Connectors of this type are known in various em- bodiments. In view of component cost and utilization of cabinet space in combination with a growing requirement for a high-density, high-speed connector, there is a growing need to miniaturize the connector. A constraint in miniatur- izing a connector is the requirement for improved signal in- tegrity in combination with increased signal clock speed.

US-A-4 734 060 discloses a connector and method of the above-mentioned type, wherein the contact elements are par- tially accommodated in cavities of the housing aligned with the grooves and partially in the grooves, wherein the reten- tion of the contact elements occurs in the passages, where the contact elements are fully surrounded by plastic mate- rial. The mounting of the contact elements requires an axial insertion of the contact elements, wherein a significant ax- ial length of the contact element has to pass through the cavity. Further, for flexibility purposes the contact ele- ments in both the male and female connectors have a longitu- dinal tapering in cross-section with a thickened contacting dome at their free end. This shape of the contact elements entails drawbacks in terms of manufacturing and results moreover in internal stress. During the mating cycle suffi- cient space must be available within the connectors for the contact elements to deflect along a distance corresponding

to twice the dimension of the thickened part. The design of this connector imposes limitations regarding miniaturizing and manufacturing the connector.

The invention aims to provide an improved connector and improved method of manufacturing the same.

To this end the connector of the invention is char- acterized in that the housing comprises at least two inter- connected housing parts having an elongated mainly rectangu- lar flat shape, each housing part having a series of open grooves in one of the main surfaces, said grooves extending transverse to the longitudinal direction of the housing part along-the full transverse dimension of the main surface, wherein the contact elements are made as single beam contact elements, each contact element having a contacting portion received with play in the groove and a mounting portion fixed in the groove.

In this manner a new connector design is obtained in which the single beam contact elements are partly extend- ing in air and even at the mounting section are only partly enclosed by insulating material. The use of single beam con- tact elements provides the possibility to reduce the pitch between successive rows of contacts and moreover reduces the effective radiating contact surface, thereby minimizing in- teraction between contacts. The use of single beam flat con- tact elements results in advantages in the production of the contact elements. The contact dimple on the spring sections in the female connector ensures a good connection between corresponding contact elements of mated male and female con- nectors.

Moreover, the use of housing parts with a grooved main surface results in a simplified manufacturing of the connector. Therefore, the invention also provides an im- proved method for manufacturing the connector, wherein a housing part is provided, said housing part having an elon- gated mainly rectangular flat shape and a series of open grooves in one of the main surfaces, said grooves extending transverse to the longitudinal direction of the housing part

along the full transverse dimension of the main surface, wherein the contact elements are made as single beam con- tacts and are inserted into said grooves in a direction per- pendicular to the main surface of the housing part. In this manner manufacturing requires insertion along a very short distance only, wherein mutual contact between the housing and plated areas of the contact elements is fully avoided.

Preferably, a plurality of interconnected contact elements is provided, wherein the interconnected contact elements are inserted into the grooves of a housing part in one step.

In this manner a connector is obtained wherein the number of contact elements in column direction can be easily adapted by adding further modules to the connector. Thereby, the connector design of the invention allows to provide any number of rows without tooling-up a new housing mould, re- sulting in a flexible and low cost manufacturing.

In order to stack two or more connectors in row di- rection to increase the number of contact elements in row direction, it is preferred that in row direction each module is provided with flat end surfaces, wherein the distance be- tween the first and last contact elements of a row of con- tact elements and the end surfaces is such that with two modules stacked in row direction the pitch of adjacent con- tact elements of stacked modules equals an integer times the pitch between successive contact elements in row direction.

In this manner any size of connector length can be used, wherein a constant pitch between all contact elements is maintained.

Preferably, the transverse dimension of one module equals twice the pitch between successive contact elements in row direction. Thereby, the number of contact elements per unit of length is the same in row and column direction.

The connector comprises a number of assembled com- ponents, wherein the mounting frame provides a mutual posi- tioning and interconnection of the components. Right-angled and straight embodiments can be manufactured using the same

front housing sections and mounting frame.

It is advantageous if the metal mounting frame is provided with location projections for mounting the connec- tor on a printed circuit board. Thereby the metal mounting frame is adapted to provide at least a strong mechanical connection to the printed circuit board so that the contact elements can be provided with terminals optimized for a sur- face mount connection.

According to the invention it is advantageous if the location projections of the mounting frame are made as contact sections for connecting the mounting frame to a ground of a printed circuit board. The mounting frame pro- vides for a connection of the ground of the connector to the ground of the printed circuit board.

