Zinc oxide in poly(arylene sulfide) compositions

Zinc oxide is used in poly(arylene sulfide compositions to improve encapsulation properties and to inhibit color shift. The invention includes electronic components encapsulated with poly(arylene sulfide) compositions containing zinc oxide.

This invention relates to poly(arylene sulfide) compositions. In one aspect 
this invention relates to electronic components encapsulated with 
poly(arylene sulfide) compositions. In another aspect this invention 
relates to poly(arylene sulfide) compositions containing a color shift 
inhibitor. 
BACKGROUND AND OBJECTS 
The encapsulation of electronic components represents an art in and of 
itself. Electronic components are encapsulated to maintain electrical 
insulation, to provide mechanical protection and to otherwise shield the 
component from exposure to its environment. As the evolution of 
electronics continues its rapid advance it becomes increasingly important 
that the art and technology of encapsulation keep pace. An area of 
significant concern and interest relates specifically to the compositions 
used to encapsulate electronic components. There is an on-going effort to 
discover new and improved encapsulation materials. A relatively recent 
development has been the use of poly(arylene sulfide) compositions such 
as, for example, poly(phenylene sulfide) compositions, as encapsulating 
materials. 
The reliability and useful life of an electronic component depends upon 
various factors. One important factor is the material used to encapsulate 
the electronic component. It is desired to employ encapsulation 
compositions which maximize the reliability and useful life of electronic 
components. 
It is one object of this invention to improve the reliability and increase 
the life of electronic components encapsulated with poly(arylene sulfide) 
compositions. It is another object of this invention to provide improved 
encapsulation compositions and electronic components encapsulated 
therewith. 
Pigmented poly(arylene sulfide) compositions are frequently processed (e.g. 
molded, extruded, etc.) at elevated temperatures. The presence of certain 
components in the composition may make the color of the composition 
temperature sensitive. For example, if identical compositions are 
processed at different temperatures the resultant materials may have 
different colors, i.e. a color shift may occur at the higher temperature. 
It is a further object of this invention to provide poly(arylene sulfide) 
compositions susceptible to color shift with a color shift inhibitor. 
Poly(arylene sulfide) compositions so inhibited are useful as laser 
printable materials and encapsulation materials and for any other 
application where a pigmented poly(arylene sulfide) is desired. 
Other objects, advantages and aspects of this invention will become 
apparent to persons skilled in the art upon study of this disclosure and 
the appended claims. 
BRIEF SUMMARY OF THE INVENTION 
It has been discovered that the addition of zinc oxide to poly(arylene 
sulfide) compositions can improve the reliability and lengthen the life of 
electronic components encapsulated therewith. It has also been discovered 
that zinc oxide can inhibit the color shift associated with poly(arylene 
sulfide) compositions containing certain pigments and silanes. This 
invention is further, and more completely, described in the disclosure 
that follows.

DESCRIPTION OF THE INVENTION 
In accordance with this invention an electronic component is encapsulated 
with a composition containing poly(arylene sulfide) and zinc oxide. This 
invention includes electronic components encapsulated with the 
above-described composition as well as certain encapsulation compositions 
that are especially well suited for the encapsulation of electronic 
components. 
In accordance with another aspect of this invention a composition 
containing poly(arylene sulfide), pigment and silane is inhibited against 
color shift by the addition thereto of zinc oxide. 
This invention includes the article of manufacture and the compositions 
described and set forth as follows. 
1. Article of Manufacture 
The article of manufacture of this invention is an electronic component 
encapsulated with a composition containing poly(arylene sulfide) and zinc 
oxide. 
For the purposes of this entire disclosure and the appended claims the term 
poly(arylene sulfide) is intended to designate arylene sulfide polymers. 
Uncured or partially cured poly(arylene sulfide) polymers whether 
homopolymer, copolymer, terpolymer, and the like, or a blend of such 
polymers, can be used in the practice of my invention. The uncured or 
partially cured polymer is a polymer the molecular weight of which can be 
increased by either lengthening of a molecular chain or by cross-linking 
or by combination of both by supplying thereto sufficient energy, such as 
heat. Suitable poly(arylene sulfide)polymers include, but are not limited 
to, those described in U.S. Pat. No. 3,354,129, incorporated by reference 
herein. 
