CONNECTOR FOR AN ELECTROACOUSTIC TRANSDUCER

Abstract: A connector for electrically connecting an electroacoustic transducer (10) to electric circuits on a printed circuit board (12) in a sound reproducing and/or sound recording device has a connector body (21; 31) of electrically isolating material with a high temperature resistance. The bottom side of the connector body is provided with a first and a second lower elongated contact element (23a, 23b; 33a, 33b) having contact points (33a', 33a", 33b', 33b") to be connected to said electric circuits on the printed circuit board (12). A first and a second resilient, elongated, upper connecting element (22a, 22b; 32a, 32b), respectively, is connected at its first end to an upper side of the connector body (21; 31) being parallel to said bottom side. The resilient connecting elements are movable in the vertical direction to be resiliently connected to a first and a second connecting pin (11a, 11b), respectively, of the electroacoustic transducer (10) and are connected at their second respective ends to the first and the second lower contact element (23a, 23b; 33a, 33b), respectively. The first and the second lower contact elements (23a, 23b; 33a, 33b) are electrically isolated from each other, and so are the first and the second upper connecting elements (22a, 22b; 32a, 32b).

Description: CONNECTOR FOR AN ELECTROACOUSTIC TRANSDUCER Technical Field The present invention relates to a connector for electrically connecting an electroacoustic transducer to electric circuits on a printed circuit board in a sound reproducing and/or sound recording device. Description of the Prior Art A well known example of such sound reproducing and/or sound recording devices is a radio telephone. Radio tele¬ phones, e.g. cellular telephones for use in cellular tele¬ communications systems such as GSM (Global System for Mobile Service) , comprise at least one microphone and at least one loudspeaker, both of which may be described as electroacoustic transducers for converting an electric signal into an acoustic signal, or vice versa. In addition to such electroacoustic transducers the radio telephones of today obviously have a variety of electric or electronic circuits or components implementing or realizing the functions of the radio telephone. Such circuits or components are for instance the modulator, local oscillator, clock signal generator, mixer, amplifier, various filter circuits, processor (CPU) with its memories, etc. These circuits are normally arranged on a printed cir¬ cuit board (PCB) . The printed circuit board is often made from glass fiber epoxy provided with copper-based conduc¬ tors, and it may be manufactured according to the following process : 1. Stencil printing of solder paste onto the circuit board. 2. Mounting of the electric and electronic components in the solder paste. 3. Treatment in a hot-air furnace at a temperature of about 210°C - 270°C, wherein the components are soldered to the circuit board at intended locations. When the acoustic components (the loudspeaker and the microphone) are connected as described above to the radio telephone circuitry on the printed circuit board, some con¬ siderations have to be made. Both the loudspeaker and the microphone are sensible to high temperatures and should consequently not be present on the printed circuit board during the soldering process described above. Quite simply, the acoustic components would be destroyed at such high temperatures, which are required for melting the solder paste. Normally a loudspeaker or a microphone can only re¬ sist temperatures of about 100°C maximum, and hence these components must be mounted separately to the normal manu- facturing process according to the above. Furthermore, strict regulations are laid upon the acoustic components by the authorities, for instance when it comes to frequency characteristics requirements. Obviously, the acoustic components are also subject to market demands, such as a high-quality speech recognition ability. For practical reasons there is provided a space between the acoustic component and the radio telephone chassis, which gives rise to an acoustic impedance with respect to the surrounding environment, and this impedance must be strictly controlled so as to fulfil the demands above. For this reason the loudspeaker/microphone is pre¬ ferably always mounted at the same position in relation to the chassis. Hence, in the radio telephones of today, the acoustic components are normally firmly arranged on the inside of a chassis front portion, while the printed circuit board, to¬ gether with the electric or electronic circuitry provided thereon, is mounted inside a chassis rear portion. The acoustic components are usually connected to the printed circuit board by soldering two metal wires between each respective acoustic component and the printed circuit board. However, such soldering has the disadvantage of being difficult to automatize, since the soldering must be made manually in this case. Consequently, the production speed as well as the cost efficiency is reduced. For faci¬ litating the soldering the metal wires must have a certain length, and when the front portion and the rear portion are finally assembled, any of the metal wires may be squeezed between mechanical parts at the risk of a broken wire or soldering. Such a fixed interconnection between an acoustic com¬ ponent arranged in a front portion and a printed circuit board arranged in a rear portion furthermore has the draw¬ back of requiring the fixed interconnection to be broken, should the front portion need to be separated from the rear portion, when the radio telephone is repaired or given ser¬ vice. From the European patent publication EP-A-0 567 850 it is known to provide an electric connection between a loudspeaker and a printed circuit board in an electric de¬ vice by means of contact springs soldered to the circuit board. Each contact spring