U.S. patent application number 11/396603 was filed with the patent office on 2006-11-09 for wiring board, multilayer wiring board, and method for manufacturing the same.
This patent application is currently assigned to FUJIKURA LTD.. Invention is credited to Yuji Inatani, Shoji Ito, Toshihiko Ohara, Yoshiharu Unami.
Application Number | 20060249833 11/396603 |
Document ID | / |
Family ID | 36809137 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060249833 |
Kind Code |
A1 |
Ohara; Toshihiko ; et
al. |
November 9, 2006 |
Wiring board, multilayer wiring board, and method for manufacturing
the same
Abstract
A method for manufacturing a wiring board comprising an
insulating member, comprising: a penetrating hole formation process
of forming a penetrating hole in the insulating member; a placement
process of inserting a conductive connecting particle into the
penetrating hole; a connecting particle pressing process of
disposing the conductive layers on both surfaces of the insulating
member, pressing the conductive layers toward the connecting
particle in the penetrating hole, and deforming the connecting
particle in the pressing direction to obtain the connecting member;
and a patterning process of patterning the conductive layers,
wherein, in the connecting particle pressing process, the pressing
is performed such that the cross-sectional area in the direction
along the insulating member surface of at least a portion of the
connecting member is greater than the contact area of the
connecting member with the conductive layers.
Inventors: |
Ohara; Toshihiko;
(Sakura-shi, JP) ; Unami; Yoshiharu; (Sakura-shi,
JP) ; Inatani; Yuji; (Sakura-shi, JP) ; Ito;
Shoji; (Sakura-shi, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
FUJIKURA LTD.
|
Family ID: |
36809137 |
Appl. No.: |
11/396603 |
Filed: |
April 4, 2006 |
Current U.S.
Class: |
257/698 ;
257/700; 257/774; 257/E23.067; 438/629 |
Current CPC
Class: |
Y10T 29/49155 20150115;
H05K 3/386 20130101; H05K 2201/0355 20130101; H05K 3/4046 20130101;
H05K 3/4617 20130101; H05K 3/4069 20130101; H05K 2201/0969
20130101; Y10T 29/49117 20150115; H05K 3/4647 20130101; H05K
2201/10234 20130101; H05K 2203/1461 20130101; H05K 2201/0394
20130101; H05K 3/4602 20130101; H05K 3/4652 20130101; H05K
2203/0733 20130101 |
Class at
Publication: |
257/698 ;
257/700; 257/774; 438/629; 257/E23.067 |
International
Class: |
H01L 23/04 20060101
H01L023/04; H01L 21/4763 20060101 H01L021/4763 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 7, 2005 |
JP |
P2005-110653 |
Claims
1. A method for manufacturing a wiring board comprising an
insulating member, comprising: forming a penetrating hole in the
insulating member; inserting a conductive connecting particle into
the penetrating hole; disposing conductive layers on both surfaces
of the insulating member pressing the conductive layers toward the
connecting particle in the penetrating hole to deform the
connecting particle in the pressing direction to obtain a
connecting member; and patterning the conductive layers, wherein
the pressing is performed such that a cross-sectional area in a
direction along a surface of the insulating member of at least a
portion of the connecting member is greater than a contact area of
the connecting member with the conductive layers.
2. The method for manufacturing a wiring board according to claim
1, wherein the dimension of the connecting particles in a thickness
direction of the insulating member is larger than a thickness of
the insulating member.
3. The method for manufacturing a wiring board according to claim
1, wherein after the pressing process, a contact area of the
connecting member with the conductive layers is greater than a
contact area of the connecting particle with the conductive layers
prior to the pressing process.
4. The method for manufacturing a wiring board according to claim
1, wherein the penetrating hole is formed such that an inner
diameter at one end is greater than the connecting particle, and an
inner diameter at the other end is smaller than the connecting
particle.
5. A method for manufacturing a multilayer wiring board, the method
comprising: manufacturing a wiring board by a method comprising:
forming a penetrating hole in an insulating member; inserting a
conductive connecting particle into the penetrating hole; disposing
conductive layers on both surfaces of the insulating member
pressing the conductive layers toward the connecting particle in
the penetrating hole to deform the connecting particle in the
pressing direction to obtain a connecting member; and patterning
the conductive layers; placing an outer-layer wiring substrate on a
surface of the manufactured wiring board; and pressing the
outer-layer wiring substrate toward the wiring board, wherein a
pressing pressure in the pressing of the outer-layer wiring
substrate is lower than a pressing pressure in the pressing of the
connecting particle.
6. The method for manufacturing a multilayer wiring board according
to claim 5, further comprising placing another outer-layer wiring
substrate on another surface of the manufactured wiring board,
wherein pressing the outer layer wiring substrate comprises
pressing both outer-layer wiring substrates toward the wiring
board, wherein a dimension of the connecting particle in a
thickness direction of the insulating member is larger than a
thickness of the insulating member.
7. The method for manufacturing a multilayer wiring board according
to claim 5, wherein the outer-layer wiring substrates comprise an
outer-layer side conductive layer of copper foil on one surface of
the insulating layer having an opening, and the opening is filled
with conductive paste so as to effect connection to the outer
layer-side conductive layer.
8. The method for manufacturing a multilayer wiring board according
to claim 5, wherein the pressing of the conductive layers toward
the connecting particle is performed such that a cross-sectional
area in a direction along a surface of the insulating member of at
least a portion of the connecting member is greater than a contact
area of the connecting member with the conductive layers.
