JP2002076193A - Semiconductor element storing package and package mounting board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor element storing package and package mounting board capable of maintaining a firm and stable connection state with an outside circuit board over a long period of time. SOLUTION: In the semiconductor element storing package A provided with a ceramic insulation board 1 mounting a semiconductor element 4 on the surface and a plurality of metallized land parts 3 formed on the rear face of the ceramic insulation board 1 and connected through the land part 13 of the outside circuit board B making a main component of an organic resin and a connection conductor 3, the thermal linear expansion coefficient of the ceramic insulation board 1 at 40-125 deg.C is 8-18 ppm/ deg.C, Young's modulus 50-150 GPa, and a projection part la mounting the semiconductor element 4 is formed on the surface of the ceramic insulation board 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package for housing a semiconductor element on which a semiconductor element is mounted, and a package mounting board in which the semiconductor element is connected to an external circuit board via a connection conductor.

[0002]

2. Description of the Related Art Conventionally, a wiring board has a structure in which a metallized wiring layer is disposed on the surface and / or inside of an insulating substrate. As a typical example of this wiring board, a semiconductor element, particularly an LSI (large scale LSI), is used. There is a package for accommodating a semiconductor integrated circuit element such as an integrated circuit). The package for accommodating a semiconductor element generally has a semiconductor element mounting portion formed on the surface of an insulating substrate made of alumina ceramics. On the surface and inside of the board,
A plurality of metallized wiring layers made of a refractory metal powder such as tungsten and molybdenum are provided and electrically connected to a semiconductor element to be mounted. Further, a metallized land portion for electrically connecting to the external circuit board is provided on the lower surface or side surface of the insulating substrate, and the metallized land portion is electrically connected to the metallized wiring layer.

In such a package for housing a semiconductor element, a metallized land provided on the lower surface of the ceramic insulating substrate and a land formed on the surface of the external circuit board are electrically connected by a connecting conductor made of solder or the like. By doing so, it is mounted on an external circuit board.

[0004] As such a package, a surface mount type package such as a ball grid array (BGA) having a spherical terminal (connection conductor) made of solder on the lower surface of an insulating substrate is known.

[0005] The demand for smaller packages has been increasing year by year. Recently, ball grid arrays (BGs)
A) Among the type packages, the shift to a chip scale package (CSP) whose package size is close to the chip size is progressing.

A ball grid array (BGA) type package is connected to an external circuit board via solder balls, while a land grid array (BGA) package is connected only by printing a solder paste without using solder balls. LGA)
There is a mold package. Land grid array (LGA)
In the mold package, the step of mounting the solder balls can be omitted, so that the cost can be reduced. Further, since the thickness of the connection conductor such as solder for connecting the insulating substrate and the external circuit board is small, there is an advantage that the height of the entire package can be reduced. However, on the other hand, since the thickness of the connection conductor is small, thermal stress generated in the connection conductor due to a difference in thermal expansion between the insulating substrate and the external circuit board is high,
There is a problem that a stable connection cannot be maintained for a long time.

In a ball grid array (BGA) or a chip scale package (CSP), a spherical terminal (connection conductor) made of a brazing material such as solder is brazed to a metallized land portion of a ceramic insulating substrate, and the spherical terminal is externally mounted. The ceramic insulating substrate is placed on and abutted on the external circuit board by placing and abutting on the land portion of the circuit board, and then heating and melting the spherical terminal at a temperature of 150 to 400 ° C. and joining the spherical terminal to the land portion. Has been implemented. With such a mounting structure, each electrode of the semiconductor element housed in the semiconductor element housing package is electrically connected to the external circuit board via the metallized land portion and the connection conductor.

[0008] The mounting of the semiconductor element in the above-described package includes connecting electrodes formed on the semiconductor element,
A wire bonding method of connecting a metallized wiring layer formed around the element mounting portion on the package side with a wire has been more widely used than before. In this method of fixing a semiconductor element by the wire bonding method, a thermosetting resin such as an epoxy resin is applied around the semiconductor element, and the semiconductor element is fixed by hardening and bonding.

