JPH04336493A - Method for forming via conductor of multilayer ceramic substrate - Google Patents

Abstract

PURPOSE:To provide a method for forming a via conductor of a multilayer ceramic substrate for enhancing reliability of the via conductor. CONSTITUTION:A via hole 2 is provided on a green sheet 1, a metal powder 3 is filled into the via hole 2, and a land 4 for connecting the via is formed on a single or both surfaces of the above green sheet 1. And then, the green sheet 1 is laminated and calcined, thus enabling the green sheet 1 to be sintered to a one-piece ceramic plate 51. In a method for manufacturing the multilayer ceramic substrate for sintering the metal powder 3 within the via hole 2 to a one-piece via conductor 52 and then performing press treatment in equal direction of the above ceramic plate 51, etc., an inorganic matter 7 with 1-10vol.% is mixed in the above metal powder 3 and then a mixture of this metal powder 3 and the inorganic matter 7 is filled into the via hole 2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer ceramic substrate, and more particularly to a method for forming via conductors in a multilayer ceramic substrate, which improves the reliability of the via conductors.

0002

2. Description of the Related Art In a conventional method for forming via conductors in a multilayer ceramic substrate, for example, as shown in FIG. d) circuit pattern formation step, (e) lamination step, and (f) firing step are performed in sequence.

In the green sheet forming step, ceramic powder and an organic solvent are kneaded into a slurry to form a sheet, which is then cut to obtain a green sheet 1 of a predetermined size. In the hole punching process, a large number of via holes 2 are punched in the green sheet 1. In the via conductor filling step, the via hole 2 is filled with metal powder 3 such as copper powder, for example. The particle size of the metal powder 3 is not particularly limited, but is 1 to 5 μm.
It is said that the amount of

In the circuit pattern forming step, lands 4 for via connections are formed on one (or both) sides of the green sheet 1, and a predetermined circuit pattern is formed as necessary. The method of forming the circuit pattern and the land 4 is not particularly limited, and for example, a known method such as screen printing may be employed. In the lamination process, a large number of green sheets 1 having circuit patterns and lands 4 formed thereon are stacked in a predetermined order and are pressed together by heating and pressure. In this lamination process, the organic solvent contained in the green sheet 1 is vaporized and diffused, but a portion of it remains in the green sheet 1 and the metal powder 3. Moreover, air exists between the particles of the metal powder 3 since the time of filling.

In the firing process, the laminated green sheets 1 are heated to a higher temperature (for example, about 1010° C.) than in the lamination process, and the laminated green sheets 1 are sintered to form an integrated ceramic plate 51, and the metal powder 3 is sintered to form via conductors. It becomes 52. In reality, after these steps, a finished product of the multilayer ceramic substrate is obtained through an external shaping step, a surface polishing step, a surface layer forming step, etc., but these subsequent steps are not directly related to the present invention. The explanation will be omitted.

By the way, most of the air remaining between the particles of the metal powder 3 in the lamination process is dissipated during the firing process, but as shown in FIG. Holes 53 are often formed. If such holes 53 are formed, the conductivity of the via conductor 52 will be impaired, and in extreme cases, disconnection will occur, and the reliability of the via conductor 52 will be impaired.

Therefore, as shown in FIG. 5, for example, the inventor of the present invention heated the ceramic plate 51 at a high temperature after the lamination process.
Isodirectional pressure treatment (hereinafter referred to as HIP treatment) in which the holes 53 are crushed by placing them in an inert atmosphere such as high-pressure argon.
I tried to do this. In the HIP process, the via conductor 5 is heated to about 850°C for about 1 hour.
Since the via conductor 52 is softened and a pressure of about 1000 atm is applied, the pores 53 in the via conductor 52 are crushed and disappear.

