WO2007076900A1

WO2007076900A1 - Interconnector and mezzanine circuit board assembly comprising such an interconnector

Info

Publication number: WO2007076900A1
Application number: PCT/EP2006/001686
Authority: WO
Inventors: Paul Johannes Marinus Potters
Original assignee: Fci
Priority date: 2006-01-06
Filing date: 2006-01-06
Publication date: 2007-07-12
Also published as: TW200735467A

Abstract

The invention relates to an interconnector (2) capable of interconnecting a first circuit board with a first connector and a second circuit board arranged parallel to said first circuit board and having a second connector, wherein said interconnector has a plurality of substantially parallel modules (7). Each module comprises a frame (10) holding an array of substantially parallel leads (S, G) separated by a dielectric medium and extending in a longitudinal direction (L) of said interconnector and constitutes contacts capable of mating with the first and second connector respectively on opposite sides of the longitudinally extending leads. The frame comprises edges (11, 12) extending in said longitudinal direction along the outer leads of said array. The interconnector further has a housing (8) for said modules and exposing said contacts on opposite sides of said leads and comprising an inner structure (19) capable of interacting with at least a portion of said longitudinal edges of said frame of at least one of said modules.

Description

Interconnector and mezzanine circuit board assembly comprising such an interconnector

FIELD OF THE 13SfVENTION

The invention relates to the field of electrical communication between circuit boards. More particularly, the invention relates to an interconnector capable of establishing high speed electrical communication between circuit boards, preferably in a mezzanine circuit board assembly.

BACKGROUND OF THE INVENTION

It is known to mount in a circuit board assembly a mezzanine card in a parallel fashion on a baseboard and to provide a signal interconnection between at least one electronic device on the baseboard and at least one electronic device on the mezzanine card.

There exists a need for increased flexibility in providing interconnection between a baseboard and one or more mezzanine cards. In particular, there exists a need for enabling operators to provide a larger distance between the base board and the mezzanine card (stack height) . This may be problematic as prior art board connectors typically only have a limited height, since beyond a certain limited length the signal and ground leads of these connectors would deflect or buckle on inserting these board connectors in corresponding circuit boards. In particular for board connectors with press-fit terminals, the insertion force for a board connector into the board may be significant . Board connectors of increased height therefore require dedicated tooling of the connectors to bridge a larger stack height, while being able to suppress buckling of the leads.

Furthermore, operators desire to have some flexibility in changing the stack height of the base board and the mezzanine card. In the prior art, an operator that desires to change the stack height is required to replace an entire circuit board or a board connector, which presents a significant amount of labor and costs . SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved mezzanine circuit board assembly.

In particular, it is an object of the invention to provide a mezzanine circuit board assembly that is able to have larger stack heights.

The invention provides an interconnector capable of interconnecting a first circuit board with a first connector and a second circuit board arranged substantially parallel to said first circuit board and having a second connector, wherein said interconnector has a plurality of substantially parallel modules. Each module comprises a frame holding an array of substantially parallel leads extending in a longitudinal direction of said interconnector and constituting contacts capable of mating with the first and second connector respectively on opposite sides of the longitudinally extending leads. The leads are separated by a dielectric medium. The frame comprises edges extending in said longitudinal direction along the outer leads of said array. The interconnector further has a housing for said modules and exposing said contacts on opposite sides of said leads and comprising an inner structure capable of interacting with at least a portion of said longitudinal edges of said frame of at least one of said modules.

The invention further provides a mezzanine circuit board assembly comprising a first circuit board with a first connector and a second circuit board arranged substantially parallel to said first circuit board and having a second connector, wherein said first connector and second connector are connected by an interconnector. The interconnector comprises a plurality of substantially parallel modules each comprising a frame holding an array of substantially parallel leads extending in a longitudinal direction of said interconnector and constituting contacts mating with the first and second connector respectively on opposite sides of the longitudinally extending leads. The leads may have a dielectric medium such as air in between. The frame comprises edges extending in said longitudinal direction along the outer leads of said array. The interconnec- tor further has a housing substantially surrounding said modules and exposing said contacts on opposite sides of said leads and comprising an inner structure capable of interacting with at least a portion of said longitudinal edges of said frame of at least one of said modules .

The invention allows for using board connectors of conventional height, i.e. headers and/or receptacles having a height of e.g. below 10 mm, on both circuit boards. Therefore, application of these board connectors on the circuit boards by a press-in force is likely to succeed without detrimental deflection or buckling of the leads. The separate interconnector may have a considerably larger height in the longitudinal direction to bridge the stack height, since the contacts of the leads of the modules accommodated within this interconnector are intended to connect to the board connectors instead of being inserted into holes of a circuit board. This operation requires a considerably reduced insertion force, which already reduces the chance of deflection or buckling of the leads. Furthermore, by providing the leads within a frame and by having these frames interact with an inner structure of the housing of the interconnector, chances of deflection or buckling of the leads are further reduced enabling a considerably large stack height between the first and second circuit boards . It should be appreciated that the housing may be any structure able to retain the modules. The housing may substantially surround or fully surround the modules as a conduit .

