JP2001127219A - Package for housing semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of a shear stress in connection terminals even in the case where a heat cycle is repeatedly applied and to enhance the reliability of the connection of a package for housing a semiconductor element with an external circuit board in the package for housing the semiconductor element of a structure, wherein the semiconductor element is flip-chip mounted on a metallized wiring layer and a high heat conductive cover body is mounted on the surface of the element. SOLUTION: For packaging a semiconductor element, the semiconductor element 2 provided with electrodes for connection is flip-chip mounted on a metallized wiring layer 3 on the surface of almost a quadrangle-shaped insulating substrate 1 formed by coating with the layer 3. A high heat conductive cover body a which is attached on the surface of the substrate 1 in such a way as to cover the element 2 and is provided with its one part bonded to the upper surface of the element 2, and a plurality of connection terminals 5 which are provide on the rear of the substrate 1 and comprise solders electrically connected with the element 2, are provided. The cover body 9 is formed into the form of almost a quadrangle, legs 11 are respectively provided on each side part of the form of almost the quadrangle, and the legs 11 are attached on the substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a package for housing a semiconductor element having a high thermal conductive lid, and more particularly to an improvement for improving the reliability of connection between an insulating substrate of a package and an external circuit board. It is about.

[0002]

2. Description of the Related Art In semiconductor device housing packages for housing recent semiconductor integrated circuit devices (hereinafter, referred to as semiconductor devices) such as LSIs, when used in workstations, personal computers, and the like, the number of pins is increased along with the improvement in performance. Is required, and BGA (Ball Grid Arra)
y) or CSP (Chip Size Package)
Etc. are used.

In general, a method of connecting a semiconductor element to a package is such that a semiconductor element is adhered to a surface of a package and an electrode on an upper surface of the semiconductor element is connected to a wiring layer of the package by a wire. Recently, a method of flip-chip mounting in which a connection electrode is formed on the lower surface of a semiconductor element and a connection terminal of a package is directly brazed has been adopted with the high integration of the semiconductor device.

As a structure for dissipating heat generated from such a flip-chip mounted semiconductor element, a high heat conductive lid is mounted on the upper surface of the semiconductor element. By changing the shape and thickness of the body, the present invention can be applied to cooling of a semiconductor element having various heat values. As a package for accommodating a semiconductor element having such a high heat conductive lid, for example, “Nikkei Electronics, August 2, 1993,”
104.

[0005] This semiconductor element storage package is shown in FIG.
As shown in a schematic cross-sectional view when mounted on an external circuit board, a plurality of layers made of a high melting point metal such as tungsten, molybdenum, etc. are formed on the surface of an insulating substrate 21 generally made of alumina ceramic or the like from the periphery of the semiconductor element 22 to the lower surface of the insulating substrate 21. A plurality of metallized wiring layers 23 are formed, and connection terminals 25 are attached to connection pads 24 on the lower surface of the insulating substrate 21. The connection pad 24 has a connection terminal 2
5, a solder ball is attached by brazing.

The semiconductor element 22 includes a metallized wiring layer 23 provided on a ceramic insulating substrate 21 and a fine conductor 26 made of a metal such as solder or gold or a conductive resin.
And the connection portion is sealed by a thermosetting resin 27.

[0007] The semiconductor device accommodating package a is formed by connecting the connection terminal 25 made of the solder to the wiring conductor 2 of the external circuit board b.
8 and then put on the spherical connection terminal 2.
5 is heated and melted at a temperature of about 150 to 250 ° C., and is mounted on the external circuit board b by joining the spherical solder to the wiring conductor 28.

The semiconductor element 2 in the package a
A high thermal conductive lid 29 is fixed to the upper part of the second semiconductor device via a thermal conductive adhesive 30, and heat generated when the semiconductor element 22 is operated is transmitted through the high thermal conductive adhesive 30. It has a structure in which heat is radiated from 29 to the outer surface. The high thermal conductive lid 29 is usually in the shape of a square, and some of the corners are provided with an R portion.

