Socket for electrical parts

BACKGROUND OF THE INVENTION

0001The present invention relates to a socket for electrical parts for detachably holding an electrical part such as semiconductor device (called as "IC package" hereinlater).

0002In a known art, as "socket for electrical parts" in this kind, there is provided an IC socket for detachably holding an IC package as "electrical part" such as disclosed in <patcit id="pcit0001" dnum="JP6044050U"><text>Japanese Utility Model Publication No. HEI 6-44050</text></patcit>.

0003One known example of an IC socket of this kind is shown in <figref idref="f0040">Figs. 35A and 35B</figref>. The shown IC socket is provided with a contact pin 1 to which a pair of clamping pieces 1a are formed. The clamping pieces 1a are each formed with a contact portion 1b contacting to or separating from a connection pin P of an IC package, not shown, and also formed with a press portion 1c which is pressed by a cam portion 3a of a movable plate 3.

0004The cam portion 3a is inserted into a space between a pair of press portions 1c, and as shown in <figref idref="f0040">Fig. 35A</figref>, when the movable plate 3 is depressed, the paired press portions 1c are depressed and widened. Under this state, the connection pin P is inserted into the contact portions 1b through an insertion hole 4a formed to a cover 4.

0005Next, as shown in <figref idref="f0040">Fig. 35B</figref>, when the movable plate 3 is raised upward, the cam portion 3a is moved upward, and the connection pin P is clamped by and between the paired contact portions 1b thereby to establish an electrical connection therebetween.

0006According to the structure mentioned above, the IC package can be mounted or dismounted, without giving no specific insertion or withdrawal force, only by moving upward or downward the movable plate 3, thus improving a working efficiency.

0007However, in such structure of the conventional IC socket, a pair of contact portions 1b are depressed and widened by inserting the cam portion 3a between a pair of press portions 1c of each of the contact pins 1, and accordingly, it is necessary to insert the cam portion 3a into the paired press portions 1c at the time of arranging the contact pin 1 and the movable plate 3, which results in an adverse workability at an assembling time, and it is also disadvantageous to arrange the contact pins 1 with narrow pitch.

0008Furthermore, in the prior art mentioned above, the connection pin P of the IC package is held between the contact portions 1b of the paired clamping pieces 1a to achieve an electrical connection. However, because this clamping structure does not attain a wiping effect, it is difficult to realize a stable electrical contacting condition.

0009In the known art, there is also provided an IC socket of the kind mentioned above such as disclosed in <patcit id="pcit0002" dnum="JP3066787A"><text>Japanese Patent Publication No. HEI 3-66787</text></patcit> showing an IC package as "electrical part", in which a number of IC leads are formed so as to project downward from a lower surface of the IC package, and these IC leads are arranged in grid shape having vertical (Y-axis direction) and horizontal (X-axis direction) rows.

0010An IC socket, as "socket for electrical parts", achieving the electrical connection by holding such IC package has an outer rectangular peripheral portion formed of an insulation material and has a substrate on which a cover member is applied to be horizontally movable.

0011This cover member is formed with a number of IC lead insertion holes having an arrangement corresponding to the grid shaped IC lead arrangement so that the arrangement of the IC lead insertion holes provides a parallelogram shape, and the vertical rows (Y) and horizontal rows (X) of the IC leads are inclined at angles of 45° with respect to the respective side lines of the rectangular outer shape of the cover member. Furthermore, the substrate of the IC socket is formed with a number of contact members having an arrangement corresponding to the arrangements of the IC leads and the IC lead insertion holes.

0012In such structure, when the cover member is moved in one diagonal direction of the IC lead grid arrangement, the IC package mounted to the cover member is also moved and, hence, the IC leads are separated from or contacted to the contact members.

0013However, in such conventional structure, in order to ensure displacement or shift amount of the contact member with respect to the IC lead, the arrangement of the IC lead insertion holes is inclined at angles of 45° with respect to the rectangular outer shape of the cover member. Accordingly, the cover member, and hence, an entire structure of the IC socket device has been made large, thus being disadvantageous and providing a problem.

0014<patcit id="pcit0003" dnum="GB2286490A"><text>GB 2 286 490 A</text></patcit> discloses a contact for an electrical part having terminals which are moved transversely to bring them into contact with contact pins which comprise a first arm which is longer than a second arm, both arms being curved in such a way that the contact-making ends face one another. The arms have surfaces to guide the terminals into the socket, wherein electrical contact is made to the terminal on two sides.

SUMMARY OF THE INVENTION

0015A primary object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a socket for electrical parts having a structure capable of improving a assembling workability of structural elements or members and being advantageous for narrow pitch arrangement of contact pins.

0016Another object of the present invention is to provide a socket for electrical parts capable of achieving an improved wiping effect at a time of contacting a contact pin to a terminal and achieving an improved contacting stability.

0017A further object of the present invention is to provide a socket for electrical parts capable of making compact an entire structure thereof while ensuring a displacement amount of contact pins.

0018These and other objects can be achieved according to the present invention by providing a socket for an electrical part comprising: <ul id="ul0001" list-style="none" compact="compact"><li>a socket body having a mount portion on which an electrical part having terminals is mounted; and</li><li>a number of contact pins capable of being contacted to or separated from the terminals of the electrical part,</li></ul> wherein each of the contact pins has an elastic piece having, at a front end portion thereof, with a contact portion which is contacted to or separated from each of the terminals of the electrical part and wherein an axis passing a root portion of the elastic piece and an axis passing the contact portion are offset from each other so that the contact portion slides on a surface of the terminal after contacting thereto by an elastic force of the elastic piece.

0019The contact portion of the contact pin has a flat contact surface contacting to the terminal, the flat contact surface has predetermined angles with respect to a direction normal to a contacting or separating direction of the contact portion.

0020In a preferred embodiment each of the contact pins has a pair of elastic pieces having, at front end portions thereof, with contact portions which are contacted to or separated from each of the terminals of the electrical part and wherein an axis passing a root portion of at least one of the elastic pieces and an axis passing the contact portion thereof are offset from each other so that the contact portions slide on a surface of the terminal after contacting thereto by an elastic force of the elastic pieces.

