JPH10173007A - Bare chip-mounting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid collapsing bump electrodes of a bare chip being connected to a wiring board with its surface made parallel to the board by providing a head having a flat plate to make the surface contact to the bare chip and a buffer elastically deformable by the force from the flat plate. SOLUTION: When a bare chip 1 is pressed to a wiring board 7 having a tapered thickness variation, bump electrodes 11 contact electrodes 31 of this board 7 at its thicker part and a buffer 22 elastically deforms due to a force exerted in the arrow mark direction just from contact points, resulting in that the bump electrodes 11 contact the electrode 31 at a thicker part of the board 7. The buffer 22 elastically deforms due to the force directly exerted from the contact points and hence the elastically deforming force may be low and hence the bump electrodes 11 of the chip 1 never collapses. The center of the force exerted from a mount 8 is deviated slightly from the center of the bare chip, but the point of force is low enough to avoid collapse of the bump electrodes 11 due to the eccentric butting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for flip-chip connection in which a semiconductor chip such as an LSI is directly (barely) directly connected to an electrode on a wiring board.

[0002]

2. Description of the Related Art In order to further reduce the size of electronic equipment, a method of soldering a packaged semiconductor element to a resin substrate such as a printed circuit board (hereinafter referred to as a wiring board) has been adopted. It has been replaced by a method of mounting an element on a wiring board. As a method of mounting the semiconductor element on a wiring board while keeping the semiconductor element naked, there is a method of bonding the back surface of the semiconductor element to the substrate with an adhesive and connecting the pad electrode of the semiconductor element and the electrode of the wiring board with a wire. In this method, since the semiconductor element and the electrodes of the wiring board are connected one by one by wires, it takes time to connect a large number of electrodes, and the electrodes of the connected substrate are arranged around the semiconductor element. The mounting area must be larger than the size of the semiconductor element. Therefore, as a method of mounting the semiconductor device in substantially the same area as the semiconductor device, a flip chip connection method has been developed in which the semiconductor device is reversed and its external electrodes are directly connected to the substrate electrodes.

There are three types of flip-chip connection methods for directly connecting an LSI directly to electrodes on a wiring board in a bare state (for example, published by the Industrial Research Institute, Hybrid Microelectronics Handbook, 1989, 487 and 48).
8 pages). First, after attaching solder or conductive adhesive to the protruding electrodes formed on the bare chip, the protruding electrodes on the bare chip are bonded to the electrodes on the wiring board, and the gap between the bare chip and the wiring board is made of epoxy or the like. This is a method realized by hardening with resin. Solder may be used instead of the conductive adhesive.

[0004] The second method is to connect a bare chip on which a protruding electrode is formed and an electrode on a wiring board via an adhesive film such as epoxy containing conductive particles (referred to as an anisotropic conductive film). is there. The third method is to connect a bare chip on which a protruding electrode is formed and an electrode on a wiring board via an adhesive having a high shrinkage such as an ultraviolet curing type.

[0005] In order to realize these methods, a bare chip mounting apparatus for aligning the projecting electrodes of the bare chip with the electrodes on the wiring board and pressing the bare chip against the wiring board is required. The bare chip mounting device includes a head that fixes the bare chip and moves in the vertical direction, a stage that fixes the wiring board and moves in a horizontal plane, and an optical lens that positions the projecting electrodes of the bare chip and the electrodes of the wiring board. FIG. 10 shows a flip chip connection process using a conductive adhesive using a conventional bare chip mounting apparatus.

In the figure, 51 is a bare chip, 61 is a protruding electrode (bump), 52 is a head, 53 is a wiring board, 7
1 is an electrode of the wiring board, 54 is a conductive adhesive, 55 is an optical lens, and 56 is a stage for moving the wiring board in the XY directions. (A) shows a state in which a conductive adhesive 54 is attached to the protruding electrodes 61 of the bare chip 51. (B) shows a state in which the position of the protruding electrode 61 of the bare chip 51 and the position of the electrode 71 of the wiring board 53 are matched using the optical lens 55. Positioning is performed by moving the head 52 or the stage 56. (C) Bare chip 51 and wiring board 5
3 shows a state in which the bare chip 51 is pressed against the wiring board 53 in order to connect the wiring 3. In the case of a conductive adhesive, the connection is made by drying the conductive adhesive 54 in an oven in this state. Also, when solder is used in place of the conductive adhesive, connection is made in the same way.To cure the solder, press the bare chip against the wiring board, then heat the head or heat in an oven. By doing so, a connection can be made.

