JP7817865B2 - Lid, manufacturing method thereof, and crystal oscillator - Google Patents

Description

The present invention relates to a lid that reduces material costs and prevents the sealing material from flowing out when joined to the base, a manufacturing method for the lid, and a quartz crystal oscillator.

In electronic components such as quartz crystal resonators and crystal oscillators, elements are mounted in the space within the package, and a sealing structure is provided within the package to protect the elements. These packages consist of a base on which the elements are mounted and a lid that serves as a cover for sealing the elements. One method of sealing the base and lid is to use a sealing material, such as a brazing filler metal. The brazing filler metal is preformed in the shape of the intended bonding area between the base and lid, and is typically welded to the lid in advance.

Fig. 5A is a perspective view showing an example of a conventional lid 70. Fig. 5B is a cross-sectional view taken along line DD in Fig. 5A.
A conventional lid 70 includes a substrate 71 made of a metal material, such as Kovar, and having a rectangular shape in a plan view; a Ni layer 72 formed by a known plating technique to cover the surface of the substrate 71; an Au layer 73 formed by a known plating technique to cover the surface of the Ni layer 72; and a ring-shaped sealing member 74 welded to the surface of the Au layer 73 along the edge of the surface of the substrate 71 that will be bonded to the base, in the area where the base and substrate 71 will be bonded. The Au layer 73 improves the wettability of the sealing member 74, but if the sealing member 74 has too high wettability, there is a risk that the sealing member 74 will flow out of the area where the base and lid will be bonded when the lid 70 is bonded to the base. If the sealing member 74 flows out of the area where the base and lid will be bonded, this can result in poor airtightness, poor appearance, and the like.

One example of a lid that solves this problem is disclosed in Patent Document 1. According to this document, there is a characteristic relationship between the thickness of the gold plating (Au layer) and the wettability of the brazing filler metal (sealing material), and it is stated that when the gold plating exceeds a certain thickness, the wettability of the brazing filler metal decreases as the plating thickness increases. Therefore, by making the gold plating 0.1 to 3 μm thick, it is possible to prevent the brazing filler metal from flowing out of the intended bonding area between the base and lid (paragraphs 0010 and 0013 of Patent Document 1).

In addition, in Patent Document 2, a substrate having a Ni plating layer (Ni layer) and an Au plating layer (Au layer) formed in that order on its surface is laser-removed along the solder (sealing member) area to expose the surface of the Ni plating layer, and the exposed surface of the Ni plating layer is oxidized to form an oxide film layer that is less wettable to solder than the Au plating layer, thereby preventing the solder from wetting and spreading.

JP 2003-224223 Patent Publication No. 2015-73027

However, these conventional techniques have the problem of increasing the material cost of the lid because they use Au. In recent years, the price of Au has been rising, and it is important to reduce the amount of Au used in order to reduce costs.
The present invention has been made in consideration of these points, and therefore, an object of this application is to provide a lid having a novel structure that reduces material costs compared to conventional methods and prevents outflow of sealing material, a method for manufacturing the same, and a quartz crystal unit.

To achieve this objective, the lid of this invention is characterized by comprising a base material made of a metal member, a Ni layer formed on the surface of the base material, and a sealing member welded to the Ni layer along the edge of the base material to join the base material to the base for the electronic component.

The quartz crystal unit of this invention is characterized by comprising a substrate made of a metal material, a lid having a Ni layer formed on the surface of the substrate and a sealing member welded to the Ni layer along the edge of the substrate, a base connected to the lid via the sealing member, and a quartz crystal blank mounted in a container formed by the lid and the base.

In addition, a method for manufacturing a lid in which a sealing member is welded along the edge of a base material made of a metal member is characterized by including the steps of forming a Ni layer on the surface of the base material and welding the sealing member onto the Ni layer in a reducing atmosphere.

