JP2005079133A - Ceramic package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable ceramic package that can be reduced in thickness and size and, in addition, can prevent the occurrence of cracks in a ceramic substrate. <P>SOLUTION: The ceramic package 10 is provided with a cavity 15 formed by brazing the ceramic substrate 11 and a metal frame 12 to each other through an annular metallized film 13. The package 10 has the metallized film 13 having a width narrower than the frame width of the frame 12 and protruded from the surface of the ceramic substrate 11 on the top surface of the substrate 11. The package 10 also has a space 16 which is formed between the inner peripheral-side bottom face of the frame 12 and the top surface of the substrate 11, so that the distances to the inner and outer peripheral-side side faces of the frame 12 may become shorter and longer than the distance from the center line of the cavity 15 to the inner peripheral-side side face of the metallized film 13 when the metallized film 13 and the frame 12 are joined to each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a ceramic package formed by bonding a metal frame to a ceramic substrate, and more specifically, an electronic component such as a semiconductor element or a crystal resonator is mounted in a cavity and a lid is bonded. The present invention relates to a ceramic package for hermetically sealing a cavity portion.

  In recent years, packages for housing electronic components such as semiconductor elements and crystal resonators have been demanded to reduce the size and height of devices equipped with electronic components, such as mobile phones and personal computers, and to improve reliability. Along with this, there is an urgent need to cope with lightness, thinness, and high reliability. In order to cope with this, a package made of a ceramic with high hermetic reliability is used.

  As shown in FIGS. 4A and 4B, a typical conventional ceramic package 50 has a KV (Fe—Ni—Co alloy, trade name “Kovar” on the outer peripheral edge of the upper surface of a ceramic base 51. ”) Or a ceramic made of 42 alloy (Fe—Ni alloy) or the like and a ring-shaped metal frame 52 having a thermal expansion coefficient approximate to each other, for example, a cavity portion for mounting a semiconductor element in the center portion 53 is formed. In order to produce the ceramic substrate 51, first, screen printing is performed on one or a plurality of ceramic green sheets using a conductive paste made of a refractory metal such as W (tungsten) or Mo (molybdenum). , A bonding pattern 54 for bonding the metal frame 52, a wire bond pad 55 for electrical connection with an electronic component, an external connection terminal pad 56 for connection to a board or the like, an external connection with the wire bond pad 55 At the same time that the terminal pads 56 are connected, casters 57 for bonding firmly to a board or the like, and conductor patterns such as wiring patterns for connecting the respective patterns are formed. Next, in the case of a plurality of ceramic green sheets, after laminating and forming a laminated body, the ceramic base 51 is produced by simultaneously firing one or the laminated ceramic green sheets and the refractory metal. . Next, after Ni plating is applied to all conductor patterns exposed on the outer surface of the ceramic substrate 51, a metal frame is formed on the bonding pattern 54 of the ceramic substrate 51 via a brazing material 58 such as Ag—Cu brazing. The body 52 is placed, heated, and brazed. The ceramic package 50 is manufactured by applying Ni plating and Au plating to all the metal surfaces exposed to the outside of the joined body of the ceramic base 51 and the metal frame 52. The ceramic package 50 is usually formed by forming a large number of packages on a large ceramic sheet and finally dividing it into individual pieces.

  As shown in FIG. 5, in this ceramic package 50, a semiconductor element 59, which is an example of an electronic component, is mounted in a cavity 53, and is electrically connected to the outside by a bonding wire 60. A lid 61 made of a metal such as KV or 42 alloy is placed on the metal frame 52, and the rollers of the pair of seam welders 62 are placed in the corners of the outer periphery of the lid 61 in the vertical and horizontal directions. The lid body 61 is welded and joined to the metal frame body 52 by moving to the metal frame 52. Thus, electronic components such as the semiconductor element 59 can be hermetically sealed with the ceramic package 50 and the lid 61.

Conventionally, a ceramic package in a form in which a metal frame is bonded to a ceramic base and an electronic component such as a crystal element or the like mounted in a cavity with a metal lid is hermetically sealed. Many packages have been proposed (see, for example, Patent Document 1, Patent Document 2, Patent Document 3, and Patent Document 4).
JP-A-5-335433 Japanese Patent No. 2889519 JP-A-11-261365 JP 2002-26680 A

