Semiconductor device package and sealing method therefore

Abstract: This invention relates to a semiconductor device package (1), ccmprising a carrier body (2) which is to be mounted with a semiconductor device (4) and which has an annular adhesion layer formed thereon, a cap (3) which is to be adhered to the carrier body (2) to hermetically seal the carrier body (2), and an adhesive applied between the adhesion layer of the carrier body (2) and the cap (3) and hardened after at least one of the carrier body (2) and the cap (3) is pivoted to be coaxial with the adhesion layer. With this arrangement, voids can be eliminated from the adhesive, and a sealing property of the package can be improved.

Description: Background of the Invention (Field of the Invention) The present invention relates to sealing apparatus and a sealing method according to the preamble of claims 1 and 12, respectively. Such a sealing apparatus and sealing method is known from EP 0 203 589 A3. Here a table and a lid holding jig are moved relative to each other, whilst an adhesion layer is disposed therebetween. First the lid holding jig is lowered with respect to the table that supports the package body and then a solder is melted while the gaps between a seal portion of the package body and a seal portion of the lid is so adjusted that the seal portions of the package body and the lid may be in contact with each other through the melted solder. Subsequently the seal portions are cooled down. Despite the sealing apparatus allowing for the relative movement of the lid holding jig and the table relative to each other for bringing them into contact voids tend to be left in a hermetic seal portion as an overlapping portion between the lid and the adhesion solder layer of the package body. JP-013-087 describes a semiconductor pressure sensor, wherein a lid is adhered to a substrate body by means of an interposing metal layer and a solder made from Au-Sn. The substrate body and the lid as well as the intermediate Au-Sn type solder exhibit an annular shape. JP 013-046 describes a sealing method for adhering the ceramic cap to a vessel. Between the ceramic cap and the vessel there are interposed in succession a sintered metallic layer composed of W, Mo and Ni metallic layer shaped to the upper section of the sintered metallic layer, an Sn metallic layer and an Au metallic layer. When arranged in a sealing jig and heated in a furnace having a reducing or neutral atmosphere, an Au-Sn alloy layer, in which the Sn metallic layer and the Au metallic layer are diffused and melted mutually, is formed. Here, the Sn metallic layer and the Au metallic layer act as a solder material for adhering the ceramic gap to the vessel. In the following paragraphs first typical problems with an hermetic seal of a semiconductor device chip together with an inert gas in a package body upon adhesion of a lid to the package body with an adhesive shall be described. A semiconductor device package generally comprises a rectangular package body and a rectangular lid adhered to it. In a conventional semiconductor device package, an adhesive is applied to an adhesion layer (plating layer) of a package body, a lid is urged against a package body while the entire structure is being heated to perform an adhesion operation. By this operation, the hermetic seal of the package body can be achieved, and the semiconductor device chip is sealed in the package. In this case, a sealing solder is generally used as an adhesive. The hermetic seal of the package is performed to protect semiconductor device chips from contamination sources (e.g., dust, chemicals, gases, and humidity) which adversely affect semiconductor device chip and from mechanical damage. Each semiconductor device chip must be, therefore, sealed in a package with an inert gas and must be protected with the inert gas. In a conventional method of adhering a lid with an adhesive while being heated under pressure, voids tend to be left in a hermetic seal portion, as an overlapping portion between the lid and the plating layer (adhesion layer) of the package body. A sealed gas inside the package tends to leak through the seal portion, thus causing sealing defects. The width of the seal portion must be minimized in consideration of swelling of the adhesive. In a recent compact package in which a LN (Low-Noise) FET or the like is mounted, the seal portion is getting short. For this reason, seal portion defects tend to frequently occur and become a cause for decreasing a semiconductor device product yield. Summary of the Invention Therefore, it is the object of the present invention - to provide a sealing apparatus and a sealing method, capable of improving the adhesion strength between the package body and the lid and the uniformity of the eutectic reaction, thus creating a seal portion between the lid and the package body having less defects. This object is solved by a sealing apparatus of claim 1 and a sealing method of claim 12. According to the invention a rotational