JP2010232360A - Forming/manufacturing of insulating film, printed wiring board, and manufacturing method for printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an insulating film on the inside of minute through-holes formed in a conductive substrate. <P>SOLUTION: An insulating film forming method has an immersion step for immersing a substrate into one-substituted trialkoxysilane solution, and an ultraviolet-light irradiating step in which the immersed substrate is irradiated with ultraviolet light so as to make one-substituted trialkoxysilane deposited on the substrate surface into a polysiloxane film. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to forming and manufacturing an insulating film, a printed wiring board, and a method for manufacturing a printed wiring board.

  In recent years, a printed circuit board that has been hardened with epoxy resin using a conventional glass fiber cloth as a reinforcing agent has been developed with a substrate made of a fiber cloth made of carbon fiber with a reduced thermal expansion coefficient and an increased elastic modulus. The printed wiring board used exists.

  A printed wiring board having a normal through hole has an insulating property because the board is formed of glass epoxy resin or the like. For this reason, holes are formed in the printed wiring board with a drill or the like to form through holes, and then metal plating or the like is applied to the through holes, thereby providing electrical conduction on both sides of the board.

  However, in a substrate using a fiber cloth made of carbon fiber as a reinforcing material as a printed wiring board, carbon fiber has electrical conductivity. Conduction through the fiber. Therefore, it is necessary to insulate the wall surface inside the through hole.

  There are several methods for such insulation treatment. When the through hole has a relatively large diameter of 500 μm or more, an insulating resin is embedded in the through hole, and a thin hole is formed in the center of the embedded insulating resin, and a metal or the like is formed inside the formed thin hole. There is a method of plating (via-in-via method). However, in the case of the via-in-via method, it is necessary to make a large first hole, and it is difficult to make the size of this hole less than 500 μm, and through holes cannot be formed with high density by this method.

  On the other hand, a substrate with through holes formed in a liquid resin is dipped, then pulled up from the liquid resin, the wall surface of the through hole is covered with the liquid resin, and then an insulating protective film is formed on the wall surface of the through hole by heat curing or ultraviolet curing. There is a method of forming (liquid resin coating method). In this liquid resin coating method, it is possible to make the through holes narrower in diameter and pitch than in the via-in-via method.

JP 2007-103605 A

  However, in the liquid resin coating method, since the viscosity of the liquid resin is high, when the diameter of the through hole is 100 μm or less, the entire hole of the through hole is buried and the yield is greatly reduced.

  Therefore, there is a demand for a method of forming an insulating film on the wall surface of the through hole without embedding the entire through hole even if the through hole has a narrow diameter in the conductive substrate.

  According to one aspect of the present embodiment, an immersion process in which the substrate is immersed in a monosubstituted trialkoxysilane solution, and ultraviolet light is applied to the immersed substrate, thereby attaching the substrate to the surface of the substrate. And an ultraviolet light irradiation step for converting the substituted trialkoxysilane into a polysiloxane film.

  According to another aspect of the present embodiment, a conductive substrate having a through hole formed thereon, a polysiloxane film covering the substrate surface and the inner wall surface of the through hole, and the poly on the substrate surface. A metal wiring formed on the siloxane film and a metal wiring for electrical connection from one surface of the substrate formed through the polysiloxane film covering the inner wall surface of the through hole to the other surface; Have

  According to another aspect of the present embodiment, a through hole forming step of forming a through hole in a conductive substrate, and the substrate on which the through hole is formed are immersed in a monosubstituted trialkoxysilane solution An immersion step, an ultraviolet light irradiation step of irradiating the immersed substrate with ultraviolet light to convert the mono-substituted trialkoxysilane adhering to the substrate surface into a polysiloxane film, and a surface of the polysiloxane film. A wiring formation step for forming the wiring.

  Further, according to another aspect of the present embodiment, a through hole forming step of forming a through hole in a conductive substrate, and heating the monosubstituted trialkoxysilane, the substrate having the through hole formed on the substrate A step of attaching a vapor of monosubstituted trialkoxysilane, a step of irradiating the substrate with ultraviolet light, and a step of irradiating the substrate with ultraviolet light to convert the monosubstituted trialkoxysilane attached to the substrate surface into a polysiloxane film, A wiring formation step of forming wiring on the surface of the polysiloxane film.

  According to the disclosed insulating film formation manufacturing, printed wiring board, and printed wiring board manufacturing method, even when a narrow through hole having a diameter of 100 μm or less is formed, the entire through hole is not embedded. An insulating film can be formed on the wall surface. Therefore, through holes can be formed with high yield and high density in a printed wiring board having conductivity.

