FR2776836A1 - CONNECTION METHOD AND SUPPORT FOR CONNECTING A CSP HOUSING WITH AN INTEGRATED CIRCUIT - Google Patents

Abstract

The invention concerns a method for electrical connection between an integrated circuit (10) housing connection pads (9i) and a CSP housing output terminals (18), which consists in connecting the integrated circuit (10) connection pads (9i) to a connecting support (1) arranged opposite and on a different level from the connecting pads (9i) via electrical conductors (8i) arranged on the connecting support (1). The method is characterised in that, after the support (1) has been arranged opposite the integrated circuit (10), it consists in moving at least part (7i) of the support to bring it in the proximity of the integrated circuit (10) connection pads (9i), and in connecting the conductors (8i) supported by the support part (7i) of the support (1) on the integrated circuit (10) connection pads (9i). The invention is particularly applicable to CSP housing interconnection technique (18).

Description

l Title Connection method and connection support for a CSP unit with

a

integrated circuit.

  The present invention is in the field of connector connectivity

  CSP type, Anglo-Saxon abbreviations for Chip Scale Package.

  It relates more particularly to a method of connection between an integrated circuit and the external terminals of a connection support disposed on the integrated circuit in an architecture of the type known under terminology.

Anglo-Saxon "'an-in".

  The invention also relates to a connection support, a circuit box

  integrated, and an electronic assembly comprising such a box.

  The connection support, for example a printed circuit board, supports a plurality of conductors and provides the interface between the integrated circuit and the external environment of the chip using, for example a connection technology by a network of balls of solder known as

  BGA, Anglo-Saxon abbreviations for Ball Grid Array.

  This connection technology being well known to those skilled in the art, it

  will only be described briefly in the following description.

  The balls are connected on the one hand to connection pads which are generally formed by a local enlargement of the conductors on the connection support, and on the other hand, for example, to another connection support coupled to the supply terminals supply voltages and

command signals.

  A fan-in type connection structure can be likened to a stack typically comprising at the lower level the integrated circuit and at the higher level, the interface with the control signals and the various

  integrated circuit power supplies comprising at least one connection support.

  The support rests on the integrated circuit by means of an insulating mat, for example an elastomer. The main function of the mattress is to absorb the mechanical stresses undergone by the integrated circuit. These constraints are mainly due to the differences in expansion between the silicon and the substrate

  o who receives the CSP when it is subjected to temperature variations.

  The multilayer assembly thus formed constitutes a housing intended to be integrated

in an electronic assembly.

  To make the connection between the connection support and the integrated circuit,

  respectively on different levels, several techniques are known.

  Among these, a technique developed by the company under American law TESSERA, consists of arranging windows in the connection support, in areas intended to be opposite the connection pads of the integrated circuit. The end parts of the conductors are generally arranged at the periphery of the support and are intended to be wired on the pads

integrated circuit connection.

  They extend across windows thus arranged and have a determined shape to undergo deformations at determined distinct locations allowing, after individual bending and breaking of the conductors, to obtain

  conductive tabs facing the connection pads of the integrated circuit.

  The legs are then individually connected to the ranges of

  connection, for example, by individual soldering.

  A first drawback of this technique is that to cause the conductors to break in the right place, namely at the interface between the conductor and the support, typically at the copper / polyimide interface, corresponding to a first window sill , the conductors must include a constriction generally difficult to achieve, typically of the order of 40 to 50 μm in width in the case of conductors having a width

typically 80 pm.

  The conductor, on the other hand, is widened at the polyimide / copper interface on the window sill, opposite the first sill, to help the bending by the effect of

  beam. This widening further reduces the pitch available between conductors.

  Furthermore, the operations after breakage consisting of folding, bending and welding, are carried out by the same tool and individually on each of the

conductive tabs.

  The operation is delicate because the camber must not cause a deviation

  axial conductors; the latter being cantilevered after breakage.

  The protection of the conductors is generally ensured by a noble coating such as gold, palladium, etc. Also, after the conductors have broken, their free ends are therefore not

  more protected against corrosion or any other external attack.

  The invention particularly aims to overcome the aforementioned drawbacks.

  To this end, the invention firstly relates to a method of electrical connection between connection pads of an integrated circuit and output terminals of a CSP box, of the type consisting in connecting the connection pads of the integrated circuit to a connection support arranged opposite and at a level different from the connection pads, by means of electrical conductors

  arranged on the connection support.

