JPH07211423A - Method for mounting ic chip on flexible circuit board and thermocompression bonding machine for ic chip - Google Patents

Abstract

PURPOSE: To lessen the degree of the deformation of board and improve the reliability of connection by forming no projected part in a portion of a chip which is in the outside of an electrode pad and making an air layer existing in a gap to the board at the time when a flexible circuit board and an IC chip are heated and pressed by a projected part of a stage. CONSTITUTION: A board 10 is mounted on a flat part of a projected part 2a of a stage 2 and while sandwiching a film-like anisotropic conductive film 12 previously and temporarily pressure connected with the board 10, an IC chip 1 is mounted on the board 10 and heated and pressed. To make the connection between the chip 1 and the conductive film 12 of the substrate 10 reliable, proper pressure is applied to the upper face of the projected part 2a at the time of pressure connection. At that time, since no projected part 2a against the stage 2 is formed in the portion which is the outside of an electrode bump 3, an air layer exists in a lower part of the substrate and the distance extension of a connection circuit on the board 10 is made possible and occurrence of edge short circuit is prevented and at the same time deformation of the board 10 except the projected part 2a can be restricted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a large scale integrated circuit (IC).
The present invention relates to a method for mounting an IC chip on a flexible circuit board for electrically and physically connecting a facing member between a chip) and a flexible circuit board (FPC board), and a thermocompression bonding machine for an IC chip for carrying out the method. .

[0002]

2. Description of the Related Art TC of a polyimide base material widely used as an IC module for driving a liquid crystal display (LCD)
P (Tape Carrier Package) is a cheaper material,
For example, attempts have been made to replace it with a polyester base material. However, such an inexpensive substrate has poor heat resistance and
With the method of connecting the C chip to the TCP substrate, the eutectic connection under high temperature (350 to 400 ° C.) as in the conventional case is impossible.
It is necessary to use a connecting material that can be connected at a low temperature, such as an anisotropic conductive film (ACF). Therefore, FP using ACF
Face down bonding of an IC chip to C is described, for example, in Japanese Patent Publication No. 62-6652, and in Japanese Patent Application Laid-Open No. 62-24635, while adsorbing an IC chip with a suction head and heating it. There is disclosed a thermocompression bonding device which presses a predetermined position on a circuit board to connect the two. Further, Japanese Utility Model Laid-Open No. 1-89492 discloses a device using an anisotropic conductive film.

[0003]

However, the above conventional configuration has the following problems. That is, for example, as shown in FIGS. 8 and 9, when attempting face-down bonding of the IC chip 1 to the FPC board 10 using a polyester film having a circuit formed of copper or aluminum material as a base material, the FPC board 10 Is thermocompression bonding (1
40-250 ° C x 20-40kgfcm ² x 10-40
When the stage 20 is simply a flat surface as in the conventional case, the circuit near the connection portion on the FPC board 10 directly contacts the chip edge portion 5 or the conductivity in the ACF 12 is increased. So-called edge short-circuiting, in which particles come into contact with each other, tends to occur. That is, as shown in FIG. 9, the chip edge portion 5 is not subjected to the insulation treatment (passivation film 4) due to the manufacturing process of the IC chip 1, and the exposed silicon of the edge portion 5 is a semiconductor. Therefore, if it comes into contact with the opposing circuit on the side of the FPC board to be connected, a short circuit will occur, causing a serious functional failure such as crosstalk. FIG. 9 shows the above-described modification of the FPC board 10 during pressure bonding according to the conventional method. Therefore, an object of the present invention is to solve the above problem, and to prevent an electrical contact (edge short circuit) between a chip edge and a counter electrode terminal on an FPC board, an IC chip for a flexible circuit board. And a thermocompression bonding machine for an IC chip for carrying out this method.

