Plastic molded type electronic device

The phenol resin molding composition used in the present invention is obtained by subjecting a resol-type phenol resin to purification until, when the resin is extracted by heating with 10 times the amount of hot water at 120.degree. C. for 100 hours or more, the extract has an electric conductivity of 100 .mu.S/cm or less, a pH of 4-7 and a halogen ion content of 10 ppm or less, then preparing a composition comprising a resin component consisting of said resol-type phenol resin and a cure rate controlling agent incorporated therewith, optionally incorporating a filler into said composition, kneading the resulting mixture, and then grinding the kneaded mixture. The composition has a good moldability and, when used for resin-sealing of electronic devices or semiconductor devices and transfer-molding of electronic devices using resin, exhibits an excellent adhesive property, electric properties, moisture resistance and heat resistance.

BACKGROUND OF THE INVENTION 
The present invention relates to a phenol resin molding composition of high 
moldability which gives cured products having excellent adhesive property, 
electric properties and heat resistance, and to semiconductor devices of 
plastic molded type sealed with said resin composition. 
DESCRIPTION OF THE RELATED ART 
The outer packagings of electronic devices and semiconductor devices, such 
as a transistor, IC, LSI and VSLI, are classified into two groups. One is 
the hermetic seal type which utilizes metals, glasses, ceramics etc., and 
the other is the plastic molded type which utilizes thermoplastic resins 
or thermosetting resins. 
The former is superior in airtightness but is very expensive. By contrast, 
the latter can be produced at a very low cost by mass production. Due to 
the low manufacturing cost and the advance in materials and production 
techniques for semiconductor devices and sealing resins in recent years, 
80% or more of the semiconductor products have come to be the plastic 
molded type semiconductors produced by transfer molding with 
thermosetting, resins, among which epoxy resins are mainly used. 
However, the semiconductor devices are becoming more highly integrated year 
after year and, as a result, the industry is advancing toward a larger 
chip size and a finer and more multi-layered wiring. As for the shape of 
packages, due to the trend toward higher density and automation of 
packaging, the package size is becoming smaller and thinner and the shape 
of the package is shifting from the conventional pin insertion type 
package, a typical example of which is DIP (Dual Inline Package), to the 
surface-mounting type packages including the QFP (Quad Flat Package), SOJ 
(Small Outline J-bended Package) and PLSCC (Plastic Leaded Chip Carrier). 
With the increase in degree of integration, the changes in size and shape 
of the package and mounting method, the surface of a chip becomes finer 
and the sealing resin layer of a package gradually becomes thinner. 
Moreover, with the shift from the pin insertion type to the 
surface-mounting type, the package has come to be exposed to higher 
temperatures than before during mounting. Consequently, when a sealed 
device is subjected to a drastic temperature change, local heating or the 
like, the thermal stress increases due to the difference between the 
thermal expansion coefficients of the constituents of semiconductor device 
(sealing resin, chip, frame etc.) and thereby the sealing resin, chip or 
passivation film formed on the chip surface is cracked or the wiring on 
the chip surface is broken, shorted or misregistrated. Thus are caused 
problems such as the fluctuation of characteristic properties of the 
device and the reduction of reliability thereof. 
These problems become more emphasized as the mounting method for packages 
shifts from the pin insertion type to the surface-mounting type. 
In manufacturing the conventional pin insertion type package, the pin is 
inserted into the through-hole of the substrate and soldered at the 
backside of the substrate. Accordingly, the temperature of the package 
mounted on the substrate is elevated to only about 100.degree.-130.degree. 
C. and hence there has scarcely arisen the problem that the reliability of 
the sealed product is reduced by the thermal stress experienced during 
mounting. In manufacturing the surface-mounting type package, on the other 
hand, mounting is conducted by means of infrared reflow or vapor reflow 
with an inert gas, whereby the whole package is exposed to an elevated 
temperature of 200.degree. C. or more. Consequently, the thermal stress 
increases due to the differences between the thermal expansion 
coefficients of the constituents of the semiconductor device (sealing 
resin, chip, frame, etc.) and thereby the sealing resin, chip or 
passivation film formed on the chip surface is cracked or the wiring is 
broken, shorted or misregistered. Thus are caused problems such as the 
fluctuation of characteristic properties of the device and the reduction 
of reliability thereof. 
