EP0053968A1 - Electrical connecting device with high contact density - Google Patents

Abstract

The invention relates to an electrical connection device, of the type comprising a plurality of conductive elements arranged relative to a support means (26) extending in a given direction and electrically isolated from each other. According to the invention, said elements (29) are stacked in said direction and are each formed by a conductive strip (30) provided with two contact surfaces (31a, 32a) elastically movable in a plane normal to said direction substantially independently of the contact surfaces of neighboring blades. The invention applies in particular to the connection with high density of contacts, for LSI integrated circuits for example.

Description

The invention relates to an electrical connection device with a high density of contacts.

A significant example of an electrical connection with high contact density will be given with reference to the plates forming supports for integrated circuit devices, generally called "substrates". The face of the substrates which carries the integrated circuit devices includes a network of interconnection conductors of these devices, and peripheral contact pads constituting the input-output terminals of the substrates. The substrates are themselves mounted on printed circuit boards intended for their electrical interconnection and consequently provided with studs intended to cooperate with the respective pads of the substrates, by means of electrical connection devices.

For a conventional substrate, square in shape, having for example 46 pads per side, with a pitch of 1 mm and a width of about 0.6 mm, the connection of the contact pads on one side of the substrate to the corresponding pads of a card printed circuits is made by means of a device set up from a comb made up of equidistant parallel pins, with the pitch of the pads and the studs. On the side of the substrate, the pins form a clamp enclosing the corresponding side of the substrate while making contact, by welding, with the pads arranged on this side; on the card, the other ends of the pins are welded to the studs, the pins being kept equidistant by means of an insulating bar or an insulating binder. This connection device had the advantage of being flexible, reliable and removable, qualities which are particularly important for this kind of connection, as will appear later. As integrated circuit devices become increasingly dense, the conductors of the interconnection network and the contact pads that a substrate comprises must likewise be increasingly dense in order to fully benefit from the advantages of large-scale integration. and the resulting miniaturization of integrated circuit devices. As an indication, the substrates currently under study are square plates of approximately 80 mm on a side, comprising 150 contact pads on each side, with a pitch of 0.5 mm and about 0.3 mm in width.

It turns out that the many electrical connection devices currently available do not provide an electrically and mechanically reliable connection, easily removable, relatively flexible and easily reproducible in large series, when they are reduced to suit the high contact densities currently desired.

The removability of the connection device is an essential factor, given the high price of a substrate equipped with large-scale integrated circuit devices. The replacement of a faulty substrate on a printed circuit board, with a view to its repair and subsequent reuse, must not alter the quality and reliability of the connection to the pads and the pads, both from an electrical point of view. than mechanical. The fineness of the contacts and the pads, and their not particularly restricted steps in the case of current substrates, constitute a great difficulty for the desired removability.

On the other hand, mainly in the context of maintenance, account is taken of the ease of fitting the connection device and its replacement, if possible without the intervention of expensive or bulky equipment.

Finally, the flexibility of the connection device is necessary for the following main reasons. On the one hand, the substrates are not always planar; for example, the various firings they undergo for the solidification of the insulating and conductive layers of the interconnection network deposited by screen printing are likely to alter more or less, locally or globally, their initial flatness. On the other hand, printed circuit boards, of large surface area since they are designed to support up to about ten substrates, have a relative flexibility. In addition, the areas of the substrates and the pads of the cards do not always have a regular thickness. Under these conditions, the connection device must be flexible enough to establish an effective connection despite the flatness defects of the substrates and of the cards entering a predetermined tolerance zone and the slight variations in levels between ranges and between pads.

The invention relates to an electrical connection device suitable for high contact densities, while satisfying the conditions of removability, flexibility and ease of execution and installation which have just been described.