movement of the lid with respect to the package body is caused, whilst simultaneously urging the package body against the lid. This allows for a scrubbing to break the surface oxide film formed on the preform, such as Au, Sn. Further advantageous embodiments may be taken from the dependent claims. With the present invention, there is obtainable a semiconductor device package comprising: a package body in which a semiconductor device chip are mounted; a lid adhered to the package body for hermetical sealing of the package body: an annular adhesion layer being formed on the package body, the adhesion between the package body and the lid being performed by applying an adhesive between the annular adhesion layer and the lid, and the hardening the applied adhesion after at least one of the package body and the lid is pivoted to be coaxial with the adhesion layer. In one aspect of the present invention, there is provided a sealing apparatus for a semiconductor device package, for hermetically sealing a package body mounted with a semiconductor device chip after a lid is adhered to an annular adhesion layer formed on the package body by using an adhesive, comprising: a table for supporting the package body; a lid holding jig for holding the lid; urging means for vertically moving the table and/or the lid holding jig such that at least one of the package body and the lid urges the other of the package body and the lid; and means for rotating the table and/or lid holding jig such that at least one of the package body and the lid is rotated to be coaxial with the annular adhesion layer. In another aspect of the present invention, there is provided a sealing method for a semiconductor device package, comprising: the first step of mounting a semiconductor device chip on a package body having an annular adhesion layer formed thereon and of applying an adhesive to the adhesion layer; the second step of urging at least one of the package body and lid for hermetically sealing the package body against the other of the package body and the lid; and the third step of rotating at least one of the package body and the lid to be coaxial with the adhesion layer. The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention. Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. Brief Description of the Drawings Fig. 1 is a sectional side view of a semiconductor device package obtainable using a sealing apparatus or method the present invention; Fig. 2 is a plan view showing a package body for a semiconductor device package shown in Fig. 1; Fig. 3 is an enlarged sectional view showing an adhesion state between a lid and a package body in the semiconductor device package shown in Fig. 1; Fig. 4 is a partially sectional side view of a sealing apparatus for a semiconductor device package according to an embodiment of the present invention; and Fig. 5 is a plan view showing an overall structure of the sealing apparatus for a semiconductor device package according to the embodiment of the present invention. Description of the Preferred Embodiment A compact ceramic package obtainable with the embodiments of the present invention will be described with reference to Figs. 1 to 3. As shown in Figs. 1 and 2, a package 1 comprises a package body 2 for carrying a semiconductor device chip 41 and a lid 3 for sealing the semiconductor device chip 41 in the package body 2. This hermetic seal is performed by adhering the lid 3 to the package body 2. Six leads are separately provided on the both sides of the package body 2. Each lead 4 is formed by coating gold (Au) on an iron-nickel (Fe/Ni) alloy plate. The distal end of an inner lead 4a of each lead 4 and each bonding pad 42 of the semiconductor device chip 41 are electrically connected by the wire bonding of an Au wire 5. As shown in Fig. 3, an annular plating layer 12 constituting an adhesion layer for adhering the lid 3 is formed on the upper edge of the package body 2. The plating layer 2a comprises a nickel (Ni) plating layer 12a and a gold (Au) plating layer 12b formed on the Ni plating layer 12a. Similarly, an annular plating layer 13 consisting of an Ni plating layer 13a and an Au plating layer 13b is formed on the lower edge of the lid 3. Prior to sealing of the package body 2, a seal-like adhesive (sealing solder) 10 is placed on the plating layer 12. The adhesive 10 consists of a eutectic alloy such as a gold/tin (Au/Sn) alloy. The plating layer 12 has almost the same shape as the plating layer 13. The package body 2 is adhered to the lid 3 as follows. The adhesive 10 is interposed between the plating layers 12 and 13, and the plating layer 12 of the package body 2 is urged against the plating layer 13 of the lid 3 while the lid 3 is being heated. In this case, the adhesive 10 is melted between the plating layers 12 and 13 to form an annular seal portion 51 consisting of eutectic bonds. In this state, at least one of the package body 2 and the lid 3 is pivoted to be coaxial with the plating layers 12 and 13, thereby completing adhesion. By