JP2002289735A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfy the requirements for an internal connection portion for mounting a semiconductor chip on a circuit board and an external connection portion for mounting the circuit board to an external mounting board, and to be generated due to a difference in thermal expansion between the semiconductor chip and the mounting board. A semiconductor device with reduced connection stress and improved connection reliability is obtained. SOLUTION: A semiconductor chip (15) is connected to a sheet-like wiring circuit board (11) having a wiring circuit by bump connection (20).
And a flexible layer (13) in at least one of the inside of the circuit board, between the circuit board and the semiconductor chip, and / or between the circuit board and the external connection section. Is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device, and more particularly to a structure of an area array type package using bump connection.

[0002]

2. Description of the Related Art Due to demands for miniaturization and thinning of semiconductor devices, semiconductor devices are required to have a package whose size is not so different from that of a semiconductor chip.

[0003] From this viewpoint, in the field of high integration, high performance and large capacity of a semiconductor device itself, a small ball grid array (BGA) type package has already been commercialized and put on the market. ing. In these packages, various techniques have been developed for their internal connection.

FIG. 11 is a sectional view illustrating a conventionally proposed wire bonding type ball grid array package.

The sheet-like substrate 1 has a thickness of, for example, 75 μm, has an opening 1a in the center, and has a conductive wiring pattern 2a made of copper foil, for example, having a thickness of 15 μm on the lower surface. On the surface of the conductive wiring pattern 2a, a resist layer 8 as a protective film is formed with a thickness of, for example, 30 μm. A solder ball 7 as an external connection terminal is formed at a predetermined portion of the wiring conductive pattern 2a through the resist layer 8.

An opening 1a is formed on the upper surface of the sheet-like substrate 1.
An elastomer layer 3 having the same opening as that described above is laminated, and a semiconductor chip 5 is mounted thereon. As the elastomer layer 3, for example, an epoxy-based material is suitable, and the thickness is preferably about 50 μm.

On the lower surface of the semiconductor chip 5, an electrode 5a for wiring is provided, and this electrode 5a is positioned with respect to the substrate 1 so as to be located in the above-mentioned opening.

The conductive wiring pattern 2a and the electrode 5a are connected by a wire 6. Then, a sealing resin 9 such as a polyimide resin or an epoxy resin
Is filled, and the wire is protected.

Note that a beam lead can be used instead of a wire, and in this case, it is called a beam lead bonding method.

[0010] Such a package has several problems as follows.

First, since a certain amount of space is required for performing wire bonding, there is a limit to further reducing the pad pitch. Secondly, the bonding wire needs a wiring margin, and it is difficult to adapt to shortening the wiring length and shortening the delay time as the speed increases. Third, there is a restriction on pad arrangement such that bonding cannot be performed immediately below the external terminals of the BGA, and the degree of freedom in design is small.

In consideration of these problems, the flip chip package using bumps as the connection method is most likely to be the next generation package.

A variety of different flip-chip connection methods have been proposed, including solder connection, ACF connection using stud bumps, connection using a conductive paste, and Au / Sn connection. Few are on the market.

The reason for this is that it is difficult to select a material for the connection portion. That is, no matter which connection method is used, it is necessary to reinforce the connection part with a strong resin or the like in order to prevent breakage of the connection part due to temperature cycling, etc. Ball connection is performed. However, in order to guarantee the durability of the connection portion against thermal stress, the reinforcement of the connection portion is required to be rather flexible. Therefore, in order to optimally reinforce the connection portion, it is necessary to satisfy conflicting characteristics, so that it is extremely difficult to select a material.

FIG. 12 shows an example of the structure of an area array type package using bump connection.

In this example, the sheet-like substrate 1 has conductive wiring patterns 2a and 2c on its lower surface and upper surface, respectively, and has a through hole 2b for conducting these components. Since the semiconductor chip 5 is mounted face-down on these, the semiconductor chip 5 has a connection pump on the lower surface.

In order to connect the pump and the conductive wiring pattern 2c, an opening is selectively formed in the insulating film 4 at a portion corresponding to the bump, and an external connection material such as solder is supplied to this portion. The two are connected by heating or pressurization to form a connection portion 10. The connection portion 10 is reinforced by, for example, injecting and curing a liquid sealing agent, or by forming a structure in which a bump is made to penetrate a sheet-like sealing layer previously attached to a substrate.

