JPH1050767A - Semiconductor device and method for mounting the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of electric connection with a wiring board, irrespective of the repetitive temp. change by laminating conductive layers of a conductive material on first electrodes formed on one surface of a semiconductor device to form bump electrodes. SOLUTION: A semiconductor device 1 has bumps 5 having a laminate structure of laminated conductive layers which will cleave in a stress acting direction perpendicular to the conductive layer laminating direction if stressed in this direction. If a bump 5 is stressed because of the thermal expansion coefficient difference between the device 1 and substrate 2, the bump will hold the electric connection of a pad 3 and land 4 whereas it deforms to escape the stress. When the ordinary temp. is recovered, the bump 5 recovers the original shape. Thus it is possible to hold the electric connection and ensure a good electric connection with the wiring board, irrespective of the repetitive temp. change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Table of Contents] The present invention will be described in the following order. BACKGROUND OF THE INVENTION Problems to be Solved by the Invention Means for Solving the Problems Embodiments of the Invention (1) First Embodiment (FIGS. 1 to 3) (2) Second Embodiment (FIG. 4 and FIG. 5) (3) Other Embodiments Advantages of the Invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a semiconductor device mounting method, and more particularly, to a semiconductor device provided with a plurality of projecting electrodes (so-called bumps) by a flip-chip method and a method suitable for mounting the semiconductor device. It is.

[0003]

2. Description of the Related Art In recent years, in electronic equipment, it has been desired to reduce the circuit configuration in size and size, and for that purpose, the technology for mounting semiconductor devices such as IC chips at high density has become an important point. . As a technique for realizing such high-density mounting, a flip-chip method is currently receiving attention.

Normally, in flip-chip mounting using a bare chip, first, tin (Sn) is formed on a plurality of electrodes (hereinafter referred to as pads) formed on the circuit surface of the bare chip by using a plating method or a vapor deposition method. ) And lead (Pb) are formed into a bump electrode (hereinafter, referred to as a bump) by using a solder as an alloy. Thereafter, the circuit surface of the bare chip and the one surface of the wiring board are opposed to each other, and the bump formed on the circuit surface of the bare chip is brought into contact with a corresponding land provided on one surface of the wiring substrate. Here, solder is applied to the lands in advance.
After the bumps are brought into contact with the corresponding lands in this way, the wiring board is heated, for example, in a reflow device. The solder applied to the bumps and lands is melted and joined by the heating, and electrically connects the pads on the circuit surface of the bare chip to the lands on the wiring board. Thus, the bare chip is mounted on the wiring board via the bump.

When a bare chip is mounted on a wiring board using such a flip-chip method, the length between the pad and the land corresponding to the pad is larger than when the bare chip is mounted using a method such as wire bonding. In addition, the inductance and the capacitance of the junction, that is, the bump, can be reduced, and the circuit configuration of the electronic device can be reduced in size and size, and the high-speed characteristics and high-frequency characteristics of the bare chip can be improved. Can be improved. Incidentally, silicon is generally used as a member forming the bare chip, and glass epoxy or ceramic is used as a member forming the wiring board.

[0006]

However, when the bare chip is mounted on the wiring board by using the flip-chip method, the bump breaks due to a change in temperature, and the reliability of the electrical connection between the bare chip and the wiring board is thereby reduced. There is a problem that is reduced.

That is, when a current is supplied to the bare chip with the circuit turned on, the internal circuit operates and consumes electric power, so that the bare chip generates heat. If the circuit is turned off to interrupt the current flowing through the bare chip, the circuit operation stops and the temperature of the bare chip drops to room temperature. Therefore, when heat is generated by turning on the circuit,
The member forming the bare chip and the member forming the wiring board extend according to their respective thermal expansion coefficients. However, since the two have different coefficients of thermal expansion, a distortion is generated in accordance with the difference in the amount of elongation between them, and a stress is applied to the bump joining the two from the distortion. Therefore, such a change in state is repeated by switching the circuit on and off, and the bump is broken due to metal fatigue. Incidentally, the breakage of the bump is not caused only by switching the circuit on and off, but may also be caused by a temperature change of the external environment.

In order to avoid such a problem, a method of encapsulating an epoxy resin or the like in a gap between the bare chip and the wiring board can be considered. By such a method, the stress applied to the bump is reduced by the encapsulated epoxy resin or the like, and the reliability can be improved. However, this method cannot completely remove the stress applied to the bump, and does not fundamentally solve the above-mentioned problem. Therefore, the breakage of the bump due to the temperature change cannot be completely avoided, and it has been difficult to obtain a reliable electrical connection for a long period of time.

