JP2006319030A - Circuit board, its manufacturing method, semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To markedly improve the strength of connection between a wiring layer and an electrode, and mounting reliability, through a process of devising the shape of an opening provided above the metal wiring layer. <P>SOLUTION: The metal wiring layer 2 is bonded on an insulating board 1, and an organic solvent-soluble resist 3a is formed on the metal wiring layer 2. A resist 3b smaller than the resist 3a is formed on the resist 3a. Thereafter, a substrate protective film 4 is applied and cured, and the resists 3a and 3b are removed by an organic solvent after the substrate protective film 4 is cured, and an opening 4a with a step 4b is provided to the substrate protective film 4 above the metal wiring layer 2. A protrudent electrode electrically connected to the metal wiring layer 2 is provided to the opening 4a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention includes a circuit board for a semiconductor device having an opening in a substrate protective film, and a protruding electrode provided on a metal wiring layer in the opening, a method for manufacturing the circuit board, and the circuit board. The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.

  2. Description of the Related Art In recent years, semiconductor devices have been required to be smaller, more accurate, and faster as electronic devices have become smaller and higher in performance. In semiconductor packages, CSPs (Chips) that are as close as possible to the size of semiconductor elements are required. Small package products such as Size Package have been developed.

  Similarly, in LGA (Land Grid Array) and BGA (Ball Grid Array), miniaturization is progressing, and the ball size and land size are miniaturized as the ball pitch and land pitch are refined. The bonding area between the substrate land (metal wiring layer) exposed from the protective film as the external electrode terminal and the ball as the protruding terminal (projecting electrode) cannot be secured sufficiently, and the connection strength can be secured. It has become difficult.

  In addition, the increase in performance of semiconductor elements has accelerated the increase in the number of pins and the size of semiconductor devices, and it has become difficult to ensure mounting reliability after the semiconductor devices are mounted on a circuit board.

  Accordingly, attention is paid to the shape of the substrate protective film, and a circuit board having a shape in which the opening of the substrate protective film has a taper toward the bottom has been proposed (see Patent Document 1).

  A circuit board having a structure in which the opening of the substrate protective film has a taper shape toward the bottom will be described with reference to FIG.

  FIGS. 6A and 6B are cross-sectional views for explaining an example of a circuit board in which the opening of the board has a taper shape toward the bottom, from the side of the adhesive 11 in the hard plate 12 with the adhesive 11. By irradiating the laser beam 13, a taper-shaped opening 14 that is expanded on the adhesive 11 side is formed (FIG. 6A), and then a copper foil 15 is laminated on the adhesive 11 side to form a circuit board. Is produced.

By using the circuit board having the above structure, it is possible to secure a bonding area between an electrode terminal provided in a later process and a board land (metal wiring layer) made of the copper foil 15, and a connection strength between the protruding electrode and the board land. It is possible to improve.
JP 2002-252312 A

  However, the conventional method has a limit in controlling the taper angle at the opening. Therefore, there is a limit to the size expansion of the substrate land with respect to the opening area, and the bonding area between the electrode terminal and the substrate land cannot be increased. This makes it difficult to improve the connection strength and mounting reliability between the substrate land and the electrode terminal.

  In addition, according to the prior art, the side surface of the substrate land opening is formed in a tapered shape, so that the taper tip becomes an acute angle, the shape formation becomes unstable, or stress is concentrated when external stress is applied. Therefore, for example, stress after mounting on a mounting circuit board may be concentrated locally, and mounting reliability may be reduced.

  The present invention solves the above-mentioned conventional problems and devise the opening shape to greatly improve the connection strength between the wiring layer and the electrode and the mounting reliability, a manufacturing method thereof, and a semiconductor device. It aims at providing the manufacturing method.

  The circuit board forming method for achieving the above object is, for example, by forming a wiring pattern with a metal layer such as a copper foil on an insulating substrate, and exposing and exposing an organic solvent-soluble photoresist on the surface of the metal layer. A pattern is formed by the above, and a photoresist having a smaller area than the photoresist is formed on the surface of the photoresist, and then a protective film of the circuit board is applied and cured, and then the photoresist is removed, and the protective film is opened. A circuit board is formed as an interposer in which a plurality of steps are formed on the side wall.

