HK1022050B - Die bonding apparatus - Google Patents

Description

Die bonding apparatus

The present invention relates to a die bonding apparatus that bonds a semiconductor chip over a chip substrate using a braze filler metal.

In the manufacturing process of semiconductor integrated circuits such as ICs and LSIs, a die bonding process for bonding a semiconductor chip to a chip substrate needs to be performed, and in order to perform the die bonding, a die bonding apparatus needs to be used. The conventional die bonding apparatus has a structure such as that shown in fig. 9. The die bonding apparatus shown has a substrate holder 4 for holding a chip substrate 2. The base holder 4 includes: a positioning member 6 for positioning the chip substrate 2 in the die bonding work area; and a support member 8 for supporting the chip substrate 2 in the die bonding work area. The positioning element 6 comprises a block-shaped element, and the positioning cavity 10 is located in the center of the positioning element 6. When die bonding is performed, the chip substrate 2 is positioned in the positioning cavity 10, the supporting member 8 includes, for example, a heating furnace having a flat top surface, and the chip substrate 2 is placed on the top surface with the heater 12 provided in the supporting member 8.

The die bonding apparatus also has a chuck 16 for transferring the semiconductor chip 14 to the chip base 2 held in the die bonding station. In the collet 16, an axially extending through-hole 18 is formed. The through-hole 18 is connected to a reduced pressure source (not shown). When the pressure reducing action from the reduced pressure source acts on the semiconductor chip 14, the semiconductor chip 14 is attracted and supported by the top of the collet 16. While attracting and supporting the chip 14, the collet 16 transfers the semiconductor chip onto the chip substrate 2 located in the die bonding work area.

The semiconductor chip 14 is bonded to the chip substrate 2 by a braze filler metal 20. The brazing filler metal 20 is interposed between the chip substrate 2 and the semiconductor chip 14, and the semiconductor chip 14 is bonded on the chip substrate 2 by thermally fusing the brazing filler metal 20. The heat staking of the braze filler metal 20 is accomplished by the heater 12 disposed in the support member 8. The lead 22 from the heater 12 is electrically connected to an ac power source 26 via a switch 24. The opening and closing, i.e. on and off, of the switch 24 is controlled by a control device 28. A temperature sensor 30 for detecting the hot-melt temperature of the brazing filler metal 20 is provided at a predetermined position of the support member 8. The detection signal from the temperature sensor 30 is supplied to the control device 28.

In the die bonding apparatus, the chip base 2 needs to be placed on the base stage 4, and the semiconductor chip 14 is placed on the chip base 2 held in this manner by the clip 16 as needed. When the bonding operation is performed, the collet 16 functions as a pressing device and presses the semiconductor chip 14 toward the chip base 2. When the chip substrate 2 is heated by the heater 12 in this state, the brazing filler metal 20 is thermally melted by heat energy from the chip substrate 2 and is disposed, thereby bonding the semiconductor chip 14 on the chip substrate 2. The temperature of the brazing filler metal 20 is controlled based on the detection signal from the temperature sensor 30. When the temperature detected by the temperature sensor 30 is lower than a predetermined lower limit temperature, the control device 28 closes (turns on) the switch 24, so that the heater 12 is heated to raise the temperature of the brazing filler metal 20. When the temperature detected by the temperature sensor 30 is higher than a predetermined upper limit temperature, the control device 28 opens (disconnects) the switch 24 so that the heater 12 stops heating to lower the temperature of the brazing filler metal 20. By controlling the on or off of the heater 12 by the control device 28 in this way, the temperature of the brazing filler metal 20 is maintained within a predetermined temperature range not lower than a predetermined lower limit temperature and not higher than a predetermined upper limit temperature, thereby ensuring the bonding of the semiconductor chip 14 to the chip substrate 2 through the brazing filler metal 20.

However, in the related-art die bonding apparatus as shown in fig. 9, the following problem to be solved arises in relation to the fact that the temperature sensor 30 is placed in the support member 8 of the substrate holder 4. Since the chip substrate 2 is placed on the top surface of the support member 8 at each die bonding, when the die bonding is repeated and the number of times of bonding increases, there arises a problem that the top surface becomes rough or dust adheres to the top surface. When the top surface becomes rough or dust adheres to the top surface, the joint between the top surface of the support member 8 and the chip substrate 2 is broken, so that the heat conduction from the heater 12 to the chip substrate 2 is broken. For this reason, there is a difference between the temperature detected by the temperature sensor 30 provided in the support element 8 and the actual heat fusion temperature of the brazing filler metal 20, so that although the actual heat fusion temperature of the brazing filler metal 20 is lower than the ideal temperature, the control device 28 assumes that the ideal temperature has been reached and controls the temperature on the basis of this determination. Therefore, the brazing filler metal 20 is not melted by heat enough, so that it is impossible to bond the semiconductor chip 14 on the chip base 2 with high reliability.

