Note: Descriptions are shown in the official language in which they were submitted.
ZOlZ633
"POLYIMIDE COMPOSITION AND PREPREG AND LAMINATE THEREOF"
SPECIFICATION
BACKGROUND OF THE INVENTION
1. Field of the Invention:
This invention relates to a polyimide composition, a
prepreg formed with the polyimide composition and a
polyimide laminate formed with the prepregs laminated and
set.
The polyimide laminate of the kind referred to is
effectively utilizable in manufacturing printed-wiring
boards, in particular, highly multilayered wiring
substrate and so on for high-density mounting use.
2. Description of the Related Art:
The polyimide laminate has been increasingly utilized
in recent years in manufacturing the multilayered wiring
substrate, because of such characteristics that polyimide
allows wiring conductor to be finely dimensioned and such
high precision work as fine perforation and the like made
possible for adaption of the wiring substrate to the
high-density mounting, that the polyimide laminate shows
! only a small thermal expansion coefficient in the
direction of thickness in laminated state of the prepregs
and is thus high in the reliability of electric conduction
attainable by means of through-hole metal plating, that
polyimide involves no smear generation during drilling
step, that high hardness and adhesion with respect to
conducting member at higher temperatures render the
mountability excellent, that the laminate is durable in
f
3 ~
consecutive use under such high -temperatures as around
200~C, and so on. The multilayered wiring substrate
employing polyimide has been disclosed in, for example,
Japanese Patent Application Laid-Open Publication No.
59-20659 or 61-40322.
It has been generally demanded, on the other hand,
that the multilayered wiring~ substrate is effectively
lowered in the dielectric constant to allow a high speed
signal propogation to be enabled, and a measure for
providing a substrate of the kind referred to which is
higher reliable in the through-hole conduction and low in
dielectric c~nstant has been disclosed.
Such known composition as well as the multilayered
wiring substrate formed by the composition as has been
referred to are, however, still defective in attaining
sufficiently highly reliable conduction for being fully
satisfactory particularly in respect of the through-hole
plating made in the substrate, and this deficiency is
required to be removed for realizing the wiring substrate
adapted to the high-density mounting.
SUMMARY OF THE INVENTION
A primary object of the present invention is,
therefore, to provide a polyimide composition capable of
improving the filling ability of polyimide with respect to
the base material, realizing the high-density mounting
with a highly reliable conduction assured in preparing the
polyimide laminate and forming the through-holes in the
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20iZ~33
~. . .".,
laminate, and elevating the safety of electronic devices
and equipments including the polyimide laminate provided
with a sufficient nonflammability.
According to the present invention, this object is
attained by means of a polyimide composition comprising
triallyl isocyanurates added in a range of 10 to 200 parts
by weight to 100 parts by weight of polyimide.
Other objects and advantages of the present invention
shall be made clear in following description of the
invention detailed with reference to preferred
embodiments.
While the present invention shall be described with
reference to the preferred embodiments, it should be
appreciated that the intention is not to limit the
invention only to the embodiments described but rather to
include all alterations, modifications and equivalent
arrangements possible within the scope of appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Polyimide employed in the present invention can be
obtained by bringing unsaturated bis-imides into reaction
with diamines, in which case it is preferable to have at
least one of alkyl group and alkylene group except
methylene group contained more that llwt.% in polyimide.
This is for the reason that, when alkyl group or alkylene
group except methylene group has a chemical structure of
less than llwt.% within resin molecules, the dielectric
constant of polyimide cannot be lowered by such group
sufficiently as a material for the multilayered wiring
-- 4
2012633
substrate.
For unsaturated bis-imide, such ones as represented by
following formula (I) may be employed and, for diamine,
such ones as represented by following formula (II) may be
employed:
CO CO
~ ~ / \
D N - A - N D ..... (I)
CO CO
in which formula (I) "D" denotes bivalent group including
double binding between carbon-carbon, and "A" denotes
bivalent group containing at least two carbon atoms;
H2N - B - NH2 ............................................. (II)
in which formula (II) "B" denotes bivalent group having
less than 30 carbon atoms.
