JP2002033408A - Package for semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a void from being formed at a joint to lower the joining strength or disable airtight sealing when the peripheral edge of a lid is joined with the top surface of a frame by seam welding. SOLUTION: The mathematical mean roughness Ra of the peripheral edge of one main surface A of the lid 3 is <=3.0 μm, and the peripheral edge of the other main surface B is made thin by etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package for accommodating a semiconductor element, and more particularly to an improvement in a mounting structure of a metal lid welded to seal a semiconductor element in the package for a semiconductor element. is there.

[0002]

2. Description of the Related Art Conventionally, a field-effect transistor, a power transistor or an MMIC (Monolithic Micr) has been used.
As shown in FIG. 6, a semiconductor element housing package (hereinafter, referred to as a semiconductor package) for housing a semiconductor element operating at a high frequency such as an Owave IC) is made of an electrically insulating material such as an aluminum oxide sintered body. A substrate 1 comprising
It is attached to the upper surface of the base 1 through a brazing material so as to surround the mounting portion of the semiconductor element 4 and is made of iron (Fe) -nickel (N
i) Notch made of an alloy such as -cobalt (Co) alloy or iron (Fe) -nickel (Ni) alloy and having a ceramic input / output terminal 6 on which a metallized wiring layer 7 is formed, provided in advance on a side portion Alternatively, a metal frame 2 fitted in the through hole, and Fe-Ni bonded to the upper surface of the frame 2
A semiconductor package comprising a metal lid 3 made of a -Co alloy or the like has been proposed (JP-A-11-12683).
No. 7).

The semiconductor element 4 is accommodated in the semiconductor package, and each electrode of the semiconductor element 4 is connected to the metallized wiring layer 7 of the input / output terminal 6 via the bonding wire 11. A metal lid 3 is welded to the upper surface by a seam welding method, and the semiconductor element 4 is accommodated in a container formed of the base 1, the frame 2, and the lid 3 and hermetically sealed, so that a final product is obtained. Become an electronic device. As such an optical semiconductor module having the same configuration as that of FIG. 6, there is known an optical semiconductor module in which a metal airtight cap is joined to the upper surface of a metal frame by seam welding (Japanese Patent Application Laid-Open No. 8-94888). Gazette).

In the above-described seam welding method, as shown in FIG. 5, the roller electrode 10 having a truncated cone shape is rolled while being brought into contact with the peripheral edge of the upper surface of the lid 3, and current is applied through the roller electrode 10. It flows from the lid 3 to the frame 2, and at this time, a Ni plating layer previously formed on the contact between the lid 3 and the frame 2 just below the roller electrode 10 is generated by Joule heat generated at the contact. This is a method in which the lid 3 is welded to the frame 2 by melting and the like to form a bonding layer again.
In this seam welding method, heat generated when welding the entire circumference of the lid 3 is limited to the vicinity of the contact portion of the roller electrode 10, and the heat is quickly transmitted to the base 1 via the frame 2. Is done. As a result, the semiconductor element 4 mounted in the semiconductor package does not suffer from thermal destruction or the like, so that the joining method of the lid 3 has been frequently used in recent years.

[0005] The metal lid 3 has relatively smooth surface properties on both main surfaces by a forming method such as roll rolling. Further, as shown in Japanese Patent Application Laid-Open No. 8-94888, the peripheral portion of the main surface of the lid 3 on the side joined to the upper surface of the frame 2 forms a thin portion 9 by etching.

The reason why the thin portion 9 is formed on the peripheral portion of the lid 3 is to reduce the cross-sectional area of the cross section of the peripheral portion of the lid 3 viewed from the plane direction (X direction), as shown in FIG. By doing so, the electric resistance in the surface direction of the peripheral portion of the cover 3 is increased to reduce the current flowing from the roller electrode 10 to the center side of the main surface of the cover 3, and the X direction of the peripheral portion of the cover 3 Can be several times or more the cross-sectional area in the X direction when viewed from a direction Y (a direction perpendicular to the main surface), which can reduce the electric resistance. This is because the current flowing in the direction (downward) of the frame 2 having a small resistance can be increased. Thereby, a large Joule heat can be generated at the contact portion between the lid 3 and the frame 2.
Further, there has been proposed a configuration in which a step is formed by forming a thin portion on a peripheral portion of the lid 3, which is also useful for positioning the lid 3 with the frame 2 (Japanese Patent Laid-Open No. 8-27420).
No. 8).

