Method of flip-chip mounting

A method of flip-chip mounting can reliably and stably mount a semiconductor chip to a mounting substrate while avoiding problems such as damage to the semiconductor chip due to a difference in thermal expansion coefficients between the semiconductor chip and the mounting substrate. The method of flip-chip mounting a semiconductor chip supports a mounting substrate on a stage in a state where a resin material has been supplied onto a chip mounting surface of the mounting substrate and presses the semiconductor chip toward the mounting substrate using a pressure/heat applying head to bond the semiconductor chip to the mounting substrate and thermally harden the resin material. A concave part is provided in a support surface of the stage that supports the semiconductor chip, and the semiconductor chip is bonded to the mounting substrate by pressing the semiconductor chip toward the mounting substrate using the pressure/heat applying head in a state where the mounting substrate is bent toward the concave part.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of flip-chip mounting and in more detail to a method of flip-chip mounting that can avoid the problem of a semiconductor chip being damaged during bonding due to differences in thermal expansion coefficients between the semiconductor chip and a mounting substrate.

2. Related Art

Among methods of mounting a semiconductor chip on a mounting substrate as a flip-chip, as shown inFIG. 5A, there is a method that connects a semiconductor chip14as a flip-chip after applying a resin material12in advance onto a semiconductor chip mounting region of a mounting substrate10.FIG. 5Bshows a state where the semiconductor chip14is supported by a pressure/heat applying head20, is positioned with respect to the mounting substrate10, and is mounted on the mounting substrate10while pressure and heat are applied to the semiconductor chip14.

When the resin material12is supplied onto the mounting substrate10in advance and the semiconductor chip14is connected as a flip-chip, as shown inFIG. 5B, the mounting substrate10is supported on a stage22that has been heated to around 70 to 80° C., and mounting is carried out after the pressure/heat applying head20has been heated to the thermal hardening temperature or higher of the resin material12(around 200° C., for example). By merely heating the semiconductor chip14for around five seconds using the pressure/heat applying head20, bumps14aof the semiconductor chip14are electrically connected to connection pads formed on the mounting substrate10and the resin material12that fills the gap between the semiconductor chip14and the mounting substrate10is thermally hardened.

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

However, since the thermal expansion coefficients of the semiconductor chip14and the mounting substrate10that is made of resin differ by a factor of around three, when the semiconductor chip14is flip-chip mounted, due to the large difference in thermal expansion between the semiconductor chip14and the mounting substrate10, after mounting, as shown inFIG. 6, the mounting substrate10becomes warped toward the semiconductor chip14.

If mounting is carried out with the mounting substrate10in a warped state and the gap between the surfaces of the mounting substrate10and the semiconductor chip14becomes narrow in a central part of the chip mounting surface of the mounting substrate10, filler such as alumina or silica added to the resin material12to make the thermal expansion coefficient match that of the semiconductor chip14is compressed by the mounting substrate10and the semiconductor chip14, resulting in the problem of damage to the circuit surface of the semiconductor chip14and in wiring formed on the circuit surface becoming disconnected.

When the bumps14aare formed on the semiconductor chip14at wide intervals, it is possible to form large, high bumps14a, and therefore even if the mounting substrate10becomes warped during flip-chip bonding, the problem of the semiconductor chip14being damaged hardly occurs. However, with a product where the bumps14aare disposed with a high density, the bumps14athemselves become small and the height of the bumps14abecomes lower (around 15 μm), and therefore there is the problem that the semiconductor chip14can be damaged even if the mounting substrate10only becomes slightly warped.

SUMMARY OF THE INVENTION

The present invention was conceived to solve the problems described above, and it is an object of the present invention to provide a method of flip-chip mounting that can reliably and stably mount a semiconductor chip while avoiding problems such as damage to the semiconductor chip due to a difference in thermal expansion coefficients between the semiconductor chip and a mounting substrate when connecting the semiconductor chip as a flip-chip to the mounting substrate.