  Furthermore, a method for forming a semiconductor device using a circuit board formed by the above means includes mounting a semiconductor element on the circuit board, and wire bonding the inner layer metal wiring exposed from the protective film of the circuit board and the semiconductor element. Connect electrically by construction method. Next, the semiconductor element on the circuit board and the part electrically connected by the wire bonding method are sealed with resin so as to cover.

  According to another method of forming a semiconductor device, the circuit board formed by the above means is used, and protrusions are formed on the electrodes of the semiconductor element with gold bumps or the like with respect to the circuit board. As a result, the inner-layer metal wiring exposed from the protective film of the circuit board and the semiconductor element are electrically connected by a flip chip method. Next, sealing is performed with resin so as to cover the gap between the circuit board and the semiconductor element and the outer periphery of the semiconductor element.

  Further, when forming a protrusion as an external terminal, for example, a solder ball is heated and melted to the inner layer metal wiring exposed from the protective film of the circuit board opposite to the semiconductor element mounting surface of the circuit board by reflow or the like. A protruding electrode is provided.

  The present invention has a structure in which a step is formed on the side surface of the substrate protective film in the land of the metal wiring layer exposed from the substrate protective film of the circuit board, thereby reducing the exposed area of the metal wiring layer to the area of the substrate protective film surface. It can be set arbitrarily. Therefore, even when the area of the protruding electrode such as a metal ball is reduced, a large area of the substrate land can be secured, so that the strength between the protruding electrode and the substrate land can be improved.

  Further, for example, by improving the hardness of the substrate protective film, the anchor effect is improved, the connection strength between the protruding electrode and the substrate land is further improved, and the mounting reliability after the semiconductor element is mounted on the substrate may be improved. it can.

  Further, the structure of the circuit board is not limited to the constituent material of the semiconductor device, and by using it as a mounting circuit board, it becomes possible to improve the mounting reliability of various electric products.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a circuit board for explaining an embodiment of the present invention.

  As shown in FIG. 1, the circuit board includes a metal wiring layer 2 bonded on the insulating substrate 1, and a substrate protective film 4 that covers the insulating substrate 1 and a part of the metal wiring layer 2. The opening 4a formed on the metal wiring 2 in FIG. 2 has a step 4b whose peripheral area is such that the exposed area of the metal wiring layer 2 is larger than the opening area of the outermost surface portion on the insulating substrate 1 and the metal wiring 2. A plurality of stages are formed.

  The step 4b is narrowly formed so that the opening 4a of the substrate protective film 4 covers the metal wiring layer 2, and a protruding electrode is formed in this portion as will be described later. In general, the protruding electrode is a solder ball formed of an alloy mainly composed of Sn, and when the solder ball is melted and bonded to the metal wiring layer 2, the molten solder ball metal is a step 4 b portion of the substrate protective film 4. It has an anchor effect of embedding and prevents the solder balls from falling off.

  An embodiment of a method for manufacturing a circuit board according to the present invention will be described with reference to cross-sectional views for explaining the manufacturing steps of FIGS.

  First, as shown in FIG. 2A, a metal wiring layer 2 made of copper foil or the like is bonded onto the insulating substrate 1.

  Next, as shown in FIG. 2B, an organic solvent-meltable photoresist 3 a is formed on the metal wiring layer 2.

  Next, as shown in FIG. 2C, a photoresist 3b having a smaller area than the photoresist 3a is formed on the photoresist 3a.

  Next, as shown in FIG. 2D, the substrate protective film 4 is applied and then cured.

  Next, as shown in FIG. 2E, after the substrate protective film 4 is cured, the photoresists 3a and 3b are removed with an organic solvent.

  The method shown in FIGS. 2A to 2E is a two-step stacking of photoresist, but a multi-step photoresist can be formed by stacking three or more steps of photoresist.

  Further, in the method of FIGS. 2A to 2E, the shape of the opening 4a and the like of the substrate protective film 4 is not formed with a photoresist, but the substrate protective film 4 of FIG. It is also possible to laminate the layers formed in advance in the shape of the above by bonding them to the insulating substrate 1 with an adhesive.

