JP2006310340A - Conductor paste, molded body, and wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductor paste capable of suppressing dispersion of a metal element from the conductor paste, and to provide a molded body and a wiring board. <P>SOLUTION: The conductor paste contains a complex metal powder 3 in which a metal oxide 3b of a thickness of ≥10 nm is formed on the surface of each of metal particles 3a, a glass powder 5, and a resin 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wiring board that is applied to various wiring boards, semiconductor element storage packages, and the like, and a conductor paste and a molded body that are preferably used in the manufacture thereof.

  Conventionally, a wiring board has a structure in which a metallized wiring layer is disposed on a through hole portion or a surface of an insulating substrate. As a typical example using this wiring board, there is an electrical element housing package for housing an electrical element, particularly a semiconductor integrated circuit element such as an LSI (Large Scale Integrated Circuit Element).

  Further, as an insulating substrate in a package for housing a semiconductor element, a glass that can be fired at around 1000 ° C. that can use a low-resistance metal such as Cu or Ag as a metallized wiring layer in place of the alumina ceramics or the like recently. An insulating material made of a sintered body such as ceramic has been proposed, and a low resistance wiring layer used for a low-temperature fired wiring board is currently a mainstream for forming a wiring layer by a copper-based material.

  As a specific method for forming a metallized wiring layer mainly composed of copper on the surface and / or inside of an insulating substrate made of glass ceramics, a slurry prepared by adding a glass ceramic raw material powder and a solvent to an organic binder is used as a doctor blade. The through hole is punched into the obtained green sheet by a method, etc., and the via hole conductor is formed by filling the through hole with a conductor paste mainly composed of copper. At the same time, copper is formed on the green sheet. This is made by printing a conductor paste mainly composed of copper on a wiring pattern by screen printing or the like, pressing and laminating a plurality of green sheets on which wiring patterns and via-hole conductors are formed, and firing at 800 to 1000 ° C. Has been.

In order to approximate the shrinkage behavior of the conductor paste to that of the green sheet with respect to the main component Cu or Cu ₂ O, or the Cu-Cu ₂ O mixture or Cu-CuO mixture as the copper-based conductor paste, Al ₂ O ₃ , ZrO ₂ , Y ₂ O ₃ , NiO, MgO, ZnO, Mg ₂ SiO ₄ , MgSiO ₃ , SiO ₂ , Nb ₂ O ₅ as oxides, or Ni, W, Mo, Si, Fe as metals , Co, and Ag, a copper metallized composition characterized by containing 0.5 to 30.0% by volume in a total amount in an inorganic component has been proposed (see, for example, Patent Document 1). ).
JP-A-10-95686

  However, in the method of Patent Document 1, when the green sheet and the conductor paste are simultaneously fired, the contraction behavior of both can be macroscopically approximated, but the metal element forming the metal powder is the green sheet or the insulating material. Diffusion to the layer side, the shrinkage of the green sheet or insulating layer around the through-hole part or metallized wiring layer proceeds faster than the shrinkage of other parts, microscopically with the through-hole part or metallized wiring layer, There was a problem that cracks occurred between the insulating layers.

  In addition, the diffusion of the metal element has problems such as a decrease in insulation of the insulating layer around the through-hole portion or the metallized wiring layer and a change in color tone.

  Accordingly, the present invention has been devised in view of the above-described problems, and an object thereof is to provide a conductor paste, a molded body, and a wiring board that can suppress diffusion of a metal element from the conductor paste. It is.

  The conductor paste of the present invention is characterized by containing a composite metal powder in which a metal oxide having a thickness of 10 nm or more is formed on the surface of the metal powder, a glass powder, and a resin.

The conductive paste of the present invention, the metal _{oxide, SiO 2, Al 2 O 3} , MgO, it is desirable to include at least one selected from the group consisting of ZrO _2.

  Moreover, as for the conductor paste of this invention, it is desirable for the said metal powder to contain at least 1 sort (s) chosen from the group of Cu, Ag, Pt, Au, and Ni.

  In the conductor paste of the present invention, the glass powder is preferably a crystallized glass powder.

  The conductor paste of the present invention contains 5 to 20 parts by volume of the crystallized glass powder with respect to 100 parts by volume of the composite metal powder, and the crystallization temperature of the crystallized glass powder is 650 to 800. It is desirable to be at ° C.