However, the conventional ceramic package as described above has the following problems.
(1) When a metal lid is joined to a metal frame of a ceramic package with a seam welder, the heating temperature from the seam welder is about 1200 ° C., and at the time of welding, the metal lid and the metal frame The temperature is locally concentrated on the body, and the metal lid is joined to the metal frame in a state where the lid is greatly expanded. As shown in FIG. 6, the thermal expansion of the metal lid 61 is intensive even if a ceramic base 51 having a thermal expansion coefficient approximate to that of the metal lid 61 is used. In particular, there is a difference from the thermal expansion of the ceramic base 51, so that distortion occurs due to the shrinkage of the metal lid 61 due to cooling after the joining is completed, and a bowl-like deflection is formed on the bottom side of the ceramic base 51. 62 occurs. As a result, tensile stress acts on the bottom surface side of the ceramic substrate, and cracks may occur from the bottom surface side, reducing the reliability of the ceramic package.
(2) To prevent the occurrence of cracks in the ceramic base, the height of the metal frame is increased to absorb the deformation caused by the contraction by the elasticity of the metal frame, or the thickness of the ceramic base is increased due to the contraction. Although it is conceivable to prevent the bending by the rigidity of the ceramic substrate, both of these are contrary to the lighter, thinner and smaller ceramic package.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a highly reliable ceramic package that can cope with light and thin packages and that prevents cracks in a ceramic substrate. .

  The ceramic package according to the present invention that meets the above-mentioned object is a ceramic package comprising a cavity formed by brazing a ceramic base and a ring-shaped metal frame through a metallized film formed on the ceramic base. A ring-shaped metallized film having a width smaller than the width of the metal frame on the upper surface of the ceramic substrate and protruding from the surface of the ceramic substrate; and when the metallized film and the metal frame are joined, Based on the distance from the center line of the metal part to the inner peripheral side surface position of the metallized film, the distance from the center line of the cavity part to the inner peripheral side surface position of the metal frame is shorter than the reference, and from the center line of the cavity part The distance to the outer peripheral side surface position of the metal frame is longer than the reference, and between the inner peripheral bottom surface of the metal frame and the upper surface of the ceramic substrate. , With a space portion.

  Here, the ceramic package has a ring-shaped ceramic frame between the ceramic base and the metal frame, and has a metallized film protruding from the surface on the surface of the ceramic frame, and the metal frame. It is good to have a space part between the inner peripheral side bottom face of a body, and the upper surface of a ceramic frame.

The ceramic package according to claim 1 and claim 2 dependent thereon has a ring-shaped metallized film on the upper surface of the ceramic substrate, the ring-shaped metallized film protruding from the surface and having a width smaller than the frame width of the metal frame. When the metal frame and the metal frame are joined, the distance from the center line of the cavity portion to the inner peripheral side surface position of the metallized film is shorter than the reference and the distance from the inner peripheral side surface position of the metal frame is shorter than the reference. The distance to the outer peripheral side surface position of the frame is longer than the reference, and since there is a space between the inner peripheral bottom surface of the metal frame and the upper surface of the ceramic base, the metal lid is contracted. The strain can be absorbed by the metallized film protruding from the surface of the ceramic substrate and the brazing material, and the metal frame can easily move in the space between the inner peripheral bottom surface of the metal frame and the upper surface of the ceramic substrate. Hardly transmitted to the click made substrate, the occurrence of deflection is able to reduce, it is possible to prevent the occurrence of cracks. Further, since it is not necessary to raise the metal frame or thicken the ceramic substrate in order to prevent cracks, a light, thin and small ceramic package can be provided.
In particular, the ceramic package according to claim 2 has a ring-shaped ceramic frame between the ceramic substrate and the metal frame, and has a metallized film protruding from the surface on the surface of the ceramic frame, Moreover, since the space portion is provided between the inner peripheral side bottom surface of the metal frame body and the upper surface of the ceramic frame body, the height of the cavity portion can be increased.

Subsequently, the best mode for carrying out the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.
1A to 1C are explanatory views of a ceramic package according to an embodiment of the present invention, FIG. 2 is an explanatory view of a modified example of the ceramic package, and FIG. It is explanatory drawing which joined the made lid bodies.

  As shown in FIGS. 1A to 1C, a ceramic package 10 according to an embodiment of the present invention has a ceramic base 11 and a ring-shaped metal frame 12 formed on the upper surface of the ceramic base 11. It is formed by brazing and joining with a brazing material 14 through the metallized film 13 and has a cavity 15 for mounting an electronic component such as a semiconductor element or a crystal resonator at a substantially central portion. .

