JP2004095913A - Printed wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board which is inexpensive and high in the degree of integration, and to provide its manufacturing method. <P>SOLUTION: First masking films 16 are formed on a metal plate 11, and then the metal plate 11 is subjected to half etching for the formation of nearly conical metal bumps 11B. Then, a prepreg (insulating material layer) 12 is superposed on the surface of the metal plate 11 where the metal bumps 11B are formed, and the metal bumps 11B are made to penetrate through the prepreg 12 by hot pressing. Then, second masking films 15 are formed on the wiring pattern corresponding part of the rear surface of the metal plate 11, and the metal plate 11 is subjected to etching from above the second masking films 15 so as to form a wiring pattern 11D on the bottom of the metal plate 11. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a so-called through-conductor type printed wiring board and a method for manufacturing a printed wiring board in which wiring layers are connected by a through-type conductive wiring portion.
[0002]
[Prior art]
Conventionally, as a method of manufacturing a printed wiring board, a method of manufacturing a through-hole type printed wiring board 100 in which an interlayer connection is formed using a through-hole plating layer is known. FIG. 12 is a sectional view schematically showing the structure of a conventional typical through-hole type printed wiring board.
[0003]
In this method, first, a two-layer board 110 in which copper foils 103 and 105 are laminated on both sides of an insulating substrate 101 is prepared, and the copper foils 103 and 105 on both sides of the two-layer board 110 are patterned to form wiring patterns 103a and 103a. 105a is formed. Thereafter, through holes 107 and 109 are mechanically formed at predetermined positions of the two-layer plate 110 by a drill or the like. Next, a metal layer is deposited by applying electroless plating or the like to the inner walls of the through holes 107 and 109 to form through holes 107a and 109a, and the through holes 107a and 109a electrically connect the wiring patterns 103a and 105a. . Next, the semiconductor element 120 such as a bare chip is mounted via the wiring pattern 105a on the lower surface side. On the other hand, portions other than the joint of the wiring pattern 103a on the upper surface side are covered with the solder resist 104, and the solder ball 130 is welded to the joint to complete the semiconductor device 100.
[0004]
By the way, the demand for miniaturization of IT equipment has been increasing day by day, and the demand for a printed wiring board is no exception. There is a high demand for miniaturization and high integration and also a demand for a low price.
[0005]
[Problems to be solved by the invention]
However, the above-described conventional through-hole type manufacturing method requires through-holes for through-hole connection in addition to the wiring pattern, which hinders high integration. Furthermore, since a mechanical drilling step and a plating step for through-hole connection are required, there is a problem that the manufacturing cost is high and an obstacle to a reduction in price is obstructed. Further, plating must be made thicker in order to plate through holes, and the resolution of the wiring pattern is reduced. Therefore, the L / S value (line and space ratio) is at most 75/75 (μm). . In addition, a step of applying a solder resist for forming a solder ball on the upper surface is required, which leads to an increase in cost. The present invention has been made to solve the above-mentioned conventional problems. That is, an object of the present invention is to provide a printed wiring board which is inexpensive and highly integrated, and a method for manufacturing the same.
[0006]
[Means for Solving the Problems]
The printed wiring board of the present invention includes an insulating substrate, a bottom portion forming a wiring pattern covering one surface of the insulating substrate, a head exposed on another surface of the insulating substrate, and A metal wiring member having a penetrating portion penetrating the insulating substrate over the head.
[0007]
In the printed wiring board, as an example of the metal wiring member, a member in which one surface of a metal plate is half-etched to form a bump can be given. In the printed wiring board, an example of the metal wiring member may include a metal plate having a substantially conical metal bump formed on one surface of a metal plate. In the printed wiring board, as an example of the metal bump, a metal bump having a shape obtained by half-etching one surface of a metal plate can be given. In the printed wiring board, an example of the metal wiring member includes a metal bump having a height of 50 to 150 μm, a head radius of 20 to 80 μm, and a bottom radius of 80 to 200 μm on one surface.
