U.S. patent application number 14/224216 was filed with the patent office on 2014-07-24 for method of manufacturing multilayer wiring substrate, and multilayer wiring substrate.
This patent application is currently assigned to NGK SPARK PLUG CO., LTD.. The applicant listed for this patent is NGK SPARK PLUG CO., LTD.. Invention is credited to Takuya HANDO, Satoshi HIRANO, Tatsuya ITO, Shinnosuke MAEDA, Atsuhiko SUGIMOTO, Tetsuo SUZUKI.
Application Number | 20140202740 14/224216 |
Document ID | / |
Family ID | 44175942 |
Filed Date | 2014-07-24 |
United States Patent
Application |
20140202740 |
Kind Code |
A1 |
MAEDA; Shinnosuke ; et
al. |
July 24, 2014 |
Method of Manufacturing Multilayer Wiring Substrate, and Multilayer
Wiring Substrate
Abstract
In a build-up step, a plurality of resin insulation layers and a
plurality of conductive layers are alternately laminated in
multilayer arrangement on a metal foil separably laminated on a
side of a base material, thereby forming a wiring laminate portion.
In a drilling step, a plurality of openings are formed in an
outermost resin insulation layer through laser drilling so as to
expose connection terminals. Subsequently, in a desmear step,
smears from inside the openings are removed. In a base-material
removing step performed after the build-up step, the base material
is removed and the metal foil is exposed.
Inventors: |
MAEDA; Shinnosuke; (Phoenix,
AR) ; SUZUKI; Tetsuo; (Niwa-gun, JP) ; HANDO;
Takuya; (Inuyama-shi, JP) ; ITO; Tatsuya;
(Kakamiganhara-shi, JP) ; HIRANO; Satoshi;
(Chita-gun, JP) ; SUGIMOTO; Atsuhiko;
(Kagamigahara-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NGK SPARK PLUG CO., LTD. |
Nagoya-shi |
|
JP |
|
|
Assignee: |
NGK SPARK PLUG CO., LTD.
Nagoya-shi
JP
|
Family ID: |
44175942 |
Appl. No.: |
14/224216 |
Filed: |
March 25, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12979474 |
Dec 28, 2010 |
8707554 |
|
|
14224216 |
|
|
|
|
Current U.S.
Class: |
174/251 |
Current CPC
Class: |
H05K 3/3452 20130101;
H01L 21/4846 20130101; H05K 1/09 20130101; Y10T 29/49155 20150115;
Y10T 29/49147 20150115; H05K 1/111 20130101; H01L 2224/16225
20130101; H05K 2201/068 20130101; Y10T 29/49117 20150115; Y10T
29/49126 20150115; Y10T 29/49128 20150115; H05K 2201/094 20130101;
H05K 1/113 20130101; H05K 2201/099 20130101; H05K 2201/0989
20130101; H05K 3/4682 20130101; H05K 1/0298 20130101; H01L 23/49822
20130101; H05K 3/0055 20130101 |
Class at
Publication: |
174/251 |
International
Class: |
H05K 1/02 20060101
H05K001/02; H05K 1/11 20060101 H05K001/11; H05K 1/09 20060101
H05K001/09 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2009 |
JP |
2009-296911 |
Claims
1. A multilayer wiring substrate having a laminate structure in
which a plurality of resin insulation layers made primarily of the
same resin insulation material, and a plurality of conductive
layers are laminated alternately in multilayer arrangement, a
plurality of first-main-surface-side connection terminals being
disposed on one side of the laminate structure where a first main
surface thereof is present, a plurality of second-main-surface-side
connection terminals being disposed on an other side of the
laminate structure where a second main surface thereof is present,
the plurality of conductive layers being formed in the plurality of
resin insulation layers and interconnected by means of via
conductors whose diameters increase toward the first main surface
or the second main surface, wherein: the plurality of resin
insulation layers are formed of a build-up material mainly formed
of a hardened resin insulation material that is not photocurable; a
plurality of openings are formed in an outermost resin insulation
layer of the laminate structure exposed as the first main surface;
at least two types of connection terminals, including IC-chip
connection terminals to which an IC chip is to be connected, and
passive-component connection terminals to which a passive component
connection is to be connected and which have a larger exposed
surface area than the IC-chip connection terminals, are present on
the first main surface as the first-main-surface-side connection
terminals; and the IC-chip connection terminals are disposed in the
plurality of openings, top surfaces of the IC-chip connection
terminals are lower in height than an outer surface of the
outermost resin insulation layer, and peripheral portions of the
IC-chip connection terminals are buried in the outermost resin
insulation layer.
2. The multilayer wiring substrate according to claim 1, wherein
each of the passive-component connection terminals has a structure
in which a plating layer of a material other than copper covers a
top surface and a side surface of a portion of a copper layer which
portion is a main constituent thereof, and each of the IC-chip
connection terminals has a structure in which a plating layer of a
material other than copper covers only a top surface of a portion
of the copper layer which portion is a main constituent
thereof.
3. The multilayer wiring substrate according to claim 2, wherein
the plating layer of a material comprises nickel and gold other
than copper is a nickel-gold plating layer or a
nickel-palladium-gold plating layer.
4. The multilayer wiring substrate according to claim 1, wherein
the plurality of resin insulation layers are formed of a build-up
material made primarily of a hardened thermosetting epoxy resin,
phenol resin, urethane resin, silicone resin, or polyimide
resin.
5. The multilayer wiring substrate according to claim 1, wherein:
each of the passive-component connection terminals has a structure
in which a plating layer of a material comprises nickel and gold
other than copper covers a top surface and a side surface of a
portion of a copper layer which portion is a main constituent
thereof; and each of the IC-chip connection terminals has a
structure in which a plating layer of a material comprises nickel
and gold other than copper covers only a top surface of a portion
of the copper layer which portion is a main constituent thereof.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a divisional of prior U.S. patent
application Ser. No. 12/979,474, filed Dec. 28, 2010, and claims
the benefit of Japanese Patent Application No. 2009-296911, filed
on Dec. 28, 2009, the disclosures of which are herein incorporated
by reference in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to a method of manufacturing a
multilayer wiring substrate having a laminate structure in which a
plurality of resin insulation layers made primarily of the same
resin insulation material, and a plurality of conductive layers are
laminated alternately in multilayer arrangement, and not having a
so-called substrate core. The present invention also relates to a
multilayer wiring substrate manufactured by use of such a
method.
