Patent ID: 12237295

MODE OF DISCLOSURE

A flip-chip laser bonding system according to the present disclosure will now be described in detail with reference to the accompanying drawings.

FIG.1is a perspective view of a flip-chip laser bonding system according to an embodiment of the present disclosure, andFIG.2is a front view of the flip-chip laser bonding system illustrated inFIG.1.

A flip-chip laser bonding system of the present embodiment is an apparatus for bonding a semiconductor chip to a substrate in a flip-chip form by using a laser beam. Solder bumps are formed on one or both of the substrate and the semiconductor chip. Accordingly, the solder bumps are instantaneously melted and solidified by the energy transmitted by the laser beam, thereby bonding the semiconductor chips on the substrate.

Referring toFIGS.1and2, the flip-chip laser bonding system according to the present embodiment includes a supply unit110, a fixing unit120, a laser unit200, and a discharge unit130.

The supply unit110is configured to supply, to the fixing unit120, a substrate for laser bonding. The substrate is supplied with a plurality of semiconductor chips arranged thereon. Typically, a flux is applied to the substrate and semiconductor chips are placed thereon. Due to the viscosity or adhesiveness of the flux, the semiconductor chips are temporarily bonded to the substrate. As long as relatively large vibrations or external forces are not applied, the semiconductor chips placed on the substrate are kept in position relative to the substrate by flux without being shaken.

The supply unit110may sequentially supply, to the fixing unit120, a plurality of substrates, each having the semiconductor chips temporarily bonded thereto. In the present embodiment, the supply unit110may supply the substrate to the fixing unit120by using belts that support opposite sides of the substrate.

The fixing unit120may also transfer, to the working position, the substrate transported from the supply unit110by using belts supporting opposite sides of the substrate. The fixing unit120may fix the substrate by adsorbing the lower surface thereof.

The laser unit200may be arranged above the fixing unit120. The laser unit200may include a laser head210and a laser transport unit220. The laser head210radiates a laser beam onto a substrate fixed on the fixing unit120to transfer energy. The laser transport unit220moves the laser head210in the vertical direction and the horizontal direction. A control unit500operates the laser unit200in such a way that the laser head210radiates a laser beam while sequentially moving above the semiconductor chip of the substrate fixed on the fixing unit120.

A mask400may be arranged above the fixing unit120on which the substrate is fixed. The mask400may be supported by a mask mounting unit300. The mask400may have transmission portions440capable of transmitting laser light. The laser beam irradiated from the laser head210reaches the semiconductor chip located thereunder through the transmission portions440of the mask400. A specific structure of the mask400will be described later.

A pressing unit350is configured to raise or lower one of the mask mounting unit300and the fixing unit120with respect to the other so as to press the semiconductor chip attached to the substrate by the transmission portions440of the mask400. In the present embodiment, the pressing unit350may raise or lower the substrate. Referring toFIG.2, the pressing unit350may raise or lower a configuration of the fixing unit120that adsorbs the lower surface of the substrate. When the pressing unit350lifts up the substrate in a state in which the mask400is mounted on the mask mounting unit300, the weight of the transmission portions440of the mask400may affect and press the semiconductor chip.

The discharge unit130may receive the substrate on which the laser bonding of the semiconductor chip has been completed in the fixing unit120and discharge the same. Like the supply unit110and the fixing unit120, the discharge unit130may receive the substrate from the fixing unit120by using belts supporting opposite sides of the substrate and discharge the substrate to an unloader.

The control unit500may control the operation of the main components of the present disclosure, including the supply unit110, the fixing unit120, the laser unit200, the discharge unit130, and the like.

An inspection camera230may be arranged above the fixing unit120. In the present embodiment, the inspection camera230is provided on the laser unit200and is moved together with the laser head210by the laser transport unit220. The inspection camera230may capture images of the substrate or the mask400disposed thereunder so as to allow the control unit500to identify the location of the semiconductor chip or to determine whether the mask400is contaminated.

An inspection lamp610may be arranged under the inspection camera230. In the present embodiment, the inspection lamp610may be provided in a mask replacement unit600, which will be described later. The inspection lamp610may be disposed under the path along which the mask400is transported. The inspection lamp610radiates light from under the mask400. The light generated by the inspection lamp610may be transmitted to the inspection camera230disposed thereabove through the transmission portions440of the mask400. By using the illumination of the inspection lamp610, the inspection camera230may effectively capture the image of the transmission portions440of the mask400. Once the control unit500receives the image captured by the inspection camera230, the control unit500inspects whether the transmission portions440of the mask400are contaminated, and based on this result, the control unit500may determine whether the mask400needs to be replaced.

Referring toFIG.3, an infrared camera240is provided above the fixing unit120. The infrared camera240captures the image of the semiconductor chip of the substrate fixed on the fixing unit120. When the mask400is disposed above the substrate, the image of the semiconductor chip may be captured through the transmission portions440of the mask400. The control unit500may identify the region-by-region temperature of the semiconductor chip by using values obtained from the image captured by the infrared camera240. The control unit500may control the operation of the laser head210in the laser unit200by using the measurement values of the infrared camera240.

