U.S. patent application number 15/818937 was filed with the patent office on 2018-06-28 for method for electroless plating.
The applicant listed for this patent is Rohm and Haas Electronic Materials LLC. Invention is credited to Yoshiyuki Hakiri.
Application Number | 20180179634 15/818937 |
Document ID | / |
Family ID | 60811940 |
Filed Date | 2018-06-28 |
United States Patent
Application |
20180179634 |
Kind Code |
A1 |
Hakiri; Yoshiyuki |
June 28, 2018 |
METHOD FOR ELECTROLESS PLATING
Abstract
To provide a conditioner having less foaming property and having
adhesion higher than the conventional conditioner using a cationic
polymer or the like and, and an electroless plating method using
the same. A method of the present invention for performing an
electroless plating including the steps of: (a) putting the
substrate in contact with a composition containing a compound
represented by the following general formula (1)
H.sub.2N--R.sub.1--NH--R.sub.2--NH.sub.2 (1) wherein, R.sub.1 and
R.sub.2 are each independently an alkylene group having 3 to 10
carbon atoms; (b) putting the substrate in contact with a catalyst
composition; and (c) putting the substrate in contact with an
electroless plating composition.
Inventors: |
Hakiri; Yoshiyuki;
(Niigata-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rohm and Haas Electronic Materials LLC |
Marlborough |
MA |
US |
|
|
Family ID: |
60811940 |
Appl. No.: |
15/818937 |
Filed: |
November 21, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 18/2086 20130101;
C23C 18/18 20130101; C23C 18/38 20130101; C23C 18/1653
20130101 |
International
Class: |
C23C 18/38 20060101
C23C018/38; C23C 18/18 20060101 C23C018/18 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2016 |
JP |
2016-250038 |
Claims
1. A method for performing an electroless plating on a substrate
comprising the steps of: (a) putting the substrate in contact with
a composition containing a compound represented by the following
general formula (1) H.sub.2N--R.sub.1--NH--R.sub.2--NH.sub.2 (1)
wherein, R.sub.1 and R.sub.2 are each independently an alkylene
group having 3 to 10 carbon atoms; (b) putting the substrate in
contact with a catalyst composition; and (c) putting the substrate
in contact with an electroless plating composition.
2. The method according to claim 1, wherein the content of the
compound, represented by general formula (1), in the composition is
from 0.1 to 10 g/L.
3. The method according to claim 1 or 2, wherein the electroless
plating is electroless copper plating.
4. A substrate having a metal film on at least a part of its
surface obtained by the method according to claim 1.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for electroless
metal plating on a resin substrate, particularly a printed wiring
board, and more particularly relates to a method of forming a metal
film having high adhesion on the surface of a resin substrate with
a pretreatment solution containing a specific compound.
BACKGROUND OF THE INVENTION
[0002] Electrical connection between layers of a printed wiring
board is generally performed via very small holes known as through
holes. As a method of forming a conductive film on the surface of
the printed wiring board and in the inner wall surface of these
through holes, a method of treating with a pretreatment solution
(also referred to as a conditioner) containing a cationic polymer
and a surfactant, applying a catalyst containing palladium and the
like, and then forming a metal film by an electroless plating
method is generally used.
[0003] In order to improve the adhesion between a resin substrate
and a conductive film, generally prior to conditioner treatment, a
resin-swelling process using a treatment solution primarily
containing solvent is performed, then a roughening process using a
treatment solution primarily containing a permanganate is
performed, and then a series of de-smear/roughening processes that
remove the manganese by a neutralization process is performed.
De-smear/roughening processes form fine unevenness on the resin
surface, thereby improving adhesion between the resin substrate and
the conductive film by an anchoring effect.
