JPH0851167A - Lid for sealing semiconductor package, semiconductor package using lid and forming method of alpha-ray shielding layer of lid - Google Patents

Abstract

PURPOSE:To reduce the quantity of alpha-rays radiated from a lid by forming an alpha-ray shielding layer consisting of the resin of a polyimide resin, etc., for shielding alpha-rays from a ceramic board. CONSTITUTION:A base metallic layer 7 is formed in the peripheral section 3 of the internal surface of a ceramic board 2, a base metallic layer 8 is formed onto a side face section 4, and a solder layer 9 as a sealing section is shaped onto the base metallic layer 7. A solder layer 10 is formed onto the base metallic layer 8, a solder-layer thickness gradient is formed to the solder layer 9 in the peripheral direction of the solder layer 9, and an alpha-ray shielding layer 5 is shaped on the inside surrounded by the solder layer 9. Resin such as polyimide resin having high purity, silicone rubber, etc., is used for the alpha-ray shielding layer 5, and the layer 5 is formed by coating with the resin. The solder layer 9 is formed onto the base metallic layer 7, the solder thickness of the solder layer on the broad section of the base metallic layer 7 is made thicker than that of the solder layer in a narrow section, and the ridgeline of the solder layer between the sections of both solder layers is formed in a gentle curved shape.

Description

Detailed Description of the Invention

[0001]

The present invention relates to relates to a package contact and α-ray shielding layer forming method of the lid using the lid and a semiconductor package sealing lid, and more particularly, a semiconductor chip mounting portion of the package base A semiconductor package sealing lid capable of preventing malfunction of a semiconductor chip such as an IC chip or an LSI chip mounted on a substrate due to α rays emitted from the ceramic plate forming the semiconductor package sealing lid, and a package using the lid. And a method for forming an α-ray shielding layer of the lid.

[0002]

2. Description of the Related Art Semiconductor chips such as IC chips and LSI chips are usually sealed with a package of ceramics or resin. Of these packages, ceramic packages are often used because of their good hermetic sealing properties.

By the way, a ceramic package is composed of a ceramic package base and a lid, and the ceramic material forming the package contains impurities such as uranium and thorium in the order of several ppm. It is known that these impurities emit α rays, and the α rays are one of the causes of malfunction (soft error) of the semiconductor chip.

Therefore, in the ceramic package, various measures are taken in order to prevent malfunction of the semiconductor chip due to α rays. That is, the device circuit is reviewed, a soft error correction circuit is provided, and the memory capacity is increased. The wiring material of the semiconductor chip is highly purified. Impurities such as uranium and thorium that emit α rays are removed from the ceramic material forming the package. The semiconductor chip is coated with an α-ray shielding material. Etc. are taken.

[0005]

However, the above-mentioned measures have the following problems. In other words, in the case of countermeasures, the device is limited to the semiconductor chip and the package size, and there is no room to install an additional circuit such as a soft error correction circuit, and there is a limit. In the case of measures, it is impossible to completely remove impurities such as uranium and thorium contained in the wiring material and the package material, and the material itself becomes expensive,
There is a limit. In the case of the countermeasure, the wiring pitch becomes very narrow in the high-density semiconductor chip, so that when the α-ray shielding material is coated, the shielding material causes contact and short circuit between the wirings. And other issues.

Therefore, in recent years, silicone rubber has been used on the inner surface of the ceramic lid for sealing the package base.
A method of providing an α-ray shielding layer made of a high-purity material such as a polyimide resin has been proposed (JP-A-55-88356).
No. 58-17642, and Japanese Utility Model Laid-Open No. 55-99153). In the case of this method, α rays emitted from the lid are shielded by the α ray shielding layer,
The radiation amount of the α rays can be reduced. in this case,
The α-ray shielding layer is formed by applying an α-ray shielding resin paste made of a high-purity material such as silicon rubber or polyimide resin by a dispenser method.

However, in the case of the structure in which the α-ray shielding layer made of a resin layer is provided on the inner surface of the ceramic lid, the package base and the ceramic lid are heated and melted by heating the solder layer provided on the peripheral portion of the lid. At the time of sealing with heat, gas is generated from the α-ray shielding layer due to the heating, the gas cannot be released to the outside of the package base, the internal pressure increases, and the molten solder in the solder layer scatters due to the internal pressure. However, there remains a problem that the solder adheres to the surface of the package substrate, the external connection terminal, and the like, which hinders the insertion of the external connection terminal into the circuit mounting board and causes contamination.

