Patent Publication Number: US-2005130456-A1

Title: Spiral terminal and method of manufacturing the same

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a spiral terminal used for attaining electrical continuity with an electrode of electronic equipment having an IC or LSI or the like by pressing the spiral terminal onto the electrode. The invention also relates to inspection equipment and electronic equipment which are equipped with such spiral terminal.  
      2. Description of the Background Art  
      An inspection socket is used for taking out electrical signals from electrodes of electronic equipment consisting of an IC or LSI through contact buttons by pressing the contact buttons onto the electrodes in order to inspect the electrical continuity of the electronic equipment. A connector for packaging is used for the purpose of maintaining electrical continuity with electronic equipment such that contact buttons are pressed on the land electrodes of the electronic equipment so as to maintain electrical continuity with the electronic equipment through the contact buttons. The inspection socket and the connector for packaging are provided with a number of contact buttons corresponding to the number of the electrodes of the electronic equipment to be connected, and higher density corresponding to high density of electrodes provided in electronic equipment is demanded of the contact buttons to be provided in the inspection socket and the connector for packaging.  
      One of such known contact buttons is, for example, a contact button for BGA (ball grid array). The contact button has a planar spiral shape before contacting a ball electrode, and the spiral shape of the contact button changes corresponding to the shape of the ball electrode as a result of contact with the ball electrode (see Japanese Patent Application Publication No. 2002-175859). It is described therein that this contact button can comply with high density of electrodes, securing electrical continuity in compliance with the shape of the ball electrode, and being highly reliable.  
      A known spiral terminal used for inspection is, for example, a cone-shaped terminal having a spiral spring whose protrusion increases gradually from the outer periphery to the center (see Japanese Patent Application Publication No. 2001-235486). It is stated that when the conical probe part arranged at the tip of the cone-shaped terminal is pressed onto a plate electrode of a subject to be inspected, the conical probe part can surely be connected to the plate electrode of the subject according to the additive force of the spring.  
      These spiral terminals are manufactured by various methods, such as a mechanical processing in which a plate is curled up, a method in which a plating method is combined with a lithography method that uses ultraviolet radiation (UV) having a wavelength of about 200 nm, a method using laser, etching or punching, and the like. However, if an attempt is made to manufacture a spiral terminal by machining process such as curling a plate, there is a limit in the miniaturization of the spiral terminal, and it is difficult to manufacture precision terminals precisely with satisfactory reproducibility in large quantities. With the lithography method using UV, or the methods using laser, etching or punching, only spiral terminals having a thickness of about 20 μm or less can be obtained, and consequently the aspect ratio is small.  
      Since the aspect ratio is small, if an attempt is made to increase a stroke (sag amount of a spring) in order to obtain a spiral terminal having high reliability of connection, the spring becomes thinner, and the spiral terminal cannot achieve electrical continuity of a large electric current of equal to or more than 0.5 A. Also, because of the small aspect ratio, the number of spirals of the terminal becomes less, and the contact load decreases if an attempt is made to enlarge the stroke, whereas the stroke decreases if the contact load is attempted to be increased. Therefore, only spiral terminals of low connection reliability are obtained.  
      When the electrode of an object to be connected is plate-shaped, the contact button must have a convex structure in order to attain sure connection reliability. However, if an attempt is made to process the contact button so as to have a convex structure after formation of a spiral spring, a special process is necessary, which results in the degradation of productivity and the increase of manufacturing cost. Moreover, the convex formation of a minute spiral spring is not easy, and consequently the yield of the product decreases. Furthermore, with a mode in which the tip of a contact button having a shape like a cone having a pointed end is pressed onto a plate electrode of an object to be connected, the electrode is vulnerable to damage because it is made of a soft material such as gold or a solder. Thus, if the electrode is damaged at the stage of inspection, the fraction defective in the subsequent step of mounting increases, and the connection reliability decreases. On the other hand, the tip of the contact button tends to be deformed, and if it is used repeatedly for a long time, a stable electrical connection cannot be attained.  