[0008]
The method for manufacturing a printed wiring board according to the present invention includes a step of masking a metal plate surface, and a step of forming a substantially conical metal bump from the bottom surface of the metal plate by half-etching the metal plate via the masking. Forming a metal plate with a bump, forming an insulating layer on a bump forming surface of the metal plate with a bump, polishing the surface of the insulating layer, and patterning a bottom surface of the metal plate with a bump to form the insulating layer. Forming a wiring pattern on the lower surface side of the layer.
[0009]
Another printed wiring board of the present invention includes an insulating substrate, a first metal bottom portion forming a wiring pattern covering one surface of the insulating substrate, and exposed to another surface of the insulating substrate. A first metal head, a first metal penetrating portion penetrating the insulating substrate from the bottom to the head, and a second metal interposed between the penetrating portion and the bottom. And a metal wiring member having a metal barrier layer.
[0010]
In the other printed wiring board, an example of the first metal may include copper or a copper alloy, and an example of the second metal may include nickel or a nickel alloy. Among the other printed wiring boards, there may be mentioned those in which the L / S value of the wiring pattern is 25/25 to 50/50 (μm / μm).
[0011]
In the printed wiring board, as an example of the metal bump, the bottom portion has a thickness of 5 to 20 μm, the barrier layer has a thickness of 0.3 to 3 μm, and the through portion has a thickness of 50 to 150 μm. Can be mentioned.
[0012]
Another method of manufacturing a printed wiring board according to the present invention includes the steps of: masking one surface of a metal plate having three layers; and half-etching the metal plate through the masking to form a substantially conical shape from the bottom surface of the metal plate. Forming a metal plate with bumps on which the metal bumps are extended; forming an insulating layer on a bump forming surface of the metal plate with bumps; polishing the surface of the insulating layer; Patterning the bottom surface of the plate to form a wiring pattern on the lower surface side of the insulating layer.
[0013]
According to the present invention, since the interlayer connection is made by using the metal wiring member of the bump penetration type, it can be manufactured at low cost. Further, since a plating step is unnecessary, a metal printed wiring board having a wiring pattern of high integration at a low cost can be obtained.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
(1st Embodiment)
Hereinafter, a method for manufacturing a printed wiring board according to an embodiment of the present invention will be described. FIG. 1 is a flowchart showing the flow of each step of the method for manufacturing a printed wiring board according to the present embodiment. FIGS. 2, 3 and 4 show steps in the course of manufacturing the printed wiring board according to the present embodiment. It is sectional drawing which showed the thing typically. To manufacture the printed wiring board 1 according to the present embodiment, as shown in FIG. 2A, first, a metal plate 11 such as a copper plate is prepared. Examples of the metal plate 11 include oxygen-free copper and copper alloy. As the copper alloy, for example, an alloy containing 0.2% of a metal such as Cr or Sn can be used. The thickness of the metal plate 11 is selected according to the height and the remaining thickness of the metal bump to be formed. For example, when a metal bump having a height of about 130 μm is formed and a remaining thickness of about 20 μm is required, the metal plate 11 having a thickness of about 150 μm is used.
[0015]
Next, as shown in FIG. 2B, of the surface of the metal plate 11 on which half etching is to be performed, for example, the first masking 16 is formed on the upper surface side of the metal plate 11 in FIG. 2B. Is formed (step 1). As a method of forming the first masking 16, a photosensitive resin is first applied, dried, selectively exposed through a mask pattern, partially cured, and then developed to remove unnecessary portions. For example, a photolithographic method of dissolving and removing is used.
[0016]
On the other hand, a protective layer 17 is formed over the entire surface of the surface of the metal plate 11 on which half etching is not performed, that is, on the lower surface side in FIG. 2B. As the protective layer 17, a material in which a resist is formed on the entire surface, a material in which an adhesive film is attached, or the like can be used. Thus, as shown in FIG. 2B, the first masking 16 is formed on the upper surface of the metal plate 11, and the protective layer 17 is formed on the lower surface of the metal plate 11.
[0017]
In this state, a half etching process is performed on the upper surface side of the metal plate 11 (Step 2). As a method of the half-etching treatment, a spray method of spraying an etching solution, a wet method of immersing the metal plate 11 on which the first masking 16 and the protective layer 17 are formed in an etching solution tank, or an energy wave such as plasma And a dry method of colliding the particles.
