JP2012060150A - Printed wiring board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board having through-hole structure which can reduce a defect such as a void and occurrence of a crack, reduce connection failure of a circuit board, and improve mechanical strength of the circuit board.SOLUTION: A printed wiring board has a through-hole obtained by filling an open hole arranged in an insulating resin base material with plating. Positions of axes of center of gravity are shifted and arranged in the respective through-holes exposed from a surface and a rear face of the insulating resin base material.

Description

  The present invention relates to a printed wiring board in which a plated conductor is formed in a through-hole formed in an insulating material. More specifically, the printed wiring board has improved conduction failure of the plated conductor and improved board strength. And its manufacturing method.

In the conventional printed wiring board, in the through-hole formed in the insulating resin base material as a plated through hole for electrically connecting the conductor circuits formed on the front and back surfaces of the insulating resin base material as the core, respectively. There are filled-type through-holes that are filled with metal by plating.
For example, Patent Document 1 describes a method of forming such a through hole as a conventional technique. In forming the through hole, first, as shown in FIG. 9A, after the through hole 2 is formed in the insulating resin substrate 1, the inner wall surface of the through hole is formed as shown in FIG. 9B. A seed layer 3 made of metal is formed by electroless plating on the surface of the insulating resin substrate 2 to be included.
Next, electrolytic plating is performed using the seed layer 3 as a power feeding layer to form an electrolytic plating layer 4 on the seed layer 3. As shown in FIG. 9C, the electrolytic plating layer 4 is thicker at the portion formed at the corner of the opening of the through hole 2 than at the inner portion of the through hole 2.
Furthermore, by performing electrolytic plating treatment, as shown in FIG. 9 (d), the through hole 2 is filled with metal to form the through hole 6, and the electrolytic plating layer 4 can have a desired thickness.
Thereafter, by patterning the electrolytic plating layer 4, desired wiring patterns are formed on the front and back surfaces of the insulating resin substrate 1, and through holes 6 for electrically connecting such wiring patterns are formed. A wiring board can be obtained.
However, as shown in FIG. 9D, there is a problem that voids 8 are easily formed in the through holes formed by such a method.
Therefore, a technique capable of forming a through hole free from defects such as voids has been proposed (see, for example, Patent Document 1 above). In this method, as shown in FIGS. 10 (a) to 10 (b), after the through-hole 2 having a drum-shaped longitudinal section is formed in the insulating resin substrate 1, the inner wall surface of the through-hole is electrolessly plated. By forming a seed layer 3 made of metal, and then performing an electroplating process using the seed layer as a power supply layer, the drum 4 through-hole is filled with the metal 4 so that defects such as voids are less likely to occur. This is a method of forming the hole 6.
JP 2004-311919 A

However, in the printed wiring board having a through hole whose longitudinal section has a drum shape as described above, the plated through hole has a so-called neck portion whose diameter decreases from the surface opening toward the center. At the same time, since the shape is almost symmetrical across the central axis, when warping occurs in the insulating resin base material, the stress tends to concentrate around the neck portion of the through hole. As a result, cracks are likely to occur in the vicinity of the neck portion, so that there is a problem that connection failure occurs due to the occurrence of the cracks, and the substrate is easily broken and sufficient mechanical strength cannot be obtained.
Accordingly, an object of the present invention is to reduce the connection failure of the substrate and reduce the mechanical strength of the substrate by reducing not only the defects such as voids but also the occurrence of cracks. It is providing the printed wiring board which has this.

  As a result of repeated studies to solve the above problems, the inventor of the present invention has a through-hole structure having a cross-sectional drum shape filled with plating, for example, a first opening exposed on one surface of the substrate, and the other of the substrate. In the through hole structure having a shape in which the second opening exposed to the surface is reduced in diameter toward the vicinity of the central portion of the substrate and integrated in the vicinity of the central portion, that is, in a cross-sectional drum shape When the centroid axis of the first opening and the centroid axis of the second opening are deviated from each other within a predetermined range, the plating fillability is good and the plating-filled through-hole receives. The inventors have found that stress is effectively relieved and have reached the present invention.

That is, the present invention
(1) In a printed wiring board having a through-hole formed by plating and filling a through-hole provided in an insulating resin base material,
The through hole is a shape having a neck portion,
The position of the center of gravity axis of each through hole exposed from the front and back surfaces of the insulating resin base material is shifted from each other,
In the printed wiring board, the position of the center of gravity of the bonding cross section at the neck portion of the through hole is shifted in the cross sectional direction of the insulating resin base material between adjacent through holes.

The present invention also provides:
(2) The surface of the insulating resin base material having a through hole formed by plating and filling the through hole provided in the insulating resin base material and electrically connected by the through hole. In the multilayer printed wiring board formed by alternately forming the core substrate having the back surface and the resin insulating layer and the outer layer conductor circuit on the core substrate,
The through hole is a shape having a neck portion,
The position of the center of gravity axis of each through hole exposed from the front and back surfaces of the insulating resin base material is shifted from each other,
In the multilayer printed wiring board, the position of the center of gravity of the bonding cross section at the neck portion of the through hole is shifted in the cross sectional direction of the insulating resin base material between adjacent through holes.

In the inventions described in (1) and (2) above,
(1) The plane region surrounded by the line connecting the neck portions is not parallel to the surface of the insulating resin base material.
(2) The through hole includes a first opening opening on the surface of the insulating resin base material and a second opening opening on the back surface of the insulating resin base material. (3) The deviation amount Is 5 to 30 μm,
(4) The first opening and the second opening have substantially the same diameter.
(5) The insulating resin base material is a glass cloth epoxy resin base material, a glass cloth bismaleimide triazine resin base material, a glass cloth polyphenylene ether resin base material, an aramid nonwoven fabric-epoxy resin base material, an aramid nonwoven fabric-polyimide resin base material. Being selected from the group consisting of
(6) The insulating resin base material has a thickness of 100 to 500 μm.
(7) The pitch between the adjacent through holes is 100 to 400 μm,
It can be.
Further, in the present invention, the through hole has a shape in which a neck portion is formed by being reduced in diameter from the front surface and the back surface of the insulating resin base material, that is, having a neck portion inside. It can be formed into a drum shape, and the diameter of the opening exposed on the front and back sides of the insulating resin substrate is 75 to 300 μm, and the diameter of the neck portion inside the insulating resin substrate is 50 to 250 μm. Can do.
Here, the “center of gravity axis” refers to a straight line that passes through the center of gravity of the opening of the through hole on the front surface (back surface) of the core substrate and is substantially perpendicular to the front surface (back surface) of the core substrate.