Also, in this die bonding apparatus, since the side face of the chip substrate 2 is heated, the chip substrate 2 is kept at a high temperature. In contrast, since the semiconductor chip 14 is pressed by the collet 16, the heat of the semiconductor chip 14 is absorbed by the collet 16, so that the temperature of the semiconductor chip 14 is lower than that of the chip base 2. Therefore, there is a temperature difference between the bottom surface of the chip base 2 in contact with the support member 8 and the top surface of the semiconductor chip 14 in contact with the collet 16. When the temperature difference is large, thermal deformation occurs between the chip base 2 and the semiconductor chip 14 due to a difference in thermal expansion coefficient. It is difficult to firmly bond the substrate 2 and the chip 14.

Another prior art is shown in unexamined japanese patent JP- ｃA-4-25137(1992) in which, when ｃA semiconductor chip is die-bonded in ｃA ceramic package, the semiconductor chip is gradually heated by ｃA heater provided in ｃA vacuum chuck while this semiconductor chip sucked and held by the vacuum chuck is transferred to the package, and the semiconductor chip is heated substantially to ｃA temperature that the package has. By such an operation, it is possible to avoid sudden heating when the semiconductor chip is brought into contact with the package, thereby preventing the semiconductor chip from being damaged due to the sudden heating.

Unexamined japanese patent application publication JP- ｃA-6-45377(1994) shows another prior art in which ｃA thermocouple and ｃA heating resistor are provided in ｃA chuck body that adsorbs ｃA semiconductor chip in order to control warpage of the semiconductor chip due to heat. And the chuck body heated by the heating resistor is controlled so that the temperature thereof is maintained at a predetermined constant temperature according to the temperature detected by the thermocouple, thereby controlling the warpage of the chip due to heat when die bonding is performed.

Yet another prior art is shown in unexamined japanese utility model publication JP-U-63-20430(1988) in which a sheathed heater and a temperature sensor are embedded in a chuck, the temperature of the sheathed heater is controlled based on temperature information from the temperature sensor, and after a semiconductor chip is vacuum-adsorbed by the chuck, the semiconductor chip is preheated to an appropriate temperature before mounting. Thereby reducing the mounting time and reducing the stress of the semiconductor chip due to a severe temperature change.

In the prior art shown in JP- ｃA-4-25137(1992), ｃA heater wire is provided in ｃA chuck that adsorbs ｃA semiconductor chip, and the chuck is gradually heated, and in the prior art shown in JP- ｃA-6-45377(1994), ｃA thermocouple and ｃA heating resistor are provided in ｃA chuck body. In the prior art shown in JP-U-63-20430(1988), a heater with an outer sheath and a temperature sensor are provided in a chuck.

In the prior art, the semiconductor chip is heated by heat from the chuck, and the braze filler metal or solder is hot melted for die bonding. Since the temperature sensor is provided in the collet to detect the temperature of the collet instead of the temperature of the surface of the collet, although the semiconductor chip is heated by heat from the collet and adsorbed by the end surface of the end of the collet, the heating temperature is controlled according to the inside temperature of the collet among the above-mentioned temperatures. Therefore, the adjustment of the cartridge heating temperature for thermally fusing the solder or the brazing filler metal is not accurate enough, so there is a case where the solder or the brazing filler metal cannot be thermally fused in an appropriate state, with the result that the reliability of bonding the semiconductor chip to the chip substrate is lowered.

An object of the present invention is to provide a die bonding apparatus capable of reliably bonding a semiconductor chip over a chip substrate by thermally melting a brazing filler metal as needed.

Another object of the present invention is to provide a die bonding apparatus capable of reducing thermal deformation due to a temperature difference between a chip substrate and a semiconductor chip, thereby reliably bonding the chip substrate and the semiconductor chip together.

The invention provides a die bonding apparatus, comprising:

a substrate holder for holding a chip substrate;

a pressing device for pressing the semiconductor chip against the substrate held by the substrate holder;

a heating device for thermally melting a brazing filler metal interposed between the chip substrate and the semiconductor chip;

the temperature sensor is at least arranged in the pressing device and used for detecting the surface temperature of the pressing device; and

control means for controlling a heating operation of the heating means on the basis of the temperature detected by the temperature sensor.

According to the present invention, since the temperature sensor detects the surface temperature of the pressing device, the hot-melt temperature of the brazing filler metal is detected at the side of the pressing device, that is, at the side where the brazing filler metal is in contact with the semiconductor chip. Since the pressing device is less likely to become rough or contaminated by dust unlike the substrate holder, the heat fusion temperature of the brazing filler metal can be accurately detected by providing the pressing device with a temperature sensor. Therefore, the actual heat fusion temperature of the brazing filler metal can be maintained within a predetermined range, and the semiconductor chip can be bonded on the chip substrate with higher reliability.

In the present invention, it is preferable that the heating means includes a heater provided at least in the pressing means.

