JP2002252252A - Semiconductor mounting apparatus for ultrasonic-flip chip connection and ultrasonic-flip chip connecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic-flip chip mounting apparatus and its method which reduce distortion of a joint spot regardless of a material of circuit substrate and a size of chip and has high reliability of connection. SOLUTION: The ultrasonic-flip chip mounting apparatus heats the circuit substrate for mounting the semiconductor chip, and the semiconductor chip is mounted on the circuit substrate by applying ultrasonic frequency to an suction nozzle when sucking the semiconductor with the suction nozzle of an ultrasonic head. Moreover, the apparatus is provided with a heating section on the ultrasonic head, the ultrasonic vibration applied to the semiconductor chip in the state that the semiconductor chip is heated with the heating section so that the amount of thermal expansion of the semiconductor chip is approximately the same as that of the circuit substrate, thereby, the semiconductor chip is joined to the circuit substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for ultrasonically flip-chip mounting a semiconductor bare chip on a circuit board.

[0002]

2. Description of the Related Art In order to satisfy the recent demand for higher performance and smaller size of electronic equipment, so-called flip-chip mounting for directly connecting a semiconductor bare chip to a circuit board has been increasing. Conventionally, soldering is generally used to connect a bare chip to a circuit board. However, since the electrode pitch of a semiconductor bare chip is as narrow as 100 μm or less, a method other than soldering is often used.

The following are known as examples of flip-chip mounting methods other than soldering. A) A method in which an anisotropic conductive film is interposed between a semiconductor bare chip electrode and a circuit board pad and pressed. B) A method in which a non-conductive resin is interposed between a semiconductor bare chip electrode and a circuit board pad as an underfill material, and heated and pressed. C) A method in which a gold bump formed on a semiconductor bare chip electrode is ultrasonically vibrated on a gold-plated circuit board pad to bond the pad and the bump. Of the above methods, the ultrasonic bonding of the item (c) is performed by the method (a),
Since the connection reliability is higher and the secular change is smaller than the pressure welding described in item a), it is suitable for flip-chip mounting of electronic equipment that requires high reliability.

[0004] This ultrasonic bonding is performed by forming a gold bump on the electrode of a semiconductor chip by wire bonding or plating, adsorbing, holding, handling, and positioning the semiconductor chip by an adsorption nozzle. The upper surface is placed facing the gold-plated pad, and in a state where the bump is pressed against the pad of the circuit board, between the support point supported so that the suction nozzle can swing and the suction surface. By applying ultrasonic vibration to the semiconductor chip to vibrate the semiconductor chip, the bump and the pad are rubbed, and the bump and the pad are joined by the frictional heat.

[0005]

A conventional ultrasonic flip-chip connecting semiconductor mounting apparatus for performing such ultrasonic bonding is to maintain a suction nozzle at a normal temperature and to maintain a temperature on a circuit board side on which a semiconductor chip is mounted. A method is adopted in which the bonding property is increased by heating the stage to 100 to 250 degrees Celsius using a hot plate on a stage. Therefore, in this conventional method, when the semiconductor chip and the circuit board are joined, the temperature of the resin-based circuit board having a large coefficient of thermal expansion is high,
Since the temperature of the semiconductor chip having a small coefficient of thermal expansion is low, when the bonding is completed and the temperature is returned to normal temperature, the circuit board side having a larger coefficient of thermal expansion and higher temperature contracts more than the semiconductor chip side. As a result, there is a problem that large distortion remains at the joint. This tendency is not limited to a resin substrate such as a glass epoxy or the like, but is the same to some extent even in the case of a glass substrate or a ceramic substrate.