9. The method for manufacturing a multilayer wiring board according
to claim 5, wherein after the pressing process, a contact area of
the connecting member with the conductive layers is greater than a
contact area of the connecting particle with the conductive layers
prior to the pressing process.
10. The method for manufacturing a multilayer wiring board
according to claim 5, wherein the penetrating hole is formed such
that an inner diameter at one end is greater than the connecting
particle, and the inner diameter at the other end is smaller than
the connecting particle.
11. A wiring board, comprising: an insulating member having a
penetrating hole; conductive layers formed on a top and a bottom
surface of the insulating member; and a conductive connecting
member provided in the penetrating hole to connect the conductive
layers together; wherein at least a portion of the connecting
member has a cross-sectional area in a direction along a surface of
the insulating member that is greater than an area of contact with
at least one of the conductive layers.
12. A multilayer wiring board, comprising: an outer-layer wiring
substrate stacked onto at least one surface of the wiring board
according to claim 6, wherein the outer-layer wiring substrate
comprises an outer layer-side conductive layer of silver foil on
one surface of an insulating layer having an opening, and the
opening is filled with a conductive paste so as to be connected to
the outer layer-side conductive layer.
13. The method for manufacturing a multilayer wiring board
according to claim 5, further comprising patterning a wire pattern
on the outer layer wiring substrate prior to pressing the
outer-layer wiring substrate toward the wiring board.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a wiring board in which
conductive layers are formed on both surfaces of an insulating
member, a multilayer wiring board in which an outer-layer wiring
substrate is stacked onto at least one side of a wiring board, and
a method for manufacturing these boards.
[0003] Priority is claimed from Japanese Patent Application No.
2005-110653, filed Apr. 7, 2005, the content of which is
incorporated herein by reference.
[0004] 2. Description of the Related Art
[0005] FIG. 27 shows an example of a conventional multilayer wiring
board. In the multilayer wiring board shown in this figure,
outer-layer wiring substrates 110 are formed on both sides of the
wiring board 100A.
[0006] In the wiring board 100A, conductive layers 102 are formed
on both sides of the insulating member 101 having a penetrating
hole (through-hole) 103. Openings are formed in the conductive
layers 102 at positions corresponding to the penetrating hole 103.
The conductive layers 102 are connected together by a conductive
layer 105 formed on the surfaces of the conductive layers 102 and
on the inner surface of the penetrating hole 103.
[0007] The outer-layer wiring substrates 110 comprise an insulating
layer 107 in contact on one side with the conductive layer 105, and
a conductive layer 106 formed on the other side of the insulating
layer 107.
[0008] As shown in FIG. 28 and FIG. 29, in order to manufacture
this multilayer wiring board, after using laser machining, drilling
or the like to form the penetrating hole 103 in the insulating
member 101, a plating method is used to form the conductive layer
105 on the surfaces of the conductive layers 102 and on the inner
surface of the penetrating hole 103, followed by formation of the
insulating layers 107 and conductive layers 106.
[0009] FIG. 30 shows another example of a conventional multilayer
wiring board. The multilayer wiring board shown in FIG. 30 has
outer-layer wiring substrates 110 formed on both surfaces of wiring
board 100B.
[0010] The wiring board 100B has conductive layers 102a and 102b
formed on the both surface of the insulating member 101 which has
an opening 104 (via). An opening is formed in the conductive layer
102a at a position corresponding to the opening 104. A conductive
layer 108 is formed on the surface of the conductive layer 102a and
on the inner surface of the opening 104. The conductive layer 108
formed on the conductive layer 102b within the opening 104 and thus
the conductive layers 102a and 102b are connected.
[0011] As shown in FIG. 31 and FIG. 32, to manufacture this
multilayer wiring board, after using laser machining or the like to
form the opening 104 in the insulating member 101, a plating method
is used to form the conductive layer 108 on the surface of the
conductive layer 102a and on the inner surface of the opening 104,
and then the insulating layer 107 and conductive layer 106 are
formed.
[0012] However, because the penetrating hole 103 and opening 104
remain opened in this multilayer wiring board, there is the
possibility that a recess may be generated in the conductive layer
106 in the portion corresponding to this penetrating hole 103 and
opening 104. If a recess is generated in the conductive layer 106,
it becomes difficult to mount an electronic component or the like
in this portion, and the component mounting density is reduced,
which is a disadvantage from the standpoint of reducing size and
thickness.
[0013] In the wiring board 100B, the conductive layer 108 formed by
a plating method is also formed on the surface of the conductive
layer 102a in addition to the inner surface of the opening 104.
Consequently, in the wiring board 100B, the conductive layer is
thick, and formation of fine wiring patterns is difficult.
[0014] FIG. 33 shows an example of a wiring board which may be used
in a multilayer wiring board. In this wiring board 100C, the
conductive layer 109 is formed on the surface of the conductive
layer 102a and in the opening 104, and the conductive layers 102a
and 102b are connected by the conductive layer 109. The conductive
layer 109 is formed so as to fill the opening 104, and accordingly
the surface is flat.
[0015] When forming the conductive layer 109 by a plating method,
the layer may be formed by continuing the supply of metallic
material until the opening 104 is completely filled.