Further, since the α-ray shielding layer is formed by applying a resin paste by a dispenser method, the applied resin paste oozes out and a certain clearance is provided between the adjacent solder layers. There is a problem that it is difficult to maintain and obtain a uniform thickness. This point can be solved, for example, by adopting a screen printing method using a mesh plate used in the step of applying the seal glass for sealing the semiconductor package. But,
When the resin paste is screen-printed using this mesh plate to form the α-ray shielding layer, at the time of printing, the portion corresponding to the grid point of the mesh plate is difficult to be sufficiently filled with the resin paste. There is a phenomenon that a void is generated due to the resin paste drooping from around the point. Then, it has been found that when the void is generated, a new problem occurs that the α-ray shielding effect is lost at the location.

The present invention has been made in response to the above-mentioned problems, and the object thereof is to provide a lid for encapsulating a semiconductor package and a package using the lid for solving the above-mentioned conventional problems. To provide. Also,
An object of the present invention is to prevent a semiconductor chip such as an IC chip or an LSI chip mounted on a semiconductor chip mounting portion of a package base from malfunctioning due to α rays emitted from a ceramic plate forming the semiconductor package sealing lid. An object of the present invention is to provide a lid for sealing a semiconductor package and a package using the lid. Further, an object of the present invention is to form a void-free resin layer with a uniform thickness for shielding α rays in the semiconductor package sealing lid, and between the adjacent solder layer and other patterns. An object of the present invention is to provide a method for forming an α-ray shield layer that can take accurate clearance.

[0010]

A lid for encapsulating a semiconductor package of the present invention as a means for solving the above-mentioned problems is provided with a base metal layer on the inner peripheral edge of the ceramic plate or on the peripheral edge and the side surface. A semiconductor package sealing lid for sealing a semiconductor chip to be mounted on a semiconductor chip mounting portion of a semiconductor package base, wherein a solder layer on at least one of the peripheral edges is a peripheral edge of the ceramic plate. Direction, a thick portion and a thin portion of the solder layer are provided, and a ridge line between the thick portion and the thin portion of the solder layer is formed in a curved shape or a straight shape, and the inside of the solder layer on the inner surface of the ceramic plate. A structure in which an α-ray shielding layer made of a resin layer such as a polyimide resin for shielding α-rays emitted from the ceramic plate is provided, or one side or two opposite sides The solder layer of the peripheral portion,
It is thinner than the thickness of the solder layer on the other three or two sides, and is made of a resin layer such as polyimide for shielding α rays emitted from the ceramic plate inside the solder layer on the inner surface of the ceramic plate. An α-ray shielding layer is provided.

Further, the semiconductor package of the present invention has a base metal layer of a lid for encapsulating a semiconductor package having a base metal layer on the peripheral edge of the inner surface of the ceramic plate or on the peripheral edge and the side surface, and the semiconductor chip inside. A semiconductor package comprising a mounting portion, and a metallization layer of a semiconductor package substrate having a metallization layer at a portion corresponding to a base metal layer at a peripheral portion of the lid, is hermetically sealed by a solder layer, wherein The base metal layer on the peripheral portion of the package sealing lid has a wide portion and a narrow portion in the peripheral direction of the lid, and the inside of the solder layer on the inner surface of the ceramic plate emits α from the ceramic plate. An α-ray shielding layer made of a resin layer such as a polyimide resin for shielding the rays is provided.

Furthermore, the method for forming an α-ray shielding layer of the lid of the present invention is a method for forming an α-ray shielding layer made of a resin layer such as a polyimide resin provided on the lid, the ceramic plate after firing. , A metal plate having an opening having the shape of the resin layer to be formed is superposed on a portion where the resin layer is formed, and a resin paste such as a polyimide resin is screen-printed on the metal plate, and then the printing is performed. The α-ray shielding layer is formed by curing the resin paste.

[0013]

The lid for encapsulating a semiconductor package according to the present invention is a resin such as a polyimide resin for shielding α rays emitted from the ceramic plate inside the solder layer on the inner surface of the ceramic plate forming the lid. By providing the α-ray shielding layer made of a layer, the amount of α-rays emitted from the lid can be reduced, and when the semiconductor package is sealed, gas is also generated from the α-ray shielding layer, Although the internal gas of the package base on which the semiconductor chip is mounted is increased,
The solder layer on the peripheral edge of the ceramic plate is provided with a thick solder layer and a thin solder layer in the peripheral direction, and a thickness gradient or a thickness difference is provided in the solder layer, or a peripheral edge of one side or two opposite sides. By forming the solder layer at a portion thinner than the solder layers at the other three or two sides, the increased internal gas can be discharged to the outside of the semiconductor package, and the hermetic sealing can be performed accurately.

In the semiconductor package of the present invention, by using the semiconductor package sealing lid, a hermetically sealed semiconductor device can be obtained and α
The malfunction of the mounted semiconductor chip due to the lines can be prevented.

