development, etching, and resist peeling. The number of man-hours can be significantly reduced.

(Example 2)
In this example, first, a filler member 4 shown in FIG. 10 was prepared. A slit 40 is formed on the surface of the filler member 4. This was embedded in the resin portion 5 in the same manner as in Example 1 to prepare a substrate 6 shown in FIG. The resin part 5 is also filled in the slit 40.

  Then, by treating the surface of the substrate 6 with ozone water in the same manner as in Example 1, the resin part 5 in the slit 40 is etched and the slit 40 is exposed as shown in FIG. Therefore, an electroless plating process and an electroplating process can be performed in the same manner as in Example 1 so that an electrolytic plating film can be selectively formed in the slit 40, and a wiring pattern is formed as in Example 1. can do.

In one Example of this invention, it is explanatory perspective view which shows the process of embedding a filler member in resin. In one Example of this invention, it is explanatory sectional drawing which shows the process of embedding a filler member in resin. In one Example of this invention, it is explanatory sectional drawing which shows the process of embedding a filler member in resin. In one Example of this invention, it is explanatory sectional drawing which shows the process of embedding a filler member in resin. It is explanatory sectional drawing which shows the process which is performing the ozone treatment in one Example of this invention. In one Example of this invention, it is a principal part expanded sectional view of the board | substrate after ozone treatment. In one Example of this invention, it is a principal part expanded sectional view of the board | substrate after an electroless-plating process. In one Example of this invention, it is a principal part expanded sectional view of the board | substrate after an electrolytic plating process. In one Example of this invention, it is a principal part perspective view of the obtained board | substrate. It is sectional drawing of the filler member used in the 2nd Example of this invention. It is sectional drawing of the board | substrate used in the 2nd Example of this invention. In 2nd Example of this invention, it is sectional drawing of the board | substrate after ozone treatment.

Explanation of symbols

  2: Resin plate 4: Filler member 5: Resin portion 6: Substrate

Claims (2)

Filler arrangement step of forming a filler-containing resin body by arranging filler members that are not activated or eroded by an ozone solution in a resin in a predetermined pattern;
An ozone treatment step in which an ozone solution is brought into contact with the filler-containing resin body to selectively activate the resin portion and to expose the surface of the filler member by etching;
A step of removing a surface portion of the filler member after the ozone treatment step when a polar group is formed on the filler member itself by the ozone treatment;
An electroless plating method comprising: performing an electroless plating treatment on the filler-containing resin body and forming an electroless plating film on a portion excluding the exposed surface of the filler member.   The electroless plating method according to claim 1, wherein an ozone concentration in the ozone solution is 100 ppm or more.

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