JP2005210030A - Ceramic wiring substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic wiring substrate with high reliability for joining a wiring conductor layer exposed to the front surface of a glass ceramic insulating substrate to the insulating substrate. <P>SOLUTION: In a wiring substrate in which a wiring conductor layer 3 formed by processing metal foil is provided on the front surface of a glass ceramic insulating substrate 2, the conductor layer 3 is joined to the front surface of the insulating substrate 2 via an insulating wiring pattern layer 10. The insulating wiring pattern layer 10 is formed of glass ceramic having a larger amount of glass than that of the insulating substrate 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a ceramic wiring board, and more particularly to a ceramic wiring board in which a wiring conductor layer formed by etching a metal foil is provided on the surface of a glass ceramic insulating substrate.

  In recent years, in order to obtain a wiring substrate with fine wiring and high wiring density, a multilayer wiring is formed by forming a wiring pattern on the surface of a ceramic green sheet by a photolithography method using a metal foil, and laminating the green sheet. A substrate has been developed. Electronic components such as semiconductor elements and capacitors, or printed boards are bonded to the surface of the wiring board via a brazing agent such as solder. Therefore, the wiring conductor layer (corresponding to the wiring pattern) on the surface of the wiring board may be subjected to a mechanical or thermal peeling load, and the bonding between the wiring conductor layer on the surface and the insulating board may occur. When the strength is low, there is a problem that the substrate is broken from this portion, and electrical reliability cannot be maintained.

As a technique for maintaining the bonding strength between the wiring conductor layer on the surface and the insulating substrate, Patent Document 1 discloses that copper is formed by forming a metal layer or particles containing at least one of Zn, Zr, and Sn on the surface of the copper foil. A method for maintaining the anchor of the foil until after firing has been proposed. According to this method, it has been reported that the connection reliability between the wiring conductor layer on the surface and the insulating substrate can be improved.
JP 2000-200909 A

  However, in the method described in Patent Document 1, the glass in the insulating substrate cannot sufficiently enter the roughened surface of the copper foil, and voids remain at the junction between the wiring conductor layer on the surface and the insulating substrate after firing. However, there is a problem that the bonding strength of the surface wiring conductor layer to the insulating substrate cannot be kept sufficiently high.

  Accordingly, an object of the present invention is to provide a ceramic wiring board having high bonding reliability between the wiring conductor layer exposed on the surface of the glass ceramic insulating board and the insulating board.

  According to the present invention, in the wiring board in which the wiring conductor layer formed by processing the metal foil is provided on the surface of the insulating substrate made of glass ceramic, the wiring conductor layer is interposed through the insulating wiring pattern layer. A ceramic wiring board is provided, which is bonded to a surface of an insulating substrate, and the insulating wiring pattern layer is formed of a glass ceramic having a larger amount of glass than the insulating substrate.

In the present invention,
(1) The insulating wiring pattern layer contains 5% by volume or more of glass,
(2) The insulating wiring pattern layer has a thickness of 0.5 to 100 μm,
(3) The wiring conductor layer is formed by etching copper foil,
(4) The wiring conductor layer is formed by etching a metal foil having a rough surface with a 10-point average surface roughness (Rz) of 0.5 μm or more on at least one surface. Being bonded to the surface of the insulating substrate through an insulating wiring pattern layer;
(5) The insulating substrate has a laminated structure in which a plurality of insulating layers are laminated, and a wiring conductor layer is provided between the insulating layers.
(6) The wiring conductor layer inside the insulating substrate is bonded to the insulating layer via the insulating wiring pattern layer.
Is preferred.

  According to the present invention, the surface wiring conductor layer is bonded to the insulating substrate via the insulating wiring pattern layer containing a larger amount of glass than the insulating substrate. Bonding strength is increased, and it becomes possible to obtain high bonding reliability of electrical components such as semiconductor elements connected to the wiring conductor layer on the surface, lead wires, or external electrodes for bonding to a printed circuit board. That is, since this insulating wiring pattern layer has a large amount of glass, the anchor effect is high, and firing is performed in a state where the surface wiring conductor layer firmly bites into the insulating wiring pattern layer, so that a high bonding strength is obtained. It can be secured. In this case, when the wiring conductor layer is formed directly on the insulating substrate having a large amount of glass, the strength of the insulating substrate itself is lowered. By forming the wiring pattern layer, such deterioration in characteristics can be effectively avoided.

