JP2009099869A - Bonding device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a current to be controlled from a rising time to a falling time so as to adapt a laser heating means to an electronic component to be bonded, thereby enabling improvement in stability and positional precision of a bonding process and an increase in lifetime of a laser oscillator. <P>SOLUTION: A bonding device includes: a bonding head that has a bonding tool for sucking and holding an electronic component at its end; and a laser heating means that has a laser oscillator for oscillating laser light by applying a current and heats the electronic component by irradiating the electronic component held by the bonding tool with laser light oscillated by the laser oscillator. The laser heating means includes: a profile setting means for setting a current profile of the current to be applied to the laser oscillator in bonding; and a control means for controlling a current value of the current to be applied to the laser oscillator in accordance with the set current profile. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an improvement of a bonding apparatus that heats and joins electronic components by irradiating a laser, and has a feature in laser heating means.

  Conventionally, as a bonding apparatus that heats and joins an electronic component by irradiating a laser from the inside of the bonding head, as shown in Patent Document 1, the bonding tool is capable of transmitting a laser to the electronic component. There is known a method of directly irradiating a laser and heating and joining electronic components.

In this type of bonding apparatus, the laser heating device can control the oscillation and stop of the laser by turning on and off the current supplied to the laser oscillator, and can control the energy intensity of the laser by increasing and decreasing the current value. It was.
Furthermore, in this type of bonding apparatus, since the laser is directly irradiated onto the electronic component, the electronic component can be rapidly heated by supplying a predetermined current, and rapid cooling can be performed only by stopping the laser. This has the advantage that the bonding time can be shortened.

  However, as shown in FIG. 4, since the control is performed only for the set current value i and the set time t, a sudden current is repeatedly turned on and off for the laser oscillator. Durability was a problem. There were also electronic components that disliked rapid cooling. For example, when an electronic component is rapidly cooled, it becomes uneven and deforms when the solder is hardened, or internal stress is generated. As a result, the stability and positional accuracy of bonding deteriorated.

  As a heating means of the bonding apparatus, there is also a method (Joule heater heating method) in which a bonding tool holding and holding an electronic component is irradiated with a laser and heated, and the electronic component is heated via the bonding tool. In this method, a thermocouple was provided in the bonding tool holding the electronic component, the actual temperature was detected, and the current value could be feedback controlled so as to follow the set temperature profile.

  However, in the method of heating by irradiating the electronic component with the laser, since the laser is directly irradiated to the electronic component and heated, measuring the temperature of the bonding tool is not useful for the control. Since it was not possible to directly measure the temperature, the current value could not be feedback controlled. In other words, the conventional laser heating method in which the electronic component is directly irradiated with a laser to heat it has not been able to cope with an electronic component that does not like rapid cooling.

Japanese Patent No. 3195970

  In the present invention, the laser heating means includes a profile setting means for setting a current profile to be applied to the laser oscillator at the time of bonding, and a control means for controlling a current value applied to the laser oscillator along the set profile. By providing, the laser heating means can be controlled from the rise of the current to the fall so as to suit the electronic component to be bonded, so that the stability and positional accuracy of the bonding can be improved and the life of the laser oscillator is extended. It is an object of the present invention to provide a bonding apparatus that can do this.

The first invention employs the following means in the bonding apparatus in order to solve the above problems.
First, there is a bonding head having a bonding tool that sucks and holds an electronic component at the tip, and a laser oscillator that oscillates a laser by applying an electric current, and the laser that is oscillated from the laser oscillator is held by the bonding tool. A bonding apparatus including a laser heating unit that irradiates and heats parts.
Second, the laser heating means includes profile setting means for setting a current profile to be applied to the laser oscillator at the time of bonding, and control means for controlling a current value applied to the laser oscillator in accordance with the set current profile. Prepare.

  A second invention is a bonding apparatus in which the matter that the profile setting means sets a current profile based on a temperature profile is added to the first invention.

  The present invention includes: profile setting means for setting a current profile to be applied to the laser oscillator during bonding by the laser heating means; and control means for controlling a current value to be applied to the laser oscillator along the set current profile. As a result, it is possible to control the current from rising to falling, improving the bonding stability and position accuracy and extending the life of the laser oscillator.

  Hereinafter, embodiments of the present invention will be described together with examples according to the drawings. The bonding apparatus in the embodiment is an apparatus for bonding a semiconductor chip 1 as an electronic component to a substrate 2. Reference numeral 13 in FIG. 1 denotes a mounting stage on which the semiconductor chip 1 is mounted and fixed and can be moved for alignment.