[0016] Because the surface of the conductive layer 109 is flat in a
multilayer wiring board which uses this wiring board 100C, there is
the advantage that recesses are not generated in the conductive
layer of the outer-layer wiring substrate formed on the top.
[0017] However, in such a multilayer wiring board, the conductive
layer 109 must be formed so as to fill the opening 104, and thus an
increase in the thickness for the conductive layer 109 is
unavoidable. As a result, formation of a fine pattern in the
conductive layer 109 is difficult. Further, the conductive layer
109 is thick and the overall thickness is increased, which are
disadvantageous for the reduction in the size and the thickness of
the electrical/electronic apparatus.
[0018] Techniques relating to a variety of the above multilayer
wiring boards are described in Kiyoshi Takagi, Birudoappu Tasou
Purinto Haisenban Gijutsu, Nikkan Kogyo Shimbunsha.
SUMMARY OF THE INVENTION
[0019] The present invention was conceived based on the above
circumstances, and has as an aspect the provision of a wiring
board, a multilayer wiring board using this wiring board, and a
manufacturing method for these boards, which enables finer wiring
patterns formed in conductive layers, while also raising the
mounting density of components on the surfaces of conductive
layers, by this means enabling greater thinness and
compactness.
[0020] A method for manufacturing a wiring board according to a
first exemplary, but nonlimiting, aspect of the invention in a
method for manufacturing a wiring board having an insulating member
having a penetrating hole; and conductive layers formed on both
surfaces of the insulating member, and a conductive connecting
member connecting the two conductive layers together is provided
inside the penetrating hole; the method of manufacture includes a
penetrating hole formation process of forming the penetrating hole
in the insulating member, a placement process of inserting a
conductive connecting particle into the penetrating hole, a
connecting particle pressing process of placing the conductive
layers on both surfaces of the insulating member, pressing the
conductive layers toward the connecting particle in the penetrating
hole, and deforming the connecting particle in the pressing
direction to obtain the connecting member, and a patterning process
of patterning the conductive layers; and, in the connecting
particle pressing process, the pressing is performed such that the
cross-sectional area in the direction along the insulating member
surface of at least a portion of the connecting member is greater
than the contact area of the connecting member with the conductive
layers.
[0021] A method for manufacturing a wiring board according to a
second exemplary, but nonlimiting, aspect of the invention is the
above method of manufacture, in which, in the placement process,
the dimension of the connecting particle in the insulating member
thickness direction is larger than the thickness of the insulating
member.
[0022] A method for manufacturing a wiring board according to a
third exemplary, but nonlimiting, aspect of the invention is the
above method of manufacture, in which, after the pressing process,
the contact area of the connecting member with the conductive
layers is greater than the contact area of the connecting particle
with the conductive layers prior to the pressing process.
[0023] A method for manufacturing a wiring board according to a
fourth exemplary, but nonlimiting, aspect of the invention is the
above method of manufacture, in which, in the penetrating hole
formation process, the penetrating hole is formed such that the
inner diameter at one end is greater than the size of the
connecting particle, and the inner diameter at the other end is
smaller than the size of the connecting particle.
[0024] A method for manufacturing a multilayer wiring board
according to a fifth exemplary, but nonlimiting, aspect of the
invention is a method for manufacturing a multilayer wiring board
in which one or more outer-layer wiring substrates is stacked onto
a wiring board having an insulating member having a penetrating
hole; and conductive layers formed on both surfaces of the
insulating member, and a conductive connecting member connecting
the conductive layers together is provided in the penetrating hole;
the method of manufacture includes an outer-layer wiring substrate
pressing process of placing an outer-layer wiring substrate on at
least one surface of a wiring board obtained by one of the above
manufacturing methods, and, by pressing the outer-layer wiring
substrate toward the wiring board, connecting the outer-layer
wiring substrates to the wiring board; and the pressing pressure in
the outer-layer wiring substrate pressing process is made lower
than the pressing pressure in the connecting particle pressing
process.
[0025] A method for manufacturing a multilayer wiring board
according to a sixth exemplary, but nonlimiting, aspect of the
invention is the above method of manufacture, in which outer-layer
wiring substrates are stacked onto both surfaces of the wiring
board, and the number of outer-layer wiring substrates provided on
one surface of the wiring board is equal to the number of
outer-layer wiring substrates provided on the other surface.
[0026] A method for manufacturing a multilayer wiring board
according to a seventh exemplary, but nonlimiting, aspect of the
invention is the above method of manufacture, in which outer-layer
wiring substrates are provided with an outer-layer side conductive
layer of silver foil on one surface of the insulating layer having
an opening, and the opening is filled with conductive paste so as
to effect connection to the outer layer-side conductive layer.
[0027] A wiring board according to an eighth exemplary, but
nonlimiting, aspect of the invention has conductive layers formed
on both sides of an insulating member having a penetrating hole,
with a conductive connecting member provided in the penetrating
hole to connect the conductive layers together, and with at least a
portion of the connecting member having cross-sectional area in the
direction along the insulating member surface greater than the area
of contact with the conductive layers.
[0028] A multilayer wiring board according to a ninth exemplary,
but nonlimiting, aspect of the invention has an outer-layer wiring
substrate stacked onto at least one surface of the above wiring
board; the outer-layer wiring substrate is provided with an outer
layer-side conductive layer of silver foil on one surface of an
insulating layer having an opening, and the opening is filled with
a conductive paste so as to be connected to the outer later-side
conductive layer.
