Intermediate connector for use between a printed circuit card and a substrate for electronic circuits

An intermediate connector is for mounting on a printed circuit card so that a first face of the connector bears against the card, and so that a second face thereof receives a substrate of an electronic circuit. It interconnects contact areas provided on the substrate and tracks on the card. The connector has an insulating support having regularly spaced apart through-passages that receive respective electrical signal contacts, each of which connects one contact area to a track. Each contact is a cut out piece of metal sheet and has a rigid branch for fastening it to the support, and a flexible branch that is S-shaped. Each passage is defined by partitions and slidably receives a corresponding rigid branch and it has abutment shoulders that are spaced apart by an interval eo, The abutment closest to the first face is at a predetermined height ho relative thereto. The rigid branch extending along the passage has two mutually facing abutment shoulders that are spaced apart by a determined interval eo greater than e. The contact projects a distance h from the shoulder closest to the second face and h is less than ho.

BACKGROUND OF THE INVENTION 
The present invention relates to an intermediate connector for use between 
a printed circuit card and a substrate carrying electronic circuits. A 
particularly important, although not exclusive application lies in devices 
having a ceramic substrate and in particular a substrate carrying a 
plurality of integrated circuits. 
The invention relates more particularly to an intermediate connector of the 
kind described in French patent FR 90 13996, designed to be mounted on a 
printed circuit card in such a manner that a first face of the connector 
bears against the card, and to receive, via a second face, an electronic 
substrate, while interconnecting contact areas provided on the surface of 
the substrate that faces the card and tracks on the card, said connector 
comprising: 
an insulating support in which regularly spaced passages are formed; and 
electrical signal contacts, each designed to connect one contact area to a 
respective track, received in at least some of the passages, 
in which at least some of the contacts are each made as a cut out metal 
sheet part, each of said contacts having a rigid branch for securing it to 
the support and an S-shaped flexible branch whose proximal end is fast 
with the rigid branch and whose distal end projects beyond the top face of 
the support, the flexible branch being curved at rest in such a manner 
that its distal end is then spaced from the rigid branch and the 
contact-receiving passage has dimensions such that it deforms the flexible 
branch on insertion of the contact into the support so as to bring the 
distal portion into contact with the rigid branch, thereby constituting a 
short circuit. 
One of the problems in implementing such connectors is obtaining uniform 
stresses on the contacts when the connector is mounted between a card and 
a substrate. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a connector of the kind defined 
above that is better at satisfying practical requirements than are 
previously known connectors, and in particular that ensures uniformity of 
pressure, as is desirable. Consequently, the invention proposes a 
connector of the above-defined type, wherein 
the passage is defined by a partition slidably receiving the rigid branch 
and having abutment shoulders that are spaced apart by a determined 
interval eo, the abutment shoulder closest to the first face of the 
connector being at a first predetermined height hO therefrom; 
the rigid securing branch that extends along the passage includes two 
mutually facing abutment shoulders that are spaced apart by a determined 
interval e, greater than eo; and 
the distance through which the contact projects from the shoulder closest 
to the second face is less than ho. 
In this disposition, each of the contacts takes up position automatically 
in such a manner that the pressures exerted on each side on the contact 
balance and the pressure forces that act on the various contacts also come 
into balance. 
The invention also provides other dispositions that are advantageously 
usable with the above dispositions but that may be used independently. All 
of these dispositions will appear more clearly on reading the following 
description of a particular embodiment, given by way of examples. The 
description refers to the accompanying drawings.

