JPH04326739A - Method and apparatus for die bonding - Google Patents

Abstract

PURPOSE:To restrain that a solder which has been melted during a die bonding operation is oxidized. CONSTITUTION:A lead frame 1 is pressed to a platen 4 by using a frame retainer 21 which surrounds a frame pad 2. Then, the air inside the frame retainer 21 is replaced with an atmosphere gas for oxidation-preventing use. In this state, a bonding collet 10 is lowered, and a semiconductor chip 9 is soldered. A solder 3 on the frame pad 2 is isolated from the open air by means of the frame retainer 21 during a bonding operation; it is leaked and spread to the frame pad 2 in the atmosphere gas. Consequently, it is possible to solder the semiconductor chip 9 in a state which restrains, as far as possible, the molten solder 3 from being oxidized by oxygen in the air.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die bonding apparatus used in manufacturing semiconductor devices, and more particularly to a structure for supplying gas to a die bonding portion to suppress oxidation of molten solder.

0002

2. Description of the Related Art Conventionally, a die bonding apparatus for bonding a semiconductor chip to a lead frame has a structure in which a lead frame transport section has a tunnel structure and an atmospheric gas is supplied into the tunnel structure. A conventional die bonding apparatus of this type will be explained with reference to FIG. Figure 2 is a cross-sectional view of a conventional die bonding device, in which 1 is a lead frame, 2
is a frame pad as a die pad of this lead frame 1, and a solder 3 is provided on the upper surface (die bonding surface) of this frame pad 2. Reference numeral 4 denotes a platen that supports the lead frame 1 and serves as a guide when conveying the lead frame 1 in the longitudinal direction.
is installed. The platen 4 also includes a frame transport unit (for example, a frame transport unit that transports the lead frame 1 by moving it in parallel from left to right in FIG. 2 on the platen 4).
(not shown) is provided. Note that 6 is a heater built into the heat block 5, and 7 is a thermocouple for measuring temperature. That is, the lead frame 1 placed on the platen 4 is heated to a predetermined temperature by the heat conducted from the heater 6, and the solder on the frame pad 2 is melted. Reference numeral 8 denotes a frame holder for pressing the lead frame 1 from above to bring the frame pad 2 into close contact with the upper heat transfer surface of the platen 4. This frame holder 8 has an opening 8a for chip insertion in the center. , are configured to be moved up and down on the platen 4 by a pressure device (not shown). 9 is a semiconductor chip; 10 is a bonding collet for holding the semiconductor chip 9 at the lower end and transferring it to the frame pad 2 on the platen 4;
This bonding collet 10 is provided so as to be movable up and down by a bonding head (not shown). Note that this bonding collet 10 is inserted into the opening 8a of the frame presser 8 by the downward movement. Reference numeral 11 denotes an atmosphere cover for covering the lead frame conveyance section of the platen 4 and isolating it from the outside of the apparatus, and the atmosphere cover 11 has a tunnel section 12 that opens downward and is connected to the lead frame conveyance section of the platen 4. A cover main body 13 formed at opposing positions and this cover main body 1
3, and a lid body 14 that closes the gas passage forming recessed part 13a at the upper part of the gas passage. Also, this atmosphere cover 1
1 bonding position (bonding collet 1
The part corresponding to the position where 0 moves up and down is the frame presser 8.
It has an opening that allows you to insert it. The cover body 1
A gas supply device (not shown) that supplies atmospheric gas consisting of a reducing gas and an inert gas is communicated with the space (concave portion 13a) formed by bringing the lid 14 into close contact with the lid 14. The atmospheric gas supplied into the recessed portion 13a is configured to be guided to the tunnel portion 12 through a communication hole 13b that communicates the recessed portion 13a of the cover body 13 with the tunnel portion 12. The atmospheric gas is supplied to suppress oxidation of the solder 3 melted on the frame pad 2. In addition, 15 is a cover side gas passage formed at the frame presser side end of the cover main body 13 so as to communicate between the inside and outside of the tunnel portion 12, and 16 is a frame presser formed on the frame presser 8 so as to communicate between the inside and outside of the tunnel portion 12. Atmospheric gas supplied into the tunnel portion 12 through the side gas passages is also introduced into the frame presser 8 through these gas passages 15 and 16.