Furthermore, the present invention provides a conductive circuit having a through hole formed by plating filling a through hole penetrating the insulating resin base material and electrically connected by the through hole. And in manufacturing printed wiring boards on the back,
At least the following steps (1) to (4):
(1) Laser irradiation is performed on a predetermined position on one surface of a copper clad laminate in which copper foil is adhered to both surfaces of an insulating resin substrate, and the diameter is reduced toward the inside of the insulating resin substrate. Forming a first opening having such a shape;
(2) Laser irradiation is performed from a location on the other surface of the copper-clad laminate facing the predetermined position across the insulating resin base material so as not to overlap with the center of gravity of the first opening. And having a shape that is reduced in diameter toward the inside of the insulating resin base material, and communicates with the first opening in the vicinity of the central portion in the thickness direction of the insulating resin base material. And forming a second opening so that a planar region surrounded by a line connecting the neck portions is not parallel to the surface of the insulating resin base material, and the first opening A step of causing the center of gravity position of the joint cross section with the second opening to be shifted in the cross-sectional direction of the insulating resin base material in the adjacent through hole;
(3) applying electroless plating to the substrate to form an electroless plating film on the inner walls of the first and second openings;
(4) performing electrolytic plating on the substrate to form an electrolytic plating film on the electroless plating film, and forming a through hole by filling the first and second openings with plating;
It is the manufacturing method of the printed wiring board characterized by including.
In the invention described above,
(1) The first opening is provided so as to reach a portion near the back surface from a central portion in the thickness direction of the insulating resin base material,
The second opening is provided so as to reach a portion close to the surface from a central portion in a thickness direction of the insulating resin substrate;
(2) The laser processing conditions for forming the first opening and the laser processing conditions for forming the second opening are the same.
It can be.
In addition, you may include the process of removing the resin residue which remains in the said 1st and 2nd opening part between the process of said (2), and the process of (3).

  Since the occurrence of defects such as voids and the occurrence of cracks can be reduced, poor connection of the substrate can be reduced and the mechanical strength of the substrate can be improved.

A printed wiring board according to the present invention is a printed wiring board having a plated conductor in a through-hole provided in an insulating resin base material, or such a printed wiring board as a core substrate, and a conductor layer on the core substrate. In multilayer printed wiring boards formed by alternately forming resin insulation layers,
The center of gravity axis position of the through hole exposed from the surface of the insulating resin base material and the center of gravity axis position of the through hole exposed from the back surface of the insulating resin base material are shifted from each other. .

In this way, by arranging the positions of the center of gravity of the through holes exposed on the front surface and the back surface of the insulating resin substrate so as to be shifted from each other, the neck portion of the through hole, that is, the surface of the insulating resin substrate or Since the portion where the cross-sectional area of the portion cut by the plane parallel to the back surface is minimized is shifted, even if the insulating resin base material is warped, the amount of displacement of the neck portion The area to which stress is applied becomes wider, or the surface that connects the surface of the core substrate and the center of gravity of each neck portion is not parallel to each other, so that the stress is relieved and cracks are less likely to occur around the neck portion. As a result, connection failure due to cracks is less likely to occur, and the mechanical strength of the substrate can be improved.
Moreover, you may form so that the gravity center position of a neck part may differ in an adjacent through hole.

  In addition, since the cross-sectional area around the neck portion of the through hole is increased, the conduction resistance is reduced, and the electrical characteristics of the substrate can be improved.

  Furthermore, in the multilayer printed wiring board according to the present invention, a part of the outermost conductor layer is formed on the bump connection pad at a predetermined pitch, and each through hole exposed from the front and back surfaces of the insulating resin base material It is desirable to keep the positions of the center of gravity of the surfaces of the two surfaces in a state shifted from each other and to form the pitch between adjacent through holes to be the same as the pitch of the bump connecting pads.

As the insulating resin base material used in the present invention, a glass cloth epoxy resin base material, a glass cloth bismaleimide triazine resin base material, a glass cloth polyphenylene ether resin base material, an aramid nonwoven fabric-epoxy resin base material, an aramid nonwoven fabric-polyimide resin It is preferable to use a hard base material selected from base materials, and a glass cloth epoxy resin base material is more preferable.
The thickness of the insulating resin substrate is preferably about 100 to 500 μm. The reason is that if the thickness is less than 100 μm, the rigidity is insufficient, and if it exceeds 500 μm, it is difficult to fill the through hole with plating, and plating voids may occur.

  As will be described later, the conductor circuit formed on both surfaces of the insulating resin base material was formed on the metal foil stuck on both surfaces of the insulating resin base material and after the plating filling of the through holes, as described later. It is desirable to form the plating layer by etching.

  The substrate composed of the insulating resin base material and the metal foil is, in particular, a double-sided surface obtained by laminating a prepreg in which a glass cloth is impregnated with an epoxy resin to form a B-stage and a copper foil, followed by hot pressing. A copper-clad laminate can be used. Such a substrate is excellent in positional accuracy because the wiring pattern and via positions are not shifted during handling after the copper foil is etched.

  The through hole according to the first embodiment of the present invention is, for example, as shown in FIG. 1, a first opening having a shape whose diameter is reduced from one surface of the insulating resin base toward the inside. And having a shape that is reduced in diameter from the other surface of the insulating resin substrate toward the inside, and communicated with the first opening in the vicinity of the central portion in the thickness direction of the insulating resin substrate. The neck portion is formed at a location where the first opening portion and the second opening portion intersect with each other. That is, the drum-shaped through-hole is plated and filled into a through-hole having a shape shifted in the substrate surface direction by a predetermined distance, and is formed on one surface and the other surface of the insulating resin base material. The center-of-gravity axes of the first opening and the second opening that are exposed (straight lines that pass through the center of gravity of the first opening and the second opening and are substantially perpendicular to the substrate surface (back surface)) are: They are arranged at positions shifted from each other.