  According to the invention, the method consists after having placed the support opposite the integrated circuit, to move at least part of the support to bring it in the vicinity of the connection pads of the integrated circuit, and to connect the conductors supported by the part of the support on the connection pads of the

integrated circuit.

  According to one characteristic, the support comprising at least a first part and a second part, separated by a determined space, and connected to each other by the conductors passing through this space, it consists in arching globally and simultaneously the conductors maintained from on either side of the space and crossing this space, to bring the first part of the support

  in the vicinity of the connection pads of the integrated circuit.

  According to one characteristic, the end parts of the conductors, supported by the first part of the support, are globally connected and

  simultaneously on the tracks of the integrated circuit.

  A second object of the invention is a connection support comprising a plurality of electrical conductors forming a network of conductors on at least one of the faces of the support, and intended to provide the interface between connection pads of an integrated circuit arranged at a different level from the connection support, and from the output terminals of a box containing the circuit

  integrated in a CSP architecture.

  According to the invention, the support comprises at least a first part, supporting the conductors to be connected on the connection pads of the integrated circuit, and capable of undergoing a difference in level with respect to a second part of the support to position themselves in the vicinity of the pads of integrated circuit connection. According to one characteristic, the connection support comprises at least one window, called the bending window, arranged in the support and defining respectively on either side of the bending window, a first part and a second part of the support; the bending window being traversed on either side by conductors held on either side and

  on the other side of the bending window and connecting the two parts.

  According to a second characteristic, the bending window defines in itself

  even, a determined zone corresponding to a space for bending the conductors passing through the bending window; the conductors passing through the bending window being able to deform globally and simultaneously to allow, by a global and simultaneous bending, a difference in level between the first part and the second part of the support being situated respectively

  on either side of the bending window.

  According to another characteristic, the first part of the support, intended to be positioned in the vicinity of the connection pads of the integrated circuit, comprises at least one window, called connection window, arranged in a determined area to be opposite the connection pads; the connection window being traversed by the end portions of the conductors, held on either side of the connection window and able to be simultaneously and globally connected to the connection pads through

of the connection window.

  According to another characteristic, the support and the bending and connection windows are of generally rectangular shape, and the bending window occupies substantially all of the bending space inside the support; the side edges of the bending window being respectively parallel to the side edges of the support and as close as possible to the side edges of the support. The third object of the invention is a CSP box comprising an integrated circuit, a differential expansion absorber, electrical insulator, arranged on the integrated circuit, and a connection support supporting a plurality of conductors defining a network of conductors on at least one of its faces, arranged on the absorber and ensuring the interface between the connection pads of the circuit

  integrated and the output terminals of the housing.

  According to the invention, the support comprises at least a first part resting on the connection pads of the integrated circuit, and at least a second part

resting on the absorber.

  According to one characteristic, the first part and the second part of the support are separated by a window, called a cambering window, arranged in

the support.

  According to another characteristic, the bending window is traversed by conductors maintained on either side of the bending window and connecting

  the first part and the second part of the support.

  According to another characteristic, the conductors passing through the bending window are deformed by a global and simultaneous bending to form a

  difference in level between the first part and the second part of the support.

  According to one characteristic, the end parts of the conductors, supported by the first part of the support resting on the integrated circuit, are

  respectively connected on pads of the integrated circuit.

  According to one characteristic, the first part of the support comprises at least one window, called connection window, arranged in a determined area of the first part of the support so as to be opposite the connection pads; the connection window being traversed by conductors maintained on either side of the connection window and respectively

  o connected to the connection pads through the connection window.

  According to one characteristic, the support and the windows for bending and

  connection are generally rectangular.

  Finally, the fourth object of the invention is an electronic assembly comprising

  at least one CSP box according to the invention.

  The method according to the invention makes it possible to carry out a connection of CSP boxes by a global and simultaneous bending of maintained conductors, and then to make an operation of global and simultaneous connection of

  conductors with the integrated circuit.

  In summary, the main advantages of the invention are therefore: - overall and simultaneous bending and wiring of the conductors; - holding of conductors during bending and wiring; - simpler production of conductors (no throttling and no widening), which implies cheaper connection supports and being able to connect integrated circuits with fine pitch (pitch between conductors less than 75 µm); and

  - no corrosion possible on the ends of the conductors after breakage.

