JP2006032531A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to assemble a flexible wiring board responding to the demand of high bonding accuracy in COF structure. <P>SOLUTION: The free region 2a of a base substrate 2 without a wiring part 4 is provided in a junction region 12 where a semiconductor chip 5 is joined to a flexible wiring board 1, and a conductor 9 composed of copper foil in a quadrangular shape is provided between inner leads 4a along the longitudinal direction of the inner leads 4a. In bonding, the base substrate 2 is exposed to high temperature so that it may be softened and spread for transformation in order to carry out eutectic fusion of a metal projection 6 and the inner leads 4a by the junction adding temperature and load. As the temperature of the junction descends to the room temperature after processing, the stress of the elasticity directed to a center arises in the free region 2a since the base substrate 2 tries to return to the original shape. Such a nonconformity point as an inner lead displacement, inner lead peeling, or the like in an assembly process is prevented by providing the conductor 9 for this stress so as to strengthen the free region 2a of the base substrate 2 so that high bonding accuracy may be made possible by inhibiting the elasticity generated in the part of this free region 2a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor device manufactured using a technique for flip-chip mounting a semiconductor chip on a flexible wiring board in a manufacturing process of the semiconductor device, particularly a chip-on-film structure.

  A conventional wiring board package using such a flexible base material is mainly used as a driver package for a liquid crystal display. Here, as one of package modules using a flexible substrate, there is a chip-on-film (hereinafter referred to as COF) structure. The shape of the semiconductor chip of the driver for driving the liquid crystal display generally has an elongated chip shape as its feature. In this case, it is known that a high value of stress is generated in the bonding region 12 shown in FIG. 4A due to heat applied during bonding of the semiconductor chip.

  One of the causes of this stress generation is a stress that the base material 2 of the flexible wiring board 1 pressed by an inner lead bonding (hereinafter referred to as ILB) process tries to recover due to elasticity. The restoring force of the base material 2 works, and the metal protrusion 6 and the inner lead 4a of the semiconductor chip 5 are pulled apart to cause physical abnormalities such as inner lead displacement and inner lead peeling, as well as an electrical open state defect. Have the problem of

Therefore, a technique for alleviating expansion and contraction of the flexible wiring board 1 due to thermal stress during bonding has been proposed. Hereinafter, the method disclosed in Patent Document 1 will be described. In the flexible wiring board 1 shown in FIG. 4B, the back conductor 8 is provided integrally or in a mesh or lattice pattern on the other surface side corresponding to the mounting region where the semiconductor chip 5 is flip-chip mounted. The back conductor 8 may be formed directly on the base material 2 by a plating method or the like, or a film formed in a separate process may be attached. The region is preferably provided over as wide a surface as possible to prevent expansion and contraction of the wiring board.
JP 2003-324129 A

  However, in the conventional technology of the semiconductor device manufactured in this way, when a conductor is provided on the back surface, processes such as bonding of conductors and film formation by plating are increased. Further, when a pattern is applied to the conductor on the back surface, a process such as pattern exposure or etching is added, which causes a problem that the lead time and its cost increase.

  Further, a semiconductor device having a COF structure for a liquid crystal display is mounted by being bent on a liquid crystal panel as shown in FIG. For this reason, it is necessary to further improve the bendability by thinning the copper foil used for the base material 2 and the wiring portion 4. The mountability of the board itself is deteriorated. Furthermore, although it is an effective method for the substrate on the back surface, there is a problem that the expansion and contraction of the substrate cannot be completely suppressed for the chip mounting surface.

  The present invention is directed to solving the problems of the prior art, and as a liquid crystal driver technology, it is expected that the pitch will be narrowed and the number of pads will increase in the future for higher definition. An object of the present invention is to provide a semiconductor device capable of assembling a wiring board with higher effect and lower cost in response to a request for bonding accuracy.

  In order to achieve the above object, a semiconductor device according to the present invention is a semiconductor device in which a semiconductor chip having bumps is flip-chip mounted on a flexible wiring substrate composed of a base material and a wiring layer. A conductor is formed on the surface of the base material between the wiring board and the wiring board.

  Further, the outer shape of the conductor is smaller than the semiconductor chip to be flip-chip mounted, and is formed between the inner leads of the wiring layer connected to the bumps of the semiconductor chip, and has a rectangular shape along the longitudinal direction of the inner leads. It is characterized by that.

  According to the said structure, it is smaller than a semiconductor chip in the empty area | region of the base material without a wiring layer on the flexible wiring board which carries out the flip-chip mounting of the semiconductor chip which has bump, and the square shape along the longitudinal direction between inner leads A conductor made of copper foil is provided, and the conductor is provided in the vicinity of the same surface as the joint portion to be flip-chip mounted to fix the base material of the flexible wiring board, so that expansion and contraction caused by thermal stress during bonding can be effectively reduced.

  According to the present invention, it is possible to provide a highly reliable semiconductor device that effectively reduces thermal stress during bonding, prevents inner lead displacement and inner lead peeling, and does not cause defects due to physical abnormalities. There is an effect.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1A is a front view of a flexible wiring board on which a semiconductor chip is mounted according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view of a semiconductor device in which the semiconductor chip is mounted on the flexible wiring board. Here, components having substantially the same functions corresponding to the components described in FIGS. 4A and 4B showing the conventional example are denoted by the same reference numerals.