  The bonding apparatus includes a bonding head 4 having a bonding tool 3 for sucking and holding the semiconductor chip 1 at the tip (lower end), and is movable. That is, the bonding head 4 sucks and holds the semiconductor chip 1 on the bonding tool 3 at the chip supply position, moves to the bonding position, descends, mounts the semiconductor chip 1 on the substrate 2, is heated and bonded, and is cooled. Thereafter, the bonding is completed to complete the bonding, and the operation of raising and returning to the chip supply position is repeated.

  The inside of the bonding head 4 is an empty portion 5, and a laser heating device 6 that heats the semiconductor chip 1 held by the bonding tool 3 by irradiating a laser from the inside of the bonding head 4 is disposed in the empty portion 5. Has been.

  A bonding tool 3 is attached to the lower end of the bonding head 4. In the embodiment, the bonding tool 3 is made of quartz glass that has a small thermal expansion and has a high transmittance of the laser 17, but any material that transmits the laser 17 may be used. A suction hole 19 for sucking and holding the semiconductor chip 1 is formed at the center of the bonding tool 3. Further, an antireflection film is formed on the surface (upper surface in FIG. 1) located on the inner side of the bonding head 4 of the bonding tool 3.

  A suction passage 7 is formed in the bonding head 4, and the empty portion 5 is sealed except for the suction passage 7 and the suction hole 19 of the bonding tool 3 attached to the lower end of the bonding head 4. Further, since the suction passage 7 is connected to the suction device 8, vacuum suction is applied to the empty portion 5 in the bonding head 4 by vacuum suction by the suction device 8, and the suction hole 19 of the bonding tool 3. In addition, the semiconductor chip 1 can be held by suction.

  The laser heating device 6 is connected to the laser oscillator 14 which is a light source, a control device 20 which determines a current profile to be applied to the laser oscillator 14 and controls a current value to be applied to the laser oscillator 14 in accordance therewith, and the laser oscillator 14. And an optical fiber 9 having a laser exit 10 positioned in the bonding head 4, a condensing lens 11 as a condensing means for focusing the laser 17 emitted from the exit 10, and an irradiation range of the laser 17. It has a shielding plate 15 for limiting. Since the laser 17 emitted from the optical fiber 9 diffuses and enters the condenser lens 11, the condensing point 12 of the laser 17 is provided below the focal position of the condenser lens 11.

  The control device 20 is connected to a CPU 25, a constant current circuit 21 with a voltage limit including a power source, an illuminance reading circuit 22 connected to a photosensor 18 for detecting disconnection, and a thermocouple 24 attached to a test chip 31. The temperature reading circuit 23 is provided.

The setting of the current profile by the control device 20 is performed according to the following procedure.
First, as a preparation for setting, a test chip 31 with a thermocouple 24 is attached to a chip position at the time of bonding.
Second, a temperature profile setting screen is displayed on the monitor screen of the control device 20, and the temperature profile during production is input.
Third, the control device 20 obtains a current profile corresponding to the input temperature profile.

A specific method for obtaining the current profile is performed as follows.
By applying a current that seems to follow the input temperature profile, the test chip 31 with the thermocouple 24 is actually heated by the laser 17, and the actual rise time of the test chip 31 up to the set temperature of the input temperature profile The applied current value is obtained by trial and error so as to achieve the set rise time, and stored. That is, as shown in FIG. 3, the set current value i1, the rise time t1 to that point, the irradiation time t2 at the set current value i1, the set current value i2, the change time t3 to that point, and the irradiation time t4 at the set current value i2. The fall time t5 is obtained.

In the above method, the current profile is obtained from the temperature profile, but the current profile may be set directly.
Furthermore, the current profile can be obtained as follows.
First, as a setting preparation, a test chip 31 with a thermocouple 24 is attached to the chip position.
Secondly, a large amount of data on the relationship between the current value and temperature and the relationship between the rise time and fall time is stored.
Third, the temperature profile setting screen is displayed on the screen, and the temperature profile during production is input.
Fourth, an appropriate current profile is obtained from data in which a current profile corresponding to the temperature profile is stored in advance.

  During production, the control device 20 controls the current with the stored current profile, and applies the current to the laser oscillator 14 via a constant current circuit 21 with a voltage limit including a power supply. As a result, the laser oscillator 14 oscillates the laser 17. The laser oscillator 14 in the embodiment is provided separately from the bonding head 4 and guides the laser to the bonding head 4 through the optical fiber 9. The laser oscillator 14 is integrated with the bonding head 4. It may be provided. In the embodiment of FIG. 1, the laser emission port 10 of the optical fiber 9 is installed facing downward to the bonding tool 3. Of course, by providing a reflecting mirror or the like, the direction is not limited.