According to the invention, since the heating means is provided in the pressing means, the heating of the brazing filler metal is done from one side of the pressing means. As described above, since the pressing means is not easily roughened or soiled like the substrate side, by providing the pressing means with the heating means, heat from the heating means can be reliably conducted to the brazing filler metal via the semiconductor chip. Thus, the braze filler metal can be hot-melted as needed to enable reliable bonding of the semiconductor chip site over the chip substrate.

In the present invention, it is preferable that the heating means comprises a first heater provided in the pressing means and a second heater provided in the substrate holder; it is preferable that the temperature sensor includes a first temperature sensor provided in the pressing device and a second temperature sensor provided in the substrate holder, and that the control device controls the heating operation of the first heater on the basis of the temperature detected by the first temperature sensor and controls the heating operation of the second heater on the basis of the temperature detected by the second temperature sensor.

According to the present invention, since the first heater and the first temperature sensor are provided in the pressing device, and the second heater and the second temperature sensor are provided in the substrate holder, the semiconductor chip is mainly heated by the first heater and the chip substrate is mainly heated by the second heater. Accordingly, the temperatures of the semiconductor chip and the chip substrate can be maintained above a desired temperature, thereby reducing a temperature difference therebetween so that thermal deformation due to the temperature difference can be controlled.

The invention is characterized in that the pressing device transfers, places and presses the semiconductor chip onto the chip base and moves the semiconductor chip bonded to the chip base out of the base station together with the chip base.

According to the present invention, since the collet functions as the pressing means at the same time, the structure of the die bonding apparatus can be simplified.

In the present invention, it is preferable that the means for transferring and placing the semiconductor chip onto the chip substrate is provided separately from the pressing means.

According to the present invention, since the means for transferring and placing the semiconductor chip to the chip base is provided separately from the pressing means, the subsequent semiconductor chip to be die-bonded can be transferred to the work area separately from the pressing operation of the semiconductor chip by the pressing means, and the die-bonded semiconductor chip can be removed from the work area together with the chip base. Therefore, the transferring/removing operation and the fusing operation can be performed in parallel, which saves time and improves efficiency.

Other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

fig. 1 is a sectional view mainly showing a part of a die bonding apparatus according to a first embodiment of the present invention;

fig. 2 is a flow chart useful in explaining the die bonding operation performed by the die bonding apparatus of fig. 1;

fig. 3 is a cross-sectional view mainly showing a part of a second embodiment of the die bonding apparatus of the present invention;

fig. 4 is a flow chart useful in explaining the die bonding operation of the die bonding apparatus of fig. 3;

fig. 5 is a cross-sectional view mainly showing a part of a third embodiment of the die bonding apparatus of the present invention;

fig. 6 is a flow chart useful in explaining the operation of the die bonding apparatus shown in fig. 5;

fig. 7A to 7C illustrate the operation of the collet 118 in a simple manner, fig. 7A illustrating a state before the semiconductor chip 116 is sucked by the collet 118, fig. 7B illustrating a state when the semiconductor chip 116 is sucked by the collet 118, and fig. 7C illustrating a state when the semiconductor chip 116 has been transferred from the collet 118 to the die bonding work area 106, located directly above the chip base 2;

fig. 8A and 8B are simplified views to help explain the operation of the pressing member 182, fig. 8A showing a state where the pressing member 182 is located at a lower start position, and fig. 8B showing a state where the pressing member 182 is pressing the semiconductor chip 116; and is

Fig. 9 is a sectional view showing a partial structure of a prior art die bonding apparatus.

Referring now to the drawings, the preferred embodiments of the present invention will be described.

First embodiment

Fig. 1 is a sectional view mainly showing relevant parts of a first embodiment of the die bonding apparatus of the present invention. The die bonding apparatus has a substrate holder 104, which may be, for example, a bar (stem) or a lead frame, for holding the chip substrate 102. The substrate holder 104 includes positioning elements 108 for positioning the chip base 102 in the die bonding work area 106, and support elements 110 for supporting the chip base 102 in the die bonding work area. The positioning element 108 comprises a block-shaped part and, in cross-section, a positioning cavity 112 perpendicular to the plane of fig. 1, which cavity, viewed from above in fig. 1, is rectangular and is arranged in the center of the positioning element 108. The planar structure of the positioning cavity 112 is a rectangle slightly larger than the chip substrate 102, as viewed from above in fig. 1, so as to conform to the structure of the chip substrate 102 positioned in the cavity 112. When die bonding is performed, positioning of the chip substrate 102 is completed as the chip substrate 102 is inserted into the positioning cavity 112.

The support member 110, which is rectangular in cross-section perpendicular to the plane of fig. 1, is slightly smaller than the die-bonded chip substrate 102 and is disposed in the center of the positioning cavity 112 of the positioning member 108 when viewed from above in fig. 1. The support member 110 includes a heating furnace having a flat top surface 111, and the top surface 111 is used for placing a chip. The chip substrate 102 is placed on a chip placement surface in a manner to be described later.

A heater 114 constituting a heating means is provided in the supporting member 110. The heater 114 heats the chip substrate 102 through the support member 110.

