JP2014022480A - Lead frame, bga substrate, semiconductor device and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide effective means for preventing an external connecting terminal surface of a lead frame or a BGA substrate from being contaminated in conveyance between semiconductor device manufacturing processes or in a process (cure process) exposed under high temperature, and means for improving quality of connection between an external connecting terminal and a bonding conductor by bringing a bonding surface of an external bonding terminal with the bonding conductor into a clean state when connecting a semiconductor element and the external connecting terminal via the bonding conductor such as a metal wire in a wire bond process or the like.SOLUTION: A surface of an external connecting terminal 2 of a lead frame or a BGA substrate to which a bonding conductor such as a metal wire should be electrically bonded is protected from an external atmosphere that causes contamination of the bonding surface, by providing a film sheet 1 comprised of at least one layer. Before a process for connecting a semiconductor element and the external connecting terminal via the bonding conductor such as the metal wire in a wire bond process or the like, the film sheet 1 is exfoliated and removed.

Description

The present invention relates to a lead frame of a semiconductor device, a structure of a BGA substrate, and a manufacturing process of the semiconductor device.

  What is the metal surface of the lead frame and the external connection terminal (inner lead) of the BGA board that is electrically connected to the semiconductor element by a connection conductor such as a metal wire to ensure the bonding quality with the connection conductor such as a metal wire? It is normal that the layers are also plated.

  However, in recent years, the thickness of the plating has been reduced and the plating structure has been simplified in order to reduce costs. As a result, the external connection terminal metal has been used during transportation between processes and in processes exposed to high temperatures (curing process). Oxidation contamination of the surface is likely to occur, and there has been a problem that the quality of bonding with a connection conductor such as a metal wire is deteriorated.

  Further, it is known that outgas generated when an epoxy resin or the like for fixing a semiconductor element is cured in a curing process contaminates the external connection terminal metal surface. The adhesion state of the outgas is complicated in terms of physical properties, and it is difficult to remove it effectively, which has been a major obstacle to bonding.

  Up to now, as a means to protect the external connection terminal from contamination by the epoxy resin outgas, etc., it is transported between processes using an expensive reducing gas, or is appropriately put into a redox furnace and oxidized or reduced, or plasma cleaning. There was a choice to do. However, both methods are inefficient in terms of cost and time, and are difficult to adopt for the purpose of cost reduction.

  For external connection terminals whose resistance to surface contamination has been reduced due to cost reduction, there has been a demand for an effective means for easily and conveniently protecting the external connection terminals from contamination.

JP 2010153825 A

The present invention relates to a lead frame and a BGA substrate of a semiconductor device, and a method for manufacturing the semiconductor device.

Provides effective means to prevent contamination of the external connection terminal metal surface that occurs during transportation between semiconductor device manufacturing processes and processes exposed to high temperatures (curing process), enabling cost reduction of semiconductor devices without sacrificing quality It is to do.

  The first means of the present invention comprises a film sheet comprising at least one layer of the metal joint surface of an external connection terminal (inner lead) connected to a pad electrode of a semiconductor element by a joint conductor such as a metal wire, The sheet is protected from the external atmosphere by a sheet.

  The second means of the present invention is a step after the die bonding step in which the semiconductor element is die-bonded with an epoxy resin, a die attach film or the like, and is electrically connected to the surface of the electrode pad of the semiconductor element with the electrode pad and the bonding conductor. And a step of sticking and adhering at least one film sheet to both or one of the metal joint surfaces of the external connection terminal.

According to the third means of the present invention, the film sheet consisting of at least one layer adhered and adhered to the external joining terminal is peeled and removed before a step such as wire bonding for connecting the semiconductor element and the external connection terminal with a joining conductor such as a metal wire. It is the manufacturing process of the semiconductor device which provided the process to perform. There are various methods for peeling and removing such as mechanical peeling or easy peeling using UV irradiation, but details are not discussed here.

