JP3183090B2 - Ceramic lid for package - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic lid for a package, and more particularly, to a ceramic lid for a package having improved conductivity and thermal conductivity in response to a high-speed operation of an IC to be mounted.

[0002]

2. Description of the Related Art In recent years, with the increase in speed of electronic devices and the frequency of communication devices, the frequency of signals used in electronic components has been increasing year by year. Therefore, ceramic circuit boards and ICs used in communication equipment and large computers
There is also a demand for a package or the like that is compatible with this high frequency.

In addition, in response to such a high frequency, there is a need for a method of connecting an IC to a package that can effectively reduce the generation of noise.

Generally, a wire bonding method is often used to connect an IC (chip) to a package. The wire bonding method is a method of connecting a bonding pad on a chip and a terminal of an external lead wire with a thin wire having a diameter of 20 to 30 μm. The method includes cleaning a clean surface of both metals at a temperature equal to or lower than the melting point of the metal. The thermocompression bonding method, in which the metal is bonded by diffusion without contacting and melting the metal, and the ultrasonic vibration is transmitted to the connecting Al wire,
There is an ultrasonic bonding method in which an oxide film on an Al surface is removed by friction between a pad and an Al line and both are joined.

However, in the wire bonding method, there is a problem that the reactance of the wire is increased as the frequency is increased, and noise is easily generated. Therefore, instead of the wire bonding method, an IC and a package are connected by a flip chip method without using a wire. In the flip chip method, Pb is formed on the Al pad of the chip via a metal thin film of Cr and Cu.
-Solder bumps such as Sn are formed by plating or vapor deposition, and the bumps are aligned with the metal electrode pads provided on the package, and the solder is reflowed by passing through a heat treatment furnace for bonding. I do.

FIG. 1 is a schematic exploded perspective view showing a conventional package. In the figure, reference numeral 13 denotes a conductor (metallization), and reference numeral 12 denotes a laminated integrated ceramic. The package 10 is made of, for example, alumina, and uses the metallization 13 and the laminated monolithic ceramics 12 described above.
4 is attached with a silver brazing material, and the lid 11 is further laminated by using a low-temperature brazing material.
2 and hermetically sealed.

[0007]

When an IC is mounted in the package 10 constructed as described above, according to the wire bonding method, the ground is taken through a die attach portion (not shown) fixing the IC. However, when the flip-chip method is employed, since a solder bump is formed on the die attach portion, it is necessary to take the ground through the lid 11. Further, it is difficult to sufficiently release the heat of the IC chip to the outside via the solder bumps, and it is necessary to improve the thermal conductivity of the lid itself to improve the heat radiation characteristics. When the lid 11 is made of an Fe alloy such as Kovar which is generally used as an electronic material, it can be grounded, but there is a problem that the thermal conductivity is low (for example, about 20 W / m · K). .

On the other hand, in general, alumina may be used as the lid material of an alumina IC package, but the same material as the package material may be used. In this case, since the lid itself becomes an insulator, the ground is passed through the lid. It is difficult to take, and there is a problem that the thermal conductivity is low.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a ceramic lid for a package having a thermal expansion coefficient close to that of alumina and having excellent electrical conductivity and thermal conductivity.

[0010]

[0011]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
The ceramic lid for a package according to the present invention contains a ceramic base mainly composed of aluminum nitride, containing metal Al or metal Cu at a ratio of 20 to 40% by volume , and
It is characterized by having conductivity ( 1 ).

[0012]

[0013]

[0014]

According to the above configuration package ceramic lid (1), a metallic Al or Cu metal to ceramic substrate mainly composed of aluminum nitride are contained in a proportion of 20 to 40% by volume, conductivity and Both thermal conductivity
You. Also, make the thermal expansion coefficient close to that of alumina
And a highly airtight ceramic lid
Can be formed. The metal is 20
If it is less than the product%, the metal circuit will not be formed stably,
The drag rate cannot be lowered. Also, with ceramics
Sintering becomes difficult, and even if sintering is possible, the pore ratio is high.
The open pores are formed and the airtightness cannot be maintained.
Therefore, it is not suitable for practical use. On the other hand, the metal
If it exceeds, the coefficient of thermal expansion is too large.
The difference between the thermal expansion coefficient of the
It becomes unsuitable for practical use, such as distortion occurring when the temperature rises.

[0015]

Examples and Comparative Examples Hereinafter, examples and comparative examples of the ceramic lid for a package according to the present invention will be described.

First, a method of manufacturing a ceramic lid for a package according to an example , a reference example, and a comparative example will be described.

The silicon carbide and the metal Cu are accurately weighed so as to have the ratios shown in Table 1, a sintering aid is added thereto and mixed well, and then an organic binder such as polyvinyl alcohol is added and mixed. Then, a green compact is produced and fired at a temperature of about 1700 ° C. to 1800 ° C. in a reducing atmosphere mainly containing nitrogen and hydrogen to produce a ceramic-metal composite. This is processed into a desired size to form a ceramic lid for a package.