The die bonding apparatus also has a chuck 118 for transferring and placing semiconductor chips 116, referred to as "dice," onto the chip substrate 102 secured in the die bonding station 106. In the collet 118, an axially extending through bore 120 is formed. The through-hole 120 is connected to a reduced pressure source 122 (e.g., a reduced pressure pump). When the decompression pump is operated, suction force from the decompression source 122 acts on the semiconductor chip 116 through the through hole 120, so that the semiconductor chip 116 is sucked and held by the top of the collet 118.

The collet 118 is movable laterally between a first position (not shown) and a second position as shown in fig. 1. When the collet 118 is positioned at the first position, the collet 118 is disposed at a pick-up area (not shown) to attract and hold the semiconductor chip 116 to be cut. When the collet 118 is moved to the second position, the collet 118 is positioned in the die bonding area 106 for placing the semiconductor chip 116 on the chip substrate 102 in the base station 104. The collet 118 is held so as to be vertically movable between a raised position (not shown) and a lowered position as shown in fig. 1. When the collet 118 is located at the lowered position at the first position, the collet 118 adsorbs and holds the semiconductor chip 116. When the collet 118 is in the lowered position of the second position, the collet 118 places the semiconductor chip 116 onto the chip base 102 and presses the semiconductor chip 116 against the base 102. When the collet 118 is in the raised position, the collet 118 moves between the first position and the second position.

Semiconductor chip 116 is bonded to chip base 102 by a braze filler metal 124. When the semiconductor chip 116 is placed on the chip substrate 102, for example, gold antimony foil is applied as a braze filler metal onto the chip substrate 102, and the braze filler metal 124 is disposed between the chip substrate 102 and the semiconductor chip 116. The heat fusing of the brazing filler metal 124 is accomplished by the heater 114 provided in the support 110. The lead 126 from the heater 114 is electrically connected to an ac power source 130 via a switch 128. The opening/closing, i.e., on/off, of the switch 128 is controlled by the control device 132.

In this embodiment, two sensors 134 and 136 are used as temperature sensors to detect the hot melt temperature of the braze filler metal 124. A first temperature sensor 134 is disposed near an end of the chuck 118. The second temperature sensor 136 is disposed at a predetermined position in the support member 110, specifically, at a position near the top surface 111. The first and second temperature sensors 134 and 136 may be, for example, thermocouples.

The first temperature sensor is used to measure the surface temperature of the semiconductor chip 116 to determine whether the heat generated by the heater 114 is completely transferred. Second temperature sensor 136 is used to determine whether heater 114 is operating properly. The control device 132 is, for example, a microcomputer, and controls the opening and closing of the switch 128 on the basis of detection signals from the first and second temperature sensors 134 and 136, thereby controlling the heating operation by the heater 114.

The bonding by the die bonding apparatus of the first embodiment is performed in accordance with the steps shown in the flowchart of fig. 2. Referring to fig. 1 and 2, first, at step S1, the chip substrate 102 is positioned in the positioning cavities 112 of the positioning members 108 of the substrate holder 104, and the chip substrate 102 is placed on the top surface of the support member 110. Then, a braze filler metal 124 is applied to the secured chip substrate 102, and the semiconductor chip 116 is placed by the clip 118 with the braze metal filler sandwiched therebetween. Thereafter, at step 2, the semiconductor chip 116 is pressed by the collet 118. In this embodiment, since semiconductor chip 116 is pressed against chip base 102 by clip 118 during die bonding, clip 118 also functions as a pressure device.

The process proceeds to step S3 where a determination is made as to whether the temperature T2 detected by the second temperature sensor 136 is within a first heating temperature interval, e.g., 250 ℃. ltoreq.T 2. ltoreq.260 ℃. The operation of the heater 114 during die bonding is controlled by the control device 132. Therefore, when the chip substrate 102 is set and the semiconductor chip 116 is placed thereon and pressed down, the heat fusion of the brazing filler metal 124 with the heat generated by the heater 114 is started, and thus the die bonding with the die bonding apparatus is started.

When the temperature T2 detected by the second temperature sensor 136 in step 3 is in the first heating temperature range, the step proceeds to S4, where it is determined whether the temperature T1 detected by the first temperature sensor 134 is in the second heating temperature range, for example, 240 ℃ C. ltoreq. T1 ℃ C. ltoreq.250 ℃. When the temperature T1 detected by the first temperature sensor 134 is within the second heating temperature range in step 4, the process proceeds to step S5, in which it is determined whether a predetermined heating time has elapsed. Steps S3 to S5 are repeatedly performed until the predetermined heating time is exhausted.

When the predetermined heating time is exhausted, the process proceeds from step S5 to step S6 to complete the die bonding by the die bonding apparatus. The heating time at step S5 is sufficient for the braze filler metal to be heat fused by the heater 114. Therefore, when the temperature T2 detected by the second temperature sensor 136 is kept within the first heating temperature range and the temperature T1 detected by the first temperature sensor 135 is kept within the second heating temperature range and a predetermined heating time elapses, the brazing filler metal 124 is thermally fused, so that the semiconductor chip 116 can be firmly bonded to the chip base 102 by the brazing filler metal 124.

