JP2004047796A - Method for manufacturing wiring board, and wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a wiring board wherein, after a through hole is filled, a process for forming lid plating immediately above the filled through hole can be eliminated, and to provide a wiring board. <P>SOLUTION: A CO<SB>2</SB>laser is irradiated to a prescribed position from the back of a core substrate 2 wherein copper foils 3, 4 are formed on the surface and the back, and a through hole 5 is formed (figure B). At this time, the CO<SB>2</SB>laser is set in a condition wherein the core substrate 2 itself can be eliminated and laser light is reflected by the copper foil 3 on the surface side of the core substrate 2. The inside of the through hole 5 which is formed in a recessed type wherein the copper foil 3 is made to be a bottom is filled with filling resin 7, the copper foil 3 is so patterned that a region in the copper foil 3 is positioned immediately above the filling resin 7 remains, a surface side wiring layer 8 is formed, and a build-up layer BU is formed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a wiring board and a wiring board.
[0002]
[Prior art]
For the purpose of realizing cost reduction and miniaturization, a build-up wiring board in which a build-up layer is formed only on the front surface (one surface) of a core substrate in which a through hole penetrating the front surface and the back surface is formed. Proposed. As a method of manufacturing such a wiring board, a through hole is formed in a core substrate so as to penetrate the front and back surfaces of the core substrate, and the inside of the through hole is plated. After filling the resin into the through-hole by printing and performing a curing process on this, a lid plating is formed on the end surface of the through-hole on the surface side of the core substrate, and an insulating layer is formed above the surface of the core substrate. A method has been adopted in which a plurality of wiring layers are alternately formed to form a build-up layer.
[0003]
[Problems to be solved by the invention]
However, as described above, in a method for manufacturing a wiring board in which a wiring layer is formed immediately above a through hole, after filling the through hole with a filling resin, immediately above the through hole filled with the filling resin, It was necessary to form a lid plating to be a wiring layer. In this case, the process amount is increased, and the production efficiency is reduced.
It is an object of the present invention to provide a method of manufacturing a wiring board which can reduce a step of forming a cover plating immediately above a filled through hole after filling the through hole.
[0004]
[Means for Solving the Problems and Functions / Effects]
In order to solve the above-mentioned problems, a method of manufacturing a wiring board according to the present invention is characterized in that a build-up layer including an insulating layer and a wiring layer is formed on a surface of a core substrate in which a through-hole is filled with a filling resin; A method of manufacturing a wiring board, wherein the wiring layer is formed immediately above a filling resin filled in a hole, wherein the through hole is formed at least from a back surface of the core substrate having a copper foil formed on the surface to a surface of the core substrate. A step of forming in a form that does not penetrate only the copper foil formed in the above, a filling step of filling the through hole with the filling resin from the back side of the core substrate, and a build-up layer on the surface of the core substrate. Forming step.
[0005]
According to the above method, a through hole is formed from the back surface of the core substrate having the copper foil formed on the surface, and the through hole penetrates the core substrate itself, but the surface of the core substrate is Is prevented from penetrating. Thereby, the opening of the through hole is not formed on the surface side of the core substrate, and the through hole is formed in a concave shape with the copper foil as the bottom. Then, the filling resin is filled from the back surface side of the core substrate to the bottom (copper foil) of the through hole in the thus formed concave through hole having the copper foil as the bottom. Then, on the surface side of the core substrate, a form in which a conductive layer (copper foil) is formed immediately above the through hole can be naturally realized. Therefore, the conductive layer can be formed immediately above the through hole without covering the area directly above the through hole filled with the filling resin with the cover plating, as has conventionally been done.
[0006]
It should be noted that in the present specification, the one that does not penetrate between the front surface and the back surface of the core substrate is also included in the concept of a through hole. Further, when a through-hole conductor is formed on the inner wall of the through-hole, a hollow portion surrounded by the through-hole conductor is referred to as a through-hole.
[0007]
Furthermore, in the present invention, the core substrate has a copper foil formed on a front surface and a rear-side wiring layer formed on a rear surface, and in a filling step, a pair of the adhesive layers formed on the rear surface. It is preferable that the core substrate is laminated with the adhesive layers facing each other and a release sheet interposed therebetween, and the through holes are filled with the adhesive layers by pressing and heating these core substrates. According to this, the filling step and the step of forming a solder resist layer on the back surface of the wiring board can be performed at the same time. That is, the resin that forms the adhesive layer becomes the filling resin that fills the through holes, and the resin that forms the solder resist layer formed on the back surface of the wiring board. Therefore, in addition to the step of forming the lid plating described above being reduced, further improvement in manufacturing efficiency can be expected.
