Patent Publication Number: US-8969734-B2

Title: Terminal assembly with regions of differing solderability

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of and claims priority to U.S. Pat. No. 8,119,926, filed on Apr. 1, 2009. The entire contents of the patent are hereby fully incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to making electrical connections between electrical contacts of a first substrate and electrical contacts of a second substrate. 
     Ball grid array (BGA) and land grid array (LGA) integrated circuit (IC) packages are becoming increasingly popular. With a BGA package, for example, the rounded solder balls of the BGA are generally soldered directly to corresponding surface mount pads of a printed circuit board rather than to plated thru-holes which receive pins from, for example, a pin grid array (PGA) package. BGA packages are advantageous due to the ability to provide a high density of connections and low profiles. In addition, BGAs, with their very short distance between the package and the printed circuit board, have low inductances and therefore have far superior electrical performance relative to leaded devices. Once soldered to a printed circuit board, however, BGAs are difficult to replace or interchange. 
     Intercoupling components are used to allow particular IC packages to be reliably interchanged without permanent connection to a printed circuit board. More recently, adaptors for use with BGA and LGA packages have been developed to allow these packages to be non-permanently connected (e.g., for testing) to a printed circuit board. 
     SUMMARY 
     This invention relates to an intercoupling component to permit reliable, non-permanent electrical connection between a first substrate and a second substrate. More particularly, the intercoupling component includes an electrically conductive terminal assembly including a first end and a second end opposed to the first end. The first and second ends of the terminal assembly are configured to receive, and form an electrical connection with, a solder ball. An axial hole extends inward from each of the first end and the second end of the terminal, and an electrically conductive core member is disposed within each hole. The core members are sized and shaped to obstruct the hole. In addition, at least an outer surface of the core members includes a first material and at least an outer surface of the body includes a second material, the first material having greater solderability than the second material. 
     In one aspect, an electrical terminal is provided that includes an electrically conductive terminal body. The terminal body includes a first end and an axial hole extending inward from the first end. The first end is configured to receive a first solder ball. The terminal body includes a second end opposed to the first end, and the second end is configured to receive a second solder ball. The electrical terminal further includes an electrically conductive core member disposed within the hole. The core member is sized and shaped to obstruct the hole. In addition, at least an outer surface of the core member includes a first material and at least an outer surface of the body includes a second material, and the first material has greater solderability than the second material. 
     The electrical terminal includes one or more of the following features: 
     The first material is one of gold, gold alloy, tin, tin-lead alloy, and palladium-nickel alloy. The second material is one of nickel and nickel alloy. The core member is fixed within the through hole. The core member includes a shank portion received within the axial hole, and a head portion connected to the shank portion. The head portion is disposed outside the axial hole and includes a side which faces toward the first end. The core member is an elongate cylindrical member having a first end and a second end, and the first end is provided with a first diameter, and the second end is provided with a second diameter. The second diameter is greater than the first diameter, and the first end is fitted within the axial hole. 
     In some aspects, an intercoupling component of the type used to electrically connect a first substrate with a second substrate is provided. The intercoupling component includes an insulating support member having an array of apertures. Each aperture extends from a first surface of the insulating support member to an opposite second surface of the insulating support member, and each aperture is configured to receive a terminal assembly. The intercoupling component also includes a plurality of terminal assemblies which provide electrical connections between connection regions of the first substrate and respective corresponding connection regions of the second substrate. A terminal assembly is disposed in at least some of the apertures. Each terminal assembly includes an electrically conductive terminal body. The terminal body includes a first end and an axial hole extending inward from the first end. The first end is configured to receive a first solder ball. The terminal body also includes a second end opposed to the first end, and the second end is configured to receive a second solder ball. Each terminal assembly also includes an electrically conductive core member disposed within the hole. The core member is sized and shaped to obstruct the hole. At least an outer surface of the core member includes a first material and at least an outer surface of the body includes a second material, and the first material has greater solderability than the second material. 
     The intercoupling component may include one or more of the following features: 
     The first material is one of gold, gold alloy, tin, tin-lead alloy, and palladium-nickel alloy. The second material is one of nickel and nickel alloy. The core member is fixed within the through hole. The insulative support member includes a thin polyamide sheet. The core member is positioned within the axial hole such that an end face of the core member is flush with respect to the first end of the body. The core member includes a shank portion received within the axial hole, and a head portion connected to the shank portion. The head portion is disposed outside the axial hole and includes a side which faces toward the first end. 
     In some aspects, a method of forming an electrical terminal is provided. The method includes the following method steps: Forming a body using a screw machining process, the body including a first end and an axial hole extending inward from the first end. Forming a core member using a screw machining process separately from the body, the core member sized to fit within and obstruct the axial hole. Assembling the core member within the axial hole so that the hole is obstructed by the core member. In the method, at least an outer surface of the core member includes a first material and at least an outer surface of the body includes a second material, and the first material has greater solderability than the second material. 
     The method may further include plating at least the outer surface of the core member with the first material, and plating at least the outer surface of the body with the second material. 
     In some aspects, a method of connecting a ball grid array of a first substrate, the ball grid array including solder balls of a first type, to electrical connections on a second substrate using an intercoupling device including solder balls of a second type, is provided. The method steps include: Providing the device including a plurality of individual electrical terminals supported on an insulative sheet member. Arranging the first substrate on an upward facing surface of the device such that each solder ball of the ball grid array contacts a corresponding terminal of the device. Heating the device and first substrate in an environment having a temperature within a first range of temperatures to form an electrical connection between each solder ball of the ball grid array and the corresponding terminal. Inverting the device so that the first substrate resides below the device. Providing a solder ball of the second type on an upward facing surface of one or more of the terminals. Heating the device, first substrate, and solder balls of the second type in an environment having a temperature within a second range of temperatures. The second range of temperatures is lower than the first range of temperatures, so as to form an electrical connection between each solder ball of the second type and the corresponding terminal. Inverting the device so that the first substrate resides above the device. Arranging the device on an upper surface of the second substrate such that each solder ball of the second type contacts an electrical contact element of the second substrate. Heating the device, first substrate, and second substrate in an environment having a temperature within the second range of temperatures so as to form an electrical connection between each solder ball of the second type and the corresponding electrical contact elements of the second substrate. 
     The method may include one or more of the following features: 
     The solder balls of the first type are lead-free, and the solder balls of the second type are a tin-lead alloy. The second range of temperatures includes a range of temperatures at which the lead-free solder balls of the ball grid array do not reflow. 
     In some aspects, an electrical intercoupling device is provided. The device includes an electrically insulative support member including an array of through holes. The through holes extend between opposed first and second surfaces of the insulative support member. The distance between the first and second surfaces define a thickness of the support member. The device further includes plural electrically conductive terminals. Each terminal is disposed in a through hole and includes a terminal head, a terminal body extending from the terminal head and a retaining member that is separable from the terminal body. The terminal body includes a length that is greater than the thickness of the insulative support member, and a cross section that is configured such that an outer surface of the terminal body is spaced apart from an inner surface of the corresponding through hole. The terminal head has a dimension that is larger than the hole dimension. In addition, each terminal is disposed in a corresponding through hole of the array of through holes such that the terminal body resides in the hole and the retaining member is disposed on an end of the terminal body and is configured to cooperate with the terminal head to maintain the terminal within the hole. 
