U.S. patent application number 11/296329 was filed with the patent office on 2006-04-27 for glass fabric base material/thermosetting resin copper-clad laminate having a high-elasticity.
Invention is credited to Morio Gaku, Nobuyuki Ikeguchi, Hidenori Kimbara, Masakazu Motegi.
Application Number | 20060089070 11/296329 |
Document ID | / |
Family ID | 16679318 |
Filed Date | 2006-04-27 |
United States Patent
Application |
20060089070 |
Kind Code |
A1 |
Gaku; Morio ; et
al. |
April 27, 2006 |
Glass fabric base material/thermosetting resin copper-clad laminate
having a high-elasticity
Abstract
A copper-clad laminate of a highly-elastic glass fabric base
material/thermosetting resin formed of prepreg obtained by
impregnating a glass fabric base material made of a glass woven
fabric having a thickness of 25 to 150 .mu.m, a weight of 15 to 165
g/m.sup.2 and a gas permeability of 1 to 20 cm.sup.3/cm.sup.2/sec.
with a thermosetting resin composition and drying it.
Inventors: |
Gaku; Morio; (Tokyo, JP)
; Kimbara; Hidenori; (Tokyo, JP) ; Ikeguchi;
Nobuyuki; (Tokyo, JP) ; Motegi; Masakazu;
(Tokyo, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
16679318 |
Appl. No.: |
11/296329 |
Filed: |
December 8, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09625493 |
Jul 25, 2000 |
|
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11296329 |
Dec 8, 2005 |
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Current U.S.
Class: |
442/232 ;
442/149; 442/175; 442/180; 442/223; 442/233 |
Current CPC
Class: |
Y10T 442/2951 20150401;
B32B 15/20 20130101; B32B 2260/046 20130101; Y10T 442/2738
20150401; Y10T 442/3415 20150401; Y10T 442/3423 20150401; B29K
2309/08 20130101; B32B 15/14 20130101; B32B 2262/101 20130101; H05K
1/0366 20130101; Y10T 428/24917 20150115; B32B 2260/021 20130101;
Y10T 442/2992 20150401; Y10T 428/24994 20150401; B32B 27/04
20130101; Y10T 442/3008 20150401; B32B 2311/12 20130101; H05K
2201/029 20130101; B29C 70/00 20130101; Y10T 428/24331 20150115;
H05K 2201/0209 20130101; Y10T 442/3341 20150401; Y10T 442/209
20150401; B32B 2457/08 20130101 |
Class at
Publication: |
442/232 ;
442/175; 442/180; 442/149; 442/223; 442/233 |
International
Class: |
B32B 27/04 20060101
B32B027/04; B32B 27/38 20060101 B32B027/38; B32B 17/02 20060101
B32B017/02; B32B 5/24 20060101 B32B005/24; B32B 15/14 20060101
B32B015/14; B32B 5/02 20060101 B32B005/02; B32B 17/04 20060101
B32B017/04; B32B 5/18 20060101 B32B005/18; B32B 27/12 20060101
B32B027/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 1999 |
JP |
215850/99 |
Claims
1-5. (canceled)
6. A process for processing a hole in a copper-clad laminate, being
used in a printed wiring board, comprising a glass
fabric/thermosetting resin base material, which comprises adding
and mixing an insulating inorganic filler with a thermosetting
resin composition in an amount of 10 to 80% by weight based on said
resin composition, impregnating a glass fabric base material made
of a glass woven fabric having a thickness of 25 to 40 .mu.m, a
weight of 15 to 27 g/m.sup.2 and a gas permeability of 1 to 20
cm.sup.3/cm.sup.2/sec, with the thermosetting resin composition
being dissolved in a solvent, drying it to obtain prepreg, placing
a copper foil on the prepreg, laminate-forming the copper foil and
the prepreg to obtain the copper-clad laminate, and irradiating the
copper-clad laminate with a carbon dioxide gas laser to form a hole
having a diameter of 0.15 mm or less.
7. A process for processing a hole according to claim 6, wherein
the output energy of a carbon dioxide gas laser is 20 to 60
mJ/pulse.
8. A process for processing a hole according to claim 6, wherein
the prepreg has a glass content of 25 to 70% by weight.
9. A process for processing a hole according to claim 6, wherein a
glass fabric material/thermosetting resin base material layer of
the copper-clad laminate has a thickness of 30 to 150 .mu.m.
10. A process for processing a hole according to claim 6, wherein
the thermosetting resin composition is a resin composition
containing, as an essential component, a polyfunctional cyanate
ester and a prepolymer of said polyfunctional cyanate ester.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a highly-elastic glass
fabric base copper-clad laminate. Further, it relates to a
high-density glass fabric base copper-clad laminate suitable for
the formation of a remarkable small-diameter penetration hole
and/or via hole by irradiation with a high-output carbon dioxide
gas laser in place of a mechanical drill. A printed wiring board
comprising the above copper-clad laminate is suitably used mainly
for a semiconductor plastic package such as a thin and small chip
scale package (CSP).
