JP3374395B2 - Package for electronic components - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package for electronic parts, and particularly to a package for electronic parts which requires hermetic sealing.

[0002]

2. Description of the Related Art Crystal-applied products such as a crystal oscillator, a crystal filter, and a crystal oscillator are given as examples of electronic parts requiring hermetic sealing. In each of these, a metal thin film electrode is formed on the surface of the crystal diaphragm, and the metal thin film electrode is hermetically sealed in order to protect the metal thin film electrode from the outside air.

Airtight sealing methods include solder joining, low melting point glass joining, resistance welding and electron beam welding. As an airtight sealing method using resistance welding, a crystal oscillator using an HC-49 / U type base is widely used. This is a structure in which a metal cap is hermetically sealed by resistance welding with a base in which a lead terminal is implanted in a metal shell in a state of being insulated from each other via insulating glass, and an electronic device having a lead terminal such as a crystal unit. It is widely used as a method for hermetically sealing components.

Further, as shown in Japanese Patent Application Laid-Open No. 8-162555, a metal frame body (seal ring) formed in an opening portion of a ceramic package in which an extraction electrode is formed and a metal lid body are resistance-welded. A joining method corresponding to surface mounting, which is hermetically sealed by one type of seam welding, is also adopted.

Further, in such a surface mounting package, as shown in Japanese Patent Laid-Open No. 8-46075, a method of hermetically sealing by electron beam welding or laser beam welding is also adopted.

FIG. 1 shows an example of an electronic component package which is hermetically sealed by electron beam welding. The concave ceramic package 1 having an open top has a ceramic base 10
A metallization layer 11 made of tungsten or the like formed in the opening around the recess, a lower plating layer 12 made of nickel or the like formed on the metallization layer, and gold or the like formed on the lower plating layer. Upper plating layer 13 consisting of
(Not shown) and. Electrode pads 14 and 15 are formed on the inner bottom surface of the ceramic package.
It is electrically drawn out as 17. An electronic component element 3 such as a crystal diaphragm is mounted between the electrode pads 14 and 15 and electrically connected thereto.

Further, the metal lid 2 for hermetically sealing has a metal layer 21 (not shown) of silver or the like formed on the lower surface of a metal base material 20 of Kovar or the like. This metal layer is formed by using, for example, a rolling method, and is generally called a clad material.
When airtight sealing is performed, the metal lid 2 and the upper plating layer 13 of the ceramic package 1 are overlapped with each other, and a portion corresponding to the upper plating layer 13 is circumferentially irradiated with an electron beam from the upper portion of the metal lid 2. Then, the metal lid 2 and the plating layer (lower plating layer and upper plating layer) are fusion-bonded.
Since such a welding method does not require a seal ring on the package side unlike seam welding, the number of manufacturing steps can be reduced,
It also had the advantage of reducing the cost of the package.

[0008]

However, when a general manufacturing method is used in which a metallized layer is formed on a ceramic substrate by a screen printing method and fired and molded, uneven waviness occurs on the surface of the metallized layer. Was. When electron beam welding or laser beam welding is performed using such a ceramic package, a gap is generated in a part between the metal lid and the plating layer, and when the region where the gap is generated is irradiated with the electron beam, Due to the size of the gap, variations in the molten state occur, the bonding yield between the plating layer and the metal lid is low, and the reliability of the airtight surface is lacking.

The present invention has been made to solve the above problems, and in an electronic component package which is hermetically sealed by electron beam welding or laser beam welding, the yield at the time of hermetic sealing is improved and the hermetic sealing is performed. It is an object of the present invention to provide a package for electronic parts that improves reliability in terms of surface.

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made by paying attention to the fact that the yield and reliability of each welding described above depend on the states of the metallized layer and the plated layer of the ceramic package. That is, it is preferable that the surface of the metallized layer is basically smooth without any waviness. However, in the actual firing of the ceramic package, it is difficult to control the metallized layer portion in such a smooth state. The present invention conducts diligent experiments on flatness and weldability and examines practically effective flatness in light of actual manufacturing, and also examines the thickness of the plating layer formed on the upper surface of the metallized layer. It was done.

According to a first aspect of the present invention, there is provided a ceramic base, a metallization layer formed circumferentially around a main surface of the ceramic base, a plating layer formed on an upper surface of the metallization layer, and An electronic component package comprising a plating layer and a metal lid joined by an electron beam or a laser beam, wherein the metallization layer has a flatness of 5 μm or less. For planarization, the metallized layer may be pressed before firing the ceramic package. The flatness indicates the dimension of the top and bottom of the unevenness formed on the upper surface, and the smaller the dimension, the better the flatness.

Further, as described in claim 2, a ceramic base, a metallization layer formed circumferentially around the main surface of the ceramic base, a plating layer formed on the upper surface of the metallization layer, and the plating. An electronic component package comprising a layer and a metal lid joined by an electron beam or a laser beam, wherein the metallization layer has a flatness of 5 μm or less and the plating layer has a thickness of 4.5 to 13 μm. It may be a structure characterized by having a thickness of.