The present invention has been made in view of the above points, and proposes a semiconductor device and a semiconductor device mounting method capable of improving the reliability of electrical connection with a wiring board regardless of repeated temperature changes. What you want to do.

[0010]

According to the present invention, a plurality of conductive layers made of a conductive material are laminated on a first electrode provided on one surface of a semiconductor device. To form

When a stress caused by a change in the temperature environment is applied to the bump electrode, each conductive layer of the bump electrode is cleaved and deformed, so that electrical connection can be maintained without breaking.

In the present invention, each protruding electrode formed on the first electrode is covered with a covering portion made of a resin material having shrinkage.

When a stress caused by a change in the temperature environment is applied to the protruding electrode, a gap due to breakage in the structure of the protruding electrode due to the contraction force of the covering portion is prevented, and the electrical connection is maintained. be able to.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

(1) First Embodiment In FIG. 1, a semiconductor device 1 is mounted on one surface of a substrate 2 which is a circuit surface, and a first electrode 3 (hereinafter, referred to as a first electrode) provided on one surface of the semiconductor device 1 is provided. This is called a pad 3 and a second electrode 4 (hereinafter referred to as a land 4) provided on the substrate 2.
Is referred to as “protruding electrode 5” formed on the surface of the pad 3.
(Hereinafter, referred to as bumps 5). A sealing resin 6 is sealed in a gap between the semiconductor element 1 and the substrate 2. The sealing resin 6 is the semiconductor element 1
The stress applied to the bumps 5 due to the difference in thermal expansion coefficient between the semiconductor element 1 and the substrate 2 is reduced, and the circuit surface of the semiconductor element 1 is covered to protect it from impurities and moisture contained in the outside air.

FIG. 2 in which parts corresponding to those in FIG.
As shown in FIG. 5, the bump 5 is a columnar projecting electrode in which a plurality of scale-like conductor layers (hereinafter, referred to as conductive layers) are stacked. Each conductive layer forming the bump 5 is in contact with another adjacent layer, and by this contact, the pad 3 and the land 4 are electrically connected.
Therefore, when a stress is applied to the bump 5 in the stacking direction of the conductive layers, the bump 5 maintains the electrical connection between the pad 3 and the land 4 without deformation.

On the other hand, as shown in FIG. 3 in which the same reference numerals are given to the portions corresponding to FIG. 1, when the temperature environment or the like changes, the expansion coefficient of the substrate 2 (for example, about 18 in the case of a general glass epoxy substrate). [ppm / ° C.]) and the expansion coefficient of the semiconductor element 1 (for example, about 3 [ppm /
[° C.])), the displacement is generated by multiplying the difference between the two expansion coefficients by the temperature difference from room temperature, and a stress is applied to the bump 5 in the direction perpendicular to the lamination direction of the conductive layer due to the displacement. Here, A shown in the figure indicates the amount of displacement of the semiconductor element 1, and B shown in the figure indicates the amount of displacement of the substrate 2.

At this time, since the respective conductive layers of the bump 5 are not physically joined, the respective conductive layers come into contact with each other to maintain the electrical connection between the pad 3 and the land 4 and to withstand the stress. Deformation (so-called cleavage) in a corresponding direction is performed. By the way, the semiconductor element 1 and the substrate 2 are returned to room temperature.
When the expansion of の has disappeared, the original state (FIG. 2) is restored.

Such bumps 5 are formed by repeating the plating under different conditions. In normal plating, when depositing and forming the plating layer little by little,
By depositing by controlling the current value and the like so that the conductive layers formed by such plating do not separate, a plurality of plating makes one layer as a whole. The bumps 5 are intentionally plated so that the conductive layers are separated, so that the conductive layers formed by the plating are not physically joined but are only in surface contact. The laminated structure is connected only electrically.

In the above configuration, the semiconductor element 1 has the bump 5 in a laminated structure in which a plurality of conductive layers are laminated, and when a stress is applied in a direction perpendicular to the laminating direction of the conductive layers, the bump 5 moves in a direction corresponding to the stress. Cleaved structure. When a stress is applied to the bump 5 due to thermal expansion due to a difference in expansion coefficient between the semiconductor element 1 and the substrate 2, the bump 5 is deformed (FIG. 3) to release the stress due to the stress, but to reduce the stress caused by the stress. By this contact, the electrical connection between the pad 3 and the land 4 is maintained. When the temperature returns to room temperature, the bumps 5 return to their original shapes. Such deformation of the bump 5 is due to cleavage, and does not break the bump 5 itself. Therefore, even when repeated stress is applied, the reduction in connection reliability due to metal fatigue does not occur as in the related art. As described above, even when stress caused by a temperature change is repeatedly applied, the semiconductor element 1 is not broken by the bumps 5 that maintain the electrical connection with the substrate 2.
Long-term connection reliability can be improved.

