JP2004031765A - Method of manufacturing wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a wiring board which comprises a process of manufacturing a core board whose front and rear surface can be kept flat even when through-holes bored in the core board are filled up with resin. <P>SOLUTION: The method of manufacturing the wiring board comprises a plugging process of separately depositing resin films 5 and 6 on the surfaces 2 and 3 of a metal plate (core material) 1, which is provided with the through-holes 4 penetrating through the surfaces 2 and 3 and pressing the resin films 5 and 6 against the metal plate 1 in the direction of thickness of the metal plate 1 to fill the through-holes 4 with resin 7a; a curing process of curing the resin 7a filling the through-holes 4 by heating; and a core board forming process of repeating the above processes two or more times to form the core board 14. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a wiring board including a step of manufacturing a core substrate using a core material as a core material.
[0002]
[Prior art]
In some cases, a metal plate is used as a core material which is a core material of a core substrate serving as a base of a wiring substrate (see Japanese Patent Application Laid-Open No. 2000-133913). A resin is filled into the through-hole penetrating between the front surface and the back surface of the metal plate in order to insulate the periphery of a through-hole conductor that penetrates the center portion coaxially. There are the following methods for filling the through hole of the metal plate with a resin.
(1) A method of filling a through-hole with a paste resin by a printing method or a dispensing method.
(2) A method in which a dry type resin film is laminated on the front and back surfaces of a metal plate and pressed along the thickness direction to press-fit the resin into the through holes.
(3) A method in which a semi-cured resin such as a prepreg flows into a through-hole by hot pressing.
[0003]
In the above methods (1) and (2), immediately after the through-hole of the metal plate (core material) is filled with the resin, even if the surface and the back surface of the metal plate are flat, the filled resin is thereafter used. When a curing process for curing is performed, dents are generated at positions just above and below the resin in the through holes, respectively, as the resin shrinks during curing.
For example, in the above method (2), as shown in FIG. 4A, a metal plate 40 having a front surface 42 and a back surface 43 and having a thickness of 0.25 mm is used. A plurality of 0.3 mm through holes 44 penetrate between the front surface 42 and the back surface 43.
Next, as shown in FIG. 4B, dry type resin films 45 and 46 having a thickness of 60 μm are laminated on the front surface 42 and the rear surface 43 of the metal plate 40.
[0004]
Next, as shown by arrows in FIG. 4B, the resin films 45 and 46 are pressed along the thickness direction so as to be pressed against the metal plate 40.
As a result, as shown in FIG. 4C, the resin films 45 and 46 become compressed resin layers 47 and 48, and a part of the resin 49 is pressed into the plurality of through holes 44, The inside of the through hole 44 is filled.
Then, the metal plate 40 on which the resin layers 47 and 48 and the resin 49 are formed is heated to cure the resin layers 47 and 48 and the like. As a result, as shown in FIG. 4D, a depression 50 is formed in the resin layers 47 and 48 immediately above and below the through-hole 44 as the resin 49 cures and contracts.
[0005]
[Problems to be solved by the invention]
When the core substrate k including the concave portion 50 and using the metal plate 40 as a core material is used, the front surface wiring layer and the rear surface wiring layer formed on the front surface and the rear surface are distorted by the concave portion 50, and the insulating layer formed thereon is distorted. The layer and the build-up wiring layer also lose flatness. For this reason, there has been a problem that the reliability of the obtained wiring board is impaired. SUMMARY OF THE INVENTION The present invention solves the above-described problems in the prior art, and a method of manufacturing a wiring substrate including a core substrate manufacturing process capable of ensuring flatness of the front and back surfaces even when a resin is filled in a through hole. To provide.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is conceived of performing a plurality of steps of laminating a resin film on the front and back surfaces of a core material having a through hole and curing a resin filled in the through hole, respectively. It was made.
That is, the method of manufacturing a wiring board according to the present invention (claim 1) is directed to a method of manufacturing a core material having a front surface and a back surface and having a through hole penetrating between the front surface and the back surface. Each resin film is individually laminated, the pair of resin films are pressed along the thickness direction of the core material, a hole filling step of filling the resin in the through hole, and filled in the through hole. A curing step of heating and curing the resin; and repeating a plurality of times to form a core substrate. The filling process and the curing process include a mode in which the curing process is performed in parallel while the filling process is performed, in addition to a mode in which the filling process and the curing process are performed in this order.
