JP2005236215A - Method for manufacturing wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board having fewer defective parts wherein insulating foundation substrate is exposed to a solder resist layer and having excellent electrical insulation reliability of the solder resist layer. <P>SOLUTION: This method for manufacturing the wiring board comprises the steps of forming a first photosensitive resin layer 3a all over the upper surface of the insulating substrate 1 having a mounting region A in the central part of the upper surface wherein a plurality of connection pads 2a are formed, then so exposing that the part of the first photosensitive resin layer 3a located at the mounting region A is left as a non-exposed part N1, then forming a second photosensitive resin layer 3b all over the first photosensitive resin layer 3a, then so exposing that the parts of the first and the second photosensitive resin layers 3a, 3b located at the central part of the connection pads 2a are left as non-exposed parts N3, then so developing the first and the second photosensitive resin layers 3a, 3b that the non-exposed parts N3 on the connection pads 2a are removed, and then curing them to form a solder resist layer 3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides a solder resist having an opening for exposing a central portion of the connection pad on an insulating substrate having a connection pad to which an electrode of an electronic component such as a semiconductor integrated circuit element is connected via a solder bump on the upper surface. The present invention relates to a method of manufacturing a wiring board formed by depositing layers.

  Conventionally, wiring boards for mounting electronic components such as semiconductor integrated circuit elements have electrodes of electronic components connected via solder bumps to the center of the upper surface of an insulating substrate on which wiring conductors are formed from the upper surface to the lower surface. A solder resist layer having a mounting area on which a plurality of connection pads for connecting electronic components are formed and having an opening exposing the central portion of the connection pads for connecting electronic components is formed thereon Has been. According to this wiring board, after solder bumps are welded to the connection pads for connecting electronic components exposed from the solder resist layer, the electrodes of the electronic components are brought into contact with the solder bumps to melt the solder bumps. Thus, the electrode of the electronic component is electrically connected to the connection pad for connecting the electronic component via the solder bump, and the electronic component is mounted on the mounting area. An electronic device is obtained by filling a so-called protective resin.

The solder resist layer in such a wiring board is for maintaining good electrical insulation between the wiring conductors and connection pads on the upper surface of the insulating substrate, and is provided on the entire upper surface of the insulating substrate on which the connection pads are formed. After the photosensitive resin paste for solder resist is printed and applied and dried to form a photosensitive resin layer, the portion located on the center of the connection pad in the photosensitive resin layer remains as an unexposed portion. Then, the photosensitive resin layer is developed so that the unexposed portion located on the connection pad is removed, and then the remaining photosensitive resin layer is formed by ultraviolet curing and heat curing. In addition, in order to expose the photosensitive resin layer for solder resist formed on the insulating substrate, an exposure mask made of a resin film or a glass plate on the photosensitive resin layer for solder resist formed on the insulating substrate. Is used, and a method of exposing from above is employed.
JP-A-6-188544

  However, in such a wiring board, a photosensitive resin layer for a solder resist layer is formed on the upper surface of an insulating substrate, and then an exposure mask is placed on the photosensitive substrate layer for exposure, usually in a clean room. However, foreign matter having a size of about several tens of μm may adhere to the photosensitive resin layer or the exposure mask due to dust remaining slightly in the clean room. And when exposed with such foreign matter attached, the photosensitive resin layer of the part corresponding to the foreign substance is not sufficiently exposed and remains as an unexposed part after exposure, and when it is developed, the part of the part corresponding to the foreign substance is developed. The unexposed part is removed, and a defect part is formed in the solder resist layer where the underlying insulating substrate is exposed. As a result, the electrical insulation reliability of the solder resist layer may be impaired by the defect part. There was a problem that there was.

  The present invention has been devised in view of such conventional problems, and the purpose thereof is that the solder resist layer is hardly formed with a defective portion that exposes the underlying insulating substrate. An object of the present invention is to provide a wiring board having excellent electrical insulation reliability.