Next, a procedure for die-bonding the semiconductor chip 9 to the lead frame 1 using the conventional die-bonding apparatus configured as described above will be described. To perform die bonding, first place the lead frame 1 on the platen 4.
The lead frame is loaded into the upper lead frame transport section and transported within the tunnel section 12 by the frame transport unit. On the other hand, the semiconductor chip 9 is held by the bonding collet 10 in the raised position. Note that atmospheric gas is supplied to the atmospheric cover 11 in advance, and the tunnel portion 12 is filled with the atmospheric gas. When the lead frame 1 is transferred, the heat of the platen 4 is transferred to the frame pad 2 while being transferred within the tunnel portion 12, and the solder 3 on the frame pad 2 begins to melt. At this time, since the tunnel portion 12 is filled with atmospheric gas, oxidation of the molten solder 3 therein is suppressed. Then, when the frame pad 2 reaches the bonding position, the lead frame 1 is stopped, the frame presser 8 is lowered, and the lead frame 1 is
Press it against platen 4. At this time, frame pad 2
is in close contact with the platen 4, and sufficient heat is transferred from the platen 4 to completely melt the solder 3. Thereafter, the bonding collet 10 is lowered to transfer the semiconductor chip 9 onto the frame pad 2. In this way, the semiconductor chip 9 is soldered to the frame pad 2, and the die bonding process is completed.

0004

[Problems to be Solved by the Invention] However, in the conventional die bonding apparatus configured as described above, the atmosphere cover 1
1 must have an opening for inserting the frame holder. Since the opening width of this opening is large compared to the chip size, outside air enters through the opening and disturbs the bonding atmosphere. For this reason, there has been a problem in that as the chip size increases, the solder as a bonding agent becomes more likely to oxidize. When the solder oxidizes, its wettability decreases, making it impossible to obtain a good bonding state.

[0005]

[Means for Solving the Problems] A die bonding method according to the present invention includes a box-lid-like frame that is attached to a bonding collet for holding a semiconductor chip so as to be movable up and down, and a lead frame on which solder is previously applied to a die pad. The frame is pressed against a heating table using a presser foot, and then the air inside this frame presser is replaced with an atmospheric gas for preventing oxidation.
After that, the bonding collet is lowered while pressing the lead frame with the frame holder, and the semiconductor chip is placed on the die pad and soldered. The die bonding apparatus according to the present invention includes a heating table with a built-in heater that supports a lead frame with solder provided on a die pad in advance, a bonding collet that holds a semiconductor chip and moves it up and down on a bonding part, and a pressing member attached to the bonding collet. a frame presser mounted so as to be vertically movable while being biased downward through the die pad, and formed in the shape of a box lid surrounding the sides and top of the die pad, and pressing the lead frame against the heating table. A gas passage of a gas replacement device for sucking gas and supplying an oxidation-preventing atmospheric gas is opened in the inner surface of the frame holder and in the vicinity of the die pad contacting part of the heating table.

[0006]

[Operation] The solder on the die pad is isolated from the outside air by pressing and fixing the lead frame to the heating stand with the frame holder, and spreads on the die pad in the atmospheric gas.

[0007]

[Embodiment] An embodiment of the present invention will be explained in detail below with reference to FIG. FIG. 1 is a sectional view of a die bonding apparatus used in carrying out the die bonding method of the present invention. In this figure, the same or equivalent members as those explained in FIG. 2 are given the same reference numerals and detailed explanations will be omitted. Figure 1
, 21 is a frame holder for pressing and fixing the lead frame 1 against the platen 4 serving as a heating table;
This frame presser 21 is formed in the shape of a box lid that opens downward, and is fitted and supported in a guide 22, which will be described later, so as to be able to move up and down. The opening width of the frame holder 21 is set to such a size that the frame pad 2 is surrounded on all four sides when the frame holder presses the lead frame 1 positioned at the bonding position. Furthermore, a plurality of gas passages 21a are bored in the upper plate portion of the frame presser 21 to communicate the inside and outside of the frame presser 21. Note that the bonding collet 10 that holds the semiconductor chip 9 is
It passes through the frame retainer 21 and extends vertically.