[0029] In a method for manufacturing a wiring board in an
exemplary, nonlimiting aspect, of the present invention, a
connecting particle is deformed into a connecting member by
pressing a conductive layer. At this time, pressing is performed
such that the cross-sectional area of at least a portion of the
connecting member is greater than the area of contact of the
connecting member with a conductive layer.
[0030] By this, sufficient pressing pressure may be applied to the
conductive layer, so that the surface may be made flat, and
consequently the component mounting density on the conductive layer
surface may be increased. Further, since the conductive layer may
be formed thinner compared with cases in which a plating method is
used to form a conductive layer in the opening, fine wiring
patterns may be formed.
[0031] Consequently, the degree of flexibility in design may be
increased, and an electrical/electronic apparatus employing this
wiring board may be made thinner, more compact, and lighter in
weight.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a cross-sectional view illustrating a
manufacturing process of a first nonlimiting exemplary embodiment
of a method for manufacturing a multilayer wiring board of the
invention;
[0033] FIG. 2 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0034] FIG. 3 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0035] FIG. 4 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0036] FIG. 5 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0037] FIG. 6 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0038] FIG. 7 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0039] FIG. 8 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0040] FIG. 9 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0041] FIG. 10 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0042] FIG. 11 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing,
[0043] FIG. 12 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0044] FIG. 13 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0045] FIG. 14 is a cross-sectional view illustrating the
manufacturing process subsequent nonlimiting exemplary embodiment
of a method for manufacturing a multilayer wiring board of the
invention;
[0046] FIG. 15 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0047] FIG. 16 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0048] FIG. 17 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0049] FIG. 18 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0050] FIG. 19 is a cross-sectional view illustrating the
manufacturing process of a third nonlimiting exemplary embodiment
of a method for manufacturing a multilayer wiring board of the
invention;
[0051] FIG. 20 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0052] FIG. 21 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0053] FIG. 22 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0054] FIG. 23 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0055] FIG. 24 is a cross-sectional view illustrating a
manufacturing process of another nonlimiting exemplary embodiment
of a method for manufacturing a multilayer wiring board of the
invention;
[0056] FIG. 25 is a configuration drawing showing another
exemplary, but nonlimiting, embodiment of an outer-layer wiring
substrate used in a multilayer wiring board of the invention;
[0057] FIG. 26 is a schematic cross-sectional view illustrating
another exemplary; but nonlimiting, embodiment of a multilayer
wiring board of the invention;
[0058] FIG. 27 is a schematic cross-sectional view illustrating an
example of a conventional multilayer wiring board;
[0059] FIG. 28 is a cross-sectional view illustrating a
manufacturing process of an example of a method for manufacturing
the multilayer wiring board of the previous drawing;
[0060] FIG. 29 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing;
[0061] FIG. 30 is a schematic cross-sectional view illustrating
another example of a conventional multilayer wiring board;
[0062] FIG. 31 is a cross-sectional view illustrating a
manufacturing process of an example of a method for manufacturing
the multilayer wiring board of the previous drawing;
[0063] FIG. 32 is a cross-sectional view illustrating the
manufacturing process subsequent to the previous drawing; and
[0064] FIG. 33 is a schematic cross-sectional view illustrating a
wiring board used in a further example of a conventional multilayer
wiring board.
DETAILED DESCRIPTION OF THE INVENTION
[0065] Hereinafter, a first nonlimiting exemplary embodiment of a
method for manufacturing a multilayer wiring board of the present
invention is explained.
[0066] First, a method for manufacturing a wiring board 10 is
explained.
[0067] As shown in FIG. 1, an insulating member 1, in a plate shape
and formed from an insulating material, is provided. The insulating
member 1 may use, for example, at least one of a polyimide resin,
an epoxy resin, an LCP (liquid crystal polymer) resin, a glass
epoxy, an aramid fiber, and Teflon.RTM.. However, one of skill in
the art would recognize that other suitable insulating materials
may be used.
[0068] By means of laser machining, drilling or the like, a
penetrating hole (through-hole) 3 is formed in the insulating
member 1. A CO.sub.2 laser, YAG laser, or the like may be used in
laser machining.
[0069] The penetrating hole 3 may be formed with the inner diameter
at one end (the inner diameter at one surface 1a of the insulating
member 1) larger than the size of the connecting particle 4, and
with the inner diameter at the other end (the inner diameter at the
other surface 1b) smaller than the size of the connecting particle
4 so that the connecting particle 4 may be prevented from dropping
out of the penetrating hole 3. In the example shown, the
penetrating hole 3 is formed with a tapered shape, in which the
inner diameter gradually becomes smaller from one end to the other
end.
[0070] The process of forming a penetrating hole 3 in the
insulating member 1 is referred to as the penetrating hole
formation process.
[0071] Next, the connecting particle 4 may be placed into the
penetrating hole 3, as shown in FIG. 2.
[0072] As the connecting particle 4, a particle of a conductive
metal, such as copper, aluminum, chromium, titanium, or another
metal is used. In particular, a copper or a copper alloy may be
used so that the conductivity with the inner layer-side conductive
layer 2 is increased. For example, the connecting particle 4 be
formed from high-purity copper, for example, copper of a purity of
99% or higher may be used.