Hereinafter, the present invention will be described in detail based on specific examples shown in the accompanying drawings.
FIG. 1 is a schematic cross-sectional view showing the structure of a multilayer wiring board as an example of the ceramic wiring board of the present invention.

  In FIG. 1, the ceramic wiring board denoted by 1 as a whole is composed of a glass ceramic insulating board 2 and a wiring conductor layer 3 formed on the surface (including the bottom face) or inside thereof.

  The insulating substrate 2 made of glass ceramic is composed of a laminated body formed by laminating a plurality of insulating glass ceramic layers 2a to 2d, and the wiring conductor layer 3 provided inside the insulating substrate 2 includes insulating layers 2a to 2d. It is formed at the 2d laminated interface.

  Each insulating layer 2a to 2d is provided with a via-hole conductor 4 having a diameter of 80 to 200 μm so as to penetrate the thickness direction, thereby connecting the wiring conductor layers 3 to achieve a predetermined circuit. A circuit network is formed. On the wiring conductor layer 3 (indicated by 3a in FIG. 1) formed on the surface of the insulating substrate 2, an electrical element 5 such as a semiconductor element is mounted and mounted with a conductive adhesive such as solder, if necessary. Further, the wiring conductor layer 3a on the surface may be used as a conductor pad for joining a conductor film for shielding or a terminal electrode for connection to an external circuit board such as a printed board.

  In the present invention, the wiring conductor layer 3a formed on the surface (or bottom surface) of the insulating substrate 2 is connected to the insulating substrate 2 (respective insulating layers 2a to 2d) through the insulating wiring pattern layer 10 formed in a wiring pattern shape. ). In this case, the insulating wiring pattern layer 10 is missing in the portion to which the via-hole conductor 4 is connected, and the via-hole conductor 4 is directly connected to the metallized wiring layer 3 on the surface. By bonding the wiring conductor layer 3a on the surface to the insulating substrate 2 through the insulating wiring pattern layer 10 as described above, the bonding strength between the wiring conductor layer 3a and the insulating substrate 2 is increased, and connection reliability is ensured. can do.

  In the present invention, the wiring conductor layer 3 (indicated by 3b in FIG. 1) formed inside the insulating substrate 2 is also interposed via the insulating wiring pattern layer 10 in the same manner as the wiring conductor layer 3a on the surface. It is preferable to be bonded to the insulating substrate 2 (respective insulating layers 2a to 2d). That is, by providing the wiring conductor layer 3b inside the insulating substrate 2 via the insulating wiring pattern layer 10 as well, the wiring conductor layer 3b inside the substrate may be generated when bending stress is applied to the substrate, for example. And the insulating layers 2a to 2d can be effectively prevented from being peeled, the substrate can be effectively prevented from being broken, and the connection reliability between the wiring conductor layer 3b and the via-hole conductor 4 can be kept high.

  Although not shown, a thick film resistor film such as tantalum silicide or molybdenum silicide, a wiring protective film, or the like may be further formed on the surface of the wiring substrate 1 as necessary.

[Insulating substrate 2 made of glass ceramic]
In the ceramic wiring board 1 of the present invention having the above structure, the glass ceramic insulating substrate 2 (insulating layers 2a to 2d) is made of glass powder or glass ceramic formed by firing glass powder and filler powder. Usually, it is preferable that it is obtained by baking the mixed powder which contains 10-70 mass% of glass powder and 30-90 mass% of filler powder. Such a glass ceramic has a low firing temperature of 800 to 1050 ° C., and insulates the formation of the above-described insulating wiring pattern layer 10 and the joint integration between the wiring conductor layer 3 and the insulating wiring pattern layer 10. Simultaneously with the formation of the substrate 2, it can be performed collectively. In addition, such a glass ceramic insulating substrate 2 is advantageous in that it generally has a low dielectric constant and reduces transmission loss of high-frequency signals and the like.