To achieve the stated object, a method of flip-chip mounting a semiconductor chip according to the present invention supports a mounting substrate on a stage in a state where a resin material has been supplied onto a chip mounting surface of the mounting substrate and presses the semiconductor chip toward the mounting substrate using a pressure/heat applying head to bond the semiconductor chip to the mounting substrate and thermally harden the resin material, wherein a concave part is formed in a support surface of the stage that supports the semiconductor chip, and the semiconductor chip is bonded to the mounting substrate by pressing the semiconductor chip toward the mounting substrate using the pressure/heat applying head in a state where the mounting substrate is bent toward the concave part.

A suction hole that is in communication with a base surface of the concave part may be provided in the stage, and when the semiconductor chip is bonded to the mounting substrate by the pressure/heat applying head, bonding may be carried out in a state where the mounting substrate is pulled by suction from the suction hole to forcibly bend the mounting substrate toward the concave part.

Another method of flip-chip mounting a semiconductor chip supports a mounting substrate on a stage in a state where a resin material has been supplied onto a chip mounting surface of the mounting substrate and presses the semiconductor chip toward the mounting substrate using a pressure/heat applying head to bond the semiconductor chip to the mounting substrate and thermally harden the resin material, wherein a surface of the pressure/heat applying head on which the semiconductor chip is held by suction is formed as a concave surface, a suction hole that is in communication with the concave surface is provided, and when the semiconductor chip is bonded to the mounting substrate by the pressure/heat applying head, the semiconductor chip is pulled by suction from the suction hole to forcibly bend the semiconductor chip toward the concave surface.

Yet another method of flip-chip mounting a semiconductor chip supports a mounting substrate on a stage in a state where a resin material has been supplied onto a chip mounting surface of the mounting substrate and presses the semiconductor chip toward the mounting substrate using a pressure/heat applying head to bond the semiconductor chip to the mounting substrate and thermally harden the resin material, wherein a spacer that supports the semiconductor chip at a distance from the mounting substrate is provided on the mounting substrate, and the mounting substrate and the semiconductor chip are bonded together so that the mounting substrate and the semiconductor chip are electrically connected and the mounting substrate and the semiconductor chip are separated by the spacer.

Yet another method of flip-chip mounting a semiconductor chip supports a mounting substrate on a stage in a state where a resin material has been supplied onto a chip mounting surface of the mounting substrate and presses the semiconductor chip toward the mounting substrate using a pressure/heat applying head to bond the semiconductor chip to the mounting substrate and thermally harden the resin material, wherein a spacer that supports the semiconductor chip at a distance from the mounting substrate is provided on a bonding surface of the semiconductor chip, and the mounting substrate and the semiconductor chip are bonded together so that the mounting substrate and the semiconductor chip are electrically connected and the mounting substrate and the semiconductor chip are separated by the spacer.

According to the method of flip-chip mounting according to the present invention, it is possible to flip-chip mount a semiconductor chip while solving the problem of a mounting substrate becoming bent during mounting due to a difference in thermal expansion coefficients between the semiconductor chip and the mounting substrate resulting in the semiconductor chip becoming damaged by filler included in a resin material, and therefore a drop in quality can be prevented.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

FIG. 1shows a first embodiment of a method of flip-chip mounting according to the present invention. In the present embodiment, the resin material12is applied in advance onto a chip mounting surface of the mounting substrate10and the semiconductor chip14is positioned relative to and mounted upon the mounting substrate10while being held by suction on the pressure/heat applying head20.

In the present embodiment, a concave part24ais formed on a support surface of a stage24that supports the mounting substrate10, a suction hole25that is in communication with an inner base surface of the concave part24ais provided in the stage24, and the suction hole25is connected to a vacuum suction apparatus (not shown). The concave part24ais formed in a region that is within a region where the bumps14aare formed on the semiconductor chip14.

In the present embodiment, after the mounting substrate10has been set on the stage24and the resin material12has been supplied onto the chip mounting surface of the mounting substrate10, the vacuum suction apparatus is operated to pull the mounting substrate10by suction via the suction hole25and the semiconductor chip14held by suction on the pressure/heat applying head20is flip-chip mounted in a state where the mounting substrate10is downwardly convex, i.e., a state where a central part of the mounting substrate10is bent downward away from the semiconductor chip14.