BACKGROUND ART
[0003] In association with recent increasing tendency toward higher
operation speed and higher functionality of semiconductor
integrated circuit devices (IC chips) used as, for example,
microprocessors of computers, the number of terminals increases,
and the pitch between the terminals tends to become narrower.
Generally, a large number of terminals are densely arrayed on the
bottom surface of an IC chip and flip-chip-bonded to terminals
provided on a motherboard. However, since the terminals of the IC
chip differ greatly in pitch from those of the motherboard,
difficulty is encountered in bonding the IC chip directly onto the
motherboard. Thus, according to an ordinarily employed method, a
semiconductor package configured such that the IC chip is mounted
on an IC chip mounting wiring substrate is fabricated, and the
semiconductor package is mounted on the motherboard.
[0004] The IC chip mounting wiring substrate which partially
constitutes such a semiconductor package is practicalized in the
form of a multilayer substrate configured such that a build-up
layer is formed on the front and back surfaces of a substrate core.
The substrate core used in the multilayer wiring substrate is, for
example, a resin substrate (glass epoxy substrate) formed by
impregnating reinforcement fiber with resin. Through utilization of
rigidity of the substrate core, resin insulation layers and
conductive layers are laminated alternately on the front and back
surfaces of the substrate core, thereby forming respective build-up
layers. In the multilayer wiring substrate, the substrate core
serves as a reinforcement and is formed very thick as compared with
the build-up layers. Also, the substrate core has conductor lines
(specifically, through-hole conductors, etc.) extending
therethrough for electrical communication between the build-up
layers formed on the front and back surfaces.
[0005] In recent years, in association with implementation of high
operation speeds of semiconductor integrated circuit devices,
signal frequencies to be used have become those of a high frequency
band. In this case, the conductor lines which extend through the
substrate core serve as sources of high inductance, leading to the
transmission loss of high-frequency signals and the occurrence of
circuitry malfunction and thus hindering implementation of high
operation speed. In order to solve this problem, a multilayer
wiring substrate having no substrate core is proposed (refer to,
for example, Patent Documents 1 and 2). The multilayer wiring
substrates described in Patent Documents 1 and 2 do not use a
substrate core, which is relatively thick, thereby reducing the
overall wiring length. Thus, the transmission loss of
high-frequency signals is lowered, whereby a semiconductor
integrated circuit device can be operated at high speed.
[0006] In the manufacturing method disclosed in Patent Document 1,
a metal foil is disposed one side of a provisional substrate, and a
plurality of conductive layers and a plurality of resin insulation
layers are alternately stacked on the metal foil to thereby form a
build-up layer. Subsequently, the metal foil is separated from the
provisional substrate so as to obtain a structure in which the
build-up layer is formed on the metal foil. The surface of the
outermost layer (the surface of a resin insulation layer and the
surfaces of a plurality of IC-chip connection terminals) is exposed
by means of removing the metal foil through etching, whereby a
multilayer wiring substrate is manufactured.
[0007] Patent Document 1 also discloses a multilayer wiring
substrate in which a solder resist film is formed on the build-up
layer as the outermost layer thereof. Notably, openings are formed
in the solder resist film so as to expose the surfaces of IC-chip
connection terminals. In a multilayer wiring substrate disclosed in
Patent Document 2 as well, a solder resist film is formed, as the
outer most layer, on the side of the wiring substrate where an IC
chip is mounted, and openings are formed in the solder resist film
so as to expose the top surfaces of IC-chip connection terminals.
The solder resist film is made primarily of a hardened photocurable
resin insulation material. The openings of the solder resist film
are formed through exposure and development performed in a state in
which a predetermined mask is disposed on the solder resist film.
Subsequently, solder bumps are formed on the top surfaces of the
IC-chip connection terminals exposed within the openings of the
solder resist film, and an IC chip is mounted via the solder
bumps.
[0008] Furthermore, there has been proposed a multilayer wiring
substrate for mounting an IC chip in which the space between an IC
chip connected to the IC-chip connection terminals and the surface
of the substrate is sealed by use of an underfill agent. [0009]
Patent Document 1: Japanese Patent Application Laid-open (kokai)
No. 2007-158174 [0010] Patent Document 2: Japanese Patent
Application Laid-open (kokai) No. 2004-111544
BRIEF SUMMARY OF THE INVENTION
[0011] Incidentally, in the above-described multilayer wiring
substrate for mounting an IC chip, a hydrophobic material is used
as an underfill agent for sealing the IC chip. Meanwhile, when
solder bumps are formed on the IC-chip connection terminals, a
hydrophilic flux is used. That is, there is a demand for enabling
the hydrophilic flux, as well as the hydrophobic underfill agent,
to wet and spread on the surface of the multilayer wiring substrate
in a proper condition. However, difficulty has been encountered in
setting the degree of surface roughness of the multilayer wiring
substrate to a proper level. Specifically, in the case of the
multilayer wiring substrate disclosed in Patent Document 1, a
copper foil is removed through etching, whereby the outermost resin
insulation layer and the IC-chip connection terminals are exposed.
However, the etching process roughens the surface of the resin
insulation layer to some degree. If the degree of surface roughness
of the resin insulation layer becomes excessively high, the
flowability of the underfill agent deteriorates, and voids or the
like may be formed. On the other hand, if the degree of surface
roughness of the solder resist film is small, the flux spreads
excessively due to its wetability, whereby reliable formation of
solder bumps becomes difficult.
[0012] Furthermore, the above-described multilayer wiring substrate
has the following drawback. When a solder resist film is formed as
the outermost layer, due to a difference in coefficient of thermal
expansion between the solder resist film and inner resin insulation
layers, the substrate warps in accordance with the difference in
coefficient of thermal expansion. In this case, since a structure
(e.g., a reinforcing plate or the like) is additionally required so
as to restrain the warpage, the manufacturing cost of the
multilayer wiring substrate increases. Moreover, the solder resist
film is inferior in electrical insulation performance to the inner
resin insulation layers. Therefore, if the inter-terminal spacing
of the IC-chip connection terminals is decreased, the insulation
provided by the solder resist film becomes insufficient, and a
short circuit may be formed between the terminals.