The through hole is preferably formed by forming through holes made of the first opening and the second opening by laser processing and then filling the through holes with metal plating.
In addition, in order to improve the absorption efficiency of the irradiation laser beam in laser processing, it is desirable to perform a known blackening process on the metal foil on the insulating resin substrate in advance.

  In order to form a through hole for forming a through hole by laser processing, first, laser irradiation is performed from a predetermined position toward one surface of the insulating resin base material, and then from one surface of the insulating resin base material. A first opening having a shape that is reduced in diameter toward the inside and extended from one surface of the insulating resin base material to the vicinity of the center thereof is formed. Thereafter, laser irradiation is performed toward the other surface of the insulating resin base material from a position shifted by a predetermined distance from the other surface position of the insulating resin base material facing the predetermined position, so that the insulating resin The diameter of the base material is reduced from the other surface of the base material toward the inside, and the second opening portion is formed so as to extend from the other surface of the insulating resin base material to the vicinity of the central portion thereof. It is desirable that a through hole for forming a through hole is formed by communicating the first opening and the second opening in the vicinity of the center of the first hole.

  In order to form through holes for through-hole formation using a laser in the insulating resin base material, a direct laser method in which a metal foil and an insulating resin base material are simultaneously drilled by laser irradiation, and it corresponds to a through hole in the metal foil. There is a conformal method in which the insulating metal substrate is perforated by laser irradiation after removing the metal foil portion to be etched, either of which may be used in the present invention.

The laser processing is preferably performed by a pulse oscillation type carbon dioxide laser processing apparatus, and the processing conditions are through-hole forming through holes (first through holes) whose diameter is reduced from the surface of the insulating resin base toward the inside. 1 opening portion and second opening portion), that is, the angle formed by the surface of the insulating resin substrate and the side wall of the through hole (hereinafter referred to as “taper angle”) and the depth of the through hole. .
For example, the taper angle and depth of the through hole for forming the through hole can be adjusted by setting the pulse width to 10 to 20 μs and the number of shots to 1 to 5.
And as for the through-hole formation through-hole which can be formed on the said process conditions, it is desirable that the diameter (it shows with the code | symbol X in FIG. 1) of the neck part inside an insulating resin base material is 50-250 micrometers. . This is because if the diameter is less than 50 μm, the connection reliability of the plated-filled through hole is poor because it is too thin, and if the diameter exceeds 250 μm, voids are likely to occur in the plated-filled through hole. . Therefore, if it is within the above range, a through hole with less void generation and excellent connection reliability can be formed.

  Further, it is desirable that the deviation amount of the center of gravity position of the through hole forming the through hole is in the range of 5 to 30 μm. The reason is that when the deviation amount is less than 5 μm, the effect of stress relaxation is small. On the other hand, when the deviation amount exceeds 30 μm, the shape of the through hole is as shown in FIGS. This is because the shape tends to be odd.

  Further, the pitch between adjacent through holes is preferably 100 to 400 μm. The reason is that if the pitch is less than 100 μm, the insulation reliability is low, and if the pitch exceeds 400 μm, it is not suitable for refinement.

In addition, it is preferable to perform a desmear process in order to remove the resin residue which remains on the side surface of the through-hole formed by laser irradiation. This desmear treatment is performed by wet treatment such as chemical treatment of an acid or an oxidizing agent (for example, chromic acid, permanganic acid), or dry treatment such as oxygen plasma discharge treatment, corona discharge treatment, ultraviolet laser treatment, or excimer laser treatment. .
Which method to select from these desmear treatment methods is selected in consideration of the amount of smear that is expected to remain depending on the type, thickness, via hole opening diameter, laser irradiation conditions, etc. of the insulating substrate. .

In the present invention, in order to form a through hole by filling the through hole with plating, an electroless plating film is first formed on the inner wall of the through hole by a normal electroless plating process, and then a plating solution is jetted onto the substrate. It is desirable to fill and fill the inside of the through hole by an electrolytic plating method such as a sparger plating method.
As the electroless plating or electrolytic plating, for example, metal plating such as copper, tin, silver, various solders, copper / tin, and copper / silver is preferable, and electroless copper plating or electrolytic copper plating is particularly preferable.

In the present invention, the conductor circuit formed on both surfaces of the insulating resin base material is preferably formed by etching the conductor layer formed simultaneously with the formation of the plating filled through hole.
In this conductor circuit forming step, a photosensitive dry film resist is first applied to the surface of the conductor layer, and then an etching resist is formed by exposing and developing along a predetermined circuit pattern. The conductor layer is etched to form a conductor circuit pattern including electrode pads.
In the treatment step, as the etching solution, at least one aqueous solution selected from an aqueous solution of sulfuric acid monohydrogen peroxide, persulfate, cupric chloride, and ferric chloride can be used.
Further, as a pretreatment for etching the conductor layer to form a conductor circuit, the entire surface of the conductor layer is etched in advance to have a thickness of 1 to 10 μm, more preferably 2 to 8 μm, in order to facilitate the formation of a fine pattern. It can be made as thin as possible.

Such a printed wiring board is used as a core substrate, and a multilayer printed wiring board is formed on the core substrate by forming a build-up wiring layer in which conductor layers and resin insulating layers are alternately formed by a conventional method. be able to. ,
In such a multilayer printed wiring board, a part of the outermost conductor layer is formed on the bump connection pad at a predetermined pitch, and the pitch between adjacent plated filling through holes formed on the core substrate is set to It is desirable to form the same pitch as the bump connection pads. According to such a configuration, the wiring resistance through the chip mounted on the PKG can be lowered, which is advantageous in securing power supply.