In the connector design of the invention, the hous- ing is an assembly modules with two identical joined housing parts, so that any waviness or curvature of the housing parts will be mutually compensated resulting in a flat mod- ule with accurate shape and dimensions.

In the connectors of the male and female type, the spring portions of the female contact elements are accu- rately centred on the true position of the male contact ele- ments, so that a correct connection between the male and fe- male contact elements is guaranteed.

The invention will be further explained by refer- ence to the drawings in which some embodiments of the con- nector of the invention are shown.

Fig. 1 shows a male and a female embodiment of the connector of the invention, the male and female connectors providing a backpanel connector assembly.

Fig. 2 shows some female contact elements used in the female connector of fig. 1; fig. 2A showing a top view of a plurality of interconnected contact elements and fig.

2B showing a side view of one contact element.

Fig. 3 shows some male contact elements of the male connector of fig. 1; fig. 3A showing a top view of a plural- ity of interconnected contact elements and fig. 3B showing a

side view of one contact element.

Fig. 4 shows an exploded view of one housing part of the female connector of fig. 1 and a plurality of inter- connected female contact elements to be inserted into the housing part.

Fig. 5 shows an exploded view of two housing parts of fig. 4 with the contact elements inserted.

Fig. 6 shows the two housing parts of fig. 5 as as- sembled.

Figs. 7-9 show an alternative embodiment of a part of a female connector in a manner corresponding to figs. 4- 6.

Fig. 10 shows two female contact elements used in the female connector of figs. 7-9.

Fig. 11 is a perspective view of a part of an em- bodiment of a female connector of the invention.

Fig. 12 is a schematically shown cross section of the female connector of fig. 11.

Fig. 13 is an exploded view of the female connector of fig. 1.

Fig. 14 is a perspective view of the female connec- tor of fig. 13 as assembled.

Fig. 15 is a front view of the female connector of fig. 14.

Fig. 16 is a rear view of the female connector of fig. 14 without tail unit and with straight female contact elements.

Fig. 17 schematically shows a cross section of the female connector of fig. 14.

Fig. 18 shows an exploded view of one housing part of the male connector of fig. 1 with a plurality of inter- connected male contact elements to be inserted into the housing part.

Fig. 19 shows an exploded view of two of the hous- ing parts of fig. 18 with the contact elements inserted.

Fig. 20 shows the two housing parts of fig. 19 as assembled.

Fig. 21 is a schematical cross section of the two assembled housing parts of fig. 20.

Fig. 22 is an exploded view of the male connector of fig. 1 including four housing parts of fig. 18.

Fig. 23 is a perspective view of the male connector of fig. 22.

Fig. 24 is a lateral cross section of the male con- nector of fig. 23.

Fig. 25 is a cross section view of the male connec- tor of fig. 23.

Fig. 26 schematically shows a front view of two male housing parts before assembly with separately shown male contact elements.

Fig. 27 shows a detail of the two housing parts of fig. 26.

Fig. 28 shows a perspective view of a further em- bodiment of the male connector of the invention.

Fig. 29 shows a further embodiment of the female connector of the invention made as a cable connector.

Fig. 30A-30C show front views of three different sizes of male connectors of the invention.

Fig. 31 shows a perspective view of three male con- nectors of the invention stacked end-to-end.

Fig. 32A-32D schematically show the guiding and centring of the female contacts during mating of the male and female connectors of the invention.

Fig. 33 shows in a larger scale a cross section of the mated male and female connectors of fig. 1 to illustrate the centring of the female contact elements on the male con- tact elements.

Fig. 34A and 34B schematically show the male and female modules of a connector of the invention unmated and mated, respectively.

Fig. 35A and 35B schematically show the male and female connectors of fig. 1 unmated and mated, respectively.

Fig. 36A and 36B show a further embodiment of male and female connectors of the invention in the same manner as

fig. 35A and B.

Fig. 37 shows by way of illustration a backpanel with two daughter boards, wherein the mother board at the left side is connected to the back panel by means of a prior art connector assembly and wherein the daughter board at the right side is connected to the back panel using a connector assembly of the invention.

Fig. 38 shows a perspective view of the female con- nector of fig. 1 with straight contact elements illustrating the manner of providing a solder reservoir on the tail ends of the contact elements and the hold downs of the connector, respectively.

Fig. 39 schematically shows three steps in a side and top view, respectively of the manner of providing a sol- der reservoir on the tail ends of the contact elements in fig. 38.

Fig. 40 further illustrates the manner of providing a solder reservoir on the tail ends of the contact elements of fig. 38.

Figs. 41A-41C show the use of the solder reservoir in the female connector of fig. 38.

