JP4034725B2 - Method for manufacturing circuit wiring board - Google Patents

Description

The present invention, electrical, electronic, a method of manufacturing a circuit wiring board used in the field of communications.

  In recent years, various electrical and electronic parts such as semiconductor devices have been highly integrated and miniaturized. Along with this, many developments have been made on circuit wiring miniaturization and multilayer wiring to enable high-density mounting even on circuit wiring boards on which electronic components are mounted. A multilayer wiring technique and a fine wiring technique for circuit wiring boards are indispensable techniques for completing a high-density circuit wiring board, and various methods have been proposed so far.

  As one of methods for forming vias that do not require via lands, ALIVH substrate technology and B2it substrates have been proposed (see, for example, Non-Patent Document 1).

  However, it is considered difficult for ALIVH to form fine vias of about several tens of μm at desired positions with high throughput. In addition, when the circuit wiring board is mechanically drilled, smear is generated, and the environmental load increases due to cleaning with chemicals. In addition, the insulation resistance between the wirings and between the layers decreases due to the residue of the processing agent and external contamination during processing, and it is difficult to cope with the narrowing of the wiring pitch. Even in the B2it method, since vias are printed and formed, there is a limit to the miniaturization of via pillars printed and formed with paste. Furthermore, in the case of fine vias of about several tens of microns, the mechanical strength in the pressure welding process with the prepreg has also been a problem.

As a method for solving the problems in the ALIVH and B2it substrates, a method has been proposed in which surface wiring and vias are simultaneously formed in an insulator having a porous structure by a simple method (see, for example, Patent Document 1). According to this method, by adjusting the amount of light transmitted through the mask, vias can be selectively formed on the surface of the insulator having a porous structure through the circuit wiring and the insulator. Moreover, no land is required at the connection between the wiring and the via.
"Build-up multilayer printed wiring technology" (published in Nikkan Kogyo Shimbun in June 2000) JP 2002-290016 A

  The circuit wiring formed by the above-described method is advantageous in that the filling rate of the conductive material is extremely high, but conversely, the connection reliability as a circuit wiring board is lowered due to the strong wiring structure resulting from this. The problem that occurred. Specifically, when a strong shearing stress is applied from the outside by bending or the like in a short time, a crack is generated at the boundary surface between the filled portion and the non-filled portion of the conductive material.

  Furthermore, since the coefficient of thermal expansion is different between the conductive material filling part and the non-filling part, when a temperature cycle is applied to the circuit wiring board, the boundary between the conductive material filling part and the non-filling part of the circuit wiring board. Shear stress distortion occurs on the surface. As a result, a problem that a crack occurs in the circuit wiring board has occurred at the same time.

The present invention has been made in view of the above problems, and an object thereof is to provide a method of manufacturing a circuit wiring board with improved connection reliability.

A method for manufacturing a circuit wiring board according to an embodiment of the present invention includes an insulator having a porous structure, and a conductive portion formed by filling a hole in a partial region of the insulator with a conductive substance. And the conductive part is a method for manufacturing a circuit wiring board comprising an outer peripheral part having a high filling rate of the conductive substance and an inner part surrounded by the outer peripheral part and having a gradually changing low filling rate. There,
A step of impregnating an insulator having a porous structure with a photosensitive material having a photosensitive group that generates an ion-exchangeable group by exposure to form a photosensitive layer;
A step of exposing a partial region of the photosensitive layer to generate an ion-exchange group in the exposed portion;
A step of binding a metal ion to the ion-exchange group,
Reducing the metal ions to obtain the conductive material; and
By immersing the insulator in a plating solution and growing the conductive material at the exposed portion of the insulator, an outer peripheral portion having a high filling rate in which the conductive material is continuously disposed, and the outer peripheral portion A step of forming the conductive portion which is surrounded by a low filling factor in which the conductive material is discontinuously disposed,
The conductive portion is formed by performing electroless plating for 1 hour while keeping the temperature of the plating solution at 15 ° C., and then performing electroless plating for 1 hour by raising the temperature of the plating solution to 45 ° C. It is characterized by that.

A method of manufacturing a circuit wiring board according to another embodiment of the present invention includes an insulator having a porous structure and a conductive portion formed by filling a hole in a partial region of the insulator with a conductive substance. And the conductive portion includes an outer peripheral portion having a high filling rate of the conductive material and an inner portion surrounded by the outer peripheral portion and having a low filling rate that changes stepwise. Because
A photosensitive agent solution containing a photosensitive material having a photosensitive group that generates an ion-exchangeable group upon exposure to an insulator having a porous structure, and a crosslinking agent blended at 10 to 27 wt% of the photosensitive material. Forming a photosensitive layer by impregnating
A step of exposing a partial region of the photosensitive layer to generate an ion-exchange group in the exposed portion;
A step of binding a metal ion to the ion-exchange group,
Reducing the metal ions to obtain the conductive material; and immersing the insulator in a plating solution to grow the conductive material at the exposed portion of the insulator, thereby continuously providing the conductive material. Forming an electrically conductive portion comprising an outer peripheral portion having a high filling rate disposed in a continuous manner and an inner portion having a low filling rate which is surrounded by the outer peripheral portion and in which the conductive material is disposed discontinuously. It is characterized by that.
A method of manufacturing a circuit wiring board according to another embodiment of the present invention includes an insulator having a porous structure and a conductive portion formed by filling a hole in a partial region of the insulator with a conductive substance. And the conductive portion includes an outer peripheral portion having a high filling rate of the conductive material and an inner portion surrounded by the outer peripheral portion and having a low filling rate that changes stepwise. Because
A step of impregnating an insulator having a porous structure with a photosensitive material having a photosensitive group that generates an ion-exchangeable group by exposure to form a photosensitive layer;
A step of exposing a partial region of the photosensitive layer to generate an ion-exchange group in the exposed portion;
A step of binding a metal ion to the ion-exchange group,
Reducing the metal ions to obtain the conductive material; and immersing the insulator in a plating solution to grow the conductive material at the exposed portion of the insulator, thereby continuously providing the conductive material. Forming a conductive portion comprising an outer peripheral portion having a high filling rate arranged in a continuous manner and an inner portion having a low filling rate surrounded by the outer peripheral portion and in which the conductive material is discontinuously arranged. ,
The exposure is performed at an exposure amount of 20 to 100 mJ in an area corresponding to 2/3 of the radius from the center of the partial area, and the remaining 1/3 outer peripheral area is set at an exposure amount of 100 to 2500 mJ. It is characterized by performing