is designed to receive and en¬ gage a respective loudspeaker connecting pin. A similar arrangement is disclosed in the European patent publication EP-A-0 490 214, wherein contact springs are mounted to a respective loudspeaker connecting pin and are arranged to be applied by spring force against the circuit board so as to provide the desired electric connection. Contact arran¬ gements of this kind eliminate the need for a directly sol- dered interconnection between the loudspeaker and the cir¬ cuit board. However, due to the advanced design thereof the contact devices may be difficult to use in a highly automa¬ tized assembly process. Additionally, this is not the most cost-efficient solution, since one contact device is re- quired for each loudspeaker connecting pin. Summary of the Invention The object of the present invention is to overcome the problems encountered as described above, when an electroacoustic transducer is to be electrically connected to a printed circuit board in a sound reproducing and/or sound recording device, for instance a radio telephone. The object is achieved by a connector, which has a strong tem¬ perature resistance and hence may be soldered onto the printed circuit board already at the time of manufacture thereof, is provided with resilient means for connection to an electroacoustic transducer in the sound reproducing and/or sound recording device, and exhibits excellent con¬ nection margins in all important directions, thanks to its design according to the appended patent claims. Further¬ more, the invention relates to a method of assembling a radio telephone using said connector. Brief Description of the Drawings The invention will be described in more detail in the following, reference being made to the accompanying drawings, in which: FIG 1 is a schematic side view of the connector according to the invention, when used for electrically connecting a loudspeaker to a printed circuit board in an exemplary radio telephone, FIG 2 is a top view of the components according to FIG 1, FIG 3 is a schematic and enlarged side view of a con- nector according to a preferred embodiment of the inven¬ tion, FIG 4 is an end view of the connector shown in FIG 3, and FIG 5 is a top view of the connector shown in FIGs 3 Detailed Disclosure of the Invention FIGs 1 and 2 provide a schematic view of a connector 20 according to the invention, when used for electric con- nection of an electroacoustic transducer to an electric printed circuit board in a radio telephone. As an example of an electroacoustic transducer such a conventional loud¬ speaker 10 has been selected, which is used in e.g. por¬ table telephones for cellular telecommunications systems, such as GSM. However, it is to be understood that the in¬ vention is applicable to all such sound reproducing and/or sound recording devices, which comprise an electric printed circuit board to be connected to an electroacoustic trans¬ ducer. Examples of such devices are pocket-size tape re- corders, dictating machines, small radio devices, etc. The loudspeaker 10 is firmly mounted to the inside of a front portion 13 of the radio telephone chassis. Prefe¬ rably, the fixing of the loudspeaker 10 to the front por¬ tion 13 is made during a separate process in accordance with well-known fixing or mounting methods, such as gluing. The front portion is designed in a conventional way for re¬ ception of the loudspeaker 10 and is preferably provided with holes or slots, through which acoustic sound waves emitted from the loudspeaker may be radiated to the sur- roundings. The design of the front portion 13, as well as the fitting of the loudspeaker 10 in the front portion, may be done at a sufficiently high accuracy - since these ac¬ tions take place in a separate process - so that the afore¬ mentioned acoustic impedance of the spacing between the front portion 13 and the loudspeaker 10 may be kept within desired limits. The front portion 13 is mounted to a chas¬ sis rear portion 14, the separation line of which being in¬ dicated by the reference numeral 15 in FIG 1. At its underside the loudspeaker 10 is provided with two connecting pins lla, lib, which are connected at their respective first ends to a respective input of the loud¬ speaker body portion. The loudspeaker as such is a common standard component of electrodynamic type, which for in¬ stance is available from KIRK A/S i Denmark and which, con- sequently, is not described in more detail here. Preferab¬ ly, the connecting pins are made from a copper-base, which is covered with a relatively thick layer of nickel, that in turn is covered with a thin golden layer (approximately 1 μm thick) , and furthermore the pins are about 2 mm wide, approximately 0,5 mm thick and extend almost 10 mm outside the circular loudspeaker. The connector 20 is arranged between the connecting pins lla, lib of the loudspeaker 10 and a printed circuit board 12 mounted in the rear portion 14. A variety of elec- trie or electronic circuits are provided on the printed circuit board 12, said circuits realizing the various func¬ tions of the radio telephone. For instance, the printed circuit board comprises a processor or CPU unit, which is not explicitly shown in the drawing and which controls the overall functions of the radio telephone. Furthermore, the printed circuit board 12 is provided with a transmitter/ receiver unit of conventional design for transmitting and receiving, respectively, electromagnetic radio-frequent signals. Such circuitry is regarded to be well-known to a man skilled in the technical field, and hence no detailed description is made here. However, the operation of the radio telephone will be briefly described below with respect to the reception of an incoming radio signal. The manufacture of the printed circuit board, as well as the mounting and the soldering of the circuits and components thereof, is essentially carried out in accordance with the corresponding