Referring to fig. 1 there is shown a backpanel 1 with a male connector 2 and a daughter board 3 with a female connector 4. In this case the male connector 2 is made as a straight connector, while the female connector 4 is made as a right-angled connector. The male connector 2 comprises a metal outer shielding 5 enclosing four housing parts 6. Each housing part 6 has an elongated mainly rectangular flat shape, wherein a series of open grooves 7 is provided in one of the main surfaces of a housing part 6. The grooves 7 ex- tend lateral to the longitudinal direction of the housing part 6. Male contact elements 8 are made as single beam con- tact elements and are mounted in the grooves 7 as will be described later.

The female connector 4 comprises also four housing parts 9, each housing part having an elongated mainly rec- tangular flat shape. In one of the main surfaces of a hous-

ing part 9 a series of open grooves 10 is provided. The fe- male connector 4 further comprises a metal frame 11 and a tail unit 12. The metal frame 11 integrates the housing parts 9 and the tail unit 12 into the complete female con- nector 4.

Each housing part 9 of the female connector 4 is provided with a plurality of female contact elements 13, wherein these contact elements 13 are made as single beam contact elements and are mounted in the grooves 10.

The male and female contacts 8,13 are shown in de- tail in fig. 2 and 3, each showing a part of a strip of fe- male contact elements 13 and male contact elements 8, re- spectively. As both the male and female contact elements 8,13 are made as single beam contact elements, the produc- tion steps of both types of contact elements are mainly the same. The female contact elements 13 comprise a neck or mounting section 14 with two small protrusions 15 for re- taining the contact element in the groove 10 of the housing part 9. The contact element 13 further comprises a tail sec- tion 16 and a spring section 17. The spring section 17 car- ries a first contact dimple 18, whereas in the preferred em- bodiment shown the mounting section 14 carries a second con- tact dimple 19. The co-operation of the contact dimples 18, 19 with the male contact elements 8 will be described later.

It is noted however that in an alternative embodiment the female contact elements can be manufactured with the first contact dimple 18 only.

At the end of the tail section 16, a recess 20 is provided for receiving a solder reservoir. Further the end of the tail section 16 is provided with a chamfer 21 to im- prove the surface mount connection with a printed circuit board. The female contact elements 13 are interconnected by carriers 22 with an intermediate pilot hole 23 and the car- riers 22 are connected to a strip 24 with corresponding pi- lot holes 25.

As shown in fig. 3, the male contact elements 8 are interconnected in the same manner by carriers 22 and a strip

24. Each male contact element 13 is provided with an inter- mediate mounting section having two small protrusions 15 for retaining the contact element in a groove 7 of the housing part 6. The distance between the two protrusions 15 can be smaller than distance shown in fig. 3. The front section of the contact element 8 between the tip and the first protru- sion 15 functions as a contact spring section 61 as will be described later. The tail end of the male contact elements 8 is also provided with a chamfer 21 and further a recess 20 is provided for a solder reservoir.

During manufacturing of the connectors 2,4, the mounting section of the contact elements 8,13 is pressed into the groove 7 or 10, respectively, onto the bottom thereof, wherein the contact elements are retained in the grooves at their mounting sections, while the spring sec- tions 17,61 extends unsupported and can deflect during mat- ing of the connectors 2,4.

The thin flat contact element design allows manu- facturing of both types of contact elements from thin mill- rolled stock material, wherein the contact elements 8,13 have a constant thickness in cross-section. During manufac- turing substantially stress free contact elements are ob- tained having a contact surface texture devoid of any rough- ness irregularities. The thin flat contact element design further lends itself for selective metal plating, wherein the co-operating parts of the male and female contact ele- ments 8,13 can be provided with a precious metal plating, whereas the tail end with recess 20 and chamfer 21 can be provided with a tin-lead plating. If necessary a nickel plating can be provided between the precious metal plating and the tin-lead plating as a separation. The precious metal plating is only necessary on one side of the contact ele- ments 8,13 as the other side faces the housing part 6,9.

Figs. 4-6 show three steps of manufacturing the fe- male connector 4 of fig. 1. Fig. 4 shows one female housing part 9 which in the embodiment shown is provided with twenty-four grooves 10 for receiving female contact elements

13. Twenty-four female contact elements 13 are provided as part of a strip of female contact elements still intercon- nected by the carrier 22 and strip 24. It will be clear that any other number of grooves and contact elements can be used as desired.

