Patent Application
20050170627
The present invention relates generally and in various embodiments to electrical interconnect devices for electrically connecting the contacts of a first component to the contacts of a second component. More specifically, the present invention is directed in various embodiments to high density miniature electrical interconnect devices having an array of closely spaced conductors and solder balls suitable for temporary or permanent solder connection to substrates such as circuit boards and the like.
Generally, solder joints or interconnect devices are used to connect semiconductor components to a substrate. Today's growing and technologically demanding semiconductor manufacturing assembly processes require high-density interconnect devices for connecting the semiconductor components to the substrates. High-density surface mount semiconductor socket connectors having over 1,000 high-density contacts often are used as interconnect devices to accommodate the increased complexity and functionality of modern semiconductor components.
Modern equipment often requires electrical interconnect devices that are capable of simultaneously connecting large numbers of electrical circuits from one electronic component to another. Generally, in such applications, the electrical interconnect devices include a frame having opposed contact surfaces. Each contact surface, for example, is provided for engaging corresponding contact surfaces on other electronic components. The interconnect frame functions to hold the midsections of a plurality of individual electrical conductors, and also to electrically isolate each conductor from the remaining conductors. In addition, the frame generally incorporates features for mechanically attaching the electronic components to one another. Conventional interconnect devices have conductors that are molded-in-place within the frame. In these connectors, each conductor has a first element that projects from a first side of the frame and a second element that projects from a second, opposed, side of the frame. The midsection of each conductor provides a connection from the first element to the second element.
In modern equipment, electronic components have become increasingly miniaturized, while the number of circuits in each electronic component has multiplied. These effects have combined to require smaller connectors having increasingly smaller spacings between adjacent conductors. Unfortunately, for mold-in-place connectors, small spacings between adjacent conductors are not readily obtainable when the conductor midsections are oriented parallel to the contact surfaces of the frame.
Interconnect devices have been specially adapted to operate in conjunction with ball grid array (BGA) type devices. The BGA package is used with integrated circuits having very high pin counts. The BGA package replaces the conventional pins with a solder “ball” structure comprised of reflowed (melted) and solidified small beads of solder paste. The BGA package saves space on the substrate. Certain BGA type interconnect devices may include, for example, contacts having first and second portions, where the first portion may be soldered directly to a printed circuit board type substrate while the second portion is provided in electrical contact with soldered balls formed on the semiconductor package. The solder balls then are compressed onto the second contacts portion of the interconnect device and reflowed during the assembly process. These types of interconnect devices work well with conventional BGA packages. In use, the semiconductor package is compressed onto the contacts portion with a predetermined force for a predetermined period. The first portion of the contacts is generally soldered directly to a printed circuit board type substrate, for example. This process, however, may lead to stress in the solder joints and thus may have limited value in high volume production parts.
Furthermore, conventional surface mountable land grid array (LGA) interconnect devices experience several common issues such as relaxation of the metal used as the electrical contacts, which causes open circuits specifically on the substrate side. Other issues include difficulties in placing the LGA interconnect device in coplanar relation with the substrate and the warping of the substrate relative to the interconnect device whenever these components are not aligned in a coplanar manner. Also, conventional interconnect devices rely on mechanical contacts rather than solder joints to provide the electrical interconnection. Also, conventional surface mountable LGA interconnect devices cannot be temporarily soldered and easily removed or permanently soldered to the substrate. In addition, it is difficult to control the solder ball height formed on the semiconductor component due to the uncontrolled wetting surface of the contacts. Other problems with conventional interconnect devices include metal contacts that experience uneven torque during assembly and metal contacts loosening after insert molding into the frame.
In one general respect, an embodiment of the present invention is directed to a connector that includes a frame having a first side and a second side; a conductor including electrically continuous first and second portions, the first portion extending outwardly from the first side of the frame and terminating in a tip, the second portion extending through the second side of the frame and terminating in a land; and a solder ball formed on the land.