For example, a circuit board has a thermal expansion coefficient of 7 ppm.
When using a ceramic substrate at a temperature of 25 ° C., the hot plate on the stage
The temperature is set to 0 ° C., and the nozzle holding the semiconductor chip is not heated. In such a case, the amount of thermal expansion from 25 ° C. to 150 ° C. for 15 mm of the circuit board corresponding to a chip length of 15 mm is about 13 μm, while the semiconductor chip is at 25 ° C.
Since the dimensions do not change as they are, the semiconductor chip receives a stress of about 13 μm shrinking from the ceramic substrate when returning to normal temperature after bonding. In addition, the distortion of the joint due to the stress becomes more remarkable as the chip size increases, and there is a disadvantage that the connection reliability is reduced accordingly. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is an ultrasonic flip-chip connection semiconductor mounting that can improve connection reliability by reducing distortion at a joint regardless of a circuit board material and a chip size. It is an object to provide an apparatus and an ultrasonic flip chip connection method.

The present invention has been made by paying attention to the fact that the conventional ultrasonic flip chip connection method heats only the circuit board, so that only the circuit board shrinks due to cooling after joining, and distortion occurs at the joint. By heating the circuit board and the semiconductor chip to a temperature corresponding to the coefficient of thermal expansion at the same time as the circuit board so that they have substantially the same amount of thermal expansion, it is possible to eliminate distortion after cooling to room temperature. It is something.

[0008]

According to a first aspect of the present invention, there is provided an ultrasonic flip-chip connecting semiconductor mounting apparatus which heats a circuit board on which a semiconductor chip is mounted and adsorbs the semiconductor chip by an ultrasonic head having an adsorption nozzle. In a semiconductor mounting apparatus for applying an ultrasonic vibration to a suction nozzle to mount the semiconductor chip on the circuit board, the ultrasonic head is provided with a heating section, and the heating section causes the semiconductor chip to thermally expand the circuit board. The method is characterized in that the semiconductor chip is joined to the circuit board by applying ultrasonic vibration in a state where the semiconductor chip is heated so as to have a thermal expansion amount substantially equal to the amount.

According to a second aspect of the present invention, an ultrasonic vibration is applied to the suction nozzle while heating the circuit board on which the semiconductor chip is mounted and suctioning the semiconductor chip with an ultrasonic head having a suction nozzle. In a semiconductor mounting apparatus for mounting the semiconductor chip on the circuit board, the ultrasonic head is provided with a heating section, and the heating section causes the semiconductor chip to expand by approximately the same amount as the thermal expansion of the circuit board. The method is characterized in that the semiconductor chip is bonded to the circuit board by applying ultrasonic vibration in a state where the semiconductor chip is heated to a certain amount.

According to a third aspect of the present invention, there is provided a semiconductor mounting apparatus for connecting an ultrasonic flip chip, which heats a circuit board on which a semiconductor chip is mounted and suctions the semiconductor chip with an ultrasonic head having a suction nozzle. In a semiconductor mounting device that applies vibration and mounts the semiconductor chip on the circuit board, a heating unit and a temperature of the heating unit are set on the ultrasonic head, and an input is provided from an input device provided separately. Heating temperature of the circuit board,
A heating temperature setting unit for setting the temperature so that the thermal expansion of the circuit board becomes substantially equal to the thermal expansion of the semiconductor chip based on the coefficient of thermal expansion of the circuit board and the coefficient of thermal expansion of the semiconductor chip. It is a feature.

According to the first or second aspect of the present invention,
The circuit board and the semiconductor chip were heated to a temperature corresponding to their respective coefficients of thermal expansion and joined so that the amounts of thermal expansion at the time of joining were substantially the same. Since the same amount of shrinkage can be set, flip-chip mounting with low connection distortion at room temperature and high connection reliability is possible.

