U.S. patent application number 12/531886 was filed with the patent office on 2010-03-11 for resin board to be subjected to ozone treatment, wiring board, and method of manufacturing the wiring board.
Invention is credited to Takeshi Bessho, Kyoko Kumagai, Manabu Osamura, Toshihisa Shimo, Takashi Yoshida.
Application Number | 20100059259 12/531886 |
Document ID | / |
Family ID | 39917682 |
Filed Date | 2010-03-11 |
United States Patent
Application |
20100059259 |
Kind Code |
A1 |
Bessho; Takeshi ; et
al. |
March 11, 2010 |
RESIN BOARD TO BE SUBJECTED TO OZONE TREATMENT, WIRING BOARD, AND
METHOD OF MANUFACTURING THE WIRING BOARD
Abstract
A resin board that consists of at least one of a mixture of a
plurality of types of resins having different degrees of
susceptibility to erosion by an ozone solution, and a resin having,
in a molecule, a plurality of types of components having different
degrees of susceptibility to erosion by the ozone solution is
treated with ozone water to form a reformed layer, and a catalyst
metal is adsorbed by the reformed layer so as to form a resin-metal
composite layer, on which a plating process is performed. In the
resin board, a component or components that is/are likely to be
eroded on by the ozone solution dissolves into the ozone solution,
and pores or clearances on the order of nanometers are formed
between the component(s) and a component or components that is/are
less likely to be eroded by the ozone solution. With the plating
deposited in the pores or clearances, the adhesion strength is
improved due to an anchoring effect. Thus, the adhesion strength of
the plating film is improved even where the resin-metal composite
layer has a thickness of 10 to 200 nm.
Inventors: |
Bessho; Takeshi; (Aichi-ken,
JP) ; Kumagai; Kyoko; (Aichi-Ken, JP) ;
Yoshida; Takashi; (Aichi-Ken, JP) ; Osamura;
Manabu; (Aichi-Ken, JP) ; Shimo; Toshihisa;
(Aichi-Ken, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Family ID: |
39917682 |
Appl. No.: |
12/531886 |
Filed: |
May 21, 2008 |
PCT Filed: |
May 21, 2008 |
PCT NO: |
PCT/IB08/01270 |
371 Date: |
September 18, 2009 |
Current U.S.
Class: |
174/257 ;
205/205; 216/13; 525/452; 525/50 |
Current CPC
Class: |
C23C 18/2086 20130101;
C23C 18/2033 20130101; C23C 18/1694 20130101; H05K 3/381 20130101;
C23C 18/2006 20130101; H05K 3/181 20130101; C23C 18/1653 20130101;
H05K 2203/087 20130101 |
Class at
Publication: |
174/257 ; 525/50;
525/452; 205/205; 216/13 |
International
Class: |
H05K 1/09 20060101
H05K001/09; C08G 18/00 20060101 C08G018/00; C25D 5/34 20060101
C25D005/34; H01B 13/00 20060101 H01B013/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 22, 2007 |
JP |
2007-15740 |
Claims
1. A resin board to be subjected to ozone treatment, which is
adapted to be treated with an ozone solution, comprising: at least
one of a mixture of a plurality of types of resins that have
different degrees of susceptibility to erosion by the ozone
solution, and a resin that has, in a molecule, a plurality of types
of components having different degrees of susceptibility to erosion
by the ozone solution.
2. The resin board to be subjected to ozone treatment according to
claim 1, wherein the resin board contains an aromatic epoxy resin
that has both an aromatic cyanate compound and an epoxy group.
3. A wiring board, comprising: the resin board as defined in claim
1; a resin-metal composite layer which is formed integrally on a
surface of the resin board and in which fine metal particles are
uniformly dispersed in a resin matrix; and a wiring portion that
comprises a plating film formed in a predetermined pattern on the
resin-metal composite layer, wherein the resin-metal composite
layer has a thickness of 10 to 200 nm.
4. A method of manufacturing a wiring board, comprising: a
preparing step of preparing the resin board as defined in claim 1;
an ozone treatment step of treating the resin board with an ozone
solution so as to form a reformed layer having polar groups on a
surface thereof; an adsorption step of bringing the reformed layer
into contact with a metal compound solution so that at least one of
colloidal particles and ions of a catalyst metal are attached to
the polar groups and fine particles of the catalyst metal are
dispersed in the reformed layer, thereby to form a resin-metal
composite layer; and a plating step of performing a plating process
on the resin-metal composite layer in a predetermined pattern so as
to form a wiring portion of the predetermined pattern, wherein the
preparing step, the ozone treatment step, the adsorption step and
the plating step are carried out in the order of description.
5. The method according to claim 4, further comprising an etching
step of removing an unnecessary portion of the resin-metal
composite layer.
