Patent Application
20050020146
The present invention generally relates to a surface mount contact configured to be carried in an electrical component, such as a socket. More particularly, the present invention relates to a surface mount contact which has multiple contact beams.
Contacts are used in a variety of applications to connect conductive members, such as processors, circuit boards and the like. In many applications, the contacts are held in a housing such as a socket. For example, a socket is generally used to connect a processor to a circuit board. The typical socket includes a body having cavities that carry several flexible contacts. A land grid array (LGA) socket holds the contacts that have a flexible body formed at one end with a contact beam and attached at an opposite end to a solder ball. The contact beam extends upward from the cavity above the top surface of the body of the socket, while the solder ball extends downward from the cavity below the bottom surface of the body. The cavities are arranged in an array and the contacts are oriented with all of the contact beams extend from the cavities in the same direction such that the contact beams in each row are aligned with one another. The solder balls attached to the contacts are soldered to electrical traces on the circuit board. The processor has several contact pads on its bottom surface and the processor is positioned on the socket such that each contact pad is aligned with a corresponding single contact beam. The processor is compressed downward onto the socket with each contact beam engaging a corresponding contact pad.
As technology advances, contacts are needed that can carry data signals at faster rates and that are more responsive to state transitions in the data signal. Sockets are also needed that are more reliable and can be manufactured at lower costs. The ability to improve these factors is affected by the socket size, as well as the internal electrical performance of the socket, such as the inductance and resistance exhibited by the contacts. A reduction in socket size allows smaller printed wiring boards to be used and creates shorter circuit paths which aid state transition response time.
Conventional sockets suffer from several drawbacks. The contacts are large and take up a large amount of space within the socket. The socket thus carries a limited number of contacts and has a limited capacity to transmit signals between the processor and the circuit board. Additionally, the contact beams are limited in size and length in order that the contact beams do not touch contact beams in the same or different rows when deflected by the processor. Short and/or small contact beams have a more limited range of vertical deflection that longer and/or larger contact beams. If the shorter, smaller contact beams are overly deflected, they become permanently deformed. Larger, longer contact beams may require too much force to be properly joined to the processor.
Further, each contact beam creates a local electromagnetic (EM) field when it carries data signals. As the contact beams are positioned closer and closer, the EM fields begin to interfere with the performance of adjacent contact beams. This interference appears as an increase in the inductance of the contacts. As inductance increases, the contacts in the socket respond more slowly to transitions in the voltage level of signals carried through the socket. Hence, while a data signal output from the processor to a contact may switch voltages (or states) in a few micro seconds, once the data signal passes through the corresponding contact in the socket, the data signal changes states over a longer period of time. It is desirable to limit the inductance exhibited by contacts to maintain the ability to quickly respond to state changes.
Moreover, as contacts are made smaller, electrical signals encounter more resistance when traveling through the contacts and thus the socket. High resistance causes the contacts to generate heat as electrical signals pass therethrough which can damage surrounding parts and shorten product life. Additionally, more energy is required to convey electrical signals through high resistance contacts which causes the electronic device to consume more energy.
A need exists for a socket and contact that addresses the above noted problems and others experienced heretofore.
An electrical socket is provided that holds an array of contacts. Each contact includes first and second contact elements that are configured to be joined in an electrically common manner. The first and second contact elements have first and second contact beams, respectively, that are oriented to project toward one another and are positioned adjacent one another. The first and second contact elements each have base portions that are formed separate from one another and are configured to be joined to a common conductive path on a circuit member.
Optionally, the first and second contact elements may each be formed with a pair of contact beams, where each pair of contact beams is formed with a corresponding base portion. The pairs of contact beams are oriented to face one another and to extend between one another in an overlapping manner without directly contacting one another. The contact beams are oriented to convey current along corresponding parallel first and second paths in a common plane. The first and second paths are associated with the first and second contact beams, respectively, and are directed in opposite directions within the common plane.
In accordance with at least one alternative embodiment, a contact formed in accordance with the manner described above is provided for use in a connector or other electrical device such as a socket.
The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, certain embodiments. It should be understood, however, that the present invention is not limited to the arrangements and instrumentality shown in the attached drawings.
The contact beams 34 of the contact element 10 extend toward the contact beams 38 of the contact element 14. The contact beams 34 and 38 of the contact elements 10 and 14 overlap, and are interleaved with, each other along a transverse axis 42. For example, one contact beam 34 of the contact element 10 is positioned between a pair of contact beams 38 of the contact element 14 and one contact beam 38 of the contact element 14 is positioned between a pair of contact beams 34 of the contact element 10.
The base portions 18 and 19 of the contact elements 10 and 14 are soldered to a common pad or electrically joined traces on a circuit board (not shown). A processor (which is then positioned on a socket containing the contact elements 10 and 14), has one or more electrically common contact pads on the bottom surface of the processor that engage the contact portions 50 of the contact elements 10 and 14. The weight of the processor pushes the contact beams 34 of the contact element 10 downward along arrow A, and the contact beams 38 of the contact element 14 downward along arrow B. The contact beams 34 and 38 of the contact elements 10 and 14 may be deflected downward, for example, until aligned in a common plane, as well as parallel with each other and with the longitudinal axis 54.
