JP4544837B2 - Copper paste for ceramic wiring board, ceramic wiring board, and method for manufacturing ceramic wiring board - Google Patents

Description

The present invention, in order to form a circuit on a ceramic substrate, a ceramic wiring board copper paste are co-fired with printing, and a method for producing a ceramic wiring substrate and the ceramic wiring board using the same, in particular wax ceramic wiring board copper paste for use in the wiring board circuit components are connected by a joining method such as with a process for producing a ceramic wiring substrate and the ceramic wiring board using the same.

  2. Description of the Related Art In recent years, wiring boards have been used in a high-frequency region of the GHz band or higher with the increase in information communication speed, and reduction of transmission loss is required. Therefore, in the wiring board, a conductor layer made of silver, copper, or the like, which has a low conductor resistance and a low melting point metal, is formed on a ceramic substrate having a relatively low dielectric constant. In particular, as the circuit density of a conductor layer increases, copper is used to prevent migration, and a ceramic substrate on which copper is printed as a conductor layer reduces transmission loss while suppressing copper oxidation. In order to obtain a low wiring board, firing is performed in a wet nitrogen atmosphere (in a mixed atmosphere of water vapor and nitrogen gas).

  In general, a wiring board is formed by forming a ceramic green sheet from a slurry prepared using a ceramic raw material powder, an organic binder, a solvent, and the like by sheet forming such as a doctor blade method, and wiring using a copper paste on the ceramic green sheet. After pattern printing and drying, the ceramic green sheet is debindered at a temperature of several hundred degrees Celsius in a mixed atmosphere of water vapor and nitrogen gas to remove the organic components contained in the copper paste and the ceramic green sheet. It is manufactured by raising the temperature to approximately 1000 ° C. or higher and performing firing.

  As circuit boards are mounted with high-density mounting and multi-functionality of devices, various circuit components such as semiconductor elements such as transistors and diodes, heat-dissipating parts, and terminals are mounted. Higher reliability is required for the adhesion strength of the layers.

  In particular, a wiring board on which a semiconductor element such as a transistor or a diode is mounted has a semiconductor element that generates heat due to an input signal and rises in temperature, thereby degrading characteristics of the semiconductor element or characteristics of other circuit components mounted on the circuit board. Heat dissipation measures are important. Therefore, a wiring board is often used with a heat sink connected through a conductor layer, and the conductor layer formed on the wiring board is required to have adhesion strength that does not cause blistering or peeling against thermal loads. Is done.

Focusing on the fact that the organic vehicle contained in the copper paste generates gas during the firing process and causes the conductor layer to blister and peel as a measure to prevent the conductor layer formed on the wiring board from blistering and peeling. Copper paste with specific oxidation, such as devitrifying glass frit selected from zinc-calcium aluminum silicate glass frit, zinc-magnesium-barium-aluminum silicate glass frit and mixtures thereof, bismuth oxide, cadmium oxide, etc. There is one that suppresses the generation of gas and prevents peeling and blistering of a conductor layer by adding an object (for example, see Patent Document 1).
JP-A-1-128488 (pages 4-7)

  However, according to the technique of Patent Document 1, since glass frit is added to the copper paste, when it is used as a conductor layer on a wiring board, the glass is raised and remains on the surface of the conductor layer, and solderability and plating properties are improved. In addition, there is a problem that the conductor layer is swollen or peeled off when the wiring board is heated, and there is a problem that measures for preventing the blister are insufficient.

The present invention solves the above problems, and in a wiring board using copper as a conductor layer, the plating property and solderability of the conductor layer are good. In addition to suppressing peeling, it also suppresses warping and undulation of the wiring substrate due to firing of the ceramic substrate and copper paste , thereby connecting various circuit components such as transistors, diodes and other semiconductor elements, heat dissipation components, terminals, etc. It is an object of the present invention to provide a highly reliable copper paste for a ceramic wiring board , a ceramic wiring board using the copper paste, and a method for manufacturing the ceramic wiring board .

In order to achieve this object, the invention according to claim 1 is to apply a ceramic green sheet as a conductor layer and to fire the ceramic green sheet at the same time to produce a ceramic wiring board having a conductor layer. A copper paste for a ceramic wiring board used for
Containing copper powder, organic vehicle and Fe ₂ O ₃ particles ,
As a material that melts into the glass contained in the ceramic green sheet by firing, it contains at least one of SiO ₂ , alkali metal , and alkaline earth metal having an average particle size of 50 nm or less in the form of an oxide. To do.
Since the copper paste for a ceramic wiring board according to claim 1 (hereinafter also referred to as copper paste) contains Fe ₂ O ₃ particles, the ceramic wiring is fired in a non-oxidizing atmosphere using this. A conductor layer having excellent adhesion strength to a substrate (hereinafter also referred to as a wiring substrate) is formed, and various circuit components such as semiconductor elements such as transistors and diodes, heat dissipation components, terminals, etc. are soldered on the wiring substrate. Even when heated and connected by a joining method such as brazing using a joining material such as a melting point alloy, the conductor layer does not bulge or peel off, and a wiring board having excellent conductor layer adhesion strength can be obtained.