[0073] There are no particular limitations on the shape of the
connecting particle 4, and shapes such as, for example, a
substantially spherical shape, a substantially ellipsoidal shape, a
substantially columnar shape, a substantially polyhedral columnar
shape, a substantially conic shape, and a substantially pyramidal
shape, may be used. In particular, however, a shape may be used
such that in the pressing process described below, the contact area
with the inner layer-side conductive layer 2 is greater than that
before pressing.
[0074] Of these shapes, a shape such that a point contact is
established with the inner layer-side conductive layer 2, such as,
for example, a substantially spherical shape, may be used. By
adopting this shape, the amount of deformation in the pressing
process when the connecting particle 4 becomes the connecting
member 5 is large, and thus the electrical resistance between the
inner layer-side conductive layers 2 and the connecting member 5
may be reduced and the bonding strength may be increased.
[0075] Also the dimension of the connecting particle 4 in the
direction of thickness of the insulating member 1 may be greater
than the thickness of the insulating member). In the example shown,
the diameter of the connecting particle 4 is greater than the
thickness of the insulating member 1, so that a portion of the
connecting particle 4 protrudes from the surfaces of the insulating
member 1.
[0076] As the connecting particle, a particle the dimension in the
insulating member thickness direction of which is smaller than the
thickness of the insulating member may also be used.
[0077] Hereinafter, the process of placing the connecting particle
4 into the penetrating hole 3 is referred to as the placement
process.
[0078] Inner layer-side conductive layers 2, each made of metal
foil, are disposed on the two surfaces of the insulating member 1.
Copper, aluminum, chromium, titanium or other metallic materials
may be used for the inner layer-side conductive layers 2. Of these,
a copper or a copper alloy may be effective.
[0079] The inner layer-side conductive layers 2 are pressed toward
the connecting particle 4 in the penetrating hole 3. That is, the
inner layer-side conductive layers 2 are pressed in the direction
to bring them closer to each other (in the thickness direction of
the insulating member 1).
[0080] At this time, a pressing pressure of 30 kgf/cm.sup.2 or
higher is appropriate. Here 1 kgf is equivalent to 9.80665 N. It is
appropriate that the temperature during pressing be 200.degree. C.
or higher.
[0081] As shown in FIG. 3, the connecting particle 4 is deformed in
the pressing direction, and becomes a connecting member 5 having a
thickness substantially equal to the thickness of the insulating
member 1, and in addition may be bonded with the inner layer-side
conductive layers 2.
[0082] The connecting member 5 is directly bonded to the inner
layer-side conductive layers 2. That is, the connecting member 5
and the inner layer-side conductive layers 2 are firmly bonded by
metallic bonding or the like, substantially without requiring an
additional member. Hence, the reliability of the connection between
the connecting member 5 and the inner layer-side conductive layers
2 may be enhanced.
[0083] The connecting member 5 extends into the entire penetrating
hole 3, and substantially assumes a shape which fills the
penetrating hole 3.
[0084] It is believed that a firm bond is formed between the inner
layer-side conductive layers 2 and the connecting member 5 because
the oxide film that is present therebetween is broken, and in this
portion the inner layer-side conductive layer 2 and the connecting
member 5 may bond directly, without an intervening oxide film.
[0085] In this manufacturing method, pressing may be performed such
that the cross-sectional area of at least a portion of the
connecting member 5, in the direction along the surface of the
insulating member 1 (the horizontal direction), is greater than the
contact area between the connecting member 5 and the inner
layer-side conductive layer 2.
[0086] In the nonlimiting exemplary embodiment shown in FIG. 3, the
cross-sectional area along the horizontal direction of the
connecting member 5, at the center in the thickness direction of
the insulating member 1, is greater than the area of contact with
the inner layer-side conductive layer 2.
[0087] By performing pressing such that the cross-sectional area of
the connecting member 5 is greater than the area of contact with
the inner layer-side conductive layer 2, sufficient pressing
pressure may be applied to the inner layer-side conductive layer 2,
so that the surface of the inner layer-side conductive layer 2 may
be made flat. Hence, the component mounting density on the surface
of the inner layer-side conductive layer 2 may be increased. Also,
fine wiring patterns may be formed in the inner layer-side
conductive layer 2.
[0088] Hereinafter, the process of deforming the connecting
particle 4 into the connecting member 5 is referred to as the
connecting particle pressing process.
[0089] The area of contact after pressing between the connecting
member 5 and the inner layer-side conductive layer 2 is greater
than the area of contact before pressing between the connecting
particle 4 and the inner layer-side conductive layer 2. By thus
performing pressing such that the contact area increases, the
amount of deformation when the connecting particle 4 becomes the
connecting member 5 may be increased sufficiently, and the
electrical resistivity between the inner layer-side conductive
layers 2 and the connecting member 5 may be reduced, while
increasing the bonding strength.
[0090] As shown in FIG. 4, the inner layer-side conductive layer 2
is patterned by etching or other techniques.
[0091] In patterning, for example, the subtractive method may be
employed. More specifically, a resist layer is formed, and after
forming the resist into a pattern according to the wiring pattern
by photolithography techniques, the inner layer-side conductive
layer 2 is etched.
[0092] Hereafter, the process of patterning the inner layer-side
conductive layer 2 is referred to as the patterning process.
[0093] After the above series of processes, a wiring board 10 is
obtained in which inner layer-side conductive layers 2, formed on
both surfaces of the insulating member 1, are connected together by
the connecting member 5.