0021In this embodiment, each of the contact portions of the contact pin has a flat contact surface contacting to the terminal, and the flat contact surface has predetermined angles with respect to a direction normal to a contacting or separating direction of the contact portion.

0022In a preferred embodiment there is provided a socket for an electrical part further comprising: <ul id="ul0002" list-style="none" compact="compact"><li>a movable plate disposed to the socket body to be movable perpendicularly with respect to the mount portion in a usable state of the socket,</li></ul> wherein each of the contact pins has a pair of elastic pieces formed at front end portions thereof with contact portions which are opened or closed in accordance with the movement of the movable plate thereby to establish an electrical connection between the contact portions and the terminals of the electrical part when the contact portions are closed, the movable plate is provided with cam portions each arranged between adjacent contact pins, respectively, and when the movable plate is moved, the elastic pieces are pressed by a pair of cam portions disposed on both the sides of each of the contact pins thereby to open the contact portions, and wherein an axis passing a root portion of at least one of the elastic pieces and an axis passing the contact portion thereof are offset from each other so that the contact portions slide on a surface of the terminal after contacting thereto by an elastic force of the elastic pieces.

0023According to these above aspects, the contact portions of the contact pin are formed with flat surface portions contacting the terminal, which has a predetermined angles with respect to the direction normal to the direction contacting to or separating from the terminal, thus achieving move improved wiping effect.

0024Furthermore, in the arrangement in which the axis passing the root portion of the elastic piece and the axis passing the contact portion are offset from each other, the contact portions further slide after contacting to the terminal by the elastic force of the elastic piece, so that the further improved wiping effect can be achieved with small change of structure, and the electrically stable contacting condition can be further improved.

0025Further, the nature and characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings, not all of which represent but relate to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