[0008]

[Problem to be solved by the invention] However, HIP
In the treatment, by continuing heating and pressurizing for about one hour, 600 ml of heat is formed in the via conductor 52 as shown in FIG.
It was found that giant single-crystal grains of about 70 μm were formed, and the grain boundaries between the grains became mechanically weak, leading to wire breakage. In addition, the land 54 of the via conductor 52
It was found that wire breaks were particularly likely to occur at the grain boundaries between the two.

The present invention was made in view of the above-mentioned circumstances, and provides a multilayer structure that prevents via conductor particles from becoming gigantic during HIP processing, thereby increasing the reliability of via conductors. An object of the present invention is to provide a method for forming via conductors on a ceramic substrate.

0010

[Means for Solving the Problems] A method for forming via conductors in a multilayer ceramic substrate according to the present invention includes, for example, as shown in FIG. Further, after forming a land 4 for via connection on one or both sides of the green sheet 1, the green sheets 1 are laminated and fired to sinter the green sheet 1 into an integrated ceramic plate 51,
In a method for manufacturing a multilayer ceramic substrate in which metal powder 3 in via hole 2 is sintered into integrated via conductor 52, the following measures are taken to achieve the above object.

That is, a method is taken in which 1 to 10% by volume of inorganic substance 7 is mixed with the metal powder 3 and the ceramic plate 51 after sintering is subjected to isodirectional pressure treatment.

0012

[Operation] In the present invention, in the HIP treatment after sintering, the particles of the inorganic substance 7 prevent the particles of the metal powder 3 from becoming gigantic, and the size of the metal particles constituting the via conductor 52 is approximately several μm. It can be kept below. The metal powder 3 used in the present invention may be composed of a metal powder that is sintered at a temperature lower than the sintering temperature of the green sheet 1 or the ceramic plate 51, and may be composed of copper powder, for example. Further, the particle size of the metal powder 3 may be appropriately selected depending on the hole diameter, aspect ratio, etc. of the via hole 2. For example, if the hole diameter of the via hole 2 is about 90 μm and the aspect ratio is about 1 to 3, the particle size of the metal powder 3 may be selected as appropriate. Similarly, the thickness may be 1 to 5 μm.

Further, the inorganic material 7 used in the present invention is not particularly limited, and for example, alumina (Al2O3), silicon oxide (SiO), silicon nitride (SiN), etc. can be used. Further, the particle size of the inorganic substance 7 may be equal to or smaller than the particle size of the metal powder 3, and in particular, the inorganic substance 7 with a particle size of about 0.1 to 3 μm is added to the metal powder 3 with a particle size of about 1 to 5 μm. In this case, it is called a surface improvement treatment or a hybridization treatment, and it is preferable because child particles smaller in diameter than the mother particles are attached to the surface of the mother particles, thereby improving the dispersibility of the metal powder 3 and the inorganic substance 7.

In the present invention, the amount of the inorganic substance 7 added is 1 to 1.
The content is preferably 10% by volume. If the amount of the inorganic substance 7 added is less than 1% by volume, the effect of suppressing grain growth will be significantly reduced, which is undesirable, and if it exceeds 10% by volume, the conductor resistance of the via conductor 52 will increase, which is not preferred. .

[0015]

Embodiment A method for forming via conductors in a multilayer ceramic substrate according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2. This method for forming via conductors in a multilayer ceramic substrate includes (a) a green sheet forming step, (b)
) hole drilling process, (c) via conductor filling process, (d) circuit pattern forming process, (e) lamination process, (f) firing process, (
g) HIP treatment steps are performed sequentially. Among these steps, (a) green sheet forming step, (b) hole punching step, (d) circuit pattern forming step, (e) laminating step, (f
) Since the firing process is the same as the conventional one, detailed explanation thereof will be omitted. Note that the diameter of the via hole 2 formed in the green sheet 1 in the hole forming process is approximately 90 μm.

Further, after the HIP process, a finished product of the multilayer ceramic substrate is obtained through an external shaping process, a surface polishing process, a surface layer forming process, etc. However, these subsequent processes are not directly related to the present invention. , the explanation thereof will also be omitted. In the via conductor filling step, the via hole 2 is filled with a mixture of metal powder 3 and inorganic substance 7 .