Some examples of poly(arylene sulfide) suitable for the purposes of our 
invention include poly(2,4-tolylene sulfide), poly(4,4'-biphenylene 
sulfide) and poly(phenylene sulfide). Because of its availability and 
desirable properties (such as high chemical resistance, nonflammability, 
and high strength and hardness) poly(phenylene sulfide) is the presently 
preferred poy(arylene sulfide). Accordingly, poly(phenylene sulfide) 
compositions are the preferred encapsulation compositions of our 
invention. 
In accordance with this invention electronic components are encapsulated 
with a poly(arylene sulfide) composition (such as, for example, a 
poly(phenylene sulfide) composition) containing zinc oxide. The 
poly(arylene sulfide) composition can be, but is not required to be, a 
mixture of more than one type of poly(arylene sulfide). The poly(arylene 
sulfide) composition can contain, in addition to zinc oxide, other 
components although the broad concept of our invention is not limited 
thereto. 
Our invention also includes electronic components encapsulated with more 
detailed poly(arylene sulfide) compositions which are especially well 
suited for successful use as encapsulation compositions. These 
compositions are described later in this disclosure. 
Zinc oxide is a material well known by, and readily available to, persons 
skilled in the art. This invention is not limited to any particular type 
or grade of zinc oxide. For a more detailed discussion of zinc oxide any 
one of numerous references can be consulted. One such reference is the 
Kirk-Othmer Encyclopedia of Technology, Second Edition, Volume 22, pages 
609+. 
Broadly this invention is not limited to any ranges of materials. It is 
contemplated, however, that the ratio of (a) the weight of poly(arylene 
sulfide) in the composition to (b) the weight of zinc oxide in the 
composition will generally be at least about 2.5 to 1 and less than about 
2,500 to 1. This ratio, called the weight ratio, is calculated with 
disregard to the presence or absence of other components in the 
composition. We prefer a weight ratio (i.e. (a) to (b) of at least about 
10 to 1 and less than about 100 to 1. Good results within this range have 
been obtained. It should be noted that the choice of a particular weight 
ratio will be greatly influenced by the presence and relative amounts of 
other components in the composition. 
The electronic components to be encapsulated in accordance with our 
invention broadly include all electronic components (i.e. devices, parts, 
etc.) for which encapsulation is desired. The term electronic component is 
intended to be broadly construed and includes, by way of non-limiting 
example, the following: 
capacitors, 
resistors, 
resistor networks, 
integrated circuits, 
transistors, 
diodes, 
triodes, 
thyristors, 
coils, 
varistors, 
connectors, 
condensers, 
transducers, 
crystal oscillators, 
fuses, 
rectifiers, 
power supplies, and 
microswitches, 
The definition of each of the above-identified electronic components is 
similarly intended to be broad and comprehensive. The term integrated 
circuit, for example, is intended to include, but is not limited to 
large scale integrated circuits, 
TTL (transistor transistor logic), 
hybrid integrated circuits, 
linear amplifiers, 
operational amplifiers, 
instrumentation amplifiers, 
isolation amplifiers, 
multipliers and dividers, 
log/antilog amplifiers, 
RMS-to-DC converters, 
voltage references, 
transducers, 
conditioners, 
instrumentation, 
digital-to-analog converters, 
analog-to-digital converters, 
voltage/frequency converters, 
synchro-digital converters, 
sample/track-hold amplifiers, 
CMOS switches and multiplexers, 
data-acquisition subsystems, 
power supplies, 
memory integrated circuits, 
microprocessors, 
and so on. 
The scope of this invention broadly allows the inclusion of fillers and 
reinforcements in the encapsulation composition. Fillers can be used to 
improve the dimensional stability, thermal conductivity and mechanical 
strength of the composition. Some suitable fillers include, for example, 
talc, silica, clay, alumina, calcium sulfate, calcium carbonate, mica and 
so on. The fillers can be in the form of, for example, powder, grain or 
fiber. In selecting a filler the following factors should be considered: 
(1) the electrical conductivity of the filler (the lower the better. 
(2) the thermal stability of the filler at encapsulation temperatures; and 
(3) the level of ionic impurities in the filler. 
