EP1685411A1 - Non-rigid conductor link measurement sensor and method for the production thereof - Google Patents

Non-rigid conductor link measurement sensor and method for the production thereof

Info

Publication number
EP1685411A1
EP1685411A1 EP04818818A EP04818818A EP1685411A1 EP 1685411 A1 EP1685411 A1 EP 1685411A1 EP 04818818 A EP04818818 A EP 04818818A EP 04818818 A EP04818818 A EP 04818818A EP 1685411 A1 EP1685411 A1 EP 1685411A1
Authority
EP
European Patent Office
Prior art keywords
pin
card
cell
arc
conductive
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP04818818A
Other languages
German (de)
French (fr)
Inventor
Philippe THALES Intellectual Property GUICHARD
Jean-Louis THALES Intellectual Property LE CORRE
Jean-Marie THALES Intellectual Property ODERMATH
Jérôme Thales Intellectual Property INGLESE
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Original Assignee
Thales SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thales SA filed Critical Thales SA
Publication of EP1685411A1 publication Critical patent/EP1685411A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P1/00—Details of instruments
    • G01P1/02—Housings
    • G01P1/023—Housings for acceleration measuring devices
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K3/00—Apparatus or processes for manufacturing printed circuits
    • H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
    • H05K3/306—Lead-in-hole components, e.g. affixing or retention before soldering, spacing means
    • H05K3/308—Adaptations of leads
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/4805—Shape
    • H01L2224/4809—Loop shape
    • H01L2224/48091—Arched
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/00011—Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/0271—Arrangements for reducing stress or warp in rigid printed circuit boards, e.g. caused by loads, vibrations or differences in thermal expansion
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/10—Details of components or other objects attached to or integrated in a printed circuit board
    • H05K2201/10613—Details of electrical connections of non-printed components, e.g. special leads
    • H05K2201/10954—Other details of electrical connections
    • H05K2201/10962—Component not directly connected to the PCB
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/20—Details of printed circuits not provided for in H05K2201/01 - H05K2201/10
    • H05K2201/2045—Protection against vibrations
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/49117—Conductor or circuit manufacturing
    • Y10T29/49204—Contact or terminal manufacturing

