Abstract:
A pusher of an IC chip handler has a pusher frame which is attached to a pusher main body to be driven by the IC chip handler and a plurality of pusher heads attached to the pusher frame. Each of the pusher heads comprises a holder which is held by the pusher frame. At least one spring post is freely protruded outward from the inside of the holder, and a compression spring has one end arranged under pressure to a spring receiving portion of the spring post. A spring push plate arranges the compression spring to the spring receiving portion of the spring post under pressure, and an adjusting member adjusts a compression force of the compression spring. A device holding unit is attached to an end of the spring post protruded outside of the holder.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a pusher of an IC chip handler, and more specifically, to a pusher for testing a plurality of IC chips one by one or simultaneously. 
   2. Description of the Related Art 
   A plurality of pushers are used for testing a plurality of IC chips simultaneously. In this case, the plurality of IC chips to be tested simultaneously are selected from, for example, a single production lot, and therefore, the external dimensions thereof such as the thickness must have been formed evenly. However in practice, these IC chips have production errors in, for example, the thickness thereof. Further, as a terminal pin of an IC chip and a test pin of a socket, various kinds of terminals such as a solder ball terminal, a film-shaped terminal, a spring-shaped terminal, and a pogo pin terminal are employed. The height of these pins also has errors from a set value owing to production errors or changes by aging. Furthermore, a leaf spring or a coil spring, etc. is employed as a test pin of a socket to be set to contact terminal pins at a predetermined pressure when they are arranged under pressure. However, the elasticity of these springs also varies, and changes by aging, which leads to incomplete contact. 
   In general, when an IC chip is set onto a socket, a pusher goes down a preset distance and stops. If the dimensions of each IC chip and terminal pin are normal, the terminal pin of the IC chip normally contacts the test pin at the test device side by the pusher at this position, and the test is performed. In this case, for example, if the thickness of the IC chip is larger than a set range, the IC chip is pushed more than required by the pusher when the pusher goes down a preset distance, so that the terminal pin of the IC chip and the test pin of the socket may be deformed or damaged. In the case where the IC chip is thinner than the set value, a pushing pressure of the IC chip to the socket by the pusher becomes insufficient if the lowering distance of the pusher is the preset value, so that test cannot be performed normally owing to incomplete contact of the terminal pin. 
   Further, there is a case where a plurality of IC chips are tested simultaneously by use of a plurality of pushers. In this case, the lowering distance of the pusher corresponding to each socket is set evenly. Therefore, if there is an error in the dimensions of the IC chip and the terminal pin, the IC chip is pushed more than the standard value, for example, when the IC chip is thicker than the set value, so that nonconformities such as breakage may occur. When the IC chip is thinner than the set value, test results may become incorrect owing to incomplete contact of the terminal due to insufficient pressure setting. 
   In order to solve these problems with the prior art, various countermeasures have been made. However, there are various types of IC chips to be tested, and testing costs will become high if pushers corresponding to these various specifications of the IC chips are to be prepared, which is not practical. Therefore, the realization of a pusher which can be applied in common to IC chips of various specifications would be desirable. 
   BRIEF SUMMARY OF THE INVENTION 
   According to an aspect of the present invention, there is provided a pusher of an IC chip handler, comprising: a holder which is held at an end of a pusher main body to be driven by an IC handler; at least one spring post which is freely protruded outward from the inside of the holder; a compression spring whose one end is arranged under pressure to a spring receiving portion of the spring post; a spring push plate which arranges the compression spring to the spring receiving portion of the spring post under pressure; adjusting means for adjusting a compression force of the compression spring; and a device holding unit attached to an end of the spring post protruded to the outside of the holder. 