Furthermore, as the interconnector constitutes a separate component of the mezzanine circuit board assembly, stack height of the assembly is easily varied by connecting an interconnector to the standard first and second board connectors of the first and second circuit boards or by removing the original interconnector and connecting an interconnector of the desired height to the standard first and second board connectors.

The invention allows for stack heights between 20 and 80 mm, preferably 25-60 mm, more preferably 25-50 mm.

The embodiment of the invention as defined in claim 3 has the advantage that the modules can be introduced into the housing virtually requiring no force along the major part of the insertion depth in the housing until a final stage where fixation of the module within the housing occurs by the shape and/or position of the • inner structure and the fixation structure of the frame .

The embodiment of the invention as defined in claim 4 has the advantage of improving the rigidity of the interconnec- tor and to avoid warpage of the walls of the housing.

The embodiment of the invention as defined in claim 5 has the advantage that assembling of the interconnector is facilitated. In particular, the leads of adjacent modules are preferably staggered relative to each other by a row pitch or less or more than a row pitch for the signal leads and have an air gap as a dielectric medium in between. The assembling of such an arrangement, which has been found to reduce incidence of cross-talk as e.g. disclosed in US 6,652,318, is facilitated by the polarization structure and/or housing and/or frame as defined in claims 6 and 7. However, staggering of contacts in adjacent modules is not always necessary.

The embodiment of the invention as defined in claim 8 has the advantage that the modules are retained within the housing of the interconnector until they are deliberately removed.

The embodiments of the invention as defined in claims 9 and 10 have the advantage that the transverse bars may resist buckling of the leads. The risk of buckling of the leads exists especially in case of relatively long leads where the insertion force is transferred to the leads of the module near the contacts of the leads that are away from the contacts to be inserted into the first or second board connector on respectively the first or second circuit board. Advantageously, as defined in claim 11, the frame comprises two or more substantially equidistant transverse bars. The equidistant transverse bars in the longitudinal direction provide optimal buckling resistance along the leads .

The embodiments of the invention as defined in claims 12 and 13 have the advantage that when such modules are placed adjacently in an interconnector housing, the projections of ad- jacent modules may abut each other or leave only a small gap in between. Buckling of the leads may then be further minimized by interaction of the projections of adjacent modules or by interaction between the projection or projections of a module with a wall of the housing of the interconnector.

The embodiments of the invention as defined in claims 14-16 have the advantage that the interconnector can be easily inserted into the first connector of the first circuit board or the second connector of the second circuit board. The force application structure or bar provides a well-defined and easily accessible structure for a pressing tool, which structure is preferably provided near the contacts of the leads that are away from the contacts to be inserted in the first or second connector at that stage. Furthermore, by deliberately introducing a predefined force transfer structure on the leads, a reliable and predictable zone is obtained where the insertion force transfers from the force application structure to the leads. Consequently, deformation of the frame, typically manufactured of plastic, may be reduced or avoided, in particular when the force application structure directly interacts with the structure on the leads. As a result, higher interconnectors can be manufactured and applied on a circuit board connector allowing an increased distance between a base board and a mezzanine card in a mezzanine circuit board assembly.

The embodiment of the invention as defined in claim 17 has the advantage of ease of manufacturing as the leads are preferably manufactured by stamping sheet metal . It should be appreciated, however, that leads having a different cross- section, including circular, oval or square, are applicable as well .

The leads of the module are preferably separated by air as a dielectric medium. There exists a delicate balance between the amount of metal, air and plastic at each point of the module to match the appropriate impedance along the leads. Typically, the impedance of each of the leads is e.g. 100 Ohms for differential signaling and 50 Ohms for single ended applications. Impedance of the leads is determined by the geometry of the leads and plastic as well the dielectric medium. A high amount of plastic at a particular location, such as e.g. at the force application structure or the transverse bars discussed above in an embodiments comprising these, is therefore compensated by a reduced amount of metal for the leads as defined by the embodiment of claim 18.

The embodiment of the invention as defined in claim 19 has the advantage of reduced complexity with regard to the manu- facturability of the interconnector, particularly the contacts thereof .

The embodiment of the invention as defined in claim 20 has the advantage that identical first and second board connectors may respectively be employed for the first and second circuit board. The staggering from the longitudinal direction introduced in the leads compensates for the staggering between arrays of leads of adjacent modules for crosstalk reduction purposes in the housing of the interconnector.