  As shown in FIGS. 1A and 1B, the base material 2 without the wiring portion 4 that is a wiring layer in the bonding region 12 where the semiconductor chip 5 is bonded to the flexible wiring substrate 1 in the embodiment of the present invention. A conductor 9 made of a rectangular copper foil along the longitudinal direction of the inner lead 4a is provided between the inner leads 4a.

  FIG. 2 is a diagram showing an outline of a process for assembling a semiconductor device having a COF structure. As shown in FIG. 2A, a flexible wiring board 1 having a COF structure has a wiring portion 4 formed on a base material 2, and a wiring protective film 3 is applied to wiring portions other than input / output external terminals. Yes. In the method of manufacturing a semiconductor device in which the semiconductor chip 5 is flip-chip mounted on the flexible wiring board 1, a metal which is a bump of the semiconductor chip 5 is provided on the surface having the wiring part 4 on the base 2 placed on a plane. There is an ILB (inner lead bonding) process for connecting the inner lead 4a drawn from the wiring portion 4 and the metal protrusion 6 by thermocompression bonding with the protrusion 6 facing each other.

  Next, the ILB process will be described with reference to FIG. As shown in FIG. 2B, the flexible wiring substrate 1 has inner leads 4 a formed on the wiring portions 4 on the base material 2 in accordance with the positions of the metal protrusions 6 of the semiconductor chip 5. The surface of the inner lead 4a is plated with tin or gold. On the semiconductor chip 5, a metal protrusion 6 is arranged along the outer periphery of the semiconductor chip 5 or on the entire surface of the semiconductor chip 5. The metal protrusion 6 on the semiconductor chip 5 and the inner lead 4a of the flexible wiring substrate 1 are aligned with a predetermined position and bonded by a thermocompression bonding method.

  In the thermocompression bonding method, the plating material applied to the metal protrusion 6 and the inner lead 4a drawn out from the wiring portion 4 are joined while applying a temperature (about 300 ° C. to 500 ° C.) and a load necessary for eutectic fusion. It is a method. A jig to be pressed from the substrate 2 side is referred to as a stage 10, and a jig to be supported on the semiconductor chip 5 side is referred to as a bonding tool 11.

  During bonding pressurization in the ILB process, the base material 2 constituting the flexible wiring board 1 is exposed to a high temperature and softens and deforms so as to spread. Thereafter, as the bonding is completed and the bonded portion is lowered to room temperature, the base material 2 tries to return to the original shape. At that time, due to the difference in coefficient of thermal expansion between the copper foil constituting the base material 2 and the wiring part 4, the portion of the exposed empty area 2a of the base material 2 tends to shrink toward the center as indicated by the arrow shown in FIG. Stress 7 is generated. The stress 7 is affected by both end portions of the vacant region 2a in the longitudinal direction of the inner lead 4a of the joining region 12 (see FIG. 1A), and the inner lead displacement and inner lead peeling described above are present there. Such a problem occurs most remarkably.

  Therefore, by providing the conductor 9 as shown in FIGS. 1A and 1B in the present embodiment, the steps such as exposure and etching, which are the manufacturing steps of the flexible wiring board 1, are completed once, and the cost is low. The lead time is not affected, and the conductor 9 is provided on the surface on the wiring portion 4 side, so that there is no loss in bending loss. And with respect to the subject of preventing the expansion-contraction which arises in the part of the empty area | region 2a of the base material 2, it is the same surface as the joining surface of the semiconductor chip 5, and also the base material by the conductor 9 in the position nearest to the joining portion. High-precision bonding can be performed by the two effects of solidifying the two empty areas 2a.

  The semiconductor device according to the present invention can effectively reduce thermal stress during bonding, prevent inner lead displacement and inner lead peeling, and prevent defects due to physical abnormalities. This method is useful for processes, particularly for techniques used for manufacturing semiconductor devices by flip-chip mounting a semiconductor chip on a flexible wiring board.

(A) is the front view of the flexible wiring board in embodiment of this invention, (b) is sectional drawing which mounted the semiconductor chip in the flexible wiring board The figure which shows the outline | summary of the process of assembling the semiconductor device of a COF structure. The figure explaining the stress which arises in the empty area part of a flexible wiring board (A) is the front view of the conventional flexible wiring board, (b) is sectional drawing which mounted the semiconductor chip on the flexible wiring board. The figure which shows the flexible wiring board which is bent and mounted on the liquid crystal panel

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flexible wiring board 2 Base material 2a Empty area 3 Wiring protective film 4 Wiring part 4a Inner lead 5 Semiconductor chip 6 Metal protrusion 7 Stress 8 Back surface conductor 9 Conductor 10 Stage 11 Bonding tool 12 Bonding area

Claims (2)

In a semiconductor device in which a semiconductor chip having bumps is flip-chip mounted on a flexible wiring board composed of a base material and a wiring layer,
A semiconductor device, wherein a conductor is formed on a surface of the base material between the semiconductor chip to be flip-chip mounted and the flexible wiring board.   The outer shape of the conductor is smaller than the semiconductor chip to be flip-chip mounted, and is formed between the inner leads of the wiring layer connected to the bumps of the semiconductor chip, and has a rectangular shape along the longitudinal direction of the inner leads. The semiconductor device according to claim 1, wherein:

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