Definitions

  • the invention relates to electronic sensors comprising an electromechanical microsensor cell such as a micro-accelerometer, and it relates more particularly to the mounting of the microsensor cell proper in a housing also comprising one (or more) printed circuit board. carrying the electronic processing circuits associated with the microsensor cell.
  • an accelerometer is very sensitive to vibrations and shocks and it would provide an electrical signal that is difficult to exploit if a parasitic signal due to vibrations of the object whose acceleration is to be measured is superimposed on the acceleration measurement itself. called.
  • vibrations and shocks could damage the sensor, which would be even more harmful.
  • the acceleration measurement is not the only case where vibrations and shocks cause breakdowns or measurement difficulties, but it constitutes a typical case to which the invention is particularly applicable. Sensors of other physical sizes, produced by micro-machining, can typically be affected.
  • the cell is then mounted in a housing with the interposition of a shock and vibration absorbing element.
  • the cell is wedged in the casing by elastomer wedging blocks whose mechanical damping properties are adapted to the shocks and vibrations to be filtered, and the cell is not in direct physical contact with the casing.
  • a possible electrical connection mode between the microsensor cell and the electronic card is shown in FIG. 1 in section and in FIG. 2 in top view.
  • the cell 10 with its electrical connection pins 12, is contained in a housing 20 closed by a cover 22; it is held in place by damping blocks 24 (in principle made of elastomer) which support it by absorbing the shocks and vibrations transmitted by the housing.
  • the housing can be fixed on an object on which a measurement is made, the fixing being possible by any means and not being shown.
  • the cell is located on the side of the rear face of an electronic card 30 which carries on its front face components 32 and printed conductors 34; the card 30 is pierced with holes 36 in which freely engage (without physical contact), from the rear of the card, the connection pins 12 of the cell; the ends of the pins are connected, by welded wires 14, to conductive pads forming part of the printed conductors 34 of the front face of the card; the wires are welded on one side to the end of the spindle and on the other to a respective stud associated with this spindle; the wires 14 are not straight but they are bent so as to act as a spring having a low stiffness in all directions (a straight wire would have a high stiffness in the direction of this straight line).
  • the wires are typically made of bare gold or aluminum or else copper insulated by plastic sheath, or copper or silver coated with enamel insulator, etc.
  • the diameter of the conductive wire is typically 50 micrometers and its length is a few millimeters.
  • the wire must be preformed before or during the welding operation to give it the curved shape which ensures low stiffness in all directions, and this preforming operation, like the operation of holding the wire during welding, is difficult to achieve. It has been found that the modules thus produced are excessively sensitive to vibrations, which prevents correct measurement.
  • Another way to make the connection between the sensor and the card can be to use a flexible printed circuit board as is done in printers, camcorders, etc.
  • the invention proposes to provide a solution at least partially improving the known solutions.
  • the sensor according to the invention comprises a housing, a microsensor cell wedged in the housing by damping blocks, and an electronic card comprising electronic circuits associated with the cell, the cell comprising connection pins, flexible conductive connections being provided. between the connection pins and the printed conductors of the card, this sensor being characterized in that each conductive link comprises a thin flexible metallic strip machined by cutting, extending between the pin and a printed conductor passing near the pin, the strip being electrically connected on one side to the conductor and on the other to the spindle and comprising between the conductor and the spindle an arc-shaped section parallel to the plane of the card and extending freely above the card with a space between the ribbon and the card.
  • the ribbon cut from a metal sheet, is preferably electrically connected to the pin and to the printed conductor by soldering.
  • the arcs (preferably arcs of a circle) corresponding to different conductive connections are preferably identical. They preferably extend over at least 180 °, and preferably over about three quarters of a turn.
  • the width of the ribbon at the location of the arc is preferably less than the width of the ribbon in sections of ribbon extending between the arc and the pin or between the arc and the conductor of the printed circuit.
  • the width of the arc may be a few tens of micrometers, for example 70 to 100 micrometers for a sheet of thickness about 50 micrometers; this small width and this small thickness, combined with the curvature of the arc, give a very low stiffness to the conductive bond in all directions, and it should be noted that the stiffness in the direction perpendicular to the sheet is much lower than that which would be necessary to support the cell, the latter being completely supported by the damping blocks.
  • the links are therefore not means of supporting the cell but means of transmitting electric voltages and currents which do not transmit mechanical stresses to the cell.
  • One end of each conductive connection preferably comprises a ring in the center of which passes the connection pin of the cell.
  • the other end of the link may also include a ring through which passes a pin welded to the printed conductor, the thin metallic strip then being welded to this pin.
  • the material of the metal foil is preferably an alloy of copper and beryllium chosen because of its elasticity properties greater than those of copper and its electrical conductivity close to that of copper. The manufacturing process proposed according to the invention is particularly economical because it uses collective machining of a set of electrical connections.
  • a method of manufacturing a sensor comprising a housing in which are mounted a microsensor cell wedged in the housing by damping blocks and a printed circuit board associated with the cell, the method comprising the operations following: - machining by cutting a thin and flexible metal sheet so as to form in this sheet several conductive connections in the form of a narrow ribbon having a very low stiffness in all directions, each connection comprising a section curved in an arc in the plane of the leaf, these connections being intended to each connect a respective connection pin of the cell to a printed circuit conductor of the card which passes near the pin, the various connections being secured to each other by bridges forming part of the sheet, - place the cell near the card, and solder each link on one side to a pin and the other to a corresponding conductor leaving a free space above the card between the arcuate section of the narrow ribbon and the card, - and cut the bridges between connections to separate them from each other.
  • the machining of the sheet is preferably a chemical machining by photolithography.
  • the cutting of the sheet preferably includes the cutting of openings at the locations where components are placed on the card, the sheet being placed on the card on which components have been previously welded. Not only the components but also conductive pins can be soldered to the card, and the conductive link is soldered to the free end of these pins.
  • the narrow ribbon can have ring-shaped endings and in this case we thread this ring around a cell pin or a conductive pin welded on the card, before soldering the ring on the pin or the pin.
  • FIGS. 1 and 2 The general constitution of the sensor according to the invention is that of FIGS. 1 and 2 with the exception of the conductive connections between pins 12 of the cell and conductors 34 of the printed circuit board, and this general constitution will therefore not be described again.
  • the cell is placed at the rear of the card and the pins cross the card to pass on the side of the front face, but we could also have the cell on the side of the front face (the one which carries electronic components), the pins do not need to pass through the card.