[0004]

In order to achieve the above object, the present invention provides a flexible circuit board and an IC chip up to the outermost part of the electrode pad group of the IC chip by providing a convex portion on the stage. Is heated and pressed, and the electrode pad of the IC chip is pressure-bonded to a predetermined portion of the flexible circuit board. That is, as described in claim 1, the IC for the flexible circuit board according to the present invention
The chip mounting method is the method of mounting an IC chip on a flexible circuit board by crimping and mounting the IC chip on the flexible circuit board using a stage, wherein the edge of the IC chip is attached to the convex portion of the stage. The flexible circuit board and the IC chip are heated and pressed to a portion corresponding to the outermost side of the electrode pad group arranged in the section, and the electrode pad of the IC chip is pressure-bonded to a predetermined portion of the flexible circuit board.

Further, as described in claim 2, in the structure of claim 1, the IC chip has a square or rectangular plate shape, and the electrode pad group is arranged on four sides thereof, and the electrode pad group is arranged. To a portion which is equal to or slightly larger than the outermost peripheral shape of the flexible circuit board by the convex portion (2a) having an area equal to or smaller than the area of the IC chip of the stage (2) of the thermocompression bonding machine to which the flexible circuit board is to be aligned. Alternatively, the flexible circuit board and the IC chip may be pressure-bonded to each other by heating and pressing the substrate and the IC chip. In addition, as described in claim 3,
A thermocompression bonding machine according to the present invention is a thermocompression bonding machine for thermocompression bonding an IC chip to a flexible circuit board to obtain an electrical connection, wherein the area of the IC chip is mounted on a stage of the thermocompression bonding machine to which the flexible circuit board is to be aligned. A convex portion having the following area is provided, and the IC chip and the flexible circuit board are heated and pressed against the convex portion to press-connect the IC chip and the flexible circuit board.

Further, as described in claim 4, in the structure of claim 3, the height of the convex portion is 0.1 to 3.0.
mm, and more preferably 0.2 to 1.0 mm. In addition, as described in claim 5, in claim 3 or 4, it may be configured such that it has a substantially conical or quadrangular pyramid-shaped recess inside the convex portion. Further, as described in claim 6, in the structure of claim 5, the deepest of the depression is 10 to 1000 μm.
m, and more preferably 20 to 500 μm.

[0007]

According to the structure of the present invention, since the flexible circuit board and the IC chip are heated and pressed by the convex portion of the stage, the convex portion of the stage is formed in a portion corresponding to the outside of the electrode pad of the IC chip. An air layer may exist between the flexible circuit board and the flexible circuit board. Therefore, this air layer serves as a heat insulating portion, and the flexible circuit board is not on the edge side of the IC chip as in the conventional case,
It deforms in a direction away from the edge of the IC chip. As a result, the distance between the edge portion of the IC chip and the connection circuit on the flexible circuit board becomes long, and the occurrence of edge short circuit can be prevented. Further, the smoothness of the FPC board can be remarkably maintained as compared with the case where the conventional smooth stage is used. This is because, in the external connection of the FPC board, if the deformation amount of the FPC board is large, it may be difficult to perform the alignment or a short circuit may occur. On the other hand, in the present invention, the deformation of the FPC board is not so large because the deformation of the flexible circuit board is restricted by the stage in the portion that does not contact the convex portion. As a result, high connection reliability can be provided for mounting the IC chip on the FPC board by ACF, for example.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described below with reference to FIGS.
It will be described in detail based on. As shown in FIGS. 1 to 3, the method of mounting the IC chip on the flexible circuit board according to the present embodiment uses the IC chip 1 and the FPC board 10 as the ACF.
In the connection method of connecting with the thermocompression bonding machine 30 via 12, the size of the stage 2 immediately below the IC chip of the thermocompression bonding machine 30 is equal to the outer circumference of the IC chip 1 or electrodes arranged on the IC chip 1. The stage 2 which is larger than the outermost periphery of the pad groups 3, ..., 3 is used. The IC chip 1 used in this mounting method has a fine circuit formed on a silicon substrate, and has a large number of electrode pad terminals (bumps) 3 on its lower surface for connection to the outside. The shape of the IC chip 1 is a square or a rectangle having a side length of 3 to 20 mm, and preferably has a thickness of 0.3 to 2 mm. Further, the circuit of the FPC board 10 used in the above mounting method is made of copper, aluminum, gold, silver or a metal thereof plated, and has a circuit width of 30 to 200 μm and a height of 10 to 10. 40μ
m, and the FPC circuit 11 is created by photoetching. The FPC base material 14 is made of polyimide, polyester, polysulfone, or the like, and has a thickness of 25 to 125 μm and an area of TAB.
(Tape automated bonding tape): 10
It is about 70 mm square, and the FPC circuit 11 is bonded onto the base material 14 by laminating with the adhesive 13.

