JP2002290022A - Wiring board, its manufacturing method, and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board which is capable of surely joining a solder bonding pad that appears from a through-hole provided to a solder-resistant resin layer to the electrode of an electronic part through the intermediary of solder and of normally operating the electronic part mounted on it for a long term. SOLUTION: A solder bonding pad 4 joined to the electrode of an electronic part 5 through the intermediary of solder is provided to an electronic part mounting region on an insulating board 1, and a solder-resistant resin layer 3 which is provided with a through-hole 10 that makes the center of the solder bonding pad 4 exposed is deposited on the electronic part mounting region, so as to cover the peripheral part of the solder bonding pad 4 for the formation of a wiring board. The through-hole 10 whose diameter 10a on a solder bonding pad side is 50 to 95% of the diameter 11b of its opening on the top surface of the resin layer 3, and the solder bonding pad 4 has a nearly spherical recess 11 at its center.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board used for mounting an electronic component such as a semiconductor element, a method of manufacturing the same, and an electronic device having the wiring board mounted with an electronic component such as a semiconductor element. It is.

[0002]

2. Description of the Related Art In general, current electronic devices are required to be small, thin, lightweight, high-performance, high-performance, high-quality, and high-reliable, as represented by mobile communication devices. Electronic devices mounted on various electronic devices have also been required to be reduced in size and density. For this reason, there has been a demand for smaller, thinner, and more terminals for the wiring boards that make up the electronic device, and in order to achieve this, the width of wiring conductors such as signal conductors has been reduced and the spacing between them has been reduced. High-density wiring has been achieved by increasing the number of wiring conductors.

As a wiring board capable of such high-density wiring, a wiring board manufactured by employing a build-up method is known. The build-up method means that, for example, a reinforcing material such as glass cloth or aramid non-woven fabric is impregnated with a thermosetting resin typified by an epoxy resin having heat resistance and chemical resistance, and a core cured by impregnation with After applying a varnish made of a thermosetting resin such as a resin and heat-curing to form an insulating layer, a via hole having a diameter of about 50 to 200 μm is formed in the insulating layer by laser light, and then the insulating layer surface and The inner wall of the via hole is chemically roughened with a roughening solution such as a potassium permanganate solution, and thereafter, a wiring conductor is formed on the inner wall of the via hole and the surface of the insulating layer using an electroless copper plating method and an electrolytic copper plating method. This is a method for manufacturing a wiring board in which an insulating layer and a wiring conductor are formed by repeating the same steps as above on the insulating layer. The wiring board has solder bonding pads formed on the outermost surface of the insulating layer and serving as connection terminals for mounting electronic components and the like and solder bonding pads connected to the wiring conductors of the external electric circuit board. And
Further, on the surface of the insulating layer including the outer peripheral portion of the solder bonding pad, a solder-resistant resin layer having a through hole exposing the central portion of the solder bonding pad is formed.

[0004] Such a solder-resistant resin layer is formed by applying an uncured resin liquid comprising a photosensitive resin, an inorganic powder filler and a photoinitiator to the outermost insulating layer or wiring conductor by using a roll coater method or a screen printing method.・ Applied to the entire surface of the solder bonding pad to a predetermined thickness and dried to form a coating on the surface of the insulating layer. The through-hole is exposed and developed on the solder-resistant resin layer to perform soldering. After being formed on the bonding pad, and after light curing and heat curing, the surface of the solder bonding pad is roughened to remove the residue of the solder resistant resin layer.
It is formed by soft etching. further,
The exposed surface of the solder bonding pad is coated with nickel / gold plating having good wettability with solder. Further, the diameter of the through hole on the solder bonding pad is substantially equal to the diameter of the solder bonding pad on the side of the solder bonding pad, and the surface of the solder bonding pad is flat.

[0005] A solder paste is filled into the through-holes on the solder bonding pads by screen printing, and the solder paste is melted and solidified by passing through a reflow furnace to form solder bumps. An electronic device is manufactured by electrically connecting the solder bonding pad of the wiring board to the connection terminal of the electronic component through the intermediary, and then bonding the wiring board and the electronic component with an underfill material. This electronic device is mounted on an external electric circuit board by connecting solder joint pads for connecting external terminals to wiring conductors of the external electric circuit board via solder bumps.

[0006]

However, in the conventional wiring board, the diameter of the through-hole of the solder-resistant resin layer on the solder-bonding pad is substantially equal to the diameter of the through-hole on the side of the solder-bonding pad. When the opening diameter of the through hole is smaller than about 90 μm, the solder paste is filled only halfway through the through hole during screen printing, and when the wiring board is passed through a reflow furnace in this state, the solder bump is not well bonded to the solder bonding pad. This causes a problem in that the solder bumps are detached from the solder bonding pads when the electronic component is mounted, resulting in poor connection.

