JPH0669278A - Connecting method for semiconductor element - Google Patents

Abstract

PURPOSE:To provide a method for connecting a semiconductor element having high yield and high reliability. CONSTITUTION:The method for connecting a semiconductor element comprises the steps of uniformly spreading a plurality of conductive particles 17 on a plane jig, pressing the element 11 provided with metal bumps 9 parallel to the jig on connecting electrodes 5 to adhere the particles 17 to the bumps 9, press-bonding the bumps 9 of the element 11 to connecting pads 3 of a circuit board 4 through the particles 17 to electrically connect the bumps 9 to the pads 3, and inserting an insulation adhesive sheet 13 to a gap between the element 11 and the board 4 to fix the element 11 to the board 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor element connecting method, and more particularly to a face-down bonding method.

[0002]

2. Description of the Related Art As one of methods for mounting a semiconductor element, a bump is formed on a connection electrode of the semiconductor element, the semiconductor element is arranged so that the bump faces a wiring board, and the bump and the wiring board are arranged on the wiring board. A so-called face-down bonding method for connecting with a connection electrode is known as one of the leading mounting methods for high-density mounting.

Particularly, a method of electrically and mechanically connecting and mounting a semiconductor element on a wiring board by using an anisotropic conductive film as a connecting material is known as a method for realizing high-density mounting easily and at low cost. Has been.

For example, as shown in the structure of FIG. 3, a substrate 303 having connection pads 301 on the upper surface, and a substrate 30.
An adhesive 30 having an electrically insulating property, which is disposed on a region including a connection pad 301 formed by extending the conductor pattern 3 of FIG.
5, the conductive particles 307 are mixed and dispersed, and the anisotropic conductive adhesive 309 has conductivity in the thickness direction by pressing and has electrical insulation in the surface direction, and on the anisotropic conductive adhesive 309. Connection with the semiconductor element 313, which is placed on the substrate and mechanically bonded to the substrate 303 by the anisotropic conductive adhesive 309, and the connection electrode 311 on the lower surface is connected to the connection pad 301. An anisotropic conductive adhesive 309 is interposed over the entire area of the lower surface 315 of the electrode 311 and the lower surfaces 317 and 319 where the connection electrode 311 is not formed. It is disclosed in Japanese Patent Publication No. 62-6652.

Such a connection technique is shown, for example, in FIG.
As shown in FIG. 3, an anisotropic conductive film having a conductive anisotropy is provided between the semiconductor element 313 and the connection pad 301 formed in advance on the substrate 303 at a position corresponding to the connection electrode 311 of the semiconductor element 313 by etching or the like. , For example, a sheet-shaped anisotropic conductive adhesive 309 is arranged, and then the semiconductor element 313 is pressed onto the substrate 303, whereby the semiconductor element 313 is pressed.
The connection electrode 311 and the connection pad 301 are electrically connected. At this time, conductivity is obtained, and the semiconductor element 313 is mechanically fixed to the substrate 303 by the adhesive effect of the anisotropic conductive adhesive 309. FIG. 4 shows a state in which the semiconductor element 313 is thus mounted on the substrate 303.
It shows in (b). Further, as shown in FIG. 4, forming metal bumps 321 on the connection electrodes 311 of the semiconductor element 313 is also effective for obtaining a reliable connection.

However, when such an anisotropic conductive adhesive 309 is used, on the lower surface of the semiconductor element 313 facing the substrate 303, the connection electrode 31 shown in FIG.
1 and the lower surfaces 317 and 319 on which the connection electrodes 311 are not formed, the conductive particles 30 are formed over the entire area.
Although the anisotropic conductive adhesive 309 containing 7 is interposed, the electrical insulating property in the plane direction is not always sufficient in practice, and when the density of the conductive particles 307 is too high, the adjacent connection electrodes 311 are not formed. The electrical insulation between them is deteriorated and, for example, in the case of connection of a semiconductor element used for a liquid crystal display element, a display defect is caused in an image of the liquid crystal display element. On the other hand, if the density of the conductive particles 307 is reduced in order to avoid such a problem of deterioration in electrical insulation, the number of conductive particles involved in the electrical connection is reduced, so that the yield in the connection step and after the connection are reduced. The reliability of both decreases.

