JP2003198136A - Wiring board - Google Patents

Abstract

(57) [Problem] To provide a wiring substrate in which the characteristic impedance of a through-hole conductor is matched and excellent in electrical characteristics, and which cannot be depressed around the through-hole and has no break in a wiring conductor layer. SOLUTION: A plurality of insulating layers 1 and a wiring conductor layer 2 each formed by impregnating a fiber base material with a thermosetting resin are laminated,
A plurality of through-hole conductors 4b penetrating the insulating layer 1 and electrically connected between the wiring conductor layers 2 located vertically above and below the insulating layer 1 are arranged in a grid pattern. Between the upper and lower wiring conductor layers 2 connected by the hole conductor 4b, the wiring conductor layer 2 not connected to the through-hole conductor 4b is provided, and the through-hole conductor 2 is provided on the same plane as the non-connection wiring conductor layer 2. A wiring substrate, comprising a grid-like dummy wiring conductor layer 5 for partitioning each through-hole conductor 4b around the periphery of the wiring conductor 4b.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board for housing electronic components such as semiconductor elements. 2. Description of the Related Art Conventionally, as a wiring board of an organic material for mounting a semiconductor element, for example, a copper foil is formed on both sides or one side of an insulating layer obtained by impregnating a fiber base material with a thermosetting resin. 2. Description of the Related Art A multilayer printed wiring board is used in which a plurality of wiring boards each having a wiring conductor layer adhered thereto are laminated via an adhesive layer made of a fiber base material impregnated with a thermosetting resin. In this wiring board, a plurality of through holes penetrating from the upper surface to the lower surface thereof are provided, and the inner wall of the through hole is used for electrically connecting wiring conductor layers located vertically above and below each insulating layer. A through-hole conductor made of a copper plating film is adhered and formed, thereby enabling three-dimensional high-density wiring. In addition, around the through-hole conductor to which the wiring conductor layer is not connected on the surface of each insulating layer, a circular shape connected to the through-hole conductor is used in order to reduce unevenness of the periphery of the through-hole conductor on the surface of the wiring board. A dummy land composed of an annular conductor layer is provided so as to surround the through-hole conductor. Such a wiring board has a thickness of 0.1%.
A plurality of wirings each having a wiring conductor layer made of a copper foil having a thickness of about 10 to 50 μm formed on both sides or one side of an insulating layer formed by impregnating a thermosetting resin into a fiber base material having a thickness of about 0.5 mm. After laminating and hot-pressing the board via an adhesive layer formed by impregnating a thermosetting resin precursor into a fibrous base material having a thickness of about 0.1 to 0.2 mm, the diameter is 200 to 5 from its upper surface to its lower surface.
A through hole of about 00 μm is drilled at an interval of about 600 to 1500 μm by drilling, and then a through-hole conductor made of a copper plating film having a thickness of about 15 to 30 μm is formed on the inner wall of the through hole by electroless plating and electrolytic plating. After filling and curing the inside of the through-hole on which the copper plating film is applied, and then curing, the excess filling resin protruding from the through-hole is polished to flatten its upper and lower surfaces. It is produced by. However, in recent years, with the increase in the operating speed of the semiconductor element mounted on the wiring board, the electrical characteristics of the wiring board have been improved so that the mounted semiconductor element does not malfunction. Is becoming necessary,
As a means thereof, it has been studied to omit the dummy land connected to the through-hole conductor and to match the characteristic impedance of the through-hole conductor to suppress the generation of noise. However, when the dummy lands are removed, a recess of several tens of μm is formed around the through-hole conductor from which the dummy lands have been removed on the surface of the wiring board after lamination of the wiring board. As a result, holes are formed inside the through-holes. When polishing the filling resin protruding from the inside of the through hole after filling the filling resin, several tens of μm