Further, in the conventional wiring board, since the surface of the solder bonding pad is flat, the corner between the surface in contact with the side surface of the through hole of the solder bump and the surface in contact with the surface of the solder bonding pad is a right angle, Due to the surface tension of the solder, it is difficult for the solder to penetrate the right-angled corners, and voids are created in the corners. As a result, the bonding area between the solder bumps and the solder bonding pads decreases, and the bonding strength between the two decreases. Had the problem that

Furthermore, in the solder bump, the corner between the surface in contact with the side surface of the through hole of the solder bump and the surface in contact with the surface of the solder bonding pad is an intersection between the solder, the solder bonding pad and the solder-resistant resin layer. The stress caused by the expansion and contraction of the solder and solder joint pads and the solder-resistant resin layer with different thermal expansion coefficients generated by the heat generated during the operation of electronic components concentrates on the corners, and such stress is applied for a long time. When voltage is repeatedly applied to the corners, cracks occur at the corners between the surface that contacts the side surface of the through hole of the solder bump and the surface that contacts the surface of the solder bonding pad, causing disconnection, and normal operation of electronic components. There was also a problem that it became impossible.

Further, in the conventional method of manufacturing a wiring board, a through-hole of a solder-resistant resin layer is formed by exposure and development, and then the surface of the solder bonding pad is roughened to remove the residue of the solder-resistant resin layer. The surface of the solder-resistant resin layer is also roughened at the same time, the resin on the surface of the solder-resistant resin layer deteriorates, and the adhesion strength between the underfill material and the surface of the solder-resistant resin layer during mounting decreases. Had the problem that

The present invention has been completed in view of the problems of the prior art, and an object of the present invention is to form a solder bump between an exposed solder joint pad provided in a solder-resistant resin layer and an electrode of an electronic component by a solder bump. It is an object of the present invention to provide a wiring board, a method of manufacturing the same, and an electronic device, which can be securely joined via a wiring board and can normally operate electronic components mounted on the wiring board for a long period of time.

[0011]

According to the present invention, there is provided a wiring board provided with a solder bonding pad to which an electrode of an electronic component is bonded via solder in an electronic component mounting area on an insulating substrate, and a solder bonding pad in the electronic component mounting area. A wiring board comprising a solder-resistant resin layer having a through hole that covers an outer peripheral portion of the pad and exposes a central portion of the solder bonding pad, wherein the diameter of the through hole has an opening diameter on the solder bonding pad side. And the solder bonding pad has a substantially spherical concave portion at the center thereof.

Further, the method of manufacturing a wiring board according to the present invention includes a step of forming a solder joint pad to which an electrode of an electronic component is joined via solder in an electronic component mounting area on an insulating substrate; A step of covering the solder bonding pad with a solder-resistant resin layer, and a step of irradiating the solder-resistant resin layer on the central part of the solder bonding pad with a laser beam having a wavelength of 8 to 11 μm to form a through hole. A step of irradiating a laser beam having a wavelength of 0.1 to 1 μm to a central portion of the solder bonding pad exposed by the through hole to form a substantially spherical concave portion.

Furthermore, an electronic device according to the present invention is characterized in that an electronic component is mounted on the electronic component mounting area of the wiring board, and a solder joint pad and an electrode of the electronic component are connected via solder. It is.

According to the wiring board of the present invention, since the diameter of the through hole of the solder-resistant resin layer on the side of the solder bonding pad is 50 to 95% of the opening diameter, the vertical cross section of the through hole has an opening diameter of solder. It becomes a funnel shape larger than the diameter of the bonding pad side, and even if the opening diameter of the through hole is smaller than about 90 μm, the solder paste can be easily and sufficiently filled into the through hole during screen printing, and as a result, the wiring board When the solder paste is melted and solidified to form solder bumps through a reflow furnace, the solder joint pads and solder bumps can be securely joined, and the solder joint pads and solder bumps may peel off when mounting electronic components. And a wiring board with good electrical connection can be obtained.

Further, according to the wiring board of the present invention, the diameter of the through hole of the solder-resistant resin layer on the side of the solder bonding pad is set to 50 to 50 mm of the opening diameter.
The corner between the surface that contacts the side surface of the through hole of the solder bump and the surface that touches the surface of the solder bonding pad because 95% is set and a substantially spherical concave portion is formed in the center of the solder bonding pad exposed from the through hole. Has a curved shape, the solder can easily penetrate into the corners, and no voids are formed in the corners, so that the bonding area between the solder bumps and the solder bonding pads increases, and as a result, The bonding strength between the bump and the solder bonding pad does not decrease. Furthermore, the stress generated by the heat generated during the operation of the electronic component due to the expansion and contraction of the solder and the solder joint pad / solder-resistant resin layer having different coefficients of thermal expansion concentrates on the corners, causing cracks at the corners. Thus, a wiring board that can normally operate electronic components for a long period of time can be provided.