Suitable reinforcements include fibers of glass or calcium silicate (e.g. 
wollastonite). Examples of other reinforcements include glass or calcium 
silicate in nonfibrous form (e.g. beads, powders, grains, etc.) and fibers 
of other materials such as asbestos, ceramics, etc. 
Although this invention is not limited thereto, a hydrogenated conjugated 
diene/monovinyl-substituted aromatic copolymer can be included in the 
poly(arylene sulfide) composition. An example of such a copolymer is 
hydrogenated butadiene/styrene copolymer. Others are known to persons 
skilled in the art. 
The electrical resistance and hydrolytic stability of the encapsulation 
compositions of this invention can be improved by the addition of an 
organosilane. Many suitable organosilanes are known in the art. Good 
results can be obtained with, for example, 
N-{2-[3-(trimethoxysilyl)propylamino]ethyl}-p-vinylbenzylammonium 
chloride. Organomercaptosilanes can also be used for this purpose. 
3-Mercaptopropyltrimethoxysilane, HSCH.sub.2 CH.sub.2 CH.sub.2 
Si(OCH.sub.3).sub.3, is most preferred because of its high utility in 
improving electrical resistance and hydrolytic stability. 
Besides reinforcements, fillers, copolymers and silanes the compositions 
can optionally contain relatively small amounts of other ingredients such 
as, but not limited to, pigments, flow improvers, and processing aids. 
2. Special Encapsulation Compositions 
It should be noted that the first list of electronic components includes 
both active components (such as, for example, integrated circuits, 
transistors and diodes) and passive components (such as, for example, 
capacitors, resistors and resistor networks). The distinction is 
frequently important and is often determinative of the type of 
poly(arylene sulfide) encapsulation composition best suited for 
encapsulation of the component. 
These more detailed poly(arylene sulfide) compositions, which are 
especially well suited for successful use as encapsulation compositions, 
broadly comprise the following: 
(a) poly(arylene sulfide), 
(b) zinc oxide, 
(c) reinforcement, and 
(d) filler. 
These compositions can optionally contain, in addition to (a), (b), (c) and 
(d) above, relatively small amounts of other components such as, for 
example, hydrogenated conjugated diene/monovinyl-substituted aromatic 
copolymers, organosilanes, pigments, flow improvers and processing aids. 
These compositions are described in more detail in A and B below. 
A. COMPOSITIONS FOR THE ENCAPSULATION OF ACTIVE COMPONENTS 
Compositions used for the encapsulation of active components can be 
prepared in accordance with the following weight percentages: 
(a) Poly(arylene sulfide) 
about 25 to about 45 wt % broad range 
about 32 to about 38 wt % preferred range 
(b) Zinc oxide 
about 0.1 to about 10 wt % broad range 
about 0.5 to about 5 wt % preferred range 
(c) Reinforcement 
about 5 to about 30 wt % broad range 
about 10 to about 20 wt % preferred range 
(d) Filler 
about 40 to about 60 wt % broad range 
about 45 to about 55 wt % preferred range 
The above weight percentages are based upon the total amount of (a), (b), 
(c) and (d) in the composition. Other components, including those 
previously identified, can optionally be present. 
The broad ranges represent the ranges within which the composition should 
be confined in order to obtain good results. The preferred ranges are 
preferred because they define a composition possessing the physical, 
chemical and electrical properties best suited for its intended 
encapsulation purposes. 
Although our invention is not limited thereto the viscosity of the 
composition used for encapsulation of active components should generally 
not exceed about 800 poise (as tested on a capillary rheometer at 
650.degree. F. and at a shear rate of 1000 (sec).sup.-1). Encapsulation of 
active electronic components with compositions having viscosities in 
excess of about 800 poise can cause damage to the components. It is 
contemplated that the viscosity of the composition will generally range 
from about 150 to about 500 poise for active components other than very 
delicate components such as, for example, integrated circuits with wire 
leads. With respect to very delicate components such as, for example 
integrated circuits with wire leads, the viscosity of the encapsulation 
composition should be below about 150 poise (as tested on a capillary 
rheometer at 650.degree. F. and at a shear rate of 1000 (sec).sup.-1). 
