CROSS-REFERENCE TO RELATED APPLICATION

The present application is a national stage filing under 35 U.S.C § 371 of PCT application number PCT/KR2019/007342 filed on Jun. 18, 2019 which is based upon and claims the benefit of priorities to Korean Patent Application No. 10-2018-0106800, filed on Sep. 7, 2018, in the Korean Intellectual Property Office, which are incorporated herein in their entireties by reference.

TECHNICAL FIELD

The present disclosure relates to a polyimide film for a semiconductor package, and more specifically, relates to a polyimide film for a semiconductor package in which a difference between average coefficients of linear thermal expansions of a base film and a thermoplastic polyimide layer is lowered such that peeling of the thermoplastic polyimide layer may be prevented, and in which the thermoplastic polyimide layer attached to a lead frame has a glass transition temperature below a packaging process temperature, thereby enabling easy peeling after the encapsulation process is completed.

DESCRIPTION OF RELATED ART

A polyimide film has excellent mechanical and thermal dimensional stability and chemical stability, and thus is widely used in electric, electronic material, space, aviation, and telecommunication fields. This polyimide film is widely used as a material for a flexible circuit board having a fine pattern due to lightness, thinness, shortness and smallness of a part, for example, as a material for a base film such as TAB (Tape Automated Bonding) or COF (Chip On Film).

Further, a semiconductor package having a structure in which only one face (semiconductor device) of the semiconductor package is encapsulated, and an exposed lead frame on an opposite face is used for connection to an external component is being developed. In the semiconductor package with such a structure, the lead frame does not protrude from an encapsulation resin, and thus, lightness, thinness, shortness and smallness of the package may be achieved. However, defects may occur in which the encapsulation resin invades a backside of the lead frame during encapsulation of the semiconductor package.

Accordingly, after attaching an adhesive film to the lead frame before the encapsulation of the semiconductor package, the encapsulation process is performed, and then the adhesive film is peeled from the lead frame, thereby preventing the encapsulation resin from invading the backside of the lead frame.

This adhesive film generally has a structure in which a thermoplastic polyimide layer to be attached to the lead frame is laminated on a base film.

In this connection, the encapsulation process performed after attaching the adhesive film on the back side of the lead frame is performed at a relatively high temperature (for example, 200° C. or higher). During the encapsulation process, the thermoplastic polyimide layer is peeled from the base film or the thermoplastic polyimide layer is denatured, so that the adhesive film is not easily peeled from the lead frame after the encapsulation.

DISCLOSURE

Technical Purpose

Under the above technical background, a purpose of the present disclosure is to provide a polyimide film for a semiconductor package in which a difference between average coefficients of linear thermal expansions of a base film and a thermoplastic polyimide layer laminated on the base film is lowered, thereby preventing peeling of the thermoplastic polyimide layer at high temperatures.

Further, a purpose of the present disclosure is to provide a polyimide film for a semiconductor package in which the thermoplastic polyimide layer attached to a lead frame has a glass transition temperature below an encapsulation process temperature, thereby achieving easy peeling after the packaging process is completed.

Technical Solution

In order to achieve the above technical purposes, according to one aspect of the present disclosure, a polyimide film for a semiconductor package including a base film, a non-thermoplastic polyimide layer positioned on the base film, and a thermoplastic polyimide layer positioned on the non-thermoplastic polyimide layer is provided.

In this connection, the non-thermoplastic polyimide layer may reduce the difference between the average coefficients of linear thermal expansions of the base film and the thermoplastic polyimide layer and thus may serves as an average coefficient of linear thermal expansion compensation layer, thereby to prevent peeling of the thermoplastic polyimide layer from the base film.

In order for the non-thermoplastic polyimide layer to act as the average coefficient of linear thermal expansion compensation layer between the base film and the thermoplastic polyimide layer, the non-thermoplastic polyimide layer also has a small difference in the average coefficient of linear thermal expansion from that of the base film such that during a high temperature process, the non-thermoplastic polyimide layer may not peel from the base film.

To this end, it is preferable that the difference between the average coefficients of linear thermal expansions of the base film and the non-thermoplastic polyimide layer at 20° C. to 200° C. is 30 ppm/K or lower.

Further, in order to reduce the possibility of peeling of the thermoplastic polyimide layer from the non-thermoplastic polyimide layer, the difference between the average coefficients of linear thermal expansions between the non-thermoplastic polyimide layer and the thermoplastic polyimide layer at 20° C. to 200° C. is preferably 30 ppm/K or lower.

Technical Effects

According to the present disclosure, reducing the difference between the average coefficients of linear thermal expansions of the base film and the thermoplastic polyimide layer laminated on the base film may prevent the peeling of the thermoplastic polyimide layer at high temperatures.

Further, since the thermoplastic polyimide layer attached to the lead frame has a glass transition temperature below the encapsulation process temperature, easy peeling thereof is possible after the packaging process is completed.

Further, when attaching to the lead frame, and when the difference between the average coefficients of linear thermal expansions of the thermoplastic polyimide layer and the base film is large, lead frame warpage may occur. However, according to the present disclosure, it is possible to reduce the lead frame warpage or the peeling of the polyimide film by reducing the difference in the average coefficient of linear thermal expansion due to the presence of the non-thermoplastic polyimide layer.