FIG. 11 shows a flip chip connection process using an anisotropic conductive adhesive film using a conventional bare chip mounting apparatus. In the figure, 51 is a bare chip, 61 is a protruding electrode, 52 is a head, 53 is a wiring board, 71 is an electrode of a wiring board, 81 is an anisotropic conductive adhesive film, 82 is conductive particles, 55 is an optical lens, and 56 is a stage. It is.
(A) shows a stage 5 in which a wiring board 53 on which an anisotropic conductive adhesive film 81 such as epoxy containing conductive particles 82 is adhered.
6 shows a state in which it is fixed. (B) shows a state in which an optical lens 55 is placed between a bare chip 51 having a protruding electrode 61 fixed to a head 52 and a wiring substrate 53, and the positioning of the protruding electrode 61 of the bare chip 51 and the electrode 71 of the wiring substrate 53 is performed. Is shown. (C) shows a state where the bare chip 1 is pressed against the wiring board 53 and heated. The connection is realized when the conductive particles 82 sandwiched between the protruding electrodes 61 of the bare chip 51 and the electrodes 71 of the wiring board 53 are crushed.

The above description has been given of the step of performing the flip chip connection using the conductive adhesive 54 or the anisotropic conductive film 81 using the conventional bare chip mounting apparatus. The third method using a UV-curable adhesive also requires a new UV irradiation device, but, like the first and second connection methods, requires a bare chip mounting device that aligns and pushes the bare chip onto the wiring board. The bare chip mounting device includes a projection electrode 61 of the bare chip 51 and an electrode 71 of the wiring electrode 53.
It is important to pressurize evenly at multiple points,
The head 52 is fixed while being kept parallel to the stage 56.

When the bare chip is pressed against a tapered wiring board having uneven thickness using the above-described bare chip mounting apparatus, the head is fixed so as to be parallel to the stage. Therefore, the entire number of the projecting electrodes of the bare chip cannot be brought into contact with the electrodes of the wiring board. for that reason,
There is a problem that an open failure occurs.

As a solution to this problem, Japanese Patent Laid-Open No. 4-243144 discloses a bonding head that automatically corrects the tilt of the head and presses the chip against the substrate while maintaining the parallel state of the substrate and the electrode forming surface of the chip. Proposed. FIG. 12 is a side sectional view of the circuit board.
3, the electrodes of the chip component 51 are connected to the wiring board 53. At this time, if the contact surface of the head is not parallel to the upper surface of the chip component 51, the elastic body 59 is deformed so that the axis of the head 52 is inclined with respect to the axis of the holding mechanism 58, and the contact surface of the head is inclined. Adhere to the chip component 51.

[0011]

The bonding apparatus shown in FIG. 12 has the following problems although the contact surface of the head and the upper surface of the chip component are in close contact with each other. (A) Assuming that the point P of the head comes into contact with the chip component first, a force acts on the point P so that the head rotates around the point O, and a force acts on the center Q of the elastic body 59 to cause the elastic body 59 to rotate.
Is a mechanism in which a force acts on the entire surface of the chip component as a result of the deformation. In this case, since the distance OQ is larger than the distance PO, it is necessary to apply a larger force to the point P to make the moments equal. Therefore, if this mechanism is applied to a bare chip instead of a chip component, the protruding electrodes will be crushed. (B) Since the chip component is pressed in a state where the axis of the head is inclined, a so-called one-sided contact state in which the strongest force is applied to a point shifted from the center point of the head contact surface, and Since a force is applied from the side and the power point is increased, a moment acts and the protruding electrode of the chip component is crushed.

According to the present invention, when connecting a bare chip to a wiring board having a tapered and uneven thickness, not only can the bare chip surface be parallel to the surface of the wiring board, but also the projection electrode of the bare chip does not collapse. It is intended to obtain a mounting device.

[0013]

A bare chip mounting apparatus according to the present invention is a device for mounting a bare chip on a wiring board by pressing a projecting electrode of the bare chip held by the head against the wiring board. It is provided with a contacting flat plate and a cushioning material which is elastically deformed by the force from the flat plate.

[0014] The bare chip mounting apparatus according to the present invention may further include a gantry for fixing the head, wherein at least one of the gantry and the flat plate has a magnet, and the other has a magnet or a magnetic material.