6. A wiring board, comprising: the resin board as defined in claim
2; a resin-metal composite layer which is formed integrally on a
surface of the resin board and in which fine metal particles are
uniformly dispersed in a resin matrix; and a wiring portion
comprising a plating film formed in a predetermined pattern on the
resin-metal composite layer, wherein the resin-metal composite
layer has a thickness of 10 to 200 nm.
7. A method of manufacturing a wiring board, comprising: a
preparing step of preparing the resin board as defined in claim 2;
an ozone treatment step of treating the resin board with an ozone
solution so as to form a reformed layer having polar groups on a
surface thereof; an adsorption step of bringing the reformed layer
into contact with a metal compound solution so that at least one of
colloidal particles and ions of a catalyst metal are attached to
the polar groups and fine particles of the catalyst metal are
dispersed in the reformed layer, thereby to form a resin-metal
composite layer; and a plating step of performing a plating process
on the resin-metal composite layer in a predetermined pattern so as
to form a wiring portion of the predetermined pattern, wherein the
preparing step, the ozone treatment step, the adsorption step and
the plating step are carried out in the order of description.
8. The method according to claim 7, further comprising an etching
step of removing an unnecessary portion of the resin-metal
composite layer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to resin boards for use in wiring
boards, wiring boards formed from the resin boards, and a method of
manufacturing the wiring boards.
[0003] 2. Description of the Related Art
[0004] Resin is finding remarkably increased use in the fields
where metal is conventionally used, owing to its features, such as
the ease with which resin can be shaped, a high degree of
flexibility in characteristic values, such as strength, and
lightness in weight. However, resin also has drawbacks, such as the
absence of electrical conductivity and low hardness, and therefore,
it has been proposed to combine resin with metal, or the like, so
as to eliminate these drawbacks.
[0005] As an example of method for providing resin with electrical
conductivity, powder of a conductive metal or carbon fibers, for
example, is mixed into the resin. However, a large amount of
conductive metal needs to be added to the resin so as to impart
sufficiently high conductivity to the resin, which may cause
adverse influences on the physical properties and increased cost.
Thus, another method is known in which a metal film, or a film of a
conductive oxide, such as ITO, is formed on a surface of the resin.
The conductive film may be formed by a physical method, such as
vapor deposition or sputtering, or a chemical method, such as
electroless plating. The physical method generally requires
large-sized equipment, such as a vacuum tank, and thus suffers from
significant restrictions in terms of space or productivity, which
undesirably results in increased cost.
[0006] In the case where a film of metal is formed on a resin
surface by electroless plating, the strength of adhesion between
the metal film and the resin is low, and the metal film is likely
to peel off from the resin. In view of this problem, the following
steps are generally carried out: chemical etching is performed on a
resin material so as to make its surface rough, and the etched
resin material is then subjected to electroless plating. However,
the method that makes the resin surface rough by etching causes a
reduction of the surface smoothness, and requires the use of a
poisonous or deleterious substance, such as chromic acid,
permanganic acid, or sulfuric acid, giving rise to a problem
concerned with treatment of waste liquid.
[0007] With this being the situation, Japanese Laid-open Patent
Publication No. 2002-309377 (JP-A-2002-309377) discloses a method
in which a resin material is brought into contact with an ozone
solution and is then treated with a solution containing a
surface-active agent or surfactant and an alkaline component, and
then electroless plating is carried out. According to this method,
the cleavage of double bonds on the surface of the resin material
takes place due to oxidation caused by ozone, and polar groups are
produced on the resin surface. Also, the alkaline component removes
an embrittled layer of the resin material, and the surface-active
agent is adsorbed by the polar groups. During catalyst treatment
prior to electroless plating, a catalyst is adsorbed by the
surface-active agent adsorbed on the polar groups. Therefore, metal
is likely to be bonded with the polar groups during electroless
plating, and the adhesion strength of the resulting
electroless-plating film is improved.
[0008] JP-A-2005-042029 also proposes a resin board having a
resin-metal composite layer, which consists of a resin substrate
and the resin-metal composite layer formed integrally on a surface
of the resin substrate and having fine metal particles uniformly
dispersed in a resin matrix, and a method of manufacturing the
resin board.
[0009] The resin-metal composite layer of the resin board imparts
some characteristics, such as electrical conductivity, wear
resistance, light resistance and flame retardancy, to the resin
board, and the resin-metal composite layer can be made transparent
or translucent. Therefore, the resin board having the resin-metal
composite layer can be used in various applications, such as liquid
crystal displays and electronic circuit boards. According to the
manufacturing method disclosed in JP-A-2005-042029, the resin-metal
composite layer can be easily formed without requiring equipment
like a vacuum tank, and therefore the resin board can be
manufactured in a short time with a reduced number of steps.