According to the method of manufacturing a wiring board of the present invention, the wavelength of 8 to 10 mm is applied to the solder-resistant resin layer on the central portion of the solder joint pad.
After irradiating a laser beam of 11 μm to form a through hole, a wavelength of 0.1 mm is applied to the center of the solder bonding pad exposed from the through hole.
Since a substantially spherical concave portion is formed by irradiating a laser beam of about 1 μm, a through hole can be easily formed in the solder-resistant resin layer with a laser beam having a wavelength of 8 to 11 μm. Even if the solder resin remains, the residual solder resin on the solder bonding pads can be completely removed with a laser beam having a wavelength of 0.1 to 1 μm, so that the roughening step can be omitted and the resin on the surface of the solder resin layer deteriorates. The bonding strength between the underfill material and the solder-resistant resin layer at the time of mounting does not decrease.

According to the electronic device of the present invention, the electronic component is mounted on the electronic component mounting area of the wiring board, and the solder bonding pad and the electrode of the electronic component are connected via the solder. Even if the stress due to the heat generated during operation is repeatedly applied to the corner between the surface in contact with the side surface of the through hole of the solder bump and the surface in contact with the surface of the solder bonding pad for a long time, the stress does not concentrate on the corner. In addition, it is possible to prevent the occurrence of cracks at the corners, and as a result, it is possible to provide an electronic device that can normally operate electronic components for a long period of time.

[0018]

Next, a wiring board and an electronic device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of an embodiment in which an electronic component is mounted on a wiring board of the present invention and applied to an electronic device, and FIG. 2 is a cross-sectional view of a main part thereof. In these figures, 1 is an insulating substrate, 2 is a wiring conductor, 3 is a solder-resistant resin layer,
Reference numeral 4 denotes solder bonding pads, which mainly constitute a wiring board of the present invention, and an electronic device of the present invention is formed by mounting an electronic component 5 such as a semiconductor element thereon.

The insulating substrate 1 has a function of mounting electronic components. For example, the insulating substrate 1 has a plate-like shape obtained by impregnating a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin into a glass cloth in which glass fibers are woven vertically and horizontally. An organic material-based multilayer board in which a plurality of insulating layers 1b made of a thermosetting resin such as an epoxy resin or a modified polyphenylene ether resin are laminated on the upper and lower surfaces of the core body 1a, respectively. A plurality of wiring conductors 2 made of a foil, a copper plating film or the like are formed.

The core 1a constituting the insulating substrate 1 functions as a support for the insulating layer 1b, has a thickness of about 0.3 to 1.5 mm, and has a plurality of through-holes having a diameter of about 0.1 to 1.0 mm from the upper surface to the lower surface. It has a hole 6. A part of the wiring conductor 2 is attached to the upper and lower surfaces and the inner wall of each through hole 6, and the upper and lower wiring conductors 2 are electrically connected through the through holes 6.

Such a core body 1a is manufactured by thermally curing a sheet in which a glass cloth is impregnated with an uncured thermosetting resin, and then drilling the sheet from the upper surface to the lower surface. The wiring conductors 2 on the upper and lower surfaces of the core 1a
Has a thickness of 3 to 50 μm on the entire upper and lower surfaces of the sheet for the core 1a.
And a predetermined pattern is formed by attaching the copper foil and etching the copper foil after curing the sheet. The wiring conductor 2 on the inner wall of the through hole 6
After the through hole 6 is provided in the core body 1a, the through hole 6 is formed by depositing a copper plating film having a thickness of about 3 to 50 μm in the through hole 6 by an electroless copper plating method and an electrolytic copper plating method.

Further, the core body 1a has its through hole 6
Is filled with a resin column 7 made of a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin.
The resin pillar 7 is for enabling the insulating layer 1b to be formed directly above and directly below the through hole 6 by closing the through hole 6, and the uncured paste-like thermosetting resin is placed in the through hole 6. Filled by screen printing method,
After being thermally cured, the upper and lower surfaces are polished so as to be substantially flat. An insulating layer 1b is laminated on the upper and lower surfaces of the core 1a including the resin columns 7.

Insulating layers 1b laminated on the upper and lower surfaces of the core 1a
Has via holes 8 each having a thickness of about 10 to 80 μm and a diameter of about 20 to 100 μm from the upper surface to the lower surface of each layer. These insulating layers 1b are made of a wiring conductor 2
In order to provide an insulating space for wiring at high density. By electrically connecting the upper layer wiring conductor 2 and the lower layer wiring conductor 2 via the wiring conductor 2 formed on the inner wall of the via hole 8, a high-density wiring can be formed three-dimensionally.