As described above, the conductive particles 30 are formed so that adjacent connection electrodes 311 are not short-circuited and that all connection electrodes 311 can be connected with good reliability.
However, it is difficult to balance the densities of the semiconductor elements, especially when used for connecting semiconductor elements having fine pitch bumps, and short circuits or connection failures between adjacent connection electrodes 311 occur frequently. As a result, there is a problem that the yield of the connection process is reduced and the reliability of the connection is reduced.

Besides using such an anisotropic conductive adhesive, a plurality of conductive resin balls having conductive plating on the surface may be sandwiched between the bumps of the semiconductor element and the pads on the substrate. The connection technology is to place the semiconductor element on the substrate mechanically on the substrate by pouring the adhesive from the insulating resin into the gap between the semiconductor element and the substrate by pressing from above to electrically connect them. Being developed.

Alternatively, Au is used as a bump for a semiconductor element.
A connection technique has been developed in which a (gold) bump is used and the Au (gold) bump is directly pressed against a pad on a substrate to electrically connect them.

More specifically, as shown in FIG. 5, such a connection method is performed by previously forming a conductive resin ball 501 on the connection electrode 311 of the substrate 303 or the semiconductor element 313 in advance.
Are arranged by performing precise alignment (positioning), and the connection electrode 3 is placed at the position of the conductive resin ball 501.
11, the semiconductor element 313 is pressed face down on the substrate 303 so that the connection pad 301 and the connection pad 301 coincide with each other to obtain an electrical connection, and the conductive resin ball 501 is crushed to a certain degree as it is. An adhesive 503 made of an insulating resin is poured into a gap between the semiconductor element 313 and the substrate 303 so that the semiconductor element 313 is attached to the substrate 3
It is to fix it mechanically on 03. Alternatively, an Au bump is used as the connection electrode 311 of the semiconductor element 313, and the Au bump is directly connected to the connection pad 301.
It is to press and connect to.

In this connection method, the connection electrode 311 of the semiconductor element 313 and the connection pad 301 of the substrate 303 are electrically connected by the conductive resin balls 501 (or Au bumps), and the semiconductor element 313 and the substrate 303 are mechanically connected. Adhesion is performed with an adhesive 503 made of an insulating resin, and electrical connection is ensured by the combined force of the compressive stress of the adhesive 503 and the restoring force and pressure of the conductive resin balls 501 (or Au bumps). I have to.

However, in the case of such a connection method, in order to dispose the conductive resin ball 501 (or Au bump) on the connection pad 301 on the substrate 303 or the connection electrode 311 of the semiconductor element 313, it is necessary to precisely It is necessary to perform precise alignment (positioning), but in recent years, with mounting technology that is becoming more dense and miniaturized, such a precise alignment process becomes more and more difficult and complicated. Therefore, there is a problem that the yield of the connection process is reduced.

[0013]

As described above, in the conventional method of connecting semiconductor elements by the face-down bonding method, there is a problem of short circuit due to defective insulation between bumps or connection pads, and a conductive resin ball as a connecting member. Alternatively, there is a problem such as a decrease in yield due to the addition of a complicated process for performing precise alignment for arranging the Au bumps.

The present invention has been made to solve such a problem, and an object thereof is a method of connecting a semiconductor element by a face-down bonding method, in which a problem of short circuit due to defective insulation between bumps and a connecting member. As a method for connecting a semiconductor element having a high yield and a high reliability, the problems such as a decrease in yield due to the addition of a complicated process for performing a precise alignment for arranging the conductive resin balls or Au bumps as described above are solved. To provide.

