AN ELECTRICAL CONTACT DEVICE FOR INTERCONNECTING ELECTRICAL COMPONENTS

Abstract: An electrical device with electrical terminals in the form of helically wound electrically conductive, resilient wire (25, 26), for electrically connecting the device to other electrical or electronic equipment. At least two of the helically wound electrical terminals (25, 26) are arranged one within the other, preferably coaxially. The device can be a component with resilient terminals that are suitable for contacting corresponding contact surfaces on a printed circuit board, or the device can be a printed circuit board with resilient terminals that are suitable for contacting corresponding contact surfaces on an electrical or electronic component. In particular, the device can be an electroacoustic transducer with a magnet system (11, 12, 13) with a central permanent magnet (11) and an air gap (14) peripheral to the magnet, where the magnet generates a magnetic field in the air gap, and a diaphragm (15) carrying a coil (16) in the air gap.

Description: An electrical contact device for interconnecting electrical components The invention relates to an electrical contact device comprising at least two helically wound electrically conductive, resilient wires, for electrically interconnecting electrical or electronic components or devices . A contact device of the invention can be used in electrical and electronic components for forming resilient terminals that are suitable for contacting corresponding contact surfaces on a printed circuit board. A contact device of the invention can also be used on a printed circuit board for forming, on the printed circuit board, resilient terminals that are suitable for contacting corresponding contact surfaces on an electrical or electronic component. In particular, but not exclusively, the invent-ion is useful in electro-acoustic transducers for forming 20 resilient contact members or terminals. Electro-acoustic transducers include in particular microphones and receiver transducers for telephone handsets and mobile telephones. In mobile telephones the transducers are often mounted onto the inner side of one of the housing shells, and electrical contact to a printed circuit board is established by means of contact springs on the printed circuit board or on the transducer. WO 98/43317 shows a contact device in the form of a helically wound electrically conductive, resilient wire, for electrically interconnecting two electrical or electronic components or devices. EP 755 165 shows an electro acoustic transducer for mounting in a telephone handset. The transducer has two helical spring contact members arranged outside the periphery of the diaphragm. The transducer must be properly oriented prior to being mounted in a telephone. EP 490 214 shows an electro acoustic transducer with spring contact members in the form of closed resilient loops . DE 9 407 781.1 Ul shows an electro acoustic transducer with two simple leaf spring contact members. WO 98/38832 shows an electro acoustic transducer with U- shaped spring contact members. WO 92/20120 discloses a screened contact especially for screened coaxial cables. The contact has two coaxially arranged helical springs terminating in contact members. Spring contact members fall in two categories: leaf springs and helical springs. Leaf spring contact members generally have the disadvantage of being resilient substantially only in one direction, ie in the axial direction of the transducer. When the telephone handset or mobile telephone with such transducer is subjected to chock eg by accidentally falling onto a floor, the spring contact members may rub on the contact surface, whereby eg a gold plating can eventually be rubbed off and leave the electrically conductive metal underneath open to attack by the atmosphere which can lead to corrosion. Corroded contacts give bad electrical connections and can become a source of electrical noise. The component of the invention has at least two helically wound electrical terminals arranged one within the other, preferably co-axially. Hereby a very compact electrical or electronic component or transducer with reliable and stable electrical termination is achieved. When the component is an electro acoustic transducer for use in eg a mobile telephone, the transducer's contacts to the printed circuit board will be less sensitive to chock, and the transducer needs not be oriented prior to it mounting in a telephone. In the following a preferred embodiment of the invention will be described with reference to the accompanying drawings, in which Figure 1 shows a contact device in a first embodiment of the invention seen from one end thereof, Figure 2 is a sectional view of the contact device in figure 1 taken along the line II-II in figure 1, Figure 3 shows the contact device in a side view, Figure 4 is a sectional view of an electroacoustic transducer including the contact device of figures 1-3, Figure 5 is a perspective view of a contact device in a second embodiment of the invention, Figure 6 is a longitudinal section through the contact device in figure 5 taken along the line VI-VI, and Figure 7 shows in perspective how the contact device in figure 6 can be mounted in an opening in a printed circuit board. Figures 1-3 show a contact device 20, which has a frame or carrying unit 21. The frame 21 is preferably of a resilient material such as a moulded plastics material. The frame has an upper, circular disc shaped portion 22 with two coaxial cylindrical shells 