JP4742485B2 - Multilayer printed wiring board and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer printed wiring board and a method for manufacturing the same, and more particularly to a multilayer printed wiring board in which a plurality of IVH (interstitial via hole) substrates are stacked with an insulator layer interposed therebetween and a method for manufacturing the same.
[0002]
In recent years, with the increase in circuit density, non-through-through holes (interstitial via holes, hereinafter also referred to as IVH) have been introduced to increase the degree of freedom of wiring and effectively use board space. The multilayer printed wiring board which has has spread.
[0003]
[Prior art]
Conventionally, when a plurality of double-sided through-hole substrates 5 are laminated in multiple layers by the prepreg insulating layer 6, the intermediate prepreg insulating layer 6 is melted and filled into each through-hole hole to form the blind via hole 11. In addition, there is known a technique in which inner interlayer circuits are connected to each other by a conductive paste 8 to form inner via hole-like conduction 12 (Patent Document 1).
[0004]
Conventionally, in an IVH substrate in which a plurality of printed wiring boards 11 are connected in a stacked state, anisotropic conductive particles 16a are formed by dispersing conductive particles 16a in an insulating sheet 16b between the wiring patterns 14 on each printed wiring board. A sheet 16 or a sheet connected by connecting means made of an anisotropic conductive adhesive is known (Patent Document 2).
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-90762 (summary, figure).
[0006]
[Patent Document 2]
JP-A-11-298148 (summary, figure).
[0007]
[Problems to be solved by the invention]
By the way, since IVH is originally made by a technique of forming a through-plated through hole, the center thereof is a cavity, and it is necessary to close this gap when stacking. For this reason, in order to electrically connect IVHs to each other, as shown in Patent Document 1, it is necessary to draw the conductor pattern from each IVH to another place and connect the conductive pattern 8 between them. . Otherwise, the conductive paste 8 permeates into the cavities during lamination, and it cannot be guaranteed that the IVHs can be reliably connected.
[0008]
On the other hand, the anisotropic conductive sheet of Patent Document 2 is a material in which a conductor is mixed with an insulating material, and the conductors are connected only in the direction in which force is applied, and conduction is obtained only in the direction of the plate thickness. However, it is necessary to apply the resist 15 in advance to the place where it is desired to be non-conductive, so that not only is the work of making it locally conductive complicated, but also the reliability of interlayer insulation is low.
[0009]
As described above, in the conventional IVH multilayer printed wiring board technology, there is no technique for directly bonding only specific inner layers IVH, so there is a limit in increasing the degree of freedom of conductor wiring and effectively using the board space. It was.
[0010]
The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a multilayer printed wiring board capable of directly and surely connecting only specific inner layers IVH and a method for manufacturing the same. is there.
[0011]
[Means for Solving the Problems]
The above problem is solved by the configuration of FIG. That is, the method for manufacturing a multilayer printed wiring board according to the present invention (1) is a method for manufacturing a multilayer printed wiring board in which a plurality of IVH substrates are stacked with an insulator layer interposed therebetween. After filling and curing the resin 19 in the plated through holes of the via holes IVHa and IVHb that are connected to each other, the conductive paste 33 is disposed at the same coordinates as the via holes of the insulator layer 30 sandwiched between these IVH substrates. and, during lamination, it is to electrically connect the lands that directly expand the surrounding plated-through hole edge of each via-hole by heating and pressure bonding to said conductive paste.
[0012]
According to the present invention (1), since the inner layer portions of the via holes IVHa and IVHb that are connected to each other in the IVH substrates 10A and 10B are previously closed with the resin 19, the conductive paste 33 is applied to each other during the lamination. The conductive paste 33 and each inner layer land can be securely connected without entering the cavities of the via holes IVHa and IVHb. Therefore, it is possible to directly and surely connect only the specific inner layers IVHa and IVHb, thereby increasing the degree of freedom of wiring and effectively using the board space.
[0013]
In the present invention (2), in the present invention (1), for example, as shown in FIG. 3, a part of the resin layer 19 on the insulator layer side previously filled in the plated through holes of the via holes IVHa and IVHb is removed. The recess 20 is formed and then laminated. Therefore, during lamination, a part of the conductive paste 33 enters the respective recesses 20 of IVHa and IVHb, and thus a more reliable connection can be obtained between them.
[0014]
Further, the above problem is solved by the configuration of FIG. That is, the multilayer printed wiring board of the present invention (3) is a multilayer printed wiring board formed by laminating a plurality of IVH substrates with an insulator layer interposed therebetween, and is provided at the same coordinates in each of the IVH substrates 10A and 10B. Via holes IVHa and IVHb whose plated through holes are closed with resin 19 and conductive resin 33 arranged through the same coordinates in insulator layer 30 sandwiched between the IVH substrates. And electrically connecting lands that are directly connected and developed around the end faces of the plated through holes of the via holes IVHa and IVHb.
[0015]
In the present invention (4), in the present invention (3), for example, as shown in FIG. 3, a conductive resin is provided in the recess 20 on the insulator layer side provided in the plated through hole of each via hole IVHa, IVHb to be connected. 33 is invading.
