This application claims priority under 35 USC § 119 to Korean Patent Application No. 10-2006-0118555, filed on Nov. 28, 2006 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Technical Field
The present invention relates to an insulation coated metal wire used for wire bonding and a wire bonding method for a semiconductor package using the same. Specifically, the present invention relates to a partially insulation coated metal wire and a wire bonding method for a semiconductor package using the same.
2. Description of the Related Art
In a semiconductor package, an interconnection substrate, e.g., a printed circuit board (PCB) or bonding pad (or a lead) of a lead frame, and a chip pad of a semiconductor chip are bonded using a metal wire so as to be electrically connected to each other. Such a process is referred to as a wire bonding process and the connection between the interconnection substrate and the semiconductor chip using the metal wire may be referred to as a wire bond. As chip pads of semiconductor chips become more miniaturized and stacked packages having multi-layered semiconductor chips stacked therein are manufactured using a wire bonding process, the instances of short circuits, which occur when metal wires contact each other, have increased. Accordingly, an insulation coated metal wire in which a surface of a metal wire is coated with an insulating layer, has been increasingly used.
Specifically, the insulation coated metal wire 15 includes a metal wire 11 having a circular cross-section, and an insulating layer 13, completely coating a surface of the metal wire 11, also having a circular cross-section. If a wire bonding process is performed with the insulation coated metal wire 15, an insulating property between metal wires is improved in a semiconductor package. However, an insulating material layer 17 exists on a bonding section of the metal wire 11 as shown in
The present invention provides a partially insulation coated metal wire for wire bonding capable of enhancing adhesion between a pad and the metal wire while maintaining an insulating property between metal wires for wire bonding. The present invention also provides a wire bonding method for a semiconductor package using a partially insulation coated metal wire for wire bonding.
According to an aspect of the present invention, there is provided an insulation coated metal wire for wire bonding, which includes: a metal wire; and an insulating layer partially coated on the surface of the metal wire to allow a contact area of the insulating layer with bonding pads to be small so that an insulating property can be maintained and adhesion of the insulation coated metal wire with the pad can be enhanced.
The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
First, the present inventors studied the process in which the insulating material layer 17 is formed on a bonding section of the conventional insulation coated metal wire 15 in a wire bonding process as shown in
Specifically, a bonding tool 109 having a capillary is used in a wire bonding process as shown in
However, the present inventors found that, since the bonding is performed while the metal wire 15 is cut by an outer edge of a chamfer portion 21 of the bonding tool 109 in the bonding process, the insulating material layer 17 remains between the metal wire 15 and a pad, i.e., on a bonding section of the metal wire 15, as shown in
Accordingly, the present inventors found that, when an insulating layer is partially coated such that the contact area between pads, e.g., chip and bonding pads, and the insulating layer of a metal wire is small, an insulating property between metal wires can be maintained and adhesion with a pad can be enhanced in wire bonding. It will be apparent that a metal wire partially insulation coated (hereinafter, referred to as a “partially insulation coated metal wire”) effectively prevents an insulating material layer from being produced on a bonding section even during ball bonding, to be described later, so that an insulating property can be maintained and adhesion with a pad can be enhanced. This will be described in detail with reference to the following embodiments.
Specifically, the partially insulation coated metal wire 54 according to an embodiment of the present invention includes a metal wire 50 with a flat-plate-shaped cross-section, and an insulating layer 52 in which a portion 56 of the metal wire 50, to be bonded to a pad in a wire bonding process on a surface thereof, e.g., a bottom section, is not coated with the insulating layer 52. As shown in
Consequently, since a portion of the partially insulation coated metal wire 54 according to this embodiment of the present invention, which is to be bonded with a pad, is not coated with the insulating layer 52 such that a contact area of the insulating layer 52 with the pad is small in a wire bonding process, an insulating property between the metal wires 50 can be maintained and adhesion (or adhesive strength) with the pad can be enhanced. Thereby, subsequent failures of the wire bonds due to either shorts between wires or opens between the wires and the pads can be prevented.
Specifically, the partially insulation coated metal wire 64 according to this embodiment of the present invention includes a metal wire 60 with a circular cross-section, and an insulating layer 62 coated in a net shape (or a lattice shape) on a surface of the metal wire 60. The metal wire 60 may be made of Al, Cu, Au, Ag or Ni.
The insulating layer 62 may be composed of silicon, polyimide resin, epoxy resin or urethane resin. As the insulating layer 62 is formed in a net shape, the surface of the metal wire 60 is not all coated but is partially coated. In other words, a portion of the lateral surface of the metal wire 60 is exposed due to the insulating layer 62 being formed in a net shape. Accordingly, in the partially insulation coated metal wire 64 according to this embodiment of the present invention, an insulating property between the metal wires 60 can be maintained in a wire bonding process, and a contact area between the insulating layer 62 and a pad is small so that adhesion with the pad can be enhanced.
Hereinafter, an exemplary wire bonding process between a chip pad of a semiconductor chip and a bonding pad of an interconnection substrate using the partially insulation coated metal wire 54 of
Referring to
The bonding tool 109 includes a guide 107 and a capillary 106. A through-hole 103 is formed in the bonding tool 109, i.e., the guide 107 and the capillary 106, as described above. After allowing the partially insulation coated metal wire 54 to pass through the through-hole 103, a ball portion 108 is formed at a front end of the partially insulation coated metal wire 54. The ball portion 108 may be formed using an electric discharge. For example, an electrode (not shown) may be placed close to the front end of the partially insulation coated metal wire 54 introducing an electric discharge through the front end of the partially insulation coated metal wire 54, which causes the front end to partially melt and form into a ball shape.