  The method for manufacturing a wiring board according to the present invention has a mounting region in which a plurality of connection pads to which electrodes of electronic components are connected via solder bumps are formed at the center of the upper surface, and the connection pads are formed from the upper surface to the lower surface. Forming a first photosensitive resin layer on the entire upper surface of the insulating substrate on which the electrically connected wiring conductor is formed, and a portion located on the mounting region in the first photosensitive resin layer; Exposing so as to remain as an unexposed portion, forming a second photosensitive resin layer on the entire exposed surface of the first photosensitive resin layer, and the first and second photosensitive resins Exposing so that a portion of the layer located on the central portion of the connection pad remains as an unexposed portion, and removing the unexposed portion on the connection pad from the first and second photosensitive resin layers Hard after developing By and is characterized by comprising the steps of forming a solder resist layer made of a cured product of said first and second photosensitive resin layer having an opening exposing the connection pads.

  In the method for manufacturing a wiring board according to the present invention, after a first photosensitive resin layer is formed on the entire upper surface of an insulating substrate having a mounting region in which a plurality of connection pads are formed, the first photosensitive resin layer After exposing so that the site | part located on a mounting area | region remains as an unexposed part, after forming the 2nd photosensitive resin layer on the whole exposed surface of the 1st photosensitive resin layer exposed next, 1st The second photosensitive resin layer is exposed so that the portion located on the center portion of the connection pad remains as an unexposed portion, and then the first and second photosensitive resin layers are exposed to the unexposed portion on the connection pad. Since the solder resist layer is formed after being developed so that the portion is removed and then cured, in the solder resist layer located on the region other than the mounting region of the insulating substrate, the first photosensitive resin layer or the first One of the two photosensitive resin layers Even if there is an unexposed portion due to foreign matter in the photosensitive resin layer, as long as the other photosensitive resin layer corresponding to the unexposed portion is exposed, the underlying insulating substrate is exposed to the solder resist layer. No defective part is formed. When there are unexposed portions that overlap each other in both the first and second photosensitive resin layers, a defective portion that exposes the underlying insulating substrate is formed in the solder resist layer at that portion. However, since the foreign matter is about several tens of μm at most and the ratio of such foreign matter is at most several percent, the first and second photosensitive elements are formed on the region other than the mounting region of the insulating substrate. The probability that the unexposed portions that overlap each other on both of the conductive resin layers is formed by foreign matters is about 1 / hundred trillion, and can be ignored. Further, in the solder resist layer located on the mounting area of the insulating substrate, there is an unexposed portion due to foreign matter in a portion other than on the connection pad of the first and second photosensitive resin layers, and the base is formed in that portion. Even if there is a defect that exposes the insulating substrate, in the mounting region of the insulating substrate, the defective part is protected by a protective resin filled between the mounting region and the electronic component after mounting the electronic component such as a semiconductor integrated circuit element. Therefore, there is no problem with the electrical insulation of the solder resist layer. Therefore, according to the method for manufacturing a wiring board of the present invention, it is possible to provide a wiring board having excellent electrical insulation reliability in the solder resist layer.

  Next, a method for manufacturing a wiring board according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an example of a wiring board manufactured by the manufacturing method of the present invention. In this figure, 1 is an insulating substrate, 2 is a wiring conductor, and 3 is a solder resist layer, and these mainly constitute a wiring substrate for mounting an electronic component 4 such as a semiconductor integrated circuit element.

  The insulating substrate 1 is made of, for example, an organic material such as glass-epoxy resin, functions as a support for the wiring conductor 2 and the solder resist layer 3, and an electronic component 4 such as a semiconductor integrated circuit element is mounted on the center of the upper surface thereof. Has a mounting area. Such an insulating substrate 1 is manufactured by laminating a plurality of uncured sheets obtained by impregnating a glass cloth with an uncured thermosetting resin, and thermally curing them.