     The device may include one or more of the following features: 
     At least an outer surface of the retaining member includes a first material and at least an outer surface of the terminal body includes a second material. At least an outer surface of the terminal body includes a solderable material and at least an outer surface of the retaining member includes a material that is resistive to solder flow. At least an outer surface of the retaining member includes nickel. The retaining member is annular in shape, has an inner diameter of substantially the same dimension as the terminal body, and has an outer dimension that is larger than the hole dimension. The terminal head is positioned adjacent the first surface of the insulative member, and the retaining member is positioned adjacent the second surface of the insulative member. The terminal body comprises a first end integral with the terminal head, and an opposed second end, the second end of the terminal body including plug formed of a material different than the material of the terminal body. The second end of the terminal body terminates in the plug. The second end of the terminal body has a cross-sectional dimension that is less than that of the first end of the terminal body, and the plug has the same cross-sectional dimension as that of the second end. At least an outer surface of the plug includes a solderable material and at least an outer surface of the retaining member includes a material that is resistive to solder flow. 
     In some aspects, an electrical intercoupling device is provided. The device includes an electrically insulative support member including an array of through holes. The through holes extend between opposed first and second surfaces of the insulative support member. The distance between the first and second surfaces defines a thickness of the support member. The device also includes plural electrically conductive terminals. Each terminal is disposed in a through hole and includes a terminal head, a terminal body having a first end integral with the terminal head, and an opposed second end. The second end of the terminal body terminates in a plug formed of a material different than the material of the terminal body. 
     The device may include one or more of the following features: 
     Each terminal further includes a retaining member, the terminal body includes a length that is greater than the thickness of the insulative support member, and the terminal head has a dimension that is larger than the hole dimension. In addition, each terminal is disposed in a corresponding through hole of the array of through holes such that the terminal body resides in the hole. In addition, the retaining member is disposed on the second end of the terminal body and is configured to cooperate with the terminal head to maintain the terminal within the hole. At least an outer surface of the plug includes a solderable material and at least an outer surface of the retaining member includes a material that is resistive to solder flow. The retaining member is annular in shape, has an inner diameter of substantially the same dimension as the second end of the terminal body, and has an outer dimension that is larger than the through hole dimension. 
     In some aspects, an apparatus is provided that includes an electrically conductive socket terminal. The socket terminal includes an electrically conductive body, the body including a first end and a first axial hole extending inward from the first end, and a second end opposed to the first end, and a second axial hole extending inward from the second end. The socket terminal also includes a resilient contact member disposed in the first axial hole, and an electrically conductive core member sized and shaped to obstruct the second axial hole, the core member disposed within the second axial hole such that the second axial hole is obstructed, where being obstructed refers to full and complete blocking of the hole whereby fluid flow between the core member and an inner surface of the hole is prevented. 
     The apparatus may include one or more of the following features: 
     At least an outer surface of the core member includes a first material and at least an outer surface of the body includes a second material, the first material having greater solderability than the second material. The first material is one of gold, gold alloy, tin, tin-lead alloy, and palladium-nickel alloy. The second material is one of tin, tin alloy, nickel and nickel alloy. At least an outer surface of the core member includes a first material and at least an outer surface of the body includes a second material, and the first material is different from the second material. The core member includes a core member first end, the core member first end sized and shaped to obstruct the second axial hole, the core member first end disposed within the second axial hole such that the second axial hole is obstructed, and a core member second end opposed to the core member first end, the core member second end disposed outside the body. The core member second end comprises a pin. The core member further comprises an outwardly protruding flange portion disposed between the core member first end and the core member second end, and the core member second end comprises a pin that protrudes from the flange portion on a side of the flange portion that is opposed to the core member first end. The flange portion has a greater cross-sectional dimension than the corresponding cross-sectional dimension of the core member first end and the core member second end. The flange portion is disposed outside the second axial hole and includes a side which faces toward the body second end. 
     The apparatus may include one or more of the following additional features: 
     The apparatus further includes an insulating support member including an array of apertures, each aperture extending from a first surface of the insulating support member to an opposite second surface of the insulating support member, each aperture configured to receive one of the socket terminals; and one or more of the socket terminals disposed in respective apertures. The apparatus further includes a pin adaptor including a plurality of pins, each pin of the pin adaptor configured to engaged with a corresponding one of the socket terminals such that the pin is received in the first axial hole of the corresponding one of the socket terminals and forms an electrical connection with the body via the resilient contact member, the apparatus providing electrical connections between connection regions of a first substrate and respective corresponding connection regions of a second substrate. At least an outer surface of the core member includes a first material and at least an outer surface of the body includes a second material, and the first material is different from the second material. At least an outer surface of the core member includes a first material and at least an outer surface of the body includes a second material, the first material having greater solderability than the second material. The first material is one of gold, gold alloy, tin, tin-lead alloy, and palladium-nickel alloy. The second material is one of tin, tin alloy, nickel and nickel alloy. The core member includes a core member first end, the core member first end sized and shaped to obstruct the second axial hole, the core member first end disposed within the second axial hole such that the second axial hole is obstructed, and a core member second end opposed to the core member first end, the core member second end disposed outside the socket terminal. 
     The apparatus may include one or more of the following additional features: 
     The resilient contact member is configured to receive and form an electrical connection with a pin contact. The first end of the socket terminal is configured to receive a pin terminal, and the second end of the socket terminal is configured to be received within a hole in a printed circuit board. At least an outer surface of the core member includes a first material and at least an outer surface of the body includes a second material, and the first material is different from the second material. 
     Because the terminal assemblies disclosed herein are constructed by assembling a core member within a terminal body, manufacturing costs are greater than for terminal assemblies which are of single-piece construction and require no assembly. However, the increased manufacturing costs associated with the assembly of the core member within the terminal body are offset by reductions in material costs. That is, the cost savings associated with plating only the core member with a material such as gold, rather than the entire terminal assembly with a material such as gold, more than compensates for the cost of assembling the core member within the terminal body. 
     Modes for carrying out the present invention are explained below by reference to an embodiment of the present invention shown in the attached drawings. The above-mentioned object, other objects, characteristics and advantages of the present invention will become apparent from the detailed description of the embodiment of the invention presented below in conjunction with the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of an intercoupling component of the type used to couple a printed circuit board to a BGA package. 
         FIG. 2  is a partial side sectional view of the intercoupling component of  FIG. 1 . 
         FIG. 3  is a partial side sectional view of another embodiment of an intercoupling component. 
         FIG. 4  is a partial side sectional view of another embodiment of an intercoupling component. 
         FIG. 5  is a partial side sectional view of another embodiment of an intercoupling component. 
         FIG. 6  is a perspective view of the core member of the terminal of  FIG. 5 . 
         FIG. 7  is a partial side sectional view of another embodiment of an intercoupling component. 
         FIG. 8  is a partial side sectional view of another embodiment of an intercoupling component. 
         FIG. 9  is a side view of another embodiment of an intercoupling component. 
         FIG. 10  is a side sectional view of a terminal of the intercoupling component of  FIG. 9 . 
         FIG. 11  is a side sectional view of another embodiment of a terminal of the intercoupling component of  FIG. 9 . 
         FIG. 12  is a side sectional view of another embodiment of a terminal of the intercoupling component of  FIG. 9 . 
         FIG. 13  is a side sectional view of another embodiment of a terminal of the intercoupling component of  FIG. 9 . 
         FIG. 14  is a side view of another embodiment of an intercoupling component. 
         FIG. 15  is a perspective view of a terminal of the intercoupling component of  FIG. 14 . 
         FIG. 16  is a perspective view of another embodiment of a terminal of the intercoupling component of  FIG. 14 . 
         FIGS. 17-20  are partial side-sectional views of the intercoupling component of  FIG. 14  illustrating the method of connecting a BGA package using lead-free solder balls to electrical connections on a printed circuit board using lead-containing solder balls. 