  Other advantages and characteristics of the present invention will become apparent from

  reading the following description made with reference to the appended figures which

  represent, respectively: - Figure 1, a top view of a connection support according to the invention before bending; - Figure 2, a sectional view of the connection support according to the invention after bending; FIG. 3, a view schematically illustrating the connection method according to the invention; go - Figure 4, a perspective view of a CSP housing according to the invention equipped with a network of solder balls; - Figure 5, a schematic sectional view of the housing illustrated in Figure 4, along the cutting axis v-v; and - Figure 6, a partial perspective view of an electronic assembly

  i5 comprising at least one housing according to the invention.

  In these figures, the homologous elements are designated by the same

  reference and scales are not respected for the sake of clarity.

  FIG. 1 illustrates an example of a connection support 1 according to the invention in top view and before trimming. The support 1 supports a plurality of conductors 2i defining a network of conductors according to a topology

  determined on one face 3 of the support 1.

  The support 1 is for example a printed circuit board produced in

  polyimide or in another type of substrate, flexible or rigid.

  Two series of windows 4i and 5i are arranged in the support 1.

  First series of windows 4i are arranged in the support 1 to correspond to the bending spaces 6i of the conductors 2i. These windows 4i, hereinafter called bending windows, are arranged in the lateral end portions 7i of the support 1 which is of generally rectangular shape in the embodiment described. The conductors 2i, forming tracks, pass over the bending windows 4i to respectively form bridges 8i bearing on either side of the bending windows 4i. Second series of windows 5i, hereinafter called connection windows, are arranged in determined zones of the support 1 so as to be opposite the connection pads 9i of an integrated circuit 10, shown at

  o Figure 2, on which the support 1 must be deposited.

  The connection windows 5i extend between the lateral outer edges of the

  support 1 and the arching windows 4i.

  In the embodiment described, a single connection window 5i is

  fitted in each end part 7i of the support 1.

  In an alternative embodiment, as illustrated in FIG. 4, several connection windows are respectively arranged in the parts

ends 7i of support 1.

  As for the bending windows 4i, the conductors 2i respectively pass through the connection windows 5i, taking support on either side

connection windows 5i.

  In this embodiment, the bending and connection windows 4i and 5i are of generally rectangular shape and the conductors 2i are of constant width. Other forms of windows 4i and 5i and of conductors 2i can also be envisaged without departing from the scope of the present invention. Likewise, the conductors 2i can pass through the windows in different directions. The different shapes and dimensions of the conductors 2i and of the windows 4i and 5i depend on the topology of the network of conductors, itself a function of the topology of the integrated circuit 10 and of the interface with the exterior of the housing.

containing the integrated circuit 10.

  The arching windows 4i are retained from the rest of the support 1 by sections 11i of the support 1 of small width, which can be precut, and allowing after their rupture, for example by trimming using a determined tool not shown, detach the end parts 7i from the support

  1 comprising the connection windows 5i, of the rest of the support 1.

  The width 6i of the bending windows 4i is determined as a function of the angle of inclination of the conductors 2i, typically of the order of 10 relative to a vertical plane perpendicular to the plane 3 of the support 1, and of the thickness d a differential expansion absorber 12, electrically insulating, typically of the order of 200 μm, illustrated in FIG. 2, disposed between the integrated circuit 10 and the

support 1.

  In the embodiment described in FIG. 2, the bending of the conductors is determined so as to allow the absorber 12, for example an elastomeric mat, to be inserted between the integrated circuit 10 and the support 1 intended to receive and support a network. 13i solder balls, in a CSP type structure. The mattress provides reliability on the order of several

  hundreds of thermal cycles between -40 C and +125 C for example.

  1! We can easily understand the advantage of the structure according to the invention, because it makes it possible to maintain a constant pitch between the conductors 2i during the bending and connection operations of the conductors 2i on the pads

  connection 9i of the integrated circuit 10.

  FIG. 2 also schematically illustrates the method of linking the

  support 1 according to the invention with an integrated circuit 10.

  There is shown by a dashed line, the support 1 according to the invention io in its initial position, bearing on the mattress 12, itself bearing on the integrated circuit 10; the mattress 12 leaving the connection pads 9i of the

integrated circuit 10.

  The support 1 being supported on the mattress 12, a tool 14 adapted to the topology of the support 1 and the integrated circuit 10 ensures the overall bending of the conductors 2i in the zones 6i corresponding to the bending windows 4i and the positioning of the end portions 7i of support 1 on the ranges of

  connection 9i of the integrated circuit 10.