On the other hand, as shown in FIGS. 2 and 3, the stage 2 of the thermocompression bonding machine 30 used for carrying out the mounting method described above.
Is 5 to 30 cm square, the material is iron, aluminum, brass, copper, zinc, alloy, glass, ceramics,
It is made of phenolic resin, epoxy resin, etc. The stage 2 is movable in two directions orthogonal to the thermocompression bonding machine body, that is, in the xy direction, and also has a function as an xy table. F on stage 2
The PC positioning device is configured to have, for example, one or more air suction pores 40c on the stage 2, as shown in FIG. If necessary, a heating device such as a heater may be provided below the stage 2 to perform the heating operation.
The convex portion 2a formed on the stage 2 preferably has a shape that conforms to the bump arrangement of the IC chip 1, and generally has a square shape, a rectangular shape, or the like. And the convex portion 2a
Has at least a flat portion for keeping the IC chip 1 flat.

The height of the convex portion 2a of the stage 2 is 0.1.
~ 3 mm is preferable, and more preferably 0.2-1.0.
mm. If it is less than 0.1 mm, the above effect is not obtained, while if it exceeds 3 mm, wear, damage, and deformation of the upper flat portion easily occur due to use, and the IC chips 1 and F
This is because reliable connection with the PC board 10 becomes difficult.
The material of the convex portion 2a of the stage 2 is not particularly limited, but the same material as that of the stage 2 may be used, and a material having excellent heat resistance and durability is preferable. Moreover, the area of the convex portion 2a is as shown in FIGS.
As shown in (1), it must be the same as or smaller than the outer shape of the IC chip 1 and larger than the bump array shape. That is, in FIGS.
The minimum width dimension of a is the interval L ₁ between the bump arrays on the opposite edges of the electrode bumps 3, and the maximum width dimension is the width dimension L ₂ of the IC chip 1. Specifically, from the outer shape of the IC chip 1,
If it is smaller than 50 to 100 μm, it is preferable, and if it is larger than the bump arrangement shape by about 50 to 100 μm, the IC chip 1 and the FPC board 10 can be reliably connected. This convex portion 2a can be formed by machining such as cutting and polishing. Alternatively, the convex portion 2a may be configured by forming a hole in the stage 2 in advance and fixing the separately formed convex member. At that time, it is possible to simply fit them, and it is also possible to fix them by welding or an adhesive. It is sufficient that at least one convex portion 2a is provided, and a plurality of convex portions 2a can be provided corresponding to the plurality of IC chips 1.

According to the above construction, as shown in FIG. 1, the flexible circuit board 10 is placed on the flat portion of the convex portion 2a of the stage 2 and then the FPC board 10 is preliminarily pressure-bonded to the film shape. The IC chip 1 is placed on the flexible circuit board 10 via the ACF 12 and heated and pressed. That is, on the upper surface of the convex portion 2a,
In order to surely connect the IC chip 1 and the FPC board 10 via the ACF 12, an appropriate pressure acts on the connection corresponding portion. At this time, the convex portion 2 a is not formed on the stage 2 in a portion corresponding to the outside of the electrode bump 3 of the IC chip 1, and an air layer exists below the flexible circuit board 10. This air layer serves as a heat insulating portion, and the flexible circuit board 10 moves away from the edge portion 5 of the IC chip 1 as shown in FIG. Transforms in the direction. As a result, the distance between the edge portion 5 of the IC chip 1 and the connection circuit on the flexible circuit board 10 becomes long, and the occurrence of edge short circuit can be prevented. Further, as compared with the case where the conventional smooth stage 20 is used, the FPC board 1 is remarkably
It is possible to maintain the smoothness of 0. because,
This is because, in the external connection of the FPC board 10, if the deformation amount of the FPC board 10 is large, alignment may be difficult or a short circuit may occur. On the other hand, in this embodiment, the deformation of the portion of the FPC board 10 that is not in contact with the convex portion 2a of the stage 2 is restricted by the portion other than the convex portion of the stage 2, so that it does not deform so much. Of. The ACF 12 may be preliminarily pressure bonded to the IC chip side.