The bare chip mounting apparatus according to the present invention may have a flat plate and a buffer provided with holes for sucking bare chips. In that case, the number of holes in the flat plate may be smaller than the number of holes in the cushioning material.

In the bare chip mounting apparatus according to the present invention, the flat plate may include a heater.

Further, the bare chip mounting apparatus according to the present invention presses the projecting electrodes of the bare chip held by the head against the wiring substrate fixed on the stage,
An apparatus for mounting a bare chip on a wiring board, comprising: a flat plate for holding the wiring board between the stage and the wiring board; and a cushioning material elastically deformed by a force from the flat plate.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a sectional view showing a case where a bare chip is mounted on a tapered wiring board having uneven thickness in the bare chip mounting apparatus according to the first embodiment of the present invention. In the figure, 1 is a bare chip, 11 is a protruding electrode, 2 is a head, 2
1 is a flat plate as a part of the head, 22 is a part of the head and is a cushioning material made of, for example, rubber, 7 is a wiring board having a tapered uneven thickness, 31 is an electrode of the wiring board, 4 is a conductive adhesive. Reference numeral 6 denotes a stage that fixes the wiring board 7 and moves in the X and Y directions, and 8 denotes an upper mount. The head 2 is also called a bonding tool. The upper gantry 8 is also referred to as a bonding tool Z axis, and moves in the vertical direction while fixing the head 2.

Next, the operation will be described with reference to FIGS. When the bare chip 1 is pressed against the wiring substrate 7 having a tapered uneven thickness, the projecting electrode 11
And the electrode 31 of the wiring board 7 are in contact at the point R. When the bare chip 1 is further pressed, the cushioning material 22 is elastically deformed by the force acting in the direction of the arrow directly from the contact point R, and the protruding electrode 11 and the electrode 31 come into contact even with the thinner one of the wiring board 7. This state is shown in FIG. Since the cushioning material 22 is elastically deformed by the force acting directly from the contact point, the force required for the deformation is small, and the projection electrode 11 of the bare chip 1 is not shaken. Further, the center of the force applied from the gantry 8 is slightly deviated from the center of the bare chip, but since the power point is low, the projection electrode is not crushed by one contact. At this time, the flat plate 21 is made of a material having high rigidity such as ceramic or stainless steel, and has a role of making surface contact with the back surface of the bare chip 1, and does not exert an influence on the bare chip 1 due to deformation of the cushioning material 22. .

In the present embodiment, the cushioning member 22 has a thickness of 0.8
mm with silicone rubber, 40μm on bare chip surface
When the conductive adhesive 4 was mounted on the wiring board 7 having a certain taper amount, good connection was obtained for all the electrodes. The flat plate 21 of this embodiment has a thickness of 2 mm.
Was used. Although silicone rubber is used for the cushioning material 22, other rubbers may be used. In this case, the conductive adhesive 4 is used, but solder may be used.

Comparative Example FIG. 4 shows a state in which the bare chip 1 is pressed against a wiring board without providing a flat plate. A force acts in the direction of the arrow in the figure from the protruding electrode 11 pressed against the electrode 31 of the wiring board 7, and the cushioning material 22 is deformed into a waveform as shown. As a result, a force is applied to the bare chip 1 so as to deform it into a waveform following the deformation of the cushioning material 22, and the bare chip 1 may be broken. In order to prevent this, a substance having high rigidity may be arranged between the bare chip 1 and the cushioning material 22.

Embodiment 2 FIG. In the first embodiment, the flat plate 21 and the cushioning material 22 are bonded with an adhesive, but as shown in FIG. 5, a magnetic material that attracts the upper base 8 holding the head 2 to a magnet or a magnet is used. , And by using the flat plate 21 made of a magnet,
Thus, there is no need to fix the cushioning material 22 and the upper gantry with an adhesive, and there is an effect that the work becomes easy.

Embodiment 3 FIG. FIG. 6 is a cross-sectional view of a bare chip mounting apparatus according to another embodiment of the present invention, in which a bare chip is mounted on a wiring substrate having a tapered and uneven thickness with high productivity. In FIG. 6, 1 is a bare chip, 11 is a protruding electrode, 2 is a head, 21 is a flat plate, 22 is a buffer, 7
Is a wiring board having a tapered uneven thickness, 31 is an electrode,
4 is a conductive adhesive, 6 is a stage, 8 is an upper mount, 23
Denotes a hole in the cushioning material, and 24 denotes a hole in a flat plate. Hole 23 for cushioning material
The bare chip 1 can be sucked and held by the pressure difference through the hole 24 of the flat plate and the flat plate, and the bare chip 1 can be easily attached and detached, so that productivity can be improved. Absorption of uneven thickness of the wiring board 7 is equivalent to that of the first embodiment.