   According to the present invention, it is possible to easily adjust a pushing force at the moment when an IC chip attached to the front end of the pusher is pushed against a socket during testing. Further, it is possible to absorb the differences of compression distances due to differences of thickness in the IC chips or devices to be tested when a plurality of IC chips are tested simultaneously. As a consequence, it is possible to provide a pusher of an IC chip handler, which can be applied in common to IC chips of various specifications and can attain a simple structure and reduce testing costs, and further can attain precise testing results. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       FIG. 1  is a cross sectional view showing a pusher according to an embodiment of the present invention; 
       FIG. 2  is a plan view showing a device pushing force adjusting unit; 
       FIG. 3  is a schematic block diagram simply showing an entire configuration of an IC chip handler to which the pusher shown in  FIG. 1  is attached; 
       FIG. 4  is a graph showing a relation between a compression distance and a compression pressure of a compression spring shown in  FIG. 1 ; 
       FIG. 5  is a cross sectional view showing a state before absorbing an error in IC chip thickness at the time of testing in correspondence to  FIG. 3 ; and 
       FIG. 6  is a cross sectional view showing a state in which an error in IC chip thickness has been absorbed in  FIG. 5 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   In  FIG. 1 , a holder  12  of a cylindrical shape with a bottom as one of components configuring a pusher head  10  is held fixedly to an end of an arm head  11  (shown in  FIG. 3 ) attached to a pusher arm to be driven by an IC handler. A circular hole  12 B is formed at the central portion of a bottom  12 A of the holder  12 , and the circular hole  12 B is blocked by a bottom plate  13  fixed to the outside of the bottom  12 A with a plurality of screws  13 A. The bottom plate  13  has a plurality of conical funnel shaped holes  13 B formed from the inside thereof to the outside. Two conical funnel shaped holes  13 B are formed in the bottom plate  13  in this embodiment, but three or more holes  13 B may be formed. 
   Spring posts  14 ,  15  are inserted to the conical-shaped portions of the funnel-shaped holes  13 B. The spring posts  14 ,  15  have conical-shaped portions corresponding to the conical shape holes  13 B, and the ends thereof are protruded from the under surface of the bottom plate  13 . Spring receiving portions  14 A,  15 A are formed in the bottoms of the conical-shaped portions of the spring posts  14 ,  15 , and ends of compression springs  16 ,  17  are engaged to the receiving portions  14 A,  15 A, respectively. The other end of each of the compression springs  16 ,  17  is arranged to a spring push plate  18  under pressure. The spring push plate  18  is fixed rotatably to the upper portion of a spring force adjusting screw  19  screwed into the central portion of the bottom plate  13 . For example, a slot  19 B is formed in a head  19 A of the spring force adjusting screw  19 , and a flange  18 A is formed in the spring push plate  18  so as to slide in the slot  19 B. 
   A disk-shaped scale plate  20  is engaged and fixed to a concave portion of the upper surface of the spring push plate  18 , as shown in  FIG. 2 . On the inner diameter portion along the head of the screw  19  of the scale plate  20 , a scale  20 A for adjusting the spring force of the springs  16 ,  17  is inscribed. A pointer  19 C is inscribed on the screw head  19 A, and the pointer  19 C moves along the scale  20 A by the rotation of the screw  19  and displays the spring force or the total compression pressure of the springs  16 ,  17 . The elasticity of the springs  16 ,  17  is set so as to apply substantially the same compression force to the spring posts  14 ,  15  respectively. 
   A disk-shaped scale plate  20  is engaged and fixed to a concave portion of the upper surface of the spring push plate  18 , as shown in  FIG. 2 . On the inner diameter portion along the head of the screw  19  of the scale plate  20 , a scale  20 A for adjusting the spring force of the springs  16 ,  17  is inscribed. On the other hand, a pointer  19 C is inscribed on the screw head  19 A, and the pointer  19 C moves along the scale  20 A by the rotation of the screw  19  and displays the spring force or the total compression pressure of the springs  16 ,  17 . Meanwhile, the elasticity of the springs  16 ,  17  is so set as to apply the substantially same compression force to the spring posts  14 ,  15  respectively. 
   The ends of the spring posts  14 ,  15  protruded from the under surface of the bottom plate  13  attached as a part of the holder  12  are screwed and fixed into a device holding plate  22 . A device suction portion  22 A is formed on the under surface of the device holding plate  22 . In the device suction portion  22 A, a vacuum suction hole which is coupled to, for example, a vacuum pump (not shown) provided in the handler via the pusher main body  11  is formed. At the time of testing, a device to be tested, for example, an IC chip  24  is sucked to the device suction portion  22 A, and transferred to the socket at a test position. Meanwhile, there is described a case in which the terminals of the IC chip  24  are a plurality of solder balls  24 A. 
     FIG. 3  is a block diagram schematically showing a configuration of a handler having two pieces of the pusher shown in  FIG. 1  and a tester to be used for testing IC chips in connection with the handler. In  FIG. 3 , a pusher arm  32  of a handler  31  is configured to be driven in the vertical direction M at testing. A plurality of pusher heads, herein, two pusher heads  10 A,  10 B are mounted on the pusher arm  32  via an arm head  11 . IC chips  24 A,  24 B are sucked to the pusher heads  10 A,  10 B, respectively. 