An electrical connection device according to the invention is of the type comprising a plurality of conductive elements arranged relative to a support means extending in a given direction and electrically isolated from each other, and is characterized in that said elements are stacked in said direction and are each formed of a blade conductive provided with two elastically movable contact surfaces in a plane normal to said direction substantially independently of the contact surfaces of neighboring blades.

Consequently, by covering for example with an insulating layer one face of each blade, of course excluding the contact surfaces, and by stacking them as indicated, the blades can move independently of each other in a perpendicular plane. to the direction of the sheath, thus giving the connection device the required flexibility and independence with respect to surface defects of the substrates and of the cards and of variations in levels between pads and between ranges. On the other hand, the blades being supported together over a large surface, they can be very thin while having sufficiently rigid contact surfaces and which can also be provided with gilding. The compactness of the elements which results therefrom, is added to the fact that the elastic means can be two simple rubber bands contained in a sheath of small bulk.

The characteristics and advantages of the invention will emerge more clearly in the description which follows, given with reference to the accompanying drawings.

• - la figure 1 est une vue schématique de côté d'une partie de carte de circuit imprimé coopérant avec un substrat formant support de dispositifs à circuits intégrés, par l'intermédiaire d'un dispositif de connexion conforme à l'invention ;
• - la figure 2' illustre schématiquement, par une vue fragmentaire de dessous suivant la ligne II-II à la figure 1, un exemple de réalisation du substrat représenté sur la figure 1 ;
• - la figure 3A illustre schématiquement, par une vue de côté selon la flèche III indiquée à la figure 1, un exemple de fixation du dispositif de connexion conforme à l'invention ;
• - la figure 3B représente l'état du dispositif de fixation illustré à la figure 3A, avant montage ou après démontage de celui-ci ;
• - la figure 4 illustre, par une vue en coupe dans un plan Oxz défini à la figure 1, un exemple de réalisation d'un dispositif de connexion conforme à l'invention ;
• - la figure 5A illustre, par une vue de côté selon l'axe 0x défini à la figure 1, un mode de réalisation de l'empilage des éléments contenus dans le dispositif de connexion représenté sur la figure 4 ;
• - la figure 5B illustre, de manière analogue la figure 5A, une variante de réalisation de l'empilage des éléments contenus dans le dispositif de connexion représenté sur la figure 4 ;
• - la figure 6 illustre, par une vue en coupe dans un plan Oxz, le dispositif représenté sur la figure 4 quand celui-ci est fixé pour relier un substrat à une carte de circuits imprimés de la manière indiquée à la figure 1 ;
• - la figure 7 illustre, par une vue analogue à celle de la figure 4, une variante de réalisation d'un dispositif de connexion conforme à l'invention ;
• - la figure 8 illustre, par une vue analogue à celle de la figure 4, une autre variante de réalisation d'un dispositif conforme à l'invention ;
• - la figure 9 illustre, par une vue analogue à celle de la figure 4, une troisième variante de réalisation d'un dispositif conforme à l'invention ;
• - la figure 10 illustre, par une vue analogue à celle de la figure 6, une autre variante de réalisation d'un dispositif conforme à l'invention, adapté à un mode de connexion autre que celui représenté sur la figure 1 ; et,
• - la figure 11 illustre, par une vue analogue à celle de la figure 4, une variante de réalisation du dispositif représenté sur la figure 9, adaptée à une connexion par soudage sur les plages du substrat et par contact sur les plots de la carte de circuits imprimés.