"A" in the formula (I) and "B" in the formula (II) may
either be identical to or different from each other, and
may be either one of linear chain or branched alkylene
group having less than 13 carbon atoms, cyclic alkylene
group having in the ring 5 or 6 carbon atoms,
heterogeneous cyclic group including at least one of O, N
and S atoms, or phenylene or polycyclic aromatic group.
These groups should preferably be the ones having a
substituent group which causes no unnecessary secondary
reaction under such reaction conditions as a reaction
temperature in a range of 70 to 170~C and a reaction time
in a range of 30 to 350 minutes.
Further, "A" and "B" in the formulas (I) and (II) may
be any of various phenylene groups or such alicyclic
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groups as the ones bound directly or by bivalent atoms or
by following molecules, for which groups there may be
employed oxygen or sulfur, alkylenes of one or three of
alkylenes, or one selected from the followings:
-NK4- ; -P(O)R3_ ; -N=N- ; -O=N- ; CO O
SO2- ; -SiR3R4- ; -CONH- : -NY-CO-X-CO-NY- ;
-o-co-x-co-o- i R
13
--C H-- --C--
~ ; . ~ 0 i ~ and
in which R3, R4 and Yl represent respectively alkyl group
of 1 to 4 carbon atoms, cyclic alkyl group having in the
ring 5 or 6 carbon atoms, or phenyl or polycyclic aromatic
group, and "X" denotes linear-chain or branched alkylene
group having less than 13 carbon atoms, cyclic alkylene
group having in the ring 5 or 6 carbon atoms, or
monocyclic or polycyclic allylene group.
For preferable unsaturated bis-imide to be employed in
the above formula (I), there may be listed such ones as
follows:
N,N'-ethylene-bis-imide maleate,
N,N'-hexamethylene-bis-imide maleate,
N,N'-methaphenylene-bis-imide maleate,
N,N'-para-phenylene-bis-imide maleate,
N,N'-4,4'-diphenylmethane-bis-imide maleate [also
called generally N,N'-methylene-bis(N-phenylmaleimide)],
N,N'-4,4'-diphenylether-bis-imide maleate,
N,N'-4,4'-diphenylsulfone-bis-imide maleate,
~ Z0~2633
N,N'-4,4'-dicyclohexylmethane-bis-imide maleate,
N,N'-~,~'-4,4'-dimethylenecyclohexane-bis-imide
maleate,
N,N'-metaxylene-bis-imide maleate,
N,N'-diphenylcyclohexane-bis-imide maleate,
1,3-bis(2-p-anilinopropylidene)benzene-bis-imide,
1,4-bis(2-p-anilinopropylidene)benzene-bis-imide,
1,4-bis(2-m-anilinopropylidene)benzene-bis-imide,
4,4'-methylene-di-2,6-xylidine-bis-imide,
4,4'-methylene-di-2,6-diethylaniline-bis-imide,
4,4'-diamino-3,3'diethyl-5,5'-dimethyldiphenylmethane-
bis-imide,
4,4'-methylene-di-2,6-diisopropylaniline-bis-imide,
2,5-dimethyl-p-phenylenediamine-bis-imide,
2,2-bis(4-aminophenyl)propane-bis-imide,
2,4-diaminomesitylene-bis-imide,
3,5-diethyl-2,4-tolylenediamine-bis-imide and the
like.
