JP3409508B2 - Pellet mounter - Google Patents

Abstract

PURPOSE: To provide a pellet mounter used for the manufacture of electronic parts such as a semiconductor device, etc. CONSTITUTION: In a pellet mounter where a suction collet 20 having a vacuum suction port 20a its bottom for sucking a pellet 2 is fixed to the tip of a horn 18 moving up and down, being given ultrasonic vibration, an opening 18a leading to the vacuum suction port 20a of the suction collet 20 and the end of a pipe 22 connected to a negative pressure source are opposed separately. Accordingly, the sucking operation of the suction collect 20 does not become the load of the horn 18, so the vibration level of the suction collet 20 can be set to optimum vibration intensity, and fused solder 7 base and the pellet 2 can be brought into contact surely and fixed with each other by crashing the oxide film on fused solder finely and shifting the fused solder 7 to the periphery without scattering the fused solder 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pellet mounter used for manufacturing electronic parts such as semiconductor devices.

[0002]

2. Description of the Related Art Electronic parts, for example, semiconductor devices, are manufactured by fixing a semiconductor pellet, which is an electronic part main body, to a supporting member such as a lead frame or a stem, and electrically connecting electrodes of the semiconductor pellet and external leads. . Here, when fixing semiconductor pellets by soldering, if an oxide film is formed on the surface of the molten solder, soldering will be incomplete and reliability will drop, so the oxide film on the surface of the molten solder will be removed and fixed. I am trying to do it. An example of such a device is shown in FIG.
Let's start with. In the figure, 1 is a supporting member such as a lead frame on which the semiconductor pellet 2 is mounted, 3 is a guide rail for guiding the supporting member 1, and although not shown, a moving mechanism for moving the supporting member 1 at a predetermined pitch, and a supporting member. A positioning mechanism for positioning 1 at a predetermined position is additionally provided, and a heating means 4 for heating the support member 1 to a predetermined temperature is embedded. The guide rail 3 is covered with a cover 5 having an opening at a predetermined position, and a non-oxidizing gas is supplied into the cover 5 to prevent the supporting member 1 from being oxidized.

Reference numeral 6 denotes a solder supplying device for supplying a fixed amount of solder 7 onto the supporting member 1 which is inserted through the opening of the cover 5 and heated on the guide rail 3, and 8 is inserted into the supporting member 1 through the opening of the cover 5. The pellet supply part which supplies the semiconductor pellet 2 on the molten solder 7 above is shown. This pellet supply unit 8
Is fixed to a tip end of an arm 9 extending from the side of the guide rail 3 onto the guide rail 3 with a suction collet 10 having a vacuum suction port opened at its lower end. It is connected to a pressure source. This device uses a suction collet 1 to ensure connection between the solder 7 melted on the support member 1 and the semiconductor pellet 2.
The semiconductor pellet 2 adsorbed at 0 is scrubbed on the solder 7 while keeping a distance from the support member 1 to remove the oxide film on the surface of the solder 7 to bring fresh solder 7 base material into contact with the back surface electrode of the semiconductor pellet 2. I am trying. However, the hard oxide film can be removed from the entire back surface in contact with the semiconductor pellet 2 only by contacting the flat back surface of the semiconductor pellet 2 with the oxide film covering the surface of the solder 7 curved by the surface tension and scrubbing in the horizontal direction. When the large crushed pieces are inserted between the solder 7 and the back surface of the semiconductor pellet 2 and soldered, the crushed pieces support the semiconductor pellet 2 because the oxide film cannot be finely crushed. It becomes a thermal obstacle with the member 1, and the heat dissipation is lowered due to the decrease in the thermal conductivity, which causes a problem that high output operation cannot be performed.

Therefore, it has been proposed to apply ultrasonic vibration to the semiconductor pellet 2 supplied to the molten solder 7 to remove the oxide film on the surface of the solder 7. (For example, JP-A-5
This is explained from FIG. 4. In the figure, the same symbols as those in FIG. 3 indicate the same things, and duplicate explanations are omitted. What is different in the figure is a semiconductor pellet supply unit 12, which has an intermediate portion supported so as to be swingable and vertically movable, and an inner end extending from a side of the guide rail 3 onto the guide rail 3. The ultrasonic transducer 14 is fixed to the outer end of the horn 13, and the suction collet 15 is fixed to the inner end of the horn 13 with its vacuum suction port facing downward. Although not shown, a negative pressure source is connected to the suction collet 15 and communicates with the vacuum suction port.