     FIG. 3  shows a configuration in the case of testing the IC chips  24 A,  24 B by use of the handler  31  and a tester  34 . A tester head  35  is attached to the tester  34 , and a socket holding plate  36  is fixed onto the tester head  35 . Pogo pin type sockets  37 A,  37 B are attached onto the socket holding plate  36 , and the IC chips  24 A,  24 B held by the pusher heads  10 A,  10 B are pushed to the sockets  37 A,  37 B. A plurality of pogo pins  38  are arranged two-dimensionally on the socket  37 A such that the pin heads protruding from the socket  37 A directly contact solder balls as terminal pins of the IC chip  24 A. Each of the solder balls protrudes by a predetermined dimension from the under surface of the IC chip  24 A, and the protrusion height may have an error more or less. The pogo pin  38  is of an elastic structure where the pin head thereof is instructed by a spring, and it is configured such that the height error of the solder ball is absorbed by the spring structure of the pogo pin  38 . The other socket  37 B is configured in the same manner as described above. The configuration of the pogo pin  38  is known to those skilled in the art, and therefore, further explanations thereof are omitted. 
   The pusher arm  32  is arranged, for example, at level, and the production dimensions of the arm head  11  and the pusher heads  10 A,  10 B attached to the under surface of the arm head  11  are precisely set. Thus, the dimension from the under surface of the pusher arm  32  to the end of the pusher head  10 A is substantially the same as the dimension from the under surface of the pusher arm  32  to the end of the pusher head  10 B at the level line L. In the same manner, the socket holding plate  36  attached onto the tester head  35  is arranged at level, and the distances from the upper surface of the socket holding plate  36  to the pin heads of the respective pogo pins  38  of the sockets  37 A,  37 B arranged thereon are set so as to be substantially the same. 
   Accordingly, if the thickness of the IC chip  24 A to the base of the solder balls is substantially the same as the thickness of the IC chip  24 B, the IC chip  24 B is pushed to the socket  37 B at substantially the same time as the IC chip  24 A is pushed to the socket  37 A by the lowering of the pusher arm  32  during testing, and the test by the tester  34  is performed to the IC chips  24 A,  24 B at substantially the same time. 
   However, as shown in  FIG. 5 , for example, it is assumed that the IC chip  24 A is, for example, 1 mm thicker than the IC chip  24 B. Then, at the moment when the IC chip  24 A is contacted to the socket  37 A during testing, the IC chip  24 B is still 1 mm before the socket  37 B. The distance between the tip of the IC chip  24 B and the socket  37 B is denoted as H, in the figure. Accordingly, the pusher arm  32  is lowered further 1 mm or H mm, until the IC chip  24 B is contacted to the socket  37 B. At this moment, the IC chip  24 A is pushed toward the socket  37 B further from the first contact position. This state will be described and is shown in  FIG. 6 . 
   Herein, the comprehensive compression force of springs of the pogo pins  38  arranged two-dimensionally in the socket  37 A is set larger than the total compression force of the springs (such as those  16 ,  17  shown in  FIG. 1 ) that push downward the IC chip  24 A in the pusher head  10 A. For example, when the pusher head  10 A is of the configuration shown in  FIG. 1 , the total compression force of the pusher head  10 A becomes the total of the compression forces of the two springs  16 ,  17 . 
   Consequently, when the pusher arm  32  goes down further 1 mm or from the position where the IC chip  24 A contacts the socket  37 A, the springs  16 ,  17  shown in  FIG. 1  are compressed further 1 mm or H mm. In this state, the IC chip  24 B is also pushed to the socket  37 B, and, simultaneous test of the IC chips  24 A,  24 B becomes possible in this state, as shown in  FIG. 6 . However, in order to increase the reliability of testing results, it is desirable to, in practice, perform the test at a position to which the pusher arm  32  is lowered further by a predetermined distance. 
   Herein, with reference to  FIG. 4 , an explanation will be given for the spring characteristic of the spring  16  shown in, for example,  FIG. 1 , in other words, the relation between the compression distance and the compression pressure at the time when the spring  16  is compressed, and in connection therewith, the operation of the spring force adjusting screw  19  shown in  FIG. 1  will be explained. The spring  16  is a coil spring, and when the compression pressure thereof is 0 (g), the compression distance thereof is also 0 (mm). The spring  16  is set so as to be compressed 1 mm when pushed with a force of 1 g, for example. Accordingly, the more the pushing force increases, the more the compression distance increases along the straight line C. The spring  17  is formed in substantially the same manner as in the spring  16 . 
