JPH08213498A - Package made of ceramic - Google Patents

Abstract

PURPOSE: To reduce stress acting by a temperature change on the inner circumferential part of a solder layer sharply than before, and to prevent a fatigue failure of the solder layer caused by the repetition of temperature changes. CONSTITUTION: Concerning a ceramic package composed of a ceramic package base substance 32 having a cavity 23 for putting a semiconductor device in, a ceramic lid 31 for sealing the cavity 23, a solder layer 36 for sealing between the package base substance and the lid airtightly, and a radiating metal board 22 joined to the external surface of the bottom part of the cavity 23 of the package base substance with brazing material, the solder layer is formed between the package-base-substance side metallized layer 40 and a lid 13 side metallized layer 35, and a seal path width W is 1.6mm or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic package, and more particularly to a ceramic package provided with a ceramic lid (lid) for sealing a heat sink and a semiconductor element mounting portion.

[0002]

2. Description of the Related Art A semiconductor element such as an integrated circuit is housed in a semiconductor element mounting portion provided on a package base, and the semiconductor element mounting portion is hermetically sealed with a lid for practical use. Since ceramics such as alumina are excellent in heat resistance, durability, reliability, etc., they are suitable as materials for the package base and lid, and IC packages made of ceramics are now actively used.

In this ceramic package, when a ceramic package base is sealed with a ceramic lid, solder is used as a sealing material. However, since it is difficult to directly bond the solder and the ceramic, a base metal layer is usually formed on the package base and the sealing portion of the lid. Therefore, the package base and the lid are joined by solder via the underlying metal layer.

The underlying metal layer formed on the package substrate is usually W, M that can be co-fired with the package substrate.
It is composed of a refractory metallization layer made of o or the like, and a Ni plating layer and an Au plating layer formed thereon. With this configuration, the bondability with solder at the time of sealing and the long-term stability as a package are ensured. On the other hand, for forming the underlying metal layer of the lid, Ag-Pt,
Metals such as Ag-Pd are often used.

Next, the structure of a general semiconductor package and a method of manufacturing a semiconductor device using the same will be specifically described.

FIG. 8 is a partial sectional perspective view schematically showing a ceramic lid with the bottom side up.
(A) And (b) is sectional drawing which showed typically the process of manufacturing the semiconductor device using a ceramic package.

As shown in FIG. 8, the lid 31 serves as a ceramic substrate 13, a metallized layer 35 formed on the peripheral portion (the outer peripheral portion and the side surface of the upper surface in the figure), and a sealing member covering the metallized layer 35. Of the solder layer 36. The solder layer 36 is usually formed by using solder containing Pb as a main component and Bi, Sn, In, Ag, etc. added to the main component.

On the other hand, a cavity portion 23 is formed in the center of the package base 32, a metallization layer 40 used for sealing with the lid 31 is formed around the cavity portion 23, and the metallization layer 40 is not shown around the metallization layer 40. External connection pins 21 for connecting to the motherboard are set up. Further, the cavity portion 23 is usually formed in a stepped shape in its peripheral portion, the pad 19 for wire bonding is formed in the middle stepped portion, and the bottom portion is L-shaped.
A semiconductor element mounting portion 17 on which SI or the like is mounted is formed. Further, a metal heat dissipation plate 22 for dissipating the heat radiated from the semiconductor element 18 is disposed on the surface opposite to the surface on which the external connection pin 21 is erected. In addition,
Usually, a metal layer (not shown) for grounding is also formed on the semiconductor element mounting portion 17.

A method of manufacturing a semiconductor device using the package base 32 and the lid 31 is as follows.

First, after bonding the semiconductor element 18 to the semiconductor element mounting portion 17 of the package base 32, the pad portion (not shown) on the semiconductor element 18 side and the pad 19 are connected by the wire bonding method (see FIG. a)).

Next, the solder layer 36 of the lid 31 is placed on the lower side and is overlaid on the metallized layer 40 formed on the upper surface of the package base 32, and the lid 31 and the package base 32 are separated by a fixing jig such as a spring or a clip. Temporarily fix. In this state, the package substrate 32 and the like are loaded into the heating furnace, the solder layer 36 formed on the lid 31 is melted to bond the lid 31 and the package substrate 32, and then the semiconductor element 18 is packaged by cooling. The base 32 is hermetically sealed (FIG. 9B).