The heat dissipation effect increases as the surface area of the high thermal conductive lid 29 increases, and therefore, the outer dimensions of the high thermal conductive lid 29 are usually larger than the semiconductor element 22.
Although it has the same size as the insulating substrate 21 of the package, the bonding area is small and unstable only by bonding to the heat conductive adhesive 30. Therefore, in order to keep the connection between the high thermal conductive lid 29 and the semiconductor element 22, a mounting portion 31 for attaching to the insulating substrate 21 is formed on the periphery of the high thermal conductive lid 29, and the solder or the silver paste is used. Is adhered to the surface of the insulating substrate 21 using the brazing material 32. As a specific shape of the high heat conductive lid 29, a so-called cap shape (FIG. 3A) in which the attachment portion 31 is formed as a frame on the periphery of the insulating substrate 21, or a high heat conductive lid For example, one in which mounting legs 31 are provided at four diagonal corners of the lid (FIG. 3B) is used.

[0010]

However, in such a BGA package, if a temperature change occurs due to a temperature change in the use environment or self-heating during operation, a difference in thermal expansion coefficient between the insulating substrate 21 of the package and the external circuit board b occurs. Due to the resulting difference in thermal expansion, a shear strain is applied to the connection terminal 25 made of solder. In particular, the thermal expansion difference is large at connection terminals located at diagonal corners where the distance from the package center is long, and large shear strain is generated.

In order to reduce the difference in thermal expansion, the insulating substrate 21 of the package tends to warp (strain) so that the semiconductor element mounting side is concave. However, since the diagonal corners of the insulating substrate 21 having the largest warp are suppressed from being deformed by the high thermal conductive lid 29 fixed to the surface of the insulating substrate 21, the difference in thermal expansion cannot be reduced. In particular, when the thermal expansion coefficient of the high thermal conductive lid 29 is larger than the thermal expansion coefficient of the insulating substrate 21, the insulating substrate 21 warps toward the external circuit board b, and the shear strain generated at the connection terminal 25 is extremely high. Become larger. When such shear strain is repeatedly applied, there is a problem that the connection terminal 25 made of solder becomes fatigued and causes thermal fatigue failure.

Accordingly, the present invention provides a semiconductor device storage package having a semiconductor device mounted flip-chip, a high thermal conductivity lid attached to an upper surface of the semiconductor device, and a connection terminal made of solder. Even if the thermal cycle accompanying the stop is repeatedly applied,
It is an object of the present invention to provide a semiconductor device housing package that suppresses generation of shear stress on connection terminals and has excellent connectivity with an external circuit board.

[0013]

According to the present invention, a semiconductor device having connection electrodes is mounted on a surface of a substantially rectangular insulating substrate on which a metallized wiring layer is formed, and the metallized wiring is formed. A layer and a connection electrode of the semiconductor element are soldered, and high heat is attached to the surface of the insulating substrate so as to cover the semiconductor element and a part of the layer is adhered to the upper surface of the semiconductor element. A conductive lid, and a semiconductor element housing package including a plurality of connection terminals made of solder provided on the back surface of the insulating substrate and electrically connected to the semiconductor element, wherein the high thermal conductive lid is ,
It has a substantially square shape, and a leg is provided on each side of the substantially square shape, and the leg and the insulating substrate are attached to each other.

In particular, the coefficient of thermal expansion of the high thermal conductive lid is
It is desirable that the coefficient of thermal expansion is smaller than the thermal expansion coefficient of the insulating substrate in order to reduce thermal stress.

Further, by bonding the upper surface of the semiconductor element to the high thermal conductive lid with a high thermal conductive adhesive, heat from the semiconductor element can be efficiently transferred to the lid. Is on the upper surface of the high thermal conductive lid,
The heat dissipation can be further enhanced by joining the heat dissipation fins. In particular, it is desirable that the high thermal conductive lid is made of a composite material of aluminum and SiC.

It is preferable that the insulating substrate is made of glass ceramic, and the metallized wiring layer is made of a conductor containing copper as a main component.

According to the package for housing a semiconductor element of the present invention, the mounting portion between the insulating substrate of the package and the high thermal conductive lid is provided not at the corner of the rectangular high thermal conductive lid but at the side. As a result, the operation of the semiconductor device /
Even if the thermal cycle accompanying the stop is repeatedly applied and the warp deformation such that the semiconductor element mounting side becomes concave on the insulating substrate due to the difference in the thermal expansion coefficient between the insulating substrate and the external circuit board occurs, The corners can be warped because they are not constrained. As a result, the shear strain of the connection terminals at the diagonal corners can be greatly reduced, and the mounting reliability of the package on the external circuit board can be increased. .