0026In the accompanying drawings: <ul id="ul0003" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> is a plan view of an IC socket according to a first embodiment;</li><li><figref idref="f0002">Fig. 2</figref> is a sectional view taken along the line II-II in <figref idref="f0001">Fig. 1</figref>;</li><li><figref idref="f0003">Fig. 3</figref> is a sectional view taken along the line III-III in <figref idref="f0001">Fig. 1</figref>;</li><li><figref idref="f0004">Fig. 4</figref> is a bottom view of an IC package for the IC socket of <figref idref="f0001">Fig. 1</figref>;</li><li><figref idref="f0005">Fig. 5</figref> is a perspective view of a contact pin, in an enlarged scale, in the first embodiment;</li><li><figref idref="f0006">Fig. 6</figref> is a sectional view showing a state that an operation member in the first embodiment is lowered;</li><li><figref idref="f0007 f0008">Fig. 7</figref> includes sectional views showing a function of the first embodiment, in which <figref idref="f0007">Fig. 7A</figref> shows a state that a pair of contact portions of the contact pin are closed, <figref idref="f0007">Fig. 7B</figref> shows a state that a pair of contact portions of the contact pin are opened, and <figref idref="f0008">Fig. 7C</figref> shows a state that a solder ball is clamped between the paired contact portions of the contact pin;</li><li><figref idref="f0008 f0009">Fig. 8</figref> includes plan views of the paired contact portions of the contact pin for showing a function of the first embodiment, in which <figref idref="f0008">Fig. 8A</figref> shows a state that a pair of contact portions of the contact pin are closed, <figref idref="f0009">Fig. 8B</figref> shows a state that a pair of contact portions of the contact pin are opened, and <figref idref="f0009">Fig. 8C</figref> shows a state that a solder ball is clamped between the paired contact portions of the contact pin;</li><li><figref idref="f0009 f0010">Fig. 9</figref> includes sectional views of a latch in the first embodiment for showing movement thereof, in which <figref idref="f0009">Fig. 9A</figref> shows a state that the operation member is positioned to a raised position and <figref idref="f0010">Fig. 9B</figref> shows a state that the operation member is positioned to a lowered position;</li><li><figref idref="f0010">Fig. 10</figref> is a perspective view of an upper portion of a contact pin according to a second embodiment;</li><li><figref idref="f0011">Fig. 11</figref> includes plan views of the paired contact portions of the contact pin for showing a function of the second embodiment, in which <figref idref="f0011">Fig. 11A</figref> shows a state that a pair of contact portions of the contact pin are closed, <figref idref="f0011">Fig. 11B </figref>shows a state that a pair of contact portions of the contact pin are opened, and <figref idref="f0011">Fig. 11c</figref> shows a state that a solder ball is clamped between the paired contact portions of the contact pin;</li><li><figref idref="f0012 f0013">Fig. 12</figref> shows a contact pin representing a third embodiment, in which <figref idref="f0012">Fig. 12A</figref> is a front view thereof and <figref idref="f0013">Fig. 12B</figref> is a right-side view thereof;</li><li><figref idref="f0014">Fig. 13</figref> is a perspective view showing an upper portion of the contact pin of the third embodiment;</li><li><figref idref="f0014 f0015">Fig. 14</figref> includes plan views of the paired contact portions of the contact pin for showing a function of the third embodiment, in which <figref idref="f0014">Fig. 14A</figref> shows a state that a pair of contact portions of the contact pin are closed, <figref idref="f0014">Fig. 14B</figref> shows a state that a pair of contact portions of the contact pin are opened, and <figref idref="f0015">Fig. 14C</figref> shows a state that a solder ball is clamped between the paired contact portions of the contact pin;</li><li><figref idref="f0015 f0016">Fig. 15</figref> represents a contact pin according to a fourth embodiment showing a state that a solder ball is clamped by a pair of contact portions of the contact pin, in which <figref idref="f0015">Figs. 15A, 15B</figref> and <figref idref="f0016">15C</figref> show contact pins having different contact portions, respectively;</li><li><figref idref="f0017 f0018">Fig. 16</figref> shows a contact pin representing a fifth embodiment, in which <figref idref="f0017">Fig. 16A</figref> is a front view thereof and <figref idref="f0018">Fig. 16B</figref> is a perspective view thereof;</li><li><figref idref="f0019">Fig. 17</figref> is a plan view showing an IC socket according to a sixth embodiment;</li><li><figref idref="f0020 f0021 f0022">Fig. 18</figref> shows a contact pin representing a seventh embodiment, according to the present invention, in which <figref idref="f0020">Fig. 18A</figref> is a front view thereof, <figref idref="f0021">Fig. 18B</figref> is a left-side view of <figref idref="f0020">Fig. 18A</figref>, <figref idref="f0022">Fig. 18C</figref> is a plan view thereof, and <figref idref="f0022">Fig. 18D</figref> is a sectional view taken along the line XVIIID-XVIIID in <figref idref="f0020">Fig. 18A</figref>;</li><li><figref idref="f0023">Fig. 19</figref> is a perspective view showing the contact pin of the seventh embodiment which holds a solder ball;</li><li><figref idref="f0024">Fig. 20</figref> is a front view, according to the seventh embodiment, showing a state of the solder ball and an elastic piece of the contact pin viewed from the side thereof;</li><li><figref idref="f0024">Fig. 21</figref> is a plan view, according to the seventh embodiment, showing a state of the solder ball and an elastic piece of the contact pin viewed from the upper side thereof;</li><li><figref idref="f0025 f0026">Fig. 22</figref> includes sectional views according to the seventh embodiment, in which <figref idref="f0025">Fig. 22A</figref> shows a state that a pair of contact portions of the contact pin are closed, <figref idref="f0025">Fig. 22B</figref> shows a state that a pair of contact portions of the contact pin are opened, and <figref idref="f0026">Fig. 22C</figref> shows a state that the solder ball is held between the paired contact portions of the contact pin;</li><li><figref idref="f0027">Fig. 23</figref> is a front view of a contact pin according to an eighth embodiment, according to the present invention;</li><li><figref idref="f0028">Fig. 24</figref> is a left side view of <figref idref="f0027">Fig. 23</figref>;</li><li><figref idref="f0029">Fig. 25</figref> is a sectional view taken along the line XXV-XXV of <figref idref="f0027">Fig. 23</figref>;</li><li><figref idref="f0029">Fig. 26</figref> is a plan view of <figref idref="f0027">Fig. 23</figref>;</li><li><figref idref="f0030">Fig. 27</figref> is a front view of a contact pin according to a ninth embodiment;</li><li><figref idref="f0031">Fig. 28</figref> is a sectional view taken along the line XXVIII-XXVIII of <figref idref="f0030">Fig. 27</figref>;</li><li><figref idref="f0031">Fig. 29</figref> is a plan view of an IC socket according to a tenth embodiment;</li><li><figref idref="f0032">Fig. 30</figref> is a sectional view taken along the line XXX-XXX of <figref idref="f0031">Fig. 29</figref>;</li><li><figref idref="f0033 f0034">Fig. 31</figref> is a sectional view taken along the line XXXI-XXXI of <figref idref="f0031">Fig. 29</figref>;</li><li><figref idref="f0035 f0036">Fig. 32</figref> shows the contact pin of the tenth embodiment with the contact portions being closed, in which <figref idref="f0035">Fig. 32A</figref> is a sectional view showing contact pin arrangement and <figref idref="f0036">Fig. 32B</figref> is a view showing an essential portion of <figref idref="f0035">Fig. 32A</figref> in an enlarged scale;</li><li><figref idref="f0037 f0038">Fig. 33</figref> shows the contact pin of the tenth embodiment with the contact portions being opened, in which <figref idref="f0037">Fig. 33A</figref> is a sectional view showing contact pin arrangement and <figref idref="f0038">Fig. 33B</figref> is a view showing an essential portion of <figref idref="f0037">Fig. 33A</figref> in an enlarged scale;</li><li><figref idref="f0038 f0039">Fig. 34</figref> includes enlarged views showing a portion A in <figref idref="f0031">Fig. 29</figref>, in which <figref idref="f0038">Fig. 34A</figref> shows a closed state of the contact portions of the contact pin and <figref idref="f0039">Fig. 34B</figref> shows an opened state of the contact portions of the contact pin; and</li><li><figref idref="f0040">Fig. 35</figref> represents a conventional example, in which <figref idref="f0040">Fig. 35A</figref> shows an opened state of contact portions of a contact pin and <figref idref="f0040">Fig. 35B</figref> shows a sectional view showing a connection pin clamped by the contact portions of the contact pin.</li></ul>

DESCRIPTION OF THE PREFERRED EMBODIMENTS

0027Various preferred embodiments will be described hereunder with reference to the accompanying drawings.

[First Embodiment]

0028The first embodiment is first mentioned hereunder with reference to <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010">Figs. 1 to 9</figref>.

0029An IC socket as "socket for electrical parts" is generally shown by a reference numeral 11, and the IC socket 11 is for a socket for achieving an electrical connection between a printed circuit board, not shown, of a tester, for example, and a solder ball 12b as a terminal of an IC package 12 as "electrical part" for carrying out a performance test thereof.

0030The IC package 12 has a structure of so-called a BGA (Ball Grid Array) type as shown in <figref idref="f0004">Fig. 4</figref>, in which a number of substantially spherical solder balls 12b project from a lower surface of a package body 12a having, for example, a rectangular structure so as to provide a matrix arrangement.

0031The IC socket 11 has a socket body 13 which is mounted on the printed circuit board and to which a number of contact pins 15 contacting to or separating from the solder balls 12b are arranged. A movable plate for displacing the contact pins 15 is also arranged to the socket body 13, and an upper plate 19 is secured to the socket body 13 on the upper side of the movable plate 17. The movable plate 17 is moved up and down by an operation member 21 also arranged to the socket body 13.

