JP2000349447A - Multilayer printed wiring board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a crack at an insulating member from reaching an inner layer circuit pattern by embedding a cracking preventive member in an insulating member corresponding to an outer part of a part mounting conductive pad. SOLUTION: Related to a multilayer printed wiring board 1, a plurality of conductor patterns 4 and insulating layers 6 are laminated on front and rear surfaces of a printed board 2 of a core member. A part mounting conductive pad 5 is provided on the front surface of the multi-layer printed wiring board 1, and the conductive pad 5 is connected to the conductor pattern 4 through an inter layer connection conductor 7. A cracking preventive member 3 is provided at the lower layer of the part mounting conductive pad 5 through the insulating layer 6 so that the outer edge part of the conductive pad 5 comes to nearly the center in the width of the crack preventive material 3. Thus, a crack at the insulating member corresponding to the outer edge part of the conductive pad 5 is prevented from reaching the inner-layer circuit pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a multilayer printed wiring board, and more particularly to a multilayer printed wiring board provided with a member for preventing the progress of cracks below conductive pads for mounting components.

[0002]

2. Description of the Related Art Ordinary multilayer printed wiring boards are manufactured by a method of alternately stacking and laminating a plurality of inner layer circuits and insulating members, or a build-up manufacturing method of alternately stacking a plurality of layers of insulating members and inner layer circuits. Have been. Electronic components such as MPU,
An LSI, a resistor, a capacitor and the like are mounted. Further, an IO pin for extracting a signal for measuring circuit characteristics of the printed wiring board is mounted. Conductive pads for connecting terminals and IO pins of these electronic components are provided on the surface of the multilayer printed wiring board. The conductive pad is soldered to the terminal of the electronic component and the IO pin.

[0003]

By the way, as described above, the conductive pad is a terminal of an electronic component to be mounted, and
Since the IO pins are connected to the solder, the heat at this time heats the conductive pad and the insulating member thereunder. However, in general, the conductive pad and the insulating member on which the conductive pad is formed have different coefficients of thermal expansion, so that the insulating member may crack at a position corresponding to the edge of the conductive pad.
In particular, in the case of a build-up manufacturing substrate in which fine metal pads are formed on the outermost layer of a thin polyimide resin insulating layer by photolithography, stress tends to concentrate under the outer peripheral line of the conductive pad and cracks tend to occur in the polyimide resin. . When a crack occurs in the insulating member, chemicals during the process and moisture in the air permeate through the crack. The so-called migration phenomenon causes a failure that the insulation resistance between the conductive pad and the inner layer circuit is reduced or short-circuited,
As a result, the reliability of the printed wiring board is reduced.

Accordingly, an object of the present invention is to provide an insulating member corresponding to the outer edge of the conductive pad due to the difference in the coefficient of thermal expansion between the conductive pad provided as the outermost layer of the multilayer printed wiring board and the insulating member thereunder. The purpose is to prevent the resulting cracks from reaching the inner layer circuit pattern.

Another object of the present invention is to improve the reliability of a printed wiring board by suppressing a migration phenomenon through a crack generated in an insulating member.

[0006]

According to a first aspect of the present invention, there is provided the insulating member corresponding to at least the outer edge of the component mounting conductive pad provided on the insulating member as the outermost layer of the multilayer printed wiring board. And a multilayer printed wiring board characterized in that a crack progress preventing member for preventing the progress of cracks generated in the insulating member is embedded. Therefore, due to the difference in the coefficient of thermal expansion between the conductive pad provided as the outermost layer of the multilayer printed wiring board and the insulating member thereunder, cracks generated in the insulating member corresponding to the outer edge of the conductive pad reach the inner layer circuit pattern. Can be prevented. In addition, the migration phenomenon through cracks generated in the insulating member can be suppressed, and the reliability of the printed wiring board can be improved.

According to a second aspect of the present invention, the width W of the crack progress preventing member according to the first aspect is such that the distance L between the component mounting conductive pad and the crack progress preventing member is W> L ×
Provided is a multilayer printed wiring board having a relationship of 2 × ２3. Accordingly, cracks generated below the outer edge of the component mounting conductive pad are prevented from progressing by the crack progress preventing member.

According to a third aspect of the present invention, there is provided a multilayer printed wiring board, wherein the crack progress preventing member according to the first aspect is provided only at a position corresponding to an inner layer circuit provided in the insulating member. provide. Therefore, a crack generated below the outer edge of the component mounting conductive pad does not propagate to the inner layer circuit provided in the intermediate layer.

