JP3490992B2 - Ultrasonic head for flip chip connection - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flip chip mounting apparatus, and more particularly to an ultrasonic head for flip chip connection.

[0002]

2. Description of the Related Art In order to improve the performance and miniaturization of electronic equipment, it is necessary to mount electronic components on a board in high density. Therefore, flip-chip mounting has been widely used for high-density mounting of semiconductor components. For flip chip mounting, a semiconductor bare chip having bumps formed on electrodes is bonded to a pad provided on a substrate. Solder reflow, adhesion with an underfill resin, adhesion with an anisotropic conductive film, thermocompression bonding are used for bonding. , Ultrasonic bonding is adopted.

Above all, the method by ultrasonic bonding has high connection reliability, and is regarded as important as a mounting method particularly suitable for high power and high reliability equipment. In this ultrasonic bonding, it is known that the application of ultrasonic vibration to the bonding portion and the heating are used together to further increase the bonding strength and obtain stable bonding. In order to heat the bonding part, the method of bringing the bottom part of the substrate into close contact with the hot plate is the simplest. This method of heating the substrate side is not a big problem if it is a ceramic substrate, but in the case of an organic substrate, the coefficient of thermal expansion is generally larger than that of the semiconductor bare chip, so that the stress that the substrate side contracts due to cooling after ultrasonic bonding However, there is a problem that it will be applied to the joint. In contrast to the method of heating the substrate side, a method of heating the semiconductor chip side is disclosed in Japanese Patent No. 3078231 as a method of heating the entire head. Further, there is a method in which both the substrate side and the semiconductor chip side are heated at a temperature such that they both have substantially the same linear expansion in accordance with their respective thermal expansion coefficients.
No. has been filed.

[0004]

However, in the method of heating the entire head described above, the weight of the heating portion increases, and the apparatus becomes large in scale to accurately control the load important for ultrasonic bonding. There was a problem. Further, the method of heating both the substrate side and the semiconductor chip side requires precise control of the respective heating temperatures, which causes a problem that the apparatus becomes complicated. The present invention has been made to solve the above problems, and can perform the necessary heating on the semiconductor bare chip side with a simple structure without increasing the head weight, and enables highly reliable ultrasonic flip chip connection. It is an object to provide an ultrasonic head.

[0005]

An ultrasonic head for flip-chip connection according to a first aspect of the present invention is an ultrasonic head for flip-chip mounting, which has the following structure. A through hole is provided at the center of the vertical axis of the ultrasonic head, the upper end thereof is sealed with an infrared transparent glass plate, and the lower end is closed with an infrared transparent perforated glass plate provided with holes for adsorbing semiconductor bare chips. The airway is branched from the through hole and is connected to a vacuum exhaust port provided on the side surface of the ultrasonic head. Infrared light is guided from the infrared light source to the infrared transmissive glass plate at the upper end of the head by an optical fiber or a mirror, and from the outside of the infrared transmissive glass plate toward the infrared transmissive perforated glass plate at the lower end via the through hole. Irradiates infrared rays.

According to the ultrasonic head for flip-chip connection of the first aspect, the substrate side is not heated during the ultrasonic flip-chip connection, and the metal part of the semiconductor bare chip is particularly heated by the infrared rays and the diffusion lens. As a result, ultrasonic bonding can be made more reliable, and stress can be less generated between the substrate and the semiconductor bare chip after bonding, and flip-chip connection with high connection reliability can be achieved.

An ultrasonic head for flip-chip connection according to a second aspect is the ultrasonic head for flip-chip connection according to the first aspect, wherein red is provided below the through hole and in front of the infrared transparent perforated glass plate. It is characterized by mounting an external light diffusion lens.

According to the ultrasonic head for flip-chip connection of the second aspect, the infrared light diffusing lens can adjust the irradiation infrared light so as to irradiate the entire surface of the semiconductor chip substantially uniformly. Can be heated substantially uniformly.

The ultrasonic head for flip-chip connection according to claim 3 is the ultrasonic head for flip-chip connection according to claim 1 or 2, wherein the irradiation of infrared rays is from immediately before ultrasonic bonding until the completion of bonding. It is characterized by being.

According to the ultrasonic head for flip chip connection of the third aspect, the heating time of the semiconductor chip can be minimized, so that the damage and deterioration of the semiconductor chip due to heating can be prevented.

The ultrasonic head for flip-chip connection according to claim 4 is the ultrasonic head for flip-chip connection according to claim 1, 2 or 3, wherein the outside of the ultrasonic head is blackened or the like. Blacken and irradiate infrared auxiliary light from the side surface of the ultrasonic head to make the entire ultrasonic head 50-100.
It is characterized by preheating to ℃.

According to the ultrasonic head for flip-chip connection of claim 4, heating of the gold bump portion of the semiconductor bare chip becomes more efficient, so that the infrared irradiation time can be shortened and the heating temperature of the gold bump portion can be shortened. It is also possible to more stably set the temperature to a high temperature.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view showing the structure of the ultrasonic head of the present invention. In FIG. 1, 1 is an ultrasonic head, 2 is a vibrator, 3 is an ultrasonic horn, 4 is a pressing jig, 5 is an auxiliary infrared light source, 11 is a through hole provided in the center axis of the head, and 12 is infrared transmissive. Glass plate, 13 is a diffusing lens, 14 is a glass plate with perforated infrared rays, 15 is a vacuum exhaust port, 16 is a suction hole, 21 is infrared rays, 22 is auxiliary infrared rays, 23 is pressure, and 24 is ultrasonic vibration. .