An outline of a thermocompression bonding machine as an example for carrying out this mounting method is shown in FIGS. In FIGS. 4 and 5, a TAB film holding a large number of IC chips 1, ..., 1 is supported by a head 60 having a heater for heating the IC chips, and each IC chip 1 is placed on the table 43 one by one. The flexible circuit board 10 is pressure-bonded and connected. The head 60 is moved up and down by the air cylinder 31 for driving the head, and the air cylinder 31 moves up and down.
The pressure of is switched between low pressure and high pressure by the low pressure / high pressure changeover switch 32. As a result, the crimping force can be adjusted.
The head 60 performs longitudinal angle adjustment and width direction angle adjustment by the two adjusting screws 37 and the four adjusting screws 38, respectively. 39 is a plate for fixing two heads, 40
Is a head mounting nail. The TAB film supported by the head 60 is supported so that it can be fed at a predetermined pitch between two reels 61, 61, and the lower part of the film is spread horizontally along with two film roll mounting rods 42, 42. I am able to do it. The feed amount of the film can be adjusted by the adjusting screw 41. On the other hand, the stage 2 measures the x of the stage 2 by the micrometer 44.
-The adjustment of the angle θ of the y-plane is performed by the micrometer 45 in the z direction.
The inclination of the direction can be adjusted, the amount of movement in the x direction can be adjusted by the micrometer 46, and the amount of movement in the stage y direction can be adjusted by the micrometer 48. Reference numeral 47 is a fixing plate that locks the stage in the x direction by tightening a screw, 49 is a fixing plate that locks the stage 2 in the y direction by tightening the screw, and 50 is a shock absorber that cushions a shock when the table is inserted. Is. Reference numeral 51 is a monitor CCD camera for observing the state of the FPC circuit board on the table 43, and 53 is a moving mechanism thereof.

The specific specifications of this thermocompression bonding machine are, for example,
The head 60 has a crimping surface dimension of 100 mm ± 0.2 in length.
mm, width 20.0 mm ± 0.1 mm, material is steel (SK
H steel), usable temperature is room temperature to 500 ° C (± 5%), low pressure side total load 5 to 50 kgf, high pressure side total load 50 to 150
kgf, stroke 75mmMAX, can be stopped at any position within the stroke, can be manually rotated by 90 °, can be manually adjusted in the longitudinal direction angle and width direction angle, and the head can be replaced. The stage 2 uses a feed cylinder and a deceleration damper to move the stage by 250.
mmMAX, table movement is 10 mm in x direction, 10 mm in y direction, 5 ° tilt adjustment in θ direction (all manual),
The table material is bakelite, the table is removable (positioning pins are used for positioning), and the table size is 350 × 350 mm. In addition, the film feed section can automatically feed the film once per cycle, the feed amount can be varied from 1 to 15 mm, the film width is 100 mm MAX, 1 inch core, and the head contact mechanism can be used only when the head is pressed. It is designed to come into contact with the surface. Also, the monitor is a CCD camera X 100 mm,
Y ± 50mm movement (manual), CCD magnification 9-inch on monitor 9-33 times, monitor 9-inch black and white monitor, X-
It comes with a Y reticle. In such a thermocompression bonding machine, one cycle of table loading, head lowering, head lifting, and table unloading is automatically performed. As an example,
The heating time of the head (heating time in the continuous heating method) by the heater with a built-in head is variable from 1 sec to 1 hr, the power supply is AC100V10A, and the working air pressure is 5 kgf / cm ² .