Such an insulating layer 1b has a thickness of 20 to 60 μm.
m of uncured thermosetting resin film is adhered to the upper and lower surfaces of the core body 1a, which is thermally cured, a via hole 8 is formed by laser processing, and the next insulating layer 1b is similarly formed thereon. Are sequentially stacked. The wiring conductor 2 formed on the surface of the insulating layer 1b and the inner wall of the via hole 8 serves as a conductive path for connecting each electrode of the electronic component 5 such as a mounted semiconductor element to an external electric circuit board (not shown). Function of each insulating layer 1b
Each time a pattern is formed, a copper plating film having a thickness of about 3 to 50 μm is formed on the surface of each insulating layer 1b and the inner wall of the via hole 8 by a conventionally known pattern forming method such as a semi-additive method or a subtractive method. It is formed by putting on.

Further, a part of the wiring conductor 2 formed on one outermost layer surface of the insulating layer 1b is joined to each electrode of the electronic component 5 via a solder bump 9 made of, for example, lead-tin. A part of the wiring conductor 2 formed on the surface of the other outermost layer of the insulating layer 1b forms a solder bonding pad 4 for connection, and a solder bump made of, for example, lead-tin is formed on each electrode of the external electric circuit board. An external connection solder bonding pad 4 connected via the wiring 9 is formed.

Such a solder bonding pad 4 has a substantially circular shape, a thickness of about 3 to 50 μm, and a diameter of about 50 to 100 μm if the solder bonding pad 4 is for connecting electronic parts.
In the case of the solder connection pad 4 for external connection, it is about 0.4 to 1.0 mm.

The insulating substrate 1 is covered with a solder-resistant resin layer 3 having a through-hole 10 exposing a central portion of the solder joint pad 4 in an electronic component mounting area including an outer peripheral portion of the solder joint pad 4 on the surface thereof. Have been. The solder-resistant resin layer 3 has a thickness of about 10 to 50 μm, and is made of, for example, a mixture of a photosensitive resin such as an acrylic-modified epoxy resin and a photoinitiator.
An insulating material containing an inorganic powder filler such as silica or talc of about 70% by weight;
It has a function of preventing an electrical short circuit between them by the solder bumps 9 and improving the bonding strength between the solder bonding pad 4 and the insulating substrate 1. The through hole 10 has a diameter of 40 to 80 μm if the diameter of the through hole 10 is for connecting electronic components.
About 0.35 to 0.9 if through hole 10 for external connection
mm.

The solder-resistant resin layer 3 is formed by forming an uncured resin film composed of a photosensitive resin, a photoinitiator and an inorganic powder filler or an uncured resin film composed of a thermosetting resin and an inorganic powder filler on an insulating substrate. 1 is adhered to the entire surface including the solder joint pads 4 on the upper and lower surfaces, and is formed by UV curing and heat curing. The through hole 10 is formed at the center of the solder joint pads 4 of the solder resistant resin layer 3. It is formed by irradiating a corresponding position with a laser beam having a wavelength of 8 to 11 μm.

The solder bonding pad 4 exposed from the through hole 10 has a substantially spherical concave portion 11 formed therein. The substantially spherical concave portion 11 has a wavelength on the exposed solder bonding pad 4.
It is formed by irradiating a laser beam of 0.1 to 1 μm.

As a laser beam having a wavelength of 8 to 11 μm, a carbon dioxide laser or the like is used, and as a laser beam having a wavelength of 0.1 to 1 μm, a YAG laser, an excimer laser, or the like is used. The energy of the laser light is about 0.5 to 2.0 mj in the through-hole 10 for connecting electronic components, and about 60 to 100 mj in the through-hole 10 for external connection.

In the wiring board of the present invention, it is important that the diameter 10a of the through hole 10 on the solder bonding pad 4 side is 50 to 95% of the opening diameter 10b. By setting the diameter 10a of the through hole 10 on the solder bonding pad 4 side to 50 to 95% of the opening diameter 10b, the vertical cross-sectional shape of the through hole 10 is such that the opening diameter 10b is
Even if the diameter of the through hole 10 becomes smaller than about 90 μm, the solder paste can be easily and sufficiently filled in the through hole 10 during screen printing, and then the wiring board is reflowed. When the solder paste is melted and solidified by passing through a furnace to form solder bumps, the solder bonding pads 4 and the solder bumps 9 can be reliably bonded, and the solder bonding pads 4 and the solder bumps 9 are mounted when the electronic component 5 is mounted. A wiring board with good electrical connection can be obtained without peeling.

