JP6414669B2 - Lead frame and manufacturing method thereof - Google Patents

Description

  The present invention relates to a lead frame and a manufacturing method thereof.

  Due to demands for miniaturization and thinning of semiconductor packages, for example, SON and QFN type packages are known as surface mount packages in which external connection terminals are exposed on the back surface of the semiconductor package.

  A conventional lead frame used for such a semiconductor package does not use a mask for partially plating, but has a plating layer formed in the order of Ni, Pd, and Au on the entire surface. . Since this plating can be wire-bonded and has connection reliability with solder, it can be used both as an internal terminal for wire bonding with a semiconductor element to be mounted and an external connection terminal for external connection. (For example, refer to Patent Document 1).

JP 2005-79524 A

  However, the bondability in wire bonding and the connection reliability with the solder in the connection of the external connection terminal are not always consistent, and depending on the application, a plating layer formed on the internal terminal for wire bonding with the semiconductor element may be used. In some cases, a metal plating layer different from the plating layer formed on the external connection terminals for external connection may be desired. In such a case, instead of uniformly forming the same plating layer on the entire surface, it is necessary to make the plating layer formed on the internal terminal different from the plating layer formed on the external terminal. In many cases, the formation of the plating layer and the formation of the plating layer of the external connection terminal need to be different manufacturing processes.

  Therefore, an object of the present invention is to provide a lead frame that can make the surface of the wire bonding terminal different from the surface of the external connection terminal, and a manufacturing method thereof.

In order to achieve the above object, a lead frame according to one embodiment of the present invention can be used as a component of a surface mount semiconductor package in which at least a part of the back surface is exposed as an external connection terminal and a semiconductor element is mounted on the surface. A lead frame formed from a metal plate,
A bonding plating layer capable of bonding to the semiconductor element is formed on the front surface and the side surface, and a film is attached to the back surface.

A method for manufacturing a lead frame according to another aspect of the present invention is a method for manufacturing a lead frame used in a surface-mount semiconductor package in which external connection terminals are exposed on the back surface and a semiconductor element is mounted on the surface.
Forming a lead frame pattern by processing a metal plate;
Attaching a film to the back surface of the lead frame pattern;
Forming a plating layer on the surface and side surfaces of the lead frame using the film as a mask.

A method for manufacturing a lead frame according to still another aspect of the present invention is a method for manufacturing a lead frame used in a surface mount type semiconductor package in which external connection terminals are exposed on the back surface and a semiconductor element is mounted on the surface.
Forming a lead frame pattern by processing a metal plate;
Forming a first plating layer on the entire surface of the lead frame pattern;
Attaching a film to the back surface of the lead frame pattern;
Forming a second plating layer on the surface and side surfaces of the lead frame using the film as a mask.

  ADVANTAGE OF THE INVENTION According to this invention, the plating layer for bonding suitable for a use can be formed.

1 is a cross-sectional configuration diagram of an example of a lead frame according to a first embodiment of the present invention. It is the figure which showed a series of processes of an example of the manufacturing method of the lead frame which concerns on Embodiment 1 of this invention. FIG. 2A is a diagram illustrating a metal plate preparation process for forming a lead frame. FIG. 2B is a diagram illustrating a process of forming a lead frame pattern. FIG. 2C is a diagram illustrating an example of a film attaching process. FIG. 2D is a diagram showing an example of the plating process. FIG. 5 is a cross-sectional configuration diagram illustrating an example of a lead frame according to a second embodiment of the present invention. It is the figure which showed a series of processes of an example of the manufacturing method of the lead frame which concerns on the 2nd Embodiment of this invention. FIG. 4A is a diagram illustrating an example of a metal plate preparation process. FIG. 4B is a diagram showing an example of a lead frame pattern forming process. FIG. 4C is a diagram showing an example of the first plating layer forming step. FIG. 4D is a diagram illustrating an example of a film attaching process. FIG. 4E is a diagram showing an example of the second plating step. It is the figure which showed an example of the surface mount type semiconductor package using the lead frame concerning a 2nd embodiment. It is the figure which showed an example of the shipment method of the lead frames 50 and 51 which concern on the 1st and 2nd embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a cross-sectional configuration of an example of a lead frame according to the first embodiment of the present invention. In FIG. 1, a lead frame 50 according to the first embodiment of the present invention includes a lead frame pattern 10, a bonding plating layer 30, and a film 40. The bonding plating layer 30 is formed on the upper surface and side surfaces of the lead frame pattern 10. The film 40 is attached to the lower surface of the lead frame pattern 10.