0032Each of the contact pins 15 is formed from a plate member having an elastic property and a conductivity through a press working in shape such as shown in <figref idref="f0005">Fig. 5</figref>.

0033That is, more in detail, an upper half of the contact pin 15 is formed into a fork shape having a pair of elastic pieces 15a and a lower half thereof is formed as a solder tail portion 15b. The elastic pieces 15a are integrated at lower end portions thereof as a common U-shaped base portion 15c so as to oppose to each other, and upper end (front end) portions of the elastic pieces 15a are formed with contact portions 15d contacting to or separating from side portions of the solder ball 12b to be capable of holding the solder ball 12b between the contact portions 15d. The contact portions 15d take a positional relationship shown in <figref idref="f0008 f0009">Fig. 8</figref> in which the contact portions 15d are displaced from the diametral line of the spherical solder ball 12b.

0034Furthermore, the paired elastic pieces 15a are formed with (-shaped bent portions 15e so as to cross each other as shown in <figref idref="f0005">Fig. 5</figref>, for example. These bent portions 15e are pressed by a cam portion 17a, mentioned herein later, thereby to open the contact portions 15d.

0035The solder tail portion 15b and the base portion 15c of the contact pin 15 are fitted, under pressure, into a press-in hole 13a formed to the socket body 13a so that a biting portion 15f formed to the base portion 15c bites the socket body 13 thereby to prevent the contact pin 15 from coming out in an upward direction. The solder tail portion 15b projecting downward from the socket body 13, when fitted, further extends downward through a location board 26 and is fitted into a through hole formed to the printed circuit board, not shown. The fitted end portion of the solder tail portion 15b is thereafter soldered to the printed circuit board to be connected thereto.

0036The movable plate 17 is, as best shown in <figref idref="f0003">Fig. 3</figref>, arranged to the socket body 13 to be vertically movable and urged upward by means of spring 22. A pair of arms 23, one of which is not illustrated, are also located so as to move upward the movable plate 17. The arm 23 is mounted to the socket body 13 to be pivotal by means of a shaft pin 24 and also mounted to the movable plate 17 to be pivotal by means of a shaft pin 25, and the upper end portion 23a of the arm 23 contacts a cam surface 21a of the operation member 21 to be slidable. According to the structure mentioned above, when the operation member 21 is lowered, the upper end portion 23a of the arm 23 is pressed by the cam surface 21a, and hence, the arm 23 itself is rotated about the shaft pin 24 in a counterclockwise direction in <figref idref="f0003">Fig. 3</figref>, thus moving downward the movable plate 17.

0037Then, with reference to <figref idref="f0007 f0008">Figs. 7A to 7C</figref>, the movable plate 17 is formed with cam portions 17a, each being positioned between adjacent contact pins 15, and on both sides of the cam portion 17a, slide portions 17b are formed so as to press the bend portions 15e of the elastic pieces 15a of the adjacent contact pins 15. That is, one cam portion 17b can press the bent portions 15e of the elastic pieces 15a of the contact pins 15 positioned on both the sides of the cam portion 17b. Therefore, both the contact portions 15d of the contact pins 15 can be opened from each other by pressing these bent portions 15e in a direction approaching each other by a pair of cam portions 17a disposed on both the sides of the contact pin 15.

0038The upper plate 19 mentioned hereinbefore has a mount surface portion 19a on which the IC package 12 is mounted and also has guide portions 19b, as shown in <figref idref="f0001">Fig. 1</figref>, at four corner portions of the upper plate 19, corresponding to four corner portions of the IC package 12, for positioning the IC package 12 at a predetermined position. The upper plate 19 is further formed with positioning ribs 19c which are to be inserted between the paired contact portions 15d of the respective contact pins 15, and under a condition that any external force is not applied to both the elastic pieces 15a of the contact pin 15 (i.e. a condition that both the contact portions 15d are closed), each of the positioning ribs 19c is clamped by both the elastic pieces 15a.

0039Furthermore, the operation member 21 has an opening 21b, as shown in <figref idref="f0001">Fig. 1</figref>, for example, having a size capable of the IC package 12 being inserted thereinto, and when the IC package 12 is inserted into the opening 21b and then mounted to the predetermined position of the mount surface portion 19b of the upper plate 19. Further, as shown in <figref idref="f0003">Fig. 3</figref>, the operation member 21 is arranged to be movable vertically with respect to the socket body 13 and urged upward by means of the spring 27. The operation member 21 is further formed with an engaging claw piece 21d, which is engaged with an engagement portion of the socket body 13 at the uppermost moved position of the operation member 21 thereby to prevent the operation member from coming off.

0040The operation member 21 is further formed with a cam surface 21a for rotating the arm 23 and an operating portion 21c rotating the latch 28 as shown in <figref idref="f0002">Fig. 2</figref>, for example. The latch 28 is secured to the socket body 13 to be rotatable about a shaft pin 28a and urged by means of a spring 29 in a counterclockwise direction in <figref idref="f0002">Fig. 2</figref> so that a press holding portion 28b formed to the front end portion of the latch 28 holds a peripheral portion of the IC package 12. The latch 28 is formed with a depressed portion 28c on which the operating portion 21c of the operation member 21 slides, and when the operation member 21 is lowered, the depressed portion 28c slides on the operating portion 21c and the latch 28 is thereby rotated in a clockwise direction as shown in <figref idref="f0010">Fig. 9B</figref> so that the press holding portion 28b is retired from the IC package arranging position.

0041The first embodiment of the structures mentioned above will operate in the following manner.

0042When the IC package 12 is set to the IC socket 11, the operation member 11 is first depressed downward, and at this time, the arms 23 are rotated by the cam surfaces 21a of the operation member 21 in the counterclockwise direction as shown in <figref idref="f0006">Fig. 6</figref> and the movable plate 17 is hence lowered. When the movable plate 17 is lowered, the cam portions 17a thereof are also lowered as shown in <figref idref="f0007">Figs. 7A and 7B</figref>, and owing to the operation of the sliding surfaces 17b of the cam portions 17a, the bent portions 15e of the contact pins 15 are pressed and the paired contact portions 15d are opened as shown in <figref idref="f0007">Fig. 7B</figref>.

