The electrical properties for phenolic isocyanate-modified bisphenol-based epoxy resins comprising benzoate group

Article abstract of DOI:10.1166/jnn.2016.11117

Epoxy resin has been required to have a low dielectric constant (Dk ), low dissipation factor (Df), low coefficient of thermal expansion (CTE), low water absorption, high mechanical, and high adhesion properties for various applications. A series of novel

Full text of DOI:10.1166/jnn.2016.11117

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Nanoscience and Nanotechnology
Vol. 16, 3009–3013, 2016
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The Electrical Properties for Phenolic
Isocyanate-Modified Bisphenol-Based Epoxy
Resins Comprising Benzoate Group
Eun Yong Lee1ꢀ2ꢀ†, Il Seok Chae3ꢀ†, Dongkyung Park4, Hongsuk Suh4, and Sang Wook Kang1ꢀ∗
1Department of Chemistry, Sangmyung University, Seoul 110-743, Republic of Korea
2Shin-A T&C Company, Gasan-dong, Geumcheon-gu, Seoul 481-10, Republic of Korea
3Department of Energy Engineering, Hanyang University, Seoul 133-791, Republic of Korea
4Department of Chemistry and Chemistry Institute for Functional Materials,
Pusan National University, Busan 609-735, Republic of Korea
Epoxy resin has been required to have a low dielectric constant (Dk ), low dissipation factor (Df), low
coefficient of thermal expansion (CTE), low water absorption, high mechanical, and high adhesion
properties for various applications. A series of novel phenolic isocyanate-modified bisphenol-based
epoxy resins comprising benzoate group were prepared for practical electronic packaging applica-
tions. The developed epoxy resins showed highly reduced dielectric constants (Dk ∼3ꢀ00 at 1 GHz)
and low dissipation values (Df∼0ꢀ014 at 1 GHz) as well as enhanced thermal properties.
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Keywords: Epoxy Resin, Dielectric Constant, Dissipation Factor, Coefficient of Thermal
Copyright: American Scientific Publishers
Expansion.
1. INTRODUCTION
phenolic compounds is too brittle; consequently, easily
cracked by low stress.9 To overcome such toughness char-
acters, a lot of efforts were made through modification
of the structure of the resin itself, in particular, refor-
mation by isocyanate compound.10–12 Although developed
chemical structures can alter bulk properties of epoxy
such as the elastic modulus and glass-transition tempera-
ture, they have the disadvantage in heat-resisting properties
and electrical properties, such as the dielectric constant
(Dk) and dissipation (Df ) values. To solve these problems,
the adamantane-containing epoxy resin diglycidyl ether of
bisphenol-adamantane (DGEBAda) was reported and their
dielectric constant was 3.74.13
We have recently reported the benzoate-group-
substituted epoxy resin with low dielectric constant (Dk),
low dielectric loss (dissipation values, Df), low coef-
ficient of thermal expansion (CTE), and high adhe-
sion properties.14 Our strategy is that the introduction
of benzoate group to the main chain, instead of the
hydroxyl group in the common bisphenol A diglycidyl
ether epoxy resin, apparently gives rise to increasing
hydrophobic nature. Note that the Dk value of water
is 78.15 In present study, through esterification using
Epoxy resins are widely used as underfill materials in elec-
trical/electronic devices due to its excellent electrical insu-
lation properties, high thermal stability, easy conversion
from liquid to non-melting solids and excellent mechanic
characteristics.1ꢀ2 Recently, with the growing demands
for miniaturization and high power density in electronic
devices, high electrical insulating epoxy resin systems with
lower coefficients of thermal expansion should be required
in electronic packaging applications.3–5 Also, at inner layer
of multilayer printed circuit board, the adhesion property
of epoxy resin is very important for practical applications.
This is strongly related to the kind of hardener, which gov-
erns the toughness character of cured resin. Since the pro-
hibition of plumbum (Pb) compound by the law, the use
of Tin/Silver (Sn/Ag) alloys requires the relatively higher
temperatures in soldering process,6ꢀ7 which have accel-
erated the change hardener from dicyandiamide (DICY)
to phenolic compounds.8 However, the cured matrix by
∗Author to whom correspondence should be addressed.
†These two authors contributed equally to this work as first authors.