PRIOR ART OF THE INVENTION
[0002] A conventional base material for the thin chip scale package
(CSP) is mainly selected from thin sheets formed of a glass epoxy
material, a polyimide film material and a ceramic material. In
packages formed of these sheets, a solder ball/solder ball distance
is generally 0.8 mm. In recent years, however, it is attempted to
decrease the thickness, the size and the weight of a printed wiring
board. Therefore, a solder ball pitch is getting smaller and
smaller, so that a line/space distance is decreasing. On this
account, there is required a copper-clad laminate which has an
excellent surface smoothness and is suited for the formation of a
fine-line circuit. Further, a penetration hole and a via hole are
coming to have a small diameter, and the holes have a diameter of
0.15 mm or less. When a hole having the above small diameter is
made, the problem is that the drill bents or breaks at a
hole-forming time or that the processing speed is low due to the
small diameter of the drill, which results in problems in
productivity and reliability. Further, when there is employed a
method in which holes having the same size are made in copper foils
on front and reverse surfaces through negative films according to a
predetermined method and a through hole reaching the front and
reverse surfaces is made with a carbon dioxide gas laser, the
problem is that the positions of the holes on the upper and lower
surfaces deviate from each other so that it is difficult to form
lands.
[0003] In a conventional method, when a via hole is made in a
thermosetting resin copper-clad laminate of a glass fabric base
material, a copper foil on a surface is removed by etching in
advance and the via hole is made by irradiation with a low-output
carbon dioxide gas laser energy. In this method, however, the
problem is that fluffing remains on the wall of the via hole. In
addition, the above method includes the precedent step of removing
the copper foil by etching, so that workability is poor. When a
hole is made with a high-output carbon dioxide gas laser energy,
the processing rates of the resin layer and glass layer of a hole
wall differ from each other so that the roughness of the hole wall
becomes large, which impair the quality of the hole.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to provide a glass
fabric base material/thermosetting resin copper-clad laminate which
is excellent in the smoothness of a surface, has a high elasticity
and is almost free from a distortion and a warpage.
[0005] It is another object of the present invention to provide a
glass fabric base material/thermosetting resin copper-clad laminate
having a high elasticity, in which each insulation layer has a
thickness of 30 to 150 .mu.m.
[0006] It is further another object of the present invention to
provide a glass fabric base material/thermosetting resin
copper-clad laminate in which a small-diameter hole, of which the
wall is highly reliable, can be formed with a high-output carbon
dioxide gas laser at a high rate.
[0007] According to the present invention, there is provided a
copper-clad laminate of a highly-elastic glass fabric base
material/thermosetting resin formed of prepreg obtained by
impregnating a glass fabric base material made of a glass woven
fabric having a thickness of 25 to 150 .mu.m, a weight of 15 to 165
g/m.sup.2 and a gas permeability of 1 to 20 cm.sup.3/cm.sup.2/sec.
with a thermosetting resin composition and drying it.
[0008] According to the present invention, further, there is
provided a copper-clad laminate of a highly-elastic glass fabric
base material/thermosetting resin according to the above, wherein
the thermosetting resin composition contains an insulating
inorganic filler in an amount of 10 to 80% by weight based on the
above resin composition.
[0009] According to the present invention, further, there is
provided a copper-clad laminate of a highly-elastic glass fabric
base material/thermosetting resin according to the above, wherein
the prepreg has a glass content of 25 to 70% by weight.
[0010] According to the present invention, further, there is
provided a copper-clad laminate of a highly-elastic glass fabric
base material/thermosetting resin according to the above, wherein a
glass fabric base material/thermosetting resin layer of the
copper-clad laminate has a thickness of 30 to 150 .mu.m.
[0011] According to the present invention, further, there is
provided a copper-clad laminate of a highly-elastic glass fabric
base material/thermosetting resin according to the above, wherein
the thermosetting resin composition is a resin composition
containing, as an essential component, a polyfunctional cyanate
ester and a prepolymer of said polyfunctional cyanate ester.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The present invention relates to a highly-elastic glass
fabric base material/thermosetting resin copper-clad laminate
having at least one copper foil layer and laminate-formed by the
use of prepreg obtained by impregnating a glass fabric base
material particularly suitable for producing a thin, small and
lightweight printed wiring board with a thermosetting resin
composition. There have been found the following. When a glass
woven fabric having a thickness of 25 to 150 .mu.m, a weight of 15
to 165 g/m.sup.2 and a gas permeability of 1 to 20
cm.sup.3/cm.sup.2/sec. is used as the above base material to
prepare a copper-clad laminate having at least one copper foil
layer, the laminate is excellent in surface-smoothness and has a
high elasticity. And, when a hole having a small diameter is made
in the laminate with a high-energy carbon dioxide gas laser, a hole
wall in the laminate is uniform.