[0010] In a typical wiring board, a spacing of 100 .mu.m or larger
is provided between adjacent wires on the board. In a wiring board
of a small-sized high-density component, however, the spacing
between adjacent wires on the board needs to be 100 .mu.m or
smaller.
[0011] In the case where a resin-metal composite layer is formed
using the technology disclosed in JP-A-2005-042029, and wires are
formed with small spacings (of, for example, 100 .mu.n or less) on
the surface of the composite layer by electroless plating, portions
of the resin-metal composite layer located between the wires need
to be removed by etching in a later process step.
[0012] In the meantime, the technology disclosed in
JP-A-2005-042029 has a problem that the adhesion strength of the
plating film is low if the thickness of the resin-metal composite
layer is small, more specifically, is about 20-200 nm. It is thus
necessary to make the thickness of the metal-composite layer
greater than 200 nm. It is, however, to be noted that the plating
film is embedded in the resin after electroless plating. Thus, if a
resin-metal composite layer having a thickness greater than 200 nm
is formed, it is difficult to completely remove the plating film
and resin-metal composite layer between wires even with etching,
causing a problem of insufficient or faulty insulation.
SUMMARY OF THE INVENTION
[0013] The invention has been developed in view of the
above-described situation, and it is therefore an object to improve
the adhesion strength of a plating film even where a resin-metal
composite layer has a small thickness of 10-200 nm, in the
manufacture of a wiring board using a resin board on which the
resin-metal composite layer is formed using the technology
disclosed in JP-A-2005-042029.
[0014] According to one aspect of the invention, a resin board to
be subjected to ozone treatment, which is adapted to be treated
with an ozone solution, is characterized by comprising at least one
of a mixture of a plurality of types of resins having different
degrees of susceptibility to erosion by the ozone solution, and a
resin having, in a molecule, a plurality of types of components
having different degrees of susceptibility to erosion by the ozone
solution.
[0015] The resin board may contain, for example, an aromatic epoxy
resin that has both an aromatic cyanate compound and an epoxy
group.
[0016] According to another aspect of the invention, a wiring board
is characterized by comprising the resin board of the invention, a
resin-metal composite layer which is formed integrally on a surface
of the resin board and in which fine metal particles are uniformly
dispersed in a resin matrix, and a wiring portion consisting of a
plating film formed in a predetermined pattern on the resin-metal
composite layer, and the resin-metal composite layer has a
thickness of 10 to 200 nm.
[0017] According to a further aspect of the invention, a method of
manufacturing a wiring board is characterized by comprising a
preparing step of preparing the resin board of the invention, an
ozone treatment step of treating the resin board with an ozone
solution so as to form a reformed layer having polar groups on a
surface thereof, an adsorption step of bringing the reformed layer
into contact with a metal compound solution so that at least one of
colloidal particles and ions of a catalyst metal are attached to
the polar groups and fine particles of the catalyst metal are
dispersed in the reformed layer, thereby to form a resin-metal
composite layer, and a plating step of performing a plating process
on the resin-metal composite layer in a predetermined pattern so as
to form a wiring portion of the predetermined pattern, wherein
these steps are carried out in the order of description.
[0018] Preferably, the manufacturing method as described above
further includes an etching step of removing an unnecessary portion
of the resin-metal composite layer.
[0019] When the resin board of the present invention is treated
with the ozone solution, the component or components that is/are
likely to be eroded by the ozone solution may dissolve into the
ozone solution, or the cleavage of molecular chains may occur. As a
result, pores or clearances on the order of nanometers are produced
on a surface of or inside the resin board, between portions formed
of the component(s) that is/are likely to be eroded by the ozone
solution and portions formed of a component or components that
is/are less likely or unlikely to be eroded by the ozone solution.
Thus, the strength of adhesion of the resin board to a
vapor-deposited film, a coating, an electroless-plating film, or
the like, which is subsequently formed on the resin board, is
improved owing to the anchoring effect.
[0020] In the adsorption step that precedes the electroless plating
step, the colloidal particles and/or ions of the catalyst metal are
admitted into the pores or clearances formed in the resin board. In
the subsequent plating step, therefore, a plating liquid finds its
way into the pores or clearances, and a plating film is also formed
in the pores or clearances.
[0021] Accordingly, in the wiring board produced using the resin
board of the invention, the adhesion strength of the plating film
is improved due to the anchoring effect even where the resin-metal
composite layer has a small thickness, more specifically, a
thickness of 10 to 200 nm,
[0022] Furthermore, the resin-metal composite layer of the wiring
board of the invention can impart characteristics, such as
electrical conductivity, wear resistance, light resistance and
flame retardancy, to the wiring board, and the resin-metal
composite layer can be made transparent or translucent. Therefore,
the wiring board can be used in various applications, such as
liquid crystal displays and electronic circuit boards.