23, 24 rigidly connected thereto. In the space between the outer and inner cylindrical shells 23, 24 there is an outer spring contact member 25, and within the inner cylindrical shell 24 there is an inner spring contact member 26. Both spring contact members 25, 26 are of helically wound electrically conductive, resilient wire, and are secured by one of their respective ends to the circular disc shaped portion 22, and the opposite ends are free. The two spring contact members 25, 26 are preferably of the type disclosed in WO 98/43317. Both spring contact members are resilient in their axial direction and also in any direction transverse to the axial direction. The inner spring contact member 26 has a conical portion whereby its free end is relatively narrow, and both spring contact members 25, 26 will thereby have a relatively large free lateral play without touching each other. Making the outer spring contact member 25 flaring towards its free end can further increase the free play. The outer cylindrical shell 23 has two diametrically opposite slots dividing the shell into two halves, which at their free ends have an outwardly protruding lip 28. Figure 4 shows an electroacoustic transducer for use in eg a mobile telephone. The transducer has a ring shaped frame 10 eg of a plastics material which carries a magnet system. The magnet system has a ring shaped permanent magnet 11, which is magnetised in its axial direction. On the two opposed plane faces of the magnet 11 are disposed upper and lower pole pieces 12, 13, respectively, of a magnetic soft material such as iron. The lower pole piece 13 is cup shaped, and the magnet system 11, 12, 13 defines a ring shaped air gap 14 between radially opposed faces of the upper and lower pole pieces. The transducer has a diaphragm 15, which in the shown embodiment has a domed shape. A coil 16 of electrically conductive wire is secured to the diaphragm 15, and the coil 16 is situated in the air gap 14 of the magnet system. This construction thus has the well-known basic properties of an electroacoustic transducer which is common to microphones and receiver transducers used eg in telephones. In figure 4 the contact device 20 of figures 1-3 is mounted in the central, though going opening in the magnet system. The contact device 20 is inserted by pressing it through the opening, whereby the lips 28 and 25 the two outer half shells 23, 24 will flex inwardly and will pass through the central opening in the magnet system. With a snap fit the lips 28 will hold the contact device 20 in the shown position in the magnet system. On the side of the disc shaped portion 22 facing the upper pole piece 12 of the magnet system there are protruding knobs 29 which touch the magnet system. The disc shaped portion 22 will thereby be slightly deformed and the contact device is fixed in the shown position by internal resilient forces in the contact device. The contact device may also be held in place in the opening in the magnet system by other means, eg by gluing or by friction. The two ends of wire of the coil 16 on the diaphragm are mechanically and electrically connected, eg by soldering or welding, to respective ones of the outer and inner spring contact members 25, 26 at the ends near the disc shaped portion 22, whereby the free ends of the spring contact members serve as the electrical terminals of the transducer . The contact device 20 has a central opening 30 and three peripheral openings 31 serving as an acoustic connection 10 from the inner side of the diaphragm to the rear of the transducer. The shown transducer will normally have a cover with acoustic openings in front of the diaphragm. The transducer is suitable for being mounted on the inner side of the housing wall of a mobile telephone. When assembling the telephone the helically coiled spring contact members 25, 26 will be brought into contact with respective ones of contact pads on a printed circuit board. The contact pads can be in the form of a "bull's eye" with two concentric contact areas. The two spring contact members 25, 26 are arranged one within the other, preferably coaxially, which entails that the transducer has no preferred angular orientation. The equipment handling the transducer in the assembly line thus needs no complicated arrangements for orienting the transducer. The narrow free end of the inner spring contact member 26 helps in reducing the requirements for a precise placement of the spring contact members on the "bull's eye" on the printed circuit board. The arrangement of the two spring contact members 25, 26 one within the other is very compact, which makes it possible to have a small magnet which can be within the coil 16 of the transducer. This makes very efficient use of the magnet, and the transducer can be made correspondingly small. The contact device 20 with the two spring contact members can be used as a surface mounted device (SMD) . It will then be mounted with its disc shaped portion 22 on a printed circuit board and the free ends of the spring contact members facing away from the printed circuit board. The frame 21 will then preferably be made of a material which is resistant to the heat from reflow soldering, such as a liquid crystal polymer (LCP) . It is clear that the two concentric spring contact members can equally well be mounted directly on a printed circuit board, ie without the frame 21, eg by soldering, and other components, such as an electroacoustic transducer, to be electrically connected to the printed circuit board