JP2010245306A - Method of bonding electronic component with bump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of bonding an electronic component with a bump that secures excellent bonding strength by actualizing a uniform bonding state in the same bump. <P>SOLUTION: In an operation to bond the bump 30a of the electronic component 30 with the bump to an electrode 32b on a surface to be pressed against by pressing the bump 30a against the electrode 32b and applying ultrasonic vibrations, a bonding head is lowered to bring the bump 30a into contact with the electrode 32b, and further lowered until the bump 30a reaches a predetermined bump height (b), and while the gap between the electronic component 30 and the electrode 32b is held at the bump height (b) as a preset target value, the electronic component 30 is applied with ultrasonic vibrations for a predetermined time. Consequently, the time for which the ultraviolet vibrations are applied is made equal over the entire range of area A by which a reverse surface of the bump 30a comes into contact with the electrode 32b to obtain the uniform bonding state, thereby securing the excellent bonding strength. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a bumping electronic component bonding method for bonding a bumped electronic component such as a flip chip to a surface to be bonded such as a substrate.

  As a method of bonding an electronic component with a bump such as a flip chip to a surface to be bonded such as a substrate, a method using ultrasonic pressure welding is known. In this method, ultrasonic vibration is applied while pressing bumps of an electronic component against a substrate, and bonding surfaces are rubbed against each other for bonding (see Patent Document 1). In the prior art example shown in this patent document, an example of applying a predetermined load and ultrasonic vibration set in advance as bonding conditions is shown in flip chip bonding for bonding a semiconductor chip adsorbed to a collet tool. Here, an example is shown in which a bonding operation is performed while monitoring the amount of bump depression due to the action of a load and ultrasonic vibration.

JP 11-297761 A

  However, in the above-described prior art examples, there is a problem that the joining state is likely to be unstable due to the application of ultrasonic vibration while the bumps are submerged. That is, in the process of sinking the bump, the contact area between the lower surface of the bump and the pressure-bonded surface of the electrode changes as the bump is crushed. In other words, the center part of the lower surface of the bump that has first contacted is subjected to the action of ultrasonic vibration for a long time, but the ultrasonic wave is applied only at the final stage of the process of sinking the bump in the peripheral part of the lower surface of the bump. Vibration acts. For this reason, there is a problem that the bonding state is not uniform between the central portion and the peripheral portion in the same bump, and a good bonding strength cannot be obtained.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for bonding an electronic component with a bump capable of realizing a uniform bonding state inside the same bump and ensuring a good bonding strength.

  In the bonding method of an electronic component with bumps according to the present invention, the bump is bonded to the electrode by applying ultrasonic vibration by pressing the bump of the electronic component with bump against the electrode on the surface to be bonded by a bonding head. A method of bonding an electronic component with a bump, wherein the bonding head holding the electronic component is lowered to bring the bump into contact with the electrode, and then the bonding head is moved until the bump reaches a predetermined height. A step of further lowering, a step of monitoring a gap between the electronic component and the surface to be pressed by a height measuring means for measuring a height position of the bonding head, and setting the gap to a preset target value. And applying ultrasonic vibration to the electronic component for a predetermined time in the maintained state.

According to the present invention, the electronic component is held in the bonding of the bumped electronic component by bonding the bump to the electrode by applying the ultrasonic vibration by pressing the bump of the electronic component with the bump against the electrode on the surface to be bonded. The bonding head is lowered, the bump is brought into contact with the electrode, the bonding head is further lowered until the bump reaches a predetermined height, and the gap between the electronic component with the bump and the surface to be pressed is set in advance. By applying ultrasonic vibration to the bonding head for a predetermined time while maintaining the same, the time during which ultrasonic vibration is applied can be made equal over the entire area in contact with the surface to be pressed on the lower surface of the bump. A uniform bonding state can be realized and good bonding strength can be ensured.