J. Nanosci. Nanotechnol. 2016, Vol. 16, No. 3
1533-4880/2016/16/3009/005
doi:10.1166/jnn.2016.11117
3009

The Electrical Properties for Phenolic Isocyanate-Modified Bisphenol-Based Epoxy Resins Comprising Benzoate Group
Lee et al.
esterification
O
O
NCO
NCO
NCO
O
O
O
Products
(P3, P4)
O
N
O
Rx
O
O
n
O
x
150 °C
cat.2E4MZ
180 °C
cat.2E4MZ
+
O
P1 or P2
O
Rx
O
where R1:
O
O
O
O
O
P3:
P4:
N
O
O
O
O
x
z
y
bisphenol A
where R2:
O
O
O
O
O
N
O
O
O
O
O
x
bisphenol Z
y
z
Scheme 1. Preparation of phenolic isocyanate-modified bisphenol-based epoxy resins comprising benzoate group.
bisphenol A dibenzolate, we report the novel phenolic
isocyanate-modified bisphenol-based epoxy resins com-
prising benzoate group (Scheme 1) for various practical
electronic packaging applications.
3. RESULTS AND DISCUSSION
Phenolic isocyanate-modified bisphenol-based epoxy
resins comprising benzoate group was prepared through 2
step, as shown Scheme 1.
Bisphenol Z diglycidyl ether: 4,4 -Cyclohexylidene-
ꢁ
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bisphenol (268.35 g, 1 mol) and epichlorohydrin (740 g,
2. EXPERIMENTAL DETAILS
Copyright: American Scientific Publishers
8 mol) were dissolved in isopropyl alcohol 300 g. NaOH
(50% wt. aqueous solution, 192 g) was added dropwise
to the reaction ꢀvessel, and the reaction allowed to proceed
for 4 hr at 50 C. Removing the residual epichlorohydrin
through vacuum, and then NaCl was washed with water
1H NMR (CDCl3, 300 MHz, ppm, TMS): ꢁ 1.43 (6 H of
cyclohexane), 2.1 (4 H of cyclohexane), 2.85 (2 H of oxi-
ran), 2.92 (2 H of oxiran), 3.15 (2 H of oxiran), 3.95 (2 H
of methylene), 4.08 (2 H of methylene), 6.9 (4 H of ben-
zene), 7.2 (4 H of benzene). 13C NMR (CDCl3, 150 MHz,
ppm, TMS): ꢁ 158.4, 141.8, 128.4, 114.5, 77.6, 69.0, 50.4,
44.9, 37.6, 23,2.
2.1. Materials
Bisphenol A diglycidyl ether (SE-187) was supplied from
our commercial product line from Shin-A T&C Co.
Bisphenol Z diglycidyl ether was prepared as below
method. The preparation of bisphenol A dibenzolate was
based on our previous report. 2-Ethyl-4-methylimidazole
was utilized as a catalyst. All the chemicals in this work
were used as received from Aldrich Chemical Co. without
further purification.
2.2. Measurements
1H spectra were recorded on a Bruker AVANCE 300
spectrometer with chemical shifts downfield from tetram-
ethylsilane as the internal standard. The epoxy equivalent
weights (EEW) were determined by the HBr-acetic acid
method.16 IR measurements were performed on a 6030
Mattson Galaxy Series FT-IR spectrometer; 64-200 scans
were signal-averaged at a resolution 2 cm−1. IR Spectro-
scopic characterization was performed using a pressure
cell equipped with quartz and CaF2 windows. Coefficient
of thermal expansion (CTE, based on ASTM E831) and
thermogravimetric analysis (TGA) were performed with
Mettler Toledo TMA and TGA devices at a heating rate
of 10 ꢀC/min, respectively. The Dk and Df were measured
by an RF impedance Material Analyzer (Agilent Co.,
E4991A, based on JIS-C-6481).
Poly[(phenyl oxazolidinone bearing bisphenol-based
epoxy)-co-formaldehyde] (P1, P2): Two kinds of
bisphenol-isocyanate modified epoxy were prepared.
Bisphenol A diglycidyl ether (186 g/eq) and bisphenol Z
epoxy (205 g/eq) were respectively allowed to react with
poly((phenyl isocyanate)-co-formaldehyde) (Mn∼375).