Encapsulation of integrated circuits with compositions any higher in 
viscosity can cause wire wash (i.e., breaking of the wires of the 
integrated circuit). It is contemplated that the viscosity of the 
composition for the encapsulation of such integrated circuits and the like 
will generally range from about 75 to about 150 poise. 
Although viscosity of the composition depends on a number of factors, to 
obtain composition viscosities below about 800 poise the viscosity of the 
poly(arylene sulfide) should generally not exceed about 130 poise (as 
tested on a capillary rheometer at 650.degree. F. and at a shear rate of 
1000 (sec).sup.-1). It is contemplated that the viscosity of the 
poly(arylene sulfide) will, in most applications, range up to about 70 
poise. To obtain composition viscosities within the desired range for 
delicate active components such as, for example, integrated circuits with 
wire leads, the viscosity of the poly(arylene sulfide) should generally be 
less than about 25 poise (as tested on a capillary rheometer at 
650.degree. F. and at a shear rate of 1000 (sec).sup.-1). 
The reinforcements can be, for example, glass fibers or calcium silicate 
fibers. 
The filler can be, for example, silica. The silica can be amorphous silica 
or crystalline silica. Silica is commercially available as a finely ground 
material having a relatively narrow particle size distribution ranging 
from about 1 to about 100 micrometers. Such commercial silica is typically 
made up of about 99.5 weight percent SiO.sub.2 with Al.sub.2 O.sub.3, 
Fe.sub.2 O.sub.3, Na.sub.2 O and K.sub.2 O as the remaining components. 
Other fillers include, for example, talc, glass, clay, mica, calcium 
sulfate and calcium carbonate. 
The preferred encapsulation composition for active components is prepared 
from: 
(a) about 32 to about 38 wt % poly(phenylene sulfide) (viscosity less than 
about 130 poise as tested on a capillary rheometer at 650.degree. F. and 
at a shear rate of about 1000 (sec).sup.-1), 
(b) about 0.5 to about 5 wt % zinc oxide, 
(c) about 10 to about 20 wt % glass fibers or calcium silicate fibers, and 
(d) about 45 to about 55 wt % silica. 
The above weight percentages are based upon the total amount of (a), (b), 
(c) and (d) in the composition. Other components, including those 
previously identified, can optionally be present. 
If the viscosity of the poly(phenylene sulfide) is below about 25 poise (as 
tested on a capillary rheometer at 650.degree. F. and at a shear rate of 
1000 (sec).sup.-1) this composition is especially well suited for the 
encapsulation of integrated circuits with wire leads. Accordingly, 
integrated circuits encapsulated with this composition, represent one 
embodiment of my invention. 
B. COMPOSITION FOR THE ENCAPSULATION OF PASSIVE COMPONENTS 
Compositions used for the encapsulation of passive components can be 
prepared in accordance with the following weight percentages: 
(a) Poly(arylene sulfide) 
about 25 to about 45 wt % broad range 
about 32 to about 38 wt % preferred range 
(b) Zinc oxide 
about 0.1 to about 10 wt % broad range 
about 0.5 to about 5 wt % preferred range 
(c) Reinforcement 
about 20 to about 50 wt % broad range 
about 25 to about 45 wt % preferred range 
(d) Filler 
about 18 to about 38 wt % broad range 
about 23 to about 33 wt % preferred range 
The above weight percentages are based upon the total amount of (a), (b), 
(c) and (d) in the composition. Other components, including those 
previously identified, can optimally be present. 
The broad ranges represent the ranges within which the composition should 
be confined in order to obtain good results. The preferred ranges are 
preferred because they define a composition possessing the physical, 
chemical and electrical properties best suited for its intended 
encapsulation purposes. 
Although our invention is not limited thereto the viscosity of the 
composition used for encapsulation of passive components should generally 
not exceed about 1200 poise (as tested on a capillary rheometer at 
650.degree. F. and at a shear rate of 1000 (sec).sup.-1). Encapsulation of 
passive electronic components with compositions having viscosities in 
excess of about 1200 poise can cause damage to the components. It is 
contemplated that the viscosity of the composition will generally range 
from about 500 to about 800 poise. 