will then have contact surfaces eg in the form of a "bulls eye" or simply two contact points which are suitable for contacting respective ones of the free ends of the spring contact members on the printed circuit board. Figures 5-7 show a contact device 40 with many similarities with the contact device 20 in figures 1-3. Like in the contact 20 this contact device 40 has two concentrically mounted helically wound spring contact members 45, 46 in a frame 41 preferably of a resilient material such as a moulded plastics material providing electrical insulation between the spring contact members. The frame is cup shaped with a closed bottom, and the cylindrical walls of the frame have two longitudinal slits 47 dividing the walls into two half-cylindrical shells resiliently interconnected by the bottom wall of the frame. The inner ends 43, 44 of each of the two spring contact members 45, 46 protrude through the slits 47. Figure 7 shows a printed circuit board 50 with an aperture 51 and two electrically conductive portions 52, 53. The contact device 40 can be mounted in the aperture 51 eg in a snap action whereby the free ends of the two spring contact members will protrude beyond the opposite side of the printed circuit board 50, and the inner ends 43, 44 will touch the electrically conductive portions 52, 53 on the printed circuit board 50. Electrically stable contact will be established eg by reflow soldering, and the frame is made of a material such as LCP which can resist the temperatures employed for the reflow soldering process. The electrically conductive portions 52, 53 can extend as shown over relative small angles around the aperture 51, or they can extend over larger angles - possibly up to 180 degrees or slightly less, whereby the contact device needs not be angularly oriented with high precision before mounting. Alternatively, the inner ends 43, 44 of the spring contact members can end on the periphery of the frame and possibly have a bent end. Correspondingly, the electrically conductive portions 52, 53 can extend into the aperture 51 and cover portions of the inner surface of the aperture. When mounted in the aperture the inner ends 43, 44 of the spring contact members will touch the electrically conductive portions radially. With the contact device of the invention received in the aperture of the printed circuit board, the resilient portions of the spring contact members will largely be accommodated within the printed circuit board resulting in a very flat and compact structure, possibly with no portions or only insignificant portions protruding from the surfaces of the printed circuit board.

Claims: Claims 1. An electrical contact device comprising at least two helically wound electrically conductive, resilient wires (25, 26) , for electrically interconnecting two electrical 5 or electronic components or devices, c h a r a c t e r i z e d in that the contact device includes two such helically wound electrically conductive, resilient wires (25, 26) arranged one within the other. 2. A device according to claim 1, c h a r a c t e r i z e d in that the two helically wound electrical wires (25, 26) are arranged co-axially. 3. A device according to any one of claims 1-2, c h a r a c t e r i z e d in that the inner one of the electrical wires (26) is tapering towards a free end thereof. 4. A device according to any one of claims 1-3, c h a r a c t e r i z e d in that the outer one of the electrical wires (25) is flaring towards a free end thereof. 5. A device according to any one of claims 1-4, c h a r a c t e r i z e d in that it includes a frame (21) holding the two electrical wires (25, 26) in predetermined positions relative to each other. 6. A device according to any one of claims 1-5, c h a r a c t e r i z e d in that the electrical wires (25, 26) have inner ends opposite the free ends, the inner ends being exposed at an outer surface of the frame (21) . 7. A device according to claim 6, c h a r a c t e r i z e d in that the exposed inner ends of the electrical wires (25, 26) protrude in a direction transverse to the axial direction of the device. 8. An electrical or electronic device with electrical terminals for electrically connecting the component to other electrical or electronic components or devices, c h a r a c t e r i z e d in that it includes a contact device according to claim 1-7 with the wires (25, 26) being suited for forming the terminals of the device. 9. A device according to claim 8, c h a r a c t e r i z e d in that the device is an electro-acoustic transducer . 10. An electro acoustic transducer according to claim 9, c h a r a c t e r i z e d in that the transducer has magnet system (11, 12, 13) with a central permanent magnet (11) and an air gap (14) peripheral to the magnet (11) , the magnet (11) generating a magnetic field in the air gap, and a diaphragm (15) carrying a coil (16) in the air gap (14) . 11. A device according to claim 8, c h a r a c t e r i z e d in that the device is a printed circuit board and the terminals are suitable for contacting corresponding contact surfaces on an electrical or electronic component. 12. A printed circuit board according to claim 11, c h a r a c t e r i z e d in that the printed circuit board has an aperture with the contact device received in the aperture.

Inventors: HANSEN KAJ BOERGE, HANSEN, KAJ, BOERGE
Applicants: HANSEN KAJ BOERGE, KIRK ACOUSTICS AS, HANSEN, KAJ, BOERGE, KIRK ACOUSTICS A/S
Application year: 2000
Main classification: H01R13
IPC codes: H01R13, H04R1, H05K3