JPH08264675A - Ceramic-made lid - Google Patents

Abstract

PURPOSE: To facilitate an undercoat metallic layer to be formed which will not generate solder dripping even when reflow of a solder paste is permitted by making the height of peripheral side walls below a specified value. CONSTITUTION: A solder paste is printed on undercoat metallic layers 14 and 34 formed on peripheral side walls 22 and 36 of sealing surfaces of lids 11 and 31, and the solder paste is printed over undercoat metallic layers 14 and 34 formed on the peripheral side walls 22 and 36. Especially the height of the peripheral side walls 22 and 36 of the ceramic-made lids 11 and 31 is under 0.7mm. Since it is this small, the undercoat metallic layers 14 and 34 are formed over the entire peripheral side walls 22 and 36. Even when a solder layer is formed by reflowing the solder paste coated on the surfaces 14 and 34 of the undercoat metallic layers 14 and 34, large solder drippings never generate and the solder layer of a shape appropriate for sealing the package substrate is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic lid, and more particularly to a ceramic lid used for sealing a ceramic package.

[0002]

2. Description of the Related Art In a semiconductor device, 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. There is. 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 ceramic IC packages made of such alumina are now actively used.

In this ceramic package, when the ceramic package base is sealed with a ceramic lid, a low cost solder which can be sealed at a low temperature 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 structure of a ceramic package (semiconductor device) on which such a semiconductor element is mounted and a method of manufacturing the semiconductor device will be specifically described. In the following, a portion of the semiconductor device excluding a semiconductor element and a wiring portion such as wire bonding will be referred to as a package.

FIG. 3A is a bottom view schematically showing a lid constituting a ceramic package, FIG. 3B is a sectional view taken along the line I-I of the lid shown in FIG. )
FIG. 4 is a cross-sectional view schematically showing a semiconductor device using this lid.

As shown in FIGS. 3 (a) and 3 (b), the lid 31 includes a ceramic substrate 33 and a base metal layer 3 formed on the peripheral portion (the upper peripheral portion and the outer peripheral side wall surface in the figure).
4 and a solder layer 35 covering the underlying metal layer 34. As shown in FIG. 3B, the solder layer 35 is usually formed to have a uniform thickness. The solder layer 35 contains, for example, Pb as a main component, and the main component is Bi,
It is formed of solder having a composition to which Sn, In, Ag, etc. are added. The detailed method of forming the solder layer 35 will be described later.

On the other hand, in a semiconductor device using such a lid 31, a cavity portion 16 is formed in the center of the package base 12 and the underlying metal layer 20 used when sealing with the lid 31 is formed around the cavity portion 16. Are formed, and external connection pins 21 for connecting to a mother board (not shown) are erected around the base metal layer 20.
In addition, the cavity portion 16 is usually formed in a stepped shape in its peripheral portion, a pad portion 19 for wire bonding is formed in an intermediate step portion, and an LS is formed in a bottom surface portion.
A semiconductor element mounting portion 17 on which I or the like is mounted is formed. Then, the package base 12 and the lid 3 are formed by the solder layer 35 via the base metal layer 20 formed on the package base 12 and the base metal layer 34 formed on the lid 31.
1 and the semiconductor element 18 are sealed.

Next, a method of manufacturing this semiconductor device will be described. First, after bonding the semiconductor element 18 to the semiconductor element mounting portion 17 of the package substrate 12, the pad portion (not shown) on the semiconductor element 18 side and the pad portion 19 on the package substrate 12 side are connected by the wire bonding method.

Next, the solder layer 35 of the lid 31 is superposed on the base metal layer 20 formed on the upper surface of the package base 12, and the lid 31 is temporarily fixed on the package base 12 by a fixing jig such as a spring or a clip. To do. Next, the package base 12 to which the lid 31 is temporarily fixed is loaded into the heating furnace, the solder layer 35 formed on the lid 31 is melted, and the lid 31 and the package base 12 are bonded to each other.
After that, the semiconductor element 18 is hermetically sealed in the package base 12 by cooling.

[0010]

However, as will be described below, when the shape of the solder layer formed on the lid 31 is not appropriate, the cavity 31 can be hermetically sealed by the lid 31. However, there is a problem in that it is not possible to cause a failure of the semiconductor device.

Generally, as a method of forming the solder layer 35 on the lid 31, the base metal layer 34 formed on the lid 31 is used.
After printing a paste containing solder on top, reflow is performed at about 310 ° C.

FIG. 4 (a) is an enlarged cross-sectional view showing a part of the lid when a solder layer having an appropriate shape is formed when the paste containing solder is printed and then reflowed.
FIG. 6B is an enlarged cross-sectional view showing a part of the lid in the case where the solder layer is not formed after the reflow. In addition, D indicates the thickness of the so-called edge relief,
An appropriate height H of the outer peripheral side wall surface 22 of the lid 11 and the lid 1
When the thickness is different from the necessary thickness for maintaining the mechanical characteristics of the lid 1 itself, a thin portion 24 having a shape as shown in FIG. 4A is formed on the outer peripheral portion 23 of the lid 11.