Similarly, aluminum nitride and metal A
1 or metal Cu is accurately weighed so as to have the ratio shown in Table 1, and a ceramic lid for a package is formed by the same method as described above.

In this embodiment, the powder molding method is used as described above. However, the present invention is not limited to this, and in another embodiment, the powder molding method is used by the doctor blade method. May be performed.

In order to examine the resistivity (μΩ · cm) of the ceramic lid for a package formed as described above, in the present embodiment , reference example and comparative example, the DC resistance value of each sample was measured by a four-terminal method. The resistivity was calculated from the sample shape as (resistivity = resistance × sample cross-sectional area / sample length). The thermal conductivity (W / m · K) in Table 1 is a value at room temperature measured by a laser flash method, and the coefficient of thermal expansion (10 ⁻⁶ / ° C.) is the average heat from room temperature to 400 ° C. The expansion coefficient is shown. The He leak indicates the hermeticity of the ceramic lid, and Table 1 shows the result of an investigation using a He leak tester for the presence or absence of the He leak.

[0021] Ten samples for measurement were produced for each example , reference example and comparative example, and each characteristic was measured for those samples, and the average value was calculated. Table 1 shows the results.

[0022]

[Table 1]

As is clear from Table 1, in the ceramic lids for packages according to Reference Examples 1 to 3, metal ceramics containing silicon carbide as a main component and metal Cu of 20 to 40 were used.
% By volume, and the resistivity (μΩ · cm) was a very small value of 18 to 80 μΩ · cm, and the conductivity could be improved. The coefficient of thermal expansion is 5 to 8
× 10 ⁻⁶ / ° C., and the thermal expansion coefficient of alumina is 7 × 10 ⁻⁶
/ ° C. Furthermore, no leakage of He was confirmed, and a highly airtight ceramics lid could be formed.

On the other hand, in the ceramic lids for packages according to Comparative Examples 1 to 3, the metal base material containing silicon carbide at a ratio of less than 20 vol. Became a body. In addition, sintering with ceramics becomes difficult, and even if sintering is possible, the leak rate of He is confirmed, as can be seen, the pore ratio increases, open pores are formed, and airtightness is not maintained.
It became unsuitable for practical use. On the other hand, 40% by volume of the metal
Exceeding the thermal expansion coefficient is 10 × 10 ⁻⁶ / ° C. or more, so that the difference from the thermal expansion coefficient of alumina becomes large, causing problems such as generation of distortion when the temperature rises, which is not suitable for practical use. It became.

In the ceramic lid for a package according to Examples 1 to 6 , the ceramic base material mainly composed of aluminum nitride contains metal Al or metal Cu at a ratio of 20 to 40% by volume, (ΜΩ · cm) is 2
The value was as very small as 0 to 90 μΩ · cm, and the conductivity was able to be improved. The addition of each metal also increased the thermal conductivity. The coefficient of thermal expansion is 6 to
It becomes 10 × 10 ^-6 / ° C, and the thermal expansion coefficient of alumina is 7 × 1
0 ^-6 / ° C could be approached. Further, a small leak of He was confirmed only in Example 4, but other leaks were observed.
No example was confirmed at all , and a ceramic lid having high airtightness could be formed.

On the other hand, in the ceramic lid for packages according to Comparative Examples 4 to 8, the ceramic base mainly composed of aluminum nitride contains metal Al or metal Cu at a ratio of less than 20% by volume, and the metal circuit is It was not formed and became an insulator. In addition, sintering with ceramics becomes difficult, and even if sintering is possible, as can be seen from the fact that He leakage was confirmed, the pore ratio was increased, and open pores were formed and airtightness was not maintained. It became unsuitable for practical use.
On the other hand, when the metal content exceeds 40% by volume, the coefficient of thermal expansion is 1
Since the temperature is 0 × 10 ⁻⁶ / ° C. or more, the difference from the coefficient of thermal expansion of the package body made of alumina, for example, becomes large, causing problems such as generation of distortion when the temperature rises, which is not suitable for practical use. .

[0027]

[0028]

As described in detail above, in the ceramic lid for a package according to the present invention, metal Al or metal C is coated on a ceramic base material mainly composed of aluminum nitride.
Since in a proportion of 20 to 40 vol% u, conductive
Properties and thermal conductivity can be increased. In addition, thermal expansion
Tension coefficient close to that of alumina,
Can provide a highly airtight ceramic lid
it can.

[Brief description of the drawings]

FIG. 1 is a schematic exploded perspective view showing a conventional package.

[Explanation of symbols]

 11 lid

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 23/02 H01L 23/06

Claims (1)

(57) [Claims] 1. A ceramic lid for a package, characterized in that a ceramic base mainly composed of aluminum nitride contains metal Al or metal Cu at a ratio of 20 to 40% by volume and has conductivity .