[0015]

According to a method of connecting a semiconductor element of the present invention, a plurality of conductive particles are dispersed on a plane, and a semiconductor element having metal bumps provided on connection electrodes is made parallel to the plane. The conductive particles are adhered to the metal bumps by pressing, and the conductive particles adhered to the metal bumps of the semiconductor element are pressed against the connection pads of the wiring board, and the metal bumps and the connection pads are connected to the conductive particles. It is characterized in that the semiconductor element and the wiring board are fixed to each other by electrically connecting the semiconductor element and the wiring board by inserting an insulating adhesive in a gap between the semiconductor element and the wiring board.

The conductive particles are preferably set to have a diameter smaller than the gap between the adjacent metal bumps of the semiconductor element and to have an appropriate size, and the diameter is plural. It is desirable that there is little variation. The material of the conductive particles may be any material that has conductivity. For example, Ni (nickel)
Such a metal ball may be used, or a conductive resin ball having a synthetic resin surface coated with a metal film may be used.

Further, when the conductive particles are dispersed on a plane, it is desirable that the distribution density on the plane is as uniform as possible.

Further, when the conductive particles are attached to the metal bumps, the conductive particles may be once fixed so that the conductive particles are pushed into the metal bumps so as not to be destroyed, or the conductive particles are attached to the metal bumps. Immediately after this, the conductive particles may be once fixed to the metal bumps by using an adhesive or the like having an appropriate viscosity such that the conductive particles do not become a nodular state.

When pressing the metal bumps of the semiconductor element and the connection pads of the wiring board through the conductive particles, the semiconductor element is pressed against the wiring board while applying heat, and these are pressed through the conductive particles. You may join in the form which melts a little.

The adhesive inserted in the gap between the semiconductor element and the wiring board may be placed on the wiring board in advance before the semiconductor element is pressed against the wiring board, or after the pressing, the gap portion is formed. May be injected into.

[0021]

According to the connection method of the present invention, the conductive particles are arranged only on the bumps of the semiconductor element, and the conductive particles are not arranged between the adjacent bumps. Therefore, good electrical insulation is provided between the adjacent bumps. Sex is obtained.

Moreover, since the bumps are convex, the conductive particles are pressed and adhered only onto the bumps, so that complicated alignment work on the bumps or the connection pads on the substrate can be performed. The conductive particles can be arranged without performing. As a result, the step of arranging the conductive particles becomes extremely simple, and a high yield can be realized.

Further, as compared with the connection using the anisotropic conductive adhesive, the number of conductive particles contributing to the conductivity on the bump can be increased, so that the connection resistance can be lowered and the connection reliability can be improved. improves.

As a result, highly reliable connection of semiconductor elements can be realized with high yield.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a semiconductor element connecting method of the present invention will be described in detail below with reference to the drawings. The semiconductor element and the wiring board used in this example for explaining the connection method according to the present invention are used in a liquid crystal display device.

As shown in FIG. 1, a connection pad 3 is formed at a predetermined position on a glass substrate 1 used in a liquid crystal display device. The connection pad 3 is, for example, a connection electrode pattern having a surface layer made of Al (aluminum) or a metal film or a metal multi-layer film mainly containing Al. In this embodiment, a Cr film and an Al film are formed in this order from the lower layer. ing. The thicknesses of the Cr film and the Al film are 70 nm,
It is set to 400 nm. Hereinafter, the metal multilayer film including the Cr film and the Al film will be simply referred to as a Cr / Al film. The wiring board 4 is configured in this way.

On the other hand, the liquid crystal driving IC, which is the semiconductor element 11 and has 120 outputs, has an outer dimension of approximately 5 mm × 9 mm. A connection electrode 5 and a passivation film 7 made of Al are formed, and although not shown on the connection electrode 5,
For example, a barrier metal layer composed of Ti, Ni, and Au in this order is formed. Metal bumps 9 made of, for example, Au are formed on the connection electrodes 5 via the barrier metal layer by a plating method or the like. The metal bump 9 has a height of about 23 μm and a size of about 100 μm square. The connection pitch is 140 μm. The surface of the semiconductor element 11, which is a liquid crystal driving IC, other than the metal bumps 9 is protected by the passivation film 7 made of silicon nitride or the like. The semiconductor element 11 is configured in this way.