The glass used for forming the insulating substrate 2 contains at least SiO ₂ , and further includes Al ₂ O ₃ , B ₂ O ₃ , ZnO, PbO, an alkaline earth metal oxide, and an alkali metal oxide. One containing at least one oxide component selected, for example, SiO ₂ —B ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ Examples thereof include borosilicate glass such as O ₃ -MO (M is Ca, Sr, Mg, Ba or Zn); alkali silicate glass; Ba glass; Pb glass; Bi glass. These glasses may be amorphous glasses that remain amorphous upon firing, or may be lithiated, quartz, cristobalite, cordierite, mullite, anorthite, serdian by firing. , Spinel, garnite, willemite, dolomite, petalite and substituted derivatives thereof may be any of crystallized glass whose composition is adjusted so as to precipitate at least one kind of crystal, but does not impair sinterability at low temperatures. From the standpoint of improving the strength, it is preferably crystallized glass. When crystallized glass is used, the glass content after firing is lower than the glass content in the mixed powder. That is, if the crystal phase is precipitated from the glass by firing, the strength of the insulating substrate 2 can be increased without reducing the amount of filler and without increasing the firing temperature. Generally, it is preferable that the glass content (residual glass amount after crystal phase precipitation) in the insulating substrate 2 is less than 50% by volume.

The filler powder includes SiO ₂ crystals such as quartz and cristobalite, Al ₂ O ₃ , ZrO ₂ , mullite, forsterite, enstatite, spinel, magnesia, calcium zirconate, strontium silicate, calcium titanate, and titanate. Barium or the like is preferably used.

  Insulating substrate 2 (insulating layers 2a to 2d) obtained by firing with glass powder and filler powder as described above decomposes components derived from the glass and filler (crystalline phases and filler components precipitated from glass). And the residual glass phase present at the grain boundaries of these crystal phases).

[Wiring conductor layer 3 (3a, 3b) and via-hole conductor 4]
The wiring conductor layer 3 is obtained by processing a metal foil mainly containing at least one selected from the group of Cu, Ag, Al, Au, Ni, Pt and Pd into a pattern shape. Usually, it is produced by etching and transferred in a state of being processed into a predetermined wiring pattern shape (this point will be described later). Considering the occurrence of migration and the ease of processing in particular, the wiring conductor layer 3 is preferably formed by processing a copper foil (particularly a purity of 99% or more).

  In the present invention, the surface of the wiring conductor layer 3 on the interface side with the insulating wiring pattern layer 10 is preferably a rough surface having a 10-point average surface roughness (Rz) of 0.5 μm or more. That is, since such a rough surface faces the insulating wiring pattern layer 10, the insulating wiring pattern layer 10 bites into the rough surface of the wiring conductor layer 3, and a high anchor effect can be secured. This is because the bonding strength of the conductor layer 3 can be further increased. The ten-point average surface roughness (Rz) is measured according to JIS B 0601-1994.

  Further, the via-hole conductor 4 is preferably formed of a metal constituting the wiring conductor layer 3, and a through-hole formed in the thickness direction of the grease sheet for forming the insulating substrate 2 (insulating layers 2a to 2d). The hole can be formed by filling the conductor paste containing the metal component in the hole and firing the green sheet.

[Insulating wiring pattern layer 10]
In the present invention, the insulating wiring pattern layer 10 interposed between the insulating substrate 2 (insulating layers 2a to 2d) and the wiring conductor layer 3 is made of a glass ceramic having a glass content higher than that of the glass ceramic forming the insulating substrate 2. Is formed. That is, by forming the insulating wiring pattern layer 10 from a glass ceramic having a high glass content, the adhesion with the wiring conductor layer 3 is enhanced by the anchor effect of the pattern layer 10 during firing, and the two are firmly bonded. In addition, the insulating wiring pattern layer 10 and the insulating substrate 2 formed of glass ceramic can be integrated by simultaneous firing. In this case, as described above, the anchor effect of the pattern layer 10 can be further enhanced by making the side surface of the insulating wiring pattern layer 10 of the wiring conductor layer 3 a predetermined rough surface.