  This tool 14 comprises a first movable member or counterplate 15 which is intended to be applied in abutment on free areas 16i of the upper face

  3 of the support 1 before and during the bending operation.

  It comprises a second movable member 16 which, once the first member 15 bears on the upper face 3 of the support 1, progressively displaces the end parts 7i of the support 1 at the connection pads 9i of the

integrated circuit 1.

  The conductors 8i deprived of support inside the bending windows 4i behave like flexible ribbons and are deformed under the effect of the pressure exerted by the second movable member16 on the end parts 7i of the support 1. The deformation is uniform on all 8i conductors whose

  end parts 17i are held on the end parts 7i of the support 1.

  The bending is carried out on a first level A, at the copper / polyimide interface and on a second level B at the interface second bending member 16 / copper. The elasticity of the conductors 8i, typically made of copper alloy, allows the arching and the positioning of the end parts 7i of the support to be preserved.

  io 1 on the integrated circuit 10, after removal of the tool 14.

  In an alternative embodiment, the bending can be carried out beforehand,

  before positioning the support 1 on the integrated circuit 10.

  The end portions 17i of the conductors 8i passing through the connection windows 5i arranged opposite the connection pads 9i of the integrated circuit, are then punctually connected to the connection pads 9i by a spot weld, for example, or globally connected to the pads 9i by a tool, not shown, taking into account all of the conductors to be connected on the pads 9i, at their end portions 17i. The one-off or global connection operation can be carried out by an independent tool, not shown, or by the same tool 14 having produced the

overall arching.

  As illustrated in FIG. 3, the profile of the card resulting from the bending presents a card profile with two levels, a first level or higher level A, corresponding to the connection plane of the balls 13i on the face 3 of the support 1, and a second level or lower level B, corresponding to the plan

  connection pads 9i of the integrated circuit 1.

  FIG. 4 illustrates in a perspective view, a CSP box 18 according to the invention, comprising a support 1 according to the invention connected to the integrated circuit 10

  according to the method according to the invention.

  Figure 5 illustrates a sectional view of the housing 18 of Figure 4 along the axis

cutting v-v.

  The housing 18 includes an integrated circuit 10, an electrical insulating mattress 12, supported on the integrated circuit 10, a support 1 of electrical conductors 2i, o supported on the mattress 12 and on the integrated circuit 10, ensuring the electrical connection between a network of balls 13i welded onto the conductors 2i and the connection pads 9i of the integrated circuit 10 via the end portions 17i of

2i conductors.

  The support 1 is divided into three parts: first lateral parts 7i distributed on either side of a second part 7, or central part of the

support 1.

  In this embodiment, the first lateral parts 7i are distributed substantially symmetrically with respect to a median axis of the central part

  7 of the support 1, and corresponds substantially to the median axis of the housing 18.

  Finally, Figure 6 illustrates in a partial perspective view, an electronic assembly 19 materialized by a card 20 on a face 21 of which are mounted CSP 18i boxes according to the invention; connection of CSP boxes

  18i on the card 20 being produced by the balls 13i.

  The invention can be applied to the connection of any passive or active electronic function such as memory, processor, etc., compatible with

CSP architectures.

Claims (15)

