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BACKGROUND OF THE INVENTION
The present invention relates to electrical device of motor bicycles, snow mobiles, or other industrial machinery which are sealed with resins so that they may be satisfactorily used under severe environmental conditions such as vibrations and cycling change in temperature over a very wide range (hereinafter referred to as cycling temperature change).
Hitherto, in order to protect the electrical devices from the severe environments, especially from vibrations, moisture and vapor, and cycling temperature change, they are sealed or enclosed with highly flexible resins such as epoxy resins, urethane resins, and so on. However, when a flexible resin is used in order to protect the electrical devices at low temperatures, the resistance to heat is not satisfactory. On the other hand, when a resin which is satisfactorily resistant to heat is used, its resistance to low temperature is not satisfactory. That is, the resistance to heat and the resistance to low temperature are incompatible with each other. In order to overcome this problem, a mixture consisting of a flexible resin and an insulating material has been used to seal or enclose electrical devices so that the coefficient of thermal expansion may be minimized. However, when an insulating material is mixed into a resin, the viscosity of the mixture is increased so that the electrical device cannot be completely set and sealed with the mixture. Thus, the use of such mixture cannot attain the satisfactory sealing effects of the electrical devices in practice.
The present invention was therefore made in order to solve the above and other problems encountered in the prior art techniques. One of the objects of the present invention is to provide resin-sealed electrical devices which may satisfactorily function even when they are subjected to severe cycling temperature change, vibrations and high humidity. In the present invention, an electrical device is not sealed with a mixture consisting of a resin and an insulating material, but is sealed by being embedded in one or more layers of the insulatng material among the particles of which sinks into a resin of low-viscosity. However, the grain size of the insulating compounds to be used must not be too coarse or too fine. When the grain size is too fine, it becomes very difficult to impregnate a resin from the top surface of an insulating material layer and as a result the impregnation time becomes inevitably longer. On the other hand, if the grain size is too coarse, the impregnated resin does not come short of the electrical elements constituting an electrical component. Therefore, when the electrical device is subjected to cycling temperature change cracks occur. It is of course easy to impregnate a resin into a layer of an insulating material of a coarse grain size. However, the grain size of the insulating material must be determined so that the desired electrical characteristics and performance of the resin-sealed electrical devices may be maintained.
Briefly stated, the present invention provides a resin sealed electrical device comprising an electrical element, a case for housing said electrical device therein, a layer of an insulating compound such as finely divided quartz (SiO.sub.2), magnesium oxide (MgO), lead oxide (PbO), borosilicate soda glass or rubber so that said electrical component may be embedded in said layer, and a cover layer consisting of a resin of low viscosity formed over said first mentioned layer, said resin of low viscosity being impregnated into said first mentioned layer.
According to one aspect of the present invention, an electrical component is embedded into a layer of a finely divided insulating material charged into a case, and a resin of low viscosity is poured into the case so that it may be impregnated into the insulating material layer and may form a cover layer over the free surface of the insulating material layer. Therefore, the resistance to moisture and vapor of the electrical device may be considerably improved, so that the deterioration of the electrical characteristics may be well prevented. Furthermore, the commercial value of the electrical device may be remarkably increased. Moreover, the performance of the electrical device sealed with resin in accordance with the present invention is very satisfactory under very severe environmental conditions; no crack is started; and the desired electrical characteristics may be maintained. According to another aspect of the present invention, the particles of different sizes of an insulating component are used so that a plurality of insulating material layers of different grain size ranges may be formed. Therefore, the impregnation of a resin of low viscosity is readily accomplished within a short time, so that the fabrication efficienty of the electrical device may be much improved.