The reason why the adhesion strength of the conductor layer is improved by adding Fe ₂ O ₃ particles to the copper paste is presumed as follows.
In general, it is known that the adhesion between the low-temperature fired porcelain material and the copper metal is poor because the wettability between the copper metal and the liquid phase component in the low-temperature fired porcelain material is poor in the firing step for producing the wiring board. In general, there is a known method of adding copper oxide to a copper paste to improve the wettability with a liquid phase component of a low-temperature fired porcelain material and to improve the adhesion of copper metal. When the obtained wiring board is heated in a joining process such as brazing, the conductor layer is swollen, and the adhesion between the conductor layer and the wiring board is insufficient.

  That is, when a copper paste to which copper oxide is added is used, the adhesion surface between the wiring board and the conductor layer is configured by mixing the interface where the metal oxide is present and the interface where the metal oxide is not present, and heating. Thus, blistering appears from the interface where the metal oxide does not exist (interface with poor adhesion), and it appears to have become obvious.

Therefore, the present invention adds Fe ₂ O ₃ particles to the copper paste to form an interface in which the metal oxide is uniformly present over the entire contact surface between the wiring board and the conductor layer, and to adhere the conductor layer to the wiring board. Improved.

When Fe ₂ O ₃ particles are added to the copper paste and the temperature shifts to a temperature higher than 700 ° C. in the firing step, the following chemical reaction (formula 1) appears.
2Cu + 3Fe ₂ O ₃ → Cu ₂ O + 2Fe ₃ O ₄ (Formula 1)
That is, it is considered that Fe ₂ O ₃ acts as an oxidizing agent for Cu in the firing temperature range and slightly oxidizes the entire Cu.

  At this time, although the oxidation of Cu is a very small amount, the entire Cu is uniformly oxidized, so that the wettability between copper and the liquid phase component of the low-temperature fired porcelain material is improved throughout the firing. It is thought that the occurrence of blistering is suppressed.

The Fe ₂ O ₃ is iron oxide particles mainly composed of Fe ₂ O ₃ , and may contain iron oxide other than Fe ₂ O ₃ (for example, Fe ₃ O ₄ or FeO) or Fe metal. good.
The average particle size of the Fe ₂ O ₃ is preferably 1 μm or less. The reason is that if the average particle diameter of Fe ₂ O ₃ exceeds 1 μm, the dispersion of Fe in the conductor layer can be uneven, and the effect of suppressing swelling of the conductor layer is reduced. The average particle diameter of Fe ₂ O ₃ is particularly preferably 500 nm or less, and more preferably 100 nm or less. The reason for this is that even if a small amount of Fe ₂ O ₃ particles is added, the blistering suppression effect is exhibited. Further, the lower limit of the average particle diameter of Fe ₂ O ₃ is preferable as it has an effect of suppressing swelling of the conductor layer, but it may be 5 nm practically.

The amount of the Fe ₂ O _3, relative to the copper powder 100 parts by weight, preferably in the range of 0.1 part by weight to 10.0 parts by weight. The reason is that if the addition amount of Fe ₂ O ₃ is less than 0.1 parts by mass, the effect of suppressing the conductor layer swelling is reduced, and if the addition amount of Fe ₂ O ₃ is more than 10.0 parts by mass, the conductor resistance is reduced. This is because it becomes larger. The amount of Fe ₂ O ₃ added is particularly preferably 0.1 to 5.0 parts by mass, more preferably 0.1 to 2.0 parts by mass. The reason is that it is an optimal range for suppressing blistering without increasing the conductor resistance.

  The copper powder preferably has an average particle size in the range of 0.5 μm to 10 μm. The reason is that if the average particle size of the copper powder is smaller than 0.5 μm, the sintering start temperature of the copper becomes too low, and the wiring substrate may be warped or wavy, and the average particle size of the copper powder is more than 10 μm. This is because if it is large, it is difficult to form a fine wiring pattern on the wiring board. The average particle diameter of the copper powder is further preferably 1 to 7 μm or 2 to 5 μm. The reason is that it is in an optimum range that achieves both swell suppression and fine wiring. At this time, the shape of the copper powder can be any of a substantially spherical shape, a dendritic shape, a flake shape and the like.