[0018]

FIG. 1 is a schematic view showing an embodiment of a mounting structure of a package for housing a semiconductor element according to the present invention. According to FIG. 1, in the package A for accommodating a semiconductor element of the present invention, a metallized wiring layer 3 is formed on the surface of the insulating substrate 1 from the periphery of the semiconductor element 2 to the lower surface of the substrate 1. Is formed with a connection pad 4, and a spherical terminal made of solder such as Sn-Pb, Sn-Pb-Bi, Sn-Ag or the like is soldered to the connection pad 4 as a connection terminal 5. .

The semiconductor element 2 is electrically connected to the upper surface of the insulating substrate 1 by fine connection terminals 5 such as solder, and the connection is sealed by a thermosetting resin 7 called a so-called underfill material. Has been stopped.

Further, a high heat conductive lid 9 for radiating heat generated by the semiconductor element is bonded to the other surface of the semiconductor element 2 via a heat conductive adhesive 10.

The highly heat-conductive lid 9 has a substantially rectangular shape, and its four sides are provided with legs 11 for attachment to the insulating substrate 1 at each side, particularly at each side. It is formed at the center. The ends of the legs 11 are attached to the surface of the insulating substrate 1 by a brazing material 12 such as a silver paste.

That is, when a thermal cycle accompanying the operation / stop of the semiconductor element 2 is repeatedly applied, the thermal expansion coefficient between the insulating substrate 1 and the external circuit board B is different due to the difference between the two.
The insulating substrate 1 is warped by stress such that the side on which the semiconductor element 2 is mounted becomes concave. By this warping deformation,
Although the shear strain generated at the connection terminals 5 at the diagonal corners of the package is reduced, the mounting portion between the high thermal conductive lid 9 and the insulating substrate 1 is connected to the high thermal conductive lid 9 as shown in FIG.
If the insulating substrate 1 is formed in a frame shape along the peripheral edge portion or at the four corners of the diagonal corner of the high thermal conductive lid 9, the warpage of the insulating substrate 1 is suppressed, so that the connection terminals 5 are formed. Cannot reduce the shear strain that occurs in

On the other hand, when the legs 11 are formed on each side of the high thermal conductive lid 9 as in the present invention, the diagonal corners of the insulating substrate 1 are not restrained. As a result, the shear strain of the connection terminal 5 at the diagonal corner is greatly reduced. In the vicinity of the center of the four sides of the insulating substrate 1, warpage of the insulating substrate 1 is naturally suppressed. However, since the shear strain generated in the connection terminals 5 in the vicinity is originally small, the life of the package is greatly extended.

When the thermal expansion coefficient of the high thermal conductive lid 9 is larger than the thermal expansion coefficient of the insulating substrate 1, the connection terminal 5 located at the center of the four sides of the insulating substrate 1 is connected to the high thermal conductive lid. In the package of the present invention, it is preferable that the thermal expansion coefficient of the high thermal conductive lid 9 is smaller than the thermal expansion coefficient of the insulating substrate 1 because the thermal expansion coefficient of the insulating substrate 1 may cause crushing.

Various materials can be used as the heat conductive adhesive 10, but a heat conductive sheet such as grease or silicon resin in which particles of high thermal conductivity such as alumina or silver are dispersed as a filler is used. Used.

The insulating substrate 1 is made of an electrically insulating material such as ceramics such as alumina and mullite, or glass ceramics fired at a low temperature. Since the relaxation of strain is a behavior that is particularly noticeably observed in glass ceramics, it is desirable that the insulating substrate 1 be made of glass ceramics in the package of the present invention.

Specifically, alumina ceramics contain sintering aids such as SiO ₂ , MgO, and CaO with respect to alumina, and for example, an organic binder suitable for a mixed powder of alumina and sintering aids; A slurry is prepared by adding and mixing a solvent and the like, and the slurry is formed into a green sheet (raw sheet) by a doctor blade method or a calendar roll method. Thereafter, the green sheet is subjected to an appropriate punching process and a plurality of sheets are formed. Laminated,
It is produced by firing at a temperature of 1500 to 1700 ° C.

The conventional alumina ceramic has a coefficient of thermal expansion of 6 to 7 ppm / ° C., and a coefficient of thermal expansion of 10 to 25 for a mother board or the like having an organic composite material such as glass epoxy generally used as an external circuit board as an insulating substrate.
It is much smaller than the printed wiring board of ppm / ° C., and the stress generated by the difference in thermal expansion becomes large.

