JPH05315732A - Manufacture of wiring board - Google Patents

Abstract

PURPOSE:To accurately form a protective coat in the parts other than the top face of a wiring pattern. CONSTITUTION:After a wiring pattern 14 having a magnetic material film 13 is formed on an insulating substrate 11, a photosensitive resin film 15 is formed on the whole surface; and after magnetic material particles 16 are scattered on the resin film, a magnetic field is generated between above and below the substrate 11. Then, magnetic flux concentrates on the wiring pattern 14 so that the magnetic material particles 16 on the wiring pattern 14 are fixed by magnetic force on the top face of the photosensitive resin film 15, and when the magnetic material particles 16 in other parts are removed in the fixed state by vacuum suction, etc., a photomask can be formed of the magnetic material particles 16 in a self-aligning manner on the top face of the photosensitive resin film 15 above the wiring pattern 14. When the photosensitive resin film 15 is exposed and developed by the use of this mask, a protective coat can be accurately formed while the photosensitive resin film 15 is accurately left in the parts other than the top face of the wiring pattern 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board manufacturing method.

[0002]

2. Description of the Related Art As one of wiring boards, there is one in which a wiring pattern is formed on an insulating substrate and the surface of the insulating substrate other than this wiring pattern is covered with a protective film thicker than the wiring pattern. This wiring board is used for connection with an IC chip having solder bumps, and the protective film formed to be thicker than the wiring pattern has a solder on a portion other than the wiring pattern when the solder bump is melt-bonded to the wiring pattern. In addition to serving as a flow stop so as not to flow out, it also serves to protect the surface of the insulating substrate.

Conventionally, such a wiring board is manufactured as shown in FIGS. First, as shown in FIG. 7, the wiring pattern 2 is formed on the insulating substrate 1. Next, as shown in FIG. 8, a negative photosensitive resin film 3 is formed on the surface of the insulating substrate 1 including the upper surface of the wiring pattern 2.
Then, a photomask 4 is provided above the photosensitive resin film 3. At this time, the photomask 4 has the wiring pattern 2
The light shielding portion 4a is located above the wiring pattern 2 and the light transmitting portion 4b is located in a portion other than above the wiring pattern 2 such as between the wiring patterns 2. Thereafter, the photosensitive resin film 3 is exposed to light such as ultraviolet light through the photomask 4. As a result, the photosensitive resin film 3 is cured by light irradiation only in the portion other than the upper surface of the wiring pattern 2.
Therefore, when the photosensitive resin film 3 is developed next, as shown in FIG. 9, the photosensitive resin film 3 on the upper surface of the wiring pattern 2 is removed, and the photosensitive resin film 3 other than the upper surface of the wiring pattern 2 is removed.
The remaining photosensitive resin film 3 completes the protective film except the upper surface of the wiring pattern 2. In this way, the wiring substrate having the wiring pattern 2 other than the upper surface covered with the protective film is completed.

[0004]

However, in the conventional manufacturing method as described above, when the photomask 4 is displaced as shown in FIG. 10, as shown in FIG. Resin film 3) partially overlaps the upper surface of the wiring pattern 2, or the protective film and the wiring pattern 2 are formed.
A gap may be formed in some cases, which makes it difficult to accurately form the protective film on a portion other than the upper surface of the wiring pattern 2. Especially, the positional accuracy of the photomask 4 is ± 50μ.
Since it is about m, for example, width 50 μm, pitch 100 μ
In the fine wiring pattern 2 of m, the wiring pattern 2
It is very difficult to form the protective film accurately. Then, when the displacement occurs as shown in FIG. 11, the wiring pattern 2
When the solder bumps of the IC chip are fused and connected to the upper side, the solder bumps are not accurately positioned on the wiring pattern 2, the reliability of the connection is lowered, and the solder flows out into the gap (insulating substrate 1). However, there is a problem that the exposed portion of the insulating substrate that is not covered with the protective film is not protected.