As a mounting method other than the above, a semiconductor element is mounted on a metallized wiring layer formed on the package side, and mounting is performed by directly connecting a connection terminal formed on the semiconductor element to the metallized wiring layer. A so-called flip-chip type mounting is also known.

In recent years, as an insulating substrate in a package for accommodating a semiconductor element, a low-temperature sintering, a low dielectric constant and a high electric conductivity copper wiring are possible. Configurations have also been proposed.

[0011]

Alumina conventionally used as an insulating substrate in the above package,
Ceramics such as mullite have a high strength of 200 MPa or more, and are often used because of their high reliability as a multi-layered technology with a metallized wiring layer. However, the thermal expansion coefficient at -40 to 125 ° C. The coefficient is 8 ppm /
Low when less than ° C.

Therefore, the insulating substrate is surface-mounted on an external circuit board such as a printed board containing an organic resin such as a glass-epoxy resin composite material or a glass-polyimide resin composite material (generally, the thermal expansion coefficient is 14 ppm / ° C. or more). In other words, when the metallized land portion formed on the back surface of the ceramic insulating substrate is connected to the land portion of the external circuit board containing the organic resin as a main component via a connection conductor, The generated heat is repeatedly applied to both the ceramic insulating substrate and the external circuit substrate, and a difference in thermal expansion coefficient between the external circuit substrate and the insulating substrate occurs.

Since this difference in thermal expansion depends on the distance from the center of the package (ceramic insulating substrate), the maximum thermal stress occurs in the metallized land farthest from the center. When this thermal stress is repeatedly applied by the operation / stop of the semiconductor element, the connection conductor connecting the ceramic insulating substrate and the external circuit board becomes fatigued and eventually breaks. In particular, the above tendency is remarkable in the surface mount type packages such as the BGA and LGA.

On the other hand, in order to reduce the thermal stress generated in the connecting conductor, a high thermal expansion glass ceramic is used for the insulating substrate of the package to reduce the difference in thermal expansion between the insulating substrate and the external circuit board, thereby reducing the thermal stress. Attempts have been made to reduce However, when a high thermal expansion glass ceramic having a thermal expansion coefficient of 8 to 18 ppm / ° C. is used,
Although the difference in thermal expansion between the insulating substrate and the external circuit board is small, the difference in thermal expansion between the semiconductor element (having a coefficient of thermal expansion of about 3 ppm / ° C.) and the insulating substrate is large.

Therefore, in a package for housing a semiconductor element using a high thermal expansion glass ceramic, the insulating substrate at the outer peripheral portion of the semiconductor element is raised to reduce thermal stress due to a difference in thermal expansion coefficient between the semiconductor element and the ceramic insulating substrate. Thermal stress is generated in the connection conductor located below the outer peripheral portion of the semiconductor element, not in the connection conductor furthest from the package center, and the electrical connection cannot be stably maintained for a long time. There was a problem.

Accordingly, it is an object of the present invention to provide a package for housing a semiconductor element and a package mounting board capable of maintaining a strong and stable connection with an external circuit board for a long period of time.

[0017]

A package for accommodating a semiconductor device according to the present invention has a ceramic insulating substrate on which a semiconductor element is mounted on a front surface, and is formed on the back surface of the ceramic insulating substrate and contains an organic resin as a main component. What is claimed is: 1. A semiconductor device housing package comprising a land portion of an external circuit board and a plurality of metallized land portions connected via connection conductors, wherein said ceramic insulating substrate has a thermal expansion coefficient at -40 to 125 ° C. of 8 to 8. 18 ppm / ° C, Young's modulus is 50 ~
150 GPa, and a projection on which the semiconductor element is mounted is formed on the surface of the ceramic insulating substrate.

In such a package for housing a semiconductor element, the thermal expansion coefficient of the ceramic insulating substrate at -40 to 125.degree. C. is 8 to 18 ppm / .degree. External circuit board (Coefficient of thermal expansion at -40 to 125 ° C is 14pp
m / ° C or more) and the semiconductor element is operated repeatedly, the difference in thermal expansion between the ceramic insulating substrate of the package and the external circuit board is small. Thermal stress acting on the electrically connected connection conductor can be reduced, breakage of the connection conductor can be suppressed, and the connection between the ceramic insulating substrate and the external circuit board can be maintained for a long time.