[0004] However, with a method that provides adhesion primarily by
an anchoring effect, if the degree of roughness of the resin
substrate surface is reduced, the adhesion between the substrate
and the metal film will be lowered, and obtaining a plating film
with high adhesion will be difficult. Accordingly, there has been a
demand for a conditioner having high adhesion even on the surface
of resin substrate having a low degree of roughness instead of a
conventional conditioner, and an electroless plating method using
this conditioner. Further, depending on the compound added to the
conditioner, bubbles may be generated on the surface of the liquid;
therefore, a conditioner free from such foaming properties has been
required.
[0005] Japanese Laid-open Patent Publication no. 2006-77289
discloses a pretreatment solution for electroless plating
containing a compound having at least two amino groups in one
molecule (specifically, a vinylamine (co)polymer or an allylamine
(co)polymer). Further, Japanese Laid-open Patent Publication no.
2010-106337 discloses a method of forming a metal film having high
adhesion by further adding ammonium hydrogen difluoride to
conditioner containing a cationic polymer and a nonionic
surfactant.
SUMMARY OF THE INVENTION
[0006] Accordingly, it is an object of the present invention to
provide a conditioner having less foaming property and having
adhesion higher than the conventional conditioner using a cationic
polymer or the like and, and an electroless plating method using
the same.
[0007] The present inventor conducted intensive studies and found
that the addition of a triamine compound having a specific alkylene
chain length to the conditioner instead of cationic polymer can
produce a conditioner having higher adhesion and less foaming
property than the cationic polymer. The present invention has been
accomplished based on these findings.
[0008] In other words, the present invention pertains to a method
for performing electroless plating on a substrate comprising the
steps of:
[0009] (a) putting the substrate in contact with a composition
containing a compound represented by the following general formula
(1):
Chemical Formula 1:
H.sub.2N--R.sub.1--NH--R.sub.2--NH.sub.2 (1)
wherein, R.sub.1 and R.sub.2 are each independently an alkylene
group having 3 to 10 carbon atoms;
[0010] (b) contacting the substrate with a catalyst composition;
and
[0011] (c) contacting the substrate with an electroless plating
composition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a SEM photograph (magnification: 2000 times)
showing an inner wall surface of the microvia hole subjected to
copper plating in Example 1.
[0013] FIG. 2 is a SEM photograph (magnification: 2000 times)
showing an inner wall surface of the microvia hole subjected to
copper plating in Example 2.
[0014] FIG. 3 is a SEM photograph (magnification: 2000 times)
showing an inner wall surface of the microvia hole subjected to
copper plating in Comparative Example 1.
[0015] FIG. 4 is a SEM photograph (magnification: 2000 times)
showing an inner wall surface of the microvia hole subjected to
copper plating in Comparative Example 2.
[0016] FIG. 5 is a SEM photograph (magnification: 2000 times)
showing an inner wall surface of the microvia hole subjected to
copper plating in Comparative Example 3.
[0017] FIG. 6 is a SEM photograph (magnification: 2000 times)
showing an inner wall surface of the microvia hole subjected to
copper plating in Comparative Example 4.
[0018] FIG. 7 is a SEM photograph (magnification: 2000 times)
showing an inner wall surface of the microvia hole subjected to
copper plating in Comparative Example 5.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The abbreviations used throughout this specification have
the following meanings unless otherwise designated.
g=gram; mg=milligram; .degree. C.=degree Centigrade; min=minute;
m=meter; cm=centimeter; L=liter; mL=milliliter; and N=Newton. The
range of all values includes the boundary values, and may be
combined in any order. In addition, percent (%) means weight %
unless otherwise stated in this specification.
[0020] In the method of the present invention, a composition
containing a compound represented by the following general formula
(1):
H.sub.2N--R.sub.1--NH--R.sub.2--NH.sub.2 (1)
is used. The composition can also be called a conditioner. In
general formula (1), R.sub.1 and R.sub.2 are each independently an
alkylene group having 3 to 10 carbon atoms. The alkylene group may
be straight chain or branched chain, but straight chain alkylene
group is preferred in the present invention. The alkylene chain
preferably has from 3 to 8 carbon atoms, more preferably from 3 to
6 carbon atoms. Specific compounds of general formula (1) include
dipropylenetriamine, bis (butylene) triamine, bis (hexamethylene)
triamine, and the like.
