JPWO2014115252A1 - Circuit board and circuit board manufacturing method - Google Patents

Abstract

The object is to improve the adhesion between the material for obtaining conduction between layers and the circuit board, and to stably obtain a low resistance in terms of electrical connection. In order to achieve the object, in a circuit board having a conductive material in which a plurality of substrates on which wirings are formed are stacked and conducting between the layers of the substrate, the conductive material includes either P or Ag and V and Te. An oxide and a conductive material are included. Further, in the method of manufacturing a circuit board in which a plurality of substrates on which wiring is formed are stacked, an oxide containing either P or Ag, V, and Te, and a conductive substance are formed in the hole formed in the substrate. A step of supplying, and a step of irradiating the oxide and the conductive material with electromagnetic waves and softening and melting them in the holes.

Description

  The present invention relates to a circuit board using an oxide glass for electrical connection between layers and a method for manufacturing the circuit board.

In recent years, with the development of the information equipment and electronic equipment fields, there has been a demand for smaller and higher density circuit boards. Conventionally, copper plating has been the mainstream for electrical connection between circuit board layers. Copper plating requires through-holes called through-holes, and the area where wiring is possible is reduced, so it is becoming difficult to increase the density of wiring. In addition, copper plating has a problem that it uses a large amount of chemicals, uses a lot of water to clean the chemicals, and discharges industrial waste such as wastewater neutralized sludge, resulting in a large global environmental impact. . In addition, since the plating process goes through a plurality of processes such as etching, drilling, plating, and washing, improvement in manufacturing efficiency is required. Therefore, recently, as an alternative method for shortening the copper plating process and reducing the environmental load, a printed wiring board has been disclosed in which a conductive paste is filled in via holes to obtain electrical connection between layers.

  For example, in Patent Document 1, an electrical connection between layers of a printed circuit board is obtained by filling a conductive paste containing metal particles and a binder resin in a via hole of the printed circuit board and then heating while applying pressure. .

Japanese Patent Laid-Open No. 7-176846

  In the above-described conventional method, electrical connection between the layers of the printed circuit board is obtained by contact between the metal particles in the via hole. However, the adhesion between the substrate and the metal particles is not sufficient, the contact between the metal particles becomes unstable, and it is difficult to obtain stable conduction. This problem becomes more serious as the density of circuit boards increases.

  An object of the present invention is to improve adhesion between a material for obtaining conduction between layers and a circuit board, and to stably obtain low resistance with respect to electrical connection.

  In order to solve the above-described problems, the present invention provides a circuit board having a conductive material in which a plurality of substrates on which wirings are formed are stacked and conducting between the layers of the substrate, wherein the conductive material is either P or Ag. It contains an oxide containing V and Te and a conductive substance.

  Further, in the method of manufacturing a circuit board in which a plurality of substrates on which wiring is formed are stacked, an oxide containing either P or Ag, V, and Te, and a conductive substance are formed in the hole formed in the substrate. And a step of irradiating the oxide and the conductive material with electromagnetic waves and softening and melting them in the holes.

  According to the present invention, it is possible to improve adhesion between a material for obtaining conduction between layers and a circuit board, and to stably obtain low resistance with respect to electrical connection.

It is an example of the DTA curve obtained by the differential thermal analysis of an oxide. It is an example of the transmittance | permeability curve of an oxide. It is an example of the cross-sectional schematic of a composite member. It is the perspective view and sectional drawing of a resin substrate with which the conductive oxide paste was filled. It is an example of a manufacturing procedure of a multilayer substrate. It is an example of a manufacturing procedure of a multilayer substrate.

  Oxides for obtaining electrical connections between circuit board layers include V (vanadium), Te (tellurium), and P (phosphorus). Alternatively, V, Te and Ag (silver) are included. These oxides are substantially free of Pb (lead) and Bi (bismuth). For example, by mixing a conductive material such as Ag, Au, Pt, Cu, Al, Sn, Zn, Bi, and In with the oxide described above, it is possible to obtain electrical conductivity between layers.

An oxide containing V, Te, and P is not only relatively low in temperature at a transition point _Tg of 340 ° C. or lower, but also has high laser absorptivity, so that it is easily heated by laser irradiation, so that it tends to soften and flow. . In addition, an oxide containing V, Te, and Ag is inferior in laser absorptivity to an oxide containing V, Te, and P. However, since the transition point _Tg is lower than 270 ° C., it can be easily irradiated by laser irradiation. Can be softened and fluidized. If these oxides are used, even a substrate such as a resin softens the oxide in a temperature range that does not deteriorate the resin, so that the layers can be connected. The oxide after softening and flowing contains at least one of amorphous (glass) and crystalline.