Further, the Young's modulus of the ceramic insulating substrate is
Since it is 150 GPa or less, which is smaller than the conventional alumina, the connection conductor electrically connecting the metallized land portion of the package and the land portion of the external circuit board, and is the largest in the connection conductor farthest from the package center. Although a thermal stress is generated, the thermal stress can be reduced by warping (bending) deformation of the ceramic insulating substrate of the package, so that the thermal stress acting on the outermost connection conductor can be further reduced.

On the other hand, when a high thermal expansion and low Young's modulus material is used as the ceramic insulating substrate, the semiconductor element (-40 to 40) can be used.
(The thermal expansion coefficient at 125 ° C. is about 3 ppm / ° C.). In order to reduce the thermal expansion difference between the semiconductor element and the ceramic insulating substrate of the package, the outer peripheral portion of the semiconductor element is easily warped locally. Since a convex portion is formed on the ceramic insulating substrate on the surface of the ceramic insulating substrate, and the semiconductor element is mounted on the convex portion, the rigidity of the convex portion of the ceramic insulating substrate can be improved, and the local warpage of the outer peripheral portion of the semiconductor element can be improved. Can be prevented, the thermal stress acting on the connection conductor below the outer peripheral portion of the semiconductor element can be reduced, the breakage of the connection conductor can be suppressed, and the connection between the ceramic insulating substrate and the external circuit board can be maintained for a long time.

Further, it is desirable that the height of the projection formed on the surface of the ceramic insulating substrate is 0.1 to 0.3 mm. By setting such a height, wire bonding is easy, the amount of resin for sealing the semiconductor element can be suppressed to a minimum, and further reduction in height can be promoted.

Furthermore, it is desirable that the ceramic insulating substrate is made of a glass ceramic sintered body.

In the package mounting board according to the present invention, the semiconductor element housing package is mounted on an external circuit board mainly composed of an organic resin, and the metallized land portion of the semiconductor element housing package is connected to the external circuit board. Are connected to each other via a connection conductor having a thickness of 0.3 mm or less.

In such a package mounting substrate, as described above, the thermal stress of the connection conductor between the metallized land portion of the package for housing the semiconductor element and the land portion of the external circuit board can be suppressed to a minimum. Even if a connection conductor having a thickness of 0.3 mm or less is used, breakage of the connection conductor can be suppressed, the connection between the ceramic insulating substrate and the external circuit board can be maintained for a long time, and a connection conductor with a thickness of 0.3 mm or less is used. Therefore, the height can be further reduced.

[0025]

FIG. 1 is a perspective view of a package according to the present invention.
This will be described in detail based on FIG. FIG. 1 shows an example of the present invention, which has a basic structure of a so-called wiring board in which a metallized wiring layer is disposed on the surface or inside of a ceramic insulating substrate. It is a circuit board.

The package A includes a ceramic insulating substrate 1, a metallized wiring layer 2, a number of metallized land portions 3, and a semiconductor element 4 mounted on the package A. There are several methods for mounting the semiconductor element 4 on the ceramic insulating substrate 1. FIG. 1A shows that the semiconductor element 4 and the metallized wiring layer 2 provided on the ceramic insulating substrate 1 are connected by a conductor such as a fine solder. This is a so-called flip-chip type connection, which is connected via the through hole 6 and sealed with an underfill 5 made of resin.

FIGS. 1B and 1C show the semiconductor device 4.
And a metallized wiring layer 2 provided on the ceramic insulating substrate 1 by wire bonding of a wire 7 made of Al, Au, or the like. In this case, as shown in FIG. 8 and a case where the cover 9 is hermetically sealed as shown in FIG.

In any of the above cases, a metallized land portion 3 is formed on the lower surface of the ceramic insulating substrate 1 and is electrically connected to the metallized wiring layer 2 disposed on the surface and inside of the insulating substrate 1. .