[0018]
Now, the spraying method will be described as an example. When the etching solution is sprayed from the upper surface side of the metal plate 11 in the state shown in FIG. The metal plate 11 on the exposed surface between the first masking 16 and the first masking 16 is eroded, and further goes down to the lower surface side of the first masking 16 to etch the metal plate 11. The following can be used as the etchant used here. For example, an etching solution composed of an aqueous ferric chloride solution, an aqueous cupric chloride solution, and an alkaline aqueous solution containing copper ammonium complex ions as a main component can be used.
[0019]
When this etching process is stopped at an appropriate point (half etching / step 2), the metal bump 11B having a sectional shape (a curved surface having a negative radius of curvature) drawn by a parabola or an elliptic curve as shown in FIG. , 11B,... Are obtained. These metal bumps 11B, 11B,... Are connected by a root portion 11A.
[0020]
Next, the first masking 16 and the protective layer 17 are removed (step 3), and the surface is washed to remove the etchant, thereby providing metal bumps 11B, 11B,... As shown in FIG. A metal plate 11C with bumps is obtained.
[0021]
FIG. 5 is a perspective view and a cross-sectional view of a metal bump obtained after the half-etching process. FIG. 6 is a perspective view of a joint between the wiring pattern and the metal bump formed by etching from the second masking 15 side. 7 is an electron micrograph of the metal bump obtained after the half-etching process, and FIG. 8 is a joint between the wiring pattern and the metal bump formed by etching from the second masking 15 side. FIG.
[0022]
As shown in FIGS. 5 and 7, by half-etching one surface of the metal plate 11, a substantially conical metal bump 11B is formed. The cross section of the metal bump 11B has a shape in which the side surface of the truncated cone is replaced with a concave curved surface, in other words, the side surface has a curved surface having a negative radius of curvature. As shown in FIGS. 5 and 7, the upper portion of the metal bump 11B can be finished in a circular shape with a radius of about 30 to 150 μm, and the height of the metal bump 11B can be finished to about 50 to 150 μm. . In an actual product, the upper part of the metal bump is preferably finished in a circular shape with a radius of about 40 to 100 μm, and the height of the metal bump 11B is preferably finished in about 70 to 120 μm.
[0023]
In the metal plate with bumps 11C provided with the metal bumps 11B, the thickness (remaining thickness) of the conductor plate other than the portion where the metal bumps are formed is preferably 40 μm or less in order to form wiring later. It is preferable to set the thickness to ± 30% or less. If the remaining thickness is larger than 40 μm, it becomes difficult to form a fine circuit in a later step. The adjustment of the remaining thickness is performed by adjusting the spray pressure of an etching solution when performing half etching. In addition, the metal bumps and the conductor plate are preferably made of the same metal material, so that the metal bumps do not peel off, the heat conductivity between the metal bumps and the conductor plate is good, and the heat dissipation effect is high. There is an advantage that it becomes.
[0024]
Next, a prepreg (not shown) having a thickness of, for example, 60 μm, formed by impregnating a glass cloth with an epoxy resin, is overlaid on the metal bumps 11B, 11B,. Pressure (heat press) is applied under heating in a state of contact with such an elastic body (step 5). As a result of this heat pressing, a wiring board unit 13 in which the metal bumps 11B, 11B,... Penetrate the insulating material layer 12 as shown in FIG.
[0025]
As the method of forming the insulating material layer 12, in addition to the above-described methods, a method of applying a photo-curable epoxy resin by vacuum lamination or roll lamination followed by curing, or a method of wet lamination using a polyamic acid resin is used. And curing after coating.
