JP2003234381A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the microconnection of a flexible substrate and an IC. <P>SOLUTION: As for the extension of a biaxially extended polyimide film 1 when it is mounted, the cumulative pitch dimension of a pattern is corrected in a state of separating MD and TD directions of FPC. Then, the pattern 2 is no longer dislocated when the IC 4 and the flexible substrate are mounted, so that a microconnection of a 30 μm pitch, etc., is stabilized. Thus, a low-cost display device can be provided by cost reduction accompanying the miniaturization of the IC. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driver IC and a memory for driving a display panel such as a passive matrix liquid crystal panel or an active matrix liquid crystal panel used for a portable device or an electronic notebook, an organic EL, and the like.
The present invention relates to a face-down mounted display device such as a controller and a mounting method thereof.

[0002]

2. Description of the Related Art Conventionally, in face-down mounting of a semiconductor IC for driving a display device, when connecting to a polyimide-based flexible substrate by adhesion, I
Using a plated bump formed by plating a bump made of Au on the pad of C or a stud bump applied by wire bonding, it is pressure-bonded to the circuit board with an anisotropic conductive film, or a silver paste is transferred to the bump and the substrate is transferred. It was connected with and was filled with underfill in between.

When metal diffusion connection is used, solder is used for the bumps of the IC, solder is applied to the electrodes of the substrate to fill the underfill, and Au is used for the bumps of the IC and Sn plating is applied to the electrodes on the substrate side. The Au-Sn eutectic connection was performed and the underfill was filled.

In recent years, a driver IC having a bump pitch of 45 μm and an electrode number of 900 has been mass-produced as an IC for driving a display panel. Usually, Au-Sn eutectic connection is used as the most suitable connection method for mounting a 45 μm pitch. The flexible substrate is a biaxially stretched polyimide film that is sputtered with 1000 Å of a seed layer made of nickel for adhering copper,
Then, sputter 2000 liters of copper. Electrolytic plating is performed so that the total thickness of the electrodes is about 8 μm. 0.2 μm electroless tin plating after patterning using photo method
Put on. The flexible substrate is completed by forming the solder resist, and the IC is heated and pressed face down to complete the connection. Inject and harden underfill to secure reinforcement and corrosion resistance, mount resistors and capacitors with SMT,
It is completed by connecting to a display panel using an anisotropic conductive film.

[0005]

Driver ICs have been miniaturized year by year, and bumps with a pitch of 30 .mu.m and ICs with more than 1000 electrodes have a displacement of the flexible substrate and mounting position. The deviation was a phenomenon in which the integrated pitches of the IC and the FPC did not match, the centers matched, but the edges did not match.

The cause of the displacement is mainly caused by the fact that the flexible substrate is thermally deformed by the heat at the time of mounting although the heating condition and the pressurizing condition differ depending on the mounting method. Particularly in the Au-Sn eutectic connection, the connection temperature is heated to 350 to 380 [deg.] C., so that a deviation occurs even if a highly heat-resistant polyimide is used. As a measure against the deviation, the entire FPC pattern or only the IC mounting portion is reduced in size to correct the extension at a constant magnification. In the corrected pattern, the degree of deviation was small, but the cause could not be resolved.

The flexible substrate is manufactured by a roll method. Since a blank of 200 to 500 width is used, the mask layout for taking more products is 0
They were arranged freely at 90 °, 90 °, 180 °, and 270 °, and the products were manufactured so as to tie the products together and to obtain the largest number of products. The original of flexible substrate is
Since the polyimide is biaxially stretched, the flow direction (MD:
Machine Direction) and width direction (T
The characteristics of D: Transfer Direction are different. In the physical properties disclosed by the film manufacturer, even if the properties of strength, elongation, Young's modulus, thermal shrinkage, thermal expansion coefficient, and humidity expansion coefficient are the same in MD and TD, the actual MD and TD directions The characteristics of dimensional changes are different. Also,
Depending on the layout of the FPC mask layout, IC
There is a case where a certain side connected to is in the MD direction or TD. The same applies to the connection terminal of the FPC with the display panel.

The present invention is to obtain a stable cumulative pattern pitch of a flexible substrate in order to realize high-density mounting of an IC and a flexible substrate.

[0009]

In order to solve this problem, an IC is face down mounted on a flexible substrate having a pattern made of copper or the like formed on an insulating film of polyimide or the like and connected to a display panel. In the display device, the insulating film is biaxially stretched, and the pattern of the flexible substrate connected to the electrodes of the IC is formed by correcting the cumulative pattern pitch with different correction factors for each stretching axis direction. The problem was solved by mounting the device face down and increasing the cumulative pattern pitch of the flexible substrate and connecting it to the bump of the IC at a predetermined position. Also, FP
By correcting the arrangement of the patterning mask of C and the MD and TD directions of the polyimide film, more stable connection became possible. The connection terminal with the display panel is also formed by separately correcting the correction factors in the MD and TD directions according to the layout, so that stable connection is possible.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The display device according to the present invention has improved accuracy by separately correcting thermal deformation that occurs during face-down mounting of an IC in the MD direction and the TD direction of the pattern pitch. The correction rate is obtained by checking the mounting of the IC and the flexible board. The cumulative pattern pitch of the FPC before IC mounting is measured, then the IC is mounted and the same position is measured, and the value obtained by dividing the cumulative pattern pitch before mounting by the pattern pitch after mounting is the correction factor. At this time, the MD direction and the TD direction are separately obtained, and the cumulative pattern pitch is corrected for the MD direction and the TD direction in the pattern of the exposure mask of the flexible substrate to create the exposure mask again.