  • FIG. 3 represents a conductive link 50 put in place (but not welded) above a connection pin 12 of the cell and a conductive pad 34 printed on the card; the link 50 is intended to connect this pin to this pad.
  • the hole 36 drilled in the card and in which the pin 12 can freely be threaded near the stud 34 is not shown in FIG. 3, being masked by a part of the conductive link which covers it.
  • the conductive link is a very low stiffness link, which is not intended to physically support the weight of the cell, and all of the conductive links associated with the different pins cannot support this weight.
  • the weight of the cell like the acceleration forces which it can undergo, is entirely supported by the damping blocks 24, made of elastomer, of FIG. 1.
  • the individual connection 50 is cut, preferably by chemical machining, from of a photolithographed drawing, in a thin flexible metallic sheet.
  • the thickness is chosen to give a very low stiffness to the connection in the plane perpendicular to the metal sheet, that is to say, in operation, in the plane perpendicular to the printed circuit board.
  • the order of magnitude of the thickness is 50 micrometers.
  • the sheet is made of elastic material and is a very good conductor of electricity.
  • the preferred material is an alloy of copper and beryllium, such as the alloy CuBe2.
  • the shape of the cut link is a narrow ribbon (the width can be of the order of 70 to 100 micrometers, for example over the major part of the length of the ribbon), the small width being chosen to give a very low stiffness to the link in the plane of the sheet.
  • the narrow ribbon is not straight but has a main part 51 curved in an arc parallel to the plane of the sheet.
  • the arc is preferably an arc of a circle, and it extends over a large sector, preferably at least 180 °, and in this example about three quarters of a turn.
  • the length of the arch can be of the order of 1 cm.
  • the circular arc is shown centered on the pin 12 in the example drawn in the figures, but this is not compulsory and the pin is not even necessarily located inside the curvature of the arc.
  • This arc shape extending over a large sector is intended to give the conductive connection a very low stiffness in all directions of the plane of the sheet.
  • One end of the ribbon portion 51 in an arc is connected by a first section 52 of small width (for example the same width as the arc of a circle) to a second section 53 wider (order of magnitude: approximately 300 or 400 micrometers) which constitutes the first termination of the link.
  • the section 52 extends radially from the center of the circular arc.
  • Another end of the ribbon portion in an arc is connected by a third section 54, here also a radial section and of small width, to a fourth section 55 which constitutes a second termination of the connection.
  • the sections 52, 54 preferably leave at a right angle from the ends of the section 51. Their function is to allow the latter to work essentially in torsion and not in bending, in the manner of a helical spring.
  • the ribbon in an arc and the various sections are configured so that the first termination can come above the conductive pad 34 when the first termination is above the pin 12.
  • the second termination 55 is shaped as a ring surrounding the pin 12 ; the width of the ring is preferably greater than the width of the section 54.
  • the first termination 53 is shown in FIG. 3 as being a linear strip whose end can be welded to the conductive pad 34; we will see later that this termination 53 can also be in a ring.
  • the solder between the first termination and the conductive pad can be indirect in the sense that one can provide that a conductive pin is inserted into a hole in the card in the center of the pad 34, this pin being welded to the conductive pad and the first termination being then welded to the upper part of the pin.
  • Figures 4 and 5 which are perspective views of the front or upper face of the card 30, represent the latter solution.
  • a conductive metal pin 38 has been welded to the center of the printed pad (in principle after inserting the pin into a hole in the center of the pad 34), at the same time as the various components 32 of the latter were welded onto the card.
  • the second termination 55 is threaded on pin 12 ( Figure 4) after the card has been placed above the cell 10 wedged in the housing by the damping blocks; the first termination is placed above the pin 38. Then, the welding operation is performed (FIG. 5), on the two terminations.
  • the ring 55 is welded over its entire periphery to the pin 12; the end of the termination 53 is welded to the conductive pin.
  • the narrowing of width between the ring 55 and the section 54, or between the termination 53 and the section 52 confines the weld to the ring 55 and the termination 53 and prevents the weld from wetting the sections 52 and 54 of small width, which would have the consequence of increasing the rigidity of the connection.
  • the angle formed by the bar 53 with the section 52, and the length of the bar 53 depend on the configuration of the printed circuit on the card and more precisely on the position of the conductive pad relative to the pin to which it is desired to connect it. .
  • the stiffness of the connection is very low in the three dimensions and a clearance is possible because the hole 36 has a larger diameter (for example greater than one millimeter) than the diameter of pin 12 and the fact that a vertical space (for example 1 millimeter) is provided between the ribbon in an arc 51 and the card.
  • the advantage of using a conductive pin 38 is that a free space can be provided between the conductive connection and the card over the entire length of the ribbon constituting the connection.
  • FIG. 6 represents the collective production of the sheet for making and simultaneously mounting the different conductive laces on the different pins of the cell.
  • the drawing cut from the sheet includes the various connections, correctly positioned with respect to each other taking into account on the one hand the relative position of the different pins of the cell and the position of the conductive pads to which these pins are to be connected.
  • the sections 51 in an arc
  • the sections 52, 54 connected to the arc
  • the rings 55 are preferably all identical from one link to another, even if they have different orientations from one link to another, in order to minimize structural asymmetries, particularly in the case of an accelerometer which is a very sensitive type of sensor to the asymmetries of constraints it undergoes.
  • the connections are connected to a frame 57 which keeps them in place during the welding operation: bridges 58 between the terminations and the frame 57 serve for this maintenance. After the welding operation, these bridges are removed by cutting.
  • the metal sheet in the form of a rectangular peripheral frame 57 inside which are arranged only the connections 50 and the bridges.
  • the cut metal sheet is constituted by a rectangle having substantially the same surface as the electronic card and which comprises on the one hand the cutouts of connections and bridges and on the other hand cutouts around each component of the card so that the sheet can be placed on the card without being hindered by the components.
  • the solid parts of the card, between the cutouts provided around the components, then constitute the frame to which the bridges are attached.
  • the thin metal sheet can be cut by photolithography in a continuous ribbon to make not only all the conductive connections between the cell and the card of a sensor but also the connections of a series of sensors in a continuous mass production, this which further reduces the manufacturing cost.
  • the operations of placing, welding and cutting the bridges can be carried out by an automatic machine.
  • the conductive termination 55 in this example, provision has been made for the conductive termination 55 to be a ring, the internal cutout of which is a grooved shape facilitating placement on the spindle at a determined height (the ring gets stuck on the spindle); it was further provided that the termination 53 also includes a ring shape (also grooved if desired) threading on a conductive pin such as pin 38, previously welded on the card.
  • the section 54 which connects the ring 55 to the circular arc 51 is turned radially towards the inside of the circular arc, and the pin 12 is in the center of this arc.
  • section 55 could leave in another direction, even towards the outside of the arc or even in the extension of the arc, the spindle not being in the center of the arc nor even necessarily inside the arc.