[0008]
Further, according to the present invention, since the through holes are formed without penetrating the copper foil formed on the front surface side of the core substrate, even if the filling resin is filled from the back surface of the core substrate, the through holes of the core substrate can be formed. The filling resin does not protrude to the surface side and is not formed. In the conventional filling process, the filling resin sometimes protrudes to the surface side of the core substrate and is formed. In this case, if the cover plating is to be formed, the surface of the core substrate must be polished. However, according to the present invention, in addition to the step of forming the lid plating, the step of polishing the surface of the core substrate can be reduced, and a significant improvement in manufacturing efficiency can be expected.
[0009]
Further, in the present invention, it is preferable to form a through-hole conductor on the entire inner surface of the through-hole before the filling step. The through-hole conductor is formed to realize connection between the front surface and the back surface of the core substrate. Therefore, in the related art, on the inner surface of the through hole penetrating the front and back surfaces of the core substrate, the through hole is formed so as to be connected to the front surface wiring layer and / or the back surface wiring layer. In the present invention, the through-hole conductor is further formed on the bottom (copper foil) of the through-hole on the side in contact with the filling resin. As a result, a through-hole conductor is formed between the copper foil remaining immediately above the through-hole on the front surface side of the core substrate and the resin filling the through-hole. According to this, in the filling step, the copper foil located immediately above the through hole is less likely to fall into the inside of the through hole due to the influence of the pressure or to protrude to the surface side of the core substrate. That is, the flatness of the copper foil on the surface of the core substrate can be maintained during the filling with the filling resin, and the flatness of the copper foil is further improved, so that the build-up layer formed thereon is also flat. Become.
[0010]
In order to form the through hole without penetrating only the copper foil formed on the surface side of the core substrate, the following method can be specifically exemplified. That is, in the step of forming a through-hole, a predetermined position on the back surface of the core substrate is irradiated with a laser so that the laser forms a through-hole in the core substrate. It is better to use something. According to this, a through hole is formed by the laser, and after the laser is irradiated on the copper foil, the copper foil is not removed by the laser. It can be formed without penetrating. Practically useful as such a laser is a carbon dioxide gas laser. If a carbon dioxide gas laser is used, the present invention can be easily realized and the speed of forming the through holes is high, which is advantageous from the viewpoint of manufacturing efficiency.
[0011]
Furthermore, the wiring board of the present invention obtained by the manufacturing method of the present invention as described above has a filling resin filled in the through holes of the core substrate in which the through holes are formed, and the surface of the core substrate has A surface-side wiring layer made of copper foil is formed so as to cover the opening of the through hole, and the filling resin is formed below the surface-side wiring layer without protruding from the surface of the core substrate. It is characterized by having.
[0012]
According to the present inventor, as described above, the wiring board of the present invention having the above-described configuration is capable of simplifying the manufacturing process, and is disposed directly above the filling resin filled in the through-hole. It was found that the flatness of the surface wiring layer to be performed was good. Further, it has been found that the flatness of the surface wiring layer formed immediately above the through hole is good, so that the build-up layer is formed even more evenly. That is, since the filling resin is formed without protruding from the surface of the core substrate, the surface-side wiring layer disposed immediately above the filling resin is formed on the surface of the core substrate while maintaining flatness. It is.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present embodiment will be described with reference to the drawings. 1 to 3 show an outline of a method of manufacturing a wiring board according to the present invention. First, in FIG. 1A, copper foils 3 and 4 are formed on the front surface 2a and the back surface 2b of the core substrate 2. The core substrate 2 is made of a glass-epoxy resin composite material having a thickness of about 800 μm. Further, as the core substrate 2, a substrate in which these copper foils 3 and 4 are formed in advance on the surface of the core substrate 2 may be used. The copper foil 4 on the back surface 2b may be thicker than the copper foil 3 on the front surface 2a, or may have a surface roughness greater than the surface of the front surface 2a.
[0014]
Then, the core substrate 2 with the copper foils 3 and 4 is perforated with a laser at a desired position as shown in FIG. 1B. At this time, according to the method according to the present invention, laser is irradiated from the back surface 2b side of the core substrate 2 and further, only the copper foil 3 formed on the front surface 2a side of the core substrate 2 is prevented from penetrating. Thereby, a concave through hole 5 having the copper foil on the surface 2a side as the bottom can be formed.