To obtain composition viscosities within the desired ranges the viscosity 
of the poly(arylene sulfide) should generally not exceed about 300 poise 
(as tested on a capillary rheometer at 650.degree. F. and at a shear rate 
of 1000 (sec).sup.-1). It is contemplated that the viscosity of the 
poly(arylene sulfide) will generally range from about 190 to about 300 
poise. 
The reinforcements can be, for example, glass fibers or calcium silicate 
fibers. 
The preferred filler is talc because of its availability and ability to 
improve the dimensional stability, thermal conductivity and mechanical 
strength of the composition. In place of talc, or in combination with 
talc, other fillers can be used. Examples of such suitable fillers 
include, silica, calcium sulfate, calcium carbonate, clay, glass and mica. 
Calcium sulfate is especially useful in compositions used to encapsulate 
connectors. 
The preferred encapsulation composition for passive components is prepared 
from: 
(a) about 32 to about 38 wt % poly(phenylene sulfide) (viscosity less than 
about 300 poise as tested on a capillary rheometer at 650.degree. F. and 
at a shear rate of about 1000 (sec).sup.-1), 
(b) about 0.5 to about 5 wt % zinc oxide, 
(c) about 25 to about 45 wt % glass fibers or calcium silicate fibers, and 
(d) about 23 to about 33 wt % talc. 
The above weight percentages are based upon the total amount of (a), (b), 
(c) and (d) in the composition. Other components, including those 
previously identified, can optionally be present. 
This composition is especially well suited for, but not limited to, the 
encapsulation of capacitors. Accordingly, capacitors, encapsulated with 
this composition, represent an embodiment of our invention. 
3. Composition Inhibited Against Color Shift 
It has been discovered that zinc oxide can be used to inhibit the color 
shift associated with the high temperature processing of a poly(arylene 
sulfide) composition containing a pigment and a silane. In the absence of 
the silane a color shift does not occur over a normal range of processing 
temperatures. The presence of the silane, however, can cause a 
temperature-sensitive shift of color to occur. To avoid this color shift, 
processing temperatures must be held lower than otherwise desired. Zinc 
oxide inhibits the color shift and allows higher temperature processing of 
the composition. 
The pigment, in this aspect of the invention, is any pigment selected from 
monoazo nickel complex pigments (see, for example U.S. Pat. No. 2,396,327, 
incorporated by reference herein), iron oxide pigments, lead chromate 
pigments, cadmium sulfo-sulfide pigments, and combinations of any two or 
more thereof (e.g. a combination of an iron oxide pigment and a lead 
chromate pigment; a combination of an iron oxide pigment and a cadmium 
sulfo-sulfide pigment; etc.). 
The silane in this aspect of the invention is any silane selected from the 
organomercaptosilanes, the organoaminosilanes and any combination thereof. 
An organomercaptosilane is an organosilane characterized by a mercapto 
(--SH) functionality in its chemical formula. An example is 
3-mercaptopropyltrimethoxysilane. An organoaminosilane is an organosilane 
characterized by an amino functionality in its chemical formula. Examples 
include 3-aminopropyltrimethoxysilane and 
N-{2-[3-(trimethoxysilyl)propylamino]ethyl}-p-vinylbenzylammonium 
chloride. 
Poly(arylene sulfide) compositions containing the above-identified silanes 
and pigments are laser printable and are useful for the encapsulation of 
electronic components. This aspect of the invention, although not limited 
thereto, has applicability to the compositions described in 1 and 2 above 
wherein those compositions further contain a pigment and a silane as 
identified above. This aspect of the invention is not limited to 
encapsulation compositions but includes any application where it is 
desired to inhibit color shift. 
Although this invention is not limited thereto it is contemplated that the 
invention will usually be practiced within the ranges provided below. 
______________________________________ 
Weight Ratio of Poly(arylene sulfide) 
Component to Component 
______________________________________ 
zinc oxide: 
at least about 2.5 to 1 
(broad range) 
less than about 2,500 to 1 
at least 10 to 1 (narrow range) 
less than about 100 to 1 
pigment: at least about 2.5 to 1 
(broad range) 
less than about 2,500 to 1 
at least about 10 to 1 
(narrow range) 
less than about 100 to 1 
silane: at least about 2.5 to 1 
(broad range) 
less than about 2,500 to 1 
at least about 10 to 1 
(narrow range) 
less than about 100 to 1 
______________________________________ 
The above weight ratios are calculated with disregard to the presence or 
absence of other components in the composition. The narrow ranges are 
preferred because good results have been obtained within those ranges. 