Abstract

The invention relates to electronic sensors comprising an electromechanical microsensor cell such as a microaccelerometer. The invention more specifically relates to the mounting of a the microsensor cell (10) in a housing comprising inter alia a printed circuit board (30) including electronic processing circuits associated with the microsensor cell. In order to ensure a non-rigid electronic connection between a conducting contact plate (34) of the board (30) and a connection pin (12) of the cell (10), a conductor link is welded in the form of a narrow ribbon cut by chemical machining in a thin, flexible metal sheet (CuBe). The ribbon comprises at least one circular arc shaped segment (51) extending over a two-quarter or three-quarter turn. The elasticity thereof results in extremely low rigidity in all directions and thus prevents transmission of vibrations or shocks to the cell. It is possible to collectively manufacture all of the sensor links and successive mass-produced sensors. The invention can be applied to accelerometers subjected to the high stress from shocks and vibrations.

Description

CAPTEUR DE MESURE A LIAISONS CONDUCTRICES SANS RAIDEUR ET PROCEDE DE FABRICATION MEASURING SENSOR WITH STRAIGHT-CONDUCTIVE CONNECTIONS AND MANUFACTURING METHOD
L'invention concerne les capteurs électroniques comportant une cellule de microcapteur électromécanique telle qu'un micro-accéléromètre, et elle concerne plus particulièrement le montage de la cellule de microcapteur proprement dite dans un boîtier comportant par ailleurs une (ou plusieurs) carte de circuit imprimé portant les circuits électroniques de traitement associés à la cellule de microcapteur. Pour des raisons tenant à la nature du capteur et à la mesure qu'on veut faire, par exemple la mesure d'une accélération d'un objet susceptible de subir de fortes contraintes, il est parfois nécessaire de monter la cellule d'une manière telle que les vibrations de l'objet qui porte le capteur, ou les chocs subis par cet objet, n'affectent pas la mesure ou même la constitution de la cellule. En effet, typiquement un accéléromètre est très sensible aux vibrations et aux chocs et il fournirait un signal électrique difficilement exploitable si un signal parasite dû à des vibrations de l'objet dont on veut mesurer l'accélération se superposait à la mesure d'accélération proprement dite. D'autre part, les vibrations et chocs pourraient endommager le capteur, ce qui serait encore plus nuisible. La mesure d'accélération n'est pas le seul cas où les vibrations et les chocs sont causes de pannes ou de difficultés de mesure mais elle constitue un cas typique auquel l'invention est particulièrement applicable. Des capteurs d'autres grandeurs physiques, réalisés par micro-usinage, peuvent typiquement être affectés. La cellule est alors montée dans un boîtier avec interposition d'un élément amortisseur de chocs et vibrations. Par exemple, la cellule est calée dans le boîtier par des blocs de calage en élastomère dont les propriétés d'amortissement mécanique sont adaptées aux chocs et vibrations à filtrer, et la cellule n'est pas en contact physique direct avec le boîtier. Cependant, il faut transmettre des tensions d'alimentations ou des signaux électriques entre la cellule et la carte électronique qui lui est associée, carte qui est également montée dans le boîtier. Il faut donc faire attention à ce que les liaisons électriques ne transmettent pas à la cellule, du fait de leur rigidité, des vibrations et chocs que les éléments amortisseurs devraient absorber. Un mode de liaison électrique possible entre la cellule de microcapteur et la carte électronique est représenté sur la figure 1 en coupe et sur la figure 2 en vue de dessus. La cellule 10, avec ses broches de connexion électrique 12, est contenue dans un boîtier 20 fermé par un couvercle 22 ; elle est maintenue en place par des blocs amortisseurs 24 (en principe en élastomère) qui la supportent en absorbant les chocs et vibrations transmis par le boîtier. Le boîtier peut être fixé sur un objet sur lequel on fait une mesure, la fixation pouvant se faire par tous moyens et n'étant pas représentée. La cellule est située du côté de la face arrière d'une carte électronique 30 qui porte sur sa face avant des composants 32 et des conducteurs imprimés 34 ; la carte 30 est percée de trous 36 dans lesquels s'engagent librement (sans contact physique), par l'arrière de la carte, les broches de connexion 12 de la cellule ; les extrémités des broches sont reliées, par des fils soudés 14, à des plots conducteurs faisant partie des conducteurs imprimés 34 de la face avant de la carte ; les fils sont soudés d'un côté sur l'extrémité de la broche et de l'autre sur un plot respectif associé à cette broche ; les fils 14 ne sont pas rectilignes mais ils sont recourbés de manière à jouer un rôle de ressort ayant une faible raideur dans toutes les directions (un fil droit aurait une forte raideur dans la direction de cette droite). Pour assurer une conductivité électrique suffisante entre la carte et la broche (de préférence moins d'un ohm), les fils sont typiquement en or ou aluminium nu ou bien en cuivre isolé par gaine plastique, ou en cuivre ou argent revêtu d'un émail isolant, etc. Le diamètre du fil conducteur est typiquement de 50 micromètres et sa longueur est de quelques millimètres. Le fil doit être préformé avant ou pendant l'opération de soudure pour lui donner la forme courbe qui assure une faible raideur dans toutes les directions, et cette opération de préformage, de même que l'opération de maintien du fil pendant la soudure, est difficile à réaliser. On a constaté que les modules ainsi réalisés sont exagérément sensibles aux vibrations, ce qui empêche une mesure correcte. Une autre manière de réaliser la liaison entre le capteur et la carte peut consister à utiliser une nappe de circuit imprimé souple comme cela est fait dans les imprimantes, les caméscopes, etc. Mais ces nappes sont en général insuffisamment souples à cause de la matière plastique isolante, relativement rigide, sur laquelle reposent les connexions électriques. Il existe donc un besoin pour un mode de connexion, simple et ayant une très faible raideur, entre la cellule et la carte électronique d'un capteur susceptible d'être soumis à des contraintes fortes de vibrations.The invention relates to electronic sensors comprising an electromechanical microsensor cell such as a micro-accelerometer, and it relates more particularly to the mounting of the microsensor cell proper in a housing also comprising one (or more) printed circuit board. carrying the electronic processing circuits associated with the microsensor cell. For reasons related to the nature of the sensor and to the measurement that one wants to make, for example the measurement of an acceleration of an object liable to be subjected to strong stresses, it is sometimes necessary to mount the cell in a way such that the vibrations of the object which carries the sensor, or the shocks undergone by this object, do not affect the measurement or even the constitution of the cell. In fact, typically an accelerometer is very sensitive to vibrations and shocks and it would provide an electrical signal that is difficult to exploit if a parasitic signal due to vibrations of the object whose acceleration is to be measured is superimposed on the acceleration measurement itself. called. On the other hand, vibrations and shocks could damage the sensor, which would be even more harmful. The acceleration measurement is not the only case where vibrations and shocks cause breakdowns or measurement difficulties, but it constitutes a typical case to which the invention is particularly applicable. Sensors of other physical sizes, produced by micro-machining, can typically be affected. The cell is then mounted in a housing with the interposition of a shock and vibration absorbing element. For example, the cell is wedged in the casing by elastomer wedging blocks whose mechanical damping properties are adapted to the shocks and vibrations to be filtered, and the cell is not in direct physical contact with the casing. However, it is necessary to transmit supply voltages or electrical signals between the cell and the electronic card which is associated with it, a card which is also mounted in the housing. Care must therefore be taken that the electrical connections do not transmit to the cell, due to their rigidity, vibrations and shocks that the damping elements should absorb. A possible electrical connection mode between the microsensor cell and the electronic card is shown in FIG. 1 in section and in FIG. 2 in top view. The cell 10, with its electrical connection pins 12, is contained in a housing 20 closed by a cover 22; it is held in place by damping blocks 24 (in principle made of elastomer) which support it by absorbing the shocks and vibrations transmitted by the housing. The housing can be fixed on an object on which a measurement is made, the fixing being possible by any means and not being shown. The cell is located on the side of the rear face of an electronic card 30 which carries on its front face components 32 and printed conductors 34; the card 30 is pierced with holes 36 in which freely engage (without physical contact), from the rear of the card, the connection pins 12 of the cell; the ends of the pins are connected, by welded wires 14, to conductive pads forming part of the printed conductors 34 of the front face of the card; the wires are welded on one side to the end of the spindle and on the other to a respective stud associated with this spindle; the wires 14 are not straight but they are bent so as to act as a spring having a low stiffness in all directions (a straight wire would have a high stiffness in the direction of this straight line). To ensure sufficient electrical conductivity between the card and the pin (preferably less than one ohm), the wires are typically made of bare gold or aluminum or else copper insulated by plastic sheath, or copper or silver coated with enamel insulator, etc. The diameter of the conductive wire is typically 50 micrometers and its length is a few millimeters. The wire must be preformed before or during the welding operation to give it the curved shape which ensures low stiffness in all directions, and this preforming operation, like the operation of holding the wire during welding, is difficult to achieve. It has been found that the modules thus produced are excessively sensitive to vibrations, which prevents correct measurement. Another way to make the connection between the sensor and the card can be to use a flexible printed circuit board as is done in printers, camcorders, etc. But these tablecloths are in general insufficiently flexible because of the relatively rigid insulating plastic material on which the electrical connections rest. There is therefore a need for a connection mode, simple and having a very low stiffness, between the cell and the electronic card of a sensor capable of being subjected to strong vibration constraints.
