JP2008227017A - Electronic component mounting apparatus and mounting method - Google Patents

Abstract

An object of the present invention is to provide a mounting apparatus capable of reliably determining whether or not a semiconductor chip mounted on a substrate is mounted.
A mounting tool for mounting a semiconductor chip by applying ultrasonic vibration while pressing a bump 4a of a semiconductor chip 4 against the substrate 1 to bond the bump to the substrate, and a bump of the semiconductor chip mounted on the substrate An infrared camera 33 for picking up an image of the semiconductor chip through the semiconductor chip, an image processing unit 34 for image processing of the image pickup signal of the infrared camera, and determining the degree of bump collapse from the image pickup signal processed by the image processing unit. A comparison unit 37 for determining the mounting state is provided.
[Selection] Figure 2

Description

  The present invention relates to a mounting apparatus and a mounting method for mounting an electronic component on a substrate using ultrasonic vibration.

  For example, when mounting a semiconductor chip with bumps, which is an electronic component, on a pad of a substrate such as a tape member made of polyimide, a method of mounting the semiconductor chip on the substrate while applying a pressing load and ultrasonic vibration is known. ing. That is, the semiconductor chip is pressurized and heated to a pad provided on the substrate with a predetermined pressure, and further, ultrasonic vibration is applied to the semiconductor chip, so that the bump of the semiconductor chip is applied to the pad of the substrate by solid phase diffusion. It is to join.

  Such a semiconductor chip is mounted using a mounting tool. The mounting tool has an ultrasonic head with a built-in heater. The ultrasonic head is integrally provided with a suction portion for sucking and holding the semiconductor chip. When the semiconductor chip is delivered to the suction portion, the mounting tool is positioned above the mounting position of the substrate and then driven in the downward direction. As a result, the semiconductor chip held on the suction portion is mounted on the substrate by pressure, heat, and ultrasonic vibration.

  When a semiconductor chip is reliably mounted on a substrate using ultrasonic vibration, it is required to efficiently transmit ultrasonic vibration that greatly contributes to bonding from the ultrasonic head of the mounting tool to the semiconductor chip.

  However, in actuality, foreign matter may be mixed between the suction part of the mounting tool and the semiconductor chip sucked and held by the suction part, or slipping may occur between the mounting tool and the semiconductor chip due to wear of the suction part. Due to variations in the pressure applied to the semiconductor device, ultrasonic vibration may not be transmitted efficiently and reliably from the mounting tool to the semiconductor chip. In such a case, since the bumps provided on the semiconductor chip are not crushed reliably, the bumps are not bonded to the pads of the substrate with a predetermined strength, resulting in a bonding failure.

  Therefore, when a semiconductor chip is mounted on a substrate, it is inspected whether or not the bump is reliably crushed, and the bonding state of the semiconductor chip is determined based on the inspection.

  When inspecting whether the bump is reliably crushed, if the semiconductor chip is mounted on the substrate, the height of the upper surface of the semiconductor chip is detected, and whether the bump is reliably crushed by that height Judgment is made.

In Patent Document 1, the position (height) of a chip (mounting tool) provided at the tip of a horn is mounted after mounting an object (semiconductor chip) on a base material (substrate) using ultrasonic vibration. It is shown that whether or not the joining state is good is determined by determining whether or not the position is in a predetermined position by the position displacement sensor.
JP 2001-105159 A

  As shown in Patent Document 1, according to the method of determining the position of the mounting tool after joining the semiconductor chips, the suction part for sucking and holding the semiconductor chip of the mounting tool is obtained by repeatedly mounting the semiconductor chip. Because of wear, the position of the mounting tool detected by the position displacement sensor changes after mounting regardless of whether the semiconductor chip is bonded or not.

  Therefore, if it is determined whether or not the bonding state of the semiconductor chip is good from the position of the mounting tool after mounting, it is not possible to cope with the wear caused by the use of the mounting tool, so whether or not the semiconductor chip is securely bonded. In some cases, the determination cannot be performed reliably.

  In addition, the height of the mounting tool after mounting changes depending on variations in bump height, board thickness, etc. before mounting regardless of whether the bonding state is good or not, so the height of the mounting tool is detected after mounting. The method may not be able to accurately determine the actual bonding state.

  The present invention can accurately determine the bonding state between the substrate and the electronic component regardless of the height of the mounting tool, thereby addressing the wear of the mounting tool, variations in the height of the bump, the thickness of the substrate, and the like. It is an object of the present invention to provide an electronic component mounting apparatus and mounting method that can be used.