According to a fourth aspect of the present invention, there is provided a multilayer printed wiring board, wherein the crack progress preventing member according to the first aspect is made of the same material as that of the component mounting conductive pad. Therefore, the number of types of multilayer printed wiring board materials and manufacturing processes are not increased more than necessary.

According to a fifth aspect of the present invention, in the method of manufacturing a multilayer printed wiring board, a step of forming an inner layer circuit and the insulating member is formed in the insulating member corresponding to at least the outer edge portion of the component mounting conductive pad. And a step of embedding a crack progress preventing member for preventing the progress of cracks. Therefore, a crack progress preventing member for preventing a crack generated in the insulating member corresponding to the outer edge portion of the conductive pad from reaching the inner layer circuit pattern due to a difference in thermal expansion coefficient between the conductive pad and the insulating member thereunder is provided. Can be.

According to a sixth aspect of the present invention, the step of manufacturing the crack progress preventing member according to the fifth aspect is the same as the step of manufacturing the inner layer circuit, that is, forming a resist layer, plating, and stripping the resist layer. To provide a multilayer printed wiring board. As a result, it is possible to manufacture in a consistent flow operation process without providing a special manufacturing process.

[0012]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a multilayer printed wiring board according to an embodiment of the present invention. 1 is a multilayer printed wiring board, 2 is a printed board, 3 is a crack progress preventing member, 4 is a conductor pattern, 5 is a conductive pad for mounting components, 6 is an insulating layer (insulating member), 7 is an interlayer connection conductor, and 8 is an interlayer. Connection joints for connecting the connection conductors.

In a general multilayer printed wiring board 1, a plurality of laminates are provided on the front and back surfaces of a printed board 2 which is a core member, with a conductor pattern 4 and an insulating layer 6 as laminates. However, in FIG. 1, a plurality of laminates are provided only on the upper surface for easy understanding.

A conductive pad 5 for mounting components is provided on the surface of the multilayer printed wiring board 1. The terminals of the components mounted on the component mounting conductive pads 5 and the IO pins are connected by soldering. The conductor pattern 4 is provided on the intermediate layer. The conductor pattern 4 is a signal, a power supply, a ground, and the like. The component mounting conductive pad 5 is electrically connected to a conductor pattern 4 (not shown) via an interlayer connection conductor 7. The connection joints 9 connecting the interlayer connection conductors 7 play a role of connection reinforcement for increasing the connection area. The central portion of the crack progress preventing member 3 is connected to the central portions of the connection joint 9 and the interlayer connection conductor 7. The insulating layer 6 insulates each of the upper and lower conductor patterns 4 from the component mounting conductive pad 5.

The crack progress preventing member 3 is provided below the component mounting conductive pad 5 with an insulating layer 6 interposed therebetween. The component mounting conductive pad 5 is provided so that the outer edge thereof is substantially at the center of the width of the crack progress preventing member 3. It has been found that the crack generated from the outer edge of the component mounting conductive pad 5 proceeds within the range of the angle θ120 degrees. Accordingly, the width W of the crack progress preventing member has the following relationship with the distance L between the component mounting conductive pad 5 and the crack progress preventing member 3.

W> L × 2 × √3 That is, the width W of the crack progress preventing member is 2 times the distance L between the component mounting conductive pad 5 and the crack progress preventing member 3.
It is twice as large as the value multiplied by √3. Therefore,
Even if a crack occurs at the outer edge of the component mounting conductive pad 5, the crack is prevented by the crack progress preventing member 3 and the conductive pattern 4 is prevented.
Unable to progress until.

FIG. 2 is a plan view for explaining the positional relationship between the component mounting conductive pad and the crack progress preventing member.

The component mounting conductive pad 5 has a disk shape, a diameter d2 of about 700 μmmΦ, and a thickness of about 5 μmm. The crack progress preventing member 3 has a hollow disk shape and an outer diameter d3 of about 720 μmm.
Φ, inner diameter d1 about 680 μmmΦ, width W about 40 μmm, thickness about 3 μmm. Therefore, the width W of the crack progress preventing member 3
The outer edge of the component mounting conductive pad 5 is provided in a superimposed manner at the center.

The component mounting conductive pad 5 according to the embodiment of the present invention.
Has been described as a disk shape, and the crack progress preventing member 3 is a hollow disk shape. However, the shape of the component mounting conductive pad 5 may be any shape, and is insulated from the crack progress preventing member 3.
The same effect is obtained if the outer edge of the component mounting conductive pad 5 overlaps the region of the crack progress preventing member 3.