Further, in the method for forming the α-ray shielding layer of the lid of the present invention, the α-ray shielding layer is formed by using the screen printing method, so that the α-ray shielding layer has a uniform thickness and is adjacent to the solder layer. It is possible to maintain a predetermined clearance between the resin layer and other patterns, and since a metal plate having an opening in the shape of a resin layer provided on the lid is used as the screen, the resin layer is formed. When screen-printing the resin paste for this purpose, unlike the mesh plate used in normal screen-printing, a void-free α-ray shielding layer can be formed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Two kinds of embodiments embodying the present invention will be described below with reference to the drawings. Figure 1
7 shows an embodiment of the present invention, FIG. 1 is a plan view of a surface of a lid for encapsulating a semiconductor package according to an embodiment of the present invention on which a solder layer and an α-ray shielding layer are provided, and FIG. A-A in FIG.
A sectional view, FIG. 3 is a sectional view taken along the line A′-A ′ of FIG. 1, FIG. 4 is a partially enlarged view for explaining the measurement positions of the metal layer width w ₁ and the metal layer width w ₂ , and FIG. FIG. 6 is a graph illustrating the relationship between the width ratio w ₂ / w ₁ and the solder layer thickness difference, FIG. 6 is a graph illustrating the relationship between the solder layer thickness difference and the solder scattering occurrence rate (splatter occurrence rate), and FIG. 8 to 9 show another embodiment of the present invention. FIG. 8 shows a solder layer of a semiconductor package sealing lid and α
9a and 9b are plan views of the surface on which the line shielding layer is provided.
9c and 9d are EE, FF, and G- of FIG.
10 is a side view and a plan view of a metal plate for providing an α-ray shielding layer.

-Embodiment 1- A semiconductor package lid 1 of this embodiment is shown in FIGS.
As shown in FIG. 1, the base metal layer 7 is provided on the peripheral edge portion 3 of the inner surface of the ceramic plate 2, and the base metal layer 8 is provided on the side surface portion 4.
Is provided, a solder layer 9 as a sealing member is provided on the base metal layer 7, a solder layer 10 is provided on the base metal layer 8, and the solder layer 9 is soldered in the peripheral direction thereof. A layer thickness gradient is provided, and an α-ray shielding layer 5 is provided on the inner side surrounded by the solder layer 9.

Here, the underlying metal layers 7 and 8 are made of Ag, Ag-Pt, Ag-Pd, Mo- by screen printing.
A thick metallized film was formed by applying a paste containing a metal such as Mn, Mo, W, or Ti and firing it. Among these, Ag-Pt-based metal is preferable, and by using this metal, wetting and spreading of solder can be improved. The thickness of these metallized layers is 10 to 2
0 μm. In the case of Mo-Mn, Mo, W, Ti, Ni plating is applied on the thick film metallization,
Further, it is preferable to apply Au plating on Ni plating. As the solder layer 9, a solder having a melting point of about 250 ° C. to 320 ° C. and a composition containing part or all of Pb, Sn, In, Bi, Ag, and Sb was used.

The α-ray shielding layer 5 is formed by coating a resin such as high-purity polyimide resin or silicone rubber, which is used. The thickness of the α-ray shielding layer 5 is 20 μm or more, and in the case of polyimide resin, 20 μm to 30 μm or more is preferable. This is based on the data obtained by measuring the relationship between the thickness of the polyimide resin and the α-ray energy. Here, the α-ray shielding layer 5 is
It is preferable to coat the base metal layers 7 and 8 before forming the solder layers 9 and 10. Then, in the case of a polyimide resin, a paste-like polyimide resin is screen-printed inside the base metal layer 7 of the ceramic plate 2, and the temperature is about 250 ° C.
The α-ray shielding layer 5 is formed by heating and curing.

The base metal layer 8 is provided on the side surface portion 4 and the solder layer 10 is formed on the base metal layer 8 when the package base is sealed with the solder layers 9 and 10 formed on the lid 1. This is because the meniscus of the solder layer having a good shape can be obtained between the sealing surfaces of the package substrate, and the sealing property is improved.
However, the base metal layer 8 and the solder layer 10 on the side surface portion 4 are not always necessary.

A wide width portion and a narrow width portion of the metal layer are provided in the peripheral direction of the base metal layer 7 of the ceramic plate 2.
The solder layer 9 is provided on the base metal layer 7, and the solder layer on the wide portion of the base metal layer 7 has a thicker solder thickness than the solder layer on the narrow portion. The ridgeline of the solder layer between the portions is formed in a gentle curved shape.