  The organic vehicle is obtained by dissolving an organic polymer in an organic solvent, and the organic polymer is at least one of ethyl cellulose, acrylic resin, polymethylstyrene, butyral resin, PTFE, alkyd resin, polyalkylene carbonate, and the like. In particular, an acrylic resin is preferable because the decomposability is improved in baking and a dense and low-resistance conductor layer can be obtained, and poly-n-butyl methacrylate and poly-2-ethylhexyl methacrylate are more preferable. .

The organic solvent is preferably a high-boiling solvent such as terpineol, butyl carbitol acetate, butyl carbitol, dibutyl phthalate or the like.
Moreover, the range of 20-40 mass parts is preferable with respect to 100 mass parts of copper powder, and, as for content of an organic vehicle, the range of 20-30 mass parts is more preferable. The reason is that when the content of the organic vehicle is less than 20 parts by mass, the fluidity of the copper paste is lowered, and when applying the copper paste to the wiring board, the workability is impaired, on the other hand, This is because if the content of the organic vehicle exceeds 40 parts by mass, it is not preferable to apply a copper paste to the wiring board and dry it, because the thickness of the conductor layer tends to vary.

  The viscosity of the copper paste is preferably in the range of 5000 poise to 30 poise. The reason for this is that when the viscosity of the copper paste exceeds 5000 poise, the fluidity of the copper paste is lowered, which is not preferable because the workability is impaired when the copper paste is applied to the wiring board. This is because if the viscosity is less than 30 poise, the thickness of the conductor layer is likely to vary when the copper paste is applied to the wiring board and dried, which is not preferable.

The copper paste may contain components such as a plasticizer, a thickener, a leveling agent, and an antifoaming agent.
Moreover, the copper paste for a ceramic wiring board according to claim 1 includes SiO ₂ having an average particle size of 50 nm or less, an alkali metal , and an alkaline earth as a material that is melted into the glass contained in the ceramic green sheet by firing. At least one type of metal is included in the form of an oxide.
More This improves the sinterability of copper powder, less wiring board warp or waviness is obtained.

In the ceramic wiring board in which the conductor layer exposed on the surface is plated, when used to form the conductor layer, the copper paste for a ceramic wiring board according to the present invention includes: As a material that does not vitrify by firing , it is preferable to include at least one of Al ₂ O ₃ , TiO ₂ , CeO ₂ , and mullite having an average particle size of 50 nm or less .
And, in this way, the plating property of the conductor layer is improved, the surface of the conductor layer can be satisfactorily plated , and even if the wiring board is heated, the conductor layer, plating or the like is blistered or peeled off. It can be prevented from arising.

Here, in the copper paste for a ceramic wiring board according to claim 1 or 2, the material such as SiO ₂ that improves the sinterability of the copper powder or the material such as TiO ₂ that improves the plating property has an average particle diameter. Is 50 nm or less.
Thus , according to the copper paste for a ceramic wiring board according to claim 1, it is possible to prevent the ceramic wiring board from being easily swelled . Further, according to the ceramic wiring board copper paste according to claim 2, in addition to this effect, there is an advantage that it prevents the plating of the conductor layer is Ru impaired.
Note that each of these materials (hereinafter, simply referred to as TiO ₂ or SiO _2, etc.) the average particle size of more have preferably is 30nm or less. The smaller the average particle diameter , the better because the above effect can be exhibited. However, the lower limit is practically 5 nm.

The amount of such TiO ₂ and SiO _2, relative to the copper powder 100 parts by weight, it is preferably added in an amount of 0.1 to 5.0 parts by weight. The reason is that if the added amount of SiO ₂ or the like is less than 0.1 parts by mass, the effect of suppressing waviness does not appear, and if the added amount of TiO ₂ or the like is less than 0.1 parts by mass, the plating property of the conductor layer is reduced. This is because if the amount of SiO ₂ or the like is deteriorated and the amount is more than 5.0 parts by mass, the copper sinterability is impaired.
The amount of such TiO ₂ and SiO ₂ is further preferably added in the range of 0.1 to 1.0 parts by weight. The reason is that it is an optimal range in which the above effects are manifested.

In addition, in the copper paste for a ceramic wiring board according to claim 1, the alkali metal used in the form of an oxide is used in order to melt into the glass contained in the ceramic green sheet by firing and improve the sinterability of copper. Examples of the alkaline earth metal include MgO, CaO, and Na ₂ O, K ₂ O or the like.
Further, in the copper paste for a ceramic wiring board according to claim 1, particularly SiO _2. Is preferable because addition of a small amount can suppress undulation and reduce glass floating on the surface of the conductor layer.