  By further containing any of Fe, Sb, W, Ba, and K in these oxides, the oxide structure can be kept more stable. In particular, when Fe or Sb is contained, the laser and microwave absorption is large and heat is easily generated. In particular, when W, Ba or K is contained, crystallization can be suppressed.

  As the wavelength of the laser to be used, 2000 nm or less which is effectively absorbed by the oxide is effective. This is because if the wavelength is 2000 nm or less, the oxide easily absorbs the laser.

In the case of an oxide containing no Ag, V ₂ O ₅ is most preferably contained in terms of oxide. Further, by containing Fe ₂ O _{3 and} Sb ₂ O ₃ , it becomes easy to absorb a laser having a wavelength range of 2000 nm.

Te and P are components for vitrification, and by including these, they can be softened and flowed easily by laser irradiation. P is effective also in a low thermal expansion, since the oxide equivalent by P ₂ O content of ₅ (mass%) of TeO ₂ are many and the transition point T _g tends to be higher than the content of P ₂ O ₅ The amount should be less than or equal to the TeO ₂ content.

The effective composition range of the oxide satisfies the above conditions, and in terms of the following oxide, V ₂ O ₅ is 17 to 50% by mass, TeO ₂ is ₂₀ to 33% by mass, and P ₂ O ₅ is 4 to 4%. 12% by mass. As a composition range in which the laser absorption characteristics are further improved, V ₂ O ₅ is 37 to 50% by mass, TeO ₂ is ₂₀ to 32% by mass, P ₂ O ₅ is 6 to 12% by mass, and Fe ₂ O ₃ is 10 to 19%. Mass% is preferred.

Alternatively, V ₂ O ₅ is 17 to 50% by mass, TeO ₂ is 25 to 35% by mass, Ag ₂ O is 20 to 50% by mass, and V ₂ O ₅ + TeO ₂ + Ag ₂ O is preferably 85% by mass or more. .

To the aforementioned oxides, _{e.g., SiO 2, ZrO 2, Al} 2 O 3, Nb 2 O 5, ZrSiO 4, Zr 2 (WO 4) (PO 4) 2, cordierite, mullite, such as eucryptite By mixing the filler, it is possible to adjust the thermal expansion coefficient to a predetermined value according to the material of the substrate to increase the bond strength between the substrate and the oxide, or to increase the strength of the oxide itself. is there. When there is a large difference in thermal expansion coefficient between the substrates to be bonded, it is possible to increase the bonding strength by stacking oxides having different thermal expansion coefficients.

  However, it is not limited to description of the Example taken up here, You may combine suitably.

In this example, an electromagnetic wave irradiation experiment was performed using a polycarbonate substrate as the substrate and 20V ₂ O ₅ -35TeO ₂ -45Ag ₂ O (mass%) as an oxide in terms of the following oxide, and the oxide was applied to the resin substrate. An adhesion confirmation test was conducted. As electromagnetic waves, lasers having wavelengths of about 400 nm, 600 nm, and 800 nm were used.

The above oxide was prepared using a reagent V ₂ O ₅ , TeO ₂ , and Ag ₂ O manufactured by High Purity Chemical Laboratory Co., Ltd., and mixed in a predetermined amount so as to be a total of 200 g, and placed in a platinum crucible. It heated to 900-950 degreeC with the temperature increase rate of 5-10 degreeC / min with the electric furnace, and fuse | melted. In order to make it uniform at this temperature, it was kept for 1 to 2 hours with stirring. Thereafter, the crucible was taken out and poured onto a stainless steel plate heated to about 150 ° C. in advance.

The oxide poured on the stainless steel plate was pulverized until the average particle size (D ₅₀ ) was less than 20 μm. This oxide is subjected to differential thermal analysis (DTA) up to 550 ° C. at a rate of temperature increase of 5 ° C./min, so that the transition point (T _g ), the yield point (M _g ), the softening point (T _s ), and the crystallization temperature. ( _Tcry ) was measured. Note that alumina (Al ₂ O ₃ ) powder was used as a standard sample.

FIG. 1 shows a typical DTA curve of an oxide. As shown in FIG. 1, T _g is the first endothermic peak start temperature, _Mg is the peak temperature, T _s is the second endothermic peak temperature, and T _cry is the start temperature of the remarkable exothermic peak due to crystallization. The oxide of this example had T _g of 163 ° C., M _g of 172 ° C., and T _s of 208 ° C. T _cry was not observed with DTA up to 263 ° C.