The mask replacement unit600is configured to store a plurality of masks and, if needed, to replace the mask400mounted on the mask mounting unit300. If needed, the control unit500may send a command for replacing the mask400to the mask replacement unit600, and the mask replacement unit600may replace the mask400mounted on the mask mounting unit300with a new mask. As described above, since the inspection lamp610is provided in the mask replacement unit600, the contamination test may be performed while the mask400to be replaced is arranged above the inspection lamp610. Once it is determined by the control unit500based on the image taken by the inspection camera230that the contamination has not occurred, the mask400is transported back to the mask mounting unit300. When the control unit500determines that the mask400has been contaminated, the contaminated mask400may be stored in the mask replacement unit600and a new mask is extracted and transported to the mask mounting unit300.

Hereinafter, the structure of the mask400will be described with reference toFIGS.4and5.

In the present embodiment, the mask400includes a mask body410, a plurality of transmission holes420, and a plurality of transmission portions440.

The mask body410may formed in a flat-plate shape. The mask body410may be prepared into a shape corresponding to the shape of the substrate and is prepared to a size similar to that of the substrate in consideration of the size of the substrate.

The mask body410may have the plurality of transmission holes420. The transmission holes420are respectively formed at positions corresponding to the positions of the semiconductor chips of the substrate to be placed under the mask400. The transmission holes420may be formed in a size and shape similar to those of the semiconductor chip. In the present embodiment, the transmission holes420of the mask body410may be slightly larger than the sizes of the semiconductor chips.

Each of the transmission holes420is provided with a locking protrusion430formed to protrude inward. In the present embodiment, as illustrated inFIG.4, the locking protrusion430is formed in a shape corresponding to the transmission holes420. As for the shape of the locking protrusion430, various other shapes other than the shape illustrated inFIG.4may be used.

Referring toFIG.5, the transmission portions440may be inserted into the transmission holes420, one by one. At this time, the lower portion of each of the transmission portions440is formed to be caught by the locking protrusion430. A lower surface of each of the transmission portions440may be formed in a planar shape. When the transmission portions440respectively press the semiconductor chips on the substrate by the operation of the pressing unit350, the semiconductor chips may be uniformly and flatly pressed by the transmission portions440, each having a flat lower surface. The transmission portions440may include a transparent material through which a laser beam may pass. Quartz, widely used for transmitting a laser beam, may be used as a material for the transmission portions440. The mask body410may include an opaque material through which the laser beam does not pass. The mask body410may prevent the laser beam from passing through the region except for the transmission portions440.

In the present embodiment, a weight indentation441may be formed on the upper surface of each of the transmission portions440. A weight442may be disposed in the weight indentation441. The weight442may further increase the force applied by the transmission portions440to press the semiconductor chip.

Hereinafter, the operation of the flip-chip laser bonding system according to the present embodiment configured as described above will be described.

First, a substrate on which semiconductor chips are arranged is prepared. As described above, the supply unit110may sequentially supply substrates with semiconductor chips arranged thereon in such a manner that the semiconductor chips having solder bumps applied with flux thereunder are temporarily bonded to the substrate.

The supply unit110supplies the substrate to the fixing unit120. The fixing unit120receives the substrate and fixes the same by adsorbing the lower surface thereof.

In this state, the laser transport unit220of the laser unit200captures the images of the semiconductor chips of the substrate by moving the inspection camera230over the substrate. The control unit500identifies the positions of the semiconductor chips by using the images received from the inspection camera230.

Next, the mask replacement unit600may transport the mask400to the upper side of the fixing unit120. The mask mounting unit300receives the mask400and mounts the same on the upper side of the substrate.

In this state, the pressing unit350may raise the substrate fixed on the fixing unit120.

When the substrate is raised by the pressing unit350, the semiconductor chips of the substrate come into contact with the lower surface of the transmission portions440of the mask400, respectively. As the pressing unit350continues to raise the substrate, each of the semiconductor chips lifts the transmission portions440against the mask body410. As described above, since the transmission portions440are caught by the locking protrusion430of the mask body410, in the case where the semiconductor chips are continuously raised, the transmission portions440may be lifted upward by the semiconductor chips. That is, in the stat that the mask body410is in a stationary state, only the transmission portions440are raised. As a result, the weight of the transmission portions440affects each semiconductor chip to flatly press the upper surface of the semiconductor chips. At this time, when the weight442is disposed in the weight indentation441of the transmission portions440as described above, the magnitude of the force pressing the semiconductor chips is increased as high as the weight of the weight442.

