JP2000216174A - Die bonder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cause less detachment of fine particles from parts of a sealed container, when an air flow takes place in a casing at the time of replacing an atmosphere within the casing, or even when the parts of container are brought into contact with each other, or even when the container and an atmosphere replacer are brought into contact with each other at the time of transporting an object into or from the container. SOLUTION: The die bonder includes a solder supply section 5 for supplying a predetermined amount of solder 7 to a lead frame 1 intermittently moving as heated along a guide rail 2 covered with a cover 3, a solder stirring section 8 for stirring the melted solder 7 on the lead frame 1 with use of a stirring rod 9, and a semiconductor pellet supply section 10 for supplying a semiconductor pellet 12 onto the stirred and melted solder 7, which sections are sequentially positioned. In this case, a heating means 13 for heating at least its contact surface with the melted solder 7 is attached to the stirring rod 9 of the die bonder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a die bonder for mounting a semiconductor pellet on a lead frame via solder.

[0002]

2. Description of the Related Art Semiconductor devices using a lead frame are:
In general, the semiconductor pellet is mounted on the island or heat sink of the lead frame, the electrodes on the semiconductor pellet are electrically connected to the leads, the main part including the semiconductor pellet is packaged, and the lead frame is exposed from the package. It is manufactured by cutting and removing the connecting portions and separating them individually. here,
In semiconductor devices for high current and high power, solder is used as an adhesive to bond the semiconductor pellets to the lead frame in order to reduce the internal resistance, transfer the heat generated by the semiconductor pellets to the islands, and release the heat to the outside efficiently. Is used. An example of this type of die bonder will be described with reference to FIG. In the drawing, 1 is a detailed description, but a lead frame in which a large number of heat sinks and a set of leads are connected and integrated as a basic unit, 2 is a lead frame,
Although not shown, a guide rail 3 for intermittently moving the lead frame 1 by a transfer mechanism is a cover for covering the guide rail 2 and shielding it from the outside air, and has three opening windows on its upper surface along the moving direction of the lead frame 1. 3a, 3b, 3
c is drilled. Reference numeral 4 denotes a heating unit for heating the lead frame 1 on the guide rail 2, and in the illustrated example, a heater unit embedded in the guide rail 2 is shown. This cover 3
A non-oxidizing gas is supplied into the inside to prevent oxidation of the heated lead frame 1. 5 is an opening window 3 on the cover 3
In the example shown in the drawing, the solder supply unit disposed at the position "a" adsorbs a fixed amount of solder 7 at the lower end of the vertically moving solder suction collet 6 and is inserted into the cover 3 through the opening window 3a.
Supply solder 7 on top. Reference numeral 8 denotes a solder stirrer which is arranged at the position of the opening window 3b and stirs the solder 7 melted on the lead frame 1 by a stirrer 9 which moves up and down and rotates around an axis. The stirrer 9 is used for heat resistance, corrosion resistance, and heat resistance. Cemented carbide and artificial ruby with good wear properties are used. Reference numeral 10 denotes a semiconductor pellet supply unit, which sucks the semiconductor pellet 12 outside the cover 3 by the pellet suction collet 11 and moves horizontally to move the semiconductor pellet 12 up and down at the position of the opening window 3c, thereby applying the semiconductor pellet 12 to the molten solder 7 on the lead frame 1. Supply. In this apparatus, when the solder pieces 7 supplied on the lead frame 1 are melted, the area is reduced or displaced due to surface tension, and if the surfaces of the lead frame 1 and the solder pieces 7 are oxidized, electrical and mechanical Target,
Since the thermal connection is incomplete and the connection between the semiconductor pellet 12 and the lead frame 1 is incomplete, the molten solder 7 on the lead frame 1 is stirred by the stirring rod 9 to spread the solder 7 and destroy the oxide film. Thus, the lead frame 1 and the solder 7 are completely connected. The ambient temperature in the cover 3 is maintained at a temperature at which the solder on the lead frame 1 melts, and the stirring rod 9 also enters and exits the cover 3 and contacts the molten solder 7 to be heated to a high temperature by conduction heat and radiation heat. I have.