Hereinafter, an example of a method for producing a printed wiring board according to the present invention will be specifically described.
(1) In manufacturing the printed wiring board according to the present invention, a material in which a copper foil is stuck on both surfaces of an insulating resin base material can be used as a starting material.
The insulating resin base material is, for example, a glass cloth epoxy resin base material, a glass cloth bismaleimide triazine resin base material, a glass cloth polyphenylene ether resin base material, an aramid non-woven fabric-epoxy resin base material, an aramid non-woven fabric-polyimide resin base material. A hard laminated substrate selected is used, and a glass cloth epoxy resin substrate is most preferable.

  The insulating resin base material preferably has a thickness in the range of about 100 to 500 μm. The reason is that if the thickness is less than 100 μm, the rigidity is insufficient, and if the thickness exceeds 500 μm, it is difficult to fill and fill the through holes, and voids may be generated.

In order to form a through-hole forming through-hole using a laser in the insulating resin base material, a direct laser method of simultaneously drilling a copper foil and an insulating base material by laser irradiation, and a portion corresponding to the through-hole of the copper foil There is a conformal method in which an insulating base material is perforated by laser irradiation after etching is removed by etching, either of which may be used in the present invention.
The thickness of this copper foil may be adjusted by half etching.

  As the insulating resin substrate and the copper foil, in particular, a double-sided copper-clad laminate obtained by laminating a prepreg in which a glass cloth is impregnated into a glass cloth and making a B-stage, and copper foil is laminated and heated. Is preferably used.

  This is because the position of the wiring pattern does not shift during the manufacturing process after the copper foil is etched, and the position accuracy is excellent.

(2) Next, through holes for forming through holes are provided in the insulating resin base material by laser processing.
When a double-sided copper-clad laminate is used to form a circuit board, first, laser irradiation is performed from a predetermined position toward the metal foil affixed to one surface of the insulating resin base material, and penetrates the metal foil. In addition, the first opening is formed in a form that is reduced in diameter from one surface of the insulating resin base material toward the inside and extended from one surface of the insulating resin base material to the vicinity of the central portion thereof, Alternatively, a hole having a diameter approximately equal to the diameter of the surface of the through hole is formed in advance at a predetermined position on one copper foil surface affixed to the insulating resin substrate by etching (laser mask), and then the hole is formed. A first opening in a form in which carbon dioxide laser irradiation is performed as an irradiation mark, the diameter is reduced toward the inside of the insulating resin base material, and extended from one surface of the insulating resin base material to the vicinity of the central portion thereof. Form.

  Next, laser irradiation is performed from a position shifted by a predetermined distance from the other surface position of the insulating resin base material facing the predetermined position toward the metal foil attached to the other surface of the insulating resin base material. And forming a second opening in a form that is reduced in diameter from the other surface of the insulating resin base material toward the inside and extended from the other surface of the insulating resin base material to the vicinity of the central portion thereof, Alternatively, a hole having a diameter substantially equal to the diameter of the surface of the through hole is formed in advance at a predetermined position on the surface of the other copper foil attached to the insulating resin substrate by etching (laser mask), and then the hole is formed. A second opening in a form in which carbon dioxide laser irradiation is performed as an irradiation mark, the diameter is reduced toward the inside of the insulating resin base material, and extended from the other surface of the insulating resin base material to the vicinity of the central portion thereof. Form.

  When forming the second opening, the first opening and the second opening communicate with each other in the vicinity of the central portion of the insulating resin base material to form a through hole for forming a through hole, and The distance between the center of gravity (shift amount) between the first opening and the second opening is set so that the plane area surrounded by the line connecting the necks is not parallel to the substrate surface (see FIG. 2). Adjust according to.

  The laser processing is performed by a pulse oscillation type carbon dioxide laser processing apparatus, and the processing conditions are determined by the shape of the through-hole forming through-hole that is reduced in diameter from the surface of the insulating resin substrate toward the inside. For example, the pulse width is 10 to 20 μs and the number of shots is 1 to 5.

  Under such laser processing conditions, the opening diameter of the through hole for forming the through hole (the opening diameter of the first opening and the second opening) is set to 75 to 300 μm, and the shortest diameter of the neck portion is set to 50 to 250 μm. The deviation amount of the center of gravity of the through hole forming the through hole can be set in the range of 5 to 30 μm.

(3) The desmear process for removing the resin residue which remains on the side wall of the through hole formed in the step (2) is performed.
This desmear treatment is performed by wet treatment such as chemical treatment of an acid or an oxidizing agent (for example, chromic acid or permanganic acid), or dry treatment such as oxygen plasma discharge treatment, corona discharge treatment, ultraviolet laser treatment, or excimer laser treatment. .

(4) Next, an electroless plating treatment is performed to form an electroless plating film on the inner wall of the through hole for the through hole and the copper foil. In this case, the electroless plating film may use a metal such as copper, nickel, or silver.

(5) Furthermore, with the electroless plating film formed in the above (4) as a lead, an electrolytic plating process is performed to form an electrolytic plating film on the electroless plating film covering the copper foil of the substrate, The plating layer deposited on the inner wall surface of the through hole is gradually thickened, and an electroplating film is filled in the through hole to form a drum-shaped through hole.

(6) Next, in the above (5), an etching resist layer is formed on the electrolytic copper plating film formed on the substrate. The etching resist layer may be either a method of applying a resist solution or a method of applying a film-like one in advance. A mask on which a circuit is drawn in advance is placed on the resist layer, and an etching resist layer is formed by exposure and development, and a metal layer in a portion where no etching resist is formed is etched to include a through-hole land. A conductor circuit pattern is formed.

  The etching solution is preferably at least one aqueous solution selected from sulfuric acid-hydrogen peroxide, persulfate, cupric chloride, and ferric chloride.

  As a pretreatment for forming the conductor circuit by the etching treatment, the thickness may be adjusted in advance by etching the entire surface of the electrolytic copper plating film in order to facilitate the formation of a fine pattern.

With the printed wiring board according to the present invention produced according to the steps (1) to (6) as a core, an insulating resin layer and a conductor circuit layer are alternately laminated on one side or both sides of the core substrate. A multilayer printed wiring board can be formed by forming the build-up wiring layer.
In this multilayer printed wiring board, a solder resist layer is formed on the outermost layer of the build-up wiring layer, that is, on the surface of the insulating resin layer on which the outermost conductor circuit is formed. In this case, the solder resist composition is applied to the entire surface of the outermost layer of the substrate, and the coating film is dried. Then, a photomask film on which the opening of the connection pad is drawn is placed on the coating film, and exposure and development are performed. By processing, the connection pad portion is exposed. In this case, a solder resist layer formed in a dry film may be attached to form an opening by exposure / development or laser.