The use of zinc oxide as a color shift inhibitor is desirable when the 
poly(arylene sulfide) composition is subjected to a temperature at which a 
color shift would occur in the absence of the zinc oxide. This color shift 
inhibiting aspect of the invention is further illustrated in Example II. 
4. How to Make 
The compositions of this invention can be made in accordance with any 
method wherein the poly(arylene sulfide), zinc oxide and other components 
(if any) are combined to form a mixture. Many suitable methods are well 
known to those of skill in the art. By way of example, the components of 
the composition can be mixed together at room temperature in a rotating 
drum blender or in an intensive mixer such as a Henschel mixer and then 
extrusion compounded at a temperature above about the melting point of the 
poly(arylene sulfide) to produce a uniform blend. 
Once made, the composition can be used to encapsulate electronic components 
in accordance with any encapsulation method suitable for thermoplastic 
encapsulation compositions. Such methods are well known in the art. The 
composition can be heated to a temperature of at least about the melting 
point of the poly(arylene sulfide) and then used to encapsulate electronic 
components. The composition can, for example, be introduced into an 
injection molding apparatus to produce a melt which is extruded into an 
injection mold wherein the electronic component to be encapsulated is 
positioned. Transfer molding processes are also acceptable. 
The following examples are presented to facilitate disclosure of this 
invention and should not be interpreted to unduly limit its scope. 
EXAMPLE I 
This example demonstrates the utility of zinc oxide in poly(arylene 
sulfide) encapsulation compositions. Two compositions, A and B, were 
prepared in accordance with Table 1 below. 
TABLE 1 
______________________________________ 
(Compositions - weight percentages.sup.g) 
A B 
______________________________________ 
poly(phenylene sulfide).sup.a 
34.0% 33.64% 
wollastonite.sup.b 14.4% 14.46% 
silica.sup.c 49.4% 48.9% 
3-mercaptopropyltrimethoxysilane.sup.d 
1.0% 1.0% 
hydrogenated random copolymer.sup.e 
1.0% 1.0% 
zinc oxide.sup.f 1.0% 
100.0% 100.0% 
______________________________________ 
.sup.a PPS, from Phillips Chemical Company, having a viscosity of about 1 
poise as tested on a capillary rheometer at 650.degree. F. and at a shear 
rate of 1000 (sec).sup.-1. 
.sup.b Calcium silicate fibers sold under the trademark Wollastokup G187 
0.5 NYCO, a division of Processed Minerals, Inc., Willsboro, N.Y. 
.sup.(c) Fused silica (GP 7I) from HarbisonWalker Refractories, a divisio 
of Dresser Industries, Inc. 
.sup.d A-189 .TM. from Union Carbide Corp. 
.sup.e Hydrogenated 41 wt. % butadiene/59 wt. % styrene linear random 
copolymer having a weight molecular weight of about 125,000. (See U.S. 
Pat. No. 3,554,911). 
.sup.f French Process zinc oxide manufactured by Pacific Smelting Co. 
.sup.g The percentages given in Table 1 are weight percentages and are 
based upon the total weight of the composition. 
Each of the compositions was prepared as follows. The silica and silane 
were premixed. The silica/silane and the other components were added to a 
Henschel mixer and mixed until completely dispersed. The resultant mixture 
was passed through a Buss-Condux cokneader extruder at 
570.degree.-600.degree. F. and pelletized. 
Each composition was used to encapsulate integrated circuits (I.C.'s) in 
the manner described below. The pelletized material of composition A was 
injection molded using a 75 ton Newberry molding machine (650.degree. F. 
stock temperature, 275.degree. F. mold temperature at 300# injection 
pressure and 10% rate setting) onto 10 copper alloy integrated circuit 
lead frames. Each of the lead frames had 10 integrated circuit components. 