[0007]

However, in order to efficiently weld the cover 3 to the frame 2 as described above, the cover 3
A thin portion 9 is formed in the peripheral portion of the bonding layer. However, voids are generated in the bonding layer 8 once melted and solidified at the time of seam welding, and the bonding strength of the lid 3 is reduced due to the voids. Problems such as deterioration of the airtightness of the package have occurred. This is because the unevenness of the surface of the peripheral portion of the lid 3 thinned by etching is large, so that the flow of the molten Ni is hindered, and the contact between the lid 3 and the frame 2 is uniformly and densely distributed. This is considered to be due to the occurrence of voids in the bonding layer 8 as a result.

Accordingly, the present invention has been completed in view of the above problems, and an object thereof is to suppress the generation of voids in the bonding layer 8 when the lid 3 is bonded to the upper surface of the frame 2. Another object of the present invention is to provide a semiconductor package which operates normally for a long period of time by improving its bonding strength.

[0009]

According to a first aspect of the present invention, there is provided a package for housing a semiconductor element, the base having a mounting portion for mounting a semiconductor element on the upper surface, and the semiconductor device package being joined to the upper surface so as to surround the mounting portion. In a semiconductor element housing package comprising a frame and a metal lid to which a peripheral portion of one main surface is joined to an upper surface of the frame by seam welding, the lid is a peripheral portion of the one main surface. The arithmetic mean roughness Ra of the portion is less than 3.0 μm, and the peripheral portion of the main surface is etched and thinned.

According to the present invention, when the lid is joined to the frame by the seam welding method, the flow of the joining material such as the Ni plating layer melted at the joint between the lid and the frame is obstructed. Since it does not occur and spreads evenly and densely at the joint between the lid and the frame, there is an operational effect that the generation of voids can be greatly suppressed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor package according to the present invention will be described below in detail with reference to the accompanying drawings. 1 and 2 show an embodiment of a semiconductor package according to the present invention, wherein 1 is a base, 2 is a frame made of metal, ceramics or the like, 3 is a metal lid, and 5 is a mounting portion of the semiconductor element 4. , 6 are input / output terminals. The base 1, the frame 2, and the lid 3 constitute a container for housing the semiconductor element 4. 1 and 2, the same parts as those in FIG. 6 showing the conventional example are denoted by the same reference numerals.

The base 1 is made of copper (Cu) or Fe—Ni—Co
Alloy, a metal material such as a Cu-W alloy, for example, when it is made of copper, it is rolled into a copper ingot (lump),
It is formed into a predetermined shape by employing a conventionally known metal working method such as a press molding method or a punching method.

The frame 2 is made of, for example, Fe--Ni--Co.
An alloy, a Fe-Ni alloy, etc., which is obtained by mixing and heating and melting powder of such a metal material to form a sheet-shaped member, which is rolled to a predetermined thickness by a roll rolling method, is obtained. The sheet-like member is formed into a pipe-like member by a conventionally known drawing method. The pipe-like member thus obtained is processed stepwise by a conventionally known drawing method to obtain a pipe having a desired rectangular cross-sectional shape. By cutting this pipe into an appropriate length, a frame 2 having a desired size and shape is manufactured.

The frame 2 is joined to the upper surface of the base 1 with a brazing material such as silver brazing surrounding the mounting portion 5 of the semiconductor element 4. At this time, the input / output terminals 6 were separately manufactured by a conventionally well-known ceramic green sheet laminating method, and a standing wall portion was laminated on a flat plate portion on which a metallized wiring layer 7 for leading the inside and outside of the frame 2 was formed on the upper surface. Configuration. The input / output terminal 6 is fitted into a notch or a through hole provided in the frame 2 via a brazing material such as silver brazing. Thereafter, the entire surface of the base 1 and the frame 2 and the input / output terminals 6
Is plated with Ni on the surface of the metallized wiring layer 7 formed on the surface of the substrate.