Further, the surface of TiO ₂ or SiO ₂ is preferably hydrophilic.
The reason is that those subjected to the hydrophobic treatment deteriorate the decomposability of the organic component and increase the amount of residual carbon .

On the other hand, in the copper paste for ceramic wiring board according to claim 2, Al ₂ O ₃ , TiO ₂ , CeO ₂ , mullite, etc. used for improving the plating property of the conductor layer are included in the ceramic green sheet and the copper paste. It is advisable to select materials appropriately so as not to react with the additives to be added .
Of these, TiO ₂ in particular Is preferable because the amount of waviness of the wiring board can be reduced and the adhesion strength of the conductor layer is further improved.

Further, in the copper paste for a ceramic wiring board according to claim 2, in order to improve the plating property of a conductor layer and a material such as an alkali metal, an alkaline earth metal , or SiO ₂ for improving the sinterability of copper. The materials such as Al ₂ O ₃ , TiO ₂ , CeO ₂ , and mullite are preferably mixed in an appropriate amount ratio that can exhibit the advantages of both in a balanced manner.
The copper paste for a ceramic wiring board according to the present invention (Claims 1 and 2) is, as described in Claim 3, in the ceramic wiring board, a radiator, a connection terminal, a lid that covers an electronic component that generates heat, And at least one of the circuit components may be used to form a conductor layer connected via a bonding material. In this manner, a ceramic substrate having high reliability can be configured when various circuit components such as semiconductor elements such as transistors and diodes, heat dissipation components, and terminals are connected to the conductor layer.

Next, the invention of claim 4 is a ceramic wiring board, characterized in that the ceramic wiring board copper paste according to claim 1 is applied to the ceramic green sheet as a conductor layer, and fired.
Therefore, according to the ceramic wiring board of the fourth aspect, there is no effect that the conductor layer does not bulge or peel off even when the wiring board is heated, and the solderability of the conductor layer is good. It is done.
The invention according to claim 5 is a method of applying the copper paste for a ceramic wiring board according to claim 2 to a ceramic green sheet as a conductor layer and firing it, and plating the conductor layer exposed to the surface after firing. Is a ceramic wiring board characterized in that
Therefore, according to the ceramic wiring board of the fifth aspect, there is no blistering or peeling of the conductor layer even when the wiring board is heated, and the plating property or solderability of the conductor layer is good. An effect is obtained.

Next, the invention according to claim 6 is the ceramic wiring board according to claim 4 or claim 5, wherein the conductor layer has a heat radiating body, a connection terminal, a lid for covering the electronic component with heat generation, and a circuit component. At least one of the, and characterized by being connected through a bonding material.

According to the ceramic wiring board of claim 6 , even if the joining material such as the brazing material is melted to connect the heat radiator, the connection terminal, the lid, and the circuit component, the conductor layer is not peeled off or blistered. . For this reason, high reliability is obtained when connecting heat-dissipating members, connection terminals for mounting, lids, circuit components, etc. that are arranged to cover electronic components (semiconductor elements, etc.) that generate heat, to the conductive layer. Can be realized.
The radiator, connection terminal, lid and circuit components may be connected directly to the surface of the conductor layer that has been fired simultaneously with the ceramic green sheet. A secondary conductor layer preferable for joining with a terminal, a lid, a circuit component, or the like may be formed and connected via the secondary conductor layer.

  Examples of the radiator include a heat sink and a thermal via. Examples of connection terminals include pin terminals, lead terminals, flip chip terminals, land terminals, solder ball terminals, and the like. Examples of the lid include a plate-shaped metal lid and a ceramic lid. Examples of the circuit components include semiconductor components, electronic components such as capacitors, inductors, and resistors.

  Various low melting point alloys such as solder (Sn—Pb alloy), Au brazing, Ag brazing, and Cu brazing can be used for the brazing material used for the metal fitting connection. The melting point of this alloy is preferably 270 ° C to 800 ° C. If the temperature is lower than 270 ° C., the alloy is melted by soldering at the time of PCB mounting, and the metal fitting position is shifted. This is because if it is higher than 800 ° C., it becomes close to the softening point of the glass used for the wiring board, and the wiring board is deformed. In particular, an alloy having a melting point of 300 ° C to 600 ° C, more preferably 300 ° C to 500 ° C is preferable. This is because these melting point alloys are easy to handle.