Thus, composition A was used to encapsulate 100 integrated circuits. Each 
of the encapsulated lead frames was cut and trimmed into the individual 
integrated circuits. Each integrated circuit was a LM 101 linear 
operational amplifier. After encapsulation, the encapsulated portion of 
each integrated circuit measured about 0.5 inch.times.0.25 
inch.times.0.125 inch. The above encapsulation procedure was repeated for 
composition B. 
Prior to encapsulation each integrated circuit was visually inspected for 
faults. Faulty integrated circuits were marked. Following encapsulation, 
cutting and trimming the marked (i.e. faulty) integrated circuits were 
discarded. Remaining for testing were 74 integrated circuits encapsulated 
with composition A and 77 integrated circuits encapsulated with 
composition B. These remaining circuits were subjected to a "Device 
Electric Yield" test. 
The "Device Electric Yield" test is a test to determine the percentage of 
integrated circuits that were successfully encapsulated. This test was 
conducted as follows. The encapsulated integrated circuits were placed on 
a Teflon board consisting of individual zero force insertion sockets. The 
sockets were connected to an Idea Box (manufactured by Global Specialties) 
which was equipped with a 5-volt power source and a signal generator. The 
Idea Box was also connected to a monitor (Oscilloscope, Model 222A, 
Hewlett Packard). Failure or passage of each encapsulated integrated 
circuit was determined by the pattern on the oscilloscope. The pattern 
corresponding to each successfully encapsulated integrated circuit 
conformed with a standard pattern. Failure (i.e. unsuccessful 
encapsulation) was indicated by nonconformance with the standard pattern. 
Of the 74 integrated circuits encapsulated with composition A 66 passed 
the test. Of the 77 integrated circuits encapsulated with composition B 68 
passed the test. 
Of the 66 successfully encapsulated integrated circuits of composition A, 
10 were tested in accordance with the "Constant Test", also known as the 
"Pressure Pot Test with Bias". The 10 integrated circuits were placed on a 
8 inch.times.10 inch Teflon board equipped with sockets to receive the 
leads of the integrated circuits. The board also had electric leads to 
each circuit. The assembled board was placed in an autoclave at 
115.degree. C. and about 10 psig. The atmosphere in the autoclave was 
saturated with water vapor. A 30-volt potential was constantly applied 
across the power leads of the integrated circuits. The integrated circuits 
were periodically removed from the autoclave for testing to determine if 
each integrated circuit was still functioning correctly. As the test 
progressed the number of failures after each time period was recorded. 
This same test was also conducted using 10 of the 68 successfully 
encapsulated integrated circuits of composition B. The results are given 
in Table 2 under the heading "without solder dipping". 
Most of the other integrated circuits not tested above were solder dipped, 
i.e. the leads of each integrated circuit were covered with solder. Of 
these soler dipped integrated circuits, 20 encapsulated with composition A 
and 20 encapsulated with composition B were tested in accordance with the 
"Constant Test" described above. The results are given in Table 3 under 
the heading "solder dipped". 
TABLE 2 
______________________________________ 
(without solder dipping) 
Failures 
Hours in Autoclave 
______________________________________ 
Composition A 1 48 
2-5 213 
6-8 282 
9 446 
10 1,624 
Composition B 1 2,118 
2 2,446 
3 2,590 
4 2,681 
______________________________________ 
TABLE 3 
______________________________________ 
(solder dipped) 
Failures 
Hours in Autoclave 
______________________________________ 
Composition A 1-2 231 
3-13 393 
14-15 487 
16 557 
17-18 651 
19 721 
20 815 
Composition B 1-2 393 
3-4 720 
-- 1,301 
______________________________________ 
Table 2 shows that the 10th and last failure of the integrated circuit 
encapsulated with composition A occurred when checked at 1,624 hours. The 
other nine integrated circuits encapsulated with composition A failed when 
tested at 446 hours or earlier. With respect to the integrated circuits 
encapsulated with composition B it is seen that the 4th failure occurred 
at 2,681 hours. After 2,681 hours 6 of the integrated circuits 
encapsulated with composition B were still functioning correctly. 
Table 3 shows that the 20th and last failure of the solder dipped 
integrated circuits encapsulated with composition A occurred at 815 hours. 
The other 19 integrated circuits encapsulatd with composition A failed at 
721 hours or earlier. With respect to the solder dipped integrated 
circuits encapsulated with composition B it is seen that the 3rd and 4th 
failures occurred at 720 hours. The other 16 integrated circuits were 
still functioning correctly when checked after 1,301 hours. 
