U.S. patent number 3,622,944 [Application Number 04/882,456] was granted by the patent office on 1971-11-23 for electrical connector.
This patent grant is currently assigned to Tokai Denki Kabushiki Kaisha. Invention is credited to Syoichi Ito, Tetsuya Ohtani, Akira Sato, Takane Tsuchiya.
United States Patent |
3,622,944 |
Tsuchiya , et al. |
November 23, 1971 |
ELECTRICAL CONNECTOR
Abstract
In this electrical connector, an electrical connection is made
through a low melting point alloy consisting essentially of gallium
and indium which is liquid at room temperature. In order to retain
the low melting point alloy, contact points may be made of a porous
solid material impregnated with the low melting point alloy, or may
be made of cadmium, bismuth or lead having interfaces between which
the low melting alloy is precipitated. In any case, gallium may be
provided at one contact point and indium at the other contact
point, so that when the two points are brought together the low
melting point alloy is formed.
Inventors: |
Tsuchiya; Takane (Yokohama-shi,
JA), Ohtani; Tetsuya (Yokohami-shi, JA),
Sato; Akira (Tokyo, JA), Ito; Syoichi
(Yokohama-shi, JA) |
Assignee: |
Tokai Denki Kabushiki Kaisha
(Tokyo, JA)
|
Family
ID: |
26402637 |
Appl.
No.: |
04/882,456 |
Filed: |
December 5, 1969 |
Foreign Application Priority Data
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|
|
|
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Aug 5, 1969 [JA] |
|
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61590 |
Aug 7, 1969 [JA] |
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62106 |
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Current U.S.
Class: |
439/179; 439/886;
439/874 |
Current CPC
Class: |
H01R
13/02 (20130101); H01R 4/22 (20130101) |
Current International
Class: |
H01R
13/02 (20060101); H01R 4/00 (20060101); H01R
4/22 (20060101); H01r 003/08 () |
Field of
Search: |
;339/118,275,278
;29/194,199 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: McGlynn; Joseph H.
Claims
We claim:
1. An electrical connector comprising two members which are adapted
to be assembled to form an electrical connection, each member
having an electrically conducting element which extends adjacent to
an electrically conducting element of the other member, and a body
of a low melting point alloy consisting essentially of gallium and
indium which is a liquid at room temperature, forming a junction
between the two elements.
2. An electrical connector according to claim 1 comprising, in
contact with the low melting point alloy, a metal which diffuses
thereinto and thereby converts the low melting point alloy into a
solid alloy.
3. An electrical connector according to claim 1 wherein each member
has an electrically conducting contact which is directly engageable
by an electrically conducting contact of the other member to form a
temporary connection, and an electrically conducting element which
is adapted to be interposed between the two contacts to form a
permanent electrical connection between the two contacts through a
body of a low melting point alloy consisting essentially of gallium
and indium which is a liquid at room temperature.
4. An electrical connector according to claim 1 wherein an
electrical connection is made through a porous solid material
impregnated with the low melting point alloy.
5. An electrical connector according to claim 1 comprising a
connecting member having a surface comprising indium, and a second
connecting member having a surface which comprises gallium and is
engageable with the surface comprising indium to form an alloy
therewith.
6. An electrical connector according to claim 5 wherein the second
connecting member has a surface comprising a material of the class
consisting of cadmium, bismuth and lead having interfaces between
which gallium is precipitated.
Description
BACKGROUND OF THE INVENTION
This invention relates to an electrical connector which can be used
for connecting electrical conductors in various types of electrical
apparatus, such as communication equipment, electrical machinery
and other electrical equipment.
In the known electrical connectors, it is conventional to form an
electrical connection by holding contact surfaces together under
pressure.
In such known electrical connectors, the contacting surfaces are
gradually corroded or contaminated by the action of the atmosphere,
so that the electrical resistance across the connection gradually
increases. Under such conditions, the minimum force with which the
contacting surfaces must be held together in order to provide a
certain minimum resistance across the connection gradually
increases. Because of the modern tendency toward miniaturization of
electrical apparatus, the contact pressure which can be provided is
limited, so that it is not possible to employ high contact pressure
in order to maintain the desired low resistance across a pair of
contacts.