As shown in FIG. 4A, when the height H of the base metal layer 14 formed on the outer peripheral side wall surface 22 of the ceramic substrate 13 constituting the lid 11 is appropriate, it is formed after the reflow. The solder layer 15 has a shape as shown in the figure, that is, the solder layer 15a formed on the outer peripheral portion 23 of the sealing surface and the solder layer 15b formed on the outer peripheral side wall surface 22 are continuously formed, By using the lid 11 having such solder layers 15a and 15b formed thereon, the package base can be hermetically sealed.

However, as shown in FIG. 4B, the outer peripheral side wall surface 36 of the ceramic substrate 33 forming the lid 31.
If the height H is too high, reflowing the solder paste causes the solder on the outer peripheral side wall surface 36 to move downward due to the flow, as shown in the figure, and forms on the sealing surface of the outer peripheral portion 37. A portion of the solder layer 35a formed on the outer peripheral side wall surface 36 and the formed solder layer 35b has no width t (hereinafter, this phenomenon is referred to as solder pull-down, and this width t is the solder pull-down width. That). If the package base is sealed using the lid 31 in which such a large solder drop occurs, airtight sealing cannot be performed,
Poor sealing occurs.

As one method for solving such a problem, Japanese Unexamined Patent Publication No. 2-180053 discloses that a notch surface is provided at a portion where an outer peripheral side wall surface and a sealing surface intersect with each other, and the sealing surface and the notch are provided. A lid having a base metal layer formed on its surface or a lid having a base metal layer formed on a part of the outer peripheral side wall surface has been proposed. FIG. 5A is a sectional view schematically showing a lid 41 having a base metal layer 44 formed on a part of the outer peripheral side wall surface 46 of the ceramic substrate 43 and an outer peripheral portion 47 of the sealing surface of the ceramic substrate 43. (B) has a cutout surface 58 at the intersection of the outer peripheral side wall surface 57 of the ceramic substrate 53 and the sealing surface of the ceramic substrate 53. Base metal layer 5
It is sectional drawing which showed typically the lid 51 in which 4 was formed.

When the lids 41 and 51 having such a configuration are used, solder reflow does not occur even when the solder paste formed on the base metal layers 44 and 54 is reflowed.
It becomes easy to form the solder layer having a good shape, and it becomes possible to hermetically seal the cavity portion of the package base by using the lids 41 and 51. However, with the lids 41 and 51 having the above-described configuration, there is another problem that it is not easy to print the paste layers for forming the base metal layers 44 and 54 on the lids 41 and 51 using a normal printing device. It occurs newly.

That is, when the base metal layer is formed on the outer peripheral side wall surface of the normal lid, a metallizing apparatus as shown in FIG. 6 is used to automatically print the metallizing paste on the outer peripheral side wall surface.

FIG. 6 is a perspective view schematically showing the metallizing device. As shown in FIG. 6, this metallizing device is composed of three parts, that is, a metallizing paste plate 62, a package holding portion 63, and a rotational movement driving portion 64.
The package holding unit 63 includes a suction plate 65, and the suction plate 65 holds the lid 66. The package holding portion 63 is attached to an elevating rod 68 arranged at the tip of a multi-axis machine 67 that constitutes the rotation movement driving portion 64. Accordingly, the outer peripheral side wall of the lid 66 held by the suction plate 65 is brought into contact with the plate body 69 coated with the metallizing paste, and the multi-axis machine 67 is driven to move the lid 66 while rotating the lid 66. , Lid 6
The metallizing paste is applied to the entire outer peripheral side wall portion of 6.

However, as shown in FIG. 5, the underlying metal layer 44 is formed on a part of the outer peripheral side wall surface of the ceramic substrate 43, or the underlying metal layer 5 is formed on the cutout surface 58 of the ceramic substrate 53.
The metallizing device cannot be used to form the underlayer 4, and the underlayer 4 having the above-described shape can be formed by other methods.
It is very difficult to automatically print the metallizing paste to form the layers 4 and 54, and it is difficult to put the lids 41 and 51 described in the above publication into practical use.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a ceramic lid capable of easily forming a base metal layer that does not cause solder drop even when the solder paste is reflowed. I am trying.

[0021]

In order to achieve the above object, a ceramic lid (1) according to the present invention is for sealing a cavity portion of a ceramic package base, and a sealing member facing the cavity portion. In a ceramic lid in which a base metal layer having solder wettability is formed on the outer peripheral portion and the outer peripheral side wall surface, and a solder layer is further formed on the surface of the base metal layer, the height of the outer peripheral side wall surface is 0. It is characterized by being 7 mm or less.