Here, the metal powder 3 has a particle size of 1 to 5.
Copper powder with a particle size of 0.1 μm is used as the inorganic substance 7.
~3 μm alumina is used. Further, the amount of the inorganic substance 7 added was 5% by volume based on the metal powder 3. Next, H
In the IP treatment process, the via conductor 52 is heated to approximately 850° C. for approximately 1 hour to soften it, and
By applying a pressure of about tm, the holes 53 in the via conductor 52 are crushed and disappear.

After this heating and pressurization is completed, the ceramic plate 51 and the via conductor 52 are cooled, and the via conductor 52 becomes a single crystal, but the inorganic substance 7 dispersed in the via conductor 52 is
suppresses the growth of metal single crystal particles, so as shown in FIG. 2, the growth of single crystal particles is suppressed to, for example, several μm or less. As a result, the contact area between the metal particles becomes larger and the conductivity is improved. Further, since the fine metal particles are sintered so as to be intricately and densely intertwined with each other via inorganic substances, the mechanical strength of the via conductor 52 is also increased. By the way, a multilayer ceramic board (Figure 2) made according to the via conductor formation method of this multilayer ceramic board
, a multilayer ceramic substrate made according to the conventional example without adding the inorganic substance 7 (Fig. 4), and a multilayer ceramic substrate made according to the conventional example without adding the inorganic substance 7, and HI
The tensile strength of the via conductor 52 and a vibration test were conducted on a multilayer ceramic substrate (FIG. 6) made according to the method for forming via conductors in a multilayer ceramic substrate that was subjected to P treatment. The results are shown in Table 1.

[0019]

[Table 1] Note 1: The breaking force was measured by pulling both the upper and lower ends of the via conductor. Note 2: The percentage of via conductors that did not break (survival rate) among all via conductors was determined by applying ultrasonic vibration to the via conductors.

[0020]

As described above, according to the present invention, via holes are filled with metal powder mixed with an inorganic substance, and after sintering, HI
Since the P treatment is performed, the metal particles constituting the via conductor are prevented from becoming gigantic after the HIP treatment, the contact area between the metal particles is increased, and conductivity is improved.
Fine metal particles interact with each other through inorganic substances,
In addition, since the via conductors are sintered in a densely intertwined manner, the mechanical strength of the via conductor is also increased. As a result, the reliability of the via conductor is significantly improved.

[Brief explanation of drawings]

FIG. 1 is a flow diagram of one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a via conductor made in accordance with one embodiment of the present invention.

FIG. 3 is a flow diagram of a conventional via conductor forming method.

FIG. 4 is a cross-sectional view of a via conductor made by a conventional via conductor forming method.

FIG. 5 is a flow diagram of another conventional method for forming via conductors.

FIG. 6 is a cross-sectional view of a via conductor made according to another conventional example.

[Explanation of symbols]

1 Green sheet, 2 Beer hall 3 Metal powder 4 Land 51 Ceramic plate 52 Via conductor

Claims (2)

[Claims] Claim 1: A via hole (2) is made in a green sheet (1), and a metal powder (3) is formed in the via hole (2).
), and after forming a land (4) for via connection on one or both sides of the green sheet (1), the green sheets (1) are stacked and fired to form the green sheet (1) into a single piece. While sintering into the ceramic plate (51), the metal powder (3) inside the via hole (2)
In the method for manufacturing a multilayer ceramic substrate in which the metal powder (3) is sintered into an integrated via conductor (52), 1
A method for forming via conductors in a multilayer ceramic substrate, characterized by mixing ~10% by volume of an inorganic substance (7) and subjecting the sintered ceramic plate (51) to isodirectional pressure treatment. 2. The method for forming via conductors in a multilayer ceramic substrate according to claim 1, wherein the inorganic material (7) has a particle size smaller than that of the metal powder (3).