information found in the Description of the Prior Art section. An incoming radio-frequent electromagnetic signal, which for instance has been transmitted from a base station used in a cellular telecommunications system, will arrive at the radio telephone to be received by means of an anten¬ na mounted to the radio telephone. The electromagnetic sig¬ nal is converted by the antenna to a high-frequency elect- ric signal, which once filtered and amplified will be mixed down to an intermediate frequency signal by means of a mi¬ xer unit. Then another filtering and amplifying step is carried out, followed by a demodulation of the signal in a demodulation unit by means of an intermediate frequency signal supplied by a local oscillator. Hereby, a so called baseband signal is obtained, which may be decoded or signal processed in accordance with methods and protocols of the cellular telecommunications system in question. A low- frequency electric signal thus obtained is then supplied to the loudspeaker 10 through an amplifier arrangement on the circuit board 12, the electric signal thereby being conver¬ ted to acoustic sound waves radiating from the loudspeaker 10. The connector 20 according to the invention will first be described on a fundamental basis according to FIGs 1 and 2. A more concrete design is then described with re¬ ference to the preferred embodiment shown in FIGs 3-5. The connector 20 comprises a connector body 21 made from an electrically isolating material with a high temperature resistance. At least a top side and a bottom side of the contact body 21 are parallel to each other. Two resilient connecting elements 22a, 22b are according to FIGs 1 and 2 arranged at their first respective ends above the connector body 21 at the top side thereof. As shown in FIGs 1 and 2 and as described in more detail below with reference to the preferred embodiment of the invention according to FIGs 3- 5, each resilient connecting element 22a, 22b extends across the upper surface of the connector body 21, thereby forming an inverted V, which provides a resilient function fundamental to the invention. Also other, more obtuse de- signs of the resilient connecting elements 22a, 22b are possible. The area between the two connecting elements 22a, 22b at the upper surface of the connector body 21 is large enough (at least about 3 mm x 3 mm) as well as plane enough for allowing the connector to be picked during an automatic assembly process described below. At their respective se¬ cond ends the resilient connecting elements 22a, 22b are connected to a respective lower contact element 23a, 23b, which are arranged at the bottom side of the connector body 21 to be connected to the afore-mentioned amplifier arran¬ gement on the printed circuit board 12. The upper resilient connecting elements 22a, 22b are, with respect to their de¬ sign, identical to each other and are preferably essential- ly shaped as leaf springs, said leaf springs being made from an electrically conductive material with a spring force small enough so as to achieve the resilient effect against the connecting pins lla, lib of the loudspeaker 10, as described below. The two upper connecting elements are electrically isolated from each other, and so are the two lower contact elements. Preferably, the upper connecting elements are made from copper, which like the loudspeaker connecting pins lla, lib described above are covered with a protective nickel-based layer as well as with a thin outer layer of gold. However, it is to be understood that all of the contact means described above may be made from other materials and may be given other dimensions than the ones described here. According to FIG 1 the resilient connecting element 22b is connected to the corresponding lower contact element 23b, the former being arranged to extend in a suitable way down through the connector body 21 along a groove or chan¬ nel formed for this reason in the otherwise homogeneous connector body. Alternatively, the upper connecting element may extend along the outside of a vertical side surface of the connector body down to the corresponding lower contact element. The actual connection between the lower portion of the upper connecting element 22b and the lower contact element 23b may for instance be achieved by soldering or a form dependent engagement. The second upper connecting element 22a extends in the opposite direction through a corresponding groove or channel in the connector body 21 down to the lower contact element 23a, and the interconnec¬ tion thereof is provided in a way similar to the one de- scribed above. In the fundamental illustration in FIGs 1 and 2 the connector 20 is shown in its depressed state, i.e. when the front portion 13 is mounted to the rear portion 14, the connecting pins lla, lib of the loudspeaker 10 mounted on the inside of the front portion resiliently engaging the upper resilient connecting elements 22a, 22b of the connector 20. In this way a satisfactory electric contact is achieved between the connecting pins lla, lib of the loudspeaker 10 and the upper resilient connecting elements 22a, 22b of the connector, said upper connecting elements in turn having electric contact with the printed circuit board 12 through the lower contact elements 23a and 23b, respectively. In FIGs 3-5 a connector 30 according to a preferred embodiment of the invention is shown. As previously men- tioned the connector body 31 consists of an electrically isolating material, which is capable of enduring the tem¬ peratures reached during the previously described manufac¬ turing of the printed circuit board. A material suitable for the connector body 31 is the plastic material PPA, but also other materials may be used. The connector body 31 is homogeneous and is essentially shaped as a rectangular parallelepiped. According to the preferred embodiment an upper leaf-spring type connecting element 32a is formed as an integrated member together