         FIG. 21  is a partial side sectional view of a socket adaptor for the intercoupling component of  FIG. 2 , illustrating an alternative embodiment of a socket. 
         FIG. 22  is a partial side sectional view of a socket adaptor for the intercoupling component of  FIG. 2 , illustrating another alternative embodiment of a socket. 
         FIG. 23  is a partial side sectional view of a socket adaptor for the intercoupling component of  FIG. 2 , illustrating another alternative embodiment of a socket. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a BGA socket converter assembly  320  for intercoupling a BGA integrated circuit package  4  to a printed circuit board  6  is shown. The BGA socket converter assembly  320 , serving as an intercoupling component, includes a socket adaptor  302  and a pin adaptor  301 . The socket adaptor  302  includes a first electrically insulative support member  310  for supporting sockets  330 , each of which is received within a corresponding one of an array of holes  316  in the first insulative member  310 . The array of holes  316  are provided in a pattern corresponding to a footprint of rounded solder balls (not shown) of BGA package  4  as well as a footprint of surface mount pads  7  of printed circuit board  6 . The pin adaptor  301  includes a second electrically insulative support member  360  supporting pins  260  positioned within an array of holes  366 . Like the array of holes  316  in the first insulative member, the array of holes  366  in the second insulative member  360  is provided in a pattern corresponding to a footprint of the rounded solder balls of the BGA package  4  as well as a footprint of the surface mount pads  7  of the printed circuit board  6 . 
     When the solder balls of the BGA package  4  are soldered to the pins  260  of pin adaptor  301 , the BGA package  4  is converted to a high density pin grid array (PGA). When the pin adaptor  301  is assembled with the socket adaptor  302 , pins  260  are received within sockets  330 . As will be discussed in detail below with respect to  FIG. 2 , each socket  330  includes a solder ball  12  attached to its lower end  342  to provide an identical mating condition to the surface mount pads  7  of the printed circuit board  6  as would have been the case if the BGA package  4  had been connected directly to the circuit board. Thus, the converter assembly  320  permits the BGA package  4  to be non-permanently electrically intercoupled with the printed circuit board  6 . 
     As seen in  FIG. 2 , each pin  260  cooperatively engages a corresponding socket  330  to provide an electrical connection between a surface mount pad  5  of BGA package  4  and a corresponding surface mount pad  7  of printed circuit board  6 . 
     The pin  260  includes a pin head  262  fixed within the hole  366 , and an integral stem  266  that extends outward from the pin head  262 . The pin  260  is configured to receive a solder ball  12  at one end of the pin head  262 . In the illustrated orientation of the socket converter assembly  320 , the solder ball  12  is received on a first, upper end  268  of the pin head  262 , and the stem  266  extends from a second, opposed, lower end  270  of the pin head  262 . 
     The socket  330  includes a socket base  336  having an end  342  configured to receive a solder ball  12 , and a socket body  332  extending integrally from the socket base  336 . The socket body  332  is supported on the electrically insulative support member  310 . The socket body  332  includes a socket cavity  334  opening at an end  340  of the socket body  332  opposed to the base end  342 , and a resilient contact member  348  is disposed within the cavity  334 . The resilient contact member  348  is fixed within cavity  334  and forms an electrical connection with the socket body  332  along mutually contacting surfaces. In use, the stem  266  of the pin  260  is slidably received within, and forms an electrical connection with, the resilient contact member  348 . 
     An axial hole  338  is provided at, and extends axially inward from, the end  342  of the socket base  336 . A core member  246  is disposed within the axial hole  338 . 
     The core member  246  is electrically conductive and is sized and shaped to obstruct the axial hole  338 , where the term obstruct as used herein refers to a full and complete blocking of, or stopping-up of, the hole, whereby fluid flow between the core members  246  and the inner surface of the axial hole  338  is prevented. The core member  246  is fixed within the axial hole  338  and forms an electrical connection with the socket head  336  along mutually contacting surfaces. The core member  246  is positioned within the axial hole  338  so that an end face  245  of the core member  246  lies flush with the outer surface of the terminal structure. That is, in the socket  330 , the core member  246  lies flush with the end  342  of the socket base  336 . Alternatively, the core member  246  may be positioned within the axial hole  338  so that an end face  245  of the core member  246  is spaced slightly inward relative to an end face of the terminal structure, forming a shallow depression (not shown) at the location of the core member  246 . The depression can be useful in positioning and retaining the solder ball  12  relative to the socket base end  342 . 
     The pin  260 , the socket  330  and core members  246  are formed of electrically conductive materials. During solder reflow, solder is prevented from flowing along a peripheral side of the socket  330  by selective use of materials in the manufacture thereof. In particular, the socket  330  is formed of, coated, or plated with a material that is resistive to solder flow or has relatively low solderability. In addition, the core member  246  is formed of, coated, or plated with material that has relatively high solderability in that it promotes solder flow, forms a good electrical contact and bonds well with a solder ball. As a result, when a solder ball  12 , positioned adjacent to an end  342  of the socket  330 , is heated to cause the solder to flow, the solder does not flow along a peripheral side of the socket  330  due to the chemical response of the solder to the materials of the terminal body. Instead, solder is generally maintained in the vicinity of the core member  246 . 
     In some embodiments, the socket  330  is manufactured entirely of an electrically conductive material that is resistive to solder flow or has relatively low solderability as compared to the material used to manufacture the core members  246 . Such materials will be referred to herein as “solder resistive materials.” Solder resistive materials generally inhibit solder flow and do not bond well with the applied solder. Examples of solder resistive materials include nickel and nickel alloys. In other embodiments, the socket  330  is manufactured of an electrically conductive material such as brass or copper, and is then coated or plated with the material that is resistive to solder flow or has relatively low solderability. 
     In some embodiments, the core member  246  is manufactured entirely of an electrically conductive material that is easily solderable, and has better solderability properties than that of the socket  330 . Such materials will be referred to herein as “solderable materials.” Examples of solderable materials include gold and gold alloys. In other embodiments, the core member  246  is manufactured of an electrically conductive material such as brass or copper, and is then coated or plated with the material that easily solderable, and has better solderability properties than that of the terminal body. Examples of solderable materials which would be used as coating or plating materials are gold, gold alloys, tin, tin-lead alloys, and palladium-nickel alloys. 
     In some embodiments, the pin  260  and contact member  348  are manufactured entirely of a solderable materials. In other embodiments, the pin  260  and/or contact member  348  are manufactured of an electrically conductive material such as brass or copper, and are then coated or plated with a solderable material. 
     Although respective examples of solderable materials and solder resistive materials are listed above, other materials are applicable, and selection of material will depend on, at least, the type of solder employed. 
     Referring now to  FIG. 3 , another embodiment of the socket converter assembly is shown. In this embodiment, the pin adaptor  301  of  FIG. 2  is used with a socket adaptor  602  to provide a socket converter assembly  620 . The socket adaptor  602  includes a socket  630  supported on the electrically insulative support member  310  as described in more detail below. As in the previous embodiment, in the socket converter assembly  620 , each pin  260  cooperatively engages a corresponding socket  630  to provide an electrical connection between a surface mount pad  5  of BGA package  4  and a corresponding surface mount pad  7  of printed circuit board  6 . 
     The socket  630  includes a socket base  636  having an end  642  configured to receive a solder ball  12 , and a socket body  632  extending integrally from the socket base  636 . The socket body  632  includes a socket cavity  634  opening at an end  640  of the socket body  632  opposed to the base end  642 , and a resilient contact member  348  is fixed within the cavity  634  so as to form an electrical connection with the socket body  632  along mutually contacting surfaces. In use, the stem  266  of the pin  260  is received within, and forms an electrical connection with, the resilient contact member  348 . 