The photosensitive resin film 3 is exposed from the back surface side of the insulating substrate 1 using the wiring pattern 2 as a photomask and developed, so that portions other than the upper surface of the wiring pattern 2 are self-aligned with the wiring pattern 2. It is conceivable to form a protective film, but in that case the insulating substrate 1 needs to have a light-transmitting property, and if the insulating substrate 1 does not have a light-transmitting property, this method cannot be adopted.

An object of the present invention is to provide a method of manufacturing a wiring board which can form a protective film accurately on a portion other than the upper surface of a wiring pattern.

[0007]

According to the present invention, after forming a wiring pattern having at least a part of a layer made of a magnetic material on an insulating substrate, the wiring pattern is formed on the surface of the insulating substrate including the upper surface of the wiring pattern. A negative photosensitive resin film is formed, and a large number of magnetic particles are provided on the upper surface of the resin film, and then a magnetic field is applied to position the upper surface of the resin film above the wiring pattern. The magnetic particles are fixed by magnetic force, the magnetic particles that are not located above the wiring pattern on the upper surface of the resin film in that state are removed, and then the remaining magnetic particles are used as a photomask for the resin film. The resin film on the upper surface of the wiring pattern is removed together with the remaining magnetic particles by exposing and then developing the resin film on a portion other than the upper surface of the wiring pattern. It is obtained by the Suyo.

[0008]

According to the present invention, when a magnetic field is applied, magnetic flux concentrates on the wiring pattern having at least a part of the layer made of a magnetic material. The magnetic particles that are fixed to the upper surface of the photosensitive resin film and are not located above the wiring pattern in that state are removed by vacuum suction or the like. The photomask can be accurately formed in a self-aligning manner. Therefore, using this photomask to expose the photosensitive resin film,
By developing, it is possible to accurately remove only the photosensitive resin film on the upper surface of the wiring pattern together with the remaining magnetic particles, and accurately leave the photosensitive resin film as a protective film only on the portion other than the upper surface of the wiring pattern. ..

[0009]

1 to 5 are sectional views showing an embodiment of the present invention in the order of steps. An embodiment of the present invention will be described below with reference to these drawings. First, as shown in FIG. 1, a metal pattern 12 made of a metal such as copper is formed in a wiring pattern shape on an insulating substrate 11 made of resin or ceramic by a known photolithography method. Next, a magnetic film 13 made of nickel or permalloy (alloy of nickel and iron) or the like is formed on the surface of the metal pattern 12 by plating, for example, electrolytic plating. As a result, a metal pattern 12 made of copper or the like and a magnetic film 13 are formed on the insulating substrate 11.
The wiring pattern 14 having a layered structure is completed. Next, a negative photosensitive resin film 15 is formed on the surface of the insulating substrate 11 including the upper surface of the wiring pattern 14 by roll coating or spin coating, as shown in FIG. Then, magnetic particles 16 made of iron or the like are dispersed on the photosensitive resin film 15.

After that, a magnetic field is generated between above and below the insulating substrate 11. Then, the magnetic flux penetrating the insulating substrate 11 thus generated is concentrated on the wiring pattern 14 having the magnetic film 13 as indicated by an arrow in FIG.
Therefore, the magnetic particles 16 above the wiring pattern 14
Will be fixed to the upper surface of the photosensitive resin film 15 by the magnetic force. Then, with the magnetic field being generated as it is, the magnetic particles 16 located on the upper surface of the photosensitive resin film 15 other than above the wiring pattern 14 where the magnetic flux is small are replaced with the magnetic particles above the wiring pattern 14. Suction and remove 16 with a vacuum pressure that does not suck up. The state after the removal by suction is shown in FIG.

Then, in the state where the magnetic field is generated as it is or the state where the magnetic field is eliminated (whichever is acceptable), the magnetic particles 16 on the upper surface of the photosensitive resin film 15 above the wiring pattern 14 are used as a photomask in FIG. As shown, the photosensitive resin film 15 is exposed to light such as ultraviolet light. As a result, only the portion of the photosensitive resin film 15 other than the upper surface of the wiring pattern 14 is cured by light irradiation. Therefore, when the photosensitive resin film 15 is developed next, the photosensitive resin film 15 on the upper surface of the wiring pattern 14 is removed together with the remaining magnetic particles as shown in FIG. Only the resin film 15 remains, and the remaining photosensitive resin film 1
By 5, the protective film is completed on the part other than the upper surface of the wiring pattern.
Thus, the wiring board in which the upper surface of the wiring pattern 14 is covered with the protective film is completed.

