Socket connector contact with helical resilient portion

[0001] 1. Field of the Invention

[0002] The present invention relates to an electrical contact, and more particularly to a high-density socket connector contact for electrical interconnection of an electrical interface such as a central processing unit (CPU) with another electrical interface such as a printed circuit board (PCB).

[0003] 2. Description of the Prior Art

[0004] Generally, an engaging portion of a socket connector contact is exposed to air prior to the socket connector being used. The engaging portion is easily oxidized, and a layer of oxidizing film forms and covers the engaging portion. This can decrease of the integrity of signal transmission through the contact. One way to resolve this problem, it is to use a contact which wipes the layer of oxidizing film off from the engaging portion when the contact is mated with a mating conductive member.

[0005] A commonly used wiping means is disclosed in FIG. 4. An LGA (land grid array) type socket connector contact 60 comprises a resilient cantilever 62 with a distal mating portion 64. During mating of the contact 60 with a mating conductive pad 80 of an IC package (not shown), the mating portion 64 wipes a bottom surface of the pad 80, thereby removing any oxidizing films that may have formed on the mating portion 64 and the bottom surface of the pad 80. Thus, unimpeded electrical engagement between the pad 80 and the contact 60 is provided.

[0006] The configuration of the cantilever 62 determines not only a horizontal wiping distance of the bottom surface of the pad 80 when the contact 60 mates with the pad 80, but also design parameters of the contact 60 such as mating force, wear and stress on the cantilever 62. In configuring the cantilever 62, all these factors need to be considered together. It is common for a good wiping configuration to be obtained only at the expense of one or more of the other factors. That is, it is very difficult to provide a cantilever 62 having an overall optimal configuration including good wiping characteristics. U.S. Pat. Nos. 5,139,427, 5,259,769, 5,378,160, 5,820,389 and 6,193,523 all disclose wiping means similar to those described above, and each of these patents manifest the problems of optimal configuring as described above.

[0007] Accordingly, a new electrical contact that overcomes the above disadvantages is desired.

[0008] An object of the present invention is to provide an electrical contact having good wiping characteristics and providing reliable electrical engagement.

[0009] Another object of the present invention is to provide an electrical contact which is easily and simply configured.

[0010] To achieve the above objects, the present invention applies an electrical contact comprising a resilient portion. The resilient portion comprises a helical body defining an axis. A mating portion extends slantingly upwardly from an upper end of the body. A mating surface is defined on a topmost portion of the mating portion, for electrically mating with a mating conductive member. When the contact mates with the mating conductive member, the mating surface of the mating portion wipes a bottom surface of the mating conductive member. This wiping action removes any oxidation films that may have formed and covered the mating surface of the mating portion and the bottom surface of the mating conductive member due to their exposure to air prior to use. Unimpeded engagement between the mating conductive member and the mating portion is assured. Furthermore, the body does not deflect relative to the axis thereof during mating. Rather, the body is compressed along the axis thereof. Due to the helical configuration of the body, it has good resilient characteristics. This helps ensure that sufficient normal force is provided for stable engagement between the mating surface of the mating portion and the bottom surface of the mating conductive member. Thus, wiping characteristics and contact force of the contact can be independently optimized respectively by configuring the mating portion and the body of the resilient portion. This makes design of the contact easy and simple.

[0011] Other objects, advantages and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

[0016] Reference will now be made to the drawings to describe the present invention in detail.

[0017] Referring to FIGS. 1 and 2, an electrical contact 10 according to the present invention is mainly applied for electrically interconnecting two electrical interfaces such as two PCBS. In the preferred embodiment, the contact 10 is used in an LGA-type socket connector (not labeled) that electrically interconnects a CPU 30 and a PCB 40. The socket connector comprises a housing 20 formed from plastic material such as liquid crystal polymer (LCP). A plurality of passages 22 is defined in the housing 20, arranged in columns and rows (not shown). A pair of recesses 24 is defined in the housing 20 at each passage 22, the recesses 24 being at opposite sides of and in communication with the passage 22.

[0018] The contact 10 is made by punching a preform from a sheet of metal plate, and then forming the particular shape shown in FIG. 1 by bending. The contact 10 comprises a plate-like retention portion 12. A pair of barbs 12a is formed on each of lateral sides of the retention portion 12, for interferentially engaging in a corresponding pair of recesses 24 of the housing 20.

[0019] A connecting portion 14 is bent from a lower end of the retention portion 12 so that it is perpendicular to the retention portion 12. The connecting portion 14 has a plate-like configuration for attaching to the PCB 40 via a soldering ball (not labeled). However, other suitable configurations may also be adopted.

[0020] A narrowed portion 18 is formed between the retention portion 12 and the connecting portion 14, to facilitate insertion of the barbs 12a of the retention portion 12 into the corresponding pair of recesses 24 of the housing 20.

[0021] A resilient portion 16 extends upwardly above a top end of the retention portion 12. The resilient portion 16 comprises a helical body 16a defining a central axis. After the perform of the contact 10 is punched, the body 16a is shaped by a bending process. A narrowed neck 16c formed on a bottom of the body 16a interconnects the body 16a with the top end of the retention portion 12. A mating portion 16b extends slantingly upwardly from a top of the body 16a. A mating face 160 is defined on a topmost part of the mating portion 16b, for mating with a corresponding contact pad 32 of the IC package 30.

[0022] Referring also to FIG. 3, in use of the socket connector, the contacts 10 are mated with corresponding pads 32 of the IC package 30. Each pad 32 presses against the mating portion 16b of a corresponding contact 10. The mating portion 16b elastically deflects downwardly at an angle relative to the axis of the body 16a. The mating surface 160 of the mating portion 16b wipes a bottom surface of the pad 32. This wiping action removes any oxidation films that may have formed and covered the mating surface 160 of the mating portion 16b and the bottom surface of the pad 32 due to their exposure to air prior to use. Unimpeded engagement between the bottom surface of the pad 32 and the mating surface 160 of the mating portion 16b is assured. Furthermore, due to the body 16a abuts an inner side wall of the passage 22, therefore the body 16a does not deflect relative to the axis thereof. As a result, a wiping distance of the mating surface 160 on the bottom surface of the pad 32 is determined only by the mating portion 16b and the extent of its deflection, and is not affected by movement of the body 16a.

[0023] Moreover, the body 16a is compressed along the axis thereof. Due to the helical configuration of the body 16a, it has good resilient characteristics. This helps ensure that sufficient normal force is provided for stable engagement between the mating surface 160 of the mating portion 16b and the bottom surface of the pad 32.

[0024] In summary, the two main features of the contact 10 of the present invention are wiping and good contact force. These features can be independently optimized respectively by configuring the mating portion 16b and the body 16a of the resilient portion 16 according to need. This makes design of the contact 10 easy and simple.

[0025] Although the present invention has been described with reference to a particular embodiment, it is not to be construed as being limited thereto. Various alterations and modifications can be made to the embodiment without in any way departing from the scope or spirit of the present invention as defined in the appended claims.