L'invention se propose de fournir une solution améliorant au moins en partie les solutions connues. Le capteur selon l'invention comporte un boîtier, une cellule de microcapteur calée dans le boîtier par des blocs amortisseurs, et une carte électronique comportant des circuits électroniques associés à la cellule, la cellule comportant des broches de connexion, des liaisons conductrices souples étant prévues entre les broches de connexion et des conducteurs imprimés de la carte, ce capteur étant caractérisé en ce que chaque liaison conductrice comprend un ruban mince métallique souple usiné par découpage, s'étendant entre la broche et un conducteur imprimé passant à proximité de la broche, le ruban étant relié électriquement d'un côté au conducteur et de l'autre à la broche et comportant entre le conducteur et la broche un tronçon en forme d'arc parallèle au plan de la carte et s'étendant librement au dessus de la carte avec un espace entre le ruban et la carte. Le ruban, découpé dans une feuille métallique, est de préférence relié électriquement à la broche et au conducteur imprimé par une soudure. Les arcs (de préférence des arcs de cercle) correspondant à différentes liaisons conductrices sont de préférences identiques. Ils s'étendent de préférence sur au moins 180°, et de préférence sur environ trois quarts de tour. La largeur du ruban à l'endroit de l'arc est de préférence inférieure à la largeur du ruban dans des tronçons de ruban s'étendant entre l'arc et la broche ou entre l'arc et le conducteur du circuit imprimé. La largeur de l'arc peut être de quelques dizaines de micromètres, par exemple 70 à 100 micromètres pour une feuille d'épaisseur environ 50 micromètres ; cette largeur faible et cette épaisseur faible, combinées à la courbure de l'arc, donnent une très faible raideur à la liaison conductrice dans toutes les directions, et il faut noter que la raideur dans la direction perpendiculaire à la feuille est largement inférieure à celle qui serait nécessaire pour supporter la cellule, celle-ci étant supportée complètement par les blocs amortisseurs. Les liaisons ne sont donc pas des moyens de support de la cellule mais des moyens de transmission de tensions et courants électriques qui ne transmettent pas de contraintes mécaniques à la cellule. L'une des extrémités de chaque liaison conductrice comprend de préférence un anneau dans le centre duquel passe la broche de connexion de la cellule. L'autre extrémité de la liaison peut aussi comprendre un anneau dans lequel passe un picot soudé au conducteur imprimé, le ruban métallique mince étant alors soudé sur ce picot. Le matériau de la feuille métallique est de préférence un alliage de cuivre et de béryllium choisi en raisons de ses propriétés d'élasticité supérieures à celles du cuivre et de sa conductivité électrique proche de celle du cuivre. Le procédé de fabrication proposé selon l'invention est particulièrement économique car il utilise un usinage collectif d'un ensemble de liaisons électriques. Selon l'invention on propose donc un procédé de fabrication d'un capteur comprenant un boîtier dans lequel sont montés une cellule de microcapteur calée dans le boîtier par des blocs amortisseurs et une carte de circuit imprimé associée à la cellule, le procédé comprenant les opérations suivantes : - usiner par découpage une feuille métallique mince et souple de manière à former dans cette feuille plusieurs liaisons conductrices en forme de ruban étroit ayant une très faible raideur dans toutes les directions, chaque liaison comportant un tronçon courbé en arc dans le plan de la feuillle, ces liaisons étant destinées à relier chacune une broche respective de connexion de la cellule à un conducteur de circuit imprimé de la carte qui passe à proximité de la broche, les différentes liaisons étant solidarisées les unes avec les autres par des ponts faisant partie de la feuille, - placer la cellule à proximité de la carte, et souder chaque liaison d'un côté à une broche et de l'autre à un conducteur correspondant en laissant un espace libre au dessus de la carte entre le tronçon en arc du ruban étroit et la carte, - et découper les ponts entre liaisons pour les séparer les unes des autres. L'usinage de la feuille est de préférence est un usinage chimique par photolithographie. Le découpage de la feuille inclut de préférence le découpage d'ouvertures aux emplacements où des composants sont placés sur la carte, la feuille étant mise en place sur la carte sur laquelle ont été préalablement soudés des composants. Non seulement les composants mais aussi des picots conducteurs peuvent être soudés sur la carte, et la liaison conductrice est soudée à l'extrémité libre de ces picots. Le ruban étroit peut comporter des terminaisons en forme d'anneau et dans ce cas on enfile cet anneau autour d'une broche de la cellule ou d'un picot conducteur soudé sur la carte, avant de souder l'anneau sur la broche ou le picot.The invention proposes to provide a solution at least partially improving the known solutions. The sensor according to the invention comprises a housing, a microsensor cell wedged in the housing by damping blocks, and an electronic card comprising electronic circuits associated with the cell, the cell comprising connection pins, flexible conductive connections being provided. between the connection pins and the printed conductors of the card, this sensor being characterized in that each conductive link comprises a thin flexible metallic strip machined by cutting, extending between the pin and a printed conductor passing near the pin, the strip being electrically connected on one side to the conductor and on the other to the spindle and comprising between the conductor and the spindle an arc-shaped section parallel to the plane of the card and extending freely above the card with a space between the ribbon and the card. The ribbon, cut from a metal sheet, is preferably electrically connected to the pin and to the printed conductor by soldering. The arcs (preferably arcs of a circle) corresponding to different conductive connections are preferably identical. They preferably extend over at least 180 °, and preferably over about three quarters of a turn. The width of the ribbon at the location of the arc is preferably less than the width of the ribbon in sections of ribbon extending between the arc and the pin or between the arc and the conductor of the printed circuit. The width of the arc may be a few tens of micrometers, for example 70 to 100 micrometers for a sheet of thickness about 50 micrometers; this small width and this small thickness, combined with the curvature of the arc, give a very low stiffness to the conductive bond in all directions, and it should be noted that the stiffness in the direction perpendicular to the sheet is much lower than that which would be necessary to support the cell, the latter being completely supported by the damping blocks. The links are therefore not means of supporting the cell but means of transmitting electric voltages and currents which do not transmit mechanical stresses to the cell. One end of each conductive connection preferably comprises a ring in the center of which passes the connection pin of the cell. The other end of the link may also include a ring through which passes a pin welded to the printed conductor, the thin metallic strip then being welded to this pin. The material of the metal foil is preferably an alloy of copper and beryllium chosen because of its elasticity properties greater than those of copper and its electrical conductivity close to that of copper. The manufacturing process proposed according to the invention is particularly economical because it uses collective machining of a set of electrical connections. According to the invention there is therefore proposed a method of manufacturing a sensor comprising a housing in which are mounted a microsensor cell wedged in the housing by damping blocks and a printed circuit board associated with the cell, the method comprising the operations following: - machining by cutting a thin and flexible metal sheet so as to form in this sheet several conductive connections in the form of a narrow ribbon having a very low stiffness in all directions, each connection comprising a section curved in an arc in the plane of the leaf, these connections being intended to each connect a respective connection pin of the cell to a printed circuit conductor of the card which passes near the pin, the various connections being secured to each other by bridges forming part of the sheet, - place the cell near the card, and solder each link on one side to a pin and the other to a corresponding conductor leaving a free space above the card between the arcuate section of the narrow ribbon and the card, - and cut the bridges between connections to separate them from each other. The machining of the sheet is preferably a chemical machining by photolithography. The cutting of the sheet preferably includes the cutting of openings at the locations where components are placed on the card, the sheet being placed on the card on which components have been previously welded. Not only the components but also conductive pins can be soldered to the card, and the conductive link is soldered to the free end of these pins. The narrow ribbon can have ring-shaped endings and in this case we thread this ring around a cell pin or a conductive pin welded on the card, before soldering the ring on the pin or the pin.