0043At the same time, the depressed portion 28c of the latch 28 is depressed by the operating portion 21c of the operation member 21 and then rotated in the clockwise direction against the urging force of the spring 29 from the state shown in <figref idref="f0009">Fig. 9A</figref> to the state shown in <figref idref="f0010">Fig. 9B</figref> and the depressed portion 28b is displaced to the retired position.

0044Under the state mentioned above, the IC package 12 is mounted to the predetermined position of the mount surface portion 19a of the upper plate 19 while being guided by the guide portions 19b, and the respective solder balls 12b of the IC package 12 are inserted into the opened paired contact portions 15d of the respective contact pins 15 under no-contacting condition.

0045Thereafter, when the downward pressing force applied to the operation member 21 is released, the operation member 21 is moved upward by means of the urging force of the spring 27 and the movable plate 17 is hence moved upward by means of the spring 22, whereby the latch 28 can be rotated in the counterclockwise direction in <figref idref="f0009 f0010">Fig. 9</figref> by the urging force of the spring 29.

0046When the movable plate 17 is rotated, the pressing force to the bent portions 15e of the contact pins 15 by the cam portions 17a is released and the paired contact portions 15d of the contact pins 15 are moved in a direction to close the same (i.e. make narrow the distance therebetween) thereby to clamp the solder balls 12b therebetween as shown in <figref idref="f0008">Fig. 7C</figref>.

0047According to the operation mentioned above, the electrical connection between the solder balls 12b of the IC package 12 and the printed circuit board can be established.

0048On the other hand, when it is required to remove the IC package 12 from its mounted condition, the operation member 21 is also moved downward thereby to separate the paired contact portions 15d of the contact pins 15 from the solder balls 12b. According to such operation, the IC package 12 can be easily removed with a force weaker than a pulling force for withdrawing the solder ball 12b from the paired contact portions 15d.

0049With the structure and operation mentioned above, since the cam portion 17a of the movable plate 17 for opening or closing the paired contact portions 15d of the contact pin 15 is not inserted into a space between both the contact portions 15d and is disposed between the adjacent contact pins 15, it is not necessary to insert the cam portion 17a between the closed contact portions 15d at the time of arranging the movable plate 17, so that the assembling workability of the IC socket can be remarkably improved.

0050Furthermore, since the paired elastic pieces 15a of one contact pin 15 cross each other, in a case where a distance L1 between one elastic piece 15a of one contact pin 15 and one elastic piece 15a of adjacent one contact pin 15 as shown in <figref idref="f0007">Fig. 7A</figref> is ensured, a distance L2 between the other one elastic piece 15e of one contact pin 15 and the other one elastic piece 15e of the adjacent other one contact pin 15 can be neglected, thus the respective contact pins 15 being arranged with narrow pitch.

0051Furthermore, the contact pin 15 has the (-shaped bent portions 15e and has substantially the same width along the entire length thereof without making a portion of the elastic piece 15a large, so that a stress is not concentrated at one point of the contact pin 15 and dispersed substantially entirely, thus the flexibility of the elastic pieces being improved.

0052Still furthermore, according to the structure of the first embodiment, since the elastic pieces 15a of both the adjacent two contact pins 15 are pressed and flexed by the one cam portion 17a of the movable plate 17, the entire structure of the IC socket can be made compact.

0053Still furthermore, since the contact pin 15 has a structure such that the base portion 15c of the contact pin 15 is bent to provide substantially U-shape to oppose a pair of elastic pieces 15a to each other, the contact pin 15 can be manufactured from one sheet of plate member through a press working. Moreover, since the positioning ribs 19c are formed to the upper plate 19, the exact arrangement or positioning can be achieved by preliminarily applying a small load to the contact portions 15d of the contact pins 15.

[Second Embodiment]

0054<figref idref="f0010">Figs. 10</figref> and <figref idref="f0011">11</figref> represent the second embodiment, and this second embodiment differs from the first embodiment in the structure of the contact portions 15d of the contact pin 15.

0055That is, with reference to <figref idref="f0010">Figs. 10</figref> and <figref idref="f0011">11</figref>, the width H between the contact portions 15d of the contact pin 15 of the second embodiment is made widen in comparison with the first embodiment, and the contact portions 15d are opposed to each other on both the sides of the solder ball 12b above the diametral line P thereof so that contacting surfaces of the contact portions 15d are perpendicular to the diametral line P.

0056According to the structure of the contact pin 15 mentioned above, the edge portions of the contact portions 15d never contact the solder ball 12b as shown in <figref idref="f0008 f0009">Fig. 8</figref>, so that the solder ball 12b can be prevented from being damaged through such contacting.

0057As the other structures are substantially the same as those in the first embodiment mentioned above, the details thereof are omitted herein.

[Third Embodiment]

0058<figref idref="f0013 f0014 f0015">Figs. 12 to 14</figref> represent the third embodiment, in which the contact pin 15 has a pair of contact portions 15d which are bent towards each other as shown in <figref idref="f0014">Fig. 13</figref> and opposed to each other on both the sides of the solder ball 12b as shown in <figref idref="f0014 f0015">Fig. 14</figref>. The contact portions 15d are positioned on the diametral line P of the solder ball 12b and the contacting surfaces of the contact portions 15d are positioned to be perpendicular to the diametral line P.

0059According to the structure of the third embodiment mentioned above, the edge portions of the contact portions 15d never contact the solder ball 12b as shown in <figref idref="f0015">Fig. 14C</figref>, so that the solder ball 12b can be prevented from being damaged through such contacting.

0060In the structure of the contact pin 15 of this embodiment, as shown in <figref idref="f0012 f0013">Fig. 12</figref>, the solder tail portion 15b is bent at a portion 15g near the base portion 15c of the elastic pieces 15a so that the center line O1 of the paired elastic pieces 15a accords with the center line O2 of the solder tail portion 15b. Further, it is to be noted that, in the structures of the first and second embodiments mentioned above, the contact pins 15 are formed so that both the center lines O1 and O2 are coincident with each other.