For preferable diamine to be employed in the foregoing
formula (II), such ones as follows are enumerated:
4,4'-diaminodicyclohexylmethane,
1,4-diaminocyclohexane,
2,6-diaminopyridine,
m-phenylenediamine,
p-phenylenediamine,
4,4'-diaminodiphenylmethane,
2,2-bis(4-aminophenyl)propane,
benzidine,
201Z633
.., ,.~
4,4'-diaminophenyl oxide,
4,4'-diaminodiphenyl sulfide,
4,4'-diaminodiphenyl sulfone,
bis-(4-aminophenyl)diphenylsilane,
bis-(4-aminophenyl)methylphosphine oxide,
bis-(3-aminophenyl)methylphosphine oxide,
bis-(4-aminophenyl)phenylphosphine oxide,
bis-(4-aminophenyl)phenylamine,
1,5-diaminonaphthalene,
m-xylylenediamine,
p-xylylenediamine,
l,l-bis(p-aminophenyl)phthalane,
hexamethylenediamine,
1,3-bis(2-p-anilinopropylidene)benzene,
1,4-bis(2-m-anilinopropylidene)benzene,
4,4'-methylene-di-2,6-diethylaniline,
4,4'-diamino-3,3'-diethyl-5,5'-diphenylmethane,
4,4'-methylene-di-2,6-diisopropylaniline,
2,5-dimethyl-p-phenylenediamine,
2,2-bis(4-aminophenyl)propane,
2,4-diaminomesitylene,
3,5-diethyl-2,4-tolylenediamine, and the like.
Further, by bringing bis-imide and diamine into
reaction with each other, it is possible to prepare an
addition type polyimide. Composition ratio of bis-imide
and diamine should preferably be in a range, in mol ratio,
of 1.7 to 2.5 of bis-imide with respect to 1 of diamine.
When bis-imide is less than 1.7, there arises a tendency
ZO~Z633
, i~,,,
that the production of polymeric mass is increased to
shorten required setting time so as to render the
composition poor in the handleability, while bis-imide
made above 2.5 causes non-reacted raw material likely to
be remained much. The reaction may be carried out in a
state in which bis-imide and diamine are solved by such
solvent as N-methyl-2-pyrrolidone (NMP),
N-N'-dimethylacetamide (DMAC) or the like, under such
reaction conditions that the heating temperature is in a
range of 70 to 170~C and the reaction time is in a range
of about 30 to 350 minutes.
According to a remarkable feature of the present
invention, the polyimide composition is prepared by
blending, with respect to 100 parts by weight (which shall
be hereinafter referred to simply as "part" or "parts") of
polyimide, 10 to 200 parts of triallyl isocyanurates
(hereinafter "TAIC"), and adding thereto imidazoles,
organic peroxides or the like as an accelerator and one or
a mixture of two or more selected from a group consisting
of dimethylformamide (DMF), DMAC, dioxane, NMP, methyl
ethyl ketone, methyl cellulose and the like as a diluting
solvent.
By increasing the added amount of TAIC in the above,
an action of lowering the dielectric constant of the
laminate eventually obtained with the foregoing
composition can be attained, while the addition less than
10 parts does not allow the dielectric constant to be
lowered to any satisfactory level and the addition
Z0~2633
."~
exceeding 200 parts allows the dielectric constant to be
lowered but causes the eventual laminate to be too high in
the hardness so as to become brittle undesirably,
rendering the product less reliable in the strength. The
addition of TAIC is effective to lower the inherent
viscosity and hence the surface tension of the composition
obtained, so as to render the infiltration of the
composition into spaces between fibers forming base
material to be excellent, and a prepreg remarkably
improved in the resin filling into the base material can
be obtained. In the laminate formed by laminating and
setting a plurality of such prepregs of the polyimide
composition, therefore, it is made possible to minimize
any undersirable infiltration of through-hole plating
solution into the structure of the laminate upon formation
of through holes for adapting the laminate to the
multilayered wiring substrate, that is, the depth or
extent of such infiltration of the plating solution on
peripheral surface of the through holes made in the
laminate can be remarkably shortened. At the same time,
the peripheral surface of the through holes can be covered
by the plated metal which shows a remarkably smooth
finishing. Consequently, a desired electric insulation of
printed circuits incorporated in the laminate from the
through holes can be well maintained while required
conduction between required ones of the circuits or the
like through the through holes can be attained at a high
stability.
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ZOlZ633
,.
