JPH09107043A - Alumina ceramic lid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the folding strength of an alumina ceramic lid which seals the cavity of a ceramic package. SOLUTION: An alumina ceramic lid 14 is bonded with solder 15 to the top face of a ceramic package 11 to seal its cavity 12. Primary grain of alumina, the raw material of the lid 14, is pulverized into a fine grain of 1-2 microns in a mean grain size and press-formed (after decay) to increase the contact points of the primary grain, thereby improving the sintering property. It is more treated to provide a sharp grain size distribution having D10-D90 (accumulated 10% and 90% grain sizes from the fine grain side) within ±70% of the mean grain size. Owing to this, the primary grain is roughly charged in the granular material before press-forming, thereby increasing the porosity to lower the granular material strength and improve the decay property (collapsing property) of the material. Thus, a compact and high-strength alumina sintered compact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumina ceramic lid (lid) for sealing a cavity of a ceramic package.

[0002]

2. Description of the Related Art In recent years, for example, PGA (Pin Grid Array)
The LSI chip is mounted in the cavity of the mold ceramic package, and the lid made of alumina ceramic is soldered over the cavity to hermetically seal the cavity, thereby protecting the LSI chip in the cavity from moisture and the like. There is something. In this case, if the thermal expansion coefficient of the ceramic package is different from that of the lid, thermal stress is applied to the solder seal parts of both and cracks or peeling occur at the solder seal parts, and the airtightness is impaired. It is preferable to be formed of a ceramic of such a material.

[0003]

The above ceramic package is subjected to a He leak pressurization test in order to check the airtight state of the cavity in the product inspection process after lid soldering. For example, in a high pressure He atmosphere of 7 kgf / cm ^2. The package is pressurized inside and the solder seal part of the lid is inspected for leaks. Nowadays,
The size of the mounted LSI chip tends to increase, and the cavities and lids tend to increase accordingly. If the lid becomes large, the pressure (= 7 kgf / cm ² × lid area) applied to the lid during the He leak pressurization test becomes large, and the lid may crack due to the pressure. Therefore, it is necessary to increase the strength of the lid (particularly the bending strength).

This lid is formed by granulating primary particles of alumina, which is a ceramic material, filling the resulting granules in a mold, press-molding them, and firing them. Generally, in order to improve the strength of the alumina ceramic, it is considered that the primary particles of alumina are made fine and the contact points of the primary particles of press molding (after collapse) are increased to improve the sinterability.

However, if the primary particles having a wide particle size distribution of alumina as in the prior art are simply miniaturized, the result shown in FIG.
As shown in, the primary particles in the granules are in a densely packed state in which fine particles are filled in the gaps between particles having a large particle size, and the fluidity of the primary particles during press molding is reduced, and The disintegration property (crushability) is deteriorated, and a dense and high-strength alumina sintered body cannot be manufactured. this is,
This is because the granule strength σ obtained by the following equation (Rump equation) increases as the primary particle size d decreases. σ = a · (1 / ε−1) · η / d (1) where a is a coefficient, ε is a porosity (ε <1), η is a surface tension, and d is a primary particle size.

Although the bending strength can be increased to some extent by increasing the thickness of the lid, making the lid thicker not only violates the demand for thinner package, but also leads to higher cost. There are drawbacks.

The present invention has been made in consideration of such circumstances, and therefore an object thereof is to increase the bending strength without increasing the thickness of the lid, and to improve the strength of the LSI chip or cavity to be mounted. It is an object of the present invention to provide an alumina ceramic lid that can meet the demand for larger size (that is, larger lid).

[0008]

In order to achieve the above object, in the alumina ceramic lid of the present invention, primary particles of alumina, which is a ceramic material, have an average particle diameter of 1 μm to 2 μm.
The particle size distribution is reduced to D10-D9.
Granules of ceramic powder prepared so that the range of 0 (where D10 and D90 are respectively 10% cumulative and 90% cumulative particle size from the fine particle side of the cumulative particle size distribution) is within ± 70% of the average particle size ( It is obtained by press-molding (granulation of primary particles) and firing it.

That is, the average particle diameter of primary particles of alumina is 1
In addition to improving the sinterability by increasing the contact points of the primary particles of press molding (after disintegration) by miniaturizing to μm to 2 μm,
By setting the sharp particle size distribution such that the range of D10 to D90 is within ± 70% of the average particle size, the filling state of the primary particles in the granules before press molding is set to the rough filling as shown in FIG. 3 (b). , Increase the porosity ε. Due to the increase of the porosity ε and the refinement of the primary particle size d, the granule strength σ obtained by the above formula (1) becomes smaller than before, and the fluidity of the primary particles during press molding is improved, and the disintegration of the granules is improved. (Crushability) is improved, and it becomes possible to make a dense and high-strength alumina sintered body.