  The bonding surface of the external connection terminal (inner lead) connected by the bonding conductor such as the pad electrode of the semiconductor element and the metal wire is protected by a film sheet composed of at least one layer, the bonding surface is contaminated from the outside, For example, it is protected from oxidation due to contact with outside air during transportation or contamination due to outgas generated when the epoxy resin is cured in the curing process.

Further, in a step after the die bonding step in which the semiconductor element is die-bonded with an epoxy resin, a die attach film, or the like, at least the electrode pad surface of the semiconductor element and the external connection terminal electrically connected to the electrode pad with a bonding conductor By sticking a film sheet consisting of at least one layer on the bonding surface, the surface of the external connection terminal and the electrode pad of the semiconductor element can be protected from contamination by the outgas generated when the epoxy resin is cured in the curing process.

  The film sheet is peeled and removed in a process provided before a process such as wire bonding for connecting a semiconductor element and an external connection terminal with a bonding conductor such as a metal wire. At this time, since the surface of the external connection terminal is a clean metal surface free from contamination, good bonding quality can be obtained in bonding with a bonding conductor such as a metal wire in a process such as wire bonding.

According to the present invention, it is possible to easily prevent oxidization and outgas contamination of the external connection terminals, thereby obtaining sufficient bonding quality even in a lead frame and a BGA substrate with a reduced plating structure and a reduced plating structure for the purpose of cost reduction. Will be able to.

FIG. 1 is an explanatory view showing the structure of an external junction terminal to which a film tape is adhered and pasted. Example 1

FIG. 2 is an explanatory view showing the structure when the semiconductor element is die-bonded with a fixing material such as an epoxy resin or a die attach film (DAF) in FIG. 1 in the die-bonding step.

FIG. 3 is an explanatory view showing a state in which a film sheet is adhered and adhered to the surface of the electrode pad and the joint surface of the external connection terminal electrically connected to the electrode pad by a joint conductor in a step after the die bonding step. (Example 2)

FIG. 4 is an explanatory view showing a state in which the film sheet is peeled and removed in the step of peeling and removing, and the electrode pads of the semiconductor element and the external connection terminals are connected by a bonding conductor such as a metal wire in the step of wire bonding and the like.

Explanation of symbols
1 Film sheet
2 External connection terminal (inner lead)
3 Die pad
4 Fixing material such as epoxy resin or die attach film (DAF)
5 Semiconductor elements
6 Semiconductor device pad electrode
7 Junction conductor
8 Joint surface between the joint conductor and external connection terminal

Embodiments of the present invention will be described with reference to FIGS. 1, 2, 3, and 4. These embodiments are merely examples of the present invention, and the present invention is not limited to these embodiments.

  FIG. 1 shows the structure of a lead frame or BGA substrate according to the present invention. A surface of the external connection terminal (inner lead) 2 to be electrically connected to a semiconductor element such as a metal wire is in close contact with the film sheet 1 and is protected from the external atmosphere. The die pad 3 to which the semiconductor element is to be die-bonded and fixed with an epoxy resin or a die attach film is not provided with the film sheet 1 and is not protected. This is because the semiconductor element must be directly fixed to the die bond pad surface by a fixing material such as an epoxy resin or a die attach film (DAF). The part not provided with the film sheet includes a method for providing a hole for semiconductor element die bonding in the film sheet in advance and sticking the film sheet to the lead frame or BGA substrate, and a part for semiconductor element die bonding before the die bonding step. A method of removing by providing a removing step is conceivable, but either method may be used.

  The lead frame or BGA substrate according to the present invention goes through each manufacturing process of the semiconductor device depending on the structure, but the surface of the external connection terminal 2 is shielded from the external atmosphere by the film sheet 1, so that it is transported between processes. Therefore, oxidation caused by changes in outside air does not occur.