Process drawing of the manufacturing method of the printed wiring board in 1st Embodiment (1) Process drawing (2) of the manufacturing method of the printed wiring board in 1st Embodiment Explanatory drawing of the manufacturing method of the printed wiring board in 2nd Embodiment Infrared absorption spectrum of the film formed according to Example 1 Molecular structure diagram of polysiloxane Measurement diagram of the film formed in Example 1 with a stylus thickness meter

  The form for implementing is demonstrated below.

[First Embodiment]
An insulating film formation manufacturing, a printed wiring board, and a manufacturing method of the printed wiring board in the first embodiment will be described. 1 and 2 are process diagrams of a method for manufacturing a printed wiring board according to the present embodiment.

  The printed wiring board in the present embodiment is a board using a fiber cloth made of carbon fiber as a reinforcing material and has conductivity.

  First, as shown in FIG. 1A, a through hole is formed in a substrate 11 which is a base material of a printed wiring board. The substrate 11 includes a fiber cloth 12 made of conductive carbon fiber. A hole is made in the substrate 11 with a drill or the like to form a through hole 13. The size of the through-hole 13 to be formed is at least 1 μm in diameter, and more preferably 10 μm in diameter. As will be described later, in order to obtain sufficient insulating performance in the formed insulating film, it is necessary to form the insulating film with a thickness of 0.5 μm or more. Therefore, in order to form a sufficient electrode inside a through hole in which an insulating film is formed by electroless plating, electrolytic plating, or the like, the diameter of the through hole needs to be 10 μm or more.

  Next, as shown in FIG. 1B, the substrate 11 on which the through holes 13 are formed is immersed in a solution 21 of monosubstituted trialkoxysilane. Many mono-substituted trialkoxysilanes have a viscosity equivalent to or lower than that of water or ethanol (about 10 mPa · s), and low viscosity equivalent to the surface tension of ethanol (20 to 40 dyn / cm). have. Specific examples of such mono-substituted trialkoxysilane include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and 3-glycidoxy. Propyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propyneamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3- Examples include mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, and 3-isocyanatopropyltriethoxysilane.

  In addition, the liquid resin mentioned above is a liquid silicon or a urethane resin etc., and a viscosity is 0.7 Pa.s or more. On the other hand, many monosubstituted trialkoxysilanes have a viscosity equivalent to or lower than the viscosity of water or ethanol (about 10 mPa · s). Therefore, based on the inventor's experience, the viscosity greatly affects the film thickness of the insulating film formed on the wall surface of the through hole. Therefore, in order to obtain the effect of the present embodiment, the viscosity is 100 mPa. -It is preferable that it is below s.

Next, as shown in FIG. 1C, the substrate 11 on which the through holes 13 are formed is taken out from the monosubstituted trialkoxysilane solution 21 and irradiated with ultraviolet light from an ultraviolet light source 30. When the substrate 11 on which the through holes 13 were formed was taken out from the monosubstituted trialkoxysilane solution 21, a film of about 0.1 μm monosubstituted trialkoxysilane was formed on the entire surface of the substrate 11. Is also formed on the inner wall surface of the through hole 13. The substrate 11 on which such a mono-substituted trialkoxysilane film is formed is irradiated with ultraviolet light having a wavelength of 300 nm or less and an exposure dose of at least 150 mJ / cm ² or more. Thereby, the substituent of monosubstituted trialkoxysilane is desorbed by the energy of the irradiated ultraviolet light, and a polysiloxane thin film is formed. In the present embodiment, 2000 mJ / cm ² of ultraviolet light is irradiated. This is because a polysiloxane thin film is almost completely formed from a monosubstituted trialkoxysilane. The thickness of the polysiloxane thin film thus formed is about 0.05 μm, and the insulation performance is not sufficient with only one layer. Therefore, the substrate 11 in which the through holes 13 are formed is again immersed in the monosubstituted trialkoxysilane solution 21 as shown in FIG. 1B, and then taken out, as shown in FIG. 1C. Irradiate with ultraviolet light. By repeating the step of immersing in the monosubstituted trialkoxysilane solution 21 and the step of irradiating with ultraviolet light a plurality of times, the polysiloxane thin film can be laminated to form a thick polysiloxane film. Based on the inventor's experience, an insulating film having high insulating performance can be obtained by forming the polysiloxane film with a thickness of 0.5 μm or more.