[0023] According to the manufacturing method of the present
invention, the resin-metal composite layer can be easily formed
without requiring equipment, such as a vacuum tank, and the wiring
board can be manufactured with a reduced number of steps in a
relatively short time. Thus, the wiring board having excellent
characteristics as described above can be manufactured with high
reliability at reduced cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The features, advantages, and technical and industrial
significance of this invention will be better understood by reading
the following detailed description of preferred embodiments of the
invention, when considered in connection with the accompanying
drawings, in which:
[0025] FIG. 1 is a graph showing the adhesion strength of plating
films of printed wiring boards obtained in Examples 1 to 6; and
[0026] FIG. 2 is a graph showing the adhesion strength of plating
films of printed wiring boards obtained in Comparative
Examples.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0027] In the following emdescription and the accompanying
drawings, the present invention will be described in greater
detail.
[0028] The resin board of the invention consists of at least one of
a mixture of two or more types of resins having different degrees
of susceptibility to erosion by an ozone solution, and a resin
having, in a molecule, two or more types of components having
different degrees of susceptibility to erosion by an ozone
solution. As a typical example of the resin, a resin containing an
aromatic cyanate compound having a cyanato-group and an aromatic
epoxy resin having an epoxy group may be used.
[0029] Preferable examples of the aromatic cyanate compound having
a cyanato-group include bisphenol A dicyanate, polyphenol cyanate
(oligo (3-methylene-1,5-phenylenecyanate)), 4,4'-methylenebis
(2,6-dimethyl-phenylcyanate), 4,4'-ethylidenephenyldicyanate,
hexafluorobisphenol A dicyanate, and prepolymers of these compounds
part of which is modified into triazine. Each of the
above-indicated cyanate compounds may be used alone, or two or more
of the cyanate compounds may be used in combination.
[0030] The aromatic epoxy resin having an epoxy group means an
epoxy resin having an epoxy group in a molecule and also having an
aromatic ring structure in a molecule. Preferable examples of the
aromatic epoxy resin having an epoxy group include bisphenol A type
epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy
resin, phenol novolak type epoxy resin, alkylphenol novolak type
epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type
epoxy resin, epoxides of condensation compounds of phenols and
aromatic aldehyde having a phenolic hydroxyl group, naphthalene
type epoxy resin, triglycidyl isocyanurate, and brominated epoxy
resins and phosphorous modified epoxy resins of these compounds.
Each of the above-indicated epoxy resins may be used alone, or two
or more types of these resins may be used in combination.
[0031] An inorganic filler may be added to the resin board of the
invention. The inorganic filler may be selected from, for example,
silica, alumina, barium sulfate, talc, clay, mica powder, aluminum
hydroxide, magnesium hydroxide, calcium carbonate, magnesium
carbonate, magnesium oxide, boron nitride, aluminum borate, barium
titanate, strontium titanate, calcium titanate, magnesium titanate,
bismuth titanate, titanium oxide, barium zirconate, and calcium
zirconate. In particular, silica is preferably used. The average
grain size of the inorganic filler is preferable 5 .mu.m or
smaller. If the average grain size exceeds 5 .mu.m, it may be
difficult to form a fine pattern with stability when forming a
circuit pattern on the resin board. In order to improve the
moisture resistance or enhance the adhesion of the inorganic filler
to the resin matrix, the inorganic filler is preferably
surface-treated with a finishing or coupling agent, such as a
silane coupling agent.
[0032] In addition to the above-indicated components, other
thermosetting resin(s) or thermoplastic resin(s), and additives,
may be used as needed in the resin board of the invention, provided
that they are not detrimental to the effect of the invention. The
thermosetting resin(s) may be selected from, for example, a
monofunctional epoxy resin serving as a diluent, alicyclic
multifunctional epoxy resin, rubber modified epoxy resin, an acid
anhydride compound serving as a curing agent for epoxy resin, block
isocyanate resin, xylene resin, and a polymerizing resin serving as
a radical generating agent. The thermoplastic resin(s) may be
selected from, for example, polyimide resin, polyamide imide resin,
polyether imide resin, polysulfone resin, polyether sulfone resin,
polyphenylene ether resin, polycarbonate resin, polyether ether
ketone resin, and polyether resin. Examples of the additives
include organic fillers, such as silicon powder, nylon powder, and
fluorine powder, thickening agents, such as orben and bentone,
silicone base, fluorine base, and high polymer base antifoaming
agents or leveling agents, imidazole base, thiazole base, triazole
base compounds, and an agent, such as a silane coupling agent, for
improving the adhesiveness.