  1. Method of electrical connection between pads (9i) of connection of an integrated circuit (10) and output terminals of a CSP box (18), of the type consisting in connecting the pads (9i) of connection of the circuit integrated (10) with a connection support (1) arranged opposite and at a different level from the connection pads (9i), by means of electrical conductors (2i) disposed on the connection support (1), characterized in what it consists of after having placed the support (1) facing the integrated circuit (10), to move at least one part (7i) of the support (1) to bring it in the vicinity of the pads (9i) for connecting the integrated circuit (10), and to connect the conductors (2i) supported by the part   (7i) of the support (1) on the pads (9i) of connection of the integrated circuit (10).   2. Method according to claim 1, characterized in that, the support (1) comprising at least a first part (7i) and a second part (7), separated by a space (6i) determined, and connected one to the other by the conductors (8i) crossing this space (6i), it consists in arching globally and simultaneously the conductors (8i) held on either side of the space (6i) and crossing this space (6i), to bring the first part (7i) of the support   (1) in the vicinity of the pads (9i) for connection of the integrated circuit (10).   3. Method according to claim 2, characterized in that the end parts (17i) of the conductors (8i), supported by the first part (7i) of the support (1), are connected globally and simultaneously on the pads (9i) of the circuit integrated (10).   4. Connection support (1) comprising a plurality of electrical conductors (2i) forming a network of conductors on at least one (3) of the faces of the support (1), and intended to provide the interface between pads (9i) for connecting an integrated circuit (10) arranged at a different level from the connection support (1), and output terminals of a box (18) enclosing the integrated circuit (10) in a CSP architecture, characterized in that that the support (1) comprises at least a first part (7i), supporting the conductors (8i) to be connected on the pads (9i) of connection of the integrated circuit (10), and capable of undergoing a drop, relative to a second part (7) of the support (1), to   position in the vicinity of the connection pads (9i) of the integrated circuit (10).   5. Support (1) connection according to claim 4, characterized in that it comprises at least one window (4i), called bending window, fitted o in the support (1) defining respectively on either side of the bending window (4i), a first part (7i) and a second part (7) of the support (1); the bending window (4i) being traversed on either side by conductors (8i) held on either side of the bending window (4i) and connecting the two parts (7 and 7i), and in this that the bending window (4i) defines, in itself, a determined zone corresponding to a space (6i) for bending the conductors (8i) passing through the bending window (4i); the conductors (8i) passing through the bending window (4i) being able to deform globally and simultaneously to allow, by a global and simultaneous bending, a difference in level between the first part (7i) and the second part (7) of the support (1 ) located respectively on either side of the window bending (4i).   6. Support (1) for connection according to claim 5, characterized in that the first part (7i) of the support (1), intended to be positioned in the vicinity of the pads (9i) for connection of the integrated circuit (10), comprises at least one window (5i), called connection window, arranged in a determined area to be opposite the connection pads (9i); the connection window (5i) being traversed by the end parts (17i) of the conductors (8i), held on either side of the connection window (5i) and capable of being simultaneously and globally connected to the pads (9i) connection to   through the connection window (5i).   7. Support (1) connection according to claim 6, characterized in that the support (1) and the bending and connection windows (4i and 5i) are of generally rectangular shape, and in that the bending window (4i ) occupies substantially all of the bending space (6i) inside the support (1); the lateral edges of the bending window (4i) being respectively parallel to the lateral edges of the support (1) and as close as possible to the lateral edges of the support (1).   8. CSP box (18), comprising an integrated circuit (10), an absorber (12) of differential expansion, electrical insulator, disposed on the integrated circuit (10), and a connection support (1) supporting a plurality of conductors (2i) defining a network of conductors on at least one (3) of its faces, arranged on the absorber (12) and ensuring the interface between the pads (9i) of connection of the integrated circuit (10) and the terminals outlet (18), characterized in that the support (1) comprises at least a first part (7i) resting on the pads (9i) for connection of the integrated circuit (10), and at least   a second part (7) resting on the absorber (12).   9. CSP housing (18) according to claim 8, characterized in that the first part (7i) and the second part (7) of the support (1) are separated by a   window, called bending window (4i), arranged in the support (1).   10. CSP box (18) according to claim 9, characterized in that the bending window (4i) is crossed by conductors (8i) held on either side of the bending window (4i) and connecting the first part (7i) and the   second part (7) of the support (1).   11. CSP housing (18) according to claim 10, characterized in that the conductors (8i) passing through the bending window (4i) are deformed by a global and simultaneous bending to form a difference in level between the first part   (7i) and the second part of the support (1).   12. CSP box (18) according to claim 11, characterized in that the end parts (17i) of the conductors (8i), supported by the first part (7i) of the support (1) resting on the integrated circuit (10), are respectively   connected on pads (9i) of the integrated circuit (10).   13. CSP box (18) according to claim 12, characterized in that the first part (7i) of the support (1) comprises at least one window (5i), called connection window, arranged in a determined area of the first part (7i) of the support (1) to be opposite the connection pads (9i); the connection window (5i) being traversed by conductors (8i) held on either side of the connection window (5i) and respectively connected   to the connection pads (9i) through the connection window (5i).   14. CSP box (18) according to claim 13, characterized in that the support (1) and the bending and connection windows (4i and 5i) are shaped general rectangular.   15. Electronic assembly (19), characterized in that it includes at least one   CSP housing (18) according to any one of claims 8 to 14.