  The molded body of the present invention is characterized in that the conductive paste according to any one of claims 1 to 5 is applied or filled into a green sheet containing ceramic powder and a resin.

  In the molded article of the present invention, the green sheet preferably contains glass powder.

  The wiring board of the present invention is obtained by firing the molded body described above.

  The wiring board of the present invention is a wiring board comprising an insulating layer made of a sintered body and a wiring layer, wherein the wiring layer comprises a metal and an inorganic coating coated with the metal. The softening point of the inorganic coating is higher than the melting point of the metal.

  According to the conductor paste of the present invention and the molded body and wiring board produced using this conductor paste, by forming a metal oxide having a thickness of 10 nm or more on the surface of the metal powder, Sintering can be inhibited, the start of sintering can be delayed, and diffusion of elements contained in the metal powder into the insulating layer can be suppressed. Moreover, even if sintering of composite metal powder is inhibited by including glass powder in this conductor paste, a substantially dense wiring layer with few voids can be formed.

Further, by using a metal oxide containing at least one selected from the group consisting of SiO ₂ , Al ₂ O ₃ , MgO, and ZrO ₂ , diffusion of the metal element can be further suppressed.

  Further, by using a metal powder containing at least one selected from the group consisting of Cu, Ag, Pt, Au, and Ni, a sufficiently low-resistance wiring layer can be formed even when coated with a metal oxide. Can do.

  In addition, when the crystallized glass powder is included in the conductor paste, it becomes easy to densify the wiring layer, and the amorphous glass component of the wiring layer is reduced by crystallization of the crystallized glass powder. The diffusion of metal elements can also be suppressed.

  Furthermore, with respect to 100 parts by volume of the composite metal powder, the content of the crystallized glass powder is 5 to 20 parts by volume, and the crystal overtemperature of the crystallized glass powder is 650 to 800 ° C. Diffusion can be suppressed and the wiring layer becomes dense and low resistance.

  The wiring board of the present invention is obtained by firing a molded body using the above-mentioned conductor paste, and suppresses diffusion of metal elements from the conductor paste to the insulating layer. Is suppressed, and the occurrence of cracks between the insulating layer and the wiring layer is suppressed.

  In the wiring board of the present invention, the metal layer is coated with an inorganic film having a softening point higher than the melting point of the metal powder in the wiring layer, and the metal element is prevented from diffusing from the metal powder to the insulating layer. It is.

  FIG. 1 is a schematic view for explaining a conductor paste 1 of the present invention.

  The conductor paste 1 contains, for example, a composite metal powder 3 in which a metal oxide 3b having a thickness of 10 nm or more is formed on the surface of the metal powder 3a, a glass powder 5, and a resin 7. Moreover, you may contain the solvent (not shown) as needed.

  As shown in FIG. 2, the molded body 11 of the present invention includes a green sheet 13 containing ceramic powder (not shown) and a resin (not shown), and a conductive paste 1 on the surface of the green sheet 13. The wiring layer molded body 15 formed by printing or the like, or the through conductor molded body 19 formed by filling the through hole 17 formed through the green sheet 13 with the conductor paste 1 is formed. Yes.

  Further, as shown in FIG. 3, the wiring board 21 of the present invention is produced by firing the molded body 11 of the present invention, for example, and an insulating layer 23 formed by firing the green sheet 13 and The wiring layer 25 is formed by firing the wiring layer molded body 15, and the through conductor 29 is formed by firing the through conductor molded body 19.

  In the conductor paste 1 of the present invention, it is important that the metal oxide 3b having a thickness of 10 nm or more is formed on the surface of the metal powder 3a, and this metal oxide 3b serves as a barrier to form the metal powder. The metal element can be prevented from diffusing from the wiring layer 25 or the through conductor 29 to the insulating layer 23.

  The reason why the thickness of the metal oxide 3b is 10 nm or more is that when the thickness of the metal oxide 3b is less than 10 nm, the effect of suppressing the diffusion of the metal element is not recognized. Further, the metal oxide 3b having a thickness of less than 10 nm can be formed even when the metal powder 3a is oxidized by oxygen in the atmosphere, and the conventional metal in which the metal oxide 3b is not substantially formed. Same as powder.

  Moreover, even if the sintering of the composite metal powders 3 is inhibited by including the glass powder 5 in the conductor paste 1, a substantially dense wiring layer 25 and a through conductor 29 with few voids are formed. can do.