[0033] The resin board as described above may be used in a
half-cured state in which the resin is not completely cured. To
bring the resin board into the half-cured state, the
above-described resin board is subjected to a half-curing heat
treatment step in which the resin board is heated at 150.degree. C.
for 30 min. With the resin board heated in this manner, reactions
between cyanato-groups and epoxy groups proceed to some extent, to
thus form the oxazoline structure or triazine rings. By placing the
resin board in the half-cured state, the degree of erosion by the
ozone solution may be varied, and the relationship between the
thickness and adhesiveness of the resin-metal composite layer may
be changed to be within a more preferable range. Nonetheless, it is
found that even where the resin board is in a fully cured state, a
certain degree of adhesion strength can be ensured.
[0034] In an ozone treatment step, the resin board is treated with
an ozone solution so that a reformed layer having polar groups on
its surface is formed. The reformed layer has pores or clearances
on the order of nanometers (nm) or smaller, which are formed on a
surface of or within the resin board between a component(s) that
is/are more likely to be eroded by the ozone solution and a
component(s) that is/are less likely to be eroded by the ozone
solution. To treat the resin board with the ozone solution, the
resin board may be immersed in the ozone solution, or the ozone
solution may be applied by spraying to the resin board. It is
preferable to immerse the resin board in the ozone solution because
ozone is less likely to be released from the ozone solution, as
compared with the case where the resin board contacts with the
ozone solution applied by spraying.
[0035] The ozone concentration in the ozone solution has a great
influence on the activation of the resin board surface. While an
effect of the activation is observed when the ozone solution is
about 10 ppm or higher, the effect of the activation remarkably
improves if the ozone solution is 20 ppm or higher, and the
treatment can be accomplished in a more shortened time. Through
oxidation by ozone contained in the ozone solution, polar groups,
such as OH groups, CO.dbd.O groups, COOH groups, are produced in
the reformed layer.
[0036] The ozone solution normally has water as a solvent, but
preferably has an organic or inorganic polar solvent as a solvent.
By using such a solvent, the treatment time can be further
shortened. Examples of the organic polar solvent include alcohols,
such as methanol, ethanol, and isopropyl alcohol, N, N-dimethyl
formamide, N, N-dimethyl acetamide, dimethyl sulfoxide,
N-methylpyrrolidone, hexamethylphosphoramide, organic acids, such
as formic acid and acetic acid, and mixtures of these compounds
with water or an alcohol base solvent. Examples of the inorganic
solvent include inorganic acids, such as nitric acid, hydrochloric
acid, and hydrofluoric acid.
[0037] While the reaction speed increases as the treatment
temperature in the ozone treatment step increases in principle, the
solubility of ozone in the ozone solution decreases as the
temperature increases. To make the ozone concentration in the ozone
solution equal to or hither than 40 ppm at a temperature that
exceeds 40.degree. C., a pressure equal to or higher than the
atmospheric pressure needs to be applied to the treatment
atmosphere, which requires large-sized equipment. The treatment
temperature may be about the room temperature.
[0038] The duration of time that the ozone solution and the resin
board are held in contact with each other in the ozone treatment
step differs depending on the type of the resin, but is preferably
2 to 30 min. If the contact time is less than 2 minutes, the effect
due to the ozone treatment is less likely or unlikely to appear
even if the ozone concentration is 20 ppm or higher. If the contact
time exceeds 30 minutes, the resin board may deteriorate.
[0039] In the ozone treatment step, it is also preferable to
irradiate the resin board with ultraviolet rays while the surface
of the resin board is held in contact with a high-concentration
ozone solution. The ultraviolet rays applied to the resin board
preferably has a wavelength of not greater than 310 nm, more
desirably, a wavelength of not greater than 260 nm, and even more
desirably, a wavelength in a range of about 150 to 200 nm. The
irradiation amount of the ultraviolet rays is desirably 50
mJ/cm.sup.2 or larger. A light source that can apply such
ultraviolet rays to the resin board may be selected from a
low-pressure mercury lamp, high-pressure mercury lamp, excimer
laser, barrier discharge lamp, and a microwave electrodeless
discharge lamp.
[0040] To irradiate the resin board with the ultraviolet rays while
immersing the resin board in the ozone solution, the ultraviolet
rays may be applied from the ultraviolet-ray light source placed in
the ozone solution, or the ultraviolet rays may be applied from
above the liquid surface of the ozone solution. If the container of
the ozone solution is formed of a material, such as transparent
quartz, through which ultraviolet rays can pass, the ultraviolet
rays can be applied from the outside of the container of the ozone
solution.
[0041] After the ozone treatment step, it is desirable to conduct a
C/C treatment step in which the reformed layer is brought into
contact with a cleaner conditioner solution containing at least an
alkali component. The alkali component has a function of making the
surface of the reformed layer soluble in water at the molecular
level, and removes an embrittled layer on the surface of the
reformed layer so that an increased number of polar groups appear
on the surface, whereby an increased number of fine particles of
metal can be formed in the later adsorption step. The alkali
component may be selected from those that can remove the embrittled
layer by dissolving the surface of the reformed layer at the
molecular level, and, more specifically, may be selected from
sodium hydroxide, potassium hydroxide, and lithium hydroxide.