The above and other objects, features and advantages of the present invention will become more apparent from the following description of some preferred embodiments and examples thereof in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2 are a schematic top and a sectional view of a conventional testing washer which is shown as an example of electrical elements constituting an electrical component according to the present invention;
FIG. 3 is a sectional view of the washer shown in FIGS. 1 and 2 and sealed with a resin in accordance with the present invention;
FIGS. 4 and 5 are a top and a sectional view, respectively, of an electrical component, i.e. semiconductor device of a condensor discharge type ignition device to be sealed with resin in accordance with the present invention; and
FIG. 6 is a sectional view thereof sealed in accordance with the present invention.
FIRST EMBODIMENT, FIGS. 1 - 3
The first embodiment of the present invention will be described in conjunction with a sample, i.e., a conventional "Olyphant" washer generally designated by 1 in FIGS. 1 - 3. The washer 1 (9 mm in diameter and 6.5 mm in height) has eight projections 2 (2.5 mm in height) protruded from both surfaces thereof. The washer 1 is embedded into a layer of an electrical insulating material 4 charged into an aluminum case 3 (50 mm in diameter and 30 mm in depth) as shown in FIG. 3. A resin of a low viscosity (whose viscosity is less than 1500.sup.CP at room temperature) is directly impregnated into the layer 4 and is poured into the aluminum case 3 so that a cover layer 5 whose thickness is thinner than that of the insulating material layer 4 may be formed over the free surface of the layer 4.
Next some examples obtained by the above described method will be described.
EXAMPLE 1
Finely divided quartz SiO.sub.2 was used as an insulating material. The degree of impregnation depending upon the grain sizes of resins of low viscosity and the appearance of the samples after they were subjected to the cycling temperature change tests were investigated. The results are shown in Tables 1 and 2.
TABLE 1
__________________________________________________________________________
Average grain Results of cycling
size in micron Impregna-
temperature change
Sample
of insulating
Constituent of low
tion test in aluminum
No. material (SiO.sub.2)
viscosity resin
property
casing
__________________________________________________________________________
1 44 poor good
2 61 Resin: bisphenol type
good good
3 88 epoxy resin good good
4 149 Hardener: methyl highmic
good good
5 177 acid anhydride
good good
6 250 Diluent: polypropylene
good good
7 350 glycol good good
8 500 Viscosity: 600 - 800.sup. cp
good good
9 840 good good
10 1680 good good
11 2830 good good
12 3360 good good
13 4760 good good
14 5660 Resin: " good poor (cracks appear
Hardener: " after 4 cycles)
15 conglomerated
Diluent: " good poor (cracks appear
Viscosity: " after 1 cycle)
__________________________________________________________________________
(Cycling temperature change test: One cycle consists of three steps of
leaving samples for one hour at -65.degree. C., leaving the samples for
five minutes at room temperature and leaving the samples for one hour at
155.degree. C.)
TABLE 2
__________________________________________________________________________
Average grain Results of cycling
size in micron Impregna-
temperature change
Sample
of insulating
Constituent of low
tion test in aluminum
No. material (SiO.sub.2)
viscosity resin
property
casing
__________________________________________________________________________
16 88 Resin: bisphenol type
good good
epoxy resin
17 149 Hardener: aliphatic
good good
amine
18 350 good good
19 500 Diluent: polypropylene
good good
glycol
Viscosity: 600 - 800.sup. cp
20 2830 good good
21 4760 good good
__________________________________________________________________________
(Cycling temperature change test: One cycle consists of three steps of
leaving samples for one hour at -65.degree. C., leaving the samples for
five minutes at room temperature and leaving the samples for one hour at
155.degree. C.)
It is seen that when the average grain size of the insulating materials is between 61 .mu. and 4760 .mu., the degree of impregnation of the resins of low viscosity is better and the results of the cycling temperature change tests were also better. Other insulating materials such as magnesium oxide MgO, ferric oxide Fe.sub.2 O.sub.3, lead oxide PbO, hollow borosilicate soda glass and rubber which have the same average grain size as the above-mentioned were also tested. The degree of impregnation as well as the results of the cycling temperature change tests were better.