[0013] Further, there is provided a copper-clad laminate which is
further excellent in elasticity and excellent in the quality of the
wall of a small-diameter hole formed with a carbon dioxide gas
laser due to the incorporation of an insulating inorganic filler
into the thermosetting resin composition. It is further found that
when a polyfunctional cyanate ester or a prepolymer of said cyanate
ester as a thermosetting resin is used as an essential component,
an obtained copper-clad laminate is excellent in electric
insulation properties after moisture absorption, anti-migration
properties and heat resistance. Further, the hole can be made in
not only a double-side copper-clad laminate but also in a
multi-layered laminate obtained by the use of the same resin
composition. These copper-clad boards may be preferably used even
when a hole is directly made with a YAG (UV) laser.
[0014] As a base material for the glass fabric base copper-clad
laminate, a glass woven fabric having a thickness of 25 to 150
.mu.m, a weight of 15 to 165 g/m.sup.2 and a gas permeability of 1
to 20 cm.sup.3/cm.sup.2/sec. is provided. An insulating inorganic
filler is added to a thermosetting resin such that the
thermosetting resin composition preferably has an insulating
inorganic filler content of 10 to 80% by weight, more preferably 20
to 70% by weight, and the resultant mixture is uniformly mixed.
Further, a polyfunctional cyanate ester or a prepolymer of said
cyanate ester as a thermosetting resin is used as an essential
component, whereby the laminate itself of the copper-clad laminate
increases in elasticity and the occurrence of a distortion, etc.,
is prevented when it is used for a particularly thin printed wiring
board. In the formation of a hole with a carbon dioxide gas laser,
there can be formed a small-diameter penetration hole and/or a via
hole, of which the wall is uniform. And, there is obtained a
copper-clad laminate which is excellent in heat resistance,
electric insulation properties after moisture absorption, and
anti-migration properties.
[0015] The double-side copper-clad laminate or copper-clad
multi-layered board obtained by according to the present invention
is a double-side copper-clad board having a uniform structure and
composition, in which a glass woven fabric is used as a base
material, and the thermosetting resin composition preferably
contains 10 to 80 wt %, more preferably 20 to 70% by weight, of an
inorganic insulating filler.
[0016] The base material can be generally selected from woven
fabrics of known glass fibers. Specifically, the glass fibers
include generally known glass fibers such as E, S, D, N, T and
quartzes. While the weaving method thereof can be selected from
known methods, a plain weaving, a mat weaving and a twill weaving
are preferably used. Woven fabrics obtained by an opening of a
fabric prepared by any one of these weaving methods are preferably
used. The glass woven fabrics are selected from glass woven fabrics
having a thickness of 25 to 150 .mu.m, a weight of 15 to 165
g/m.sup.2 and a gas permeability of 1 to 20
cm.sup.3/cm.sup.2/sec.
[0017] The resin of the thermosetting resin composition used in the
present invention can be selected from generally known
thermosetting resins. Specific examples thereof include an epoxy
resin, a polyfunctional cyanate ester resin, a polyfunctional
maleimide-cyanate ester resin, a polyfunctional maleimide resin and
an unsaturated-group-containing polyphenylene ether resin. These
resins are used alone or in combination. In view of the form of a
through hole formed by processing by the irradiation with a
high-output carbon dioxide gas laser, the use of a thermosetting
resin composition having a glass transition temperature of
150.degree. C. or more is preferred. In view of humidity
resistance, anti-migration properties and electric characteristics
after moisture absorption, the use of a polyfunctional cyanate
ester resin composition is preferred.
[0018] A polyfunctional cyanate ester compound which is a
thermosetting resin component in the present invention refers to a
compound having at least 2 cyanato groups per molecule. Specific
examples thereof include 1,3- or 1,4-dicyanatobenzene,
1,3,5-tricyanatobenzene, 1,3-, 1,4-, 1,6-, 1,8-, 2,6- or
2,7-dicyanatonaphthalene, 1,3,6-tricyanatonaphthalene,
4,4-dicyanatobiphenyl, bis(4-dicyanatophenyl)methane,
2,2-bis(4-cyanatophenyl)propane,
2,2-bis(3,5-dibromo-4-cyanatophenyl)propane,
bis(4-cyanatophenyl)ether, bis(4-cyanatophenyl)thioether,
bis(4-cyanotophenyl)sulfone, tris(4-cyanatophenyl)phosphite,
tris(4-cyanatophenyl)phosphate, and cyanates obtained by reacting
novolak with cyan halide.