[0008] The guide 22 is formed into a downwardly facing cylindrical shape with a bottom in the same way as the frame presser 21, and a portion serving as an upper plate thereof is fixed to the bonding head portion 23. A protrusion 21 of the frame presser 21 is provided at the lower end opening of the guide 22.
A stopper 22a against which b comes into contact is integrally provided, and a bonding collet 10 is attached to the inner upper part. Reference numeral 24 denotes a compression coil spring for urging the frame holder 21 downward, and is elastically mounted between the upper plate of the frame holder 21 and the upper plate of the guide 22. Reference numeral 25 denotes an atmospheric gas supply port for supplying an atmospheric gas consisting of a reducing gas and an inert gas into the guide 22, and this atmospheric gas supply port 25 has a gas supply port connected to a gas supply device (not shown). A tube 26 is connected. The atmosphere cover 11 used in this embodiment has an opening for inserting a frame presser that is wider than that of a conventional one, so that the guide 22 can be inserted therein. As shown in FIG.
b is pressed by the compression coil spring 24 so as to come into contact with the stopper 22a. Furthermore, when the bonding head section 23 is moved downward with the lower end of the frame presser 21 in contact with the lead frame 1, the bonding collet 1
0, the guide 22 descends, but the frame presser 21 remains in contact with the lead frame 1 because the compression coil spring 24 is compressed. That is, by lowering the bonding collet 10 and the guide 22 with the lower end of the frame presser 21 in contact with the lead frame 1, the lead frame 1 can be pressed against the platen 4 by the spring force of the compression coil spring 24.

Reference numeral 27 denotes a suction passage for sucking out air around the frame pad 10 positioned at the bonding position. A platen-side through hole 28 bored through the heat block 5, a groove 29 formed on the top surface of the heat block 5, and a groove 29 formed on the top surface of the heat block 5.
The heat block side through hole 30 is formed so as to penetrate vertically through the heat block side. A suction device (not shown) that constitutes a gas replacement device together with the gas supply device is communicated with the lower opening of the heat block side through hole 30.

Next, a die bonding method according to the present invention will be explained using the die bonding apparatus configured as described above. In order to solder and bond the semiconductor chip 9 to the lead frame 1, first, the lead frame 1 is loaded onto the lead frame transport section on the platen 4 in the same manner as in the conventional method, and is transported within the tunnel section 12 by the frame transport unit. let On the other hand, the bonding collet 10 holds the semiconductor chip 9 with the bonding head portion 23 raised. Then, the guide 22 and the bonding collet 10 are lowered to such an extent that the frame presser 21 does not come into contact with the lead frame 1. Note that atmospheric gas is supplied to the atmosphere cover 11 in advance, and the tunnel portion 12 is
Fill the atmosphere with gas. Next, the lead frame 1 is positioned so that the frame pad 2 is positioned at the bonding position, and the bonding head section 23 is moved down. Even when the frame presser 21 contacts the lead frame 1, the lead frame 1 is pressed against the platen 4 by the spring force of the compression coil spring 24 by continuing to lower the frame holder 21. Further, when the frame presser 21 comes into contact with the lead frame 1, the gas supply device and the suction device are activated. When these devices start, guide 2
The atmospheric gas sent into the frame holder 21 is supplied from above through the gas passage 21a into the frame holder 21, and the air in the space inside the frame holder 21 is sucked from below through the suction passage 27. , the air in the frame holder 21 is replaced with atmospheric gas. After the gas replacement work is completed, the bonding head 23 is continuously lowered to transfer the semiconductor chip 9 onto the frame pad 2. In this way, the semiconductor chip 9 is soldered to the frame pad 2, and the die bonding process is completed.

Therefore, according to the present invention, the solder 3 on the frame pad 2 is isolated from the outside air by pressing and fixing the lead frame 1 to the platen 4 with the frame holder 21, and is melted in the atmospheric gas. Wetness spreads to the frame pad 2. Therefore, the semiconductor chip 9 can be soldered while the oxidation of the molten solder 3 by oxygen in the air is suppressed as much as possible.