The present invention is a mounting apparatus for mounting an electronic component on a substrate via bumps provided on the electronic component,
A mounting tool for mounting the electronic component by applying ultrasonic vibration while pressing the bump of the electronic component against the substrate and bonding the bump to the substrate;
Imaging means for imaging the bumps of the electronic component mounted on the substrate through the electronic component;
An image processing unit that performs image processing on an imaging signal of the imaging unit;
An electronic component mounting apparatus comprising: determination means for determining a degree of collapse of the bump from the imaging signal processed by the image processing unit and determining a mounting state of the electronic component by the bump.

The imaging means is
It is preferable that the light source is configured to include a light source that emits irradiation light in a wavelength region that passes through the electronic component, and an imaging camera that captures the irradiation light that is transmitted through and reflected by the electronic component.

This invention is a mounting method for mounting an electronic component on a substrate via bumps provided on the electronic component,
A process of applying ultrasonic vibration while pressing the bumps of the electronic component against the substrate to bond the bumps to the substrate and mounting the bumps;
Imaging a bump of the electronic component mounted on the substrate;
A step of obtaining the degree of collapse of the bump from the imaging signal of the bump;
And a step of determining a mounting state of the electronic component from a degree of collapse of the bump.

  It is preferable to irradiate with irradiation light in a wavelength region that passes through the electronic component, and obtain the degree of collapse of the bump by irradiation light reflected by the bump.

  It is preferable to obtain a change in area due to the degree of collapse of the bumps and determine the mounting state of the electronic component based on the change in area.

  According to the present invention, when an electronic component is mounted on the substrate, the mounting state of the electronic component is determined by measuring the degree of bump collapse, so that the wear of the mounting tool, the height of the bump, the variation in the thickness of the substrate, etc. Regardless of this, it is possible to accurately determine the bonding state of the electronic component to the substrate.

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a front view showing a schematic configuration of a flip-chip mounting device, and FIG. 2 is a side view of the mounting device. The mounting device includes a transport device 2 for transporting a substrate 1 such as a lead frame along a predetermined direction. I have. The transport device 2 has a pair of guide rails 3 arranged in parallel at a predetermined interval, and the substrate 1 is intermittently pitched along the guide rails 3. Each time the substrate 1 is pitch-fed, it is positioned and held on the guide rail 3 by a clamper (not shown).

  When the substrate 1 is transported to the mounting position by the transport device 2, a thin semiconductor having a thickness of several hundred microns as an electronic component supplied from a component supply unit 21 (shown in FIG. 1) described later is provided at the mounting position. Chip 4 is mounted. At this mounting position, a stage tool 5 that supports the lower surface of the substrate 1 is provided so as to be driven by the first drive mechanism 6 in the horizontal X and Y directions and the vertical Z direction.

  A mounting tool 7 for mounting the semiconductor chip 4 on the upper surface of the substrate 1 is provided above the stage tool 5 so as to be driven in the X, Y, and Z directions by the second driving mechanism 8.

  The mounting tool 7 has a base 11, and an ultrasonic head 12 is provided on the lower surface of the base 11. The ultrasonic head 12 has a horn 13, and a vibrator 14 is provided at one end of the horn 13. A suction portion 15 is provided on the lower surface of the horn 13, and the semiconductor chip 4 is sucked and held on the suction portion 15 as will be described later.

  An oscillator (not shown) is connected to the vibrator 14, and a high frequency voltage of 40 kHz, for example, is applied from this oscillator. Accordingly, the horn 13 is ultrasonically vibrated together with the vibrator 14.

  The component supply unit 21 has a wafer stage 22 driven in the X and Y directions by a drive source (not shown). On the wafer stage 22, a semiconductor wafer 23 divided into a large number of semiconductor chips 4 is held on a wafer sheet 24.

  As shown in FIG. 3, the semiconductor chip 4 has a plurality of bumps 4a (shown in FIG. 4A) electrically connected to the pads 1a formed on the substrate 1 on one surface. Then, the wafer sheet 24 is held with the surface on which the bumps 4a are formed facing upward.

  Among the semiconductor chips 4 held on the wafer sheet 24, the semiconductor chip 4 at a predetermined position is pushed up by a push-up pin (not shown). The semiconductor chip 4 pushed up by the push-up pin is sucked by the suction nozzle 26 that constitutes the pickup device 25. The suction nozzle 26 is attached to a rotary head 28 provided in the reversing unit 27.

  The rotary head 28 is driven to rotate. Accordingly, the suction nozzle 26 is positioned at a position where the suction surface 26a indicated by a solid line in FIG. 1 faces downward, and a position where the suction surface 26a rotates 180 degrees from that position and faces upward (shown by a chain line in FIG. 1). Is done.