Further, the ceramic lid (2) according to the present invention is characterized in that a thin portion is formed on the outer peripheral portion of the ceramic substrate, and the thickness of the thick portion excluding the thin portion exceeds 0.7 mm. I am trying.

The material of the ceramic lid according to the present invention is not particularly limited, but specific examples thereof include alumina, aluminum nitride, mullite and the like. The size of the lid is usually such that the length of the short side is 25.4 to 34.0 mm and the length of the long side is 25.
It is about 4 to 54.1 mm. The height of the outer peripheral side wall surface is preferably in the range of 0.4 to 0.7 mm. The material of the underlying metal layer formed on the lid is preferably Ag-Pt, and its thickness is preferably about 20 μm.

The composition of the solder layer formed on the surface of the underlying metal layer is not particularly limited, but Pb is the main component, and Sn is 4.0% by weight and In is 1.0% by weight. , Ag of about 1.0% by weight and Bi of about 8.0% by weight are preferable.

The lid preferably has a certain thickness so that cracks or the like do not occur even if warpage or the like occurs after the package base is sealed. In the ceramic lid according to the present invention, the height of the outer peripheral side wall surface is set to 0.7 mm or less. Therefore, when the thickness of most of the ceramic lid is set to exceed 0.7 mm, An edge relief for forming a thin portion is formed on the outer peripheral portion on the opposite side, and a thick portion is formed by the other portions. On the other hand, the sealing surface is flat.

When the thickness of the thick portion of the lid exceeds 0.7 mm, the upper limit is more preferably about 1.2 mm. Also, the width of the thin portion is preferably narrow, but from the viewpoint of ease of manufacturing, the width is 0.15 to 0.25 m.
m is preferred.

[0027]

According to the ceramic lid (1) of the present invention, the height of the outer peripheral side wall surface of the ceramic lid is 0.7 m.
Since it is as small as m or less, a base metal layer is formed on the entire outer peripheral side wall surface, and the solder paste applied to the peripheral portion of the sealing surface and the base metal layer surface on the outer peripheral side wall surface is reflowed to form a solder layer. Even if formed, a large amount of solder drop does not occur, and a solder layer having a shape suitable for sealing the package base is formed. Therefore, it is easy to form the base metal layer, and when the package base is sealed using the lid, the cavity of the package base is hermetically sealed.

Further, according to the ceramic lid (2) of the present invention, the thin portion is formed on the outer peripheral portion of the ceramic substrate, and the thickness of the thick portion excluding the thin portion exceeds 0.7 mm. , In addition to the action described in (1) above,
High mechanical strength is obtained, and the semiconductor device manufactured using the ceramic lid (2) has excellent reliability.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a ceramic lid according to the present invention will be described below with reference to the drawings. The structure of the ceramic lid according to the embodiment is the same as that of the ceramic lid shown in FIGS. 3A and 3B (FIG. 4A) except that the height of the outer peripheral side wall surface is different from the conventional one. Yes, the structure of the ceramic package manufactured using the lid is also shown in FIG.
Since it is almost the same as that of the conventional example shown in FIG. 2, detailed description of its configuration is omitted, and here, its material and dimensions will be described. The same applies to the case of the comparative example.

The ceramic lids 11 and 31 (FIG. 4) according to the embodiment and the comparative example are replaced with the edge relief 1 made of alumina.
3a and 33a, and the side length is 25
mm × 25 mm, the material of the underlying metal layers 14 and 34 formed on the outer periphery thereof is Ag—Pt alloy, and the thickness thereof is about 2
It was set to 0 μm. The height H of the outer peripheral side wall surfaces 22 and 36 is set to 0.53 mm (D = 0.23 mm), 0.66 m.
m (D = 0.36 mm), 0.83 mm (D = 0.36)
mm) and 200 pieces were produced.

Next, solder paste is printed by screen printing on the underlying metal layers 14 and 34 formed on the outer peripheral portions 23 and 37 of the sealing surfaces of the lids 11 and 31, and the outer peripheral side wall surfaces 22 and 36 are printed. Solder paste was printed on the formed base metal layers 14 and 34 using the metallizing apparatus shown in FIG. The solder paste at this time is composed of solder particles, resin, solvent, etc., and the composition of the solder itself is Pb as a main component, in addition to 4.1 wt% Sn, 1.0 wt% Ag, and In. 1.1 wt% and Bi of 8.2 wt% were contained.

Next, the lids 11 and 31 are introduced into a heating furnace, and the lids 30 and 30 are placed in a nitrogen atmosphere containing less than 0.1 ppm of oxygen.
The solder paste was reflowed by heating at 0 ° C.