According to one aspect of the present invention, a manufacturing method of a circuit wiring board with improved connection reliability is provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a cross-sectional view of a circuit wiring board according to an embodiment of the present invention. As shown in the figure, a circuit wiring board 10 according to an embodiment of the present invention includes an insulator sheet 11 having a porous structure and a conductive material filled in pores in selected partial regions of the insulator sheet 11. Conductive parts 12 and 13 formed by doing so. The conductive portion 12 is a wiring, and includes an outer peripheral portion 12a having a high filling rate of a conductive material and an inner portion 12b surrounded by the outer peripheral portion and having a low filling rate. The conductive portion 13 is a via and, like the wiring 12, includes an outer peripheral portion 13a having a high filling rate of a conductive material and an inner portion 13b surrounded by the outer peripheral portion and having a low filling rate.

  An enlarged view of a wiring portion in the circuit wiring board 10 is shown in FIG. As shown in the figure, in the wiring 12, the regions (12 a, 12 b) in which the pores of the porous insulator sheet 11 are filled with the conductive material, and the regions where the conductive material is deposited on the sheet 11. 12c exists. The region 12c can be referred to as a high surface filling portion.

With reference to FIG. 3, the filling rate of the conductive material will be described. As shown in the drawing, using the volume V _{v of the} pores V in the porous insulator sheet S and the volume V _{M of} the conductive material M filled in the pores, the filling rate P ( %) Is defined by the following mathematical formula (1). The volume of the pores V can be measured by observing the cross section of the porous insulator sheet with a laser ultra-deep shape measuring microscope VK-8500 (KEYENCE), and the volume of the conductive material M can also be measured by the same method. Can be measured.

P (%) = (V _M / V _v ) × 100 (1)
In the circuit wiring board according to the embodiment of the present invention, it is desirable that the filling rate P of the conductive material filled in the entire conductive portion is 30% or more. When it is less than 30%, it becomes difficult to satisfy the function as the electric circuit wiring. Considering the electric resistance value as the electric circuit wiring, the filling rate of the conductive substance is more preferably 50% or more.

  The conductive portion is composed of an outer peripheral portion having a high filling rate and an inside having a low filling rate, with the filling rate of the conductive material changing stepwise. “Change stepwise” means a state in which the filling rate P is different from the cross-sectional width of the wiring by 1/100 interval. The filling ratio of the conductive material in the outer peripheral portion is preferably 60% or more. If it is less than 60%, the electrical resistivity may be significantly increased. Moreover, it is preferable that the filling rate of the electroconductive substance in an inside is 30% or more. If it is less than 30%, the wiring resistance increases and it becomes difficult to exhibit the electric circuit wiring function. However, in order to ensure an effective stress relaxation effect, it is desirable that the difference in filling rate from the outer peripheral portion is 20% or more. Moreover, it is desirable that the filling rate in the whole conductive part is 40% or more.

  Below, with reference to FIG. 4, the manufacturing method of the circuit wiring board concerning embodiment of this invention is demonstrated in detail.

  First, as shown in FIG. 4A, an insulator sheet 21 having a porous structure is prepared.

  Any insulator material can be used as the porous insulator, and specific examples thereof include resins and ceramics.

  Examples of the resin include glass epoxy resins, bismaleimide-triazine resins and PPE resins, polyimide resins frequently used for base films, other polyfluorinated ethylene-based, fluorinated ethylene-propylene copolymers, and polyvinyl fluoride. Examples of such resins include fluorine-containing polymers such as polyolefin, acrylic polymers, polyethers such as polyallyl ethers, polyesters such as polyarylates, polyamides, and polyethersulfones.

  Moreover, as ceramics, nonwoven fabrics, such as glass, an alumina, and aluminum nitride, are mentioned, for example.

  The insulator as described above may contain ultrafine fibers, and examples thereof include fluorine fibers, nylon fibers, acrylic fibers, polyester fibers, aramid fibers, phenol fibers, glass fibers, and carbon fibers. . It is also possible to mix naturally derived components such as cellulose fibers.

  In the case of forming conductive parts penetrating the front and back of the insulating sheet, the conductive part forming region is reflected by the ultraviolet / visible light exposure region. Therefore, light needs to reach the back surface of the porous insulator, and the pore diameter of the porous body is preferably sufficiently small with respect to the exposure wavelength. However, if the pore diameter is too small, the photosensitive material may be difficult to impregnate or exposure light may be difficult to transmit. The pore diameter of the porous body is preferably 30 to 3000 nm, more preferably 50 to 1500 nm, and most preferably set in the range of 100 to 800 nm.

  Even when the pore diameter deviates from the above-mentioned range and is considerably larger than the exposure wavelength, a liquid having a refractive index close to or the same as that of the porous body or an amorphous solid having a low melting point is filled in the pores to prevent scattering. For example, it is possible to improve light transmittance by preventing scattering during exposure. However, if the hole diameter becomes too large, it will be difficult to sufficiently fill the hole with metal by plating or the like, and it will be difficult to reduce the width of the metal wiring to a few tens of micrometers or less. Taking these into consideration, it is desirable that the pore size of the porous body be set to 5000 nm or less even when a liquid for preventing scattering is used during exposure.