[0021] The present inventor has found that the adhesion is
characteristically improved by using a triamine compound having an
alkylene chain having 3 to 10 carbon atoms. Although this is not
bound by theory, it is believed that triamines having an alkylene
chain having 3 to 10 carbon atoms have excellent
hydrophilic-lipophilic balance, are easily adsorbed on a resin
substrate and at the same time, are easy to bond with the catalyst
in the subsequent catalyst application step. Thus, it is possible
to form a metal film with high adhesion. Further, although the
commonly used cationic polymer has a high adhesion to a resin, it
is believed to be easily over-adsorbed because of its large
molecular weight. Thus, a relatively large amount of cationic
polymer remains between the resin surface and the metal film,
thereby deteriorating the adhesion. The content of the compound,
represented by general formula (1), in the conditioner is
preferably 0.1 to 10 g/L, more preferably 1 to 8 g/L, and most
preferably 2 to 5 g/L. One of the characteristics of the
conditioner used in the present invention is that the metal film
having high adhesion can be formed even if it does not contain a
surfactant. The conditioner containing cationic polymer usually
contains a surfactant to increase penetrability of conditioner
ingredients into through holes and blind vias, and to impart
uniform conditioning action to glass and resin. However, depending
on the use condition, the conditioner containing surfactant may
produce bubbles on the liquid surface, thereby deteriorating the
workability. By using the compound represented by general formula
(1), the conditioner of the present invention exhibits higher
adhesion than the conventional conditioner even without containing
a surfactant.
[0022] The conditioner used in the present invention may contain
any component in addition to the compound represented by general
formula (1). For example, it may contain a chelating agent as an
optional component. The chelating agent plays a role in extending
the life of the conditioner by forming a chelate compound with the
metal ion when the metal ion dissolves into the conditioner.
Examples of preferred chelating agents include ethanolamine,
triethanolamine, ethylenediaminetetraacetic acid (EDTA),
ethylenediamine n, n'disuccinic acid (EDDS), and iminodiacetic acid
(IDA). The amount of chelating agent added is preferably 0.1 to 0.2
mol/L relative to the conditioner.
[0023] If necessary, the conditioner used in the present invention
can also contain additives such as pH-adjusting agents and the
like, as additional optional components. The conditioner used in
the present invention preferably contains water as a solvent. Any
water can be used such as deionized water, tap water, and the like.
Further, a solvent such as alcohol may be mixed with water and
used.
[0024] The resin substrate can be a printed wiring board, and the
printed wiring board can have glass cloth/resin. The resin
substrate may have small holes known as through holes or small
non-through holes known as blind vias. Furthermore, with a
high-density printed wiring board represented by high-performance
semiconductor package boards, a functional insulative resin
material board is used as the resin substrate. With the method of
the present invention, plating can be uniformly deposited not only
on the surface of the printed wiring board but also on the inner
wall surface of holes if holes such as through holes or the like
exist in the substrate.
[0025] Examples of the resin substrate include substrates made from
epoxy resin, cyanate resin, bismaleimide triazine resin, polyamide,
ABS, polyphenyl ether, polysulfone, fluorine resin, polycarbonate,
polyacetal, polyphenylene oxide, polypropylene, and liquid crystal
polymer, and the like.
[0026] Any method that brings the conditioner into contact with the
resin substrate is used. For example, the treatment can be
performed by immersing a substrate in the conditioner after being
subjected to so-called de-smearing or roughening process if
necessary, or spraying the conditioner on the substrate. At the
time of immersion, the substrate may be immersed in the conditioner
at a temperature of 30 to 60.degree. C., preferably 40 to
50.degree. C., for 1 to 10 minutes, preferably 2 to 6 minutes.