  The metal oxide 3b preferably has a softening point higher than the melting point of the metal powder 3a. In particular, the difference is preferably 50 ° C., more preferably 200 ° C. or more.

Then, the high softening point metal oxide _{3b, SiO 2, Al 2 O} 3, MgO, it is desirable to include at least one selected from the group consisting of ZrO _2.

  Moreover, it is desirable that these metal oxides do not contain a plurality of metal elements from the viewpoint of increasing the softening point.

  Further, the metal oxide 3b may contain a glass component, and crystals and glass may be mixed.

  The thickness of the metal oxide 3b needs to be 10 nm or more, and is desirably 0.05 μm or more in order to prevent the metal oxide 3b from being lost.

  Further, as shown in FIG. 4, as the molded body 11 is fired, the metal powders 3 a come into contact with each other to form a neck, and the surface of the network 33 formed by the metal powder 3 a Although it is formed by 3b, the structure is covered. Moreover, the glass component 35 resulting from glass powder is filling between these networks.

  When crystallized glass is used as the crow powder, the glass component 35 and crystals (not shown) deposited from the glass fill the space between the networks. In this case, since the proportion of crystals having a higher effect of suppressing the diffusion of metal elements than amorphous glass increases, a higher effect can be obtained.

  When such crystallized glass is used for the conductor paste 1, the use of crystallized glass having a crystallization temperature in the range of 650 to 800 ° C. means that the elements constituting the metal powder diffuse into the insulating layer. In addition to being able to be suppressed, a dense and low resistance wiring layer can be formed, which is desirable.

  The amount of the crystallized glass powder is preferably 5% by volume or more, more preferably 8% by volume or more, and particularly preferably 10% by volume or more with respect to 100 parts by volume of the composite powder from the viewpoint of preventing generation of voids. . Further, from the viewpoint of reducing the resistance of the wiring layer 25 and the through conductor 29, the amount of the crystallized glass powder is 20% by volume or less, further 17% by volume or less, particularly 15% with respect to 100 parts by volume of the composite powder. It is desirable to make it volume% or less.

Then, for example, as the glass _powder, SiO 2 35 to 55 _{wt%, Al} 2 O 3 5 to 30 wt%, MgO 0 to 20 _{wt%, B} 2 O 3 5 to 30 wt%, CaO 5 to 30 wt% The composition of BaO 0-20 mass%, SrO 0-10 mass% can be exemplified, and when glass powder having such a composition is used, the elements constituting the metal powder diffuse into the insulating layer. In addition to being able to be suppressed, a dense and low-resistance wiring layer can be formed.

  In order to facilitate the formation of a network in which metal powders are connected to each other, the thickness of the metal oxide 3b in the conductor paste 1 is preferably 1 μm or less, more preferably 0.5 μm or less, particularly 0 It is desirable to be 2 μm or less. In the wiring board 21, the thickness of the metal oxide 3b formed on the surface of the metal powder 3a substantially maintains the form of the conductor paste 1.

  Further, when glass powder is used for the green sheet 13, it becomes easy to fire at a low temperature of 1050 ° C. or less, and a metal powder having a low melting point and low resistance such as Ag, Cu, Au, or Ni can be used.

As the glass powder, for example, at least _{SiO 2, Al 2 O 3,} MgO, ZnO, B 2 O 3, can be exemplified the borosilicate glass powder containing, for example, from 60 to 99.5 weight the more silicate glass powder %, And at least 0.5 to 20% by weight of cordierite powder and 0 to 35% by weight of ceramic powder, the coefficient of thermal expansion and Young's modulus of the glass ceramic sintered body can be reduced. .

  Further, the wiring layer 25 and the through conductor 29 of the wiring board 21 of the present invention include at least a metal network 33 formed of a metal powder 3a and a metal oxide 3b as shown in the enlarged view of the main part of FIG. And an inorganic film 35 covering the metal network 33 formed from the origin. The metal network 33 has a structure in which a metal powder 3a used as a raw material is bonded to form a network, and the conductivity is imparted to the wiring layer 25 and the through conductor 29 of the wiring board 21 by this network.

  Further, the wiring layer 25 and the through conductor 29 contain a glass phase 37 in addition to the metal 31 and the inorganic coating 35 to suppress the formation of pores in the wiring layer 25 and the through conductor 29. Is desirable.