The pilot holes 23,25 provide for an easy handling of the strip of female contact elements 13 which are mass inserted in one step into the grooves 10 of the female hous- ing part 9. During the insertion step of the contact ele- ments 13, the contact elements 13 are separated from the carriers 22. In this manner a female housing part 9 with in- serted female contact elements 13 is obtained as shown in fig. 5. During the insertion step the neck or mounting sec- tion 14 with the protrusions 15 is forced into a mounting part 26 of the corresponding groove 10 to retain the contact element 13 in the groove. The contacting spring section 17 is received with play in the corresponding groove 10 so that the spring action of the contact element can provide a con- tacting force through deflection during a mating cycle, when the contact dimple 18 is in contact with an opposing contact element 8.

As stated above, during the manufacturing process, the array of substantially flat thin contact elements 13 connected to the carrier 22 and lying in one plane can be severed en masse from this carrier by a suitable punch tool.

This tool moves further perpendicularly with respect to the plane of the contact elements 13 towards the grooves 10 of the female housing part 9 located below the contact ele- ments. In this manner the punch tool mass-inserts the con- tact elements 13 in one step into the housing part 9. The protrusions 15 of each contact element 13 are forced into the material of the walls of the corresponding grooves 10.

The forces caused in successive grooves 10 are in opposite directions and are staggered with respect to each other. The material of the housing part 9 between the staggered protru- sions provides a spring function to retain the contact ele- ments in the grooves. Moreover the plated contacting sur-

faces of the contact elements can not be scratched during insertion.

Two identical female housing parts 9 together with metal end plates 27 provide one female connector module 28 shown in fig. 6. In the embodiment of figs. 4-6, the re- cesses 20 are provided with a solder lump or dot 29. How- ever, such a solder dot 29 can also be provided in the re- cesses 20 in a later manufacturing step. The end plates 27 provide for a mutual positioning of the female housing parts 9.

The female housing parts 9 shown in figs. 4-6 are selectively metallized at their outer surface 30 and edges 30'providing a shielding of the connector module 28. In an alternative embodiment shown in figs. 7-10, a shielding of the contact elements 13 is provided by using female housing parts 9 made as metal die cast components. In this embodi- ment the end plates 27 can be made as an integral part of the housing part 9. The female contact elements 13 are pro- vided with an insulating mounting element 31 at the neck section 14 (see figs. 7 and 10). This mounting element 31 is received in a mounting part 32 of the grooves 10. Just as in the embodiment of figs. 4-6, a strip of female contact ele- ments 13 including twenty-four contact elements is provided for mass insertion of the contact elements 13 into the grooves 10 of a housing part 9. Two housing parts 9 with in- serted contact elements 13 are assembled to provide one fe- male connector module 28 shown in fig. 9.

Although in the embodiment shown in figs. 4-6 the end plates 27 are shown as separate elements, the end plates 27 generally are provided as an integral part of the metal frame 11. In the embodiment of figs. 11 and 12 a metal frame 11 is shown by way of example for a female connector of the invention including eight female connector modules 28 so that the female connector comprises sixteen rows of contact elements 13, each row including twenty-four contact elements in the embodiment shown.

Fig. 13 shows an exploded view of the female con-

nector 4 of fig. 1, the female connector 4 being shown at a larger scale in fig. 14. In this case, the female connector comprises two female connector modules 28 so that the con- nector comprises four rows of contact elements 13, each row including twenty-four contact elements in the embodiment shown. As the female connector is an assembly of one or more female connector modules 28, wherein each connector module is an assembly of two identical housing parts 9, it will be understood that the design of the female connector provides for a high flexibility in manufacturing a connector with any desired number of rows of connector elements. In the connec- tor design described the number of rows of contact elements can be incremented in steps of two rows by simply adding a connector module of two housing parts. All housing parts are held together as an integral housing. Expensive tooling to manufacture a new housing is not necessary.

As mentioned above, the number of contact elements in one row can be chosen as desired. The number of twenty- four contact elements 13 in one row is only given by way of example. In the embodiments described, the lateral or trans- verse dimension of the connector module 28 is 2,0 mm whereas the length of the module is 25 mm. The pitch of the contact elements 13 in longitudinal direction is 1,0 mm. At both longitudinal ends the distance of a contact element from the end is such that, when more contact elements 13 in a longi- tudinal array are required, two or more modules 28 can be stacked end-to-end, wherein a pitch between adjacent contact elements 13 of adjacent modules is obtained which is an in- teger times the pitch of the elements 13 within a module.

In the embodiment shown in figs. 11,12, the female connector is made as a straight connector, wherein all con- tact elements 13 have the same length. In the embodiment of figs. 1 and 13, the female connector 4 is a right-angled fe- male connector, wherein the female contact elements 13 in successive rows have a different length.