  Porous insulators are porous with three-dimensionally continuous pores in order to produce conductive parts that form a pattern in the film thickness direction, especially a line-shaped part that is continuously conductive in the two-dimensional direction. The body is desirable.

  It is preferable that the continuous vacancies existing in the insulator are regularly and uniformly formed in order to prevent excessive scattering of the exposure light. This is also effective for miniaturizing the wiring as the conductive portion. The continuous pores need to be open to the outside of the porous body, and it is desirable that the number of closed cells having no open end is as small as possible. Further, in order to improve the dielectric constant of the wiring, it is desirable that the porosity is higher in a range where the mechanical strength of the porous body is maintained. Specifically, the porosity is preferably 30%, and more preferably 50% or more.

  The porous insulator sheet having three-dimensionally continuous pores as described above can be produced by various techniques. For example, beads laminated, green sheets, porous bodies prepared using a laminated structure of beads as a template, porous bodies formed using a laminate of bubbles or liquid bubbles as a template, silica obtained by supercritical drying of silica sol A porous body made by removing an appropriate phase from a phase-separated structure such as an airgel, a porous body formed from a microphase-separated structure of a polymer, a co-continuous structure generated by spinodal decomposition of a mixture of polymer or silica, A porous material produced by an emulsion templating method or the like; H. Cumpston et al. (Nature, vol. 398, 51, 1999) and M.C. A porous body produced using a three-dimensional stereolithography as reported by Campbell et al. (Nature, vol. 404, 53, 2000) can be used.

  The insulating sheet is impregnated with a photosensitive material having a photosensitive group that generates an ion-exchange group by exposure to form a photosensitive layer 22 as shown in FIG. 4B.

Examples of the ion-exchange group include hydrophilic functional groups such as —COOX group, —SO ₃ X group, —PO ₃ X ₂ group (where X is a hydrogen atom, alkali metal or alkaline earth metal, and periodic table 1). , typical metal belonging to group 2, and are selected from ammonium groups) and -NH ₂ OH, and the like.

In particular, a cation exchange group is desirable because it easily exchanges ions with metal ions. Examples of such a cation exchange group include acidic groups such as —COOX group, —SO ₃ X group, and —PO ₃ X ₂ group (where X is a hydrogen atom, alkali metal or alkaline earth metal, periodic table I, A typical metal belonging to Group II, an ammonium group) is particularly preferred. If these are contained, after the metal ion exchange, which is a subsequent step, stable adsorption with the reduced metal or metal fine particles can be obtained.

  Of the above-described cation exchange groups, those having a pKa value of 7.2 or less determined from ion dissociation properties in water are more preferable. An ion-exchange group having a pKa value exceeding 7.2 has few bonds per unit area in the subsequent step of bonding metal ions or metals. Therefore, there is a possibility that desired and sufficient conductivity cannot be obtained for the metal wiring to be formed thereafter.

  The photosensitive group that generates an ion-exchange group by light irradiation is preferably a group that is sensitive to light irradiation with a wavelength of 280 nm or more. This is because, when an organic polymer material system is used as a porous insulator, depending on the structure, light irradiation with a wavelength of 280 nm or less may cause deterioration in strength.

  Specific examples of such a compound having a photosensitive group include naphthoquinone diazide derivatives and o-nitrobenzyl ester derivatives, p-nitrobenzyl ester sulfonate derivatives and naphthyl or phthalimide trifluorosulfonate derivatives.

  In particular, when a naphthoquinone diazide derivative is used, sufficiently fine patterning is possible in a short time with light having a wavelength of 280 nm or more with low energy. Further, the naphthoquinonediazide derivative causes light bleaching during exposure and becomes transparent in a wavelength region of about 300 nm or more. Therefore, it is possible to expose deeply in the film thickness direction, which is very suitable for exposure through the film thickness direction of the porous sheet.

  The photosensitive layer is exposed to a metal ion-containing aqueous solution, alkali or acidic aqueous solution in a subsequent step. Since the photosensitive material ionized by the ion exchange reaction is easily dissolved in the aqueous solution, it is easily peeled off from the insulator as the base material. Therefore, in order to prevent peeling from the substrate, it is preferable that a group causing an ion-exchange group generating reaction is supported or bonded to a polymer or a polymer compound. From such a viewpoint, 1,2-naphthoquinonediazidosulfonyl-substituted phenol resin derivatives, 1,2-naphthoquinonediazidesulfonyl-substituted polystyrene derivatives, and the like are preferable as compounds that generate ion-exchangeable groups upon irradiation with light having a wavelength of 280 nm or longer. It is.

  Another example of a compound that generates an ion-exchange group by irradiation with light having a wavelength of 280 nm or longer is a compound in which a protective group is introduced into an ion-exchange group such as a carboxyl group contained in the polymer structure. It is done. When this compound is used, a photoacid generator that generates an acid by irradiating light with a wavelength of 280 nm or more is added to the photosensitive material. An acid is generated from the photoacid generator by subsequent exposure, and the protecting group is decomposed by the generated acid to generate an ion-exchange group. Examples of the polymer include phenolic resins such as phenol novolac resin, xylenol novolac resin, vinylphenol resin, and cresol novolac resin, and carboxyl group-containing polymers such as polyamic acid, polyacrylic acid, and polymethacrylic acid.

  Examples of the protecting group for the phenolic resin include tert-butyl ester derivative substituents such as a tert-butoxycarbonylmethyl group and a tert-butoxycarbonylethyl group.