The wiring 2a on the lower surface of the substrate has an area array wiring design. The entire lower surface is covered with the insulating film 8, but a part of the area array wiring 2a is opened. In the case of a BGA package, solder is supplied to this opening to form a solder ball, and connection with a mounting board is performed.

The problem with the bump connection type package is that it is difficult to achieve both the reliability of the internal connection and the reliability of the external connection when thermal stress is applied, as described above. That is, since the package structure has a simple structure of a semiconductor chip, a sealing layer, and a wiring circuit board, thermal stress generated due to a difference in linear expansion between the semiconductor chip and the mounting board after the package is mounted on the mounting board is sealed. Must be mitigated by a stop layer / wiring circuit board. If the structure does not sufficiently reduce the stress, the connection between the package and the mounting substrate is easily broken. On the other hand, the connection portion between the semiconductor chip and the printed circuit board needs to be reinforced by a sealing layer that is somewhat strong. As a result, the above-mentioned thermal stress must be reduced only by the printed circuit board.

At present, as a printed circuit board for such a package, a PCB such as glass epoxy or a polyimide TAB film having a linear expansion coefficient close to that of a mounting substrate, a ceramic material having a linear expansion coefficient close to that of a semiconductor chip, or a ceramic-based material having a linear expansion coefficient close to a semiconductor chip A high α type ceramic substrate or the like devised so as to be located in the middle of the linear expansion coefficient of the material has been considered.

[0021]

However, even when any of these materials is used, for example, the thickness of the chip, the thickness of the sealing layer, the thickness of the printed circuit board, and the like are optimized and the internal connection portion and the external The best thing is to balance the reliability of the connections.
It does not dramatically improve the reliability of both.

A flip-chip connection type package having a so-called fan-out type structure, in which the chip outer dimensions are smaller than the area of the external electrodes, is required to secure contact with socket contact pins during an electrical test and to improve the package. A certain degree of rigidity is required as a substrate material in order to ensure flatness during mounting. For example, in the case of a connection method in which batch bump bonding is performed by heat and pressure bonding, when the flip chip is used for batch connection due to the rigidity of this board, if the assembly tool is out of parallel and there is a phenomenon of one-sided In the worst case, a bump that is extremely crushed is formed, and in the worst case, a bonding failure bump occurs. It also affects the parallelism of the entire package.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a semiconductor device capable of satisfying conflicting requirements of an internal connection portion and an external connection portion.

[0024]

According to the present invention, there is provided a semiconductor device having a semiconductor chip in which a semiconductor chip is internally connected to an upper surface of a sheet-like wiring circuit board having a wiring circuit by bump connection and an external connection portion is provided on a lower surface. A flexible layer is provided in at least one of the substrate, between the circuit board and the semiconductor chip, and between the circuit board and the external connection portion.

The flexible layer is laminated on the circuit board, and a first wiring conductor layer for bump connection with the semiconductor chip is provided thereon, or the flexible layer forms the external connection portion. It is provided between a second wiring conductor and the circuit board, or the flexible layers are respectively laminated on both surfaces of the circuit board, and the first wiring conductor and the second wiring conductor are respectively formed on the surfaces thereof. Or the circuit board is composed of a plurality of layers, and the flexible layer is laminated between them.

It is preferable that the flexible layer is made of a material having a lower elastic modulus than the circuit board.

Preferably, the flexible layer also functions as an adhesive layer for fixing the wiring conductor on the circuit board.

Preferably, the external connection portion is provided corresponding to an internal connection portion of the semiconductor chip.

A semiconductor device can be formed by vertically stacking a plurality of any of the above semiconductor devices.

In the semiconductor device according to the present invention, the flexible layer is provided inside the circuit board, between the circuit board and the semiconductor chip, or between the circuit board and the external connection portion. Since the difference is absorbed to prevent the occurrence of stress, the reliability of the connection can be improved.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of the present invention will be described below in detail with reference to the drawings. In addition, portions common to the embodiments described below are denoted by the same reference numerals, and detailed description thereof will be omitted.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a cross-sectional view of an element showing the embodiment.