[0019] Besides the above compound, the above resin can be also
selected from polyfunctional cyanate ester compounds disclosed in
Japanese Patent Publications Nos. 41-1928, 43-18468, 44-4791,
45-11712, 46-41112 and 47-26853 and JP-A 51-63149. Further, there
may be used a prepolymer having a molecular weight of 400 to 6,000
and having a triazine ring formed by trimerizing cyanato group of
any one of these polyfunctional cyanate ester compounds. The above
prepolymer is obtained by polymerizing the above polyfunctional
cyanate ester monomer in the presence of an acid such as a mineral
acid or a Lewis acid, a base such as sodium alcoholate or tertiary
amine, or a salt such as sodium carbonate, as a catalyst. The
prepolymer partially contains unreacted monomer and is in the form
of a mixture of a monomer and a prepolymer, and the prepolymer in
the above form is suitably used in the present invention. When the
above resin is used, generally, the resin is dissolved in an
organic solvent in which it is soluble.
[0020] The epoxy resin can be selected from generally known epoxy
resins. Specifically, it includes a liquid or solid bisphenol A
type epoxy resin, a bisphenol F type epoxy resin, a phenol novolak
type epoxy resin, a cresol novolak type epoxy resin, an alicyclic
epoxy resin, a polyepoxy compound obtained by epoxidi zing the
double bond of butadiene, pentadiene, vinylcyclohexene or
dicyclopentyl ether, a polyol, and a polyglycidyl compound obtained
by a reaction between a hydroxyl-group-containing silicone resin
and epohalohydrin. These resins may be used alone or in
combination.
[0021] The polyimide resin can be selected from generally known
polyimide resins. Specifically, it includes reaction products from
polyfunctional maleimides and polyamines, and polyimides having
terminal triple bonds, disclosed in JP-B-57-005406.
[0022] The above thermosetting resins maybe used alone, while it is
preferred to use a combination thereof properly in view of a
balance of characteristics.
[0023] The thermosetting resin composition used in the present
invention may contain various additives as required so long as the
inherent properties of the composition are not impaired. Examples
of the above additives include monomers containing a polymerizable
double bond such as an unsaturated polyester and prepolymers
thereof; liquid elastic rubbers having a low molecular weight and
elastic rubbers having a high molecular weight such as
polybutadiene, epoxidized butadiene, maleated butadiene, a
butadiene-acrylonitrile copolymer, polychloroprene, a
butadiene-styrene copolymer, polyisoprene, butyl rubber, fluorine
rubber and natural rubber; polystyrene, an AS resin, an ABS resin,
an MBS resin, styrene-isoprene rubber, a polyethylene-propylene
copolymer and ethylene tetrafluoride-ethylene hexafluoride
copolymers; high-molecular-weight prepolymers or oligomers such as
polycarbonate, polyphenylene ether, polysulfone, polyester and
polyphenylene sulfide; and polyurethane. These additives are used
as required. Further, the above thermosetting resin composition may
also contain various additives such as a generally known organic
filler, a dye, a pigment, a thickener, a lubricant, an anti-foamer,
a dispersing agent, a leveling agent, a photosensitizer, a flame
retardant, a brightener, a polymerization inhibitor and a
thixotropic agent. These additives may be used alone or in
combination as required. A curing agent or a catalyst is
incorporated into a compound having a reactive group, as
required.
[0024] The thermosetting resin composition used in the present
invention undergoes curing itself under heat. However, since its
curing rate is low, it is poor in workability and economic
performances, etc. Therefore, a known heat-curing catalyst may be
incorporated into the thermosetting resin. The amount of the
catalyst per 100 parts by weight of the thermosetting resin is
0.005 to 10 parts by weight, preferably 0.01 to 5 parts by
weight.
[0025] The inorganic insulating filler can be selected from
generally known fillers. Specifically, it includes silicas such as
natural silica, calined silica and amorphous silica, white carbon,
titanium white, aerogel, clay, talc, wollastonite, naturalmica,
syntheticmica, kaolin, magnesia, alumina, perlite, aluminum
hydroxide and magnesium hydroxide. The amount of the above filler
is 10 to 80% by weight, preferably 20 to 70% by weight. The average
particle diameter thereof is preferably 1 .mu.m or less.
[0026] The copper foil used as the outermost layers can be selected
from generally known copper foils. Preferably, an electrolytic
copper foil having a thickness of 3 to 12 .mu.m is used. As a
copper foil used as an internal layer, an electrolytic copper foil
having a thickness of 9 to 35 .mu.m is preferably used.
[0027] The glass fabric base copper-clad laminate is prepared as
follows. First, the above glass fabric base material is impregnated
with a thermosetting resin composition, and the composition is
dried and B-staged to form a prepreg which preferably has a glass
content of 25 to 70 wt %. A predetermined number of the so-obtained
prepregs are provided, copper foils are placed on the upper and
lower surfaces of the prepregs, and the resultant set is
laminate-formed under heat and under pressure, whereby a
double-side copper-clad laminate is obtained. The above copper-clad
laminate has a cross section where the resin and the inorganic
filler other than glass are homogeneously dispersed. Therefore, a
hole is uniformly made with a laser. Further, the glass is
uniformlydisposed so that the roughness of a hole wall is decreased
when the hole is made with a laser. Further, a copper-clad
multi-layered board obtained by forming circuits on the double-side
copper-clad laminate, surface-treating the copper foils as
required, providing the same prepreg(s) and laminate-forming the
resultant set, has the similar characteristics.