When TAIC is added along with, for example, a TAIC
polymer, it is preferable to add them in a range of 0 to
100 parts of TAIC with respect to 1 part of the TAIC
polymer. Their addition in this range of TAIC and its
5polymer renders TAIC prepolymer to be contained in the
TAIC polymer, so that any abrupt volatilization of TAIC
during required drying in the prepreg manufacturing steps
to be effectively restrained, whereby the polyimide
composition with which the base material of the prepreg is
10impregnated can be half-set in a sufficiently stabilized
state to obtain excellent prepregs, so that the prepregs
remarkably improved in the resin filling into the base
material can be eventually prepared.
When TAIC polymer is added concurrently with TAIC, the
15addition of TAIC polymer by about 1 part with respect to
100 parts of polyimide will be effective to have the
foregoing effect shown, and even the addition of TAIC
polymer only may suffice the purpose. Further, it is
preferable to use TAIC polymer of a weight-average
20molecular weight in a range of 500 to 10,000 and, more
particularly, 500 to 3,000. In the case of TAIC polymer
less than 500 weight-average molecular weight, TAIC
polymer does not cause the desired action to take place
while TAIC polymer exceeding 10,000 weight-average
molecular weight renders the eventual composition to be
lowered in the plasticity, so that the obtained prepreg
will be deteriorated in the interlaminar bonding and
resultant laminate becomes too hard and brittle. When the
2012633
~w
laminate formed with such brittle polyimide composition is
subjected to the work of making the through holes for
utilizing the laminate as the wiring substrate, the
laminate shows a tendency of easily forming cracks in the
peripheral surface of the through holes made, and this
tendency becomes more remarkable when the through holes
are provided at a higher density in order to adapt the
substrate to the high density mounting. When the through
holes involves the cracks, the conductor metal of the
through-hole plating is caused to enter into such cracks,
so as not to allow the required insulation to be kept
between the through holes and the incorporated circuits in
the substrate, and the highly reliable conduction cannot
be assured any more. The weight-average molecular weight
of TAIC polymer is to be obtained by means of the THF-GPC
measurement, on the basis of monomer calibration curve.
In securing the nonflammability required for the
safety of the electronic devices and equipments employing
the multilayered wiring substrate made of the synthetic
resin composition, it is required to mix the polyimide
composition with bromic resin having a reactive group as a
flame retardant, and it is particularly preferable to
employ the bromic resin having the reactive group in a
range of 1 to 50 parts in bromine content weight with
respect to 100 parts of the polyimide resin. In this
case, the bromine content of less than 1 part does not
allow the nonflammability to be attained while the content
exceeding 50 parts render the eventual laminate to be
2012633
.,~
deteriorated in its function with the thermal resistance
lowered and the dielectric constant raised. When the
bromic resin having the reaction group is used as the
flame retardant, the bromic resin reacts to side chain and
end group of the polyimide resin to be taken into
structural frame of the polyimide resin, so as to provide
to the polyimide resin concurrently such functions as the
interlaminar bonding, reliability of the through-holes,
thermal resistance and nonflammability.
Therefore, the bromic resin can be properly employed
as selected from such ones having epoxy group, allyl
group, vinyl group and so on as the reactive group as
alkyl, phenyl or polycyclic aromatic series having 1 to 4
carbon atoms, linear-chain or branched alkylene having
less than 13 carbon atoms, cyclic alkylene having 5 to 6
carbon atoms in the ring, monochain or polycyclic allylene
and the like. As the most preferable reactive group, in
particular, the epoxy group may be enumerated in respect
of its capability of maintaining or improving the thermal
resistance and interlaminar bonding.
In obtaining the prepreg from the polyimide
composition referred to in the above, the base material is
impregnated with the polyimide composition, thereafter the
reaction of polyimide to TAIC polymer or TAIC is made to
advance while drying and evaporating the diluting solvent,
and the composition filling the base material can be
half-set. While thus obtaining the prepreg, the bromic
resin having the reactive group and mixed in the
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2~1Z633
.,.,,,,,~
composition for providing thereto the nonflammability is
also made to react at the reactive group to the side chain
and end group of polyimide and to be taken into the
structural frame of polyimide.
