JPH09172121A - Lead frame for semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive lead frame for semiconductor device which has excellent heat resistance, connectability, solder wettability, and corrosion resistance and is highly reliable for a long period. SOLUTION: A coating layer 15 composed of palladium or a palladium alloy is formed on the substrate 10 of a lead frame which is made of copper or copper alloy and is provided with an element mounting section 11, inner leads 12, and outer leads 13. In such a lead frame, protective coating layers 17 composed of a heat-resistance organic compound, such as mercaptobenzimidazole, thiourea, etc., are provided on the surfaces of coating layers 15 formed on the surface of the element mounting section 11 and at least the surfaces of coating layers 15 formed on the surfaces of the outer leads 13 formed on the front end sides of the inner leads 12 excluding wiring bonding sections 16. The coating layers 15 composed of plated palladium layers are formed on the surface of the substrate 10 of the lead frame with base coating layers 14 composed of plate nickel layers in between.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device lead frame and a method for manufacturing the same, and more particularly, to a substrate of a semiconductor device lead frame made of copper or a copper alloy, either directly or via an undercoat layer. The present invention relates to a lead frame for a semiconductor device in which a protective coating layer of a heat-resistant organic compound is provided on a portion except a part of the coating layer of palladium or its alloy provided as described above, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Generally, a lead frame for a semiconductor device (hereinafter, simply referred to as a lead frame) is manufactured by pressing a thin plate made of copper or a copper alloy as a base material.
An element mounting portion on which a semiconductor element is mounted, a predetermined number of inner leads and outer leads connected to the element mounting portion, a support lead for supporting the element mounting portion, a tie bar connecting them and a surrounding outer frame. It has and. Then, an undercoating layer made of palladium or an alloy thereof is formed on the surface of the processed leadframe base material via an undercoating layer such as nickel to form a leadframe. However, when a semiconductor device is assembled using the lead frame configured as described above, the thermal history of heating or the like associated with the assembly oxidizes the coating layer or the underlying coating layer or the like made of palladium or its alloy, and the solder wettability decreases. There was a problem. In order to solve such a problem, for example, JP-A-4-11555.
In No. 8, an example of a noble metal is formed on the base material made of copper or copper alloy directly or through a nickel (Ni) undercoating layer, and then a conventional plating method is applied to the coating layer. There is proposed a lead frame in which a protective coating layer such as silver (Ag) or gold (Au) is thinly formed.

[0003]

However, in the lead frame, since the protective coating layer of expensive noble metal plating such as Ag or Au is provided on the coating layer, in order to reduce the cost, Ag or If the Au plating film layer is made unnecessarily thin, pinholes are generated in the Ag or Au plating layer, and the oxygen in the atmosphere permeates the protective film layer on the surface due to heating in the oxidizing atmosphere in the semiconductor device assembly process. The phenomenon that the undercoat layer and the surface of the base material are oxidized has occurred. In addition, a galvuni potential is generated between the Au or Ag coating layer and the copper base material, and the force of this potential causes the copper ions of the base material to pass through the pinholes and move to the surface, causing a phenomenon of precipitation. There is a problem that the solder wettability is deteriorated while contaminating the solder. As a result, there is a problem that the adhesiveness to the undercoating layer is lowered, and peeling of the Ag or Au, blister, etc. occur. Furthermore, since a protective coating layer of a noble metal such as Ag or Au is formed on the coating layer of Pd or Pd alloy by a plating method, there is a problem in economical efficiency such as a decrease in production efficiency and an increase in manufacturing cost. It was In addition, a galvanic potential is generated between the Pd coating layer and the copper base material, and the force of this potential causes copper ions in the base material to pass through the pinholes and move to the surface, causing a phenomenon of precipitation and contaminating the surface. In addition, there is a problem that solder wettability is reduced. Therefore, the present inventor previously disclosed in Japanese Patent Application No. 6-284282 a protective coating layer made of a heat-resistant organic compound such as mercaptobenzimidazole or thiourea instead of Au or Ag plating for forming the protective coating layer. We have proposed a lead frame with the above structure, which makes it possible to prevent the plating coating layer from being oxidized in the semiconductor assembly process.