0061The arrangement of the coincidence of these center lines O1 and O2 can facilitate the setting of the IC package 12 to a plurality of IC sockets 11 mounted on the printed circuit board by conveying the IC package by an automatic machine, for example.

0062That is, the coincidence of both the center lines O1 and O2 means the coincidence of positional arrangement of the solder balls 12b with positional arrangement of the through holes formed to the printed circuit board as viewed in plane. Accordingly, in a setting such that the IC package 12 is conveyed by the automatic machine with an optional position of the printed circuit board being the reference, the IC package can be set to the predetermined positions of the IC sockets 11 with high accuracy only by grasping the positional relationship between the reference position of the printed circuit board and the through holes formed thereto without paying any attention to the positional relationship between the printed circuit board and the IC sockets 11.

0063The above merit may not be a so significant matter as far as the structure of a straight contact pin 15 is adopted. However, the contact pin 15 has the base portion 15c bent so that a pair of elastic pieces 15a are opposed to each other and the solder tail portion 15b extends downward therefrom, and accordingly, the center lines O1 and O2 cannot be made coincident with each other only by extending downward the solder tail portion 15b. In order to obviate such fact, as mentioned above, the portion 15g near the base portion 15c is bent to achieve the coincidence of both the center lines O1 and O2. Hence, according to such structure, the advantageous effects mentioned above is obtainable.

0064The other structures of this embodiment are substantially the same as those mentioned with reference to the first embodiment, so that the details thereof are omitted herein.

[Fourth Embodiment]

0065<figref idref="f0015 f0016">Fig. 15</figref> represents the fourth embodiment, in which <figref idref="f0015">Figs. 15A, 15B</figref> and <figref idref="f0016">15C</figref> show modified embodiments of the first, second and third embodiments mentioned hereinbefore, respectively, wherein a pair of contact portions 15d have contacting surfaces contacting the spherical solder ball 12b which are inclined with respect to displaced or biased directions N1 of the contact portions 15d as shown by arrows in the respective figures.

0066According to such arrangements, the contact portions 15d slide on the surface of the solder ball 12b when the paired contact portions 15d clamp the solder ball 12b and an oxide film on the surface of the solder ball 12b is broken thereby to establish a stable electrical contact.

0067The other structures of this embodiment are substantially the same as those mentioned with reference to the first embodiment, so that the details thereof are omitted herein.

[Fifth Embodiment]

0068<figref idref="f0017 f0018">Fig. 16</figref> represents the fifth embodiment, in which a contact pin 35 of this embodiment differs from the contact pin 15 of the first embodiment.

0069The contact pin 35 has a pair of elastic pieces 35a and a solder tail portion 35b formed below the elastic pieces 35a, and the lower portions thereof are formed as a bent base portion 35c in U-shape so that the paired elastic pieces 35a are opposed to each other. The front, i.e. upper as viewed, end portions are formed as contact portions 35d contacting the solder ball 12b. Projecting pieces 35e projecting towards each other are formed to the elastic pieces at portions below the contact portions 35d by cutting portions of the elastic pieces 35a and raising the cut portions so as to extend obliquely downward. These projecting pieces 35e are formed so as to open both the contact portions 35d when pressed by the cam portion 17a of the movable member 17 as mentioned with reference to the first embodiment.

0070The other structures of this embodiment are substantially the same as those mentioned with reference to the first embodiment, so that the details thereof are omitted herein.

[Sixth Embodiment]

0071<figref idref="f0019">Fig. 17</figref> represents the sixth embodiment, in which a number of contact pins 15 are arranged in matrix shape in a manner that the displaced direction N1 of the paired contact portions 15d of the respective contact pins 15 are arranged at predetermined angle (45° in this embodiment) with respect to the arrangement direction N2 of the contact pins 15.

0072According to such arrangement, the contact pins 15 can be arranged with narrow pitch. That is, the contact portions 15d are opened or closed along their displaced direction N1, and accordingly, it is necessary to ensure a space for allowing the contact portions to be opened or closed in the direction N1. Therefore, the narrow pitch of the contact pin 15 can be ensured by changing the direction of the contact portions 15d with certain constant angles with respect to the arrangement direction N2 of the contact pins 15.

0073The other structures of this embodiment are substantially the same as those mentioned with reference to the first embodiment, so that the details thereof are omitted herein.

[Seventh Embodiment]

0074<figref idref="f0022 f0023 f0024 f0025 f0026">Figs. 18 to 22</figref> represent the seventh embodiment, according to the present invention, in which a contact pin 16 has a structure different from the contact pin 15 of the first embodiment.

0075That is, in this seventh embodiment, the contact pin 16 has a pair of elastic pieces 16a and 16b to an upper portion thereof and one solder tail portion 16c formed at the lower portion of the contact pin 16. The lower portions of the elastic pieces 16a and 16b are formed as a bent base portion 16d in U-shape so that the paired elastic pieces 35a are opposed to each other as shown in <figref idref="f0020 f0021 f0022">Fig. 18</figref>.

0076Contact portions 16e and 16f are formed to the upper, as viewed, i.e. front, end portions of the elastic pieces 16a and 16b so as to be contacted to or separated from the side portions of the spherical solder ball 12b as shown in <figref idref="f0023">Fig. 19</figref> thereby to clamp the solder ball 12b to establish the electrical connection. The contact portions 16e and 16f are positioned substantially on the diametral line of the spherical solder ball 12b.

0077The elastic pieces 16a and 16b of the contact pin 16 are formed with portions 16g bent in (-shape, which are pressed by the cam portions 17a of the movable plate 17 thereby to open the contact portions 16e and 16f as in the first embodiment.