  Here, examples of the ceramic substrate of the ceramic substrate 11 used for forming the ceramic package 10 include alumina, aluminum nitride, and low-temperature fired ceramic, and the material is not particularly limited. This ceramic substrate 11 is first formed into a sheet-like ceramic green sheet made from any of the above materials. For example, if the ceramic green sheet is fired at a high temperature such as alumina or aluminum nitride, W or The pattern of the metallized film 13 for bonding the metal frame 12 through the brazing material 14 by screen printing using a conductive paste made of a high melting point metal such as Mo, and other desired conductor patterns (FIG. (Not shown). Next, the ceramic green sheet and the dried conductor paste are simultaneously fired in a firing furnace to form a ceramic substrate 11 made of a fired body. Furthermore, for example, in the case of a ceramic substrate 11 made of alumina or aluminum nitride, Ni plating is applied to all the conductor patterns including the metallized film 13 exposed on the outer surface. In the case of using a ceramic green sheet made of alumina for the ceramic base, first, the ceramic green sheet is a powder obtained by adding an appropriate amount of a sintering aid such as magnesia, silica, calcia to aluminum oxide powder, dioctiphthalate, etc. A plasticizer, a binder such as an acrylic resin, and a solvent such as toluene, xylene, and alcohols are added, and the mixture is sufficiently kneaded and defoamed to prepare a slurry having a viscosity of 2000 to 40000 cps. Next, it is formed into a sheet having a desired thickness, for example, 0.12 mm by a doctor blade method, and then dried and cut into a rectangular shape having a desired size.

  On the other hand, the metal frame 12 is formed in a ring shape by punching press, etching, or the like using a metal having a thermal expansion coefficient similar to that of ceramic such as KV or 42 alloy. The metal frame 12 is placed on the metallized film 13 of the ceramic substrate 11 via a brazing material 14 such as Ag-Cu brazing, and is heated and fired in a brazing furnace to perform brazing and joining. Yes. The metallized film 13 formed on the upper surface of the ceramic substrate 11 has a ring shape so that the ring-shaped metal frame 12 can be placed, and the frame width of the ring is larger than the frame width of the ring of the metal frame 12. It is formed so as to protrude from the surface of the ceramic substrate 11 with a small width. In the case where an insulating film made of the same material as that of the ceramic substrate 11 is formed on the surface of the ceramic substrate 11 on the conductor pattern including the formed metallized film 13, a part of the pattern being exposed from the opening. In this case, however, it is necessary that the upper surface of the metallized film 13 exposed from the opening protrudes from the surface of the insulating film.

  In the ceramic package 10, when the metal frame 12 is placed on the metallized film 13 via the brazing material 14 and brazed, the metallized film is seen from the center line in the X direction in plan view of the cavity portion 15. The distance b from the center line of the cavity 15 to the inner peripheral side surface position of the metal frame 12 is shorter than the reference distance a (b <a) when the distance a to the inner peripheral side surface position 13 is used as a reference. In addition, the distance c from the center line of the cavity 15 to the outer peripheral side surface position of the metal frame 12 is longer than the reference distance a (c> a), that is, c> a> b. Similarly, in the Y direction in a plan view of the cavity portion 15, the reference distance d from the center line to the inner peripheral side surface position of the metallized film 13, and the inside of the metal frame 12 from the center line of the cavity portion 15. There is a relationship of f> d> e between the distance e to the circumferential side surface position and the distance f from the center line of the cavity portion 15 to the outer circumferential side surface position of the metal frame 12. Moreover, this ceramic package 10 has a space 16 between the inner peripheral bottom surface of the metal frame 12 and the upper surface of the ceramic substrate 11.

  Next, a ceramic package 10a as a modification of the ceramic package according to the embodiment of the present invention will be described with reference to FIG. The ceramic package 10a is basically the same as the ceramic package 10 described above, but one or a plurality of ring shapes are formed when the ceramic substrate 11 is formed between the ceramic substrate 11 and the metal frame 12. For example, two ceramic frames 17 and 17a are formed by laminating ceramic green sheets. And the metallized film | membrane 13 which protrudes from the surface is provided in the surface of the ceramic frame 17 of the upper layer side of these ceramic frames 17 and 17a. Further, a space 16 is provided between the inner peripheral bottom surface of the metal frame 12 and the upper surface of the upper ceramic frame 17.

  Next, as shown in FIG. 3, for example, a semiconductor element (not shown), which is an example of an electronic component, is mounted on the ceramic substrate 11 of the cavity portion 15 in the ceramic packages 10 and 10a. A bonding wire (not shown) is electrically connected to the outside. A lid 18 made of a metal such as KV or 42 alloy is placed on the metal frame 12 via a brazing material such as Au-Sn brazing. The lid 18 is welded to the metal frame 12 by moving the rollers of the pair of seam welders in the vertical and horizontal directions. In this welding joining, since the temperature around the lid joint portion is about 1200 ° C. at the time of joining, the lid is joined to the metal frame 12 in a thermally expanded state. After the bonding, the lid shrinks with cooling. The distortion caused by the shrinkage is caused by the space 16 formed by the thickness of the metallized film 13 protruding from the surface of the ceramic substrate 11 and the brazing material 14. Can absorb. As a result, the bottom surface side of the ceramic substrate 11 is not bent, so that the ceramic substrate 11 is not cracked. 10a and the lid 18 can be sealed with high airtight reliability.