Next, the invention according to claim 7 is an invention relating to a method for manufacturing a ceramic wiring board, wherein the ceramic wiring board is manufactured using the copper paste for a ceramic wiring board according to claim 1.
  A first step of applying the copper paste for a ceramic wiring board according to claim 1 to a ceramic green sheet; and a ceramic green sheet to which the copper paste for a ceramic wiring board is applied in the first step is wet at 650 to 900 ° C A second step of removing organic components by exposure to a nitrogen atmosphere;
  A third step of firing the ceramic green sheet from which organic components have been removed in the second step at 850 to 1050 ° C. to form the conductor layer and the insulating layer;
  It is characterized by including.
Therefore, according to the method for manufacturing a ceramic wiring board according to claim 7, the conductor layer does not bulge or peel off even when heated, and the solderability of the conductor layer is good. The described ceramic wiring board can be manufactured.

Next, the invention according to claim 8 is a method for manufacturing a ceramic wiring board, wherein a ceramic wiring board is manufactured using the copper paste for a ceramic wiring board according to claim 2.
  A first step of applying the copper paste for a ceramic wiring board according to claim 2 to a ceramic green sheet;
  A second step of removing the organic component by exposing the ceramic green sheet coated with the copper paste for a ceramic wiring board in a first step to a wet nitrogen atmosphere at 650 to 900 ° C .;
  A third step of firing the ceramic green sheet from which organic components have been removed in the second step at 850 to 1050 ° C. to form the conductor layer and the insulating layer;
  A fourth step of plating the conductor layer which is baked in the third step and exposed on the surface of the ceramic wiring board;
  It is characterized by including.
Therefore, according to the method for manufacturing a ceramic wiring board according to claim 8, there is no blistering or peeling on the conductor layer even when heated, and the plating property and solderability of the conductor layer are also good. The ceramic wiring board according to Item 5, can be manufactured.

The invention according to claim 9 is the method for manufacturing a ceramic wiring board according to claim 7 or claim 8, wherein the conductor layer covers the radiator, the connection terminal, and the electronic component that generates heat. The method includes a step of connecting at least one of the body and the circuit component through a bonding material.
  Therefore, according to the method for manufacturing a ceramic wiring board according to claim 9, the cover member and the circuit component disposed so as to cover the heat radiation member, the connection terminal for mounting, the electronic component (semiconductor element or the like) that generates heat. The ceramic wiring board according to claim 6 can be manufactured with high reliability when connected to the conductive layer.

Hereinafter, the present invention will be described with reference to one embodiment.
"Production of ceramic green sheets"
First, 50 parts by mass of glass powder having a composition of 63.3 parts by mass of SiO ₂ , 24.1 parts by mass of B ₂ O ₃ , 5.7 parts by mass of Al ₂ O ₃ , and 6.9 parts by mass of CaO; A mixed powder having a particle size of 2.5 μm was prepared by mixing 50 parts by mass of an alumina filler.

  Next, 20 parts by mass of a binder composed of an acrylic resin, 10 parts by mass of a plasticizer composed of dibutyl phthalate, and an appropriate amount of a toluene / MEK mixed solvent were added to 100 parts by mass of the mixed powder to prepare a slurry.

  Next, a ceramic green sheet having a thickness of 250 μm was formed by sheet forming such as a doctor blade method using the slurry. This ceramic green sheet is a green sheet for low-temperature firing that can be fired at a relatively low temperature (here, 1000 ° C.).

"Preparation of copper paste"
Next, with respect to 100 parts by mass of copper powder having an average particle size of 2.8 μm, 25 parts by mass of the vehicle and the additives shown in (Table 1) were added and mixed with a three roll mill to prepare a copper paste. . A vehicle prepared by dissolving 30 parts by mass of polyisobutyl methacrylate in 70 parts by mass of terpineol was used.

（表１）に示すように、本発明の実施例として実施例Ａ、Ｂの組成を有する銅ペーストを作製するとともに、本発明の効果と比較するために比較例Ａ〜Ｃの組成を有する銅ペーストを作製した。

As shown in Table 1, copper having the compositions of Examples A and B as examples of the present invention and copper having the compositions of Comparative Examples A to C were compared with the effects of the present invention. A paste was prepared.

Example A is a copper paste in which 1.0 part by mass of Fe ₂ O ₃ having an average particle diameter of 21 nm and 1.0 part by mass of SiO ₂ having an average particle diameter of 12 nm are added to 100 parts by mass of copper powder. It is.
In Example B, 100 parts by mass of copper powder was 1.0 part by mass of Fe ₂ O ₃ having an average particle diameter of 21 nm, 1.0 part by mass of SiO ₂ having an average particle diameter of 12 nm, and an average particle diameter of 21 nm. This is a copper paste to which 0.5 part by mass of TiO ₂ is added.