When the depression m is completely flattened, the surface of the wiring substrate is excessively polished, thereby causing a problem that the wiring conductor layer on the surface of the wiring substrate is disconnected. SUMMARY OF THE INVENTION The present invention has been completed in view of the above-mentioned problems of the prior art. It is an object of the present invention to match the characteristic impedance of a through-hole conductor and prevent the through-hole conductor from being recessed on the surface of the wiring board around the through-hole conductor. Another object of the present invention is to provide a wiring board having no disconnection of a wiring conductor layer. According to the present invention, there is provided a wiring board in which a plurality of insulating layers each formed by impregnating a fiber base material with a thermosetting resin and a plurality of wiring conductor layers are laminated, and the insulating layer is penetrated. And
It comprises a plurality of through-hole conductors arranged in a grid for electrically connecting the wiring conductor layers located vertically above and below the insulating layer, and the upper and lower conductors connected by the grid-like through-hole conductors are provided. A wiring conductor layer that is not connected to the through-hole conductor between the wiring conductor layers and that defines each through-hole conductor around the through-hole conductor on the same plane as the non-connection wiring conductor layer Is provided. According to the wiring board of the present invention, between the upper and lower wiring conductor layers connected by the grid-like through-hole conductor,
A wiring conductor layer that is not connected to the through-hole conductor is provided, and a dummy wiring conductor layer in a grid shape that partitions each through-hole conductor is provided around the through-hole conductor on the same plane as the unconnected wiring conductor layer. As a result, no pits are formed around the through holes on the upper and lower surfaces of the wiring board. As a result, after filling the inside of the through holes with the filling resin and curing, the extra holes protruding from the inside of the through holes are filled. Even if the upper and lower surfaces are polished by polishing the resin, the surface of the wiring substrate is not excessively polished, and the wiring conductor layer on the surface of the wiring substrate is not broken. The dummy wiring conductor layer is arranged so as to partition each through-hole conductor around the through-hole conductor, and is not connected to the through-hole conductor, so that the characteristic impedance of the through-hole conductor is matched. Does not inhibit. Next, a wiring board according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view illustrating an example of an embodiment of a wiring board according to the present invention, and FIG. 2 is a plan view of a main part of an insulating layer on which a grid-like dummy wiring conductor layer is formed. In this embodiment, a wiring board with a heat sink, in which a heat sink is joined to the lower surface of the wiring board, will be described as an example. In these figures, 1 is an insulating layer, 2 is a wiring conductor layer, 3 is a wiring board composed of the insulating layer 1 and the wiring conductor layer 2, 4a is a through hole, 4b is a through hole conductor, 5
Is a dummy wiring conductor layer, and 6 is an adhesive layer, and these mainly constitute the wiring board of the present invention. The insulating layer 1 has a hole H for accommodating a semiconductor element (not shown) at the center thereof.
Function as a support, for example, the thickness of an organic insulating material impregnated with a thermosetting resin of epoxy resin or bismaleimide triazine resin / polyphenylene ether resin on a fiber base material such as glass cloth or aramid nonwoven fabric is 0.1 to 0.1
It is a 0.3 mm flat plate. A wiring conductor layer 2 made of a copper foil having a thickness of 7 to 12 μm is adhered on both upper and lower surfaces thereof, thereby forming a so-called double-sided copper-clad board serving as the wiring board 3. A plurality of wiring boards 3 having a hole H in the center are made of a thermosetting resin such as an epoxy resin, a bismaleimide triazine resin or a polyphenylene ether resin on a fiber base such as glass cloth or aramid nonwoven fabric. The layers are laminated via the impregnated adhesive layer 6, thereby forming a laminated substrate. Note that, in this example, a case is shown in which the laminated substrate includes the three-layered wiring board 3. The laminated substrate has a diameter of 200 to 500 μm penetrating from the upper surface to the lower surface, and is 600 to 1500 μm.
