JP4330713B2 - Via-on-via structure of wiring board and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wiring board formed by alternately laminating conductor layers and insulating layers. More specifically, the present invention relates to a via-on-via structure in which a via for conducting a conductor layer and a conductor layer and an upper via are disposed close to each other and a manufacturing method thereof .
[0002]
[Prior art]
Examples of the conventional via-on-via structure include a full offset type shown in FIG. 5 and a lid plating type shown in FIG. FIG. 5 shows a structure in which the upper via 102 is offset with respect to the inner via 101. This is intended to ensure conduction between the conductor layer 104 and the conductor layer 105 by bringing the upper layer via 102 into contact with the land portion 106 of the inner layer via 101. 6 has a structure in which the resin portion 113 and the land portion 116 of the inner layer via 111 are covered with a cover plating layer 117, and the upper layer via 112 is provided immediately above. In this case, the resin portion 113 is covered with a conductive lid plating layer 117 so that the conductor layer 114 and the conductor layer 115 are reliably connected by the upper via 112.
[0003]
[Problems to be solved by the invention]
However, all the conventional via-on-via structures described above have problems. That is, in the case of the full offset type structure of FIG. 5, the overall size in the horizontal direction in the figure becomes considerably large. This is an obstacle to finer wiring patterns. That is, if the inner layer via 101 has a diameter of about 300 μm and the upper layer via 102 has a diameter of about 100 μm, and an interval of about 150 μm is provided between them, W in FIG. 5 becomes 550 μm.
[0004]
In the case of the lid plating structure of FIG. 6, although there is no problem in size, the number of steps for forming the lid plating layer 117 increases. Moreover, since the lid plating layer 117 is easily peeled off, the conduction is not so good in practice. The cause is a thermal action when the insulating layer 118 is laser-processed to form the upper layer via 112. This is because, since the resin portion 113 is usually a 100% resin component, the volatile component forms bubbles between the lid plating layer 117 and the lid plating layer 117 slightly lifted by the heat of the laser.
[0005]
The present invention has been made to solve the problems of the conventional via-on-via structure. That is, the problem is to provide a wiring board having a via-on-via structure that is excellent in size, manufacturing process, and conductivity, and a manufacturing method thereof .
[0006]
[Means for Solving the Problems]
In order to solve this problem, the present invention includes a first conductor layer, a second conductor layer, a first insulation layer therebetween, and a second insulation layer deposited on the second conductor layer. And a third via layer formed on the second insulating layer, wherein the first conductor layer and the second conductor layer are electrically connected to each other, and a first via filled with a conductive paste is provided. , Having a second via formed in the second insulating layer by drilling by laser processing, and electrically connecting the second conductor layer and the third conductor layer, the second via having a larger diameter than the first via. In addition, there is a via-on-via structure that covers half or more of the outer periphery of the first via.
[0007]
In a wiring board having such a via-on-via structure, the second via that is the upper layer via inevitably lies on the land portion of the first via that is the inner layer via. For this reason, even if it does not form a lid plating layer, conduction | electrical_connection with a 2nd conductor layer and a 3rd conductor layer is reliable. Therefore, the number of steps that do not require the lid plating layer is small. Specifically, the number of steps is the same as that of the full offset type structure shown in FIG. Further, the second via also extends inside the first via. For this reason, the amount of the second via protruding from the inside of the first via is not so large. Thus, size issues can be minimized. Needless to say, the second via is preferably formed so as to cover the entire first via. However, even if the second via is slightly deviated from the first via, it is sufficient to cover more than half of the outer periphery of the first via. Why Te Biaonbia structure odor of the present invention the inside of the first via is filled with a conductive paste, the interior of the first via is mere resin, laser processing the second insulating layer for forming the second via This is because the resin is greatly swollen. The conductive paste is obtained by dispersing conductive powder such as metal in a resin, and is more resistant to the influence of laser than a simple resin. For this reason, by using a conductive paste as the filling material inside the first via, it is possible to prevent erosion due to laser processing. Further, the resistance between the second conductor layer and the third conductor layer in the second via can be further reduced.