      If the pointed structure of cone is formed by machining, which is the only practically available process, the manufacturing cost becomes high since such machining is done piece by piece. If the pointed structure of the cone is formed by machining, the variations of the products becomes tens of μm, which results in the variations in the height of the terminals, causing variation in the stroke and the contact load at the occasion of contact with the electrodes, and accordingly the connection reliability decreases.  
     SUMMARY OF THE INVENTION  
      The present invention was accomplished in view of the above-mentioned problems, and an object of the invention is to provide a low cost and highly reliable spiral terminal for inspection equipment or for mounting in electronic equipment.  
      A spiral terminal of the present invention is a minute terminal to attain electrical continuity with an electrode of electronic equipment or inspection equipment. The spiral terminal has a columnar spiral spring and a protrusion protruding outward at the center of the spiral of the spiral spring. The protrusion has a contact surface to be in contact with an electrode, and the shape of the contact surface is a part of a spherical surface or a part of paraboloid of revolution.  
      The columnar spiral spring may be structured such that the outer peripheral part thereof has a hollow ring structure. The spiral terminal may be made of nickel or nickel alloy and may have a coating layer consisting of a precious metal or alloy of a precious metal.  
      A manufacturing method of the present invention is a method of manufacturing such a columnar spiral terminal having a spiral spring structure, and the method typically includes a step of forming a layer consisting of metallic material in a resist structure by means of electroforming so as to form a columnar spiral spring, a step of forming a resist structure on the spiral spring by lithography, and a step of forming a layer consisting of metallic material in the resist structure by electroforming in order to form a protrusion protruding outward.  
      Another manufacturing method of the present invention may include a step of forming a resist structure by a metal mold, a step of forming a layer consisting of metallic material in the resist structure by means of electroforming so as to form a columnar spiral spring, a step of forming a resist structure on the spiral spring by lithography, and a step of forming a layer consisting of metallic material in the resist structure by electroforming in order to form a protrusion protruding outward.  
      Inspection equipment of the present invention may have a socket equipped with such spiral terminals and may be used for the inspection of semiconductors of land grid array arrangement. On the other hand, electronic equipment of the present invention may have a connector equipped with such spiral terminals and may be connected with land electrodes.  
      The spiral terminal of the present invention exhibits high connection reliability since it does not give a mechanical damage to an electrode of an object to be connected and its aspect ratio is high. With a manufacturing method according to the present invention, a minute contact button can be produced precisely with satisfactory reproducibility and at low cost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1 ( a ) is a perspective view of a spiral terminal of the present invention, and  FIG. 1 ( b ) is a sectional view of the spiral terminal of the present invention, taken along a longitudinal plane passing the center thereof.  
       FIG. 2 ( a ) is a sectional view showing a spiral terminal of the present invention, in which a cross-section perpendicular to the longitudinal direction is circular.  FIG. 2 ( b ) is a sectional view showing a spiral terminal having two arms of the present invention.  
      FIGS.  3 ( a )- 3 ( d ) schematically show a process of manufacturing an inspection socket of the present invention.  
      FIGS.  4 ( a )- 4 ( j ) schematically show a process of manufacturing a spiral terminal of the present invention.  
      FIGS.  5 ( a )- 5 ( l ) show another process of manufacturing a spiral terminal of the present invention.  
      FIGS.  6 ( a )- 6 ( d ) show cross-sections of various modifications of spiral terminals of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Hereinafter, embodiments of the spiral terminals of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, and redundant description will be omitted.  