The base material to be impregnated with the polyimide
composition may not be particularly limited in the type,
but it is general that glass cloth is employed therefor.
Further, any one of such inorganic fiber cloth as quartz
fiber cloth and the like and such highly thermally
resisting organic fiber cloth as polyimide fiber cloth and
the like may be used.
The half-setting for forming the prepreg should
preferably be carried out at a temperature of 110 to
155~C, since the temperature exceeding 155~C causes in
particular TAIC to become likely to volatile much and the
reaction to be too accelerated so that the interlaminar
bonding of the resultant prepreg will be lowered and the
effect of lowering the dielectric constant will be less
while the temperature below 110~C renders required
processing time to be prolonged to impair the
productivity. Here, the half-set state of the resin
composition forming the prepreg is to represent so-called
B-stage between A-stage and C-stage in the setting process
of thermosetting resin, in which state the resin can be
fluidized when heated to advance further the setting
reaction.
From the foregoing prepreg of the polyimide
composition, next, it is possible to prepare the laminate.
2012633
.".. ,
As occasion demands, a plurality of the prepregs may be
laminated with circuit patterns of foils or layers of such
a metal as copper, nickel, aluminum or the like. In this
case, laminating and molding themselves of the prepregs
may be carried out in any manner well known to ones
skilled in the art. In forming the laminate, the
polyimide composition comprising polyimide of the
foregoing chemical structure and combined with TAIC's is
employed, and the impregnation of the base material with
the composition can be sufficiently realized. With this
laminate employed, the dielectric constant of the laminate
can be lowered, and the filling ability made high of the
polyimide composition with respect to the base material
allows to realize such effects that the smear is less
lS generated upon the drilling work for the through holes,
and that the infiltrating depth of the through-hole
plating solution into the laminate at the peripheral
surface of the through holes is practically minimized so
that the through-hole plating can be smoothly formed, the
insulating ability of the through holes with respect to
the circuit patterns incorporated can be well improved
and, as a whole, the highly reliable conduction can be
ensured. In the case of the laminate formed with the
polyimide composition containing TAIC and combined with
the bromic resin having the reactive group, further, the
laminated is concurrently provided with such functions as
the interlaminar bonding, through-hole reliability,
thermal resistance and nonflammability, which functions
- 15 -
2012633
.~,.", ~
will be extremely useful characteristics of the laminate
when the same is made multilayered particularly to be more
than eight layers.
EXAMPLES 1-25
The polyimide composition was obtained in many ways
with such varying composition ratio as shown in Tables 1
and 2 attached herewith. Except for the one of Example 7,
the thus obtained composition was used for the
impregnation of E-glass cloth O.lmm thick and 95g/m , and
their prepregs were obtained through a drying carrying out
in a dryer at 140~C for 40 minutes. In the case of
Example 7, D-glass cloth O.lmm thick and 105g/m was used
instead of the E-glass cloth and the prepreg was obtained
through the same drying step as above.
Both-surface-roughened copper foils 18~m thick were placed
on both surfaces of each of the prepregs, the lamination
molding was carried out with a steam press under molding
conditions of a temperature of 130~C, molding pressure of
30kg/cm and for 90 minutes, and both-surface copper-clad
laminates for use in making internally printed wiring
board were obtained. The copper foils on the thus
obtained both-surface copper-clad laminates were subjected
to an etching process for forming the circuit pattern to
prepare the internally printed wiring boards, 35 sheets of
such wiring boards were stacked with 4 sheets of the same
prepregs as in the above interposed between the respective
wiring boards, a copper foil 35~m thick was further
stacked on each of top and bottom surfaces of the thus
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2012633
stacked boards, with 4 sheets of the prepregs interposed,
the entire stack was then accommodated in a mold of 6mm,
and the stack was subjected to the steam press under the
conditions of 5kg/m and 130~C for 20 minutes.