Thus, by sharpening the particle size distribution with an average particle size of 1 μm to 2 μm, the size of the lid can be increased to, for example, 54 mm × 34 mm (thickness of about 1 mm) without increasing the thickness of the lid. It is possible to prevent the lid from cracking due to the high pressure He during the He leak pressurization test.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described with reference to PGA (Pin Grid).
An embodiment applied to an array type alumina ceramic package will be described with reference to the drawings. First, the structure of the alumina ceramic package 11 will be described with reference to FIG. The alumina ceramic package 11 is formed by laminating a plurality of alumina green sheets by a green sheet laminating method and firing the laminated sheets. An LSI chip (not shown) is provided on the upper surface side of the alumina ceramic package 11.
Is formed, and a large number of external lead pins 13 are vertically joined with a silver brazing material on the upper surface side or the back surface side. Although not shown, the joint portion of each external lead pin 13 is electrically connected to the lead-out terminal formed around the cavity 12 through the through-hole conductor and the inner-layer wiring conductor. These through-hole conductors and inner layer wiring conductors are formed by printing with a high melting point metal such as W or Mo, and are simultaneously fired with the alumina ceramic package 11.

A lid 14 made of an alumina ceramic manufactured by a process described later is attached to the upper surface of the alumina ceramic package 11 to hermetically seal the cavity 12. The dimensions of the lid 14 are, for example, a thickness of 1 mm, a width of 54 mm and a length of 34 mm. The joining of the lid 14 is performed by the solder 15. For this reason, a metal layer 16 for solder joining is formed so as to surround the cavity 12 on the lower surface outer peripheral portion and the seal portion of the side end surface of the lid 14, and correspondingly, A metal layer 17 for solder bonding is also formed on the upper surface of the alumina ceramic package 11 so as to surround the cavity 12, and both metal layers 16 and 1 are formed.
7 are airtightly joined with solder 15. The metal layer 16 on the lid 14 side is made of Ag / Pd, Ag after firing the ceramic.
/ Pt, Cu, Ag, Au or other metal paste is printed and fired, while the metal layer 17 on the side of the alumina ceramic package 11 is made by printing a high melting point metal paste such as W or Mo before firing the ceramic. Simultaneous firing with Ni
Plating, Au plating, etc. are applied.

Next, the manufacturing process of the lid 14 will be described with reference to FIG. First, 90% of an alumina raw material and 10% of a flux / colorant are mixed with a binder and a plasticizer, and the primary particles of alumina are pulverized to have an average particle size of 1 μm to 2 μm. At this time, by using an alumina powder having a uniform particle size that has been classified in advance as the alumina raw material, D10
Grind so that the range of D90 is within ± 70% of the average particle diameter to produce an alumina powder having a sharp particle size distribution.
Here, D10 and D90 are the particle sizes of 10% cumulative and 90% cumulative from the fine particle side of the cumulative particle size distribution, respectively, and D50
(Cumulative 50%) is the average particle size. As shown in FIG.
When D50 = 1 μm, -70% is D10 = 0.3.
In the case of μm and + 70%, D90 = 1.7 μm. Also, D
In the case of 50 = 2 μm, -70% is D10 = 0.6 μ
m and + 70% are 3.4 μm.

After crushing, the slurry raw material was spray dried (disk rotation speed 9000 rpm, drying temperature 18
Spray drying is performed at 0 ° C.), and primary particles of alumina are granulated so as to be spherical granules of about 90 μm, for example. Then, the granules are filled in a mold and, for example, 1.8 t / cm.
Press molding is performed with a pressing force of ² , and the lid 14 is manufactured by firing it at 1400 ° C. Furthermore, a metal paste such as Ag / Pt is printed on the lower surface seal portion of the lid 14
The metal layer 16 for solder bonding is formed by baking at 50 ° C.
Next, a solder paste is applied on the metal layer 16 by a screen printing method or the like and reflowed at 300 ° C.

Next, the influence of the average particle size and particle size distribution of the primary particles of alumina on the bending strength of the lid 14 will be considered. Table 1 below shows that the average particle size and the particle size distribution are different.
The bending strength of each of the samples A, B, and C was measured.

[0016]

[Table 1]

In Table 1 above, sample A has an average primary particle diameter of alumina of 3.25 μm and a particle size distribution (range of D10 to D90) of 0.5 μm to 6.0 μm. In this sample A, the average bending strength is 30k
Although it is gf / mm ² , the minimum value is 26 kgf / mm ² . According to the test results of the present inventor, unless the bending strength of the lid is 30 kgf / mm ² or more, H of 7 kgf / cm ² is performed to confirm the airtight state after the soldering of the lid.
e It has been found in the leak pressure test that cracks occur in the lid. Therefore, with the minimum bending strength of less than 30 kgf / mm ² , such as sample A, the lid cracks in the He leak pressure test.

Sample B had an average primary alumina particle size of 1.75 μm and a particle size distribution (D10 to D9).
0 range) is 0.5 μm to 3.0 μm. In this sample B, the average value of the bending strength is 33 kgf / mm ² , and the minimum value is 30 kgf / mm ² . Therefore, the sample B has a higher bending strength than the sample A and can prevent the lid from cracking in the He leak pressure test.