[0007]
According to this, after the first hole filling step and the curing step, the same depression is formed on the surface of the resin layer located directly above and below the through hole of the core material, but the second and subsequent steps By performing the hole filling step and the curing step described above, it is possible to eliminate the concave portion or to suppress it to an extremely fine concave portion. That is, the hole-filling step and the curing step, which were conventionally performed once, are divided into a plurality of times, and a relatively thin resin film is laminated on each, filled into the through-holes, and cured, whereby the first-time dent is formed. It can be shallower than before. Subsequently, by performing the hole filling step and the curing step after the second time using the thin resin film, it is possible to eliminate the concave portion or to suppress the concave portion to a fine concave portion having almost no adverse effect.
[0008]
Therefore, a highly reliable wiring board in which the front surface wiring layer and the back surface wiring layer formed on the front and back surfaces of the core substrate obtained by the above process, and the insulating layer and the build-up wiring layer formed thereon are formed flat. Can be reliably manufactured.
The core material includes a resin plate, a resin plate on which metal foils on the front and rear surfaces are adhered, in addition to a metal plate described later. Further, the resin film includes a film made of an electrically conductive resin in addition to a film made of an insulating resin.
In addition, according to the present invention, a resin film is individually laminated on the front surface and the back surface of the core material having a front surface and a back surface and having a through hole penetrating between the front surface and the back surface. Then, pressing the pair of resin films along the thickness direction of the core material, forming a resin layer on the front surface and the back surface of the core material, respectively, and filling the through-hole with a resin, A step of forming a core substrate by repeating a curing step of heating and curing the resin filled in the resin layer and the resin filled in the through-holes respectively formed on the front surface and the back surface of the core material, and alternately a plurality of times. It is also possible to include a method of manufacturing a wiring board.
[0009]
The present invention also provides a method for manufacturing a wiring board, wherein in the filling step, the thickness of the resin film used for the first time is equal to or greater than the thickness of the resin film used for the second time and thereafter (claim 2). included.
According to this, in the first hole filling step, by pressing the laminated resin film with a press or the like, the inside of the through-hole of the core material can be reliably filled with the resin of the film, and is generated in the subsequent curing step. It is more certain that the recesses are eliminated or made into fine recesses by the second and subsequent hole filling and curing steps.
The thickness of the resin film laminated in the first hole filling step is 1 to 4 times the thickness of the resin film laminated in the second and subsequent hole filling steps, and particularly preferably 2 times or more from the viewpoint of obtaining the above effects.
[0010]
Furthermore, the present invention also includes a method of manufacturing a wiring board, wherein the core material is a metal plate having the front and back surfaces and a through hole.
According to this, it is possible to reliably manufacture a core substrate having a required strength, a core material made of a metal plate in which the inside of the through hole is filled with a resin, and a flat resin layer formed on the front and back surfaces. It is possible to manufacture a solid wiring substrate including a flat front surface wiring layer and a rear surface wiring layer formed on the front surface and the rear surface of the core substrate, and a flat insulating layer and a build-up wiring layer formed thereon. It becomes possible.
In addition, a copper alloy such as Cu-2.3 wt% Fe-0.03 wt% P (194 alloy), pure copper, oxygen-free copper, Fe-42 wt% Ni (42 alloy), Fe-36 wt% Plates made of Fe—Ni alloys such as Ni (invar), other steel types, titanium and its alloys, and aluminum and its alloys are included.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.
FIG. 1A shows a cross section of a metal plate 1 which is a core material used in the present invention. The metal plate 1 is made of, for example, the copper alloy (194 alloy) having a thickness of 0.25 mm, and has a front surface 2 and a back surface 3 as shown in FIG. A plurality of through holes 4 having an inner diameter of about 0.3 mm penetrate between them. The plurality of through holes 4 are formed by punching the metal plate 1 or by etching.