When it is detected at step S3 that the temperature T2 detected by the second temperature sensor 136 is outside the first heating temperature range, the processing proceeds from step S3 to step S7. When the temperature T1 detected by the first temperature sensor 134 at step S4 is outside the second heating temperature range, the processing proceeds from S4 to S7. In step S7, it is determined whether the operating time for die bonding has been exhausted. When the operating time has not been exhausted, the processing proceeds to step S8, where the heater is controlled by the control device 132. At step 5, the on time is slightly longer than the heating time and is set to a length of time sufficient to allow the braze filler metal 124 to be melted after the end of the collet 118 is heated by the heater 114.

In step S8, when the temperature T2 detected by the second temperature sensor 136 is lower (or higher) than the first heating temperature range, the control device 132 turns off (or turns on) the switch 128 to cause the heater 114 to perform (or stop) the heating operation. Thus, the operation of the heater 114 is controlled such that the reflow temperature of the braze filler metal is maintained within a predetermined temperature range.

When the temperature T1 detected by the first temperature sensor 134 is lower (or higher) than the second heating temperature range, the control device 132 closes (or opens) the switch 128 to cause the heater 114 to perform the heating operation (or stop the heating operation). Thus, the operation of the heater 114 is controlled such that the reflow temperature of the braze filler metal 124 is maintained within a predetermined temperature range. After the control is completed in step S8, the processing returns to step S3.

When the temperature T2 detected by the second temperature sensor 136 is brought to a temperature within the first heating temperature range by controlling the heater 114, the processing proceeds to step S4. When the temperature T1 detected by the first temperature sensor is brought to a temperature within the second heating temperature range by controlling the heater, the process proceeds to step S5, and thus steps S3 to S5 are performed.

When the temperature T2 detected by the second temperature sensor 136 falls outside the first heating temperature range even if the heater 114 is controlled, or when the temperature T1 detected by the first temperature sensor 134 falls outside the second heating temperature range even if the heater 114 is controlled, the processing proceeds to step S7 again, where it is determined whether the operating time for die bonding has been exhausted, and when the operating time has been exhausted, the processing proceeds to step S9, where it is determined that the die bonding apparatus has failed, and the apparatus is stopped.

Thus, in the die bonding apparatus of the first embodiment, since the heat fusion temperature of the brazing filler metal 124 is detected by the first temperature sensor 134 in the collet 118 and the second temperature sensor 136 in the support member 110, and the heater 114 is controlled in accordance with the temperatures T1 and T2 detected by the temperature sensors 134 and 136, the brazing filler metal 124 can be maintained at a predetermined heat fusion temperature so that the semiconductor chip 116 can be firmly bonded to the chip substrate 102. In particular, because the first temperature sensor 134 is disposed in the collet 118, the fuse temperature of the braze filler metal 124 may be accurately detected. The end surface 119 of the collet 118 is not roughened for use and dust does not adhere to the top surface 119. Therefore, the heat from the braze filler metal 124 is well transferred so that the fuse temperature of the braze filler metal 124 is accurately detected.

In the first embodiment described above, the heat fusion temperature of the braze filler metal 124 is sensed by a first temperature sensor 134 disposed in the collet 118 and a second temperature sensor 136 disposed in the support element 110. However, two sensors are not necessarily provided, the hot melt temperature of the braze filler metal 124 may be accurately maintained within a predetermined temperature range by controlling the heater 114, and the control of the heater 114 may be accomplished based solely on the temperature detected by the first sensor 134 in the collet 118.

Second embodiment

Fig. 3 is a sectional view mainly showing a relevant part of the second embodiment of the die bonding apparatus of the present invention. In the second embodiment shown in fig. 3, the same parts as those in the first embodiment are denoted by the same reference numerals.

Referring to fig. 3, in the second embodiment, first and second heaters 152 and 154 are provided as heating means to heat fuse the brazing filler metal 124 sandwiched between the chip substrate 102 and the semiconductor chip 116, and first and second temperature sensors 156 and 158 are provided as temperature sensors to detect the heat fuse temperature of the brazing filler metal 124. The first heater 152 is disposed at an end of the chuck 118. Heat from the first heater 152 is transferred through the collet 118 to the braze filler metal 124 and the semiconductor chip 116. Similar to the first embodiment, the second heater 154 is provided in the support member 110, including a heating furnace, and heat from the second heater 154 is transferred to the brazing filler metal 124 through the support member 110 and the chip substrate 102. The first heater 152 is electrically connected to an ac power source 164 via a lead 162 provided with a first switch 160. The second heater 154 is electrically connected to an ac power source 172 via a lead 170 provided with a second switch 168.