  Before describing the lead frame according to the first embodiment in detail, a surface mount semiconductor module using the lead frame according to the embodiment of the present invention will be described.

  FIG. 5 is a view showing an example of a surface mount semiconductor module using the lead frame according to the embodiment of the present invention. In FIG. 5, the semiconductor element 60 is mounted on the surface of the lead frame 51, and the whole is sealed with a resin 80. The lead frame pattern 10 has a central semiconductor element mounting region 11 and terminal regions 12 provided on both sides thereof, and the semiconductor element 60 is installed on the semiconductor element mounting region 11. A terminal 61 of the semiconductor element 60 is connected to the terminal region 12 by wire bonding via a wire 70. Here, the upper surface of the terminal region 12 is an internal terminal for bonding, and the lower surface is an external connection terminal. In FIG. 5, the film 40 is affixed to the entire lower surface, but when the film 40 is peeled off, the lower surface of the terminal region 12 is exposed, and an external connection terminal that can be electrically connected to an external device. It becomes. The lead frame according to the present embodiment can be used as a component of such a surface mount semiconductor module.

  Returning to FIG. 1, the lead frame 50 according to the first embodiment of the present invention will be described in detail.

  The lead frame pattern 10 is a metal pattern obtained by processing a metal plate into the shape of a lead frame. The metal plate may be made of various metal materials suitable for the lead frame, but may be made of, for example, a copper material or a copper alloy material. As described with reference to FIG. 5, the lead frame pattern 10 includes at least a region where a semiconductor element is mounted, an internal terminal for bonding that electrically connects the terminals of the semiconductor element by wire bonding, and an external terminal. And an external connection terminal for electrical connection. In the lead frame according to the present embodiment, the semiconductor element is mounted on the surface side of the lead frame pattern 10, and bonding terminals connected to the terminals of the semiconductor element by wire bonding are also formed on the surface side. In FIG. 1, the upper surface side corresponds to the front surface side, and the lower surface side corresponds to the back surface side.

  In FIG. 1, a plating layer 30 is formed so as to cover the upper surface (front surface) and side surfaces of the lead frame pattern 10. Since the surface of the lead frame pattern 10 constitutes a bonding terminal, the plating layer 30 is made of a plating material that can be bonded. The plating layer 30 may be determined according to the type, application, and the like of the semiconductor element 60 to be mounted, but may be made of silver (Ag), for example.

  A film 40 is attached to the back surface of the lead frame pattern 10. Therefore, when the film 40 is peeled off, the lead frame pattern 10 is exposed. As described with reference to FIG. 5, the back surface of the lead frame pattern 10 functions as an external connection terminal that can be electrically connected to an external device. Therefore, the surface of the metal material constituting the lead frame pattern 10 functions as an external connection terminal, and when this is a copper material or a copper alloy material, the surface becomes the external connection terminal.

  The film 40 can function as a mask during the plating process, and can also function as a mask during resin sealing, and is selected from materials that do not allow the resin to flow out. Various materials can be used for the film 40 as long as the material can function as a mask at the time of plating treatment and resin sealing. For example, a film made of polyimide may be used. Since polyimide has high heat resistance and can function as a mask during plating and resin sealing, it can be suitably used.

  In addition, various adhesives or adhesives can be used for adhesion of the film 40 to the back surface of the lead frame pattern 10. For example, when the above-described polyimide is used for the film 40, a polyimide-based thin film tape is commercially available, and such a thin film tape may be used. Bonding of the film 40 to the back surface of the lead frame pattern 10 can be easily performed.

  Next, the manufacturing method of the lead frame according to the first embodiment of the present invention will be described with reference to FIG. FIG. 2 is a diagram showing a series of steps of an example of the lead frame manufacturing method according to the first embodiment of the present invention.

  FIG. 2A is a diagram illustrating a metal plate preparation process for forming a lead frame. The metal plate 15 is initially prepared in a state where no pattern or the like is formed. In addition, although the metal plate 15 may be comprised from various metal materials according to a use, as mentioned above, you may be comprised from a copper material or a copper alloy material, for example.

  FIG. 2B is a diagram illustrating a process of forming a lead frame pattern. The lead frame pattern 10 is obtained by processing the metal plate 15 into a lead frame shape. The metal plate 15 may be processed by various processing methods including etching and pressing. In consideration of cost, processing accuracy, etc., the processing method of the metal plate 15 can be determined according to the application.

  The lead frame pattern 10 is formed by the lead frame pattern forming step, and at least the semiconductor element mounting region 11 and the terminal region 12 are formed. Although not shown in FIG. 2B, the lead frame pattern 10 may have a height difference or the like formed by bending or the like.