To receive the two female connector modules 28, the metal frame 11 is provided with three flat ribs 33, wherein

the upper and lower ribs 33 are provided with circular open- ings 34 for receiving mounting pegs 35 of the tail unit 12 and the housing parts 9. In the embodiment shown in the drawings, the pegs 35 are integral plastic parts of the housing part 9 and tail unit 12, respectively. However the pegs 35 can also be provided as metal parts which are in- sert-moulded with the housing parts 9 and/or tail unit 12.

Further it will be clear that instead of round openings 34 and pegs 35 different shapes may be used. The central rib 33 is provided with elongated openings 36 to receive the pegs 35 of two female housing parts 9. All ribs 33 are provided with a rectangular saw form providing recesses 37 receiving the tail sections 16 of the female contact elements 13 as shown in detail in fig. 16. The upper and lower ribs 33 are further provided with rectangular recesses 38 for receiving rectangular pegs 39 of the tail unit 12 to provide a further mutual fixation of the tail unit 12 and metal frame 11. Fur- ther the upper rib 33 is provided with larger recesses 40 aligned with slots 41 provided in the upper surface of the tail unit 12. The location and size of the recesses 40 and slots 41 can be varied to provide a polarisation and coding area.

The tail unit 12 is also selectively metallized at its outer surface to provide a shielding of the contact ele- ments 13. Further the front face, including the pegs 35 and 39 is metallized, so that the metal frame 11 is connected with the metallization of the tail unit 12. In the same man- ner, the edge of the housing parts 9 and the pegs 35 are metallized to interconnect the metallization of the housing parts 9 with the metal frame 11. In this manner an integral shielding of the female connector 4 is obtained.

The metal frame 11 is bent perpendicularly to form a surface mount hold-down ledge 42 along the length of the connector 4. This ledge 42 is provided with a plurality of contact dimples 43 supporting the lower female housing part 9 and contacting the metallization of this housing part as can be seen in fig. 17.

The metal frame 11 also comprises three contact terminals 44 with a semi-circular end and a solder reservoir recess 45, which contact terminals 44 can be used to posi- tion and fix the connector 4 on a printed circuit board. In the embodiment described the contact terminals 44 provide a hold-down function to mount the connector on the printed circuit board. Further, the terminals 44 can be connected to a common ground of the printed circuit board to connect the shielding of the connector to ground. Recess areas 46,47 of the metal frame 11 have the function to properly position and accept corresponding protrusions of the outer shielding 5 of the male connector 2. This outer shielding 5 further contacts the end plates 27 which are provided with contact dimples 48 for this purpose.

When the female connector parts are assembled, the elongated openings between the ribs 33 are aligned with channels 49 in the tail unit 12, which channels 49 are sepa- rated by an intermediate wall 50 of insulating material.

This intermediate wall 50 is provided with elongated pegs 35 engaging the elongated openings 36 of the central rib 33. At the end of each channel 49 an end wall 51 is provided as shown in fig. 17. During assembly of the female connector, the female contact elements 13 are straight and can pass through the channels 49 and the spacing between the end walls 51 and the intermediate and upper walls of the tail unit 12. When the housing parts 9, the metal frame 11 and the tail unit 12 are assembled, the tail sections 16 of the female contact elements 13 are bent 90° to provide the right-angled female connector. As can be seen in fig. 17, the rear side of the end walls 51, intermediate wall 50 and lower wall 52 are inclined to the front end, so that the tail sections 16 of the contact elements 13 can be suffi- ciently bent to obtain a right-angled rest position.

Figs. 18-20 show in a manner similar to figs. 4-6 successive manufacturing steps in manufacturing the male connector 2 of fig. 1. Fig. 18 shows a male housing part 6 made of insulating material having twenty-four grooves 7 for

receiving the male contact elements 8 and extending lateral to the longitudinal direction of the housing part 6. A strip of twenty-four male contact elements 8 interconnected by the carriers 22 and strip 24 is shown in fig. 18 and these con- tact elements 8 are mass inserted into the grooves 7, wherein the pilot holes 23,25 provide for an easy handling of the strip of contact elements during insertion. During the insertion step the male contact elements 8 are separated from the carriers 22. The assembly step of contact elements and housing part is the same as described with respect to the female housing part.

As described by reference to fig. 3, the male con- tact elements 8 are provided with retention protrusions 15 for retaining the male contact elements 8 in the grooves 7.

Retention of the contact elements 8 in the housing part 6 occurs in the same way as described above. Two identical housing parts 6 with male contact elements 8 are assembled to obtain one male connector module 52 shown in fig. 20.

Such a male connector module 52 can be mated with a female connector module 28 by inserting the module into the receiv- ing space of the female connector module 28 as will be de- scribed later.