Comparative Example A is a copper paste obtained by adding 1.0 part by mass of SiO ₂ having an average particle diameter of 12 nm and 0.5 part by mass of TiO ₂ having an average particle diameter of 21 nm to 100 parts by mass of copper powder. .
In Comparative Example B, 100 parts by mass of copper powder is 1.0 part by mass of CuO having an average particle diameter of 20 nm, 1.0 part by mass of SiO ₂ having an average particle diameter of 12 nm, and TiO ₂ having an average particle diameter of 21 nm. Is a copper paste to which 0.5 part by mass is added.

"Production of fired samples"
Next, the copper pastes of Examples A and B and Comparative Examples A, B, and C shown in (Table 1) are printed on the ceramic green sheets to prepare respective fired samples.

  First, a ceramic green sheet is cut into a size of 50 mm in length and 60 mm in width to produce a ceramic green sheet piece, and a copper paste with a size of 2 mm in length, 2 mm in width and 20 μm in thickness is provided at the approximate center of the ceramic green sheet piece. A printed test piece A and a test piece B in which a copper paste was printed in a size of 15 mm in length, 15 mm in width, and 20 μm in thickness at a substantially central portion of the ceramic green sheet piece were prepared.

  Next, a total of four test pieces A and three green sheets on which copper paste is not printed are laminated and pressed to produce a laminate A in which the print surface of the test piece A appears on the upper surface. Then, a total of four test pieces B and three green sheets on which copper paste was not printed were laminated and pressed to prepare a laminate B in which the printing surface of the test piece B appeared on the upper surface. .

  Next, the laminates A and B are exposed to a furnace in which a mixed atmosphere of water vapor and nitrogen gas (a mixed atmosphere having a dew point of water vapor and nitrogen gas of 70 ° C.) is prepared and left at a temperature of 850 ° C. Degreasing the organic components contained in the copper paste and the ceramic green sheet, and subsequently raising the temperature to 1000 ° C., leaving it for 2 hours, firing, and producing fired samples A and B having a conductor layer on the upper surface did.

  The fired sample A was obtained by firing the laminate A, and was used for the evaluation of the adhesion strength in the later operation. Further, the fired sample B was obtained by firing the laminated body B, and was used for evaluation of the swelling of the conductor layer described later.

"Evaluation of adhesion strength"
Next, a tin-plated wire having a diameter of 0.45 mm is soldered on the upper surface of the conductor layer of the fired sample A, the wire is pulled, and a tensile load in the direction perpendicular to the upper surface of the fired sample A is applied. The load at which the peeled off was shown as adhesion strength (Table 1).

"Evaluation of bulge of conductor layer"
Next, Ni plating with a thickness of 4 μm was performed on the upper surface of the conductor layer of the fired sample B by electrolytic plating, and Au plating with a thickness of 0.5 μm was further performed on the upper surface of the Ni plating by electrolytic plating.

Next, the fired sample subjected to Au plating was placed in a furnace heated to 390 ° C. for several minutes, and then the presence or absence of swelling of the conductor layer was visually confirmed, and the results are shown in Table 1.
As shown in (Table 1), Examples A and B of the present invention obtained a good appearance without swelling of the conductor layer even when heated to 390 ° C. On the other hand, in Comparative Examples A, B, and C, the conductor layer was swollen by heating to 390 ° C.

Comparing Comparative Example A and Example B of the present invention, it can be seen that Fe ₂ O ₃ was not added as an additive to Comparative Example B, and as a result, blistering occurred due to heating.
Further, when comparing Comparative Example B with Example B of the present invention, Comparative Example B was added with CuO instead of Fe ₂ O ₃ as an oxide, and as a result, the adhesion strength was the same as that of Example B of the present invention. Although it is substantially equivalent, it turns out that the blister was generated by heating.

Further, comparing Comparative Example C with Example B of the present invention, Comparative Example B has NiO added instead of Fe ₂ O ₃ as an additive, and as a result, blistering occurs due to heating, and adhesion strength is also increased. It turns out that it is low.

In addition, when Examples A and B of the present invention are compared, it can be seen that the adhesion strength is further improved by further adding TiO ₂ as an additive.
"Production of wiring board"
A wiring board was produced using the ceramic green sheet produced as described above and the copper paste having the composition shown in Example B. FIG. 1 is a cross-sectional view showing a configuration of a wiring board according to an embodiment to which the present invention is applied.

  In FIG. 1, reference numeral 1 denotes a wiring board. The wiring board 1 is joined to a ceramic substrate 2 formed by laminating and firing a plurality of ceramic green sheets, and a lower surface of the ceramic substrate 2 via a brazing material 12. The heat dissipation body 3, the semiconductor element 4 inserted in the hole of the ceramic substrate 2 and installed on the upper surface of the heat dissipation body 3, the hole of the ceramic substrate 2 is shielded so as to cover the semiconductor 4, and the conductor layer 10 is brazed. 13, the lid 7 connected via 13, and the connection terminals 6 and 7 connected via the brazing material 14 to the conductor layer 10 on the upper surface of the ceramic substrate 2.