  On the other hand, in polyamic acid, polyacrylic acid, etc., as a protective group for the carboxyl group in the structure, methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group, tert-butyl group Group, benzylalkoxy group, 2-acetoxyethyl group, 2-methoxyethyl group, methoxymethyl group, 2-ethoxyethyl group, 3-methoxy-1-propyl group, etc., trimethylsilyl group, triethylsilyl group, and tri Examples thereof include alkylsilyl groups such as a phenylsilyl group.

Suitable photoacid generators for the deprotection of such protecting groups include onium salts and diazonium salts having CF ₃ SO ₃ ⁻ , p-CH ₃ PhSO ₃ ⁻ , p-NO ₂ PhSO ₃ ^— or the like as a counter anion. , Salts such as phosphonium salts and iodonium salts, organic halogen compounds, and orthoquinone-diazide sulfonic acid esters can be used.

  Moreover, o-nitrobenzyl ester group is mentioned as a protective group which produces | generates ion exchange groups, such as carboxylic acid, only by light irradiation, without using a photo-acid generator.

  Next, a predetermined region of the photosensitive layer 22 formed on the insulator sheet 21 is exposed. For example, pattern exposure can be performed by irradiating light through a mask on which a predetermined conductive pattern is formed. Alternatively, exposure may be performed by drawing according to a conductive pattern using a laser beam or the like. Further, the periodic pattern may be exposed using a periodic light intensity pattern such as an interference fringe generated by light interference.

  In order to expose the planned wiring area, light may be irradiated from one direction of the insulator sheet 21 on which the photosensitive layer 22 is formed. Further, when exposing the planned via area, exposure is performed from both surfaces of the insulator sheet 21.

  By performing pattern exposure, ion exchange groups are selectively generated in the exposure unit 23 as shown in FIG.

  As exposure light irradiated in order to produce | generate an ion exchange group, a wavelength is 280 nm or more. Note that the wavelength of the exposure light is preferably 300 nm or more, and more preferably 350 nm or more in order to suppress deterioration of the insulator due to exposure.

  In particular, when a porous body composed of an aromatic compound is exposed internally in the thickness direction, it is important to use exposure light having a long wavelength. When the porous body is composed of aromatic polyimide or the like, there are many cases where the absorption edge of polyimide absorption is 450 nm or more. In such a case, it is preferable to perform pattern exposure at a longer wavelength of 500 nm or more.

  As an exposure light source, in addition to an ultraviolet light source and a visible light source, a light source that generates exposure light of a predetermined wavelength can be selected from among light sources such as β rays (electron beams) and X rays. Specifically, the ultraviolet light source or visible light source is selected from hydrogen discharge tubes, rare gas discharge tubes, continuous spectrum light sources such as tungsten lamps and halogen lamps, discontinuous spectrum light sources such as various lasers and mercury lamps. Use.

  In the exposure step, in order to increase the binding amount of metal ions in the subsequent step with respect to the ion-exchange group of the photosensitive layer, neutralization of the ion-exchange group or the portion where the ion-exchange group is formed Swelling may be performed. For this purpose, the insulator is brought into contact with the acid or alkali solution by a technique such as spraying or dipping. In particular, hydroxides such as lithium hydroxide, potassium hydroxide and sodium hydroxide as alkali solutions, alkali metal salts such as lithium carbonate, potassium carbonate and sodium carbonate, metal alkoxides such as sodium methoxide and potassium ethoxide and hydrogenation It is preferable to use at least one kind of aqueous solution such as sodium boron and soak in these solutions. These solutions can be used alone or in combination.

  Next, metal ions are selectively bonded to the ion exchange groups formed in the exposure unit 23. As shown in FIG. 4D, the exposure part 23 becomes a metal ion part 24.

  In order to cause an exchange reaction between the ion-exchange group and the metal ion, for example, the insulator after pattern exposure may be immersed in an aqueous solution containing a metal salt. Examples of the metal element used as the metal ion include copper, silver, palladium, nickel, cobalt, tin, titanium, lead, platinum, gold, chromium, molybdenum, iron, iridium, tungsten, and rhodium.

  These metal elements are contained in the solution as metal salts such as sulfates, acetates, nitrates, chlorides, carbonates and the like. In particular, copper sulfate is preferable. It is appropriate to mix such metal salts so that the concentration of metal ions in the solution is 0.001 to 10M, preferably 0.01 to 1M. The solvent for dissolving the metal salt may be water or an organic solvent system such as methanol or isopropanol.

  In some cases, a solution in which metal fine particles are dispersed can also be used. The ion-exchange group and the colloidal metal fine particles are selectively bonded by electrostatic interaction or the like. Therefore, the bond between the ion exchange group and the metal fine particles can be easily generated only by immersing the insulator in the solution in which the metal fine particles are dispersed.

  For example, a palladium-tin colloid used as a catalyst for electroless plating prepared by mixing palladium chloride and tin chloride in an acidic aqueous solution of hydrochloric acid, or an insulator in a dispersion of palladium halide, oxide or acetylated complex Soak. As a result, the fine metal particles are easily bonded to the ion-exchange group in a position-selective manner.

  Any metal nucleus may be used as long as it is a metal on which the electroless plating is deposited because the metal ion to be used becomes a nucleus for metal deposition in the subsequent electroless plating process. However, it is desirable to select the same metal nucleus as the electroless plating solution from the viewpoint of conductivity.

  Thereafter, the metal ions are reduced to form conductive metal portions 25 as shown in FIG.

  The reducing agent used is not particularly limited, but dimethylamine borane, trimethylamine borane, hydrazine, formalin, sodium borohydride, hypophosphites such as sodium hypophosphite, peroxides such as potassium permanganate, Examples include sodium thiosulfate and hydroquinone. Metal ions can be metallized by immersing the aforementioned insulator sheet in a solution containing such a reducing agent.

