JP4906258B2 - Wiring board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a wiring board on which an electrical element such as a semiconductor element is mounted, and particularly excellent in productivity, and a manufacturing method thereof.

  In recent years, low-resistance metal conductors such as silver and copper have been used as wiring layer materials for wiring layers in order to reduce the resistance of wiring layers of wiring boards, and the insulating layer can be fired below the melting point of these metals. Glass ceramic is used. Recently, since the amount of information handled by electronic components will increase in the future, the transmission signal becomes higher in frequency, and therefore, it is required to commercialize a wiring board with low transmission loss at high frequency. Since the high-frequency signal is concentrated on the outer peripheral surface of the wiring due to the skin effect, in the wiring board that transmits high frequency, the transmission loss can be efficiently reduced by reducing the resistance of the outer peripheral portion of the wiring layer.

  In addition, in electronic components for communication equipment, there is a growing demand for components that process high-frequency DC and low-frequency power at the same time as processing high-frequency signals, and wiring boards with low transmission loss at various frequencies are required. .

  Then, in a wiring board using a low-resistance metal conductor such as silver or copper, as a technique for further reducing the resistance of the wiring layer, the wiring layer is formed with metal powder and sintered to produce the wiring layer. Instead of the method, a method of forming a wiring layer in advance by forming a wiring layer with a dense metal foil, laminating it between ceramic green sheets, and firing it has been introduced (for example, see Patent Document 1). .

In addition, it has been proposed that the conductor paste is made of metal powder having a particle size of 1 to 4 μm, the metal powder is fused and integrated by firing, and the wiring layer is formed into a dense metal structure by increasing the diameter. (For example, refer to Patent Document 2).
JP 2001-68852 A JP 7-082041 A

  However, the method proposed in Patent Document 1 has a problem that a large capital investment is required because a photolithography method, an etching method, or the like is used for forming a wiring layer.

  Further, in the method proposed in Patent Document 2, although the grain boundary is reduced by the fusion and integration of the metal particles in the wiring layer and the resistance can be reduced, oxygen-containing nitrogen, water-vapor containing nitrogen, or water-vapor containing The metal particles constituting the wiring layer are oxidized in the process of debinding or firing the green sheet laminate in a hydrogen-nitrogen mixture atmosphere, increasing the resistance value of the wiring layer after firing or making the sinterability unstable. There are problems such as becoming.

  Therefore, the firing of the wiring board requires highly precise control and is generally very time consuming, which causes the productivity of the wiring board to be reduced and the cost to be increased.

  Accordingly, an object of the present invention is to provide an inexpensive wiring board that is insensitive to changes in the firing atmosphere and that is easy to produce, and a method for manufacturing the wiring board.

The wiring board of the present invention is obtained by laminating and firing a plurality of green sheets serving as insulating layers coated with a conductive paste serving as a wiring layer, from the laminate of the insulating layers including the wiring layer. In the resulting wiring board, the average content of P as a metal in the wiring layer is 160 to 430 × 10 ⁻⁴ mass%.

Moreover, as for the wiring board of this invention, it is desirable for the average content of P as a metal in the said wiring layer to be 160-250 * 10 < ^-4 > mass%.

In the wiring board of the present invention, it is desirable that the content of P as a metal in the surface portion of the wiring layer is 80 to 200 × 10 ⁻⁴ mass% in the cross section of the wiring layer.

In the wiring board of the present invention, the wiring layer is preferably composed mainly of copper or silver.

The method for manufacturing a wiring board according to the present invention uses a conductive paste containing a metal powder containing 500 to 1000 × 10 ⁻⁴ mass% of P as a metal and a resin, and a circuit molded body on the main surface of the green sheet. A step of forming, a step of producing a laminate by laminating a plurality of the green sheets on which the circuit molded bodies are formed, and a step of firing the laminate at 850 to 1000 ° C. To do.

  In the method for manufacturing a wiring board according to the present invention, the metal powder is preferably composed mainly of copper or silver.

  As a result of diligently devising a method for improving the productivity of the wiring board, the inventors of the present application can suppress the oxidation of the metal powder by using the metal powder containing P as the raw material of the conductor paste. The inventors have found that an increase in resistance due to oxidation of the layer can be suppressed, and have reached the present invention.

That is, the wiring board of the present invention is a laminate of the insulating layers provided with the wiring layer obtained by laminating and firing a plurality of green sheets serving as insulating layers coated with a conductive paste serving as a wiring layer. In the wiring board comprising a body, the average content of P as a metal in the wiring layer is 160 to 430 × 10 ⁻⁴ mass%.