According to the above configuration, the bumps 5 serving as the protruding electrodes of the semiconductor element 1 have a laminated structure in which a plurality of conductive layers are laminated, and when a stress is applied in a direction perpendicular to the laminating direction of the conductive layers, the stress is increased. , The electrical connection with the substrate 2 can be maintained without breaking the bump 5 even when the stress due to the temperature change is repeatedly applied to the bump 5. Therefore, long-term connection reliability can be improved.

(2) Second Embodiment In FIG. 4 in which the same reference numerals are given to the parts corresponding to those in FIG. 2, the bumps 7 are formed by soldering,
The pad 3 and the land 4 are electrically connected to each other by melting and joining the surface in contact with the land 4.
The bump 7 is covered with the resin 8 on the peripheral side surface that does not contact the pad 3 and the land 4 without any gap.

The resin 8 for covering the bump 7 is made of a resin material having shrinkage, for example, a silicon resin or the like.
The resin 8 is coated so as to conform to the shape of the bump 7 at room temperature. When the resin is deformed by applying stress to the bump 7, the resin is deformed. Restores to the original shape. Such a bump 7
Is formed by a method described below. That is, as shown in FIG. 5, the bumps 7 previously formed on the surface of the pad 3 of the semiconductor element 1 are immersed in the resin reservoir 9. Here, the resin pool 9 is filled with the resin 8. After being immersed in the resin pool 9, the bump 7 is lifted up and covers the resin 8 by curing the resin 8 attached to the outside. On this occasion,
The resin 8 coated on the surface in contact with the land 4 is removed by a laser beam. Since the surface of the bump 7 from which the resin 8 has been removed is in a state in which the solder is exposed, the surface is brought into contact with the land 4 and heat is applied to the land 4 by the molten solder as usual. And can be joined.

In the above configuration, the bump 7 is covered with the resin 8 on the peripheral side surface without any gap, thereby preventing the breakage of the electrical connection between the pad 3 and the land 4 due to the destruction of the structure inside the bump 7. That is, conventionally, when a stress due to a change in the temperature environment is applied to the bump, the bump is deformed by the stress and the tissue is destroyed. The tissue thus destroyed creates gaps therein, thereby breaking the electrical connection. Even if the structure is destroyed by deformation when stress is applied, the bumps 7 hold down the broken structure due to the shrinkage force of the resin 8 coated on the outside without gaps, and prevent gaps from being formed inside the tissue. Can be. Accordingly, the bumps 7 prevent the electrical connection from being broken, and the reliability of the electrical connection can be maintained for a long time.

According to the above configuration, since the outside of the bump 7 is covered with the shrinkable resin 8 without any gap, the deformation of the bump 7 due to the stress caused by the change in the temperature environment is allowed and the deformation due to the deformation is allowed. Even if tissue destruction occurs, it is possible to prevent a gap from being formed inside due to the contraction force of the resin 8, thereby preventing breakage of the electrical connection of the bump 7, and thus, long-term connection reliability. Can be improved.

(3) Other Embodiments In the first embodiment described above, a case was described in which the bumps 5 having a structure in which a plurality of scale-like conductor layers were stacked were provided. The present invention is not limited to this, and a plurality of conductive materials may be used to form each conductive layer made of a conductor. For example, the layer in contact with the pad on the semiconductor element side has C
r (chromium), Ti (titanium), or the like is used, and Ni (nickel) is used for a layer in contact with a land on the substrate side. In general, aluminum is used for the pad and copper is used for the land. Thus, by using a metal that is compatible with the abutting metal for each conductive layer, the connection between the pad and the land can be made. Performance can be improved.

In the first embodiment described above, the bumps 5 which are columnar protruding electrodes formed by laminating scale-like layers are used.
However, the present invention is not limited to this, and may be, for example, a prismatic shape in which layers having a flat plate shape are stacked. That is, irrespective of the shape, the same effect as in the first embodiment can be obtained if the structure is cleaved when each layer is stressed.

Further, in the first embodiment described above, the case of the bump 5 formed by depositing a plurality of conductive layers by plating has been described. However, the present invention is not limited to this, and the present invention is not limited thereto. It may be formed by lamination. Even in this case, the first
The same effect as that of the embodiment can be obtained.