  Furthermore, electroless plating is performed on the metal formed on the exposed portion of the insulator sheet to improve the conductivity of the metal portion, whereby the conductive portion 26 is obtained as shown in FIG. It can be said that the conductive part is formed by selectively growing the conductive substance by generating a metal substance from the solution ionic substance by a reduction reaction.

  The metal is most preferably copper with low electrical resistance and relatively low corrosion. Specifically, the metal wiring obtained in the previous step is brought into contact with the electroless plating solution using the catalyst core. Examples of the electroless plating solution include those containing metal ions such as copper, silver, palladium, nickel, cobalt, platinum, gold, and rhodium.

  In addition to the metal salt aqueous solution described above, this electroless plating solution includes reducing agents such as formaldehyde, hydrazine, sodium hypophosphite, sodium borohydride, ascorbic acid, glyoxylic acid, sodium acetate, EDTA, tartaric acid, malic acid. In addition, complexing agents such as citric acid and glycine, precipitation control agents, and the like are included, and many of these are commercially available and can be easily obtained. Therefore, the insulator sheet may be immersed in these electroless plating solutions until the desired conductive film thickness or filling of the porous interior is completed.

  In the case of electroless plating, it is preferable to fix the insulator sheet using a jig that does not directly contact the patterned part. Thereby, it is possible to promote removal of bubbles generated during electroless plating to the liquid surface.

  As the material of the jig, general-purpose resins such as PTFE, polyimide, polyethylene, polypropylene, and polyethylene terephthalate are desirable. Even if such a resin is immersed in an electroless plating solution in contact with the porous insulator sheet, it does not cause abnormal deposition of the plating and can be easily molded. Moreover, the material which gave special processing to the surface, such as stainless steel, may be used. Furthermore, a metal, glass, cloth, organic resin or the like that has been subjected to water repellent treatment with polyether ether ketone (PEEK) or the like can also be used.

  The insulator sheet is affixed to the fixing jig using an adhesive. Examples of the adhesive include polyolefin resins such as polyimide, polyamide, polypropylene, polybutene, α-olefin copolymer, vinyl acetate copolymer, acrylic ester copolymer, and methacrylic ester copolymer, and polyester-based heat. Plastic elastomers and polyurethane thermoplastic elastomers can be used. In particular, an acrylic polymer or a polyimide derivative is preferable because it hardly causes plating deposition. In order to improve operability, the pressure-sensitive adhesive is preferably in the form of a tape.

  During electroless plating, it is preferable to install a fixing jig in the electroless plating solution so as to be perpendicular or parallel to the liquid surface. If necessary, the liquid surface can be inclined. That is, the installation shape is not particularly limited as long as the porous insulator sheet is sufficiently immersed in the electroless plating solution.

  As the electroless plating progresses, the plating solution concentration distribution may be uneven. In this case, it is desirable to circulate the plating solution so that the concentration distribution of the plating solution is uniform. For example, the plating solution can be circulated by rotating the fixing jig in a state perpendicular to the liquid level. Further, the plating solution may be circulated by bubbling or spraying.

  By performing electroless plating in this manner, the conductive portion 26 is formed as shown in FIG. 4F, and the circuit wiring board according to the embodiment of the present invention is manufactured.

  However, the conductive portion 26 in the circuit wiring board according to the embodiment of the present invention must be composed of an outer peripheral portion that is highly filled with a conductive material and a low filling rate inside that is formed inside. In the outer peripheral portion, the metal particles which are conductive materials are continuously arranged, and in one inside, the metal particles are discontinuously arranged. The difference in the filling rate of the conductive material is due to the difference in the arrangement density of the metal particles. By controlling the deposition rate during electroless plating, the filling rate of the conductive material can be controlled so that the filling rate of the outer peripheral portion is higher than the inside.

  For example, the plating deposition rate can be changed by changing the temperature of the plating solution. An example of the relationship between the electroless copper plating temperature and the deposition rate is shown in the graph of FIG. As shown in the figure, the deposition rate tends to increase as the temperature of the plating solution rises. The relationship between the deposition rate and the temperature depends on the pore diameter and the porosity of the porous insulator sheet. For example, plating is performed on a porous insulator sheet having a pore diameter of 400 to 1200 nm and a porosity of 50 to 70%. When the temperature of the plating solution is 20 ° C., the deposition rate is about 0.4 μm / 15 minutes. When the temperature of the plating solution rises to 40 ° C., the deposition rate increases to about 0.9 μm / 15 minutes.

  The deposition rate of the plating can also be controlled by changing the composition of the photosensitive material forming the photosensitive layer. Specifically, a crosslinking agent may be blended at a rate of 10 to 27 wt% with respect to the resin component that is a photosensitive material. The photosensitive material is dissolved in a solvent at a concentration of about 50 to 300 mmol / L to prepare a solution of the photosensitive material. For example, when a naphthoquinone diazide derivative is used as the photosensitive material and diazide chalcone is used as the crosslinking agent, the photosensitive material is dissolved in a solvent at a concentration of about 200 mmol / L, and 20 wt. % Crosslinker is used. In addition to diazide chalcone, a biphenyl epoxy compound, a polymer having an azido group, an epoxy novolac derivative, or the like can be used as a crosslinking agent.

  In this case, even if the temperature of the electroless plating solution is constant, it is possible to make the outer peripheral portion and the inner portion of the conductive portion different by changing the filling rate of the conductive material. For example, when the temperature of the plating solution is 30 ° C., the deposition rate is 0.62 μm / 15 minutes. By performing electroless plating for 3 hours at such a temperature, it is possible to form a conductive portion having a filling ratio of the outer peripheral portion of about 80 to 100% and an internal filling ratio of about 30 to 60%.