[0013] The present invention has been conceived in view of the
above problems, and an object of the invention is to provide a
method of manufacturing a multilayer wiring substrate which can set
the degree of surface roughness of the outermost layer to a proper
level. Another object of the present invention is to provide a
multilayer wiring substrate in which the degree of surface
roughness of the outermost layer is set to a proper level, to
thereby enable an IC chip to be mounted thereon reliably.
[0014] A means (first means) for solving the above problems is a
method of manufacturing a multilayer wiring substrate having a
laminate structure in which a plurality of resin insulation layers
made primarily of the same resin insulation material, and a
plurality of conductive layers are laminated alternately in
multilayer arrangement, a plurality of first-main-surface-side
connection terminals being disposed on one side of the laminate
structure where a first main surface thereof is present, a
plurality of second-main-surface-side connection terminals being
disposed on an other side of the laminate structure where a second
main surface thereof is present, the plurality of conductive layers
being formed in the plurality of resin insulation layers and
interconnected by means of via conductors whose diameters increase
toward the first main surface or the second main surface. The
method comprises a build-up step of alternately laminating the
plurality of resin insulation layers and the plurality of
conductive layers in multilayer arrangement on a side of a base
material where a metal foil is separably laminated (i.e.,
alternately laminating the plurality of resin insulation layers and
the plurality of conductive layers in multilayer arrangement on a
metal foil separably laminated on a side of a base material),
thereby forming the laminate structure; a drilling step of forming
a plurality of openings in an outermost resin insulation layer
through laser drilling so as to expose the first-main-surface-side
connection terminals; a desmear step of, after the drilling step,
removing smears from inside the openings; and a base-material
removing step of, after the build-up step, removing the base
material and exposing the metal foil.
[0015] According to the invention described in the first means, the
outermost resin insulation layer is formed of the same resin
insulation material as the inner resin insulation layers of the
laminate structure. Therefore, as compared with the case where the
outermost resin insulation layer is formed of a different resin
insulation material, the influence of a difference in coefficient
of thermal expansion in the laminate structure can be mitigated. As
a result, warpage of the multilayer wiring substrate can be
suppressed. Since the outermost resin insulation layer is formed of
the same resin insulation material as the inner resin insulation
layers, it is difficult to form openings by a lithography process.
However, openings can be reliably formed in the outermost resin
insulation layer through performance of laser drilling.
Furthermore, the desmear step is performed after the build-up step,
the degree of surface roughness of the outermost resin insulation
layer can be set to an arbitrary level. Accordingly, the surface of
the outermost resin insulation layer, which constitutes the
multilayer wiring substrate, can have a surface roughness suitable
to flux and underfill agent, whereby they can be spread in a proper
state by their wetability.
[0016] Preferably, the outermost resin insulation layer is formed
of a build-up material mainly formed of a hardened resin insulation
material that is not photocurable. The build-up material can be
selected as appropriate in consideration of electrical insulation
performance, heat resistance, humidity resistance, etc. Preferred
examples of the build-up material include thermosetting resins,
such as epoxy resin, phenol resin, urethane resin, silicone resin,
and polyimide resin; and thermoplastic resins, such as
polycarbonate resin, acrylic resin, polyacetal resin, and
polypropylene resin. Additionally, there may be used a composite
material consisting of any one of these resins, and glass fiber
(glass woven fabric or glass nonwoven fabric) or organic fiber,
such as polyamide fiber, or a resin-resin composite material in
which a three-dimensional network fluorine-containing resin base
material, such as continuously porous PTFE, is impregnated with a
thermosetting resin, such as epoxy resin.
[0017] The conductive layers are made primarily of copper and are
formed by a known process, such as a subtractive process, a
semi-additive process, or a fully-additive process. Specifically,
for example, etching of a copper foil, electroless copper plating,
or copper electroplating is applied. Also, the conductive layers
and the connection terminals can be formed by forming a thin film
by sputtering, CVD, or a like process, followed by etching.
Alternatively, the conductive layers and the connection terminals
can be formed through application of conductive paste or the like
by printing.
[0018] There may be successively performed a connection-terminal
forming step of, after the base-material removing step, forming the
second-main-surface-side connection terminals in a state in which
etching resist films cover an entirety of the first main surface
and the metal foil in a predetermined pattern corresponding to the
second-main-surface-side connection terminals, and subsequently
etching the metal foil to form the second-main-surface-side
connection terminals; and a resist removing step of removing the
etching resist films to thereby expose the first-main-surface-side
connection terminals and the second-main-surface-side connection
terminals. In this method, the step of forming openings through
laser drilling is performed before performance of the base-material
removing step. In this case, since the laminate structure on the
base material has a relatively large strength, it can be maintained
in a warpage-free state, whereby openings can be formed on the
surface of the laminate structure at accurate positions.
[0019] There may be performed a connection-terminal forming step
of, after the base-material removing step, forming the
second-main-surface-side connection terminals by patterning the
metal foil by a subtractive method in a state in which an etching
resist film is provided on the second main surface; wherein the
drilling step is performed after the connection-terminal forming
step. In this case, in the connection-terminal forming step, the
outermost layer on the first main surface side is covered with the
resin insulation layer; and no opening is provided in the resin
insulation layer. Accordingly, the outermost resin insulation layer
can be caused to function as an etching resist film. Therefore,
separate formation of an etching resist film on the first main
surface side becomes unnecessary, and the second-main-face-side
connection terminals can be formed in a state in which an etching
resist film is provided on the second main surface only.
[0020] The drilling step my be performed such that the
first-main-surface-side connection terminals are exposed, and a
portion of one of the plurality of conductive layers other than the
first-main-surface-side connection terminals is exposed.
Specifically, for example, a portion of a conductive layer which
will become an alignment mark may be exposed, whereby positioning
of the wiring substrate is facilitated.