Moreover, the transmission loss of a signal can be reduced because the average content of P as a metal in the wiring layer is 160 to 250 × 10 ⁻⁴ mass%.

Further, in the cross section of the wiring layer, the content of P as a metal in the surface portion of the wiring layer is 80 to 200 × 10 ⁻⁴ mass%, so that the wiring has low resistance and low transmission loss of high-frequency signals. It can be a substrate. The surface portion of the wiring layer means a range of 2 μm from the interface between the wiring layer and the insulating layer.

  In addition, by using a metal mainly composed of copper or silver as a metal for forming the wiring layer, a wiring substrate having a wiring layer having low resistance and excellent high-frequency characteristics can be obtained.

Further, according to the method of manufacturing the wiring substrate of the present invention, by using the inclusive conductor paste and the metal powder and a resin containing 500 to 1000 × 10 ^-4 wt% of P as a metal, the main surface of the green sheet A step of forming a circuit molded body, a step of stacking a plurality of the green sheets on which the circuit molded body is formed to produce a laminated body, and a step of firing the laminated body at 850 to 1000 ° C. Thus, the wiring board of the present invention can be easily manufactured.

  In addition, by using a metal mainly composed of copper or silver as the metal powder, a wiring substrate having a wiring layer having a low resistance and excellent high-frequency characteristics can be easily manufactured.

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

  According to the wiring substrate 1 of the present invention, the insulating substrate 3 is constituted by a laminated body formed by laminating a plurality of insulating layers 3a to 3c, and the wiring layer 5 is provided between the insulating layers 3a to 3c and on the surface of the insulating substrate 3. Is deposited. Further, each insulating layer 3a to 3c is formed with a through conductor 7 having a diameter of 50 to 300 μm formed so as to penetrate the thickness direction, thereby connecting the wiring layers 5 to achieve a predetermined circuit. A network is formed.

  An electrical element (not shown) such as a semiconductor element is mounted on one main surface of such a wiring board 1, and a connection layer of the electrical element and a wiring layer 5 formed on the surface of the wiring board 1 are provided. Is connected. Further, the wiring layer 5 formed on the other main surface of the wiring board 1 is connected to a connection terminal of an external circuit board (not shown).

  In such a wiring substrate 1, for example, as shown in FIG. 2, the wiring layer 5 is formed of a metal 9 and an inorganic oxide 11. The wiring layer 5 is formed by simultaneously firing a conductor paste containing metal powder such as W, Mn, Cu, and Ag and a green sheet to be the insulating layer 3.

  Further, by using a low-resistance metal such as Ag or Cu as the metal 9 constituting the wiring layer 5, the wiring substrate 1 having the wiring layer 5 further excellent in signal transmission characteristics is obtained.

  In the present invention, the wiring layer 5 is formed by co-firing with the green sheet to be the insulating layer 3, and it is important that the metal constituting the wiring layer 5 contains P.

  That is, the wiring layer 5 of the present invention is formed by simultaneously firing a conductive paste containing metal particles containing P with a green sheet that becomes the insulating layer 3.

By including P as a metal in the metal 9 constituting such a wiring layer 5, the sinterability and resistance value of the wiring layer 5 are hardly changed even when fired under a wide range of conditions. Therefore, the wiring board 1 in which the characteristic variation is easily suppressed can be obtained.

Usually, a ceramic wiring board is made of a metal paste placed on a green sheet and laminated, and then debindered by heating to 300 ° C. or higher in an oxygen-containing nitrogen, water-vapor containing nitrogen, or water vapor-containing hydrogen-nitrogen mixture atmosphere. Thereafter, a metal paste and a green sheet are sintered. The reason why the weak oxidizing atmosphere is used in the process of removing the binder is to prevent the soot- like carbon from remaining due to the decomposition of the binder in the process of removing the binder. However, since the metal 9 is oxidized at this time, the electrical resistance of the wiring layer 5 increases. However, by previously adding P to the metal paste, it is possible to prevent the metal 9 of the wiring layer 5 from being oxidized during this process.

However, since the resistance of the wiring layer 5 tends to increase when the P content is too large, the average content of P contained in the metal 9 of the wiring layer 5 is 160 to 430 × 10 ⁻⁴ mass. %, More preferably 160 to 250 × 10 ⁻⁴ mass% or less, and when the average content of P in the metal 9 of the wiring layer 5 is 160 to 250 × 10 ⁻⁴ mass % , the wiring layer The overall resistance can be reduced. For example, even a DC signal or a low-frequency signal can improve transmission characteristics.