[0015]
In order not to penetrate only the copper foil 3 formed on the surface 2a side of the core substrate 2, a laser reflected by the copper foil 3 is employed as described above. At this time, the core substrate 2 itself can be perforated, but a laser having a wavelength in the range of 900 nm to 1000 nm is adopted so that the laser is reflected by the copper foil. Lasers in such a wavelength range are easily reflected by the copper foil. Among them, a carbon dioxide laser can be preferably used. The carbon dioxide laser satisfies the above-mentioned conditions and can perforate the core substrate 2 quickly, so that it can be particularly preferably employed. Further, the pulse output, pulse width, pulse number, and the like of the carbon dioxide laser need to be appropriately changed so as not to penetrate only the copper foil. For example, the peak output is preferably 5 kW to 20 kW, the pulse width is preferably 1 μsec to 20 μsec, and the number of pulses is preferably 1 to 10. The diameter of the through hole 5 formed by the carbon dioxide laser is about 50 μm to 300 μm. In addition, other than the carbon dioxide laser, any other laser that is reflected by the copper foil 3 may be employed, and other gas lasers (eg, excimer laser) and solid-state lasers such as Nd: YAG laser It is also possible to employ.
[0016]
Furthermore, when the through hole 5 is formed without penetrating only the copper foil, it is also possible to employ a mechanical perforating means such as a drill. At this time, the thickness data of the core substrate 2 and the copper foil 3 are prepared in advance, and the mechanical drilling means is NC-controlled based on this data, so that the through-hole where only the copper foil is not penetrated is provided. Holes can be formed.
[0017]
Next, as shown in FIG. 1C, copper plating is performed on the inner wall of the through hole 5 of the core substrate 2 having the plurality of through holes 5. At this time, copper plating may be performed by either panel plating or pattern plating. As a result, a through-hole conductor 6 is formed on the inner wall of the through-hole 5. The thickness of the through-hole conductor 6 made of copper plating is about 15 μm. When the through-hole conductor 6 is formed by panel plating, the thickness of the copper foils 3 and 4 formed on the front surface 2a and the back surface 2b of the core substrate 2 increases, and the copper plating films 3a and 4a (for convenience, The thickness is the same as that of the copper foils 3 and 4). The through-hole conductor 6 is formed not only on the inner side surface of the through-hole 5 but also on the bottom (copper foil 3) side of the through-hole 5. That is, as shown in FIG. 1C, a copper foil 3 and a bottom-side through-hole conductor 6a as a copper plating layer are sequentially formed from the front surface 2a side of the core substrate 2, and the bottom-side through-hole conductor 6a is formed through the through-hole conductor 6a. It is the direct bottom of hole 5. Further, it is possible to selectively prevent copper plating on the surface side of the core substrate. Therefore, when the copper foil 3 or the copper plating layer 3a is indicated, it is hereinafter referred to as a copper foil 3 (copper plating 3a). 1C and subsequent drawings show the case of the copper plating layer 3a.
[0018]
The formation of the through holes 5 and the copper plating may be performed in a state of a panel (a multi-piece substrate) including a plurality of core substrates 2 (product units).
[0019]
Next, an etching resist (not shown) is formed on the copper plating layer 4a located on the back surface 2b of the core substrate 2, and the copper plating layer 4a exposed from between the resist patterns is etched. As a result, as shown in FIG. 1D, the copper plating layer 4a formed on the back surface 2b side of the core substrate 2 becomes the back surface side wiring layer 9 according to the resist pattern on the back surface 4a side.
[0020]
Here, as shown in FIG. 2A, an adhesive layer (prepreg) 11 and a release layer r (release sheet) are prepared. The adhesive layer 11 is made of a resin such as epoxy, bismaleimide / triazine, phenol, polyimide, or polyester, and has inside thereof an inorganic material such as a piece of filler paper, glass cloth, glass nonwoven fabric, synthetic fiber, or silica filler. Contains Fira. The release layer r is, for example, a sheet having a cushion material made of a thermoplastic resin interposed between a pair of films, and sealed at the periphery with the film.
Note that a thermoplastic resin (trade name: Pacotan Plus) having flexibility (weak elasticity) is used for the cushion material. Alternatively, a PET film, a fluororesin (registered trademark: Teflon) sheet, or the like may be used as the cushion material.
[0021]
As shown in FIG. 2A, an adhesive layer 11 is separately formed below the back surface 2b and the back surface wiring layer 9 of the pair of core substrates 2, and a release layer r is disposed between the adhesive layers 11, 11. Incidentally, the adhesive layers 11 and 11 may be formed on both surfaces of the release layer r in advance.