According to the lid of this invention, there is no need to provide an Au layer on the surface of the Ni layer formed on the surface of the base material, thereby reducing material costs. Furthermore, because Ni forms an oxide film when exposed to the atmosphere, an oxide film is formed on the Ni layer in areas where no sealing material is provided. The oxide film has lower wettability with respect to the sealing material than the Au layer and does not weld to the sealing material, preventing the sealing material from flowing out when the lid is bonded to the base.
Furthermore, according to the quartz crystal resonator of the present invention, the lid for sealing the quartz crystal blank does not require an Au layer to be formed on the surface of the Ni layer formed on the surface of the base material, thereby reducing material costs.
Furthermore, the lid manufacturing method includes forming a Ni layer on the surface of the base material and welding a sealing member to the Ni layer in a reducing atmosphere, so that the oxide film on the Ni layer is removed in the reducing atmosphere, making it possible to weld the sealing member onto the Ni layer. Therefore, it is not necessary to provide an Au layer on the Ni layer, and it is possible to manufacture a lid in which the sealing member is welded directly onto the Ni layer.

Fig. 1A is a perspective view showing an outline of a lid according to an embodiment of the present invention, and Fig. 1B is a cross-sectional view showing an outline of the lid according to an embodiment of the present invention. 2A is a perspective view showing an outline of a quartz crystal resonator according to an embodiment of the present invention, and FIG. 2B is a cross-sectional view showing an outline of a quartz crystal resonator according to an embodiment of the present invention. 1A to 1C are explanatory views illustrating an embodiment of a method for manufacturing a lid according to the present invention. FIG. 4 is an explanatory diagram of a manufacturing method example following FIG. Fig. 5A is a perspective view showing an outline of a conventional lid, and Fig. 5B is a cross-sectional view showing an outline of the conventional lid.

Hereinafter, embodiments of the lid, the manufacturing method thereof, and the crystal resonator of this application will be described with reference to the drawings.
The drawings used in the description are merely schematic illustrations to the extent that these inventions can be understood. In the drawings used in the description, similar components are denoted by the same reference numerals, and their explanation may be omitted. The shapes, materials, etc. described in the following description are merely preferred examples within the scope of the present invention. Therefore, the present invention is not limited to the following embodiments.

1. Lid Configuration Fig. 1A is a perspective view showing an outline of a lid according to an embodiment of the present invention, and Fig. 1B is a cross-sectional view taken along line AA in Fig. 1A.
The lid 10 of the present invention includes a substrate 11 made of a metal material, such as Kovar, and having a rectangular shape in plan view, a Ni layer 12 formed by a known plating technique to cover the surface of the substrate 11 and to weld a sealing member 13 to the substrate 11, and a ring-shaped sealing member 13 welded to the surface of the Ni layer 12 along the edge of the surface of the substrate 11 that will be bonded to the base of an electronic component, in a region where the base and the substrate 11 will be bonded to each other. The Ni layer 12 has an oxide film covering the area other than the region where the sealing member 13 is welded. The thickness of the Ni layer 12 is determined based on the design of the substrate 11 to ensure environmental resistance, etc.

The oxide film formed on the Ni layer has low wettability and does not bond to the sealing material 13. This prevents the sealing material 13 from flowing out of the intended bonding area between the electronic component base and lid 10 when bonding the lid 10 to the quartz crystal oscillator base.

In addition, the sealing member 13 is preferably made of AuSn (melting point 280°C to 300°C), as this not only has excellent corrosion resistance but also a higher melting point than the solder (melting point 180°C to 230°C) used in the device assembly process, allowing the package to maintain its airtightness without remelting during the assembly process.

2. Crystal Unit Configuration The lid of the present invention can be used as a lid material, which is a component of the packaging of various electronic components. Below, we will explain an example of a crystal unit configured using the lid of the present invention as the lid material of a crystal unit package. Figure 2 is an explanatory diagram, and Figure 2A is a perspective view of a crystal unit that uses a base for mounting a crystal element, a crystal element mounted on the base, and a lid of the present invention for sealing the crystal element. Furthermore, Figure 2B is a cross-sectional view of the crystal unit taken along line B-B in Figure 2A.

The lid 10 of the present invention, a crystal blank 20 of any shape (in this example, rectangular in plan view), and a base, such as a well-known ceramic base 30 (hereinafter sometimes abbreviated as base 30), are prepared. In this case, the base 30 is rectangular in plan view and, as shown in Figures 2A and 2B, comprises a recess 30a for housing the crystal blank 20, a bank portion 30b along the edge of the base 30, bumps 30c for fixing the crystal blank on the bottom surface of the recess 30a, and mounting terminals 30d on the back surface of the base 30. The bumps 30c and mounting terminals 30d are electrically connected by via wiring (not shown).