The embodiment of the invention as defined in claim 21 has the advantage of allowing the outer lead or leads to be signal carrying leads in the absence of an associated ground lead or leads . The absence of such a ground lead or leads would introduce skew delay for these signal carrying leads . It has been found that an increased width for the penultimate signal lead or leads may reduce or eliminate the skew delay for the outer signal carrying lead pair or pairs. The same effect of reducing or eliminating skew delay effects is obtained by introducing an air gap between the outer signal lead and the plastic longitudinal edge of the frame as defined in claim 22.

Preferably, the housing of the interconnector is a one- piece housing of plastic as defined in claim 23, since such a housing has optimal shapability and can be manufactured relatively easily. Metal plating or metal may be used for the housing, e.g. for improving the electromagnetic shielding performance .

The embodiment of the invention as defined in claim 24 has the advantage of retaining the interconnector on the first or second board connector during mating, unmating and handling. The embodiment of the invention as defined in claim 25 has the advantage of a light-weight interconnector capable of accomplishing an adequate high speed e.g. 2 Gigabits/sec to 10 Gigabits/sec or more, performance. It should be appreciated, however, that the dielectric medium may also be another dielectric, including a plastic or composite.

The invention further provides an interconnector capable of interconnecting a first circuit board with a first connector and a second circuit board arranged substantially parallel to said first circuit board and having a second connector, wherein said interconnector has a plurality of substantially parallel, preferably air-separated modules, each comprising a frame holding an array of substantially parallel leads extending in a longitudinal direction of said interconnector and constituting contacts capable of mating with the first ^' and second connector respectively on opposite sides of the longitudinally extending leads. The frame comprises edges extending in said longitudinal direction along the outer leads of said array and one or more transverse bars extending between said longitudinal edges of said frame. The interconnector further has a housing for said modules and exposing said contacts on opposite sides of said leads and comprising an inner structure capable of interacting with at least a portion of said longitudinal edges of said frame of at least one of said modules .

The invention further provides an assembly comprising a first connector, a second connector and an interconnector as mentioned above.

The invention also provides an improved interconnector and mezzanine circuit board assembly a first circuit board with a first connector, a second circuit board arranged substantially parallel to said first circuit board and having a second connector, and an interconnector as mentioned above.

The embodiment of the invention as defined in claim 30 is advantageous in that standard board connectors can be used for both the first and second connector.

The embodiments of the invention as defined in claims 31-33 have the advantage that the leads in the interconnector may remain substantially parallel to the longitudinal direction along the entire leads between the contacts.

The embodiment of the invention as defined in claim 34 has the advantage of reduced complexity with regard to the manu- facturability of the interconnector.

The embodiment of the invention as defined in claim 35 has the advantage of retaining the interconnector on the first or second board connector during mating, unmating and handling.

The interconnector of the mezzanine circuit board assembly may have one or more features, or aspects thereof, as described above .

The invention will be further illustrated with reference to the attached drawings, which schematically show preferred embodiments according to the invention. It will be understood that the invention is not in any way restricted to these specific and preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings :

FIGS. IA and IB show a schematic illustration of a mezzanine circuit board assembly and an interconnector according to an embodiment of the invention;

FIG. 2 shows a schematic illustration of cross-section along II-II of the interconnector of the mezzanine circuit board assembly of FIG. IA;

FIGS. 3A-3E show modules and details of portions of these modules of an interconnector according to embodiments of the invention;

FIGS. 4A and 4B respectively show a housing of an interconnector without and with a plurality of modules as illustrated in FIG. 3 according to an embodiment of the invention;

FIG. 5 shows a mezzanine circuit board assembly according to an embodiment of the invention comprising the interconnector of FIG. 4B; FIG. 6 shows a mezzanine circuit board assembly with an interconnector comprising latching means according to an embodiment of the invention;

FIG. 7 shows a schematic cross-section of a regular first board connector and an inverted second board connector for a mezzanine circuit board assembly according to an embodiment of the invention;

FIGS. 8A and 8B show schematic illustrations of mezzanine circuit board assemblies according to further embodiments of the invention, and

FIG. 9 shows a schematic illustration of an alternative embodiment of an interconnector along II-II in FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. IA and IB show a schematic illustration of a mezzanine circuit board assembly 1 and an interconnector 2 of such an assembly 1 according to an embodiment of the invention. The mezzanine circuit board assembly 1 comprises a first circuit board 3 with a first board connector 4 and a second circuit board 5 arranged parallel to the first circuit board 3 having a second board connector 6. The first board connector 4 and second board connector 5 are connected by the interconnector 2. Consequently, signal transfer may occur between components (not shown) on the first circuit board 3 and second circuit board 5. The interconnector 2 comprises a plurality of substantially parallel modules 7. Preferably, the interconnector 2 is a shieldless interconnector, i.e. no metallic shield or shields are provided between the modules 7. The interconnector extends in a longitudinal direction L between the circuit boards 3,5.