  FIG. 2C is a diagram illustrating an example of a film attaching process. In the film attaching process, the film 40 is attached to the back surface (lower surface) of the lead frame pattern 10. As described above, the film 40 is selected from materials that can be masked during plating and resin sealing. The film 40 may be attached using an adhesive, or may be attached using a film 40 such as a thin film tape in which an adhesive layer is formed on one side of the film 40 from the beginning. . In the following description, the adhesive that solidifies after bonding and the adhesive that does not require a solidification process even after bonding are not necessarily distinguished strictly, and are called adhesives. Even if it is a case, it shall also contain an adhesive.

  FIG. 2D is a diagram showing an example of the plating process. In the plating step, the plating process is performed with the film 40 adhered to the back surface of the lead frame pattern 10. Thereby, the plating layer 30 is formed only on the upper surface (front surface) and the side surface of the lead frame pattern 10 not covered with the film 40. As a material of the plating layer 30, various plating materials may be used depending on the application. For example, an Ag plating layer may be formed using Ag.

  In the plating step, for example, an electroplating process may be performed. The electroplating is performed by immersing the lead frame pattern 10 in a plating solution, using the lead frame pattern 10 as a cathode, and energizing with the anode immersed in the plating solution. The film 40 functions as a mask for the plating process, and the plating layer 30 is formed only on the upper surface and the side surface that are not covered with the film 40, whereby the lead frame 50 is completed.

  The upper surface of the plating layer 30 later becomes an internal terminal for bonding, and the lower surface of the lead frame pattern 10 to which the film 40 is attached functions later as an external connection terminal.

  As described above, according to the lead frame and the manufacturing method thereof according to the first embodiment, after the lead frame pattern 10 is formed, the film 40 is attached to the back surface, so that the terminal region 12 can be easily formed through a single plating process. The upper surface and the lower surface can be configured as different surfaces, and various requests required for the terminals of the lead frame 50 can be flexibly met.

  FIG. 3 is a cross-sectional configuration diagram showing an example of a lead frame according to the second embodiment of the present invention. In the lead frame 51 according to the second embodiment, the entire surface of the lead frame pattern 10 is covered with the plating layer 20, the plating layer 30 is formed on the upper surface and the side surface of the plating layer 20, and the film 40 is attached to the lower surface. This is different from the lead frame 50 according to the first embodiment. That is, the lead frame pattern 10 is different from the lead frame 50 according to the first embodiment in that the plating layer 20 is formed like a coating layer on the surface of the lead frame pattern 10, but the other configurations are the same as those in the first embodiment. This is the same as the lead frame 50 according to the embodiment.

  Thus, the plating layer 30 may be formed by covering the entire surface of the lead frame pattern 10 with the plating layer 20 made of a material different from that of the plating layer 30 and then attaching the film 40 to the lower surface. With this configuration, the surface of the external connection terminal formed on the lower surface of the terminal region 12 is configured by the plating layer 20. That is, when it is desired to form an external plating terminal with an arbitrary metal material by forming an arbitrary plating layer 20 instead of the material of the metal plate 15 used for the lead frame pattern 10, the lead frame according to the second embodiment. By setting it as 51, the surface of an external connection terminal can be made into a desired metal material.

  The plating material of the plating layer 20 can be various materials depending on the application. For example, Ni is formed on the surface of the lead frame pattern 10 using Ni as a base layer, Pd on the surface of Ni, and further Pd A plating layer (hereinafter referred to as “palladium plating layer”) in which Au is formed and laminated on the surface may be used. A palladium plating layer in which Ni, Pd, and Au are laminated in order from the lower layer is generally used as a plating layer suitable for solder bonding. Specifically, when copper or a copper alloy material is used as the lead frame pattern 10, Ni in the underlayer suppresses copper diffusion, uses noble metal Au on the bonding surface, has good characteristics, and Au By sandwiching cheaper Pd between Ni and Au, an external connection terminal excellent in quality and cost is obtained. Therefore, you may make it use the plating layer suitable for such solder joining as the plating layer 20 which comprises an external connection terminal.

  The plated layer 20 is preferably suitable for solder bonding, but if it is made of a material that can be soldered, the plating layer 20 can fully fulfill its role. The material can be selected.

  Since other components are the same as those of the lead frame 50 according to the first embodiment, the same reference numerals are given to the same components and the description thereof is omitted.

  FIG. 4 is a diagram showing a series of steps of an example of a lead frame manufacturing method according to the second embodiment of the present invention.

