JPH1012669A - Connection of flip chip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for connecting a flip chip, which can simplify its steps with a good yield and high reliability. SOLUTION: In this connecting method, upon connection of a group of electrodes on a flip chip 5 to a corresponding group of terminals 3a to be connected on a board 3, ultrasonic vibration is applied to the bumps 5a to remove oxidized films from the bumps and to realize frictional contact connection therewith. More specifically, at least one of a mount head 4 of a flip chip bonder or a board stage 1 is provided with a vibrator 2a or 2b for ultrasonic output, the bumps 5a or electrodes for connection of the flip chip 5 are positioned with respect to the connecting terminals 3a of the board 3, the electrode terminals are opposed to the connecting terminals 3a with the bumps 5a disposed therebetween. Under this condition, a load is applied to the mount head 4 and then the ultrasonic vibrator 2a or 2b is operated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting flip chips.

[0002]

2. Description of the Related Art As a semiconductor element mounting technique, it is known to bond (mount) a semiconductor element chip (flip chip) to a wiring board by a face-down method. That is, as an effective means for forming (constructing) a semiconductor device, a corresponding electrode group of a semiconductor element chip is opposed to a substrate surface on which a required connected terminal group is provided, and a connected terminal surface or an electrode surface is provided. A method of performing crimping via a bump provided in the above and making electrical and mechanical connection is being adopted. The flip-chip connection method can collectively connect the flip-chip electrode group and the connected terminal group of the corresponding substrate, as compared with the conventional general wire bonding method, thereby improving productivity (or mass productivity). Is excellent.

In connection with flip chip connection, in order to obtain the reliability of the electrical and mechanical connection, the surface oxide layer (oxide film) of the bump which forms the connection main body.
Is important, and the following treatment is generally performed.

(1) Use of flux A rosin-based or water-soluble flux is previously applied to a bump or a terminal to be connected to a substrate by a printing method or dispensing, and a flip chip is mounted on the substrate.
For example, by performing reflow in an inert atmosphere such as a nitrogen gas, an oxide layer on the bump surface or the connected terminal surface of the substrate is removed, and required connection is performed. (2) Physical removal For example, using a gas such as argon or sulfur hexafluoride,
The oxide layer on the bump surface or the connected terminal surface of the substrate is removed by sputtering.

(3) Removal by reduction For example, the oxide layer on the surface of the bump is removed by a chemical reaction (reduction reaction) by leaving it in a nitrogen-hydrogen atmosphere or a carbon monoxide gas atmosphere.

[0006]

However, the flip chip connection method including the oxide layer removing means has the following problems and is not practically sufficient.

First, (1) in the case of using a flux, connection failure of open / short of the bump is likely to occur depending on the amount of application, so it is necessary to control the amount of application with high precision.
Further, after the connection operation, if the flux adheres or remains, it causes corrosion and the reliability of the connection is impaired. Therefore, it is necessary to wash and remove the flux. The control of the flux application amount and the cleaning and removal of the flux complicate the connection operation and impair the feature of mass productivity.

Next, (2) in the case of physical removal, the management of the sputtering atmosphere and the treatment immediately after the sputtering are complicated, and there is a problem in terms of implementation. For example, in the case of argon gas sputtering,
Although the oxide layer has been removed from the bump immediately after sputtering, the oxide layer is formed again when the bump comes into contact with the air from the argon atmosphere even for a moment. Therefore, spatter-mount-
It is necessary to perform the process up to the reflow in an argon gas atmosphere, resulting in a problem that the equipment and facility costs are enormous. On the other hand, also in the case of sulfur hexafluoride gas sputtering, the atmosphere management is difficult and the practicality is poor.

Further, (3) also in the case of reduction removal, there is a problem in the point of atmosphere control. For example, in a reduction treatment in a nitrogen-hydrogen atmosphere, important factors are an oxygen gas concentration of 1 ppm or less, a dew point of -60 ° C. or less, and a hydrogen gas partial pressure and dew point management. Therefore, effective or efficient reduction processing is based on these appropriate conditions and controls, but it is practically difficult to select and set appropriate conditions and controls. Also,
In a nitrogen-hydrogen atmosphere, the mixing ratio of nitrogen gas and hydrogen gas is 4: 1, 1: 1 and the ratio of hydrogen gas is relatively high, so there is concern about danger in handling operations. On the other hand, it is difficult to control the reducing atmosphere and the standing time of carbon monoxide gas, and it can be said that the utility is inferior.