     The first end  640  of the socket body is provided with a widened portion  641  having an outer dimension (e.g. diameter) that is greater than that of the socket body  632  and the hole  316 . The second end  642  of socket  630  includes a narrowed portion  643  having a smaller cross-sectional dimension (e.g. diameter) than the socket body  632 . An annular ring  560  is fitted on the periphery of the narrowed portion  643 , and has an outer dimension (e.g. diameter) greater than that of the hole  316 . The annular ring  560  cooperates with widened portion  641  of the socket body  632  to maintain the socket  630  within the hole  316  and to substantially prevent vertical movement of the socket  630  relative to support member  310 . This configuration permits the socket  630  to have smaller cross-sectional dimensions that that of the hole  316  to an extent that a gap g exists between the socket  630  and the hole  316 , a feature that reduces stress within the support member  310 , and in turn can prevent warping of the socket adaptor  602 . 
     Annular ring  560  encircles the narrowed portion  643 . In addition, the narrowed portion  643  is dimensioned to be fitted within the inner diameter of the annular ring  560  so that fluid flow is prevented between the narrowed portion  643  and the inner diameter surface of the annular ring  560 . In some embodiments, the socket  630 , including the narrowed portion  643 , is formed of, coated, or plated with an electrically conductive, solderable material, and the annular ring  560  is formed of a solder-resistive material. By selection of materials in this way, solder is permitted to flow and connect to the exposed end face  642  of the narrowed portion  643 , but is substantially prevented from flowing along the inner diameter surfaces of the annular ring  560 . 
     Referring now to  FIG. 4 , another embodiment of the intercoupling device is shown. In this embodiment, the pin adaptor  301  of  FIG. 2  is used with a socket adaptor  202  to provide a socket converter assembly  220 . The socket adaptor  202  includes a plurality of sockets  230  supported by support members  40 ,  50 , in an arrangement which corresponds to the pattern of surface mount pads  5 ,  7  of the substrates  4 ,  6  to be interconnected. As in the previous embodiments, in the socket converter assembly  220 , each pin  260  cooperatively engages a corresponding socket  230  to provide an electrical connection between a surface mount pad  5  of BGA package  4  and a corresponding surface mount pad  7  of printed circuit board  6 . 
     The support members  40 ,  50  include an array of through holes  46 ,  56  each dimensioned to receive a socket  230  and arranged in the pattern described above. The support members  40 ,  50  are formed of a thin sheet (e.g. 5-7 mils) of insulative material. In some embodiments, the sheet may be somewhat flexible as embodied by a polyamide film. The polyamide film may be, for example, a Kapton® sheet (Kapton is a registered trademark of E.I. DuPont de Nemours &amp; Co., Wilimington, Del.). In other embodiments, the sheet may be sufficiently rigid to retain a planar configuration when supported in a cantilevered manner, as embodied by a molded plastic sheet of FR4 printed circuit board material. 
     The lower end of the socket  230  includes a socket base  236  configured to receive a solder ball  12 , and a socket body  232  extends from the socket base  236 . The socket body  232  includes a socket cavity  234  opening at an upper end  240  of the socket body  232  opposed to the base end  242 , and a resilient contact member  348  is fixed within the cavity  234  so as to form an electrical connection with the socket body  232  along mutually contacting surfaces. In use, the stem  266  of the pin  260  is received within, and forms an electrical connection with, the resilient contact member  348 . 
     Circumferential grooves  244 , provided about the periphery of each of the base end  236  and upper end  240 , cooperatively engage the edge portions of the insulative support members  40 ,  50  at each respective hole  46 ,  56 . That is, holes  46 ,  56  of the insulative support members  40 ,  50  are sized and shaped to correspond to the size and shape of the grooves  244  such that portions of the insulative support members reside within circumferential grooves  244 . As a result, the axial position of the insulative support members  40 ,  50  relative to the socket  230  is easily maintained. 
     An axial hole  238  is provided at, and extends axially inward from, the end  242  of the socket base  236 , and a core member  246  is disposed within the axial hole  238 . 
     The core member  246  is sized and shaped to obstruct the axial hole  238 , and forms an electrical connection with the socket base  236  along mutually contacting surfaces. As in the previous embodiment, the pin  260 , the socket  230 , and the core member  246  are each formed of electrically conductive materials. In socket converter assembly  220 , solder is prevented from flowing along peripheral sides of the socket base  236  during solder reflow by selective use of materials in manufacturing the socket  230 . In particular, the socket  230  is formed of, coated, or plated with a material that is resistive to solder flow or has relatively low solderability. In addition, the core member  246  is formed of, coated, or plated with material that has relatively high solderability in that it promotes solder flow, forms a good electrical contact and bonds well with a solder ball. As a result, during use when a solder ball  12 , positioned adjacent to an end face  242  of the socket  230  is heated to cause the solder to flow, the solder does not flow along a peripheral side of the socket base  236  due to the due to the chemical response of the solder to the materials of these members, and is generally maintained in the vicinity of the core member  246 . 
     Referring now to  FIG. 5 , another embodiment of the intercoupling device is shown. In this embodiment, the pin adaptor  301  of  FIG. 2  is used with a socket adaptor  702  to provide a socket converter assembly  720 . The socket adaptor  702  includes a plurality of sockets  730  supported by a support member  315  in an arrangement which corresponds to the pattern of surface mount pads  5 ,  7  of the substrates  4 ,  6  to be interconnected. As in the previous embodiments, in the socket converter assembly  720 , each pin  260  cooperatively engages a corresponding socket  730  to provide an electrical connection between a surface mount pad  5  of BGA package  4  and a corresponding surface mount pad  7  of printed circuit board  6 . 
     The support member  315  is formed of an electrically insulative material. In some embodiments, support member  315  is of single-piece construction. In the illustrated embodiment, support member  315  is of two-piece construction and includes a base layer  312 , and an outer layer  314  pressed onto an outward-facing surface of the base layer  312 . The base layer  312  and outer layer  314  may be formed of the same insulative material, or formed of different insulative materials. The outer layer  314  is thin relative to the base layer  312 . For example, the base layer  312  may be in the range of 5 to 20 times the thickness of the outer layer  314 . The support member  315  is provided having an overall thickness that is about or slightly less than the axial length l 3  of the socket  730 . Each layer  312 ,  314  of the support member  315  includes a respective array of through holes  316 ,  318  arranged in the pattern described above. The through holes  316  of base layer  312  are dimensioned to correspond to the shape and size of the socket  730 , and the through holes  318  of the outer layer  314  are dimensioned to correspond to the shape and size of a shank portion  352  of the socket core  350  ( FIG. 6 , described below). 
     The socket  730  includes a socket base  736 , and a socket body  732  extending from the socket base  736 . The socket body  732  includes a socket cavity  734  opening at the first end  740  of the socket body  732 . A resilient contact member  348  is fixed within the cavity  734  so as to form an electrical connection with the socket base  736  along mutually contacting surfaces. In use, the stem  266  of the pin  260  is received within, and forms an electrical connection with, the resilient contact member  348 . 