The housing parts 6 are selectively metallized at least at the surface opposite of the grooved surface with male contact elements 8. The metallized surface 53 is pro- vided with protrusions 54 which are also metallized. These protrusions are fittingly received in openings 55. The sur- faces 53 with protrusions 54 and openings 55 provide cou- pling surfaces for joining the housing part 6, the protru- sions 54 and openings 55 being examples of coupling members.

As the assembled housing parts 6 are identical, any waviness or curvature due to moulding of thin parts, is identical and opposite so that the mutual retention of the two housing parts by the protrusions 54 and openings 55 ensure a flat male connector module 52. The metallized protrusions 54 pro- vide for a partial shielding between adjacent contact ele- ments 8.

As can be seen in figs. 18-20, two of the contact elements 8 have a greater length providing for a first make, last break operation when mating and unmating the male and female connectors. The metallization of the protrusions 54 is indicated by a shading in a section of the male connector 2 shown in fig. 25. Fig. 26 shows an exploded view of one male connector module 52 with corresponding male contact elements 8 and fig. 27 shows a detail of the male connector module at a larger scale. The metallization 53 of the male housing part 6 is schematically indicated by a dashed line.

This metallization 53 provides for the shielding between the two rows of male contact elements 8 of one connector module 52.

At both longitudinal ends the housing part 6 is provided with a coupling section 56 for connecting the male connector module 52 to the outer shielding 5. These coupling sections 56 are also metallized to connect the metallization 53 to the outer shielding 5. The coupling sections 56 are partially separated from the housing part 6 by a slot 57.

Between the coupling sections 56 and the housing part 6 a raised edge 58 is provided as a stacking element. Two male connector modules 52 can be positioned with these raised edges 58 upon each other with the centre planes of the two connector modules 52 located at a distance of 2 mm from each other in the embodiment shown.

At the rear end of the housing part 6 protrusions 59 with sloping ends are provided, which protrusions less high than the raised edges 58. These sloping protrusions 59 allow for a free passage of thermal energy through the male connector 2.

Fig. 21 schematically shows a cross section of a male connector module 52 showing that the front end 60 of the housing parts 6 of the connector module 52 slightly ta- pers such that the front ends of the contact elements 8 are supported in air and can operate as a contact spring section 61. The location of the retaining protrusions 15 is such that the spring section 61 of the contact element 8 is in-

deed flexible.

Fig. 22 shows an exploded view of the male connec- tor 2 of fig. 1 showing the outer shielding 5 as two shield- ing halves 62,63 and an inner shielding strip or plate 64 located between the two male connector modules 52. If such an inner shielding strip 64 is used the ends of this strip are received between the stacking elements 58 as shown in fig. 24. The distance of 2 mm between the centre planes of successive modules is in this case determined by the raised edges 58 and the thickness of the strip 64. The generally U- shaped shielding halves 62,63 can be interconnected by in- terconnection members 62'and 63'at the ends of their legs.

In the interconnected position the shielding halves 62,63 provide an elongated receiving space for the two connector modules 52. The shielding halves 62,63 each have two slots 65 which during assembling the connector are slit into the slots 57 between the coupling sections 56 and the housing parts 6 and in the assembled situation shown in fig. 23 re- ceive the body of these housing parts 6. As shown in fig. 23 the shielding provides the outer wall of the connector 2, which outer wall directly faces the contact elements 8.

The metallization of the coupling sections 56 pro- vide for an interconnection of the metallization with the outer shielding 5. Between the slots 65 an opening 66 can be seen in fig. 22 for receiving an extension 64'of the inner shielding strip 64.

Fig. 24 schematically shows a cross section of the male connector 2 showing the location of the inner shielding strip 64.

The outer shielding 5 is provided with polarization and coding fingers 67 which during mating are received in the polarization and coding slots 41 of the tail unit 12 of the female connector 4. These polarization fingers 67 are provided with contact dimples 68 for contacting an optional metal cap (see fig. 35B) of the female connector 4 not shown in fig. 1. In fig. 23 the outer shielding 5 is further pro- vided with optional hold down press-fit terminals 69 to con-

nect the outer shielding to a printed circuit board. At the rear end of the outer shielding 5, ridges 70 are provided for connection to the printed circuit board. At the backside of the male connector 2 plastic pegs 71 provide for a proper alignment of the male connector with respect to the printed circuit board or backpanel 1 where they are received in cor- responding holes. The circuit strips 72a for the ridges 70 and holes 72b, 72c for the terminals 69 and the pegs 71, re- spectively, for mounting the connector on the printed cir- cuit board and for accurately orientation and positioning of the modules are shown in fig. 1 and 31. The tail ends of the male contact elements 8 are surface mounted to contact pads 72d of the back panel also shown fig. 1 and 31.