In another general respect, an embodiment of the present invention is directed to a method of forming a connector including a solder ball. The method includes depositing solder mask on a conductive pad of a conductor, the solder mask defining an area for receiving solder paste; depositing solder paste in the area defined by the solder mask; and forming a solder ball by reflowing the solder paste.
In yet another general respect, an embodiment of the present invention is directed to a method of forming a connector including a solder ball. The method includes depositing a first solder paste on a first substrate comprising a convex region; introducing a conductive pad of a conductor in communication with the first solder paste; reflowing the first solder paste to form a first solder ball defining a reservoir; depositing a second solder paste of lower melting temperature on a second substrate; introducing the reservoir portion of the first solder ball in communication with the second solder paste; and reflowing the second solder paste to form a second solder ball within the reservoir of the first solder ball.
In still another general respect, an embodiment of the present invention is directed to an interconnect system. The system includes a first component including a first contact pad thereon; a second component including a second contact pad thereon; and a connector. The connector includes a frame having a first side and a second side; a conductor including electrically continuous first and second portions, the first portion extending outwardly from the first side of the frame and terminating in a tip in electrical communication with the first contact pad, the second portion extending through the second side of the frame and terminating in a land in electrical communication with the second contact pad; and a solder ball attached on the land.
Other apparatuses, systems, and/or methods according to embodiments of the present invention will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional apparatuses, systems, and/or methods be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.
Embodiments of the present invention are described herein in conjunction with the following figures, wherein:
FIGS. 5A-E illustrate a process sequence according to one embodiment of the present invention for forming solder balls on an electrical connector according to one embodiment of the present invention;
FIGS. 6A-H illustrate a process sequence according to the present invention for forming dual solder balls on a connector according to the present invention; and
It is to be understood that the figures and descriptions of the various embodiments of the present invention described herein, among others, have been simplified to illustrate representative elements of apparatuses, systems, and methods for electrically connecting a first component to a second component while eliminating, for purposes of clarity, other elements. Those of ordinary skill in the art will appreciate and readily understand, however, that other elements that may be found in conventional communications interconnect devices may be included in the various embodiments of the present invention.
As used herein, the term “first component” may comprise a semiconductor component which may include, for example, microprocessors, application specific integrated circuit (ASIC) devices, programmable logic array devices, packaged semiconductor devices, semiconductor multichip modules, semiconductor chip set arrays, other digital, analog, and/or mixed signal integrated circuit components, etc. Furthermore, the term “second component” may comprise a substrate which may include, for example, printed circuit boards, ceramic boards, flexible circuits, other substrates suitable for permanently or temporarily attaching semiconductor components and interconnect devices thereto, etc.
One embodiment of the present invention provides an interconnect device such as a molded electrical connector suitable for temporary or permanent connection to a substrate through electrical connections such as solder joints, for example. In one embodiment of the present invention the electrical connector is a surface mountable LGA socket suitable for temporary or permanent connection to the substrate. One embodiment of the LGA socket according to the present invention is formed to receive an LGA type semiconductor integrated circuit (IC) package therein.
Further, one embodiment of the LGA socket according to the present invention includes a plurality of resilient metal contacts formed on a lead frame, which are embedded within a body portion of a frame. On one side of the interconnect device, the resilient contacts provide an electrical connection to a first component such as a semiconductor IC package inserted therein. On another, opposed side of the interconnect device, the resilient contacts provide an electrical connection to a second component such as a substrate. Various embodiments of the present invention include resilient contacts comprising a layer of solder mask on the lead frame, anti-pivot elements, and primary and secondary spring force features.
Referring now to the several drawings in which identical elements are numbered identically throughout, a description of the present invention will now be provided, in which exemplary embodiments are shown in the several figures. The present invention, however, may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those having ordinary skill in the art. Furthermore, all statements herein reciting embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Moreover, it is intended that such equivalents include both currently-known equivalents as well as equivalents developed in the future for performing the same function, regardless of structure. Thus, those skilled in the art will appreciate that the schematic drawings presented herein, and the like, represent conceptual views of illustrative structures which may embody the various aspects of this invention.