[0021] Another means (second means) for solving the above problems
is a multilayer wiring substrate having a laminate structure in
which a plurality of resin insulation layers made primarily of the
same resin insulation material, and a plurality of conductive
layers are laminated alternately in multilayer arrangement, a
plurality of first-main-surface-side connection terminals being
disposed on one side of the laminate structure where a first main
surface thereof is present, a plurality of second-main-surface-side
connection terminals being disposed on an other side of the
laminate structure where a second main surface thereof is present,
the plurality of conductive layers being formed in the plurality of
resin insulation layers and interconnected by means of via
conductors whose diameters increase toward the first main surface
or the second main surface. The plurality of resin insulation
layers are formed of a build-up material mainly formed of a
hardened resin insulation material that is not photocurable; a
plurality of openings are formed in an outermost resin insulation
layer exposed on the side where the first main surface of the
laminate structure is present (i.e., exposed as the first main
surface); at least two types of connection terminals, including
IC-chip connection terminals to which an IC chip is to be
connected, and passive-component connection terminals to which a
passive component connection is to be connected and which are
larger in area (i.e., have a larger exposed surface area) than the
IC-chip connection terminals, are present on the first main surface
as the first-main-surface-side connection terminals; and the
IC-chip connection terminals are disposed in the plurality of
openings, top surfaces of the IC-chip connection terminals are
lower in height than (i.e., recessed from) an outer surface of the
outermost resin insulation layer, and peripheral portions of the
IC-chip connection terminals are buried in the outermost resin
insulation layer.
[0022] According to the invention described in the second means,
the multilayer wiring substrate is formed such that a plurality of
resin insulation layers made primarily of the same resin insulation
material, and a plurality of conductive layers are laminated
alternately, and assumes the form of a coreless wiring substrate
having no substrate core. In this multilayer wiring substrate, the
outermost resin insulation layer is formed of a resin insulation
material which is the same as that used for forming the inner resin
insulation layers and which is not photocurable, as compared with
the case where the outermost resin insulation layer is formed of a
different resin insulation material, the influence of a difference
in coefficient of thermal expansion can be mitigated. As a result,
warpage of the multilayer wiring substrate can be suppressed.
Furthermore, two types of connection terminals, including IC-chip
connection terminals to which an IC chip is to be connected, and
passive-component connection terminals to which a passive component
connection is to be connected and which is larger in area than the
IC-chip connection terminals, are present on the first main surface
as the first-main-surface-side connection terminals; and the
IC-chip connection terminals are disposed in the plurality of
openings. The top surfaces of the IC-chip connection terminals are
lower in height than the surface of the outermost resin insulation
layer, and peripheral portions of the IC-chip connection terminals
are buried in the outermost resin insulation layer. Accordingly,
the outermost resin insulation layer functions as a solder resist
film, whereby solder bumps can be reliably formed on the top
surfaces of the IC-chip connection terminals. Moreover, since the
outermost resin insulation layer is formed of a build-up material
which is the same as that used to form the inner resin insulation
layers and which is excellent in electrical insulation performance,
the intervals of the IC-chip connection terminals can be narrowed,
whereby the degree of integration of the multilayer wiring
substrate can be increased.
[0023] Preferably, each of the passive-component connection
terminals has a structure in which a plating layer of a material
other than copper covers a top surface and a side surface of a
portion of a copper layer which portion is a main constituent of
the passive-component connection terminal, and each of the IC-chip
connection terminals has a structure in which a plating layer of a
material other than copper covers only a top surface a portion of
the copper layer which portion is a main constituent of the IC-chip
connection terminal. This configuration enables reliable formation
of relatively large filets on the top and side surfaces of the
passive-component connection terminals. Also, solder bumps can be
reliably formed on the top surfaces of the IC-chip connection
terminals. The inter-terminal spacing of the passive-component
connection terminals is greater than that of the IC-chip connection
terminals, and the passive-component connection terminals have a
relatively large size. Therefore, passive components can be
reliably solder-connected to the passive-component connection
terminals with a sufficiently large strength via filets formed on
the top and side surfaces of the passive-component connection
terminals. Meanwhile, since the inter-terminal spacing of the
IC-chip connection terminals is small, if solder bumps bulge from
the side surfaces of the IC-chip connection terminals, a
short-circuit may be formed between the terminals. In contrast, in
the present invention, since solder bumps are formed only on the
top surfaces of the IC-chip connection terminals, solder bumps do
not bulge laterally, whereby formation of a short-circuit between
the terminals can be avoided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 Sectional view schematically showing the structure of
a multilayer wiring substrate according to a first embodiment.
[0025] FIG. 2 Plan view schematically showing the structure of the
multilayer wiring substrate according to the first embodiment.
[0026] FIG. 3 Explanatory view showing a method of manufacturing
the multilayer wiring substrate according to the first
embodiment.
[0027] FIG. 4 Explanatory view showing the method of manufacturing
the multilayer wiring substrate according to the first
embodiment.
[0028] FIG. 5 Explanatory view showing the method of manufacturing
the multilayer wiring substrate according to the first
embodiment.
[0029] FIG. 6 Explanatory view showing the method of manufacturing
the multilayer wiring substrate according to the first
embodiment.
[0030] FIG. 7 Explanatory view showing the method of manufacturing
the multilayer wiring substrate according to the first
embodiment.
[0031] FIG. 8 Explanatory view showing the method of manufacturing
the multilayer wiring substrate according to the first
embodiment.
[0032] FIG. 9 Explanatory view showing the method of manufacturing
the multilayer wiring substrate according to the first
embodiment.
[0033] FIG. 10 Explanatory view showing the method of manufacturing
the multilayer wiring substrate according to the first
embodiment.
[0034] FIG. 11 Explanatory view showing the method of manufacturing
the multilayer wiring substrate according to the first
embodiment.
[0035] FIG. 12 Explanatory view showing the method of manufacturing
the multilayer wiring substrate according to the first
embodiment.
[0036] FIG. 13 Explanatory view showing a method of manufacturing a
multilayer wiring substrate according to a second embodiment.
[0037] FIG. 14 Explanatory view showing the method of manufacturing
the multilayer wiring substrate according to the second
embodiment.
[0038] FIG. 15 Explanatory view showing the method of manufacturing
the multilayer wiring substrate according to the second
embodiment.
[0039] FIG. 16 Sectional view schematically showing the structure
of a multilayer wiring substrate according to another
embodiment.
[0040] FIG. 17 Sectional view schematically showing the structure
of a multilayer wiring substrate according to another
embodiment.
[0041] FIG. 18 Sectional view schematically showing the structure
of a multilayer wiring substrate according to another
embodiment.