In the thermocompression bonding machine 30, the head holding the IC chips 1, ..., 1 by driving the air cylinder 31 after the FPC circuit board 10 is loaded on the table 43 to a predetermined position. 60 descends, AC
Through the F12, one IC chip 1 is heated and pressed by the head 60 to a predetermined position on the FPC circuit board 10 to be thermocompression-bonded to be electrically and physically bonded. afterwards,
The head 60 is raised by the air cylinder 31, and the IC
The FPC circuit board 10 to which the chip 1 is connected is the table 4
It is carried out together with 3. By repeating this operation, the IC chips 1 can be automatically and continuously pressed onto the FPC circuit board 10. Below is a more practical example. In this example, the pressure bonding of the IC chip to the FPC board was performed by a pulse heat heating type flip chip bonder having a 12 mm square metal head. The crimping temperature is the effective temperature applied to the ACF part, and the crimping pressure is I
The total load applied to the C chip is shown. (Example-1) Chip outer peripheral size 6.86 mm square, bump size 100 μm square × height 25 μm, number of bumps 120, bump pitch 200 μm, bump group outermost peripheral size 6.54 mm
Corner test chip is aluminum circuit 15μm thick / Laminated material 1
F composed of 0 μm thickness / polyester substrate 38 μm thickness
A PC board with a height of 400 μm and 6.86 mm square and 6.
Crimping was performed using a stage having a convex shape of 54 mm square, and the presence or absence of an edge short circuit was electrically confirmed. ACF
Was a prototype using a thermosetting binder containing 2% by volume of a metallic nickel part having a film thickness of 13 μm and an average particle size of 5 μm. As a comparative example, a sample was manufactured using a flat stage. All crimping conditions are 240 ℃ × 6kg
f / chip × 15 seconds. The results are shown in Table 1. When the stage having a convex shape corresponding to the present example is used, the occurrence rate of edge shorts is extremely small for both of the two convex shapes, which is clear from the comparative example of 10%. The effect was seen in.

[0015]

[Table 1]

(Example-2) The same test chip as in Example-1 and an FPC board on which a circuit having the same material structure and capable of measuring connection resistance characteristics are formed, and a convex portion having the same outer peripheral dimension as the bump group. Crimping was performed using a shape stage, and the presence or absence of an edge short and the resistance characteristics were measured. ACF is an example-
I used the same as No. 1, but the crimping condition was 240 ° C ×
6 kgf / chip x 15 seconds, 240 ° C x 4 kgf / chip x 15 seconds, 220 ° C x 6 kgf / chip x 20 seconds, 2
Four conditions of 20 ° C. × 4 kgf / chip × 20 seconds were prepared, and pressure bonding was performed under each condition. It should be noted that the presence or absence of the edge short circuit cannot be measured as the occurrence rate like in Example-1 because the circuit on the FPC board is formed for resistance measurement, and therefore only the presence or absence of the occurrence is confirmed.
As the environment resistance test condition of the pressure-bonded sample, holding at -20 ° C for 2 hours, transition time for 2 hours, 70 ° C / 90%
Retaining in RH state is repeated for 2 hours as one temperature / humidity cycle, and left in this temperature / humidity cycle.
The resistance value after a lapse of time was measured. The results are shown in Table 2, and in the case of high temperature compression and high pressure compression, the effect equivalent to that of this example was remarkable, no edge short circuit was observed, and the resistance value was stable. In the comparative example, 220 ° C. × 4 kgf /
Although the edge short circuit did not occur only under the condition of chip × 20 seconds, the stability of resistance value was inferior to that of the example.