[0016]
In the present invention (5), in the present invention (3) or (4), for example, as shown in FIG. 5, the diameter of the lower hole before plating of each via hole to be connected is φ1, and the via hole is directly connected around the end face of the plated through hole. When the outer peripheral diameter of the land to be developed is φ2, the cross-sectional diameter φ of the conductive resin 33 that electrically connects the inner layer lands is expressed by the following equation:
φ1 ≦ φ ≦ {φ1 + (φ2-φ1) / 2}
Is within the range of Therefore, even when there is a slight misalignment between the insulator layer 30 and the IVH substrate 10 during lamination, a reliable connection is established between each via hole IVHa, IVHb to be connected and the conductive paste 33. can get.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a plurality of preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings.
[0018]
FIG. 1 and FIG. 2 are views (1) and (2) showing a method for producing a multilayer printed wiring board according to the first embodiment, and at least a portion of an IVH inner layer where an inner via hole is formed Is previously covered with resin. Here, the inner via hole (also referred to as a belly via hole) means a through hole for connecting different conductors in the inner layer.
[0019]
First, as shown in FIG. 1A, a double-sided copper-clad laminate 13 having copper foils 12a and 12b provided on both sides of a base material (glass epoxy resin or the like) 11 is used as a base, and as shown in FIG. , A through hole 14 is drilled at a place where IVH is provided. Next, as shown in FIG. 1C, copper plating 15 is applied to the entire surface of the copper-clad laminate 13 to form a double-sided through-hole substrate 17 having plated through holes 16. Next, as shown in FIG. 1D, necessary etching is performed on the double-sided through-hole substrate 17 to form a conductor circuit pattern, and thus a printed wiring board 10A is formed. Here, 18 is a land. Note that the etching may be performed at least on the inner layer surface to be stacked. Then, as shown in FIG. 1 (E), a thermosetting resin 19 made of an epoxy resin or the like is embedded in the hollow portion of the plated through hole 16 and heated and cured in advance. Note that the resin 19 may be any material that at least closes the inner layer surface side of the plating through-hole 16. Further, the resin 19 may be conductive.
[0020]
On the other hand, as shown in FIG. 2 (A), a through-hole 32 is drilled in a portion of the prepreg insulating layer 31 that requires an inner via hole. The prepreg insulating layer (prepreg) 31 is an adhesive sheet in which a glass cloth reinforcing material is impregnated with an uncured thermosetting resin to be in a semi-cured B stage state. Further, a conductive paste 33 is applied to the through holes 32 by printing or the like. The conductive paste 33 is a paste obtained by mixing fine particles of carbon (C), silver (Ag), or copper (Cu) with a binder of a thermoplastic resin having a high concentration and viscosity. Thus, the prepreg material 30 is formed.
[0021]
Next, as shown in FIG. 2 (B), the two printed wiring boards 10A and 10B are arranged so as to sandwich the intermediate prepreg material 30. Further, as shown in FIG. The multilayer printed wiring board 10 is formed by applying pressure. At that time, the intermediate prepreg material 30 is melted and bonded to the inner layer surfaces of the printed wiring boards 10A and 10B. At the same time, the conductive paste 33 is connected to the copper-plated land surface 18 of IVHa and IVHb to conduct between IVHa and IVHb. At this time, since the inner layer surface portions of IVHa and IVHb are previously blocked by the resin 19, reliable connection can be obtained between the IVHa and IVHb by an appropriate amount of the conductive paste 33.
[0022]
FIG. 3 is a diagram showing a method for manufacturing a multilayer printed wiring board according to the second embodiment, and a recess for allowing an appropriate amount of conductive paste 33 to enter into each resin layer blocking the inside of IVHa and IVHb to be connected is provided. Shows the case. First, as shown in FIG. 3A, a recess 20 is provided in advance in a portion to be connected to the conductive paste 33 with respect to the resin 19 that plugs at least the IVHa and IVHb to be connected. The recess 20 can be formed by a chemical or the like that dissolves the resin 19. Further, two printed wiring boards 10A and 10B are arranged so as to sandwich the intermediate prepreg material 30, and the multilayer printed wiring board 10 is formed by heating and pressing in this state as shown in FIG. 3C. . In that case, since the recess 20 is formed in advance on each inner layer surface portion of IVHa, IVHb, the conductive paste 33 penetrates and adheres to a part of the exposed portion of the inner wall of each IVHa, IVHb, and is cured. Thus, more reliable electrical connection characteristics can be obtained by bonding through a large area between IVHa and IVHb.
[0023]
FIG. 4 is a diagram showing a method of manufacturing a multilayer printed wiring board according to another embodiment, and shows a case where the number of multilayer boards is increased by increasing the number of layers of the printed board 10 and the prepreg material 30. In the same manner as described above, the prepreg materials 30A and 30B are inserted between the printed boards 10A, 10B and 10C, and these are overheated, pressurized and bonded. In this case, the IVHa and IVHb are connected by the conductive paste 33a and the IVHc and IVHd are connected by the conductive paste 33b. Thus, there is no through-hole penetrating the whole, but a multilayer that can achieve the same effect is obtained. A printed wiring board 10 is formed. Furthermore, the connection between IVHe and the conductor pattern 21 can be easily obtained, the degree of freedom in wiring design is improved, and the board space can be effectively used. Moreover, since it is not necessary to perform through-hole copper plating for through holes on the outer layer copper foil, the thickness of the outer layer copper foil can be reduced, and the patterning accuracy is improved.