Embodiment 4 FIG. 7 is a cross-sectional view of a bare chip mounting apparatus according to another embodiment of the present invention, in which bare chips of various sizes are mounted on a tapered wiring board having uneven thickness. In FIG. 7, 1 is a bare chip,
11 is a protruding electrode, 2 is a head, 21 is a flat plate, 22 is a buffer material, 7 is a wiring board having a tapered uneven thickness, 31 is an electrode, 4 is a conductive adhesive, 6 is a stage, and 8 is an upper frame. , 23 indicate holes in the cushioning material, and 24 indicates holes in the flat plate.

When the bare chip 1 is pressed against the wiring board 7, it is necessary to apply a force on the projecting electrodes 11 of the bare chip 1, so that the size of the flat plate 21 needs to be equal to that of the bare chip 1. Therefore, if the size of the bare chip 1 is different, it is necessary to change the size of the flat plate 21 accordingly.
In the present embodiment, by reducing the number of the holes 24 of the flat plate to the number of the holes 23 of the buffer material, the flat plate 21 and the bare chip can be held by suction, and the size of the bare chip 1 can be easily adjusted. The flat plate 21 can be replaced and held, and the bare chips 1 having different sizes can be mounted with high productivity.

Embodiment 5 FIG. 8 is a cross-sectional view of a bare chip mounting apparatus according to another embodiment of the present invention in which a bare chip is mounted on a wiring substrate having a tapered uneven thickness by applying heat to the bare chip using an anisotropic conductive adhesive film. In the figure, 1 is a bare chip, 11 is a protruding electrode, 2 is a head,
21 is a flat plate, 22 is a cushioning material, 7 is a wiring board having a tapered uneven thickness, 8 is an upper frame, 31 is an electrode, 41 is an anisotropic conductive adhesive film, 42 is conductive particles, 25 is a heater, 26 Is made of heat insulating material. An anisotropic conductive adhesive film 41 is bonded to the wiring board 7 in advance, and the heater 25
When the bare chip 1 heated by the above is pressed, the anisotropic conductive adhesive film 41 is softened by heat, and is fixed with the conductive particles 42 sandwiched between the protruding electrodes 11 and the electrodes 31,
Electrical conduction can be obtained between the protruding electrode 11 and the electrode 31 via the conductive particles 42. The heat insulating material 26 is used to prevent the heat of the heater from being conducted to the bare chip mounting device main body. As the heat insulating material, a porous ceramic which is hard and excellent in heat dissipation is used.

Embodiment 6 FIG. FIG. 9 is a cross-sectional view of a bare chip mounting apparatus according to another embodiment of the present invention, in which a bare chip is mounted on a tapered wiring substrate having uneven thickness. In the figure, 1 is a bare chip, 11 is a protruding electrode, 2
Denotes a head, 21 denotes a flat plate, 22 denotes a buffer, 7 denotes a wiring board having a tapered uneven thickness, 31 denotes an electrode, 4 denotes a conductive adhesive, and 6 denotes a stage. In this embodiment,
This shows a case where a flat plate 21 and a buffer material 22 having the same size as the size of the bare chip 1 are provided between the wiring board 7 and the stage 6. Also in this embodiment, it is possible to connect the bare chip to the wiring board having the same thickness unevenness as that of the first embodiment while making the surface of the bare chip parallel to the wiring board, and the projecting electrodes of the bare chip are not crushed. The effect can be obtained.

[0028]

The bare chip mounting apparatus according to the first aspect of the present invention is an apparatus for mounting a bare chip on a wiring board by pressing a projecting electrode of the bare chip held by the head against the wiring board surface. Since it has a flat plate that comes into surface contact and a cushioning material that is elastically deformed by the force from this flat plate, it can be connected not only with the bare chip surface parallel to the uneven thickness of the wiring board surface, but also with the bare chip protrusion. The effect that the electrodes are not crushed is exerted.