[0094] In the wiring board 10, the inner layer-side conductive
layers 2 are connected by the connecting member 5 obtained by
pressing and deforming the connecting particle 4; hence the
electrical resistance between the inner layer-side conductive
layers 2 and the connecting member 5 is reduced, and the
conductivity between the inner layer-side conductive layers 2 may
be increased.
[0095] Next a method for manufacturing an outer-layer wiring
substrate 13 is explained according to a nonlimiting exemplary
embodiment.
[0096] As is shown in FIG. 5, a metal-clad stacked substrate 12
(e.g., copper-clad stacked substrate), in which an outer layer-side
conductive layer 6 is formed on one surface (the upper surface) of
an insulating layer 7, is provided. Copper, aluminum, chromium,
titanium, or other metallic materials is used in the outer
layer-side conductive layer 6. In particular, a copper foil or
other metal foils are appropriate. The same material as is used in
the insulating member 1 may be used in the insulating layer 7.
[0097] Next, a pattern of wiring is formed in the outer layer-side
conductive layers 6 by etching or other techniques, as shown in
FIG. 6.
[0098] Next, an adhesive layer 8 is formed on the other surface
(the lower surface) of the insulating layer 7, as shown in FIG. 7.
As the adhesive used in the adhesive layer 8, epoxy resin,
polyimide resin, acrylic resin, or the like may be used.
[0099] Next, as shown in FIG. 8, an opening (via) 9 is formed in
the insulating layer 7 and adhesive layer 8 from the lower-surface
side of the metal-clad stacked substrate 12. The opening 9 is
formed so as to reach the outer layer-side conductive layer 6.
[0100] The opening 9 may be formed by laser machining, drilling, or
other techniques. Also, a mold or die may be used in molding or
stamping to fabricate an insulating layer 7 having the opening
9.
[0101] Next, as shown in FIG. 9, the opening 9 may be filled with a
conductive paste to form a connecting portion 11 which is connected
to the outer layer-side conductive layer 6.
[0102] As the conductive paste, a mixture of a conducting material
and a binder resin may be used.
[0103] As the conducting material, at least one of silver, nickel,
carbon, and copper may be used. The conducting material may be in
particle form. As the binder, at lest one of an acrylic resin,
vinyl acetate resin, epoxy resin, and polyester resin may be used.
The amount of the binder used may be from 0.2 to 10 parts by weight
to 100 parts by weight of the conducting material, and 0.5 to 5
parts by weight may be used.
[0104] The opening 9 may be filled with the conductive paste using
a printing method or a dot injection method.
[0105] By this, an outer-layer wiring substrate 13 is obtained in
which an outer layer-side conductive layer 6 is formed on one
surface of the insulating layer 7, and a connecting portion 11 is
provided in the opening 9.
[0106] Next a method of manufacturing a multilayer wiring board
using the wiring board 10 and outer-layer wiring substrates 13 is
explained according to a nonlimiting exemplary embodiment.
[0107] As shown in FIG. 10 and FIG. 11, outer-layer wiring
substrates 13 may be stacked onto both surfaces of the wiring board
10, the outer-layer wiring substrates 13 may be pressed toward the
wiring board 10, and the outer-layer wiring substrates 13 may be
bonded to the wiring board 10 by the adhesive layer 8. The
connecting portion 11 of the outer-layer wiring 13 may be connected
to the inner-layer side conductive layer 2 of the wiring board
10.
[0108] This process of pressing the outer-layer wiring substrates
13 toward the wiring board 10 is referred to as the outer-layer
wiring substrate pressing process.
[0109] The pressing pressure in the outer-layer wiring substrate
pressing process may be lower than the pressing pressure in the
above-described connecting particle pressing process. The pressing
pressure may be less than 30 kgf/cm.sup.2.
[0110] By lowering the pressing pressure below the pressing
pressure in the connecting particle pressing process, softening of
the adhesive layer 8 may be prevented, and misalignment of the
positions of the outer-layer wiring substrates 13, as well as the
squeeze-out of adhesive, may be prevented. Further, deformation of
the insulating member 1 may be prevented.
[0111] The temperature in the outer-layer wiring substrate pressing
process is lower than the temperature in the connecting particle
pressing process; for example, a temperature of under 200.degree.
C. is may be used and a temperature of under 180.degree. C. may
also be used. By setting the temperature in this range, softening
of the adhesive layer 8 may be prevented, and misalignment of the
positions of the outer-layer wiring substrates 13, as well as the
squeeze-out of adhesive, can be prevented.
[0112] By this, a multilayer wiring board 15 is obtained in which a
wiring board 10 and outer-layer wiring substrates 13 are
stacked.
[0113] As shown in FIG. 12 and FIG. 13, a additional outer-layer
wiring substrates 13 may be stacked onto the multilayer wiring
board 15.
[0114] That is, by stacking outer-layer wiring substrates 13 onto
both surfaces of the multilayer wiring board 15, and performing
pressing in the thickness direction, the outer-layer wiring
substrates 13 may be connected to the multilayer wiring board 15 by
means of adhesive layers 8. The pressing pressure, the temperature
and other conditions during pressing may be made the same as the
conditions used when stacking outer-layer wiring substrates 13 onto
the wiring board 10.
[0115] By this, a multilayer wiring board 16 is obtained in which
two outer-layer wiring substrates 13 are stacked onto each of the
surfaces of a wiring board 10.