D'autres caractéristiques et avantages de l'invention apparaîtront à la lecture de la description détaillée qui suit et qui est faite en référence aux dessins annexés dans lesquels : - les figures 1 et 2, déjà décrites, représentent la liaison d'une cellule de microcapteur à une carte par des fils de cuivre ; - la figure 3 représente, en vue de dessus, une liaison conductrice individuelle destinée à relier une broche de la cellule à un plot conducteur de la carte ; - la figure 4 représente, en perspective, le montage d'une liaison conductrice sur la carte avant soudure de la liaison ; - la figure 5 représente la liaison conductrice soudée ; - la figure 6 représente une feuille métallique comportant plusieurs liaisons conductrices découpées ; - la figure 7 représente une variante de réalisation des liaisons conductrices ;Other characteristics and advantages of the invention will appear on reading the detailed description which follows and which is made with reference to the appended drawings in which: - Figures 1 and 2, already described, show the connection of a microsensor to a card by copper wires; - Figure 3 shows, in top view, an individual conductive connection intended to connect a pin of the cell to a conductive pad of the card; - Figure 4 shows, in perspective, the mounting of a conductive connection on the card before welding of the connection; - Figure 5 shows the welded conductive connection; - Figure 6 shows a metal sheet having several cut conductive connections; - Figure 7 shows an alternative embodiment of the conductive connections;
La constitution générale du capteur selon l'invention est celle des figures 1 et 2 à l'exception des liaisons conductrices entre broches 12 de la cellule et conducteurs 34 de la carte de circuit imprimé, et cette constitution générale ne sera donc pas décrite à nouveau. Dans l'exemple préféré, la cellule est placée à l'arrière de la carte et les broches traversent la carte pour passer du côté de la face avant, mais on pourrait aussi avoir la cellule du côté de la face avant (celle qui porte des composants électroniques), les broches n'ayant pas besoin de traverser la carte. La figure 3 représente une liaison conductrice 50 mise en place (mais non soudée) au dessus d'une broche de connexion 12 de la cellule et d'un plot conducteur 34 imprimé sur la carte ; la liaison 50 est destinée à relier cette broche à ce plot. Le trou 36 percé dans la carte et dans lequel peut librement s'enfiler la broche 12 à proximité du plot 34 n'est pas représenté sur la figure 3, étant masqué par une partie de la liaison conductrice qui le recouvre. La liaison conductrice est une liaison à très faible raideur, qui n'est pas destinée à supporter physiquement le poids de la cellule, et l'ensemble des liaisons conductrices associées aux différentes broches ne peut pas supporter ce poids. Le poids de la cellule, comme les forces d'accélération qu'elle peut subir, est entièrement supporté par les blocs amortisseurs 24, en élastomère, de la figure 1. La liaison individuelle 50 est découpée, de préférence par usinage chimique, à partir d'un dessin photolithographié, dans une feuille métallique souple mince. L'épaisseur est choisie pour donner une très faible raideur à la liaison dans le plan perpendiculaire à la feuille métallique,c'est-à-dire, en fonctionnement, dans le plan perpendiculaire à la carte de circuit imprimé. L'ordre de grandeur de l'épaisseur est de 50 micromètres. La feuille est en matériau élastique et très bon conducteur de l'électricité. Le matériau préféré est un alliage de cuivre et de béryllium, tel que l'alliage CuBe2. La forme de la liaison découpée est un ruban étroit (la largeur peut être de l'ordre de 70 à 100 micromètres par exemple sur la majeure partie de la longueur du ruban), la faible largeur étant choisie pour donner une très faible raideur à la liaison dans le plan de la feuille. Le ruban étroit n'est pas rectiligne mais comporte une partie principale 51 recourbée en arc parallèle au plan de la feuille. L'arc est de préférence un arc de cercle, et il s'étend sur un secteur important, de préférence au moins 180°, et dans cet exemple environ trois quarts d'un tour. La longueur de l'arc peut être de l'ordre de 1 cm. L'arc de cercle est représenté centré sur la broche 12 dans l'exemple dessiné sur les figures, mais ce n'est pas obligatoire et la broche n'est même pas forcément située à l'intérieur de la courbure de l'arc. Cette forme en arc s'étendant sur un secteur important est destinée à donner à la liaison conductrice une très faible raideur selon toutes les directions du plan de la feuille. Une extrémité de la partie de ruban 51 en arc de cercle est reliée par un premier tronçon 52 de faible largeur (par exemple la même largeur que l'arc de cercle) à un deuxième tronçon 53 plus large (ordre de grandeur : environ 300 ou 400 micromètres) qui constitue une première terminaison de la liaison. Dans cet exemple, le tronçon 52 s'étend radialement à partir du centre de l'arc de cercle. Une autre extrémité de la partie de ruban en arc de cercle est reliée par un troisième tronçon 54, ici aussi un tronçon radial et de faible largeur, à un quatrième tronçon 55 qui constitue une deuxième terminaison de la liaison. Les tronçons 52, 54 partent de préférence à angle droit des extrémités du tronçon 51. Ils ont pour fonction de permettre à ce dernier de travailler essentiellement en torsion et non en flexion, à la manière d'un ressort hélicoïdal. Le ruban en arc de cercle et les différents tronçons sont configurés de manière que la première terminaison puisse venir au dessus du plot conducteur 34 lorsque la première terminaison est au dessus de la broche 12. La deuxième terminaison 55 est conformée en anneau entourant la broche 12 ; la largeur de l'anneau est de préférence supérieure à la largeur du tronçon 54. La première terminaison 53 est représentée sur la figure 3 comme étant une barrette linéaire dont l'extrémité peut être soudée au plot conducteur 34 ; on verra plus loin que cette terminaison 53 peut aussi être en anneau. Cependant, la soudure entre la première terminaison et le plot conducteur peut être indirecte en ce sens qu'on peut prévoir qu'un picot conducteur est inséré dans un trou de la carte au centre du plot 34, ce picot étant soudé au plot conducteur et la première terminaison étant alors soudée à la partie supérieure du picot. Les figures 4 et 5, qui sont des vues en perspective de la face avant ou supérieure de la carte 30, représentent cette dernière solution. Un picot métallique conducteur 38 a été soudé au centre du plot imprimé (en principe après insertion du picot dans un trou au centre du plot 34), en même temps qu'étaient soudés sur la carte les différents composants 32 de celle-ci. La deuxième terminaison 55 est enfilée sur la broche 12 (figure 4) après que la carte ait été placée au dessus de la cellule 10 calée dans le boîtier par les blocs amortisseurs ; la première terminaison est mise en place au dessus du picot 38. Puis, l'opération de soudure est exécutée (figure 5), sur les deux terminaisons. L'anneau 55 est soudé sur toute sa périphérie à la broche 12 ; l'extrémité de la terminaison 53 est soudée au picot conducteur. On notera que le rétrécissement de largeur entre l'anneau 55 et le tronçon 54, ou entre la terminaison 53 et le tronçon 52, cantonne la soudure sur l'anneau 55 et la terminaison 53 et évite que la soudure mouille les tronçons 52 et 54 de faible largeur, ce qui aurait pour conséquence d'augmenter la rigidité de la liaison. L'angle que forme la barrette 53 avec le tronçon 52, et la longueur de la barrette 53 dépendent de la configuration du circuit imprimé sur la carte et plus précisément de la position du plot conducteur par rapport à la broche à laquelle on veut le raccorder. Après l'opération de soudure, on voit que les mouvements relatifs de la carte et de la cellule sont possibles : la raideur de la liaison est très faible dans les trois dimensions et un débattement est possible du fait que le trou 36 a un diamètre supérieur (par exemple supérieur d'un millimètre) au diamètre de la broche 12 et du fait qu'un espace vertical (par exemple 1 millimètre) est ménagé entre le ruban en arc de cercle 51 et la carte. L'avantage de l'utilisation d'un picot conducteur 38 est qu'on peut ménager un espace libre entre la liaison conductrice et la carte sur toute la longueur du ruban constituant la liaison. Mais même en l'absence de picot, on prévoira de toutes façons qu'au moins la partie 51 en arc de cercle de la liaison est espacée de la carte afin de ne pas gêner les mouvements verticaux de la cellule de capteur par rapport à la carte en cas de choc ou de vibrations. La figure 6 représente la fabrication collective de la feuille pour réaliser et monter simultanément les différentes laisons conductrices sur les différentes broches de la cellule. Le dessin découpé dans la feuille comporte les différentes liaisons, correctement positionnées les unes par rapport aux autres compte-tenu d'une part de la position relative des différentes broches de la cellule et de la position des plots conducteurs auxquels ces broches doivent être reliées. Les tronçons 51 (en arc de cercle), les tronçons 52, 54 (connectés à l'arc de cercle), et les anneaux 55, sont de préférence tous identiques d'une liaison à l'autre, même s'ils ont des orientations différentes d'une liaison à l'autre, afin de minimiser les disymétries de structure, particulièrement dans le cas d'un accéléromètre qui est un type de capteur très sensible aux dissymétries de contraintes qu'il subit. Les liaisons sont reliées à un cadre 57 qui les maintient en place pendant l'opération de soudure : des ponts 58 entre les terminaisons et le cadre 57 servent à ce maintien. Après l'opération de soudure, ces ponts sont éliminés par découpage. Dans l'exemple de la figure 6, on a représenté la feuille métallique sous forme d'un cadre périphérique rectangulaire 57 à l'intérieur du duquel sont disposés seulement les liaisons 50 et les ponts. On peut aussi prévoir que la feuille métallique découpée est constituée par un rectangle ayant sensiblement la même surface que la carte électronique et qui comprend d'une part les découpes de liaisons et de ponts et d'autre part des découpes autour de chaque composant de la carte afin que la feuille puisse être posée sur la carte sans être gênée par les composants. Les parties pleines de la carte, entre les découpes prévues autour des composants, constituent alors le cadre auquel sont rattachés les ponts. La feuille métallique mince peut être découpée par photolithographie dans un ruban continu pour réaliser non seulement toutes les liaisons conductrices entre la cellule et la carte d'un capteur mais aussi les liaisons d'une série de capteurs dans une fabrication continue en grande série, ce qui réduit encore le coût de fabrication. Les opérations de mise en place, de soudure et de découpe des ponts peuvent être effectuées par une machine automatique. La figure 7 représente une variante de réalisation d'une liaison individuelle : dans cet exemple, on a prévu que la terminaison conductrice 55 est un anneau dont la découpe intérieure est une forme cannelée facilitant la mise en place sur la broche à une hauteur déterminée (l'anneau se coince sur la broche) ; on a prévu