  Further, the amount of glass in the insulating wiring pattern layer 10 is preferably 5% by volume or more, particularly preferably in the range of 10 to 50% by volume. That is, if the amount of glass is less than 5% by volume, the anchor effect of the insulating wiring pattern layer 10 is low, the bonding strength of the wiring conductor layer 3 may be reduced, and if the amount of glass is too large, While reducing the strength of the pattern layer 10 itself, the pattern may be deformed during firing.

  Such an insulating wiring pattern layer 10 having a high glass content can be obtained by firing the glass powder exemplified in the section of the insulating substrate 2 or a mixed powder of the glass powder and the filler powder, like the insulating substrate 2. In order to increase the amount of glass compared to the insulating substrate 2, use a glass powder having a crystallinity lower than that of the insulating substrate 2 (with a small amount of precipitated crystals), or increase the amount of glass powder in the mixed powder. By doing, the amount of glass can be adjusted easily.

  The thickness of the insulating wiring pattern layer 10 is preferably in the range of 0.5 to 100 μm, more preferably 5 to 50 μm, and most preferably 10 to 20 μm. If this thickness is too thin, the connection reliability between the wiring conductor layer 3 and the insulating substrate 2 (or insulating layers 2a to 2d) is reduced, and if it is thicker than necessary, the electrical characteristics of the substrate may be deteriorated. There is. By setting the thickness of the insulating pattern layer 10 within the above range, high bonding reliability between the wiring conductor layer 3 (particularly the wiring conductor layer 3a on the surface) and the insulating substrate 2 is obtained while maintaining the electrical characteristics of the substrate. be able to.

[Manufacture of wiring boards]
The ceramic wiring board of the present invention having the above-described structure can be manufactured, for example, according to the processes shown in FIGS.

  First, a green sheet for forming the insulating layers 2a to 2d constituting the insulating substrate 2 described above is produced. That is, a glass powder for forming the insulating substrate 2 or a mixed powder of glass powder and filler powder is used as a raw material powder, and an organic binder, a solvent, a plasticizer, etc. are added to this raw material powder to prepare a molding slurry, Using the slurry, a green sheet 11 having a thickness of about 50 to 500 μm is prepared by a known method such as a doctor blade method, a rolling method, or a press method (FIG. 2A).

  Next, a through hole having a diameter of 80 to 200 μm is formed at a predetermined position of the green sheet 11 by laser, micro drill, punching or the like, and a via paste is formed by filling the inside with a conductor paste (FIG. 2). (B)). This conductor paste usually contains a metal component (Cu, Ag, etc.) of the same type as the metal foil for forming a wiring conductor layer, an organic binder made of acrylic resin, and an organic solvent such as toluene, isopropyl alcohol, acetone, etc. It is formed by mixing. The organic binder is mixed in an amount of 0.5 to 15.0 parts by mass with respect to 100 parts by mass of the metal component, and the organic solvent is mixed in a ratio of 5 to 100 parts by mass with respect to 100 parts by mass of the solid component and the organic binder. It is desirable. In addition, you may add some glass components etc. in this conductor paste.

  Further, an insulating paste pattern layer 14 corresponding to the insulating wiring pattern layer is applied to the green sheet 11, and a wiring conductor layer 13 is formed on the pattern layer 14 (FIG. 2C).

  The insulating paste uses a material whose glass powder content in the raw material powder for forming the insulating substrate 2 is increased or a material whose crystallinity of the glass powder in the raw material powder is lowered. It can be prepared by kneading with an organic binder and a solvent. The pattern layer 14 can be formed by applying such an insulating paste, for example, by screen printing to a wiring pattern shape with a predetermined thickness excluding a portion where the via-hole conductor 12 is exposed on the green sheet 11.

The wiring conductor layer 13 is formed as follows.
That is, a metal foil (for example, copper foil) for forming the wiring conductor layer 13 is bonded to the surface of a transfer film made of a polymer such as a polyethylene terephthalate film (PET film) using an appropriate adhesive material. On the transfer film, the metal foil is processed into a wiring pattern shape, and this is aligned and pressure-bonded to the green sheet 11 on which the pattern layer 14 made of an insulating paste and the via-hole conductor 12 are formed, and the transfer film is pulled. By peeling off, the wiring conductor layer 13 can be formed on the grease sheet 11. In this case, the wiring conductor layer 13 can be formed on both sides of the green sheet on which the insulating layers corresponding to the internal insulating layers 2b and 2c are formed.