     A socket axial hole  738  is provided at, and extends axially inward from, the end  742  of the socket base  736 . A shaped socket core  350  is disposed within the socket axial hole  738 . As seen in  FIG. 6 , the shaped core member  350  includes a shank portion  352  sized to be received within the socket axial hole  738 , and a head portion  354  connected to an end of the shank portion  352 . In some embodiments, the shank portion  352  is fitted within the socket axial hole  738 . When the socket  730  is received within the support member  315 , the head portion  354  is disposed outside the through hole  318  of the outer layer  314 . The shank portion  352  of the shaped core member  350  has a shank cross-sectional dimension d 3  (e.g. diameter), the head portion  354  has a head cross-sectional dimension d 4  (e.g. diameter), and the head cross-sectional dimension d 4  is greater than the shank cross-sectional dimension d 3 . As shown in  FIG. 5 , when the shank portion  352  is received within the socket axial hole  738 , the head portion  354  is disposed outside the axial hole  738 , and extends in a plane that is perpendicular to an axial direction of the shank portion  352  so that a side  356  of the head portion  354  is spaced apart from and faces toward the end  742  of the socket base  736 . The outer layer  314  of the support member  315  is interposed between the side  356  of the head portion  354  and the end  742  of the socket base  736 . 
     The core member  350  is electrically conductive, and the shank portion  352  is sized and shaped to obstruct the socket axial hole  738  and form an electrical connection with the socket base  736  along mutually contacting surfaces. As in previous embodiments, the socket  730  and the core member  350  are each formed of electrically conductive materials. In socket  730 , solder is prevented from flowing along a peripheral side of the socket base  736  during solder reflow by selective use of materials. In particular, the socket  730 , including the socket base  736 , is formed of, coated, or plated with a material that is resistive to solder flow or has relatively low solderability. In addition, the core member  350  is formed of, coated, or plated with material that has relatively high solderability in that it promotes solder flow, forms a good electrical contact and bonds well with a solder ball. As a result, during use when a solder ball  12  positioned adjacent to a lower side  358  of the core member  350  is heated to cause the solder to flow, the solder does not flow along a peripheral side of the socket base  736  due to the due to the chemical response of the solder to the materials of these members, and is generally maintained in the vicinity of the head portion  354  of the core member  350 . In some embodiments, solder retention in the vicinity of the head portion  354  may be enhanced by use of a solder resist coating an outward-facing surface of the outer layer  314  of the support member  315 . 
     Referring now to  FIG. 7 , another embodiment of the intercoupling device is shown. In this embodiment, the pin adaptor  301  of  FIG. 2  is used with a socket adaptor  502  to provide a socket converter assembly  520 . The socket adaptor  502  includes a plurality of sockets  530  supported by a support member  510  in an arrangement which corresponds to the pattern of surface mount pads  5 ,  7  of the substrates  4 ,  6  to be interconnected. As in the previous embodiments, in the socket converter assembly  520 , each pin  260  cooperatively engages a corresponding socket  530  to provide an electrical connection between a surface mount pad  5  of BGA package  4  and a corresponding surface mount pad  7  of printed circuit board  6 . 
     The socket  530  is supported on one of an array of holes  516  formed in an insulative support member  510 , and includes a socket base  536 , and a socket body  532  extending from the socket base  536 . The socket body  532  includes a socket cavity  534  opening at the first end  540  of the socket body  532 . A resilient contact member  348  is fixed within the cavity  534  so as to form an electrical connection with the socket base  536  along mutually contacting surfaces. In use, the stem  266  of the pin  260  is received within, and forms an electrical connection with, the resilient contact member  348 . 
     The first end  540  of the socket body  532  is provided with a widened portion  541  having an outer dimension (e.g. diameter) that is greater than that of the socket body  532  and the hole  516 . The second end  542  of socket  530  includes a narrowed portion  543  having a smaller cross-sectional dimension (e.g. diameter) than the socket body  532 . An annular ring  560  is fitted on the narrowed portion  543 , and has an outer dimension (e.g. diameter) greater than that of the hole  516 . The annular ring  560  cooperates with widened portion  541  of the socket body  532  to prevent vertical movement of the socket  530  relative to support member  510 . This configuration permits the socket  530  to have smaller cross-sectional dimensions than that of the hole  516  to an extent that a gap g exists between the socket  530  and the hole  516 , a feature that reduces stress within the support member  510 , and in turn can prevent warping of the intercoupling device  520 . 
     The narrowed portion  543  terminates at a plug  550 . In some embodiments, the plug  550  is formed separately from the socket  530 , and is fixed to the narrowed portion  543  by conventional means in such a way as to provide an electrically conductive path therethrough. For example, in some embodiments, an interference fit between the annular ring  560  and the plug  550 , and between the annular ring  560  and the narrowed portion  543  retains the plug  550  in electrical contact with the narrowed portion  543 . 
     The annular ring  560  encircles both the narrowed portion  543  and plug  550 . In addition, the narrowed portion  543  and plug  550  are dimensioned to be fitted within inner diameter of the annular ring  560  so that fluid flow is prevented between either of the narrowed portion  543  or plug  550 , and the inner surface of the annular ring  560 . In some embodiments, the socket  530  including the narrowed portion  543  are formed of an electrically conductive material such as brass, the plug  550  is formed of a solderable material, and the annular ring  560  is formed of, or plated with a solder-resistive material. By selection of materials in this way, solder is permitted to flow and connect to the plug  550 , but is substantially prevented from flowing along the surfaces of the annular ring  560 . 
     Referring now to  FIG. 8 , another embodiment of the intercoupling device is shown. In this embodiment, the pin adaptor  301  of  FIG. 2  is used with a socket adaptor  402  to provide a socket converter assembly  420 . The socket adaptor  402  includes a plurality of sockets  430  supported by support members  40 ,  50  (described above with reference to  FIG. 4 ) in an arrangement which corresponds to the pattern of surface mount pads  5 ,  7  of the substrates  4 ,  6  to be interconnected. As in the previous embodiments, in the socket converter assembly  420 , each pin  260  cooperatively engages a corresponding socket  430  to provide an electrical connection between a surface mount pad  5  of BGA package  4  and a corresponding surface mount pad  7  of printed circuit board  6 . 
     The socket  430  includes a socket base  436 , and a socket body  432  extending from the socket base  436 . The first, upper end  440  of socket  430  is supported in a corresponding hole  46  of the support member  40  and the second, lower end  442  of socket  430  is supported in a corresponding hole  56  of the support member  50 . 
     A circumferential groove  444  is provided about the periphery of first end  440 , which cooperatively engages the edge portion of the insulative support members  40  at each respective hole  46 . That is, holes  46  of the insulative support members  40  are sized and shaped to correspond to the size and shape of the grooves  444  such that portions of the insulative support members reside within circumferential grooves  444 . 
     The socket body  432  includes a socket cavity  434  opening at the first end  440  of the socket body  432 . A resilient contact member  348  is fixed within the cavity  434  so as to form an electrical connection with the socket base  436  along mutually contacting surfaces. In use, the stem  266  of the pin  260  is received within, and forms an electrical connection with, the resilient contact member  348 . 
     The second end  442  of socket  430  includes a narrowed portion  443  having a smaller cross-sectional dimension (e.g. diameter) than the socket body  432 . The holes  56  of the insulative support member  50  are sized and shaped to substantially correspond to the size and shape of the narrowed portion  443 , and in use, the narrowed portion  443  is received in a corresponding hole  56 . The narrowed portion  443  terminates at a plug  450 . 
     An annular ring  460  is fitted about the narrowed portion  443  and plug  450 , and has an outer dimension (e.g. diameter) greater than that of the hole  56 . The annular ring  460  prevents vertical movement of the socket  430  relative to support member  50 . This configuration permits the narrowed portion  443  of socket  430  to have a smaller cross-sectional dimension that that of the hole  56  to an extent that a gap exists between the narrowed portion  443  and the hole  56 , a feature that reduces stress within the support member  50 , and in turn can prevent warping of the intercoupling device. 