According to the third aspect of the present invention, by inputting the heating temperature of the circuit board, the coefficient of thermal expansion of the circuit board, and the coefficient of thermal expansion of the semiconductor chip, the amounts of thermal expansion of the circuit board and the semiconductor chip become substantially equal. Since the temperature of the semiconductor chip is automatically set at the time of execution, complicated calculations are not required when the ultrasonic flip chip connecting method according to the second aspect of the present invention is executed, and errors can be prevented.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of an ultrasonic flip-chip connecting semiconductor mounting device according to an embodiment of the present invention. In FIG. 1, 1 is a semiconductor chip, 2 is a gold bump formed on an electrode of the semiconductor chip 1, 3 is a circuit board on which the semiconductor chip 1 is mounted, 4 is a pad formed on the circuit board 3, 5 is a suction nozzle 5a, An ultrasonic head having a unit 5b and an ultrasonic vibration transmitting unit 5c; 6, a hot plate for mounting the circuit board 3 and heating the circuit board 3 to a predetermined temperature; An ultrasonic generator 8 serving as an ultrasonic vibration source is a heating temperature setting unit that controls the temperature of the heating unit 5b provided in the ultrasonic head 5 and controls the hot plate 6 at a predetermined temperature.

Here, the gold bump 2 formed on the electrode of the semiconductor chip 1 may be a bump formed by plating or a bump formed by a wire bonder. Further, it is necessary to apply gold plating to the surface of the pad 4 formed on the circuit board 3. The suction nozzle 5a that holds the semiconductor chip 1 has a structure that performs ultrasonic vibration from the ultrasonic generator 7 via the ultrasonic vibration transmitter 5c. Although the heating section 5b is provided in the ultrasonic head 5, it has a structure having a mounting method and a mass that do not adversely affect the ultrasonic vibration. For example, a method of fixing the Peltier element between the ultrasonic vibration transmitting unit 5c and the suction nozzle 5a with a heat-resistant adhesive can be used. Here, the heating method may be a simple constant heating method or a pulse heating method.

Next, the operation of the ultrasonic flip chip connection according to the present invention will be described. First, with respect to the heating temperature setting unit 8 from the input device separately provided (not shown), and inputs the thermal expansion coefficient alpha ₁ of the heating temperature t ₂ and the semiconductor chip 1 in thermal expansion coefficient alpha ₂ and the circuit board 3 of the circuit board 3 . Subsequently, the circuit board 3 is placed on the hot plate 6, and the hot plate 6 is heated under the setting from the heating temperature setting unit 8.
Heat. Subsequently, the semiconductor chip 1 is sucked by the suction nozzle 5a.
Is held by suction, and is positioned and mounted on the semiconductor chip mounting position of the circuit board 3.

Thereafter, the heating unit 5b provided in the ultrasonic head 5 is heated to a predetermined temperature under the setting of the heating temperature setting unit 8, and the ultrasonic wave is generated by the ultrasonic wave generating unit 7, and the ultrasonic vibration is transmitted. The ultrasonic wave is transmitted to the suction nozzle 5a via the portion 5c,
By applying ultrasonic vibration to the suction nozzle 5a to vibrate the semiconductor chip 1 held by suction, the gold bump 2
The semiconductor chip 1 is ultrasonically bonded to the circuit board 3 by the frictional heat.

At this time, the heating unit 5 provided in the ultrasonic head 5
temperature b is set by obtaining the t ₁ of the thermal expansion amount of the circuit board 3 and the thermal expansion of the semiconductor chip 1 is to be equal, the following equation (1) is satisfied. (T ₁ −t ₀ ) α ₁ = (t ₂ −t ₀ ) α ₂ (1) where t ₀ is room temperature, t ₁ is a semiconductor chip heating temperature, and t ₂
Is the circuit board heating temperature, α ₁ is the coefficient of thermal expansion of the semiconductor chip, α ₂
Indicates the coefficient of thermal expansion of the circuit board.