A plurality of through-holes 4a are formed at intervals of μm, and through-hole conductors 4b for electrically connecting the wiring conductor layers 2 located above and below via an insulating layer 1 are formed on the inner wall of the through-hole 4a. Are applied by a plating method. The laminated substrate has a thickness of 0.5 to 2.0 mm. If the thickness is less than 0.5 mm, heat and external force may be generated when a plurality of through holes 4a are formed through the upper and lower surfaces of the laminated substrate described later. There is a large risk that the wiring board will be warped or deformed due to the influence of the above, and the flatness required for the wiring board will not be secured. On the other hand, if it exceeds 2.0 mm, the through hole 4a will When the through-hole conductor 4b is formed on the inner wall, the plating solution does not easily enter the inside of the through-hole 4a, and the through-hole conductor 4b
Is difficult to form satisfactorily. Therefore, the thickness of the laminated substrate is preferably in the range of 0.5 to 2.0 mm. The through-hole conductor 4b has an inner wall of the through-hole 4a coated with a copper plating layer of 1 to 3 μm by electroless copper plating and further coated with an electrolytic copper plating layer of 15 to 30 μm by electrolytic copper plating. It is formed by doing. Further, the inside of the through hole 4a is filled with a filling resin 7 composed of a photosensitive resin, a photoinitiator and an inorganic insulating filler. As a method of filling the hole filling resin 7, screen printing is generally adopted. Then, after the through-hole conductor 4b is formed on the inner wall of the through-hole 4a, the inside of the through-hole 4a is filled with the hole-filling resin 7 and hardened. The surface of the wiring board is flattened by polishing. If the surface of the wiring board is not sufficiently flattened, there is a concern that the reliability of connection between the wiring board and the external electric circuit board may be deteriorated when the wiring board is mounted on the external electric circuit board. In the wiring board of the present invention, as shown in the plan view of the main part in FIG. 2, the through-hole conductor 4b is provided between the upper and lower wiring conductor layers 2 connected by the grid-like through-hole conductor 4b. And a grid-like dummy wiring conductor layer 5 for partitioning each through-hole conductor 4b around the through-hole conductor 4b on the same plane as the non-connection wiring conductor layer 2. Is provided.
This is important for the wiring board of the present invention. According to the wiring board of the present invention, the upper and lower wiring conductor layers 2 connected by the grid-like through-hole conductors 4b.
A wiring conductor layer 2 that is not connected to the through-hole conductor 4b is disposed therebetween, and a grid-like shape that partitions each through-hole conductor 4b around the through-hole conductor 4b on the same plane as the non-connection wiring conductor layer 2 Since the dummy wiring conductor layer 5 is provided, the dummy wiring conductor layers 5 arranged in a lattice pattern between the through-hole conductors 4b do not cause depressions around the through holes 4a on the upper and lower surfaces of the wiring board. As a result, after filling the inside of the through-hole 4a with the hole-filling resin 7 and hardening, the surface of the wiring board is flattened even if the upper and lower surfaces thereof are flattened by polishing the excess hole-filling resin 7 protruding from the through-hole 4a. There is no excessive polishing, and no breakage of the wiring conductor 2 on the surface of the wiring board. Also,
Since the dummy wiring conductor layers 5 are arranged in a lattice pattern between the through-hole conductors 4b and are not connected to the through-hole conductors 4b, the matching of the characteristic impedance of the through-hole conductors 4b is hindered. Absent. Such a grid-like dummy wiring conductor layer 5
Is formed simultaneously with the wiring conductor layer 2 and has a width of 100 to 800
It is preferably μm. The width of the dummy wiring conductor layer 5 is
If the thickness is smaller than 100 μm, after the wiring board 3 is laminated, irregularities in the periphery of the through-hole conductor 4b surrounded by the dummy wiring conductor layers 5 arranged in a grid on the surface of the wiring board tend not to be favorably reduced. If it is wider than 800 μm, it tends to be difficult to match the characteristic impedance of the through-hole conductor 4b by contact with the through-hole conductor 4b. Therefore, the grid-like dummy wiring conductor layer 5 has a width of 100 to 800
It is preferably μm. In addition, the dummy wiring conductor layer 5
Is preferably equal to the thickness of the wiring conductor layer 2 from the viewpoint of reducing unevenness on the surface of the wiring board. The wiring conductor layer 2 on the surface of the wiring board according to the present invention forms a wiring pattern including a power supply wiring, a ground wiring and a signal wiring. Electrodes of an external electric circuit board (not shown) are connected to exposed portions of 2 through solder bumps 11, and a radiator plate 13 is joined to the lower surface of the substrate 2 via an adhesive 12. The radiator plate 13 functions to radiate the heat generated by the mounted semiconductor element to the outside well,
It is formed of a metal having good heat dissipation such as copper. Further, the surface of the wiring conductor layer 2 on the surface of the wiring board is prevented from being oxidized and corroded, and the solder bumps 11 are formed.