     The annular ring  460  encircles both the narrowed portion  443  and plug  450 . In addition, the narrowed portion  443  and plug  450  are dimensioned to be fitted within the annular ring  460  so that fluid flow is prevented between either of the narrowed portion  443  or plug  450 , and the inner surface of the annular ring  460 . In some embodiments, the socket  430 , including the narrowed portion  443 , is formed of an electrically conductive material such as brass, the plug  450  is formed of, coated, or plated with a solderable material, and the annular ring  460  is formed of a solder-resistive material. By selection of materials in this way, solder is permitted to flow and connect to the plug  450 , but is substantially prevented from flowing along the surfaces of the annular ring  460  or the socket body  432 . 
     Referring now to  FIG. 9 , an intercoupling device  20 , used to provide an electrical connection between electrical contacts (e.g. surface mount pads  5 ) of a first substrate (e.g. BGA package  4 ) and corresponding electrical contacts (e.g. surface mount pads  7 ) of a second substrate (e.g. printed circuit board  6 ), will now be described. The intercoupling device  20  includes a plurality of electrically conductive, single-piece terminals  80 , a support member  40  which supports a first end (illustrated here as the upper end)  88  of each terminal  80 , and a support member  50  which supports a second end (illustrated here as the lower end)  90  of each terminal  80 . The terminals  80  are supported by the support members  40 ,  50  in an arrangement which corresponds to the pattern of surface mount pads  5 ,  7  of the substrates  4 ,  6  to be interconnected. 
     The support members  40 ,  50  are substantially similar to those described above with respect to  FIG. 4 , and their description is not repeated here. 
     Each terminal  80  includes an electrically conductive terminal body  82 . In the embodiment illustrated in  FIGS. 8-10 , the terminal body  82  is an elongate member. For example, the axial length l 1  of the terminal body  82  is at least twice the cross-sectional dimension (e.g. diameter d 1 ) of the terminal body  82 . In some embodiments, the terminal body  82  is generally cylindrical, although the cross-sectional shape of the terminal body  82  is not limited to a circular shape. Each of the first and second ends  88 ,  90  is configured to receive a solder ball  12 . 
     Circumferential grooves  83  may be provided adjacent to each of the first and second ends  88 ,  90 , which cooperatively engage the edge portions of the insulative support members  40 ,  50  at each respective hole  46 ,  56 . That is, holes  46 ,  56  of the insulative support members  40 ,  50  are sized and shaped to correspond to the size and shape of the groove  83 , such that portions of the insulative support members reside within circumferential grooves  83 . As a result, the axial position of the insulative support members  40 ,  50  relative to the terminal body  82  is easily maintained. 
     As seen in  FIG. 10 , a first axial hole  84  is provided at, and extends axially inward from, the first end  88  of the terminal body  82 . Similarly, a second axial hole  86  is provided at, and extends axially inward from, the second end  90  of the terminal body  82 . A core member  70  is disposed within each of the first axial hole  84  and second axial hole  86 . 
     The core members  70  are electrically conductive and are sized and shaped to obstruct the respective axial hole  84 ,  86 , whereby fluid flow between the core member  70  and the inner surface of the respective axial hole  84 ,  86  is prevented. The core members  70  may be fixed within the respective axial hole  84 ,  86  and form an electrical connection with the terminal body  82  along mutually contacting surfaces. The core members  70  may be positioned within the respective axial hole  84 ,  86  so that an end face  76  of the core member  70  lies flush with the corresponding end face of the terminal body  82  ( FIGS. 10 ,  12 ). 
     Alternatively, the core members  70  may be positioned within the respective axial hole  84 ,  86  so that an end face  76  of the core member  70  is spaced slightly inward relative to an end face of the terminal body  82 , forming a shallow depression at the location of the core member  70  ( FIG. 11 ). The depression can be useful in positioning and retaining the solder ball  12  relative to the terminal  80 . 
     As discussed above, both the terminal body  82  and core members  70  are formed of electrically conductive materials. In terminal  80 , solder is prevented from flowing along a peripheral side  92  of the terminal body  82  during solder reflow by selective use of materials in manufacturing the terminal  80 . In particular, terminal body  82  is formed of, coated, or plated with a material that is resistive to solder flow or has relatively low solderability. In addition, core members  70  are formed of, coated, or plated with material that has relatively high solderability in that it promotes solder flow, forms a good electrical contact and bonds well with a solder ball. As a result, during use when a solder ball  12 , positioned adjacent to an end face of the terminal  80 , is heated to cause the solder to flow, the solder does not flow along a peripheral side  92  of the terminal body  82  due to the chemical response of the solder to the materials of the terminal body  82 , and is generally maintained in the vicinity of the core members  70 . 
     In some embodiments, the terminal body  82  is manufactured entirely of an electrically conductive material that is resistive to solder flow or has relatively low solderability as compared to the material used to manufacture the core members  70 . In other embodiments, the terminal body  82  is manufactured of an electrically conductive material such as brass or copper, and is then coated or plated with the material that is resistive to solder flow or has relatively low solderability. 
     In some embodiments, the core member  70  is manufactured entirely of an electrically conductive material that is easily solderable, and has better solderability properties than that of the terminal body  82 . In other embodiments, the core member  70  is manufactured of an electrically conductive material such as brass or copper, and is then coated or plated with the material that easily solderable, and has better solderability properties than that of the terminal body  82 . 
     Referring now to  FIG. 12 , in some embodiments, a terminal  80 ′ may include a single axial through hole  84 ′, and core members  70  are provided within the through hole  84 ′ such that a first core member  70  is disposed adjacent to the first end  88  of the terminal body  82 ′, and a second core member  70  is disposed adjacent to the second end  90  of the terminal body  82 ′. As in earlier embodiments, the core members  70  are electrically conductive and are sized and shaped to obstruct the respective axial hole  84 ′. In addition, the core members  70  are formed of, coated or plated with a solderable material, and the terminal body  82 ′ is formed of, coated or plated a solder resistive material. 
     Referring now to  FIG. 13 , in some embodiments, a terminal  80 ″ may include a single axial through hole  84 ′, and a single, elongate core member  70 ′ is provided within the through hole  84 ′ such that the elongate core member  70 ′ extends from the first end  88  of the terminal body  82 ′ to the second end  90  of the terminal body  82 ′. As in earlier embodiments, the elongate core member  70 ′ is electrically conductive and is sized and shaped to obstruct the respective axial hole  84 . In addition, the core member  70 ′ is formed of, coated or plated with a solderable material, and the terminal body  82 ′ is formed of, coated or plated with a solder resistive material. 
     Referring now to  FIGS. 14-16 , another embodiment of the intercoupling device is shown. Intercoupling device  120  is used to provide an electrical connection between surface mount pads of BGA package  4  and corresponding surface mount pads of printed circuit board  6 . The intercoupling device  120  includes a plurality of electrically conductive terminals  180  supported by a single support member  40 , in an arrangement which corresponds to the pattern of surface mount pads  5 ,  7  of the substrates  4 ,  6  to be interconnected. 
     Each terminal  180  includes an electrically conductive terminal body  182 . The terminal body  182  is a member in which the axial length l 2  of the terminal body  182  is less than the cross-sectional dimension (e.g. diameter d 2 ) of the terminal body  182 , whereby the terminal body  182  is a substantially disk-shaped member. In some embodiments, the terminal body  182  is generally cylindrical, although the cross-sectional shape of the terminal body  182  is not limited to a circular shape. The terminal body  182  has a first end  188 , and a second end  190  opposed to the first end  188 . Each of the first and second ends  188 ,  190  is configured to receive a solder ball  12 . 