EXAMPLE 2
The upper and lower layers of finely divided quartz SiO.sub.2 of different grain sizes were formed in the case so that electrical elements were embedded therein. An epoxy resin of low viscosity was impregnated into the upper and lower layers. The degree of impregnation as well as the results of the samples subjected to the cycling temperature change tests were investigated. The results are shown in Table 3.
TABLE 3
__________________________________________________________________________
Average grain
size in micron
of insulating Results of cycling
material (SiO.sub.2) Impregna-
temperature change
Sample
upper
lower
Constituent of low
tion test in aluminum
No. layer
layer
viscosity resin
property
casing
__________________________________________________________________________
22 149 840 good good
23 177 840 good good
24 350 840 Resin: bisphenol type
good good
epoxy resin
25 840 149 good good
26 840 177 Hardener: aliphatic
good good
amine
27 840 350 Diluent: polypropylene
good good
glycol
28 350 2830 good good
29 500 2830
Viscosity: 400 - 600.sup. cp
good good
30 840 2830 good good
__________________________________________________________________________
(Cycling temperature change test: One cycle consists of three steps of
leaving samples for one hour at -65.degree. C., leaving the samples for
five minutes at room temperature and leaving the samples for one hour at
155.degree. C.)
It is seen that both the degree of impregnation and the results of the cycling temperature change tests were better even when the two layers of the insulating material, finely divided quartz SiO.sub.2, of different grain sizes were formed. Furthermore, the degree of impregnation was improved and the impregnation time was reduced because of the two layers of the insulating material of different grain sizes. Other insulating material such as magnesium oxide MgO, ferric oxide Fe.sub.2 O.sub.3, lead oxide PbO, hollow borosilicate soda glass and rubber were also tested. The results were quite satisfactory.
EXAMPLE 3
Finely divided quartz was charged so as to form three layers of different grain sizes. Electrical elements were embedded into an intermediate layer of finest grain sizes. The upper and lower layers had the grain sizes greater than that of the intermediate layer. An epoxy resin of low viscosity was impregnated into these layers. The results of the impregnation tests and the cycling temperature change tests are shown in Table 4.
TABLE 4
__________________________________________________________________________
Average grain size in
micron of insulating
material (SiO.sub.2) Results of cycling
inter- Impregna-
temperature change
Sample
upper
mediate
lower
Constituent of low
tion test in aluminum
No. layer
layer
layer
viscosity resin
property
casing
__________________________________________________________________________
31 1680
88 350 Resin: bisphenol type
good good
epoxy resin
Hardener: aliphatic
32 350 80 1680
amine good good
Diluent: polypropylene
glycol
33 840 177 840 Viscosity: 400 - 600 .sup.cp
good good
__________________________________________________________________________
(Cycling temperature change test: One cycle consists of three steps of
leaving samples for one hour at -65.degree. C., leaving the samples for
five minutes at room temperature and leaving the samples for one hour at
155.degree. C.)
It is seen that both the degree of impregnation and the results of the cycling temperature change tests were satisfactory even when the three layers of the insulating material, finely divided quartz SiO.sub.2, of different grain sizes were formed. The impregnation time was also reduced. The results of the tests of other insulating material such as magnesium oxide MgO, ferric oxide Fe.sub.2 O.sub.3, lead oxide PbO, hollow borosilicate soda glass and rubber were also satisfactory.
SECOND EMBODIMENT, FIGS. 4 - 6
In the second embodiment shown in FIGS. 4 - 6, an electrical component, i.e., a semiconductor device (CD amplifier) for a condenser discharge type ignition device for use with a motor bicycle is sealed with resin. That is, the semiconductor device comprises, as best shown in FIGS. 4 and 5, an aluminum case 6, a lead wire cover 7, a lead wire 8, grommets 9, a printed circuit board 10, a rubber bush 11 for a lead wire, electrical circuit elements 12, a semiconductor circuit complete 13. As shown in FIG. 6, an insulator or insulating material 15 is charged into the aluminum case 6 so that the electrical elements 10, 12 and 13 are embedded into the layer of the insulating material. Thereafter, a resin of low viscosity is impregnated into the layer of the insulating material 15 and is poured into the aluminum case 6 so that a cover layer 14 may be formed over the free surface of the insulating material layer. Thus, the electrical component is sealed with the resin. As best shown in FIG. 6, the thickness of the cover layer 14 is smaller than that of the insulating material layer.