In the first embodiment described above, the case of the bump 5 having a structure in which each of the stacked conductive layers is cleaved when a stress is applied thereto has been described. However, the present invention is not limited to this. The peripheral side surface of the bump having such a cleavage structure may be covered with a resin having shrinkage.
As a result, when the bump deformed due to the stress caused by the change in the temperature environment returns to the normal temperature and restores the shape before the deformation, the bump easily deforms due to the shrinkage of the resin covering the bump. Shape can be restored.

Further, in the above-described second embodiment, the case where the bump 5 is covered by using a silicone resin as the shrinkable resin is described. However, the present invention is not limited to this.
Resins other than silicon resin may be used. That is, if the resin has shrinkage, the same effect as in the second embodiment can be obtained.

Further, in the second embodiment described above, a case was described in which the bump 5 was covered by using a silicone resin as the shrinkable resin. However, the present invention is not limited to this. The shrinkable resin may be used as the sealing resin sealed in the gap. In this case, there is no need to use a resin for covering the bumps separately from the sealing resin, and the same effect as in the second embodiment can be obtained with a simple configuration.

[0032]

As described above, according to the present invention, a plurality of conductive layers made of a conductive material are laminated on a first electrode provided on one surface side of a semiconductor device to form a projecting electrode. By doing so, when a stress due to a change in the temperature environment is applied to the bump electrode, each conductive layer of the bump electrode is cleaved and deformed, so that electrical connection can be maintained without breaking, Thus, the reliability of the electrical connection with the wiring board can be improved irrespective of the repeated temperature change.

Further, according to the present invention, each of the projecting electrodes formed on the first electrode is covered with the covering portion made of a resin material having shrinkage, so that the temperature of the projecting electrode is reduced. When a stress due to an environmental change is applied, it is possible to prevent a gap from being formed in the structure of the protruding electrode due to the contraction force of the covering portion, thereby maintaining the electrical connection. In addition, the reliability of the electrical connection with the wiring board can be improved regardless of the repeated temperature change.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a state in which a semiconductor element is mounted on a substrate.

FIG. 2 is an enlarged view showing a structure of a bump according to the first embodiment.

FIG. 3 is an enlarged view for explaining a connection state between a semiconductor element and a substrate in a high temperature state.

FIG. 4 is an enlarged view showing a structure of a bump according to a second embodiment.

FIG. 5 is a schematic diagram for explaining a bump according to a second embodiment.

[Explanation of symbols]

1 ... semiconductor element, 2 ... substrate, 3 ... pad, 4 ...
Land 5, 7, bump, 6 sealing resin, 8 resin, 9 resin pool.

Claims (6)

[Claims] A semiconductor device mounted on the substrate such that a plurality of first electrodes are provided on one surface side and each of the first electrodes is joined to a corresponding one of the second electrodes on the substrate; 2. The semiconductor device according to claim 1, further comprising: a plurality of conductive layers made of a conductive material, each of which is formed by laminating a plurality of conductive layers, and each of the first electrodes includes a protruding electrode. 2. The projection electrode according to claim 1, wherein the conductive layer bonded to the first electrode is formed using a conductive material having a good bonding property with the first electrode, and the conductive layer is bonded to the second electrode. 2. The semiconductor device according to claim 1, wherein the conductive layer to be formed is formed using a conductive material having a good bonding property with the second electrode. 3. A semiconductor device having a plurality of first electrodes provided on one surface side and mounted on the substrate such that each of the first electrodes is joined to each corresponding second electrode on the substrate. 3. The semiconductor device according to claim 1, further comprising: a protruding electrode formed on each of the first electrodes; and a covering portion made of a contractible resin material for covering each of the protruding electrodes. 4. A semiconductor device having a plurality of first electrodes provided on one surface side and mounted on the substrate such that each of the first electrodes is joined to each of the corresponding second electrodes on the substrate. In the mounting method of the first aspect, a first step of forming a plurality of conductive layers made of a conductive material on each of the first electrodes to form a bump electrode made up of the plurality of stacked conductive layers, A method of mounting a semiconductor device, comprising: a second step of joining the first electrode to the second electrode via a protruding electrode. 5. The method according to claim 4, wherein in the first step, the conductive layers are formed by sequentially depositing the conductive material by plating. 6. In the first step, the conductive layer to be bonded to the first electrode of the protruding electrode is formed using a conductive material having a good bonding property with the first electrode. 5. The method according to claim 4, wherein the conductive layer bonded to the second electrode is formed using a conductive material having good bonding properties with the second electrode.