For example, an epoxy substrate containing glass cloth having a thickness of 0.1 mm or a sheet substrate 11 made of a TAB tape having a thickness of 75 μm has a wiring pattern 12a on the lower surface and an elastic modulus lower than that of the epoxy substrate containing glass cloth on the upper surface. The flexible layer 13 is laminated, a wiring pattern 12c is provided thereon, and a through-hole conductor 12b for front / back conduction is provided to conduct the two.
Here, Young's modulus (longitudinal modulus) of each material at normal temperature
Is 10 to 30 G for an epoxy board containing glass cloth.
Preferably, the pressure is 1 to 10 GPa for Pa and TAB tapes, and 0.01 GPa or less for the flexible layer.

Flexible layer 13 and wiring pattern 1
2c is covered with the insulating layer 14 as in the case of FIG.
Since the semiconductor chip 5 having the bumps thereon is mounted face down, the portion of the insulating film 4 corresponding to the bumps is formed.
Is selectively formed with an opening, a material for external connection such as solder is supplied to this portion, and the two are connected by heating or pressurization to form a connection portion 20. Its diameter is about 50-100 μm.

On the surface of the conductive wiring pattern 12a, a resist layer 18 as a protective film is formed with a thickness of, for example, 30 .mu.m, and a predetermined portion of the wiring conductive pattern 12a penetrates through the resist layer 18 for external connection. A solder ball 17 as a terminal is formed.

Next, a process for obtaining such a mounting structure will be described.

A conductive sheet such as Cu is attached to the lower surface of the sheet-like substrate 11 by heating and pressing, and a sheet-like flexible sheet 13 is attached to the upper surface thereof by a roll laminating method or the like. A conductive sheet such as Cu is attached.

Here, the flexible layer 13 must be a flexible layer having a lower elastic modulus than that of the TAB tape. However, care must be taken in selecting this material in the low temperature region (particularly the minus temperature region). , For example MI
The elastic modulus at -65 ° C under the condition C of the L standard.
In other words, some materials have a low elastic modulus from normal temperature to high temperature, but the elastic modulus rises sharply in the minus temperature range, and the elastic modulus may be higher than the base material of the printed circuit board. . In this case, the structure becomes the same as the structure of the printed circuit board single layer, or more adversely, so the elastic modulus of the printed circuit board base material in the operating temperature range or the guaranteed temperature range of the package. It is more important to select a flexible layer material having a low modulus of elasticity more reliably. As a flexible layer material satisfying such conditions, 0.01 GPa or less at room temperature, -65
It is desirable that the temperature be 3 GPa or less at ℃.

Materials satisfying such requirements include:
Usually, a thermosetting or thermoplastic insulating sheet, for example, a silicone rubber sheet is used, but a liquid sealing material is directly applied to a wiring circuit board base material, and a conductive sheet is applied in a semi-cured state and roll-formed. You may do it.
When a material having no adhesive property is selected as the flexible layer, a conductive sheet can be attached using an adhesive.

Thereafter, in the same manner as in the process of a normal printed wiring board or the like, through holes are opened by laser, punching, drilling, etc., through hole plating is performed to form through hole conductors 12b, and the conductive sheets on both surfaces are patterned Thus, wiring patterns 12a and 12c are formed.

Subsequently, an insulating film 14 is selectively formed corresponding to the wiring pattern 12c, and metallization is performed on a connection portion as necessary.

Further, a resist layer 18 as a protective film is formed on the surface of the conductive wiring pattern 12a with a thickness of, for example, 30 μm, and a predetermined portion of the wiring conductive pattern 12a penetrates through the resist layer 18 to form an external connection terminal. Is formed. Its diameter is 300-700
It is preferably about μm.

The printed circuit board manufactured as described above may be singulated for each package in advance, but may be left as a sheet. In this case, the semiconductor device is manufactured through a normal flip chip assembly process. Is done.