[0042] It is also desirable that the cleaner conditioner solution
further contains a surface-active agent or surfactant. It is
considered that the surface-active agent has hydrophobic groups
that are likely to be attached to the polar groups present on the
reformed layer, and can be thus adsorbed by a large portion of the
polar groups. Accordingly, an increased number of metal particles
can be formed in the later adsorption step.
[0043] The surface-active agent may be selected from those having
hydrophobic groups that are likely to be attached to one or more
types of polar groups selected from COOH, C.dbd.O and C--OH.
Examples of the surface-active agent include sodium lauryl sulfate,
potassium lauryl sulfate, sodium stearyl sulfate, potassium stearyl
sulfate, and polyoxyethylene dodecyl ether.
[0044] While a polar solvent, a typical example of which is water,
is desirably used as a solvent of the cleaner conditioner solution
containing the surface-active agent and the alkali component, an
alcohol base solvent or a solvent containing a mixture of water and
alcohol may also be used in some cases. To bring the reformed layer
into contact with the cleaner conditioner, the resin board may be
immersed in the cleaner conditioner solution, or a coating of the
cleaner conditioner solution may be applied to the reformed
layer.
[0045] The concentration of the surface-active agent in the cleaner
conditioner solution is preferably controlled to be within a range
of 0.01 to 10 g/L. If the concentration of the surface-active agent
is lower than 0.01 g/L, the amount of metal particles to be
produced is reduced. If the concentration of the surface-active
agent is higher than 10 g/L, the reformed layer and the
surface-active agent are brought into an association state, and an
excess surface-active agent remains as an impurity, whereby the
amount of metal particles to be produced is reduced. In this case,
the resin board may be washed with water, so that the excess
surface-active agent may be removed.
[0046] The concentration of the alkali component in the cleaner
conditioner is desirably 10 or greater in pH. Although a reasonable
effect can be obtained even if the pH value is 10 or less, it takes
time for the alkali component to remove the embrittled layer on the
surface of the reformed layer. If the pH value is 10 or greater,
the process of removing the embrittled layer is accomplished in a
shorter time.
[0047] While there is no limitation to the duration of time that
the cleaner conditioner solution and the reformed layer are held in
contact with each other, it is preferable to hold the cleaner
condition and the reformed layer in contact with each other at
10.degree. C. for 1 min. or longer. If the contact time is too
short, the amount of the surface-active agent attached to the polar
groups may be insufficient. If the contact time is too long,
however, the cleaner conditioner solution may dissolve a layer on
which the polar groups appear, as well as the embrittled layer.
Thus, about 1 to 10 minutes is a sufficient or adequate duration of
time for contact between the cleaner condition solution and the
reformed layer. With regard to the temperature at which the
conditioner solution and the reformed layer are held in contact
with each other, a higher temperature is more desirable, and the
contact time can be shortened as the temperature is higher. It is,
however, to be noted that about 10 to 70.degree. C. is a sufficient
or adequate temperature range.
[0048] In the C/C treatment step, the surface-active agent may be
adsorbed by the reformed layer after the reformed layer is treated
with a cleaner conditioner solution containing only the alkali
component. In this case, however, an embrittled layer may be formed
again by the time that the surface-active agent is adsorbed by the
reformed layer. It is thus desirable to perform the C/C treatment
while both the surface-active agent and the alkali component are
present in the cleaner conditioner solution.
[0049] While it is preferable that the C/C treatment step is
carried out after the ozone treatment step, the ozone treatment
step and the C/C treatment step can be carried out at the same time
as the case may be. In this case, a mixture of the ozone solution
and the cleaner conditioner solution is prepared, and the resin
board is immersed in the mixed solution, or the mixed solution is
applied by spraying to the resin board. In this case, the reaction
between ozone and the resin board becomes a rate-determining step,
and therefore the process time is determined depending on the ozone
concentration in the mixed solution. The C/C treatment step may be
followed by a step of washing the resin board with water and
removing the alkali component.
[0050] The adsorption step is a step of bringing the reformed layer
into contact with a solution of a metal compound containing
colloidal particles and/or ions of a catalyst metal, so that the
metal compound solution is admitted into the reformed layer so as
to form a resin-metal composite layer. Since polar groups are
formed on the reformed layer through cleavage of molecular chains
of the resin, for example, the colloidal particles and/or ions of
the catalyst metal are attached to the polar groups, whereby the
resin-metal composite layer is formed.