Sample C has an average primary alumina particle size of 1.75 μm and a particle size distribution (D10 to D9).
0 range) is 1.0 μm to 2.5 μm. In this sample C, the average value of the bending strength is 35 kgf / mm ² , and the minimum value is 32 kgf / mm ² . Therefore, the sample C has a higher bending strength than the sample B, and the occurrence of cracks in the lid in the He leak pressurization test can be more reliably prevented.

Generally, the bending strength of the lid 14 is 30 kg.
In order to increase f / mm ² or more, the primary particles of alumina are refined to have an average particle size of 1 μm to 2 μm, and the particle size distribution is D70 to ± 70 of the average particle size (particle size of D50). It may be adjusted so that it is within%.

That is, the average particle diameter of alumina primary particles is 1
When the size is reduced to μm to 2 μm, the contact points of the primary particles of press molding (after collapse) are increased, and the sinterability is improved. On the other hand, when the average particle size of the primary particles is larger than 2 μm, the contact points of the primary particles for press molding are reduced and the sinterability is lowered, while when the average particle size is smaller than 1 μm, the primary particles are excessively large. It is easy to form various agglomerated particles, the disintegration property (crushability) of the granules during press molding is reduced, and the sintered density of alumina is reduced.

Further, when a sharp particle size distribution is set such that the range of D10 to D90 is within ± 70% of the average particle size (particle size of D50), as shown in FIG. The filling state of the primary particles becomes coarse filling, and the porosity ε
Can be increased. Due to the increase of the porosity ε and the refinement of the primary particle size d, the granule strength σ obtained by the above formula (1) becomes smaller than before, and the fluidity of the primary particles during press molding is improved, and the disintegration of the granules is improved. (Crushability)
It is possible to make a dense and high-strength alumina sintered body.

As a result, the bending strength of the lid 14 is 30 kgf / mm ² without increasing the thickness of the lid 14.
The lid 14 can be raised to 54 m or more, for example.
Even if the size is increased to about mx 34 mm (thickness about 1 mm), H
e It is possible to prevent the lid 14 from cracking due to the high pressure He during the leak pressure test, and to mount the LSI.
It is possible to increase the size of the chip or the cavity 12 and the size of the lid 14. Moreover, since it is not necessary to increase the thickness of the lid 14, it is possible to satisfy the demand for thinning of the package and it is advantageous in terms of cost.

In the above embodiment, the present invention is applied to a PGA type package, but the QFP (Quad Flat Pa
ckage) type package, etc., and may be applied to other ceramic packages that require a lid. Also, D10-D
Alumina powder with a sharp particle size distribution in which the range of 90 is within ± 70% of the average particle size (1 μm to 2 μm) is obtained by previously pulverizing and classifying the average particle size to 1 μm to 2 μm and making it into a slurry. You may make it granulate.

Further, in the above embodiment, the ceramic package is made of alumina ceramic, but the present invention is not limited to this, and it may be made of other ceramic materials such as AlN, mullite and glass ceramics. In addition, according to the present invention, the size of the lid 14 may be appropriately changed according to the size of the cavity 12 in which the LSI chip is mounted.
It goes without saying that various modifications can be implemented.

[0026]

As is apparent from the above description, according to the present invention, the primary particles that are the raw material of the alumina ceramic lid are refined to have an average particle size of 1 μm to 2 μm, and the particle size distribution is D10 to D90. Since the lid was fired using the ceramic powder prepared so that the range was within ± 70% of the average particle size, it was possible to increase the bending strength of the lid without increasing the thickness of the lid. It can withstand a leak pressurization test, and can meet the demand for a larger LSI chip or cavity to be mounted (that is, a larger lid).

[Brief description of the drawings]

1A and 1B show an embodiment of the present invention, in which FIG. 1A is a vertical sectional view of an alumina ceramic package, and FIG.

FIG. 2 is a process diagram showing a lid manufacturing process.

3A is an enlarged view showing a state of granules having a wide particle size distribution, and FIG. 3B is an enlarged view showing a state of granules having a sharp particle size distribution.

FIG. 4 is a diagram showing a particle size distribution of alumina.

[Explanation of symbols]

11 ... Alumina ceramic package, 12 ... Cavity, 13 ... External lead pin, 14 ... Lid, 15 ... Solder, 16, 17 ... Solder joining metal layer.

Claims (1)

[Claims] 1. A lid made of alumina ceramic for hermetically sealing a cavity of a ceramic package, wherein primary particles of alumina, which is a ceramic material of the lid, are finely divided into particles having an average particle diameter of 1 μm to 2 μm and a particle size distribution thereof. A ceramic powder prepared so that the range of D10 to D90 (where D10 and D90 are respectively 10% cumulative and 90% cumulative particle size from the fine particle side of the cumulative particle size distribution) is within ± 70% of the average particle size. Alumina ceramic lid made by press-molding the granules of and firing.