      (Spiral Terminal)  
      A typical example of a spiral terminal of the present invention is shown in  FIG. 1 .  FIG. 1 ( a ) is a perspective view of a spiral terminal of the present invention, and  FIG. 1 ( b ) is a sectional view of the spiral terminal of the present invention, showing a cross-section taken along a longitudinal plane passing the center thereof. As shown in FIGS.  1 ( a ) and  1 ( b ), the spiral terminal of the present invention has a columnar spiral spring  1   u  and a protrusion it protruding outward at the center  1   uc  of the spiral spring  1   u . The protrusion it has a contact surface  1   tc  to be in contact with an electrode of electronic equipment or inspection equipment, and the shape of the contact surface  1   tc  is a part of spherical surface or a part of paraboloid of revolution.  
      When a spiral terminal is pressed on an electrode of an object to be connected, it gives the electrode a mechanical damage if it has a conically sharp pointed tip structure as in the case of a conventional spiral terminal. However, as shown in  FIG. 1 , a spiral terminal of the present invention has a protrusion it which has a contact surface  1   tc  for contacting an electrode of an object to be connected, and the contact surface  1   tc  has a shape like a part of the spherical surface or a part of paraboloid of revolution. Therefore, the spiral terminal of the present invention does not damage an electrode of an object to be connected. Thus, even with repeated use for connection, the tip of the protrusion will not crush or vary in its height, nor will the contact surface be deformed, and the reliability of electrical connection of the spiral terminal of the present invention will not be degraded. The spiral terminal can maintain a constant connection with an electrode even if they happen to contact each other in an inclined manner.  
      The outer peripheral part  1   ug  of the columnar spiral spring  1   u  preferably has a hollow ring structure. If the outer peripheral part  1   ug  has a hollow ring structure, it is easy to mount the spiral terminal onto a substrate, and holding the spiral terminal can be done easily. Since the spiral terminal can be held easily, it can be fixed stably. As no end of the spiral spring exists in the outer peripheral part, repeated connection with an electrode does not cause the substrate to be shaved by the end of the spiral spring, and therefore the reliability is high.  
      The spiral terminal of the present invention is a minute terminal, as shown in FIGS.  1 ( a ) and  1 ( b ), having an outer diameter D is equal to or less than 1 mm, the thickness b of the spiral spring  1   u  is 100 μm-500 μm, and the height c of the protrusion  1   t  is 50 μm-200 μm, for example. The FIGS.  1 ( a ) and  1 ( b ) show an example in which the protrusion  1   t  has a neck; however, the present invention also includes an embodiment which does not have a neck. FIGS.  1 ( a ) and  1 ( b ) show an example where a spiral terminal has an approximately circular cross-section when cut with a plane perpendicular to the longitudinal direction of the spiral terminal. However, the spiral terminal of the present invention is not limited to such a circular shape: it may be an elliptical shape or a circular shape having a partly warped circumference, or a polygonal shape, such as triangle, square, etc. The polygonal shape may have sides of different length, not limited to a regular polygon.  
      The FIGS.  2 ( a ) and  2 ( b ) show examples of columnar spiral springs having a circular cross-section when cut with a plane perpendicular to a longitudinal direction of the spiral terminal.  FIG. 2 ( a ) is a sectional view of a spiral terminal whose spiral spring consists of one arm.  FIG. 2 ( b ) is a sectional view of a spiral terminal whose spiral spring consists of two arms. The present invention includes an embodiment in which the spiral spring has three or more arms. In the example of  FIG. 2 ( b ), the tips of two arms are connected at the central part, wherein a protrusion (not illustrated in the figure) exists. The modified embodiments of the spiral terminal of the present invention may have a structure such that a plurality of springs are arranged meandering from the outer peripheral part thereof to the center. The examples of such structure are shown in FIGS.  6 ( a )- 6 ( d ). This type of structure allows signal electric currents to flow radially from the center, whereby mutual electromagnetic effects are offset, and accordingly satisfactory high frequency characteristics can be obtained.  
      An example of an inspection socket equipped with spiral terminals of the present invention is shown in  FIG. 3 ( d ). As shown in  FIG. 3 ( d ), one pair of spiral terminals  31   a  and  31   b , which are arranged with their respective protrusions face outward and a ring  39  interposed between them, are engagedly put in each through-hole of an electrically insulative substrate  32 . The ring  39  functions to secure a space for the spiral terminals  31   a  and  31   b  to perform a stroke, and thereby the spiral terminals are prevented from being in contact with each other when they are transformed.  