Then, after measuring the solder pull-down width t for all the samples, the samples (lids 11, 31)
Then, the package base 12 (FIG. 3) is sealed by a method similar to the method described in the “Prior Art” section, and whether or not the sealing is completely performed is evaluated by MIL-STD-. 8
83 method 1014.

The package base 12 used at this time is made of alumina, and the length of its side portion is 44 mm × 44 mm.
The thickness of the central portion where the cavity 16 is formed is 1.3.
The thickness of the outer peripheral portion was set to 2 mm, the thickness of the outer peripheral portion was set to 2.80 mm, and the outer dimension of the cavity portion 16 was set to 20 mm × 20 mm.

FIG. 1 is a graph showing the relationship between the solder pull-down width t (μm) obtained as a result of the above-mentioned evaluation and the sealing defect occurrence rate.

As is clear from the graph shown in FIG.
When the solder withdrawal width t exceeds 80 μm, the sealing defect occurrence rate is rapidly increasing. In order to prevent the sealing defect of the ceramic package from occurring, the solder withdrawal width t when the solder paste is reflowed is set. It must be smaller than 80 μm.

The outer peripheral side wall surface 2 of the lids 11 and 31
The relationship between the heights H of 2 and 36 and the probability that the solder pull-down width t is 80 μm or more (hereinafter, referred to as a solder pull-down occurrence rate) is tabulated and a graph is created. The result is shown in FIG.

As is clear from the results shown in FIG.
When the height H of the outer peripheral side wall surface 36 of No. 1 exceeds 0.7 mm, the solder drop occurrence rate sharply increases. If such a lid 31 having a solder pull-down width t of 80 μm or more is used, sealing failure will occur. Become. From the results shown in FIGS. 1 and 2, at least the outer peripheral side wall surface 22 of the lid 11
It was confirmed that in the ceramic lid according to the present invention having a height H of 0.7 mm or less, solder drop did not occur, and therefore, the ceramic package did not have defective sealing.

[0039]

As described above in detail, in the ceramic lid according to the present invention, since the height of the outer peripheral side wall surface of the ceramic lid is as small as 0.7 mm or less, the entire outer peripheral side wall surface is grounded. Even if a metal layer is formed to form a solder layer by reflowing the solder paste applied to the outer peripheral portion of the sealing surface and the outer peripheral side wall surface of the underlying metal layer surface, large solder pull-down does not occur, A solder layer having a shape suitable for sealing the package base can be formed. Therefore, the base metal layer can be easily formed, and when the package base is sealed using the lid, the cavity of the package base can be hermetically sealed.

Further, in the ceramic lid (2) according to the present invention, the thin portion is formed on the outer peripheral portion of the ceramic substrate, and the thickness of the thick portion excluding the thin portion exceeds 0.7 mm. Therefore, in addition to the effect described in (1) above, the mechanical properties of the lid can be further improved, and the semiconductor device to be manufactured can be made highly reliable.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a solder pull-down width t and a defective sealing occurrence rate.

FIG. 2 is a graph showing the relationship between the height H of the outer peripheral side wall surface of the lid and the solder pull-down occurrence rate.

3A is a bottom view schematically showing a lid that constitutes a ceramic package, FIG. 3B is a sectional view taken along the line I-I of the lid shown in FIG. 3A, and FIG. FIG. 4 is a cross-sectional view schematically showing a semiconductor device using this lid.

FIG. 4A is an enlarged cross-sectional view showing a part of a lid when a solder layer having an appropriate shape is formed when a paste containing solder is printed and then reflowed, and FIG. It is an expanded sectional view showing a part of lid in the case where a portion where a solder layer is not formed occurs after reflow.

5A is a cross-sectional view schematically showing a lid in which a base metal layer is formed on a part of an outer peripheral side wall surface of a ceramic substrate and an outer peripheral portion of a sealing surface, and FIG. A cross-sectional view schematically showing a lid having a notch surface at a portion where the outer peripheral side wall surface and the sealing surface intersect, and a base metal layer is formed on the outer peripheral portion and the notch surface of the sealing surface of the ceramic substrate. It is a figure.

FIG. 6 is a perspective view schematically showing a metallizing device.

[Explanation of symbols]

 11 lid 14 base metal layer 15, 15a, 15b solder layer 22 outer peripheral side wall surface 23 outer peripheral portion

Claims (2)

[Claims] 1. A base metal layer having solder wettability for sealing a cavity portion of a ceramic package base, wherein a peripheral metal layer and a peripheral side wall surface of a sealing surface facing the cavity portion are formed. A ceramic lid in which a solder layer is formed on the surface of a base metal layer, wherein the height of the outer peripheral side wall surface is 0.7 mm or less. 2. The ceramic lid according to claim 1, wherein a thin portion is formed on an outer peripheral portion of the ceramic substrate, and a thickness of the thick portion excluding the thin portion exceeds 0.7 mm.