[0042] FIG. 19 Sectional view schematically showing the structure
of a multilayer wiring substrate according to another
embodiment.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
First Embodiment
[0043] A multilayer wiring substrate according to a first
embodiment of the present invention will next be described in
detail with reference to the drawings. FIG. 1 is an enlarged
sectional view schematically showing the structure of the
multilayer wiring substrate of the present embodiment. FIG. 2 is a
plan view of the multilayer wiring substrate.
[0044] As shown in FIG. 1, a multilayer wiring substrate 10 is a
coreless wiring substrate having no substrate core and has a
multilayer wiring laminate portion 30 (laminate structure) in which
four resin insulation layers 21, 22, 23, and 24 made primarily of
the same resin insulation material, and conductive layers 26 made
of copper are laminated alternately. The resin insulation layers 21
to 24 are formed of a build-up material made primarily of a
hardened resin insulation material that is not photocurable;
specifically, a hardened thermosetting epoxy resin. In the
multilayer wiring substrate 10, a plurality of connection terminals
41 and 42 (first-main-surface-side connection terminals) are
disposed on one side (first main surface side) of the wiring
laminate portion 30 where a top surface 31 thereof is present.
[0045] As shown in FIGS. 1 and 2, in the multilayer wiring
substrate 10 of the present embodiment, a plurality of the
connection terminals 41 and 42 disposed on the top surface 31 side
of the wiring laminate portion 30 are IC-chip connection terminals
41 to which an IC chip is to be connected, and capacitor connection
terminals 42 (passive-component connection terminals) to which chip
capacitors (passive components) are to be connected. On the top
surface 31 side of the wiring laminate portion 30, a plurality of
the IC-chip connection terminals 41 are arrayed in a chip mounting
region 43 provided at a central portion of the multilayer wiring
substrate 10. The capacitor connection terminals 42 are greater in
area than the IC-chip connection terminals 41 and are disposed
externally of the chip mounting region 43.
[0046] Meanwhile, on the other side (second main surface side) of
the wiring laminate portion 30 where a bottom surface 32 thereof is
present, a plurality of connection terminals 45 (motherboard
connection terminals serving as second-main-surface-side connection
terminals) for LGA (land grid array) to which a motherboard is to
be connected are arrayed. The motherboard connection terminals 45
are greater in area than the IC-chip connection terminals 41 and
the capacitor connection terminals 42 on the top surface 31
side.
[0047] Via holes 33 and filled-via conductors 34 are provided in
the resin insulation layers 21, 22, 23, and 24. The via conductors
34 are shaped such that their diameters increase in the same
direction (in FIG. 1, in the direction from the bottom surface
toward the top surface). The via conductors 34 electrically
interconnect the conductive layers 26, the IC-chip connection
terminals 41, the capacitor connection terminals 42, and the
motherboard connection terminals 45.
[0048] On the top surface 31 side of the wiring laminate portion
30, a plurality of openings 35 and 36 are formed in the fourth
resin insulation layer 24 serving as an outermost layer and exposed
to the outside. The IC-chip connection terminals 41 are formed in
the openings 35 such that their top surfaces are lower in height
than the surface (reference surface) of the resin insulation layer
24. Peripheral portions of the IC-chip connection terminals 41 are
buried in the resin insulation layer 24. Furthermore, the capacitor
connection terminals 42 are formed in the openings 36 such that
their top surfaces are lower in height than the surface of the
resin insulation layer 24. Peripheral portions of the capacitor
connection terminals 42 are buried in the resin insulation layer
24. The IC-chip connection terminals 41 and the capacitor
connection terminals 42 are mainly formed by a copper layer. Each
of the IC-chip connection terminals 41 and the capacitor connection
terminals 42 has a structure in which a plating layer 46 or 47 of a
material other than copper (specifically, a nickel-gold plating
layer) covers only the top surface of a portion of the copper layer
which portion is the main constituent of the IC-chip connection
terminal 41 or the capacitor connection terminal 42.
[0049] On the bottom surface 32 side of the wiring laminate portion
30, the substantially entirety of the surface of the resin
insulation layer 21 is covered with a solder resist film 37.
Openings 38 are formed in the solder resist film 37 so as to expose
the motherboard connection terminals 45. In the present embodiment,
the openings 38 are smaller than the motherboard connection
terminals 45, and peripheral portions of the motherboard connection
terminals 45 are buried in the solder resist film 37. The
motherboard connection terminals 45 are mainly formed by a copper
layer. Each motherboard connection terminal 45 has a structure in
which a plating layer 48 of a material other than copper
(specifically, a nickel-gold plating layer) covers only the bottom
surface of a portion of the copper layer which portion is the main
constituent of the motherboard connection terminal 45.
[0050] The thus-configured multilayer wiring substrate 10 is
fabricated by, for example, the following procedure.
[0051] First, in a build-up step, a support substrate (a glass
epoxy substrate or the like) having sufficient strength is
prepared. On the support substrate, the resin insulation layers 21
to 24 and the conductive layers 26 are alternately built up,
thereby forming the wiring laminate portion 30.
[0052] More specifically, as shown in FIG. 3, a sheet-like
electrically insulative resin base material made of epoxy resin and
serving as a ground resin insulation layer 51 is attached onto a
support substrate 50, thereby yielding a base material 52
consisting of the support substrate 50 and the ground resin
insulation layer 51. Then, as shown in FIG. 4, a metal laminate
sheet 54 is disposed on one side of the base material 52
(specifically, on the upper surface of the ground resin insulation
layer 51). Through disposition of the metal laminate sheet 54 on
the ground resin insulation layer 51, there is ensured such
adhesion that, in the subsequent fabrication process, the metal
laminate sheet 54 is not separated from the ground resin insulation
layer 51. The metal laminate sheet 54 is configured such that two
copper foils 55 and 56 (a pair of metal foils) are separably in
close contact with each other. Specifically, the copper foils 55
and 56 are laminated together with metal plating (e.g., chromium
plating, nickel plating, titanium plating, or composite plating
thereof) intervening therebetween, thereby forming the metal
laminate sheet 54.
[0053] Subsequently, as shown in FIG. 5, the sheet-like resin
insulation layer 21 is disposed on and attached onto the base
material 52 in such a manner as to cover the metal laminate sheet
54. At this time, the resin insulation layer 21 comes into close
contact with the metal laminate sheet 54 and comes into close
contact with the ground resin insulation layer 51 in a region
around the metal laminate sheet 54, thereby sealing in the metal
laminate sheet 54.