[0051] While alkaline solutions containing metal complex ions and
acidic solutions containing metal colloidal particles are known and
either of these solutions may be used as the metal compound
solution, it is preferable to use alkaline solutions having metal
particles of a smaller size, because the small-sized metal
particles are more likely to be admitted into and dispersed in the
reformed layer, thus assuring improved adhesion strength of the
resulting plating film to the reformed layer. The catalyst metal,
which serves as a catalyst when electroless plating is conducted,
is typically Pd, but Ag, or the like, may be used as the catalyst
metal.
[0052] To bring the reformed layer into contact with the metal
compound solution, the metal compound solution may be applied by
spraying to the surface of the resin board on which the reformed
layer is formed, or the resin board may be immersed in the metal
compound solution. As a result, the metal compound solution spreads
from the surface of the reformed layer and penetrates into the
reformed layer, and the ions or colloidal particles of the metal
compound are attached to the polar groups of the reformed layer, so
that the metal compound is converted through reduction into fine
metal particles on the order of nanometers, to thus form the
resin-metal composite layer.
[0053] The thickness of the resin-metal composite layer is
preferably in a range of 10 to 200 nm. If the thickness is less
than 10 nm, it is difficult for the resulting resin board to
exhibit electrical conductivity. If the thickness is greater than
200 nm, it is difficult to remove portions of the resin-metal
composite layer located between wires during etching as described
later, causing a problem of insufficient or faulty insulation. If
the thickness of the resin-metal composite layer is controlled to
be within the range of 10 to 200 nm, the unnecessary portions of
the resin-metal composite layer can be easily removed by etching,
and a fine wiring pattern having L/S=10/10 .mu.m or less can be
formed.
[0054] In the subsequent plating step, a wiring portion is formed
by performing a plating process on the resin-metal composite layer
in a predetermined pattern. To form the predetermined pattern, a
resist may be initially formed, and then a plating process may be
conducted. The wiring portion may be plated with Cu or Ni. Where
the wiring portion is plated with Ni, for example, it is further
plated with Cu. The heat treatment step as described above may be
carried out after the plating step.
[0055] To form the wiring portion, a resist pattern may be
preliminarily formed on the resin board, and a resin-metal
composite layer may be formed only on the wiring portion. In this
case, a wiring board can be produced with the resist left thereon.
Another method has the following steps of: forming a resin-metal
composite layer over the entire area of the surface of the resin
board, conducting electroless plating, forming a certain pattern
with a resist, conducting electroplating, and removing the resist
and removing the electroless plating other than the wiring portion.
A still another method has the following steps of: forming a
resin-metal composite layer over the entire area of the surface of
the resin board, conducting electroless plating and electroplating,
then forming a certain pattern with a resist, removing the plating
of a portion on which no resist exists, and then removing the
resist. In these cases, since the resin-metal composite layer of
the invention has a small thickness, the resin-metal composite
layer located in an unnecessary portion of the pattern can be
easily removed by etching, and insufficient or faulty insulation
can be avoided in advance.
[0056] There is no limitation to the conditions on the plating
process, and the plating process may be performed in a manner
similar to those of conventional plating processes. For etching,
selected portions of the resin-metal composite layer may be
physically removed by, for example, polishing, or may be subjected
to acid etching, or may be dissolved by a reverse electrolytic
method.
[0057] After the plating step, a heat treatment step is desirably
carried out in which the resin board is heated at 100 to
210.degree. C. As a result, a curing reaction proceeds in the
interior of the resin board, and the particles of catalyst metal
are firmly retained in the resin matrix, thus assuring further
improved adhesion strength of the plating film.
[0058] In the following, the present invention will be more
specifically described with reference to some examples of the
invention and comparative examples.
EXAMPLE 1
[0059] (1) Half-curing Heat Treatment Step: A resin board
consisting of aromatic cyanate compound ("BA230S75" manufactured by
LONZA Japan Ltd.), resin ("828EL" manufactured by Japan Epoxy
Resins Co., Ltd.) containing aromatic epoxy resin, spherical silica
and methyl ethyl ketone as a solvent, was prepared and heated at
150.degree. C. for 30 min., into a half-cured state.
[0060] (2) Ozone Treatment Step: The resin board in the half-cured
state was subjected to ozone treatment in which the board was
immersed in an ozone solution containing 40 PPM of ozone, and held
in the ozone solution at room temperature for 4 min. As a result of
analyses of the surface of the resin board before and after the
ozone treatment step with FT-IR (Fourier Transform Infrared
Spectrometer), absorption peaks derived from carbonyl groups
(--C.dbd.O) and hydroxyl groups (--OH) were observed on the surface
of the resin board after the ozone treatment step.
[0061] (3) C/C Treatment Step: The resin board obtained after the
ozone treatment step was immersed for 5 min. in a cleaner
conditioner solution ("OPC-370 CONDICLEAN" manufactured by OKUNO
CHEMICAL INDUSTRIES CO., LTD.) heated to 65.degree. C.