de plus que la terminaison 53 comporte également une forme d'anneau (également cannelée si on le souhaite) venant s'enfiler sur un picot conducteur tel que le picot 38, préalablement soudé sur la carte. Sur les figures qui précèdent, le tronçon 54 qui relie l'anneau 55 à l'arc de cercle 51 est tourné radialement vers l'intérieur de l'arc de cercle, et la broche 12 est au centre de cet arc. Toutefois, le tronçon 55 pourrait partir dans une autre direction, même vers l'extérieur de l'arc ou même dans le prolongement de l'arc, la broche n'étant pas au centre de l'arc ni même forcément à l'intérieur de l'arc. Ces solutions sont moins compactes que la solution avec la broche au centre de l'arc mais elles peuvent être utilisées aussi. The general constitution of the sensor according to the invention is that of FIGS. 1 and 2 with the exception of the conductive connections between pins 12 of the cell and conductors 34 of the printed circuit board, and this general constitution will therefore not be described again. . In the preferred example, the cell is placed at the rear of the card and the pins cross the card to pass on the side of the front face, but we could also have the cell on the side of the front face (the one which carries electronic components), the pins do not need to pass through the card. FIG. 3 represents a conductive link 50 put in place (but not welded) above a connection pin 12 of the cell and a conductive pad 34 printed on the card; the link 50 is intended to connect this pin to this pad. The hole 36 drilled in the card and in which the pin 12 can freely be threaded near the stud 34 is not shown in FIG. 3, being masked by a part of the conductive link which covers it. The conductive link is a very low stiffness link, which is not intended to physically support the weight of the cell, and all of the conductive links associated with the different pins cannot support this weight. The weight of the cell, like the acceleration forces which it can undergo, is entirely supported by the damping blocks 24, made of elastomer, of FIG. 1. The individual connection 50 is cut, preferably by chemical machining, from of a photolithographed drawing, in a thin flexible metallic sheet. The thickness is chosen to give a very low stiffness to the connection in the plane perpendicular to the metal sheet, that is to say, in operation, in the plane perpendicular to the printed circuit board. The order of magnitude of the thickness is 50 micrometers. The sheet is made of elastic material and is a very good conductor of electricity. The preferred material is an alloy of copper and beryllium, such as the alloy CuBe2. The shape of the cut link is a narrow ribbon (the width can be of the order of 70 to 100 micrometers, for example over the major part of the length of the ribbon), the small width being chosen to give a very low stiffness to the link in the plane of the sheet. The narrow ribbon is not straight but has a main part 51 curved in an arc parallel to the plane of the sheet. The arc is preferably an arc of a circle, and it extends over a large sector, preferably at least 180 °, and in this example about three quarters of a turn. The length of the arch can be of the order of 1 cm. The circular arc is shown centered on the pin 12 in the example drawn in the figures, but this is not compulsory and the pin is not even necessarily located inside the curvature of the arc. This arc shape extending over a large sector is intended to give the conductive connection a very low stiffness in all directions of the plane of the sheet. One end of the ribbon portion 51 in an arc is connected by a first section 52 of small width (for example the same width as the arc of a circle) to a second section 53 wider (order of magnitude: approximately 300 or 400 micrometers) which constitutes the first termination of the link. In this example, the section 52 extends radially from the center of the circular arc. Another end of the ribbon portion in an arc is connected by a third section 54, here also a radial section and of small width, to a fourth section 55 which constitutes a second termination of the connection. The sections 52, 54 preferably leave at a right angle from the ends of the section 51. Their function is to allow the latter to work essentially in torsion and not in bending, in the manner of a helical spring. The ribbon in an arc and the various sections are configured so that the first termination can come above the conductive pad 34 when the first termination is above the pin 12. The second termination 55 is shaped as a ring surrounding the pin 12 ; the width of the ring is preferably greater than the width of the section 54. The first termination 53 is shown in FIG. 3 as being a linear strip whose end can be welded to the conductive pad 34; we will see later that this termination 53 can also be in a ring. However, the solder between the first termination and the conductive pad can be indirect in the sense that one can provide that a conductive pin is inserted into a hole in the card in the center of the pad 34, this pin being welded to the conductive pad and the first termination being then welded to the upper part of the pin. Figures 4 and 5, which are perspective views of the front or upper face of the card 30, represent the latter solution. A conductive metal pin 38 has been welded to the center of the printed pad (in principle after inserting the pin into a hole in the center of the pad 34), at the same time as the various components 32 of the latter were welded onto the card. The second termination 55 is threaded on pin 12 (Figure 4) after the card has been placed above the cell 10 wedged in the housing by the damping blocks; the first termination is placed above the pin 38. Then, the welding operation is performed (FIG. 5), on the two terminations. The ring 55 is welded over its entire periphery to the pin 12; the end of the termination 53 is welded to the conductive pin. It will be noted that the narrowing of width between the ring 55 and the section 54, or between the termination 53 and the section 52, confines the weld to the ring 55 and the termination 53 and prevents the weld from wetting the sections 52 and 54 of small width, which would have the consequence of increasing the rigidity of the connection. The angle formed by the bar 53 with the section 52, and the length of the bar 53 depend on the configuration of the printed circuit on the card and more precisely on the position of the conductive pad relative to the pin to which it is desired to connect it. . After the welding operation, we see that the relative movements of the card and the cell are possible: the stiffness of the connection is very low in the three dimensions and a clearance is possible because the hole 36 has a larger diameter (for example greater than one millimeter) than the diameter of pin 12 and the fact that a vertical space (for example 1 millimeter) is provided between the ribbon in an arc 51 and the card. The advantage of using a conductive pin 38 is that a free space can be provided between the conductive connection and the card over the entire length of the ribbon constituting the connection. But even in the absence of a pin, it will in any case be provided that at least the part 51 in an arc of a circle of the link is spaced from the card so as not to hinder the vertical movements of the sensor cell relative to the card in case of shock or vibration. FIG. 6 represents the collective production of the sheet for making and simultaneously mounting the different conductive laces on the different pins of the cell. The drawing cut from the sheet includes the various connections, correctly positioned with respect to each other taking into account on the one hand the relative position of the different pins of the cell and the position of the conductive pads to which these pins are to be connected. The sections 51 (in an arc), the sections 52, 54 (connected to the arc), and the rings 55, are preferably all identical from one link to another, even if they have different orientations from one link to another, in order to minimize structural asymmetries, particularly in the case of an accelerometer which is a very sensitive type of sensor to the asymmetries of constraints it undergoes. The connections are connected to a frame 57 which keeps them in place during the welding operation: bridges 58 between the terminations and the frame 57 serve for this maintenance. After the welding operation, these bridges are removed by cutting. In the example of Figure 6, there is shown the metal sheet in the form of a rectangular peripheral frame 57 inside which are arranged only the connections 50 and the bridges. It can also be provided that the cut metal sheet is constituted by a rectangle having substantially the same surface as the electronic card and which comprises on the one hand the cutouts of connections and bridges and on the other hand cutouts around each component of the card so that the sheet can be placed on the card without being hindered by the components. The solid parts of the card, between the cutouts provided around the components, then constitute the frame to which the bridges are attached. The thin metal sheet can be cut by photolithography in a continuous ribbon to make not only all the conductive connections between the cell and the card of a sensor but also the connections of a series of sensors in a continuous mass production, this which further reduces the manufacturing cost. The operations of placing, welding and cutting the bridges can be carried out by an automatic machine. FIG. 7 represents an alternative embodiment of an individual connection: in this example, provision has been made for the conductive termination 55 to be a ring, the internal cutout of which is a grooved shape facilitating placement on the spindle at a determined height ( the ring gets stuck on the spindle); it was further provided that the termination 53 also includes a ring shape (also grooved if desired) threading on a conductive pin such as pin 38, previously welded on the card. In the preceding figures, the section 54 which connects the ring 55 to the circular arc 51 is turned radially towards the inside of the circular arc, and the pin 12 is in the center of this arc. However, section 55 could leave in another direction, even towards the outside of the arc or even in the extension of the arc, the spindle not being in the center of the arc nor even necessarily inside the arc. These solutions are less compact than the solution with the pin in the center of the arc but they can be used too.