  A corrosion resistant layer such as nickel-gold is formed on the connection pad exposed from the solder resist layer. At this time, the thickness of the nickel layer is desirably 1 to 7 μm, and the thickness of the gold layer is desirably 0.01 to 0.1 μm. In addition to these metals, nickel-palladium-gold, gold (single layer), silver (single layer), or the like may be formed.

  Thereafter, a solder body is supplied onto the connection pad, and solder bumps are formed by melting and solidifying the solder body, thereby forming a multilayer circuit board.

  In the multilayer printed wiring board formed by the process as described above, a part of the outermost conductor layer is formed as a connection pad at a predetermined pitch, and the pitch of the connection pad formed on the core substrate is filled with adjacent plating. Forming the same pitch between the through holes is advantageous from the viewpoint of securing power supply because the wiring resistance through the chip mounted on the PKG can be lowered.

(Example 1-1)
(1) First, a circuit board (core) as one unit constituting a multilayer printed wiring board is manufactured. This circuit board is a board to be a lamination center among a plurality of insulating layers to be laminated. By laminating a prepreg and a copper foil made by impregnating a glass cloth with an epoxy resin and hot pressing, The obtained double-sided copper-clad laminate 10 is used as a starting material (see FIG. 4A).

  The insulating resin substrate 12 has a thickness of 300 μm, and the copper foil 14 has a thickness of 3 μm. You may adjust the thickness of copper foil to 3 micrometers by an etching process using the copper foil of this laminated board thicker than 3 micrometers.

(2) Carbon dioxide laser irradiation is performed on a predetermined position on one surface of the double-sided circuit board 10 to penetrate one copper foil 14 and the other surface from the central portion in the thickness direction of the insulating resin substrate 12 The first opening 16 is formed so as to reach a portion close to (see FIG. 4B), and carbon dioxide laser irradiation is performed at a position shifted by 15 μm from the position corresponding to the predetermined position on the other surface of the double-sided circuit board 10. Second, such that the second copper foil 14 penetrates the other copper foil 14 and communicates with the first opening 16 from the central portion in the thickness direction of the insulating resin base material 12 to the portion close to the one surface. Opening 18 is formed. As a result, the first and second openings 16 and 18 communicate with each other to form a through hole 20 for forming a through hole.

  In this embodiment, the through hole 20 for forming the through hole is formed by using, for example, a high peak short pulse oscillation type carbon dioxide gas laser processing machine manufactured by Hitachi Via, with a pulse width of 10 to 20 μs and a shot. Number: Performed under 1 to 5 laser processing conditions. The opening diameters of the first opening 16 and the second opening 18 are approximately 150 μm, and the diameter of the neck near the center of the substrate in the thickness direction, that is, the shortest distance of the most contracted portion The through holes 20 (indicated by X in FIG. 1) are approximately 87 μm, and the displacement of the center of gravity of the first and second openings 16 and 18 is 15 μm, with a pitch of 150 μm.

  The through hole 20 formed under such conditions has first and second openings 16 and 18 arranged with their center axes shifted from each other, and the inner wall thereof is tapered with respect to the surface of the insulating resin substrate 12. It is formed from a part of a truncated cone that forms an (inner angle), and is formed in a form joined at a common joining cross section in the vicinity of the center in the thickness direction of the base material.

  This joining cross section (see FIG. 2) is not parallel to the surface of the insulating resin substrate. Moreover, it is preferable that the center-of-gravity position of adjacent joint cross sections is shifted in the cross-sectional direction of the insulating resin base material (see FIG. 3).

(3) Thereafter, a desmear treatment is performed in the through-hole 20 formed by laser processing by a physical method such as O ₂ plasma or CF ₄ plasma to remove a resin or particle residue remaining on the inner wall. Further, the substrate after the desmear treatment may be washed with water and acid degreased, and then subjected to a soft etching treatment.

(4) Next, the substrate subjected to the desmear treatment is immersed in an electroless copper plating aqueous solution having the following composition, and is applied to the entire surface of the copper foil 14 and the inner walls of the through holes 20 attached to both surfaces of the substrate. An electroless copper plating film 22 having a thickness of 0.6 μm was formed. (FIG. 4 (d)).
(Electroless copper plating solution)
Copper sulfate: 0.03 mol / l
EDTA: 0.200 mol / l
HCHO: 0.18 g / l
NaOH: 0.100 mol / L
α, α′-bipyridyl: 100 mg / l
Polyethylene glycol: 0.10 g / l
(Plating conditions)
Liquid temperature: 30-50 degreeC
Time: 40-60 minutes

(5) Next, the substrate was washed with water at 50 ° C., degreased, washed with water at 25 ° C. and further washed with sulfuric acid, and then subjected to electrolytic plating under the following conditions to form an electrolytic plating film 24. (See FIG. 5 (a)).
[Electrolytic copper plating solution]
Sulfuric acid 2.24 mol / l
Copper sulfate 0.26 mol / l
Additive 19.5ml / l
Leveling agent 50mg / l
Brightener 50mg / l
[Electrolytic plating conditions]
Current density 1.0A / dm ²
Time 30-90 minutes Temperature 22 ± 2 ℃

(6) In FIG. 5, the display of the electroless plating film 22 is omitted for simplification. An etching resist layer 28 is formed by attaching a film resist film on the substrate on which the electrolytic copper plating film is formed, placing a mask on which a circuit is drawn in advance, and exposing and developing the resist film. (See FIG. 5B). Thereafter, the metal layer in the portion where the etching resist is not formed is etched to form an inner conductor circuit 30 having a thickness of 20 to 30 μm on the front and back surfaces of the insulating resin base material, and is positioned immediately above the through hole 26. By forming through-hole lands 32, a core substrate was manufactured (see FIG. 5C).
Note that a wiring in which 100 through holes are connected via the conductor circuit 30 and the through hole land 32 is formed.
Next, an interlayer resin insulating layer and a conductor layer are alternately laminated on the core substrate to form a build-up wiring layer, thereby forming a multilayered printed wiring board.