In particular, from the viewpoint of reducing the resistance of the wiring layer 5, the average content of P in the metal 9 of the wiring layer 5 is set to 160 to 200 × 10 ⁻⁴ mass %, and further to 160 to 180 × 10 ⁻⁴ mass % . It is desirable.

In addition, since content of P of the metal component contained in the conductor paste decreases in the firing step, the content of P of the metal component contained in the conductor paste is 160 to 43 as the wiring layer 5 that has undergone the firing process. 0 × ^{10 -4%} by weight and not good if.

In particular, the resistance of the surface portion 9b of the central portion 9a and the surface portion 9b of the metal 9 constituting the wiring layer 5 greatly affects the transmission characteristics of high-frequency signals due to the so-called skin effect. The amount of P contained in the metal 9 of 9b is desirably 80 to 200 × 10 ⁻⁴ mass % .

  The surface portion 9 b means a range of 2 μm from the interface between the wiring layer 5 and the insulating layer 3.

Further, the P content in the metal of the surface portion 9b of the wiring layer 5 is preferably 80 to 150 × 10 ⁻⁴ mass % in terms of improving high frequency characteristics.

In any case, in the surface portion 9b of the wiring layer 5 as the constituent member of the wiring substrate 1, the P content is set to 80 to 200 × 10 ⁻⁴ mass %, so that the wiring layer particularly excellent in high frequency characteristics. Thus, the wiring board 1 having 5 is obtained.

A metal powder having an average particle diameter of 0.1 to 20 μm is preferably used as the metal powder 9 serving as the metal 9 of these wiring layers 5. In particular, it is desirable to use a metal powder having an average particle size of 5 μm or less in terms of densifying the wiring layer 5 and causing electric resistance. From the same viewpoint, it is desirable to use a metal powder having a specific surface area of 0.2 to 2.0 m ² / g.

  Examples of the inorganic oxide 11 contained in the wiring layer 5 include alumina, silica, glass, and the like, and those having an average particle size in the range of 0.1 to 5 μm are preferably used. In addition, the content of the inorganic oxide 11 in the wiring layer 5 is desirably 1% by volume or more from the viewpoint of improving the adhesive force between the wiring layer 5 and the insulating layer 3, and the resistance of the wiring layer 5 is reduced. From a viewpoint, it is desirable to set it as 15 volume% or less.

  In the present invention, the insulating substrate 3 composed of the insulating layers 3a to 3c is preferably formed of glass ceramics formed by firing glass powder or a mixture of glass powder and ceramic filler powder. It is desirable to fire a composition comprising 10 to 70% by weight of the component and 30 to 90% by weight of the ceramic filler component. Such a glass ceramic is advantageous in that the firing temperature is as low as 800 to 1050 ° C., so that it can be co-fired with a low-resistance conductor, which will be described later, and because the dielectric constant is generally low, Transmission loss such as can be reduced.

Here, the glass component used includes at least SiO ₂ and contains at least one of Al ₂ O ₃ , B ₂ O ₃ , ZnO, PbO, alkaline earth metal oxide, and alkali metal oxide. For example, SiO ₂ —B ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ system—MO system (where M represents Ca, Sr, Mg, Ba or Zn), etc. Borosilicate glass, alkali silicate glass, Ba glass, Pb glass, Bi glass and the like.

  These glasses are amorphous glass that remains amorphous when fired, and lithium silicate, quartz, cristobalite, cordierite, mullite, anorthite, serdian, spinel, garnite, willemite by firing. Any crystallized glass that precipitates at least one kind of crystals of dolomite, petalite, and substituted derivatives thereof.

As the ceramic filler, quartz, and SiO ₂ of _{cristobalite, Al 2 O 3, ZrO 2} , mullite, forsterite, enstatite, spinel, magnesia, calcium zirconate, strontium silicate, calcium titanate, barium titanate , Etc. are preferably used.

  In the wiring board 1 of the present invention, the wiring layer 5 on the surface is used as a pad for mounting various electronic components 5 such as an IC chip, as a conductor film for shielding, and further as a terminal electrode connected to an external circuit. Used, various electronic components are joined to the wiring layer 5 via solder, conductive adhesive, or the like. Although not shown, a thick film resistor film such as tantalum silicide or molybdenum silicide, a wiring layer protective film, or the like may be further formed on the surface of the wiring substrate 1 as necessary.

