Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – With provision to conduct electricity from panel circuit to...
Reexamination Certificate
2000-06-28
2001-09-18
Luebke, Renee (Department: 2833)
Electrical connectors
Preformed panel circuit arrangement, e.g., pcb, icm, dip,...
With provision to conduct electricity from panel circuit to...
C439S071000
Reexamination Certificate
active
06290507
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to interposer assemblies used for forming electrical connections between spaced contact pads on circuit members.
BACKGROUND OF THE INVENTION
Interposer assemblies electrically connect between densely spaced contact pads on adjacent parallel circuit members. Interposer assemblies are used wherever dense connections are required. The assemblies are particularly well suited for use in portable electronic devices such as cell phones, digital assistants, notebook computers and the like. The assemblies enable a reduction in the size and weight of the electronic devices.
The pads on the circuit members are arranged in identical patterns. Commonly, the circuit members are a circuit board and a ceramic plate carrying integrated circuits. The interposer assembly includes an insulating plate and a plurality of through-contacts carried in the plate and arranged in the same pattern as the pads on the circuit members. The contacts project above the top and bottom sides of the plate. The interposer assembly is sandwiched between the two members which are held together with the contacts forming electric connections between aligned pairs of pads.
Interposer assemblies form electrical connections between contact pads arranged in a very close proximity to each other. The pads may be arranged on a one millimeter center-to-center grid. Each assembly may have as many as 961 contacts. Four assemblies are conventionally mounted on a single frame with a total of 3,844 contacts in the frame.
In addition to requiring contacts which can be spaced very close to each other, the contacts must make reliable electrical connections with the pads during the lifetime of the electronic device. The circuit members may move towards and away from each other due to changes in operating temperature, handling of the device, or the like. The contacts must make reliable electrical connection with the pads despite the relative movement of the circuit members. Failure of a single contact to make a reliable connection may render the entire electronic device useless.
The individual electrical contact in the assembly acts as a spring that extends or compresses in response to the circuit members moving away or towards one another. The contact is compressed and deforms elastically when sandwiched between the contact pads. The contact must be able to extend outwardly when the circuit members move apart and compress when the circuit members move back together.
Interposer assemblies must occupy a minimum width between the circuit members. This requires that the individual electrical contacts in the assembly have a limited height. Yet the contacts must possess the required resiliency for maintaining reliable electrical contact with the pads throughout repeated cycles of extension and compression.
Further, the contacts must be compressed with a low mechanical closure force when the interposer assembly is sandwiched between the circuit members. Low closure force is required in order to prevent undue stress on the contact or a ceramic circuit member. A high closure force could distort or possibly break the contact or the ceramic member. Permanent distortion or deformation of the contact member may reduce or destroy the resiliency of the contact. The contact cannot lose resiliency to the extent that the contact is unable to maintain reliable electrical connections between the pads.
Conventional interposer assemblies use contacts which occupy a relatively large amount of space in the supporting plate making it difficult to meet closely spaced grid requirements. These assemblies are relatively expensive to manufacture and assemble.
Applicants' U.S. patent application Ser. No. 09/455,989, assigned to the assignee of the present invention, discloses an interposer assembly including metal through contacts loosely confined in closely spaced passages extending through an insulating plate. On rare occasions, contacts inserted into the passages in the above interposer assembly do not work properly.
SUMMARY OF THE INVENTION
The invention is improved interposer assemblies of the type having metal through contacts loosely confined in closely spaced passages extending through an insulating plate. The plate is a one-piece design and includes contact retention projections extending into the passages and sloped cam surfaces provided on both sides of the individual projections. The cam surfaces are preferably symmetrical about a central plane of the plate. Cam followers on the free ends of the contacts engage the cam surfaces and are guided past the projections which then hold the contacts in place. The contacts may be inserted from either side of the plate.
The sloped cam surfaces extend to the adjacent walls of the his contact passages and do not form sharp corners with the passage walls. The sloped cam surfaces assure that during insertion of the contacts into the passages the lead ends of the contacts are guided smoothly over the projections and do not hang up in the corners or junctions between the projections and the adjacent walls.
When sandwiching the interposer assembly between the circuit members, the cam followers engage the cam surfaces and slide on the cam surfaces towards the end of the projection. The cam followers remain in contact with the cam surfaces while sandwiched between the circuit members. Because the cam followers engage the projections, the free ends of the uncompressed contacts can be spaced sufficiently close together that the arms of the contact always remain within the passage. The contacts cannot fall out of the passage nor can the arms become sandwiched between the plate and a circuit member.
In a first embodiment interposer assembly sloped cam surfaces on each projection are planar and extend inwardly from one side of a passage into the passage to the inner end of the projection. The cam surfaces slope at a shallow angle with respect to the axis of the contact passage. In the first embodiment the cam surfaces preferably slope at an angle of about 25 degrees with respect to the axis of the contact passage and do not intersect at the end of the retention projection.
On occasion, it has been found that a large closure force is necessary to sandwich the first embodiment interposer assembly between the circuit members. Sliding of the cam followers on the cam surfaces generates frictional forces that resist the motion of the cam followers. The closure force must overcome the frictional forces to slide the cam followers on the cam surfaces. It is believed that the frictional forces may increase the closure force. The large closure force may permanently deform the contacts and cause the contacts to lose the resiliency needed for reliable electrical connections between the pads.
In other embodiments, the cam surfaces are configured to reduce the frictional forces generated by the cam followers sliding on the cam surfaces. The cam surfaces include portions that extend inwardly into the passage at an angle less than 25 degrees. When sandwiching the second embodiment interposer assembly between the circuit members, the cam followers slide more readily along these cam surfaces. The shallow angle of these cam surfaces reduce the frictional forces and reduces the closure force.
In second and third embodiment interposer assemblies the shallow cam surfaces are planar and extend inwardly from the plate and into the passages to free ends at the ends of the projection. The cam surfaces slope at angles of about 12 degrees. The free ends of the cam surfaces on each projection intersect at the free end of the projection.
In a fourth embodiment interposer assembly, the cam surfaces have variable slopes. The individual cam surfaces have a first slope near the plate and a second, preferably shallower, slope away from the plate near the free end of the projection. The cam surfaces may be curved to continually change the camming slope from the first slope to the second slope, or the individual cam surfaces may include two or more portions having different slopes. The cam surface portions may incl
Neidich Douglas A.
Walden John D.
Hammond Briggitte R.
InterCon Systems, Inc.
Luebke Renee
Thomas Hooker, P.C.
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