(7) After washing the substrate with water and acid degreasing, soft etching is performed, and then an etching solution is sprayed on both sides of the substrate to spray the surface of the inner layer conductor circuit 30 (including the through-hole land 32). Thus, a roughened surface (not shown) was formed on the entire surface of the inner layer conductor circuit 30 (including the through-hole land 32).
As an etchant, an etchant (MEC Etch Bond, manufactured by MEC Co.) consisting of 10 parts by weight of imidazole copper (II) complex, 7 parts by weight of glycolic acid, and 5 parts by weight of potassium chloride was used.

(8) A resin film for an interlayer resin insulation layer (for example, ABF manufactured by Ajinomoto Co., Inc.) slightly larger than the substrate is placed on both sides of the substrate, and the pressure is 0.4 MPa, the temperature is 80 ° C., and the bonding time is 10 seconds. After the temporary pressure bonding under the above conditions and cutting, the interlayer resin insulation layer 36 was further formed by pasting using a vacuum laminator apparatus by the following method.
That is, a resin film for an interlayer resin insulation layer was subjected to main pressure bonding on a substrate under conditions of a degree of vacuum of 67 Pa, a pressure of 0.4 MPa, a temperature of 80 ° C., and a pressure bonding time of 60 seconds, and then thermally cured at 170 ° C. for 30 minutes.

(9) Next, with a CO ₂ gas laser having a wavelength of 10.4 μm through a mask in which a through hole having a thickness of 1.2 mm is formed in the interlayer resin insulation layer 36, a beam diameter of 4.0 mm, top hat mode A via hole opening 38 having a diameter of 60 μm was formed in the interlayer resin insulation layer under the conditions of a pulse width of 8.0 μsec, a mask through-hole diameter of 1.0 mm, and 1 to 3 shots (see FIG. 5D). .

(10) The substrate on which the via hole opening 38 is formed is immersed in an 80 ° C. solution containing 60 g / l permanganic acid for 10 minutes to remove particles present on the surface of the interlayer resin insulating layer 36. The surface of the interlayer resin insulation layer 36 including the inner wall of the via hole opening 38 was a roughened surface (not shown).

(11) Next, the substrate after the above treatment was immersed in a neutralization solution (manufactured by Shipley Co., Ltd.) and washed with water.
Further, by applying a palladium catalyst to the surface of the roughened substrate (roughening depth 3 μm), catalyst nuclei are attached to the surface of the interlayer resin insulation layer 36 and the inner wall surface of the via hole opening 38. (Not shown). That is, the substrate was immersed in a catalyst solution containing palladium chloride (PdCl ₂ ) and stannous chloride (SnCl ₂ ), and the catalyst was applied by depositing palladium metal.

(12) Next, a substrate provided with a catalyst is immersed in an electroless copper plating aqueous solution having the following composition to form an electroless copper plating film having a thickness of 0.6 to 3.0 μm on the entire rough surface. A substrate having an electroless copper plating film (not shown) formed on the surface of the interlayer resin insulation layer 36 including the inner wall of the via hole opening 38 was obtained.
[Electroless copper plating aqueous solution]
Copper sulfate: 0.03 mol / l
EDTA: 0.200 mol / l
HCHO: 0.18 g / l
NaOH: 0.100 mol / L
α, α′-bipyridyl: 100 mg / l
Polyethylene glycol: 0.10 g / l
(Plating conditions)
Liquid temperature: 30-50 degreeC
Time: 40-60 minutes

(13) A commercially available photosensitive dry film is pasted on the substrate on which the electroless copper plating film is formed, a mask is placed, exposed at 100 mJ / cm ² , and developed with a 0.8% aqueous sodium carbonate solution. Thus, a plating resist (not shown) having a thickness of 20 μm was provided.

(14) Next, the substrate was washed with 50 ° C. water for degreasing, washed with 25 ° C. water, and further washed with sulfuric acid, and then subjected to electrolytic plating under the following conditions to form an electrolytic plated film.
[Electrolytic plating solution]
Sulfuric acid 2.24 mol / l
Copper sulfate 0.26 mol / l
Additive 19.5 ml / l
Leveling agent 50 mg / l
Brightener 50 mg / l
[Electrolytic plating conditions]
Current density 1 A / dm ²
Time 65 minutes Temperature 22 ± 2 ℃

  In this plating treatment, an electrolytic copper plating film having a thickness of 20 μm was formed in the plating resist non-forming portion, and the via hole opening 38 was filled with the electrolytic plating film.

(15) Further, after removing and removing the plating resist with 5% KOH, the electroless plating film under the plating resist is dissolved and removed by etching with a mixed solution of sulfuric acid and hydrogen peroxide. 40 and independent outer layer conductor circuit 44 were formed (see FIG. 6A).

(16) Next, the same process as in (8) above was performed to form a roughened surface (not shown) on the surface of the outer conductor circuit 44 and the surface of the filled via 40.

(17) By repeating the steps (8) to (15) above, an outer interlayer insulating layer 46, an outer conductor circuit 48, and a filled via 50 were formed to obtain a multilayer wiring board (FIG. 6B). reference).

(18) Next, a commercially available solder resist composition is applied to both sides of the multilayer wiring board at a thickness of 20 μm, and after drying at 70 ° C. for 20 minutes and 70 ° C. for 30 minutes, the solder is applied. A photomask having a thickness of 5 mm on which a pattern of the resist opening was drawn was brought into close contact with the solder resist layer, exposed to 1000 mJ / cm ² of ultraviolet light, and then developed to form an opening 54 having a diameter of 60 μm (see FIG. 6 (c)).

  Further, the solder resist layer is cured by heating at 80 ° C. for 1 hour, 100 ° C. for 1 hour, 120 ° C. for 1 hour, and 150 ° C. for 3 hours. A solder resist pattern layer 52 having a thickness of 20 μm was formed.