  Hereinafter, a method for producing the wiring board 1 of the present invention will be described with reference to an example.

  First, a non-crystalline glass or crystallized glass as described above and the ceramic filler component are mixed to prepare a ceramic composition. After adding an organic binder to the mixture, the doctor blade method, rolling method, pressing method A green sheet having a thickness of about 20 to 300 μm is formed by forming into a sheet shape by the above.

  A through hole having a diameter of 50 to 300 μm is formed in the green sheet by laser, micro drilling, punching or the like, and a conductive paste is filled therein to form a through conductor. The conductive paste is formed by mixing P-containing metal powder with an organic binder made of an acrylic resin and an organic solvent such as toluene, isopropyl alcohol, and acetone.

  As the metal powder, it is desirable to use a metal powder mainly composed of silver and copper in order to reduce the resistance of the wiring layer 5.

  Moreover, it is desirable that 2 to 15 parts by mass of the organic binder and 3 to 20 parts by mass of the organic solvent are added to 100 parts by mass of the metal component.

  A slight glass component or ceramic filler may be added to the conductor paste. As a result, the connection reliability between the through conductor and the ceramic is improved, and the protrusion and depression of the through conductor on the substrate surface can be easily controlled. As the glass or ceramic filler, for example, those described above that can be used when forming a green sheet can be used.

  Next, a pattern of an arbitrary shape can be formed on the surface of the green sheet by printing the conductor paste on the surface of the green sheet by, for example, a method such as screen printing. Of course, the printing method may be offset printing, ink jet, or the like other than screen printing.

Metal powder in the conductive paste have an average particle size of 0.01 to 10 [mu] m, preferably contains an average particle size of 500 ~ 1000 × ^{10 -4} wt% spherical powder 0.1 to 0.5 [mu] m P .

  In addition, the addition of P to the metal powder is a method of incorporating into the metal powder during the formation of the metal powder, a method of adding to the metal before the metal powder formation, or a method of performing a surface treatment after the powder formation, etc. Either method is acceptable. Moreover, as a method of performing the surface treatment after the formation of the metal powder, it is possible to carry out simultaneously in the paste production process.

  Further, as the binder added to the conductor paste, it is desirable to use a methacrylic acid resin excellent in thermal decomposability in a nitrogen atmosphere, specifically polybutyl methacrylate, polybutyl normal, or the like. Moreover, as a solvent used for the conductor paste, dibutyl phthalate, α-terpineol and the like are suitable, and the binder is suitably 2 to 15 parts by mass with respect to 100 parts by mass of the copper powder. -50 mass parts is suitable.

  Next, a plurality of green sheets produced in the same manner as described above are laminated and pressed to form a laminate. For the lamination of green sheets, a method of applying heat and pressure to the stacked green sheets and thermocompression bonding, a method of applying an adhesive composed of organic binder, plasticizer, solvent, etc. between the sheets, and thermocompression bonding are adopted. Is possible. Next, this laminate is cut into a desired size.

The laminated body to be an unfired wiring board thus obtained was subjected to solvent removal and binder removal at a temperature of 300 to 850 ° C. for 2 hours in an oxygen-containing nitrogen, water-vapor containing nitrogen, or water vapor-containing hydrogen-nitrogen mixed atmosphere. Do. At this time, the carbon including the soot-like material decomposed by the binder is completely removed. Next, the ceramic is sintered at 850 to 1000 ° C. Atmosphere at this time the previous oxygen-containing nitrogen, a water vapor-containing nitrogen or water vapor-containing hydrogen-nitrogen mixed gas atmosphere, no matter, also not adversely structure be a non-oxidizing atmosphere.

  During the heat treatment, the metal powder is exposed to an oxidizing atmosphere. However, according to the present invention, P added to the metal powder has a reducing action, so even if the oxidizing atmosphere becomes stronger, the metal in the wiring layer is oxidized. It can be suppressed.

Then, P contained in the metal of the wiring layer 5 is preferably 160 to 250 × 10 ⁻⁴ mass % after the completion of the baking of the wiring substrate 1 in order to reduce the transmission loss of the wiring layer 5.

  Hereinafter, the wiring board of the present invention will be described in detail based on examples.