Next, a method for manufacturing a multilayer printed wiring board according to the present invention will be described. <First Embodiment> FIGS. 3 and 4 are process diagrams illustrating a method for manufacturing a multilayer printed wiring board according to the present invention. The following processing is performed in each of the following steps.

In the step shown in FIG. 3A, the conductor pattern 4, the connection joint 9, and the interlayer connection conductor 7 are provided on the surface of the printed circuit board 2 which is a core material. The thickness of the conductor pattern 4, the connection joint 9, and the interlayer connection conductor 7 is about 5 μm. An insulating layer 6 is provided on the conductor pattern 4 by spin coating of an insulating resin, for example, a polyimide resin. Further, copper is vapor-deposited on the insulating layer 6 by a sputtering method to form a copper layer 1.
Form one. The thickness of the copper layer 11 is about 5000 angstroms. This copper layer 11 is used as an electrode terminal for plating in the next plating step.

Next, in the step of FIG. 3B, a photosensitive etching resist material is applied on the upper surface of the copper layer 11 to a thickness of about 10 μm. This etching resist material is exposed to the shape of the conductor pattern 4 and the connection joint 9 and then developed to form a resist layer 12.

Further, in the step of FIG. 3 (c), a copper plating process is performed, and in this copper plating, the conductor pattern, 41 and the connection joint 9 are formed only on the electrode terminals, that is, only on the upper surface of the copper layer 11. The thickness of the conductor pattern 41 and the connection joint 9 is about 5 μm.
mm.

Next, the step of FIG.
2 is removed by the etching solution.

Further, in the step of FIG. 3E, a photosensitive etching resist material is applied on the copper layer 11 provided with the conductor pattern 41 and the connection joint 9 to a thickness of about 20 μm. Then, the etching resist material is exposed to the shape of the interlayer connection conductor 7 and then developed to form the resist layer 13.

Further, in the step of FIG. 3 (f), a copper plating process is performed, and in the copper plating, an interlayer connection conductor 71 having a thickness of about 15 μm is formed only on the electrode terminals, that is, on the copper layer 11. After that, the resist layer 13 is peeled off with an etching solution,
The conductor pattern 41 and the copper layer 11 that later appeared on the surface are etched. The etching process is performed until the copper layer 11 excluding the copper layer 11 under the conductor pattern 41 disappears. That is, since the thickness of the copper layer 11 is about 5000 Å, which is very thin compared to the thickness of the conductor pattern 41 of about 5 μm, the etching of the copper layer 11 is completed before the conductor pattern 41 is etched. Then, the respective conductor patterns 41 connected by the copper layer 11 are separated.

Next, in the step of FIG. 3G, an insulating layer 61 is formed. The insulating layer 61 is formed by a spin coating method or a polyimide resin sheet attachment to a thickness of about 20 μm in which the interlayer connection conductor 71 and the conductor pattern 41 are sufficiently covered with the polyimide resin. Then, heat and cure.

4H, the copper layer 111 is formed on the insulating layer 61 by a sputtering method.
As described above, the thickness of the copper layer 111 is about 500
0 Angstrom. This copper layer 111 is used as an electrode terminal for plating in the next plating step.

Next, in the step of FIG. 4I, a photosensitive etching resist material is applied on the upper surface of the copper layer 111. This etching resist material is exposed to the shape of the crack progress preventing member 3 and then developed to form the resist layer 1.
4 is formed. Accordingly, the shape of the crack progress preventing member 3 formed on the resist layer 14 is a hollow disk centered on the center of the interlayer connection conductor 71 and has an outer diameter d3 of about 720 μmmΦ and an inner diameter d1 of about 680 μmmΦ.

Further, in the step of FIG. 4 (j), a copper plating process is performed, and the copper plating is applied to the electrode terminals, that is, the copper layer 111.
Provided only on the upper surface of the
Is formed. The thickness of the crack progress preventing member 3 is about 3 μmm. Thereafter, the resist layer 111 is peeled off with an etchant, and then the crack progress preventing member 3 and the copper layer 111 are etched. The etching is performed until the copper layer 111 excluding the copper layer 111 below the crack progress preventing member 3 disappears. As described above, the thickness of the copper layer 111 is about 500
The etching of the copper layer 112 is completed before the crack progress preventing member 3 is etched because it is very thin at 0 Å.

Further, in the step of FIG. 4 (k), a photosensitive etching resist material is coated with a crack progress preventing member 3 having a thickness of about 5 mm.
The insulating layer 611 is formed by applying a thickness of μm. Then, heat and cure.