(19) Next, the substrate on which the solder resist layer 52 is formed is made of nickel chloride (2.3 × 10 ⁻¹ mol / l), sodium hypophosphite (2.8 × 10 ⁻¹ mol / l), A nickel plating layer (not shown) having a thickness of 5 μm is formed in the opening 54 by immersing in an electroless nickel plating solution containing sodium acid (1.6 × 10 ⁻¹ mol / l) at pH = 4.5 for 20 minutes. Formed. Furthermore, the substrate gold potassium cyanide ^{(7.6 × 10 -3 mol / l} ), ammonium chloride ^{(1.9 × 10 -1 mol / l} ), sodium citrate (1.2 × 10 ^-1 mol / l) Immerse in an electroless gold plating solution containing sodium hypophosphite (1.7 × 10 ⁻¹ mol / l) at 80 ° C. for 7.5 minutes to form a thickness of 0 on the nickel plating layer. A 0.03 μm gold plating layer (not shown) was formed.

(20) Furthermore, a solder paste containing tin-lead is printed on the opening 54 of the solder resist layer 52 on the surface on which the IC chip of the substrate is placed, and tin is further formed on the opening 54 of the solder resist layer 52 on the other surface. -After printing the solder paste containing antimony, the solder bump 56 was formed by reflowing at 230 degreeC, and it was set as the multilayer printed wiring board (refer FIG.6 (d)).

(Example 1-2)
Example 1-1 except that the through-hole 20 having a displacement amount of the center of gravity of the first opening 16 and the second opening 18 of 5 μm and a neck portion having a diameter of 76 μm was formed by laser beam irradiation. A multilayer printed wiring board was produced in the same manner as described above.

(Example 1-3)
Example 1-1, except that the through hole 20 having a displacement of the center of gravity of the first opening 16 and the second opening 18 of 10 μm and the neck diameter of 80 μm was formed by laser beam irradiation. A multilayer printed wiring board was produced in the same manner as described above.

(Example 1-4)
Example 1-1 except that the through-hole 20 having a displacement amount of the center of gravity of the first opening 16 and the second opening 18 of 20 μm and a neck diameter of 91 μm was formed by laser beam irradiation. A multilayer printed wiring board was produced in the same manner as described above.

(Example 1-5)
Example 1-1, except that a through hole 20 having a displacement of the center of gravity of the first opening 16 and the second opening 18 of 25 μm and a neck diameter of 97 μm was formed by laser beam irradiation. A multilayer printed wiring board was produced in the same manner as described above.

(Example 1-6)
Example 1-1 except that the through-hole 20 having a displacement amount of the center of gravity of the first opening 16 and the second opening 18 of 30 μm and a neck diameter of 110 μm was formed by laser beam irradiation. A multilayer printed wiring board was produced in the same manner as described above.

(Reference Example 1-1)
Example 1-1, except that the through-hole 20 having a displacement amount of the center of gravity of the first opening 16 and the second opening 18 of 3 μm and a neck diameter of 74 μm was formed by laser beam irradiation. A multilayer printed wiring board was produced in the same manner as described above.

(Reference Example 1-2)
Example 1-1, except that the through hole 20 having a displacement of 35 μm in the center of gravity of the first opening 16 and the second opening 18 and having a neck diameter of 95 μm was formed by laser beam irradiation. A multilayer printed wiring board was produced in the same manner as described above.

In Examples 1-1 to 1-6 and Reference Examples 1-1 to 1-2, a double-sided copper-clad laminate in which the thickness of the insulating resin substrate is 100 μm is used. A multilayer printed wiring board was produced in the same manner except that the carbon dioxide laser irradiation conditions were changed and the diameters of the first opening 16 and the second opening 18 were set to 75 μm. −6 and Reference Examples 2-1 to 2-2.
Tables 1 and 2 show the displacement amount of the center of gravity axis and the diameter of the neck portion at this time.

Similarly, in Examples 1-1 to 1-6 and Reference Examples 1-1 to 1-2, a double-sided copper-clad laminate in which the thickness of the insulating resin base material is 500 μm is used. A multilayer printed wiring board was manufactured in the same manner except that the diameters of the first opening 16 and the second opening 18 were changed to 300 μm by changing the opening diameter and the carbon dioxide laser irradiation condition, and these were used in Example 3-1. To 3-6 and Reference Examples 3-1 to 3-2.
Table 2 shows the deviation amount of the center of gravity axis and the diameter of the neck portion at this time.

  The multilayer printed wiring boards manufactured according to Examples 1-1 to 3-6 and Reference Examples 1-1 to 3-2 were subjected to evaluation tests such as A below. The results of these evaluation tests are shown in Table 1 and Table 2.

A. Heat cycle test Measure the connection resistance of the wiring with 100 through-holes connected by the conductor circuit on the front and back of the core substrate of the multilayer printed wiring board (initial value), and then -55 ° C x 5 minutes ⇔ 125 ° C x 5 minutes The cycle test is repeated 1000 times under the heat cycle condition of 1 cycle, and the connection resistance is measured again.
Here, if the amount of change in connection resistance (100 × (connection resistance value after heat cycle−connection resistance value of initial value) / connection resistance value of initial value) is within 10%, then pass (indicated by ○) A product exceeding 10% is regarded as defective (indicated by x).
The measurement results are all acceptable in each example, and all are unacceptable in each reference example.

Regarding the core substrate of the multilayer printed wiring board of each reference example, an X-ray television system (manufactured by Shimadzu Corporation, trade name “SMX-100”) is used to determine whether voids are present in the plating (through holes) filled in the through holes. ). 100 through-holes were randomly selected and observed.
The presence of many voids was confirmed in the core substrate of each reference example. It is presumed that when the amount of deviation is small, voids are generated because the plating solution entering the through-holes from the front and back of the core substrate collides front. On the other hand, when the amount of deviation exceeds 30 μm, the amount of deviation is too large, and it is assumed that the through hole is likely to have an odd shape as shown in FIGS.

  From the results of the evaluation test A described above, in the printed wiring board manufactured according to each example, the occurrence of cracks around the central portion where the diameter of the plating-filled through hole was reduced was prevented, and good electrical connectivity and mechanical properties were achieved. It was confirmed that strength was obtained.