this pivotal movement, the plating layer 12 of the package body 2 can be perfectly adhered to the plating layer 13 of the lid 3 to eliminate voids from the seal portion 51. The outer dimensions of the lid 3 are slightly smaller than those of the package body 2. Therefore, sagging of the molten adhesive 10 and projections of the hardened adhesive on the side surfaces of the package body 2 can be prevented. A package sealing apparatus according to an embodiment of the present invention will be described with reference to Figs. 4 and 5. This package sealing apparatus comprises a table 21 and a collet 22 including a heating element. The package body 2 is placed at the center of the table 21, and the lid 3 is held by the collet 22. The table 21 is arranged to be rotatable, and the lower surface of the table 21 is connected to a link mechanism 23 eccentric from a rotating shaft 21a of the table 21. The link mechanism 23 comprises an arm 24 and a disc 25. A motor 26 is connected to the disc 25 to rotate the disc 25. The link mechanism 23 is driven upon rotation of the motor 26, and then the table 21 is rotated. In this embodiment, the motor 26 is rotated by two revolutions, and the table 21 is then reciprocated twice within an angle of 30°. A recessed chuck portion 22a is formed in the lower surface of the collet 22. The chuck portion 22a is connected to a vacuum pump 27. The lid 3 is chucked in vacuum by the chuck portion 22a of the collet 22 and is conveyed onto the package body 2. A hydraulic actuator 28 is connected to the upper end of the collet 22, and the lid 3 which has conveyed onto the package body 2 is urged against the package body 2 by the hydraulic actuator 28 during adhesion. In addition, since the collet 22 includes a heating element, the lid 3 is heated to be 300°C during adhesion. The package body 2 and the lid 3 which are set on the table 21 are stored together with the lower portion of the collet 22 in a chamber 29 provided on the table 21. Nitrogen gas (N₂) or a mixture of nitrogen and hydrogen gases (N₂ + H₂) is supplied to the chamber 29 as a sealing gas. The adhesion operation is performed in an inert gas (sealing gas) atmosphere. When the package body 2 is hermetically sealed by the above adhesion operation, the semiconductor device chip 41 sealed inside the package 1 is kept in an inert condition by such a sealing gas. As shown in Fig. 4, the collet 22 and the hydraulic actuator 28 are fixed on a support plate 30. This support plate 30 is mounted at the distal end of a support arm 31 shown in Fig. 5. The support arm 31 is fixed on a vertical pivot shaft 33, and a counterbalance 32 is mounted at the base end portion of the pivot shaft 33. A gear 33a is formed at the lower portion of the vertical pivot shaft 33 and is meshed with an output gear 34a of a drive motor 34. Upon forward or reverse rotation of the drive motor 34, the support arm 31 is pivoted between a position of the table 21 and a feed position of the lid 3. A convey path 35 is formed at the feed position of the lid 3, so that the lid 3 is continuously fed along the convey path 35. The sealing method of the invention with respect to the afore described package sealing apparatus will be further described below. The collet 22 which receives the lid 3 at the position of the convey path 35 is moved to the position of the table 21 by the drive motor 34. The package body 2 having the adhesive 10 is placed on the table 21. The collet 22 is driven to coaxially align the plating layer 13 of the lid 3 with the plating layer 12 of the package body 2. When this positioning is completed, the hydraulic actuator 28 is driven to move the collet 22 downward, thereby covering the lid 3 on the package body 2 so as to interpose the adhesive between the plating layers 12 and 13. Meanwhile, the lid 3 and the adhesive are heated to 300°C by the collet 22, and N₂ gas or the like is supplied to the chamber 29. The lid 3 is urged against the package body 2 by the hydraulic actuator 28. When the adhesive 10 is melted by heat, the table 21 is pivotally reciprocated twice, thereby completing the adhesion operation. When the plating layers 12 and 13 have an annular shape and the package body 2 is pivoted twice during adhesion, the plating layers 12 and 13 are perfectly adhered to each other. As a result, voids can be eliminated from the seal portion 51, and a sealing property of the package 1 can be improved. In this embodiment, the package body 2 had a size of 1.5 mm X 1.5 mm, and each of the plating layers 12 and 13 had an outer diameter of 1.3 mm and an inner diameter of 1.1 mm. A preformed body of an Au/Sn eutectic alloy (thickness : 30 µm) was used as the adhesive 10. In this embodiment, the table 21 is provided. However, the collet 22 may be pivoted. Alternatively, the table 21 and the collet 22 may be pivoted relative to each other. In this case, as a means for pivoting the table 21 and the collet 22, for example, a stepping motor may be used in place of a link mechanism used in this embodiment.