However, in the lead frame proposed in Japanese Patent Application No. 6-284282, a protective coating layer made of a heat-resistant organic compound is formed on the entire lead frame, so that the surface becomes smooth and a semiconductor element is formed. The bonding force is weak even when bonded to the element mounting portion covered with the protective coating layer via an adhesive, the semiconductor element moves laterally when a large load is applied to the semiconductor element in the wire bonding process,
There is a problem in that it causes problems during wire bonding work and resin sealing. Further, since the protective coating layer is also formed on the wire bonding pad portion formed on the tip portion of the inner lead, it is necessary to break the protective coating layer to perform bonding in wire bonding. However, if it is not broken, there is a problem that bonding failure may occur. The present invention has been made in view of such circumstances, and makes maximum use of the characteristics of the protective coating layer made of a heat-resistant organic compound, and is applied to an actual semiconductor device to provide heat resistance, connectivity, solder wettability, and corrosion resistance. It is an object of the present invention to provide an inexpensive lead frame for a semiconductor device which is excellent in reliability and has high long-term reliability, and a manufacturing method thereof.

[0005]

According to the present invention, there is provided a semiconductor device comprising:
The described lead frame for a semiconductor device is made of copper or a copper alloy, and is provided with an element mounting portion, a large number of inner leads provided around the element mounting portion, and outer leads extending therefrom and protruding to the periphery of the package. In a lead frame for a semiconductor device in which a coating layer of palladium or its alloy is formed on the base material of the frame, provided on at least the outer lead surface except for the wire bonding portions formed at the tip of the element mounting portion and the inner lead. Further, a protective coating layer made of a heat resistant organic compound such as mercaptobenzimidazole or thiourea is provided on the surface of the coating layer. The method of manufacturing a lead frame for a semiconductor device according to claim 2 is made of copper or a copper alloy, and is provided on the element mounting portion, a plurality of inner leads provided around the element mounting portion, and on the periphery of the package extending therewith. A method of manufacturing a lead frame for a semiconductor device, comprising a protruding outer lead, comprising: a plating step of forming a coating layer of palladium or its alloy on a base material of the lead frame for a semiconductor device; and a plating step formed by the plating step. A masking step for masking at least the element mounting portion on the coating layer and the wire bonding portion formed on the tip of the inner lead; and a lead frame base material partially masked in the masking step. Coating with a protective film-forming liquid consisting of a heat-resistant organic compound such as mercaptobenzimidazole or thiourea A protective film forming step that, and a masking removal step of removing the masking.

[0006]

A lead frame for a semiconductor device according to claim 1,
And a lead frame for a semiconductor device manufactured by the method according to claim 2, except for at least the wire bonding pad portion at the tip of the element mounting portion and the inner lead, mercaptobenzimidazole or Since the protective coating layer of a heat-resistant organic compound such as thiourea is provided, the heat resistance of the inner coating layer can be improved and the surface of the coating layer can be prevented from being oxidized. Further, copper of the base material of the lead frame for a semiconductor device made of copper or a copper alloy and the heat resistant organic compound are polymerized to form a protective coating layer for protecting the surface of the base material exposed in the pinhole. Further, since the protective coating layer made of the heat-resistant organic compound is not provided on the element mounting portion and the coating layer is exposed, the bondability of the adhesive is good and the fixing strength of the semiconductor element can be maintained. . Also, since the protective coating layer made of the heat-resistant organic compound is not provided on the wire bonding pad portion at the tip of the inner lead and the coating layer made of palladium or palladium alloy layer is exposed, the wire bonding connection is made. Can maintain strength.