  Moreover, it may replace with the glass phase 37 and may contain the inorganic powder 35, and may contain both the glass phase 37 and inorganic powder (not shown).

  In such a configuration, the softening temperature of the inorganic coating 35 is higher than the melting point of the metal network 33, and the metal element contained in the metal network 33 is suppressed from diffusing into the insulating layer 23.

  Accordingly, various problems caused by diffusion of the metal element into the insulating layer 23 are suppressed. That is, it is possible to suppress the occurrence of cracks between the wiring layer 25, the through conductor 29, and the insulating layer 23.

  In addition, a change in color tone and a decrease in insulating properties of the wiring layer 25 and the insulating layer 23 around the through conductor 29 are also suppressed.

  In particular, since the through conductor 29 has a larger amount of metal than the wiring layer 25, it is desirable to use the conductor paste 1 of the present invention in forming the through conductor 29.

Note that the thermal expansion coefficient of the insulating layer 23 at −40 to 400 ° C. is 2 to 2 in terms of improving the mounting reliability between the semiconductor element (not shown) mounted on the wiring board 21 and the wiring board 21. It is desirable to set it as 5 * 10 < ^-6 > / degreeC.

  Further, by setting the Young's modulus of the insulating layer 23 to 150 GPa and further to 120 GPa or less, the wiring board 21 can be easily deformed, and the wiring board 21 and an external circuit board (not shown) on which the semiconductor element or the wiring board 21 is mounted. It is possible to relax the stress generated between the two.

  Further, the strength of the insulating layer 23 is preferably 200 MPa or more, more preferably 230 MPa or more, and particularly preferably 260 MPa or more in consideration of preventing cracking and chipping of the wiring board and improving handling properties. .

  Below, the manufacturing method of the molded object 11 produced using the conductor paste 1 of this invention and the wiring board 21 is demonstrated.

  First, a green sheet containing ceramic powder and resin is produced by a doctor blade method or the like.

For this green sheet, it is desirable to use a filler such as Al ₂ O ₃ and SiO ₂ and glass powder as ceramic powder from the viewpoint that low temperature firing is possible and various characteristics can be easily expressed.

Moreover, so-called filler, B ₂ O ₃ and PbO to enable low-temperature sintering as a sintering aid, it may be used a compound containing an alkali metal.

  Next, through holes are formed in the green sheet by using punching or laser light, and the conductive paste 1 of the present invention is filled into the through holes. Further, the circuit-shaped conductor paste 1 is printed on the surface of the green sheet.

  A plurality of green sheets filled and printed with the conductor paste 1 produced in this way are stacked to produce the molded body 11 of the present invention.

  Furthermore, by firing the molded body 11 at a predetermined temperature, the wiring board 21 of the present invention can be manufactured.

First, borosilicate glass powder having a composition of 42 mass% SiO ₂ -5 mass% B ₂ O ₃ -6 mass% Al ₂ O ₃ -22 mass% BaO-12 mass% ZnO: 72 mass%, cordierite powder : 5% by mass, alumina: 20% by mass, CaZrO ₃ : 3% by mass, an acrylic resin as an organic binder is added to this mixture, and further pulverized with toluene as a solvent, followed by a doctor blade method. A green sheet having a thickness of 100 μm was produced.

  Moreover, glass powders A to E having an average particle size of 1.0 to 3.0 μm having the composition shown in Table 1 were prepared.

  Moreover, the composite metal powder which comprises the film formed with the metal oxide described in Table 2 on the surface of the metal powder whose average particle diameter is 5.0 micrometers, and the copper powder whose average particle diameter is 5 micrometers were prepared.

And glass powder AE is added in the ratio shown in Table 2 with respect to 100 weight part (Cu conversion) of composite metal powder and copper powder, and also acrylic resin is used as an organic binder with respect to 100 weight part of inorganic substance components. 10 parts by weight of α-terpineol as an organic solvent was added and kneaded to prepare a conductor paste.

  Next, the green sheet was drilled so that the shape after firing was 200 μmφ, and the through-hole thus fabricated was filled with a conductor paste.

  Next, a conductive paste was printed on the surface of the green sheet to form, and four green sheets were pressure-laminated to form a molded body.

  Next, in order to decompose and remove organic components such as an organic binder, the molded body was degreased by holding at a temperature of 750 ° C. for 1 hour in a steam-containing nitrogen atmosphere, and then heated to 900 ° C. in a nitrogen atmosphere. Held for 1 hour to fabricate a wiring board.