      The socket for inspection equipment shown in  FIG. 3 ( d ) is used placed between a semiconductor  35  and a transformer  38  of measurement equipment. As a result of being put between the semiconductor  35  and the transformer former  38 , the socket connects with the electrode  36  of semiconductor  35  and the electrode  37  of transformer former  38  with a moderate contact load due to the additive force of the spiral spring. Thus, an electrical signal obtained from the semiconductor  35  is led to measurement equipment via the transformer former  38 .  
      The spiral terminal of the present invention is useful as a spiral terminal of a socket for inspection equipment used in the inspection of a semiconductor of land grid array arrangement, and the like. Likewise, the spiral terminal of the present invention is useful as a spiral terminal of a connector mounted in the land electrodes of communication equipment such as a cellular phone or electronic equipment such as a personal computer. The electrode of inspection equipment or electronic equipment is preferably plate-shaped in order to secure a sure connection with a spiral terminal having a protrusion. However, an electrode having an uneven or depressed surface can also be used.  
      (Method of Manufacturing a Spiral Terminal)  
      The manufacturing method of the present invention for the spiral terminal typically includes a step of forming a resist structure by X-ray lithography, a step of forming a layer consisting of metallic material by electroforming in the resist structure so as to make a columnar spring, a step of forming a resist structure by X-ray lithography on the spring, and a step of forming a layer consisting of metallic material by electroforming in the resist structure so as to make a protrusion protruding outward.  
      With such method, in which the spiral spring of a spiral terminal is produced using X-rays and electroforming in combination, a high aspect ratio can be attained as compared with a case of manufacture using a method such as a lithography method using IW, a laser processing method, or a method using etching or punching. For example, spiral terminals having an aspect ratio (b/a) of 2 or more as shown in  FIG. 1 ( a ) can easily be manufactured, and it is also possible to manufacture spiral terminals having a aspect ratio of 30 or more than. Since a high aspect ratio is obtained, the stroke can be increased by designing the width a of the spring thinner and increasing the number of spirals. Also, the contact load can be increased by increasing the thickness b of the spring. Therefore, spiral terminals exhibiting high connection reliability can be manufactured.  
      More specifically, spiral terminals exhibiting a stroke of 100 μm or more and a contact load of 0.03 N can be easily manufactured. The contact load can be made 0.1 N or more. Since the thickness b can be increased even if the width a of the spring is thin, the spiral terminal can achieve electrical continuity of a large electric current equal to or more than 0.5 A.  
      In the manufacturing method of the present invention, X-rays (wavelength of 0.4 nm) which are shorter wavelength than UV (wavelength of 200 nm) are used because a spiral terminal having a high aspect ratio can thereby be obtained. In particular, synchrotron X rays (hereinafter, called “synchrotron radiation”) among the X-rays are preferably used in view of their high directivity. The LIGA (Lithographie Galvanoformung Abformung) process which uses synchrotron radiation is advantageous because deep lithography is possible with it, whereby it is possible to produce metal microstructures having a height of several hundreds μm order with precision of micron order and in large quantities.  
      If an attempt to manufacture a spiral terminal by machining process such as curling up of a plate, there is a limit to miniaturization of the spiral terminal, and a possible smallest spiral terminal that can be made by such machining process will have a thickness b of 1000 μm and a diameter D of about 500 μm-1000 μm. With this size, it is difficult to comply with high density packaging of semiconductors. It is also difficult to manufacture precision spiral terminals in large quantities, precisely with satisfactory reproducibility.  