In this embodiment, the peripheral corner portion (corner) 11
The metal layer width w ₂ is larger than the metal layer width w ₁ of the peripheral edge center portion (center portion between adjacent corners) 12. The metal layer width w ₂ of the peripheral corner portion 11 and the peripheral edge central portion 12
The metal layer width w ₁ is preferably formed such that metal layer width w ₂ / metal layer width w ₁ has a relationship of 1.1 to 1.7. The metal layer width w ₁ and the metal layer width w ₂ are continuously formed with a gradually changing width. For example, the metal layer width w ₁ is 1.8 mm, the metal layer width w ₂ is 2.5 mm, and both metal layer widths w ₁ and w ₂ are
Continue with a gentle arc and curve (see Fig. 1). Then, the solder layer 9 is formed on the upper surface thereof.

The metal layer widths w ₁ and w ₂ are defined as follows when the planar shape of the ceramic plate 2 is rectangular.
That is, in FIG. 4, a metal layer width w ₁ is the distance between the narrowest portion between the outer lines n _a and the inner line m _a underlying metal layer 7 at the peripheral edge center part 12a. Metal layer width w
_2, the extension line of the inner line m _b extension line r _a and the peripheral side 12b of the inner line m _a of the peripheral edge 12a of the underlying metal layer 7 r
intersection Q of the _point O _b intersects an outer line n _a or line S perpendicular to the extension P street underlying metal layer 7 a point O
And the distance is O-Q.

As shown in FIGS. 1 to 4, in the lid for a semiconductor chip housing package of this embodiment, first, the base metal layer 7a is provided on the peripheral corner portion 11 of the peripheral portion 3 of the ceramic plate 2, and The base metal layer 7 is formed on the peripheral central portion 12a.
b is provided. Here, the metal layer width w ₂ of the base metal layer 7a
Is wider than the metal layer width w ₁ of the base metal layer 7b.

Next, as described above, prior to the formation of the solder layer, a paste-like polyimide resin is screen-printed on the inside of the base metal layer 7 and heated to about 250 ° C.
The line shielding layer 5 is formed. That is, this α-ray shielding layer 5
At the portion of the ceramic plate 2 where the α-ray shielding layer 5 is formed,
As shown in FIG. 10, a metal plate 32 having an opening 31 in the shape of the α-ray shielding layer 5 made of the resin layer is used, and the metal plate 32 is used as the α-ray shielding layer 5 of the ceramic plate 2. Formed by superimposing it on the surface to be formed, positioning the opening 31 of the metal plate 32 at the position, screen-printing the paste-like polyimide resin with a squeegee 33, and further curing the polyimide resin. There is. Here, as the metal plate 32, it is preferable to use a Teflon-coated stainless steel plate having a thickness of about 80 μm to 200 μm.

Then, on the base metal layers 7a and 7b, a normal mesh plate is used to print or apply a solder paste having a uniform thickness in the same width as the base metal layer 7 by screen printing, and nitrogen is applied. 270 ° C or above in atmosphere, 20
Reflow under the condition of the second (maximum temperature: 310 ° C.). The solder layer can also be formed by an immersion method in which the lid 1 provided with the base metal layer 7 is immersed in a solder bath. Here, since the solder has a constant wetting angle with respect to the base metal layers 7a and 7b, the base metal layer 7a after the reflow or after the dipping is performed.
The solder layer thickness y ₁ on the base metal layer is thicker than the solder layer thickness x ₁ on the base metal layer 7b. Therefore,
The ridge of the solder layer 9 is the metal layer width w of the base metal layers 7a and 7b.
₂ , a curve formed according to w ₁ or a curve including a straight line portion is drawn (see FIG. 2).

According to the manufacturing method of the present embodiment, the difference in the solder thickness of the solder layer can be obtained by changing the metal layer width of the base metal layer 7 formed on the surface of the ceramic plate 2, and the production thereof. Will be easier. That is, since the wetting angle of the solder with respect to the underlying metal layer 7 is the same in terms of the physical properties of the solder, it is possible to increase the solder thickness of the solder layer by increasing the metal layer width of the underlying metal layer 7. A solder layer thickness gradient can be easily formed in the solder layer length direction (peripheral direction of the ceramic plate 2). By the way, in order to confirm the relationship between the metal layer width of the base metal layer 7 and the solder thickness of the solder layer, a solder layer is formed on the base metal layer 7 having a different metal layer width, and the solder layer is formed for each solder layer. When the solder thickness was examined, it was confirmed that the solder thickness difference was proportional to the metal layer width ratio of the base metal layer 7, as shown in FIG. Therefore, in the case of this embodiment, it is possible to obtain a ceramic lid having a desired thickness solder thickness gradient without adding a thickness gradient forming means.
Here, the solder layer 9 is preferably provided at a position where the inner end portion thereof cannot be directly viewed from the semiconductor chip 16 mounted on the semiconductor chip mounting portion 14 of the package base 13 to be sealed. In this embodiment, the solder layer 9 is provided at a position where it is pulled down from the semiconductor chip mounting portion 14. This is because the α rays are emitted not only from the ceramic plate 2 but also from the solder forming the solder layer 9, so that the α rays can be prevented from reaching the semiconductor chip 16 directly from the solder layer 9. However, it is considered that the semiconductor chip is prevented from malfunctioning due to α rays.