  The ceramic substrate 2 was printed by printing the copper paste of Example B on a ceramic green sheet and dried to form a laminate, and in a wet nitrogen atmosphere at 850 ° C. (the dew point of water vapor and nitrogen gas was 70). The mixture is degreased in a mixed atmosphere at 0 ° C., and is then replaced with dry nitrogen and fired at 1000 ° C. for 2 hours. Further, every time the ceramic green sheets are stacked, the conductor layers 11 are connected to connect the wiring circuits of the plurality of ceramic green sheets to each other.

  The conductor layer 10 is subjected to Ni plating with a thickness of 4 μm by an electroless plating method on a portion exposed on the surface of the ceramic substrate 2. Further, an Au layer with a thickness of 0.5 μm is formed on the upper surface of the Ni plating by an electroless plating method. Plating is done.

  The radiator 3 is formed of an alloy of copper and tungsten with Ni—Au plating, and is joined to the conductor layer with Ni—Au plating on the back surface of the ceramic substrate 2 by brazing. Yes. At this time, brazing is performed by using a brazing material 12 made of an alloy of gold and germanium and heating at approximately 390 ° C.

  The semiconductor element 4 has a lower surface bonded to the upper surface of the radiator 3, and a terminal (not shown) formed on the upper surface of the semiconductor element 4 is a conductor in which Ni—Au plating is applied to the ceramic substrate 2 by wire bonding 8, 9. Connected to layer 10.

  The lid 7 is formed by Ni—Au plating on an alloy of Ni, Co, and Fe, and brazing the Ni—Au plated conductor layer 10 on the upper surface of the ceramic substrate 2. It is joined. At this time, brazing is performed by using a brazing material 13 made of an alloy of gold and germanium and heating at approximately 390 ° C.

  The connection terminal 6 is formed of an alloy of copper and Fe with Ni—Au plating, and is joined to the conductor layer 10 with Ni—Au plating on the upper surface of the ceramic substrate 2 by brazing. Yes. At this time, brazing is performed by using a brazing material 14 made of an alloy of gold and germanium and heating at approximately 390 ° C.

The effects of the copper paste and the wiring board using the same in the embodiment of the present invention having the above-described configuration will be described below.
According to the copper paste of the embodiment of the present invention, the adhesion strength between the ceramic substrate 2 and the conductor layer 10 is excellent in the wiring substrate 1, and the semiconductor device 4 such as a power transistor and a diode and the radiator 3 are provided on the wiring substrate 1. Even when the connection terminals 6 and the like are heated and connected by brazing, the conductor layer 10 does not bulge or peel off, and a highly reliable wiring board can be obtained.

In addition, according to the copper paste of the embodiment of the present invention, the copper sinterability is further improved, the plating property and the solderability are good, and a wiring board with less warpage and undulation can be obtained.
In addition, according to the wiring board 1 of the embodiment of the present invention, the plating property and solderability of the conductor layer 10 are good, and even if the wiring board 1 is heated, plating blistering or peeling does not occur. A wiring board excellent in density mounting can be obtained.

  Further, according to the wiring board 1 of the embodiment of the present invention, the conductor layer 10 is peeled off or blistered even if the brazing materials 12 to 14 are melted and the radiator 3, the lid 7, the connection terminal 6, etc. are connected. Therefore, high reliability can be obtained particularly in a wiring board on which a radiator, a connection terminal between circuit components, a semiconductor element that generates heat, and the like are mounted.

  In the embodiment of the present invention, Ni and Au are plated on the upper surface of the conductor layer 10, and the radiator 3, the connection terminal 6, the lid 7 and the like are placed on the Au plating surface via the brazing materials 12-14. Although connected, other metal having low resistance may be plated instead of Ni and Au plating. In addition, the present invention is not limited to the Au plating process, and the plating process may be omitted when the brazing can be surely performed without the plating process.

In the embodiment of the present invention, an alloy of gold and germanium is used as the brazing material, but solder, copper alloy, or the like may be used.
Moreover, when manufacturing a wiring board using the copper paste of the example of the present invention, the ceramic green sheet coated with the copper paste is placed in wet nitrogen at 650 to 900 ° C. (dew point of water vapor and nitrogen gas is 70 ° C. The organic component is removed in a mixed atmosphere) (debinding step), and then fired at 850 to 1050 ° C. Here, the binder removal step is set in a range not exceeding the subsequent firing temperature.