  An effective land and ball pitch is 0.5 mm pitch or less as a range in which the present embodiment exhibits a desired effect. As the pitch becomes smaller, the area of the metal wiring layer 2 where the solder balls as the protruding electrodes are melt-bonded must also be reduced, and the bonding strength between the solder balls and the metal wiring layer 2 also decreases.

  Further, Sn-Pb has been conventionally used as the material for the solder ball, but from the viewpoint of environmental problems, a material such as Sn-Ag-Cu, which is a Pb-free material, is currently used. In such a Pb-free material, compared with conventional Sn-Pb, there are various connection conditions such as a melting temperature condition in the case of connection, a connection state after connection (presence / absence of voids), oxidation problems, and the like. It is getting stricter.

  Under such circumstances, it is necessary to implement this embodiment at a fine pitch with a land and ball pitch of 0.5 mm or less. However, considering that the land and ball pitches are practically limited to 0.25 mm pitches due to limitations in handling and dimensional design, the range in the present embodiment is 5 to 5 mm in diameter at the substrate protective film opening of the substrate. The effective land and ball pitch is 0.25 mm to 0.5 mm.

  The height of each step is 2 to 20 μm pitch.

  FIG. 3 is a cross-sectional view for explaining an embodiment of a semiconductor device using the circuit board according to the present invention.

  In FIG. 3, reference numeral 5a denotes a package circuit board prepared by the method shown in FIGS. 2A to 2E. The package circuit board 5a includes a semiconductor element 6 and wiring of the package circuit board 5a (not shown). And a semiconductor element 6 electrically connected by a thin metal wire 7, a resin 8 sealing the outer periphery of the semiconductor element 6 on the package circuit board 5a, and the bottom surface of the package circuit board 5a The protruding electrode 9 provided on the metal wiring layer 2 is provided.

  As the protruding electrode 9, a solder ball is generally used. Conventionally, Sn—Pb has been used as the material for the solder balls, but from the viewpoint of environmental problems, a material such as Sn—Ag—Cu, which is a Pb-free material, is currently used.

  A method for manufacturing a semiconductor device capable of improving the connection strength between the substrate land and the protruding electrode using the circuit board will be described with reference to FIGS.

  First, FIG. 4A shows a package circuit board 5a created by the method of FIGS. 2A to 2E.

  Next, as shown in FIG. 4B, the semiconductor element 6 is mounted on the package circuit board 5a.

  Next, as shown in FIG. 4C, the wiring of the package circuit board 5a and the semiconductor element 6 are electrically connected using the fine metal wires 7 by the wire bonding method.

  Next, as shown in FIG. 4D, the outer periphery of the semiconductor element 6 on the package circuit board 5 a is sealed with a resin 8.

  Next, as shown in FIG. 4E, the metal wiring exposed at the opening 4a of the substrate protective film 4 formed on the back surface of the package circuit board 5a with respect to the semiconductor element 6 mounting surface. The bumps 9 are provided on the back surface of the package circuit board 5a by heating and melting metal balls, printed solder paste, or the like on the substrate land of the layer 2 by reflow.

  FIG. 5 is a cross-sectional view for explaining an example of a mounting form using the circuit board formed according to each of the embodiments.

  In FIG. 5, the package circuit board 5 a is a connection in which the semiconductor element 6 mounted thereon, a wiring (not shown) of the package circuit board 5 a, and the semiconductor element 6 are electrically connected by a thin metal wire 7. Means, a resin 8 sealing the outer periphery of the semiconductor element 6 on the package circuit board 5a, and a protruding electrode (not shown) provided on the bottom surface of the package circuit board 5a. A metal lump 10 is formed between the board land 2b formed on the electronic component mounting circuit board 5b and the board land 2a of the package circuit board 5a produced by the same method.

  The metal lump 10 is, for example, a solder ball on the package circuit board 5a side, and a solder paste on the electronic component mounting circuit board 5b. The solder balls on the circuit board 5a side are temporarily held at room temperature, and then heated (240 to 260 ° C.) to melt the solder balls and the solder cream to form the metal lump 10.