[0012]

As described above, the package base 32 and the lid 31 are bonded to each other via the solder layer 36. However, when the semiconductor device is exposed to a high temperature or low temperature environment, the package base 32 is exposed. The package base 32 and the lid 31 are warped due to the difference in thermal expansion coefficient between the lid 31 and the lid 31.

In particular, when the metal heat dissipation plate 22 is disposed on the outer surface of the ceramic package base 32, the thermal expansion coefficient of the metal heat dissipation plate 22 is larger than that of the package base 32. A large warp is likely to occur in the package base 32. For this reason, even if the package base 32 and the lid 31 are made of materials having the same expansion coefficient, a difference occurs in warpage between them.

A conventional semiconductor device provided with a heat sink is not configured to withstand warpage or the like caused by a large temperature change. That is, although a strain or a stress resulting from the strain is generated between the respective members constituting the semiconductor device due to the thermal expansion due to the temperature change, the solder layer 36 connecting the package base 32 and the lid 31 is sufficient. In the case where the solder layer 36 does not have strength, there is a problem in that the plastic deformation is locally caused by the stress caused by the strain, and the fatigue fracture occurs from the inner peripheral side of the solder layer 36 as a starting point.

[0015]

In view of the above problems, the present inventor has made a ceramic package (hereinafter referred to as a semiconductor device, such as a semiconductor element and a wire bonding of a semiconductor device) capable of avoiding the destruction of the solder layer due to thermal stress. As a result of an examination for the purpose of designing a part excluding the wiring part), the seal path width W (the definition of the seal path width will be described later) of the solder layer connecting the package base and the lid is sufficient. When it is extremely wide, the tensile stress caused by the temperature change becomes small, so that it is difficult for the solder layer to locally undergo plastic deformation and fatigue fracture does not occur, and the present invention has been completed.

The ceramic package according to the present invention is
A ceramic package base having a cavity for housing a semiconductor device; a ceramic lid for sealing the cavity; a solder layer for hermetically sealing the package base and the lid; In a ceramic package composed of a metal radiator plate joined to the outer surface of the package base opposite to the cavity by a brazing material, the solder layer is a metallization layer on the package base and a metallization on the lid. Solder formed between layers and between the outer peripheral portion of the lid and either the inner peripheral portion of the metallized layer of the package base or the inner peripheral portion of the metallized layer of the lid, which is closer to the outer peripheral portion of the lid. Layer width (hereinafter referred to as seal path width) W is 1.6 m
It is characterized by being m or more (1).

The ceramic package according to the present invention is the ceramic package according to the above (1), in which the package base and the lid are mainly composed of alumina, and the solder layer is Sn-Ag-In-Bi-Pb. It is characterized by containing five components (2).

[0018]

FIG. 1A is an enlarged cross-sectional view schematically showing the main part of a conventional ceramic package in which no warpage has occurred, and FIG. 1B shows the warpage caused by a change in temperature. It is an expanded sectional view which showed typically the important part of a ceramic package, and (c) is an expanded sectional view which showed typically the important part of the ceramic package concerning the present invention which warped by temperature change. . Further, in FIG. 1A, the width indicated by W is the seal path width, and
In (c), the display is omitted.

As shown in FIG. 1 (a), warping hardly occurs at normal room temperature, and almost no stress (tensile stress) acts on the inner peripheral portion of the solder layer 36, but the ceramic package has When the temperature rises, since the thermal expansion coefficient of the heat dissipation plate 22 is larger than that of the substrate such as alumina forming the package base 32, the package base 32 is warped such that the lid 31 side becomes a recess. For that purpose,
As shown in (b), a bending moment D is generated in the package base 32 and the lid 31. When such warpage occurs in the package base 32, stress B (tensile stress) acts on the inner peripheral portion of the solder layer 36. Further, when the temperature of the package base 32 decreases, the package base 32 returns to a warp-free state. In this way, when the temperature rise and the temperature decrease are repeated, the stress B repeatedly acts on the solder layer 36, so that fatigue breakdown occurs in the solder layer 36.