  FIG. 4A is a diagram illustrating an example of a metal plate preparation process. Since this step is the same as the step described with reference to FIG.

  FIG. 4B is a diagram showing an example of a lead frame pattern forming process. This step is also the same as the step described with reference to FIG.

  FIG. 4C is a diagram showing an example of the first plating layer forming step. In the first plating layer forming step, the first plating layer 20 is formed on the entire surface of the lead frame pattern 10. The formation of the first plating layer 20 may be performed by a general electroplating process in which the first plating layer 20 is immersed and energized. This point is the same as that described with reference to FIG. Since there is no mask on the entire surface of the lead frame pattern 10, the first plating layer 20 is formed on the entire surface.

  Since the first plating layer 20 is used as an external connection terminal, the first plating layer 20 is formed of a plating material capable of solder connection, and is preferably formed of a plating material suitable for solder connection. The palladium plating layer in which Ni, Pd, and Au are stacked in order from the lower layer is also suitable as an external connection terminal. Therefore, the palladium plating layer may be the first plating layer 20. When the palladium plating layer is formed, first, the lead frame pattern 10 is dipped in a Ni plating solution and electroplated, and then the lead frame pattern 10 in which the Pd plating solution is subjected to Ni plating is formed. Electroplating may be performed by dipping, and finally, the lead frame pattern 10 that has been subjected to Ni and Pd plating may be immersed in a plating solution of Au to perform electroplating. Since it is sufficient to pass through the three electroplating tanks in order, the palladium plating layer can be easily formed.

  FIG. 4D is a diagram illustrating an example of a film attaching process. This process is also the same as the process described with reference to FIG. 2C except that the film 40 is applied to the lead frame pattern 10 having the first plating layer 20 formed on the entire surface. Is omitted.

  FIG. 4E is a diagram showing an example of the second plating step. The second plating step is also the same as the step described in FIG. 2D except that the object to be subjected to the second plating process is the lead frame pattern 10 whose entire surface is covered with the first plating layer 20. Yes, a similar electroplating process may be performed. Therefore, the description is omitted.

  According to the lead frame and the manufacturing method thereof according to the second embodiment, an arbitrary plating layer is formed on the surface of the external connection terminal by adding the first plating process for plating the entire surface of the lead frame pattern 10. The external connection terminal suitable for the application can be formed.

  FIG. 5 is a view showing an example of a surface mount semiconductor package using the lead frame 51 according to the second embodiment.

  In FIG. 5, the semiconductor element 60 is mounted on the semiconductor element mounting region 11 while the film 40 is stuck to the lead frame pattern 10, and the wire 70 is used from the terminal 61 of the semiconductor element 60 to the upper surface of the terminal region 12. A surface-mounted semiconductor package that has been bonded and sealed with a resin 80 is shown. Thus, the lead frame 51 can be shipped without peeling off the film 40, and the resin sealing can be performed with the film 40 still attached. By using a material having a material from which the resin 80 does not flow out for the film 40, packaging can be easily performed.

  Since the upper surface (front surface) and side surfaces of the terminal region 12 are covered with the second plating layer 30 made of a material such as Ag suitable for wire bonding, the wire 70 is connected to the upper surface of the terminal region 12. Bonding can be performed appropriately.

  After the resin sealing, by peeling off the film 40, the back surface of the terminal region 12 is exposed and functions as an external connection terminal on which the first plating layer 20 is formed. Since the first plating layer 20 is made of a material suitable for external connection, external connection can also be appropriately performed.

  As described above, the lead frame 51 according to the second embodiment can easily perform resin sealing on the film 40 from which the resin 80 does not flow out while the film 40 is attached to the lead frame 51. There is also a great advantage for the person performing the video recording.

  In FIG. 5, the lead frame 51 according to the second embodiment has been described as an example. However, the lead frame 50 according to the first embodiment can be easily sealed with a resin in the same manner.

  FIG. 6 is a diagram showing an example of a method for shipping the lead frames 50 and 51 according to the first and second embodiments of the present invention. As shown in FIG. 6, the lead frames 50 and 51 according to the present embodiment can be shipped with a plurality of lead frames 50 and 51 formed in the metal plate 15. The lead frame pattern 10 including the semiconductor element mounting region 11, the terminal region 12, and the like is formed by forming one lead frame pattern 10 in one frame in the metal plate 15, and the lead frame pattern 10 from the frame. It can be performed in a state in which the frame is not completely cut and is connected and supported by the frame. A plurality of lead frames 50 and 51 can be manufactured in a lump by affixing the film 40 and performing a plating process in a lump.