Next, the step of adhering the conductive particles according to the present invention to the semiconductor element will be described with reference to FIG.

First, as shown in FIG. 2 (a), conductive particles 17 are sprayed on a flat jig 15 such as flat glass so that the density becomes uniform in a plane. Specifically, once the conductive particles 17 are scattered on the plane jig 15, and spread with a squeegee 19 on the plane jig 15 so as to have a substantially uniform thickness and a uniform planar density. The conductive particle layer 21 is formed. This state is shown in FIG.

The thickness of the conductive particle layer 21 is not more than the height of the metal bumps 9 of the semiconductor element 11 and not more than the gap between the adjacent metal bumps 9.

The conductive particles 17 are, for example, Ni.
Particles made of (nickel) are used. This conductive particle 17
The shape of does not have to be a perfect spherical shape, and may be, for example, a worm shape other than the spherical shape.

Next, the semiconductor element 11 provided with the metal bumps 9 on the connection electrodes 5 is pressed in parallel with the flat jig 15 on which the conductive particle layer 21 is formed by using, for example, a pressing jig 23. Then, at room temperature, a load of about 9 kg is applied for 5 seconds to push the conductive particles 17 onto the metal bumps 9 to some extent as shown in FIG. Then, as shown in FIG.
1 is separated from the flat jig 15.

The conductive particles 17 can be spread on the flat jig 15 by the simple method as described above, but if the conductive particle layer 21 is spread to a uniform height as much as possible, the conductive particles 17 can be spread over the metal bumps 9. Besides, it becomes easy to adhere only on the metal bumps 9 without adhering, it is possible to avoid the occurrence of a short circuit between the adjacent metal bumps 9, and the yield in the connection process is improved.

As a method of spreading the conductive particles 17 on the flat jig 15 to have a uniform thickness and a uniform planar density, a highly volatile liquid such as an organic solvent such as acetone is used. A method may be used in which the viscosity is adjusted so that the conductive particles do not become agglomerate, and the conductive particles 17 are dispersed in this liquid and applied onto the flat jig 15.

Further, for example, the conductive particles 1 are placed on the flat jig 15.
It is also possible to scatter 7 once and apply ultrasonic waves to this so as to level the height of the conductive particle layer 21. In this case, it is more effective to use a jig having fine irregularities having a size close to the diameter of the conductive particles 17 on the plane jig 15.

In the above method, the conductive particles 17 are used for the flat jig 1.
5, the conductive particles 17 are easily scattered when the semiconductor element 11 is pressed against the flat jig 15 to adhere the conductive particles 17 onto the metal bumps 9 of the semiconductor element 11.

Therefore, a highly volatile liquid, for example, a solvent such as polyvinyl alcohol, or a film that easily volatilizes due to heat during the connection step by thermocompression bonding which is a step subsequent to this adhesion step, for example, a film such as polyvinyl alcohol is used. make use of,
It is also effective to coat the conductive particles 17 and once fix the conductive particles 17 on the flat jig 15 by the weak force of the film.

Next, the semiconductor element 11 is mounted on the wiring board 4 by the face-down bonding method, and the metal of the liquid crystal driving IC, which is the semiconductor element 11, is connected to the connection pad 3 made of the Cr / Al film on the wiring board 4. The process of electrically connecting the bumps 9 will be described mainly with reference to FIG.

In this embodiment, the insulating adhesive sheet 13 is used as the insulating adhesive. This insulating adhesive sheet 13
Is adhesive and is made of a material that melts when the metal bumps 9 of the semiconductor element 11 are heated and pressed, and the resin of the pressed metal bumps 9 flows out. This is attached to a region on the wiring board 4 whose outer size is slightly larger than that of the semiconductor element 11. This is shown in FIG.
It shows in (b).