The through hole 10 in which the diameter 10a on the solder bonding pad 4 side is 50 to 95% of the opening diameter 10b has a wavelength of 8 to 11 μm in the solder resistant resin layer 3 on the center of the solder bonding pad 4. It is formed by irradiating a laser beam several times with a predetermined energy.

The diameter of the through hole 10 on the side of the solder bonding pad 4
If 10a is less than 50% of the opening diameter 10b, the bonding area between the solder bonding pad 4 and the solder bump 9 tends to be small, and the bonding strength between them tends to decrease. At times, it becomes difficult to fill the through-hole 10 with solder paste, and when the wiring board is passed through a reflow furnace, there is a tendency that solder bumps 9 that are not well bonded to the solder bonding pads 4 are generated. Therefore, it is important that the diameter 10a of the through hole 10 on the solder bonding pad 4 side is 50 to 95% of the opening diameter 10b. The diameter of the through hole 10 on the solder bonding pad 4 side
10a indicates the diameter of the through hole 10 in contact with the solder bonding pad 4, and 10b indicates the diameter of the opening of the through hole 10 on the surface of the wiring board.

Further, in the wiring board of the present invention, it is important that the central portion of the solder bonding pad 4 be a substantially spherical concave portion 11. By forming the central portion of the solder bonding pad 4 into a substantially spherical concave portion 11, the shape of the corner between the surface of the solder bump 9 that contacts the side surface of the through hole 10 and the surface that contacts the surface of the solder bonding pad 4 becomes curved. Since the corners can be easily filled with solder and no voids are formed in the corners, the bonding area between the solder bumps 9 and the solder bonding pads 4 increases, and as a result, the solder bumps 9 and the solder bonding It is possible to provide a wiring substrate in which the bonding strength with the pad 4 does not decrease.

Further, it is preferable that the depth 12 of the recess 11 is 1/10 to 1/2 of the thickness of the solder bonding pad 4. The depth 12 of the recess 11 is 1/10 of the thickness of the solder joint pad 4
If it is less than the above, the shape of the corner between the surface of the solder bump 9 contacting the side surface of the solder-resistant resin layer 3 and the surface contacting the surface of the solder bonding pad 4 will not be sufficiently curved, and When the stress exceeds 1/2, the thickness of the central portion of the solder bonding pad 4 becomes thin and the solder bonding pad 4 becomes insulated. 1 tends to be easily peeled off. Therefore, the depth 12 of the recess 11 is preferably 1/10 to 1/2 of the thickness of the solder bonding pad 4.

The recess 11 having a substantially spherical shape is formed in the through hole 10.
0.1 to 1 µm at the center of the solder bonding pad 4 exposed by
Is formed by irradiating a laser beam having a predetermined wavelength several times with predetermined energy.

In this wiring board, the electrodes of the electronic component 5 are bonded to the solder bonding pads 4 via the solder bumps 9 to mount the electronic component 5 and to connect the wiring board and the electronic component 5 to each other with an underfill material. An electronic device is formed by bonding the electronic component 5 with a cover 13 and sealing the electronic component 5 with a lid or a potting resin (not shown). The solder bonding pad 4 in the electronic device is connected to an external electric circuit board via a solder bump 9. By connecting to the wiring conductor, the electronic device of the present invention is mounted on the external electric circuit board.

Thus, according to the wiring board of the present invention and the electronic device using the same, the solder bonding pad 3 in which the through hole 10 provided in the solder-resistant resin layer 3 is exposed and the electrode of the electronic component 5 are connected via the solder. It is an object of the present invention to provide a wiring board and an electronic device using the same, which can securely and securely join the electronic component 5 mounted on the wiring board for a long period of time to operate normally.

The present invention is not limited to the above-described embodiment, and it goes without saying that various changes can be made without departing from the scope of the present invention. For example, in the example of the above-described embodiment, a through-hole 10 is formed in the solder-resistant resin layer 3 above the solder bonding pad 4 connected to the electronic component 5 and a substantially spherical concave portion is formed on the through-hole 10.
Although the example in which 11 is formed has been described in detail, the present invention is also applicable to the solder joint pad 4 connected to the wiring conductor of the external electric circuit board.

Next, a method of manufacturing a wiring board according to the present invention will be described with reference to an example of manufacturing the above-described wiring board.

First, a core 1a constituting the insulating base 1 is prepared. The core 1a is formed by temporarily curing a sheet in which a glass cloth in which glass fibers are woven vertically and horizontally is impregnated with a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin.