[0028] The copper surface of the glass fabric base copper-clad
laminate in a hole-forming portion to be irradiated with a carbon
dioxide gas laser is treated to form a metal oxide or treated with
a chemical. Otherwise, a coating or a sheet of a resin composition
containing at least one powder selected from the group consisting
of a metal compound powder, a carbon powder and metal powder is
disposed on the above copper surface. The resultant copper surface
is directly irradiated with a carbon dioxide gas laser having a
diameter focussed to an intended diameter, to make a hole in the
copper foil on the front surface or the copper foil on the reverse
surface. As a backup sheet, it is preferred to use a sheet obtained
by forming a resin layer on a metal sheet having a surface gloss in
view of preventing the occurrence of deformation of a hole portion
on the reverse surface due to the reflection of a penetrated carbon
dioxide gas laser.
[0029] When a penetration hole or a via hole is made by several
pulses of irradiation with a carbon dioxide gas laser at an output
energy preferably selected from 20 to 60 mJ/pulse, burrs occur
around the hole. After the irradiation with the carbon dioxide gas
laser, therefore, both the copper foil surfaces of the copper-clad
laminate are two-dimensionally etched to remove part of the
thickness thereof and at the same time to remove the burrs. The
resultant copper foils are suitable for forming fine patterns
thereon, the penetration hole is plated, and the copper foils
suitable for a high-density printed wiring board are retained
around the hole on both the surfaces.
[0030] In the present invention, an oxidation treatment to form a
metal oxide, which treats a copper foil surface where a hole is to
be made by direct irradiation with a carbon dioxide gas laser, can
be selected from generally known treatments. Specifically, a
treatment to form black copper oxide, a MM treatment (supplied by
MacDarmid), and the like, are preferably used. The treatment with a
chemical is also selected from generally known treatments. Example
thereof includes a CZ treatment (supplied by Meck K. K.). Further,
a resin composition containing a metal compound powder, a carbon
powder or a metal powder is disposed on the copper foil surface and
used for a direct formation of a hole in the copper foil with a
carbon dioxide gas laser. The metal oxide powder is selected from
powders of metal compounds having a melting point of 900.degree. C.
or more and a bond energy of 300 kJ/mol or more. Specifically,
oxides are used. The oxides include titanias such as titanium
oxide, magnesias such as magnesium oxide, oxides of iron such as
iron oxide, oxides of nickel such as nickel oxide, oxides of zinc
such as zinc oxide, silicon dioxide, manganese dioxide, aluminum
oxide, rare earth metal oxides, oxides of tin such as tin oxide and
oxides of tungsten such as tungsten oxide. Non-oxides may be also
used. The non-oxides include generally known non-oxides such as
silicon carbide, tungsten carbide, boron nitride, silicon nitride,
titanium nitride, aluminum nitride and barium sulfate. Carbon may
be also used. Further, there may be used simple substances of
silver, aluminum, bismuth, cobalt, copper, iron, manganese,
molybdenum, nickel, tin, titanium and zinc or alloys of these.
These are used alone or in combination. The average particle
diameter of these is not specially limited, while it is preferably
1 .mu.m or less. The amount of these is not specially limited,
while it is 3 to 97 vol %. These are incorporated into an organic
substance, particularly a resin composition, and used. The resin
composition is preferably selected from water-soluble resins in
view of removing the remains after laser-processing. Although not
specially limited, the water-soluble resin is selected from those
which do not peel off when they are kneaded, coated on a copper
foil surface and dried or formed into a sheet. For example, the
water-soluble resin includes generally known resins such as
polyvinyl alcohol, polyester, polyether and starch.
[0031] The method of preparing composition containing a metal
compound powder, a carbon powder or a metal powder and a resin is
not critical. There are used methods such as a method of kneading
materials without any solvent at a high temperature with a kneader,
etc., and extruding the kneaded mixture in the form of a sheet to
bond it to a thermoplastic film surface, and a method of dissolving
a water-soluble resin in water, adding the above powder thereto,
homogeneously mixing them with stirring, applying the mixture as a
coating composition to a thermoplastic film and drying it to form a
coating or directly applying it to a copper foil surface and drying
it to form a coating. The thickness is not specially limited, while
the thickness of the coating is preferably 30 to 100 .mu.m. When
the mixture is bonded to the film, a sheet having a total thickness
of preferably 30 to 200 .mu.m is formed. When the sheet is formed,
a resin layer is preferably disposed on a copper foil side and the
resultant set is preferably laminated under heat and pressure for
use.
[0032] Concerning a backup sheet, preferably, the above
water-soluble resin layer is disposed on the reverse surface of the
copper-clad board, a metal sheet is disposed on the outside
thereof, and a hole is made. It is preferred to use the
water-soluble resin by bonding it to a copper foil.