The pressure/heat applying head20is heated to around 200° C. The semiconductor chip14is held by suction on the pressure/heat applying head20and is pressed toward the mounting substrate10so that the bumps14aof the semiconductor chip14are bonded to connection terminals provided on the mounting substrate10by soldering or the like. The resin material12held between the semiconductor chip14and the mounting substrate10fills the gap between the semiconductor chip14and the mounting substrate10and is thermally hardened. Since the stage24is formed as a flat surface at positions where the bumps14aof the semiconductor chip14are formed, the pressing force acts reliably on the mounting substrate10and the semiconductor chip14so that electrical connections can be reliably produced between the bumps14aand the connection terminals of the mounting substrate10.

The resin material12seals and protects the bonded parts of the semiconductor chip14and the mounting substrate10from the outside. When the semiconductor chip14heats up and thermal stress acts between the semiconductor chip14and the mounting substrate10, the resin material12also acts so as to firmly hold the semiconductor chip14and the mounting substrate10together so that the electrical connections between the bumps14aand the connection terminals do not become unreliable.

In the method of flip-chip mounting according to the present embodiment, when the mounting substrate10is supported on the stage22, mounting is carried out with the mounting substrate10forcibly bent so as to be downwardly convex. By doing so, after mounting, even if the mounting substrate10deforms so as to become bent toward the semiconductor chip14, the gap between the mounting substrate10and the circuit surface of the semiconductor chip14is prevented from becoming excessively narrow. By keeping the gap between the semiconductor chip14and the chip mounting surface of the mounting substrate10at a predetermined distance or above, it is possible to avoid the problem of the circuit surface of the semiconductor chip14being damaged by the filler included in the resin material12after mounting.

In a method of flip-chip mounting that forcibly bends the mounting substrate10by pulling the mounting substrate10by suction from the concave part24aside of the stage24, by controlling the vacuum suction force, the amount by which the mounting substrate10bends can be adjusted, and therefore it is possible to control the gap between the mounting substrate10and the semiconductor chip14after mounting in accordance with the product. It is effective to adjust the amount by which the mounting substrate10bends since the size, thickness, and material of the mounting substrate10differ from product to product.

Note that in the method of flip-chip mounting where the concave part24ais provided in the stage24, it is also possible to mount the semiconductor chip14as a flip-chip with the mounting substrate10set on the stage24but without pulling the mounting substrate10by suction from the suction hole25to forcibly bend the mounting substrate10.

That is, after the resin material12has been supplied onto the mounting substrate10, when the semiconductor chip14held by suction on the pressure/heat applying head20is pressed toward the mounting substrate10, the mounting substrate10bends toward the concave part24avia the resin material12. This method is effective in cases where the semiconductor chip14will not be damaged by the filler included in the resin material12even if the mounting substrate10is not greatly bent during flip-chip mounting, since the construction of the apparatus can be simplified.

Second Embodiment

FIG. 2shows a second embodiment of a method of flip-chip mounting according to the present invention. The method of flip-chip mounting according to the present embodiment is characterized by using a stage22where the support surface that supports the mounting substrate10is formed as a flat surface and using a pressure/heat applying head26where a concave surface26athat allows the semiconductor chip14to bend away from the chip mounting surface of the mounting substrate10is provided on a surface on which the semiconductor chip14is held and a suction hole27is provided so as to be in communication with a center position of the concave surface26a. The suction hole27is also in communication with a vacuum suction apparatus (not shown).

FIG. 2shows a state where, after the mounting substrate10has been set on the stage22and the resin material12has been supplied onto the chip mounting surface of the mounting substrate10, the semiconductor chip14is held by suction on the pressure/heat applying head26, and the semiconductor chip14is heated while being pressed onto the mounting substrate10so as to be flip-chip mounted. By pulling the semiconductor chip14by suction from the suction hole27provided in the pressure/heat applying head26, the semiconductor chip14is flip-chip mounted in a state where the semiconductor chip14is upwardly convex as shown inFIG. 2, i.e., where a central part of the semiconductor chip14is bent in a direction away from the mounting substrate10.

The resin material12held between the mounting substrate10and the semiconductor chip14is heated by the pressure/heat applying head26, fills the gap between the semiconductor chip14and the mounting substrate10, and thermally hardens.