Next, as shown by the arrow in FIG. 2A, the pair of core substrates 2 and 2 having the adhesive layer 11 formed on the back surface 2b are placed with the adhesive layers 11 facing each other and with the release sheet r interposed therebetween. The layers are laminated, and pressed and heated in the thickness direction of the core substrates 2 and 2 using a hot press (not shown) (filling step). Such a filling step may be performed using a pair of panels (multi-piece substrates) including a plurality of core substrates 2 (product units).
[0022]
As a result, as shown in FIG. 2B, the adhesive layers 11, 11 are adhered to the back surface 2b of the core substrates 2, 2 with a required thickness, and become the solder resist layer (insulating layer) 11. At the same time, a part of the adhesive layers 11, 11 is filled into the hollow portions (through holes 5) inside the through-hole conductors 6, 6 of each core substrate 2, and becomes filling resins 7, 7. At this time, the through-hole 5 is formed in a concave shape having a bottom (copper foil 3 and bottom through-hole conductor 6a) on the surface 2a side of the core substrate 2, so that the filling resin 7 is formed on the surface 2a side of the core substrate 2 The filler is filled without contacting the bottom through-hole conductor 6a up to the position where the bottom through-hole conductor 6a is formed. After filling the through-hole 5 with the filling resin 7, the filling resin 7 and the solder resist layer 11 are cured by curing.
[0023]
Then, an etching resist (not shown) is formed on the copper foil 3 (copper plating layer 3a) formed on the surface 2a side of the core substrate 2, and the copper foil 3 (copper plating layer 3a) exposed from between the resist patterns. Etch). As a result, as shown in FIG. 3A, the copper foil 3 (copper plating layer 3a) formed on the surface 2a side of the core substrate 2 becomes the surface side wiring layer 8 according to the resist pattern on the surface 2a side. At this time, the copper foil (copper plating layer) 3 a immediately above the filling resin 7 filled in the through hole 5 is not removed by etching, but is left as the surface side wiring layer 8. As described above, in the present invention, the copper foil 3 (copper plating layer 3a) formed on the surface 2a of the core substrate 2 in advance becomes the surface side wiring layer 8, so that the lid plating step is unnecessary. Further, in forming the front-side wiring layer 8, the surface of the core substrate 2 does not need to be surface-polished. Therefore, manufacturing efficiency can be further improved.
[0024]
In the present embodiment, the front side wiring layer 8 formed on the front surface 2a side of the core substrate 2 is formed after filling the through hole with the filling resin. The surface-side wiring layer 8 may be formed at the same time as the formation. At this time, the resist pattern on the front side that determines the pattern of the front-side wiring layer 8 is configured such that the copper foil 3 (copper plated layer 3a) immediately above the through hole 5 remains in FIG. .
[0025]
Next, after the front-side wiring layer 8 is formed, the insulating layer 12 is formed on the front-side wiring layer 8 as shown in FIG. Thereafter, as shown in FIG. 4, the insulating layer 13, the wiring layer 18, the wiring layer 19, the filled via conductors 15, 16 and the solder resist layer 14, which constitute the build-up layer BU together with the insulating layer 12, etc. It is formed by a process (semi-additive method, full-additive method, subtractive method, formation of an insulating layer by laminating a film-like resin material, photolithography technology, etc.) (build-up process).
The insulating layers 12, 13 and the like are epoxy resins containing inorganic fillers such as silica fillers with a thickness of about 30 μm, and the thickness of the solder resist layer 22 is about 25 μm.
Such a build-up process may also be performed using a pair of panels (multi-piece boards) including a plurality of core boards 2 (product units).
[0026]
Further, on the wiring layer 16, a plurality of solder bumps 17 protruding higher than the first main surface 1a are formed. The solder bump 17 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 used for connection with connection terminals of an IC chip (not shown) mounted on the one main surface 1a.
Note that a build-up layer BU and the like are formed above the surface 2a of the remaining core substrate 2 in the same manner as described above.
[0027]
Then, as shown in FIG. 4, the solder resist layer (adhesive layer) 11 on the back surface 2b side of the core substrate 2 having the buildup layer BU and the like separated by removing the release sheet r by laser processing or the like. An opening 23 is formed at a predetermined position. The wiring layer 24 extending from the back wiring layer 9 and exposed from the inside of the opening 23 toward the second main surface 1b is coated with a Ni plating film and an Au plating film (not shown) on the surface, and the wiring substrate 1 itself is mounted. To be connected to a printed circuit board such as a motherboard (not shown).
As a result, as shown in FIG. 4, it is possible to obtain the wiring board 1 immediately before mounting a semiconductor element such as an IC chip.