This device operates similarly to the device shown in FIG. 3, but when the semiconductor pellet 2 is supplied onto the molten solder 7 of the supporting member 1, the ultrasonic vibrator 14 is operated and the suction collet is applied via the horn 13. Semiconductor pellets 2 held by 15
Apply ultrasonic vibration to. As a result, the semiconductor pellet 2 vibrates finely, and the molten solder 7 contacting the back surface of the semiconductor pellet 2 also vibrates finely, and the oxide film covering the surface is crushed into many fine pieces and moved to the peripheral portion of the molten solder 7. Since it is possible to reduce the amount of oxide film fine pieces remaining in the heat transfer path between the semiconductor pellet 2 and the supporting member 1, the thermal connection between the semiconductor pellet 2 and the supporting member 1 can be ensured. It is possible to improve reliability. At this time,
The horn 13 can also be scrubbed like the device of FIG. In this way, after the oxide film formed on the surface of the molten solder 7 is removed, the operation of the ultrasonic vibrator 14 is stopped, the suction operation from the negative pressure source is stopped, and the semiconductor pellet 2 is sucked into the suction collet 15. And the horn 13 is raised to complete the supply of the semiconductor pellets 2. After this,
The support member 1 is moved, the pellet supply unit 12 is moved outward from the guide rail 3, the next semiconductor pellet 2 is held, and the above operation is repeated.

[0006]

By the way, the precondition technique of the apparatus of FIG. 4 does not clearly show how to connect the negative pressure source for operating the suction collet 15, but in general, the horn is used. A through hole 13a is bored in 13, a suction collet 15 is connected to the lower end of this through hole 13a, and a negative pressure source (not shown) is connected to the upper end via a flexible pipe 16. . However, since the flexible pipe 16 has a pressure resistant structure so as not to be crushed by the atmospheric pressure, it is hard and heavy, and a large load is applied to the ultrasonic vibration. Even if the drive signal is linearly supplied from the level, the minute vibration is absorbed by the pipe 16, the semiconductor pellet 2 does not minutely vibrate during this time, and when the drive signal level exceeds a certain level, the semiconductor pellet 2 suddenly has a large amplitude. Since the vibration starts at, there is a problem that the molten solder 7 is scattered.

Although it is necessary to remove the solder thus scattered and attached to the undesired portion, the work in the high temperature apparatus covered with the cover 5 is complicated. Therefore, the through hole 13a is made to extend in the middle portion thereof in the axial direction of the horn 13,
It is conceivable to open the other end to the horn 13 support portion that has a small effect on ultrasonic vibration and connect the pipe 16 to this opening portion, but since the horn 13 is made of cemented carbide, it is difficult to process. In addition, it is not preferable to form the through hole 13a along the ultrasonic vibration transmission path from the viewpoint of ultrasonic vibration transmission efficiency.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been proposed for the purpose of solving the above-mentioned problems, and a vacuum suction port is opened at the lower end at the tip of a horn that is moved vertically by ultrasonic vibration and pellets are formed. In a pellet mounter with a fixed suction collet to be sucked, a pipe connected to a negative pressure source is formed on the horn, with one end communicating with the vacuum suction port of the suction collet and the other end exposed to the outer periphery of the horn. There is provided a pellet mounter, characterized in that the end portion thereof is separated from the horn to face the through hole.

[0009]

By the above means, the horn to which ultrasonic vibration is applied and the pipe for operating the suction collet fixed to the horn can be mechanically separated and connected.
Ultrasonic vibration of the suction collet is not affected by the holding mechanism of the semiconductor pellet, enabling micro vibration operation.
It is possible to prevent the solder from scattering.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG.
In the figure, the same reference numerals as those in FIG. 3 and FIG. 4 indicate the same things, and duplicate explanations are omitted. In the figure, the difference from the conventional device is that
Only the semiconductor pellet supply unit denoted by reference numeral 17 is provided. The semiconductor pellet supply unit 17 has a horn whose middle portion is swingably and vertically movable and whose inner end extends from the side of the guide rail 3 onto the guide rail 3. 18, an ultrasonic vibrator 19 fixed to the outer end of the horn 18, a vacuum suction port 20a opened at the lower end, and connected and fixed to the lower end of a through hole 18a that vertically penetrates the inner end of the horn 18. Adsorption collet 2
0, one end of which is connected to a negative pressure source (not shown) and the other end of which is supported by an arm 21 which extends along the horn 18 and swings and moves up and down in conjunction with the horn 18, the open end of which is The pipe 2 facing the through hole 18a of the horn 18 apart from each other.
It is composed of 2 and.