Next, a thickness of 3 to 50 is applied to the surface of the core 1a.
By overlaying and pressing and heating copper foil of μm,
A copper foil serving as a wiring conductor 2 is adhered and formed on the surface of the core body 1a,
Thereafter, through holes 6 are drilled from the upper surface to the lower surface of the core body 1a having the copper foil to be the wiring conductor 2 formed on the surface thereof, and then the copper foil to be the wiring conductor 2 is etched. To form a predetermined pattern,
Furthermore, a copper plating film having a thickness of about 3 to 50 μm is deposited on the inner wall of the through hole 6 by using an electroless copper plating method and an electrolytic copper plating method, so that the surface of the core body 1 a and the inner wall of the through hole 6 are formed. The wiring conductor 2 is formed. The through-hole 6 has a resin column 7 made of a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin inside, and an uncured paste-like thermosetting resin inside the through-hole 6 by screen printing. It is preferable to fill it, and it is preferable to polish the upper and lower surfaces thereof substantially flat after heat curing.

Next, an insulating layer 1b made of a thermosetting resin such as an epoxy resin or a modified polyphenylene ether resin is formed on the upper and lower surfaces including the resin pillars 7 of the core 1a having the wiring conductor 2 formed on the surface and the inner wall of the through hole 6. Are laminated. Such an insulating layer 1b is formed by attaching an uncured thermosetting resin film to the upper and lower surfaces of the core 1a and thermally curing the same.

Further, a via hole 8 is formed in the insulating layer 1b by using a laser beam, and a copper plating film having a thickness of about 3 to 50 μm is formed on the surface of the insulating layer 1b and the inner wall of the via hole 8 by a conventionally known semi-additive. It is formed in a predetermined pattern by a method or the like. In the embodiment of the present invention, a plurality of insulating layers 1b having the wiring conductors 2 on the surface and the inner wall of the via hole 8 are formed on the upper and lower surfaces of the core 1a.

Next, a part of the wiring conductor 2 formed in the electronic component mounting area on one outermost layer surface of the insulating layer 1b is etched to form a solder joint pad 4 for electronic component bonding and to form the insulating layer. A part of the wiring conductor 2 formed on the other outermost layer surface of 1b is etched to form a solder bonding pad 4 for external bonding. The solder bonding pad 4 has a substantially circular shape, a thickness of about 3 to 50 μm, and a diameter of about 50 μm if the solder bonding pad 4 is for connecting electronic components.
About 100 μm, and about 0.4 to 1.0 mm for the solder connection pad 4 for external connection.

Next, as shown in an enlarged sectional view of a main portion in FIG. 3A, a solder-resistant resin layer 3 is formed on the surface of the insulating substrate 1 in the electronic component mounting area including the solder bonding pads 4. The solder-resistant resin layer 3 has a thickness of about 10 to 50 μm. For example, 30 to 70% by weight of an inorganic powder such as silica or talc is added to a mixture of a photosensitive resin such as an acrylic-modified epoxy resin and a photoinitiator. The mixture containing the filler is formed by printing on the electronic component mounting area on the surface of the insulating substrate 1 by using a conventionally known screen printing method, and then heating and curing.

Next, as shown in an enlarged sectional view of a main part in FIG.
A through hole 10 is formed in the substrate. Such through-holes 10 are 8 to 11
It is formed by irradiating a laser beam having a wavelength of μm to a position corresponding to the center of the solder joint pad 4 of the solder resistant resin layer 3. In addition, for forming the through hole 10, for example, 8 to
A carbon dioxide laser having a wavelength of 11 μm is used. The energy of the laser beam at this time is about 0.5 to 2.0 mj when the through hole 10 for connecting electronic components is formed, and is about 60 to 100 mj when the through hole 10 for connecting external parts is formed.

Next, as shown in an enlarged sectional view of a main part in FIG. 3C, a laser beam having a wavelength of 0.1 to 1 μm is applied to the central portion of the solder bonding pad 4 exposed from the through hole 10 to substantially emit the laser beam. A spherical recess 11 is formed. For forming the substantially spherical concave portion 11, for example, a YAG laser or an excimer laser having a wavelength of 0.1 to 1 μm is used. The energy of the laser beam at this time is about 0.5 to 2.0 mj when the through hole 10 for connecting electronic components is formed, and is about 60 to 100 mj when the through hole 10 for connecting external parts is formed.

In the method for manufacturing a wiring board of the present invention,
Solder bonding pads 4 to which the electrodes of the electronic component 5 are bonded via solder are formed in the electronic component mounting area on the insulating substrate 1, and then the solder resistant pad 4 is covered in the electronic component mounting area by covering the solder bonding pads 4. Further, the through hole 10 is formed by irradiating a laser beam having a wavelength of 8 to 11 μm to the solder resistant resin layer 3 on the central portion of the solder bonding pad 4.
The wavelength is set to 0.
It is important to form a substantially spherical concave portion 11 by irradiating a laser beam of 1 to 1 μm.