   Hereinafter, the spring force adjusting screw  19  shown in  FIG. 1  will be explained with reference to  FIG. 4 . Herein, since, in  FIG. 1 , two springs  16 ,  17  are used to one pusher head  10 , the inclination of the spring characteristic curve C in  FIG. 4  becomes half in practice. However, for convenience of explanations, it is assumed that  FIG. 4  shows the comprehensive spring characteristic of the two springs  16 ,  17 . In  FIG. 1 , when the springs  16 ,  17  are assembled between the spring push plate  18  and the spring posts  14 ,  15 , the springs are compressed by only a compression distance Ds in  FIG. 4  by turning the spring force adjusting screw  19 . In this manner, the IC chip  24  is pushed downward with a pressure Ps by the springs  16 ,  17 . The pressure Ps is set to such a value that, for example, in the case of the pusher head  10 A in  FIG. 3 , the solder balls as the terminal pins of the IC chip  24 A are pushed to the pogo pins  38  as the test pins of the socket  37 A with an appropriate pressure, and a preferable contact is kept therebetween and no disadvantageous influence is given to the IC chip  24 A. Further, the more the spring force adjusting screw  19  is fastened, the more the compression distance increases, and concurrently, the more the compression pressure becomes. At the compression distance Ds+D shown in  FIG. 4 , the compression pressure reaches an allowable maximum pressure Pm. At the allowable value Pm or less, the compression pressure is set such that there occurs no trouble such as breakage of the IC chip  24 A by being pushed at the socket  37 A. 
   For example, as shown in  FIG. 2 , the scale plate  20  is formed on the upper surface of the spring push plate  18 , and the pressure pointer  19 C is formed on the head portion of the spring force adjusting screw  19 . Therefore, by entering the allowable value Pm on the scale plate  20 , it is possible to set the compression pressure precisely by rotating the screw  19 , and to easily check the allowable value Pm by visual inspection. 
   As described previously, it is assumed that, for example, the initial compression pressures of the respective compression springs of the pusher heads  10 A,  10 B are set to Ps. Herein, assuming that the IC chip  24 A as the device to be tested is 1 mm thicker than the IC chip  24 B, the spring of the pusher head  10 A is compressed 1 mm more than the spring of the pusher head  10 B. Accordingly, when the compression distance of the pusher head  10 B at the time of an actual test is at point C 1  on the curve C in  FIG. 4 , the compression distance of the pusher head  10 A is at point C 2  that is 1 mm more than the point C 1 . 
   In the pusher head  10  of the embodiment shown in  FIG. 1 , the configuration thereof is made so as to hold the IC chip  24  as the device to be tested by use of the two springs  16 ,  17 . However, it is desirable that the IC chip  24  is held at level precisely, and the IC chip  24  is held at least at three points, for example, at four points. Thus, it is desirable that four springs are used to one pusher head in the same configuration as shown in  FIG. 1 . 
   Further, in the embodiment shown in  FIG. 3 , an explanation has been given for the case where two pusher heads  10 A,  10 B are attached onto one pusher arm  32 , and thereby two IC chips  24 A,  24 B are tested at the same time. However, further more pusher heads may be attached to the pusher arm  32  via the arm head  11  to test more IC chips simultaneously. 
   Furthermore, in the embodiment in  FIG. 3 , the tester  34  including the sockets  37 A,  37 B is of substantially the same configuration as that of a commercially available tester. In addition, the arm head  11  may be applied to not only the pusher arm  32  of the handler  31 , but also to many commercially available handlers merely through modification of the attachment structure thereof. Further, a plurality of pusher heads may be mounted directly to the pusher arm without using the arm head  11 . Accordingly, the pusher according to the present invention is a general purpose pusher, and the application thereof is extremely wide, thereby reducing users&#39; testing costs remarkably. 
   According to the present invention, it is possible to easily adjust the pushing force at the moment when the IC chip attached to the end of the pusher is pushed to the socket during testing. As a consequence, it is possible to provide a pusher of an IC chip handler, which can be applied in common to IC chips of various specifications and can attain a simple structure and reduce testing costs, and further can attain precise testing results. 
   Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.