In both physical removal and reduction removal, the flip chip is mounted on the substrate at the time of mounting, so that even small vibrations can easily cause a positional shift. There is also a problem that it is difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a flip-chip connection method capable of simplifying the process while achieving a high-yield and highly reliable connection.

[0012]

According to a first aspect of the present invention, in connecting a corresponding electrode group on a flip chip surface to a connected terminal group on a substrate surface via a bump, an ultrasonic vibration is applied to the bump. In addition, a flip chip connection method is characterized in that an oxide film on the bump surface is removed and connection is performed by friction.

According to a second aspect of the present invention, there is provided a step of bringing a bump provided on a corresponding electrode surface of a flip chip surface into contact with a group of connected terminals on a substrate surface, and an ultrasonic wave being applied to at least one of the substrate and the flip chip. Applying vibration to remove the oxide film on the bump surface and performing connection by friction.
The invention according to claim 3 is a step of bringing a bump provided on a corresponding connected terminal surface of a substrate surface into contact with an electrode group on the flip chip surface, and applying ultrasonic vibration to at least one of the flip chip and the substrate. And removing the oxide film from the bump surface and performing connection by friction. That is, in these inventions, a vibrator for ultrasonic output is provided and mounted on at least one of the mount head of the flip chip bonder and the substrate stage, and a bump and an electrode terminal or a substrate are connected for flip chip connection. The ultrasonic vibrator is operated after a load is applied to the mount head in a state where the electrode terminal and the connected terminal are brought into contact with each other via the bumps. In other words, the essential point is to apply a required ultrasonic vibration to the electrode terminal portion with which the bump contacts or the connected terminal portion with which the bump contacts.

Here, the ultrasonic vibration reaches the contact surface of the bump-electrode terminal or the contact surface of the bump-connected terminal via the flip chip or the substrate. Due to the transmitted ultrasonic vibration, the oxide layer on the contact surface of the bump-electrode terminal or on both contact surfaces of the bump-connecting terminal is destroyed, and the exposed new surfaces come into contact with each other, so that the tacking is performed simultaneously. Will be Then, the final connection between the electrode terminal and the connected terminal via the bump is completed by reflow in an inert atmosphere.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described below with reference to FIGS. 1 and 2 (a) to 2 (e).

FIG. 1 is a sectional view schematically showing the structure of the connecting portion of the connecting device (bonding device) used in this embodiment. In FIG. 1, reference numeral 1 denotes a substrate stage having a built-in first ultrasonic transducer 2a for positioning (placing) a substrate 3 having a required group of connected terminals 3a on one main surface. Reference numeral 4 denotes a mount head which incorporates the second ultrasonic vibrator 2b and vacuum-adsorbs the flip chip 5 to the front end surface.
The substrate stage 1 is arranged so as to face the substrate 3 mounting surface. Although not shown, the substrate stage 1
The mount head 4 is relatively separated from and connected to the mount head 4 by a mechanism (not shown), and includes a power supply circuit for operating the ultrasonic transducers 2a and 2b. Next, a description will be given of an embodiment of a flip chip connection method using the connection device. 2 (a) to 2 (e) are cross-sectional views schematically showing main parts of the embodiment in the order of flip chip connection steps. First, as shown in FIG. 2A, a substrate 3 having a group of connected terminals 3a on one main surface is transferred onto the substrate stage 1, while a flip chip 5 sucked and held by a mount head 4 is opposed to the substrate. Perform positioning. Here, the flip chip 5 has an electrode terminal group corresponding to the connected terminal group 3a on one main surface, and a bump 5a is provided on each electrode terminal surface. It will be aligned with the connection terminal group 3a. In addition, this alignment
Check the bump 5a group and the corresponding connected terminal 3a pattern with a bonder, make fine adjustments, and
Align the center with 3a.

Next, the mount head 4 is lowered, and the corresponding bump 5a and the connected terminal 3a are brought into contact with each other in a state where no impact is applied, as shown in FIG. 2B. Thereafter, as shown in FIG. 2 (c), a required load (for example, about) is applied to the mount head 4, and the corresponding bump 5a and the connected terminal 3a are sufficiently brought into contact with each other. The load here is set to such an extent that the flip chip 5 is not damaged.