In the method of manufacturing a lead frame for a semiconductor device according to a second aspect of the present invention, after forming a coating layer made of palladium or its alloy, at least the element mounting portion and the wire bonding pad portion are masked to obtain a mercaptobenz. Although a protective coating layer made of a heat-resistant organic compound such as imidazole or thiourea is formed, the formation of this protective coating layer can be performed by dipping or spraying in the heat-resistant organic compound solution, so that the coating treatment can be performed. The treatment is simple compared to the conventional Au and Ag plating. Since the material is cheaper than conventional Au and Ag, the cost of the semiconductor device as the final product is reduced.

[0008]

The lead frame for a semiconductor device according to claim 1 and the lead frame for a semiconductor device manufactured by the manufacturing method according to claim 2 exclude the element mounting portion and the wire bonding pad portion at the tip of the inner lead. Since a protective coating layer made of a heat-resistant organic compound is provided on the coating layer made of palladium or its alloy layer, the surface of the copper base material exposed in the pinhole formed in the coating layer is protected. Since the heat resistance of the coating layer is improved and the oxidation of the surface is prevented, heat resistance equivalent to that when a protective coating layer of a noble metal is formed by a plating method on the conventional coating layer,
It is possible to inexpensively manufacture a semiconductor device having excellent connectivity, solder wettability, and corrosion resistance and high long-term reliability. Since the protective coating layer made of a heat-resistant organic compound is not formed on the element mounting portion of the lead frame and the wire bonding pad portion of the inner lead, the semiconductor element is bonded to the element mounting portion for wire bonding. In this case, it is possible to prevent the semiconductor element from moving due to poor adhesion. Further, in the wire bonding pad portion of the inner lead, since the coating layer made of palladium or its alloy is exposed, the electric conductivity at the time of contact with the bonding wire is secured, and defects such as defective wire bonding are eliminated.

Particularly, in the method for manufacturing a lead frame for a semiconductor device according to the second aspect, the process for forming the protective coating layer is simple and inexpensive, so the cost of the lead frame for a semiconductor device is reduced, and Since the reliability is improved, the semiconductor device becomes cheaper as a whole.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, referring to the attached drawings, an embodiment in which the present invention is embodied will be described to provide an understanding of the present invention. 1 is an explanatory view of a lead frame for a semiconductor device according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view showing a state of a coating layer of a heat-resistant organic compound, and FIG. 3 is an embodiment of the present invention. FIG. 6 is a flow chart of a method for manufacturing a lead frame for a semiconductor device according to the embodiment.

As shown in FIG. 1, a base material 10 of a lead frame for a semiconductor device according to an embodiment of the present invention is a base material made of copper or copper alloy, which is formed by pressing or etching a central element mounting portion. 11, an inner lead 12 radially provided around the inner lead 12, and an outer lead 13 connected to the inner lead 12 and acting as an external connection terminal. Note that, in FIG. 1, a support for supporting the central element mounting portion 11, a tie bar for connecting adjacent leads, and a surrounding outer frame are omitted. A base coating layer 14 made of a nickel plating layer having a thickness of 0.5 μm is formed on the surface of the base material 10, and a coating layer 15 made of a palladium plating layer having a thickness of 0.1 μm is formed on the base coating layer 14. Has been done.

A protective coating layer 17 of mercaptobenzimidazole, which is an example of a protective coating layer made of a heat-resistant organic compound, is provided on portions other than the wire bonding pad portion 16 at the tip of the element mounting portion 11 and the inner lead 12.
have. As a result, as shown in FIG. 2, mercaptobenzimidazole is polymerized on the copper exposed in the pinholes 18 that connect the coating layer 15 and the underlying coating layer 14 to protect the surface of the base material 10 and to prevent galvanic potential. Prevent occurrence. Further, since the protective coating layer 17 covers the exposed surface of the coating layer 15, the surface of the coating layer 15 is prevented from being contaminated, the heat resistance is improved, and the exposed coating layer 15 is prevented from being oxidized. The wettability can be remarkably improved.