In this state, the control unit500operates the laser unit200to sequentially bond the semiconductor chips of the substrate. The laser transport unit220sequentially places the laser head210on each of the semiconductor chips, and when the laser head210radiates a laser beam thereto, the semiconductor chips are bonded to the substrate. When the laser beam passes through the transmission portions440and the body of the semiconductor chips and is delivered to the solder bumps, the temperature thereof is raised so that the solder bumps are adsorbed to the pad of the substrate.

Since the laser beam instantaneously increases the temperature of the solder bumps, the temperature of the semiconductor chips is not raised beyond an appropriate level. Even when the semiconductor chip is warped or subjected to thermal deformation, since the transmission portions440of the mask400press the upper surface of the semiconductor chip, the semiconductor chip may be prevented from being warped or bent. When the semiconductor chip is prevented from being bent in this manner, the defect in which some of the solder bumps of the semiconductor chip are not bonded to the substrate, may be prevented.

As described above, since the laser beam may only pass through the transmission portions440of the mask400and may not pass through the mask body410, the laser beam irradiated from the laser head210is transmitted only to the semiconductor chips. In this way, by using the mask400having the transmission portions440and the mask body410, the irradiation of the laser beam to the portion of the substrate that does not need to receive the energy of the laser beam, may be prevented.

Also, it is possible to simultaneously bond a plurality of semiconductor chips to the substrate. When the laser head210is operated to widen the irradiation area of the laser beam, two or more semiconductor chips may be simultaneously irradiated with the laser beam. Since the laser beam may not pass through the mask body410of the mask400, even in the case where the laser beam is irradiated to a wide area, it is possible to transmit the energy of the laser beam only to the semiconductor chip that needs bonding. By bonding a plurality of semiconductor chips to the substrate at the same time in this manner, the productivity of the overall processes may be improved. In some cases, the mask400may be entirely irradiated with a laser beam so as to bond all of the semiconductor chip to the substrate at the same time.

Meanwhile, the region in which the weight indentation441and the weight442of the transmission portions440are disposed, may be formed in a region in which the solder bumps of the semiconductor chip are not formed. In the present embodiment, since solder bumps are not present in the central portion of each of the semiconductor chips, but only in the edge portion of each of the semiconductor chips, the weight indentation441and the weight442are disposed in the central portion of each of the transmission portions440as illustrated in the corresponding drawing.

The substrate, which has been completely bonded through the process as described above, is transported from the fixing unit120to the discharge unit130. The discharge unit130receives the substrate and transports the same to the unloader.

The control unit500may operate the mask replacement unit600to perform a contamination test or replace, when the number of times the mask400is used exceeds a certain level.

For example, after the mask400is used 20 times, the control unit500may controls such that the mask400is transported from the mask mounting unit300to the upper side of the inspection lamp610by the mask replacement unit600. In this state, the control unit500turns on the inspection lamp610, and the inspection camera230captures the image of the mask400. When dust particles are found in the image of the mask400indicating that the transmission portions440are contaminated, the control unit500operates the mask replacement unit600to replace the mask400. The mask replacement unit600replaces the contaminated mask and transports a new mask to the mask mounting unit300and mounts the same thereon. When it is determined that the mask400is not contaminated as a result of the inspection by the control unit500, the mask400, which is on the upper side of the inspection lamp610, is transported to the mask mounting unit300again and reused.

On the other hand, the control unit500may measure the temperature of the semiconductor chips in real time using the infrared camera240and control the operation of the laser head210based on the temperature measurements. In the case where the mask400is used, the infrared camera240measures the temperature of the semiconductor chips indirectly through the temperature of the mask400.

The flip-chip laser bonding system of the present embodiment may not use the mask400in some cases. In the case where there is no possibility that the semiconductor chip placed on the substrate is bent or warped, the semiconductor chip may be irradiated directly with the laser beam without pressing the semiconductor chips by using the mask400. In this case, the image of the upper surface of the semiconductor chips is directly captured by using the infrared camera240, and based on the measurements, the control unit500may feedback-control the operation of the laser head210.

Although preferred examples have been described above for present disclosure, the scope of present disclosure is not limited to the embodiments described and illustrated above.

For example, although it has been described above that the pressing member raises the substrate, it is also possible for the pressing member to lower the mask400by pressing the semiconductor chips.

In addition, although it has been described that, in the transmission portions440of the mask400, the weight indentation441is formed and the weight442is disposed. However, in some embodiments, the mask400may not have the weight indentation441and the weight442.

In addition, although in the previous embodiments, a flip-chip laser bonding system including a mask replacement unit600has been described, in other embodiments, a flip-chip laser bonding system that does not include the mask replacement unit600may be used. In this case, the mask400may be continuously used without the inspection test to identify whether the mask400has been contaminated. In some embodiments the flip-chip laser bonding system may be configured such that the mask400is manually replaced.

In some embodiment, the flip-chip laser bonding system may be configured such that the infrared camera240, the inspection lamp610, the inspection camera230, and the like are not included.