In the method of flip-chip mounting according to the present embodiment, since the semiconductor chip14is mounted in a state where the semiconductor chip14is bent so as to be upwardly convex, it is possible to mount the semiconductor chip14while preventing the gap between the semiconductor chip14and the mounting substrate10from becoming excessively narrow after mounting. By doing so, it is possible to avoid the problem of the circuit surface of the semiconductor chip14becoming damaged by the filler included in the resin material12. Note that the filler included in the resin material12is mixed in so as to constitute around 30 to 40% by weight, and therefore is a large proportion of the resin material12.

When air is evacuated to pull the semiconductor chip14from the suction hole27provided in the pressure/heat applying head26, by controlling the vacuum suction force of the vacuum suction apparatus, mounting can be carried out with the amount of bending of the semiconductor chip14being suitably controlled. In the same way as when mounting is carried out with the mounting substrate10in a bent state in the first embodiment, when mounting is carried out with the semiconductor chip14in a bent state, by slightly bending the semiconductor chip14by only a slight amount, it is possible to control the gap between the semiconductor chip14and the chip mounting surface of the mounting substrate10to an extent where the circuit surface of the semiconductor chip14is not damaged.

Third Embodiment

FIG. 3shows a third embodiment of a method of flip-chip mounting according to the present invention. The method of flip-chip mounting according to the present embodiment is characterized by providing a spacer11, which supports the semiconductor chip14at a distance from the mounting substrate10, in advance on a chip mounting surface of the mounting substrate10and mounting the semiconductor chip14with the spacer11between the mounting substrate10and the semiconductor chip14.

As shown inFIG. 3, a spacer11is formed using a resist in advance on the chip mounting surface of the mounting substrate10and after the resin material12has been supplied onto the chip mounting surface of the mounting substrate10, the semiconductor chip14is mounted on the mounting substrate10using the pressure/heat applying head20. By setting the thickness of the spacer11at a thickness where the semiconductor chip14is supported at a distance from the mounting substrate10without bonding of the connected parts of the semiconductor chip14and the mounting substrate10being obstructed and without the circuit surface of the semiconductor chip14being damaged, when the semiconductor chip14is flip-chip mounted on the mounting substrate10, mounting can be carried out without the filler included in the resin material12damaging the semiconductor chip14.

The spacer11is formed in a predetermined pattern by applying a resist or using a resist material formed as a film. When forming the spacer11, it is possible to form the spacer11at a position that does not adversely affect the semiconductor chip14during mounting. By using a photosensitive resist material, the spacer11can be formed in a desired pattern.

Fourth Embodiment

FIG. 4shows a fourth embodiment of a method of flip-chip mounting according to the present invention. The method of flip-chip mounting according to the present embodiment is characterized by forming a spacer13on the circuit surface of the semiconductor chip14, that is, a surface that faces the mounting substrate10when mounting is carried out, instead of forming the spacer11on the mounting substrate10.

As the method of forming the spacer13on the circuit surface of the semiconductor chip14, it is possible to use a method that applies a resin (an adhesive) on the circuit surface of the semiconductor chip14and then hardens the resin to produce the spacer13. In the manufacturing process of the semiconductor chip14, it is judged whether the characteristics of individually formed semiconductor chips are defective or non-defective at the semiconductor wafer-stage and marking is carried out to indicate whether the individual semiconductor chips are defective or non-defective. When marking is carried out to indicate whether the individual semiconductor chips are defective or non-defective, instead of marking, it is possible to apply the resin that forms the spacer13described above, with the actual spacer13being formed in a later process. This method is efficient in that the marking of the semiconductor chips and the formation of the spacers13can be carried out simultaneously.

In the same way as the spacer11of the third embodiment, the protruding height of the spacer13is set so that a predetermined gap is kept between the semiconductor chip14and the mounting substrate10without obstructing the operation that electrically connects the semiconductor chip14to the mounting substrate10. In the present embodiment also, the spacer13is formed at a position on the circuit surface of the semiconductor chip14that does not adversely affect the semiconductor chip14after mounting.

In this way, by flip-chip mounting with a spacer13provided on the surface of the semiconductor chip14that faces the mounting substrate10, it is possible to reliably mount the semiconductor chip14on the mounting substrate10without damaging the semiconductor chip14.