SUMMARY OF THE INVENTION
The present invention overcomes these and other disadvantages of
the known connectors and affords addition advantages. In an
electrical connector embodying the present invention, an electrical
connection is made through a low melting point alloy consisting
essentially of gallium and indium which is a liquid at room
temperature. The preferred alloy is a eutectic alloy of gallium and
indium.
A primary object of the invention is to provide a low contact
resistance by forming an electrical connection through an alloy
which is a liquid at room temperature, consisting essentially of
gallium and indium, which is present on the contacting
surfaces.
A secondary object of the invention is to prevent the gradual
increase which takes place in the resistance of the known
connectors, so that high contact pressure is not required.
Other objects of the invention are to eliminate the need for
periodic cleaning of contacts, to eliminate the need for
appreciable contact pressures, and to make it possible to produce
perfect and permanent electrical connections by mere assembly
without the use of complicated operations such as soldering. A
permanent, solid connection may be achieved in the practice of the
present invention, by providing, in contact with the indium-gallium
alloy which is a liquid at room temperature, a metal which diffuses
there into and thereby converts the low melting point alloy into a
solid alloy. Such conversion of the normally liquid alloy into a
solid alloy is a gradual process, so that the electrical connection
may be repeatedly broken and remade during assembly, and the
connection does not solidify until sometime after all assembly
operations are completed.
Thus the present invention saves labor and makes possible more
economical manufacturing methods, in addition to providing a more
dependable and lasting electrical connection.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of a conventional electrical connector
in its assembled state.
FIG. 2 is a side elevation of a preferred form of electrical
connector embodying the invention, showing its appearance prior to
assembly of the connector.
FIG. 3 is a side elevation of the electrical connector of FIG. 2 in
its assembled state.
FIG. 4 is a longitudinal section of another connector embodying the
invention.
FIG. 5 is a similar section showing the elements of FIG. 4 before
assembly.
FIG. 6 is a longitudinal section of a third form of connector
embodying the invention.
FIG. 7 is a section similar to FIG. 6, showing the elements of the
connector before assembly.
FIG. 8 is a perspective view of a terminal block embodying the
invention.
FIG. 9 is a perspective view of another terminal block embodying
the invention.
FIG. 10 is a longitudinal section of another connector embodying
the invention, showing the parts before assembly.
FIG. 11(A) is a fragmentary diagrammatic view showing the parts of
the connector of FIG. 10 assembled to form a temporary
connection.
FIG. 11(B) is a fragmentary diagrammatic view showing the parts of
the connector of FIG. 10 in their final assembled condition.
FIG. 12 is a longitudinal section of another connector embodying
the invention, showing the parts before assembly.
FIG. 13(A) is a fragmentary diagrammatic view showing the parts of
the connector of FIG. 12 partially assembled.
FIG. 13(B) is a fragmentary diagrammatic view showing the parts of
the connector of FIG. 12 in their final assembled condition.
FIG. 14 is a diagrammatic view of a further connector embodying the
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a conventional electrical connector, in which the two
contacts consist of a plug 1 fixed in a holder of suitable
insulating material and a jack 3,3 fixed in another holder 4 of
insulating material. The jack 3,3 is resilient, so that when the
plug is inserted into the jack a certain amount of force must be
used, and the assembled contacts are then held together under
sufficient pressure to provide the necessary low resistance across
the connector. A disadvantage of this connector is that the
resistance gradually increases because of the action of the
atmosphere in corroding or contaminating the connecting surfaces,
and the accumulation of dust and dirt upon the contacting
surfaces.
In order that the connector may form part of an electrical circuit,
connecting members such as the plug 1 and the jack 3,3 are
permanently connected to wire leads 5,5.
The low melting alloy used in the practice of the present invention
is an alloy consisting essentially of gallium and indium. When
gallium is contacted with indium, a liquid alloy is formed at a
temperature as low as 16.5.degree. C. If the indium contains zinc
or tin, a liquid alloy may be produced by contacting it with
gallium at a temperature as low as 9.degree. C.
In the connector embodying the invention shown in FIG. 2, gallium
or a eutectic alloy of gallium is applied at 6 to the contact
portion of the plug 1, and indium or a eutectic alloy of indium is
applied at 7 on the surface of the jack 3,3 which is contacted when
the plug 1 is inserted.