  The insulating substrate 1 has through holes 5 from the upper surface to the lower surface, and a plurality of wiring conductors 2 made of copper foil or a copper plating layer are covered on the upper and lower surfaces and the inner surface of the through holes 5. It is formed. Further, the through hole 5 is filled with a hole filling resin 6 made of a thermosetting resin such as an epoxy resin.

  The wiring conductor 2 deposited on the insulating substrate 1 functions as a conductive path for connecting the electrode of the electronic component 4 mounted on the wiring substrate to an external electric circuit, and the wiring formed on the upper surface of the insulating substrate 1. A part of the conductor 2 is exposed to the mounting region to form a connection pad 2a for connecting an electronic component, and a part of the wiring conductor 2 formed on the lower surface forms a connection pad 2b for external connection. .

  In addition, a solder resist layer 3 having an opening that exposes the central portion of the connection pad 2a for connecting electronic components is deposited on the upper surface of the insulating substrate 1.

  The solder resist layer 3 is made of a heat-resistant resin such as an acrylic-modified epoxy resin, and protects the insulating substrate 1 from heat at the time of soldering and provides good electrical insulation between the wiring conductors 2 formed on the upper surface of the insulating substrate 1. It is formed by the method described later.

  According to this wiring board, the electrode of the electronic component 4 and the wiring conductor 2 are electrically connected by connecting the electrode of the electronic component 4 to the connection pad 2a for connecting the electronic component via the solder bump 7. At the same time, the electronic component 4 is mounted in the mounting region, and then the electronic component 4 is mounted on the wiring board by filling a protective resin 8 called underfill between the electronic component 4 and the mounting region.

  Next, a method for forming the solder resist layer 3 on the wiring board described above according to the manufacturing method of the present invention will be described. First, as shown in a sectional view of FIG. 2A, a first photosensitive resin layer 3a is formed on the entire upper surface of the insulating substrate 1 on which connection pads 2a for connecting electronic components are formed. The first photosensitive resin layer 3a is formed by applying a resin paste containing an acrylic modified epoxy resin having photosensitivity on the upper surface of the insulating substrate 1 using a screen printing method, and then performing a hot air drying method or an infrared drying method. It is formed by drying.

  Next, as shown in FIG. 2B, a first exposure mask (not shown) that shields a portion corresponding to the mounting area A of the insulating substrate 1 is placed on the first photosensitive resin layer 3a. Then, by irradiating with ultraviolet rays from above, exposure is performed so that the portion located on the mounting region A in the first photosensitive resin layer 3a remains as the unexposed portion N1. At this time, if foreign matter adheres on the first photosensitive resin layer 3a or the first exposure mask, the unexposed portion N2 is formed on the first photosensitive resin layer 3a corresponding to the portion where the foreign matter has adhered. It is formed.

  Next, as shown in FIG. 2C, a second photosensitive resin layer 3b is formed on the entire surface of the first photosensitive resin layer 3a. The second photosensitive resin layer 3b is formed by applying a resin paste containing an acrylic modified epoxy resin having photosensitivity on the first photosensitive resin layer 3a using a screen printing method, followed by a hot air drying method. Or by drying by infrared drying.