  The present inventor uses alumina as a ceramic base material, W as a conductor paste, a ceramic base body having a ceramic frame with an outer dimension of 3 × 2 mm, and brazes a KV metal frame with Ag—Cu brazing. After the joining, the stress generated in the ceramic substrate when the lid made of KV was seam welded to the metal frame with Au—Sn brazing was analyzed by a finite element method simulation. As an example, the ring-shaped metallized film of the ceramic substrate had a frame width of 150 μm and a protrusion height from the ceramic frame of 50 μm. Further, the frame width of the metal frame is 200 μm, and the inner peripheral side surface of the metal frame from the center line of the cavity portion with respect to the reference of the distance from the center line of the cavity portion to the inner peripheral side surface position of the metallized film. Five types of models with 25, 50, 80, 100, and 120 μm lengths minus the distance to the position, and a space provided between the inner peripheral bottom surface of the metal frame and the upper surface of the ceramic frame, respectively. Created. In addition, as a comparative example, the frame width of the conventional metallized film is larger than the frame width of the metal frame, the metallized film does not protrude from the surface of the ceramic frame, the inner peripheral side bottom surface of the metal frame and the ceramic frame A model with no space between the top surface was created. And the relative value of the stress which arises in the ceramic base body of five types of models of an Example with respect to the model of a comparative example was measured. The results are shown in Table 1.

  In the example, it was confirmed that the stress was reduced as compared with the conventional comparative example. This is because the strain due to shrinkage after the lid is joined is less likely to be transmitted to the ceramic substrate because the metal frame is easily moved by the space formed between the ceramic substrate and the metal frame. It is thought to be due to. Further, in the examples, the distance from the center line of the cavity part to the inner peripheral side surface position of the metal frame relative to the reference of the distance from the center line of the cavity part to the inner peripheral side surface position of the metallized film It was confirmed that the stress was reduced as the length of subtracting was larger. Further, the distance from the center line of the cavity portion to the inner peripheral side surface position of the metal frame is subtracted from the reference of the distance from the center line of the cavity portion to the inner peripheral side surface position of the metallized film in the embodiment. In comparison between the case where the difference in length was 0 and the case of 0 in the comparative example which was originally 0 or minus, it was confirmed that the stress was reduced in the example. This is considered to be due to the fact that in the examples, the metallized film protrudes from the surface of the ceramic base material, which makes the metal frame easier to move.

  The ceramic package of the present invention is mounted on an electronic device such as a mobile phone or a notebook-type personal computer, which is small and highly reliable by mounting electronic components such as a semiconductor element and a crystal resonator. It can be incorporated and used.

(A)-(C) are explanatory drawings of the ceramic package which concerns on one embodiment of this invention, respectively. It is explanatory drawing of the modification of the same ceramic package. It is explanatory drawing which joined the metal cover body to the ceramic package. (A), (B) is explanatory drawing of the conventional ceramic package, respectively. It is explanatory drawing of the joining method which joins a metal cover body to the conventional ceramic package. It is explanatory drawing which joined the metal cover body to the ceramic package.

Explanation of symbols

  10, 10a: Ceramic package, 11: Ceramic substrate, 12: Metal frame, 13: Metallized film, 14: Brazing material, 15: Cavity, 16: Space, 17, 17a: Ceramic frame, 18: Lid body

Claims (2)

In a ceramic package comprising a cavity formed by brazing a ceramic base and a ring-shaped metal frame through a metallized film formed on the ceramic base,
The upper surface of the ceramic substrate has a ring-shaped metallized film that has a width smaller than the width of the metal frame and protrudes from the surface of the ceramic substrate, and the metallized film and the metal frame are bonded to each other. The distance from the center line of the cavity portion to the inner peripheral side surface position of the metal frame is based on the distance from the center line of the cavity portion to the inner peripheral side surface position of the metallized film. The distance from the center line of the cavity portion to the outer peripheral side surface position of the metal frame is longer than the reference, and between the inner peripheral bottom surface of the metal frame and the upper surface of the ceramic substrate. And a ceramic package having a space.   2. The ceramic package according to claim 1, wherein a ring-shaped ceramic frame is provided between the ceramic substrate and the metal frame, and the metallized film protruding from the surface is formed on the surface of the ceramic frame. And a ceramic package comprising the space between the inner peripheral bottom surface of the metal frame and the upper surface of the ceramic frame.

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