  When the wiring conductor layer 13 is formed, as described above, it is preferable to roughen at least one surface of the metal foil so that the surface roughness (Rz) is 0.5 μm or more. That is, by overlapping the wiring conductor layer 13 on the green sheet 11 so that the rough surface faces the pattern layer 14, the insulating paste forming the pattern layer 14 bites into the rough surface, and the anchor effect is enhanced. Will be.

  Further, in order to process the metal foil into a wiring pattern shape, it is preferable to use a photolithography method. For example, a photoresist is applied to the metal foil on the transfer film, light is irradiated through a predetermined mask, and etching treatment is performed. Then, the portion of the metal foil not irradiated with light is removed, and the remaining resist is further removed, whereby the wiring conductor layer 13 (mirror image) having a wiring pattern shape can be processed.

  Next, the plurality of green sheets with the wiring conductor layer 13 manufactured in the same manner as described above are positioned (for example, with respect to the inner wiring conductor layer, the wiring conductor layers formed in adjacent insulating layers are The laminated body 15 is formed by laminating and pressing so as to face each other (FIG. 2D). In the following drawings, the insulating pattern layer 14 is omitted.

  The green sheet laminate 15 is produced by applying heat and pressure to the stacked green sheets by thermocompression bonding, and applying an adhesive composed of an organic binder, plasticizer, solvent, etc. between the sheets and thermocompression bonding. A method or the like can be adopted.

  Next, if necessary, non-sinterable sheets 16 that are not sintered at the firing temperature of the insulating substrate (the firing temperature of the green sheet 11) are preferably laminated on both surfaces of the laminate 15 obtained above (FIG. 2 ( e)). By laminating such a non-sinterable sheet 16, the firing shrinkage of the laminate can be effectively suppressed during firing performed in the following steps, and the position of the wiring conductor layer 13 due to the firing shrinkage. Inconveniences such as deviation and disconnection can be effectively suppressed. In particular, in order to manufacture a wiring board in which the fine wiring conductor layer 13 is applied at a high density, the method using the non-sinterable sheet 16 as described above can maintain the dimensional accuracy of the board and is extremely effective. It is.

The non-sinterable sheet 16 is obtained by forming a slurry obtained by adding an organic binder, a plasticizer, a solvent and the like to a hardly sinterable ceramic powder having a high sintering temperature. The hardly sinterable ceramic powder is specifically composed of a ceramic composition that does not become densified at a temperature of 1100 ° C. or lower, specifically, Al ₂ O ₃ , SiO ₂ , MgO, ZrO ₂ , BN, Examples thereof include powders of at least one TiO ₂ or a compound (forsterite, enstatite, etc.) containing these components. Moreover, as an organic binder, a plasticizer, and a solvent, the same material used for formation of the green sheet 11 mentioned above can be used. Further, in this non-sinterable sheet, by adding 0.5 to 15% by volume of a glass component, the adhesion to the green sheet 11 is increased, and the action of suppressing shrinkage is increased. It has the advantage that the generation of voids due to the diffusion of the glass component can be suppressed. In order to laminate the non-sinterable sheet 16 on the laminate 15, the same method as that for producing the laminate 15 of the green sheet 11 can be employed. It is also possible to laminate the binding sheets 16.

  The thickness of the non-sintered sheet 16 varies depending on the thickness of the laminated body 15 (the number of laminated green sheets 11), but it is usually preferable to be in the range of about 0.1 to 2 mm. If it is too thick, it may take time to remove the non-sintered sheet 16 in the final step, which may reduce the production efficiency. If it is too thin, the effect of suppressing firing shrinkage may be reduced.

  Next, debinding and firing are performed, and then the non-sintered sheet 16 is removed, whereby the glass ceramic wiring board of the present invention in which the wiring conductor layer 13 is firmly bonded to the insulating board can be obtained (FIG. 2 ( f)).