On the other hand, as shown in FIG. 1 (c), the ceramic package according to the present invention has the seal path width W wider (1.6 mm or more) than in the usual case.
Even if a bending moment D having a similar magnitude is generated between the lid 11 and the package base 12, the tensile stress acting on the inner peripheral surface of the solder layer 16 with the end surface of the lid 11 as a fulcrum is reduced by the principle of leverage. . That is, the stress C becomes small, and fatigue failure does not occur in the solder layer 16.

According to the ceramic package of the present invention, in the ceramic package according to the above (1), the package base and the lid are composed mainly of alumina, and the solder layer is Sn-Ag-In-Bi-. P
Since the solder layer is composed of the five components b, the solder layer has excellent thermal shock resistance, and fatigue failure does not occur in the solder layer.

[0022]

EXAMPLES AND COMPARATIVE EXAMPLES First, using a conventional ceramic package having a shape similar to that shown in FIG. 9, the finite element method was used to determine which part of the solder layer and how much stress was applied. It was obtained by the simulation.

The package base 32 is made of alumina, the side length is 44 mm × 44 mm, the alumina layer at the bottom of the cavity 23 has a thickness of 1.32 mm, and the outer peripheral thickness has a thickness of 2.80 mm. The outer dimensions of the cavity 23 were set to 20 mm × 20 mm. Further, the metallized layer 35 made of W formed on the surface of the package base 32 has a thickness of 10 μm and a seal path width W of 1.27.
It was set to mm. The metal heat dissipation plate 22 disposed on the package base 32 is a W (tungsten) porous sintered body impregnated with Cu and has an outer shape of 30 mm.
The thickness was set to 30 mm and the thickness was set to 1.0 mm.

The lid 31 is made of alumina, and the length of the side portion is 25 mm × 25 mm and the thickness is 0.76 m.
m, the material of the metallized layer 35 was Ag-Pt alloy, the thickness was set to 15 μm, and the width was set to 1.78 mm.

Further, the lid 31 and the package base 32
Solder layer 36 for bonding with Sn is 4.1 wt%, A
g: 1.0 wt%, In: 1.1 wt%, Bi: 8.2
The composition was composed of wt% and the balance Pb.

FIG. 2 shows a portion where a stress acting on the inner peripheral surface of the solder layer of the ceramic package is simulated. FIG. 3 is a graph showing the result of the simulation of the stress, in which the ordinate represents the stress and the abscissa represents the position in the ceramic package. Also,
In FIG. 3, σ _Z is a stress acting in the direction perpendicular to the main surface of the package base 12 (hereinafter, referred to as vertical stress), σ _X is the X-direction component of the main stress, and σ _l is the main stress. Shows.

As is clear from the graph shown in FIG.
The stress in the vertical direction and the principal stress are greatest in the portion (c) that is closer to the side portion by about 1/4 from the corner. The cause of fatigue failure is mainly the stress σ _Z in the vertical direction,
In the following, a simulation was performed for the stress σ _{Z in the} vertical direction at the position c where the stress σ _z has the maximum value.

That is, various conditions for the ceramic package were changed in the following order, and the stress σ _Z in the vertical direction at that time was obtained by simulation. Note that the simulation is performed as it is under the constant conditions for the portions other than the changed portion.

The thickness of the alumina layer at the bottom of the cavity is changed. Change the thickness of the heat sink. Change the size of the heat sink. Change the seal pass width. 4 shows the relationship between the thickness of the alumina layer at the bottom of the cavity and the stress σ _{Z in the} vertical direction when the thickness of the alumina layer at the bottom of the cavity was changed, and FIG. Figure 6 shows the relationship between the thickness of the heat sink and the vertical stress σ _Z.
Is the relationship between the size of the heat sink and the vertical stress σ _Z when the size of the heat sink is changed, and FIG. 7 is the relationship between the seal path width and the vertical stress σ _Z when the seal path width is changed. It is the graph which showed each.

As is apparent from the graphs shown in FIGS. 4 to 6, the solder layer 36 may be changed depending on the thickness of the alumina layer at the bottom of the cavity, the thickness of the heat sink, and the size of the heat sink. The value of the acting vertical stress σ _Z hardly changes. However, as shown in FIG. 7, the seal pass width W
The stress σ _{Z in the} vertical direction acting on the inner peripheral surface of the solder layer 36 is greatly reduced as is increased. In this way, by increasing the seal path width W, the solder layer 36
It is possible to greatly reduce the stress σ _Z in the vertical direction acting on the inner peripheral surface of the solder layer 36, and to prevent the fatigue fracture of the solder layer 36 due to the temperature change of the ceramic package.