In the method for manufacturing a wiring board according to the present invention,
A through hole 10 is formed by irradiating a laser beam having a wavelength of 8 to 11 μm to the solder resistant resin layer 3 on the central portion of the solder bonding pad 4.
Thereafter, a substantially spherical concave portion 11 is formed by irradiating a laser beam having a wavelength of 0.1 to 1 μm to the central portion of the solder bonding pad 4 exposed through the through hole 10, so that the wavelength is 8 to 11 μm.
Even if the through hole 10 can be easily formed in the insulating layer 1b by the laser beam, and the solder-resistant resin remains on the solder bonding pad 4, the subsequent laser beam having a wavelength of 0.1 to 1 .mu.m forms a substantially spherical surface on the solder bonding pad 4. When the concave portion 11 is formed, the residual solder-resisting resin on the solder bonding pad 4 can be completely removed, so that the roughening and etching steps can be omitted, and the resin on the surface of the solder-resistant resin layer 3 is deteriorated. A method of manufacturing a wiring board without any problem can be achieved. As a result, when the electronic component 5 is mounted on the wiring board and then the electronic component 5 is bonded to the electronic component 5 with the underfill material 13, the adhesion strength between the solder-resistant resin layer 3 and the underfill material 13 decreases. Never.

When the through hole 10 is formed by laser light,
By irradiating the laser beam having a uniform energy distribution several times, the vertical sectional shape of the through hole 10 is changed to the solder bonding pad 4 of the through hole 10.
Even if the diameter of the through hole 10 is smaller than about 90 μm, the solder paste can be easily and sufficiently filled into the through hole 10 during screen printing by setting the diameter 10a of the side to be 50 to 95% of the opening diameter 10b. Then, when the solder paste is melted and solidified by passing the wiring board through a reflow furnace to form the solder bumps 9, the solder bonding pads 4 and the solder bumps 9 can be reliably bonded, and the electronic component 5 It is possible to provide a wiring board with good electrical connection without peeling of the solder bonding pad 4 and the solder bump 9 during mounting.

When forming the substantially spherical concave portion 11 with laser light, a laser beam having a wavelength of 0.1 to 1 μm is irradiated several times with a predetermined energy, and the depth 12 is adjusted to the thickness of the solder bonding pad 4. By making it 1/10 to 1/2, the shape of the corner between the surface of the solder bump 9 in contact with the side surface of the solder-resistant resin layer 3 and the surface in contact with the surface of the solder bonding pad 4 is curved. The solder bumps 9 can be easily filled in the corners and no voids are formed in the corners.
And the soldering pad 4 has a larger bonding area, and as a result,
It is possible to provide a wiring board in which the bonding strength between the solder bumps 9 and the solder bonding pads 4 does not decrease.

Thus, according to the method for manufacturing a wiring board of the present invention, the solder-resistant resin layer 3 on the central portion of the solder joint pad 4 is formed.
Then, a through hole 10 is formed by irradiating a laser beam having a wavelength of 8 to 11 μm, and then a laser beam having a wavelength of 0.1 to 1 μm is radiated to a central portion of the solder bonding pad 4 exposed by the through hole 10. Since the substantially spherical recess 11 is formed, the residue of the solder-resistant resin on the solder bonding pad 4 can be completely removed, so that the roughening and etching steps can be omitted, and the resin on the surface of the solder-resistant resin layer 3 can be eliminated. Is not deteriorated, and as a result, it is possible to provide a method of manufacturing a wiring board in which the adhesive strength between the underfill material 13 and the solder-resistant resin layer 3 does not decrease.

The present invention is not limited to the above-described embodiment, and may be modified or improved without departing from the scope of the present invention.

[0055]

According to the wiring board of the present invention, the diameter of the through hole of the solder-resistant resin layer on the side of the solder bonding pad is 50 to 95% of the opening diameter.
As a result, the vertical cross section of the through hole has a funnel shape with an opening diameter larger than the diameter of the solder joint pad side. Even if the opening diameter of the through hole becomes smaller than about 90 μm, solder paste can be easily formed into the through hole during screen printing. When the wiring board is passed through a reflow furnace and the solder paste is melted and solidified to form solder bumps, the solder bonding pads and the solder bumps can be securely bonded, and the electronic component The solder bonding pads and the solder bumps are not separated at the time of mounting, and a wiring board with good electrical connection can be obtained.