  Furthermore, by adjusting the amount of plating nuclei generated inside the porous insulator by controlling the exposure energy irradiated during pattern exposure, a conductive material is applied to the outer periphery with a higher filling rate than the inside. It can also be filled.

  Specifically, an inner equivalent area having a radius of 2/3 from the center of the via is exposed with an exposure amount of about 20 to 100 mJ, and the remaining 1/3 outer circumference corresponding area is about 100 to 2500 mJ. The exposure is performed in the amount. Since the generation amount of metal nuclei increases as a whole, the conductive material is preferentially filled in the outer peripheral portion during plating, and as a result, the internal filling rate is lowered.

  In this case as well, the temperature of the electroless plating solution can be kept constant and the outer peripheral portion and the inner portion of the conductive portion can be made separately. For example, when the temperature of the plating solution is 30 ° C., the deposition rate is 0.62 μm / 15 minutes. By performing electroless plating at such a temperature for 3 hours, the filling rate of the outer peripheral portion is about 70 to 90%, A conductive portion having an internal filling rate of about 30 to 60% can be formed.

  In any case, the inside is electrolessly plated first compared to the outer peripheral portion, and the electroless plating solution is less likely to penetrate into the inner portion, so that the deposition rate is different between the inner portion and the outer peripheral portion. As a result, the conductive material can be filled at a filling rate in which the filling rate increases stepwise from the inside toward the outer periphery.

  As described above, the conductive portion 26 of the circuit wiring board according to the embodiment of the present invention is the simplest to form by electroless plating, and the filling rate can be reliably controlled, but is not limited thereto. It is not something. For example, the same applies when adopting a method of changing the temperature of the electroless plating solution over time, or a method of plating with an electroless plating solution with a high deposition rate after plating with an electroless plating solution with a low deposition rate. It is possible to fill the conductive material by changing the filling rate stepwise from the inside to the outer peripheral portion to form the conductive portion.

  The circuit wiring board on which the conductive portion having a desired filling rate is formed is lifted from the plating solution while being held by a fixing jig, washed with water, and then dried by spraying dry air or nitrogen to remove moisture. In order not to impair the dimensional stability of the porous insulator sheet, it is desired to perform uniform spraying when spraying dry air.

  A region of the insulator sheet where the conductive portion is not formed can be impregnated with a curable resin as necessary. As the impregnating resin, thermosetting, photocurable, electron beam curable resins such as epoxy resin, polyimide, BT resin, benzocyclobutene resin, cross-linked polybutadiene resin, urethane resin, phenol resin, silicone resin, polycarbodiimide resin are used. be able to. By performing the resin impregnation, it is possible to satisfactorily control electromagnetic wave characteristics, high frequency characteristics, etc. of the circuit wiring board.

  In the conductive portion of the circuit wiring board according to the embodiment of the present invention, the filling rate of the conductive material increases stepwise from the inside toward the outer peripheral portion. It can be said that the conductive portion is a porous hollow structure. For this reason, even when the circuit wiring board is deformed by an external stress due to bending or the like, the wiring of the porous hollow structure is freely deformed toward the inside of the wiring, thereby reducing the shear stress strain. It becomes possible.

  Thus, the breakage of the wiring can be effectively prevented, and the connection reliability as the circuit wiring can be remarkably enhanced. The above-described shear stress distortion also occurs when a temperature cycle is applied to the circuit wiring board. In the circuit wiring board according to the embodiment of the present invention, the stress strain caused by the difference in the thermal expansion coefficient difference between the conductive material filled portion and the non-filled portion is effectively alleviated by the hollow circuit wiring. As a result, the reliability as a circuit wiring board can be improved.

  Hereinafter, the present invention will be described in more detail with reference to specific examples.

Example 1
As the porous insulator sheet 21, a tetrafluoroethylene (PTFE) resin sheet (area 5 cm ² , thickness 30 μm) was prepared. In order to improve wettability to an aqueous solvent, the surface of the porous structure was coated with polyvinyl alcohol (PVA). The hole diameter in the insulator sheet used was 700 nm, and the porosity was 57.3%.

  As the photosensitive material, a naphthoquinonediazide-containing phenol resin was used. The weight average molecular weight of a phenol resin is 4500, and the content rate of a naphthoquinone diazide is 46 equivalent mol%. As the solvent, an equivalent mixed solvent of acetone and tetrahydrofuran was used, and the above-described photosensitive material was dissolved so that the concentration became 66.7 mmol / L. Further, diazide chalcone as a crosslinking agent was added at a ratio of 20 wt% of the photosensitive material to prepare a photosensitive agent solution.

  The porous insulating sheet was immersed in this solution for 30 seconds, pulled up, and allowed to stand at room temperature for 1 hour to dry, thereby forming a photosensitive layer 22 as shown in FIG. 4B.

Next, pattern exposure was performed on the photosensitive layer 22 by an exposure apparatus (Cannon-PLA 501) through an exposure mask having a line width of 50 μm and a space width of 400 μm. The exposure was contact exposure, and from one side of the photosensitive layer, an exposure amount of 1000 mJ / cm ² and a wavelength of 436 nm (mercury lamp i-line) were performed to form a planned wiring area. In the exposure of the via planned area, the same exposure was performed from both sides of the photosensitive layer. By such exposure, a pattern latent image composed of ion exchange groups was formed on the photosensitive layer.

  The insulator sheet having the exposed photosensitive layer was immersed in a 2.38% solution of tetramethylammonium hydroxide (TMAH) for 10 minutes. This was washed with pure water for 30 seconds, and further immersed in a 50 mmol / L aqueous solution of copper acetate for 30 minutes. Copper ions adhered to the ion-exchangeable group generated in the exposed portion of the photosensitive layer, and a metal ion portion 24 as shown in FIG. 4 (d) was formed.