According to the manufacturing method as described above, the magnetic flux penetrating the insulating substrate 11 when the magnetic field is generated between the upper side and the lower side of the insulating substrate 11 is concentrated on the wiring pattern 14 and the wiring pattern 14 is formed. The upper magnetic particles 16 are the photosensitive resin film 1
Since a photomask for exposure can be accurately formed in a self-aligned manner with the magnetic particles 16 on the upper surface of the photosensitive resin film 15 above the wiring pattern 14 by being fixed to the upper surface of the photomask by magnetic force. Using a photosensitive resin film 1
By exposing and developing 5, the protective film can be accurately formed by leaving the photosensitive resin film 15 on the portion other than the upper surface of the wiring pattern 14 accurately. Therefore, when the IC chip 22 having the solder bumps 21 is mounted on the wiring board by the above manufacturing method as shown in FIG. 6, the solder bumps 21 are accurately aligned on the wiring pattern 14 and the reliability of connection is improved. At the same time, the protective film (photosensitive resin film 15) reliably prevents the solder from flowing out onto the insulating substrate 11. In addition, the wiring pattern 1 on the insulating substrate 11
Since the part between 4 is completely covered by the protective film,
The surface of the insulating substrate 11 can be reliably protected.

In the above embodiment, the wiring pattern 1
Although only the surface layer of No. 4 is formed of the magnetic film 13, the entire wiring pattern may be formed of the magnetic film.

[0014]

As described above, according to the present invention, a photomask can be accurately formed in a self-aligned manner by magnetic particles on the upper surface of the photosensitive resin film above the wiring pattern. The protective film can be accurately formed by leaving the photosensitive resin film exactly at the portion, and the mounted state can be improved when the IC chip having the solder bump is mounted, for example.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a wiring pattern forming step in an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a step that follows FIG. 1 in one embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a step that follows FIG. 2 in one embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a step that follows FIG. 3 in one embodiment of the present invention.

5 is a cross-sectional view showing a step that follows FIG. 4 in an embodiment of the present invention. FIG.

FIG. 6 is a sectional view showing a state in which an IC chip is mounted on a wiring board manufactured according to an embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a wiring pattern forming step in a conventional manufacturing method.

FIG. 8 is a cross-sectional view showing a step that follows the step of FIG. 7 in a conventional manufacturing method.

FIG. 9 is a cross-sectional view showing a step that follows the step of FIG. 8 in the conventional manufacturing method.

FIG. 10 is a cross-sectional view showing a state where a photomask is displaced in a conventional manufacturing method.

FIG. 11 is a cross-sectional view showing a state in which the protective film is displaced in the conventional manufacturing method.

[Explanation of symbols]

 11 Insulating Substrate 13 Magnetic Film 14 Wiring Pattern 15 Photosensitive Resin Film 16 Magnetic Particles

Claims (1)

[Claims] 1. A negative photosensitive resin film is formed on a surface of the insulating substrate including an upper surface of the wiring pattern after forming a wiring pattern having at least a part of a layer made of a magnetic material on the insulating substrate. After forming a large number of magnetic particles on the upper surface of the resin film, a magnetic field is applied to fix the magnetic particles located above the wiring pattern on the upper surface of the resin film by magnetic force. In that state, removing the magnetic particles not located above the wiring pattern on the upper surface of the resin film, exposing the resin film with the remaining magnetic particles as a photomask, and then developing. The resin film on the upper surface of the wiring pattern is removed together with the remaining magnetic particles so that the resin film is left on a portion other than the upper surface of the wiring pattern. Wiring board manufacturing method.