By the way, the difference in thickness between the solder thickness x ₁ and the solder thickness y ₁ of the solder layer is preferably 40 μm or more for a 25 mm × 25 mm ceramic plate. This is a numerical value obtained as a result of testing the relationship between the solder thickness difference of the solder layer and the solder scattering occurrence rate (splatter occurrence rate) (see FIG. 6). When the solder thickness difference is 20 μm, the solder scattering occurrence occurs. While the rate is as high as about 20%, the solder scattering rate is 0% when the solder thickness difference is 40 μm or more.
This is because it can be

Therefore, the peripheral central portion 12 of the base metal layer 7
Changing of the metal layer width w _1, the metal layer width w ₂ of the peripheral corner 11,
The solder thickness of the central portion 12 of the peripheral edge of the base metal layer 7 is 100 μm.
m, 150 μm, 200 μm metal layer width ratio (w ₂ /
The relationship between w ₁ ) and the difference in solder thickness between the peripheral side central portion 12 and the peripheral corner portion 11 was investigated. As a result, as shown in FIG.
In order to provide a good solder thickness gradient, the solder thickness difference should be 4
The metal layer width ratio (w ₂ / w ₁ ) is 1.
1 or more, and the metal layer width ratio (w ₂ / w ₁ ) is 1.
When it is 0 or less, a solder thickness difference of about 30 μm cannot be obtained, and when it is 1.8 or more, the solder is wasted and excess solder may enter the semiconductor chip mounting portion at the time of sealing. I knew that. Even when the thickness of the peripheral side central portion 12 is different, the metal layer width ratio (w ₂ / w ₁ ) is 1.1 to
It was confirmed that the range of 1.7 is preferable.
As a result, it has been found that under this condition, a good solder thickness difference can be obtained without wasting the solder. As described above, in this embodiment, since the metal layer width w ₂ of the peripheral corner portion 11 is wide and the metal layer width w ₁ of the peripheral side central portion 12 is narrow, When stopping, the amount of solder in the solder layer in the central portion 12 of the peripheral side can be reduced,
Since it is possible to minimize the influence of the package base on the semiconductor chip mounting portion, it is possible to reduce the shape of the lid itself.

Next, a method of sealing the package base using the lid 1 described above will be described. First, as shown in FIG. 7, a metallization layer 19 is formed on the package base 13 at a position corresponding to the solder layer 9 of the lid 1. The metallized layer 19 is usually formed by applying Ni plating to a sintered body layer of W, Mo or the like, and then subjecting it to Au plating. The semiconductor chip 16 is bonded and mounted on the semiconductor chip mounting portion 14 of the package substrate 13 with a die attach agent, and the wire bonding wire 17 is used to electrically connect the semiconductor chip 16 to the external connection terminal 15.
Bonding is performed on the bonding pattern 18 connected to Next, the lid 1 is placed with the solder layer 9 side facing down, and the lid 1 is pressed and set via a spring, a clip, etc., and then placed in a furnace at 280 to 320 ° C., and the solder layer 9 melts. , The package base 1 by the solder
The semiconductor chip mounting locations 14 of 3 can be sealed. here,
By the heating, the solder layer 9 is melted and gas is generated from the polyimide resin forming the α-ray shielding layer 5, so that the amount of internal gas between the package base 13 and the lid 1 is increased and the internal pressure is increased. However, when the solder layer 9 is set, only the solder layer 9a portion of the peripheral corner portion 11 having a thick solder thickness is in contact with the package base 13, but the temperature rise due to heating causes the solder layer 9a Due to the solder thickness gradient, the solder wets and spreads on the solder layer 9b of the peripheral edge central portion 12 having a small solder thickness, and the peripheral edge central portion 12 is gradually closed, and the increased internal gas in the package base 13 is smoothly released into the atmosphere. It is discharged inside, and when it is closed, the narrow portion of the seal path disappears, and good sealing can be performed.

From the above experimental results, a wide portion and a narrow portion are provided in the width of the base metal layer on the upper surface of the peripheral portion of the ceramic plate, and the metal layer width w _{1 of the} narrow portion and the metal layer width w _{2 of the} wide portion are provided.
It was confirmed that a solder layer having a good solder thickness gradient can be accurately obtained when w ₂ / w ₁ = 1.1 to 1.7.