  The binder removal is performed by heat treatment in a nitrogen atmosphere at 100 to 850 ° C., particularly 400 to 750 ° C., whereby the organic components in the green sheet 11 and the via-hole conductor 12 paste are decomposed and removed. In addition, the baking performed following the binder removal is performed in a nitrogen atmosphere at 800 to 1050 ° C., whereby the green sheet 11 and the insulating pattern layer 14 become dense, and an insulating substrate (insulating layer) corresponding thereto. And an insulating wiring pattern layer is formed. In addition, when the wiring conductor layer 13 is formed using Ag foil, baking can be performed in air | atmosphere.

  The non-sinterable sheet 16 can be removed by ultrasonic cleaning, polishing, water jet, chemical blasting, sand blasting, wet blasting, or the like.

  The invention is illustrated by the following experimental example.

(Experimental example 1)
Crystalline glass powder having an average particle diameter of 3 μm having a composition of SiO ₂ : 37% by mass, Al ₂ O ₃ : 27% by mass, CaO: 11% by mass, ZnO: 12% by mass, and B ₂ O ₃ : 13% by mass ( A glass ceramic raw material powder comprising 73% by mass (softening point 850 ° C.) and 27% by mass of silica powder (ceramic filler) having an average particle diameter of 2 μm was prepared.

  11 parts by mass of isobutyl methacrylate resin (organic binder) and 5 parts by mass of dibutyl phthalate (plasticizer) are added to 100 parts by mass of the above glass ceramic raw material powder, and toluene (solvent) is added to a ball mill. Was mixed for 36 hours to prepare a slurry. A green sheet for an insulating substrate having a thickness of 0.2 mm was prepared from the obtained slurry by a doctor blade method.

  Further, with respect to 100 parts by mass of the mixed powder composed of 10% by mass of the glass powder and 90% by mass of alumina powder having an average particle diameter of 2 μm, 11 parts by mass of isobutyl methacrylate resin (organic binder) in solid content, dibutyl phthalate 5 parts by mass of (plasticizer) was added, and a non-sinterable sheet having a thickness of 0.4 mm was produced in the same manner as the previous green sheet.

Next, in order to form an insulating wiring pattern layer (referred to as an interface layer), the following composition:
SiO ₂ : 60% by mass
Al ₂ O ₃ : 15% by mass
BaO: 12% by mass
CaO: 7% by mass
B ₂ O ₃ : 6% by mass
In addition, 14 parts by mass of butyl acrylate is mixed with 100 parts by mass of a mixed powder obtained by mixing a glass powder having a low crystallinity with an average particle diameter of 2 μm and a silica powder with an average particle diameter of 2 μm at a ratio shown in Table 1. Part and 20 parts by mass of terpineol to prepare an insulating paste for the interface layer.

  This interfacial layer paste is applied to the previous green sheet so that the thickness after baking is the value shown in Table 1 by screen printing in a slightly larger wiring pattern shape than the wiring conductor layer formed of copper foil. Applied.

  Next, a copper foil having a thickness of 0.02 mm (both sides are rough surfaces having a 10-point average roughness Rz of 3 μm) is pasted on the PET film, and becomes 2 mm in length and 2 mm in width by a photoetching method. A copper foil pattern (wiring conductor layer pattern) was formed and transferred to a green sheet on which the previous interface layer was printed. Thereafter, the green sheet is used as the uppermost layer, and the green sheet to which the copper foil pattern is not transferred is overlaid and pressure laminated to obtain a laminate, and then the non-sinterable sheet is formed on both sides of the laminate. Were laminated one by one on each side and thermocompression bonded at 80 ° C. and 10 MPa.

  Next, the laminated body on which the non-sintered sheets are laminated is subjected to heat treatment for 3 hours at a temperature of 750 ° C. in a nitrogen atmosphere containing water vapor to reduce the residual carbon amount to 200 ppm or less, and then the atmosphere is dried. The ceramic wiring substrate was prepared by switching to nitrogen, raising the temperature to 900 ° C., holding it for 1 hour, and performing blasting with an alumina projection material to provide the wiring conductor layer on the surface of the insulating substrate made of glass ceramic. In this case, the amounts of the glass and the crystal phase constituting the insulating substrate (insulating layer) were 3% by volume (glass) and 97% by volume (crystalline phase) as measured with a Rietveld belt.

