Method for fixing semiconductor chip on circuit board

A method for fixing a semiconductor chip on a circuit board is provided, which includes following steps. The circuit board is provided, which sequentially includes a substrate having a chip connecting portion, at least one metal wire and an insulating layer. An organic insulating material is formed on the insulating layer of the outside edge of the chip connecting portion. An anisotropic conductive film (ACF) is then formed to cover the chip connecting portion and a portion of the organic insulating material. Finally, a semiconductor chip is hot-pressed on the ACF. The organic insulating material formed on the insulating layer is used to prevent the metal wires beneath the insulating layer from occurring of corrosion. A semiconductor chip package structure is also provided.

RELATED APPLICATIONS

This application claims priority to Taiwan Application Serial Number 101113975, filed Apr. 19, 2012, which is herein incorporated by reference.

BACKGROUND

1. Technical Field

The present invention relates to a method for fixing a semiconductor chip on a circuit board and the structure thereof. More particularly, the present invention relates to method for fixing a semiconductor chip on a circuit board and the structure thereof for liquid crystal display devices.

2. Description of Related Art

In recent years, the development of electronic products is moving toward high packaging density and high electrical reliability. As such, techniques like chip on film (COF) and chip on glass (COG) have been developed, in which the COG technique has been applied in liquid crystal display devices.

A COG process is described as follows. Firstly, an anisotropic conductive film (ACF) is covered on contact pads and an insulating layer surrounding those pads. A semiconductor chip is then hot-pressed on the ACF to make bumps of the semiconductor chip respectively electrically connected the contact pads through the ACF. However, at the reliability test of a panel under high temperature and high humidity, the metal ire beneath the insulating layer are randomly corroded and broken, such that the panel may be scrapped.

Accordingly, there is still a need for a method for fixing a semiconductor chip on a circuit board and the structure thereof, in order to solve the problems described above.

SUMMARY

An objective of the present invention is to provide a method for fixing a semiconductor chip on a circuit board to prevent metal wires from corrosion during a reliability test under high temperature and high humidity.

According to one embodiment of the present invention, the method includes following steps. The circuit board is provided, in which the circuit board includes a substrate, at least a metal wire and an insulating layer. The substrate has a chip connecting portion. The metal wire is disposed on the substrate and extending from outside to inside of the chip connecting portion, and the metal wire has a contact pad disposed in the chip connecting portion. The insulating layer is disposed on the metal wire, and the insulating layer has an opening to expose the contact pad. An organic insulating material is formed on the insulating layer of an outside edge of the chip connecting portion. An ACF is formed to cover the chip connecting portion and a portion of the organic insulating material. The semiconductor chip is hot-pressed on the ACF to make a bump of the semiconductor chip electrically connected to the contact pad through the ACF.

In another embodiment, the method includes following steps. The circuit board is provided, in which the circuit board includes a substrate, at least a metal wire and an insulating layer. The substrate has a chip connecting portion. The metal wire is disposed on the substrate and extending from outside to inside of the chip connecting portion, and the metal wire has a contact pad disposed in the chip connecting portion. The insulating layer is disposed on the metal wire, and the insulating layer has an opening to expose the contact pad. A non-conductive film is formed on the chip connecting portion and the insulating layer of an outside edge of the chip connecting portion, in which the non-conductive film is covering a portion of the metal wire. An ACF is formed on the non-conductive film of the chip connecting portion and the insulating layer of the outside edge of the chip connecting portion. The semiconductor chip is hot-pressed on the ACF to make a bump of the semiconductor chip electrically connected to the contact pad through the ACF.

Another aspect of the present invention is to provide a semiconductor chip package structure which includes a substrate, at least a metal wire, an insulating layer, an organic insulating material, an ACF, and a semiconductor chip. The substrate has a chip connecting portion. The metal wire is disposed on the substrate and extending from outside to inside of the chip connecting portion, and the metal wire has a contact pad disposed in the chip connecting portion. The insulating layer is disposed on the metal wire, and the insulating layer has an opening to expose the contact pad. The organic insulating material is disposed on the insulating layer of an outside edge of the chip connecting portion. The ACF is covering the chip connecting portion and a portion of the organic insulating material. The semiconductor chip is disposed on the ACF of the chip connecting portion, in which a bump of the semiconductor chip is electrically connected to the contact pad through the ACF.