Further, using a metal plate having an opening in the shape of the α-ray shielding layer on a ceramic plate (Al ₂ O ₃ ), printing pressure: 1.2 kg / cm ² , squeegee speed: 1
The polyimide resin paste was screen-printed at 0 cm / sec and further heated and cured to measure the α dose of the lid having a 45 μm thick α-ray shielding layer. Here, as the polyimide resin paste, boilimide resin: 20% by weight, solvent (N-methyl-2-pyrrolidone): 80% by weight, and a viscosity of 10,000 to 25
A resin paste adjusted to 000 CPS was used, and a metal plate having a metal thickness of 0.1 mm was used.
Then, as a result of the measurement, in the case of a normal ceramic plate (Al ₂ O ₃ ) not provided with an α-ray shielding layer, 0.03 ct /
cm ² Hr level α dose is 0.001ct / c
It was confirmed that the m ² Hr level could be reduced. Also,
In the semiconductor package using the lid of this embodiment, the occurrence rate of malfunction of the semiconductor chip can be reduced. In addition, in addition, the α-ray shielding layer was formed by screen printing using a conventional stainless steel mesh plate (mesh size: 80 M), and the α-ray dose was similarly measured. As a result, the α dose was 0.00
The level was 5 ct / cm ² Hr. It is considered that this is because voids are generated in the formed α-ray shielding layer at the grid points of the mesh of the mesh plate when the resin paste is screen-printed. In this way, when the α-ray shielding layer is formed on the lid by screen-printing using the metal plate having the opening in the shape of the α-ray shielding layer made of the resin layer, the α-ray shielding effect is excellent. It was confirmed that an α-ray shielding layer could be formed.

-Embodiment 2-As shown in FIGS. 8 and 9, the semiconductor package lid 21 of this embodiment has one side (inner side) of the ceramic plate 22.
A base metal layer 27 is provided on the peripheral edge portion 23 of the substrate, a base metal layer 28 is provided on the side surface portion 24, and a solder layer 29 as a sealing member is provided on the base metal layer 27. A solder layer 30 is provided on the top. Also, α
A polyimide resin layer 25, which is a line shielding material, is provided inside the solder layer 29.

The ceramic plate 22 has a rectangular shape in plan view, and as shown in FIGS. 8a, 9a and 9b, the thickness of the solder layer 29b on the two opposite sides is the same as that of the solder layer 2 on the other two sides.
9a, which is thinner than the thickness of 9a, or in FIGS.
As shown in c and d, the thickness of the solder layer 29b on one side is set to be smaller than the thickness of the solder layer 29a on the other three sides.

The lid 21 for the semiconductor package of this embodiment
Copes with the difference in the thickness of the solder layer 29 having a constant wetting angle with respect to the base metal layer 27, and the metal layer width w ₁ of the base metal layer 27b on one side of the ceramic plate 22 or on the opposite two sides. Is narrower than the metal layer width w ₄ of the base metal layer 27a on the other 3 or 2 sides. Then, as in the case of Example 1, first, the α-ray shielding layer 25 made of polyimide resin is formed inside the solder layer 29. Next, the base metal layer 27
It is manufactured by screen-printing a paste containing solder on a and 27b and reflowing in a nitrogen atmosphere at 270 ° C. or higher for 20 seconds (maximum temperature: 310 ° C.).
Here, since the solder has a certain amount of wetting with respect to the base metal layer 27, as described in the first embodiment, the solder layer 29 on the base metal layer 27a after the reflow process.
The solder thickness y _{2 of a} is the solder layer 2 on the base metal layer 27b.
It is formed thicker than the solder thickness x _{2 of} 9b. The lower limit of the thickness difference between the solder thickness y ₂ of the solder layer 29 and the solder thickness x ₂ and the metal layer width ratio (w
The appropriate range of ₄ / w ₁ ) is the same as in Example 1 and is 40 μm or more and 1.1 to 1.7, respectively.

In the semiconductor package lid 21 according to the present embodiment, the solder layer 29 is set on the package base in the same manner as in the case of the first embodiment, and the temperature of the solder layer 29 is increased by heating so that the solder in the solder layer 29a portion is removed. Due to the difference in the solder thickness, the solder layer 29b having a small solder thickness wets and spreads and gradually closes, and the internal gas in the package base such as gas generated from the polyimide resin is smoothly discharged to the atmosphere.