      According to the present invention, it is possible to comply with high density packaging of electronic equipment since spiral terminals having a thickness b of 100 μm-500 μm and a diameter D of 100 μm-1000 μm can easily be manufactured precisely with satisfactory reproducibility and in large quantities. Moreover, because of the manufacturing method in which lithography and electroforming are combined, the microstructure can be formed integrally, the number of parts can be decreased, and the part cost and assembling cost can be reduced.  
      Since the method uses lithography and electroforming in combination, the protrusion at the center of the whirlpool in the spiral spring can be formed more easily with the method as compared with the method of making convex formation mechanically after forming the spiral spring, and accordingly the productivity and the product yield are high. Moreover, since the protrusion can be formed precisely, it is possible to reduce the variation in the height of the terminal, and accordingly it is possible to reduce the variations in the stroke and the contact load to about {fraction (1/10)} as compared with those in the case of forming by machining, and thereby the connection reliability can be enhanced.  
      In the manufacturing method of the present invention, a resin layer  42  is formed on an electroconductive substrate  41  as shown in  FIG. 4 ( a ). The electroconductive substrate is, for example, a substrate made of metal such as copper, nickel, or stainless steel, or a silicon substrate to which a metallic material such as chrome or titanium is applied by sputtering. The resin layer is made of a resin material containing polyester methacrylate such as polymethyl methacrylate (PMMA) as a main component, or chemical amplification type polymer material having susceptibility to X-rays, or the like. The thickness of the resin layer can be optionally set according to the thickness of the spiral spring to be formed; for example, it can be designed to be 100 μm-500 mm.  
      Next, a mask  43  is arranged on the resin material  42 , and X-rays  44  are irradiated thereto through the mask  43 . Preferably, the X-ray is synchrotron radiation. The mask  43  consists of a transparent substrate material  43   b  and an X-ray absorption layer  43   a  formed according to the pattern of the spiral spring. The transparent substrate material  43   b  is made of silicon nitride, diamond, silicon, titanium or the like. The X-ray absorber layer  43   a  is made of a heavy metal such as gold, tungsten, or tantalum, or a compound thereof, or the like. A resin layer portion  42   a  of the resin layer  42  is exposed to the irradiation of X-rays  44 , and its quality changes, but a resin layer portion  42   b  is not exposed because of the X-ray absorber layer  43   a . Therefore, only the part in which the quality has changed because of the X-rays  44  is removed by the development and consequently a resist structure  42   b  as shown in  FIG. 4 ( b ) is obtained.  
      Subsequently, a metallic material  45  is deposited by electroforming in the resist structure  42   b  as shown in  FIG. 4 ( c ). The electroforming means that a layer consisting of a metallic material is formed, using a metallic ion solution, on an electroconductive substrate. The metallic material  45  can be deposited in the resist structure  42   b  by electroforming using the electroconductive substrate  41  as a cathode electrode. In a case where the metallic material is deposited to a degree in which the space of the resist structure is substantially buried, the spiral spring can be obtained from the accumulated metallic material layer. In a case where the metallic material has been deposited in the resist structure beyond the height of the resist structure, a metal microstructure having a space is obtained by removing the resist structure and the substrate. The metal microstructure thus obtained can be used as a mold in the method of manufacturing a spiral terminal according to the present invention as described later. Nickel, copper or their alloy is used as the metallic material, and particularly nickel or a nickel alloy such as nickel manganese is preferable from the viewpoint of enhancing the wear resistance of the spiral terminal.  
      After electroforming, the thickness is adjusted to a predetermined measure by polishing or machining ( FIG. 4 ( d )), and thereafter, for example, a resin layer  46  made of negative resist is formed on the spiral spring ( FIG. 4 ( e )). When UV47 or X-rays are irradiated through a mask  48 , the portion  46   b  of the resin layer  46  is exposed and the portion  46   a  of the resin layer  46  is not exposed ( FIG. 4 ( f )). Therefore, a resist structure  46   b  is produced by removing the other part by the development, leaving the part hardened due to UV or the like ( FIG. 4 ( g )). The mask  48  may be a mask having the similar specification as the mask  43 .  