Fig. 28 shows an alternative embodiment of the male connector of the invention which is made as a right-angled male connector 73. In this case a tail unit 74 is combined with the straight male connector 2, the tail unit 74 corre- sponding to the tail unit 12 of the female connector 4. Fur- ther, instead of male connector elements 8 with equal length, the length of the contact elements of successive rows will be different in this case. Although not shown in fig. 28, a metal mounting frame 11 can be used to intercon- nect the front housing and tail unit and to provide a hold- down and electrical connection to the printed circuit board as described with respect to the female connector.

As a further alternative embodiment, fig. 29 shows a female cable connector 75, wherein instead of the tail unit 12 a straight tail unit 76 is used to introduce the ca- ble 77 into the connector 75.

Figs. 30A-30C show front views of three different embodiments of male connectors having four, six or eight rows of male contact elements 8, respectively. Accordingly, the male connector is provided with two, three, or four male connector modules 52.

Fig. 31 shows by way of example three male connec- tors 2 stacked end-to-end and mounted on a back panel 1.

The co-operation of the male and female contact

elements 8,13 during mating of the male and female connec- tors 2,4 and the mating operation will be explained by ref- erence to figs. 32-36.

Fig. 32A schematically shows a part of a male hous- ing part 6 with three grooves 7 wherein for the sake of sim- plicity a male contact element 8 is shown in the central groove 7 only. As can be seen in the drawings the spring portion 61 of the contact element 8 lies at a distance from the front end of the groove 7, so that the female contact element 13 will be guided and centred before contacting the contact element 8. Further only one female contact element 13 is shown wherein the female housing part 9 is only sche- matically indicated. The width of the grooves 7 is smaller than the width of the spring portion 17 of the female con- tact element 13 to facilitate the receipt of the spring por- tion by the groove. Fig. 32B shows section A-A of fig. 32A indicating the manner in which the contact dimple 18 is guided and centred by oblique sides 78 of the groove 7 in the male housing part 6. In this manner a centring of the female contact element 13 with respect to the groove 7 and thereby with respect to the male contact element 8 is ob- tained. Therefore, if due to manufacturing tolerances the longitudinal axis of the female contact elements 13 is slightly skew with respect to the longitudinal axis of the grooves and the male contact elements 8, the female contact element will be oriented by the male groove 7, wherein the mounting section 14 acts as a pivot, so that the tail sec- tion 16 is also centred.

When the male connector is further mated with the female connector 4, the full engagement position of figs.

32C and 32D is obtained, wherein the contact dimple 18 has wiped along the contact section 61 of the male contact ele- ment 8 and wherein the contact dimple 19 contacts the spring section 61. As shown in section B-B in fig. 32D, the spring section 17 of the female contact element 13 is slightly pressed upwardly into the groove 10 of the female housing part 9.

Fig. 33 partially shows a cross section of the fully mated connectors 2,4. The schematically indicated met- allization 30,53 of the male and female housing parts 6,9 provides for a shielding surrounding each row of mated con- tact elements 8 and 13.

Figs. 34A and 34B show by way of example one female connector module 28 and one male connector module 52 unmated (fig. 34A) and mated (fig. 34B). In the mated position of fig. 34B the contact dimples 18,19 are contacting the male contact element 8, wherein the spring section 17 of the fe- male contact element 13 provides for the required flexibil- ity and contact force for contact dimple 18, whereas the free support of the spring section 61 of the male contact element 8 provided by the tapering front end 60 of the male connector module 52, provides for the flexibility and con- tacting force for the contact dimple 19. As noted above, in an alternative female contact elements 13 can be used having one contact dimple 18 at the front end only. However, to in- crease safety margins the use of two contact dimples 18,19 is generally desired in telecommunication applications for example. The provision of both contact dimples 18,19 on the female contact elements 13 only shows the advantage, that it is not necessary for two contact dimples to pass each other as would be the case if both male and female contact ele- ments were provided with one contact dimple.

Fig. 34B further shows that the opening between the ribs 33 of the metal frame 11 provides a passage for the male connector module 52 in the fully mated position.

Figs. 35A and 35B show schematically cross sections of the male and female connectors 2 and 4 of fig. 1 in the unmated and mated positions, respectively. In fig. 35B the female connector 4 is provided with a metal cap 79. The con- tact dimples 68 of the outer shielding 5 contact the inner side of this metal cap 79.

Figs. 36A and 36B show as an alternative a right- angled male connector 80 and a straight female connector 81 in the unmated and mated positions, respectively.