Poly[(phenyl isocyanate)-co-formaldehyde] (100 g) and
bisphenol A (or Z) diglycidyl ether (900 g) was loaded
into the reaction vessel in the presence of an imidazole
catalyst (0.5 g), 2-ethyl-4-methyl-imidazole, and the reac-
ꢀ
1
tion was allowed to proceed at 150 C for 2 hr. H NMR
of P1 (CDCl3, 300 MHz, ppm, TMS): ꢁ 1.60 (–CH3ꢂ,
2.78 (–CH2 in oxirane), 2.86 (–CH2 in oxirane), 3.37
(–CH in methine), 3.94 (–CH2−O), 4.19 (–CH2−O) 4.22
(methylene), 6.81 (benzene or phenol), 7.16 (benzene or
3010
J. Nanosci. Nanotechnol. 16, 3009–3013, 2016

Lee et al.
The Electrical Properties for Phenolic Isocyanate-Modified Bisphenol-Based Epoxy Resins Comprising Benzoate Group
Figure 1. FT-IR spectra of (a) bisphenol A based and (b) bisphenol Z based epoxy resin.
phenol), 7.46 (–CH phenol). 1H NMR of P2 (CDCl3,
300 MHz, ppm, TMS): ꢁ 1.44 (–CH2 in cyclohexane),
1.62 (–CH3ꢂ, 2.1 (–CH2 in cyclohexane), 2.78 (–CH2 in
oxirane), 2.86 (–CH2 in oxirane), 3.37 (–CH in methine),
3.94 (–CH2−O), 4.19 (–CH2−O) 4.2 (methylene), 6.81
(benzene or phenol), 7.16 (benzene or phenol), 7.44 (–CH
phenol).
Poly[(phenyl oxazolidinone bearing bisphenol-based
epoxy)-co-formaldehyde] comprising benzoate group (P3,
P4): P3 or P4 was prepared from P1 or P2 (100 g)
1H signal of the carbinol methine proton in was appeared
at about 5.6 ppm in P3 or P4, which was not observed in
P1 or P2 state.
Figure 1 shows the FT-IR spectra for epoxy resins pre-
pared as described above. The characteristics absorption
bands of the glycidyl group of epoxide were observed at
920 and 835 cm−1 in addition to the absorption peaks
at 3048 and 1178 cm−1, indicating the presence of an
aromatic ring in every epoxy compound. The reaction of
cyano and epoxide was confirmed by IR spectrum: vC
O
and bisphenol A dibenzolate (20 g) via the transester-
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absorbance at 1720 cm−1 i.e., the carbonyl peak of oxa-
zolidone group in P1 and 2. After esterification, in par-
ticular, the absorption of epoxide peak appeared at around
920 cm−1 for P3 and P4 decreased when the epoxide
was reacted with bisphenol A dibenzolate. Conversely,
the absorbance at 1720 cm−1 increased due to the car-
bonyl peak of benzoate group. Thus, these FT-IR spectra
could demonstrate the preparation of phenolic-isocyanate-
modified bisphenol-based epoxy resins comprising ben-
zoate group.
9
IP: 37.9.40.66 On: Mon, 24 Oct 2016 16:42:46
fication reaction in the presence of an imidazole cata-
Copyright: American Scientific Publishers
lyst (0.02 g), 2-ethyl-4-methyl-imidazole, and the reaction
ꢀ
1
was allowed to proceed at 180 C for 5 hr. H NMR of
P3 (CDCl3, 300 MHz, ppm, TMS): ꢁ 1.60 (–CH3ꢂ, 2.78
(–CH2 in oxirane), 2.86 (–CH2 in oxirane), 3.37 (–CH in
methine), 3.94 (–CH2−O), 4.17 (–CH2−O) 4.38 (methy-
lene), 5.62 (methine), 6.81 (benzene or phenol), 7.16 (ben-
zene or phenol), 7.39 (benzoate), 7.46 (–CH in phenol),
1
7.57 (1H of benzoate), 8.02 (2H of benzoate). H NMR
of P4 (CDCl3, 300 MHz, ppm, TMS):): ꢁ 1.44 (–CH2
in cyclohexane), 1.62 (–CH3ꢂ, 2.1 (–CH2 in cyclohexane),
2.78 (–CH2 in oxirane), 2.86 (–CH2 in oxirane), 3.37 (–CH
in methine), 3.94 (–CH2−O), 4.19 (–CH2−O), 4.3 (methy-
lene), 5.62 (methine), 6.81 (benzene or phenol), 7.16 (ben-
zene or phenol), 7.39 (benzoate), 7.46 (–CH in phenol),
7.57 (1H of benzoate), 8.02 (2H of benzoate). Note that
The resin properties such as epoxy equivalent weight
(E.E.W), water absorption values and thermal property
were summarized in Table I (5 times test and their average
value). After introduction of polymeric isocyanate, the for-
mation of oxazolidone led to the increased glass-transition
temperature in P1 and P2. Also, due to the hydrophilic
Table I. Characterization of epoxy resins.