[0054] Then, as shown in FIG. 6, the via holes 33 are formed in the
resin insulation layer 21 at predetermined positions by means of
performing laser beam machining by use of, for example, excimer
laser, UV laser, or CO.sub.2 laser. Next, by use of etchant, such
as a potassium permanganate solution, a desmear step is performed
for removing smears from inside the via holes 33. In the desmear
step, in place of treatment by use of etchant, plasma asking by use
of, for example, O.sub.2 plasma may be performed.
[0055] After the desmear step, electroless copper plating and
copper electroplating are performed by a known process, thereby
forming the via conductors 34 in the via holes 33. Further, etching
is performed by a known process (e.g., semi-additive process),
thereby forming the conductive layer 26 in a predetermined pattern
on the resin insulation layer 21 (see FIG. 7).
[0056] Also, the second to fourth resin insulation layers 22 to 24
and the corresponding conductive layers 26 are formed in layers on
the resin insulation layer 21 by processes similar to those used to
form the first resin insulation layer 21 and the associated
conductive layer 26. By the above-described steps, there is formed
a wiring laminate 60 in which the metal laminate sheet 54, the
resin insulation layers 21 to 24, and the conductive layers 26 are
laminated on the base material 52 (see FIG. 8). Notably, a portion
of the wiring laminate 60 which is located above the metal laminate
sheet 54 will become the wiring laminate portion 30 of the
multilayer wiring substrate 10. Furthermore, portions of the
conductive layer 26 formed between the fourth resin insulation
layer 24 and the third resin insulation layer 23 will become the
IC-chip connection terminals 41 and the capacitor connection
terminals 42.
[0057] Subsequently, as shown in FIG. 9, laser drilling is
performed on the outermost resin insulation layer 24, thereby
forming a plurality of the openings 35 and 36, to thereby expose
the top surfaces of the IC-chip connection terminals 41 and the
capacitor connection terminals 42 (drilling step). Next, there is
performed a desmear step of removing smears from inside the
openings 35 and 36 by use of, for example, a potassium permanganate
solution or O.sub.2 plasma.
[0058] After the desmear step, the wiring laminate 60 is cut by a
dicing apparatus (not shown) so as to remove a surrounding portion
around the wiring laminate portion 30 (cutting step). At this time,
as shown in FIG. 9, cutting progresses along the boundary
(indicated by the arrows in FIG. 9) between the wiring laminate
portion 30 and a surrounding portion 64 and along the extension of
the boundary for further cutting of the base material 52 (the
support substrate 50 and the ground resin insulation layer 51)
located under the wiring laminate portion 30. As a result of this
cutting, a peripheral edge portion of the metal laminate sheet 54
which has been sealed in the resin insulation layer 21 is exposed.
That is, as a result of removal of the surrounding portion 64, a
bonded portion between the ground resin insulation layer 51 and the
resin insulation layer 21 is lost. Consequently, the wiring
laminate portion 30 and the base material 52 are connected together
merely through the metal laminate sheet 54.
[0059] As shown in FIG. 10, the wiring laminate portion 30 and the
base material 52 are separated from each other at the interface
between a pair of the copper foils 55 and 56 of the metal laminate
sheet 54, thereby removing the base material 52 from the wiring
laminate portion 30 and exposing the copper foil 55 present on the
bottom surface of the wiring laminate portion 30 (the resin
insulation layer 21) (base-material removing step). Subsequently,
the copper foil 55 of the wiring laminate portion 30 is subjected
to patterning by a subtractive process (connection-terminal forming
step). Specifically, a dry film is laminated on the top surface 31
and the bottom surface 32 of the wiring laminate portion 30. The
dry films are subjected to exposure and development, thereby
forming an etching resist film on the top surface 31 of the wiring
laminate portion 30 so as to cover the entirety of the top surface,
and forming an etching resist film on the bottom surface 32 of the
wiring laminate portion 30 in a predetermined pattern corresponding
to the motherboard connection terminals 45. In this condition, the
copper foil 55 of the wiring laminate portion 30 is etched for
patterning. As a result, the motherboard connection terminals 45
are formed on the resin insulation layer 21.
[0060] Notably, those regions of the copper foil 55 which are not
covered by the etching resist film are gradually etched away. That
is, the copper foil 55 is gradually etched away from the bottom
surface, which is a side toward the etching resist film. Thus, the
motherboard connection terminals 45 are formed in such a manner as
to have a trapezoidal cross section such that the top surfaces of
the motherboard connection terminals 45 are greater in area than
the bottom surfaces of the motherboard connection terminals 45.
Then, the etching resist films formed on the top surface 31 and the
bottom surface 32 of the wiring laminate portion 30 are separated
and removed (see FIG. 11).
[0061] Next, a photosensitive epoxy resin is applied onto the resin
insulation layer 21 and is cured, whereby the solder resist film 37
is formed. After that, exposure and development are performed in a
state in which a predetermined mask is disposed on the solder
resist film, whereby openings 38 are formed in the solder resist
film 37 in a predetermined pattern (see FIG. 12).
[0062] Subsequently, electroless nickel plating and electroless
gold plating are sequentially performed on the surfaces (top
surfaces) of the IC-chip connection terminals 41 exposed from the
openings 35, the surfaces (top surfaces) of the capacitor
connection terminals 42 exposed from the openings 36, and the
surfaces (bottom surfaces) of the motherboard connection terminals
45 exposed from the openings 38, thereby forming the nickel-gold
plating layers 46, 47, and 48 (plating step). By going through the
above-mentioned steps, the multilayer wiring substrate 10 of FIG. 1
is manufactured.
[0063] Therefore, the present embodiment can yield the following
effects.
[0064] (1) In the multilayer wiring substrate 10 of the present
embodiment, the outermost resin insulation layer 24 is formed of
the same thermosetting resin insulation material as the inner resin
insulation layers 22 and 23. In this case, a photo lithography
process encounters difficulty in formation of the openings 35 and
36 in the outermost resin insulation layer 24. However, through
performance of laser drilling, the openings 35 and 36 can be
reliably formed in the resin insulation layer 24. Furthermore,
since the desmear step is carried out after the build-up step, the
surface roughness of the outermost resin insulation layer 24 can be
set to an arbitrary level. Accordingly, the surface of the
outermost resin insulation layer 24 can have a surface roughness
suitable for flux and underfill agent, to thereby enable them to
spread over the surface by their wetability when an IC chip or the
like is mounted onto the multilayer wiring substrate 10.