The invention allows for using board connectors 4,6 of conventional height, i.e. headers or receptacles having a height of e.g. below 10 mm, on both circuit boards 3,5. Therefore, application of these board connectors 4,6 on the circuit boards 3,5 by a press-in force is likely to succeed without detrimental deflection or buckling of the leads of these connectors 4,6. By introducing the interconnector 2, the stack height SH between the circuit boards 3,5 can be varied. Preferably, the stack height SH is in the range of 20-80 mm, preferably 30-80 mm, such as 50 mm.

The receptacles 4,6 may have a standard signal/ground order and pattern. Alternatively, as will be discussed with reference to FIG. 7, the signal/ground order and pattern of a receptacle may be modified.

The interconnector 2 has a housing 8 substantially surrounding the modules 7 forming a conduit with open ends 9 on both sides, as will be further described with reference to PIGS. 4A and 433. In practice the edges of the housing defining the open ends 9 do not necessarily contact the circuit boards 3,5. It should be appreciated that the walls of the housing 8 are not necessarily completely closed, but may comprise one or more openings or even (partially) contain a fretwork type of wall. Further, the housing 8 may comprise several parts, such as two separate substantially planar parts with an inner structure capable of retaining the modules 7 on opposite sides without interacting directly with each other, i.e. a sandwich configuration.

The interconnector 2 preferably allows high speed, i.e. in excess of 1 Gbit/s, preferably 2 Gbit/s, such as 10 Gbit/s, differential signal transmission between the circuit boards 3,5.

FIG. 2 shows a schematic illustration of a cross- section along II-II of the interconnector 2 of the mezzanine circuit board assembly 1 of FIG. IA. Each one of the modules 7 comprises a frame 10 (see FIG. 3) holding an array of substantially parallel signal leads S and ground leads G extending in the longitudinal direction L of the interconnector 2 and constituting contacts capable of mating with the first board connector 4 and second board connector 6 respectively on opposite sides of the longitudinally extending leads S, G. The signal leads S are indicated by the white rectangular header contacts, whereas the ground leads G are indicated by the black rectangular header contacts. Although in the presented embodiment the leads have one outer signal lead and one outer ground lead, it is noted that alternative configurations may be applied, including ground leads G for both outer leads of each module 7. As illustrated in FIG. 2, the housing 8 and modules 7 are structured such that adjacent modules 7 are rotated 180 degrees with respect to each other. Furthermore, the housing 8 and modules 7 are structured such that corresponding leads S, G of adjacent modules 7 have an staggering O in order to minimize crosstalk between the signal carrying leads S. Similarly, a first set of differential signal pairs Sl, S2 in one module is offset with respect to a corresponding first set of differential signal pairs Sl, S2 in an adjacent module by a row pitch, less than a row pitch, or more than a row pitch.

In the embodiment of FIG. 2, each module 7 has one side in the array of leads S, G that is not bounded by a ground lead G. This may result in skew delay for the signals leads Sl, S2 that do not have an associated ground lead G. To compensate, the penultimate leads S2 have an increased width W2 with regard to the widths W of the other signal and ground leads S, G. The width W of the leads S, G may be e.g. 1.05 mm, whereas the width W2 of the leads S2 is e.g. 1.15 mm. The pitch of the leads S, G within a module is constant and measures e.g. 1.4 mm. The staggering O may be e.g. 0.1 mm. The leads S, G within the module 7 are preferably separated by air as. a dielectric medium. However, any dielectric medium, including plastic, may be used between the leads and/or between the modules 7.

The maximum stack height SH of the interconnector 2 may be dependent on e.g. the number of signal and ground leads S, G of each module 7 and the number of modules 7 in the housing 8. In general , the stack height SH of the interconnector 2 may be higher for a wider interconnector 2.

FIGS . 3A and 3B show modules 7 for an interconnector 2 according to embodiments of the invention. These modules 7 may also be referred to as insert molded lead frame assemblies (IMLA' s) .

The module 7 has a frame 10 comprising edges 11,12 extending in the longitudinal direction L of the interconnector 2 along the outer leads Sl, G. The frame 10 holds an array of substantially parallel leads S, G terminating respectively in contacts. These contacts are capable of mating with the first board connector 4 and the second board connector 6 on opposite sides of the leads S, G as illustrated in FIGS. 5 and 6. For skew compensation purposes, the lead Sl not having an associated ground lead G, is separated from the longitudinally extending edge 11 of the frame 10 by an air gap AG along the entire edge 11. Further, the opposite outer ground lead G abuts the longitudinally extending edge 12 along its entire length. It should be appreciated that the contacts of the leads S, G may be of different length as illustrated in FIGS. 3A and 3B₇ but may alternatively be all of (substantially) equal length in the longitudinal direction L.