According to this embodiment, since the flexible layer is provided between the internal connection portion sealing layer and the printed circuit board, the internal connection portion is fixed with a sealing material having a considerably high elastic modulus. Even so, the flexible layer can sufficiently absorb the thermal stress. On the other hand, even if a sealing material with a low elastic modulus is used to some extent, if the flexible layer has sufficient flexibility, it can absorb the thermal expansion of the semiconductor chip applied to the internal connection and the thermal expansion caused by the difference in the thermal expansion of the mounting board. As a result, the reliability against thermal stress can be improved, and the range of selecting the sealing material can be expanded. Furthermore, as described above, the individual bumps are stable against the inclination of the assembly tool, and the flexible layer can absorb even if the sheet-shaped wiring circuit board itself has warpage or unevenness in flatness, so that stable bumps can be obtained. Becomes

FIG. 2 is a cross-sectional view showing a modification of the semiconductor device of FIG. 1. In the configuration of FIG. 1, front and back conductive through holes 12b are provided only at the central portion. 12b is provided, and the connection portion 10 with the semiconductor chip 15 is increased accordingly. Particularly, the example shown here is characterized in that the position of the connection portion 10 and the solder ball 17 for external connection are arranged at the same position on the opposite surfaces of the substrate. In such a configuration,
The number of front and back conductive through holes is almost equal to the number of external electrodes.

FIG. 3 is a cross-sectional view showing a modification of the semiconductor device of FIG. 2, in which the external connection solder balls 17 are located outside the outer shape of the semiconductor chip 15.

In this example, since a rigid substrate material can be used, coplanarity can be ensured.

FIG. 4 is a cross-sectional view showing a further modified example of FIG. 3, and shows an example in which a structure in which a metal stiffener 21 or the like is attached to the periphery of the substrate 11 for reinforcement is adopted. Even in this case, the influence of the peripheral sealing or the reinforcing material can be reduced by the buffer effect of the flexible layer.

As the reinforcing material, a ring-shaped stiffener, a cover-shaped stiffener, or the like can be used.

As the solder to be used, a lead-free silver-tin solder or the like is used in consideration of environmental issues, but a solder containing indium may be used from the viewpoint of fatigue resistance.

Further, the semiconductor device shown in FIG. 1 has a structure in which the chip itself is not sealed in order to improve the heat dissipation of the semiconductor chip. However, as shown in FIG. Only the side surface, or as shown in FIG. 6, the upper surface and the side surface of the semiconductor chip may be simultaneously sealed with, for example, the liquid hardening resin 22.

Also in these modified examples, by providing a flexible layer in the sheet-like wiring board, the difference between the thermal expansion of the semiconductor chip and the thermal expansion of the mounting board is absorbed by this flexible layer, and the stress is reduced. The reliability of the connection between the connection part and the external connection terminal can be improved.

(Second Embodiment) FIG. 7 shows a second embodiment of the present invention.
FIG. 3 is a cross-sectional view of an element showing the configuration of the embodiment.

This embodiment is similar to the first embodiment except that the flexible layer 13 is provided between the wiring conductive pattern 12a and the substrate base material 11 on the lower surface, that is, on the substrate facing the mounting substrate. It differs in that it is provided.

Such a structure is used when a large load is required for flip-chip connection with a large number of pins and the flexible layer may be damaged, or when the adhesion between the flexible layer and the wiring pattern is broken. Applied.

In this structure, since the flexible layer is provided between the circuit board and the external connection portion, the flexible layer absorbs the thermal stress generated between the entire package and the mounting board, and almost no thermal stress is applied to the external connection portion. This does not occur, and the connection reliability of the external electrodes can be improved. In addition, since the flexible layer also has flexibility in the vertical direction, individual external electrodes can move freely in the vertical direction even when making contact with multi-pin external connection terminals with socket pins etc. during testing, ensuring reliable contact. .

(Third Embodiment) FIG. 8 shows a third embodiment of the present invention.
FIG. 6 is a cross-sectional view of an element showing a configuration of the embodiment, using a plurality of core substrates.

That is, in the second embodiment, the second substrate 16 is provided on the lower surface of the flexible layer 13. That is, the flexible layer 13 is sandwiched between the first substrate 11 and the second substrate 16.

Such a laminated structure can be easily realized by using a laminating method or the like.

In this structure, for example, the substrate material on the side facing the semiconductor chip has an elastic modulus and a linear expansion coefficient close to that of Si, such as ceramic, and the substrate material on the side facing the mounting substrate has an elastic modulus and a linear expansion coefficient. The rate is close to the mounting board,
For example, by using a printed circuit board or a TAB tape, a mounting structure with the least generated stress can be obtained.

In particular, by laminating materials having different characteristics, the reliability of the internal connection portion and the external connection portion can be optimally improved.

(Fourth Embodiment) FIG. 9 shows a fourth embodiment of the present invention.
FIG. 4 is a cross-sectional view of the device showing the configuration of the embodiment, wherein the flexible layer has two layers.