The bare chip mounting apparatus according to a second aspect of the present invention is further provided with a mount that fixes the head and moves vertically, at least one of the mount and the flat plate has a magnet, and the other has a magnet or a magnetic material. Therefore, there is an effect that the flat plate and the cushioning material constituting the head can be fixed to the gantry without using an adhesive.

The bare chip mounting device according to claim 3 of the present invention is the same as the bare chip mounting device according to claim 1, since the flat plate and the cushioning material are provided with holes for sucking bare chips.
Easy attachment and detachment of bare chips.

The bare chip mounting device according to claim 4 of the present invention is the device according to claim 1, wherein the number of holes in the flat plate is smaller than the number of holes in the cushioning material. In addition, the attachment and detachment of the flat plate becomes easy.

The bare chip mounting apparatus according to claim 5 of the present invention is the apparatus according to claim 1, wherein the flat plate is provided with a heater, so that the anisotropic conductive adhesive can be easily softened by heat. The connection between the bare chip and the wiring board is facilitated.

The bare chip mounting device according to the sixth aspect of the present invention presses the projecting electrode of the bare chip held by the head against the wiring board fixed to the stage,
In a device for mounting a bare chip on a wiring board, a flat plate for holding the wiring board and a cushioning material that is elastically deformed by the force from the flat plate are provided between the stage and the wiring board, so that the surface of the wiring board having a non-uniform thickness is provided. Not only can the connection be made with the surface of the bare chip being parallel, but also the projection electrode of the bare chip can be prevented from being crushed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a bare chip mounting apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a state in which a bare chip and a wiring board have started to contact with each other in the bare chip mounting device of FIG. 1;

FIG. 3 is a view showing a state in which the bare chip is pressed against the wiring board in the bare chip mounting device of FIG. 1;

FIG. 4 is a diagram showing a state in which a bare chip is pressed against a wiring board in a device of a comparative example in which a flat plate is removed from the bare chip mounting device of FIG. 1;

FIG. 5 is a sectional view showing another embodiment of the bare chip mounting device of the present invention.

FIG. 6 is a sectional view showing another embodiment of the bare chip mounting device of the present invention.

FIG. 7 is a sectional view showing another embodiment of the bare chip mounting device of the present invention.

FIG. 8 is a sectional view showing another embodiment of the bare chip mounting device of the present invention.

FIG. 9 is a sectional view showing another embodiment of the bare chip mounting apparatus of the present invention.

FIG. 10 is a diagram illustrating a process of connecting a bare chip and a wiring board according to an example of a conventional bare chip mounting apparatus.

FIG. 11 is a view showing a process of connecting a bare chip and a wiring board by a conventional bare chip mounting apparatus.

FIG. 12 is a cross-sectional view showing another example of a conventional bare chip mounting device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Bare chip 2 Head 4 Conductive adhesive 6 Stage 7 Wiring board 8 Upper pedestal 11 Protrusion electrode 21 Flat plate 22 Buffer material 23 Hole 24 Hole 25 Heater 26 Insulating material 41 Anisotropic conductive adhesive film 42 Conductive particles

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Toda 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Yoichi Kitamura 2-3-2 Marunouchi, Chiyoda-ku, Tokyo 3 (72) Inventor Yoshiro Isobe 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Sanishi Electric Co., Ltd.

Claims (6)

[Claims] 1. An apparatus for mounting a bare chip on a wiring board by pressing a projecting electrode of the bare chip held by a head against a wiring board surface, wherein the head has a flat plate in surface contact with the bare chip and an elastic force generated by the flat plate. A bare chip mounting device comprising a deformable cushioning material. 2. A gantry for fixing a head and moving vertically, wherein at least one of the gantry and the flat plate has a magnet, and the other has a magnet or a magnetic material. A bare chip mounting device according to claim 1. 3. The bare chip mounting apparatus according to claim 1, wherein the flat plate and the cushioning material have holes for sucking bare chips. 4. The bare chip mounting device according to claim 3, wherein the number of holes in the flat plate is smaller than the number of holes in the cushioning material. 5. The bare chip mounting device according to claim 1, wherein the flat plate is provided with a heater. 6. An apparatus for mounting a bare chip on a wiring board by pressing a projecting electrode of a bare chip held by a head against a surface of a wiring board fixed on a stage, wherein the wiring board is provided between the stage and the wiring board. A bare chip mounting device, comprising: a flat plate for holding the flat plate; and a cushioning material elastically deformed by a force from the flat plate.