Generally, one embodiment of the present invention comprises an interconnect device that includes solder balls formed thereon.
As shown, the electrical connector 10 includes a plurality of spaced apart electrical conductors 16. Similarly, the first component 12 includes a plurality of spaced apart contact pads 18 on a first side 15 thereof and the second component 14 includes a plurality of spaced apart conductive contact pads 20 on a first side 17 thereof. The contact pads 18, 20 can be lands or pads of various shapes and sizes. In the illustrated embodiment, each contact pad 18, 20 is a land and is a rectangular shaped flat surface. The plurality of contact pads 18, 20 or lands constitute a “land grid array.” Alternatively, the contact pads 18, 20 on the components 12, 14 can be constructed as balls or lands. Also, as further described below and for the purposes of this description, the conductors 16 exposed on the first side 24 of the electrical connector 10 are compression connected to the contact pads 18 on the first component while the conductors 16 exposed on the second side 30 of the electrical connector 10 are soldered to the contacts 20 on the second component. Those skilled in the art will appreciate, however, that the electrical connector 10 may be implemented such that both sides may be soldered connected to the first and second components 12, 14, without departing from the scope of the present invention.
As shown in
The frame 22 is formed with a first side 24 opposed to the second side 30. The first side 24 is for contact with the first component 12 (shown in
The second side 30 of the frame 22 also includes a plurality of substantially coplanar solder collapsed control posts 32. The posts 32 extend outwardly from the second side 30 of the frame 22 and are substantially perpendicular to the base surface 25 of the frame 22. The posts 32 include a plurality of solder balls 34 formed therebetween. The posts 32 ensure the coplanarity of the electrical connector 10 with the second component 14. The posts are designed so that their feet are tapered and align the solders balls 34 in their position. When the electrical conductor 10 is reflow soldered to the second component 14, the electrical conductor 10 moves towards the second component 14 and the posts 32 make physical contact with the first side 17 of the second component 14. The solder collapsed control posts 32 can then distribute the force needed to compress the electrical conductors 16.
In one embodiment of the present invention, each one of the first surfaces 26 forming the strengthening ribs is formed with a first wall 36, a second wall 38, and a top 40. In one embodiment of the present invention, the walls 36, 38 of each first surface 26 are substantially flat while the top 40 of each first surface 26 is substantially curved. Nevertheless, the walls 36, 38, and the top 40 may be formed substantially flat and/or curved without departing from the scope of the present invention. For each first surface 26, the first and second walls 36, 38 extend from a front surface 42 to one of the plurality of the posts 32. Further, each one of the first and second walls 36, 38 is substantially perpendicular to a base surface 25 of the frame 22. Consequently, the top 40 of each first surface 26 is substantially parallel to the base surface 25.
Similarly, each one of the second surfaces 28 forming the strengthening ribs is formed with a first wall 44, a second wall 46, and a top 48. In one embodiment of the present invention, the walls 44, 46 of each one of the second surfaces 28 is substantially flat while the top 48 of each second surface 28 is substantially curved. Nevertheless, the walls 44, 46, and the top 48 may be formed substantially flat and/or curved without departing from the scope of the present invention. For each second surface 28, the first and second walls 44, 46 extend from a front surface 50 to one of the plurality of the posts 32. Further, each first and second wall 44, 46 are substantially perpendicular to the base surface 25. Consequently, the top 48 of each second surface 28 also is substantially parallel to the base surface 25.