Next, the step of FIG.
Is polished to make the interlayer connection conductor 71 and the insulating layer 611 on the same surface. Therefore, an insulating layer 611 having a thickness of about 5 μm is formed on the upper surface of the crack progress preventing member 3.

Further, the step of FIG.
Copper is vapor-deposited on 11 by a sputter manufacturing method. Therefore, the copper layer 112 is formed on the insulating layer 611. This copper layer 112 has a thickness of about 5000 angstroms and is used as an electrode terminal in a plating process in the next process.

Next, in the step of FIG. 4 (n), a photosensitive etching resist material is coated on the upper surface of the copper layer 112 to a thickness of about 10 μm.
Applied to This etching resist material is exposed to the shape of the component mounting conductive pad 5, developed, and a resist layer 15 is formed. Therefore, the component mounting conductive pad 5 formed on the resist layer 15 has a disk shape centered on the center of the interlayer connection conductor 71 and a diameter d2 of about 700 μm.
Is Φ.

In FIG. 1 as a final step, a copper plating process is performed. In the copper plating, the component mounting conductive pads 5 are provided only on the electrode terminals, that is, only on the upper surface of the copper layer 112. Thereafter, the resist layer 15 is peeled off with an etching solution. Next, the component mounting conductive pad 5 and the copper layer 112 are etched. As described above, the thickness of the copper layer 112 is about 500
The etching of the copper layer 112 is completed before the component mounting conductive pad 5 is etched because it is as thin as 0 Å.

By using such a manufacturing method, the insulating member corresponding to at least the outer edge portion of the component mounting conductive pad provided on the insulating member as the outermost layer of the multilayer printed wiring board is provided. In this case, a multilayer printed wiring board can be manufactured by burying a crack progress preventing member for preventing the progress of cracks.

As a result, due to the difference in the coefficient of thermal expansion between the conductive pad provided as the outermost layer of the multilayer printed wiring board and the insulating member thereunder, cracks generated in the insulating member corresponding to the outer edge of the conductive pad are generated in the inner layer. The circuit pattern can be prevented from reaching. In addition, it is possible to suppress the migration phenomenon through cracks generated in the insulating member, and to improve the reliability of the printed wiring board. <Second Embodiment> FIGS. 5 and 6 are process diagrams illustrating a second embodiment of the multilayer printed wiring board according to the present invention.

In the second embodiment, the same processes as those of the first embodiment shown in FIG. 4 (a) to FIG. 4 (g) are performed, so that the description will be omitted. The following processing is performed after the step of FIG.

In the step of FIG. 5 (o), the thickness of the interlayer connection conductor 71 on the connection joint 9 and the thickness of the insulating layer 61 on the upper surface of the conductor pattern 41 are polished to about 5 μm. Therefore, the interlayer connection conductor 71 and the insulating layer 61 are on the same plane.

Further, in the step of FIG. 5 (p), the copper layer 121 is formed on the insulating layer 61 by a sputtering manufacturing method.
The thickness of this copper layer 121 is about 5000 angstroms. This copper layer 121 is used as an electrode terminal for plating in the next plating step.

Next, in the step of FIG. 5 (q), a photosensitive etching resist material is applied on the upper surface of the copper layer 121. This etching resist material is exposed to the shape of the crack progress preventing member 3 and the connection joint 9, then developed, and a resist layer 16 is provided. Thereafter, a copper plating process is performed. In the copper plating, the crack progress preventing member 3 and the connection joint 9 are provided with a thickness of about 5 μm only on the upper surface of the copper layer 121 as an electrode terminal. Therefore, the shape of the crack progress preventing member 3 formed in the resist layer 16 is a hollow disk shape centered on the center of the connection joint 9 and has an outer diameter d3 of about 720 μmmΦ,
The inner diameter d1 is about 680 μmmΦ.

Further, the step of FIG.
6 is peeled off by an etching solution.

Next, in the step of FIG. 5 (s), a photosensitive etching resist material is applied on the crack progress preventing member 3 and the connection joint 9. This etching resist material is exposed to the shape of the interlayer connection conductor 71 and then developed.
Therefore, a resist layer 16 is provided.

Further, in the step of FIG. 6 (t), a copper plating process is performed, and the copper plating is provided only on the upper surface of the copper layer 121 of the electrode terminal, and the interlayer connection conductor 71 is formed. Thereafter, the resist layer 17 is peeled off with an etching solution. Next, the crack progress preventing member 3 and the copper layer 121 are etched.
Similarly to the above, since the thickness of the copper layer 121 is very thin, about 5,000 angstroms, the etching of the copper layer 111 is completed before the crack progress preventing member 3 is etched.