  Next, as shown in FIG. 2D, a second exposure mask (not shown) that shields light from a portion corresponding to the central portion of the connection pad 2a for connecting electronic components on the second photosensitive resin layer 3b. And the portion formed on the central portion of the connection pad 2a for connecting the electronic component in the second photosensitive resin layer 3a remains as an unexposed portion N3. Exposure. At this time, if foreign matter is adhered on the second photosensitive resin layer 3b or the second exposure mask, the unexposed portion N4 is formed on the second photosensitive resin layer 3b corresponding to the portion where the foreign matter is adhered. It is formed. Even if the unexposed portion N2 caused by the foreign matter is formed in the first photosensitive resin layer 3a and the unexposed portion N4 caused by the foreign matter is also formed in the second photosensitive resin layer 3b, the foreign matter is not detected. Has a small size of about several tens of μm and a foreign matter adherence ratio of about several percent, so that the unexposed portion N2 and the second photosensitive resin layer 3b formed on the first photosensitive resin layer 3a. The probability that the unexposed portions N4 formed in the upper and lower portions overlap each other is extremely low, about 1 / hundred trillion. Further, if the unexposed portion N2 of the first photosensitive resin layer 3a is caused by a foreign matter adhering to the first exposure mask, the unexposed portion is exposed when the second photosensitive resin layer 3b is exposed. Since N2 is also exposed at the same time, there is no unexposed portion N2. Therefore, the unexposed portion N2 formed on the first photosensitive resin layer 3a and the unexposed portion N4 formed on the second photosensitive resin layer 3b are hardly overlapped with each other.

  Next, as shown in FIG. 2 (e), the first and second photosensitive resin layers 3a and 3b are developed so that the unexposed portions N3 on the connection pads 2a for connecting electronic components are removed, UV cure and heat cure. At this time, even if the unexposed portion N2 due to the foreign matter is formed on the first photosensitive resin layer 3a, the second photosensitive resin layer 3b is present on the unexposed portion N2, so that development is performed. The unexposed portion N2 is not removed. Even if the unexposed portion N4 due to the foreign matter is formed on the second photosensitive resin layer 3b, the exposed first photosensitive resin layer 3a exists under the unexposed portion N4. Even if the unexposed portion N4 is removed by development, a defective portion that exposes the underlying insulating substrate 1 is not formed.

  Thus, according to the manufacturing method of the present invention, there is almost no defect that exposes the underlying insulating substrate 1 in the solder resist layer 3 located on the region other than the mounting region A of the insulating substrate 1. . Therefore, after the electrodes of the electronic component 4 are connected via the solder bumps 7 to the connection pads 2a for connecting the electronic components of the wiring board manufactured according to the present invention, the protective resin 8 is provided between the electronic component 4 and the mounting area A. When the electronic component 4 is mounted on the wiring board by filling the wiring board, it is possible to provide a wiring board that is extremely excellent in electrical insulation reliability in the solder resist layer 3.

  The present invention is not limited to the above-described embodiment, and for example, a build-up substrate in which wiring conductor layers and insulating layers are alternately stacked on an insulating base may be used as the wiring substrate.

It is sectional drawing which shows the embodiment of the wiring board manufactured by the manufacturing method of this invention. It is sectional drawing for every process for demonstrating the embodiment of the manufacturing method of the wiring board of this invention.

Explanation of symbols

1: Insulating substrate 2: Wiring conductor 2a: Connection pad to which electrode of electronic component is connected 3: Solder resist layer 3a: First photosensitive resin layer 3b: Second photosensitive resin layer 4: Semiconductor as electronic component Element 7: Solder bump A: Mounting area N1, N3: Unexposed area

Claims (1)

A wiring region electrically connected to the connection pad is formed from the upper surface to the lower surface, as well as having a mounting area in which a plurality of connection pads to which the electrodes of the electronic component are connected via solder bumps are formed at the center of the upper surface Forming a first photosensitive resin layer on the entire upper surface of the insulating substrate, and exposing the first photosensitive resin layer so that a portion located on the mounting region remains as an unexposed portion. A step of forming a second photosensitive resin layer on the entire exposed surface of the first photosensitive resin layer; and on a central portion of the connection pad in the first and second photosensitive resin layers. Exposing the first and second photosensitive resin layers so that the unexposed portions on the connection pads are removed, and exposing the exposed portion so as to leave the position as an unexposed portion; Exposed connection pad Wherein the first and second method for manufacturing a wiring substrate, characterized by comprising the steps of forming a solder resist layer made of a cured product of the photosensitive resin layer having openings for.

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