[0033] In the present invention, the method of removing the copper
burrs occurring on the hole portions by etching is not specially
limited, while it includes methods of dissolving and removing a
metal surface with a chemical (called a SUEP method) disclosed, for
example, in JP-A-02-22887, JP-A-02-22896, JP-A-02-25089,
JP-A-02-25090, JP-A-02-59337, JP-A-02-60189, JP-A-02-166789,
JP-A-03-25995, JP-A-03-60183, JP-A-03-94491, JP-A-04-199592 and
JP-A-04-263488. The etching is carried out at a rate of 0.02 to 1.0
.mu.m/second.
[0034] A carbon dioxide gas laser generally uses a wavelength of
9.3 to 10.6.mu.m in an infrared wavelength region. The copper-clad
board of the present invention may be also used in processing with
a UV laser. The UV laser generally preferably uses a wavelength of
200 to 400 nm.
[0035] Further, the method of forming a hole by processing is not
specially limited. Specifically, when a penetration hole is made, a
mechanical drill, a laser, etc., is used. When a hole for a via
hole is made, a sandblasting method, a router, a laser, etc., may
be used.
EXAMPLES
[0036] The present invention will be explained more in detail with
reference to Examples and Comparative Examples hereinafter. In
Examples and Comparative Examples, "part" stands for "part by
weight" unless otherwise specified.
Example 1
[0037] 900 Parts of 2,2-bis(4-cyanatophenyl)propane and 100 parts
of bis(4-meleimidephenyl)methane were melted at 150.degree. C. and
allowed to react for 4 hours with stirring, to prepare a
prepolymer. The prepolymer was dissolved in mixed solvents of
methyl ethyl ketone and dimethylformamide. To this solution were
added 400 parts of a bisphenol A type epoxy resin (trade name:
Epikote 1001, supplied by Yuka-Shell Epoxy K. K.) and 600 parts of
a cresol novolak type epoxy resin (trade name: ESCN-220F, supplied
by Sumitomo Chemical Co., Ltd.), and these materials were
homogeneously dissolved and mixed. Further, as a catalyst, 0.4 part
of zinc octylate was added, and these materials were dissolved and
mixed. To the resultant mixture were added 500 parts of an
inorganic insulating filler (trade name: Calcined Talc, average
particle diameter 0.4 .mu.m, supplied by Nippon Talc K. K.) and 8
parts of a black pigment, and these materials were homogeneously
stirred and mixed to prepare a varnish A. The above varnish A was
used to impregnate a twilled glass woven fabric having a thickness
of 40 .mu.m, a weight of 27 g/m.sup.2 and a gas permeability of 19
cm.sup.3/cm.sup.2/sec., and the impregnated twilled glass woven
fabric was dried at 150.degree. C. to prepare prepreg (prepreg B)
having a gelation time of 120 seconds at 170.degree. C. and having
a glass fabric content of 40% by weight. Three sheets of the
prepregs B were stacked, 12 .mu.m thick electrolytic copper foils
were placed on the upper and lower surfaces of the stacked
prepregs, and the resultant set was laminate-formed at 200.degree.
C. at 20 kgf/cm.sup.2 under a vacuum of 30 mmHg or less for 2
hours, to obtain a double-side copper-clad laminate B having an
insulation layer thickness of 136 .mu.m.
[0038] Separately, 800 Parts of a black copper oxide powder having
an average particle diameter of 0.86 .mu.m was added to a varnish
prepared by dissolving a polyvinyl alcohol powder in water, and
these materials were homogeneously stirred and mixed (varnish C) .
The varnish C was applied to one surface of the above double-side
copper-clad laminate to form a coating having a thickness of 30
.mu.m, and the coating was dried at 110.degree. C. for 30 minutes
to obtain a coating having a metal oxide content of 50 vol %. A
backup sheet is obtained by applying a water-soluble polyester
resin on a 100 .mu.m thick aluminum foil having a surface gloss to
form a coating having a thickness of 100 .mu.m. The backup sheet
was placed on the other surface. The resultant upper surface was 3
pulses (shots) irradiated directly with a carbon dioxide gas laser
at an output of 35 mJ/pulse to form 900 penetration holes having a
diameter of 100 .mu.m each. Copper foil burrs around the holes were
dissolved and removed by the SUEP method, and at the same time, the
copper foil on the surface was dissolved until the copper foil had
a thickness of 4 .mu.m. Copper was plated on the resultant board by
a known method to form a 15 .mu.m thick layer (total thickness: 19
.mu.m). Circuits (line/space= 50/50 .mu.m) were formed on the
surface, and lands for solder balls, and the like were formed on
the reverse surface according to a known method. Portions other
than the semiconductor chip-mounting portion, a bonding pad portion
and a solder ball pad portion were coated with a plating resist,
and nickel plating and gold plating were carried out to obtain a
printed wiring board having a square size of 25 mm.times.25 mm. A
semiconductor chip having a square size of 4 mm.times.4 mm was
mounted on the semiconductor-mounting portion of the printed wiring
board with a silver paste, followed by wire-bonding and
encapsulation with a resin, to obtain a semiconductor plastic
package. Tables 1 and 2 show the evaluation results.