The results presented in Table 2 and Table 3 demonstrate the utility of 
zinc oxide in improving reliability and prolonging the life of 
encapsulated electronic components. Composition B (zinc oxide) drastically 
outperformed composition A (without zinc oxide). 
EXAMPLE II 
This example shows the color shift problem associated with 
organomercaptosilane-containing poly(arylene sulfide) compositions and 
demonstrates the color shift inhibiting utility of zinc oxide. Three 
compositions, C, D and E, were prepared in accordance with Table 4 below. 
TABLE 4 
______________________________________ 
(compositions-weight percentages.sup.i) 
C D E 
______________________________________ 
poly(phenylene sulfide).sup.a 
35% 35% 35% 
fiberglass.sup.b 35% 35% 35% 
talc.sup.c 12.75% 11.75% 9.75% 
titanium dioxide.sup.d 
15% 15% 15% 
3-mercaptopropyltrimethoxysilane.sup.e 
1% 1% 
pigment.sup.f 2% 2% 2% 
processing aid.sup.g 
.25% .25% .25% 
zinc oxide.sup.h 2% 
100% 100% 100% 
______________________________________ 
.sup.a PPS, from Phillips Chemical Company, having a viscosity of about 
210 poise as tested on a capillary rheometer at 650.degree. F. and at a 
shear rate of 1000 (Sec).sup.-1. 
.sup.b Fiberglass Grade 197 from OwensCorning, Amarillo, Texas. 
.sup.c Talc type 2620 from Pioneer Talc Co., Van Horn, Texas. 
.sup.d Titanium dioxide, Unitane 0110 .TM. from American Cyanamid Co. 
.sup.e A-189 .TM. from Union Carbide Corp. 
.sup.f Yellow pigment, Harmon Y5694 .TM. from Harmon Chemical Co., 
Hawthorne, New Jersey. 
.sup.g Polyethylene, Marlex .RTM. EMNTR885 from Phillips Chemical Company 
.sup.h Zinc oxide, U.S.P. grade, from Mallinkrodt, Inc. 
.sup.i The percentages given in Table 4 are weight percentages and are 
based upon the total weight of the composition. 
Each composition was separately prepared as follows. The composition 
components were mixed together in a Henschel mixer until the components 
were completely dispersed. The resultant mixture was passed through a 
Buss-Condux cokneader extruder at 570.degree.-600.degree. F. and 
pelletized. 
Each composition thus produced was used to make discs (21/8 inch diameter, 
1/16 inch thick) in the following manner. The pelletized material was 
injection molded, using an Arburg molding machine, into the discs. From 
composition C a first disc was molded at 575.degree. F. and a second disc 
was molded at 650.degree. F. From composition D a first disc was molded at 
600.degree. F. and a second disc was molded at 650.degree. F. From 
composition E a first disc was molded at 600.degree. F. and a second disc 
was molded at 650.degree. F. 
Each disc was carefully observed for color. The observed color 
corresponding to each disc is reported in Table 5 below. 
TABLE 5 
______________________________________ 
(Observed Disc Color) 
Composition 
575.degree. F. 
600.degree. F. 
650.degree. F. 
______________________________________ 
C yellow gold -- yellow gold 
D -- yellow gold green gold 
E -- yellow gold yellow gold 
______________________________________ 
Composition C was color stable over the temperatures tested. There was no 
significant difference in color between the first (575.degree. F.) and 
second (650.degree. F.) discs. Composition D, containing the silane, 
exhibited a color shift. The first disc (600.degree. F.) was yellow gold, 
however, the second disc (650.degree. F.) was green gold. Composition E, 
containing both the silane and zinc oxide, was color stable, i.e. there 
was no significant difference in color between the first (600.degree. F.) 
and second (650.degree. F.) discs. The results associated with composition 
E demonstrate the utility of zinc oxide in inhibiting color shift in 
organomercaptosilane-containing poly(arylene sulfide) compositions. 
Composition E represents a material suitable for the encapsulation of 
electronic components. It can be used, for example, to encapsulate 
capacitors. Composition E is also a laser printable material.