[0008]
Furthermore, in the via-on-via structure of the present invention, it is also preferable that the second via is formed so as not to protrude from the land portion of the first via. If the second via protrudes from the land portion of the first via to the outside, when the second insulating layer is laser processed for forming the second via, the first insulating layer is also processed at the protruding portion. It is. For this purpose, the diameter of the land portion of the first via may be made larger than that of the second via.
[0009]
The present invention includes a first conductor layer, a second conductor layer, a first insulation layer therebetween, a second insulation layer deposited on the second conductor layer, and a second insulation layer. A wiring board having a formed third conductor layer, a first via that conducts the first conductor layer and the second conductor layer, and a second via that conducts the second conductor layer and the third conductor layer; A first via is formed in the first insulating layer, and the inside thereof is filled with a conductive paste, a second insulating layer is formed, and a hole is formed in the second insulating layer by laser processing so that the diameter is larger than that of the first via. In addition, the present invention extends to a manufacturing method by forming a second via that covers 1/2 or more of the outer periphery of the first via.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described in detail with reference to the drawings. The wiring board according to the present embodiment has the via-on-via structure shown in FIG. This wiring board includes a core insulating layer 10, front and back wiring pattern layers 11, 12, an interlayer insulating layer 13 deposited on the wiring pattern layer 11, and a wiring formed on the interlayer insulating layer 13. And a pattern layer 14.
[0011]
An inner layer via 15 is provided for conducting the wiring pattern layer 11 and the wiring pattern layer 12. The inner layer via 15 forms a drill hole in the core insulating layer 10, forms a plating layer 16 extending from the wall surface to the front and back surfaces to establish electrical connection between the wiring pattern layer 11 and the wiring pattern layer 12, and further contains a silver paste 17 Filled with. A portion of the wiring pattern layer 11 near the inner layer via 15 is referred to as a land 19.
[0012]
An upper via 18 having a diameter larger than that of the inner via 15 is provided at a position immediately above the inner via 15 in the drawing. The upper via 18 is a hole formed in the interlayer insulating layer 13 by laser processing to partially expose the wiring pattern layer 11 and the silver paste 17 and form a plating layer extending inside and outside the hole. As a result, the wiring pattern layer 11 and the wiring pattern layer 14 are electrically connected.
[0013]
In this wiring board, the core insulating layer 10 has a thickness of 500 μm, and the interlayer insulating layer 13 has a thickness of 50 μm. The thickness of the plating layer 16 of the inner layer via 15 is 15 μm. The total thickness of the wiring pattern layers 11 and 12 is 27 μm, which is 12 μm of copper foil and 15 μm of plating. The inner layer via 15 has a diameter (drill hole diameter) of 300 μm, and the upper layer via 18 has a diameter (laser machining diameter) of 350 μm. The thickness of the wiring pattern layer 14 is 15 μm.
[0014]
In this wiring board, the upper layer via 18 is provided so as to cover the entire inner layer via 15. This is shown in the plan perspective view of FIG. FIG. 2 shows the inner layer via 15, its land 19, and the upper layer via 18. The land 19 is provided with a width of 150 μm around the inner layer via 15. The diameter D ₁ of the via-on-via structure is equal to the diameter of the upper layer via 18 and is 350 μm. The diameter D _{2 of the} land 19 is 600 μm. If the full offset type structure as shown in FIG. 5 is adopted, the maximum diameter of the via-on-via structure is required to be about 550 μm and the maximum diameter of the land is about 850 μm as described above. In the present embodiment, increasing the size of the upper layer via 18 contributes to the refinement of the wiring pattern.
[0015]
Next, a manufacturing process of the wiring board of FIG. 1 will be described. FIG. 3 shows a state in which the inner layer via 15 is filled with a silver paste 17 to flatten the surface, and an interlayer insulating layer 13 is deposited. Since the process until obtaining this state is a combination of known techniques, a description thereof is avoided. However, it should be noted that it is not necessary to cover the inner via 15 with a lid plating before depositing the interlayer insulating layer 13. This is because the upper layer via 18 is provided in relation to the land 19 of the inner layer via 15, so that the conduction between the wiring pattern layer 11 and the wiring pattern layer 14 can be sufficiently ensured even without lid plating. If lid plating is formed, the number of processes increases considerably, such as application of catalyst, electroless plating, and electroplating. In the present embodiment, no extra process is performed by not forming the lid plating.