Dk
Df
Epoxy resin
E.E.W.a/g equiv−1
Tgb/ꢀC
CTE (ꢀꢂC ppm
Water uptake
Tdd5 /ꢀC
at 1 GHz
bisphenol A
P1
P3
bisphenol Z
P2
P4
187
145.5
153.3
119.6
146.8
174.7
130.0
66.2
57.9
59.2
69.1
57.4
68.9
0.47
0.54
0.35
0.53
0.61
0.41
397.6
393.1
384.1
398.2
396.7
387.2
3.22
3.21
3.09
3.17
3.16
3.00
0.023
0.022
0.016
0.025
0.020
0.014
224ꢃ6
377ꢃ55
205
272ꢃ8
495ꢃ2
Notes: aDetermined by the HBr acetic acid method; bDetermined by differential scanning calorimetry; cCalculated by thermomechanical analysis; dDetermined by thermo-
gravimetric analysis.
J. Nanosci. Nanotechnol. 16, 3009–3013, 2016
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The Electrical Properties for Phenolic Isocyanate-Modified Bisphenol-Based Epoxy Resins Comprising Benzoate Group
(a) (b)
Lee et al.
Figure 2. TGA of (a) bisphenol A based and (b) bisphenol Z based epoxy resin.
3.8
(a)
(b)
P1
P3
P2
P4
P1
P3
P2
P4
0.03
0.02
3.6
3.4
3.2
3.0
2.8
0.01
108
109
106
107
108
109
Frequency (Hz)
Frequency (Hz)
Figure 3. (a) Frequency-dependent dielectric constant, and (b) dissipation value of epoxy resins.
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property of oxazolidone, the water absorption values of
4. CONCLUSIONS
P1 and P2 slightly increased, which were not desirable.
However, after esterification, the water absorption values
of P3 and P4 were improved by increasing the portion of
hydrophobic moiety, i.e., benzoate, in molecular structure.
To investigate the thermal stability for developed epoxy
resins, TGA was performed at a heating rate of 10 ꢀC/min,
as shown in Figure 2. 5% weight loss ꢀtemperature (Td5ꢂ
In summary, the phenolic isocyanate-modified bisphenol-
based epoxy resins comprising benzoate group were syn-
thesized from the commercial product line, and thermal
and dielectrical properties (Dk and Df ) were investi-
gated. The polymeric isocyanate modified epoxy resins,
P1 and P2, showed lower coefficient of thermal expansion
(CTE) than the corresponding bisphenol A and Z epoxy.
More curiously, phenolic isocyanate-modified bisphenol-
based epoxy resins comprising benzoate group, P3 and
P4, exhibited low water absorption values and intrigu-
ing dielectrical behavior, which were ascribed to the
hydrophobic character of benzoate group.
ꢀ
relatively decreased to 384 C and 387 C for P3 and P4,
respectively. However, these values could be still regarded
as stable. Therefore, it could be concluded that the effect
of the introduction of polymeric isocyanate or benzoate
group on the thermal stability is not critical or negligible.
Figure 3 shows the dielectric properties of the devel-
oped epoxy resins. For the applications of high-frequency
appliances, the Dk and Df values are very important fac-
tors. In the case of the cured sample of P3, its Dk and Df
values were 3.09 and 0.016 at 1 GHz, respectively.
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respectively. Compared with P1 or P2, the decreased
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Received: 21 February 2015. Accepted: 21 March 2015.
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