Then, the connection pads 3 and the metal bumps 9 are aligned with each other by an automatic bonding apparatus, and then, as shown in FIG.
As shown in FIG.
While heating from the back side of 1 to a temperature of about 190 ° C, apply a pressure of about 9 kg and hold for about 30 seconds.

At this time, the entire liquid crystal display element including the wiring board 4 is placed on a stage (not shown) heated to about 60 ° C.

Subsequently, when the bonding tool 23 is separated from the semiconductor element 11, the metal bumps 9 and the connection pads 3 are connected via the conductive particles 17 as shown in FIG.

In this way, the semiconductor element 11 is fixedly mounted on the wiring board 4, and the metal bumps 9 thereof and the connection pads 3 are connected via the conductive particles 17.

Insulating adhesive sheet 13 used in this example
Is an epoxy-based thermosetting resin, and is 190 ° C when connected.
By heating and holding for about 30 seconds, the curing proceeds, and the liquid crystal driving IC is firmly bonded to the passivation film 7 as the surface protection layer of the semiconductor element 11 and the wiring board 4. Since the entire semiconductor element 11 which is a liquid crystal driving IC is firmly and mechanically fixed on the wiring board 4 in this manner, it is not necessary to reinforce the fixation by potting or the like thereafter.

When the contact resistance of the connection portion of the semiconductor element 11 which is the liquid crystal driving IC of the liquid crystal display device thus connected is measured and evaluated, the initial values are averaged for 182 connection points. It was 0.1Ω, the maximum value was 0.2Ω, and it was confirmed that there were no open or short circuits.

Further, a thermal shock test in which -30 ° C. (30 minutes) / 85 ° C. (30 minutes) is repeated 500 cycles, and 65 ° C. RH
95% (relative humidity) 1000 hours high temperature and high humidity storage test, 85
High temperature storage test at 1000 ℃ for 1000 hours and RH at -10 ℃ to 65 ℃
The liquid crystal display is subjected to various reliability tests such as a 95% 5-cycle temperature / humidity cycle test, an operation test, and a mechanical durability test such as a vibration test and an impact test, and the durability reliability is evaluated. As a result, the result was that there was no occurrence of open or short at the connection point.

Thus, according to the connection method of the present invention,
Since the conductive particles 17 are arranged only on the metal bumps 9 of the semiconductor element 11 and the conductive particles 17 are not arranged in the gaps between the adjacent metal bumps 9, good electrical insulation between adjacent metal bumps 9 is obtained. Can be obtained.

Moreover, since the conductive particles 17 can be arranged on the metal bumps 9 or the connection pads 3 of the wiring board 4 without performing a complicated alignment work, the arrangement process is extremely simple and a high yield is realized. it can.

Further, as compared with the connection using the anisotropic conductive adhesive, the conductive particles 17 contributing to the conductivity on the metal bumps 9 are formed.
Since a large number can be taken, the connection resistance can be reduced and the connection reliability is improved.

As a result, highly reliable connection of semiconductor elements can be realized with high yield.

It is desirable that the conductive particles 17 have a diameter smaller than the gap between the adjacent metal bumps 9 of the semiconductor element 11 and the thickness of the metal bumps 9 and have an appropriate size. Further, it is desirable that the diameter of the plurality of conductive particles has little variation. In this embodiment, the width of the adjacent metal bumps 9 of the semiconductor element 11 is 10
The pitch is 0 μm, the pitch is 140 μm, and the gap is 40 μm. The thickness of the metal bump 9 is 23 μm. The diameter of the conductive particles 17 is set to 2 to 6 μm. As described above, an effective connection is realized by such a combination.