1 is a front view of a bonding apparatus for electronic components with bumps according to an embodiment of the present invention. The flowchart which shows the bonding method of the electronic component with bump of one embodiment of this invention The graph which shows the time change of the height of the bonding head in the bonding method of the electronic component with bump | vamp of one embodiment of this invention, and the drive power supply output of an ultrasonic transducer drive part The figure which shows the behavior of the bump in the bonding method of the electronic component with a bump of one embodiment of this invention

  Next, embodiments of the present invention will be described with reference to the drawings. 1 is a front view of a bonding apparatus for electronic components with bumps according to an embodiment of the present invention, FIG. 2 is a flowchart showing a bonding method for electronic components with bumps according to an embodiment of the present invention, and FIG. FIG. 4 is a graph showing temporal changes in the height of the bonding head and drive power output of the ultrasonic transducer drive unit in the method for bonding electronic components with bumps according to an embodiment of the present invention. It is a figure which shows the behavior of the bump in the bonding method of the electronic component with a bump of form.

  First, the overall structure of a bonding apparatus for electronic components with bumps will be described with reference to FIG. A first elevating plate 2 and a second elevating plate 3 are provided on the front surface of the support frame 1 arranged vertically so as to be movable up and down. A cylinder 4 is mounted on the first lifting plate 2 in a vertical posture with the rod 5 facing downward, and the rod 5 is coupled to the second lifting plate 3. The cylinder 4 always urges the second lifting plate 3 downward, and a bonding head 10 is attached to the second lifting plate 3. A Z-axis motor 6 is provided on the upper surface of the support frame 1, and the Z-axis motor 6 rotationally drives a vertical feed screw 7. The feed screw 7 is screwed into a nut 8 provided on the back surface of the first elevating plate 2. When the feed screw 7 is rotationally driven by the Z-axis motor 6, the nut 8 moves up and down along the feed screw 7. Thus, the first elevating plate 2 and the second elevating plate 3 also move up and down.

  In FIG. 1, a substrate 32 is placed on a substrate holder 33 with an upper surface 32a, which is a pressure-bonded surface, facing upward, and electrodes 32b to which bumps 30a of electronic components 30 are bonded (see FIG. 4). ) Is formed. The substrate holder 33 is placed on the movable table 34. By driving the movable table 34, the substrate holder 33 moves horizontally in the X direction and the Y direction, whereby the substrate 32 is positioned at a predetermined position.

  The control system will be described. The main control unit 35 controls the Z-axis motor 6 via the motor drive unit 36 and controls the movable table 34 via the table control unit 37. The main control unit 35 controls the projecting output of the rod 5 of the cylinder 4 via the load control unit 38. Thereby, the pressing load for pressing the electronic component 30 with bumps against the substrate 32 by the bonding tool 20 is controlled.

A holder 12 is coupled to a lower end portion of the main body 11 of the bonding head 10 via a load cell 13. A block 14 is attached to the holder 12, and a bonding tool 20 is fixed to the block 14. The bonding tool 20 includes an ultrasonic transducer 21 that generates ultrasonic vibrations, and the ultrasonic transducer 21 is driven by an ultrasonic transducer drive unit 39. The bonding tool 20 sucks and holds the electronic component 30 on a holding portion 20a provided to protrude from the lower surface of the central portion. The bonding head 10 is lowered while holding the electronic component 30, and the ultrasonic vibrator 21 is driven while pressing the bumps 30 a of the electronic component 30 against the electrodes 32 b of the substrate 32, so Sonic vibration is applied, and the bumps 30 a are bonded to the electrodes 32 b of the substrate 32.

  In the bonding process, the following three types of measurement values are set as monitoring targets. First, the pressing load at the time of bonding is detected by the load cell 13, read as load data by the load reading unit 42, and transmitted to the main control unit 35. The height position of the bonding head 10 is measured by the linear scale unit 40 provided on the second lifting plate 3, read as height data by the height reading unit 41, and transmitted to the main control unit 35. . The linear scale unit 40 and the height reading unit 41 constitute a height measuring unit that measures the height position of the bonding head 10.

  The reference surface used as a reference for height measurement at this time is the upper surface 32a of the substrate 32. A fixed reference surface may be set in advance assuming a standard reference surface. Therefore, the reference surface may be corrected by measuring the height position of the upper surface of the substrate 32 at each bonding operation. By measuring the height position of the bonding head 10 by the above-described height measuring means, the gap between the upper surface 32a of the substrate 32 and the electronic component 30 at that time, in other words, somewhat in the height direction due to the pressing load. The height of the bump 30a that has been crushed and deformed can be measured.