The IC is mounted using the flexible substrate manufactured by the corrected exposure mask. The same applies to the connection terminal with the display device.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1 is a top view of a flexible substrate, which is a polyimide film 2 produced by biaxial stretching.
A pattern 2 having a thickness of 6 μm is formed on 5 μm. The pattern is made of copper and the surface is electroless tin plated 0.2 μm
Are formed. Further, a solder resist is formed on the pattern 2. FIG. 2 is a top view of the circuit surface of the IC 4, on which bumps 5 made of gold are formed. The bump pitch is 30 μm. Inner leads 2-1 and 2-2 of the flexible substrate connected to the bumps 5 of the IC 4
Is formed by applying a different correction to each of the MD direction and the TD direction to reduce the extension during mounting. Since the elongation of the pattern 2-1 on the longitudinal side in the TD direction is 100.1% during mounting, the correction rate is 99.9% of the design value. The pattern 2-2 in the lateral direction has an elongation of 100.3% when mounted in the MD direction.
% Has been corrected. FIG. 3 is a diagram showing a process of mounting the IC 4 and the flexible substrate 7. The IC 4 is the heating / pressurizing head 6
It is chucked with a vacuum through a fine adsorption hole provided in the head and heated to a head temperature of 450 ° C. After aligning with the pattern 2 of the flexible substrate 7, pressure is applied to perform eutectic connection of tin and gold. FIG. 4 is a perspective view of the polyimide film 1 of the flexible substrate seen through to confirm the displacement of the mounting pattern. The patterns and bumps are almost connected to the center due to the elongation during mounting. The correction may be the same as the correction that occurs in the manufacturing process of the flexible substrate. The connection between the IC and the flexible substrate is not limited to Au-Sn eutectic connection, but Au-Au
For connection, NCP in which a contact is held only with an adhesive, connection with an anisotropic conductive film, or another method may be used.

(Embodiment 2) FIG. 5 is a top view of tin-plated after the flexible substrate is rolled. A seed layer made of Ni or the like is vapor-deposited on a biaxially stretched polyimide film by 1000Å and Cu by 2000Å and then 6 μm copper is formed by electroplating. ,
A solder resist was formed and secondary tin plating was performed.

The layout of the products is 0 °, 90 °, 180 °, 2 in order to maximize the number of products to be taken.
It is arranged at a position of 70 °. TD after and after each placement direction
Since the patterning is performed by making a correction for each MD direction, the cumulative pitch dimension of the finished product differs between the layouts of 0 °, 180 ° and 90 °, 180 °. The same effects could be obtained by mounting the IC as in the first embodiment without reducing the number of FPCs to be taken. By correcting the connection terminals with the display panel in the same manner as above, more stable connection was made possible.

[0016]

EFFECTS OF THE INVENTION It has become possible to provide an inexpensive display module in response to higher IC pitch density, stable yield, and cost reduction of miniaturized IC. Also, stable connection with the display panel is now possible.

[Brief description of drawings]

FIG. 1 is a top view of a flexible substrate according to a first embodiment.

FIG. 2 is a top view of a circuit surface of an IC according to the first embodiment.

FIG. 3 is a diagram showing an IC mounting process according to the first embodiment.

FIG. 4 is a perspective view showing a connection state between the IC of Example 1 and a flexible substrate.

FIG. 5 is a top view of a flexible substrate according to the second embodiment after tin plating.

FIG. 6 is a perspective view showing a connection state between a conventional IC and a flexible substrate.

[Explanation of symbols]

1 Polyimide film 2 patterns 2-1 Pattern on the long side 2-2 Short side pattern 3 Solder resist 4 IC 5 bumps 6 heating and pressing head 7 Flexible substrate

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Claims (2)

[Claims] 1. A flexible substrate having a pattern formed on a biaxially stretched insulating film, an IC mounted on the flexible substrate, and a display panel connected to the flexible substrate, and mounting the IC. At this time, the cumulative pattern pitch of the patterns of the flexible substrate connected to the electrodes of the IC is corrected separately for each stretching axis direction so that the cumulative pattern pitch of the flexible substrate is extended and connected to the bumps of the IC at predetermined positions. A display device characterized by being corrected by a rate. 2. A flexible substrate having a pattern formed on a biaxially stretched insulating film, an IC mounted on the flexible substrate, and a display panel connected to the flexible substrate, wherein the pattern has the A display device characterized in that the pitch is corrected according to the layout direction in manufacturing the flexible substrate and the stretching axis direction of the polyimide film.