Therefore, according to the semiconductor package sealing lid of the present embodiment, the solder layer is provided with the thick solder portion and the thin solder portion and the solder thickness gradient in the peripheral direction is provided. By causing a positional shift in the timing of sealing the package base and the ceramic lid,
The gas generated by the internal pressure and the gas generated from the α-ray shielding layer can be smoothly released to the outside. In addition, the amount of gas trapped inside can be reduced. this is,
When the package base and the ceramic lid are sealed, the solder thickness gradient causes the solder to spread to a thinner part than a thicker part, so that gas escapes from the gap between the solder layer of the lid and the package base during that time. This is because. Therefore, it is possible to prevent the scattering of the solder when the package is sealed, and it is possible to prevent foreign matter from adhering to or contamination of the package substrate, pins, or the like. Further, in the case of the package using the lid for sealing the semiconductor package of this embodiment, since the above-described effects are obtained, it is possible to obtain the semiconductor device having good sealing property, and at the same time, the α rays emitted from the lid are Since it is shielded by the α-ray shielding layer provided on the inner surface thereof, the semiconductor chip can reduce the occurrence of malfunctions (soft errors) due to α-rays.

It should be noted that the present invention is not limited to the above description of the embodiments, and it is obvious that the present invention includes configurations that can be modified and implemented without changing the gist of the present invention.
Incidentally, in the above-described first embodiment, the ridgeline between the thick solder portion and the solder thin portion of the solder layer has been described as being curved, but it may be linear. . Further, in the above-described embodiment, the solder thickness of the peripheral corner portion of the ceramic lid is described as being thicker than the solder thickness of the peripheral side portion. As a matter of course, the thick portion may be formed at any one of 1 to 3 places on the peripheral portion, or may be formed at 5 or more places.

Further, in the above-described first embodiment, the metal layer width of the base metal layer at the corner portion of the ceramic plate is wider than the metal layer width at the central portion. Of course, the width may be wider than the width of the metal layer in the corner portion. As the ceramic plate, a flat rectangular insulating substrate is used, and the narrow width portion w ₁ and the wide width portion w are provided on each of the four base metal layers of the peripheral edge portion.
₂ is provided, but the narrow width portion w ₁ and the wide width portion w ₂ are
The structure may be provided only on the side and the other side may be a normal pattern. Furthermore, the ceramic plate may have a configuration using a planar polygonal shape (triangular shape, pentagonal shape, etc.) other than a quadrangle, and a circular insulating base.

[0040]

As is apparent from the above description, according to the lid for encapsulating a semiconductor package of claim 1 of the present invention,
By providing an α-ray shielding layer made of a resin layer such as a polyimide resin for shielding α-rays emitted from the ceramic plate inside the solder layer on the inner surface of the ceramic plate forming the lid, The amount of emitted α-rays can be reduced, and when the semiconductor package is sealed, gas is also generated from the α-ray shielding layer to increase the internal gas at the semiconductor chip mounting portion of the package base. By providing the solder layer on the peripheral portion of the ceramic plate with a thick solder layer portion and a thin solder layer portion in the peripheral direction, and by providing a thickness gradient or a thickness difference in the solder layer, the increased internal gas is discharged to the outside of the semiconductor package. It has the effect that it can be discharged and the airtight sealing can be performed accurately.

According to the lid for encapsulating a semiconductor package of claim 2 of the present invention, in addition to the effect of claim 1, the lid has a rectangular shape, and the solder layer is provided on one side of the ceramic plate or on two opposite sides. Is thinner than the thickness of the solder layer on the other three sides or two sides, and there is no thickness difference in the solder layer on each side, so that the solder layer can be easily formed.

According to the semiconductor package of claim 3 of the present invention, by using the lid for sealing the semiconductor package, a hermetically sealed semiconductor device can be obtained and a semiconductor mounted by α-rays. This has the effect of preventing malfunction of the chip.

Further, according to the method for forming an α-ray shielding layer of the lid of the present invention, the α-ray shielding layer is formed by using the screen printing method, so that the α-ray shielding layers have a uniform thickness and are adjacent to each other. Since a predetermined clearance can be maintained between the solder layer and other patterns and a metal plate having an opening in the shape of a resin layer provided on the lid is used as the screen, the resin layer When screen-printing a resin paste for forming a film, unlike a mesh plate used in normal screen-printing, it has an effect that a void-free α-ray shielding layer can be formed at a portion corresponding to a lattice point of the mesh. .

[Brief description of drawings]

FIG. 1 is a plan view of a surface of a lid for encapsulating a semiconductor package of an embodiment of the present invention on which a solder layer and an α-ray shielding layer are provided.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along the line A′-A ′ of FIG.

FIG. 4 is a partially enlarged view for explaining measurement positions of a metal layer width w ₁ and a metal layer width w ₂ .

FIG. 5 is a graph illustrating the relationship between the width ratio w ₂ / w _{1 of the} underlying metal layer and the solder layer thickness difference.

FIG. 6 is a graph illustrating a relationship between a solder layer thickness difference and a solder scattering occurrence rate (splatter occurrence rate).

FIG. 7 is a cross-sectional view of a semiconductor package of the present invention in a sealed state.