  As described above, the present embodiment can be used for both a package circuit board and an electronic component mounting board, and when the package circuit board and the electronic mounting board are mounted, the board of the present embodiment is used for both boards. As a result, the mounting reliability can be improved.

  In this embodiment, when a circuit board is manufactured as an interposer of a semiconductor device, an opening is formed in the protective film of the circuit board to expose an inner wiring layer of the circuit board as an external terminal. By forming a plurality of steps on the side wall of this, it is a kind of technique that can secure a larger exposed area of the inner wiring layer with respect to the opening area of the outermost surface portion of the protective film opening.

  For example, a wiring pattern is formed on a metal substrate such as a copper foil on an insulating substrate, an organic solvent-soluble photoresist is exposed on the surface of the metal layer, the pattern is formed by exposure, and the photo resist is formed on the surface of the photoresist. A circuit board in which a photoresist having a smaller area than the resist is formed, and then a protective film for the circuit board is applied and cured, and then the photoresist is removed, and a circuit board having a plurality of steps formed on the side walls of the protective film and its manufacture It is about the method.

  According to the present invention, by forming a semiconductor device using the circuit board formed as described above, an exposed area of the inner wiring layer can be secured larger than the opening area of the substrate protective film (LGA). The present invention is effective when applied to semiconductor devices represented by Land Grid Array) and BGA (Ball Grid Array) and their manufacture.

Sectional drawing of the circuit board for demonstrating embodiment of this invention (A)-(e) is sectional drawing which shows the process of the manufacturing method of the circuit board based on this embodiment. Sectional drawing of the semiconductor device for describing embodiment of this invention (A)-(e) is sectional drawing which shows the process of the manufacturing method of the semiconductor device which concerns on this embodiment. Sectional drawing for demonstrating the example of the mounting form using the circuit board formed by this embodiment (A), (b) is sectional drawing which shows the process of the manufacturing method of the conventional circuit board

Explanation of symbols

1 Insulating board 2 Metal wiring layer 2a Board land (package circuit board)
2b Board land (Electronic component mounting circuit board)
3a Photoresist (Large)
3b Photoresist (small)
4 Substrate protective film 4a Opening 4b Step 5a Package circuit board 5b Electronic component mounting circuit board 6 Semiconductor element 7 Metal wire 8 Resin 9 Projection electrode 10 Metal lump

Claims (5)

An insulating substrate;
A metal wiring layer bonded on the insulating substrate;
A substrate protective film formed on the insulating substrate and the metal wiring layer and having an opening on the metal wiring layer;
A circuit in which a step is formed in the periphery of the opening of the substrate protection film so that the exposed area of the metal wiring layer is larger than the opening area of the outermost surface portion in the opening of the substrate protection film. substrate.   The circuit board according to claim 1, wherein the substrate protective film is bonded to the insulating substrate with an adhesive. A manufacturing method for manufacturing the circuit board according to claim 1,
Bonding a metal wiring layer on an insulating substrate;
Forming an organic solvent-meltable resist on the metal wiring layer;
Forming a resist smaller than the resist on the resist;
After forming both the resists, applying and curing a substrate protective film;
And a step of removing both the resists after the substrate protective film is cured. A circuit board according to claim 1;
A semiconductor element mounted on an insulating substrate of the circuit board;
A fine metal wire for electrically connecting the wiring of the circuit board and the semiconductor element;
A resin for sealing the outer periphery of the semiconductor element on the circuit board;
A semiconductor device comprising: a protruding electrode provided on a metal wiring layer in an opening of a substrate protective film of the circuit board. A manufacturing method for manufacturing the semiconductor device according to claim 4,
Mounting a semiconductor element on a circuit board manufactured by the circuit board manufacturing method according to claim 3;
Electrically connecting the wiring of the circuit board and the semiconductor element by a wire bonding method using a fine metal wire;
Sealing the outer periphery of the semiconductor element on the circuit board with a resin;
A method of manufacturing a semiconductor device, comprising: providing a protruding electrode on the back surface of the circuit board by heating and melting metal balls on the bottom surface of the circuit board by reflow.

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