  As the condenser lens 11, a single convex lens is used in the embodiment of FIG. 1, but a plurality of lenses may be used. The condenser lens 11 is supported by a holder 16 in the bonding head 4. A condensing point 12 of the laser by the condensing lens 11 is provided in the empty portion 5 inside the bonding head 4. An antireflection film is formed on the front and back surfaces of the condenser lens 11. Moreover, you may use a concave mirror as a condensing means.

  The shielding plate 15 is for preventing the laser 17 that has passed through the condenser lens 11 from protruding from the semiconductor chip 1 to be irradiated. Although the shielding plate 15 exists in the embodiment shown in FIG. 1, it is not necessary to provide the shielding plate 15 when the irradiation range can be adjusted to be limited to the semiconductor chip 1 only by the condenser lens 11.

  If the laser 17 protrudes from the semiconductor chip 1, there is a risk that the substrate 2 is irradiated with the laser 17 and heated to expand. When the substrate 2 is made of a resin, the substrate 2 is greatly expanded as compared with the substrate 2 made of silicon. When bonding is performed in a state where the substrate 2 is heated and expanded, the positions of the bumps and the electrodes are shifted, and even when the substrate 2 is cooled and returned to the original state, the semiconductor chip 1 may bend and become defective. The shielding plate 15 is provided to avoid this danger.

  A reflected light detection photosensor 18 for detecting the reflected light of the laser 17 irradiated on the semiconductor chip 1 adsorbed to the bonding tool 3 is provided obliquely above the bonding tool 3 in the bonding head 4. ing. Since the bonding head 4 reciprocates between the chip supply position and the bonding position, the photosensor 18 tries to detect such a situation because the optical fiber 9 may be repeatedly broken and disconnected. It is provided to do. A signal from the photosensor 18 is input to the CPU 25 via the illuminance reading circuit 22.

  Hereinafter, the bonding operation will be described. First, the substrate 2 is supplied onto the mounting stage 13 at the bonding position. On the other hand, at the chip supply position, the bonding head 4 sucks and holds the semiconductor chip 1 on the bonding tool 3. Thereafter, the bonding head 4 moves to the bonding position, descends, and performs load control. At the same time, the control device 20 controls the current with the stored current profile, and controls the laser oscillator 14 with a voltage limit including a power source. A current is applied from the current circuit 21.

  The laser oscillator 14 irradiates a laser 17 toward the semiconductor chip 1 and pressurizes and heats the semiconductor chip 1 for bonding. The semiconductor chip 1 is properly fixed to the substrate 2 because the cooling is avoided when the irradiation of the laser 17 is turned off, but rapid cooling is avoided along the current profile. Thereafter, the bonding head 4 moves up and repeats the next bonding operation.

Cross-sectional explanatory drawing which shows the outline | summary of the bonding apparatus which concerns on an Example Block diagram showing relationship between control device and bonding head Current control graph according to current profile Conventional current control graph

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor chip 2 ... Board | substrate 3 ... Bonding tool 4 ... Bonding head 5 ... Empty part 6 ... Laser heating apparatus 7. ········································· 8.・ Place 14 ・ ・ ・ ・ Laser oscillator 15 ・ ・ ・ ・ Shielding plate 16 ・ ・ ・ ・ Holder 17 ・ ・ ・ ・ Laser 18 ・ ・ ・ ・ Photo sensor 19 ・ ・ ・ ・ Suction hole 20 ・ ・ ・ ・ Control Device 21 ... Constant current circuit 22 .... Illuminance reading circuit 23 ... Temperature reading circuit 24 ... Thermocouple 25 ... CPU
31 ... Test chip

Claims (2)

A bonding head having a bonding tool for adsorbing and holding electronic components at the tip;
In a bonding apparatus comprising: a laser heating unit that has a laser oscillator that oscillates a laser by applying an electric current, and irradiates and heats an electronic component held by the bonding tool with a laser oscillated from the laser oscillator.
The laser heating means includes profile setting means for setting a current profile to be applied to the laser oscillator during bonding, and control means for controlling a current value to be applied to the laser oscillator along the set current profile. A characteristic bonding apparatus.

  2. The bonding apparatus according to claim 1, wherein the profile setting means sets a current profile based on the temperature profile.

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