The first temperature sensor 156 is provided in association with the first heater 152, and detects the heat fusion temperature of the brazing filler metal 124 heated by the first heater 152. A second temperature sensor 158 is disposed in association with the second heater 154 and detects the hot melt temperature of the braze filler metal 124 heated by the second heater. The first temperature sensor 156 is provided to detect the preheating temperature of the chuck 118, which is employed to improve the heating efficiency of the semiconductor chip 116 by reducing the temperature difference between the chip base 102 and the semiconductor chip 116. A second temperature sensor 158 is provided to determine whether the heater 154 is operating properly.

Detection signals from the first and second temperature sensors 156 and 158 are supplied to the control device 132, and the control device 132 controls the opening and closing of the first and second switches 160 and 168 based on the detection signals from the sensors 156 and 158. In addition, the die bonding apparatus of the second embodiment has substantially the same structure as that of the first embodiment, and thus, the description thereof is omitted.

The bonding by the die bonding apparatus of the second embodiment is completed through the steps shown in the flowchart in fig. 4. Referring to fig. 3 and 4, first, in step S11, the chip substrate 102 is placed in the positioning cavities 112 of the positioning members 108 and the chip substrate 102 is placed on the top surface of the support member 110, and then the solder filler metal 124 is placed on the chip substrate 102 and the semiconductor chip 116 is placed on the solder filler metal 124. Then, in step S12, the semiconductor chip 116 is pressed by the collet 118.

The process proceeds to step S13, where a determination is made as to whether the temperature T2 detected by the second temperature sensor 158 is within the first heating temperature range, e.g., whether the temperature T2 detected by the second temperature sensor 158 is within the range 250 ℃. ltoreq.T 2 ≦ 260 ℃. When the temperature T2 detected by the second temperature sensor 158 is within the first heating temperature range in step 13, the process proceeds to step S14, where it is determined whether the temperature T1 detected by the first temperature sensor 156 is within the second heating temperature range, e.g., whether the temperature T1 detected by the first temperature sensor 156 is within the range of 240 ℃. ltoreq.T 1. ltoreq.260 ℃.

When the temperature T1 detected by the first temperature sensor 156 falls within the second heating temperature range at step S14, the process proceeds to step S15, where it is determined whether the predetermined heating time has been exhausted. The steps of S13 to S15 are repeatedly performed until the predetermined heating time is exhausted. When the predetermined heating time has been exhausted, the process proceeds from step S15 to step S16 where the die bonding is completed by the die bonding apparatus.

The heat staking time referred to in step S15 is a time sufficient for the braze filler metal to be heat staked by the first and second heaters 152 and 154. Therefore, when the temperature T2 detected by the second temperature sensor 158 is maintained in the first heating temperature range and the temperature T1 detected by the first temperature sensor 156 is maintained in the second heating temperature range and a predetermined heating time elapses, the solder filler metal 124 is thermally fused so that the semiconductor chip 116 is bonded to the chip substrate 102 by the solder filler metal 124.

When the temperature T2 detected by the second temperature sensor 158 at step S13 is outside the first heating temperature range, the process proceeds from step S13 to S17, where it is determined whether the operating time for performing die bonding has been exhausted. When the working time has not been used up, the processing proceeds to step S18, where the second heater 154 is controlled by the control device 132. A time longer than the heating time at step 15 is set as the operation time. In step S18, when the temperature T2 detected by the second temperature sensor 158 is lower (or higher) than the first heating temperature range, the control device 132 turns off (or turns on) the second switch 168 to cause heating by the second heater 154 (or stops heating). In this way, the conduction of heat from the support member 110 through the chip substrate 102 to the brazing filler metal 124 is controlled, and the operation of the second heater 154 is also controlled so that the heat fusion temperature of the brazing filler metal 124 is maintained within a predetermined temperature range. After the control at step S18, the processing returns to step S13. When the temperature T2 detected by the second temperature sensor 158 becomes a temperature within the first heating temperature range by controlling the second heater 154 at step S18, the processing proceeds to step S14. Thus, steps S13 to S15 are performed.

When the temperature T2 detected by the second temperature sensor 158 is outside the first heating temperature range even though the second heater 154 is controlled, the process proceeds to step S17 where it is determined whether the operating time for performing die bonding has been exhausted. When the operating time has been exhausted, the process proceeds to step S19, where it is determined that the die bonding apparatus is malfunctioning, and the apparatus is stopped.

In step S14, when the temperature T1 detected by the first temperature sensor 156 is outside the second heating temperature range, the flow proceeds from step S14 to S20, where it is determined whether the working time for performing the die bonding has been exhausted. When the operating time has not been exhausted, the processing proceeds to step S21, where the first heater 152 is controlled by the control device 132. A predetermined time longer than the heating time at step S15 is set as the operating time. At step S21, similar to the case at step S18, when the temperature T1 detected by the first temperature sensor 156 is lower (or higher) than the second heating temperature range, the control device 132 turns off (or turns on) the first switch 160 to cause the first heater 152 to perform heating (or stop heating). Thus, the amount of heat conducted from the collet 118 through the semiconductor chip 116 to the braze filler metal 124 is controlled, while the operation of the first heater 152 is also controlled so that the fuse temperature of the braze metal 124 is maintained within a predetermined temperature range. After the control at step S21, the processing returns to step S13, and when the temperature T1 detected by the first temperature sensor 156 is made a temperature within the second heating temperature range by controlling the first heater 152 at step S21, the processing proceeds to step S15. Thus, steps S13 to S15 are performed.