In the following, description will be made by applying specific numerical values. The same conditions as in the example described in “Problems to be Solved by the Invention”, that is, the thermal expansion coefficient α ₂ = 7 pp for the circuit board 3
When a ceramic substrate of m / ° C. is used, when the hot plate 6 is set to 150 ° C. at a room temperature of 25 ° C. and the heating temperature t ₂ of the circuit board 3 is set to 150 ° C., the coefficient of thermal expansion α ₁ =
The heating temperature t ₁ of the semiconductor chip 1 of 3 ppm / ° C. is 316 ° C. from the equation (1). By heating the suction nozzle 5a to this temperature and joining the semiconductor chip 1 to the circuit board 3, when the temperature of the semiconductor chip 1 is returned to room temperature of 25 ° C. after the completion of the joining, the semiconductor chip 1 is moved from the heating state similarly to the circuit board 3. 13 μm
Because of contraction, bonding with less stress between the circuit board 3 and the semiconductor chip 1 becomes possible.

Although a ceramic substrate having a coefficient of thermal expansion of 7 ppm / ° C. has been described by way of example, even a glass substrate or a resin substrate having a different coefficient of thermal expansion has the lowest stress after cooling to room temperature according to equation (1). The semiconductor chip heating temperature at the time of ultrasonic bonding can be set. However, if the semiconductor chip heating temperature calculation result exceeds the heat resistance limit of the semiconductor chip, it is necessary to set the temperature at the heat resistance limit of the semiconductor chip so that the distortion is reduced as much as possible.

[0020]

According to the present invention, an ultrasonic vibration is applied to the suction nozzle while heating the circuit board on which the semiconductor chip is mounted and suctioning the semiconductor chip with the ultrasonic head having the suction nozzle. In a semiconductor mounting device for mounting a chip on the circuit board, the ultrasonic head is provided with a heating unit, and the heating unit causes the semiconductor chip to have a thermal expansion amount substantially equal to a thermal expansion amount of the circuit board. The semiconductor chip is bonded to the circuit board by applying ultrasonic vibration in a heated state, so that the shrinkage when returning to room temperature after the bonding is completed is almost the same and distortion due to stress is reduced, so connection reliability is reduced. It is possible to provide a high ultrasonic flip chip connection semiconductor mounting device and an ultrasonic flip chip connection method.

[Brief description of the drawings]

FIG. 1 is a schematic view of a semiconductor mounting device for ultrasonic flip-chip connection according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor chip 2 Gold bump 3 Circuit board 4 Pad 5 Ultrasonic head 5a Suction nozzle 5b Heating part 5c Ultrasonic vibration transmission part 6 Hot plate 7 Ultrasonic wave generating part 8 Heating temperature setting part

Claims (3)

[Claims] An ultrasonic vibration is applied to the suction nozzle while heating the circuit board on which the semiconductor chip is mounted and adsorbing the semiconductor chip with an ultrasonic head having a suction nozzle. In the semiconductor mounting device, the ultrasonic head is provided with a heating unit, and the heating unit heats the semiconductor chip to have a thermal expansion amount substantially equal to the thermal expansion amount of the circuit board. Bonding a semiconductor chip to a circuit board by applying ultrasonic vibration; and a semiconductor mounting device for connecting an ultrasonic flip chip. 2. An ultrasonic vibration is applied to the suction nozzle while heating the circuit board on which the semiconductor chip is mounted and adsorbing the semiconductor chip by an ultrasonic head having a suction nozzle, so that the semiconductor chip is placed on the circuit board. In the semiconductor mounting device, the ultrasonic head is provided with a heating unit, and the heating unit heats the semiconductor chip to have a thermal expansion amount substantially equal to the thermal expansion amount of the circuit board. Bonding a semiconductor chip to a circuit board by applying ultrasonic vibration. 3. An ultrasonic vibration is applied to the suction nozzle while heating the circuit board on which the semiconductor chip is mounted and adsorbing the semiconductor chip with an ultrasonic head having a suction nozzle. A heating unit for the ultrasonic head, for setting a temperature of the heating unit, wherein a heating temperature of the circuit board input from an input device provided separately; A heating temperature setting unit that sets a temperature so that the thermal expansion of the circuit board and the semiconductor chip becomes substantially the same according to the coefficient of thermal expansion and the coefficient of thermal expansion of the semiconductor chip. The semiconductor mounting device for connecting an ultrasonic flip chip according to claim 1.