[0012]
1B and 1C show a first hole filling step in the present invention. As shown in FIG. 1 (B), dry type resin films 5 and 6 each having a thickness T of 40 μm and made of an epoxy resin are laminated (laminated) on the front surface 2 and the rear surface 3 of the metal plate 1.
Next, as shown by arrows in FIG. 1B, the resin films 5 and 6 are pressed along the thickness direction of the metal plate 1 by a press (not shown) or the like.
As a result, as shown in FIG. 1 (C), the resin films 5 and 6 are compressed to become resin layers 7 and 7 which are in close contact with the front surface 2 and the back surface 3 of the metal plate 1, and a part of the resin films is penetrated. Resins 7a, 7a that enter and fill holes 4 and 4 are filled (hole filling step).
[0013]
Next, the metal plate 1 having the resin layers 7 and 7 and the resin 7a in the through holes 4 shown in FIG. 1C is inserted into a heating furnace (not shown), and is heated to about 150 ° C. for about 60 minutes in the atmosphere. A curing process is performed (curing process).
As a result, as shown in FIG. 1D, the resin layers 7, 7 and the resin 7a harden and shrink, and the surfaces of the resin layers 7, 7 located directly above and directly below the through holes 4, 4, respectively. 8 and the back surface 9 are each provided with a spherical concave portion 10.
[0014]
Next, a second hole filling step and a curing step are performed.
As shown in FIG. 2A, resin films 11 and 12 made of an epoxy resin having a thickness t of 20 μ are laminated on the front surface 8 and the back surface 9 including the concave portions 10 of the resin layers 7 and 7. Next, as shown by arrows in FIG. 2A, the resin films 11 and 12 are pressed along a thickness direction of the metal plate 1 by a press (not shown) or the like.
As a result, as shown in FIG. 2B, the resin films 11 and 12 are compressed and integrated with the resin layers 7 and 7 so that the resin layers 15 and 12 adhere to the front surface 2 and the back surface 3 of the metal plate 1. In addition, some of them become the resins 17, 17 which enter the through holes 4, 4 and fill them more densely (second hole filling step).
[0015]
Then, the resin layers 15 and 16 adhered to the metal plate 1 and the resin 17 in the through holes 4 shown in FIG. 2B are subjected to the same curing treatment as described above (second curing step).
As a result, as shown in FIG. 2 (C), the resin layers 15 and 16 and the resin 17 harden and shrink, but the surfaces of the resin layers 15 and 16 located immediately above and below the through holes 4 and 4 are formed. 18 and the back surface 19 are almost flat. This is because the resin layers 15 and 16 shrink and adhere to the lower resin layers 7 and 7 by the curing treatment, so that the concave portion 10 located between them is eliminated.
[0016]
As a result, as shown in FIG. 2C, the metal plate 1 having the plurality of through holes 4 and 4, the resin 17 filled in the through holes 4, and the flat surface 18 formed on the surface 2 of the metal plate 1 The core substrate 14 having the resin layer 15 of FIG. 1 and the resin layer 16 of the flat back surface 19 formed on the back surface 3 of the metal plate 1 is obtained.
After the second hole filling step and the curing step, small concave portions may remain on the front surface 18 and the rear surface 19 of the resin layers 15 and 16 located directly above and below the through holes 4 and 4, respectively. At this time, if the depth of the recess is not within the allowable range, the third hole filling step and the hardening step are further performed. The thickness of the resin film used in the third hole filling step is equal to or less than the resin films 11 and 12 used in the second time.
The filling step and the curing step are performed so that the resin films 11 and 12 are pressed by a press (hole filling step) and simultaneously heated to cure the filled resin 17 and the like (curing step). Is also possible.
[0017]
Hereinafter, a manufacturing process of the wiring board K using the core substrate 14 will be described.