In place of the metal frame 2, ceramics may be used. In this case, for example, aluminum oxide (Al ₂ O ₃ ) powder and silica (SiO ₂ ), Calcia (CaO), magnesia (M
gO) and a suitable binder and solvent to form a slurry, which is then formed into a ceramic green sheet having a predetermined thickness by a conventional tape forming method such as a doctor blade method. Prepare multiple sheets. Next, the ceramic green sheet is punched, a metallized layer is formed on a predetermined portion to be joined to the frame 2 and the base 1, a metallized wiring layer is formed on the input / output terminal portion, and seam welding is performed. Sometimes a metallized wiring layer that becomes a conductive path is formed, and then a ceramic green sheet is laminated,
The ceramic frame 2 is obtained by firing at a temperature of about 1600 ° C.

Then, as shown in FIG. 4, the periphery of the lid 3 made of an Fe--Ni--Co alloy, Fe--Ni alloy, or the like is seam-welded to the upper surface of the frame 2, and this periphery is thinned. By doing so, the following operation occurs. That is, by reducing the cross-sectional area of the cross section viewed from the surface direction (X direction) of the peripheral portion of the lid 3, the electric resistance in the surface direction of the peripheral portion of the lid 3 is increased, and The current flowing to the center side of the main surface of No. 3 is reduced. In addition, since the cross-sectional area of the peripheral portion of the lid 3 viewed from the direction Y (perpendicular to the main surface) perpendicular to the X direction can be several times or more the cross-sectional area in the X direction, the electric resistance is reduced. Can be smaller.
Therefore, the frame 2 having a small electric resistance from the roller electrode 10
The current flowing in the direction (downward) is increased, and a large Joule heat can be generated in the contact portion between the lid 3 and the frame 2.

In the present invention, the metal lid 3 has an arithmetic mean roughness Ra of the peripheral portion 9 of the one main surface A of less than 3.0 μm. The contact area between the peripheral portion of the main surface A and the upper surface of the frame 2 is reduced, the electrical resistance is increased, the flowing current is reduced, and the joint between the lid 3 and the frame 2 during seam welding. The heating of the portion becomes insufficient and the joining becomes difficult.

The two main surfaces of the metal lid 3 are initially formed by, for example, a roll rolling method, and the surface of the roll has a smoothest Ra of about 0.3 μm.
Since the surface of the rolling roll is almost directly transferred to the main surface of the lid 3, the Ra of the peripheral portion of the main surface A is actually about 0.3 μm or more and less than 3.0 μm. Therefore, Ra at the peripheral portion of main surface A is preferably 0.3 μm or more and less than 3.0 μm. Also, from this, the other main surface (upper surface)
Ra of both main surfaces except the peripheral portion of B is 0.3 μm or more and 3.0.
Preferably less than μm.

One principal surface (lower surface) A of the lid 3 is not subjected to a surface treatment such as etching, while the peripheral portion of the other principal surface (upper surface) B has a reduced cross-sectional area as viewed in the X direction. It is etched to make it thinner. In this thin portion, the flow of current in the surface direction of the lid 3 is suppressed. The peripheral portion 9 of the other main surface B obtained by etching is 3.0 to 3.0.
Since it has an arithmetic average roughness Ra of about 6.3 μm,
When joining to the upper surface of the frame 2, the other main surface B is set to the upper side, and one main surface A is seam-welded to the upper surface of the frame 2 with the main surface A as the joining surface.

The thickness of the thin portion 9 is 0.05 to 0.15.
If the thickness is less than 0.05 mm, a part of the thin portion 9 is likely to be melted and lost or chipped during seam welding. When the thickness of the thin portion 9 is 0.15 mm or more,
The electric resistance in the surface direction (X direction) of the lid 3 is reduced, and a large current flows in this direction. The entire lid 3 is heated by Joule heat, and the heating of the thin portion 9 tends to be insufficient.

The thickness of the lid 3 is about 0.1 to 0.3 mm, so that the thin portion 9 has a thickness of 17 to 50 mm of the lid 3.
% Thickness is good. If it is less than 17%, a part of the thin portion 9 is unsuitable in that it melts and disappears during seam welding, or chipping easily occurs. If it exceeds 50%, the lid 3
The electrical resistance in the surface direction (X direction) becomes small, a large current flows in this direction, the entire lid 3 is heated by Joule heat, and the heating of the thin portion 9 tends to be insufficient.