Thereafter, the stack was heated at 200~C under a pressure
of 30kg/m for 120 minutes, then the stack was cooled down
to the room temperatures with the pressure kept applied,
and a multilayered both-surface copper-clad laminate was
eventually obtained.
In Tables 1 and 2, #1 denotes a synthetic of
N,N'-4,4'-diphenylmethane-bis-imide maleate and
4,4'-diaminodiphenylmethane, which does not have any alkyl
group or alkylene group in resin molecules; #2 denotes a
synthetic of 4,4'-methyledyne-2,6-xyledine-xylidine-bis-
imide and 4,4'-diaminodiphenylmethane, which contains
13wt.% of alkyl group in the resin molecules; #3 denotes
4,4'-methylene-di-2,6-diethylaniline-bis-imide and 1,4-bis
(2-p-anilinopropylidene), which contains 24.5wt.% of alkyl
group in the resin molecules; #4 denotes a synthetic of
4,4'-methylene-di-2,6-diisopropylaniline-bis-imide and
1,4-bis(2-p-anilinopropylidene)benzene, which contains
30wt.% of alkyl group in the resin molecules; and #5 is a
synthetic of 1,4-bis(2-p-anilinopropylidene)benzene-bis-
imide and 1,4-bis(2-m-anilinopropylidene)benzene, which
contains 17wt.% of alkyl group in the resin molecule.
Further, the bromic resin employed as the flame
retardant is one of four products (1)-(4) as listed in
Tables 1 and 2, in which (1) is a bromic phenol-novolak
'_ 2 ~
type epoxy resin of a reaction type, known as BREN-S,*
produced by a Japanese firm NIPPON KAYAKU, (2) is a bromic
bis-phenol A type epoxy resin of reaction type, known as
YDB-400 produced by a Japanese firm TOHTO KASEI, (3) is a
non-reaction type multicyclic aromatic series bromic
resin, known as BC58 produced by a U.S. firm GREATLAKE,
and (4) is another non-reaction type multicyclic aromatic
series bromic resin, known as BC52 produced also by
GREATLAKE. In this case, these bromic resins used as the
flame retardant are represented by such chemical structure
formulas as follows:
* Trade-marks
~'
- 18 -
2012633
.",_
(1)
/o \ /o \ /o \
O-CHz-CH -CH2 O-CH2-CH -CHz O-CH2-CH -CH2
B r ~ B r ~ B r
*n=3~ 4
~2)
CHz- CII~CH -~0~
O Br CH 3 Br
OH CH 3
( CH2 CHCH20 - ~ C ~ O ~CH2-CH -/CH2
CH 3 0
*m,n= 2~ 4
(3)
Br Br CH 3 Br
B r ~ O--C 0 ( O--<~ C <~--O - C O
Br Br CH 3 Br
* n= 10 ~ 20
4) Br CH3 .Br
H- ( O- ~ C - ~ - O-CO ~
Br CH~ Br *n=4~ 5
-- 19 --
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~ i "",~
For the setting accelerator, 2-ethyl-4-methyl
imidazole known as 2E4MZ produced by a Japanese firm
SHIKOKU KASEI was used in the respective Examples 1-25,
with DMF used as the diluting solvent so as to render the
solid resin component to be 60~.
COMPARATIVE EXAMPLES 1 & 2
The polyimide composition was prepared with such
composition ratio as shown in Table 2 in the same manner
as in Examples 1-25, and the prepreg as well as the
laminate were obtained in the same manner as in Examples
1-25.
With respect to respective samples obtained through
Examples 1-25 and Comparative Examples 1 and 2,
measurement of the dielectric constant was carried out in
accordance with the standard JIS-C6481, results of which
were as shown also in Tables 1 and 2, and these results
have proved that, as would be clear when the measurement
results of Examples 1-25 are compared with those of
Comparative Examples 1 and 2, the dielectric constant is
effectively lowered by the addition of TAIC's to
polyimide. Further, from comparison of the chemical
structure between Examples 1-5 and 8-19 and Examples 6, 7
and 20-25, it has been found that the dielectric constant
could be lowered to a larger extent in the case where more
than llwt.% of alkyl group was contained in the resin
molecules.