Example 2
[0039] 1,400 Parts of an epoxy resin (trade name: Epikote 5045),
600 parts of an epoxy resin (trade name: ESCN-220F), 70 parts of
dicyandiamide and 2 parts of 2-ethyl-4-methylimidazole were
dissolved in mixed solvents of methyl ethyl ketone and
dimethylformamide, to give a varnish D. The varnish D was used to
impregnate a twilled glass woven fabric having a thickness of 130
.mu.m, a weight of 136 g/m.sup.2 and a gas permeability of 3
cm.sup.3/cm.sup.2/sec., and dried to give prepreg (prepregs E)
having a gelation time of 120 seconds and having a glass fabric
content of 50 wt % and prepregs F having a gelation time of 136
seconds and having a glass fabric content of 45 wt %. One sheet of
the prepreg E was provided, a 70 .mu.m thick electrolytic copper
foil was placed on one surface of the prepreg E, and the resultant
set was laminate-formed at 190.degree. C. at 20 kgf/cm.sup.2 under
a vacuum of 30 mmHg or less for 2 hours, to obtain a single-side
copper-clad laminate. The insulating layer thereof had a thickness
of 140 .mu.m. Circuits were formed on this copper surface, followed
by a treatment to form copper oxide. Then, sheets of the above
prepreg F were placed on both the surfaces, one sheet on one
surface and one sheet on the other surface, release films were
placed thereon, and the resultant set was similarly laminate-formed
to obtain a board having one copper foil layer as an internal
layer.
[0040] A ball pad portion on the reverse surface was 2 pulses
(shots) irradiated with a carbon dioxide gas laser at an output of
17 mJ/pulse to form via holes. Holes were made in a bonding pad
portion on the front surface so as to reach the internal copper
foil according to a sandblasting method. After desmearing
treatment, Example 1 was repeated to complete a printed wiring
board having a square size of 25 mm.times.25 mm. A semiconductor
chip having a square size of 15 mm.times.15 mm was mounted on the
printed wiring board with a silver paste, wire-bonding was carried
out and encapsulation with an epoxy compound was entirely carried
out. Tables 1 and 2 show the evaluation results.
Comparative Example 1
[0041] In Example 1, no inorganic insulating filler was used, and
the varnish A was used to impregnate a twill-woven glass fabric
having a thickness of 50 .mu.m, a weight of 48 g/m.sup.2 and a gas
permeability of 180 cm.sup.3/cm.sup.2/sec., as a glass woven
fabric, and dried to give prepreg having a gelation time of 122
seconds and having a glass fabric content of 40 wt %. Two sheets of
the prepreg were provided, 12 .mu.m thick electrolytic copper foils
were placed on the upper and lower surfaces of the prepregs, and
the resultant set was similarly laminate-formed, to obtain a
double-side copper-clad laminate having an insulation layer
thickness of 129 .mu.m. Thereafter, penetration holes were
similarly made by irradiation with a carbon dioxide gas laser, and
a printed wiring board was prepared without the SUEP treatment.
Similarly, the printed wiring board was used to obtain a
semiconductor plastic package. Tables 1 and 2 show the evaluation
results.
Comparative Example 2
[0042] In Example 2, 2,000 Parts of only Epikote 5045 was used as
an epoxy resin, and no inorganic filler was used to prepare a
varnish G. The varnish G was used to impregnate a twill-woven glass
fabric having a thickness of 100 .mu.m, a weight of 105 g/m.sup.2
and a gas permeability of 28 cm.sup.3/cm.sup.2/sec. and dried to
give prepreg G having a gelation time of 133 seconds and having a
glass fabric content of 45 wt %. Other procedures were carried out
in the same manner as in Example 1, and laminate-formation was
similarly carried out to obtain a double-side copper-clad laminate
having an insulation layer thickness of 115 .mu.m. Thereafter, the
SUEP treatment was not carried out, and a printed wiring board and
a semiconductor plastic package were obtained in the same manner as
in Example 2.
[0043] Tables 1 and 2 show the evaluation results. TABLE-US-00001
TABLE 1 Example Comparative Example 1 2 1 2 Form of holes Almost
Almost Almost Almost Circular Circular Circular Circular Form of
hole walls Almost no Almost no remarkable remarkable roughness
roughness roughness roughness Pattern breakage 0/200 0/200 50/200
52/200 and short circuit, number Glass transition 235 160 235 139
temperature, .degree. C. Through hole via hole-heat cycle test, %
2.5 -- 15.9 5.3 Insulation resistance value after pressure cooker
treatment, .OMEGA. Normal state 5 .times. 10.sup.14 -- -- 6 .times.