The crystal blank 20 is fixed onto the bumps 30c with, for example, a conductive adhesive (not shown), and then the oscillation frequency of the crystal blank 20 is adjusted to a predetermined value using a well-known method. Next, the inside of the base 30a of the base 30 is made into an appropriate vacuum or inert gas atmosphere, and the recess 30a is sealed with the lid 10 using a well-known method.
In this way, a crystal unit 40 is obtained, which has a structure in which the crystal blank 20 is housed in the lid 10 and the base 30.

3 is an explanatory diagram illustrating an embodiment of the lid manufacturing method of the present invention. First, a base material 51 made of a metal member, for example, Kovar, and having a rectangular shape in a plan view is prepared. Ni plating is applied to the surface of the base material 51 by a well-known plating technique so as to cover the surface of the base material 51, thereby forming a Ni layer 52 on the surface of the base material 51.

Next, the substrate 51 having the Ni layer 52 formed on its surface is carried into a processing chamber 60 as shown in FIG. 4A. After the substrate 51 is carried into the processing chamber 60, a reducing gas is injected into the processing chamber 60 to create a reducing atmosphere in the processing chamber 60. The reason for this is as follows. Normally, the Ni layer 52 forms an oxide film on its surface, and since this oxide film has low wettability, the sealing member 53 cannot be welded to the substrate 51. However, by placing the substrate 51 in a reducing atmosphere, the oxide film on the surface of the Ni layer 52 can be removed. This allows the sealing member 53 to be welded to the substrate 51.
After the atmosphere in the processing chamber 60 becomes a reducing atmosphere, a sealing member 53 that has been preformed into a ring shape is superimposed on the joining surface side of the base material 51 along the edge of the base material 51 on the area where the base and base material 51 are to be joined.

The reducing gas used here can be, for example, hydrogen or formic acid. Furthermore, considering the risk of explosion, the concentration of the reducing gas is preferably 5 vol% or less by volume. The concentration of the reducing gas can be controlled, for example, using a flow meter.

Next, the temperature of the reducing gas atmosphere in the processing chamber 60 is increased until it reaches the melting point of the sealing member 53. This causes the sealing member 53 to melt and be welded to the Ni layer 52 formed on the surface of the substrate 51. At this time, the temperature of the reducing gas atmosphere must be increased to the melting point and then rapidly decreased after the sealing member 53 has melted. This is because if the temperature is maintained at an elevated level, the sealing member 53 will continue to melt and the preformed shape will be distorted.

Here, assuming that AuSn is used as the sealing material, the temperature of the reducing gas atmosphere is preferably 280°C to 300°C, which is the melting point of AuSn.

When the substrate 51, with the sealing member 53 welded to the Ni layer 52, is removed from the processing chamber 60 and exposed to the atmosphere, the surface of the Ni layer 52 in areas where the sealing member 53 is not welded oxidizes, forming an oxide film. The oxide film has low wettability, and therefore prevents the sealing member 53 from flowing out of the intended bonding area between the base and lid when the base is bonded to the lid.

10: Lid according to an embodiment of the present invention 11: Base material 12: Ni layer 13: Sealing member 20: Crystal blank 30: Base 30a: Recess 30b: Bank portion 30c: Bump 30d: Mounting terminal 40: Crystal unit according to an embodiment of the present invention 50: Lid according to an embodiment of the present invention 51: Base material 52: Ni layer 53: Sealing member 60: Processing chamber 70: Conventional lid 71: Base material 72: Ni layer 73: Au layer 74: Sealing member

Claims (3)

A method for manufacturing a lid having a base material made of a metal member,
When welding the sealing member along the edge of the base material,
forming a Ni layer on the surface of the substrate;
a step of welding the sealing member onto the surface of the Ni layer in a reducing atmosphere;
A method for manufacturing a lid, comprising: 2. The method for manufacturing a lid according to claim 1 , wherein the reducing atmosphere is a reducing gas atmosphere containing hydrogen or formic acid. 3. The method for manufacturing a lid according to claim 2 , wherein the reducing gas atmosphere has a concentration of hydrogen or formic acid of 5 vol % or less in terms of volume ratio.