In the present embodiment, the substrate 11 is immersed in the solution as it is without hydrolyzing the monosubstituted trialkoxysilane, and a polysiloxane thin film is formed to have a thickness of 0.5 μm or more by stacking. As described above, since the ultraviolet light exposure amount of the ultraviolet light source 30 shown in FIG. 1C is 2,000 mJ / cm ² or more per time, the steps from FIG. 1B to FIG. 1C are performed five times. When it is repeated, the integrated irradiation amount is required to be 10 J / cm ² or more. It should be noted that the polysiloxane thin film can be formed thicker by further repeating the steps from FIG. 1B to FIG. 1C, and in this case, the cumulative irradiation amount of ultraviolet light further increases.

  Examples of the ultraviolet light source 30 include an ultrahigh pressure mercury lamp (emission wavelength: 254 nm), a low pressure mercury lamp (emission wavelength: 254 nm, 185 nm), a xenon excimer lamp (emission wavelength: 172 nm), and the like. Anything that emits can be used.

  By repeating the steps of FIG. 1B and FIG. 1C a plurality of times, as shown in FIG. 1D, polysiloxane which becomes an insulating film on the surface of the substrate 11 and the inner wall surface of the through hole 13 A film having a film 23 of 0.5 μm or more can be obtained.

  Next, as shown in FIG. 2E, a metal film 31 is formed on the surface of the substrate 11 and inside the through hole 13 with a polysiloxane film 23 serving as an insulating film interposed therebetween. The metal film 31 is formed by performing electroless plating and electrolytic plating.

  Next, as shown in FIG. 2F, a photoresist is formed on the metal film 31, exposed by an exposure apparatus, and then developed to form a resist pattern 32.

  Thereafter, wet etching is performed on the substrate 11 on which the resist pattern 32 is formed on the metal film 31 to remove a portion where the metal film 31 that is not covered with the resist pattern 32 is exposed. Remove. As a result, as shown in FIG. 2G, a printed wiring board in which the metal wiring 33 is formed on both surfaces of the substrate 11 is manufactured. In this embodiment, the substrate 11 includes a fiber cloth 12 made of carbon fiber having conductivity. However, a printed wiring board is similarly used for a substrate made of another material having conductivity. It is possible to produce.

[Second Embodiment]
Next, a second embodiment will be described. This embodiment relates to the formation and manufacture of an insulating film, a printed wiring board, and a method of manufacturing a printed wiring board. By a method different from the first embodiment, the substrate 11 on which the through holes 13 are formed is formed on the substrate 11. A polysiloxane film to be an insulating film is formed.

  This embodiment will be described with reference to FIG. In the present embodiment, a monosubstituted trialkoxysilane solution 53 is placed in a container 51, and the monosubstituted trialkoxysilane solution 53 is heated to about 150 ° C. by a heating device 55. The container 51 is provided with an opening 52, and the monosubstituted trialkoxysilane solution 53 heated by the heating device 55 evaporates to become a monosubstituted trialkoxysilane vapor 54. The monosubstituted trialkoxysilane vapor 54 exits from the opening 52 and adheres to the surface of the substrate 11 and the inner wall surface of the through hole 13. Above the opening 52, an ultraviolet light source 56 is provided via the substrate 11, and the monosubstituted trialkoxysilane adhering to the inner wall surface of the through hole 13 becomes polysiloxane by irradiation with ultraviolet light, thereby A polysiloxane film 57 is formed.

  Since the substrate 11 moves in the direction of the arrow, a polysiloxane film 57 serving as an insulating film is sequentially formed on the inner wall surface of the through hole 13. If the polysiloxane film 57 having a sufficient thickness is not formed in the through-hole 13 by a single movement, the polysiloxane film 57 is formed thick by moving it in the direction opposite to the arrow direction. Is possible. Furthermore, by repeating this movement, the polysiloxane film 57 can be formed thicker.

  As described above, for the substrate 11 in which the insulating film of the polysiloxane film 57 is formed in the through hole 13, the metal plating shown in FIG. 2E and the resist pattern shown in FIG. Form. Thereby, a printed wiring board similar to that of the first embodiment as shown in FIG. 2G can be manufactured.

Example 1
Examples of forming a polysiloxane film will be described. In this example, a few drops of vinyltrimethoxysilane were dropped on a silicon substrate having a diameter of 4 inches, and spin coating was performed by rotating at a rotational speed of 200 rpm for 20 seconds with a spin coater. Thereafter, ultraviolet light from a low-pressure mercury lamp was irradiated for 120 seconds. At this time, the exposure amount of ultraviolet light is 2700 mJ / cm ² . This process of spin coating with vinyltrimethoxysilane and irradiation with ultraviolet light was repeated 10 times, and the infrared absorption spectrum of the polysiloxane film formed on the silicon substrate was measured. The result is shown in FIG. The cumulative exposure amount of ultraviolet light is 27 J / cm ² .

