WO2007008654A2

WO2007008654A2 - Formed cylindrical lga contact

Info

Publication number: WO2007008654A2
Application number: PCT/US2006/026507
Authority: WO
Inventors: Douglas A. Neidich
Original assignee: Amphenol Corporation
Priority date: 2005-07-13
Filing date: 2006-07-07
Publication date: 2007-01-18
Also published as: WO2007008654A3

Abstract

A cylindrical LGA contact is formed by folding and collapsing a thin, flat metal preform having a plurality of integral beams into a cylindrical body with the beams bowed to form spring contact points on the ends of the body and the ends of the beams located within the body. The metal in the body occupies about fifty percent of the cylindrical volume of the contact to permit elastic collapse of the body between contact pads.

Description

FORMED CYLINDRICAL LGA CONTACT

The invention relates to a small LGA contact formed from thin gauge metal strip stock; a preform; a wrinkled preform; and methods for making the contact .

Figure 1 is a view of an etched or stamped contact preform;

Figure 2 is a view of a wrinkled preform;

Figure 3 is a view of a folded and collapsed cylindrical contact formed from the preform; and

Figure 4 is a sectional view illustrating the contact in place in a hole extending through an insulated interposer assembly plate.

The contact 24 is preferably formed from metal strip stock having a thickness in the range of 0.005 to 0.001 inches and may have a height of 0.098 inches when sandwiched between contact pads .

The metal strip stock is etched, preferably using continuous etching techniques, or stamped to form flat contact preforms 10 each including an integral metal body 12 attached to carrier strips 14 and having a number of elongate deformable beams 16 separated by slots 18. In preform 10, both ends of each beam 16 are joined to the body. Alternatively, only one end of a beam may be joined to the body with the other end of the beam being free of the body.

Preform 10 is square and includes four like 90 degree- oriented fields 20 with parallel beams and slots in each field. The beams and slots in each field extend perpendicular to the beams and slots in adjacent fields and parallel to a diagonal line extending through the field and between the corners of body 12.

The body need not be square and may have a different shape. Different arrangements of beams and slots are contemplated. Straight beams are disclosed. Serpentine or curved beams may be used. The beams may extend across the entire width of the body or partially across the width of the body, as shown in Figure 1. If desired, the beams may be separated by slits rather than by slots.

After etching or stamping the preforms 10, the preforms are plated to cover sheared surfaces and provide conductive contact surfaces .

After plating, the preforms 10 are removed from strips 14 and wrinkled between matched forming tools to create a desired wrinkled body 22 shown in Figure 2. Wrinkling bends the metal in body 12 to a desired shape to facilitate controlled folding and collapse of the wrinkled body 22 into a dense folded cylindrical contact 24 show in Figure 3 for insertion into a hole 26 extending through the thickness of an insulating substrate or interposer assembly plate 28 as shown in Figure 4. During folding and collapse of the wrinkled body 22, the flat beams in the preform are bent or bowed to form a plurality of springs 30. The springs are stressed to provide contact pressure when the contact is sandwiched between contact pads .

Folding and collapse of the wrinkled body 22 to form cylindrical contact 24 may be preformed by placing the wrinkled body in a cylindrical forming tool with the edges of the body engaging the surface of the tool and then reducing the cross sectional area of the tool to collapse and fold the body inwardly and bend or bow the beams to form springs 30 located throughout the length of contact 24. After circumferential folding and collapse, body 22 is formed into a cylindrical body having a diameter appropriate for insertion into hole 26. Next, punches are inserted into the ends of the forming tool to collapse the body axially and reduce the height of the cylindrical body, further bending or bowing of the beams and completing forming of contact 24. As shown in Figure 3, the plurality of bowed formed springs 30 are spaced along the length of the contact .

After forming has been completed, each contact 24 is moved from the forming tool and inserted directly into a hole 26 extending through interposer assembly plate or substrate 28. The diameter of contact 24 in the hole is less than the diameter of hole 26. The contact is held in place in the hole by an internal circumferential ridge 32 located in the center of the hole to space the contact from the sides of the hole and reduce friction between the contact and the hole when the contact is collapsed by opposed contact pads to form an electrical connection between the pads. The ends of beams in the contact are located inside the contact. Inadvertent short circuits with adjacent circuit members are avoided.

The metal in contact 24 occupies approximately 50 percent of the cylindrical volume of contact 24 to permit elastic flexing of springs 30 when the ends of a contact in plate 28 are sandwiched between opposed contact pads lowered onto the plate. Elastic stressing of the springs provides high contact pressure between the contact and the pads. The contact includes a large number of contact points at bent portions of the beams on each end to provide redundant electrical connections with the pads and a reliable, low resistance electrical connection between the pads. In one embodiment, each end of inserted contact 24 extends a distance 34 of about 0.008 inches above the board. The contact is collapsed 0.016 inches when sandwiched between pads engaging plate 28.

Collapsed cylindrical contacts 24 with springs 30 manufactured as described are all made in the same way and all have the same or essentially the same shape and location of springs 30. Manufacture of identical or nearly identical contacts 24 assures that all contacts mounted in a multi- contact interposer plate have like contact pressure and conductivity. Alternatively, folding and collapse of preform body 12 may be performed in steps by forcing the body into successive forming stations to fold and collapse the body progressively and form cylindrical contact 24.

Claims

WHAT I CLAIM AS MY INVENTION IS:

1. A contact for placement in a hole extending through an insulating substrate to form an electrical connection between pads on opposite sides of the substrate, the contact comprising a generally cylindrical body formed by folding and collapsing a thin, integral metal strip ^' member having a plurality of elongate, flat beams, the body comprising a plurality of bowed springs bent from the beams, the ends of the springs located inside the body, a plurality of said springs located at each end of the body to form plural contacts for engaging a contact pad, the folded and collapsed strip occupying less than the total volume of the cylindrical body to permit flexing of the springs, wherein sandwiching of the body between opposed contact pads elastiσally stresses the springs in the body to establish redundant electrical contacts between each pad and end of the body.

2. The contact as in claim 1 wherein the strip member has a thickness of about 0.001 to 0.005 inches.

3. The contact as in claim 1 wherein the body has a height of about 0.098 inches when sandwiched between contact pads .

4. The contact is in claim 1 wherein the collapsed strip occupies approximately fifty percent of the volume of the cylindrical body.

5. The combination of a contact as in claim 1 and an insulating substrate, the substrate including a through hole having a diameter greater than the diameter of the cylindrical body and an internal circumferential ridge located adjacent the center of the hole; the cylindrical body located in the hole; the ridge engaging the cylindrical body with the portions of the body to either side of the ridge spaced from the substrate, each end of the body extending beyond the adjacent side of the substrate.

6. The combination as in claim 5 wherein each end of the body extends approximately 0.008 inches above the adjacent edge of the substrate.

7. The method of manufacturing a cylindrical contact for forming an electrical connection between pads on opposite sides of a substrate, comprising the steps of:

A) providing a thin, flat metal strip-stock preform having a plurality of elongate beams integral with the preform;

B) folding and collapsing the flat preform inwardly to form a generally cylindrical body; and

C) bending the flat beams in the preform to form a plurality of bowed springs at each end of the body with the metal in the body occupying less volume than the volume of the cylindrical body to permit elastic flexing of the springs when the contact is sandwiched between opposed contact pads.

8. The method of claim 7 including the step of:

E) wrinkling the strip-stocked preform before folding and collapsing the preform.