Although the temperature at which plastic molded type semiconductors are 
usable has been generally considered to be about 125.degree. C. at the 
highest, heat-resistant plastic molded type semiconductor devices usable 
at more elevated temperatures have come to be required as the range of use 
is widened. Plastic molded type semiconductors of the prior art develop 
defective connection at the joint between the gold wire and aluminum 
electrode when allowed to stand for a long time at an elevated temperature 
of 200.degree. C. or more and are thus poor in so-called high-temperature 
life. Therefore, a material having a high heat resistance, adhesive 
property, low stress development, and moisture resistance has been desired 
for semiconductor sealing material. 
As the conventional molding materials for sealing semiconductors, there 
have been widely used epoxy resin molding materials with a curing agent 
such as phenol novolak resin and acid anhydrides. However, the heat 
resistance of the epoxy resins are, when the glass transition temperature 
of cured product is taken as the measure of the heat resistance for 
example, 150.degree.-180.degree. C. and are not satisfactory for meeting 
the above-mentioned requirements. Nevertheless, the heat resistance alone 
can be considerably improved by using multi-functional epoxy resins, 
phenol resins of higher molecular weight, or multi-functional acid 
anhydrides as a curing agent. 
However, the cured product of these resin compositions are not satisfactory 
in adhesive property, moisture resistance and electric properties and it 
has not been possible to use the cured products in practice as materials 
for electronic parts. As heat-resistant resins other than epoxy resins, 
for example, polyimide resin and polyphenylene sulfide (PPS) have already 
been known. However, as compared with epoxy resin molding materials, 
conventional molding materials using polyimide resin are markedly poor in 
curing characteristics, mold release, etc. They are also unsatisfactory in 
adhesion to chips and lead frames and in moisture resistance. PPS is 
unsatisfactory in resistance to soldering heat. Thus, these resins have 
not yet been applied to any practical uses as molding materials for 
electronic device. 
The present invention has been made in view of such situations, and an 
object thereof is to provide a phenol resin composition of high 
moldability which gives cured products excellent in adhesive property, 
electric properties and heat resistance, and is useful particularly for 
electronic parts, a process for producing said composition, and 
semiconductor devices of the plastic molded type which utilize said 
composition. 
SUMMARY OF THE INVENTION 
According to the present invention, there are provided a phenol resin 
molding composition comprising a resin component consisting of a 
resol-type phenol resin and a modifier in a weight ratio of 30:70 to 95:5; 
a process for producing a resol-type phenol resin suitable for a phenol 
resin molding phenol resin suitable for a phenol resin molding composition 
in which said resin is subjected to purification until, when the purified 
resin is extracted by heating with 10 times the amount of hot water at 
120.degree. C. for 100 hours or more, the extract has an electric 
conductivity of 100 .mu.S/cm or less, a pH of 4-7 and a halogen ion 
content of 10 ppm or less; a process for producing a phenol resin molding 
composition which comprises (A) subjecting a resol-type phenol resin to 
purification comprising neutralization with an acid followed by washing 
with water until, when the purified resin is extracted by heating with 10 
times the amount of hot water at 120.degree. C. for 100 hours or more, the 
extract has an electric conductivity of 100 .mu.S/cm or less, a pH of 4-7 
and a halogen ion content of 10 ppm or less, (B) preparing a composition 
comprising a resin component consisting of said resol-type phenol resin 
and a modifier (e.g. epoxy resins) incorporated therewith in a weight 
ratio of 30:70 to 95:5, (C) incorporating into said composition 55-80% by 
volume of a filler relative to the total volume of the composition, (D) 
kneading the resulting mixture, and (E) grinding the kneaded mixture; and 
a cured product obtained by curing the phenol resin composition described 
above.

The numerals in the Figures mean the following. 1: silicon chip, 2: gold 
wire, 3: lead frame, 4: silver paste, 5: cured resin, 6: glass ampoule. 
In order to solve the above-mentioned problems, the present inventors have 
made extensive studies on phenol resins, which had been regarded as almost 
practically unusable as a material for electronic parts due to their high 
content of ionic impurities and poor electric properties, including 
studies on methods for increasing the purity, improving the electric 
properties, and application to molding materials, of phenol resins. As a 
result, it has been found unexpectedly that the phenol resin composition 
described above has a good moldability, adhesive property, electric 
properties, moisture resistance and heat resistance and gives sealed 
products excellent in resistance to soldering heat and in the strength and 
life of the connection of the joint of gold wire with an aluminum 
electrode after standing at high temperatures for a long period of time. 
Thus, the present invention has been attained. 
The present invention has an excellent feature of making it possible, 
particularly by use of a resol-type phenol resin, to attain the flame 
resistance V-O without incorporation of a flame retardant. 