FIG. 3A shows an example in which the center of the through holes 4 and 4 of the metal plate 1 built in the core substrate 14 is irradiated with, for example, a carbon dioxide gas laser, and the center of the resin layers 15 and 16 and the resin 17 is formed. Next, a step of forming through holes h, h penetrating between the front surface 18 and the back surface 19 of the core substrate 14 will be described. The inner diameter of the through hole h is about 100 μm. The through hole h may be formed by using a small diameter drill instead of the laser. Next, after coating a plating catalyst containing Pd on the front surface 18, the back surface 19, and the inner walls of the through holes h, h of the core substrate 14, electroless copper plating and electrolytic copper plating are applied to the entire surface. As a result, as shown in FIG. 3B, a cylindrical through-hole conductor 20 is formed along the inner wall of each through-hole h. A conductive or non-conductive filling resin 21 is formed in the hollow portion of the through-hole conductor 20. Thereafter, copper plating is performed on the front surface 18 and the back surface 19 of the core substrate 14.
[0018]
Next, a resin film (not shown) made of a photosensitive resin and having a thickness of about 10 μm is attached onto the copper plating films formed on the front surface 18 and the back surface 19 of the core substrate 14. After a mask (not shown) having a predetermined pattern is placed on the film, the film 19 is exposed and developed (photography technique) to remove an etching resist (not shown) having the predetermined pattern. Form. Further, a developing (etching) liquid is brought into contact with the copper plating film via the resist to etch the copper plating film exposed from between the resist patterns.
As a result, as shown in FIG. 3B, a front surface wiring layer 22 and a back surface wiring layer 23 are formed on the front surface 18 and the back surface 19 of the core substrate 14 according to the above-mentioned pattern, and these are formed by through-hole conductors. 20 is connected to the upper end or the lower end, and the filling resin 21 is plated with a lid.
[0019]
Further, as shown in FIG. 3C, an insulating layer 24 made of an epoxy resin film containing an inorganic filler such as a silica filler and having a thickness of 30 μm is formed on the surface wiring layer 22. Photolithography or laser processing (using a carbon dioxide laser or the like) is performed on a predetermined position of the insulating layer 24 to form a plurality of via holes (not shown). The surface wiring layer 24 is exposed at the bottom of the via hole. Next, after the same plating catalyst as described above is applied to the surface of the insulating layer 24 and the inner wall surface of the via hole, electroless copper plating and electrolytic copper plating are performed, and a copper plating film is formed on the surface of the insulating layer 24. As shown in FIG. 3C, a via (filled via) conductor 26 is formed in the via hole.
[0020]
Next, an etching resist similar to the above is formed on the insulating layer 24 on which the copper plating film is formed, and development is performed. As a result, as shown in FIG. 3C, a wiring layer (build-up wiring) 28 having a predetermined pattern is formed on the insulating layer 24. This wiring layer 28 is connected to surface wiring layer 22 via via conductor 26.
Similarly to the above, an insulating layer 30, a via conductor 32, and a wiring layer 34 are formed as shown in FIG. The via conductor 32 connects the wiring layers 28 and 34, and the insulating layers 24 and 30 and the wiring layers 28 and 34 form a build-up layer BU.
[0021]
Further, as shown in FIG. 3C, an uppermost insulating layer (solder resist layer) 36 having a thickness of 20 μm is formed on the wiring layer 34. A solder bump 38 projecting higher than the first main surface 37 from an appropriate position on the wiring layer 34 penetrates through the insulating layer 36. The solder bump 38 is made of a low melting point alloy such as Sn-Ag, Pb-Sn, Sn-Ag-Cu, Sn-Cu, or Sn-Zn (in this embodiment, Sn-Ag). It is individually connected to connection terminals of an IC chip (not shown) mounted on one main surface 37. The plurality of solder bumps 38 and the connection terminals of the IC chip are buried and protected by an underfill material.
[0022]
On the other hand, as shown in FIG. 3C, a back wiring layer 23 having a predetermined pattern is formed on the back surface 19 of the core substrate 14 in the same manner as described above, and an insulating layer (solder resist layer) similar to the above is formed thereunder. ) 25 is formed. The wiring 27 extending from the back wiring layer 23 is located on the bottom surface of the opening 29 that opens toward the second main surface 31 in the insulating layer 25. The surface of the wiring 27 is coated with Ni plating and Au plating, and is used as a connection terminal to a printed board such as a motherboard (not shown).