When the temperature T1 detected by the first temperature sensor 156 is outside the second heating temperature range even though the control is performed on the first heater 152, the process proceeds again to step S20, where it is determined whether the operating time for die bonding has been exhausted. When the operating time has been exhausted, the process proceeds to step S22, where it is determined that the die bonding apparatus is malfunctioning, and the apparatus is stopped from operating.

In this way, in the die bonding apparatus of the second embodiment, since the reflow temperature of the solder filler metal 124 is detected by the first temperature sensor 156 located in the collet 118 and the second temperature sensor 158 located in the support member 110 while the first and second heaters 152 and 154 are controlled in accordance with the temperatures T1 and T2 detected by the temperature sensors 156 and 158, the solder filler metal 124 is maintained at a predetermined reflow temperature, similarly to the case of the first embodiment, so that the semiconductor chip 116 can be reliably bonded to the chip base 102. Heat from the first heater 152 is conducted primarily through the collet 118 to the semiconductor chip 116 and heat from the second heater 154 is conducted through the support element 110 to the chip base 102 so that the braze filler metal 124 is effectively heat staked. Also, in this way, the temperature difference between the chip base 102 and the semiconductor chip 116 can be reduced, so the occurrence of thermal deformation due to the temperature difference can be controlled.

Fig. 5 is a cross-sectional view mainly showing a die bonding apparatus according to a third embodiment of the present invention. In the third embodiment, a pressing member 182 specially designed, that is, a pressing member 182 for pressing the semiconductor chip 14 downward against the chip base on which the brazing filler metal 20 is placed in die bonding is used as a pressing means for completing die bonding. In the third embodiment, elements corresponding to those in the second embodiment are denoted by the same reference numerals as in the second embodiment, and are not described again.

In the third embodiment, since the first heater 152 and the first temperature sensor 156 are provided in the pressing member 182 for pressing the semiconductor chip 116, and the second heater 154 and the second temperature sensor 158 are provided in the supporting member 110 for supporting the chip substrate 102, effects similar to those in the case of the second embodiment can be obtained. In the third embodiment, since the pressing member 182 for pressing the semiconductor chip 116 is required in addition to the chuck for transferring the semiconductor chip 116, the apparatus structure is somewhat complicated.

Fig. 6 is a flowchart useful in explaining the operation of the die bonding apparatus shown in fig. 5. Fig. 7A to 7C are views showing the operation of the chuck in a simple manner. Fig. 7A shows the condition before the semiconductor chip 116 is adsorbed by the chuck 118. Fig. 7B shows a state where the semiconductor chip 116 is attracted by the chuck 118. Fig. 7C shows the semiconductor chip 116 as it has been moved by the chuck 118 to the die bonding station 106, directly above the chip base 102.

When the die bonding operation is started, as shown in fig. 7A, a plurality of semiconductor chips 116 are arranged on the attachment plate 186 such that one of the semiconductor chips 116 evenly spaced in the length direction on the attachment plate is placed in line with the transfer chuck 118 and the push-up cusp 119. In this case, the attachment plate 186 and one of the plurality of semiconductor chips 116 are disposed between the transfer chuck 118 and the push-up cusp 119. Thus, at step m1, one of the semiconductor chips 116 is accurately positioned on the axis common to the moving jaw 118 and the push-up cusp 119. At step m2, the transfer chuck 118 is lowered as shown in fig. 7B while the push-up tip 119 is raised, so that the semiconductor chip 116 is pushed up from the attaching plate 186. The pushed-up semiconductor chip 116 is vacuum-sucked by the end face of the end of the transfer chuck 118.

At step m3, the chuck 118 moves upward while sucking the semiconductor chip 116, and thus the semiconductor chip is peeled off at the side of the attaching plate 186 and separated upward. Thereafter, at step m4, the semiconductor chip 116 lifted up to a position away from the attaching plate 186 is moved in the horizontal direction while being vacuum-sucked by the transfer chuck 118, and is accurately positioned directly above the chip base 102 provided with the brazing filler metal 124, as shown in fig. 7C. In this state, the moving gripper 118 moves down at step 5, and after the semiconductor chip 116 is placed on the braze filler metal 124 on the chip base 102, the process proceeds to step n1 where the reduced pressure source 122 releases the suction and the moving gripper 118 is raised back to the return position shown in fig. 7A. When die bonding of all the semiconductor chips 116 is completed at step m6, die bonding is completed. When the die bonding has not been completed, the steps m2 to m5 are repeatedly performed.