A reducing solution for reducing metal ions was prepared by blending 1 wt% AD-10 (TMAH containing a surfactant, Tama Chemical) in a 50 mmol / L sodium borohydride (NaBH ₄ ) solution. . By dipping the insulator sheet in which the metal ion portion was formed in this reducing solution for 10 minutes, the copper ions were reduced and metal copper was deposited. Thereby, the metal part 25 as shown in FIG.4 (e) was formed.

  The electroless copper plating solution was prepared by mixing 1: 1 a solution obtained by diluting PB-503A and PB-503B (both manufactured by Ebara Eugelite) 5 times. The above-mentioned insulator sheet was immersed in this electroless plating solution, and electroless plating was performed at 30 ° C. for 3 hours. The deposition rate at this time is 0.62 μm / 15 minutes. As a result, the conductive portion 26 was formed as shown in FIG. When the conductive part observed with the ultra-deep laser microscope VK-8500 (KEYENCE) was observed, it was composed of an outer peripheral part with a filling rate of 87% and an inside with a filling rate of 32%, and the filling ratio in the whole conductive part was 82. %. Moreover, the filling rate changed in steps at the boundary between the outer peripheral portion and the inside.

  The reliability of the obtained circuit wiring board was evaluated. Specifically, the shear stress strain caused by external stress was examined by a strain gauge KLM (manufactured by Kyowa Denki), and the influence of shear stress strain caused by a temperature cycle was examined by a strain gauge KFH (manufactured by Kyowa Denki). . In either case, the wiring breakage due to the influence of shear stress strain could be prevented.

  For comparison, a conductive portion was formed by filling a predetermined region of a porous insulator sheet with a conductive material in the same manner as described above except that the addition rate of the crosslinking agent was changed to 27 to 30 wt%. When the conductive portion of the circuit wiring board thus obtained was observed in the same manner as described above, it was confirmed that the conductive material was filled with a uniform filling rate. The reliability of this circuit wiring board was evaluated by the same method as described above. As a result, the wiring broke due to shear stress strain caused by external stress and temperature cycle.

  This is considered as follows. That is, in the circuit wiring board having the conventional porous structure, the stress cannot be relaxed at the interface between the via and the board, and the fracture has occurred. On the other hand, in the structure according to the embodiment of the present invention, the filling rate formed in the insulator having a porous structure is increased stepwise. By compressing the voids inside the via, the stress strain from the outside is relaxed and no breakage occurs.

  The circuit wiring board according to the embodiment of the present invention can sufficiently relax the applied shear stress strain. This will be described with reference to FIG. FIG. 6 is a cross-sectional view in the wiring direction, and the wiring 33 includes a high filling portion 33 a on the outer peripheral portion and a low filling portion 33 on the inside. When the bending stress 31 is applied, the high filling portion 33a on the outer peripheral portion is deformed in the direction of the low filling portion 33b as indicated by an arrow 32. As a result, since stress is relieved, it is possible to prevent breakage. As a result, connection reliability as circuit wiring can be remarkably improved.

  This shear stress strain also occurs when a temperature cycle is applied to the circuit wiring board. The stress strain caused by the difference in the thermal expansion coefficient difference between the conductive material filled portion and the non-filled portion is alleviated to improve the reliability as a circuit wiring board.

  It was confirmed that the effect of alleviating shear strain and stress strain was greatest when the filling ratio of the conductive material in the entire conductive portion was 30% to 80%. When the filling rate is 30% to 50%, the electrical resistivity shows a value of about twice, and by placing a high filling portion with a filling rate of 60% to 100% around this, the electrical resistance The rate dropped to about 1.3 times.

(Example 2)
By changing the temperature of the plating solution, a high-filled portion at the outer peripheral portion and a low-filled portion inside were separately formed. The porous insulating sheet was impregnated with the same photosensitive material as described above except that it did not contain a crosslinking agent to form a photosensitive layer. Further, exposure was performed under the same conditions as described above, and reduction treatment was performed to form a metal in the exposed portion.

  In electroless plating, first, electroless plating was performed for 1 hour at a deposition rate of 0.23 μm / 15 minutes by keeping the temperature of the plating solution at 15 ° C. Thereafter, the temperature of the plating solution was heated at a rate of 0.5 ° C./min over 1 hour, and the temperature was raised to 45 ° C. At this temperature, the plating deposition rate increased to 1.15 μm / 15 minutes, and plating was performed for 1 hour at this deposition rate. The conductive portion 26 was formed by controlling the temperature in this way. When the conductive portion was observed in the same manner as described above, it was confirmed that the conductive portion was composed of an outer peripheral portion having a filling rate of 92% and an inside having a filling rate of 38%, and the filling rate in the entire conductive portion was 71%. . Moreover, the filling rate changed in steps at the boundary between the outer peripheral portion and the inside.

(Example 3)
By controlling the exposure energy, the outer peripheral part and the inner part of the conductive part were made separately. The porous insulating sheet was impregnated with the same photosensitive material as described above except that it did not contain a crosslinking agent to form a photosensitive layer. The inner equivalent area with a radius of 2/3 from the center of the via was exposed at 50 mJ, and the remaining outer equivalent area of 1/3 was exposed at 2000 mJ.

  After conducting reduction treatment under the same conditions as in Example 1 above to form a metal in the exposed area, electroless plating was further performed under the same conditions. As a result, the conductive area 26 was formed. When the conductive portion was observed in the same manner as described above, it was confirmed that the conductive portion was composed of an outer peripheral portion having a filling rate of 86% and an inside having a filling rate of 33%, and the filling rate in the entire conductive portion was 70%. . Moreover, the filling rate changed in steps at the boundary between the outer peripheral portion and the inside.