The material of the conductive particles 17 may be any material having conductivity. For example, it may be made of a metal such as Ni (nickel) as in this embodiment,
Alternatively, a conductive resin ball having a surface of synthetic resin coated with a metal film may be used.

The insulating adhesive sheet 13 inserted in the gap between the semiconductor element 11 and the wiring board 4 is
May be previously arranged on the wiring board 4 before being pressed against the wiring board 4, or may be injected into the gap portion after the pressing.

In the present embodiment, the case where the metal bumps 9 of the semiconductor element 11 as the liquid crystal driving IC is Au has been described in detail as an example. However, as the metal bumps 9, other conductive particles 17 are used. It may be a metal bump made of a material that bites well, for example, a Pb-Sn-based or Pb-In-based solder bump.

Further, a semiconductor element with a metal bump formed by forming a barrier metal on the connection electrode 5 of the semiconductor element 11 and plating is described in detail. The structure of the barrier metal is, for example, a Pt / Ti film. It may be. In addition to the plating method, the connection method of the present invention can be applied to the case where bumps formed by the dip method or the ball bonding method are used.

In the present embodiment, the case where the connection pad 3 formed on the glass substrate 1 is made of a Cr / Al film has been described as an example. However, the connection pad 3 is a metal or a metal multi-layer film and its surface layer is The present invention can be applied not only when the material is Al or Al alloy, but also when other thin metal is formed on Al or Al alloy, for example. As such an example, Mo on the glass substrate 1,
Connection pad 3 in which Al and Mo are formed in this order (thicknesses are 70 nm, 400 nm, 500 nm, etc.)
It is also applicable when using.

In each of the above embodiments, the liquid crystal display device has been described as an example, but the connection method of the present invention is not limited to application to the semiconductor element of the liquid crystal display device. It can be applied to all semiconductor devices mounted face down on a substrate.

In a liquid crystal display device using the connection method of the present invention for its liquid crystal driving IC, the liquid crystal driving IC
Since the connection of C has sufficiently high reliability, it is not necessary to cover it from the back surface or the side surface with resin for sealing, but it goes without saying that it may be covered with sealing resin in such a manner.

[0059]

As described above in detail, the connection method of the present invention is a face-down type semiconductor element connection method, in which the problem of short circuit due to defective insulation between bumps and the conductivity as a connection member. It is possible to solve a problem such as a decrease in yield due to the addition of a complicated process for performing a precise alignment for arranging a resin ball or Au bump, and realize a highly reliable and highly reliable connection of semiconductor elements. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a process of connecting a semiconductor device according to the present invention.

FIG. 2 is a diagram showing a process of attaching conductive particles according to an example onto metal bumps of a semiconductor element.

FIG. 3 is a diagram showing an example of a conventional semiconductor element connection technique using an anisotropic conductive adhesive.

FIG. 4 is a diagram showing an example of a conventional semiconductor element connection process using an anisotropic conductive adhesive.

FIG. 5 is a diagram showing an example of a conventional semiconductor element connection technique using conductive resin balls.

[Explanation of symbols]

1 ... Glass substrate, 3 ... Connection pad, 4 ... Wiring substrate, 5 ...
Connection electrode, 7 ... passivation film, 9 ... metal bump,
11 ... Semiconductor element, 13 ... Insulating adhesive sheet, 15 ... Planar jig, 17 ... Conductive particles, 19 ... Squeegee, 21 ... Conductive particle layer, 23 ... Pressing jig

Claims (1)

[Claims] 1. A plurality of conductive particles are scattered on a plane, and a semiconductor element having metal bumps on connection electrodes is pressed in parallel with the plane to attach the conductive particles to the metal bumps. The conductive particles attached to the metal bumps of the semiconductor element are pressed against the connection pads of the wiring board to electrically connect the metal bumps and the connection pads through the conductive particles, and the semiconductor element and the wiring. A method of connecting a semiconductor element, wherein the semiconductor element and the wiring board are fixed to each other by interposing an insulating adhesive in a gap between the board and the substrate.