  The reversing unit 27 is driven along the guide rod 29. The guide rod 29 is installed horizontally from the wafer stage 22 toward the mounting position of the transfer device 2. As a result, the suction nozzle 26 that sucks the semiconductor chip 4 from the wafer sheet 24 is driven to the side of the transfer device 2 with the suction surface 26a sucking the semiconductor chip 4 upward as shown by a chain line in FIG. Positioned. This position is the delivery position.

  When the suction nozzle 26 is positioned at the delivery position, the mounting tool 7 is driven as indicated by a chain line in the drawing, and the semiconductor chip 4 sucked on the suction surface 26a of the suction nozzle 26 is received. Next, the mounting tool 7 is positioned at a mounting position above the substrate 1 as indicated by a solid line.

  At the same time, the stage tool 5 is driven in the upward direction to support the lower surface of the substrate 1. When the mounting tool 7 is driven in the downward direction, the semiconductor chip 4 held by the mounting tool 7 is mounted on the portion of the substrate 1 supported by the stage tool 5.

  The stage tool 5 and the mounting tool 7 have horns 13 provided with heaters (not shown). Accordingly, the semiconductor chip 4 and the portion of the substrate 1 where the semiconductor chip 4 is mounted are heated, and the semiconductor chip 4 is thermocompression bonded to the substrate 1 while applying ultrasonic vibration. That is, the bumps 4a provided on the semiconductor chip 4 are crushed and joined to the pads 1a provided on the substrate 1 by solid phase diffusion.

  The substrate 1 on which the semiconductor chips 4 are mounted is intermittently transferred at a predetermined pitch along the guide rails 3 of the transfer device 2, and the semiconductor chips 4 are sequentially mounted on the substrate 1 at predetermined intervals as shown in FIG. Is done. When the semiconductor chip 4 mounted on the substrate 1 by the mounting tool 7 is transported from the mounting position by a predetermined pitch (2 pitches in this embodiment), the semiconductor chip 4 has a wavelength in an infrared region such as near infrared or mid infrared. Irradiation light L having Irradiation light L is emitted from the light source 31 with the optical axis horizontal, and is reflected downward by the semi-transparent mirror 32 disposed at an angle of 45 degrees above the substrate 1 to irradiate the upper surface of the semiconductor chip 4. .

  Irradiation light L irradiating the semiconductor chip 4 is transmitted through the thin semiconductor chip 4 having a thickness of several hundreds μm because the wavelength is in the infrared region, and reflected by the crushed bump 24, the pad 1a of the substrate 1, or the like. To do. The reflected irradiation light L passes through the semi-transparent mirror 32 and is received by an infrared camera 33 as an imaging camera that constitutes an imaging means with the semi-transparent mirror 32.

  The irradiation light L incident on the infrared camera 33 is binarized by the image processing unit 34. That is, since the reflectance of the portion other than the bump 4a and the bump 4a differs depending on the material, the luminance between the irradiation light L reflected by the bump 4a and the irradiation light L reflected by the portion other than the bump 4a. Therefore, binarization is performed based on the difference in luminance.

  The imaging signal binarized by the image processing unit 34 is output to the control device 35. The control device 35 compares the area of the bump 4a calculated by the arithmetic processing unit 36 with a calculation area 36 for obtaining the area of the bump 4a from the binarized imaging signal, and compares the area of the bump 4a with a preset reference area. And a comparison unit 37 serving as a determination unit that determines the degree of collapse of the bump 4a and outputs a determination signal.

  When the semiconductor chip 4 is mounted on the substrate 1, it can be determined that the bump 24 is sufficiently crushed if the area of the bump 24 is enlarged by about 20 to 30%. Therefore, the comparison unit 37 compares the area of the bump 24 after mounting measured with respect to the area of the bump 24 before mounting and outputs a determination signal.

  According to the mounting apparatus having such a configuration, the semiconductor chip 4 is mounted on the substrate 1 by the mounting tool 7 every time the substrate 1 is pitch-fed by the transfer device 2. The semiconductor chip 4 is solid-phase diffusion bonded to the pads 1 a of the substrate 1 by crushing the bumps 4 a by the applied pressure, heat and ultrasonic vibration applied from the mounting tool 7.

  4A shows the bump 4a of the semiconductor chip 4 before being mounted on the substrate 1, and FIG. 4B shows the bump 4a crushed by being mounted. Assuming that the area of the bump 4a before mounting is S1, and the area of the bump 4a after mounting is S2, S1 <S2, and as described above, if S2 is about 1.2 to 1.3 times S1, This means that the bump 4a is sufficiently crushed and the semiconductor chip 4 is mounted.