The module 7 of FIG. 3A comprises leads S,G extending substantially in the longitudinal direction L. However, in case identical first and second board connectors 4,6 are used while maintaining the staggering O between leads of adjacent modules 7 shown in FIG. 2, a compensation for this staggering may be provided within the leads S, G. As an example, staggering compensation can be accomplished by having a, preferably short, section SIc at an angle from the longitudinal direction L, between a first lead section SIa and a second lead section SIb that extend in the longitudinal direction L.

In contrast, the module 7 shown in FIG. 3B does not include means for staggering compensation. In that case, compensation may e.g. be found in modification of a board connector 4,6 at the first circuit board 3 or second circuit board 5 respectively.

The frame 10 may have a force application structure 13 in the form of a force application bar having a T-shaped cross- section extending between the edges 11, 12 of the frame 10. As indicated in the detailed image of FIG. 3C, the force application bar 13 tightly fits with a predefined force transfer structure 14 in the leads S, G facilitating the transfer of an insertion force F from the force application bar 13 to the leads S₁G at the transfer structure 14. The force application bar 13 has a T-shape arranged such that the horizontal part is available for application of the force F, whereas the vertical leg is molded over the force transfer structure 14 to establish a tight shape fit .

The force transfer structures 14 of the leads S, G may- have an undulating structure or cobra-shaped structure as illustrated in detail in FIG. 3C. The force transfer structures 14 have a reduced width as compared to the width W of the leads S, G. Further, the force transfer structures 14 are shaped such that the air gap between transfer structures 14 of adjacent leads S, G in the module 7 has a substantially uniform width.

Furthermore, the frame 10 has transverse bars 15 extending between the edges 11 and 12. Since the insertion force F is transferred to the leads S, G already at the force transfer structures 14, i.e. near the contacts of the leads S, G, that are away from the contacts to be inserted into the board connector 4 or 6, these transverse bars 15 act as a barrier against buckling of the leads S, G. The transverse bar 15 shown in FIG. 3C is shown transparently to illustrate that the leads S, G are undercut, i.e. have a reduced width, at the location of these bars 15 to compensate for the presence of the plastic of the bars 15 in view of the impedance matching considerations. The transverse bars 15 are located at the edges 11, 12 in the longitudinal direction L such that the substantially open frame space between the longitudinally extending edges 11, 12 is divided in substantially equal portions. It is noted that the amount of transverse bars depends e.g. on the height of the module 7. A module of 20 mm may e.g. have two transverse bars 15, whereas a module of 50 mm may e.g. have six transverse bars 15.

It should further be appreciated that other anti- deflection structures 15 to prevent buckling of the leads S, G have been envisaged, such as bars that cross the frame space in a diagonal fashion.

As illustrated in FIGS. 3A and 3B the transverse bars 15 have projections 16 extending in a direction substantially perpendicularly to the plane of the leads S, G. FIGS. 3D and 3E illustrate detailed cross-sections of portions of a single module 7 and a plurality of modules 7. The projections 16 ^' of the transverse bars 15 of adjacent modules 7 may abut, as shown in FIG. 3E. The projections 16 of the outer modules 7 may similarly abut to the inner surface of the wall of housing 8 (not shown) . If a lead S, G of a module 7 deflects sideways, which is perpendicularly to the plane of leads S, G of a module 7, on application of a force, e.g. the insertion force F, the abutting projections 16 of adjacent modules 7 resist the deflection of the leads.

It should be appreciated that the module 7 does not necessarily contain transverse bars 15 and/or projections 16. It should further be noted that modules 7 with and without projections 16 may be alternately inserted in the housing 8 of the interconnector 2, wherein the projection 16 of a first module 7 abuts with the transverse bar of an adjacent second module 7. Further, it should be appreciated that the projections 16 not necessarily abut but may leave a small gap of e.g. smaller than 0.1 mm in between. Moreover, the modules 7 may be interconnected, e.g. by dove-tail joints or similar connecting means disposed on the transverse bars 16 or the other bars 11, 12, 13 of the frame 10.

The longitudinal edges '11, 12 of the frame 10 comprise fixation structures 17A, 17B and a guiding rail for insertion of the modules 7 in the internally structured housing 8, shown in more detail in FIG. 4A. Structures 17A, 17B are of different shape in order to provide for polarization in cooperation with structures in the housing 8. In the present embodiments of FIGS. 3A and 3B, the dimension of structure 17A in the direction of the projections 16, i.e. parallel to the vector defining the plane of the leads S, G, is larger than for structure 17B to guarantee correct insertion of the modules 7 in the housing 8 of the interconnector 2. In FIGS. 3A and 3B, this dimension of structure 17A exceeds the corresponding dimension of the edge 11, whereas for structure 17B this dimension is smaller than the corresponding dimension of the edge 12 as illustrated in FIG 3D.