FIG. 4 is a graph showing the flatness of the metallized layer and the yield during welding. The ceramic substrate used for the measurement is an alumina substrate, a metallized layer made of tungsten is formed on the upper surface of the alumina substrate with a thickness of 35 μm, and the plating layer formed on the upper surface of the metallized layer is made of nickel. The metal lid is made of Kovar and has a thickness of 0.1 mm. Silver having a thickness of 15 μm is formed as a clad material on the welding surface of the metal lid.

Under the above conditions, data (graph A) in which a nickel plating having a thickness of 2 μm was formed, and a gold plating having a thickness of 0.5 μm was formed on the upper surface thereof, and a nickel plating having a thickness of 4 μm was formed. FIG. 4 shows data (graph B) obtained by forming a gold plating having a thickness of 0.5 μm on the upper surface (graph B) and data obtained by forming a nickel plating having a thickness of 8 μm and forming a gold plating having a thickness of 1 μm on the upper surface (graph C). ing. From each of these graphs, it can be understood that if the flatness of the metallized layer is 5 μm or less, a good welding yield can be obtained without being significantly affected by the thickness of the nickel plating.

As described above, the better the flatness is, the more the airtight yield in welding is improved. However, the flattening process, for example, the flattening by the press process has a technical limit and is generally limited. The flatness of about 1 μm is the limit. A method of polishing the upper surface of the metallized layer after firing the ceramic package may be considered to obtain a flatness higher than that, but the cost is high. Practically, a sufficient degree of flatness can be obtained by treatment with a press or the like, so generally, even in a special case, the above-mentioned polishing or the like is not used.

Further, in Graph A, the plating layer is 2.5 μm.
The thickness of the graph B is 4.5 μm, and that of the graph C is 9 μm, which is relatively thicker than that of the graph A. From the airtight yields in these graphs, by setting the thickness of the plating layer to 4.5 μm or more, it is possible to obtain more stable joining together with the metallization layer having a flatness of 5 μm or less, and it is expected that the welding yield is improved.

FIG. 5 is a graph showing the relationship between the plating thickness and the welding strength. Since the welding strength depends on various conditions such as the welding area, it is shown as a relative value when the strength is 1 when a plating layer having a thickness of 2 μm is formed on a metallization layer having a flatness of 3 μm. When the plating thickness was 2 μm, the welding strength was weak and the airtightness was sometimes deteriorated by the environmental test. However, as shown in FIG. 5, when the plating thickness is 4.5 μm, the strength is about 3 times,
A reliable hermetic seal can be performed.

The welding strength increases in proportion to the plating thickness. However, as is clear from FIG.
From around m, the welding strength is not improved even if the thickness is further increased. On the other hand, by increasing the plating thickness, the internal stress increases and the bonding strength with the metallization layer (tungsten) that is the base metal decreases. In addition, it is not preferable to make the plating layer thicker than necessary in terms of cost. Therefore, from the viewpoint of the bonding strength between the metallized layer and the plating layer or the cost, it is considered that the plating thickness of 13 μm or less is appropriate. Therefore, by setting the flatness of the metallized layer to 5 μm or less and setting the plating layer formed on the metallized layer to the range of 4.5 μm to 13 μm, the yield at the time of hermetic sealing is further improved, and the reliability of the hermetic surface is improved. It is possible to further improve the sex.

According to a third aspect of the present invention, in the electronic component package of the second aspect, the plating layer is composed of a plurality of layers, the lower layer is a nickel plating layer having a thickness of 4 to 12 μm, and the upper layer is 0. A gold plating layer having a thickness of 5 to 1 μm may be used.

According to the above structure, the flatness of the metallized layer is 5 μm or less, the lower plated layer is the nickel plated layer, and the upper layer is the thin gold layer.
Since the structure has a thickness of 13 μm, it is possible to obtain a good yield at the time of hermetic sealing and a good reliability on the hermetic surface. Further, the gold layer protects the nickel plating layer from oxidation and the like.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS. 1, 2 and 3 by taking a surface mount type crystal resonator as an example. The basic configuration is the configuration described in the conventional example and is as shown in FIG. That is, although partially overlapped with the above description, a concave ceramic package 1 having an open top
And a crystal vibrating plate 3 which is an electronic component element housed in the package, and a metal lid 2 bonded to the opening of the package.

The concave ceramic package 1 includes a ceramic substrate 10, a metallized layer 11 made of tungsten or the like formed in an opening around the concave, and a lower plating layer made of nickel or the like formed on the metallized layer. 12
And an upper plating layer 13 made of gold or the like formed on the lower plating layer. The plating layer is a region mainly contributing to welding. Before firing, the metallized layer is pressed with a punch P from the upper portion of the metallized layer with the molds F, F arranged around it, as shown in FIG. As a result, the flatness t of the upper surface of the metallized layer after firing is flattened to 5 μm or less, and the entire metallized layer is partially embedded in the ceramic substrate, so that the bonding strength between the two is improved. The flatness t indicates the dimension of the top and bottom of the unevenness formed on the surface of the metallized layer.