[0116] In the multilayer wiring board 16, since a plurality of
outer-layer wiring substrates 13 are formed on both surfaces of a
wiring board 10, the wiring density may be increased.
[0117] In the multilayer wiring boards 15 and 16 shown in FIG. 11
and FIG. 13, since the number of outer-layer wiring substrates 13
provided on one surface of the wiring board 100 and the number of
outer-layer wiring substrates 13 provided on the other surface are
equal, the forces applied to both surfaces of the wiring board 10
during heating and the like are equal, and thus warping does not
readily occur.
[0118] In a method for manufacturing the above multilayer wiring
boards 15 and 16, since the connecting member 5 of the wiring board
10 fills the penetrating hole 3, there is no void left in the
penetrating hole 3 and no recess is generated on the surface of the
outer layer-side conductive layers 6. Consequently, it is possible
to prevent problems during mounting of other components (integrated
circuits and the like) on the multilayer wiring board 15 or 16.
[0119] Hence, the component mounting density may be raised, the
degree of flexibility in design may be enhanced, and an
electric/electronic apparatus may be made smaller, thinner, and
more lightweight.
[0120] In the multilayer wiring boards 15 and 16, the inner
layer-side conductive layers 2 may be formed thinner than in cases
in which conductive layers are formed within openings by a plating
method (shown in FIG. 30 and FIG. 33).
[0121] Therefore, a finer pattern may be formed in the inner
layer-side conductive layers 2. Also, since the wiring board 10 may
be formed thinner, the multilayer wiring boards 15 and 16 may be
made thinner.
[0122] Hence an electrical/electronic apparatus may be made even
smaller, thinner, and lighter in weight.
[0123] Further, because the inner layer-side conductive layers 2
may be made thinner, the flexibility in the wiring board 10 may be
enhanced, for still greater freedom of design.
[0124] According to the above method of manufacture, since the
outer layer-side conductive layers 6 and inner layer-side
conductive layers 2 are connected by means of a connecting portion
11 formed from the conductive paste 11 in the outer-layer wiring
substrates 13, the connecting portion 11 adheres closely to the
inner layer-side conductive layers 2 without a void and the
conductivity therebetween may be increased. Hence, the reliability
of connection between the outer layer-side conductive layers 6 and
the inner layer-side conductive layers 2 may be improved.
[0125] According to the above method of manufacture, a method is
adopted in which, after bonding the outer-layer wiring substrates
13 to the wiring board 10 by stacking and pressing, additional
outer-layer wiring substrates 13 are stacked and pressed; but
manufacture is not limited to this method, and a method may be
employed in which a plurality of outer-layer wiring substrates 13
are stacked onto the wiring board 10 and are all pressed at once.
The pressing pressure, the temperature, and other conditions during
pressing may be made the same as the conditions when stacking
outer-layer wiring substrates 13 to the wiring board 10.
[0126] When this method is adopted, a plurality of outer-layer
wiring substrates 13 may be bonded at once to the wiring board 10,
the number of processes may be reduced, which is advantageous from
the standpoint of manufacturing costs.
[0127] In the present invention, a configuration is also possible
in which one or a plurality of outer-layer wiring substrates are
stacked onto only one surface of a wiring board. Further, in the
multilayer wiring board 16, although two outer-layer wiring
substrates 13 are stacked onto each surface of the wiring board 10,
the number of stacked outer-layer wiring substrates per surface of
the wiring board may be three or greater.
[0128] Next, a second nonlimiting exemplary embodiment of a method
for manufacturing a multilayer wiring board of the present
invention is explained.
[0129] The manufacturing method of this embodiment differs from
manufacturing method of the first embodiment in that, after first
stacking onto the wiring board 10 an outer-layer wiring substrate
13 on which a wiring pattern has not yet been formed, the wiring
pattern is formed in the outer layer-side conductive layer 6. The
following is a detailed explanation.
[0130] As shown in FIG. 14 and FIG. 15, outer-layer wiring
substrates 13 in the outer layer-side conductive layers 6 of which
a wiring pattern has not been formed are stacked onto both surfaces
of a wiring board 10, and by performing pressing in the thickness
direction, the outer-layer wiring substrates 13 and wiring board 10
are bonded together.
[0131] Next, as shown in FIG. 16, a pattern of wiring is formed in
the outer layer-side conductive layers 6 of the outer-layer wiring
substrates 13, to obtain the multilayer wiring board 15.
[0132] As shown in FIG. 17 and FIG. 18, additional layers may be
added to the multilayer wiring board 15.
[0133] That is, the outer-layer wiring substrates 13 in the outer
layer-side conductive layers 6 of which wiring patterns have not
been formed are stacked onto the multilayer wiring board 15, and by
performing pressing in the thickness direction, the outer-layer
wiring substrates 13 are bonded to the multilayer wiring board;
then, a wiring pattern is formed in the outer layer-side conductive
layers 6, to obtain the multilayer wiring board 16.
[0134] According to the manufacturing method of the above second
embodiment since a wiring pattern is formed in the outer layer-side
conductive layers 6 after stacking outer-layer wiring substrates 13
onto a wiring board 10, adverse effects of the pressing process on
wiring may be prevented. Hence, the wiring of the outer layer-side
conductive layers 6 may be made even finer.
[0135] Next a third nonlimiting exemplary embodiment of a method
for manufacturing a multilayer wiring board of the present
invention is explained.