First, as a crystalline glass powder, _SiO 2: 40 parts by _weight, Al ₂ O 3: 30 parts by weight, MgO: 15 parts by weight, ZnO: 5 parts by _weight, B ₂ O 3: 10 parts by weight of the crystallizable glass powder: 80 parts by mass and 100 parts by mass of a glass ceramic raw material powder consisting of 20 parts by mass of alumina as a ceramic filler, 14 parts by mass of an isobutyl methacrylate resin as a solid binder and 7 parts of dibutyl phthalate as a plasticizer A green sheet having a thickness after firing of 0.15 mm was prepared by a doctor blade method using a slurry in which parts by mass were added and toluene was added as a solvent.

  Next, Cu powder and Ag powder having an average particle size of 2 μm having a P content shown in Table 1 were prepared, and 7 parts by mass of a binder made of polyisobutyl methacrylate and 100 parts by mass of these metal powders, and terpineol 15 A conductor paste was prepared by adding 5 parts by mass of dibutyl phthalate.

  Next, using these green sheets and conductor paste, a transmission loss measurement substrate having a microstrip line was prepared.

  First, a pattern having a width after firing of 0.1 mm, a thickness of 10 μm, and a length of 30 mm was printed on a green sheet by screen printing using the above conductor paste. In this green sheet, a VIA in which a conductive paste is embedded is prepared in advance for connection to a ground layer at a predetermined position. Also, a ground pattern was printed on the back surface of the green sheet with a conductive paste.

  Further, five green sheets were heat-pressed on the back surface of the green sheet.

  The thus obtained laminate was debindered at 700 ° C. for 2 hours in a nitrogen atmosphere containing the amount of oxygen shown in Table 1, and then 950 ° C. × 1 in a nitrogen atmosphere containing the amount of oxygen shown in Table 1. Time firing was performed.

The transmission coefficient S ₂₁ of the wiring resistance and 30GHz the wiring substrate obtained in this way was measured with a network analyzer. Further, the average content of P in the wiring layer was measured by ICP emission spectroscopic analysis after scraping off the wiring layer. Further, the P content in the surface portion of the wiring layer was obtained by polishing the wiring layer in the cross-sectional direction, measuring the location 1 μm inside from the interface with the insulating layer by SIMS (secondary ion mass spectrometry), and calculating from the calibration curve. These results are shown in Table 1.

Sample No. which does not contain P in the metal powder outside the scope of the present invention and does not contain P in the wiring layer. In 1-5 and 23-27, both the resistance and the transmission coefficient of the wiring layer were high, and it was practical only when processed under some limited firing conditions. In particular, sample No. 1 using Cu powder and having an oxygen concentration of 1 × 10 ⁻⁴ mass%. In 2-5, the wiring layer is oxidized, and peeled off from the insulating layer, it was not the resistance and measurement of the transmission coefficient S ₂₁ of the wiring layer.

  On the other hand, sample no. In 6-22 and 28-42, even if the oxygen concentration changed, the resistance and the permeability coefficient changed sufficiently to withstand practical use, and precise control was unnecessary in the firing process.

It is sectional drawing of the wiring board of this invention. It is an expanded sectional view of the wiring layer of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Wiring board 3a, 3b, 3c ... Wiring layer 3 ... Insulating substrate 5 ... Wiring layer 7 ... Through conductor 9a ... Center part 9b ... Surface part

Claims (6)

In a wiring board comprising a laminate of the insulating layers provided with the wiring layer, obtained by laminating and firing a plurality of green sheets serving as insulating layers coated with a conductive paste serving as a wiring layer, the wiring The wiring board, wherein an average content of P as a metal in the layer is 160 to 430 × 10 ⁻⁴ mass%. The wiring board according to claim 1, wherein an average content of P as a metal in the wiring layer is 160 to 250 × 10 ⁻⁴ mass%. 3. The wiring board according to claim 1, wherein, in a cross section of the wiring layer, a content of P as a metal in a surface portion of the wiring layer is 80 to 200 × 10 ⁻⁴ mass%.   4. The wiring board according to claim 1, wherein the wiring layer contains copper or silver as a main component. A step of forming a circuit molded body on the main surface of the green sheet using a conductive paste containing a metal powder containing 500 to 1000 × 10 ⁻⁴ mass% of P as a metal and a resin; A method for manufacturing a wiring board, comprising: a step of producing a laminate by laminating a plurality of the formed green sheets; and a step of firing the laminate at 850 to 1000 ° C.   The method for manufacturing a wiring board according to claim 5, wherein the metal powder contains copper or silver as a main component.

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