In operation, electrical current travels through the contact elements 10 and 14 between the circuit board and the processor. When signals are conveyed from the circuit board to the processor, the current flows in the direction of arrow C from the base portion 18 to the contact portions 50 of the contact beams 34. In the contact element 14, the current flows in the direction of arrows D from the base portion 19 to the contact portions 50 of the contact beams 38. As current travels through the contact elements 10 and 14, electromagnetic (EM) fields are created about the corresponding contact beams 34 and 38. However, because the contact beams 34 and 38 of the contact elements 10 and 14 are interleaved and overlap along the transverse axis 42 and face one another, adjacent contact beams 34 and 38 carry current in opposite directions.
As the current flows in opposite directions (e.g., see arrows C and D) in adjacent contact beams 34 and 38, adjacent EM fields are created of equal amplitude that rotate in opposite directions. By way of example only,
As noted above, multiple contact elements 10 and 14 are joined to one or more electrically common pads or traces on the circuit board at a plurality of solder ball paddles 22 and 23. Hence, all of the contact beams 34 and 38 in the contact 8 operate in parallel. This parallel operation enables each individual contact beam 34 and 38 to be small, while the contact beams 34 and 38 of a single contact 8 collectively operate to afford a low resistance connection between the processor and circuit board. Therefore, electrical signals encounter less resistance when traveling through the contact 8 and create less heat and require less energy.
Overlapping contact beams 34 and 38 in an interleaved manner increase the usable space within the socket and allow for more contacts 8 to be used in a socket because adjacent contact elements 10 and 14 within the socket are located in the same space without engaging each other. Therefore, larger and longer contact beams 34 and 38 may be used in each contact 8 without touching a neighboring contact beam 34 or 38. Thus, the contact beams 34 and 38 have a larger vertical deflection range to accommodate tolerance issues between the processor and the contacts 8.
The contact beams 70 and 71 are U-shaped with lower arms 59 and 61 joining the base portions 63 and 65, respectively. Upper arms 63 and 69 of each contact beam 70 and 71 join contact tips 73 and 75, respectively. The contact tips 73 and 75 are bent upward from the upper arms 63 and 69 of the contact beams 70 and 71 to engage contact pads, traces or pins on a processor. The upper arms 63 and 69 of the contact beams 70 and 71 extend upward at an acute angle from a longitudinal axis 77 of the contact 56. The contact tips 73 and 75 flex along arrows G and H, respectively.
The contact 56 of
The contact elements 70 and 71 are formed separate from one another, yet organized in an interleaved order and arranged facing one another. Once the prongs 66 and 67 are joined to a circuit board, all of the contact elements 70 and 71 in contact 56 are electrically common with one another. Arrows J and K denote the direction of current flow as electrical signals are passed from the circuit board to the processor. Current flows in opposite directions within adjacent contact elements 70 and 71, thereby creating adjacent EM fields which offset and cancel out one another.
Contact beams 96 and 98 extend from the support plates 94 and 95 in an overlapping and facing manner. The contact beams 96 and 98 are U-shaped with upper arms 81 and 85, lower arms 83 and 93. The upper arms 81 and 85 extend at an acute angle to the longitudinal axis 92. The upper arms 81 and 85 include contact tips 99. The upper arms 81 and 85 of the contact elements 82 and 84 flex along arrows L and M, respectively. The current flows in the direction of arrows N and P when signals are passed from the circuit board to the processor to form offsetting EM fields.
The contact beams 116 extend from the end wall 109 toward the opposite end wall 111 and the contact beams 118 extend from the end wall 111 toward the opposite end wall 109. The first contact beams 116 and 118 overlap each other along a transverse axis 120.
The embodiment of
Each end wall 152 and 154 has a curved arm formed with a thin center beam 156. The center beam 156 extends parallel to the longitudinal axis 170 between the end walls 152 and 154. The center beam 156 includes a slot 157 cut in the center thereof to form thin side walls on opposite sides of the slot 157. The center beam 156 includes center termination leads 158 extending perpendicularly from opposite sides of the center beam 156. The center termination leads 158 are formed with circular pads on outer ends thereof that carry solder balls (not shown). End termination leads 160 are provided on opposite ends of the center beam 156 proximate the end walls 152 and 154. The end termination leads 160 extend laterally from the center beam 156 at an acute angle, such as a generally 45 degree angle, to the longitudinal axis 170 and toward the nearest end wall 152 and 154. The end termination leads 160 also are formed with circular pads that carry the solder balls (not shown).
Optionally, the contacts need not be configured to be surface mounted to a circuit board. Instead, the contacts may be configured to be pressed into through-holes in a conductive member.
Optionally, the contacts may not be loaded into a socket, but instead may be held in a connector housing or mounted directly on a circuit board separate and apart from a socket or other connector housing.
While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