[0136] The manufacturing method of this embodiment differs from the
manufacturing method of the fist embodiment in that, after first
stacking onto the wiring board 10 an outer-layer wiring substrate
13a in which an opening 9 and connecting portion 11 have not yet
been formed, the opening 9 and connecting portion 11 are formed.
The following is a detailed explanation.
[0137] As shown in FIG. 19, outer-layer wiring substrates 13a in
which an opening 9 and connecting portion 11 are formed are stacked
onto both surfaces of the wiring board 10, and by performing
pressing in the thickness direction, the outer-layer wiring
substrates 13a are bonded to the wiring board 10 by means of the
adhesive layers 8.
[0138] As shown in FIG. 20 and FIG. 21, openings 9 are formed in
the outer layer-side conductive layers 6, insulating layers 7 and
adhesive layers 8, and by filling the openings 9 with a conductive
paste, the connecting portions 11 are formed.
[0139] As shown in FIG. 22, by forming a pattern of wiring in the
outer layer-side conductive layers 6, a multilayer board 15 is
obtained.
[0140] As shown in FIG. 23, by bonding outer-layer wiring
substrates 13a to the multilayer wiring board 15, and then forming
openings 9 and connecting portions 11 in the outer-layer wiring
substrates 13a, the number of stacked outer-layer wiring substrates
13 may be increased.
[0141] According to the method of manufacturing of the above third
embodiment, after stacking outer-layer wiring substrates 13a to a
wiring board 10, the openings 9 and connecting portions 11 are
formed, so that the connecting portions may be reliably brought
into contact with the conducting layers 2 and 6, and the
conductivity therebetween may be improved. Hence, the reliability
of electrical connections may be improved.
[0142] According to the manufacturing methods of the first through
third embodiments, as shown in FIG. 1 through FIG. 4, when
manufacturing the wiring board 10, the connecting particle 4 is
placed into the penetrating hole 3, and by performing pressing in
the thickness direction, the particle is deformed into the
connecting member 5. However, the wiring board 10 may also be
manufactured by the method described below.
[0143] As shown in FIG. 24, printing or other means are used to
provide a protrusion for connection 18 on one surface (the lower
surface) of an inner layer-side conductive layer 2.
[0144] The protrusion for connection 18 may be formed from copper
or a copper alloy, and the thickness of the protrusion for
connection 18 may be a little larger than the thickness of the
insulating member 1.
[0145] The inner layer-side conductive layer 2 is stacked onto the
insulating member 1 such that the protrusion for connection 18 is
placed into the penetrating hole 19, and the two are pressed
together in the thickness direction. The temperature, the pressure
and other conditions during pressing may be the same as in the
above connecting particle pressing process.
[0146] The protrusion for connection 18 is deformed in the
thickness direction by pressing to become a connecting member 5,
and the wiring board 10 shown in FIG. 3 is obtained.
[0147] As shown in FIG. 25, an outer-layer wiring substrate 13 may
be provided with an exhaust hole 21, the inner diameter of which is
smaller than the opening 9, in the outer layer-side conductive
layer 6 at a position equivalent to the opening 9.
[0148] By this configuration, when the opening 9 is filled with
conductive paste from the side of the adhesive layer 8 to form the
connecting portion 11, air in the opening 9 may be discharged from
the exhaust hole 21.
[0149] Hence, since the lingering of bubbles in the opening 9 may
be prevented, and the conductive paste may be made to fill the
opening 9 without voids, defects in formation of the connecting
portion 11 may be prevented. Consequently, the reliability of the
electrical connection may be improved.
[0150] When the wiring formed in outer layer-side conductive layers
need not be fine, the following configuration may also be adopted
in a multilayer wiring board of the present invention.
[0151] In the multilayer wiring board 22 shown in FIG. 26,
outer-layer wiring substrates 23 are formed on both surfaces of a
wiring board 10.
[0152] In the outer-layer wiring substrates 23, an outer layer-side
conductive layer 26 is formed on one surface of the insulating
layer 25 having an opening 24, and the outer layer-side conductive
layer 26 is formed so as to fill the opening 24.
[0153] When using a plating method to form an outer layer-side
conductive layer 26, the supply of metallic material may be
continued until the opening 24 is completely filled to form the
conductive layer.
[0154] In some cases an oxide layer, with a higher oxygen
concentration than in other portions, may be formed at the boundary
between the conductive layer and the connecting member. This oxide
layer has a portion with high oxygen concentration (high-oxygen
region), and a portion with low oxygen concentration (low-oxygen
region).
[0155] It is believed that the low-oxygen region may, for example,
be formed by the destruction of the oxide film at the surface due
to deformation of the connecting particle in the process to form
the connecting member. In the low-oxygen region, the conductive
layer and the connecting member are bonded by metallic bonds and
the like, the electrical resistance tends to be low, and the
bonding strength tends to be high.
[0156] A wiring board of the present invention may be employed as a
printed wiring board or other circuit board or semiconductor board
on which are mounted display devices or sensor devices.
[0157] While nonlimiting exemplary embodiments of the invention
have been described and illustrated above, it should be understood
that these are for illustrating the invention and are not to be
considered as limiting. Additions, omissions, substitutions, and
other modifications may be made without departing from the spirit
or scope of the present invention. Accordingly, the invention is
not to be considered as being limited by the foregoing description,
and is only limited by the scope of the appended claims.
* * * * *