In the composition of the present invention, the resin component consisting 
of a resol-type phenol resin and an epoxy resin preferably has a low 
content of ionic impurities such that when extracted with 10 times the 
amount of hot water at 120.degree. C. for 100 hours or more the extract 
has an electric conductivity of 100 .mu.S/cm or less, a pH of 4-7 and a 
content of extracted halogen ions of 10 ppm or less. Fillers may be added 
as occasion demands. Although the filler is not particularly restricted, 
it is preferably an inorganic particulate substance. More preferably, it 
is at least one inorganic particulate substance selected from fused 
silica, crystalline silica, and alumina, each having an average particle 
diameter of 1-30 .mu.m. Particularly preferred is spherical fused silica. 
Since the resol-type phenol resin used in the present invention has a 
reactive methylol group and hydroxyl group in the molecule, principally it 
can be heat-cured by itself. Moreover, even when no curing agent is used, 
the cure rate is considerably higher than that of such thermosetting 
resins as epoxy resin. However, when such a fast-curing resin is used for 
a molding material, coating material or laminating material for electronic 
parts, it is difficult to mold the resin into a specified shape, or mold 
it without developing voids or damaging the insert, due to the excessively 
short flowable time of the material. Accordingly, in the present invention 
an epoxy resin is used together with the resol-type phenol resin in order 
to regulate the curing property, viscosity, flowability etc. of the resin. 
The weight ratio of the resol-type phenol resin to the epoxy resin is 30:70 
to 95:5, preferably 60:40 to 90:10, more preferably 70:30 to 80:20. 
The reason why the proportion of the epoxy resin (a modifier) should be 
5-70% by weight relative to the total resin component is that when the 
proportion is less than 5% by weight, the curing property, viscosity, 
flowability etc. of the resin cannot be regulated sufficiently, whereas 
when it exceeds 70% by weight the advantageous characteristics inherent to 
the resol-type phenol resin such as heat resistance (or high-temperature 
property), flame resistance, etc. are deteriorated. 
The resol-type phenol resin referred to in the present invention is a resin 
synthesized by the condensation of a phenol such as phenol or cresol with 
formaldehyde in the presence of a basic catalyst such as ammonia, 
hexamine, amines and organic metal salts. In the reaction, it is 
preferable to carry out the reaction for the time long enough to reduce 
the amount of unreacted starting materials. It is also preferable that the 
molecular weight is properly large in view of the curing property and 
flowability of the resulting resin. Further, in order to remove the 
unreacted starting materials and ionic impurities, the reaction product 
is, after neutralized with an acid, preferably washed with water or 
subjected to steam distillation and then thoroughly dried under reduced 
pressure, or as occasion demands, treated with an ion-exchange resin, 
ion-exchanger or the like. The epoxy resin referred to in this invention 
is any molecule containing more than two epoxy groups (whether situated 
internally, terminally, or on cyclic structures) capable of being 
converted to a useful thermoset form. It is, for example, a resin obtained 
by the condensation of bisphenol A or a phenol novolak resin with 
epichlorohydrin. Also with said epoxy resin, the reaction product is 
preferably freed thoroughly of unreacted starting materials and ionic 
impurities. Since the ionic impurities contained in these resin components 
are of many varieties, it is difficult to specify an allowable content for 
each individual impurity. However, it is preferable that when the resin 
component is extracted with 10 times the amount of hot water at 
120.degree. C. for 100 hours or more, the extract has an electric 
conductivity of 100 .mu.S/cm or less, a pH of 4-7 and a content of 
extracted halogen ions of 10 ppm or less. 
The composition of the present invention may be incorporated with an 
inorganic filler with the aim of improving the thermal expansion 
coefficient, thermal conductivity, elastic modulus, etc. of the cured 
product. Usually, the filler is used in the range of 55-80% by volume, 
preferably 50-70% by volume, relative to the total volume of the 
composition. This is because when the proportion is less than 55% by 
volume, it is difficult to satisfactorily improve the above-mentioned 
properties, whereas when the proportion exceeds 80% by volume, the 
resulting material tends to undergo a marked increase in viscosity and 
decrease in flowability. The kind of inorganic fillers is not critical and 
various compounds can be used. For electronic part materials, however, it 
is preferable that thermally and chemically stable fillers are used. 