EXAMPLE 4
As an example of electrical devices, semiconductor devices (CD amplifiers) for condenser type ignition devices for outboard engines were sealed with resins according to the method of the present invention and the prior art methods. After the resin-sealed semiconductor devices underwent the moisture and vapor tests and the cycling temperature change tests, their electrical characteristics performance and appearances were investigated. The results are shown in Table 5.
TABLE 5
__________________________________________________________________________
Electrical
charac-
Appearance
teristics
after cycling
after cycling
A resin-sealed Dampproof
temperature
temperature
Synthetic
electrical device
Constituent of resin
test change test
change test
decision
__________________________________________________________________________
Prior Art 1 cracks appear
(CD amplifier for
Resin:polyurethane
good after one
inoperable
poor
outboard engines)
resin cycle
Prior Art 2
Resin:flexible epoxy foaming and
(CD amplifier for
resin good swelling after
inoperable
poor
outboard engines)
Hardener: amines one cycle
Resin:flexible epoxy
Prior Art 3
resin mixed with
(CD amplifier for
silica good cracks appear
inoperable
poor
outboard engines)
(25 parts hundred epoxy resin)
Hardener: acid anhydrides
Prior Art 4 good in
(CD amplifier for
silicone rubber
poor good operation
poor
outboard engines)
Electrical device
Resin:bisphenol A type
according to the
epoxy resin
present invention
Hardener: acid anhydride
good good good in
good
(CD amplifier for
Insulating material: SiO.sub.2
operation
outboard engines)
(grain size: 840.mu.)
Sample No. 34
Resin:bisphenol A type
epoxy resin
Hardener: acid anhydride
" Insulating material: SiO.sub.2
Sample No. 35
##STR1## good good good in operation
good
Resin:bisphenol A type
epoxy resin
Hardener: acid anhydride
" Insulating material: SiO.sub.2
Sample No. 36
##STR2## good good good in operation
good
__________________________________________________________________________
(Dampproof test: Samples were left for 240 hours at humidity of 95 %)
(Cycling temperature change test: One cycle consists of three steps of
leaving samples for one hour at -65.degree. C., leaving the samples for
five minutes at room temperature and leaving the samples for one hour at
155.degree. C.)
The results of the tests of the semiconductor devices sealed with resins in accordance with the present invention were quite satisfactory, and it has been found that they may be satisfactorily used in the outboard engines.
EXAMPLE 5
As an example of electrical devices, semiconductor devices (DC amplifiers) of the condenser discharge type ignition devices for snowmobile engines were sealed with various insulating materials and resins, and were subjected to the moisture and vapor tests and the cycling temperature change tests. The results are shown in Table 6.
TABLE 6
__________________________________________________________________________
Electrical
characteri-
Appearance
stic after
Constituent of low after cycling
cycling
A resin-sealed
viscosity resin and
Dampproof
temperature
temperature
Synthetic
electrical device
insulating material
test change test
change test
decision
__________________________________________________________________________
Electrical device
Resin: bisphenol type
according to the
epoxy resin
present invention
Diluent: polypropylene good in
(CD amplifier for
glycol good good operation
good
snow mobiles)
Hardener: aliphatic amine
Sample No. 37
Insulating material: SiO.sub.2
(grain size: 420.mu.)
Resin: "
Diluent: "
" Hardener: " good in
Sample No. 38
Insulating material:
good good operation
good
SiO.sub.2 + CaCO.sub.3 (30 parts)
hundred SiO.sub.2)
(grain size: 420.mu.)