As shown in FIG. 3, when the plug 1 is inserted into the jack 3,3,
a liquid alloy 6,7 of gallium and indium is formed, and this liquid
alloy forms a junction between the contacting surfaces of the plug
and the jack.
In a connector embodying the invention, such as that shown in FIG.
3, substantial pressure is not required to form a connection of low
resistance, and mere contact between the connecting members which
are separated by the liquid alloy is sufficient to provide a
contact or electrical connection of low resistance.
The quantity of the liquid alloy which is required in a connector
embodying the invention is very small, and the liquid alloy is
maintained on the contact surfaces by adhesion and cohesion. In a
connector embodying the invention, the electrical connection is not
impaired by vibration or shock, because the connecting members are
electrically joined by the liquid alloy. Moreover, in a connector
embodying the invention there is no danger that the resistance may
be increased by the action of gases in the atmosphere or by
accumulation of dust or dirt.
In a connector embodying the invention, the connecting members,
which are usually made of copper, may be plated with chromium or
titanium. The diffusion of chromium or titanium into a liquid alloy
of gallium and indium is very slow so that the liquid form of the
alloy is preserved for a very extended period of time when the
connecting members are plated with chromium or titanium.
An automatic telephone exchange usually is assembled from a large
number of panels or shelves. When these panels are mounted in
place, it is necessary to make wire connections between the shelves
and the wiring operation is very tedious. In order to expedite the
work of wiring the panels in an automatic telephone exchange,
attempts to use electrical connectors have been made, but is has
been found that electrical connectors which can be provided upon
the panels are not reliable.
When the connector shown in FIGS. 2 and 3 is to be used on panels
for an automatic telephone exchange, excellent and reliable results
can be obtained by making the plug and jack of phosphorous bronze,
galvanized with silver or gold. Gallium is applied to the plug at
6, and indium or a eutectic alloy of indium is applied to the jack
at 7. In the connector shown in FIG. 2, the gallium at 6 and the
indium at 7 are solid materials before the plug is inserted into
the jack. As soon as the plug is inserted, a liquid alloy is formed
from the gallium and indium between the contacting surfaces of the
plug and jack. Gold, silver or copper surfaces on the plug or jack,
when in contact with the liquid gallium-indium alloy, diffuse into
the liquid alloy and thus gradually convert the liquid alloy into a
solid by raising the melting point of the alloy. However, the
resulting solid alloy is relatively soft so that the plug can be
pulled out of the jack without difficulty, particularly when the
connector is warm.
In the connector shown in FIGS. 4 and 5, a plug is formed by a
holder 8 of insulating material carrying a resilient contact member
9. A jack is formed of a holder 10 of insulating material provided
with a contact member 11 adapted to extend adjacent to the contact
member 9. The contact member 11 does not need to be resilient. Lead
wires 12 are connected to the contact members 9 and 11. A
cylindrical receptacle 13, made of elastic material, is open at the
top and contains a low melting point alloy 14 which is a liquid at
room temperature and consists essentially of gallium and indium.
The alloy 14 is covered with a thin film A, which is made of
paraffin, rubber, a plastic material or the like, and which retains
the low melting point alloy 14. The contact members 9 and 11 may be
made of copper or a copper alloy, and the contact portions 9' and
11' of these contact members may be left bare or may be galvanized
with gold or silver. When the receptacle 13 is inserted in place as
shown in FIG. 4, the contact portions 9' and 11' puncture the film
A and are then surrounded with the gallium-indium alloy in the
receptacle, which wets the contact portions 9' and 11' and forms
the electrical connection between them. The alloy forms a perfect
electrical connection which does not depend upon pressure between
the contact members. If the contact portions 9' and 11' have been
plated with titanium or chromium, or are made of stainless steel,
the alloy will remain liquid at room temperature for an extended
period of time. On the other hand, if the surfaces of the contact
portions 9' and 11' consist of copper, a copper alloy, gold, silver
or the like, gradual diffusion of the metal from the surfaces of
the contact portions 9' and 11' into the gallium-indium alloy
occurs to produce a eutectic alloy which has a melting point above
room temperature, so that a solid connection between the contact
portions 9' and 11' is formed after a period of time.