     As seen in  FIG. 15 , an axial through hole  184  is provided in the terminal body  182 , and a core member  170  is provided within the through hole  184  such that the core member  170  extends from the first end  188  of the terminal body  182  to the second end  190  of the terminal body  182 . As in earlier embodiments, the core member  170  is electrically conductive and is sized and shaped to obstruct the axial hole  184 , forming an electrical connection with the terminal body  182  along mutually contacting surfaces. In addition, the core member  170  is formed of, coated, or plated with a solderable material, and the terminal body  182  is formed of, coated or plated with a solder resistive material. 
     The core member  170  may be positioned within the axial hole  184  so that one or both end faces  176  of the core member  170  lie flush with the corresponding end face of the terminal body  182  ( FIG. 15 ). Alternatively, the core member  170  may be positioned within the axial hole  184  so that the end faces  176  of the core member  170  are spaced slightly inward relative to an end face of the terminal body  182 , forming a shallow depression at the location of the core member  170  ( FIG. 16 ). 
     A method of forming the electrical terminals  80 ,  180  will now be described. 
     The terminals  80 ,  180  are each formed individually. In addition, the terminal body  82 ,  182  is formed separately from the core members  70 ,  170 . In some embodiments, the terminal body  82 ,  182  is formed using a screw machining process, including formation of the axial hole  84 ,  86 ,  184  in one or both ends. The core members  70 ,  170  may be formed using a screw machining process, or alternatively may be formed using other processes including stamping or riveting. 
     In some embodiments, the terminal body  82 ,  182  and core members  70 ,  170  are formed of an electrically conductive material such as brass. An outer surface of the terminal body  82 ,  182  is then plated or coated with a solder resistive material, and the outer surface of the core members  70 ,  170  is plated or coated with a solderable material. 
     Then, the core members  70 ,  170  are assembled within the corresponding axial holes of the terminal body  82 ,  182  so that the axial hole is obstructed. 
     In the converter assembly  220 ,  320 ,  420 ,  520 ,  620 ,  720  ( FIGS. 2-5  and  7 - 8 ) which employs an assembly of a pin and a socket to provide an electrical terminal, the socket  230 ,  330 ,  430 ,  530 ,  630 ,  730  is formed separately from its respective core (plug) member  246 ,  350 ,  450 ,  550  and/or annular ring  460 ,  560 , as well as from the pin  260 . The socket  230 ,  330 ,  430 ,  530 ,  630 ,  730  and annular ring  460 ,  560  (if required) are then plated or coated with a solder resistive material. The pin  260  and core (plug) member  246 ,  350 ,  450 ,  550  are plated or coated with a solderable material. 
     The core (plug) members  246 ,  350 ,  450 ,  550  and annular ring  460 ,  560  (if required) are then assembled with the corresponding socket body  230 ,  330 ,  430 ,  530 ,  630 ,  730  as described above. 
     By this procedure, at least an outer surface of the pin  260  and core (plug) member  70 ,  170 ,  246 ,  350 ,  450 ,  550  includes a first material and at least an outer surface of the body  82 ,  182 ,  232 ,  332 ,  432 ,  532 ,  632  and/or annular ring  460 ,  560  includes a second material, the first material having greater solderability (being more solderable) than the second material. 
     Recent regulatory efforts to limit certain hazardous substances in some geographic areas and/or in some industries, such as the Restriction of Hazardous Substances in Electrical and Electronic Equipment (RoHS), have resulted in inconsistencies in the products that are manufactured, such that some electronic components, including IC packages and/or printed circuit boards, are compliant with regulations and some are not. Thus, it can be advantageous to provide an intercoupling device which permits, for example, a lead-free component to be assembled to a lead-containing component. A method of connecting a lead-free substrate (e.g. BGA package  4 ) using lead-free solder balls  12   a , to electrical connections on a second, lead-containing substrate (e.g. printed circuit board  6 ) using lead-containing solder balls  12   b  is accomplished using the intercoupling devices described above. The method will be described herein with reference to  FIGS. 17-20  using the intercoupling device  120  as an example. 
     The connecting method includes the following method steps: 
     The intercoupling device  120  is provided which includes a plurality of individual electrical terminals  180  supported on an insulative sheet member  40 , the terminals arranged in a pattern corresponding to that of the electrical connections of the substrates  4 ,  6  to be connected. In  FIG. 17 , only two terminals  180  are shown for simplicity of illustration. However, it is understood that the number and arrangement of terminals  180  may correspond to the number and arrangement of electrical contacts of one or both substrates  4 ,  6 . 
     The first substrate (BGA package  4 ) is arranged on an upward-facing surface of the intercoupling device  120  such that each lead-free solder ball  12   a  of the ball grid array contacts a corresponding terminal  180  ( FIG. 18 ). The lead free solder balls  12   a  are formed, for example, of a tin-silver-copper alloy. 
     The intercoupling device  120  and BGA package  4  are placed in an environment having a temperature within a first range of temperatures. The first range of temperatures will depend on the specific material(s) used to form solder ball  12   a , and is selected to be appropriate for causing reflow of the solder ball  12   a  described above and for forming an electrical connection between each solder ball  12   a  of the ball grid array and the corresponding terminal  180 , while being sufficiently low to avoid causing damage to the BGA package  4 . For a lead-free solder ball  12   a  formed of a tin-silver-copper alloy, the corresponding first temperature range is about 235-245 degrees Celsius. 
     The intercoupling device  120  is then inverted so that the BGA package  4  resides below the device ( FIG. 19 ). 
     Lead-containing solder balls  12   b  are provided on upward facing surfaces of one or more of the terminals  180 . The lead-containing solder balls  12   b  may be formed of a tin-lead alloy. 
     With the lead-containing solder balls  12   b  provided on the upward facing surfaces of the one or more terminals  180 , the intercoupling device  120 , BGA package  4 , and solder balls  12   b  are then heated in an environment having a temperature within a second range of temperatures. The second range of temperatures will depend on the specific materials used to form the lead-containing solder balls  12   b , and is selected to be sufficient to permit the lead-containing solder balls  12   b  to bond to corresponding terminals  180 , but insufficient to cause reflow of the lead-free solder balls  12   a . For a lead-containing solder ball  12   b  formed of a tin-lead alloy, the corresponding second range of temperatures is about 200-210 degrees Celsius. In this step, duration of heating is sufficiently short to prevent complete reflow of the lead-containing solder balls  12   b , and is sufficiently long to permit an electrical connection to be established between each lead-containing solder ball  12   b  and the corresponding terminal  180 . 
     The intercoupling device  120  is then inverted so that the BGA package  4  resides above the device ( FIG. 20 ). 
     The intercoupling device is arranged on an upper surface of the printed circuit board  6  such that each lead-containing solder ball  12   b  contacts an electrical contact element of the printed circuit board  6 . 
     The BGA package  4 , the intercoupling device  120 , and the printed circuit board  6  are heated in an environment having a temperature within the second range of temperatures until an electrical connection is formed between each lead-containing solder ball  12   b  and the corresponding electrical contact elements of the printed circuit board  6 . 
     Referring now to  FIG. 21 , a socket adaptor  802  of another embodiment of the intercoupling device is shown. In this embodiment, the pin adaptor  301  of  FIG. 2  can be used with the socket adaptor  802  to provide a socket converter assembly. The socket adaptor  802  includes a plurality of sockets  830  supported by a support member  310  in an arrangement which corresponds to the pattern of surface mount pads  5  or pin-receiving connectors (not shown) of the substrates  4 ,  6  to be interconnected. In a manner similar to the previous embodiments, in the socket converter assembly, each pin  260  cooperatively engages a corresponding socket  830  to provide an electrical connection between a surface mount pad  5  of BGA package  4  and a corresponding pin-receiving connector (not shown) such as a hole formed in a surface of a printed circuit board  6 . 