FIG. 8 is a plan view showing a solder layer and an α-ray shielding layer of a lid for sealing a semiconductor package according to another embodiment of the present invention.

9a, 9b, 9c, 9d are respectively shown in FIG.
FIG. 7 is a sectional view taken along line EE, FF, GG, and HH of FIG.

FIG. 10 is a side view and a plan view of a metal plate for providing an α-ray shielding layer on a lid.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lid for semiconductor package, 2 ... Ceramic plate, 3 ... Peripheral part, 4 ... Side part, 5 ... Alpha ray shielding layer, 7, 8 ... Base metal layer, 9 , 10 ... Solder layer, 11 ... Perimeter corner of ceramic plate,
12 ... Central part of peripheral edge (center part between adjacent corners),
12a, 12b ... Central part of peripheral edge, 13 ... Package base, 14 ... Semiconductor chip mounting part, 15 ...
External connection terminals, 16 ... Semiconductor chip, 17 ... Wire bonding wire, 18 ... Bonding pattern, 19 ... Metallization layer, 21 ... Semiconductor package lid, 22 ... Ceramic plate, 23 ...
Peripheral part, 24 ... Side part, 25 ... Polyimide resin layer (α-ray shielding layer), 27, 28 ... Base metal layer, 2
9, 30 ... Solder layer, 31 ... Opening portion, 32 ...
Metal plate, 33 ... Squeegee, w ₁ , w ₂ , w ₄ ...
・ Base metal layer width, n _a ... Outer line, m _a ... Inner line, r _a ... Extension line of inner line, m _b ...
Inside Line, r _b ··· the extension of the inside line, O ···
The intersection of the extension line r _a and the extension line r _b, P ··· extension of the outer line, S · · · intersection O and vertical lines the extension of the outer lines, Q · · · line S and the outer line Intersection of the extension lines of
y ₁ , y ₂ , x ₁ , x ₂ ... Solder layer thickness

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ritsunobu Omoto 2701-1 Iwakura, East branch, Omine Town, Mine City, Yamaguchi Prefecture Sumitomo Metal Ceramics Co., Ltd.

Claims (4)

[Claims] 1. A semiconductor package for encapsulating a semiconductor chip mounted on a semiconductor chip mounting portion of a semiconductor package base, comprising a solder layer on an inner peripheral edge or a peripheral edge and a side surface of a ceramic plate via a base metal layer. In the sealing lid, at least one side of the solder layer at the peripheral portion includes a thick portion and a thin portion of the solder layer in the peripheral direction of the ceramic plate, and a portion between the thick portion and the thin portion of the solder layer is provided. The ridge line is formed in a curved line or a straight line, and an α-ray shielding layer made of a resin layer such as a polyimide resin for shielding α-rays emitted from the ceramic plate inside the solder layer on the inner surface of the ceramic plate A lid for encapsulating a semiconductor package, wherein the lid is provided. 2. A semiconductor package encapsulating lid for encapsulating a semiconductor chip to be mounted on a semiconductor chip mounting portion of a semiconductor package base, wherein a solder layer is provided on a peripheral portion of an inner surface of a ceramic plate via a base metal layer. The solder layer at the peripheral edge of one side or two opposite sides is thinner than the thickness of the solder layer at the other three sides or two sides, and is discharged from the ceramic plate to the inside of the solder layer on the inner surface of the ceramic plate. To α
A lid for encapsulating a semiconductor package, wherein an α-ray shielding layer made of a resin layer such as polyimide for shielding rays is provided. 3. A base metal layer of a lid for encapsulating a semiconductor package having a base metal layer on the inner peripheral edge of the ceramic plate, or on the peripheral edge and side surfaces, and a semiconductor chip mounting portion inside the lid. In a semiconductor package in which a solder layer is airtightly sealed between a metallization layer of a semiconductor package base having a metallization layer at a portion corresponding to the underlying metal layer in the peripheral edge of the semiconductor package, a periphery of the semiconductor package sealing lid. Of the base metal layer has a wide portion and a narrow portion in the peripheral direction of the lid, and polyimide for shielding α rays emitted from the ceramic plate inside the solder layer on the inner surface of the ceramic plate. A semiconductor package comprising an α-ray shielding layer made of a resin layer such as a resin. 4. A method for forming an α-ray shielding layer made of a resin layer such as a polyimide resin provided on the lid according to any one of claims 1 to 3, wherein the ceramic plate after firing comprises: A metal plate having an opening having the shape of the resin layer to be formed is superposed on a portion where the resin layer is formed, a resin paste such as a polyimide resin is screen-printed on the metal plate, and the printed resin is then printed. A method for forming an α-ray shielding layer of a lid, which comprises forming the α-ray shielding layer by curing the paste.