In order to reduce the stress caused by such a difference in thermal expansion, the thermal expansion coefficient of the package is 8 to 2
Desirably, it is 0 ppm / ° C.

As an insulating material having such a coefficient of thermal expansion, for example, a glass having a low softening point and a high thermal expansion containing 5 to 60% by weight of BaO is used, mixed with a predetermined filler, and fired. Glass ceramics having high thermal expansion properties are desirable. Examples of the glass ceramic having a high thermal expansion include, for example, lithium silicate glass, PbO glass, and the like described in the specification of Japanese Patent Application No. 8-322038.
A composite material obtained by adding a composite material of a high thermal expansion filler such as enstatite, forsterite, silica, and various ceramic fillers such as MgO, ZrO ₂ and petalite to a glass component such as ZnO-based glass and BaO-based glass. Can be

The metallized wiring layer 3 and the connection pad 4 are appropriately selected depending on the material of the insulating substrate. Metal paste obtained by adding and mixing an appropriate organic binder, plasticizer, and solvent to the high melting point metal powder of
A conductor paste containing a low-resistance metal such as u or Ag is printed and applied in a predetermined pattern on a green sheet serving as the insulating substrate 1 by a conventionally known screen printing method, and is fired simultaneously with the insulating substrate.

The connection terminal 5 made of the spherical solder is
For example, one in which solder is applied to the connection pads 4 of the insulating substrate 1, excessive solder is applied, and then,
The solder may be made into a spherical shape by the surface tension of the solder melted by being heated and melted at 250 ° C. In some cases, a spherical solder made of a high melting point solder may be soldered with a low melting point solder.

The semiconductor element housing package A on which the semiconductor element 2 is mounted is provided with a connection terminal 5 made of the spherical solder and a wiring conductor 8 formed on the surface of the external circuit board B.
Then, the spherical connection terminal 5 is heated and melted at a temperature of about 150 to 250 ° C., and the connection terminal 5 made of the spherical solder is joined to the wiring conductor 8. Implemented above.

[0034]

Embodiments 5 × by various ceramic materials shown in Table 1.
After preparing sintered bodies having a shape of 4 × 40 mm, the Young's modulus and the average thermal expansion coefficient from room temperature to 400 ° C. of each sintered body were measured, and the results are shown in Table 1.

[0035]

[Table 1]

Next, using the glass ceramic materials A and B shown in Table 1 as an insulating substrate, a metallized wiring layer connected to a semiconductor element, an internal wiring layer and a via hole conductor on the surface thereof, and 256 conductors for attaching a conductor to the bottom surface. The connection lands were simultaneously fired at a temperature of 900 ° C. by printing or filling a copper paste in accordance with a well-known method to produce a package substrate.

For comparison, an alumina ceramic of material C shown in Table 1 as an insulating material was co-fired at 1550 ° C. using tungsten as each of the above-mentioned conductor materials to obtain a package substrate having the same size as above. Was prepared.

The semiconductor element 2 is made of silicon (coefficient of thermal expansion: 3 ppm / ° C.), and the spherical connection terminal 5 has a diameter of 63% by weight of Sn-37% by weight of Pb of 0.7 m in diameter.
m of solder balls.

The size of the package is the same as that of the insulating substrate 1.
Is 17 mm long × 17 mm wide × 0.75 mm thick, and the semiconductor element is 9 mm long × 9 mm wide × 0.3 mm thick. The connection pad diameter in the package is 0.6 mm, and the pitch between the connection pads is 1 mm.

The high thermal conductive lid has a coefficient of thermal expansion of 4, 8, 12 containing 30 to 80% of silicon carbide in aluminum.
It was manufactured using a material of ppm / ° C. Then, for attachment to the insulating substrate, as shown in FIG. 1, the highly heat-conductive lid (type) of the present invention in which legs are disposed on each side, and for comparison, the cap shape shown in FIG. And a highly heat-conductive lid (type) having legs disposed at diagonal corners in FIG. 3B.

On the other hand, as an external circuit board, a printed board having a land portion made of a copper foil formed on the surface of an insulator made of a glass-epoxy substrate and having an average thermal expansion coefficient from 20 ° C. to a glass transition temperature of 15 ppm / ° C. Was prepared.