DETAILED DESCRIPTION

An aspect of the present invention is to provide a method for fixing a semiconductor chip on a circuit board.FIG. 1is a flow chart of a method100.FIG. 2Ais a top view schematically illustrating a circuit board according to one embodiment of the present invention.FIG. 2Bis a cross-sectional view schematically illustrating a circuit board according to one embodiment of the present invention, which is taken along the line2A-2A′ ofFIG. 2A.FIG. 3Ais a top view schematically illustrating a semiconductor chip package structure according to one embodiment of the present invention.FIGS. 3B and 3Care cross-sectional views schematically illustrating process steps of method100, which are taken along the line3A-3A′ ofFIG. 3A.

In step110, the circuit board210is provided, which includes a substrate202, metal wires204,206and an insulating layer208, as shown inFIGS. 2A and 2B. The circuit board210may be a portion of a thin film transistor substrate, such as a portion for mounting gate driver chips. The substrate202has at least one chip connecting portion212and an outside edge214of the chip connecting portion. The metal wires204,206disposed on the substrate202may respectively be an outer metal wire and a metal wire of a terminal portion. The metal wires204,206are extending from outside to inside of the chip connecting portion212. Also, the metal wires204,206respectively have contact pads204a,206adisposed in the chip connecting portion212. The insulating layer208is disposed on the metal wires204,206, and it has an opening208ato expose the contact pads204a,206a. In one embodiment, the insulating layer208is made of an inorganic material, such as silicon nitride.

In step120, an organic insulating material220is formed on the insulating layer208of an outside edge214of the chip connecting portion, as depicted inFIGS. 3A and 3B. It is used to isolate an anisotropic conductive film (ACF) and the insulating layer208to avoid corrosion of the metal wires after forming the ACF (in step130) and hot-pressing a semiconductor chip (in step140). A mechanism of corrosion of metal wires in a conventional structure would be described in step130. The organic insulating material220may be sticky, such as rubber or a non-conductive film (NCF). Alternatively, a surface of the organic insulating material220has an adhesive layer (not shown) to adhere the insulating layer208, such as insulating tape.

In step130, an ACF230is formed to cover the chip connecting portion212and a portion of the organic insulating material220, as shown inFIGS. 3A and 3B. That is, the organic insulating material220isolates the ACF230and the insulating layer208to avoid corrosion of the metal wires. The mechanism of corrosion of metal wires in a conventional structure is inferred hereinafter. When supplying a voltage to the metal wires, those wires and conductive particles of the anisotropic conductive film would form an induced electric field, which may lead the insulating layer beneath the ACF to rupture. While performing a reliability test under high temperature and high humidity, moisture may penetrate from cracks and then react with the metal wires to cause corrosion. Thus, in the embodiment, the organic insulating material220is employed to isolate the ACF230and the insulating layer208to reduce the induced electric field and further to prevent rupture of the insulating layer208. In one embodiment, the organic insulating material220has a thickness W2greater than a thickness W1of the insulating layer208. Specifically, the thickness W1of the insulating layer208may less than 1 μm, and the thickness W2of the organic insulating material220may be much larger than 1 μm.

In step140, the semiconductor chip240is hot-pressed on the ACF230to make a bump242electrically connected to the contact pads204a,206athrough the ACF230, as depicted inFIGS. 3A and 3C. The semiconductor chip240may be used to provide voltage larger than 10 V for the metal wires204,206. The semiconductor chip240may be a gate driver chip. The ACF230flows and fills into the opening208aduring the hot-pressing step. The ACF230is isolated from an upper surface of the insulating layer208by the organic insulating material220to avoid corrosion of the metal wires. In addition, the bumps242can be vertically and electrically connected to the contact pads204a,206athrough deformed conductive particles.