That is, in the first embodiment shown in FIG. 1, the second flexible layer 19 is provided also on the lower surface side of the substrate 11, and the wiring conductive pattern 12a and the resist layer 18 are provided on the lower surface. Are different.

The functions of the two flexible layers are as follows. The effect of the thermal expansion of the semiconductor chip is reduced by the first flexible layer 13, and the effect of the thermal expansion of the mounting substrate is reduced by the second flexible layer 19. Furthermore, the inclination of the assembly tool and the coplanarity of the printed circuit board itself can be absorbed, and the contact property during an electrical test can be improved. Therefore, the effects of Embodiment 1 and Embodiment 2
Effect can be realized at the same time. In this case, one flexible layer can be made of a material having a different property than the other, for example, an elastomer having a high elastic modulus. Also in this case, it is necessary to satisfy the conditions of 0.01 GPa or less at normal temperature and 3 GPa or less at -65 ° C.

If the flexible layer is provided on the circuit board in advance as an adhesive for the conductive wiring sheet, the opening of the through-hole, the plating of the through-hole, the wiring patterning, and the like are exactly the same as those of the PCB substrate forming process. Can be easily manufactured, and manufacturing becomes easy.

(Fifth Embodiment) FIG. 10 is a sectional view showing a fifth embodiment of the present invention, in which the semiconductor device shown in FIG. 4 has a four-layer structure.

In this configuration, the semiconductor devices 100, 200, 300, and 400 completed as described above are vertically stacked, and a through hole provided in a substrate on an outer peripheral portion of a semiconductor chip and a through hole provided in a stiffener portion. Connecting pin 5
0 connects each layer. The solder balls 17 for external connection are provided only on the lowermost semiconductor device 100. Further, the pin 50 can be used as a power supply line or a ground line that requires a large capacity. In addition, the module to be stacked is not limited to the area array package, and a stacked module formed in advance may be a part of the stacked configuration.

In such a configuration, the degree of integration is extremely high.
A highly reliable semiconductor device can be easily obtained.

[0069]

As described above, according to the present invention, in a semiconductor device in which a semiconductor chip is internally connected to a sheet-shaped wiring circuit board having a wiring circuit by bump connection and an external connection portion is provided on a lower surface, Since a flexible layer is provided between the circuit board and the semiconductor chip and / or between the circuit board and the external connection portion, the flexible layer absorbs the difference between the thermal expansion of the semiconductor chip and the thermal expansion of the mounting board. Since the stress is relieved, the reliability of the connection between the internal connection and the external connection terminal can be improved.

When a flexible layer is laminated on a circuit board and a first wiring conductor layer for bump connection with the semiconductor chip is provided on the flexible layer, the stress due to the thermal expansion of the semiconductor chip is reduced. Can be effectively reduced.

When a flexible layer is provided between the second wiring conductor forming the external connection portion and the circuit board, stress due to a difference in thermal expansion between the entire semiconductor device and the mounting board is effectively reduced. be able to.

A flexible layer is laminated on both sides of the circuit board, and the first wiring conductor and the second wiring conductor are respectively formed on the surfaces thereof, and a flexible layer is provided between a plurality of circuit boards. When the layers are stacked, the flexible layer absorbs the difference between the thermal expansion of the semiconductor chip and the thermal expansion of the mounting board to relieve the stress, thereby improving the reliability of the connection between the internal connection and the external connection terminal. Can be.

When a material having a low elastic modulus is used for the flexible layer, the difference in thermal expansion between the chip, the sheet-like wiring board base material and the mounting board is absorbed, and the thermal stress applied to the internal connection portion and the external connection portion are reduced. Can reduce the thermal stress that is applied to the joint, improving the reliability of the connection part against thermal stress, and even if the partial contact with the inclination of the assembly tool occurs during the batch internal connection, the flexible layer follows the inclination of the tool Is easily deformed, so that the bumps are evenly crushed and the bumps can be connected evenly. Accordingly, the individual bumps can also have a stable shape and a stable connection area, and can reduce the variation in strength.

When the flexible layer also functions as an adhesive layer for fixing the wiring conductor on the circuit board,
Since it can be treated as an adhesive for a conductive wiring sheet or an adhesive between sheet substrates, bonding of wiring conductors can be realized by, for example, lamination, thermocompression bonding, casting, or the like without requiring a complicated process.