[0027] After bringing the conditioner into contact with the resin
substrate, a catalyst application step is performed to bring the
resin substrate into contact with the catalyst composition to
adsorb the catalyst on the surface of the resin substrate. However,
before bringing the resin substrate into contact with the catalyst
composition, a step of immersing the resin substrate (also referred
to as microetch) in an aqueous solution such as sodium persulfate,
ammonium persulfate, sulfuric acid and hydrogen peroxide mixed
solution and a step of washing the surface of the resin substrate
with an acid such as sulfuric acid can also be optionally
performed. The conditioner used in the present invention can remain
on the surface of the resin substrate and on the inner wall surface
of the holes even after performing such steps, and a sufficient
amount of catalyst can be adsorbed on the surface of the resin
substrate and the inner wall surface of the holes in the subsequent
catalyst application step. The microetch step can usually be
performed using an aqueous solution at a temperature of 20 to
35.degree. C. for 0.5 to 10 minutes, preferably 1 to 3 minutes, and
the acid washing step can usually be performed at a temperature of
20 to 35.degree. C., preferably 25 to 30.degree. C., for 0.5 to 5
minutes, preferably 1 to 3 minutes.
[0028] A conventionally known catalyst composition may be used.
Examples of the catalyst composition include a palladium-tin
colloid solution, a composition containing metal ions such as
palladium, platinum, silver or copper, and the like. For example,
CIRCUPOSIT.TM. ADV 8530 Catalyst and CIRCUPOSIT.TM. 6530 Catalyst
(both manufactured by Rohm and Haas Electronic Materials Co., Ltd.)
can be used. In the case of using CIRCUPOSIT.TM. ADV 8530 catalyst
as a catalyst composition, for example, the resin substrate is
immersed in the catalyst composition at a temperature of 35 to
60.degree. C., preferably 40 to 50.degree. C., for 1 to 10 minutes,
preferably 3 to 5 minutes, and then a deduction treatment of
palladium ions can be performed with CIRCUPOSIT.TM. 6540
reducer.
[0029] A conventionally known electroless plating composition may
be used. For example, an electroless plating composition containing
metals such as copper, nickel, cobalt, iron or the like or a
mixture thereof can be used. Electroless copper plating is usually
preferred when using a printed wiring board as the resin substrate.
For example, CIRCUPOSIT.TM. 6550 electroless copper, CIRCUPOSIT.TM.
ADV 8550 electroless copper, and CIRCUPOSIT.TM. 328 copper mix
concentrate (all manufactured by Rohm and Haas Electronic Materials
Co., Ltd.) can be used.
[0030] Hereinafter, the present invention will be described in more
detail with reference to examples, but the present invention is not
limited to these examples.
[0031] In the following Examples and Comparative Examples, plating
deposition on the inner wall surface of the through holes was
evaluated by SEM observation. Adhesion strength was also evaluated
according to the following procedure: The surface of the substrate
subjected to the electroless plating was washed with deionized
water for 3 minutes at room temperature and heated and dried
(120.degree. C., 30 minutes). Then, the surface of the material to
be plated was immersed in an acid cleaner (liquid temperature of
35.degree. C., 2 minutes) containing sulfuric acid. Thereafter,
acid washing was performed, and electrolytic copper plating
treatment was performed with electrolytic copper plating MICRO
FILL.TM. EVF. The surface of the resultant plated material was
washed with deionized water at room temperature for 3 minutes, and
then heated and dried (180.degree. C., 60 minutes). The resulting
copper plating film had a film thickness of 20 to 25 .mu.m, and
this plating film was cut in 1-cm widths. The adhesion strength
(peel strength) between the substrate resin and the plating film
was measured using an INSTRON.TM. 5564 tester at a tensile speed of
50 mm/minute and at an angle of 90.degree. in accordance with the
JIS C5012 printed wiring board test method.