In the drawings:

• - Figure 1 is a schematic side view of a printed circuit board part cooperating with a substrate forming a support for integrated circuit devices, via a connection device according to the invention;
• - Figure 2 'illustrates schematically, by a fragmentary view from below along line II-II in Figure 1, an embodiment of the substrate shown in Figure 1;
• - Figure 3A schematically illustrates, by a side view along arrow III indicated in Figure 1, an example of attachment of the connection device according to the invention;
• - Figure 3B shows the state of the fixing device illustrated in Figure 3A, before assembly or after disassembly thereof;
• - Figure 4 illustrates, in a sectional view in an Oxz plane defined in Figure 1, an embodiment of a connection device according to the invention;
• - Figure 5A illustrates, by a side view along the axis 0x defined in Figure 1, an embodiment of the stack of elements contained in the connection device shown in Figure 4;
• - Figure 5B illustrates, similarly to Figure 5A, an alternative embodiment of the stack of elements contained in the connection device shown in Figure 4;
• - Figure 6 illustrates, in a sectional view in an Oxz plane, the device shown in Figure 4 when it is fixed to connect a substrate to a printed circuit board as shown in Figure 1;
• - Figure 7 illustrates, in a view similar to that of Figure 4, an alternative embodiment of a connection device according to the invention;
• - Figure 8 illustrates, in a view similar to that of Figure 4, another alternative embodiment of a device according to the invention;
• - Figure 9 illustrates, in a view similar to that of Figure 4, a third alternative embodiment of a device according to the invention;
• - Figure 10 illustrates, in a view similar to that of Figure 6, another alternative embodiment of a device according to the invention, suitable for a connection mode other than that shown in Figure 1; and,
• - Figure 11 illustrates, in a view similar to that of Figure 4, an alternative embodiment of the device shown in Figure 9, suitable for connection by welding on the pads of the substrate and by contact on the pads of the card printed circuits.

Referring to Figure 1, there is shown, by a schematic side view, two electrical connection devices with high contact density according to the invention (10) connecting the electrical circuits of a substrate (11) carrier of integrated circuit devices (12) to a printed circuit board (13). The card (13) shown is only limited to the part supporting the substrate (11), it being understood that in reality a printed circuit board is capable of receiving up to about ten substrates in the same manner as that illustrated in Figure 1. In addition, for clarity of the drawings, the substrate (11) is assumed to cooperate with the card (13) only by its two opposite sides to which are added in Figure 1 the two respective connection devices (10) , when in reality each of the four sides of a substrate is connected to the card by a connection device such as (10).

It appears from FIGS. 1 and 2 that the face of the substrate (11) which carries the integrated circuit devices (12) is provided with a network of interconnection conductors (14) leading to generally aligned contact pads (15) near the edges of the substrate. The other side of the substrate usually receives a finned radiator (16) for dissipating the heat produced by the devices (12). As for the card (13), the printed circuits (17) which it generally presents on one of its faces includes studs (18) arranged to be connected respectively to the pads (15) of a substrate (11).

In the example of FIG. 1, the two devices (10) according to the invention are of a type analogous to that illustrated for example in FIG. 4, that is to say establishing only a simple electrical connection by contacts under the effect of pressure, so that these connection devices must be associated with a mechanical fixing system of the substrate to the card which, preferably, will simultaneously exert the pressure necessary for the electrical connection devices (10 ). According to the example illustrated in FIGS. 1, 3A and 3B, the two fixing systems (19) relating to the two electrical connection devices (10) are clamping systems consisting essentially of two flanges (20, 21) cooperating respectively with the card (13) and the substrate (11) and enclosing a connection device (10) by means of two fixing members (22) arranged at the two respective ends of the flanges (20, 21). According to the example illustrated in FIG. 3A, the fixing members (22) each consist of a threaded rod (23) passing through the ends of the flanges (20 and 21) by orifices (24) and comprising at each end tightening nuts (25). If the pressure exerted on the contacts of the connection device (10) must be relatively constant over the entire length of one side of the substrate (11), advantage will be taken of the system (19) by ensuring that at least one of the flanges (20, 21) takes, in the rest position, the shape illustrated by the blade 21 in FIG. 3B and described in more detail in French patent application 80 25 858. In short, the shape that the flange 21 takes at rest is substantially equivalent to the elastic deformation of an initially rectilinear beam, of uniform section and of the same length as the flange (21), placed on two simple supports spaced apart by this length, namely the length which separates the two threaded rods (23) in the example of FIG. 3A, and uniformly loaded over this length, the clamping force applied to each end of the flange (21) then having to correspond substantially to half of the load uniformly distributed on this beam.