Specifically, at least one inorganic particulate substance selected from 
fused silica, crystalline silica, and alumina is more preferable. In 
particular, spherical fused silica is most preferable. Because it has 
recently come to be commercially produced in a large scale, not only has 
itself a small thermal expansion coefficient but also gives, when mixed 
with resin, a slight increase in viscosity and decrease in flowability to 
the product. These fillers preferably have an average particle diameter in 
the range of 1-30 .mu.m. This is because when the average particle 
diameter is less than 1 .mu.m, an increase in viscosity and marked 
decrease in flowability of the resin composition tend to occur. Whereas 
when it exceeds 30 .mu.m, the resin composition is liable to undergo 
separation of the resin component from the filler during molding, 
resulting in non-uniform cured products and fluctuation of physical 
properties of cured products, or to show a poor capability in filling 
narrow crevices. 
In the present composition, various additives other than those mentioned 
above may be used according to necessity. Such additives include curing 
catalysts for encouraging the setting reaction of resin, 
flexibility-imparting agents for increasing the toughness or decreasing 
the elastic modulus of the cured product, coupling agents for enhancing 
the adhesion of the resin component with the filler, dyes or pigments for 
coloring, mold release agents for improving the mold release of the cured 
product from the mold and flame retardants, within a range not deleterious 
to the object of the invention. 
When the filler or the respective additives mentioned above contain a large 
amount of ionic impurities, the reliability of the final product is 
greatly reduced as is reduced in the case of the resin component. 
Therefore, it is preferable that, when the additive is extracted with 10 
times the amount of hot water at 120.degree. C. for 100 hours or more, the 
extract has an electric conductivity of 100 .mu.S/cm or less, a pH of 4-7 
and a content of extracted halogen ions of 10 ppm or less with regard to 
these additives either. 
To reduce the adverse effect of such ionic impurities exerted on the 
reliability of the final products, fine particles of an ion-exchange resin 
or an ion-exchanger may also be incorporated directly to the resin 
composition. Particularly preferable are the so-called inorganic 
ion-exchangers such as hydroxide and hydrated oxide of antimony or 
bismuth, phosphorus antimonic acid, zirconium antimonate, titanium 
antimonate, tin antimonate, chromium antimonate, and tantalum antimonate. 
Fine particles of direct ion-exchange resins or ion-exchangers may be 
incorporated in a proportion of 5 parts by weight or less, preferably in 
the range of 0.015 parts by weight, more preferably 0.1-1 part by weight 
relative to 100 parts by weight of the resin composition. Thereby a 
remarkable improvement can be obtained in preventing corrosion and 
breaking of aluminum wiring and electrodes in the moisture resistance test 
for plastic molded type semiconductors, and in preventing defective 
connection at the gold wire-aluminum electrode joint in the 
high-temperature standing test for plastic molded type semiconductors. 
The epoxy-modified phenol resin of the present invention is assumed to 
exhibit desirable electric and other properties as compared with prior 
molding resins attributable to the removal of ionic impurities attained by 
high degree of purification. The success in attaining the flame resistance 
V-0 is assumed to be due to the phenol resin component itself. 
PREFERRED EMBODIMENT 
The methods of preparation and purification o resol-type phenol resin used 
in the present composition is shown below by way of one example. 
Preparation Example 1 
Synthesis of resol-type phenol resin 
In a 3-liter flask were placed 500 g of phenol, 550 g of 30% formalin and 
25 g of 25% aqueous ammonia solution, and the resulting mixture was 
gradually heated with stirring and then heated under reflux at 90.degree. 
C. for 60 minutes. The inner pressure of the flask was then reduced to 20 
mmHg to remove condensation water and unreacted components. 
Then, 500 g of the reaction product was placed in another 3-liter flask, 1 
liter of deionized water was added thereto, and the mixture was stirred 
vigorously at 90.degree. C. for 15 minutes. 
After cooling, the upper, aqueous layer was removed, 1 liter of deionized 
water was again added to the remaining lower layer, and the mixture was 
stirred vigorously at 70.degree. C. for 15 minutes, then cooled, and the 
upper, aqueous layer was removed. 
After the above operation had been repeated 5 times, the reaction product 
was heated up to 90.degree. C. under reduced pressure to remove water, 
whereby an intended resol-type phenol resin was obtained. 
The melting point and curing characteristic of the resol-type phenol resin 
obtained above are shown in Table 1. Further, 50 g of deionized water was 
added to 5 g of the resol-type phenol resin and heated at 120.degree. C. 
for 120 hours. The pH and electric conductivity of the water after said 
heating and the result of analysis of extracted ionic impurities by ion 
exchange chromatography are also shown in Table 1. 
TABLE 1 
______________________________________ 
Softening point (.degree.C.) 
65 
Gellation time (min), 170.degree. C. 