Examples 1 to 6 and Comparative Examples 1 to 5
[0032] The following resin substrates 1 to 3 were used as the resin
substrate of the material to be treated.
Resin Substrates
[0033] Resin substrate 1: Ra: 100 (nm)
[0034] Resin substrate 2: Ra: 250 (nm)
[0035] Epoxy resin substrate 3: Ra: 80 (nm)
Note: Ra represents an arithmetic average roughness.
[0036] Each compound shown in Table 1 or Table 2 was added to
deionized water in the amounts shown in Table 1 or Table 2 to
prepare a conditioner. The resin substrates 1 to 3 were subjected
to a de-smearing/roughening process using a permanganate salt, and
then immersed in the conditioner at a temperature of 45.degree. C.
for 5 minutes. Next, soft etching was performed using sodium
persulfate. After washing with acid, a catalyst imparting treatment
using an alkaline palladium catalyst (CIRCUPOSIT.TM. ADV 8530
Catalyst) and a reduction treatment using a CIRCUPOSIT.TM. 6540
Reducer were performed. Then, electroless copper plating was
performed by immersing in an electroless copper plating solution
(CIRCUPOSIT.TM. ADV 8550 electroless copper) at a temperature of
32.degree. C. for 20 minutes. Between each treatment, washing with
deionized water was performed at room temperature for 2 minutes.
The state of plating deposition in the micro via hole after
electroless copper plating was observed with SEM. Next,
electrolytic copper plating treatment was performed and then
adhesion testing was performed. The evaluation results are also
shown in Table 1 or Table 2.
[0037] In Examples 1 and 2, dipropylenetriamine and
bis(hexamethylene) triamine were added, respectively, as the
compounds (conditioner components) of the conditioner. In
Comparative Examples 1 and 2, diethylenetriamine and
monoethanolamine were used instead of the compounds of Examples,
and in Comparative Example 3, the test was carried out only with
deionized water without adding any conditioning components. In
Comparative Examples 4 and 5, commercial conditioners 231 and 3328
were used, respectively, (both manufactured by Rohm and Haas
Electronic Materials, containing cationic polymer, chelating agent,
nonionic surfactant, and water, pH: about 10 and 1)
TABLE-US-00001 TABLE 1 Example 1 2 Compound Dipropylenetriamine
Bis(hexamethylene) triamine Addition amount (g) 5.0 2.0 Copper
deposition state Good (FIG. 1) Good (FIG. 2) Peel strength Resin 1
0.506 0.520 (kN/m) Resin 2 0.338 0.410 Resin 3 0.272 0.284
Comprehensive Good Good evaluation (Good copper (Good copper
deposition with deposition with high peel strength) high peel
strength)
TABLE-US-00002 TABLE 2 Comparative Example 1 2 3 Compound
Diethylenetriamine Monoethanolamine -- Addition 5.0 2.0 amount (g)
Copper Partial deposition Almost no Almost no deposition (FIG. 3)
deposition deposition state (FIG. 4) (FIG. 5) Peel Resin 0.528
0.568 Not strength 1 performed (kN/m) due to poor deposition Resin
0.376 0.413 Not 2 performed due to poor deposition Resin 0.275
0.289 Not 3 performed due to poor deposition Comprehensive Good
peel Good peel Poor evaluation strength but strength but poor
copper poor copper plating plating deposition deposition
TABLE-US-00003 TABLE 3 Comparative Example 4 5 Commercial 231 3328
conditioner Copper deposition Good (FIG. 6) Good (FIG. 7) state
Peel Resin 1 0.463 0.493 strength Resin 2 0.345 0.366 (kN/m) Resin
3 0.176 0.125 Comprehensive Good copper Good copper evaluation
deposition but low deposition but low adhesion strength adhesion
strength (peel strength) (peel strength)
* * * * *