Then, after solder (Sn 63 wt% -Pb 37 wt%) paste is applied to the land of the printed board by screen printing, the connection terminals of the package are aligned with the land of the printed board.
The package was mounted on the surface of the printed circuit board by heating and melting. As an external circuit board, 67 mm long x 67 mm wide x
The one having a thickness of 1.25 mm was used.

Next, the package substrate mounted on the printed circuit board surface as described above was placed in an air atmosphere.
A maximum of 1 cycle of holding the test sample for 15 minutes / 15 minutes in a thermostat controlled at each temperature of 40 ° C. and 125 ° C.
This was repeated up to 700 cycles.

Then, the electric resistance between the wiring conductor of the printed circuit board and the package substrate was measured every 100 cycles for each cycle, and Table 2 shows the number of cycles until the electric resistance changed.

[0045]

[Table 2]

As is clear from Table 2, in the package of the type in which the high thermal conductive lid and the insulating substrate were attached by the legs provided on each side of the high thermal conductive lid, the resistance was up to 1000 cycles in each case. No change was observed, and a good electrical connection state could be maintained. In particular, when the thermal expansion coefficient of the high thermal conductive lid is smaller than the thermal expansion coefficient of the insulating substrate, and when the insulating substrate is a glass ceramic sintered body, an extremely stable and good electrical connection state can be maintained. I have.

However, in the conventional high thermal conductive lid type package and the conventional package, the resistance change was detected at an early stage of less than 1000 cycles, and it was found that the reliability after mounting was lacking.

[0048]

As described in detail above, according to the present invention, the connection between the insulating substrate and the high thermal conductive lid is performed by the legs provided on each side of the high thermal conductive lid. Even when shear strain occurs due to the difference in thermal expansion between the external circuit board and the insulating board, the high thermal conductive lid suppresses the generation of shear stress on the connection terminals without restraining the warpage of the insulating board. In addition, the package can be stably electrically connected to the external circuit board for a long period of time.

[Brief description of the drawings]

FIG. 1A is a plan view and FIG. 1B is a schematic cross-sectional view illustrating a package for housing a semiconductor element according to the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a conventional semiconductor device housing package.

FIG. 3 is a view for explaining the structure of a conventional high heat conductive lid of a semiconductor element storage package.

[Explanation of symbols]

 Reference Signs List A Package for semiconductor element storage B External circuit board 1 Insulating substrate 2 Semiconductor element 3 Metallized wiring layer 4 Connection pad 5 Connection terminal 6 Conductor 7 Thermosetting resin 8 Wiring conductor 9 High thermal conductive lid 10 Thermal conductive adhesive 11 Leg Department

Claims (7)

[Claims] A semiconductor device having a connection electrode is mounted on a surface of a substantially rectangular insulating substrate on which a metallized wiring layer is formed, and the metallized wiring layer is connected to a connection electrode of the semiconductor device. A high thermal conductive lid attached to the surface of the insulating substrate so as to cover the semiconductor element, and a part thereof is adhered to the upper surface of the semiconductor element; And a plurality of connection terminals made of solder electrically connected to the semiconductor element, wherein the high thermal conductive lid has a substantially square shape, and A semiconductor element housing package, wherein legs are provided on each side of a quadrangular shape, and the legs are attached to the insulating substrate. 2. The package for accommodating a semiconductor element according to claim 1, wherein the thermal expansion coefficient of the high thermal conductive lid is smaller than the thermal expansion coefficient of the insulating substrate. 3. The semiconductor device according to claim 1, wherein an upper surface of the semiconductor element is bonded to the high thermal conductive lid with a high thermal conductive adhesive.
The package for housing a semiconductor element according to the above. 4. The high thermal conductive lid is made of aluminum and sulfur.
2. The package for accommodating a semiconductor element according to claim 1, comprising a composite material with iC. 5. The package according to claim 1, wherein said insulating substrate is made of glass ceramics, and said metallized wiring layer is made of a conductor containing copper as a main component. 6. The semiconductor device according to claim 1, wherein said semiconductor element is flip-chip mounted on a metallized wiring layer on a surface of said insulating substrate.
The package for housing a semiconductor element according to the above. 7. The package according to claim 1, wherein said connection terminals are made of solder.