      Next, a layer consisting of metallic material is formed by electroforming in the resist structure  46   b , and a protrusion  49  is grown, protruding outward, by plating. The protrusion  49  has a contact surface with a shape of a part of paraboloid of revolution as shown in  FIG. 4 ( h ), for contacting with an electrode. The protrusion having a contact surface which is a part of a spherical surface (not shown in the figure) can also be formed. During electroforming, electric line of force spreads in the space of the resist structure  46   b  and the equivalent points thereof form a spherical surface or paraboloid of revolution, and accordingly a protrusion having a plating surface in a shape of a part of a spherical surface or part of paraboloid of revolution can easily be formed when the protrusion is grown by plating.  
      After formation of the protrusion  49 , the resist structures  42   b  and  46   b  are removed by wet etching or plasma etching as shown in  FIG. 4 ( i ). Subsequently, the electroconductive substrate  41  is removed by wet etching using acid or alkali, or by mechanical processing, and consequently a spiral terminal of the present invention having a columnar spiral spring  45  and a protrusion  49  can be obtained as shown in  FIG. 4 ( j ).  
      In order to enhance its electrical continuity, the spiral terminal thus obtained is preferably coated, by a barrel plating or the like, with a precious metal, such as Au, Rh, Ag, Ru, Pt, or Pd, or an alloy of these materials, with a thickness of 0.05 μm-1 μm. Such coating layer can also be formed in the step ( FIG. 4 ( i )) before the removal of a substrate.  
      FIGS.  3 ( a ) to  3 ( d ) show a method of manufacturing an inspection socket from spiral terminals. A connector to be mounted in electronic equipment can also be manufactured by a similar method. The method of manufacturing such an inspection socket or a connector for mounting is not limited to the method illustrated in FIGS.  3 ( a ) to  3 ( d ). However, such method is advantageous in view of its ease for manufacturing. First, as shown in  FIG. 3 ( a ), through-holes are formed in an electrically insulative substrate  32 , at positions corresponding to the positions of the electrode of a semiconductor to be inspected. The diameter of the through holes is adjusted according to the outer diameter of the spiral terminals to be accommodated therein. Subsequently, a lower-cover sheet  33 , in which through holes are formed similarly at the positions corresponding to the arrangement of the electrodes of the semiconductor, is attached to the substrate  32 . The diameter of the through holes of the lower-cover sheet is smaller than the outer diameter of the spiral terminals to be accommodated therein such that the spiral terminals do not drop off the substrate.  
      Thereafter, a pair of spiral terminals  31   a  and  31   b , which are arranged with their protrusions facing outward, and a ring  39  interposed between the spiral terminals  31   a  and  31   b  are engagedly put in each of the through-holes of the substrate  32  as shown in  FIG. 3 ( b ). Subsequently, an upper-cover sheet  34  similar to the lower-cover sheet  33  is attached to the substrate  32 . Thus, an inspection socket according to the present invention is obtained as shown in  FIG. 3 ( c ). The material of the substrate  32 , lower-cover sheet  33 , and upper-cover sheet  34  may be an electrically insulative material such as a polyimide resin or general fiber reinforced plastic (FRP), for example.  
      A method of manufacturing a spiral terminal according to another embodiment of the present invention includes a step of forming a resist structure with a metal mold and a step of forming a layer consisting of metallic material in the resist structure by electroforming, thereby producing a columnar spring, and a step of forming a layer consisting of metallic material in the resist structure by electroforming so as to produce a protrusion protruding outward. With such method also, as in the case of the above-mentioned manufacturing method in which a minute spiral spring is formed by X-ray lithography, it is possible to fabricate a minute terminal precisely with a satisfactory reproducibility. The spiral terminal thus fabricated has a high aspect ratio and accordingly a protrusion at the center thereof can be formed precisely. Consequently, the contact reliability thereof is high. Moreover, the method is advantageous in that a mass production of spiral terminals is possible using the same mold.  