  In the delivery destination of the lead frames 50 and 51, after packaging as shown in FIG. 5 is performed at once, the film 40 is peeled off, and finally the frame is cut to separate each package. The lead frames 50 and 51 and the surface mount semiconductor package can be manufactured in a lump.

  As described above, the lead frame and the manufacturing method thereof according to the embodiment of the present invention can appropriately cope with mass production, and efficient mass production is possible.

  Hereinafter, examples in which the lead frame and the manufacturing method thereof according to the embodiment of the present invention are implemented will be described.

  As the lead plate metal plate 1, a strip-shaped copper material having a thickness of 0.2 mm and a width of 180 mm (manufactured by Kobe Steel, Ltd .: KLF-194) is used, and a photosensitive resist having a thickness of 20 μm is formed on both surfaces of the metal plate 1. A layer (manufactured by Asahi Kasei E-Materials Co., Ltd .: negative photosensitive resist AQ-2058) was formed.

  Then, it exposed using the glass mask (Konica Minolta Advanced Layer Co., Ltd. product: HY2-50P) which gave the lead frame pattern, Then, the lead frame bear material was formed by peeling of development, an etching, and the photosensitive resist. Thereafter, a very thin plating layer of Ni, Pd, and Au was formed on the entire front and back surfaces. At this time, the Ni film thickness was 0.6 μm, the Pd film thickness was 0.015 μm, and the Au film thickness was 0.0065 μm.

Thereafter, a polyimide-based thin film tape (Innox) was attached to the back surface, and an extremely smooth Ag plating (high cyan Ag plating) layer having a glossiness of 1.7 GAM was formed on the surface with a thickness of 2.5 μm. As a result, a lead frame having different metal plating layers on the front surface and the back surface was obtained. After that, the backside polyimide thin film tape does not peel off, it is cut into a strip shape as it is pasted, put into the LED device assembly process, the front surface is an Ag plating layer, and the back surface is Ni / Pd / Au plating Layer LED device was completed.

  A polyimide-based thin film tape (manufactured by Yodogawa Paper) was attached to the back surface of the lead frame bear material formed in the same manner as in Example 1, and plated in the order of Ni, Pd, and Au. Then, it assembled in the semiconductor assembly process, and the back surface polyimide system thin film tape was peeled after mold enclosure. In this state, Cu was exposed on the back surface side, but electrolytic Sn plating was applied to the Cu surface as exterior plating, and a lead frame according to Example 2 was obtained.

  A polyimide-based thin film tape (manufactured by Nitto) was attached to the back surface of the lead frame bear formed in the same manner as in Example 1, and Ni plating (Ni plating of sulfamate) with a thickness of 0.8 μm was performed. On top of that, Ag Strike (Dow Chemical's Silveron GT-820 Strike) is applied to a thickness of 0.05μm, and Ag / Sn alloy plating (Dow Chemical's Silveron GT-820 Cyanide-free AgSn Plating) is 1.2μm thick. I gave it. Then, it assembled in the semiconductor assembly process, and the back surface polyimide system thin film tape was peeled after mold enclosure. In this state, Cu was exposed on the back surface side, but electrolytic Sn plating was applied to the Cu surface as an exterior plating to obtain a lead frame according to Example 3.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

DESCRIPTION OF SYMBOLS 10 Lead frame pattern 11 Semiconductor element mounting area 12 Terminal area 15 Metal plate 20, 30 Plating layer 40 Film 50, 51 Lead frame 60 Semiconductor element 70 Wire 80 Resin

Claims (4)

A method of manufacturing a lead frame used in a surface-mount semiconductor package in which external connection terminals are exposed on the back surface and a semiconductor element is mounted on the surface,
Forming a leadframe pattern by forming a metal plate,
Forming a first plating layer on the entire surface of the lead frame pattern;
Attaching a film to the back surface of the lead frame pattern;
And a step of forming a second plating layer on the surface and side surfaces of the lead frame using the film as a mask. The lead frame according to claim 1 , wherein the film is a tape-like film having an adhesive layer or an adhesive layer, and the film is attached to the back surface of the lead frame pattern using the adhesive layer or the adhesive layer. Method. The first plating layer is a plating layer in which Ni, Pd, and Au are stacked in order from the lower layer, and the step of forming the first plating layer includes forming Ni, Pd, and Au in order on the lead frame pattern. the method for manufacturing a lead frame as claimed in claim 1 or 2 comprising the step of plating. Wherein the step of forming the second plating layer, the manufacturing method of lead frame according to any one of claims 1 to 3 comprising the step of plating the Ag to the lead frame pattern.

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