  The drive current of the ultrasonic transducer 21 in the bonding process is measured by the current measurement unit 43 and the measurement result is transmitted to the main control unit 35. A display unit 44 is connected to the main control unit 35, and the monitor screen of the display unit 44 has the above measured value, that is, the height of the bonding head 10 (FIG. 3A) and The power output (FIG. 3B) by the ultrasonic transducer drive unit 39 is displayed in a graph. In the bonding method of the electronic component with bump shown in the embodiment of the present invention, the bonding operation is controlled without referring to the load data detected by the load cell 13 and read by the load reading unit 42. ing.

  This bonding apparatus for electronic components with bumps is configured as described above. Next, the bonding head 10 presses the bumps 30a of the electronic components 30 with bumps against the electrodes on the surface to be bonded, and ultrasonically applies the electronic components 30 to the electronic components 30. A bonding method of an electronic component with a bump for bonding the bump 30a to the electrode 32b by applying vibration will be described along the flow of FIG. 2 with reference to the graph of FIG.

  First, the electronic component 30 is vacuum-sucked and held on the holding portion 20a of the bonding tool 20, and the flow of FIG. 2 starts from a state where the electronic component 30 is positioned above the substrate 32 and aligned with the electrode 32b. . First, at timing t0, the Z-axis motor 6 is driven to lower the bonding head 10 holding the electronic component 30 (ST1). Thereafter, the bonding head 10 is lowered, and the bump 30a of the electronic component 30 contacts the electrode 32b of the substrate 32 at timing t1. Then, the output of the load cell 13 changes and this contact is detected by the main control unit 35 (ST2).

After this timing t1, the bonding head 10 is further lowered, the electronic component 30 is pushed down by the bonding tool 20, and bump pressing is started (ST3). That is, the electronic component 30 is further lowered to press the bump 30 a against the substrate 32. In addition, the bump height is monitored by the height reading unit 41 when the bump pressing is started (ST4). In other words, the height position of the bonding head 10 is measured by the height measuring means including the linear scale unit 40 and the height reading unit 41, whereby the bump height indicated by the dimension of the gap between the electronic component 30 and the substrate 32 is displayed. That is, the height of the bump 30a in a state where the bump 30a is crushed and deformed somewhat in the vertical direction is always measured.

  In the process from timing t1 to timing t2, the bump 30a of the electronic component 30 is crushed and deformed by the bonding tool 20 as the bonding head 10 descends from h1 to h2, and the bump height decreases. As a result of this reduction in bump height, the contact state of the bump 30a with the substrate 32 is made uniform. That is, at the timing t 1 when the bump 30 a first contacts the substrate 32, only a small part of the bump 30 a is in contact with the substrate 32 due to the variation in the height of the bump 30 a or the undulation of the substrate 32. However, at the timing t2 when the bonding head 10 is lowered to the predetermined target height h2, all the bumps 30a are crushed and deformed to the predetermined bump height b (see FIG. 4). All the bumps 30a are in contact with the substrate 32.

  The target height h2 of the bonding head 10 is determined as follows. First, data indicating the variation state of the height of the bump 3a in the target electronic component 30 is acquired. In consideration of these height variations, when the bumps 30a are uniformly pressed from above and deformed in the vertical direction, the bump height b is such that all the bumps 30a are in a substantially uniform contact state. Is estimated. Then, the target height h2 of the bonding head 10 is set corresponding to the bump height b. In other words, the height measuring means monitors the height position of the bonding tool 10 to monitor the bump height b of the bump 30a (the gap between the electronic component 30 and the substrate 32). become.

  In this bump height monitoring, it is determined whether or not the bump height has reached the bump height b set as a prescribed target value (ST5). If the bump height reaches the target value b at timing t2, that is, if the bonding head height h reaches h2, as shown in FIG. 3A, the driving of the Z-axis motor 6 is stopped. Then, the height of the Z axis (the height position of the bonding head 10) is held (ST6). Thereby, the clearance gap between the electronic component 30 and the board | substrate 32 is maintained by the preset target value b.