Referring to
Accordingly, the present invention can maintain an insulating property between the partially insulation coated metal wires 54 on the semiconductor chip 102 and enhance adhesion between the partially insulation coated metal wires 54 and corresponding chip pads 112. Subsequently, the metal wire 54 forms a predetermined loop while the bonding tool 109 is moved toward the bonding pad 104.
Referring to
Since a lower section 56 of the partially insulation coated metal wire 54 is exposed in wedge or stitch bonding, a contact area of the insulating layer 52 with the bonding pad 104 is small. Thus, the amount of an insulating material layer formed on a bonding section of the metal wire 54 can be reduced. Accordingly, the present invention can maintain an insulating property between the partially insulation coated metal wires 54 on the semiconductor chip 102 and enhance adhesion with the bonding pad 104.
Specifically,
Furthermore,
Referring to
A first partially insulation coated metal wire 54a is bonded on the first chip pad 112 of the first semiconductor chip 102 and the first bonding pad 104 using a bonding tool 109 through a compression method as described above. The bonding may be performed by any of a ball, wedge or stitch bonding method. The first partially insulation coated metal wire 54a allows a contact area of the insulating layer with the pads 112 and 104 to be small, thereby reducing the amount of an insulating material layer formed on a bonding section. Accordingly, in the first partially insulation coated metal wire 54a on the first semiconductor chip 102 and the first bonding pad 104, an insulating property can be maintained, and adhesion with pads, i.e., the first chip pad 112 and the first bonding pad 104, can be enhanced. Particularly, a portion which is not coated with an insulating layer is configured to face downward during wire bonding, thus, an insulating property between partially insulation coated metal wires 54a and 54b can be more enhanced once the second semiconductor chip 102a is wire bonded in the following process.
Referring to
Furthermore, in the present invention, a portion which is not coated with an insulating layer is configured to face downward in wire bonding, so that an insulating property between the partially insulation coated metal wires 54a and 54b can be enhanced. It will be apparent that, although the partially insulation coated metal wires 54a and 54b may be influenced by a sealant, e.g., epoxy resin or the like, in a molding process after wire bonding, an insulating property can be enhanced.
As described above, according to embodiments of the present invention, a partially insulation coated metal wire includes an insulating layer partially coated to allow a contact area of the insulating layer with a bonding pad to be small, so that an insulating property can be maintained and adhesion of the partially insulation coated metal wire with a pad can be enhanced.
The partially insulation coated metal wire according to an embodiment of the present invention is a metal wire with a flat-plate-shaped cross-section, and a portion bonded to a pad in a surface of the metal wire is not coated. Furthermore, the partially insulation coated metal wire according to another embodiment of the present invention is a metal wire with a circular cross-section, and an insulating layer is coated on the metal wire in a net shape.
In addition, the present invention provides a wire bonding method for a semiconductor package using a partially insulation coated metal wire. Particularly, the partially insulation coated metal wire includes an insulating layer partially coated to allow a contact area of the insulating layer with pads bonded in wire bonding to be small, so that an insulating property can be maintained and adhesion of the partially insulation coated wire with the pads can be enhanced.
According to an aspect of the present invention, there is provided an insulation coated metal wire for wire bonding, which includes: a metal wire; and an insulating layer partially coated on the surface of the metal wire to allow a contact area of the insulating layer with bonding pads to be small so that an insulating property can be maintained and adhesion of the insulation coated metal wire with the pad can be enhanced, wherein a portion of a lateral surface of the metal wire is exposed by the insulating layer.
The metal wire may be a metal wire having a flat-plate-shaped cross-section, and the surface of a portion of the metal wire to be bonded to a pad may not be coated with the insulating layer. The surface of a bottom section of the metal wire to be bonded to the pad may not be coated. The metal wire having a flat-plate-shaped cross-section may be a ribbon-shaped or tape-shaped metal wire. The metal wire may be a metal wire having a circular cross-section, and the insulating layer may be coated in a net shape.
According to another aspect of the present invention, there is provided an insulation coated metal wire for wire bonding, which includes: a metal wire having a flat-plate-shaped cross-section; and an insulating layer partially coated on the surface of the metal wire to allow the surface of a portion of the metal wire, which is to be bonded to pads, not to be coated so that an insulating property can be maintained and adhesion of the insulation coated metal wire with the pad can be enhanced.
The surface of a bottom section of the metal wire to be bonded to the pads may not be coated. The metal wire having a flat-plate-shaped cross-section may be a ribbon-shaped or tape-shaped metal wire.
According to a further aspect of the present invention, there is provided an insulation coated metal wire for wire bonding, comprising: a metal wire having a circular cross-section; and an insulating layer coated in a net shape on a surface of the metal wire so that an insulating property can be maintained and adhesion of the insulation coated metal wire with the pad can be enhanced.
According to a still further aspect of the present invention, there is provided a wire bonding method for a semiconductor package, which includes: bonding a partially insulation coated metal wire included in a bonding tool on a chip pad of a semiconductor chip; moving the bonding tool after bonding the partially insulation coated metal wire on the chip pad and then bonding the partially insulation coated metal wire on a bonding pad of an interconnection substrate such that the chip pad and the bonding pad are connected electrically to each other; and moving the bonding tool after bonding the partially insulation coated metal wire on the bonding pad and then cutting the partially insulation coated metal wire included in the bonding tool while the bonding tool is spaced apart from the bonding pad, wherein the partially insulation coated metal wire comprises a metal wire and an insulating layer partially coated on the surface of the metal wire to allow a contact area of the insulating layer with bonding pads to be small so an insulating property can be maintained and adhesion of the insulation coated metal wire with the pad can be enhanced.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
Number | Date | Country | Kind |
---|---|---|---|
2006-0118555 | Nov 2006 | KR | national |