The operation of this device will be described below. First,
With the ultrasonic transducer 19 not operated, a negative pressure source is operated outside the guide rail 3 to adsorb the semiconductor pellets 2 onto the adsorption collet 20, and the adsorption collet 20 is moved onto the guide rail 3 to support the support member. Solder 7 melted on 1
Position the semiconductor pellet 2 on top. Then, a driving current is supplied to the ultrasonic oscillator 19 to operate it, and the horn 18 is lowered while the semiconductor pellet 2 is vibrated, and the back surface of the semiconductor pellet 2 is brought into contact with the molten solder 7. Alternatively, the horn 18 is lowered to bring the back surface of the semiconductor pellet 2 into contact with the molten solder 7, and then. The semiconductor pellet 2 is vibrated by supplying a drive current to the ultrasonic oscillator 19 to operate it. At this time, the pipe 22 has a distance from the horn 18 that does not hinder the suction operation of the suction collet 20, for example, 50 μm.
The ultrasonic vibrations are separated from each other by 200 μm or more, and the ultrasonic vibrations propagate in the axial direction of the horn 18 which is orthogonal to the suction direction.

Therefore, the ultrasonic vibration applied to the semiconductor pellet 2 can be arbitrarily adjusted over a wide range from a fine vibration level to a vibration level at which the solder 7 scatters in accordance with the level of the driving current, and the melting is performed. The solder 7 does not scatter and the strength can be set to be sufficient for removing the oxide film formed on the surface of the molten solder 7. Therefore, the oxide film on the surface of the molten solder 7 is finely crushed and moved to the peripheral edge of the molten solder 7, so that the fresh solder 7 base and the back surface of the semiconductor pellet 2 can be surely brought into contact with each other. In addition, even if a minute piece of an oxide film remains on the back surface region of the semiconductor pellet 2, the amount is very small and the semiconductor pellet 2
The influence on the heat conduction from the support member 1 to the support member 1 is small and can be ignored. Furthermore, the heat generated by the semiconductor pellet 2 can be radiated well, and the foreign matter in the solder 7 can be suppressed to an extremely small amount.
It is possible to suppress deterioration of soldering due to differences in the thermal expansion coefficients of the semiconductor pellet 2, the solder 7, and the support member 1 due to repeated on / off operations, to prolong the life, and to realize a highly reliable semiconductor device.

The present invention is not limited to the above-described embodiments, and can be applied to not only semiconductor devices but also general electronic components having a structure in which the electronic component main body 2 is fixed to the support member 1 via the solder 7. . Further, as the supporting member 1, not only a lead frame having a heat radiating plate but also a metal stem, a heat resistant insulating substrate such as a ceramic substrate having a conductive pattern formed thereon can be used. Further, in the above embodiment, the through hole 18a is formed in the tip of the horn 18 and the suction collet 20 is connected to the through hole 18a, but a cylindrical suction collet may be fixed to the tip of the horn 18. .
In this case, the outer shape of the suction collet is not limited to a cylindrical shape, but can be formed into an arbitrary prismatic shape in consideration of the connection with the pipe. Further, in the illustrated example, the opening portion that is connected to the pipe 22 while being separated is opened upward, but as shown in FIG.
8 on both sides with respect to the axis of 8 and the pipe 22
The ends may be opposed to each other. As a result, the suction force acting on the horn 18 is evenly applied to both sides with respect to the axis of the horn 18 and cancels out, so that the load on the horn 18 is reduced and the ultrasonic vibration can be further stabilized.

[0013]

As described above, according to the present invention, since the pipe for operating the suction collet does not load the horn for transmitting ultrasonic vibration, the vibration level of the suction collet can be continuously adjusted from small vibration. Since the vibration strength can be set to any value, the oxide film on the surface of the molten solder can be finely crushed and finely crushed by setting the vibration strength to the optimum conditions such as pellet size, state of molten solder, amount of molten solder, etc. By moving to the periphery, the fresh solder base and the pellet can be surely brought into contact with each other and fixed. As a result, the heat generated by the pellets can be dissipated well, and the amount of foreign matter in the solder can be suppressed to an extremely small amount, suppressing the deterioration of soldering due to the difference in the thermal expansion coefficient of the pellets, solder, and support members due to repeated on / off operations. It is possible to realize electronic components with high reliability and long life.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is a front view of a main part showing a modified example of the present invention.

FIG. 3 is a side sectional view showing a conventional pellet mounter.

FIG. 4 is a side sectional view showing an improved conventional pellet mounter.

[Explanation of symbols]

2 pellets 7 Solder 18 horn 19 Ultrasonic transducer 20 adsorption collet 20a Vacuum suction port 18a opening 22 pipes

Claims (2)

(57) [Claims] 1. A suction collet having a vacuum suction port opened at its lower end is fixed to the tip of a horn that is vertically moved by applying ultrasonic vibration, and the pellet held by this suction collet is supplied onto molten solder. In the pellet mounter, an opening communicating with the vacuum suction port of the suction collet and a pipe end connected to a negative pressure source are spaced apart from each other and faced each other. 2. The suction collet openings are arranged on both sides of the horn axis, and the end portions of the pipes are spaced apart from and face each other in the suction collet openings.
Pellet mounter described in.