35 
Properties of extract 
(after 120 hr/120.degree. C.) 
pH 6.0 
Electric conductivity 
30 
(.mu.S/cm) 
Cl.sup.- (ppm)* 10 
Br.sup.- (ppm)* &lt;1 
______________________________________ 
Note 
*Calculated in terms of concentration in resin 
Further, the molecular weight distribution was determined by gel permeation 
chromatography. The result is shown in FIG. 3 as a graph which relates the 
retention time (as abscissa) with the relative intensity (as ordinate). 
These results reveal that the purified resol-type phenol resin contains 
only a very small amount of ionic impurities. 
Further, it is apparent from FIG. 3 that the reaction product comprises 
mainly multinuclear components of two, three or more nuclei and contains 
little of the unreacted low molecular weight components. 
The present invention will be described further in detail below with 
reference to the following Examples. 
EXAMPLES 1-3 
Molding materials were prepared by using, in mixing ratios shown in Table 2 
later, a resol-type phenol resin purified by the above-mentioned method 
and a bisphenol A-type epoxy resin as the resin component, spherical fused 
silica having an average particle diameter of 15 .mu.m as the filler, 
epoxysilane as the coupling agent, montanic acid ester wax as the mold 
release agent, and carbon black as the coloring agent. The respective 
starting materials were kneaded by using a two-axle roll at a roll surface 
temperature of about 60-75.degree. C. for about 10 minutes. 
EXAMPLES 4-6 
Three kinds of molding materials were prepared in the same manner as 
described above and by using the same starting materials as in the above 
Examples in mixing ratios shown in Table 2. 
EXAMPLE 7 
A molding material of the same mixing ratio as in Example 2 as shown in 
Table 2 was prepared by using as the resin component an unpurified 
resol-type phenol resin (softening point: 60.degree. C.; gellation time: 
30 sec; pH, electric conductivity, and extracted Cl ion content of aqueous 
extract after 120 hours of extraction at 120.degree. C.: respectively 9.5, 
4500 .mu.S/cm and 1540 ppm). 
EXAMPLE 8 
A molding material was prepared by kneading 90 parts by weight of an 
o-cresol novolak-type epoxy resin (epoxy equivalent: 195, softening point: 
75-80.degree. C.) and 10 parts by weight of a brominated bisphenol A-type 
epoxy resin (epoxy equivalent: 394, softening point: 65.degree. C.) as the 
resin component, 55 parts by weight of a phenol novolak resin (hydroxyl 
equivalent: 106, curing temperature: 65.degree. C.) as the curing agent, 
1.0 part by weight of triphenylphosphine as the cure accelerator, 470 
parts by weight of fused silica having an average particle diameter of 15 
.mu.m as the filler, 10 parts by weight of antimony trioxide as the flame 
retarding assistant, 3.0 parts by weight of epoxysilane as the coupling 
agent, 1.0 part by weight of montanic acid ester wax as the mold release 
agent, and 1.0 part by weight of carbon black as the coloring agent, with 
a two-axle roll in the same manner as in the above Example. 
EXAMPLE 9 
A non-flame resistant type epoxy resin molding material was prepared by 
kneading 100 parts by weight of an o-cresol novolak-type epoxy resin 
(epoxy equivalent: 195, softening point: 75.degree.-80.degree. C.) as the 
resin component, 58 parts by weight of a phenol novolak resin (hydroxyl 
equivalent: 106, softening point: 65.degree. C.) as the curing agent, 1.0 
part by weight of triphenylphosphine as the cure accelerator, 480 parts by 
weight of spherical fused silica having an average particle diameter of 15 
.mu.m as the filler, 3.0 parts by weight of epoxysilane as the coupling 
agent, 1.0 part by weight of montanic acid ester wax as the mold release 
agent, and 1.0 part by weight of carbon black as the coloring agent, with 
a two-axle roll in the same manner as the above Example. 
Each of the molding materials thus obtained was examined for its 
moldability at 170.degree. C. Separately, it was molded at a mold 
temperature of 170.degree. C., molding pressure of 70 kg/cm.sup.2 and a 
molding time of 90 sec and then post-cured at 180.degree. C. for 15 hours. 
The molded product was examined for its various properties. Further, the 
molded product was ground to pass through a 100-mesh screen, then 50 g of 
deionized water was added to 5 g of the resulting powder, the mixture was 
heated at 120.degree. C. for 120 hours, and the resulting water was 
examined for pH and electric conductivity and analyzed for ionic 
impurities extracted. The results of these tests are collectively shown in 
Table 2. The adhesive property in the Table refers to the value obtained 
by sealing the tip of a 42 alloy specimen 0.25 mm thick and 5 mm wide with 
each molding material (sealed part: 10 mm) and subjecting the specimen to 
a drawing test. 