Claims: A sealing apparatus for hermetically sealing a lid (3) and a semiconductor package body (2) by means of an interposing adhesion layer (10, 12, 13), comprising (a) a table (21) for supporting said package body (2); (b) a lid holding jig (22) for holding said lid (3); and (c) a movement means (28) for moving said lid holding jig (22) and said table (21) relative to each other, such that said package body (2) and said lid (3) can be brought into contact having said adhesion layer (10, 11, 12) disposed therebetween; characterized in that (d) said movement means (28) is further provided for urging said lid (3) held by said lid holding jig (22) against said package body (2) supported by said table (21) relative to each other; (e) said adhesion layer has an annular shape; and (f) rotation means (23-26) are provided for rotating said table (21) and said lid holding jig (22) relative to each other such that at least one of said package body (2) and said lid (3) is rotated coaxially to said annular adhesion layer (10, 12, 13). The sealing apparatus according to claim 1, characterized in that said rotation means are provided for rotating said table (21) and said lid holding jig (22) coaxially to said annular adhesion layer (10, 12, 13). The sealing apparatus according to claim 1 or 2, characterized in that said adhesion layer (10, 12, 13) comprises (a) a first plating layer (12) formed on said package body (2) and including a nickel (Ni) plating layer (12a) and a gold (Au) plating layer (12b) formed on said nickel plating layer (12a); (b) a second plating layer (13) formed on said lid (3) and including a nickel (Ni) plating layer (13a) and a gold (Au) plating layer (13b) formed on said nickel plating layer (13a); and (c) an adhesive (10) placed on the first plating layer (12) and consisting of a gold/tin (Au/Sn) eutetic alloy. The sealing apparatus according to claim 3, characterized in that said first and second plating layers (12, 13) have the same annular shape. The sealing apparatus according to anyone of the preceding claims, characterized in that said lid holding jig (22) comprises a collet for chucking said lid (3) in vacuum. The sealing apparatus according to anyone of the preceding claims, characterized in that said movement means (23-26) comprise a hydraulic actuator. The sealing apparatus according to anyone of the preceding claims, characterized in that said movement means (23-26) comprise a link mechanism (23). The sealing apparatus according to anyone of the preceding claims, characterized in that said movement means (23-26) comprise a motor (26). The sealing apparatus according to anyone of the preceding claims, characterized by a sealing gas supply chamber (29) for housing said package body (2) and said lid (3). The sealing apparatus according to claim 9, characterized in that said sealing gas supply chamber (29) is provided for containing a hydrogen and nitrogen inert gas atmosphere. The sealing apparatus according to anyone of the preceding claims, characterized by additional movement means (28) provided for moving said lid holding jig (22) and said table (21) relative to each other in a vertical direction. A sealing method for hermetically sealing a lid (3) and a semiconductor package body (2) by means of an interposing adhesion layer (10, 12, 13), comprising the steps of (a) forming an adhesion layer (10, 12, 13) on said package body (2); and (b) moving said lid (3) and said package body (2) relative to each other, having said adhesion layer (10, 12, 13) disposed therebetween; characterized by (c) urging said package body (2) and said lid (3) relative to each other for hermetically sealing said package body (2) and said lid (3) against each other; and (d) rotating said package body (2) and said lid (3) relative to each other; wherein (e) said adhesion layer (10, 12, 13) is being formed so as to have an annular shape; and (f) at least one of said package body (2) and said lid (3) is being rotated to be coaxial with said annular adhesion layer (10, 12, 13). The sealing method according to claim 12, characterized in that forming of the adhesive layer (10, 12, 13) comprises the following steps: (a) forming on said package body (2) a first plating layer (12) including a nickel (Ni) plating layer (12a) and a gold (Au) plating layer (12b) formed on said nickel plating layer (12a); (b) forming on said lid (3) a second plating layer (13) including a nickel (Ni) plating layer (13a) and a gold (Au) plating layer (13b) formed on said nickel plating layer (13a); and (c) placing on the first plating layer (12) an adhesive (10 consisting of a gold/tin (Au/Sn) eutetic alloy. The sealing method according to claim 13, characterized in that said first and second plating layers (12, 13) are formed so as to have the same annular shape. The sealing method according to anyone of the claims 12 to 14, characterized in that an adhesive (10) of said adhesive layer (10, 12, 13) hardens after at least one of said package body (2) and said lid (3) is pivoted. The sealing method according to anyone of the claims 12 to 15, characterized in that said lid (3) is being heated while said package body (2) and said lid (3) are urged against each other whereby the adhesive (10) of said adhesive layer (10, 12, 13) melts. The sealing method according to claim 16, characterized in that relative rotation between said package body (2) and said lid (3) is performed after said adhesive (10) starts melting. The sealing method according to anyone of the claims 12 to 17, characterized in that the adhesion operation is carried out in a hydrogen and nitrogen inert gas atmosphere. The sealing method according to anyone of the claims 12 to 18, characterized in that said lid (3) and said package body (2) are urged relative to each other by moving them relative to each other in a vertical direction.

Inventors: NISHIGUCHI MASANORI C O YOKOHA, NISHIGUCHI, MASANORI, C/O YOKOHAMA WORKS OF
Applicants: SUMITOMO ELECTRIC INDUSTRIES, SUMITOMO ELECTRIC INDUSTRIES, LTD.
Application year: 1990
Main classification: H01L23
IPC codes: H01L23, H01L21