[0065] (2) In the present embodiment, the step of forming holes
through laser drilling is performed before performance of the
base-material removing step. In this case, since the wiring
laminate portion 30 on the base material 52 has a relatively large
strength, it can be maintained in a warpage-free state. Therefore,
the openings 35 and 36 can be formed on the surface of the
outermost resin insulation layer 24 of the wiring laminate portion
30 at accurate positions corresponding to the connection terminals
41 and 42.
[0066] (3) In the present embodiment, two types of connection
terminals; i.e., the IC-chip connection terminals 41, to which an
IC chip is to be connected, and the capacitor connection terminals
42, to which a chip capacitor is to be connected, are present on
the top surface 31 of the multilayer wiring substrate 10; and these
connection terminals 41 and 42 are disposed within the plurality of
openings 35 and 36. These connection terminals 41 and 42 are formed
such that their top surfaces are lower in height than the surface
of the outermost resin insulation layer 24, and their peripheral
portions are buried in the outermost resin insulation layer 24.
Therefore, the outermost resin insulation layer 24 functions as a
solder resist film, to thereby enable solder bumps and solder
filets to be reliably formed on the top surfaces of the connection
terminals 41 and 42. In the case of the multilayer wiring substrate
10, since the inter-terminal distance of the IC-chip connection
terminals 41 is small, if solder bumps bulge from the side surfaces
of the IC-chip connection terminals 41, a short-circuit may be
formed between the terminals. In contrast, in the present
embodiment, since solder bumps are formed only on the top surfaces
of the IC-chip connection terminals 41, solder bumps do not bulge
laterally, whereby formation of a short-circuit between the
terminals can be avoided. Moreover, since the outermost resin
insulation layer 24 is formed of a build-up material which is the
same as that used to form the inner resin insulation layers 22 and
23 and which is excellent in electrical insulation performance, the
intervals of the IC-chip connection terminals 41 can be narrowed,
whereby the degree of integration of the multilayer wiring
substrate 10 can be increased.
Second Embodiment
[0067] Next, a second embodiment of the present invention will be
described with reference to the drawings. The present embodiment
differs from the first embodiment in the method of manufacturing
the multilayer wiring substrate 10.
[0068] In the present embodiment as well, as in the first
embodiment, a build-up step is first performed so as to form the
wiring laminate 60 in which the metal laminate sheet 54, the resin
insulation layers 21 to 24, and the conductive layers 26 are
laminated on the base material 52 (see FIG. 8).
[0069] After that, the wiring laminate 60 is cut by a dicing
apparatus (not shown) so as to remove a surrounding portion around
the wiring laminate portion 30 (cutting step). Subsequently, as
shown in FIG. 13, the wiring laminate portion 30 and the base
material 52 are separated from each other at the interface between
the copper foils 55 and 56 of the metal laminate sheet 54, thereby
removing the base material 52 from the wiring laminate portion 30
and exposing the copper foil 55 present on the bottom surface of
the wiring laminate portion 30 (the resin insulation layer 21)
(base-material removing step).
[0070] After completion of the base-material removing step, the
copper foil 55 of the wiring laminate portion 30 is subjected to
patterning by a subtractive process (connection-terminal forming
step). Specifically, a dry film is laminated on the bottom surface
32 of the wiring laminate portion 30. The dry film is subjected to
exposure and development, thereby forming an etching resist film on
the bottom surface 32 of the wiring laminate portion 30 in a
predetermined pattern corresponding to the motherboard connection
terminals 45. In this condition, the copper foil 55 of the wiring
laminate portion 30 is etched for patterning. As a result, the
motherboard connection terminals 45 are formed on the resin
insulation layer 21. Then, the etching resist film formed on the
bottom surface 32 of the wiring laminate portion 30 are separated
and removed (see FIG. 14).
[0071] Subsequently, as shown in FIG. 15, laser drilling is
performed on the outermost resin insulation layer 24, thereby
forming a plurality of the openings 35 and 36, to thereby expose
the top surfaces of the IC-chip connection terminals 41 and the
capacitor connection terminals 42 (drilling step). Next, there is
performed a desmear step of removing smears from inside the
openings 35 and 36 by use of, for example, a potassium permanganate
solution or O.sub.2 plasma.
[0072] Next, a photosensitive epoxy resin is applied onto the resin
insulation layer 21 and is cured, whereby the solder resist film 37
is formed. After that, exposure and development are performed in a
state in which a predetermined mask is disposed on the solder
resist film, whereby openings 38 are formed in the solder resist
film 37 in a predetermined pattern (see FIG. 12).
[0073] Subsequently, electroless nickel plating and electroless
gold plating are sequentially performed on the surfaces of the
IC-chip connection terminals 41 exposed from the openings 35, the
surfaces of the capacitor connection terminals 42 exposed from the
openings 36, and the surfaces of the motherboard connection
terminals 45 exposed from the openings 38, thereby forming the
nickel-gold plating layers 46, 47, and 48 (plating step). By going
through the above-mentioned steps, the multilayer wiring substrate
10 of FIG. 1 is manufactured.
[0074] As described above, in the present embodiment, in the
connection-terminal forming step, the outermost resin insulation
layer 24 on the top surface 31 side of the wiring laminate portion
30 is covered with the resin insulation layer 24; and the openings
35 and 36 are not provided in the resin insulation layer 24. Since
the resin insulation layer 24 functions as an etching resist film,
formation of an etching resist film on the top surface 31 side
becomes unnecessary, and the motherboard connection terminals 45
can be formed in a predetermined pattern in a state in which an
etching resist film is provided on the bottom surface 32 only.
[0075] Notably, the embodiments of the present invention may be
modified as follows.
[0076] In the multilayer wiring substrates 10 according to the
embodiments, the solder resist film 37 is formed on the bottom
surface 32 of the wiring laminate portion 30. However, as in a
multilayer wiring substrate 10A shown in FIG. 16, the solder resist
film 37 may be omitted. Furthermore, the multilayer wiring
substrates 10 are configured such that the openings 38 formed in
the solder resist film 37 is smaller than the motherboard
connection terminals 45, and peripheral portions of the motherboard
connection terminals 45 are buried in the solder resist film 37.