The thickness of each layer is 18 to 20 μm for the metallized layer 11 and 6 μm for the lower plating 12 in this embodiment.
The upper plating layer 13 has a thickness of 1 μm. The thickness of the metallized layer may be about 15 to 35 μm, but the flatness of the upper surface is improved when a pressing process is performed, and therefore the thickness may be less than that. Especially when a low profile of the package itself is required, press processing is performed to improve the flatness.
By increasing the thickness to about 3 μm, the thickness is reduced to 10
Even if the thickness is reduced to about 20 μm, it is possible to obtain the strength that is practically no problem. By flattening the metallized layer, each plated layer formed on the metallized layer is also formed with its upper surface kept flat.

Further, electrode pads 14 and 15 are formed on the inner bottom surface of the ceramic package, and these electrode pads are electrically led out to the bottom surface outside the package as lead electrodes 16 and 17. The electrode pad 14,
An electronic component element 3 such as a crystal diaphragm is housed between the parts 15.

The metal lid 2 for hermetically sealing has a metal layer 21 made of silver or the like formed on the lower surface of a metal base material 20 such as Kovar. The metal layer 21 is formed by using, for example, a rolling method. When airtight sealing is performed, the metal lid 2 and the plating layer (the lower plating 12 and the upper plating layer 13) of the ceramic package 1 are overlapped with each other, and a portion corresponding to the upper plating layer 13 from the upper portion of the metal lid 2 is overlapped. By circumferentially irradiating with an electron beam, the metal base material 20 of the metal lid 2, the metal layer 21, and the plating layers (the lower plating 12 and the upper plating layer 13) are melted and joined.

The flatness of the upper surface of the metallized layer is 5 μm.
It is necessary to be the following, but more preferably 1 to 3
A flatness of μm is sufficient. However, even if the thickness is 3 μm or more, the welding strength may be ensured by making the thickness of the plating layer relatively thick and absorbing the influence of unevenness. Also,
Although electron beam welding is used in the above embodiment, laser beam welding may be used.

Although the present invention exemplifies the surface mount type crystal unit, the present invention may be applied to a package for a piezoelectric filter or a piezoelectric oscillator, and may be applied to other electronic parts requiring hermetic sealing. You may apply.

[0028]

According to the present invention, in a package for electronic parts which is hermetically sealed by electron beam welding or laser beam welding, the manufacturing yield at the time of hermetic sealing is improved and the reliability in the hermetic surface is improved. A package for electronic components is provided.

That is, according to the electronic component package of the first aspect, since the flatness of the metallization layer is 5 μm or less, the flatness of the surface of the plating layer formed on the metallization layer becomes good, and the metallization layer has a good flatness. The airtight yield of joining with the lid using an electron beam or a laser beam is improved, and the reliability of the joining is also improved.

According to the electronic component package of the second aspect, a more stable bond can be obtained in combination with the metallized layer having a flatness of 5 μm or less, and the hermetic yield can be improved.

According to the above construction, the flatness of the metallized layer is 5 μm or less, the lower plated layer is a nickel plated layer, and the upper layer is a thin gold layer.
Since the structure has a thickness of 13 μm, the unevenness of the welding surface is reduced, and the yield at the time of hermetic sealing is further improved.
The reliability of the airtight surface can be further improved. Further, the gold layer protects the nickel plating layer from oxidation and the like.

[Brief description of drawings]

FIG. 1 is an internal sectional view according to a first embodiment.

FIG. 2 is a partially enlarged view showing the manufacturing method according to the first embodiment.

FIG. 3 is a partially enlarged view of FIG.

FIG. 4 is a graph showing comparative data.

FIG. 5 is a graph showing comparative data.

[Explanation of symbols]

1 Ceramic package 10 Ceramic substrate 11 Metallized layer 12 Lower plating layer 13 Upper plating layer 2 metal lid 20 Metal base material 21 metal layer 3 Crystal diaphragm (electronic component element)

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 23/02 B23K 26/00 310 H03H 9/02 H03H 9/19

Claims (3)

(57) [Claims] 1. A ceramic substrate, a metallization layer formed circumferentially around the main surface of the ceramic substrate, a plating layer formed on the upper surface of the metallization layer, the plating layer and an electron beam or a laser beam. An electronic component package comprising a metal lid to be joined, wherein the metallized layer has a flatness of 5 μm or less. 2. A ceramic base, a metallization layer formed circumferentially around the main surface of the ceramic base, a plating layer formed on the upper surface of the metallization layer, the plating layer and an electron beam or a laser beam. An electronic component package comprising a metal lid to be joined, wherein the metallized layer has a flatness of 5 μm or less and the plated layer has a thickness of 4.5 to 13 μm. A package for electronic parts characterized by the following. 3. The plating layer comprises a plurality of layers, the lower plating layer is a nickel plating layer having a thickness of 4 to 12 μm, and the upper plating layer is a gold plating layer having a thickness of 0.5 to 1 μm. The electronic component package described in 2.