In particular, the polarization structures of the frame 10 and the housing 8 are such that a first module 7 and a second adjacent module 7 are positioned in the housing rotated over 180 degrees with respect to each other around an axis parallel to the longitudinal direction L, as illustrated in FIG. 2.

Furthermore, the frame 10 comprises a retention structure 18 adapted to interact with a corresponding retention structure in the housing 8 (see FIG. 3B) .

FIGS. 4A and 4B respectively show the housing 8 of an interconnector 2 without and with a plurality of modules as illustrated in FIG. 3A according to an embodiment of the invention. The housing 8 is a one-piece housing with open ends 9 configured as a conduit exposing the contacts of the leads S, G of the modules 7. Preferably, the housing 8 is made of plastic, as this facilitates manufacturing of the internal structure 19 of the housing. As an example, the housing 8 is made of liquid crystal polymers (LCPs) and shaped and structured by molding. Alternatively, the plastic housing may be metal plated or completely of metallic material in situations of increased sensitivity to electromagnetic interference.

The internal structure 19 comprises a series of slots and stops that are structured^ to cooperate with the complementary structured longitudinally extending edges 11,12 of the frames 10. In particular, the slots of the internal structure 19 may have a dovetail shape in order to fixate the frames 10 and to prevent warpage of the walls of the housing 8. The slots are structured and/or positioned .such that the fixation structures 17A, 17B and the inner structure interact substantially only in a final position of the module 7 within the housing 8 for fixation of the module 7, as illustrated in FIG. 4B. The retention structures 18 of the frames 10 may lock the modules 7 within the housing 8. The modules 7 are^{" ''}preferably inserted in the direction of the arrow A in FIG. 4A^;;.^V

It is noted that any! type of cooperating structures of the modules 7 and IHe^Λ housing 8 or portions of the housing 8 may be applied to accomplish the retaining effect of the housing 8. As an example, the modules 7 may have barbs, including metallic barbs, interacting with the housing 8 of the interconnector 2 for retaining the modules 7. It should be appreciated that, while basically in PIGS. 4A and 4B only two walls comprise internal structures 19, one or more further walls of the housing 8 may comprise internal structures 19 as well, as shown by structure 19A. Such a structure may be advantageously structured to cooperate with the modules 7 as well to maintain the shape of the interconnector housing 8. As the molding of the housing may result in curvature of the walls of the housing by crimp effects, such an additional structure 19A may be particularly advantageous for molded housings.

FIGS. 5 and 6 respectively show mezzanine circuit board assemblies 1 comprising an interconnector 2 without and with a latch 20 on the housing 8. The modules 7 are provided and retained within the housing 8 as described with reference to FIGS. 3 and 4.

The separate interconnector 2 may have a considerably larger height in the longitudinal direction than the board connectors 4,6 to bridge the stack height SH, since the contacts of the leads S,G of the modules 7 accommodated within this interconnector 2 are intended to connect to the board connectors 4 , 6 instead of being inserted into holes of a circuit board 3,5. This operation requires a considerably reduced insertion force F, which already reduces the chance of deflection or buckling of the leads S, G. It has been found that the insertion force for the leads S, G of the interconnector 2 in the board connector 4,6 is below 5%, preferably below 1%, of the force required to insert press-fit terminals of the board connectors 4,6 into the circuit board 3,5. Furthermore, by providing the leads S, G within the frame 10 and by having these frames interacting with an inner structure 19 of the housing 8 of the interconnector 2, chances of deflection or buckling of the leads S, G are further reduced enabling a considerable stack height SH between the first and second circuit boards 3,5.

In FIG. 6, the housing 8 of the interconnector 2 has a latch 20 capable of locking onto a corresponding structure 21 of the first board connector 4. The latch 20 retains the interconnector 2 on the receptacle 4 during unmating and handling of the second board connector 6. Furthermore, the latch 20 may be used for visual polarization of the interconnector 2 within the mezzanine circuit board assembly 1.

For reasons of manufacturability of the interconnector 2, the board connectors 4,6 preferably are receptacles, whereas the leads S, G in the interconnector 2 terminate as header contacts. However, a receptacle interconnector 2 can also be used with blade-type connectors 4.

FIGS. 7 and 8A, 8B show alternative embodiments according to the invention, wherein an offset section SIc in the leads may be omitted as a result of measures taken at the end of the board connectors 4,6.

FIG. 7 shows a schematic cross-section of a regular first board connector 4 and an inverted second board connector 6 for a mezzanine circuit board assembly 1. White rectangles indicate signal leads/contacts S and black rectangles indicate ground leads/contacts G of the first and second board connector 4,6. In particular, the first board connector 4 and second board connector 6 are mirror images of each other. Consequently, when the board connectors 4,6 are positioned face-to-face on the respective circuit boards 3,5 the leads S, G of the interconnector 2 do not need an intermediate section SIc to compensate for the staggering 0 between leads of adjacent modules as illustrated in FIG. 2.