~ urther, the nonflammability test was carried out in
accordance with the standard UL-94, results of which test
- 20 -
20~2633
."
were also as shown in Tables 1 and 2, and it has been
found that Examples 8-16 and 19-25 in which the reaction
type bromic resin having the reaction group was added
could secure sufficient nonflammability while maintaining
high level interlaminar bonding and thermal resistance, in
contrast to Examples 17 and 18 in which the non-reaction
type bromic resin having no reaction group is used.
Then, the prepreg weight Wl prior to the drying as
well as the prepreg weight W2 after the drying at 180~C
for 30 minutes were measured, and volatilization component
of the prepreg was determined by means of a formula
lOOx(Wl-W2)/Wl. Results have shown that, as in
Comparative Example 2, the use only with TAIC added
entails in an abrupt volatilization at the drying step to
render the half-setting, i.e., a stable achievement of the
prepreg to be difficult and the volatilization during
retainable prepreg state to be large, and the use only
with TAIC added is considered to be a cause of blister or
void involved in the laminate employing this prepreg.
With the further presence of the TAIC polymer in addition
to TAIC, as in Examples 1-25 and Comparative Example 1,
the half-setting of the resin at the drying step can be
achieved as stabilized with the volatilization component
in the state of the prepreg is made less so that, as will
be readily appreciated by the one skilled in the art, the
blister or void in the laminate due to the volatilization
in the prepreg can be effectively prevented from
occurrlng.
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20~2633
~.,~
Further, the interlaminar bonding was measured by
peeling one of layers forming the laminate off from others
at right angles, according to which it has been found that
the addition of the TAIC polymer by the weight-average
molecular weight 20,000 as in Example 5 has resulted in a
reduction of the interlaminar bonding to a large extent in
contrast to other Examples, so as to render resultant
compound to be not desirable. The respective laminates
prepared through Examples 1-25 and Comparative Examples 1
and 2 were then subjected to a perforation of 1,000 pieces
of the through holes with drill bits of a diameter of
0.4mm under the conditions of 40,000rpm and a feeding rate
per revolution of 50~/rev., and also to the through hole
plating with the electroless plating and electroplating
carried out concurrently in known manner, and the depth of
infiltration of plated metal at the through holes as well
as the roughness of peripheral wall of the through holes
were measured by microscopically observing cross-section
at the through holes of the laminates with respect to
990th to l,OOOth ones of the through holes. As a result,
the laminates according to any of Examples 1-7 employing
the TAIC polymer of the weight-average molecular weight of
1,000, 8,000 and 20,000 and Examples 8-16 and 19-25
employing the reaction type flame retardant have clearly
reduced the infiltration depth of the through-hole plated
metal and the peripheral wall roughness, in contrast to
Comparative Example 1. In respect of provision of the
nonflammability, on the other hand, Examples 17 and 18
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,...
employing the non-reaction type bromic resin as further
added but in the same amount as the reaction type bromic
resin as in other Examples show that no sufficient
nonflammability can be attained and still the thermal
resistance is to be lowered. As the thermal resistance is
lowered, a heat generated upon the perforation work with
drills causes the peripheral wall surface of the through
holes to be roughened and the infiltration depth of the
plated metal enlarged even in contrast to Comparative
Example 1. In addition, Example 7 shows that, while D
glass can be employed as the base material for the prepreg
to be contributive to a remarkable reduction of the
dielectric constant, it is seen that the infiltration
depth is rather apt to be expanded.
According to the present invention, proper composing
members and their ratio of the polyimide composition are
to be selected depending on the function having priority
over others in the purpose of use of the compound.
In Tables 1 and 2 as in the followings, figures of the
composition are denoted in parts by weight.
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