[0024]
FIG. 5 is a view for explaining the filling hole diameter of the conductive paste. In FIG. 5A, when the diameter of a pilot hole (hole formed by drilling or laser processing) before IVH copper plating is φ1 and the outer diameter of the IVH inner layer land 18 is φ2, the connection is made to the land 18. The cross-sectional diameter φ of the conductive paste 33 is given by
φ1 ≦ φ ≦ {φ1 + (φ2-φ1) / 2}
It is in the range. Therefore, even if there is a slight misalignment between IVHa, IVHb and the conductive paste 33 at the time of lamination, a reliable connection can be obtained between them.
For this reason, there is a margin in the processing accuracy of the prepared hole, and the multilayer printed wiring board can be mass-produced.
[0025]
FIG. 5B shows examples of the outer peripheral diameter φ2 of various lands 18. In general, the outer peripheral shape of the land 18 includes a circle, a rectangle, an octagon, and the like. In the case of a circle, the diameter is φ2, and in the case of a square, one side is φ2, and in the case of a rectangle, the short side is φ2. Further, in the case of a polygon including an octagon, the diameter of the inscribed circle can be set to φ2.
[0026]
In each of the above embodiments, an example of the conductive paste 33 is shown. However, a wide variety of materials such as a paste that is metalized by heating can be applied.
[0027]
Further, instead of the insulating resin 19, the conductive paste 33 may be filled in the copper plating through holes 16 in advance and cured.
[0028]
Moreover, although several embodiment suitable for the said invention was described, it cannot be overemphasized that the structure of each part, a process, and these various combinations can be changed within the range which does not deviate from this invention thought.
[0029]
【The invention's effect】
As described above, according to the present invention, only specific inner layers IVH can be directly and reliably connected, so that the degree of freedom of conductor wiring can be increased and the board space can be used more effectively. The place that contributes to high density of the plate is extremely large.
[Brief description of the drawings]
FIG. 1 is a diagram (1) illustrating a method for producing a multilayer printed wiring board according to a first embodiment.
FIG. 2 is a diagram (2) showing the method for producing the multilayer printed wiring board according to the first embodiment.
FIG. 3 is a diagram showing a method for producing a multilayer printed wiring board according to a second embodiment.
FIG. 4 is a diagram illustrating a method of manufacturing a multilayer printed wiring board according to another embodiment.
FIG. 5 is a view for explaining a filling hole diameter of a conductive paste.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Multilayer printed wiring board 10A, 10B Printed wiring board 11 Base material 12a, 12b Copper foil 13 Double-sided copper clad laminated board 14 Through-hole 15 Copper plating 16 Plating through-hole 17 Double-sided through-hole board 18 Land (copper foil, copper plating)
19 Thermosetting resin 20 Recess 30 Prepreg material 31 Prepreg insulating layer 32 Through hole 33 Conductive paste IVH Interstitial via hole

Claims (5)

A method of manufacturing a multilayer printed wiring board in which a plurality of IVH substrates are stacked with an insulator layer interposed therebetween, and after filling resin in the plated through holes of via holes connected to each other in each IVH substrate in advance, these conductive paste through arranged on the same coordinates and the via-hole of the insulator layer sandwiched by the IVH board, during lamination, the conductive between lands that directly expand the surrounding plated-through hole edge of each via hole A method for producing a multilayer printed wiring board, wherein the connection is electrically made by heating and pressure bonding to a conductive paste. 2. The method for producing a multilayer printed wiring board according to claim 1, wherein a part of the resin layer filled in the plated through hole of the via hole in advance is removed to form a recess and then laminated. . A multilayer printed wiring board formed by laminating a plurality of IVH substrates with an insulator layer interposed therebetween, and is a via hole provided at the same coordinate in each IVH substrate, and the plated through hole is blocked with resin. and stuff, electrically connecting the land to directly expand a said through arranged conductive resin in the same coordinates of the insulator layer surrounding the plated through hole end surface of each via hole is sandwiched by the respective IVH board A multilayer printed wiring board comprising: 4. The multilayer printed wiring board according to claim 3, wherein a conductive resin penetrates into a recess on the insulator layer side provided in a plated through hole of each via hole to be connected. When the via hole diameter before plating of each via hole to be connected is φ1, and the outer peripheral diameter of the land directly connected and developed around the end surface of the plated through hole of the via hole is φ2, the conductive resin that electrically connects the lands 5. The multilayer printed wiring board according to claim 3, wherein the cross-sectional diameter φ is in the range of the following formula: φ1 ≦ φ ≦ {φ1 + (φ2−φ1) / 2}.

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