Claims

REVENDICATIONS
1. Capteur comportant un boîtier (20), une cellule de microcapteur (10) calée dans le boîtier par des blocs amortisseurs (24), et une carte électronique (10) comportant des circuits électroniques associés à la cellule, la cellule comportant des broches de connexion (12), des liaisons conductrices souples étant prévues entre les broches de connexion et des conducteurs imprimés de la carte, ce capteur étant caractérisé en ce que chaque liaison conductrice (50) comprend un ruban métallique mince et souple usiné par découpage, s'étendant entre la broche (12) et un conducteur imprimé (34) passant à proximité de la broche, le ruban étant relié électriquement d'un côté au conducteur et de l'autre à la broche et comportant entre le conducteur et la broche un tronçon (51) en forme d'arc parallèle au plan de la carte et s'étendant librement au dessus de la carte avec un espace entre le ruban et la carte. 1. Sensor comprising a housing (20), a microsensor cell (10) wedged in the housing by damping blocks (24), and an electronic card (10) comprising electronic circuits associated with the cell, the cell comprising pins connection (12), flexible conductive connections being provided between the connection pins and printed conductors of the card, this sensor being characterized in that each conductive connection (50) comprises a thin and flexible metallic strip machined by cutting, s extending between the pin (12) and a printed conductor (34) passing near the pin, the ribbon being electrically connected on one side to the conductor and on the other to the pin and comprising between the conductor and the pin a section (51) in the form of an arc parallel to the plane of the card and extending freely above the card with a space between the strip and the card.
2. Capteur selon la revendication 1 , caractérisé en ce que le ruban est relié électriquement à la broche et au conducteur imprimé par une soudure. 2. Sensor according to claim 1, characterized in that the ribbon is electrically connected to the pin and to the printed conductor by a solder.
3. Capteur selon l'une des revendications 1 et 2, caractérisé en ce que le tronçon en forme d'arc est un arc de cercle centré sur la broche.3. Sensor according to one of claims 1 and 2, characterized in that the arc-shaped section is an arc centered on the spindle.
4. Capteur selon l'une des revendications 1 à 3, caractérisé en ce que le tronçon en forme d'arc s'étend sur un secteur angulaire d'au moins 180°. 4. Sensor according to one of claims 1 to 3, characterized in that the arc-shaped section extends over an angular sector of at least 180 °.
5. Capteur selon l'une des revendications 1 à 4, caractérisé en ce que le ruban comporte au moins une terminaison en anneau enfilée sur la broche ou sur un picot conducteur, l'anneau étant soudé à cette broche ou à ce picot. 5. Sensor according to one of claims 1 to 4, characterized in that the ribbon comprises at least one ring termination threaded on the pin or on a conductive pin, the ring being welded to this pin or to this pin.
6. Capteur selon l'une des revendications 1 à 5, caractérisé en ce que le tronçon (51) en arc est complété par deux tronçons (52 , 54) s'étendant sensiblement radialement par rapport à un centre constitué par la broche.6. Sensor according to one of claims 1 to 5, characterized in that the arc section (51) is completed by two sections (52, 54) extending substantially radially with respect to a center constituted by the spindle.
7. Capteur selon la revendication 6, caractérisé en ce que les tronçons (52, 54) s'étendant radialement sont complétés par des tronçons de largeur supérieure à celle de ces derniers.7. Sensor according to claim 6, characterized in that the sections (52, 54) extending radially are completed by sections of width greater than that of the latter.
8. Capteur selon l'une des revendications 1 à 7, caractérisé en ce que le ruban est découpé dans une feuille en alliage de cuivre et de béryllium.8. Sensor according to one of claims 1 to 7, characterized in that the ribbon is cut from a sheet of copper and beryllium alloy.
9. Capteur selon l'une des revendications précédentes, caractérisé en ce qu'il comporte plusieurs liaisons conductrices en forme de ruban ayant un tronçon en forme d'arc, caractérisé en ce que les tronçons en forme d'arc des différentes liaisons sont tous identiques.9. Sensor according to one of the preceding claims, characterized in that it comprises several conductive links in the form of a ribbon having an arc-shaped section, characterized in that the arc-shaped sections of the different connections are all identical.
10. Procédé de fabrication d'un capteur comprenant un boîtier (20) dans lequel sont montés une cellule de microcapteur calée dans le boîtier par des blocs amortisseurs (24) et une carte de circuit imprimé associée à la cellule, le procédé comprenant les opérations suivantes : - usiner par découpage une feuille métallique mince et souple de manière à former dans cette feuille plusieurs liaisons conductrices en forme de ruban étroit ayant une très faible raideur dans toutes les directions, chaque liaison comportant un tronçon (51) courbé en arc dans le plan de la feuillle, ces liaisons étant destinées à relier chacune une broche respective de connexion (12) de la cellule à un conducteur (34) de circuit imprimé de la carte qui passe à proximité de la broche, les différentes liaisons étant solidarisées les unes avec les autres par des ponts (58) faisant partie de la feuille, - placer la cellule à proximité de la carte et souder chaque liaison d'un côté à une broche et de l'autre à un conducteur correspondant en laissant un espace libre au dessus de la carte entre le tronçon en arc du ruban étroit et la carte, - et découper les ponts (58) entre liaisons pour les séparer les unes des autres. 10. A method of manufacturing a sensor comprising a housing (20) in which are mounted a microsensor cell wedged in the housing by damping blocks (24) and a printed circuit board associated with the cell, the method comprising the operations following: - machining by cutting a thin and flexible metal sheet so as to form in this sheet several conductive connections in the form of a narrow ribbon having a very low stiffness in all directions, each connection comprising a section (51) curved in an arc plane of the sheet, these connections being intended to each connect a respective connection pin (12) of the cell to a conductor (34) of the printed circuit of the card which passes near the pin, the different connections being secured together with the others by bridges (58) forming part of the sheet, - place the cell close to the card and weld each connection from one side to one pin and the other to a corresponding conductor leaving a free space above the card between the arcuate section of the narrow ribbon and the card, - and cut the bridges (58) between connections to separate them from each other .
11. Procédé selon la revendication 10, caractérisé en ce que l'usinage de la feuille est un usinage chimique par photolithographie.11. Method according to claim 10, characterized in that the machining of the sheet is a chemical machining by photolithography.
12. Procédé selon l'une des revendications 10 à 11 , caractérisé en ce que le découpage de la feuille inclut le découpage d'ouvertures aux emplacements où des composants sont placés sur la carte, la feuille étant mise en place sur la carte sur laquelle ont été préalablement soudés des composants.12. Method according to one of claims 10 to 11, characterized in that the cutting of the sheet includes the cutting of openings at the locations where components are placed on the card, the sheet being placed on the card on which components have been previously welded.
13. Procédé selon l'une des revendications 10 à 12, caractérisé en ce que non seulement les composants mais aussi des picots conducteurs (36) sont soudés sur la carte, et la liaison conductrice est soudée à l'extrémité libre de ces picots.13. Method according to one of claims 10 to 12, characterized in that not only the components but also conductive pins (36) are welded to the card, and the conductive connection is welded to the free end of these pins.
14. Procédé selon l'une des revendications 10 à 13, caractérisé en ce que le ruban étroit comporte au moins une terminaison en forme d'anneau14. Method according to one of claims 10 to 13, characterized in that the narrow strip has at least one ring-shaped termination
(55), et qu'on enfile cet anneau autour d'une broche de la cellule ou d'un picot conducteur soudé sur la carte, avant de souder l'anneau sur la broche ou le picot. (55), and that this ring is threaded around a cell pin or a conductive pin welded to the card, before soldering the ring on the pin or pin.
EP04818818A 2003-11-18 2004-10-27 Non-rigid conductor link measurement sensor and method for the production thereof Withdrawn EP1685411A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR0313495A FR2862413B1 (en) 2003-11-18 2003-11-18 MEASURING SENSOR WITH CONDUCTIVE CONNECTIONS WITHOUT STIFFNESS AND METHOD OF MANUFACTURE
PCT/EP2004/052680 WO2005050227A1 (en) 2003-11-18 2004-10-27 Non-rigid conductor link measurement sensor and method for the production thereof

Publications (1)

Publication Number Publication Date
EP1685411A1 true EP1685411A1 (en) 2006-08-02

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EP04818818A Withdrawn EP1685411A1 (en) 2003-11-18 2004-10-27 Non-rigid conductor link measurement sensor and method for the production thereof

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US (1) US7400514B2 (en)
EP (1) EP1685411A1 (en)
FR (1) FR2862413B1 (en)
WO (1) WO2005050227A1 (en)

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CN100531543C (en) * 2005-09-09 2009-08-19 鸿富锦精密工业（深圳）有限公司 Grounding device for reducing electromagnetic interference
CN100555752C (en) * 2005-09-16 2009-10-28 鸿富锦精密工业（深圳）有限公司 Arrangement for resilient contacting and use the electronic equipment of this arrangement for resilient contacting
CN106881537A (en) * 2015-12-15 2017-06-23 航天科工惯性技术有限公司 A kind of assembly method of accelerometer binding post and torquer
CN210224218U (en) * 2019-07-09 2020-03-31 天佑电器（苏州）有限公司 Battery pack

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Also Published As

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US20060276063A1 (en) 2006-12-07
FR2862413B1 (en) 2006-02-17
WO2005050227A1 (en) 2005-06-02
FR2862413A1 (en) 2005-05-20
US7400514B2 (en) 2008-07-15

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