TABLE 2 
__________________________________________________________________________ 
Item 
Example 4 
Example 1 
Example 2 
Example 3 
Example 5 
__________________________________________________________________________ 
Composition (part by weight) 
Resol-type phenol resin 
100 90 80 75 70 
Epoxy resin 0 10 20 25 30 
Filler 300** 300 300 300 300 
Coupling agent 2 2 2 2 2 
Mold release agent 1 1 1 1 1 
Coloring agent 1 1 1 1 1 
Moldability 
Melt viscosity (P) 2500 600 350 310 205 
Spiral flow (inch) 3 32 50 56 60 
Gellation time (sec) 
15 18 23 25 25 
Properties of cured product 
Glass transition temp. (.degree.C.) 
250 235 230 220 210 
Linear expansion coefficient (10.sup.-5 /.degree.C.) 
1.5 1.6 1.6 1.6 1.7 
Bending strength 
Room temp. 20 19 18 19 18 
(kg/mm.sup.2) 
250.degree. C. 
4.5 2.5 3.2 3.0 2.0 
Flame resistance V-0 V-0 V-0 V-0 V-1 
(UL-94, 1.6 mmt specimen) 
Extract pH 6.0 5.8 5.6 5.5 5.5 
properties 
Conductivity (.mu.S/cm) 
60 68 70 76 72 
(120 h/120.degree. C.) 
Cl (ppm) &lt;1 2 5 4 6 
Br (ppm) &lt;1 &lt;1 &lt;1 &lt;1 &lt;1 
Adhesive property (kg/mm.sup.2)*** 
0.3 1.2 1.5 1.5 1.6 
__________________________________________________________________________ 
Item 
Example 6 
Example 7 
Example 8 
Example 9 
__________________________________________________________________________ 
Composition (part by weight) 
Resol-type phenol resin 60 80* Described in the text 
Epoxy resin 40 20 
Filler 300 300 
Coupling agent 2 2 
Mold release agent 1 1 
Coloring agent 1 1 
Moldability 
Melt viscosity (P) 115 515 200 240 
Spiral flow (inch) 90 28 40 38 
Gellation time (sec) 40 19 25 25 
Properties of cured product 
Glass transition temp. (.degree.C.) 
180 230 170 170 
Linear expansion coefficient (10.sup.-5 /.degree.C.) 
1.8 1.6 2.0 1.9 
Bending strength 
Room temp. 14 18 13 12 
(kg/mm.sup.2) 250.degree. C. 
1.0 3.4 0.8 0.7 
Flame resistance HB V-0 V-0 HB 
(UL-94, 1.6 mmt specimen) 
Extract pH 4.8 8.8 4.5 4.5 
properties Conductivity (.mu.S/cm) 
75 1500 120 80 
(120 h/120.degree. C.) 
Cl (ppm) 10 500 15 12 
Br (ppm) &lt;1 &lt;1 20 &lt;1 
Adhesive property (kg/mm.sup.2)*** 
1.4 1.3 0.8 0.9 
__________________________________________________________________________ 
Note 
*Unpurified resoltype phenol resin was used. 
**Corresponding to about 62% by volume 
***In terms of drawing strength of realed product (sealed part: 10 mm) of 
42 alloy specimen (0.25 mm thick, 5 mm wide) 
Further, the following test was made to reveal the influence the molding 
material of the present invention exerted, when the material is used for 
electronic parts, on the corrosion and the connection reliability of the 
aluminum electrode and the gold wire-aluminum electrode joint of 
semiconductor devices. As shown in FIG. 2, each of the various molded 
articles was placed together with a bare element to which a gold wire had 
been bonded in a glass ampoule having an inner diameter of 30 mm and a 
length of 150 mm, then the whole was heated at 230.degree. C., and the 
change of the joining strength of gold with aluminum with the elapse of 
time during heating was determined. The results obtained are shown in FIG. 
1. 
Thus, FIG. 1 is a graph showing the influences of a variety of molding 
materials (in the form of molded products) on the connection reliability 
at high temperature of the gold wire - aluminum electrode joint in terms 
of a relation between the heating time at 225.degree. C. (hours, as 
abscissa) and the gold/aluminum joining strength (g, as ordinate). 
FIG. 2 is a schematic cross-sectional view of the test apparatus and the 
specimen used in the test method of FIG. 1. In FIG. 2, numeral 1 denotes a 
silicon chip, 2 gold wire, 3 lead frame, 4 silver paste (adhesive agent), 
5 cured resin (molded product) and 6 glass ampoule. 