With respect to the sample thus prepared, the penetration conductor, the color tone change around the wiring layer, the presence or absence of cracks, the insulation between the wiring layers, and the resistance of the penetration conductor were investigated. In addition, about the color tone change and the presence or absence of cracks, the sintered body was prepared by mirror polishing the surface layer / cross section, and was confirmed using a metal microscope. As for insulation between the wiring layers, the sample was put into a reliability test (high temperature and high humidity bias test: 85 ° C./85%/5.5 V), and after 1000 hours, an insulation resistance of 10 ⁹ Ω or more was not deteriorated. It was. Further, the resistance of the through conductor was measured by preparing a sample having a length of 1 mm and φ100 μm.

  Regarding the color change, a sample having a color change area of less than 5 μm is determined as “◯”, a sample having a color change area of 5 to 20 μm is determined as “Δ”, and the color change area is 20 μm. A sample exceeding “x” was judged as “×”.

The measurement results are shown in Table 2.

  Sample No. produced using a conventional conductor paste in which an oxide of 10 nm or more is not formed on the surface of the metal powder which is outside the scope of the present invention. In 1-4, the crack generate | occur | produced between the penetration conductor and the insulating layer.

  On the other hand, sample no. 5 to 25, no cracks are generated between the through conductor and the insulating layer, the color of the insulating layer does not change, the insulation reliability between wirings is low, the resistance of the wiring layers is low, and all the required functions are satisfied. It was possible to secure high reliability.

  Sample No. 2 produced using a conductor paste containing glass powder having a crystallization temperature of 600 ° C. In 5, the resistance value was slightly higher. Sample No. 2 produced using a conductor paste containing glass powder having a crystallization temperature of 850 ° C. In 8, the resistance value was slightly higher.

  Sample No. using amorphous glass powder was used. In No. 9, although there was no problem in practical use, there was a slight color change in the insulating layer.

  In addition, the amount of glass powder was 26 parts by volume of sample No. In No. 17, although there was no problem in practical use, the resistance slightly increased.

  In addition, the metal oxide of the composite metal powder, that is, Sample No. whose softening point of the inorganic coating is lower than the melting point of the metal. In 24, although there was no problem in practical use, there was a slight color change in the insulating layer.

It is a schematic diagram of the electrically conductive paste of this invention. It is sectional drawing which shows the molded object of this invention. It is sectional drawing which shows the wiring board of this invention. It is a principal part enlarged view of the wiring layer of the wiring board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Conductive paste 3 ... Composite metal powder 3a ... Metal powder 3b ... Metal oxide 5 ... Glass powder 7 ... Resin 11 ... Molded body 13 ... Green sheet 15 ... Wiring layer Molded body 17 .. Through hole 19 .. Through conductor molded body 21 .. Wiring substrate 23 .. Insulating layer 25 .. Wiring layer 29 .. Through conductor 33 .. Network 35 .. Inorganic coating 37.

Claims (9)

A conductor paste comprising a composite metal powder in which a metal oxide having a thickness of 10 nm or more is formed on the surface of a metal powder, a glass powder, and a resin. _2. The conductor paste according to claim 1, wherein the metal oxide contains at least one selected from the group of SiO ₂ , Al ₂ O ₃ , MgO, and ZrO ₂ . The conductor paste according to claim 1 or 2, wherein the metal powder contains at least one selected from the group consisting of Cu, Ag, Pt, Au, and Ni. The conductor paste according to any one of claims 1 to 3, wherein the glass powder is crystallized glass powder. The crystallized glass powder is contained in an amount of 5 to 20 parts by volume with respect to 100 parts by volume of the composite metal powder, and the crystallization temperature of the crystallized glass powder is 650 to 800 ° C. Item 5. The conductor paste according to Item 4. A green body containing a ceramic powder and a resin, wherein the conductor paste according to any one of claims 1 to 5 is applied or filled. The molded body according to claim 6, wherein the green sheet contains glass powder. A wiring board obtained by firing the molded body according to claim 6 or 7. A wiring board comprising an insulating layer made of a sintered body and a wiring layer, wherein the wiring layer comprises a metal and an inorganic film coated with the metal, and has a melting point higher than that of the metal. A wiring board having a high softening point of the inorganic coating film.

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