0078Furthermore, one 16b of the paired elastic pieces 16a and 16b of the contact pin 16 is formed with a crank portion 16j at a portion above the bent portion 16g so that an axis O1 passing a root portion 16k of one elastic piece 16b and an axis O2 passing the contact portion 16f are offset from each other as shown in <figref idref="f0021">Fig. 18B</figref>, for example.

0079When the solder tail portion 16c and the base portion 16d of the contact pin 16 are press fitted into the press-in hole 13a formed to the socket body 13, a come-off preventing portion 16m formed to the base portion 16d bites the socket body 13 thereby to prevent the contact pin 16 from coming off upward. Of course, a number of such press-in holes 13a are formed to the socket body 13 so as to correspond to a number of contact pins 16. The solder tail portions 16c projecting downward from the socket body 13 further extend downward through a location board 26 and are then inserted into the through holes formed to the printed circuit board and soldered thereto, thus being connected.

0080Furthermore, as shown in <figref idref="f0025 f0026">Fig. 22</figref>, the upper plate 19 has the mount surface portion 19a on which the IC package 12 is mounted and is formed with positioning ribs 19c each being inserted between the paired contact portions 16d of each contact pin 16 in a manner such that each of the positioning ribs 19c is clamped by both the elastic pieces 16a and 16b in a state that any external force is applied to the elastic pieces 16a and 16b (in a state that both the contact portions 16e and 16f are closed) as shown in <figref idref="f0025">Fig. 22A</figref>.

0081In this seventh embodiment of the structure mentioned above, when the movable plate 17 is lowered, as in the first embodiment, both the bent portions 16g of the contact pin 16 are pressed by the sliding surfaces 17b of the cam portions 17a and the paired contact portions 16e and 16f are hence opened as shown in <figref idref="f0025">Fig. 22B</figref>. Under this state, the IC package 12 is guided by the guide portions 19b on the mount surface portion 19a of the upper plate 19 and mounted to the predetermined position thereof. Then, the respective solder portions 12b of the IC package 12 are inserted into the paired contact portions 16e and 16f now opened with the no-contacting state.

0082Thereafter, when the downward pressing force to the operation member 21 is released and the movable plate 17 is moved upward, the pressing force of the cam portions 17a to the bent portions 16g of the contact pin 16 is also released, and then, the paired contact portions 16e and 16f are moved in the closing direction thereof so as to clamp the solder ball 12b therebetween as shown in <figref idref="f0026">Fig. 22C</figref>.

0083At this operation, since the axis O1 passing the root portion 16k of one elastic piece 16b and the axis O2 passing the contact portion 16f are offset from each other, when the contact portion 16f abuts against the solder ball 12b, the wiping effect is caused by a slight sliding motion thereof thereby to achieve an improved electrical contact stability.

0084That is, one contact portion 16f is returned by the elastic force of one elastic piece 16b from the state of the elastic piece 16b being opened and abuts against the solder ball 12b as shown with a solid line in <figref idref="f0024">Fig. 21</figref>, and this one elastic piece 16b is further returned to the original position. In this operation, since the axis O1 passing the root portion 16k of one elastic piece 16b and the axis O2 passing the contact portion 15f are offset from each other, the returning force F due to the elastic piece acts on the position offset with respect to the contacting point of the contact portion 16f. As a result, the contact portion 16f is shifted in an arrowed direction shown with two dots and chain line in <figref idref="f0024">Fig. 21</figref> and slides on the side surface of the solder ball 12b, thus achieving the wiping effect. Accordingly, as mentioned above, the improved wiping effect can be achieved by making the simple change of the contact pin 16, and hence, the improved contact stability can be also realized.

0085The other structures of this embodiment are substantially the same as those mentioned with reference to the first embodiment, so that the details thereof are omitted herein.

[Eighth Embodiment]

0086<figref idref="f0027 f0028 f0029">Figs. 23 to 26</figref> represent eighth embodiment, according to the present invention, in which both the elastic pieces 16a and 16b of the contact pin 16 have symmetrical shape and a pair of contact portions 16e and 16f are formed to the upper sides of the bent portions 15g through crank portions 15j, respectively. According to the location of these crank portions 16j, the axis passing root portions 16k of both the elastic pieces 16a and 16f and the axis passing both the contact portions 16e and 16f are offset from each other.

0087The contact portions 16e and 16f have flat contact surfaces 16n to which the solder ball 12b contacts, and these flat contact surfaces 16n have predetermined angles with respect to the direction N normal to the contacting or separating direction of the solder ball 12b (7° ± 2° in this embodiment). The solder ball 12b is held by these flat contact surfaces 16n as shown with two dots and chain line in <figref idref="f0029">Fig. 26</figref>.

0088According to the structure of this embodiment mentioned above, since the axis O1 passing the root portions 15k of both the elastic pieces 16a and 16b and the axis O2 passing the contact portions 16e and 16f are offset from each other, an improved wiping effect can be achieved as in the former embodiments. In addition, since the flat contact surfaces 16n have predetermined angles with respect to the direction N normal to the contacting or separating direction of the solder ball 12b (7°± 2° in this embodiment), the wiping effect can be further improved.

0089The structures other than the above are substantially the same as those mentioned hereinbefore with reference to the former seventh embodiment, and the details thereof are hence omitted herein.

[Ninth Embodiment]

0090<figref idref="f0030">Figs. 27</figref> and <figref idref="f0031">28</figref> represent the ninth embodiment, in which the contact pin 16 has a base portion 16d different in shape from that of the seventh embodiment such that one portion of the U-shaped base portion 16d has a length longer than that of the other one portion as shown in <figref idref="f0031">Fig. 28</figref>. According to this structure, the center line 03 of both the elastic pieces 16a and 16b and the center line 04 of the solder tail portion 16c are offset from each other.

0091According to this structure, it is not necessary to locate the through holes of the printed circuit board, not shown, directly below the corresponding solder balls 12b, respectively, and the positional relationship between the corresponding solder ball 12b and the through hole can be offset by optionally setting the offset amount therebetween.

0092The structures other than the above are substantially the same as those mentioned above with reference to the former eighth embodiment, and the details thereof are hence omitted herein.