10.sup.14 200 hours 6 .times. 10.sup.12 3 .times. 10.sup.8 500
hours 3 .times. 10.sup.11 <10.sup.8 750 hours 6 .times.
10.sup.10 1,000 hours 4 .times. 10.sup.10 Surface roughness, 0.6
0.7 1.8 2.2 .mu.m
[0044] TABLE-US-00002 TABLE 2 Example Comparative Example 1 2 1 2
Anti-migration properties, .OMEGA. Normal state 3 .times. 10.sup.13
-- -- 4 .times. 10.sup.13 200 hours 3 .times. 10.sup.11 1 .times.
10.sup.9 500 hours 2 .times. 10.sup.11 <10.sup.8 750 hours 2
.times. 10.sup.11 -- 1,000 hours 8 .times. 10.sup.10 Elasticity,
.times.10.sup.10dyne/ 2.2 1.7 1.2 1.1 cm.sup.2 Distortion, 250
.times. 250 4 3 15 17 mm, printed wiring board
Measurement methods 1) Form of Hole Walls, and Time Period for
Making Holes
[0045] 900 Holes/block, each hole having a diameter of 100 .mu.m,
were made at intervals of 300 .mu.m in 70 blocks in a work having a
square size of 250.times.250 mm (63,000 holes in total) . The form
of the holes from a surface and the cross section were observed to
check roughness on wall.
2) Circuit Pattern Breakage and Short Circuit
[0046] In Examples and Comparative Examples, boards having no holes
made were similarly prepared, comb-like patterns having a
line/space= 50/50 .mu.m were prepared, and then 200 patterns were
visually observed through a magnifier after etching. A numerator
shows the total of patterns which had a circuit pattern breakage
and a short circuit.
3) Glass Transition Temperature and Elasticity Measured by a DMA
method.
4) Through Hole and Via HoleHeat Cycle Test
[0047] A land having a diameter of 200 .mu.m was formed in each
through hole, and 900 holes were connected alternately. One cycle
consisted of immersion for soldering at 260.degree. C. for 30
seconds and standing at room temperature for 5 minutes, and 200
cycles were repeated. The maximum value of change ratios of
resistance values was shown.
5) Insulation Resistance Value After Pressure Cooker Treatment
[0048] A comb-shaped pattern between terminals (line/space= 50/50
.mu.m) was formed, after a chemical treatment, one sheet of each
prepreg used was placed thereon, and the resultant set was
laminate-formed. The resultant laminate was treated at 121.degree.
C. at 203 kPA for a predetermined period of time and then treated
at 25.degree. C. at 60% RH for 2 hours. 500 VDC was applied, and 60
seconds after the application, an insulation resistance between
terminals was measured.
6) Anti-Migration Properties
[0049] The test piece in the above 5) was measured for an
insulation resistance value between terminals at 85.degree. C. at
85% RH under an applied charge of 50 VDC.
7) Distortion
[0050] A printed wiring board having a work size of 250.times.250
mm, coated with 30 .mu.m-thick solder resist on both sides, was
placed on a flat plate and measured for a maximum value of
distortion.
8) Surface Roughness
[0051] The surface roughness of a copper-clad laminate having 12
.mu.m-thick copper foils on both surfaces was measured with a
surface-roughness-measuring device, and the maximum value was
shown.
Effect of the Invention
[0052] According to the present invention, there is provided a
glass fabric base material/thermosetting resin copper-clad laminate
comprising prepreg obtained by impregnating a woven fabric having a
thickness of 25 to 150 .mu.m, a weight of 15 to 165 g/m.sup.2 and a
gas permeability of 120 cm.sup.3/cm.sup.2/sec. as a glass fabric
base material with a thermosetting resin and drying it. According
to the present invention, there is provided a thermosetting resin
copper-clad laminate, of which the surfaces are flat and smooth,
which has a high elasticity and which is almost free from
distortion and warpage when it is used to prepare a remarkably thin
printed wiring board.
[0053] According to the present invention, there is further
provided a copper-clad laminate or multi-layered board having a
high elasticity, which laminate or board is obtained by using a
polyfunctional cyanate ester composition as a thermosetting resin
and incorporating an insulating inorganic filler, wherein each one
layer of glass fabric base material/thermosetting resin layers has
an insulation layer thickness of 30 to 150 .mu.m. In the
copper-clad laminate, with the treatment or the material on one
surface to help a CO.sub.2 laser drilling, penetration holes and
via holes can be formed by direct irradiation with a high-output
carbon dioxide gas laser, and the wall of the obtained holes is
almost free from roughness and is uniform. There is obtained a
printed wiring board excellent in reliabilities such as electric
insulation properties of through holes and via holes after moisture
absorption and anti-migration properties and also excellent in heat
resistance. A semiconductor plastic package comprising the above
printed wiring board shows little distortion and excellent
connection properties to a mother board.
* * * * *