Resin: "
" Diluent: "
Sample No. 39
Hardener: K61-B (amine)
good good good in
good
Insulating material: SiO.sub.2
operation
(grain size: 420.mu.)
Resin: "
" Diluent: "
Sample No. 40
Hardener: aliphatic amine good in
Insulating material:
good good operation
good
SiO.sub.2 + CaCO.sub.3 (30 parts
hundred SiO.sub.2)
(grain size: 420.mu.)
" Resin: urethane resin
good good good in
good
Sample No. 41
Insulating material: SiO.sub.2
operation
(grain size: 420.mu.)
__________________________________________________________________________
(Dampproof test: Samples were left for 240 hours at humidity of 95 %)
(Cycling temperature change test: One cycle consists of three steps of
leaving samples for one hour at -65.degree. C., leaving the samples for
five minutes at the room temperature and leaving the samples for one hour
at 155.degree. C.)
The results were quite satisfactory, and it has been found that the semiconductor devices sealed with resins in accordance with the present invention may be satisfactorily used in the snowmobile engines.
EXAMPLE 6
As an example of electrical devices, non-contact voltage regulators for engines of agricultural machinery were sealed with various insulating materials and resins, and subjected to the moisture and vapor tests and the cycling temperature change tests. The results are shown in Table 7.
TABLE 7
__________________________________________________________________________
Electrical
characteri-
Appearance
stics after
Constituent of low after cycling
cycling
A resin-sealed
viscosity resin and
Dampproof
temperature
temperature
Synthetic
electrical device
insulating material
test change test
change test
decision
__________________________________________________________________________
Electrical device
Resin: bisphenol type
according to the
epoxy resin
present invention
Diluent: polypropylene
(non-contact volt-
glycol good in
age regulator for
Hardener: acid anhydride
good good operation
good
agricultural
(MHAC)
machinery)
Insulating material: SiO.sub.2
Sample No. 42
(grain size: 420.mu.)
Resin: "
Diluent: "
" Hardener: aliphatic amine good in
Sample No. 43
Insulating material:
good good operation
good
SiO.sub.2 + CaCO.sub.3 (30 parts)
hundred SiO.sub.2)
(grain size: 420.mu.)
Resin: "
Diluent: "
" Hardener: K61-B (amines)
good good good in
good
Sample No. 44
Insulating material: SiO.sub.2
operation
(grain size: 420.mu.)
__________________________________________________________________________
(Dampproof test: Samples were left for 240 hours at humidity of 95 %)
(Cycling temperature change test: One cycle consists of three steps of
leaving samples for one hour at -65.degree. C., leaving the samples for
five minutes at room temperature and leaving the samples for one hour at
155.degree. C.)
The results were quite satisfactory, and it has been found that the semiconductor devices sealed with resins in accordance with the present invention may be satisfactorily used in agricultural machinery engines.
EXAMPLE 7
As an example of electrical device, semiconductor devices (CD amplifiers) of the condenser dischage type ignition devices for motor bicycle engines were sealed with various insulating materials and resins and subjected to the moisture and vapor tests and the cycling temperature change tests. The results are shown in Table 8.
TABLE 8
__________________________________________________________________________
Electrical
characteri-
Appearance
stics after
Constituent of low after cycling
cycling
A resin-sealed
viscosity resin and
Dampproof
temperature
temperature
Synthetic
electrical device
insulating material
test change test
change test
decision
__________________________________________________________________________
Electrical device
Resin: bisphenol type
according to
epoxy resin
present invention
Diluent: polypropylene good in
(CD amplifier for
glycol good good operation
good
motor bicycles)
Hardener: aliphatic amine
Sample No. 45
Insulating material: SiO.sub.2
(grain size: 840.mu.)
Resin "
" Diluent: " good in
Sample No. 46
Hardener: K61-B (amines)
good good operation
good
Insulating material: "
(grain size: 840.mu.)
