JP2000012726A - Formation of bump electrode on semiconductor mounting board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming bump electrodes required at the time of mounting a semiconductor chip on a circuit board by facedown mounting, in which the bump electrodes can be formed accurately on an electrode pattern formed on the circuit board without requiring a highly accurate mask or a process hard to implement even in the case of fine pitch. SOLUTION: This method comprises a step of forming a plating resist layer 3 on the entire semiconductor mounting face of a circuit board 1 where a circuit pattern 2 is formed, a first plating resist removing step for removing the plating resist layer 3 on the circuit pattern 2 which is bonded to a semiconductor element by means of laser, a step for applying electrolytic plating of same thickness as the plating resist layer 3 or less, and a second plating resist removing step for removing all of the plating resist layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming projecting electrodes on a circuit board in a so-called face-down mounting method in which bonding is performed with the circuit surface of a semiconductor chip facing the circuit board.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become lighter, thinner, smaller, and more multifunctional, the necessity of mounting semiconductor chips at high density has increased. In response to such needs, attention has been paid to flip-chip mounting in which a semiconductor chip is directly bonded face-down to a circuit board. In flip-chip mounting, it is common to form connection bumps called bumps on connection terminals of a semiconductor chip or a circuit board.

Conventionally, to form a bump on a circuit board, a thick glass paste film 7 is provided on the circuit board 1 and the circuit pattern 2 as shown in FIG.
(A)), and a photoresist 8 is applied thereon (FIG. 4)
(B)), and further, using a mask 9 to expose (FIG. 4 (C)), develop and provide an opening 10 at a bump forming position on the photoresist (FIG. 4 (D)), and then, a thick glass paste film 7 The bumps 5 are formed in the openings 11 formed by etching (FIGS. 4E to 4G).
No. 111338).

[0004]

However, the recent 200
In order to form the bumps 5 on the circuit pattern 2 formed at a narrow pitch of not more than μm by such a method, an extremely expensive high-precision mask 9 is required.
At the time of exposure, it is necessary to smooth the surface of the photoresist 8 so that the photoresist 8 and the mask 9 are firmly adhered. Further, in order to form the bumps 5 at a narrow pitch, it is necessary to accurately etch the glass paste film 7 with a very small diameter. It is very difficult, and it is difficult to form the bumps 5 on the circuit board at a narrow pitch according to the related art.

Accordingly, the present invention solves the above-mentioned problems, and realizes a high-precision mask and realization even at a narrow pitch when forming a projection electrode necessary for mounting a semiconductor chip on a circuit board by a face-down mounting method. It is an object of the present invention to provide a method for forming a protruding electrode on a semiconductor mounting substrate, which can accurately form a protruding electrode on an electrode pattern on a circuit board without requiring a difficult process.

[0006]

According to the present invention, there is provided a method for forming a protruding electrode on a substrate for mounting a semiconductor device, comprising the steps of: A plating resist layer forming step of forming a plating resist layer, a first plating resist removing step of removing a plating resist layer on a circuit pattern to be joined to a semiconductor element with a laser, and plating on a portion removed by the laser. An electrolytic plating forming step of performing electrolytic plating of the same thickness as or less than the resist layer, and a second plating resist removing step of removing all plating resist layers; Is achieved.

In the present invention, in the plating resist layer forming step, a plating resist layer is formed on the entire semiconductor mounting surface of the circuit board on which the circuit pattern has been formed. In the first plating resist removing step, the plating resist layer on the circuit pattern to be joined to the semiconductor element is removed by a laser.
In the electrolytic plating forming step, the portion removed by the laser is subjected to electrolytic plating having a thickness equal to or less than that of the plating resist layer. In the second plating resist removing step,
Remove all plating resist layers. In this way, the protruding electrodes formed by electrolytic plating are formed accurately by using a laser without using a high-precision jig or a process that is difficult to realize even on a narrow-pitch circuit pattern. can do.

In the present invention, preferably, the circuit pattern and the projecting electrode are made of copper, and the surface of the projecting electrode is plated with nickel and gold. Thus, it is possible to prevent an oxide film from being formed on the surface of the bump electrode made of copper, and to eliminate poor electrical connection.

In the present invention, preferably, the circuit pattern and the projecting electrode are made of copper, and the surface of the projecting electrode is plated with nickel and palladium. Thus, it is possible to prevent an oxide film from being formed on the surface of the bump electrode made of copper, and to eliminate poor electrical connection.

The object of the present invention is to provide a method for forming a bump electrode on a semiconductor mounting substrate, wherein a plating resist layer is formed on the entire semiconductor mounting surface of the circuit substrate on which a circuit pattern is formed. A plating resist layer forming step, a first plating resist removing step of removing a plating resist layer on a circuit pattern to be joined to the semiconductor element by a laser, and a plating resist layer having a thickness less than the plating resist layer on the surface on which the plating resist layer is formed. This is achieved by a method for forming a protruding electrode on a semiconductor mounting substrate, which includes an electroless plating forming step of performing electroless plating and a second plating resist removing step of removing all plating resist layers.