     The socket  830  includes a socket body  832  and a socket core  950 . The socket body  832  includes a first end  840 , and a second end  842  opposed to the first end  840 . A socket cavity  834  opens at the first end  840  of the socket body  832 . A resilient contact member  348  is fixed within the cavity  834  so as to form an electrical connection with the socket body  832  along mutually contacting surfaces. In use, the stem  266  of the pin  260  is received within, and forms an electrical connection with, the resilient contact member  348 . The socket body  832  further includes a base  836  adjacent to and including the second end  842 , and a socket axial hole  838  that extends axially inward from the second end  842  is provided in the base  836 . 
     The socket core  950  is disposed within the socket axial hole  838 . The socket core  950  is pin-shaped, and includes a shank portion  952  sized to be received within the socket axial hole  838 , a flange portion  954  at an end of the shank portion  952 , and a pin portion  956  extending from the flange portion  954  on a side of the flange portion  954  that is opposed to the shank portion  952 . In some embodiments, the shank portion  952  is fitted or press-fit within the socket axial hole  838 . When received within the socket axial hole  838 , the shank portion  956  serves to orient and/or align the socket core  950  relative to the socket body  832 . 
     In addition, the flange portion  954  and pin portion  956  of the socket core  950  are disposed outside the socket base  836 . The shank portion  952  of the pin-shaped core member  950  has a shank cross-sectional dimension d 6  (e.g. diameter), the flange portion  954  has a flange cross-sectional dimension d 7  (e.g. diameter), and the pin portion  956  has a pin cross-sectional dimension d 8  (e.g. diameter). The flange cross-sectional dimension d 7  is greater than the shank cross-sectional dimension d 6  and the pin cross-sectional dimension d 8 . In the illustrated embodiment, the shank cross-sectional dimension d 6  and the pin cross-sectional dimension d 8  are approximately the same. When the shank portion  952  is received within the socket axial hole  838 , the flange portion  954  is disposed outside the axial hole  838 , and abuts the socket base end face  842 . In particular, the flange portion  954  serves as a stop member that limits the depth of insertion of the socket core  950  within the socket  830 . 
     In contrast to previous embodiments, in which the socket base  336  and core member  246 ,  350 ,  450 ,  550  are configured to receive a solder ball, the pin portion  956  of the socket core  950  is configured to be received in a hole in a printed circuit board. The pin portion  956  forms an electrical connection with the interior surface of the hole through direct contact with the interior surface of the hole or through indirect contact via solder paste provided within the hole. In some embodiments, the pin portion  956  includes surface features (not shown) such as knurls or resilient protrusions that permit and/or enhance contact with the interior surface of the hole. Alternatively, the pin portion  956  of the socket core  950  is configured to be received in a secondary socket member that is connectable to a printed circuit board or integrated circuit package. 
     The core member  950  is electrically conductive, and the shank portion  952  is sized and shaped to obstruct the socket axial hole  838  and form an electrical connection with the socket base  836  along mutually contacting surfaces. As in previous embodiments, the socket  830  and the core member  950  are each formed of electrically conductive materials. The socket  830  and the core member  950  are formed of different materials. 
     In some embodiments, the socket  830  is formed of, coated, or plated with a material that is resistive to solder flow or has relatively low solderability. In these embodiments, the core member  950  is formed of, coated, or plated with material that has relatively high solderability in that it promotes solder flow, forms a good electrical contact and bonds well with solder. As a result, during use when solder paste or other solder mass that is positioned adjacent to the pin portion  956  of the core member  950  is heated to cause the solder to flow, the solder does not flow along a peripheral side of the socket base  836  due to the due to the chemical response of the solder to the materials of these members, and is generally maintained in the vicinity of the flange portion  954  and pin portion  956  of the core member  950 . In some embodiments, during use, the pin portion  956  forms an electrical connection without solder, for example, via direct physical contact. 
     In some embodiments, the socket  830  is formed of, coated, or plated with tin, tin-lead alloy, nickel or nickel alloy, and the core member  950  is formed of, coated, or plated with gold, gold alloy, tin, tin-lead alloy, and palladium-nickel alloy. 
     In the illustrated embodiment, the socket cavity  834 , which opens at the first end  840  of the socket  830 , and the socket axial hole  838 , which opens at the second end  842  of the socket  830 , intersect to form continuous opening  844  from the first end  840  to the base end  842 . In particular, the socket cavity  834  has a larger cross-sectional dimension than the socket axial hole  838 , whereby the continuous opening  844  is non-uniform in dimension along the direction from the first end  840  to the second end  842  of the socket  830 . 
     Referring to  FIG. 22 , it is understood that the socket adaptor  802  is not limited to this configuration. For example, an alternative embodiment socket adaptor  802 ′ includes sockets  830 ′ which are similar to the socket  830  in form and function except that the socket cavity  834 ′, which opens at the first end  840 ′ of the socket  830 ′, and the socket axial hole  838 ′, which opens at the base end  842 ′ of the socket  830 ′, intersect to form continuous opening  844 ′ from the first end  840 ′ to the base end  842 ′. In this embodiment, the socket cavity  834 ′ has the same cross-sectional dimension as the socket axial hole  838 ′, whereby the continuous opening  844 ′ is uniform in dimension along the direction from the first end  840 ′ to the base end  842 ′ of the socket  830 ′. Accordingly, the dimensions of the shank portion  952 ′ of the socket core  950 ′ are adapted to correspond to the dimensions of the socket axial hole  838 ′. In this example, the shank cross-sectional dimension d 6  is greater than the pin cross-sectional dimension d 8 . 
     Referring to  FIG. 23 , another alternative embodiment socket adaptor  802 ″ includes sockets  830 ″ which are similar to the socket  830  in form and function except that the socket cavity  834 ″, which opens at the first end  840 ″ of the socket  830 ″, and the socket axial hole  838 ″, which opens at the base end  842 ″ of the socket  830 ″, do not intersect. In this embodiment, the socket cavity  834 ″ has the same cross-sectional dimension as the socket axial hole  838 ″, but the respective openings  834 ″,  838 ″ are separated by a socket mid-portion  835 ″. As in the previous example, the dimensions of the shank portion  952 ″ of the socket core  950 ″ are adapted to correspond to the dimensions of the socket axial hole  838 ″. 
     In the illustrated embodiment, the socket  830  is dimensioned so that when the socket  830  is received within the support member  310 , the socket base  836  is disposed outside the support member through hole  316 . The socket  830  is not limited to this configuration, and the dimensions of the socket  830  and/or the support member  310  may be adjusted so that the socket base  836  is disposed within the through hole  316 . For example, in some embodiments, the second end  842  may be aligned with the surface of the support member  310 . 
     Selected illustrative embodiments of the invention are described above in some detail. It should be understood that only structures considered necessary for clarifying the present invention have been described herein. Other conventional structures, and those of ancillary and auxiliary components of the system, are assumed to be known and understood by those skilled in the art. 
     Moreover, while working examples of the present invention have been described above, the present invention is not limited to the working examples described above, but various design alterations may be carried out without departing from the present invention as set forth in the claims. 
     For example, although the embodiments disclosed herein illustrate devices which intercouple a printed circuit board and a BGA package, it is understood that the devices can also be use to intercouple a first printed circuit board to a second printed circuit board, and/or a first integrated circuit package to a second integrated circuit package.