The optical properties of the oxide were evaluated by transmittance using an ultraviolet-visible spectrophotometer. The evaluation sample is a paste for printing by pulverizing an oxide with a jet mill until the average particle size (D ₅₀ ) is 2 μm or less, and adding and mixing a solvent in which 4% of a resin binder is dissolved in the oxide powder. Was made. Here, ethyl cellulose was used as the resin binder, and butyl carbitol acetate was used as the solvent.

  The paste was applied to the slide oxide by screen printing and dried at 150 ° C. The viscosity of the paste and the printing method were controlled so that the average thickness of the coating film was about 5 μm, 10 μm, and 20 μm, respectively. The transmittance curve in the wavelength region of 300 to 2000 nm was measured for the coating film formed on the slide oxide using an ultraviolet-visible spectrophotometer. At that time, the transmittance curve of only the slide oxide was subtracted as a baseline so that the transmittance curve of only the oxide fired coating film was obtained as much as possible. FIG. 2 shows a transmittance curve for each film thickness of the oxide of this example. In the wavelength region of 300 to 2000 nm, this oxide has a smaller transmittance as the wavelength is smaller, and hardly transmits ultraviolet rays having a wavelength of less than 400 nm.

In the electromagnetic wave irradiation experiment, the oxide was pulverized with a jet mill until the average particle size (D ₅₀ ) was 2 μm or less as described above. A slurry for spray spraying was prepared by adding and mixing a solvent in which 1% of a resin binder was dissolved in the oxide powder. Here, ethyl cellulose was used as the resin binder, and butyl carbitol acetate was used as the solvent. This slurry was sprayed uniformly onto a polycarbonate substrate by spraying and dried at about 70 ° C. Thereafter, semiconductor lasers with wavelengths of about 400 nm, 600 nm, and 800 nm were respectively irradiated. FIG. 3 shows a schematic cross-sectional view of the composite member.

  By moving the laser head, the slurry on the resin substrate 1 was irradiated with the laser 3. Since the oxide absorbs the laser and is heated to soften and flow at a relatively low temperature, the oxide 2 film can be formed on the resin substrate 1 without deteriorating the resin substrate 1. Moreover, this film was firmly adhered and adhered to the resin substrate. The oxide was firmly adhered and adhered to the polycarbonate substrate regardless of the wavelength of the laser. Further, even when the laser was irradiated from the substrate side as in the laser 3 indicated by a broken line, the laser transmitted through the resin substrate was absorbed by the oxide, and the same result was obtained.

In this example, a conductive oxide paste is prepared by further mixing a conductive material with the oxide, resin binder, and solvent of Example 1, and filling the via hole of the circuit board with the conductive oxide paste. The conductivity was evaluated. FIG. 4 is a perspective view and a sectional view of a resin substrate in which a via hole is filled with a conductive oxide paste. 4 is a via hole and 5 is a metal particle. The via hole contains oxide 2 and metal particles (conductive substance).
(Preparation of conductive oxide paste)
As the metal particles, silver particles: AGC-103 (spherical particles, average particle size of 1.4 μm) manufactured by Fukuda Metal Foil Industry Co., Ltd. were used. The content of the oxide powder in the paste was 10% by volume with respect to the silver particles. Moreover, the content rate of solid content (silver particle, oxide powder) in a paste was 80-85 mass%.
(Paste filling and electrical evaluation)
Using the paste prepared above, the via hole was filled on the polycarbonate substrate and the polyimide substrate by a printing method. After drying at 150 ° C., a laser beam was irradiated into the via hole using a semiconductor laser having a wavelength of about 800 nm to soften and solidify. The conductive oxide paste was firmly adhered in the via hole. As a result of measuring the resistance value of the holes, the average was 0.48 mΩ / hole, and an excellent electrical resistance was shown.

  The above paste has a lower oxide softening point than before (softens and flows at a lower temperature than before) and absorbs a laser having a wavelength of 200 to 2000 nm. I was able to.

  In this example, via holes are formed on a substrate or film of polyamideimide, polyarylate, polysulfone, epoxy resin, fluororesin, fluororubber, silicone rubber, acrylic rubber, etc., and the conductive oxide paste of Example 2 is filled. Then, it was softened and solidified by laser irradiation. A semiconductor laser having a wavelength of about 800 nm was used. The conductive oxide paste was in close contact with the via hole, and the metal particles were firmly fixed.

  As a result of measuring the electrical resistance of the formed via holes, the average was 0.51 mΩ / hole, indicating an excellent electrical resistance. It was confirmed that the paste can be applied to a wide variety of resins as in this embodiment as a resin substrate for forming a circuit by adjusting the laser irradiation conditions.