In order to prevent the fatigue fracture of the solder layer 36, it is necessary that the stress σ _{Z in the} vertical direction is about 2.5 kgf / mm ² or less. From FIG. 7, the seal path width W at this time is It is about 1.6 mm. Therefore, with respect to the ceramic package of the present invention having the seal path width W of 1.6 mm or more shown in FIG. 1C, fatigue failure of the solder layer 16 due to temperature change of the ceramic package can be prevented.

[0032]

As described above in detail, in the ceramic package according to the present invention, a ceramic package base having a cavity for accommodating a semiconductor device,
A ceramic lid that seals the cavity, a solder layer that hermetically seals the package base and the lid, and a brazing material to the outer surface of the package base opposite to the cavity. In a ceramic package composed of a metal heat dissipation plate, the solder layer is formed between the package base metallization layer and the lid metallization layer, and the seal path width W is 1.6 mm or more. Therefore, by utilizing the lever principle, the stress acting on the inner peripheral portion of the solder layer of the package due to the temperature change can be greatly reduced as compared with the conventional case, and the fatigue breakdown of the solder layer due to the repeated temperature change can be prevented. .

The ceramic package according to the present invention is the ceramic package according to the above (1), in which the package base and the lid are mainly composed of alumina, and the solder layer is Sn-Ag-In-Bi-Pb. Since it is composed of five components, the stress acting on the inner peripheral portion of the solder layer of the package due to the temperature change can be further reduced than ever before, and the fatigue breakdown of the solder layer due to repeated temperature changes can be prevented. be able to.

[Brief description of drawings]

FIG. 1A is an enlarged cross-sectional view schematically showing a main part of a conventional ceramic package in which warpage has not occurred, and FIG. 1B is the ceramic in which warpage has occurred due to temperature change. It is an expanded sectional view which showed typically the principal part of a manufactured package, and (c) is an expanded sectional view which showed typically the important part of the ceramic package which generate | occur | produced the curvature by the temperature change.

FIG. 2 is a plan view showing a portion where a stress acting on a ceramic package is simulated.

FIG. 3 is a graph showing stress measurement results.

FIG. 4 is a graph showing the relationship between the thickness of the alumina layer and the vertical stress σ _Z when the thickness of the alumina layer at the bottom of the cavity is changed.

FIG. 5 is a graph showing the relationship between the thickness of the heat sink and the vertical stress σ _Z when the thickness of the heat sink is changed.

FIG. 6 is a graph showing the relationship between the size of the heat dissipation plate and the vertical stress σ _Z when the size of the heat dissipation plate is changed.

FIG. 7 is a graph showing the relationship between the seal path width and the vertical stress σ _Z when the seal path width is changed.

FIG. 8 is a partial cross-sectional perspective view schematically showing a ceramic lid with the bottom side facing up.

9A and 9B are cross-sectional views schematically showing a process of manufacturing a semiconductor device using a ceramic package.

[Explanation of symbols]

 11 Lid 12 Package Base 16 Solder Layer 22 Heat Sink 23 Cavity

Claims (2)

[Claims] 1. A ceramic package base having a cavity for housing a semiconductor device, a ceramic lid for sealing the cavity, and a hermetic seal between the package base and the lid. In a ceramic package composed of a solder layer and a metal heat dissipation plate joined to the outer surface of the package base opposite to the cavity portion with a brazing material, the solder layer includes a metallization layer on the package base side and It is formed between the metallization layers on the lid side, and either the outer peripheral portion of the lid and the inner peripheral portion of the metallized layer of the package base or the inner peripheral portion of the metallized layer of the lid, which is closer to the outer peripheral portion of the lid. The width W of the solder layer between and is 1.6 mm or more, a ceramic package. 2. The package base and the lid are composed mainly of alumina, and the solder layer is Sn-Ag-In-B.
The ceramic package according to claim 1, which is configured to include five components of i-Pb.