As is apparent from Table 2, while the molding material of Example 4, in 
which resol-type phenol resin is singly used as the resin component, has a 
high melt viscosity and very poor moldability, the molding materials of 
Examples 1 to 3 of the present invention, which contain epoxy resin 
compounded therein, not only have a good moldability but also show good 
high-temperature properties (glass transition temperature and bending 
strength) as molded products. However, when the amount of compounded epoxy 
resin is increased as shown in Examples 5 and 6, the high-temperature 
properties of the molded product deteriorate as in the epoxy resin molding 
materials shown in Examples 8 and 9, and further the flame resistance of 
the molded product lowers and becomes unable to attain the flame 
resistance grade V-0 of the UL standards. Further, the properties of 
extracts determined with pulverized molded products show that when the 
resol-type phenol resin is used after purification, the pH shows 
neutrality to weak acidity, electric conductivity is low, and the amount 
of extracted halogen ions is also low. The adhesive property to 42 alloy 
is also substantially good as compared with prior epoxy resin molding 
materials. 
FIG. 1 shows one of the most important features of the present invention. 
It is apparent from FIG. 1 that the molded product according to the 
present invention gives only an extremely little influence on the 
corrosion of the aluminum electrode and the connection reliability of the 
gold wire-aluminum joint. Such phenomena of corrosion or deterioration of 
reliability are generally considered to be due to the effect of the 
thermal decomposition product of a brominated compound incorporated into a 
molding material as a flame retardant. This is evidenced from the 
comparison of Example 8 with Example 9. The molding material of the 
present invention can be highly flame resistant without incorporation of 
such a flame retardant and thus exhibits excellent characteristic 
properties as described above. 
EXAMPLE 10 
Semiconductor devices were sealed by using each of the molding materials 
obtained above and the various reliabilities were evaluated. The 
semiconductor device used had an aluminum wiring on the surface, and a 
chip 6.times.8 mm square in size was adhered to the tab of a lead frame 
with silver paste, the aluminum electrode on the chip and the lead frame 
being connected electrically with gold wire. The package was 15.times.20 
mm in size and 2 mm in thickness, and the semiconductor device was sealed 
so as to be situated around the center of the package. Sealing was 
conducted with a transfer molding machine. Molding was carried out under 
conditions of a mold temperature of 170.degree. C., molding pressure of 70 
kg/cm.sup.2 and molding time of 1.5 minutes. The molded products were 
thereafter post-cured at 170.degree. C. for 15 hours. Then the sealed 
products thus obtained were subjected to a pressure cooker test (PCP) at 
121.degree. C. and 2 atm. to examine the time which elapsed until the 
development of corrosion and defect of aluminum wiring. Further, the 
sealed products were allowed to stand in a high-temperature bath at 
225.degree. C. to examine the time which elapsed until the development of 
defective connection at the joint of gold wire with aluminum wiring. 
Further, the sealed products were allowed to stand at 65.degree. C. and at 
a relative humidity of 95% for 168 hours and then heated in a vapor reflow 
bath at 215.degree. C. for 150 seconds to examine the development of 
package cracks. The results of these tests are collectively shown in Table 
3. 
It is apparent from Tables 2 and 3 that the respective properties examined 
of the molded product of the present invention are highly excellent as 
compared with those of the prior art products. 
TABLE 3 
__________________________________________________________________________ 
Item 
Example 4 
Example 1 
Example 2 
Example 3 
Example 5 
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Development rate of 
After 300 h 
Sample 0/10 0/10 0/10 0/10 
corrosion defect of 
After 500 h 
preparation 
0/10 0/10 0/10 0/10 
aluminum wiring*.sup.1 
After 1000 h 
was impossible 
5/10 3/10 2/10 6/10 
After 2000 h 
owing to 
10/10 10/10 7/10 10/10 
Development rate of 
After 50 h 
breaking of 
0/10 0/10 0/10 0/10 
defective connection 
After 100 h 
gold wire dur- 
0/10 0/10 0/10 0/10 
at gold/aluminum 
After 200 h 
ing molding. 