[Tenth Embodiment]

0093<figref idref="f0031 f0032 f0033 f0034 f0035 f0036 f0037 f0038 f0039">Figs. 29 to 34</figref> represent the tenth embodiment, in which the contact portions 16e and 16f of the contact pin 16 have displacing directions different from those of the former first and seventh embodiments. The contact pin 16, as a single piece, has the same structure as that of the seventh embodiment, and the functions of the socket body 12, the movable plate 17, the upper plate 19, the operation member 21, the latch 28 etc. are substantially identical to those of the first embodiment though the shapes thereof are somewhat different.

0094That is, as shown in <figref idref="f0031 f0032 f0033 f0034 f0035 f0036 f0037 f0038 f0039">Figs. 29 to 34</figref>, such contact pins 16 are arranged in matrix having vertical and horizontal rows, and respective sides of a rectangular outer edge portion K1 of the matrix arrangement and those of a rectangular outer shape K2 of the IC socket 11 are made substantially parallel to each other in a plan view, i.e. in a state of using the IC socket 11.

0095The displaced direction N1 of the paired contact portions 16e and 16f of the respective contact pins 16 has predetermined angles, 45° in this embodiment, with respect to the arrangement direction N2 of the vertical rows or horizontal rows of the contact pins 16.

0096In this tenth embodiment of the structure mentioned above, when it is required to set the IC package 12 to the IC socket 11, the operation member 21 is first depressed downward. Then, the arms 23 are rotated in a counterclockwise direction by the cam surface 21a of the operation member 21 from the state shown in <figref idref="f0033">Fig. 31A</figref> to the state shown in <figref idref="f0034">Fig. 31B</figref> thereby to lower the movable plate 17. According to the lowering of the movable plate 17, the cam portions 17a thereof are also lowered from the state shown in <figref idref="f0035 f0036">Figs. 32</figref> and <figref idref="f0038">34A</figref> to the state shown in <figref idref="f0037 f0038">Figs. 33</figref> and <figref idref="f0039">34B</figref>. Then, both the bent portions 16g of the contact pins 16 are pressed by the sliding surfaces 17b of the cam portions 17a, thus opening the paired contact portions 16e and 16f as shown in <figref idref="f0037 f0038">Fig. 33</figref>.

0097At the same time, according to the operation of the operating portion of the operation member 21, the depressed portion of the latch 28 is pressed and rotated in the clockwise direction against the urging force of the spring 19 from the state shown with the solid line in <figref idref="f0032">Fig. 30</figref> to the state shown with the two dots and chain line in <figref idref="f0032">Fig. 30</figref>, and the pressing portion 28b of the latch 28 is displaced to its retired position.

0098Under the state mentioned above, the IC package 12 is guided by the guide portions 19b and then mounted to the predetermined position on the mount surface portion 19a of the upper plate 19, and the respective solder balls 12b of the IC package 12 are inserted into the space between the opened contact portions 16e and 16f of the respective contact pins 16 with no-contacting state as shown in <figref idref="f0038">Fig. 33B</figref>.

0099Thereafter, the releasing of the downward pressing force to the operation member 21 allows the operation member 21 to be moved upward by the urging force of the spring 27 or the like, the movable plate 17 is also moved upward, and the latch 28 is then rotated in the clockwise direction in <figref idref="f0037 f0038">Fig. 33</figref> by the urging force of the spring 29.

0100When the movable plate 17 is moved upward, the pressing force of the cam portions 17a to the bent portions 16g of the contact pins 16 is released, and the bent portions 16g are then moved in the closing direction thereby to clamp the solder balls 12b therebetween. In thus manner, the electrical connection between the solder balls 12b of the IC package 12 and the printed circuit board can be established through the contact pins 16.

0101In this structure, as shown in <figref idref="f0031 f0032 f0033 f0034 f0035 f0036 f0037 f0038 f0039">Figs. 29 to 34</figref>, the respective sides of the rectangular outer edge portion K1 of the matrix arrangement and those of the rectangular outer shape K2 of the IC socket 11 are made substantially parallel to each other in a plan view, i.e. in a state of using the IC socket 11. The displaced direction N1 of the paired contact portions 16e and 16f of the respective contact pins 16 has predetermined angles, 45° in this embodiment, with respect to the arrangement direction N2 of the vertical rows or horizontal rows of the contact pins 16. Accordingly, the shifting amount of the contact portion 16f of the contact pin 16 can be ensured, and moreover, the IC socket 11 can be made itself compact.

0102Furthermore, since the solder balls 12b of the IC package 12 are clamped by displacing each other the contact portions 16e and 16f formed to the paired elastic pieces 16a and 16b of the contact pins 16, the moving amount of the movable plate 17 displacing the contact portions 16e and 16f can be made small because the displacing amount of the respective contact portions 16e and 16f can be made small in comparison with the structure in which one of the contact portions is displaced. In this regard, the IC socket 11 can be also made compact in addition to the advantageous effects mentioned above.

0103Still furthermore, In this embodiment, since the contact portions 16e and 16f of the contact pin 16 can be displaced by the vertical movement of the movable plate 17, and accordingly, in comparison with the case that the contact portions are displaced by horizontally sliding the movable plate, the IC socket can be made further compact in addition to the advantageous effects mentioned above.

0104It is to be noted that the present invention is not limited to the described embodiments and many other changes and modifications may be made without departing from the scopes of the appended claims.

0105For example, in the above-mentioned embodiments, although the present invention is applied to the IC socket as a socket for electrical parts, the present invention is not limited to such IC socket and is applicable to other devices. Furthermore, although the present invention is applied to the IC socket for the BGA type IC package 12, the present invention is not limited to such IC socket and is applicable to the IC socket for a PGA (Pin Grid Array) type IC package. Still furthermore, a pair of elastic pieces 16a and 16b are formed to the contact pins 16 of the seventh to tenth embodiments, a modified example, in which only one elastic piece is formed to the contact pin, may be adopted.