FIG. 4is a flow chart of a method400. Step410may be the same as step110ofFIG. 1. There are two embodiments exemplified below.FIG. 5AandFIG. 5Bare top views respectively illustrating two semiconductor chip package structures according to the two embodiments.FIGS. 5C and 5Dare cross-sectional views schematically illustrating process steps for fixing a semiconductor chip on a circuit board, which is taken along the line5A-5A′ ofFIG. 5Aor the line5B-5B′ ofFIG. 5B.

In step420, a non-conductive film222is formed on the chip connecting portion212and the insulating layer208of an outside edge214of the chip connecting portion, as shown inFIG. 5C. Also, the non-conductive film222is covering a portion of the metal wires204,206. In one embodiment, the non-conductive film222is used to cover one chip connecting portion212and the insulating layer208of the outside edge214of the chip connecting portion, as depicted inFIG. 5A. In another embodiment, the non-conductive film222is employed to cover a plurality of chip connecting portions212and the portions outside thereof, as shown inFIG. 5B.

In step430, an ACF230is formed on the non-conductive film222over the chip connecting portion212, as shown inFIG. 5C. Similar to the organic insulating material220of method100, the non-conductive film222is employed to isolate the insulating layer208and the ACF230. In one embodiment, the non-conductive film222has a dimension D1larger than a dimension D2of the ACF230, as depicted inFIGS. 5A and 56. The term “dimension” herein refers to a two-dimension constructed by a length and a width, used to prevent an overflow of the ACF230from being contacted with an upper surface of the insulating layer208. In one embodiment, the non-conductive film222has a thickness W3greater than a thickness W1of the insulating layer208. The adhesive composition of the ACF230is substantially the same as the adhesive composition of the non-conductive film222, but the non-conductive film222does not include any conductive particle.

In step440, the semiconductor chip240is hot-pressed on the ACF230to make a bump242electrically connected to the contact pads204a,206athrough the ACF230, as depicted inFIG. 5D. Both the non-conductive film222and the ACF230flow and then merge, and thus fill into the opening208aduring the hot-pressing step. In addition, the bumps242can be vertically and electrically connected to the contact pads204a,206athrough deformed conductive particles.

The metal wires do not corrode during a reliability test under high temperature and high humidity in the structures manufactured by two embodiments mentioned above. Therefore, the embodiments disclosed in the present invention can effectively solve the conventional problem of corrosion of metal wires.

Another aspect of the present invention is to provide a semiconductor chip package structure. As shown inFIGS. 3C and 5D, each of the semiconductor chip package structures300,500includes a substrate202, at least one metal wire204, an insulating layer208, an organic insulating material220, an ACF230a, and a semiconductor chip240.

The substrate202may be a glass substrate, and has a chip connecting portion212.

The metal wires204,206disposed on the substrate202may respectively be an outer metal wire and a metal wire of a terminal portion. The metal wires204,206are extending from outside to inside of the chip connecting portion212. Further, the metal wires204,206respectively have contact pads204a,206adisposed in the chip connecting portion212.

The insulating layer208is disposed on the metal wires204,206, and it has an opening208ato expose the contact pads204a,206a. In one embodiment, the insulating layer208is made of an inorganic material, such as silicon nitride.

The organic insulating material220is disposed on the insulating layer208of an outside edge214of the chip connecting portion. In one embodiment, the organic insulating material220is rubber, insulating tape or a non-conductive film, as depicted inFIG. 3C. In another embodiment, the organic insulating material220is a non-conductive film222, as depicted inFIG. 50.

The ACF230ais covering the chip connecting portion212and a portion of the organic insulating material220. In the semiconductor chip package structure300, the ACF230ais formed by hot-pressing the ACF230. In the semiconductor chip package structure500, the ACF230ais formed by hot-pressing the non-conductive film222and the ACF230.

The semiconductor chip240is disposed on the ACF230aof the chip connecting portion212. A bump242is electrically connected to the contact pads204a,206athrough the ACF230a.

As mentioned above, an organic insulating material disposed on the insulating layer can prevent the metal wires beneath the insulating layer from corrosion. Furthermore, it can reduce amount of scrapped panels and scrap costs.

It will be apparent to those ordinarily skilled in the art that various modifications and variations may be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations thereof provided they fall within the scope of the following claims.