[0026]
Next, the surface of the wiring board unit 13 on which the insulating material layer is formed (the upper surface in the figure) is polished (step 6). As shown in FIG. 3F, the entire thickness of the wiring board unit 13 is reduced to about 100 to 150 μm by this surface polishing step. The head of the metal bump 11B is polished together with the surface of the insulating material layer 12, for example, until the radius of the head becomes 70 to 100 μm. After these steps, as shown in FIG. 3G, a second masking 15 is formed on the exposed side of the metal plate of the wiring board unit 13 (the lower surface in the figure) by a known method such as a photolithographic method (see FIG. 3G). Step 8). After the upper surface side of the wiring board unit 13 is covered with a protective layer (omitted in the figure), the bottom 11A of the metal plate with bumps 11C is etched by dipping in an etchant or the like (step 9), and is patterned, as shown in FIG. As shown in h), the wiring pattern 11D is formed on the lower surface side of the wiring board unit 13. Next, when the protective layer and the second masking 15 are removed, a wiring board unit 13a as shown in FIG. 3 (i) is obtained. The semiconductor element 30 such as a bare chip is mounted on the wiring pattern 11D of the wiring board unit 13a thus formed (step 10), and the solder balls 40 are welded to the heads of the metal bumps 11B exposed on the upper surface of the wiring board unit 13a. Thus, the semiconductor device 50 is obtained.
[0027]
As described above, in the method for manufacturing a printed wiring board according to the present embodiment, since it is not necessary to form a through hole, the number of steps can be reduced, and the manufacturing cost can be reduced. Further, since it is not necessary to secure a space for drilling through holes, a wiring pattern can be formed on the entire surface of the printed wiring board, and a wiring pattern with a high integration density can be formed. Further, in the method according to the present embodiment, a plating step is unnecessary, so that the manufacturing cost can be reduced, and a wiring pattern with a high integration density can be formed. For example, in the printed wiring board shown in FIG. 3I, a high-density wiring pattern with an L / S value of about 40/40 (μm / μm) could be formed. Further, since it is not necessary to form a solder resist layer on the surface of the printed wiring board, manufacturing costs can be reduced.
[0028]
Further, in the method according to the present embodiment, interlayer connection is performed using the metal bumps 11B, 11B,... Formed by etching the metal plate 11, so that the height variation of the metal bumps 11B, 11B,. A highly reliable interlayer connection can be formed.
[0029]
Further, in the printed wiring board according to the present embodiment, the metal plate 11 made of a single material is processed by half etching from the upper surface side and etching from the rear surface side to form metal bumps 11B, 11B,... And a wiring pattern. Therefore, an inexpensive material can be used, and the product cost can be reduced.
[0030]
In this embodiment, the wiring pattern 11D and the solder ball 40 are arranged on the opposite side of the printed wiring board as shown in FIG. 3 (j). However, as shown in FIG. May be arranged on the opposite side of the printed wiring board.
[0031]
(Second embodiment)
Hereinafter, a method for manufacturing a printed wiring board according to the second embodiment of the present invention will be described. FIG. 9 is a flowchart showing the flow of each step of the method for manufacturing a printed wiring board according to the present embodiment. FIGS. 10 and 11 show steps in the course of manufacturing the printed wiring board according to the present embodiment. It is sectional drawing which showed typically. In order to manufacture the printed wiring board 1A according to the present embodiment, as shown in FIG. 10A, first, a metal plate 21 such as a copper plate is prepared. The metal plate 21 has a three-layer structure, and includes a first layer 21a and a third layer 21c made of a first metal, and a second layer 21b made of a second metal. The thickness of each layer is preferably 100 to 150 μm for the first layer 21a, 0.3 to 3 μm for the second layer 21b, and 5 to 20 μm for the third layer 21c.
[0032]
Examples of the first metal include oxygen-free copper and copper alloy. As the copper alloy, for example, an alloy containing 0.2% of a metal such as Cr or Sn can be used. Examples of the second metal include a metal that functions as an etching barrier against etching of the first metal, for example, nickel or a nickel alloy.
[0033]
The thickness of each layer is selected according to the height and remaining thickness of the metal bump to be formed. For example, when a metal bump having a height of about 130 μm is formed and a remaining thickness of about 20 μm is required, the first layer 21a and the second layer 21b having a total thickness of about 130 μm are used, and the third layer 21c is used. Having a thickness of about 20 μm.
[0034]
Next, as shown in FIG. 10B, the first masking 26 is formed on the surface of the metal plate 21 to be etched, for example, on the upper surface side of the metal plate 21 in FIG. 10B. (Step 1).