In order to improve the connection with the solder, a plating layer of nickel-gold or the like having good wettability with solder and excellent corrosion resistance is applied. Further, on the surface of the wiring board, a solder-resistant resin layer 14 having an opening exposing a central portion of the wiring conductor layer 2 is attached. Such a wiring board is manufactured by the method described below. First, copper foil is applied to both surfaces of an insulating layer 1 in which a resin such as an epoxy resin, a bismaleimide triazine resin, a polyphenylene ether resin is impregnated and cured on a glass cloth or an aramid nonwoven fabric, and a wiring board 3 is laminated. The wiring board 3 having the wiring conductor layer 2 and the lattice-shaped dummy wiring conductor layer 5 formed thereon is manufactured by etching a copper foil other than the surface serving as the outermost layer of the substrate into a wiring pattern, and an appropriate punching method is employed. Then, a hole H for accommodating the semiconductor element is formed in the center of the wiring board 3. The lattice-shaped dummy wiring conductor layer 5 is formed in advance on each insulating layer 1 in a region where the through-hole conductors 4b to which the wiring conductor layer 2 is not connected are present in a lattice pattern. Next, a hole H was formed at the center through an adhesive layer formed by impregnating a thermosetting resin such as an epoxy resin, a bismaleimide triazine resin, or a polyphenylene ether resin into a glass cloth or an aramid nonwoven fabric. Wiring board 3
Are laminated, the degree of vacuum is 660 to 8000 Pa, and the temperature is 180 to
A laminated substrate is formed by hot pressing at 210 ° C. under a pressure of 2 to 5 MPa for several hours. Further, through holes 4a having a diameter of 200 to 500 μm and penetrating the laminated substrate at intervals of 600 to 1500 μm are formed by using a drill. At this time, as described above, in the region where the through-hole conductors 4b to which the wiring conductor layer 2 is not connected are formed in a lattice pattern on the insulating layers 1 by design, a grid-like dummy surrounding the through-hole conductor 4b is formed. The wiring conductor layer 5 is formed. Next, the wiring board is immersed in a roughening solution such as an aqueous solution of permanganate to remove the residual resin inside the through-hole 4a, and then immersed in an aqueous solution of a palladium catalyst for electroless plating to immerse the wiring board in the through-hole 4a. A palladium catalyst is attached to the inner wall of copper, and copper sulfate, Rossell salt, formalin, E
Immerse for several minutes in an electroless copper plating solution composed of DTA sodium salt, stabilizer, etc.
