Various embodiments of the present invention will be described with reference to the accompanying drawings. It is to be noted that the same or similar reference numerals are applied to the same or similar parts and elements throughout the drawings, and the description of the same or similar parts and elements will be omitted or simplified.
In the following descriptions, numerous specific details are set fourth such as specific signal values, etc. to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details.
As shown in
As shown in
A calculated value of inductance L′ of the contact 1 in the state where the spring 12 is not compressed to the length Y (for example, the not compressed state shown in
L′=L1+L2 (1)
Assuming that an average winding radius of the spring 12 is r, the effective winding number is N, a width of a coil (the spring 12) is W, magnetic permeability of air is μ0, and a Nagaoka coefficient is K with reference to
L1=(K·μ0·π·r2·N2)/W (2)
Meanwhile, assuming that a wire diameter of the arm 10 is d and a length of the arm 10 is 1 with reference to
L2=μ0·1/2·[log (4·1/d)−3/4] (3)
Here, when the average winding radius r of 2.5×10−4 m, the effective winding number N of 3.0, the width of a coil W of 6.4×10−4 m, the magnetic permeability of airμ0 of 1.3×10−6 Hm, and the Nagaoka coefficient K of 7.1×10−1 are assigned to the equation (2) as a specific example, the inductance L1 is calculated as 2.5 nH. Moreover, when the magnetic permeability of air μ0 of 1.3×10−6 Hm and the wire diameter d of 2.0×10−4 m are assigned to the equation (3) as the specific example, the inductance L2 is calculated as 0.34 nH. The inductances L1 and L2 figured out from the equations (2) and (3) are assigned to the equation (1), and the inductance L′ is calculated as 208 nH. In recent years, the inductance allowed as a specification of an IC socket is around 1.0 nH. Given that the inductance L1 of the spring 12 made of the torsion spring is equal to 2.5 nH by assigning the values in this specific example to the calculating formula, it is apparent that the inductance L1 of the spring 12 of the torsion spring becomes a problem.
Next, inductance L of the contact 1 in the case of compressing the spring 12 to meet the length Y as shown in
L=μ
0·1/2·[log (4·(1+2rπ·N/d)−3/4] (4)
Here, when the same values assigned for obtaining the above-described inductance L′, namely, the magnetic permeability of air μ0 of 1.3×10−6 Hm, the average winding radius r of 2.5×10−4 m, the Nagaoka coefficient K of 7.1×10−1, and the wire diameter d of 2.0×10−4 m are assigned to the equation (4) as a specific example, the inductance L is calculated as 0.43 nH. This value satisfies the inductance allowed as a specification of an IC socket in recent years. Such an effect of reducing the inductance only requires the condition that the coil portions of the spring 12 come into contact with each other and is therefore conductive in the shortest distance. In other words, this portion does not have to be fixed. Therefore, the contact 1 can work as the torsion spring from the mechanical perspective and can achieve required moment and strokes by adjusting the effective winding number, the length of the arms 10, the wire diameter, and the average winding radius.
As for the contact 1, it is possible to use a metal material such as a copper alloy or stainless steel, or a resilient nonmetal material such as rubber or synthetic resin for metal plating to obtain conductivity. The metal plating process may be copper (Cu) plating, nickel (Ni) plating, gold (Au) plating, or the like. Moreover, when Ni/Au plating formed by plating Au on a Ni-plated surface is used, it is possible to increase mechanical strength with the Ni plating and to enhance conductivity while reducing contact resistance with the Au plating.
When manufacturing the contact 1, the effect of the plating varies depending on the geometry of the contact 1. Here, effects of the plating that vary depending on the geometry of the contact 1 in the plating process will be described below.
In a first method, the plating process is executed when the contact 1 is still a wire rod. In short, this is the method of executing the plating process before forming the spring 12 into the spring shape. In this case, since the entire wire rod is plated, the coil portions of the spring 12 that come into contact with each other when compressing the spring 12 is plated in the state of the wire rod before forming the spring 12. This is advantageous in reduction of the inductance. However, as the plating process takes place in the form of the wire rod, cut surfaces after forming the contact 1 are not plated and an additional countermeasure is required.