Further, in the step of FIG. 6 (u), the insulating layer 621 is provided by applying a crack progress preventing member 3 and an interlayer connecting conductor 71 to a thickness of about 10 μm using a polyimide coater with a spin coater. Then, heat and cure.

Next, the step of FIG.
Is polished so that the interlayer connection conductor 71 and the insulating layer 621 are flush with each other. At this time, the thickness of the insulating layer 621 on the crack progress preventing member 3 is about 5 μmm.

Further, the step of FIG.
Copper is deposited on 21 by a sputter manufacturing method. Accordingly, a copper layer 122 is formed. As in the above description, it is used as an electrode terminal in the subsequent plating step.

Next, in the step of FIG. 6 (x), a photosensitive etching resist material is applied on the upper surface of the copper layer 122, and this etching resist material is exposed to the shape of the component mounting conductive pad 5 and developed. , And a resist layer 18 is provided. Therefore, the component mounting conductive pad 5 formed on the resist layer 18 has a disk shape centered on the center of the interlayer connection conductor 71 and a diameter d2 of about 700 μmmΦ.

As a final step, FIG. 1 is subjected to a copper plating process, and the copper plating is provided only in the groove in contact with the copper layer 122, and the component mounting conductive pad 5 is formed. Thereafter, the resist layer 18 is peeled off with an etching solution. Next, the component mounting conductive pad 5 and the copper layer 122 are etched. Copper layer 12 below conductive pad 5 for mounting components
The etching process is performed until the copper layer 122 excluding 2 disappears.

Although the first and second embodiments have been described with respect to a two-layer printed wiring board, similar effects can be obtained with other multilayer printed wiring boards. Further, although the build-up manufacturing method has been described, a lamination method in which a plurality of inner layer circuits and insulating members are alternately laminated may be employed.

[0052]

As described above, by employing the method for manufacturing a multilayer printed wiring board as in the present invention, the heat conduction between the conductive pad provided as the outermost layer of the multilayer printed wiring board and the insulating member thereunder can be improved. Due to the difference in expansion coefficient, it is possible to prevent cracks generated in the insulating member corresponding to the outer edge of the conductive pad from reaching the inner layer circuit pattern. In addition, it is possible to suppress the migration phenomenon through cracks generated in the insulating member, and to improve the reliability of the printed wiring board.

[Brief description of the drawings]

FIG. 1 is a sectional view of a multilayer printed wiring board according to the present invention;

FIG. 2 is a plan view illustrating the positional relationship between the component mounting conductive pad of the present invention and a crack progress preventing member.

FIG. 3 is a process chart illustrating a method for manufacturing a multilayer printed wiring board according to the first embodiment;

FIG. 4 is a process chart illustrating a method for manufacturing a multilayer printed wiring board according to the first embodiment;

FIG. 5 is a process chart illustrating a method for manufacturing a multilayer printed wiring board according to a second embodiment;

FIG. 6 is a process chart for explaining a method of manufacturing a multilayer printed wiring board according to a second embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 multilayer printed wiring board 2 printed board 3 crack progress preventing member 4 conductive pattern 5 conductive pad for component mounting 6 insulating layer 7 interlayer connection conductor

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference)

Claims (6)

[Claims] 1. A crack for preventing a crack from occurring in an insulating member in an insulating member corresponding to at least an outer edge portion of a component mounting conductive pad provided on an insulating member as an outermost layer of a multilayer printed wiring board. A multilayer printed wiring board comprising a progress preventing member embedded therein. 2. The crack progress preventing member according to claim 1, wherein the width W of the crack progress preventing member has the following relationship with the distance L between the component mounting conductive pad and the crack progress preventing member. Multilayer printed wiring board. W> L × 2 × √3 3. The multilayer printed wiring board according to claim 1, wherein the crack progress preventing member is provided only at a position corresponding to the inner layer circuit provided in the insulating member. 4. The multilayer printed wiring board according to claim 1, wherein the crack progress preventing member is made of the same material as the component mounting conductive pad. 5. A method for manufacturing a multilayer printed wiring board, comprising: a step of forming an inner layer circuit; And a step of burying a crack progress preventing member. 6. The multilayer printed wiring board according to claim 5, wherein the step of manufacturing the crack progress preventing member is the same as the step of manufacturing the inner layer circuit, including forming a resist layer, plating, and removing a resist layer.