Furthermore, with reference to FIGS. 1 and 2, a system of orthogonal axes Oxyz has been defined to facilitate the presentation of the figures.

FIG. 4 shows a first embodiment of an electrical connection device (10) according to the invention, seen in a section in the Oxz plane. In Figure 4, the device (10) illustrated consists of a sheath (26) of rectangular parallelepiped shape extending along the axis Oy and having two openings (27, 28) formed in the direction Oy in the two walls opposite of the sheath (26) which are intended to come respectively vis-à-vis with the pads (15) of the substrate (11) and the pads (18) of the card (13) of Figure 1.

In the sheath (26) are stacked, in the axis Oy, a plurality of conductive elements (29) electrically isolated from each other. With reference to FIGS. 4 and 5A, it appears that each element (29) comprises a conductive strip (30) provided with two tabs (31, 32) ending in two contact surfaces (31a, 32a) emerging at least partially from the sheath (26) through the respective openings (27, 28) in the plane of the corresponding blade (30). Preferably, the contact surfaces (31a, 32a) will include a gilding (33) or a similar coating facilitating electrical contact.

The blades (30) are separated from each other by electrically insulating elements (34). These elements can be insulating sheets or, advantageously, layers respectively disposed on at least one face of the blades (30). In the example of FIG. 5A, the elements (34) are insulating layers deposited on only one face of each conductive strip (30), at least with the exception of the surfaces of the strips provided with gilding (33). According to the variant shown in FIG. 5B, the two faces of each strip comprise at least partially two respective layers of insulation (34a, 34b), so that each insulating element (34) separating two neighboring conducting strips (30) is then composed of two insulating layers (34a and 34b) integral with the two faces opposite the conductive strips (30). Thus, each element 29 is composed of a strip (30) and the two insulating layers (34a and 34b).

According to another characteristic of the invention, elastic means are incorporated between the sheath (26) and the stack of elements (29) to urge the contact surfaces (31a, 32a) of the blades (30) towards the outside of the sheath through the respective openings (27, 28). According to the example described in Figure 4, these elastic means are formed of two beads (35, 36) made of a flexible material such as rubber. These two beads extend parallel to the openings (27, 28) and are held in position, by means of grooves (37) formed in the sheath (26) and corresponding grooves (38) in the side walls of the blades (30 ) and possibly insulating elements (34), as illustrated.

FIG. 6 represents the connection device (10) illustrated in FIG. 4 when it is tightened, in a manner analogous to FIG. 1, between the pads (15) of a substrate (11) and the pads (18) a card (13) by means of a clamping system (19) with two flanges (20, 21) similar to that shown in Figures 3A and _3B . It appears from FIG. 6 that the conductive blades (30) tilt more or less to establish themselves in fixed contact positions, as illustrated, by exerting reaction forces on the pads (15) and the pads (18) respectively. produced by the elastic beads (35, 36) in opposition to the clamping force exerted by the flanges (20 and 21). Depending on the clamping force and the variable thicknesses between the areas (15) and between the studs (18), each blade (30) will tilt more or less. Because the elements (29) are stacked, they tilt independently of each other, by simple friction between them (for example, between an insulating layer (34) of a blade (30) and the next blade (30) in the example of FIG. 5A and between the two adjacent insulating layers (34a, 34b) of two successive strips (30) in the example of FIG. 5B). Another advantage of using a device according to the invention lies in the fact that the tilting of the blades has repercussions by a slight stroke of the contact surfaces (31a, 32a) against the range (15) and the corresponding pad (18), which produces a so-called self-cleaning effect, ensuring a frank connection between the elements in contact. In addition, thanks to the stacking of the elements (29) in the sheath (26) and the presence of the beads (35 and 36) and insofar as the sheath is sufficiently flexible, the latter can be subjected to a slight twist around the axis Oy to match the shapes of the surfaces of the substrate (11) and of the card (13), without altering the quality of the connection. In addition, the device (10) can tolerate slight deformations in the Oz direction which, in practice, will not affect the quality of the connection. Furthermore, since the elements (29) stacked in the device (10) can support each other over practically the entire surface of the blades, with the exception of course of the contact surfaces (31a and 32a) of the blades (30 ), these can be made very fine while giving the contact surfaces the required rigidity, which is moreover generally increased by the contact gilding (33). It follows that a connection device according to the invention can very well be adapted to an electrical connection with high contact density, such as the density given by way of example in the first part of this description (ranges and 0.3mm studs, 0.5mm pitch).