[0003]

By the way, the moving speed of the lead frame 1, the ambient temperature in the cover,
The intervals a, 3b and 3c are set so that the solder 7 supplied onto the lead frame 1 is sufficiently melted at the position of the solder agitating section 8, but in order to improve the productivity, the solder supplying section 5,
The operating conditions are set so that the operation speed of the solder stirring section 9 and the semiconductor pellet supply section 10 is increased to complete the work at each work position in about 1 second or less. Here, it is necessary to rotate the stirring rod 9 around its axis with its lower end in contact with the molten solder 7. In order to operate at high speed, the stirring rod 9 must be lowered while rotating from the ascending position. Therefore, the molten solder 7 in contact with the stirring rod 9 is pushed and spread, and at the same time, a rotational force is applied and the molten solder 7 is stirred. However, as shown in FIGS. If the protrusions 7a protrude, the protrusions 7a may be scattered in the direction of the arrow shown by the rotational force, not only reducing the amount of solder but also adhering to undesired portions on the lead frame 1 and the guide rails 2. Was. When the amount of solder at the mounting position is reduced in this way, a power cycle test is performed, the semiconductor device is turned on and off, and the semiconductor pellet is heated and cooled, and the bonding interface between the solder 7 and the lead frame 1 and the semiconductor pellet 12 is reduced. Thus, there is also a problem that stress due to a difference in each coefficient of thermal expansion is concentrated and cracks are easily generated, and the life is shortened. Further, if the scattered solder adheres to an undesired portion of the guide rail 2, it may adhere to a subsequent lead frame and cause trouble, so that the operation of the equipment is stopped and the cover 3 is opened to clean the guide rail 2. And there is a problem that productivity is reduced. As a device that can solve such a problem, there is a device in which a stirring rod is arranged coaxially with a cylinder, and the stirring rod is rotated in the cylinder. (For example, 58-
According to this, since the stirring rod is surrounded by the cylindrical body, even if the molten solder is scattered, the molten metal can be prevented from scattering outside the lead frame. However, when the operating speed is increased, it is difficult to synchronize the cylinder and the stirring rod, and there is a limit to the high-speed operation.

[0004]

SUMMARY OF THE INVENTION The present invention has been proposed for the purpose of solving the above-mentioned problems, and is provided on a lead frame which moves intermittently on a guide rail covered with a cover. A die bonder in which a solder supply unit for supplying solder, a solder stirring unit for stirring the solder melted on the lead frame with a stirring bar, and a semiconductor pellet supply unit for supplying semiconductor pellets on the stirred molten solder are sequentially arranged. There is provided a die bonder characterized in that a heating means for heating at least a surface in contact with molten solder is provided on a stirring rod.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A die bonder according to the present invention is provided with a heating means attached to a stirring rod for stirring solder supplied on a heated lead frame. A cavity can be formed in the rod and the heater can be located within the cavity. In addition, at least the outer peripheral surface of the lower end of the stirring rod may be formed of an electrically insulating member, and a heater may be disposed on the outer peripheral surface of the lower end. In this case, the heater can be formed of a conductive pattern. The temperature of the lower end of the stirring rod heated by the heater may be set to be substantially the same as the temperature of the molten solder on the lead frame.

[0006]