  When the semiconductor chip 4 mounted on the substrate 1 at the mounting position is transported above the infrared camera 33, the irradiation light L having a wavelength in the infrared region that is emitted from the light source 31 and reflected by the semi-transparent mirror 32 to the semiconductor chip 4. Irradiated.

  Since the thickness of the semiconductor chip 4 is very thin such as several hundred microns, the irradiation light L is transmitted through the semiconductor chip 4 and reflected by the bumps 4a, the pads 1a of the substrate 1, etc., and passes through the semi-transparent mirror 32 and the infrared rays. The light enters the camera 33.

  The irradiation light L incident on the infrared camera 33 is binarized by the image processing unit 34, and then the area of the bump 4 a crushed by the arithmetic processing unit 36 of the control device 35 is obtained. The degree of collapse of the bump 4a is determined by comparing with the area.

  That is, when the semiconductor chip 4 is mounted on the substrate 1, it is determined whether or not the semiconductor chip 4 is reliably mounted on the substrate 1 from the change in area according to the degree of collapse of the bump 4a after mounting. .

  Therefore, the mounting state of the semiconductor chip 4 on the substrate 1 is ensured without being affected by the wear of the suction portion 15 accompanying the use of the mounting tool 7 or the variation in the thickness of the substrate 1 or the semiconductor chip 4 as in the prior art. Moreover, since it becomes possible to make a precise determination, it is possible to prevent the occurrence of defective products.

  In the above embodiment, the semiconductor chip is irradiated with the irradiation light of the infrared region in order to image the degree of collapse of the bumps of the semiconductor chip mounted on the substrate. However, the irradiation light is limited to the light of the infrared region. However, the present invention is not limited to this, and other wavelengths of light that are optically transparent to the semiconductor chip, such as laser light and X-rays, may be used.

  In the embodiment described above, the reflected light reflected from the bumps and pads by the irradiation light emitted from the root of the hole is imaged by the camera. However, the bumps are crushed by the transmitted light transmitted through the semiconductor chip and the substrate. It is also possible to measure the amount.

  In that case, when the bump is crushed, its area increases, so that the measured transmitted light is less if the crushed bump is appropriate. Therefore, if the ratio of the transmitted light amount is measured, it can be determined whether or not the bump is properly crushed.

BRIEF DESCRIPTION OF THE DRAWINGS The front view which shows schematic structure of the mounting apparatus of one embodiment of this invention. Similarly side view. The enlarged view of the semiconductor chip adsorbed and held by the adsorption part. (A) is a top view of the semiconductor chip for explaining the size of the bump before mounting, (b) is a plan view of the semiconductor chip for explaining the size of the bump after mounting.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 4 ... Semiconductor chip (electronic component), 7 ... Mounting tool, 12 ... Ultrasonic head, 14 vibrators, 15 ... Adsorption part, 4a ... Bump, 31 ... Light source, 32 ... Semi-transparent mirror, 33 ... Infrared camera (Imaging camera), 34... Image processing unit, 35... Control device, 36.

Claims (5)

A mounting device for mounting electronic components on a substrate via bumps provided on the electronic components,
A mounting tool for mounting the electronic component by applying ultrasonic vibration while pressing the bump of the electronic component against the substrate and bonding the bump to the substrate;
Imaging means for imaging the bumps of the electronic component mounted on the substrate through the electronic component;
An image processing unit that performs image processing on an imaging signal of the imaging unit;
An electronic component mounting apparatus comprising: determination means for determining a degree of collapse of the bump from the imaging signal processed by the image processing unit and determining a mounting state of the electronic component by the bump. The imaging means is
The light source which emits the irradiation light of the wavelength range which permeate | transmits the said electronic component, and the imaging camera which images the said irradiation light which permeate | transmitted and reflected the said electronic component, It is comprised. Electronic component mounting equipment. A mounting method for mounting an electronic component on a substrate via bumps provided on the electronic component,
A process of applying ultrasonic vibration while pressing the bumps of the electronic component against the substrate to bond the bumps to the substrate and mounting the bumps;
Imaging a bump of the electronic component mounted on the substrate;
A step of obtaining the degree of collapse of the bump from the imaging signal of the bump;
And a step of determining a mounting state of the electronic component from a degree of collapse of the bump.   4. The method of mounting an electronic component according to claim 3, wherein irradiation light in a wavelength region that passes through the electronic component is irradiated, and a degree of collapse of the bump is obtained by irradiation light reflected by the bump.   5. The electronic component mounting method according to claim 3, wherein a change in area due to the degree of collapse of the bump is obtained, and a mounting state of the electronic component is determined based on the change in area.

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