  The wiring conductor layer on the surface of the ceramic wiring board thus obtained was plated with Ni of 2.5 μm in thickness, and then plated with Au of 0.1 μm in thickness. Then, a Cu lead was formed on the plated coating layer. The wires were joined vertically with solder. The lead wire was pulled in the vertical direction at a pulling speed of 10 mm / min, and the load when the lead wire was peeled was shown in Table 1 as the adhesive strength (surface electrode bonding strength) of the conductor layer.

  Further, the number of voids in the wiring conductor layer joint portion was measured with an electron microscope (500 times) after polishing the cross section, and the results are also shown in Table 1.

  According to the results in Table 1, sample No. In No. 1, since the wiring conductor layer was formed on the surface of the insulating substrate without interposing the interface layer (insulating wiring pattern layer), the surface electrode bonding strength was as weak as 3 MPa.

  Sample No. In No. 10, since the glass amount of the interface layer was smaller than the glass amount of the insulating substrate (insulating layer), the strength of the surface electrode was as low as 1 MPa.

  On the other hand, in the wiring board of the present invention in which the wiring conductor layer is formed through the interface layer (insulating wiring pattern layer) whose glass amount is larger than that of the insulating board (insulating layer) (Sample Nos. 2 to 9) , The surface electrode bonding strength is extremely high, and the number of conductor layer bonding portion voids is also the same as that of Sample No. Compared to 1,10, it was significantly less.

(Experimental example 2)
On the other hand, a copper foil pattern having a length of 5 mm and a width of 5 mm was formed on a copper foil having a thickness of 0.02 mm formed on a PET film by a photo-etching method, and an interface layer was printed by the same method as in Experimental Example 1 Transferred to a green sheet. Next, after the interface layer was formed on the back surface of the green sheet in the same manner, a copper foil pattern having a length of 5 mm and a width of 5 mm was transferred to a position overlapping the previous copper foil pattern. This was baked in the same manner as described above, and the capacitance between the electrodes was measured. That is, the composition of the insulating substrate (insulating layer) and the interface layer (insulating wiring pattern layer) is the same as in Experimental Example 1. For example, the insulating substrate is 3% by volume of glass and 97% by volume of crystal phase. The composition of the interface layer of each sample No. is the same as the composition of the interface layer of the corresponding sample No. of Experimental Example 1.

  According to the results in Table 2, it can be seen that the capacitance decreases as the thickness of the interface layer increases, and the interface layer is desirably 50 μm or less, and more desirably 20 μm or less.

It is a schematic sectional drawing of an example of the structure of the ceramic wiring board of this invention. It is a figure which shows the manufacturing process of the ceramic wiring board of this invention.

Explanation of symbols

2: Insulating substrate 3: Wiring conductor layer 10: Insulating wiring pattern layer

Claims (7)

  In a wiring substrate in which a wiring conductor layer formed by processing a metal foil is provided on the surface of a glass ceramic insulating substrate, the wiring conductor layer is bonded to the insulating substrate surface via an insulating wiring pattern layer. A ceramic wiring board, wherein the insulating wiring pattern layer is made of glass ceramic having a larger amount of glass than the insulating board.   The ceramic wiring substrate according to claim 1, wherein the insulating wiring pattern layer contains 5% by volume or more of glass.   The ceramic wiring board according to claim 1, wherein the insulating wiring pattern layer has a thickness of 0.5 to 100 μm.   The ceramic wiring board according to claim 1, wherein the wiring conductor layer is formed by etching a copper foil.   The wiring conductor layer is formed by etching a metal foil having a rough surface with a 10-point average surface roughness (Rz) of 0.5 μm or more on at least one surface, and the rough surface side is an insulating wiring. The ceramic wiring board according to claim 1, wherein the ceramic wiring board is bonded to the surface of the insulating substrate through a pattern layer.   6. The ceramic wiring substrate according to claim 1, wherein the insulating substrate has a laminated structure in which a plurality of insulating layers are laminated, and a wiring conductor layer is provided between the insulating layers.   The ceramic wiring substrate according to claim 6, wherein the wiring conductor layer inside the insulating substrate is bonded to the insulating layer via the insulating wiring pattern layer.

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