FIG. 2 is an explanatory view showing the structure when the semiconductor element is die-bonded with a fixing material 4 such as an epoxy resin or a die attach film (DAF) in FIG. 1 in the die-bonding step. After the semiconductor element 5 is die-bonded with the fixing material 4 such as epoxy resin or die attach film (DAF) in the die bonding process, the fixing material such as epoxy resin or die attach film (DAF) is used in the furnace in the next curing process. A thermal history for curing 4 is received. At this time, the metal surface of the external connection terminal 2 is usually contaminated by the outgas generated when the fixing material 4 such as epoxy resin or die attach film (DAF) is cured. Since the surface of the connection terminal 2 is protected by the film sheet 1, it is not contaminated.

When the film sheet 1 is peeled and removed after the curing process is completed, the metal surface of the external connection terminal 2 appears as a clean metal surface without contamination. This clean metal surface provides good bonding quality when bonded to the bonding conductor in the next step such as wire bonding. FIG. 4 is an explanatory view showing a state in which the film sheet is peeled and removed in the step of peeling and removing, and the electrode pads of the semiconductor element and the external connection terminals are connected by a bonding conductor such as a metal wire in the step of wire bonding and the like. The present invention is particularly excellent as a means for protecting the joint surface 8 between the joint conductor and the external connection terminal. It is known that the quality of metal bonding improves as the bonding surface becomes cleaner. According to the present invention, the cleanliness and resistance to contamination of the joint surface 8 between the joint conductor and the external connection terminal are improved, and the joint quality between the joint conductor 7 and the external joint terminal 2 is improved. Therefore, even lead frames and BGA substrates designed to reduce the cost and reduce the plating structure for the purpose of cost reduction can be given resistance to oxidation and contamination, and sufficient bonding quality can be obtained. It becomes like this.

  FIG. 3 shows the structure of the semiconductor device in the manufacturing process in which a film sheet is attached to the surface of the electrode pad and the joint surface of the external connection terminal that is electrically connected to the electrode pad by a joint conductor in the process after the die bonding process. Show.

In this state, the epoxy resin or the die attach film (DAF) 4 is not yet cured. In the curing process, the fixing material 4 such as epoxy resin or die attach film (DAF) is subjected to a heat history for curing in a furnace. At this time, outgas is generated from the epoxy resin or the die attach film, but the surface of the electrode pad 6 of the semiconductor element and the surface of the external connection terminal 2 are protected by the film sheet 1 and thus are not contaminated by the outgas. When the film sheet 1 is peeled and removed in the process after the curing process, the metal surface of the semiconductor element pad electrode 6 and the metal surface of the external connection terminal 2 appear as clean metal surfaces without contamination. This clean metal surface is satisfactorily bonded to the bonding conductor in the subsequent process such as wire bonding, and provides stable bonding quality.
In recent years, a PAD structure made of a material that is excellent in electrical characteristics such as a copper PAD electrode but is sensitive to oxidation and contamination has been put into practical use. The present invention is particularly effective for such a demand.

Claims (3)

  A lead frame or a BGA substrate having a die pad to which a semiconductor element is bonded and a plurality of external bonding terminals (inner leads) arranged around the die pad are electrically bonded to the semiconductor element by a bonding conductor such as a metal wire. A lead frame or a BGA substrate, wherein at least one film sheet is adhered and adhered to at least a part of the metal surface of the external connection terminal (inner lead)   A lead having a plurality of external joint terminals (inner leads) arranged around a die pad bonded to a lead frame or a die pad of a BGA substrate by attaching a fixing material such as an epoxy resin or a die attach film to the back surface of the semiconductor element. In the frame or BGA substrate, a step of closely attaching at least one film sheet to the pad electrode surface of the semiconductor element and / or the metal surface of the external joint terminal (inner lead) is provided. Assembling method of semiconductor device 3. At least one or more film sheets adhered and adhered to both or either of the pad electrode surface of the semiconductor element according to claim 1 and the metal surface of a lead frame or an external joint terminal (inner lead) of a BGA substrate. The film sheet is peeled and removed in a process provided between the curing process and the wire bonding process.

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