Fig. 8A and 8B are simplified views to help explain operations related to the pressing member 182, and fig. 8 shows a state when the pressing member 182 is placed at a lower initial position. Fig. 8B shows the pressing element 182 pressing against the semiconductor chip 116. When the semiconductor chip 116 is accurately positioned on the braze filler metal 124 on the chip base 102 by the moving jaw 118 as described above, the hold-down element 182 begins to descend at step n 1. At this time, since the first heater 152 is provided in the pressing member 182 and the temperature is controlled by the control device 132, the temperature is kept constant.

At step n2, such a pressing member 182 is moved down and presses the semiconductor chip 116 placed on the chip base 102, as shown in fig. 8B, with the braze filler metal 124 between the chip base 102 and the semiconductor chip 116, and heats the semiconductor chip 116. At this time, since the temperature of the chip base 102 and the brazing filler metal 124 is heated by the second heater 154 to an appropriate constant temperature before the semiconductor chip 116 is transferred to the chip base 102 as shown in fig. 7A to 7C, the semiconductor chip 116 is heated to a desired temperature and the brazing filler metal 124 can be completely melted in a short time. For example, gold antimony foil may be used as the braze filler metal 124. The chip substrate is a metal rod or guide post (lead). The semiconductor chip may be, for example, a flat-plate type element having a rectangular shape with a side of 0.4 to 1mm and a thickness of about 0.1 to 0.2mm, and may be, for example, an NPN-type transistor.

For such a braze filler metal 124 that requires heat staking, a predetermined time, such as 5 to 30 seconds, is necessary and during this time, the transfer chuck 118 begins picking up the next semiconductor chip 116 from the bond plate 186 as described above. When the heat staking time is exhausted and the braze filler metal 124 is completely melted, the hold-down element 182 is again moved from the hold-down condition shown in FIG. 8B to the lower starting position shown in FIG. 8A and then back to the predetermined stand-by position. The transfer chuck 118, which has vacuum-sucked the next semiconductor chip 116, is positioned at the position of the pressing member 182 in fig. 8A, and the semiconductor chip 116 bonded to the chip base 102 is transferred to a subsequent process together with the chip base 102. Thereafter, a new chip substrate 102 is placed on the positioning cavity 112 of the support member 110 and the solder filler metal 124 is placed on the new chip substrate 102, and then the above-described steps m2 to m6 are repeated and the steps n1 to n4 are repeated until all parts of the die bonding are completed at step n 4.

This transfer and take-out, and pressing and fusing processes are performed in parallel, that is, in fig. 6, the process X from step m2 to m6 and the process Y from step n1 to n4 are performed in parallel. Accordingly, the power consumption of the first and second heaters 152 and 154 is minimized, so that high productivity can be obtained.

In a third embodiment, the first heater 152 may be omitted and the second heater 154 and the hot melt braze filler metal 124 may be used. In addition, the second temperature sensor 158 may be omitted in addition to the first heater 152.

Having described various embodiments of the die bonding apparatus of the present invention, it will be understood that the invention is not limited to these embodiments, but is capable of numerous variations and modifications without departing from the scope of the invention.

Claims (9)

1. A die bonding apparatus comprising:

a substrate holder for holding a chip substrate;

a pressing device for pressing the semiconductor chip against the chip base held by the base;

a heating device for thermally melting the brazing filler metal sandwiched between the chip base and the semiconductor chip, the heating device including at least one heater provided on the base;

a temperature sensor for detecting a surface temperature of the pressing device, the temperature sensor including a first temperature sensor provided in the pressing device and a second temperature sensor provided in the base stand; and

and a control device for controlling the heating operation of the heating device on the basis of the temperature detected by the temperature sensor.

2. The die bonding apparatus of claim 1 wherein the heating means further comprises a heater disposed in the pressing means.

3. The die bonding apparatus according to claim 2, wherein the control device controls an operation of a heater provided in the pressing device on the basis of the temperature detected by the first temperature sensor, and controls a heating operation of a heater provided on the substrate holder by the second temperature sensor.

4. The die bonding apparatus according to claim 1, wherein the pressing means transfers, places and presses the semiconductor chip onto the chip base, and removes the semiconductor chip, which has been bonded to the chip base, together with the chip base from the base station.

5. The die bonding apparatus according to claim 2, wherein the pressing means transfers, places and presses the semiconductor chip onto the chip base, and removes the semiconductor chip joined to the chip base together with the chip base from the base table.

6. The die bonding apparatus according to claim 3, wherein the pressing means transfers, places and presses the semiconductor chip onto the chip base, and removes the semiconductor chip bonded to the chip base together with the chip base from the base station.

7. The die bonding apparatus according to claim 1, wherein the means for transferring and placing the semiconductor die on the die substrate is provided separately from the pressing means.

8. The die bonding apparatus according to claim 2, wherein the means for transferring and placing the semiconductor die on the die substrate is provided separately from the pressing means.

9. A die bonding apparatus according to claim 3, wherein said means for transferring and placing semiconductor chips on the chip substrate is provided separately from said pressing means.