DETAILED DESCRIPTION 
The connector 10 shown in FIG. 1 has a structure that is generally similar 
to that described in French patent No. 90 13996, to which reference may be 
made. It is designated to be mounted on a printed circuit card 12 that is 
to be connected to a substrate 14 for active electronic circuits. The 
substrate may be constituted, in particular, by a multi-layer ceramic 
plate (optionally surmounted by thin film structures) that is designed to 
receive integrated circuit chips 16. However, the invention is also 
applicable when the substrate is designed to receive a single integrated 
circuit and/or is made of a material other than ceramic (e.g. organic 
material). 
The connector includes an insulating support 20. In the example shown in 
FIG. 3, the support is in the form of a frame. 
Through passages are formed in the insulating support 20 and they are 
aligned in rows. They are sized to receive respective contacts that may be 
of various different kinds. The contacts 22 shown in FIGS. 1 and 2 are 
intended to transmit signals. Other contacts may be for setting up 
equipotential connections, e.g. ground or power supply connections. 
Each contact 22 (FIG.2) is generally cut out from a sheet or foil of a 
conductive material that has good resiliency, e.g. beryllium bronze. It 
may be considered as having a relatively rigid branch 28 for fastening to 
the support and a relatively flexible branch 34 for making electrical 
contact. 
Each contact-receiving passage is laterally defined by two partitions 26 
that do not occupy the full height of the insulating support 20. These 
partitions, which are all of the same height, form pairs of abutment 
shoulders that are spaced apart by a predetermined interval eo. When the 
insulating support is mounted on the card 12, each shoulder closest to the 
first face of the support, i.e. that face which bears against the card 12, 
is at a height ho from said card 12. 
The rigid branch 28 of each contact extends along a respective passage and 
also includes two mutually facing abutment shoulders that are spaced apart 
by a predetermined interval e that is slightly greater than eo (e.g. 1.1 
to 1.4 times eo), thereby allowing the contact to "float" in the passage. 
In the embodiment shown in FIGS. 1 and 2, the abutment shoulder closest to 
the first face of the support is constituted by a stump 29 extending 
transversely to the direction of the rigid branch 28. The other shoulder 
is constituted by the root of a swelling 22 having a rounded shape to 
prevent the contact jamming when it is being inserted into a passage. 
In immediate proximity to its connection with the flexible branch, the 
rigid branch has a swelling 32 for abutment against a track of the card 12 
(and optionally for being soldered thereto). The distance h between the 
shoulder closest to the first face and the end of the swelling 32 is less 
than ho. For example, h may lie in the range 0.6 ho to 0.9 ho. 
The flexible branch 34 is generally S-shaped. Its proximal end merges with 
the rigid securing branch 38, close to the swelling 32. 
The shape of the contact 22 at rest, as shown in FIG. 2, is such that the 
distal end of the flexible branch is laterally offset by a distance d from 
the top end of the rigid securing branch 28. On the other hand, the 
transverse size of the contact-receiving passages formed through the 
support 20 is such that the pressure exerted by the sides of the passage 
cause the flexible branch 34 to take up the shape shown in FIG. 1, i.e. to 
come into contact with the fastening branch 28. Nevertheless, it is not 
essential that this condition be satisfied. The shape of the flexible 
portion 34 is also such that the pressure exerted by the substrate 14, 
when forced into contact with the support 20, advantageously brings that 
the last bend of the flexible branch into contact with the proximal end of 
the same branch. This establishes a short circuit, thereby reducing signal 
transit time. 
In the example shown in FIG. 1, means for forcing the substrate 14 against 
the support 20 comprise a movable assembly having a pressure plate 64 and 
screws 66. A spring is typically interposed between each screw and the 
plate 64. 
Since the distance h is less than ho, the danger of exerting a pressure 
force on the stump 29 is avoided. Since e is greater than eo, the position 
of the rigid branch 28 of each contact adapts automatically so that the 
force exerted by the flexible branch 34 on the rigid branch exactly 
balances the reaction force exerted on the swelling 32. This serves to 
reduce the stresses to which the contacts are subjected and to balance the 
stresses over the connector as a whole. 
A contact force is thus guaranteed both on the substrate and on the printed 
circuit, in spite of dimensional variations in the distance between the 
substrate and the printed circuit as may arise particularly--but not 
exclusively--because of inaccuracies of planeness.