[0016]
FIG. 4 shows a state in which a hole 18 is formed in the interlayer insulating layer 13 by laser processing. At this time, the heat of the laser also affects the silver paste 17 filling the inner via 15 at the end of processing. However, since the silver paste 17 is far more resistant to heat than a simple resin, it hardly deforms. Further, the range in which the hole 18 is formed does not protrude from the land 19 of the inner layer via 15. If protruding, not only the interlayer insulating layer 13 but also the core insulating layer 10 may be processed at the protruding portion. There is no such fear in the present embodiment. In the state of FIG. 4, when a plating layer is formed over the inside and outside of the hole 18 and subjected to pattern processing, a wiring pattern 14 is obtained as shown in FIG. 1.
[0017]
As described above in detail, in the via-on-via structure of the wiring board according to the present embodiment, the upper-layer via 18 having a larger diameter is provided immediately above the inner-layer via 15. As a result, the in-plane dimensions of the via-on-via structure are kept small. Even if no lid plating is formed on the inner layer via 15, the wiring pattern 14 is in direct contact with the land 19 (wiring pattern 11) of the inner layer via 15, and conduction is ensured. Also, the manufacturing process is simple. Further, since the filling material of the inner layer via 15 is the silver paste 17, damage to the inside of the inner layer via 15 during the laser processing for forming the upper layer via 18 can be minimized. Further, the contact resistance between the wiring pattern 14 and the wiring pattern 11 is also reduced because the silver paste 17 has conductivity. Further, since the upper layer via 18 does not protrude from the land 19, the possibility that the core insulating layer 10 is also processed during the laser processing for forming the upper layer via 18 is eliminated. Thus, a via-on-via structure of a wiring board that is excellent in size, process, and conductivity is realized.
[0018]
Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the dimension of each part may be a different value. Further, as the filler for the inner layer via 15, a material using other metal such as copper paste instead of silver paste may be adopted.
[0019]
【The invention's effect】
As is apparent from the above description, according to the present invention, a wiring board having a via-on-via structure excellent in all of size, manufacturing process, and conductivity and a manufacturing method thereof are provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a wiring board having a via-on-via structure according to an embodiment.
FIG. 2 is a plan perspective view of a via-on-via structure.
FIG. 3 is a cross-sectional view showing a state in which an interphase insulating layer is deposited.
FIG. 4 is a cross-sectional view showing a state in which laser processing for forming an upper layer via is performed.
FIG. 5 is a cross-sectional view showing an example of a conventional via-on-via structure (full offset type).
FIG. 6 is a cross-sectional view showing an example of conventional via-on-via structure (lid plating type).
[Explanation of symbols]
10 Core insulating layers 11, 12, 14 Wiring pattern 13 Interlayer insulating layer 15 Inner layer via 17 Silver paste 18 Upper layer via 19 Land

Claims (3)

A first conductor layer, a second conductor layer, a first insulating layer therebetween, a second insulating layer deposited on the second conductor layer, and formed on the second insulating layer. In a wiring board having a third conductor layer,
A first via having conduction between the first conductor layer and the second conductor layer and filled with a conductive paste inside;
A second via formed in the second insulating layer by drilling by laser processing and electrically connecting the second conductor layer and the third conductor layer;
A via-on-via structure of a wiring board, wherein the second via has a larger diameter than the first via and covers more than half of the outer periphery of the first via. In the via-on-via structure of the wiring board according to claim 1,
A via-on-via structure of a wiring board, wherein the second via is formed so as not to protrude from a land portion of the first via. A first conductor layer, a second conductor layer, a first insulating layer therebetween, a second insulating layer deposited on the second conductor layer, and formed on the second insulating layer. A wiring board comprising: a third conductor layer; a first via for conducting the first conductor layer and the second conductor layer; and a second via for conducting the second conductor layer and the third conductor layer. In the manufacturing method of
Forming the first via in the first insulating layer and filling the interior with a conductive paste;
Forming the second insulating layer;
The second insulating layer has a diameter larger than that of the first via by drilling the second insulating layer by laser processing, and forms the second via covering at least half of the outer periphery of the first via. A method of manufacturing a wiring board.

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