  First, the organic components contained in the ceramic green sheet and the copper paste are removed (debindering step) in wet nitrogen at 650 to 900 ° C. Here, the binder removal step is set in a range not exceeding the subsequent firing temperature. Since the binder is removed in a state where the ceramic particles are dispersed around the copper powder in the copper paste, the sintering start of the copper powder is suppressed during the binder removal, but in the subsequent firing process at high temperature Since the sintering of the copper powder is promoted by exposure to wet nitrogen during debinding, a dense conductor layer can be obtained.

  In the firing process performed after the binder removal step, copper and the ceramic green sheet are fired simultaneously in nitrogen at 850 to 1050 ° C. or wet nitrogen. Since each sintering start temperature and firing shrinkage timing are controlled to be close to each other, it is possible to obtain a wiring board with less warping and undulation, a dense and low resistance, and a low transmission loss of high frequency signals. .

It is sectional drawing showing the structure of the wiring board of the Example to which this invention was applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Wiring board, 2 ... Board | substrate, 3 ... Heat sink, 4 ... Semiconductor element, 5 ... Cover body, 6 ... Connection terminal, 7 ... Cover body, 8, 9 ... Wire bonding, 10, 11 ... Conductor layer, 12, 13, 14 ... brazing material.

Claims (9)

A copper paste for a ceramic wiring board used for making a ceramic wiring board having a conductor layer by being applied to the ceramic green sheet as a conductor layer and being fired simultaneously with the ceramic green sheet,
Containing copper powder, organic vehicle and Fe ₂ O ₃ particles ,
As a material that melts into the glass contained in the ceramic green sheet by firing, it contains at least one of SiO ₂ , alkali metal , and alkaline earth metal having an average particle size of 50 nm or less in the form of an oxide. Copper paste for ceramic wiring board. The ceramic wiring board is subjected to a plating treatment on a conductor layer exposed on the surface,
In the copper paste for ceramic wiring board,
The ceramic according to claim 1, further comprising at least one of Al ₂ O ₃ , TiO ₂ , CeO ₂ , and mullite having an average particle size of 50 nm or less as a material that does not vitrify by firing. Copper paste for wiring boards. The copper paste for ceramic wiring board is
Wherein the ceramic wiring board, the heat radiating body, the connection terminals, a lid for covering the electronic component with fever, and at least one of the conductor layers that will be connected by means of a bonding material of the circuit components,
Characterized in that it is used to form the claim 1 or claim 2 ceramic wiring board copper paste according to. A ceramic wiring board, wherein the copper paste for a ceramic wiring board according to claim 1 is applied as a conductor layer to a ceramic green sheet and fired. A ceramic wiring board characterized in that the copper paste for a ceramic wiring board according to claim 2 is applied to a ceramic green sheet as a conductor layer and fired, and the conductor layer exposed to the surface after firing is plated. substrate. 5. The device according to claim 4, wherein at least one of a radiator, a connection terminal, a lid that covers an electronic component that generates heat, and a circuit component is connected to the conductor layer via a bonding material. Item 6. The ceramic wiring board according to Item 5. A method for producing a ceramic wiring board, comprising producing a ceramic wiring board using the copper paste for a ceramic wiring board according to claim 1,
  A first step of applying the copper paste for a ceramic wiring board to a ceramic green sheet;
  A second step of removing the organic component by exposing the ceramic green sheet coated with the copper paste for a ceramic wiring board in the first step to a wet nitrogen atmosphere at 650 to 900 ° C .;
  A third step of firing the ceramic green sheet from which the organic component has been removed in the second step at 850 to 1050 ° C. to form the conductor layer and the insulating layer;
  A method for producing a ceramic wiring board, comprising: A method for producing a ceramic wiring board, comprising producing a ceramic wiring board using the copper paste for a ceramic wiring board according to claim 2,
  A first step of applying the copper paste for a ceramic wiring board to a ceramic green sheet;
  A second step of removing the organic component by exposing the ceramic green sheet coated with the copper paste for a ceramic wiring board in the first step to a wet nitrogen atmosphere at 650 to 900 ° C .;
  A third step of firing the ceramic green sheet from which the organic component has been removed in the second step at 850 to 1050 ° C. to form the conductor layer and the insulating layer;
  A fourth step of plating the conductor layer which is baked in the third step and exposed on the surface of the ceramic wiring substrate;
  A method for producing a ceramic wiring board, comprising: 8. The method according to claim 7, further comprising a step of connecting to the conductor layer at least one of a heat radiating body, a connection terminal, a lid that covers an electronic component that generates heat, and a circuit component via a bonding material. Item 9. A method for manufacturing a ceramic wiring board according to Item 8.

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