Figs. 35 and 36 clearly show that the main elements of the male and female connectors 2,80 and 4,81 are the same in the straight and right-angled embodiments. Further, each connector is a modular construction of one or more male or female connector modules 52,28 and especially in case of a right-angled embodiment, each connector further comprising a metal frame 11 a tail unit 12. The connector design de- scribed thereby shows the advantage that a connector with a desired number of rows of contact elements can be provided using the same production tooling equipment. It is not nec- essary to design special customised moulds for customised housings. The mass insertion of the male and female contact elements 8,13 into the respective grooves 7,10 of the hous- ing parts 6,9 provides for an efficient manufacturing. The contact element design as single beam contact elements al- lows the use of the mill-rolled surface of the starting strip material as contact surface, resulting automatically in a contact surface with low roughness without the neces- sity of additional manufacturing steps to reduce contact surface roughness. Moreover, the use of single beam contacts provides the possibility to increase the density of the con- tact elements by reducing the pitch between adjacent rows of contacts. Moreover the use of single beam contacts reduces the effective contact radiating surface, thereby minimizing intercontact interaction, i. e. reducing cross talk.

By way of example fig. 37 shows a backpanel 82 with at the left side a daughter board 83 and at the right side a daughter board 84. The daughter board 83 is connected to the backpanel by male and female connectors 85,86 of the prior art having four rows of male and female contacts. The daugh- ter board 84 is connected to the backpanel by male and fe- male connectors 2,4 of the present invention also having four rows of male and female contact elements 8,13. A com- parison of the prior art male and female connectors 85,86 and the male and female connectors 2,4 of the present inven- tion shows a significant reduction of the space occupied by the connectors and a significant increase in contact den-

sity.

A further advantage of the connectors of the inven- tion described is the surface mount connection to the printed circuit boards. As also indicated in fig. 37, the surface mount connection of the contact elements 8,13 to the printed circuit boards 82,84 allows for a smaller pitch of the contact pads on the printed circuit boards. In view of the use of chamfered ends 21 of the contact elements 8,13 and the presence of the solder reservoir at the tail ends of the contact elements a reliable surface mount connection can be obtained despite tolerances in coplanarity of the tail ends of the connector elements and bow of the printed cir- cuit board.

Figs. 38-40 shows by way of example a manner of providing solder balls in the recesses 20 of the female con- tact elements 13. To this end a string 91 of solder balls 92 interconnected by thin strips of solder material is taken from a supply reel 93, wherein twenty-four solder balls 92 are aligned with the tail ends 16 of the female contact ele- ments 13. The solder balls 92 are arranged at substantially the same pitch as the contact elements. By means of a tool 94 the solder balls 92 each having a slot 95 are slid on the tail sections 16 as indicated by an arrow in fig. 38. The tool 94 has an array of positioning openings 97 for receiv- ing the solder balls and channels 98 joining these openings for receiving the tail ends of the contact elements during pushing the solder balls on these tail ends. The first step of providing the solder balls 92 on the tail sections 16 is shown in step 1 of fig. 39. When the solder balls 92 are aligned with the recesses 20 as shown in step 2 of fig. 39, two compression tools 96 are moved towards each other as in- dicated by arrows in fig. 38 and fig. 39, step 3. The com- pression tools 96 flatten the solder balls 92 on the tail sections 16 and press the solder material into the recess 20. Fig. 40A schematically shows the way in which a solder ball is provided in a side view. When the solder balls 92 are mounted on the tail sections 16, the tail sections 16 of

the contact elements 13 can be bent along 90° as shown in fig. 40B.

Fig. 38 also shows a manner to provide the recesses 45 of the contact terminals 44 with a solder reservoir.

It is noted that although in the embodiment of figs. 38-40 solder balls are used, it is also possible to use solder material in other shapes. The use of the solder balls or other type of solder lumps results in the advantage that an accurately predetermined amount of solder material can be provided as a solder reservoir. Thereby there is no chance to cause short circuiting by an excess amount of sol- der material. The solder material used is preferably a pre- flux solder material. The interconnection strips break dur- ing soldering and the material flows to the tail ends and is sub-divided to the two adjacent tail ends.

Fig. 41A-41C show the way in which the solder res- ervoirs provided on the tail sections 16 of the contact ele- ments 13 and the contact terminals 44 are used in practice.

In the detail shown in fig. 41B it is indicated how the sol- der dot in the recess 20 reflows during soldering to provide the desired surface mount connection. The contact sections 44 are received in holes 97 of the printed circuit board where reflow of the solder towards the interface between the surface of the printed circuit board and the lower face of the ledge 42 of metal frame 11 occurs.

The invention is not restricted to the above de- scribed embodiments which can be varied in a number of ways within the scope of the attached claims.