FIGS. 8A and 8B show schematic alternative solutions, wherein contacts X of the first and second board connectors 4,6 remain unused. This may e.g. be accomplished by displacing the board connectors 4,6 relative to each other on the circuit boards 3,5 as shown in FIG. 8A or by using a smaller board connector 4 as shown in FIG. 8B .

Finally, FIG. 9 shows a cross-section of an interconnector 2 with a plurality of modules 7 deviating from the modules shown in FIG. 2. A ground lead G is omitted, at least at the contacts of the module 7, in comparison to the embodiment of FIG. 2 and consequently, both outer pairs of leads Sl, S2 do not have an associated ground lead G. Therefore, the widths W2 of both penultimate signal leads S2 are increased with respect to the widths of the other leads. Further, in the absence of the ground lead G, the housing 8 may be of metallized plastic or metal to reduce electromagnetic interference effects.

The interconnector 2 of FIG. 9 is capable of mating with standard vertical receptacles 4,6 leaving one outer receptacle contact unused. The interconnector 2 may be completely symmetrical with respect to the plane dividing the interconnector in two halves with a normal in the longitudinal direction L and does neither require modification of the first and second board connector 4,6 from their standard layout nor an intermediate section SIc for the leads S, G within the module 7.

Claims

1. An interconnector (2) capable of interconnecting a first circuit board (3) with a first connector (4) and a second

^■ circuit board (5) arranged substantially parallel to said first circuit board and having a second connector (6) , wherein said interconnector has a plurality of substantially parallel modules (7) each comprising a frame (10) holding an array of substantially parallel leads (S, G) separated by a dielectric medium a.nd extending in a longitudinal direction (L) of said interconnector and constituting contacts capable of mating with the first and second connector respectively on opposite sides of the longitudinally extending leads, said frame comprising edges (11,12) extending in said longitudinal direction along the outer leads of said array, and a housing (8) for said modules and exposing said contacts on opposite sides of said leads and comprising an inner structure (19) capable of interacting with at least a portion of said longitudinal edges of said frame of at least one of said modules.

2. The interconnector (2) according to claim 1, wherein said housing (8) has a longitudinal dimension in said longitudinal direction (L) of 20-80 mm, preferably 25-60 mm, more preferably 25-50 mm.

3. The interconnector (2) according to claim 1 or 2, wherein said longitudinal edges (11,12) of said frame (10) comprise fixation structures (17A, 17B) complementary to said inner structure (19) of said housing (8) shaped and/or positioned with respect to each other such that said fixation structure and said inner structure interact substantially only in a final position of said module (7) within said housing for fixation of said module .

4. The interconnector (2) according to claim 3, wherein said inner structure (19) of said housing has slots of an at least partially dovetail shape.

5. The interconnector (2) according to one or more of the preceding claims, wherein said longitudinal edges (11,12) of said frame (10) further comprise polarization structures (17A,17B) corresponding to complementary housing polarization structures (19) .

6. The interconnector (2) according to claim 5, wherein said polarization structures (17A,17B) are such that a first module (7) and a second adjacent module (7) are positioned in said housing (8) rotated over 180 degrees with respect to each other around an axis parallel to said longitudinal direction (L) .

7. The interconnector (2) according to one or more of the preceding claims, wherein at least one of said housing (8) and said frame (10) are structured to establish a staggering (O) between leads (S, G) of arrays of adjacent modules (7) in said housing in a direction perpendicular to said longitudinal direction (L) within the plane of said leads.

8. The interconnector (2) according to one or more of the preceding claims, wherein said frame (10) comprises a retention structure (18) adapted to interact with a retention structure in said housing.

9. The interconnector (2) according to one or more of the preceding claims, wherein said frame (10) comprises one or more transverse bars (15) extending between said longitudinal edges (11,12) substantially in the plane of said leads (S, G).

10. The interconnector (2) according to claim 9, wherein said transverse bars (15) extend substantially perpendicularly to said longitudinal direction (L) .

11. The interconnector (2) according to claim 9 or 10, wherein said frame (10) comprises two or more transverse bars

(15) fixated at said longitudinal edges (11,12) at substantially equidistant locations in said longitudinal direction (L) .

12. The interconnector (2) according to one or more of the claims 9-11, wherein said transverse bars (15) comprise projections (16) extending in a direction substantially perpendicular to said plane of said leads (S, G) .

13. The interconnector (2) according to claim 12, wherein said projections (16) extend in a direction substantially perpendicular to said plane of said leads such that projections of transverse bars (15) of a frame (10) of an adja- cent module (7) abut with said projections or define a gap with said projections less than 0.1 mm, preferably less than 0.05 mm.

14. The interconnector (2) according to one or more of the preceding claims, wherein said frame (10) comprises a force application structure (13) for inserting said module into said first or second circuit board (3,-5).