with a lower contact element 33a. The free end of the upper connecting element 32a is arranged to touch a longitudinal side of the upper surface of the connector body 31, when unloaded, while said free end, when loaded (i.e. when a loudspeaker connecting pin lla according to the above is pressed against the con- necting element 32a) , contacts a groove or a recess, which is formed vertically or along a side surface of the con¬ nector body 31. The connector 30 is shown in its loaded state in FIGs 3-5, and it appears from FIG 4 in particular in what way the depressed upper connecting element 32b con- nects to a side surface of the connector body 31. Starting from this free end, each upper connecting element 32a, 32b extends in an obtuse-angled shape across the upper side of the connector body 31, and then extends vertically down the opposite side surface of the connector body 31 so as to connect to its respective lower contact element 33a, 33b. The uppermost point of each respective upper connec¬ ting element 32a, 32b, i.e. the tip of the angular shape, is arranged to contact a respective loudspeaker connecting pin lla, lib, when the front portion 13 is mounted to the rear portion 14 and the resilient connecting elements 32a, 32b are depressed, as described above. The two upper con¬ necting elements 32a, 32b are arranged in opposite direc¬ tions with respect to each other across the upper side of the connector body 31, the free end of one connecting element 32a being located at an opposite side of the con¬ nector body 31 with respect to the other connecting element 32b. The spring stiffness of the resilient connecting elements 32a, 32b will have to be adapted to the force exerted by the respective loudspeaker connecting pin lla, lib on the respective connecting element 32a, 32b. Accor¬ ding to a prototype of the preferred embodiment of the invention a spring force of about 60 ± 15 g has proven suitable. The two lower contact elements 33a, 33b are firmly arranged on the bottom side of the connector body 31 along its longitudinal axis. The lower contact elements protrude from each side of the connector body, and according to FIG 4 these protruding ends are twice bent at an angle of ap¬ proximately 45° so as to form the contact surfaces 33a' , 33a", 33b', 33b". These contact surfaces are arranged to be soldered to the printed circuit board 12 for electrical interconnection between the loudspeaker 10 and an electric circuitry on the circuit board 12 through the connector according to the invention. Thanks to the connector 20, 30 according to the invention it is possible to connect an electroacoustic transducer to an electric circuit board in a radio tele¬ phone with a high level of automatization, as will be described in the following. When the printed circuit board 12 is manufactured during a soldering process like the one previously described in section Description of the Prior Ar , the connector 20 is surface-mounted at the proper location on the printed circuit board 12. Due to the plane upper side of the connector body 21, 31 the connector may be picked and mounted to the circuit board 12 in an auto¬ matic assembly process (a so-called "pick and place" pro¬ cess) . Thanks to the symmetrical arrangement of the contact surfaces 33a', 33a", 33b', 33b" of the lower contact ele¬ ments 33a, 33b, it makes no difference if the connector 20, 30 is rotated 180° during the automatic assembly process, and hence this assembly process may be carried out more easily. Then the circuit board may, together with the electric and electronic circuits and components mounted thereon as well as the connector 20, 30 provided thereon according to the above, be heat-treated in a hot-air fur¬ nace at such a high temperature, which is required for allowing the soldering process. As previously described, the loudspeaker 10 is arranged together with its connecting pins lla, lib at the intended position on the inside of the front portion 13. Finally, the front portion and the rear portion 14 are brought together, the electric connection between the prin¬ ted circuit board 12 and the loudspeaker 10 being estab¬ lished by means of the connecting pins lla, lib being pressed against the resilient upper connecting elements 22a, 22b; 32a, 32b. Thanks to the arrangements described above satisfac¬ tory margins are achieved in all directions during the mounting of the connector 20; 30 on the printed circuit board 12, during the mounting of the loudspeaker 10 in the front portion 13 as well as during the assembly of the front portion 13 and the rear portion 14. In addition there is no longer any need for a manual operation so as to sol¬ der electric connector wires between the loudspeaker and the printed circuit board. The lack of such wire connec¬ tions has the additional advantage of allowing the front portion 13 to be fully removable from the rear portion 14, when there is a need of doing so (such as service or repair of the radio telephone) , without requiring any interruption of a fixed connection. Trials and calculations have proven that the spring arrangement withstands at least some fifty depressions, which by far should cover the entire operatio¬ nal life of the radio telephone, since it has to be regar¬ ded as highly unlikely, that the radio telephone will have to be opened for reasons such as service or repair more than a few times during its lifetime. The above description of the invention and the pre¬ ferred embodiment thereof has been carried out for exampli- fying but not limiting purposes. Hence, the invention may be realized in other ways than the ones described above within the scope of the appended patent claims. In parti¬ cular, it should be noted, that even if the electroacoustic transducer has been described above as being an elect- rodynamic loudspeaker, the invention may be applied to- gether with other kinds of loudspeakers as well as with microphones of various known designs.