a) and then immersed in an electrolytic copper plating solution composed of sulfuric acid / copper sulfate pentahydrate / chlorine / brightener for several hours while applying a current of several A / dm ² for several hours. An electrolytic copper plating layer is deposited on the copper plating layer, and the thickness is 15 ~ 30μ
m through-hole conductors 4b are formed. At the same time, a copper plating layer having a thickness of 15 to 30 μm is deposited on a copper foil having a wiring substrate surface having a thickness of 12 to 18 μm. Thereafter, by etching and polishing the copper plating layer on the surface of the wiring board into a wiring pattern, the thickness of the wiring board becomes 15 to
A wiring conductor layer 2 of 30 μm is formed. A part of the wiring conductor layer 2 formed on the surface of the wiring board forms a mounting electrode 15 that is electrically connected to an external electric circuit board via the solder bump 11. On the surface of the wiring board, a solder-resistant resin layer 14 having an opening for exposing the mounting electrode 15 is applied. The solder-resistant resin layer 14 has a thickness of 20 to 60 μm,
For example, it is made of an insulating material containing 30 to 70% by weight of an inorganic powder filler such as silica or talc in a mixture of a photosensitive resin such as an acrylic-modified epoxy resin and a photoinitiator. Is prevented from being electrically short-circuited by the solder bumps 11 and the mounting electrodes 15
Has a function of improving the bonding strength between the semiconductor device and the insulating layer 1. The solder-resistant resin layer 14 is formed by applying an uncured resin film composed of a photosensitive resin, a photoinitiator, and an inorganic powder filler to the surface of the outermost insulating layer 1 or by using a thermosetting resin. And an uncured resin varnish composed of an inorganic powder filler and an uncured resin varnish is applied to the surface of the outermost insulating layer 1 and dried. Thereafter, an opening is formed by exposure and development.
This is formed by curing with ultraviolet light and heat. Thus, according to the wiring board of the present invention, the characteristic impedance of the through-hole conductor 4b is well matched, and the surface of the wiring board around the through-hole conductor 4b cannot be depressed. No wiring board can be provided. It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the scope of the present invention. In the above-described embodiment, an example is shown in which the wiring board of the present invention is applied to a wiring board with a heat sink. However, it goes without saying that the present invention can be applied to a wiring board having no central hole. According to the wiring board of the present invention, a wiring conductor layer not connected to the through-hole conductor is provided between the upper and lower wiring conductor layers connected by the grid-like through-hole conductor. In addition, a dummy wiring conductor layer in the form of a grid that divides each through-hole conductor is provided around the through-hole conductor on the same plane as the unconnected wiring conductor layer, so that depressions are formed around the through-holes on the upper and lower surfaces of the wiring board. As a result, after filling the inside wall of the through-hole conductor with the filling resin and hardening, as a result, the excess filling resin protruding from the inner wall of the through-hole conductor was polished and the upper and lower surfaces were flattened. Does not excessively polish the surface of the wiring board,
The wiring conductor layer on the surface of the wiring board is not disconnected. The dummy wiring conductor layer is arranged so as to partition each through-hole conductor around the through-hole conductor, and is not connected to the through-hole conductor, so that the characteristic impedance of the through-hole conductor is matched. Does not inhibit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of an example of an embodiment when a wiring board of the present invention is applied to a wiring board with a heat sink. FIG. 2 is a plan view of a principal part of an insulating layer on which a grid-like dummy wiring conductor layer is formed. [Description of Signs] 1 ... Insulating layer 2 ... Wiring conductor layer 4a ... Through hole 4b ... Through hole conductor 5 ... ... Lattice dummy wiring conductor layers

   ────────────────────────────────────────────────── ─── Continuation of front page    F term (reference) 5E317 AA27 BB02 BB12 CC31 CD25                       CD27 CD31 GG20                 5E346 AA01 AA12 AA15 AA22 AA43                       AA60 BB01 BB06 BB11 BB16                       CC02 CC08 CC31 DD02 DD32                       EE02 EE06 EE09 FF04 GG22                       GG25 GG28 HH03 HH07 HH11                       HH32

Claims (1)

Claims: 1. An insulating layer formed by impregnating a fibrous base material with a thermosetting resin, and a plurality of wiring conductor layers are laminated, and the insulating layer is penetrated by the insulating layer. It comprises a plurality of through-hole conductors arranged in a grid for electrically connecting the wiring conductor layers located above and below, between the upper and lower wiring conductor layers connected by the lattice-shaped through-hole conductors. A wiring conductor layer that is not connected to the through-hole conductor and a grid-like dummy wiring conductor layer that divides each through-hole conductor around the through-hole conductor on the same plane as the non-connected wiring conductor layer; A wiring board, characterized by being provided.