On the other hand, the external circuit board B is formed of a so-called printed board, and Cu, Au, Al, Ni, Ni is formed on the surface of the insulator 12 made of a material containing an organic resin such as a glass-epoxy resin or a glass-polyimide resin composite material. , Sn-Pb
And a land portion 13 made of metal such as a metal, and may be simply referred to as a printed circuit board.

To mount the BGA type package A on the external circuit board B, the metallized land 3 on the lower surface of the insulating substrate 1 of the package A is placed on the land 13 of the external circuit board B by connecting conductors 11 such as solder. It is connected to the.

In the package A of the present invention, the thermal expansion coefficient of the ceramic insulating substrate 1 at -40 to 125 ° C. is 8 to 18 ppm / ° C., and the Young's modulus is 50 to 150 GP.
a, a semiconductor element 4 is mounted on the surface of the ceramic insulating substrate 1, and a projection 1a made of the same material as the ceramic insulating substrate 1 is integrally formed. The height of the projection 1a formed on the surface of the ceramic insulating substrate 1 is 0.1 to
Desirably, it is 0.3 mm.

The projection 1a on which the semiconductor element 4 is mounted may be manufactured separately from the ceramic insulating substrate 1 and may be attached later. The size of the convex portion 1a is desirably the same as that of the semiconductor element 4, but may be slightly larger. Further, the material may be different from that of the ceramic insulating substrate 1, but it is desirable that the material is the same from the viewpoint of integral firing.

In such a package A, generally, when the semiconductor element is repeatedly operated, the metallized land portion 3 on the package A side and the land portion 1 on the external circuit board B side are generally used.
Thermal stress is generated in the connection conductor 11 that electrically connects the third and third components 3 due to a difference in thermal expansion between the package A and the external circuit board B.

Since the difference in thermal expansion between the package A and the external circuit board B increases with the distance from the center of the package A, if the thermal expansion coefficient of the package A is less than 8 ppm / ° C., the package A is arranged on the array. Many connecting conductors 11
Among them, the highest thermal stress occurs in the connection conductor farthest from the center of the package A. When thermal stress is repeatedly applied by the operation / stop of the semiconductor element 4, the package A
The connection conductor furthest from the center of the wire breaks due to fatigue and cannot maintain an electrical connection.

According to the present invention, by using a ceramic having a high thermal expansion having a thermal expansion coefficient of 8 to 18 ppm / ° C. for the ceramic insulating substrate 1 of the package A, the thermal expansion difference with the external circuit board B is reduced. Outermost connection conductor 1
1 can be reduced. The coefficient of thermal expansion of the ceramic insulating substrate 1 is particularly 10 to 15 ppm / ° C.
Is desirable for the above reason.

Further, by using a ceramic having a low Young's modulus of 150 GPa or less as the ceramic insulating substrate 1 of the package A, a difference in thermal expansion between the package A and the external circuit board B is reduced by warpage (bending) deformation of the package A. Therefore, the thermal stress of the outermost connection conductor can be further reduced. On the other hand, if the Young's modulus of the package A is less than 50 GPa, the reliability is reduced due to the influence of the sealing resin 8 and the lid 9.
Young's modulus of the ceramic insulating substrate 1 is 50 to 150 GP.
a is desirable. It is desirable that the Young's modulus of the ceramic insulating substrate 1 is particularly 80 to 120 GPa.

On the other hand, when the thermal expansion coefficient of the ceramic insulating substrate 1 of the package A is large, the semiconductor element 4 and the ceramic insulating substrate 1 of the package A have a small thermal expansion difference between the package A and the external circuit board B. Has a large thermal expansion difference. As a result, even if the thermal stress of the outermost connection conductor 11 can be reduced, a high stress is generated in the connection conductor 11 located below the outer peripheral portion of the semiconductor element 4.
This is because the outer peripheral portion of the semiconductor element 4 is locally warped in order to reduce the difference in thermal expansion between the semiconductor element 4 and the ceramic insulating substrate 1 of the package A.

From this viewpoint, the thermal stress of both the connection conductor 11 farthest from the center of the package A and the connection conductor 11 located below the outer periphery of the semiconductor element 4 is reduced, and a highly reliable semiconductor element storage package is provided. To get A,
It is necessary to use ceramics having a high thermal expansion and a low Young's modulus for the material of the package A, and to provide a convex portion 1a on the side of the package A on which the semiconductor element 4 is mounted to increase rigidity.
By providing the protrusion 1a, warpage due to a difference in thermal expansion between the semiconductor element 4 and the package A can be reduced, and a stable connection structure can be maintained for a long time.