Claims: CLAIMS 1. A connector for electrically connecting an electroacoustic transducer (10) to electric circuits on a printed circuit board (12) in a sound reproducing and/or sound recording device , c h a r a c t e r i z e d by a connector body (21; 31) of an electrically isola¬ ting material with a high temperature resistance, a first and a second lower elongated contact element (23a, 23b; 33a, 33b) , said contact elements being arranged at a bottom side of the connector body (21; 31) and being provided with at least one contact point (33a', 33", 33b', 33b") each for connection to said electric circuits on the printed circuit board (12) , and a first and a second resilient, elongated, upper connecting element (22a, 22b; 32a, 32b) , each of which at its first end being connected to an upper side of the con¬ nector body (21; 31) parallel to said bottom side and being movable in the vertical direction so as to achieve a resi¬ lient connection to a first and a second connecting pin (lla, lib) , respectively, of the electroacoustic transducer (10) , and each of which at its second end being connected to the first and the second lower contact element (23a, 23b; 33a, 33b) , respectively, the first and the second lower contact elements (23a, 23b; 33a, 33b) being electrically isolated from each other, and the first and the second upper connecting elements (22a, 22b; 32a, 32b) being electrically isolated from each other. 2. A connector according to claim 1, c h a r a c t e r i z e d in that each upper connecting element (22a, 22b; 32a, 32b) forms an angular or bent shape protruding from the upper side of the connector body (21; 31) . 3. A connector according to claim 1 or 2, c h a r a c t e r i z e d in that the upper connecting elements (22a, 22b; 32a, 32b) are formed as leaf springs. 4. A connector according to any preceding claim, c h a r a c t e r i z e d in that the first upper connec¬ ting element (22a; 32a) extends in parallel with and in a direction opposite to the second upper connecting element (22b; 32b) . 5. A method of assembling a radio telephone using the connector according to any preceding claim, the radio tele¬ phone comprising a front portion (13) , to which the elect- roacoustic transducer (10) is mounted, and a rear portion (14) , in which the printed circuit board (12) is arranged, c h a r a c t e r i z e d by the steps of a) soldering the connector at its contact points (33a', 33a", 33b' , 33b") to the printed circuit board (12) in a heat-treatment process known per se carried out in a hot-air furnace at a temperature t 1# at the same time sol¬ dering the electric circuits to the printed circuit board, and then mounting the printed circuit board in the rear portion (14) , b) mounting the electroacoustic transducer (10) to the front portion (13) according to any conventional mounting method at a temperature t 2 , which is lower than the temperature λ according to a) and which is low enough not to damage the electroacoustic transducer, c) mounting the front portion to the rear portion in such a way that the first and the second connecting pins (lla, lib) , respectively, of the electroacoustic transducer engages the first and the second upper connecting elements (22a, 22b; 32a, 32b) , respectively, the electric inter- connection thereof being maintained due to the resilient engagement of the upper connecting elements with the con¬ necting pins.

Inventors: BRODIN MALTE BENGT GUSTAV, BRODIN, MALTE, BENGT, GUSTAV
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Application year: 1997
Main classification: H01R23
IPC codes: H01R13, H04M1