The plurality of solder bumps 17 and connection terminals of an IC chip (not shown) mounted on the first main surface 1a are buried and protected by an underfill material (not shown).
[0028]
In the wiring board 1 of the present invention shown in FIG. 4 described above, the build-up layer BU is formed on the front surface 2a side of the core substrate 2 and the solder resist layer 11 is formed on the back surface side 2b. The through holes 5 formed in the core substrate 2 are filled with a resin (filling resin) forming the solder resist layer 11. Further, a surface-side wiring layer 8 made of copper foil 3 (3a) is formed on the surface 2a of the core substrate 2 so as to cover the through hole 5, and the filling resin 7 is provided below the surface-side wiring layer 8 in the core. It is formed without protruding from the surface 2 a of the substrate 2. Further, a copper plating layer (bottom through-hole conductor) 6a is formed between the filling resin 7 and the front-side wiring layer 8.
[0029]
In the wiring board 1 having such a configuration, as described above, since the filling resin 7 is formed without protruding from the surface 2a of the core substrate 2, the surface-side wiring layer 8 disposed immediately below the filling resin 7 is formed. Good adhesion. Further, the front-side wiring layer 8 is formed more evenly. Therefore, a flatter build-up layer BU can be realized.
[0030]
As described above, according to the method for manufacturing a wiring board of the present invention, after filling the through holes with the filling resin, the front side wiring layer is formed directly above the filling resin without performing the lid plating step. can do. Further, the step of polishing the surface of the core substrate, which has been performed before the lid plating step, is not required. Therefore, further improvement in production efficiency can be expected. Furthermore, the wiring board manufactured in this manner has good adhesion between the filling resin and the surface-side wiring layer immediately above the filling resin, and also has good flatness of the surface-side wiring layer and thus the build-up layer.
[0031]
In the present embodiment, an epoxy resin is used as the material of the core substrate. However, the present invention is not limited to this, and a material in which the inside of the core substrate is made of metal can be used. . Such a core substrate can be obtained by coating the surface of a metal base material with a resin. Further, as the material of the core substrate, ceramic may be adopted instead of epoxy resin.
[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 and 2B are schematic views showing the manufacturing process of the present invention following FIG. 1D.
3 (A) and 3 (B) are schematic views showing the manufacturing process of the present invention following FIG. 2 (B).
FIG. 4 is a schematic view showing a wiring board obtained by the present invention.
[Explanation of symbols]
1 ……………………… Wiring board 2 …………………………… Core board 2a …………………………… Surface 2b ……… Back face 3 ………………… Copper foil 5 …………………………… Through-hole 6 ………………………… … Through-hole conductor 7… Filling resin 9 ……………… Back wiring layer 8 …………………………… Surface-side wiring layer 11 Adhesive layer BU Build-up layer 8 Surface-side wiring Layers 18 and 19 Wiring layers 12 and 13 Insulating layers

Claims (7)

A wiring in which a build-up layer including an insulating layer and a wiring layer is formed on a surface of a core substrate in which a filling resin is filled in a through-hole, and the wiring layer is formed immediately above the filling resin filled in the through-hole. A method for manufacturing a substrate, comprising:
A step of forming the through hole in a form that does not penetrate only the copper foil from at least the back surface of the core substrate on which the copper foil is formed,
A filling step of filling the through-hole with the filling resin from the back side of the core substrate;
Forming the build-up layer on a surface of the core substrate. The core substrate, a copper foil is formed on the front surface, the back surface side wiring layer is formed on the back surface,
A pair of core substrates having an adhesive layer formed on the back surface, the respective adhesive layers are opposed to each other, and laminated via a release sheet, and by pressing and heating these core substrates, the adhesive layer is formed. 2. The method according to claim 1, wherein the through holes are filled. 3. The method of claim 1, wherein a through-hole conductor that covers an entire inner surface of the through-hole is formed before the filling step. 4. In the step of forming the through hole, a predetermined position on the back surface of the core substrate is irradiated with a laser so that the laser forms a through hole in the core substrate,
4. The method according to claim 1, wherein the laser is a laser that is reflected on the surface of the copper foil. 5. 5. The method according to claim 4, wherein the laser is a carbon dioxide laser. Filling resin is filled in the through hole of the core substrate in which the through hole is formed, and a surface side wiring layer made of copper foil is formed on the surface of the core substrate in a form covering the through hole. A wiring board, wherein the filling resin is formed below the surface-side wiring layer without protruding the surface of the core substrate. The wiring board according to claim 6, wherein a copper plating layer is formed between the filling resin and the front-side wiring layer.

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