[0035]
On the other hand, a protective layer 27 is formed on the entire surface of the metal plate 21 on the side not subjected to etching, that is, on the lower surface side in FIG. 10B. Thus, as shown in FIG. 10B, the first masking 26 is formed on the upper surface of the metal plate 21, and the protective layer 27 is formed on the lower surface of the metal plate 21. In this state, an etching process is performed on the upper surface side of the metal plate 21 (Step 2).
[0036]
The following can be used as the etchant used here. For example, an etching solution composed of an aqueous alkali solution containing copper ammonium complex ions as a main component is exemplified.
[0037]
When this etching proceeds and the first layer 21a disappears, and the second layer 21b is exposed, the etching stops and the state as shown in FIG. That is, the metal bumps 22, 22,... Exhibiting a cross-sectional shape (curved surface having a negative radius of curvature) drawn by a parabola or an elliptic curve are obtained. Are connected by a second layer 21b and a third layer 21c at the roots thereof.
[0038]
Next, the second layer 21b is etched by changing the etchant (step 3). Here, only the second layer 21b is selectively etched by selecting an etching solution. The second layer 21b is selectively removed by using, for example, a mixture of a fluorine-based chemical (MN-956 manufactured by Meltex Corporation), sulfuric acid, and hydrogen peroxide as an etchant.
[0039]
Next, the first masking 26 and the protective layer 27 are removed (step 4), and the surface is washed to remove the etchant, thereby providing metal bumps 22, 22,... As shown in FIG. A bumped metal plate 28 is obtained.
[0040]
In the metal plate with bumps 28 provided with the metal bumps 22, the thickness (remaining thickness) of the conductor plate other than the portion where the metal bumps are formed, that is, the thickness of the third layer 21c is 40 μm in order to form wiring later. Or less, and the variation is preferably ± 30% or less with respect to the remaining thickness. If the remaining thickness is larger than 40 μm, it becomes difficult to form a fine circuit in a later step.
[0041]
Next, a prepreg (not shown) having a thickness of, for example, 60 μm, which is formed by impregnating a glass cloth with an epoxy resin, is overlaid on the metal bumps 22, 22,. A pressure (heat press) is applied under heating while being in contact with such an elastic body (step 6). As a result of this heat pressing, a wiring board unit 23 in which the metal bumps 22, 22,... Penetrate the insulating material layer 24 as shown in FIG.
[0042]
Next, the surface of the wiring board unit 13 on which the insulating material layer is formed (the upper surface in the figure) is polished (step 7). As shown in FIG. 11F, the entire thickness of the wiring board unit 23 is reduced to about 100 to 150 μm by this surface polishing step. The head of the metal bump 22 is polished together with the surface of the insulating material layer 24, for example, until the radius of the head becomes 20 to 80 μm. After such a step, as shown in FIG. 11G, a second masking 29 is formed on the exposed side of the metal plate of the wiring board unit 23 (the lower surface in the figure) by a known method such as a photolithographic method (for example). Step 8). After the upper surface side of the wiring board unit 23 is covered with a protective layer (omitted in the figure), the bottom of the bumped metal plate 28 is etched by dipping in an etchant or the like (step 9) and is patterned, as shown in FIG. As shown in ()), the wiring pattern 22A is formed on the lower surface side of the wiring board unit 23. Next, when the protective layer and the second masking 29 are removed (step 10), a wiring board unit 23a as shown in FIG. 11 (i) is obtained. A semiconductor element 30 such as a bare chip is mounted on the wiring pattern 22A of the wiring board unit 23a thus formed (step 11), and a solder ball 40 is welded to the head of the metal bump 22 exposed on the upper surface of the wiring board unit 23a. Thus, the semiconductor device 60 is obtained.
[0043]
In the method according to the present embodiment, the metal bumps and the wiring patterns are formed using the three-layer metal plate 21 interposed with the second layer 21b functioning as an etching barrier. And the density of the wiring pattern can be increased.
[0044]
Further, since the thickness of the wiring layer is uniform, the thickness of the wiring layer can be reduced to about 5 to 20 μm by etching before forming the wiring. Thereafter, by forming wiring, the wiring density can be increased. For example, in the wiring pattern having the structure shown in FIGS. 11I and 11J, the wiring density can be increased to an L / S value = 25/25 (μm / μm).