The electrical connector 10 also includes a plurality of electrical conductors 16 molded in place within the frame 22. As shown, each electrical conductor 16 includes electrically continuous first and second portions 54, 56. The first portion 54 extends outwardly from the first side 24 of the frame 22 and terminates in a tip 58, designed to make a direct compression electrical contact with the contact pad 18 of the first component 12. The second portion 56 of the electrical conductor 16 extends through the frame 22 to the second side 30 of the frame 22 and provides a conductive land or conductive pad for receiving the solder ball 34. The electrical conductor 16 is shown stamped, shaped, preformed, and molded in place within the frame 22. In one embodiment of the present invention the electrical conductor 16 may be formed of an electrically conductive metal spring material, such as BeCu 172. In one embodiment, the electrical conductors 16 are stamped or formed from strips of electrically conductive metal spring material that are approximately 0.001 to 0.003 inches in thickness. Further, portions of the electrical conductor 16, or the entire electrical conductor 16, may be completely or selectively gold-plated on one side to a thickness of between 3 and 50 micro-inches to enhance the conductivity of the conductor 16. The solder mask is deposited on the top of the conductive land or conductive pad to define the footprint for the solder ball 34.
The electrical conductor 62 is shown stamped, shaped, preformed, and molded in place in the frame 22. In one embodiment of the present invention, the electrical conductor 62 may be made from an electrically conductive metal spring material, such as BeCu 172. In the preferred embodiment, the electrical conductors 62 are stamped or formed from strips that are approximately 0.001 to 0.003 inches in thickness. Further, portions of the electrical conductor 62, or the entire electrical conductor 62, may be completely or selectively gold-plated on one side to a thickness of between 3 and 50 micro-inches to enhance the conductivity of the conductor 62.
The electrical conductor 62 also includes first and second spring force elements 70, 72. The first and second spring force elements 70, 72 provide the electrical conductor 62 with a resilient property when compressed after receiving the contact pad 18 of the first component 12. In one embodiment of the present invention the secondary spring force element 72 comprises a generally arcuate shaped member having a second tip 74 that extends in a direction substantially opposite to the first tip 68.
The electrical conductor 82 also includes first and second spring force elements 90, 92. The first and second spring force elements 90, 92 provide the electrical conductor 82 with a resilient property when compressed after receiving the contact pad 18 of the first component 12. In one embodiment of the present invention the secondary spring force element 92 comprises a generally arcuate shaped member having a second tip 94 that extends substantially in the same direction as the first tip 88.
FIGS. 5A-E illustrate a process sequence for attaching solder balls 34 on the electrical connector 60 according to one embodiment of the present invention. The process illustrate the sequence of depositing a solder mask 76 on the electrically conductive pad 67. The solder balls 34 allow the electrical conductors 16, 62, 82 of the electrical connectors 10, 60, 80, respectively, to be soldered to contact pads 20 of the second component 14. The process illustrated in FIGS. 5A-E may be applied to attach the solder balls 34 on any one of the previously described surface mountable electrical connectors 10, 80, however, for brevity, the process will be described only with respect to the electrical connector 60.
Solder balls 34 can be attached to the contact pad 162 by solder reflow or formed by solder paste stenciled then reflowed on the surface area on the contact pad 162 with the footprint defined by the solder mask 76. FIGS. 6A-H illustrates a process sequence for forming a dual solder ball array type electrical connector 110 according to one embodiment of the present invention on any one of the electrical connectors 10, 60, 80 discussed above. For the sake of brevity, however, the process of forming the dual solder ball array type electrical connector 110 will be described with respect to the electrical connector 110 shown in FIGS. 6B-H.
As shown in
As shown in
As shown in
Although the present invention has been described with regard to certain embodiments, those of ordinary skill in the art will recognize that many modifications and variations of the present invention may be implemented. The foregoing description and the following claims are intended to cover all such modifications and variations. Furthermore, the components and processes disclosed are illustrative, but are not exhaustive. Other components and processes also may be used to make systems and methods embodying the present invention.
Furthermore, in the claims appended hereto any element expressed as a means for performing a specified function is to encompass any way of performing that function including, for example, a combination of elements that perform that function. Furthermore the invention as defined by such means-plus-function claims resides in the fact that the functionalities provided by the various recited means are combined and brought together in the manner that the claims called for. Therefore, any means that can provide such functionalities may be considered equivalents to the means shown herein.