[0017]

[Table 2]

The present invention is not limited to the above embodiment, but can be implemented in various other modes. For example,
As shown in FIGS. 6 and 7, a conical or quadrangular pyramid-shaped recess 40b having a taper from the bump 3 toward the center of the IC chip is formed at a substantially central portion of the flat portion of the convex portion 40a of the stage 40.
Is preferably provided. This is because the adhesive of the anisotropic conductive film or the conductive adhesive can flow uniformly and firmly bond the IC chip 1 and the FPC board 10 to each other. The depth of the recess 40b is preferably 10 to 1000 μm, and more preferably 20 μm.
Is about 500 μm. If it is less than 10 μm, there is no remarkable effect.
However, it is largely deformed by the depression, the effective adhesive amount is reduced, and the adhesive force is reduced. Such depressions can be created by cutting by mechanical processing, laser processing, or etching. Here, with the anisotropic conductive film, a predetermined amount of conductive particles are mixed and dispersed in a thermosetting adhesive or a thermoplastic adhesive so that conduction between adherends can be obtained only in the vertical direction. It is a thing. As a specific example,
Anisotropic conductive film 5350R, 5 manufactured by Sumitomo 3M Limited
There are 303R and the like.

[Brief description of drawings]

FIG. 1 is an IC by a mounting method according to an embodiment of the present invention.
It is a cross-sectional side view which shows the connection state of a chip and a flexible circuit board.

FIG. 2 is a plan view of an IC chip used in the mounting method of FIG.

3 is a cross-sectional side view of the stage shown in FIG.

FIG. 4 is a front view of a thermocompression bonding machine used to carry out the mounting method.

5 is a side view of the thermocompression bonding machine of FIG. 4. FIG.

FIG. 6 is a plan view of a stage according to another embodiment of the present invention.

7 is a cross-sectional side view of the stage of FIG.

FIG. 8 is an enlarged side view of the lower end portion of the IC chip.

FIG. 9 is a sectional side view showing a connection state between an IC chip and a flexible circuit board by a conventional mounting method.

[Explanation of symbols]

1 ... IC chip, 2, 40 ... Stage, 2a, 40a ...
Projections, 3 ... Electrode bumps, 4 ... Passivation film, 5 ...
Edge part (silicon exposed surface), 10 ... FPC board, 11
... FPC circuit, 12 ... ACF, 13 ... Laminating material (adhesive), 14 ... FPC base material, 30 ... Thermocompression bonding machine, 40b ... Recess, 40c ... Suction pores.

Claims (6)

[Claims] 1. A method for mounting an IC chip on a flexible circuit board, wherein the IC chip (1) is mounted on the flexible circuit board (10) by pressure bonding using the stage (2, 40). For (2a, 40a), the above I
Flexible circuit board and IC up to the outermost part of the electrode pad group (3) arranged at the edge of the C chip
A method for mounting an IC chip on a flexible circuit board, characterized in that an electrode pad of the IC chip is pressure-bonded to a predetermined portion of the flexible circuit board by heating and pressing the chip. 2. The IC chip has a square or rectangular plate shape, the electrode pad group is arranged on four sides thereof, and the flexible circuit board is provided up to a portion equal to or slightly larger than the outermost peripheral shape of the electrode pad group. The flexible circuit board and the IC chip are heated and pressed by the convex portions (2a, 40a) having an area equal to or smaller than the IC chip area of the thermocompression bonding machine stage (2, 40) to be aligned. The flexible circuit board IC according to claim 1, wherein the board and the IC chip are pressure-bonded to each other.
Chip mounting method. 3. A thermocompression bonding machine for thermocompression-bonding an IC chip (1) to a flexible circuit board (10) to obtain an electrical connection, the stage (2,40) of a thermocompression bonding machine to which the flexible circuit board is to be aligned. ), A convex portion (2a, 40a) having an area equal to or smaller than the area of the IC chip is provided, and the IC chip and the flexible circuit board are heated and pressed against the convex portion to pressure-connect the IC chip and the flexible circuit board. A thermocompression bonding machine for IC chips, which is characterized in that 4. The height of the convex portions (2a, 40a) is 0.
The thermocompression bonding machine for IC chips according to claim 3, which has a length of 1 to 3.0 mm. 5. A substantially conical or quadrangular pyramidal depression (40b) is provided inside the convex portion (2a, 40a).
Alternatively, the thermocompression bonding machine for IC chips described in 4. 6. The thermocompression bonding machine for an IC chip according to claim 5, wherein the deepest portion of the depression is 10 to 1000 μm.