That is, since the rigidity is proportional to the cube of the thickness,
The higher the height of the convex portion 1a, the smaller the thermal stress applied to the connection conductor 11 located below the outer peripheral portion of the semiconductor element 4, but if it is too high, 1) wire bonding becomes difficult, 2) sealing. Requires a large amount of resin, and 3) the height of the package is increased. Therefore, the height of the convex portion 1a is desirably 0.1 to 0.3 m.

Further, since the semiconductor element housing package of the present invention has a high thermal expansion, even the outermost connection conductor 11 generates very little thermal stress. Therefore, in the package A of the present invention, the thickness h of the connection conductor 11 is set to 0.3 m.
m or less, a stable connection structure can be maintained for a long period of time, and the thickness of the connection conductor 11 is thin, so that the entire mounting structure can be reduced in height.

As the material of the ceramic insulating substrate 1 of the package A, for example, lithium silicate glass, PbO as described in the specification of JP-A-10-167822
For glass components such as base glass, ZnO base glass and BaO base glass, enstatite, forsterite, S
A mixture obtained by mixing various ceramic fillers such as an iO ₂ filler, MgO, ZrO ₂ , petalite, and the like and then firing is preferable.

For example, a slurry is prepared by appropriately adding an organic binder to a mixture of 20 to 90% by volume of the glass and 80 to 10% by volume of the filler, and the slurry is formed into a sheet. C on the body surface
A conductive paste containing a low-resistance metal such as u, Au, or Ag is applied by printing. Further, if necessary, a through hole is formed at a predetermined position of the sheet-like molded body by a microdrill, a laser, or the like, and the hole is filled with the conductive paste.

Then, after laminating a plurality of the sheet-shaped compacts to form a laminate, the laminate is degreased in a nitrogen atmosphere or a nitrogen atmosphere containing water vapor, and then 800 to 100
By firing at a temperature of 0 ° C., the ceramic insulating substrate 1 can be manufactured.

In the package configured as described above, the thermal stress of both the connection conductor 11 farthest from the center of the ceramic insulating substrate 1 of the package A and the connection conductor 11 located below the outer peripheral portion of the semiconductor element 4 is reduced. And connection conductor 1
1 can be suppressed, the connection between the ceramic insulating substrate 1 and the external circuit board B can be maintained for a long time, and a highly reliable semiconductor element housing package A can be obtained.

[0045]

EXAMPLE For the glass ceramic materials shown in Table 1,
After preparing a sintered body having a shape of 5 × 4 × 40 mm, the Young's modulus and the coefficient of thermal expansion at −40 to 125 ° C. of each sintered body were measured.

Further, using various glass ceramic materials shown in Table 1 as a ceramic insulating substrate, a metallized wiring layer, an internal wiring layer and a via hole conductor connected to a semiconductor element on the surface thereof, and a connecting conductor on a bottom surface for attaching a connecting conductor.
Print 08 metallized lands with copper paste
Simultaneous firing at a temperature of 00 ° C. produced a ceramic insulating substrate of the package. Ceramic insulating substrate size is 15 vertical
mm × width 15 mm × thickness 0.8 mm, semiconductor element size is height 9 mm × width 9 mm × thickness 0.27 mm, protrusion is length 9
mm × 9 mm × 0.1 mm

For comparison, alumina ceramics and mullite ceramics as shown in Table 1 as insulating materials were simultaneously fired at 1550 ° C. using tungsten as the respective conductor materials, and the same size as above was obtained. Was manufactured.

Then, a solder (Sn 63% -Pb 37%) paste was applied to the metallized land portion of the substrate by screen printing, and was heated and melted to form a solder layer.

On the other hand, as an external circuit board, a printed board made of a glass-epoxy board and having a land portion made of copper foil formed on the surface of an insulator having a thermal expansion coefficient of 15 ppm / ° C. at −40 to 125 ° C. is prepared. did.