In the present invention, in the plating resist layer forming step, a plating resist layer is formed on the entire semiconductor mounting surface of the circuit board on which the circuit pattern has been formed. In the first plating resist removing step, the plating resist layer on the circuit pattern to be joined to the semiconductor element is removed by a laser.
In the electroless plating forming step, the surface on which the plating resist layer is formed is subjected to electroless plating with a thickness equal to or less than the plating resist layer. In the second plating resist removal step, all plating resist layers are removed. Thereby, a protruding electrode made of electroless plating can be formed. That is, even on a narrow-pitch circuit pattern, a protruding electrode can be accurately formed without requiring a high-precision jig or a process that is difficult to realize.

In the present invention, preferably, the circuit pattern and the projecting electrode are made of copper, and the surface of the projecting electrode is plated with nickel and gold. Thus, it is possible to prevent an oxide film from being formed on the surface of the bump electrode made of copper, and to eliminate poor electrical connection.

In the present invention, preferably, the circuit pattern and the projecting electrode are made of copper, and the surface of the projecting electrode is plated with nickel and palladium. Thus, it is possible to prevent an oxide film from being formed on the surface of the bump electrode made of copper, and to eliminate poor electrical connection.

[0014]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limits are given, the scope of the present invention is not limited to these modes unless otherwise specified in the following description.

FIG. 1 shows steps for explaining the bump forming method of the present invention. As shown in FIG. 1A, a plating resist layer 3 is formed on a circuit board 1 on which a circuit pattern 2 is formed and on the circuit pattern 2. Circuit pattern 1
Is generally copper, and the circuit board 1 is a glass epoxy board, a ceramic board, a polyimide board, or the like.

Next, as shown in FIG. 1B, the portion of the plating resist layer in the electrode pattern portion of the circuit pattern 2 is removed using a laser beam L generated by a laser drilling device LU. An opening 4 is formed in 3.
By using the laser beam L, a jig such as a mask is not required, so that the opening 4 can be formed by a simple process of simply irradiating the laser beam L. Here, if a laser such as a CO ₂ laser is used, for example, it is easy to selectively remove only the plating resist layer 3 without removing the circuit pattern 2, which is suitable for the present process. Other types of lasers can also be used by adjusting the conditions of lasing.

After the opening 4 is formed, as shown in FIG. 1C, the electrode pattern 2A in the opening 4 is grown by electrolytic plating, and a bump (protruding electrode) 5 is formed.
Electroplating generally uses copper plating, but can also be realized using other metal plating. Also, by setting the thickness of the plating equal to or less than the thickness of the plating resist layer 3, the bumps 5 having a uniform shape can be formed. Further, as shown in FIG. 1D, the circuit board 1 having the bumps 5 is formed by removing all the remaining plating resist layers 3. In addition, bump 5
Is formed by electrolytic copper plating, an oxide film is likely to be formed on the bump surface.
In some cases, nickel and gold plating or nickel and palladium plating may be performed after the bumps 5 are formed, since electrical connection failures may occur.

Next, an embodiment of the present invention using electroless plating will be described below. FIG. 2 shows steps for explaining a method for forming a bump electrode of the present invention using electroless plating. In the same manner as the above-described method of forming the protruding electrodes by the electrolytic plating, the plating resist layer 3 is entirely formed on the circuit board 1 as shown in FIG. As shown in FIG. 2B, the opening 4 is formed by removing the portion of the plating resist layer 3 of the electrode pattern portion 2 with the laser light L of the laser drilling device LU.

Next, as shown in FIG. 2C, electroless plating 6 is applied to the entire surface of the circuit board 1 on which the semiconductor is mounted. In the opening 4, an electroless plating layer 6 is formed on the plating resist layer 3 at the same time when the electroless plating bump 5 </ b> A is formed. Electroless plating generally uses copper plating, but can also be realized by using other metal plating.
Further, in the step of removing all the plating resist described later, the thickness of the plating is set to be equal to or less than the thickness of the plating resist layer 3 so that the electroless plating layer 6 can be removed. Furthermore,
By removing the plating resist layer 3, all of the electroless plating layer 6 is also removed, thereby forming a circuit board having the bumps 5A. Further, for the same reason as the case where the bumps 5 are formed by the electrolytic copper plating, nickel and gold plating or nickel and palladium plating may be performed after the bumps are formed. That is, the bump 5A is
If formed by electrolytic copper plating, an oxide film is likely to be formed on the bump surface, which may cause electrical connection failure in face-down mounting. In such a case, nickel and gold plating or nickel plating It is preferable to perform palladium plating after the formation of the bump 5A.