As shown in FIG. 3, a method of manufacturing a lead frame for a semiconductor device according to an embodiment of the present invention uses a pressing process or an etching process to remove unnecessary portions of a metal strip made of a copper material. A shape processing step 20 of removing and forming the base material 10 of the lead frame for a semiconductor device, and a pretreatment step 21 of performing degreasing / cleaning processing of the shape processed base material 10.
And Ni which is an example of the base coating layer 14 on the surface of the base material 10.
A base plating step 22 for forming a cover layer, and a cover layer 1 made of thin palladium on the surface of a base material 10 which has been base coated.
Plating step 23 for forming 5; masking step 24 for masking the element mounting portion 11 of the base material 10 on which the coating layer 15 is formed and the wire bonding pad portion 16 at the tip of the inner lead 12; 24
After the formation of the protective film layer 17, a protective film forming step 25 of forming the protective film layer 17 of the heat-resistant organic compound by immersing the base material 10 masked by 1. in a liquid containing the heat-resistant organic compound of mercaptobenzimidazole. And a masking removing step 26 for removing the masking formed in the masking step 24.

The masking material used in the masking step may be any material having good heat resistance that does not dissolve in the liquid containing the heat resistant organic compound used in the next step, and may be masked with a dry film, for example. ,
A masking material is applied by screen printing to the element mounting portion 11
You may print on the predetermined part containing. In addition, the liquid for forming the protective coating layer 17 in the coating forming step contains 1 to 100 ppm of mercaptobenzimidazole, and the lead frame for a semiconductor device is completed by immersing in the solution and then drying.

In the above-mentioned embodiment, mercaptobenzimidazole is used as the heat-resistant organic compound forming the protective coating layer, but it may be a solution of thiourea, and it has a strong permeability and is well permeable to pinholes. Other materials may be used as long as they penetrate, have heat resistance, and have solder wettability. Further, in the above-described embodiment, it is also possible to form the heat-resistant organic compound forming the protective coating layer 17 by printing on the portion excluding the element mounting portion 11 and the wire bonding pad portion 16. Further, in the above-mentioned embodiment, the protective coating layer 17 made of a heat-resistant organic compound is formed on the portion excluding the element mounting portion 11 and the wire bonding pad portion 16, but only the portion of the outer lead 13 protruding from the package is heat-resistant. It is also possible to form a protective coating layer.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a lead frame for a semiconductor device according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing a state of a heat-resistant organic compound coating layer.

FIG. 3 is a process drawing of the manufacturing method of the semiconductor device lead frame according to the embodiment of the present invention.

[Description of sign]

10 Base Material 11 Element Mounting Part 12 Inner Lead 13 Outer Lead 14 Undercoating Layer 15 Overcoating Layer 16 Wire Bonding Pad Part 17 Protective Coating Layer 18 Pinhole 20 Shape Processing Step 21 Pretreatment Step 22 Undercoating Step 23 Plating Step 24 Masking Step 25 protective film forming step 26 masking removing step

Claims (2)

[Claims] 1. An element mounting portion made of copper or a copper alloy,
Lead for a semiconductor device in which a coating layer of palladium or its alloy is formed on a base material of a lead frame provided with a large number of inner leads provided around the lead and outer leads that extend to the periphery of the package. In the frame, on the surface of the coating layer provided on at least the outer lead surface excluding the wire bonding portion formed at the tip of the element mounting portion and the inner lead, from a heat-resistant organic compound such as mercaptobenzimidazole or thiourea A lead frame for a semiconductor device, which is provided with a protective coating layer. 2. An element mounting portion made of copper or a copper alloy,
A method of manufacturing a lead frame for a semiconductor device, comprising a plurality of inner leads provided around the inner lead and outer leads extending to the inner lead and projecting to the periphery of a package, comprising: Performing a plating step of forming a coating layer of palladium or its alloy, and masking at least the element mounting portion on the coating layer formed in the plating step and a wire bonding portion formed at the tip of the inner lead. A masking step, and a protective film forming step of applying a protective film forming liquid consisting of a heat-resistant organic compound such as mercaptobenzimidazole or thiourea on the substrate of the lead frame partially masked in the masking step, And a masking removing step of removing the masking. Method for manufacturing a lead frame for a semiconductor device.