Resin: "
Diluent: "
" Hardener: " good in
Insulating material:
good good operation
good
Sample No. 47
SiO.sub.2 + CaCO.sub.3 (30 parts
hundred SiO.sub.2 )
(grain size: 840.mu.)
__________________________________________________________________________
(Dampproof test: Samples were left for 240 hours at humidity of 95 %)
(Cycling temperature change test: One cycle consists of three steps of
leaving samples for one hour at -65.degree. C., leaving the samples for
five minutes at room temperature and leaving the samples for one hour at
155.degree. C.)
As a result, it has been found that both the appearance and the electrical properties of the semiconductor devices sealed with resins are quite satisfactory.
EXAMPLE 8
As an example of electrical devices, semiconductor devices (CD amplifiers) of the condenser discharge type ignition devices for the snowmobile engines were sealed with hollow borosilicate soda glass, and subjected to the moisture and vapor tests and the cycling temperature change tests in order to investigate their electrical characteristics and appearance. The results are shown in Table 9.
TABLE 9
__________________________________________________________________________
Electrical
characteri-
Appearance
stics after
Constituent of low after cycling
cycling
A resin-sealed
viscosity resin and
Dampproof
temperature
temperature
Synthetic
electrical device
insulating material
test change test
change test
decision
__________________________________________________________________________
Electrical device
Resin: bisphenol type
according to the
epoxy resin
present invention
Diluent: polypropylene good in
(CD amplifier for
glycol good good operation
good
snow mobiles)
Hardener: aliphatic amine
Insulating material: hollow
Sample No. 48
borosilicate soda glass
(grain size: 65.mu.)
Resin: "
" Diluent: " good in
Sample No. 49
Hardener: " good good operation
good
Insulating material: "
(grain size: 840.mu.)
__________________________________________________________________________
(Dampproof test: Samples were left for 240 hours at humidity of 95 %)
(Cycling temperature change test: One cycle consists of three steps of
leaving samples for one hour at -65.degree. C., leaving the samples for
five minutes at room temperature and leaving the samples for one hour at
155.degree. C.)
As a result, it has been found that both the appearance and the electrical properties of the semiconductor devices sealed with resins are quite satisfactory even when hollow borosilicate soda glass is used as insulating material, and that such semiconductor devices may be practically used in the snowmobile engines.
EXAMPLE 9
As an example of electrical devices, semiconductor devices (CD amplifiers) of the condenser discharge type ignition devices for the snowmobile engines were sealed with the insulating material consisting of finely divided rubber, and were subjected to the moisture and vapor tests and the cycling temperature change tests in order to investigate the electrical characteristics and appearance after the tests. The results are shown in Table 10.
TABLE 10
__________________________________________________________________________
Electrical
characteri-
Appearance
stics after
Constituent of low after cycling
cycling
A resin-sealed
viscosity resin and
Dampproof
temperature
temperature
Synthetic
electrical device
insulating material
test change test
change test
decision
__________________________________________________________________________
Electrical device
Resin: bisphenol type
according to the
epoxy resin
present invention
Diluent: polypropylene
(CD amplifier for
glycol good in
snow mobiles)
Hardener: aliphatic amine
good good operation
good
Insulating material: natural
Sample No. 50
rubber
(grain size: 1000.mu.)
Resin: "
Diluent: "
" Hardener: " good in
Sample No. 51
Insulating material: silicon
good good operation
good
rubber
(grain size: 1000.mu.)
__________________________________________________________________________
(Dampproof test: Samples were left for 240 hours at humidity of 95 %)
(Cycling temperature change test: One cycle consists of three steps of
leaving samples for one hour at -65.degree. C., leaving the samples for
five minutes at room temperature, and leaving the samples for one hour at
155.degree. C.)
As a result, it has been found that both the electrical characteristics and the appearance of the semiconductor devices sealed with resins are quite satisfactory even when rubber is used as insulating material, and that such semiconductor devices may be practically used in the snowmobile engines.
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