  Next, as shown in FIG. 3B, driving of the ultrasonic transducer 21 is started when the ultrasonic vibration is turned on (ST7), and then a predetermined time (time t2 to t3) has passed since the ultrasonic vibration was turned on. Is monitored (ST8). If it is confirmed that the predetermined time has passed, the ultrasonic vibration is turned off (ST9), and then the bonding head 10 after the electronic component 30 is bonded to the substrate 32 is raised (ST10). Thereby, one cycle of the bonding operation for the electronic component 30 with one bump is completed.

  That is, in the bonding method of the electronic component 30 with the bump described above, the bump 30a is applied to the electrode 32b by pressing the bump 30a of the electronic component 30 against the electrode 32b on the surface to be bonded by the bonding head 10 and applying ultrasonic vibration. The bonding head 10 that holds the electronic component 30 is lowered to bring the bump 30a into contact with the electrode 32b, and then the bonding head 10 is set until the bump 30a reaches a predetermined bump height b. And a step of monitoring the gap between the electronic component 30 and the electrode 32b, which is the pressure-bonded surface, by a height measuring means for measuring the height position of the bonding head 10, and setting this gap in advance. Applying ultrasonic vibration to the bonding tool 20 for a predetermined time while maintaining the set target value It has become a form that contains a.

In the step of applying ultrasonic vibration to the bonding tool 20 for a predetermined time (t2 to t3), as shown in FIG. 4, the bonding head height h is always kept at h2, and therefore the bump 30a of the electronic component 30 is The bump height b is always maintained at a preset target value. Accordingly, the area A of the contact portion where the lower surface of the bump 30a is pressed against the electrode 32b is always kept constant throughout the vibration action time (t2 to t3) when the ultrasonic vibration is turned on.

  That is, in the bonding operation shown in the present embodiment, the lower end portion of the bump 30a is always pressed against the pressure-bonded surface with the same area A from the beginning to the end of the vibration acting time on the bump 30a. Therefore, in the entire range of the area A where the bump 30a is in contact with the surface to be pressed, the ultrasonic vibration acts for the same time from the beginning to the end of the vibration action time. As a result, a uniform bonding state is realized for the entire range of the area A within the same bump 30a, and good bonding strength can be ensured.

  In the bonding method of the electronic component with bumps shown in the above embodiment, the bonding head 10 may be controlled so as to deform the bump 30a of the electronic component 30 to the bump height b set as a target value. Therefore, it is not necessary to consider the bonding load that presses the electronic component 30 against the substrate 32 as an element that defines the bonding conditions. As a result, in the condition finding operation performed to find appropriate bonding conditions, various element conditions such as the combination of the target substrate and bump and the presence / absence of resin applied prior to bonding are different. However, it is possible to simplify the combination of bonding conditions in the condition setting operation, and it is possible to easily set appropriate bonding conditions.

  The method for bonding an electronic component with bumps according to the present invention has an effect that a uniform bonding state can be realized inside the same bump and a good bonding strength can be ensured. This is useful in the field of mounting electronic components on a substrate with a bonding tool.

DESCRIPTION OF SYMBOLS 10 Bonding head 20 Bonding tool 21 Ultrasonic vibrator 30 Electronic component 30a Bump 32 Substrate 32a Upper surface (surface to be bonded)
32b Electrode 40 Linear scale unit (height measuring means)

Claims (1)

In the bonding method of an electronic component with a bump for bonding the bump to the electrode by pressing the bump of the electronic component with the bump against the electrode on the surface to be bonded by a bonding head and applying ultrasonic vibration to the electronic component. There,
A step of lowering the bonding head holding the electronic component to bring the bump into contact with the electrode and then lowering the bonding head until the bump reaches a predetermined height; and a height of the bonding head. A step of monitoring a gap between the electronic component and the surface to be bonded by a height measuring means for measuring a position, and an ultrasonic vibration in the electronic component in a state where the gap is maintained at a preset target value. And a step of applying for a predetermined time. A method for bonding electronic components with bumps.

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