The clamping of the flanges (20 and 21) is adjusted to apply a given force, 100 grams for example, on each contact surface (31a and 32a) of a blade (30), in order to ensure a reliable contact of good quality between the blades and the corresponding pads and pads. Thanks to the clamping system illustrated in FIG. 3B, it has been seen that this pressure can be uniformly distributed over all the contacts of the device. The pressure received by the contact surfaces (31a and 32a) of each blade (30) is transmitted by the beads (35 and 36) to the corresponding walls of the sheath (26) of the device (10). However, it will be noted that at the contact density per unit of length given previously by way of example, the application of a pressure of 100 grams per contact leads to exerting a total pressure of 2 kilos per centimeter of sheath according to the axis Oy. The transmission of this pressure to the walls of the sheath thus risks modifying the shape of these walls and affecting the quality of the contacts. The arrangement of the beads (35 and 36) which is illustrated in FIGS. 4 and 6 is advantageous, in that a deformation of the upper and lower walls of the sheath (26) will be limited by the pads (15) and the studs (18 ) subjected to the opposite clamping pressure. However, the arrangement of the elastic means in the sheath of a device according to the invention may be different from that which has just been described. FIG. 7 shows a device according to the invention (10a), in every point similar to that of FIG. 4, with the exception of the arrangement of the beads (35 and 36) on the side walls of the sheath (26). The device (10a) can thus be more flattened than the device (10) shown in FIG. 4, but the side walls of the sheath must be thick enough to resist the pressures transmitted by the contact surfaces (31a and 32a) of the blades (30) of the device.

FIG. 8 illustrates, in a manner similar to FIGS. 4 and 7, an alternative embodiment of a connection device according to the invention. In FIG. 8, the device (10b) has a structure similar to that of FIG. 4, so that its elements are referenced by the same numbers as those indicated in FIG. 4. In the device (10b), the lateral edges blades (30) (along the axis Ox) are segments of a center circle 39 and cooperate with the inner lateral faces of the sheath (26), also shaped into segments of concentric circles. On the other hand, the blades are substantially rectangular and their contact surfaces (31 and 32) are two vertices of the blades instead of being the ends of the legs as in the device (10). As a result, the device (10b) can be more compact and more robust than the device (10). In addition, due to the form of concentric arcs of the lateral edges of the blades (30) and of the sheath (26), the blades pivot around the center (39) so that the deformations of the elastic elements (the beads 35 and 36) are practically only made along the axis Oz in the example of FIG. 8, while in the device (10) the deformations are the result of two components along Ox and Oz.