In a second method, the plating process is executed after forming the spring 12 of the contact 1 and processing tip end shapes. Since the finished contact 1 is subjected to plating, the cut surfaces on the tip ends are also plated. However, since the plating process is executed after winding the wire rod to form the spring 12, it is difficult to plate efficiently on the coil portions of the spring 12 that come into contact with each other when compressing the spring 12. Therefore, it is necessary to find a way to secure uniform plating.
In a third method, the plating process is executed when the contact 1 is still a wire rod, then the spring 12 of the contact 1 is formed and another plating process is executed after processing the tip end shapes. According to this method, it is possible to achieve sufficient plating on the cut surfaces on the tip ends as well as the coil portions that come into contact with each other when compressing the spring 12, and thereby to ensure the performance. However, the additional plating process incurs additional works and costs.
A cross-sectional shape of the contact 1 is preferably formed into a circle or a rectangle. By forming the contact 1 having the circular or rectangular cross-sectional shape, it is easier to form the torsion spring.
As shown in
A typical method of inserting the contact 1 into the contact insertion hole 22 is to deform the contact 1 within an allowable range of elastic deformation and then to push the contact 1 into the contact insertion hole 22. Alternatively, there is another method to split the housing 20 vertically and to combine the spilt pieces of the housing 20 together after placing the contact 1 therebetween.
Next, a fitting operation of the IC socket according to the first embodiment of the present invention will be described with reference to
First, as shown in
Housing guides 26 are fitted onto the printed circuit board 30 of the mounted device shown in
The mounted device shown in
The IC socket according to the first embodiment shown in
As described above, according to the IC socket of the first embodiment, by using the torsion springs as the contacts, it is possible to adjust various parameters including the wire diameter, the average winding radius, the effective winding number, and the an arm length without causing deterioration in productivity. Consequently, it is easier to improve the design freedom and to meet required mechanical characteristics. Moreover, as the compressed spring 12 is inserted into the contact insertion hole 22, the coil portions of the spring 12 come into contact with each other and is electrically conductive in the shortest distance to achieve connection at low inductance. Accordingly, this IC socket can correspond to the demands for the IC package of more pins, a finer pitch, a larger current and higher speed. Further, the contacts 1 apply the structure that enables double-sided contact by means of the torsion springs. Thus, the IC socket is easily replaceable and has an excellent feature in maintenance which is essential for the server use. In addition, as the oxide films formed on the surfaces of the terminals and the like are removed by the wiping effect, it is possible to realize contacts between fresh metal surfaces and thereby to keep the contact resistance low.
As shown in
The housing lid 28 prevents the contacts 1 from dropping off the contact insertion holes 22. Moreover, the housing lid 28 prevents breakages of the springs 12 at the time of handling. Although the housing lid 28 is provided only on one surface of the housing 20 in
According to the IC socket of the second embodiment, it is possible to prevent the contacts 1 from dropping off and to prevent breakage of the springs 12 by providing the housing lid 28. Therefore, it is possible to improve durability and reliability of the IC socket.
Although the present invention has been described with reference to certain embodiments, it is to be understood that the description and drawings constituting part of this disclosure will not limit the scope of this invention. It is obvious to those skilled in the art that various alternative embodiments, examples, and technical applications are possible from the teachings of this disclosure.
The embodiment discloses that the tip ends of the arms 10 of the contact 1 have the wiping effect. The most important feature of the wiping effect is removal of the oxide films on the metal surfaces. In this context, it is possible to remove the oxide films more effectively when the tip end shape is sharper. However, the sharper tip end shape is more likely to damage the terminals on the printed circuit board 30 and the IC package 40. Moreover, the degree of removal of the oxide films also varies depending on the design of the degree of contact pressure between the arms 10 and the terminals. Here, it is possible to remove the oxide films more effectively when the contact pressure is higher. Therefore, the IC socket having low contact pressure should be equipped with the arms 10 having a sharper tip end shape. On the contrary, it is necessary to design the tip end shape so as not to cause excessive damage to the terminals in the case of the IC socket having high contact pressure.
Accordingly, it is preferable to design an appropriate tip end shape in order to avoid excessive damage to the terminals with the IC socket having the high contact pressure. For example, as shown in
Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.
Number | Date | Country | Kind |
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2006-199538 | Jul 2006 | JP | national |