In this embodiment, the atmospheric gas is supplied from the guide 22 side, and the air inside the frame presser 21 is sucked from the platen 4 side. It is also possible to adopt a structure in which atmospheric gas is supplied from the side and air is sucked from the guide 22 side. In addition, in this embodiment, the mechanism for raising the frame presser 21 relative to the guide 22 and releasing it during bonding is configured by the compression coil spring 24, but instead of the compression coil spring 24, an actuator such as a linear motor is used for bonding. It can also be installed in addition to the head drive device. Even in this case, the same effect as in the above embodiment can be obtained. Furthermore, in this embodiment, the gas replacement device (gas supply device and suction device) was started after the frame presser 21 came into contact with the lead frame 1, but if the solder 3 melts quickly, the frame The gas replacement device is started before the frame holder 21 comes into contact with the lead frame 1 so that the inside of the frame holder 21 is filled with atmospheric gas almost at the same time as the lead frame 1 is pressed and fixed by the holder 21.

[0013]

As explained above, in the die bonding method according to the present invention, a lead frame on which solder has been previously applied to a die pad is attached to a bonding collet for holding a semiconductor chip so as to be movable up and down, and a box lid-like structure surrounding the die pad is attached. The frame holder is used to press the lead frame against the heating table, and then the air inside the frame holder is replaced with an anti-oxidation atmosphere gas.Then, with the frame holder pressing the lead frame, the bonding collet is lowered and the semiconductor chip is placed on the die pad. It is mounted and soldered, and
The die bonding apparatus according to the present invention includes a heating table with a built-in heater that supports a lead frame with solder provided on a die pad in advance, a bonding collet that holds a semiconductor chip and moves it up and down on a bonding part, and a pressing member attached to the bonding collet. a frame presser mounted so as to be vertically movable while being biased downward through the die pad, and formed in the shape of a box lid surrounding the sides and top of the die pad, and pressing the lead frame against the heating table. Therefore, the gas passage of the gas replacement device that sucks gas and supplies the oxidation-preventing atmospheric gas is opened near the inner surface of the frame holder and the part of the heating table that contacts the die pad.
The solder on the die pad is isolated from the outside air by pressing and fixing the lead frame to the heating table with a frame holder, and the solder spreads on the die pad in the atmospheric gas. Therefore, the semiconductor chips can be soldered while the oxidation of the molten solder by oxygen in the air is suppressed as much as possible, in other words, the semiconductor chips can be soldered in a good soldering state. Therefore, even if the semiconductor chip is large, a semiconductor device with high quality soldered parts can be obtained. In addition, since the air in the frame holder is forcibly replaced with atmospheric gas, the time during which the lead frame is stopped during bonding can be shortened as much as possible, reducing process time and increasing productivity. It also has the effect of increasing it.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a die bonding apparatus used in carrying out the die bonding method of the present invention.

FIG. 2 is a sectional view of a conventional die bonding device.

[Explanation of symbols] 1 Lead frame 2 Frame pad 3 Solder 4 Platen 5 Heat block 9 Semiconductor chip 10 Bonding collet 21 Frame presser foot 22 Guide 24 Compression coil spring 26 Gas supply pipe 27 Suction passage

Claims (2)

[Claims] 1. A lead frame on which solder has been applied to a die pad in advance is pressed against a heating table by a box-lid-like frame holder that is attached to a bonding collet for holding a semiconductor chip so as to be movable up and down and surrounds the die pad, and then the frame holder is pressed against a heating table. A die bonding method characterized in that the air inside is replaced with an atmospheric gas for preventing oxidation, and then a bonding collet is lowered while pressing a lead frame with a frame holder, and a semiconductor chip is placed on a die pad and soldered. 2. A heating table with a built-in heater that supports a lead frame on which solder is preliminarily applied to a die pad, a bonding collet that holds a semiconductor chip and moves it up and down on a bonding part, and a pressing member that is connected to the bonding collet through a pressing member. a frame presser mounted so as to be vertically movable while being biased downward and formed in the shape of a box lid surrounding the sides and top of the die pad and pressing the lead frame against the heating table; A die bonding device characterized in that a gas passage of a gas replacement device for sucking gas and supplying an oxidation-preventing atmospheric gas is opened in the inner surface of the frame holder and in the vicinity of the die pad contacting portion of the heating table.