FIG. 1 shows an embodiment of the present invention.
In the figure, the same components as those in FIG. 7 are denoted by the same reference numerals, and redundant description will be omitted. The apparatus according to the present invention is characterized in that the stirring rod 9 is provided with a stirring rod heating means 13 for setting the temperature of the surface of the lower end in contact with the molten solder 7 to be substantially the same as the temperature of the molten solder. The stirring rod heating means 13 is a rod-shaped electric heater and is housed in a cavity 9 a formed in the stirring rod 9. More specifically, as shown in FIG. 2, a rotating shaft 15a of a motor 15 supported at one end of an arm 14 that moves up and down is extended downward, and a stirring rod 9 made of a hard material is connected to the rotating shaft 15a. The two annular electrodes 16a and 16b are electrically and thermally insulated on the outer periphery of the rotating shaft 15a, and the leads 13a and 13b of the heater 13 are connected to the annular electrodes 16a and 16b. On the other hand, the leg pieces 17 extending downward from the arm 14 are attached to the annular electrodes 16a, 16b.
Terminals 18a and 18b electrically connected to the heater are fixed, and the heater 13 is energized from the terminals 18a and 18b. Thereby, the heater 13 in the stirring rod 9 rotating up and down and rotating around the axis can be continuously energized, and the temperature can be adjusted. In the apparatus of the present invention, the stirrer rod 9 separates from the lead frame 1 when ascending, and even if the stirring rod 9 comes into contact with the outside air, the heater 13 can maintain at least the temperature of the lower end surface in contact with the molten solder at substantially the same as the melting temperature of the solder. Even if the molten solder on the frame is locally eccentrically raised, the temperature of the molten solder in contact with the stirring rod 9 does not decrease, and the contact surface between the molten solder 7 and the stirring rod 9 slides well. Viscosity rise and solidification can be prevented, and solder scattering can be prevented, so that the solder can be well stirred even for a short time. Particularly, if necessary, the operation of the equipment is temporarily stopped, and even after the operation of the equipment is started with the lower end of the stirring rod 9 being out of the cover 3 for a long time, the solder can be scattered and good stirring can be performed. In addition, since the amount of the molten solder that is agitated is kept constant, a semiconductor device that can withstand a long-term power cycle test and has a long life and high reliability can be realized.
Furthermore, it is not necessary to temporarily stop and clean the equipment due to the scattering of the solder, thereby improving the productivity. FIG. 3 shows another embodiment of the present invention. In the figure, the same components as those in FIGS. 7, 1 and 2 are denoted by the same reference numerals, and redundant description will be omitted. 2 is different from the apparatus shown in FIG. 2 in that a stirring rod 9 and a heater 19 for heating the stirring rod 9 are made of cemented carbide if the peripheral surface thereof is electrically insulating and has heat resistance. Materials having an insulating layer, ceramics, artificial jewels, and the like can be used. The heater 19 is constituted by a resistive film pattern formed on the peripheral surface of the stirring rod 9 which is electrically insulated. Both ends of this resistive film pattern are connected to the annular electrodes 16a and 16b, and operate in the same manner as the device shown in FIGS. This device also has a stirring rod 9 like the device of FIG.
The temperature at the lower end of the cover 3 can be appropriately maintained, and the same curing as that of the apparatus shown in FIG. 1 can be achieved. I'm done. FIG. 4 shows another embodiment of the present invention. In the figure, the same components as those in FIG. 2 are denoted by the same reference numerals, and duplicate description will be omitted. In this device, the stirring rod 9 is directly connected to the arm 1.
4 and is rotationally driven by a motor 15 arranged in parallel. A heat source 20 such as an infrared lamp for heating the rotating stirring rod 9 is disposed above the stirring rod 9. As shown in FIG. 5, the stirring rod 9 is formed in a cylindrical shape having a bottom, and by making the bottom thinner, heat supplied from the heat source 20 can be efficiently transmitted to the lower end surface of the stirring rod 9. Further, as shown in FIG. 6, the stirring bar 9 can be made of a transparent artificial gem having heat resistance, corrosion resistance and wear resistance. In this case, since the heat supplied from the heat source 20 passes through the stirring rod 9, the lower end surface may be blackened, or the heat absorbing member 21 may be disposed inside the lower end. The stirring bar 9 has an optimum material and diameter set according to the semiconductor pellet 12 to be mounted, and the embodiment shown in FIGS. 2 to 6 can be selected and applied.

[0007]

As described above, according to the present invention, even when the equipment is operated at high speed, the scattering of the molten solder can be prevented, the production efficiency can be improved, and a semiconductor device having a long life and high reliability can be obtained. Can be realized.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional side view showing a die bonder according to the present invention.

FIG. 2 is an enlarged side view of a main part of the apparatus in FIG. 1;

FIG. 3 is an enlarged side view of a main part showing another embodiment of the present invention.

FIG. 4 is an enlarged side view of a main part showing another embodiment of the present invention.

FIG. 5 is an enlarged side view of a main part showing another embodiment of the present invention.

FIG. 6 is an enlarged side view of a main part showing another embodiment of the present invention.

FIG. 7 is a partially sectional side view showing a conventional example of a die bonder.

FIG. 8 is a cross-sectional plan view showing a stirring state of molten solder by the apparatus in FIG. 7;

9 is a sectional view taken along line AA of FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lead frame 2 Guide rail 3 Cover 4 Frame heating means 5 Solder supply part 7 Solder 8 Solder stirring part 9 Stirring rod 10 Semiconductor pellet supply part 12 Semiconductor pellet 13 Stirring rod heating means (heater)

Claims (5)

[Claims] 1. A guide rail for guiding and intermittently moving a lead frame, a cover covering the guide rail and opening an opening at a predetermined position on an upper surface along a moving direction of the lead frame, and heating the lead frame on the guide rail. A frame heating means, a solder supply unit which is disposed at the opening window position of the cover and is inserted into the cover, and supplies the solder on the lead frame, and a solder stirring unit for stirring the molten solder on the lead frame with a stirring rod. In a die bonder having a semiconductor pellet supply unit for supplying semiconductor pellets onto the stirred molten solder, a heating means for heating at least a surface in contact with the molten solder is provided on the stirring rod of the solder stirring unit. Die bonder characterized. 2. The die bonder according to claim 1, wherein a cavity is formed in the stirring rod, and a heater is disposed in the cavity. 3. The die bonder according to claim 1, wherein at least the outer peripheral surface of the lower end portion of the stirring rod is formed of an electrically insulating member, and a heater is disposed on the outer peripheral surface of the lower end portion. 4. The die bonder according to claim 3, wherein the heater is formed by a conductive pattern. 5. The die bonder according to claim 1, wherein the temperature of the lower end of the stirring rod is set substantially equal to the temperature of the molten solder on the lead frame.