FIG. 9 illustrates another embodiment of a connection device according to the invention. In the device (10c) shown in Figure 9, the blades (30) each include a base (30a), two legs (30b, 30c), and two contact tabs (31, 32). The base (30a) is fixed to the sheath (26) and is provided with an insulation layer (34); the branches (30b and 30c) are perpendicular extensions of the base (30a) which, in the example illustrated, rest on the sheath (26) without being attached to it. The contact tabs (31 and 32) are perpendicular extensions of the branches (30b, 30c). Their respective contact surfaces (31a, 32a) are coated with the contact gilding (33), while the remaining surface of at least one of their lateral faces, with an insulation layer (34). In this way, the elastic means consist of the branches (30b and 30c) of the blades (30) which, by bending, will adapt to the slight displacement that the contact surfaces (31 and 32) will undergo when the pads are tightened and studs, as in the case of FIG. 6. FIG. 10 illustrates, in a manner analogous to FIG. 6, an alternative embodiment (10d) of a device according to the invention connecting the pads (15) of a substrate (11) to the studs (18) d '' a card (13), the tracks (15) and the studs (18) being side by side and no longer opposite as in the cases corresponding to Figures 1 to 9. Despite the total change of the arrangement ranges and pads, it will be noted that the device (10d) has a lot of similarity with the device (10) and is mainly distinguished from the latter only by the fact that the contact tabs (31 and 32) are arranged on a same side of the sheath (26). The elastic elements consist of three beads (35, 36 and 41). The clamp (21) of a clamping system similar to that of FIG. 3B is then directly applied to the wall of the sheath (26) which is opposite to the wall having the contact surfaces (31a and 32a).

Finally, FIG. 11 illustrates an alternative embodiment (10th) of a device according to the invention, offering the possibility of making, on one side, a connection by soldering, and on the other side, a connection by contact. . The exemplary embodiment illustrated in FIG. 11 is similar to the device (10c) represented in FIG. 9, the difference between the devices (10c) and (10e) residing essentially in that the contact tab (31) intended to come in contact with a pad (15) of a substrate (11) extends, in the device (10e), the branch (30b) to form a tab (31 ') suitable for welding on a pad of a substrate. Optionally, as illustrated, the tab (31 ') can include an insulation layer (34), in order to provide electrical insulation between tabs (31 ¹ ) at the same time as a uniform spacing between them.

Claims (9)

1. Electrical connection device (10), of the type comprising a plurality of conductive elements arranged relative to a support means (26) extending in a given direction (Oy) and electrically isolated from each other, characterized in that that said elements (29) are stacked in said direction and are each formed of a conductive strip (30) provided with two contact surfaces (31a, 32a) elastically movable in a plane (Oxz) normal to said direction substantially independently of the surfaces of contact of neighboring blades. 2. Device according to claim 1, characterized in that the conductive strips are separated from each other by insulating strips. 3. Device according to claim 2, characterized in that the conductive strips are each provided with an insulating layer (34; 34a, 34b) on at least one of their faces. 4. Device according to any one of claims 1 to 3, characterized in that the blades are substantially rectangular, two vertices of which constitute said contact surfaces (Fig. 8). 5. Device according to any one of claims 1 to 3, characterized in that the blades have two tabs (31, 32) whose ends constitute said contact surfaces (Fig. 4, 7, 9, 10, 11). 6. Device according to claim 5, characterized in that the blades comprise a base (30a - Fig. 9) integral with said support means and two branches (30b, 30c) comprising said legs (31, 32) and constituting elastic means for said elastic displacement of the contact surfaces (31a, 32a). 7. Device according to claim 5, characterized in that the blades are connected to said support means by bands or beads (35, 36, 41) elastically deformable for said elastic movement of the contact surfaces (31a, 32a). 8. Device according to claim 5 characterized in that one of the contact surfaces is a surface (31 ¹ ) of contact by welding (Fig. 11). 9. Assembly applying the connection device defined by any one of claims 1 to 8, characterized in that it comprises a substrate (11) provided with an interconnection network (14) of integrated circuit device ( 12), pads (15) and a printed circuit board (13) provided with pads (18), said connection device connecting pads (15) of said substrate to the corresponding pads (18) of the board (13), and in that it comprises a clamping device (19) for exerting a contact pressure between at least one of said contact surfaces (31a, 32a) of each blade (30) and a corresponding pad or pad.

Images