15. The interconnector (2) according to claim 14, wherein one or more of said leads (S, G) comprises a predefined force transfer zone (14) structured to transfer a force (F) applied on said force application structure (13) to said leads.

16. The interconnector (2) according to claim 14 or 15, wherein said force application structure (13) comprises a force application bar, said bar extending substantially transverse to said longitudinal direction (L) substantially parallel to the plane of said leads and being located at a height in said longitudinal direction substantially at said predefined force transfer zone (14) .

17. The interconnector (2) according to one or more of the preceding claims, wherein said leads (S, G) are blade-shaped having a width dimension (W) and a thickness dimension in a direction perpendicular to said longitudinal direction (L) and to each other and wherein said width dimension (W) is wider than said thickness dimension.

18. The interconnector (2) according to claim 17, wherein said width dimension (W) of said leads is reduced at locations where said frame crosses said leads.

19. The interconnector (2) according to one or more of the preceding claims, wherein said contacts of said leads (S, G) are header contacts.

20. The interconnector (2) according to one or more of the preceding claims, wherein each of said leads (S₁G) comprises a first lead section (SIa) and a second lead section (SIb) extending substantially in said longitudinal direction (L) and wherein said first lead section and second lead section are connected by a lead section (SIc) at an angle from said longitudinal direction.

21. The interconnector (2) according to one or more of the preceding claims, wherein at least one of the leads (S2) adjacent to said outer leads (Sl) in said frame (10) is wider than the other leads (Sl, S, G) in said frame.

22. The interconnector (2) according to one or more of the preceding claims, wherein a longitudinally extending air gap (AG) is present between one of said outer leads (Sl) and a longitudinal edge (11;11,12) of said frame (10).

23. The interconnector (2) according to one or more of the preceding claims, wherein said housing (8) is a one-piece housing, preferably of plastic, metal-plated plastic or metal.

24. The interconnector (2) according to one or more of the preceding claims, wherein said housing (8) comprises at least one latch (20) capable of attaching said interconnector to said first connector (4) on said first circuit board (3) or said second connector (6) on said second circuit board (5) .

25. The interconnector (2) according to one or more of the preceding claims, wherein said dielectric medium is air.

26. An interconnector (2) capable of interconnecting a first circuit board (3) with a first connector (4) and a second circuit board (5) arranged substantially parallel to said first circuit board and having a second connector (6) , wherein said interconnector has a plurality of substantially parallel modules (7) each comprising a frame (10) holding an array of substantially parallel leads (S,G) extending in a longitudinal direction (L) of said interconnector and constituting contacts capable of mating with the first and second connector respectively on opposite sides of the longitudinally extending leads, said frame comprising edges (11,12) extending in said longitudinal direction along the outer leads of said array and one or more transverse bars (15) extending between said longitudinal edges of said frame, and a housing (8) for said modules and exposing said contacts on opposite sides of said leads and comprising an inner structure (19) capable of interacting with at least a portion of said longitudinal edges of said frame of at least one of said modules .

27. An interconnector (2) according to claim 26, wherein said transverse bars comprise projections (16) extending in a direction substantially perpendicularly to said plane of said leads such that projections of transverse bars of a frame of an adjacent module (7) abut with said projections or define a gap with said projections less than 0.1 mm, preferably less than 0.05 mm.

28. An assembly of a first board connector (4), a second board connector (6) and an interconnector (2) according to one or more of the preceding claims .

29. A mezzanine circuit board assembly (1) comprising a first circuit board (3) with a first connector (4) and a second circuit board (5) arranged substantially parallel to said first circuit board and having a second connector (6) , wherein said first connector and second connector are connected by an inter- connector (2) according to one or more of the claims 1-27.

30. The mezzanine circuit board assembly (1) according to claim 29, wherein said first connector (4) and second connector (6) are identical board connectors.

31. The mezzanine circuit board assembly (1) according to claim 29, wherein said first connector (4) and said second connector (6) are mirror images of each other.

32. The mezzanine circuit board assembly (1) according to claim 29, wherein said contacts of said leads (S, G) of said interconnector leave one or more arrays of contacts of at least one of said first connector (4) and second connector (6) unconnected.

33. The mezzanine circuit board assembly (1) according to claims 29, wherein said leads (S, G) comprise signal leads and ground leads, said outer leads (Sl) functioning as signal leads.

34. The mezzanine circuit board assembly (1) according to one or more of the claims 29-33, wherein said first connector (4) and second connector (6) are board connector receptacles receiving header-type contacts of said interconnector (2) .

35. The mezzanine circuit board assembly (1) according to one or more of the claims 29-34, wherein said housing (8) of said interconnector (2) comprises at least one latch (20) and said first connector or second connector comprises a structure (21) capable of locking with said latch.