[0045]
【The invention's effect】
According to the present invention, since the interlayer connection is made by using the metal wiring member of the bump penetration type, it can be manufactured at low cost. Further, since a plating step is unnecessary, a metal printed wiring board having a wiring pattern of high integration at a low cost can be obtained.
[Brief description of the drawings]
FIG. 1 is a flowchart illustrating each step of a printed wiring board manufacturing method according to a first embodiment.
FIG. 2 is a cross-sectional view showing each step of the printed wiring board manufacturing method according to the first embodiment.
FIG. 3 is a cross-sectional view illustrating each step of the printed wiring board manufacturing method according to the first embodiment.
FIG. 4 is a cross-sectional view illustrating each step of the printed wiring board manufacturing method according to the first embodiment.
FIG. 5 is a perspective view and a sectional view of a metal bump according to the first embodiment.
FIG. 6 is a perspective view and a sectional view of a metal bump and a wiring pattern according to the first embodiment.
FIG. 7 is an electron micrograph of a metal bump according to the first embodiment.
FIG. 8 is an electron micrograph of a metal bump according to the first embodiment.
FIG. 9 is a flowchart showing each step of the printed wiring board manufacturing method according to the second embodiment.
FIG. 10 is a cross-sectional view showing each step of the printed wiring board manufacturing method according to the second embodiment.
FIG. 11 is a cross-sectional view showing each step of the printed wiring board manufacturing method according to the second embodiment.
FIG. 12 is a cross-sectional view of a conventional wiring board.
[Explanation of symbols]
11C: metal wiring member, 11D: wiring pattern, 13: printed wiring board, 11: metal plate, 11B: metal bump, 16: first masking, 15: second masking, 12: insulating material layer (prepreg).

Claims (11)

An insulating substrate;
A bottom part constituting a wiring pattern covering one surface of the insulating substrate, a head exposed on the other surface of the insulating substrate, and a penetrating part penetrating the insulating substrate from the bottom to the head. Printed circuit board comprising: a metal wiring member having The printed wiring board according to claim 1, wherein the metal wiring member is a member in which one surface of a metal plate is half-etched to form a bump. The printed wiring board according to claim 1, wherein the metal wiring member has a shape in which a substantially conical metal bump is formed on one surface of a metal plate. The printed wiring board according to claim 1, wherein the metal bump has a shape obtained by half-etching one surface of a metal plate. 5. The metal wiring member according to claim 1, wherein a metal bump having a height of 50 to 150 μm, a head radius of 20 to 80 μm, and a bottom radius of 80 to 200 μm is provided on one side. Printed wiring board. Masking the metal plate surface;
Forming a bumped metal plate in which a substantially conical metal bump is extended from the bottom surface of the metal plate by half-etching the metal plate via the masking;
Forming an insulating layer on the bump forming surface of the bumped metal plate,
Polishing the insulating layer surface,
Patterning a bottom surface of the metal plate with bumps to form a wiring pattern on the lower surface side of the insulating layer. An insulating substrate;
A first metal bottom portion forming a wiring pattern covering one surface of the insulating substrate;
A first metal head exposed on the other surface of the insulating substrate, a first metal penetrating portion penetrating the insulating substrate from the bottom to the head, the penetrating portion, A metal wiring member having a second metal barrier layer interposed between the metal wiring member and the bottom portion. The printed wiring board according to claim 7, wherein the first metal is copper or a copper alloy, and the second metal is nickel, a nickel alloy, titanium, or a titanium alloy. The L / S value of the wiring pattern is 25/25 to 50/50 　　　 The printed wiring board according to claim 7, wherein the thickness is (μm / μm). The thickness of the bottom portion is 5 to 20 μm, the thickness of the barrier layer is 0.3 to 3 μm, and the thickness of the through portion is 50 to 150 μm. A printed wiring board according to any one of the preceding claims. A step of masking one surface of the three-layer metal plate,
Forming a bumped metal plate in which a substantially conical metal bump is extended from the bottom surface of the metal plate by half-etching the metal plate via the masking;
Forming an insulating layer on the bump forming surface of the bumped metal plate,
Polishing the insulating layer surface,
Patterning a bottom surface of the metal plate with bumps to form a wiring pattern on the lower surface side of the insulating layer.

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