  In each of the above embodiments, the through hole provided in the insulating resin base material (core substrate) is filled with plating, but a through-hole conductor is formed on the inner wall of the through-hole, and the void surrounded by the through-hole conductor The heat cycle test result with respect to the amount of deviation is the same for the through hole (see FIG. 8) formed by filling the filler with the filler.

  As described above, the present invention provides a printed wiring board that reduces the occurrence of defects such as voids and cracks, reduces board connection failures, and is advantageous in improving the mechanical strength of the board.

It is the schematic for demonstrating the shape of the through hole in the printed wiring board of this invention. It is the schematic which shows the junction cross section of the neck part of a through hole. It is the schematic which shows the example from which the gravity center position of an adjacent through hole differs. (A)-(d) is a figure which shows a part of process of manufacturing the printed wiring board concerning one Example of this invention. (A)-(d) is a figure which shows a part of process of manufacturing the printed wiring board concerning one Example of this invention. (A)-(d) is a figure which shows a part of process of manufacturing the printed wiring board concerning one Example of this invention. (A)-(b) is the schematic which shows the odd shape when the deviation | shift amount of the gravity center position of a through hole is large. It is the schematic which shows the through hole formed by forming a through-hole conductor in the inner wall of a through-hole, and also filling the space | gap enclosed with the through-hole conductor with the filler. (A)-(d) is a figure which shows the manufacturing process of the printed wiring board concerning a prior art. (A)-(b) is a figure for demonstrating the through-hole shape of the other printed wiring board concerning a prior art.

DESCRIPTION OF SYMBOLS 10 Double-sided copper clad laminated board 12 Insulating resin base material 14 Copper foil 16 1st opening part 18 2nd opening part 20 Through-hole 22 Electroless plating film 24 Electrolytic plating film 26 Plating filling through hole 30 Inner-layer conductor circuit 32 Through-hole land 36 Interlayer resin insulation layer 40 Via hole 44 External conductor circuit 46 Interlayer resin insulation layer 50 Via hole 52 Solder resist layer 56 Bump

Claims (12)

In a printed wiring board having a through-hole formed by plating and filling in a through-hole provided in an insulating resin base material,
The through hole is a shape having a neck portion,
The position of the center of gravity axis of each through hole exposed from the front and back surfaces of the insulating resin base material is shifted from each other,
The printed wiring board according to claim 1, wherein the center of gravity position of the bonding cross section at the neck portion of the through hole is shifted in the cross sectional direction of the insulating resin base material between adjacent through holes. On the front and back surfaces of the insulating resin substrate, there are through-holes formed by plating and filling the through-holes provided in the insulating resin substrate, and the inner layer conductor circuit electrically connected by the through-holes. In a multilayer printed wiring board formed by alternately forming a core substrate having a resin insulating layer and an outer layer conductor circuit on the core substrate,
The through hole is a shape having a neck portion,
The position of the center of gravity axis of each through hole exposed from the front and back surfaces of the insulating resin base material is shifted from each other,
The multilayer printed wiring board characterized in that the center of gravity position of the bonding cross section at the neck portion of the through hole is shifted in the cross sectional direction of the insulating resin base material between adjacent through holes. 3. The printed wiring board according to claim 1, wherein a planar region surrounded by a line connecting the neck portions is not parallel to a surface of the insulating resin base material. The said through-hole consists of the 1st opening part opened to the surface of the said insulating resin base material, and the 2nd opening part opened to the back surface of the said insulating resin base material, The Claim 1 or 2 characterized by the above-mentioned. Printed wiring board as described in 1. The printed wiring board according to claim 1, wherein the shift amount is 5 to 30 μm. The printed wiring board according to claim 4, wherein the first opening and the second opening have substantially the same diameter. The insulating resin base material is a group consisting of a glass cloth epoxy resin base material, a glass cloth bismaleimide triazine resin base material, a glass cloth polyphenylene ether resin base material, an aramid nonwoven fabric-epoxy resin base material, an aramid nonwoven fabric-polyimide resin base material. The printed wiring board according to claim 1, wherein the printed wiring board is selected from the following. The printed wiring board according to claim 1, wherein the insulating resin base material has a thickness of 100 to 500 μm.   The printed wiring board according to claim 1, wherein a pitch between adjacent through holes is 100 to 400 μm. Printed wiring having through-holes that are plated and filled in through-holes that penetrate the insulating resin base material, and conductor circuits that are electrically connected by the through-holes on the front and back surfaces of the insulating resin base material In manufacturing the board,
At least the following steps (1) to (4):
(1) Laser irradiation is performed on a predetermined position on one surface of a copper clad laminate in which copper foil is adhered to both surfaces of an insulating resin substrate, and the diameter is reduced toward the inside of the insulating resin substrate. Forming a first opening having such a shape;
(2) Laser irradiation is performed from a location on the other surface of the copper-clad laminate facing the predetermined position across the insulating resin base material so as not to overlap with the position of the center of gravity of the first opening. And having a shape that is reduced in diameter toward the inside of the insulating resin base material, and communicates with the first opening in the vicinity of the central portion in the thickness direction of the insulating resin base material. And forming a second opening so that a planar region surrounded by a line connecting the neck portions is not parallel to the surface of the insulating resin base material, and the first opening A step of causing the center of gravity position of the joint cross section with the second opening to be shifted in the cross-sectional direction of the insulating resin base material in the adjacent through hole;
(3) applying electroless plating to the substrate to form an electroless plating film on the inner walls of the first and second openings;
(4) performing electrolytic plating on the substrate to form an electrolytic plating film on the electroless plating film, and forming a through hole by filling the first and second openings with plating;
The printed wiring board manufacturing method characterized by including this. The first opening is provided so as to reach a portion near the back surface from the central portion in the thickness direction of the insulating resin base material,
The method for manufacturing a printed wiring board according to claim 10, wherein the second opening is provided so as to extend from a central portion in a thickness direction of the insulating resin base material to a portion close to the surface. The method for manufacturing a printed wiring board according to claim 10 or 11, wherein a laser processing condition for forming the first opening and a laser processing condition for forming the second opening are the same.

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