  Next, the paste of Example 2 was filled in the via hole of the fluororesin substrate. Using a μ reactor manufactured by Shikoku Keiki Co., Ltd., microwaves in a 2.45 GHz band (wavelength: 125 mm) were irradiated to soften and solidify the conductive oxide paste. It was softened and flowed in the same manner as the laser irradiation, and the resin substrate was not deteriorated and was firmly adhered in the via hole. As a result of measuring the electric resistance of the formed via hole, the average was 0.48 mΩ / hole, and an excellent electric resistance was shown. Since the oxide has semiconducting conductivity, it can absorb and soften microwaves in the 2.45 GHz band (wavelength: 125 mm). From this result, even in the microwave having a wavelength in the range of 0.1 to 1000 mm, the oxide can be softened and solidified as represented by the 2.45 GHz band.

  Further, even when other metal particles, Au, Al, Cu, Pt, Pd, Sn, Zn, Bi, and In were added, the same result as that obtained when Ag particles were added was obtained, and stable conductivity was obtained. .

  In this example, alumina was used for the substrate, and the conductive oxide paste of Example 2 was filled in the via hole formed on the alumina substrate, and softened and solidified by irradiation with laser or microwave. The laser was a semiconductor laser having a wavelength of about 800 nm, and the microwave was irradiated with a microwave of 2.45 GHz band (wavelength: 125 mm) using a μ reactor manufactured by Shikoku Keiki Co., Ltd. In both cases of laser and microwave, the conductive oxide paste was in close contact with the via hole, and the metal particles were firmly fixed.

  As a result of measuring the electrical resistance of the formed via holes, the average was 0.51 mΩ / hole, indicating an excellent electrical resistance. It was confirmed that the paste was also effective for the ceramic substrate.

In this example, the composition and characteristics of the oxide were examined. Table 1 shows the composition and characteristics of the examined oxides. The oxide raw materials include reagents V ₂ O ₅ , TeO ₂ , P ₂ O ₅ , Fe ₂ O ₃ , Ag ₂ O, WO ₃ , Sb ₂ O ₃ , BaO, and K ₂ O manufactured by High Purity Chemical Laboratory. The oxide was prepared in the same manner as in Example 1. The transition point of the produced oxide was measured by DTA in the same manner as in Example 1. The softening fluidity of the produced oxide was obtained by compacting an oxide powder by hand pressing, and then using a titanium sapphire laser (wavelength: 808 nm), a YAG laser (wavelength: 1064 nm), and a 2.45 GHz band (wavelength: 125 mm). ) Microwaves were respectively irradiated.

  It was evaluated as “◎” when the oxide was able to flow well, “◯” when it was able to flow, and “x” when it was not able to flow or soften. Oxide No. In Examples 1 to 35, it was possible to absorb and flow the laser and microwave well, and the resin substrate and the ceramic substrate could be solidified without deteriorating. In addition, by including a conductive material in these oxides, it has become possible to obtain conduction through the via hole.

In this example, an example in which a multilayer substrate is manufactured using the conductive oxide paste of Example 2 will be described. A paste containing 10% by volume of oxide powder in the paste with respect to silver particles was used as a filling material for via holes.
FIG. 5 shows an example of a manufacturing procedure. 6 is a substrate, 7 is a copper foil, 8 is a single layer substrate, and 9 is a multilayer substrate. Glass epoxy was used for the substrate.
First, via holes 4 were formed on the substrate 6 by a laser 3 at predetermined positions as shown in FIG. Next, (c) the copper foil 7 was pressure-bonded, and (d) the conductive oxide paste was filled by screen printing. After filling, the mixture was heated at 120 ° C. for 10 minutes to volatilize the solvent. (e) The filled paste was softened and solidified using the semiconductor laser 3 having a wavelength of about 800 nm. Next, (f) the copper foil 7 was pressure-bonded on the substrate 6, and (g) a conductor pattern was formed on the copper foil 7 by photolithography. (h) The single-layer substrate 8 to which the copper foil 7 was pressure-bonded only on one side was stacked on the single-layer substrate prepared in (g), and multilayered by vacuum press. (I) A conductor pattern was formed on the copper foil 7 by photolithography.

  As described above, in this example, the multilayer substrate 9 having three layers was manufactured. In this embodiment, a semiconductor laser is used as a heat source, but a microwave can also be used. In this embodiment, glass epoxy is used for the substrate, but other resin substrates and ceramic substrates can be similarly produced. In this embodiment, copper foil is used for the wiring, but other metal such as aluminum is also possible. Further, in this example, the via hole was formed by the laser of (b), and (c) the copper foil was pressure-bonded. However, before the copper foil was pressure-bonded, the conductive oxide paste was filled, dried, and irradiated with the laser. Then, it can also be produced by crimping a copper foil.