      First, as shown in  FIG. 5 ( a ), a depressed resist structure  52  as shown in  FIG. 5 ( b ) is formed by press or injection molding or the like using a mold  50  having a protruding portion. Thermoplastic resins, including acrylic resins such as polymethyl methacrylate, polyurethane resin, or polyacetal resin such as polyoxymethylene, are used as the material of the resist structure. As for the mold  50 , since it is a metal microstructure similar to the spiral terminal of the present invention, it is formed preferably by the above-mentioned method, in which an X-ray lithography method and electroforming are combined.  
      Next, after reversing the top and the bottom of the resist structure  52 , it is attached on the electroconductive substrate  51  as shown in  FIG. 5 ( c ). Subsequently, the resist structure  52  is polished to form a resist structure  52   b  as shown in  FIG. 5 ( d ). The subsequent steps are the same as described above: a metallic material  55  is deposited in the resist structure  52   b  by electroforming ( FIG. 5 ( e )), the thickness is adjusted by polishing or grinding ( FIG. 5 ( f )), a resin layer  56  is formed ( FIG. 5 ( g )), and UV  57  or X-rays are irradiated thereto through a mask  58 . Of the resin layer  56 , a resin layer portion  56   b  is exposed but a resin layer portion  56   a  is not exposed ( FIG. 5 ( h )). Therefore, a resist structure  56   b  can be produced by removing the other part by development, leaving the part hardened by UV or the like ( FIG. 5 ( i )).  
      Subsequently, a protrusion  59  having a contact surface to contact with an electrode is formed by electroforming and plating. As shown in  FIG. 5 ( j ), the contact surface has a shape equivalent to a part of paraboloid of revolution or the like. After formation of the protrusion  59 , the resist structures  52   b  and  56   b  are removed ( FIG. 5 ( k )), and the electroconductive substrate  51  is removed. Thus, the spiral terminal of the present invention having a columnar spiral spring  55  and a protrusion  59  can be produced ( FIG. 5 ( l )). The spiral terminal is preferably provided with a coating layer made of Au, Rh, or alloy thereof, or the like.  
     EXAMPLE 1  
      First, a resin layer  42  was formed on an electroconductive substrate  41  as shown in  FIG. 4 ( a ). A silicon substrate to which titanium is applied by sputtering was used as the electroconductive substrate. The material for forming a resin layer was a copolymer of methyl methacrylate and methacrylic acid, and the thickness of the resin layer was 200 μm.  
      Next, a mask  43  was arranged on the resin layer  42 , and X-rays  44  were irradiated through the mask  43 . As for the X-rays, synchrotron radiation by SR equipment (NIJI-III) was adopted. The mask  43  had an X-ray absorber layer  43   a , which was formed on a transparent substrate material  43   b  corresponding to the pattern of the spiral terminal. The transparent substrate material  43   b  of the mask  43  was consisted of silicon nitride, and the X-ray absorber layer  43   a  was made of tungsten nitride.  
      After the irradiation of X-rays  44 , development was performed by methyl isobutyl ketone, and the part  42   a  in which the quality has been changed by the X-rays  44  was removed. As a result, a resist structure  42   b  as shown in  FIG. 4 ( b ) was obtained. Then, as shown in  FIG. 4 ( c ), a metallic material  45  was deposited by electroforming in the space of the resist structure  42   b . Nickel was used as the metallic material. After the electroforming was completed, the unevenness of the surface was eliminated by polishing so as to have a uniform thickness as shown in  FIG. 4 ( d ), and a resin layer  46  was formed on the spiral spring ( FIG. 4 ( e )). Thereafter, UV  47  was irradiated through the mask  48  ( FIG. 4 ( f ). The resin layer  46  was a UV resist (SU-8 made by Microchem Corp.), and the thickness of the resin layer  46  was 50 μm. The mask  48  was a generally available photomask. Subsequently, the part other than the portion hardened by the UV irradiation was removed by development, and the resist structure  46   b  having a hole at the center of the spiral ( FIG. 4 ( g )).  