Further, according to the wiring board of the present invention, the diameter of the through hole of the solder-resistant resin layer on the side of the solder joint pad is set to 50 to 50 mm of the opening diameter.
The corner between the surface that contacts the side surface of the through hole of the solder bump and the surface that touches the surface of the solder bonding pad because 95% is set and a substantially spherical concave portion is formed in the center of the solder bonding pad exposed from the through hole. Has a curved shape, the solder can easily penetrate into the corners, and no voids are formed in the corners, so that the bonding area between the solder bumps and the solder bonding pads increases, and as a result, The bonding strength between the bump and the solder bonding pad does not decrease. Furthermore, the stress generated by the heat generated during the operation of the electronic component due to the expansion and contraction of the solder and the solder joint pad / solder-resistant resin layer having different coefficients of thermal expansion concentrates on the corners, causing cracks at the corners. Thus, a wiring board that can normally operate the electronic component can be provided.

According to the method for manufacturing a wiring board of the present invention, the wavelength of 8 to 8 is applied to the solder-resistant resin layer on the central portion of the solder joint pad.
After irradiating a laser beam of 11 μm to form a through hole, the wavelength is applied to the center of the solder joint pad exposed by the through hole.
Since a substantially spherical concave portion is formed by irradiating a laser beam of 0.1 to 1 μm, a through hole can be easily formed in the solder-resistant resin layer with a laser beam having a wavelength of 8 to 11 μm. Even if solder-resistant resin remains, the wavelength is 0.1-1μ
Since the residual solder-resisting resin on the solder bonding pad can be completely removed by the laser beam of m, the roughening / etching step can be omitted and the resin on the surface of the solder-resisting resin layer does not deteriorate.

According to the electronic device of the present invention, the electronic component is mounted on the electronic component mounting area of the wiring board, and the solder bonding pad and the electrode of the electronic component are connected via the solder. Even if the stress due to the heat generated during operation is repeatedly applied to the corners of the surface in contact with the side surface of the through hole of the solder and the surface in contact with the surface of the solder bonding pad for a long time, the stress does not concentrate on the corner, A crack can be prevented from being generated at the corner, and as a result, an electronic device that can normally operate the electronic component can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of an embodiment in which an electronic component is mounted on a wiring board of the present invention and applied to an electronic device.

FIG. 2 is an enlarged sectional view of a main part of an example of an embodiment of a wiring board and an electronic device of the present invention.

FIGS. 3A, 3B, and 3C are enlarged cross-sectional views of a main part for describing a method of manufacturing a wiring board according to the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating board 1a ... Core body 1b ... Insulating layer 2 ... Wiring conductor 3 ... Solder-resistant resin layer 4 ... ..Solder joint pad 5 ... Electronic component 10 ... Through hole 10a ... Diameter of through hole on solder joint pad side 10b ...・ ・ ・ ・ ・ ・ Recess 12 ・ ・ ・ ・ ・ ・ Depth of recess

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H05K 3/28 H05K 3/46 Q 3/46 H01L 23/12 NF term (Reference) 5E314 AA25 AA27 BB02 BB10 BB11 BB12 CC15 FF01 GG26 5E319 AA03 AA07 AB05 AC01 AC11 AC12 AC13 BB05 CC33 CD29 GG03 5E346 AA12 AA15 AA17 BB01 BB15 BB16 CC02 CC08 CC31 CC40 DD02 DD31 FF45 GG15 HH21 HH33 5F044 KK02 KK17 KK25 LL01

Claims (4)

[Claims] An electronic component mounting region on an insulating substrate is provided with a solder bonding pad to which an electrode of an electronic component is bonded via solder, and the electronic component mounting region covers an outer peripheral portion of the solder bonding pad and the solder bonding pad. A wiring board comprising a solder-resistant resin layer having a through hole exposing a central portion of a bonding pad, wherein the through hole has a diameter on the solder bonding pad side of 50 to 95% of an opening diameter. The wiring board, wherein the solder bonding pad has a substantially spherical concave portion at a central portion thereof. 2. The wiring board according to claim 1, wherein the depth of the recess is 1/10 to 1/2 of the thickness of the solder bonding pad. 3. A step of forming a solder joint pad to which an electrode of an electronic component is joined via solder in an electronic component mounting area on an insulating substrate; A step of applying a resin layer, a step of irradiating a laser beam having a wavelength of 8 to 11 μm to the solder-resistant resin layer on the central portion of the solder bonding pad to form a through hole, and a step of exposing through the through hole. Forming a substantially spherical concave portion by irradiating a laser beam having a wavelength of 0.1 to 1 μm to a central portion of the solder bonding pad. 4. An electronic component is mounted on an electronic component mounting region of the wiring board according to claim 1, and the solder bonding pad and an electrode of the electronic component are connected via solder. Electronic devices.