[0062] (4) Catalyst Adsorption Step: After the resin board
resulting from the C/C treatment step was washed with water and
dried, the resin board was immersed at 40.degree. C. for 5 min. in
an alkaline catalyst ("OPC-50 INDUCER A and C" manufactured by
OKUNO CHEMICAL INDUSTRIES CO., LTD.) containing Pd complex ions,
and then immersed at room temperature for 6 min. in a Pd reducing
liquid ("OPC-150 CRYSTER MU" manufactured by OKUNO CHEMICAL
INDUSTRIES CO., LTD.).
[0063] As a result of analysis of a section of the obtained wiring
board with TEM, it was found that Pd was concentratedly distributed
in a range from the surface to a depth of 70 nm, and it was
confirmed that a resin-metal composite layer having a thickness of
70 nm was formed.
[0064] (5) Electroless Plating Step: The board obtained in the
manner as described above was immersed in a Cu chemical plating
bath kept at 32.degree. C., and a Cu plating film was deposited on
the board for 20 min. The thickness of the deposited Cu plating
film was 0.5 .mu.m.
[0065] (6) Heat Treatment Step: The board thus obtained was heated
at 105.degree. C. for 30 min., and then heated at 150.degree. C.
for 30 min.
[0066] (7) Pattern Forming Step: Subsequently, a photoresist was
applied to the board, and a pattern was formed through exposure and
development processes.
[0067] (8) Electroplating Step: Subsequently, current was applied
at a current density of 3 A/dm.sup.2 to the board for 45 min. in a
copper plating path, so that a Cu plating film having a thickness
of 25 .mu.m was further formed on the wiring pattern. Thereafter,
the photoresist was removed by a chemical agent, and the board was
heated at 180.degree. C. for 120 min. so as to be fully cured, to
provide a printed wiring board. Thereafter, unnecessary chemical Cu
plating portions located between wires were removed using an
etching liquid. On the printed wiring board was formed a fine
wiring pattern having L/S=10/10 .mu.m.
EXAMPLE 2-EXAMPLE 6
[0068] Printed wiring boards of Examples 2 to 6 were obtained in
substantially the same manner as that of Example 1, except that the
duration of time that the board was immersed in the ozone solution
in the ozone treatment step was 8 min., 12 min., 16 min., 20 min.
and 24 min., respectively.
Comparative Examples
[0069] Printed wiring boards of Comparative Examples were obtained
in substantially the same manner as those of Examples 1 to 6,
except that a resin board formed from epoxy resin ("ABF-GX13"
manufactured by AJINOMOTO CO., INC.) was used as the resin
board.
[0070] Test and Evaluation
[0071] With regard to each of the printed wiring boards of Examples
1 to 6 and Comparative Examples, the adhesion strength of the
plating film was evaluated by measuring the peel strength defined
by JISH8504. The results of the measurements are shown in FIG. 1
and FIG. 2.
[0072] It is apparent from FIGS. 1 and 2 that the plating films of
the printed wiring boards of Examples 1 to 6 according to the
invention have higher adhesion strength than those of Comparative
Examples, owing to the effect of the use of the resin board formed
from the resin containing the aromatic cyanate compound and the
aromatic epoxy resin having the epoxy group.
[0073] It is understood from comparisons of Examples 1 to 6 that
the adhesion strength improves as the ozone treatment time
increases up to 12 min. It is found, from another analysis, that
the thickness of the resin-metal composite layer increases as the
ozone treatment time increases. Thus, it may be considered that the
adhesion strength is improved because of the increase of the
thickness of the resin-metal composite layer.
[0074] It is also recognized from FIG. 1 that the adhesion strength
gradually decreases as the ozone treatment time further increases
to be equal to or longer than 16 min. The reduction in the adhesion
strength is caused by a cohesive failure of the resin itself due to
the progression of degradation of the resin board during the ozone
treatment, but not caused by peeling at the interface between the
plating film and the resin board.
[0075] According to the method of producing the wiring boards of
Examples 1 to 6, the plating film has an adequate adhesion strength
from a practical standpoint, even if the thickness of the
resin-metal composite layer is equal to or less than 200 nm.
Accordingly, unnecessary portions of the resin-metal composite
layer located between wires can be easily removed by etching, and a
fine wiring pattern can be formed without causing a problem of
insufficient or faulty insulation.
[0076] Since the ozone treatment is employed, the surface roughness
measured at the wiring portion of the wiring board of the invention
is 0.05 .mu.m in Ra value, and 1.0 .mu.m in Rz value. Thus, the
wiring portion of the wiring board of the invention has high
smoothness, and exhibits excellent high-frequency
characteristics.
* * * * *