  The plating deposition rate can also suppress the filling rate even if the immersion time in the electroless plating solution is changed. Furthermore, if necessary, the filling ratio can be suppressed by controlling the combination of the pH region, complexing agent, and stabilizer of the electroless plating solution. Specifically, the pH region may be changed in the range of pH 7 to 14 according to the deposition characteristics of electroless plating. Examples of the complexing agent include potassium sodium tartrate and EDTA (ethylenediaminetetraacetic acid), and examples of the stabilizer include PEG (polyethylene glycol) and 2,2'-bipyridyl. What is necessary is just to select such conditions suitably and to control it to the optimal precipitation rate.

Sectional drawing of the circuit wiring board concerning one Embodiment of this invention. Sectional drawing of the circuit wiring board concerning one Embodiment of this invention. Schematic explaining the filling rate of an electroconductive substance. Process sectional drawing showing the manufacturing method of the circuit wiring board concerning one Embodiment of this invention. The graph showing the relationship between the electroless plating temperature and the deposition rate. The schematic diagram explaining the stress relaxation in a wiring part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Circuit wiring board; 11 ... Insulator sheet | seat which has porous structure; 12 ... Wiring 12a ... Outer peripheral part; 12b ... Inside; 12c ... High surface filling part; 13 ... Via 13a ... Outer peripheral part; Porous insulator sheet V ... hole; M ... conductive material 21 ... insulator sheet having porous structure; 22 ... photosensitive layer; 23 ... exposed portion 24 ... metal ion portion; 25 ... metal portion; 31 ... Bending stress 32 ... Stress relaxation direction; 33 ... Wiring; 33a ... High filling part; 33b ... Low filling part.

Claims (4)

An insulator having a porous structure; and a conductive part formed by filling a hole in a partial region of the insulator with a conductive substance, wherein the conductive part has a filling rate of the conductive substance Is a manufacturing method of a circuit wiring board consisting of a high outer peripheral part and an inner part surrounded by the outer peripheral part and having a low filling factor that changes in stages,
A step of impregnating an insulator having a porous structure with a photosensitive material having a photosensitive group that generates an ion-exchangeable group by exposure to form a photosensitive layer;
A step of exposing a partial region of the photosensitive layer to generate an ion-exchange group in the exposed portion;
A step of binding a metal ion to the ion-exchange group,
Reducing the metal ions to obtain the conductive material; and immersing the insulator in a plating solution to grow the conductive material at the exposed portion of the insulator, thereby continuously providing the conductive material. Forming a conductive portion comprising an outer peripheral portion having a high filling rate arranged in a continuous manner and an inner portion having a low filling rate surrounded by the outer peripheral portion and in which the conductive material is discontinuously arranged. ,
The conductive portion is formed by performing electroless plating for 1 hour while keeping the temperature of the plating solution at 15 ° C., and then performing electroless plating for 1 hour by raising the temperature of the plating solution to 45 ° C. A method of manufacturing a circuit wiring board. An insulator having a porous structure; and a conductive part formed by filling a hole in a partial region of the insulator with a conductive substance, wherein the conductive part has a filling rate of the conductive substance Is a manufacturing method of a circuit wiring board consisting of a high outer peripheral part and an inner part surrounded by the outer peripheral part and having a low filling factor that changes in stages,
A photosensitive agent solution containing a photosensitive material having a photosensitive group that generates an ion-exchangeable group upon exposure to an insulator having a porous structure, and a crosslinking agent blended at 10 to 27 wt% of the photosensitive material. Forming a photosensitive layer by impregnating
A step of exposing a partial region of the photosensitive layer to generate an ion-exchange group in the exposed portion;
A step of binding a metal ion to the ion-exchange group,
Reducing the metal ions to obtain the conductive material; and immersing the insulator in a plating solution to grow the conductive material at the exposed portion of the insulator, thereby continuously providing the conductive material. Forming an electrically conductive portion comprising an outer peripheral portion having a high filling rate disposed in a continuous manner and an inner portion having a low filling rate which is surrounded by the outer peripheral portion and in which the conductive material is disposed discontinuously. A method for manufacturing a circuit wiring board. An insulator having a porous structure; and a conductive part formed by filling a hole in a partial region of the insulator with a conductive substance, wherein the conductive part has a filling rate of the conductive substance Is a manufacturing method of a circuit wiring board consisting of a high outer peripheral part and an inner part surrounded by the outer peripheral part and having a low filling factor that changes in stages,
A step of impregnating an insulator having a porous structure with a photosensitive material having a photosensitive group that generates an ion-exchangeable group by exposure to form a photosensitive layer;
A step of exposing a partial region of the photosensitive layer to generate an ion-exchange group in the exposed portion;
A step of binding a metal ion to the ion-exchange group,
Reducing the metal ions to obtain the conductive material; and immersing the insulator in a plating solution to grow the conductive material at the exposed portion of the insulator, thereby continuously providing the conductive material. Forming a conductive portion comprising an outer peripheral portion having a high filling rate arranged in a continuous manner and an inner portion having a low filling rate surrounded by the outer peripheral portion and in which the conductive material is discontinuously arranged. ,
The exposure is performed at an exposure amount of 20 to 100 mJ in an area corresponding to 2/3 of the radius from the center of the partial area, and the remaining 1/3 outer peripheral area is set at an exposure amount of 100 to 2500 mJ. A method for manufacturing a circuit wiring board, comprising:   The conductive part is formed by generating a metal substance from a solution ionic substance by a reduction reaction and selectively growing the conductive substance. The manufacturing method of the circuit wiring board as described in any one of.

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