The embodiment shown in FIGS. 4 and 5 is useful in forming a
permanent connection as distinguished from a connection which is
frequently broken and remade, for example, in wiring a panel. An
electrical connection formed in this manner does not deteriorate
with age, and a permanent connection is formed which may gradually
increase in strength by diffusion of metal into the gallium-indium
alloy.
In the embodiment shown in FIGS. 6 and 7, the contact portions 9'
and 11' are initially coated with indium or an indium alloy, while
the filling in the receptacle 13 is gallium or a gallium alloy
covered with the film A. Alternatively, the coating 14a on the
contact portions 9' and 11' may consist of gallium or a gallium
alloy, if the filling 14b in the receptacle 13 consists of indium
or an indium alloy. In either case, the coating 14a and the filling
14b consist of solid materials.
When the parts are assembled as shown in FIG. 6, the indium and
gallium come into contact, thus forming an alloy having a melting
point below room temperature which is normally liquid.
Except as described above, the connector illustrated in FIGS. 6 and
7 functions like the connector illustrated in FIGS. 4 and 5.
FIG. 8 shows how the invention may be embodied in a terminal bar
having terminals to be connected with lead wires. In this
embodiment, a group of terminals 15 are to be permanently connected
to lead wires. The terminals 15 are mounted upon a terminal bar 16
of insulating material. The receptacle 17 is similar to the
receptacle 13 of FIGS. 4 and 5, and is filled with a gallium-indium
alloy covered with a film A.
The lead wire 19 is placed with its end extending into a notch 15a
in a terminal 15, and the receptacle 17 is then telescoped over the
terminal 15 so that the terminal 15 and the lead wire 19 become
embedded in the liquid alloy 18. The indium-gallium alloy then wets
the wire 19 and the terminal 15, to complete an electrical
connection between them.
The embodiment of FIG. 9 differs from the embodiment of FIG. 8 in
that initially the gallium or gallium alloy is separate from the
indium or indium alloy, one of these materials being contained in a
coating 18a on each of the terminals 15, and the other of these
materials constituting a filling 18b in each of the receptacles 17,
covered with a film A. When the embodiment shown in FIG. 9 is
assembled as described in connection with the embodiment of FIG. 8,
a gallium-indium alloy is formed in each of the receptacles 17
which is a liquid at room temperature. This liquid alloy may be
gradually converted into a solid alloy by diffusion of the metal
constituting the terminal 15.
The embodiments shown in FIGS. 10 to 14 are designed to protect
against escape of the liquid alloy. For this purpose, the gallium
which is to be converted into a liquid alloy by contacting it with
indium may be present as a precipitate in the interfaces of a body
of cadmium, bismuth or lead. Also, the gallium or the liquid alloy
itself may be present as an impregnant in a porous body made of
glass or a plastic, or made of a metal powder by powder metallurgy
techniques. These embodiments are useful not only for retaining the
liquid alloy, but also for retaining gallium in cases in which the
melting point of gallium (30.degree. C.) may be exceeded.
A solution of gallium in cadmium, bismuth or lead, containing from
10 to 20 percent of gallium be weight, can be produced by heating
to several hundred degrees C. Upon coding, such a solution of
gallium becomes supersaturated, and when the solidified material is
held at a reduced temperature, particles of gallium precipitate at
the interfaces between the crystals of cadmium, bismuth or lead.
The size of the gallium particles can be increased by heat
treatment. In the resulting system, the gallium is effectively
retained and does not escape even when the material is heated above
30.degree. C. When the surface of such a material, having gallium
precipitated at the interfaces, is brought into contact with a
surface containing indium, a liquid alloy of gallium and indium is
produced which forms a good electrical connection by wetting the
contacting surfaces.
Gallium or a gallium-indium alloy also may be retained and
protected against escape by incorporating it in a porous material
as an impregnant. If the porous material is made by powder
metallurgy techniques, it should be produced by use of a metal
powder of titanium, chromium, tungsten, or another metal which is
inert to gallium. The diameter of the pores in such a porous
material may be about 50 microns.
The impregnation of the porous material may be carried out by
heating the material in a vacuum and then exposing it to gallium
vapor, if desired while subjecting the material to ultrasonic
vibration.