When the external connection portion is provided corresponding to the internal connection portion of the semiconductor chip, the place where stress is generated is limited, so that the effect of stress reduction can be easily confirmed.

In the case of a semiconductor device in which a plurality of these semiconductor devices are stacked in the vertical direction, a semiconductor device in which the reliability of connection is prevented from being reduced due to stress generated while achieving high integration by multilayering is provided. can do.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a first embodiment of a BGA type semiconductor device according to the present invention.

FIG. 2 is a cross-sectional view showing a modification of the semiconductor device of FIG. 1, in which the positions of internal connection portions and external connection portions correspond to each other.

FIG. 3 is a cross-sectional view illustrating a modification of the semiconductor device of FIG. 2, in which an external connection portion is provided outside a semiconductor chip.

FIG. 4 is a cross-sectional view showing a modification of the semiconductor device of FIG. 3, in which a reinforcing stiffener is attached to an outer peripheral portion.

FIG. 5 is a cross-sectional view showing a modification of the semiconductor device of FIG. 1, showing an example in which resin sealing is performed on a side surface of a semiconductor chip.

FIG. 6 is a cross-sectional view showing a modification of the semiconductor device of FIG. 1, showing an example in which the side and top surfaces of a semiconductor chip are sealed with a resin.

FIG. 7 is a cross-sectional view of a second embodiment of a BGA type semiconductor device according to the present invention, showing an example in which a flexible layer exists on the lower surface side of a circuit board.

FIG. 8 is a sectional view of a third embodiment of a BGA type semiconductor device according to the present invention, wherein
An example in which the layers are stacked between two circuit boards is shown.

FIG. 9 is a sectional view of a BGA type semiconductor device according to a fourth embodiment of the present invention, showing an example in which flexible layers are provided on the upper and lower surfaces of a circuit board.

FIG. 10 is a cross-sectional view of a BGA type semiconductor device according to a fifth embodiment of the present invention, showing a state in which a plurality of semiconductor devices according to the present invention are stacked to form a stacked module.

FIG. 11 is a cross-sectional view of a conventional wire bonding type BGA package.

FIG. 12 is a cross-sectional view of a conventional flip chip type BGA package.

[Explanation of symbols]

 1,11 Sheet-shaped substrate 2a, 2c, 12a, 12c Wiring conductor 2b, 12b Through hole 3,13 Flexible layer 4,14 Insulating layer 5,15 Semiconductor chip 7,17 Solder ball 8,18 Resist layer 10,20 Internal connection Part 21 stiffener 22 sealing resin 50 pin 100, 200, 300, 400 laminated semiconductor device

Claims (9)

[Claims] A semiconductor chip internally connected by bump connection to an upper surface of a sheet-shaped wiring circuit board having a wiring circuit;
A semiconductor device having an external connection portion on a lower surface, wherein a flexible layer is provided in at least one of the circuit board, between the circuit board and the semiconductor chip, and / or between the circuit board and the external connection portion. apparatus. 2. The semiconductor device according to claim 1, wherein the flexible layer is laminated on the circuit board, and a first wiring conductor layer for performing bump connection with the semiconductor chip is provided thereon. 13. The semiconductor device according to claim 1. 3. The semiconductor device according to claim 1, wherein the flexible layer is provided between a second wiring conductor forming the external connection portion and the circuit board. 4. The circuit according to claim 1, wherein the flexible layers are laminated on both surfaces of the circuit board, and the first wiring conductor and the second wiring conductor are respectively formed on the surfaces thereof. 13. The semiconductor device according to claim 1. 5. The semiconductor device according to claim 1, wherein said circuit board comprises a plurality of layers, and said flexible layer is laminated between said plurality of layers. 6. The semiconductor device according to claim 1, wherein said flexible layer is made of a material having a lower elastic modulus than said circuit board. 7. The semiconductor device according to claim 1, wherein said flexible layer also functions as an adhesive layer for fixing said wiring conductor on said circuit board. 8. The semiconductor device according to claim 1, wherein said external connection portion is provided corresponding to an internal connection portion of said semiconductor chip.
6. The semiconductor device according to any one of items 5 to 5. 9. A semiconductor device comprising a plurality of semiconductor devices according to claim 1 stacked vertically.