Then, after solder (Sn 63% -Pb 37%) paste is applied to the land of the printed board by screen printing, the metallized land of the package and the land of the printed board are aligned with each other and heated. After being melted, a metallized land portion of the package was joined to a land portion of the printed circuit board by a connection conductor made of solder having a thickness shown in Table 2 to produce a package mounting board.

The thickness of the connection conductor made of solder is 0.1
When manufacturing a package mounting board of mm, solder paste was not printed on the ceramic insulating substrate side of the package, but solder paste was printed only on the printed board side.

Next, the step of holding the test samples in the thermostat controlled at -40 ° C. and 125 ° C. in the air atmosphere for 25 minutes each for the package mounting board as described above is a maximum of 1500 cycles. The cycle was repeated.

The electrical resistance between the printed circuit board and the package substrate was measured for each cycle. Table 2 shows the number of cycles until the electrical resistance changed.

[0054]

[Table 1]

[0055]

[Table 2]

As is clear from Tables 1 and 2, -40 to -1
A package for semiconductor element storage using an insulating substrate material having a thermal expansion coefficient of 8 to 18 ppm / ° C. at 25 ° C. and a Young's modulus of 50 to 150 GPa has a connection conductor thickness (solder height) of 0.1 mm. However, no change in resistance was observed at all up to 1500 cycles, and an extremely stable and good electrical connection state could be maintained. However, in a package outside the above range, the resistance change is detected from an early stage of 900 cycles or less, which indicates that the reliability after mounting is lacking.

Further, the sample No. The reliability test was performed under the same conditions as above, with the height of the projections of 17 (material F, connection conductor thickness (solder height) 0.3 mm) being varied from 0 to 0.5 mm as shown in Table 3. Was.

[0058]

[Table 3]

As is apparent from Table 3, the height of the convex portion is 0.1.
At ~ 0.3 mm, up to 1500 cycles could be cleared.

[0060]

As described in detail above, the semiconductor device housing package of the present invention reduces the thermal stress of both the connection conductor farthest from the center of the package and the connection conductor located below the outer periphery of the semiconductor device. And, even if the thickness of the connection conductor is small, the semiconductor element housing package and the external circuit board are
It is possible to make accurate and strong electrical connection over a long period of time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a package mounting board of the present invention, in which (a) is a flip chip type, (b) is a wire bonding type hermetically sealed with a sealing resin, and (c) is a lid. 1 shows a wire bonding type that is hermetically sealed.

FIG. 2 is an enlarged sectional view of a main part showing a connection part between the package of FIG. 1 and an external circuit board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ceramic insulating substrate 1a ... Convex part 3 ... Metallized land part 4 ... Semiconductor element 11 ... Connection conductor 13 ... Land part of external circuit board A ... For semiconductor element accommodation Package B: External circuit board

Claims (5)

[Claims] 1. A ceramic insulating substrate on which a semiconductor element is mounted on a front surface, and formed on a back surface of the ceramic insulating substrate,
A semiconductor element housing package comprising a land portion of an external circuit board mainly composed of an organic resin and a plurality of metallized land portions connected via connection conductors; The thermal expansion coefficient at 8 ° C. is 8 to 18 ppm / ° C., and the Young's modulus is 50 to 150.
A semiconductor element storage package, which is GPa and has a projection on which the semiconductor element is mounted on the surface of the ceramic insulating substrate. 2. The package for accommodating a semiconductor element according to claim 1, wherein the projection is made of the same material as the ceramic insulating substrate and is formed integrally with the ceramic insulating substrate. 3. The package for housing a semiconductor element according to claim 1, wherein the height of the projection formed on the surface of the ceramic insulating substrate is 0.1 to 0.3 mm. 4. The package for housing a semiconductor element according to claim 1, wherein the ceramic insulating substrate is made of a glass ceramic sintered body. 5. The package for storing a semiconductor element according to claim 1, wherein the package for mounting a semiconductor element is mounted on an external circuit board containing an organic resin as a main component. A package mounting board which is joined to a land portion of the external circuit board via a connecting conductor having a thickness of 0.3 mm or less.