FIG. 3 is a perspective view of a bump formed on a circuit pattern of the circuit board according to the present embodiment. Electrolytic plating,
Alternatively, bumps 5 and 5A formed by electroless plating are formed on the electrode pattern portion 2A on the circuit pattern 2. The diameters a of the bumps 5 and 5A are shown in FIGS. 1B and 2B.
Various values can be set according to the oscillation condition of the laser beam L in the step. By setting appropriate laser light conditions, the diameter a of the bumps 5, 5A can be set to 50 μm.
Alternatively, it can be less. Therefore, even if the pitch b of the electrode pattern portion 2A of the circuit pattern 2 is a very narrow value of, for example, 60 μm, by setting the diameter a of the bumps 5, 5A to 50 μm or less,
The bumps 5 and 5A can be formed. The height c of the bumps 5 and 5A is very small because the bumps 5 and 5A are formed by plating, so that there is little variation. It is possible to form the bumps 5 and 5A with high precision.

As is apparent from the above description, according to the embodiment of the present invention, by using a laser (laser light), a narrow pitch can be obtained by a simple process that does not require a jig such as a mask. Corresponding bumps can be formed on the electrode pattern portion on the circuit pattern of the circuit board. In addition, by using the plating method, the height of the bump can be freely set, and the bump can be formed with high accuracy with little variation in height. Furthermore, when the circuit pattern and plating are copper, nickel and gold plating or nickel and palladium plating after bump formation can prevent poor electrical connection during face-down bonding.
By using the laser and the plating method, it is possible to form bumps with high accuracy and with a simple process even on a narrow-pitch electrode pattern, which has been conventionally difficult.

According to the present invention, when forming bumps necessary for mounting a semiconductor chip on a circuit board by a face-down mounting method, a highly accurate mask and a process difficult to realize are required even at a narrow pitch. The bumps can be accurately formed on the electrode patterns on the circuit board. According to the bump forming method of the present invention, a bump can be formed accurately even on a narrow-pitch circuit pattern without requiring a high-precision jig or a process that is difficult to realize.

[0023]

As described above, according to the present invention,
By using the face-down mounting method, when forming the protruding electrodes necessary for mounting a semiconductor chip on a circuit board, the protruding electrodes can be formed without requiring a highly accurate mask or a process difficult to realize even at a narrow pitch. It can be accurately formed on the electrode pattern on the circuit board.

[Brief description of the drawings]

FIG. 1 is a view showing a preferred embodiment of a method for forming a bump electrode on a semiconductor mounting substrate of the present invention.

FIG. 2 is a diagram showing another embodiment of a method for forming a bump electrode on a semiconductor mounting substrate according to the present invention.

FIG. 3 is a perspective view showing an example of a bump electrode on the semiconductor mounting substrate obtained in FIG. 1 or FIG. 2;

FIG. 4 is a diagram showing an example of forming a conventional bump electrode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Circuit board, 2 ... Circuit pattern, 2A ...
Electrode pattern portion of circuit pattern, 3 ... plating resist layer, 4 ... opening formed in plating resist layer,
5 ... Bump formed by electrolytic plating, 5A ...
· Bumps formed by electroless plating, 6 · · · electroless plating layer on plating resist layer, 7 · · · thick glass paste film, 8 · · · photoresist, 9 · · mask · 10 · · · · An opening formed in a photoresist, 1
1. Opening formed in thick glass paste

Claims (6)

[Claims] 1. A method for forming a protruding electrode on a substrate for mounting a semiconductor, comprising: a plating resist layer forming step of forming a plating resist layer on an entire surface of a semiconductor mounting surface of a circuit board on which a circuit pattern is formed; A first plating resist removing step of removing a plating resist layer on a circuit pattern to be joined with a laser, and electrolytic plating of a thickness equal to or less than that of the plating resist layer on a portion removed by the laser. A method for forming a protruding electrode on a semiconductor mounting substrate, comprising: an electrolytic plating forming step to be performed; and a second plating resist removing step for removing all plating resists. 2. The method according to claim 1, wherein the circuit pattern and the projecting electrode are made of copper, and the surface of the projecting electrode is plated with nickel and gold. 3. The method according to claim 1, wherein the circuit pattern and the protruding electrode are made of copper, and the surface of the protruding electrode is plated with nickel and palladium. 4. A method for forming a bump electrode on a substrate for mounting a semiconductor, comprising: a plating resist layer forming step of forming a plating resist layer over the entire semiconductor mounting surface of a circuit board on which a circuit pattern is formed; A first plating resist removal step of removing a plating resist layer on a circuit pattern to be joined with a laser by using a laser; And a second plating resist removing step of removing all plating resist layers. 5. The method according to claim 4, wherein the circuit pattern and the protruding electrode are made of copper, and the surface of the protruding electrode is plated with nickel and gold. 6. The method according to claim 4, wherein the circuit pattern and the protruding electrode are made of copper, and the surface of the protruding electrode is plated with nickel and palladium.