  In this example, an example in which a multilayer substrate is manufactured using the conductive oxide paste of Example 2 will be described. A paste containing 10% by volume of oxide powder in the paste was used as a filling material for via holes, and glass epoxy was used for the substrate.

  FIG. 6 shows an example of a manufacturing procedure. First, (i) the via hole 4 was formed by the laser 7 at a predetermined position as shown in (k) on the substrate 6 to which the foil 7 was bonded. Next, (l) a conductive oxide paste was filled in the via hole 4 by screen printing. The conductive oxide paste was filled until it contacted the copper foil 7. After filling, the mixture was heated at 120 ° C. for 10 minutes to volatilize the solvent. (M) The filled paste was softened and solidified using the semiconductor laser 3 having a wavelength of about 800 nm. Next, (n) a conductor pattern was formed on the copper foil 7 by photolithography. (O) A single-layer substrate 8 to which a copper foil 7 was pressure-bonded only on one side was overlaid on the single-layer substrate prepared in (n), and multilayered by vacuum press. (P) A conductor pattern was formed on the copper foil 7 by photolithography. As described above, in this example, the multilayer substrate 9 having three layers was manufactured. In this embodiment, a semiconductor laser is used as a heat source, but a microwave can also be used. In this embodiment, glass epoxy is used for the substrate, but other resin substrates and ceramic substrates can be similarly produced. In this embodiment, copper foil is used for the wiring, but other metal such as aluminum is also possible.

1 Resin substrate 2 Oxide 3 Laser 4 Via hole 5 Metal particle (conductive substance)
6 Substrate 7 Copper foil 8 Single layer substrate 9 Multilayer substrate

Claims (14)

  In a circuit board having a conductive material in which a plurality of substrates on which wiring is formed are stacked and conducting between the layers of the substrate, the conductive material includes an oxide containing either P or Ag, V and Te, and a conductive material A circuit board comprising a substance.   The circuit board according to claim 1, wherein the oxide includes V, Te, and P, and has a transition point of 340 ° C. or lower. _{2. The} oxide according to claim 1, wherein the oxide contains V ₂ O ₅ , TeO ₂ , and P ₂ O ₅ , and V ₂ O ₅ > TeO ₂ > P ₂ O ₅ (mass%) in terms of oxide. Circuit board to do.   The circuit board according to claim 1, wherein the oxide includes V, Te, and Ag, and a transition point is 270 ° C. or lower. The circuit board according to claim 1, wherein the oxide contains V ₂ O ₅ , TeO ₂ , and Ag ₂ O, and V ₂ O ₅ + TeO ₂ + Ag ₂ O ≧ 85 mass% in terms of oxide.   The circuit board according to claim 1, wherein the oxide contains any one of Fe, Sb, W, Ba, and K.   2. The circuit board according to claim 1, wherein the conductive substance is at least one of Au, Ag, Al, Cu, Pt, Pd, Sn, Zn, Bi, and In.   2. The circuit board according to claim 1, wherein the oxide is formed by being softened by irradiation with electromagnetic waves.   9. The circuit board according to claim 8, wherein the wavelength of the electromagnetic wave is a laser having a wavelength of 2000 nm or less or a microwave having a wavelength of 0.1 to 1000 mm.   In a method of manufacturing a circuit board in which a plurality of substrates on which wirings are formed are stacked, an oxide containing P or Ag, V, and Te and a conductive material are supplied to holes formed in the substrate. A method of manufacturing a circuit board comprising: a step; and a step of irradiating the oxide and the conductive material with electromagnetic waves to soften and melt the oxide in the hole. The oxide according to claim 10, wherein the oxide contains V ₂ O ₅ , TeO ₂ , and P ₂ O ₅ , and V ₂ O ₅ > TeO ₂ > P ₂ O ₅ (mass%) in terms of oxide. Circuit board manufacturing method. The circuit board according to claim 10, wherein the oxide contains V ₂ O ₅ , TeO ₂ , and Ag ₂ O, and V ₂ O ₅ + TeO ₂ + Ag ₂ O ≧ 85 mass% in terms of oxide. Production method.   11. The method for manufacturing a circuit board according to claim 10, wherein the conductive substance is at least one of Au, Ag, Al, Cu, Pt, Pd, Sn, Zn, Bi, and In.   The method of manufacturing a circuit board according to claim 10, wherein the wavelength of the electromagnetic wave is a laser having a wavelength of 2000 nm or less or a microwave having a wavelength of 0.1 to 1000 mm.

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