[0023]
Thus, the wiring board K as shown in FIG. 3C is manufactured. Since the wiring board K uses the core substrate 14 having the flat surface 18, the surface wiring layer 22 formed on the surface 18 and the wiring layer 28 in the build-up layer BU formed thereon are formed. , 34 are formed flat. Further, the thicknesses of the insulating layers 24 and 30 do not vary and are averaged. Therefore, according to the manufacturing method of the present invention, it is possible to reliably manufacture the core substrate 14 having the flat front surface 18 and the rear surface 19 and to reliably manufacture the highly reliable wiring board K using the core substrate 14. It becomes possible.
[0024]
The present invention is not limited to the embodiments described above.
The core material used for the core substrate is not limited to the copper alloy, and may be a metal plate made of an Fe—Ni-based alloy, titanium or its alloy, aluminum or its alloy, or the like. Alternatively, a core material made of a synthetic resin or a composite material including an inorganic filler such as a glass filler or a glass cloth may be used.
The resin film may be made of a conductive resin in addition to an insulating resin. By using together such a conductive resin film and a core material made of an insulating material such as the above synthetic resin, it is also possible to form a through-hole conductor or the like in a through hole of the core material.
Furthermore, it is also possible to change the characteristics of the resin film used for the first time and the resin film used for the second time and thereafter. For example, by using a resin film having a low coefficient of thermal expansion for the first time and using a resin film having a higher coefficient of thermal expansion for the second and subsequent times, the resin film along the axial direction of the through hole of the core material can be used. It is possible to further reduce the thickness and the thickness of all the resin layers formed on the front and back surfaces of the core material.
[0025]
【The invention's effect】
According to the method of manufacturing a wiring board of the present invention (claim 1), the core filling step or the hardening step is repeated twice or more, so that a core substrate having no recesses on the front and back surfaces or a fine one is reliably obtained. Can be For this reason, it is possible to reliably form a highly reliable wiring board in which the front surface wiring layer and the back surface wiring layer formed on the front and back surfaces of the core substrate, and the insulating layer and the build-up wiring layer formed thereon are formed flat. It can be manufactured.
According to the method of manufacturing a wiring board of the second aspect, the resin film used in the second and subsequent hole filling steps is thinned and the curing step is performed to eliminate a concave portion on the surface of the core substrate or to make a fine concave portion. Is more certain.
Further, according to the method for manufacturing a wiring board of the third aspect, the metal plate having the required strength, the inside of the through hole of the core material is filled with the resin, and the front and back surfaces of the metal plate are formed with a flat resin layer is formed. A core substrate as a material can be reliably manufactured.
[Brief description of the drawings]
FIGS. 1A to 1D are schematic views showing steps in a method for manufacturing a wiring board according to the present invention.
FIGS. 2A to 2C are schematic diagrams showing each step in the manufacturing method of the present invention following FIG. 1D.
3 (A) to 3 (C) are schematic diagrams showing each step in the manufacturing method of the present invention following FIG. 2 (C).
FIGS. 4A to 4D are schematic views showing respective steps in a conventional method for manufacturing a wiring board.
[Explanation of symbols]
1 ... Metal plate (core material), 2 ... Surface,
3 ……………… Back side, 4 ………………… Through-hole,
5, 6, 11, 12 ... resin film, 7a, 17 ... resin 14 ... core substrate,
K ………………… Wiring board

Claims (3)

For a core material having a front surface and a back surface and having a through hole penetrating between the front surface and the back surface,
Resin films are individually laminated on the front and back surfaces of the core material, respectively, and the pair of resin films are pressed along the thickness direction of the core material, and a hole filling step of filling the resin in the through holes,
A curing step of heating and curing the resin filled in the through-hole, and including a step of forming a core substrate by repeating a plurality of times,
A method for manufacturing a wiring board, comprising: In the filling step, the thickness of the resin film used for the first time is equal to or greater than the thickness of the resin film used for the second time or later.
2. The method for manufacturing a wiring board according to claim 1, wherein: The method for manufacturing a wiring board according to claim 1, wherein the core material is a metal plate having the front and rear surfaces and a through hole.

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