The ultrasonic vibration generated by the vibrator 2 is transmitted to the ultrasonic head 1 via the ultrasonic horn 3 supported by the pressing jig 4. In the example of FIG. 1, the one-wavelength type head has two pressure jigs 4 at non-vibration points, but a half-wavelength type head fixed at one non-vibration point may be used. A through hole 11 is provided in the central axis of the ultrasonic head 1, an upper end of which is covered with an infrared permeable glass plate 12, and a lower end thereof is covered with an infrared permeable perforated glass plate 14.

A vacuum exhaust port 15 provided on the side surface of the head 1 is connected from the through hole 11 so as to branch the airway, and air is exhausted from the vacuum exhaust port 15 to depressurize the inside of the through hole 11. The semiconductor bare chip is adsorbed in the adsorption hole 16 provided in 14. On the other hand, infrared rays 17 are guided from the infrared permeable glass plate 12 at the upper end of the head along the through holes 11, and the back surface of the bare semiconductor chip can be heated via the diffusion lens 13. From the characteristics of infrared,
The gold bumps are efficiently heated because they penetrate the ceramic of the semiconductor bare chip and mainly heat the metal part.

The method of introducing infrared rays from the infrared light source (not shown) to the infrared transparent glass plate 12 at the upper end of the head is as follows.
It may be connected by an optical fiber or may be irradiated from the side surface of the head 1 and reflected by a mirror. It is not necessary to irradiate the infrared rays 21 continuously, and it is sufficient to irradiate the infrared rays 21 instantaneously for a necessary time from immediately before ultrasonic bonding to completion of bonding. The timing of irradiation of the infrared rays 21 and the amount of light can be adjusted in consideration of the heat capacity of the semiconductor chip and the ultrasonic head 1, and the heat resistance of the semiconductor chip.

Further, the auxiliary infrared light source 6 constantly irradiates the auxiliary infrared light 22 from the side of the head 1 to cover the entire head 5
Preheating to about 0 to 100 ° C. is more efficient, and it is possible to shorten the irradiation time of the infrared rays 21 and set the heating temperature of the gold bump portion to a more stable high temperature.
The surface of the ultrasonic head is preferably blackened by a blackening treatment or the like in preparation for using the auxiliary infrared light source 6.

In flip-chip connection, a substrate is placed at a predetermined position on a stage (not shown), a semiconductor bare chip is sucked and fixed at a predetermined position of the head 1, and a pressure 23 is applied to a pressure jig 4 to apply the substrate. This is performed by applying infrared rays 21 and applying ultrasonic vibration 24 while applying pressure between the semiconductor bare chip and the semiconductor bare chip.

[0019]

According to the present invention, the metal portion of the semiconductor bare chip can be intensively heated with a simple structure without heating the entire head, so that the head can be controlled in a small size and with high accuracy without increasing the weight. The ultrasonic head can be easily realized. Further, since the semiconductor bare chip side is heated without heating the substrate side, it is possible to realize highly reliable flip chip mounting without leaving a large stress in the joint even in the case of an organic resin base material having a coefficient of thermal expansion larger than that of ceramic. You can

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention.

[Explanation of symbols]

1 ultrasonic head 2 oscillators 3 ultrasonic horn 4 Pressure jig 5 Auxiliary infrared light source 11 Through hole provided on the center axis of the head 12 Infrared transparent glass plate 13 Diffusing lens 14 Infrared transparent perforated glass plate 15 Vacuum exhaust port 16 suction holes 21 infrared 22 Auxiliary infrared 23 Pressure 24 ultrasonic vibration

Claims (4)

(57) [Claims] 1. An ultrasonic head for flip-chip mounting, which has the following structure. A through hole is provided at the center of the vertical axis of the ultrasonic head, the upper end thereof is sealed with an infrared transparent glass plate, and the lower end is closed with an infrared transparent perforated glass plate provided with holes for adsorbing semiconductor bare chips. The airway is branched from the through hole and is connected to a vacuum exhaust port provided on the side surface of the ultrasonic head. Infrared light is guided from the infrared light source to the infrared transmissive glass plate at the upper end of the head by an optical fiber or a mirror, and from the outside of the infrared transmissive glass plate toward the infrared transmissive perforated glass plate at the lower end via the through hole. Irradiates infrared rays. 2. An ultrasonic head for flip-chip connection according to claim 1, wherein an infrared light diffusing lens is mounted below the through hole and in front of the glass plate with perforated infrared rays. 3. The ultrasonic head for flip-chip connection according to claim 1 or 2, wherein the irradiation of infrared rays is performed immediately before ultrasonic bonding until completion of bonding. 4. The outside of the ultrasonic head is blackened by a blackening treatment or the like, infrared auxiliary light is radiated from the side surface of the ultrasonic head, and the entire ultrasonic head is preheated to 50 to 100 ° C. The ultrasonic head for flip-chip connection according to claim 1, claim 2 or claim 3.