However, the structures of the multilayer wiring substrates 10 are
not limited thereto. As in a multilayer wiring substrate 10B shown
in FIG. 17, the solder resist film 37 may be formed such that
openings 38A are larger than the motherboard connection terminals
45, and the entire side surface and the entire bottom surface of
each motherboard connection terminal 45 are exposed. Notably, the
multilayer wiring substrates 10A and 10B have a structure in which
the bottom surface and the side surface of each motherboard
connection terminal 45 are covered with a plating layer 48.
Accordingly, relatively large solder fillets can be formed on the
bottom surfaces and the side surfaces of the motherboard connection
terminals 45, whereby a sufficiently large connection strength can
be secured between each of the multilayer wiring substrates and a
motherboard. Furthermore, in the case of the multilayer wiring
substrate 10A, since the solder resist film 37 is not formed, it is
possible to avoid warpage of the multilayer wiring substrate 10A,
which would otherwise occur due to a difference in coefficient of
thermal expansion between the resin insulation layers 21 to 24 and
the solder resist film 37.
[0077] In the multilayer wiring substrates 10 of the
above-described embodiments, the openings 35 and 36 formed in the
outermost resin insulation layer 24 are smaller than the connection
terminals 41 and 42, and peripheral portions of the connection
terminals 41 and 42 are buried in the resin insulation layer 24.
However, the structures of the multilayer wiring substrates 10 are
not limited thereto. As in a multilayer wiring substrate 10C shown
in FIG. 18, the resin insulation layer 24 may be formed such that
openings 36A are larger than the capacitor connection terminals 42,
and the entire top surface and the entire side surface of each
capacitor connection terminal 42 are exposed. The multilayer wiring
substrate 10C has a structure in which the top surface and the side
surface of each capacitor connection terminal 42 are covered with
the plating layer 47. Accordingly, relatively large solder fillets
can be formed on the top surfaces and the side surfaces of the
capacitor connection terminals 42, whereby a sufficiently large
connection strength can be secured between the multilayer wiring
substrate and a chip capacitor.
[0078] Furthermore, as in a multilayer wiring substrate 10D of FIG.
19, the resin insulation layer 24 may be formed such that openings
35A are larger than the IC-chip connection terminals 41, and the
entire top surface and the entire side surface of each IC-chip
connection terminal 41 are exposed. In the case of this multilayer
wiring substrate 10D, relatively large solder fillets can be formed
on the top surfaces and the side surfaces of the IC-chip connection
terminals 41, whereby a sufficiently large connection strength can
be secured between the multilayer wiring substrate and an IC
chip.
[0079] In the above-described embodiments, in the drilling step,
the plurality of openings 35 and 36 are formed in the outermost
resin insulation layer 24 so as to expose the IC-chip connection
terminals 41 and the capacitor connection terminals 42. However,
their structures are not limited thereto. For examples, in the
drilling step, in addition to the connection terminals 41 and 42,
other portions (e.g., a portion forming an alignment mark) of the
corresponding conductive layer 26, other than the connection
terminals may be exposed. Moreover, other portions of the
conductive layer 26 may be exposed so as to form a serial number, a
direction identification mark, etc. in addition to the alignment
mark.
[0080] In the above-described embodiments, the desmear step is
performed immediately after the drilling step. However, the
embodiments may be modified such that the desmear step is performed
after formation of the solder resist film 37.
[0081] The above-described embodiments are configured such that the
plurality of conductive layers 26 formed in the plurality of resin
insulation layers 21 to 24 are connected with one another through
the via conductors 34 whose diameters increase in a direction from
the bottom surface 32 to the top surface 31. However, their
structures are not limited thereto. The via conductors 34 formed in
the plurality of resin insulation layers 21 to 24 may have any
shape so long as their diameters increase in the same direction;
and the plurality of conductive layers 26 may be connected with one
another through via conductors whose diameters increase in a
direction from the top surface 31 to the bottom surface 32.
[0082] In the above-described embodiment, each of the plating
layers 46, 47, and 48, which cover the connection terminals 41, 42,
and 45, respectively, is a nickel-gold plating layer. However, the
nickel-gold plating layer can be replaced with any other plating
layer, such as nickel-palladium-gold plating layer, so long as the
plating layer is formed of a material other than copper.
[0083] Next, a technical idea that the embodiments described above
implement is enumerated below.
[0084] (1) A method of manufacturing a multilayer wiring substrate
has a laminate structure in which a plurality of resin insulation
layers made primarily of the same resin insulation material, and a
plurality of conductive layers are laminated alternately in
multilayer arrangement. A plurality of first-main-surface-side
connection terminals are disposed on a first main surface of the
laminate structure. A plurality of second-main-surface-side
connection terminals are disposed on a second main surface of the
laminate structure. The plurality of conductive layers are formed
in the plurality of resin insulation layers and interconnected by
means of via conductors whose diameters increase toward the first
main surface or the second main surface. The method includes a
build-up step of alternately laminating the plurality of resin
insulation layers and the plurality of conductive layers in
multilayer arrangement on a side of a base material where a pair of
metal foils are separably laminated, thereby forming a laminate
structure; a drilling step of forming a plurality of openings in
the outermost resin insulation layer through laser drilling so as
to expose the first-main-surface-side connection terminals; a
base-material removing step of, after the build-up step, removing
the base material and exposing the metal foil by separating the
pair of metal foils from each other; and a desmear step of, after
the drilling step, removing smears from inside the openings.
DESCRIPTION OF REFERENCE NUMERALS
[0085] 10, 10A to 10D: multilayer wiring substrate [0086] 21 to 24:
resin insulation layer [0087] 26: conductive layer [0088] 30:
wiring laminate portion serving as laminate structure [0089] 31:
top surface serving as first main surface [0090] 32: bottom surface
serving as second main surface [0091] 33: via conductors [0092] 35,
36: opening [0093] 41: IC-chip connection terminal [0094] 42:
capacitor connection terminal serving as passive-component
connection terminal [0095] 45: motherboard connection terminal
serving as second-main-surface-side connection terminal [0096] 46,
47: plating layer [0097] 52: base material [0098] 55: copper foil
serving as metal foil
* * * * *