Contacts employing the system just described preferably are not
subjected to repeated making and breaking, and preferably are used
as static or permanent contacts. FIG. 10 and 11 show an embodiment
in which ordinary metal-to-metal contacts are provided for
temporary use during trials and testing and the gallium-indium
alloy connection of the present invention is effected during final
assembly of the apparatus after all preliminary tests and checks
have been performed.
In FIG. 10 the holder 20 of insulating material contains a
resilient plate 22 having its end bent in the shape of an inverted
U, and a second resilient plate 21 having a hooked end 21a and a
slot 21c. A boxlike space is provided between the bent portion 22a
of the member 22 and the hooked portion 21a of the contact member
21. The boxlike space 23 is used to hold a connecting body 24
consisting of cadmium, bismuth or lead having gallium precipitated
in the interfaces. The resilient member 22 acts as a keeper,
holding the body 24 against the slot 21c. The contact member 21 and
the keeper member 22 preferably are plated with nickel, chromium,
titanium, or another metal which does not appreciably diffuse into
a gallium-indium alloy.
A plug is formed by a holder 25 of insulating material carrying a
contact prong 26 for engaging the contact member 21. On the upper
surface of the contact prong 26 is provided a connecting surface
consisting of indium or an indium alloy. Lead wires 28 are
connected to the contact member 21 and the contact prong 26.
FIGS. 11A and 11B illustrate the operation of the connector shown
in FIG. 10.
FIG. 11A shows a condition in which the prong 26 is only partially
inserted, in order to make a temporary electrical connection
without bringing the indium surface 27 in contact with the
gallium-containing material 24. In the condition, the electrical
connection is by metal-to-metal contact. This is a "primary contact
state" in which no liquid alloy is formed. Such partial insertion
of the prong 26 is employed during trial assembly, for testing and
checking when repeated making and breaking of the connection may
occur. After all connections have been checked and found to be
correct, the final connection is formed by pressing the parts fully
together to insert the prong 26 completely as shown in FIG. 11B.
When this is done, the indium-containing material 27 is brought
into contact with the gallium-containing material 24 so that a
liquid alloy of indium and gallium is formed between the contacting
surfaces. This connection is formed through the slot 21c, into
which the indium-containing body 27 projects to contact the
gallium-containing body 24.
It will be understood that the prong 26 is wider than the slot 21c,
so that the prong 26 slides under the corner 21b of the contact
member 21 and does not enter the slot 21c.
In the modification shown in FIG. 12, the contact member 21 and the
prong 26 are both provided with a coating of an indium-containing
material 29. Upon assembly of the elements shown in FIG. 12, as
illustrated in FIG. 13A, a temporary electrical connection is made
between the indium-containing surfaces 29. When a permanent
connection is to be effected, it is necessary to interpose a holder
31 of insulating material which may cooperate with a series of
aligned connectors of the type shown in FIG. 12. The holder 31 has
a series of holes, each of which is filled with a connecting
material 30 consisting of cadmium, bismuth or lead containing
gallium precipitated at the interfaces. The holder 31 is inserted
in proper alignment with a series of connectors so that a body of
connecting material 30 in one of the holes is brought between the
indium-containing surfaces 29 of each connector. In this way, a
permanent connection is produced by forming some of the liquid
alloy on both of the indium-containing surfaces 29 of each
connector.
In the embodiment shown in FIG.14, the contact members 32 and 33
are provided with contact points 32a and 33a each of which consists
of a body of porous metal impregnated with a liquid alloy of
gallium and indium. The contact points 32a and 33a perform well
with repeated making and breaking, because the liquid alloy in the
pores of the porous metal forms a liquid connection when the
contact points 32a and 33a are brought together. Whenever these
contact points are separated, the liquid alloy is retained in the
pores of the porous metal by capillarity.
In the practice of the present invention, an electrical connection
is made through an alloy consisting essentially of gallium and
indium which is a liquid at room temperature. When the electrical
connection is thus formed by a liquid alloy, the resistance across
the connector is stable and does not vary with contact pressure or
increase upon exposure to the atmosphere.
The liquid alloy consisting essentially of gallium and indium which
is used in the practice of the present invention is superior to
mercury in that it does not emit a toxic vapor.
* * * * *