Next, the corresponding bump 5a and the connected terminal
In a state where a constant load is applied to 3a, as shown in FIG. 2D, for example, the second ultrasonic vibrator 2b built in the mount head 4 is operated. By the operation of the second ultrasonic vibrator 2b, the ultrasonic vibration is transmitted in the order of the mount head 4, the flip chip 5, and the bump 5a, so that the connected terminal 3a on the substrate 3 and the bump 5a on the flip chip 5 are connected. Friction occurs in the area of contact. Owing to this local friction, the oxide layer (oxide film) formed on the surface of the connected terminal 3a and the surface of the bump 5a is destroyed, and the new surface is changed into contact with each other. The connected terminal 3a and the bump 5a, which are in contact with each other, are connected at the contact point, and the flip chip 5 is temporarily attached to the substrate 3.

After the corresponding connected terminals 3a and the new surfaces of the bumps 5a have been joined together, the mount head 4 releases the vacuum suction of the flip chip 5 and rises to complete the mounting. After completion of the mounting, the substrate 3 to which the flip chip 5 has been temporarily attached is passed through, for example, a riff furnace in a nitrogen atmosphere, whereby the entire bump 5a is melted, and as shown in FIG. The required 5 electrical and mechanical connections are made.

For example, in the above, the flip chip 5 in which the bumps 5a are provided on the corresponding electrode terminal surfaces is mounted on the substrate 3 on which the connected terminals 3a are provided on the periphery of one main surface at a small pitch. When the reliability of the connection and the like of the connected mounted circuit components were evaluated and examined, it was found to be greatly improved as compared with the conventional connection method.
In connecting the flip chip 5 to the substrate 3, the second ultrasonic vibrator 2b built in the mount head 4 is operated to apply required ultrasonic vibration to the contact portion between the bump 5a and the terminal 3a to be connected. However, the first ultrasonic vibrator 2a built in the substrate stage 1 is operated to apply the required ultrasonic vibration to the contact portion between the bump 5a and the connected terminal 3a, or the first ultrasonic vibration Similar operations and effects were observed when the second ultrasonic transducer 2b was simultaneously operated with the second transducer 2a. Further, in the above description, the connection example of the flip chip 5 having the bump 5a on the electrode terminal surface is shown. However, the flip chip without the bump on the electrode terminal surface is provided on the substrate 3 having the bump 3 on the connected terminal 3a surface. The same operation and effect were also observed when was connected.

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention.

[0022]

As described above, according to the flip chip connection method of the present invention, an oxide layer at a portion to be connected can be easily removed, and highly reliable electrical connection can be performed. In other words, the oxide film such as the bump surface is removed without complicated operations or delicate process control,
Since the electrical and mechanical connection can be performed by the new surface, a highly reliable semiconductor mounting device (or a semiconductor mounting circuit device) can be provided with high yield and mass production.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a connection device used in an embodiment.

FIGS. 2A and 2B schematically show an embodiment of a flip chip connection method, in which FIG. 2A is a cross-sectional view of a state in which a corresponding connected terminal and a bump are aligned, and FIG. Sectional view of the contact state between the connection terminal and the bump, (c) is a cross-sectional view of the state where a load is applied to the connection-to-be-connected terminal and the bump, and (d) is the state of temporary attachment using ultrasonic vibration. FIG. 3E is a cross-sectional view showing a connection end state after the reflow processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate stage 2a, 2b ... Ultrasonic transducer 3 ... Substrate 3a ... Connected terminal 4 ... Mount head 5 ... Flip chip 5a ... Bump

Claims (3)

[Claims] When connecting a corresponding electrode group on a flip chip surface to a connected terminal group on a substrate surface via a bump, an ultrasonic vibration is applied to the bump to remove an oxide film on the bump surface and friction. A connection method for a flip chip, wherein connection is performed. 2. A step of bringing a bump provided on a corresponding electrode surface of a flip chip surface into contact with a group of connected terminals on a substrate surface, and applying ultrasonic vibration to at least one of the substrate and the flip chip. Removing the oxide film from the bump surface and performing connection by friction. 3. A step of bringing a bump provided on a corresponding connected terminal surface of a substrate surface into contact with an electrode group on a flip chip surface, and applying ultrasonic vibration to at least one of the flip chip and the substrate; Removing the oxide film from the bump surface and performing connection by friction.