The width of the thin portion 9 is preferably 0.1 to 1.5 mm. If the width is 0.1 mm or less, the electric resistance in the surface direction of the lid 3 becomes small, and a large current easily flows in the surface direction. Further, when the width of the thin portion 9 is 1.5 mm or more, the strength of the lid 3 is reduced at the thin portion 9, and the thin portion 9 is deformed during a He leak test for testing the airtightness of the semiconductor package. Is easy to occur.

Thus, the semiconductor element 4 is accommodated in the container constituted by the base 1 and the frame 2, and thereafter, the semiconductor element 4
The upper electrodes and the metallized wiring layer 7 on the input / output terminals 6 are electrically connected by bonding wires 11, and finally, the semiconductor element 4 is hermetically sealed by the lid 3, thereby forming a semiconductor device.

In the conventional example, the step of the thin portion 9 formed by etching is said to be useful for positioning the lid 3 at the time of seam welding. It is not practical to perform alignment by steps in seam welding. Accordingly, there is almost no problem in using the main surface A as the joining surface while the step is not provided.

It should be noted that the present invention is not limited to the above embodiment, and that various changes can be made without departing from the spirit of the present invention. For example, as shown in FIG. 3, the input / output terminal 6 may be a flat plate made of ceramics and may be fitted into a notch on the lower surface of the frame 2 made of ceramics. The semiconductor package is reduced in thickness because there is no standing wall.

[0026]

According to the semiconductor device housing package of the present invention, a base having a mounting portion for mounting a semiconductor element on the upper surface, a frame joined to the upper surface so as to surround the mounting portion, A metal lid to which the peripheral portion of the one main surface is joined by seam welding on the upper surface of the frame, wherein the lid has an arithmetic average roughness Ra of 3.0 μm on the peripheral portion of the one main surface. And the peripheral portion of the other main surface is thinned by etching, so that the N at the joint at the time of seam welding is reduced.
Since the flow of the bonding material such as i-plating is not hindered and uniformly and densely reaches the contact portion between the lid and the frame, voids generated at the bonding portion can be significantly suppressed.
As a result, the joining strength of the lid does not decrease, and the airtightness inside the semiconductor package does not deteriorate.
Furthermore, the current during seam welding can be efficiently flowed from the periphery of the lid to the lower frame, so that the current can be reduced and uniform welding can be achieved over the entire circumference of the lid. In addition, the welding time can be reduced, and the semiconductor package can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of a semiconductor device housing package of the present invention.

FIG. 2 is a partial cross-sectional view of a main part of the semiconductor device housing package of FIG. 1;

FIG. 3 is a cross-sectional view of another embodiment of the semiconductor device housing package of the present invention.

FIG. 4 is a partial cross-sectional view for explaining seam welding between the frame and the lid in the semiconductor element housing package of the present invention, and showing a welded portion between the roller electrode and the semiconductor element housing package.

FIG. 5 is a partial cross-sectional view for explaining seam welding of a frame and a lid in a conventional semiconductor element housing package, and showing a welded portion between a roller electrode and the semiconductor element housing package.

FIG. 6 is a cross-sectional view of a conventional semiconductor element storage package.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Base body 2 ... Frame body 3 ... Metal lid 4 ... Semiconductor element 5 ... Placement part 6 ... Input / output terminal 7 ... Metallized wiring layer 8 ... -Bonding layer 9-Thin portion 10-Roller electrode 11-Bonding wire A-One main surface B-Other main surface

Claims (1)

[Claims] A base having a mounting portion for mounting a semiconductor element on an upper surface, a frame joined to the upper surface so as to surround the mounting portion, and one of the frames being seam-welded to the upper surface of the frame. In the semiconductor device housing package provided with a metal lid to which a peripheral portion of the main surface is joined, the lid has an arithmetic average roughness Ra of the peripheral portion of the one main surface less than 3.0 μm. A semiconductor element housing package, wherein a peripheral portion of the other main surface is thinned by etching.