As a result, it confirmed that peaks due to the peak and 3300 cm ^-1 vicinity of the hydroxyl groups due to the SiO ₂ of 1100 cm ^-1 vicinity, it was confirmed that the polysiloxane of the structure shown in FIG. 5 is formed. Moreover, the result of having measured the film thickness of the formed polysiloxane by the stylus type film thickness diameter is shown in FIG. As shown in the figure, the average thickness of the polysiloxane film M with respect to the surface R of the silicon substrate was measured and found to be 1.15 μm. This confirmed that a polysiloxane film having an average film thickness of about 1.15 μm was formed.

  In addition, when a polysiloxane film was formed by a process similar to the above using a copper plate instead of the silicon substrate, and a tester was brought into contact with the surface of the formed polysiloxane film, the electrical resistance was infinite. Thereby, the electrical insulation of the formed polysiloxane film was confirmed.

(Example 2)
100 through-holes having a diameter of 50 μm were formed at a pitch of 70 μm on a 2 mm-thick 100 mm square laminate plate made of a carbon fiber cloth prepreg impregnated with an epoxy resin. This substrate was immersed in the solution of vinyltrimethoxysilane used in Example 1, then pulled up, and using an ultraviolet light source in the same manner as in Example 1, the exposure amount of ultraviolet light at the center of the through hole was 2000 mJ / cm. Exposure was performed by irradiating with ultraviolet light so as to be ² . In order to perform exposure so that the ultraviolet light exposure amount at the center of the through hole is 2000 mJ / cm ² , the exposure amount at the surface portion of the substrate is 40 J / cm ² .

This process was repeated 10 times to form an insulating film made of a polysiloxane film in the through hole. In this case, the cumulative exposure amount of ultraviolet light at the center of the through hole is 20 J / cm ² . Thus, when the insulating film which consists of a polysiloxane film was observed with the optical microscope in the through hole, it confirmed that the through hole was not completely embedded and the film without a pinhole was formed.

  Although the embodiment has been described in detail above, it is not limited to the specific embodiment, and various modifications and changes can be made within the scope described in the claims.

DESCRIPTION OF SYMBOLS 11 Substrate 12 Fiber cloth made of carbon fiber 13 Through hole 21 Monosubstituted trialkoxysilane solution 23 Polysiloxane film 30 Ultraviolet light source 31 Metal film 32 Resist pattern 33 Metal wiring 51 Container 52 Opening 53 Solution of monosubstituted trialkoxysilane 54 Monosubstituted trialkoxysilane vapor 55 Heating device 56 Ultraviolet light source 57 Polysiloxane film

Claims (7)

An immersion step of immersing the substrate in a mono-substituted trialkoxysilane solution;
Irradiating the soaked substrate with ultraviolet light, thereby irradiating the substrate surface with a mono-substituted trialkoxysilane to form a polysiloxane film, an ultraviolet light irradiation step;
A method for forming an insulating film, comprising:   The method for forming an insulating film according to claim 1, wherein the polysiloxane film is laminated by repeatedly performing the dipping step and the ultraviolet light irradiation step. A conductive substrate having through holes formed thereon;
A polysiloxane film covering the substrate surface and the inner wall surface of the through hole;
Electrical connection is made from one surface of the substrate formed through the metal wiring formed on the polysiloxane film on the substrate surface and the polysiloxane film covering the inner wall surface of the through hole to the other surface. Metal wiring for,
A printed wiring board comprising: A through hole forming step of forming a through hole in a conductive substrate;
An immersion step of immersing the substrate in which the through hole is formed in a solution of monosubstituted trialkoxysilane;
Irradiating the soaked substrate with ultraviolet light, thereby irradiating the substrate surface with a mono-substituted trialkoxysilane to form a polysiloxane film, an ultraviolet light irradiation step;
Forming a wiring on the surface of the polysiloxane film; and
A method for forming a printed wiring board, comprising:   The method for forming a printed wiring board according to claim 4, wherein the polysiloxane film is formed by repeatedly performing the dipping step and the ultraviolet light irradiation step. A through hole forming step of forming a through hole in a conductive substrate;
Heating the monosubstituted trialkoxysilane and attaching the vapor of the monosubstituted trialkoxysilane to the substrate in which the through hole is formed;
Irradiating the substrate with ultraviolet light to form a mono-substituted trialkoxysilane adhering to the substrate surface into a polysiloxane film;
Forming a wiring on the surface of the polysiloxane film; and
A method for forming a printed wiring board, comprising:   The method for forming a printed wiring board according to any one of claims 4 to 6, wherein the wavelength of ultraviolet light in the ultraviolet light irradiation step is 300 nm or less.

Images