2/10 0/10 0/10 1/10 
joint*.sup.2 
After 500 h 10/10 10/10 6/10 10/10 
Crack development rate of 
0/10 0/10 0/10 0/10 0/10 
humidified package in reflow*.sup.3 
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Item 
Example 6 
Example 7 
Example 8 
Example 9 
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Development rate of 
After 300 h 
0/10 5/10 0/10 0/10 
corrosion defect of 
After 500 h 
3/10 10/10 1/10 0/10 
aluminum wiring*.sup.1 
After 1000 h 
10/10 -- 8/10 3/10 
After 2000 h 
-- -- 10/10 10/10 
Development rate of 
After 50 h 
0/10 1/10 8/10 0/10 
defective connection 
After 100 h 
1/10 7/10 10/10 0/10 
at gold/aluminum 
After 200 h 
4/10 10/10 -- 2/10 
joint*.sup.2 
After 500 h 
10/10 -- -- 10/10 
Crack development rate of 
2/10 0/10 10/10 10/10 
humidified package in reflow*.sup.3 
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EXAMPLES 11 AND 12 
Molding materials were prepared by using, relative to 100 parts by weight 
of the resol-type phenol resin prepared in Preparation Example 1 described 
above used as the resin component, an inorganic ion exchanger of antimony 
type (IXE-300, mfd. by Togosei Chemical Industry Co., Ltd.), of bismuth 
type (IXE-500, ditto), or of the binary mixture type of the two (IXE-600, 
ditto) as the ion exchanger, spherical fused silica having an average 
particle size of 15 .mu.m as the filler, montanic acid ester wax as the 
mold release agent, and carbon black as the coloring agent respectively in 
the mixing ratios shown in Table 4. The respective starting materials were 
kneaded by using two-axle roll 20 inches in diameter at a roll surface 
temperature of about 60.degree. C. for about 10 minutes. 
EXAMPLE 13 
A molding material was prepared in the same manner as in Example 11 but 
with incorporation of 20 parts by weight of epoxy resin and without 
incorporation of the ionic impurity-uptaking agent. 
EXAMPLE 14 
A molding material was prepared by using a conventional unpurified 
resol-type phenol resin (aqueous extract after 120 hours of extraction at 
120.degree. C. showed a pH of 9.5, electric conductivity of 4500 .mu.S/cm 
and extracted Cl ion content of 1540 ppm) and according to the compounding 
ratio shown in Table 4. 
A variety of tests were made in the same manner as in Tables 1 to 3 with 
the molding materials of Examples 11 to 14 described above. The results of 
the tests are collectively shown in Table 4. 
TABLE 4 
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Item 
Example 10 
Example 11 
Example 12 
Example 13 
Example 14 
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Composition (part by weight) 
Purified resol-type phenol resin 
80 80 80 80 -- 
Unpurified resol-type phenol resin 
-- -- -- -- 80 
Epoxy resin 20 20 20 20 20 
Inorganic ion exchanger IXE-300 
5 -- -- -- 5 
Inorganic ion exchanger IXE-500 
-- 5 -- -- -- 
Inorganic ion exchanger IXE-600 
-- -- 5 -- -- 
Fused silica 300 300 300 300 300 
Coupling agent 2 2 2 2 2 
Mold release agent 2 2 2 2 2 
Coloring agent 1 1 1 1 1 
Moldability 
melt viscosity (P) 300 320 315 305 175 
Spiral flow (inch) 33 30 32 33 58 
Gellation time (sec) 18 17 18 17 17 
Properties of cured product 
Glass transition temp. (.degree.C.) 
230 232 228 230 235 
Linear expansion coefficient (10.sup.-5 /.degree.C.) 
1.5 1.6 1.5 1.6 1.6 
Bending strength 
Room temp. 20 20 19 20 19 
(kg/mm.sup.2) 
250.degree. C. 
3.6 3.5 3.5 3.4 3.4 
Flame resistance (UL-94, 1.6 mmt specimen) 
V-0 V-0 V-0 V-0 V-0 
Adhesive property (kg/mm.sup.2) 
1.6 1.5 1.6 1.5 1.3 
Extract pH 5.0 4.8 5.2 6.2 8.2 
properties 
Conductivity (.mu.S/cm) 
55 63 60 125 650 
(120 h/120.degree. C.) 
Cl.sup.- (ppm) 
&lt;1 &lt;1 &lt;1 &lt;1 45 
Br.sup.- (ppm) 
&lt;1 &lt;1 &lt;1 &lt;1 25 
NH4.sup.+ (ppm) 
5 6 5 25 135 
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As described above, the resin composition of the present invention is 
useful as a molding material for electronic parts for which an excellent 
heat resistance, flame resistance and electric properties and a low ionic 
impurity content are required. 
Further, the plastic molded type semiconductor device of the present 
invention is excellent in such properties as moisture resistance 
reliability, connection reliability of the gold wire - aluminum joint, and 
crack resistance of a package which has been solder-mounted in a 
humidified state. Thus, the present invention can provide highly reliable 
semiconductor devices.