      Subsequently, electroforming was performed, and the protrusion  49  protruding outward was formed by growing a plating metal to the height of 50 μm from the top surface of the resist structure  46   b  ( FIG. 4 ( h )). After the formation of the protrusion  49 , the resist structures  42   b  and  46   b  were removed by plasma etching as shown in  FIG. 4 ( i ). Subsequently, the electroconductive substrate  41  was separated, by a mechanical method, from the spiral terminal having the protrusion. Thereafter, a coating layer (not shown in the figure) consisting of gold was formed with a thickness of 0.1 μm by barrel plating. The separation of the spiral terminal from the substrate may be accomplished by etching the electroconductive substrate. The total height of the protrusion formed on the spiral spring was 100 μm.  
      The spiral terminal thus obtained is shown in FIGS.  1 ( a ) and  1 ( b ). The spiral terminal had a columnar spiral spring  1   u  and a protrusion  1   t  protruding outward at the center  1   uc  of the spiral of the spiral spring  1   u . The protrusion had a contact surface  1   tc  for contacting with an electrode, and the shape of contact surface  1   tc  was a part of paraboloid of revolution. The outer peripheral part  1   ug  of the spiral spring  1   u  has a hollow ring structure. The diameter D was 480 μm and the thickness b of the spiral spring was 150 μm. The width a of the spring was 10 μm, and the aspect ratio (b/a) was 15. The number of spirals was 3.3 turns, and the stroke of the spring was 100 μm. The spiral spring had a protrusion with a neck at the center thereof and the height c was 100 μm.  
      Subsequently, as shown in  FIG. 3 ( a ), the lower-cover sheet  33  and the substrate  32 , both of which had through-holes at the positions corresponding to the positions of the electrodes of a semiconductor to be inspected, were attached together. The substrate  32  was made of a polyimide resin and had the thickness of 500 μm, and through-holes having a diameter of 500 μm were formed therein. Also, the lower-cover sheet  33  was made of a polyimide resin, and had the thickness of 20 μm, in which holes having a diameter of 400 μm were formed at the positions corresponding to the positions of the through-holes of the substrate  32 .  
      Next, as shown in  FIG. 3 ( b ), the spiral terminals  31   a  and  31   b  were arranged with their respective protrusions facing outward and the hollow ring  39  having an outer diameter of 480 μm and a height of 200 μm was interposed therebetween. Thus, they were engaged in each through-hole of the substrate  32 , and an upper-cover sheet  34  similar to the lower-cover sheet  33  was attached to the substrate  32 , whereby an inspection socket of the present invention was produced as shown in  FIG. 3 ( c ).  
      As shown in  FIG. 3 ( d ), the inspection socket thus obtained was mounted on the electrodes  37  of the transformer former  38  of inspection equipment, and a semiconductor  35  to be inspected was placed on the inspection equipment. When a pressure of 70 mN force was applied in this state in the direction indicated by the arrows, electrical continuity was attained between the plate-shaped electrodes  36  of the semiconductor  35  and the electrodes  37  on the transformer former  38  because of the additive force of the spiral spring. Thus, the inspection of the semiconductor could be accomplished based on electrical signals obtained in this manner.  
      In this example, the diameter D of the spiral terminal was 480 μm. However, it was found that spiral terminals having a diameter D of about 100 μm can be produced according to the manufacturing method of the present invention, and that such spiral terminals can comply with the high density packaging of electronic equipment.  
      It should be noted that the embodiments and the examples disclosed in this specification are exemplary in all respects and that the present invention is not limited to them. It is intended that the scope of the present invention be shown by the claims rather than the description set forth above and include all modifications and equivalents to the claims.  
      According to the present invention, it is possible to provide inspection sockets and connectors for mounting, both having spiral terminals exhibiting high connection reliability.