Patent Publication Number: US-9837747-B2

Title: Burn-in socket for packaged integrated circuits

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Under 35 U.S.C. §119(e), this application claims the benefit of and priority to U.S. Provisional Application 62/311,957, filed on Mar. 23, 2016, the entirety of which is hereby incorporated herein by reference. 
    
    
     FIELD 
     This disclosure relates to the field of integrated circuit testing. More particularly, this disclosure relates to burn-in sockets for integrated circuit testing. 
     BACKGROUND 
     Burn-in sockets with active thermal control are often used for accelerated reliability testing of packaged integrated circuits. 
     A packaged integrated circuit such as a dual inline packaged IC (DIP), a packaged IC with ball bonds (BGA), or a Quad Flat No Lead packaged IC (QFN) may be plugged into the burn-in socket. The burn-in socket may then be closed to bring a heater into contact with the packaged integrated circuit to perform accelerated thermal cycling reliability testing. 
     SUMMARY 
     An integrated circuit burn-in socket with a spring-loaded contact pin built into the socket base and an electrical receptacle built into the socket lid wherein the electrical receptacle is configured to mate with the spring-loaded contact pin when the burn-in socket is closed. A clam-shell integrated circuit burn-in socket with a spring-loaded contact pin built into the socket base and an electrical receptacle built into the socket lid wherein the electrical pad is configured to mate with the spring-loaded contact pin when the clam-shell burn-in socket is closed. An integrated circuit burn-in socket where the socket lid is separate from the socket base and with a spring-loaded contact pin built into the socket base and with an electrical receptacle built into the socket lid wherein the electrical receptacle is configured to mate with the spring-loaded contact pin when the socket lid is clamped to the socket base. An integrated circuit burn-in socket with a spring-loaded contact pin built into the socket lid and an electrical receptacle built into the socket base wherein the electrical receptacle is configured to mate with the spring-loaded contact pin when the burn-in socket is closed. 
    
    
     
       DESCRIPTION OF THE VIEWS OF THE DRAWINGS 
         FIG. 1  is a front view of an integrated circuit clam-shell burn-in socket in an open position. 
         FIG. 2  is a backside view of an integrated circuit clam-shell burn-in socket. 
         FIG. 3  is an example spring-loaded contact pin for bond pads. 
         FIG. 4  is an example spring-loaded contact pin for ball bonds. 
         FIG. 5  is an example spring-loaded contact pin for electrical pads. 
         FIG. 6  is view of a clam shell integrated circuit burn-in socket formed according to the principles of the disclosure and displayed in an open position. 
         FIG. 7  is view of a clam shell integrated circuit burn-in socket formed according to the principles of the disclosure and displayed in an open position. 
         FIGS. 8A, 8B, and 8C  are views of an integrated circuit burn-in socket formed according to the principles of the disclosure and displayed in an open position. 
         FIGS. 9A and 9B  are views of an integrated circuit burn-in socket formed according to the principles of the disclosure and displayed in an open position. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure are described with reference to the attached figures. The figures are not drawn to scale and they are provided merely to illustrate the disclosure. Several aspects of the embodiments are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide an understanding of the disclosure. The present disclosure is not limited by the illustrated ordering of acts or events, as some acts may occur in different orders and/or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the present disclosure. 
     A burn-in socket  100  is illustrated in  FIG. 1  and  FIG. 2 . This burn-in socket  100  is a clam shell type burn-in socket with the lid  106  connected to the base  102  with a hinge  110 . The burn-in socket  100  is mounted on a circuit board  111 . 
     Flexible heater wires  114  connect the heater  108  in the lid  106  to power and ground leads  109  on the circuit board  111 . A flexible wire  112  may also connect a heater thermocouple in the lid  106  to the circuit board  111  to enable temperature measurement and thermal feedback control. During several test conditions, the flexible wires  112  and  114  may be damaged, thereby impacting the reliability of the overall burn-in socket  100 . 
     More specifically, the flexible wire connections  112  and  114  used in the socket  100  (as shown in  FIG. 2 ) may be subject to temperature cycling during burn-in testing and repeated flexing stress during the opening and closing of the socket  100 . The repeated temperature cycling and repeated flexing of the flexible wire connections  114  and  112  may result in wire fatigue and wire breakage. 
     In addition, the flexible wires,  112  and  114 , are external to the burn-in socket  100  and may be damaged by being struck against objects when the burn-in board is being loaded into or unloaded from testing equipment such as a burn-in oven. 
     To address the reliability issues caused by the flexible wires  112  and  114 , spring-loaded contact pins are used on electrical testers to provide electrical connection to probe pads on circuit boards and packaged integrated circuits (IC). Examples of spring-loaded contact pins are shown in  FIGS. 3, 4, and 5 . 
       FIG. 3  shows a spring-loaded contact pin  300  used to electrically contact an electrical pad  308  such as a probe pad on an IC. When the probe pad  308  comes into contact with pin  302 , the spring  304  is compressed and the pin  302  is partially pushed into the cylindrical housing  306  providing reliable electrical connection during repeated usage. 
       FIG. 4  shows a spring-loaded contact pin  400  used to electrically contact a ball bond  408  on an IC. When the ball bond  408  comes into contact with pin  402 , the spring  404  is compressed and the pin  402  is partially pushed down into the cylindrical housing  406 . 
       FIG. 5  shows a spring-loaded electrical contact  500  used to electrically contact an electrical pad  508  such as a probe pad on an IC. When the probe pad  508  comes into contact with the electrical contact  502  portion of the spring-loaded electrical contact  500 , spring  504  is compressed and the electrical contact  502  is partially compressed into the housing  506  of the spring-loaded electrical contact  500 . 
     In general, burn-in sockets are expected to go through tens of thousands of use cycles. Because spring-loaded contact pins are in the  100 &#39;s of thousands of use cycles, they improves the reliability of burn-in sockets by rendering these sockets wire-free, thereby reducing the reliability risks associated with the flexible wire configurations (e.g.,  112  and  114 ). 
     According to an aspect of the present disclosure, for example, a wire-free clam shell burn-in socket  600  is depicted in  FIG. 6 . The burn-in socket  600  provides electrical power to the lid mounted heater  608  using spring-loaded contact pins  610  built into the base  602  and electrical receptacles  612  (which may also include electrical contact pads) built into the lid  606 . The spring-loaded contact pins  610  built into the socket base  602 , mate with the electrical receptacles  612  in the socket lid  606  when the burn-in socket  600  is closed. Examples of spring loaded contact pins are illustrated in  FIGS. 3 and 5 . Other spring loaded contact pin designs may alternatively be used. The spring-loaded contact pins  610  avoid the need for flexible wires to bypass the hinge  614 . The avoidance of flexible wire connections significantly improves the reliability of the burn-in socket  600 . The spring-loaded contact pin  610  electrical connections significantly reduce operating costs by reducing replacement cost, by reducing down time of burn-in circuit boards during replacement of failed burn-in sockets, and by reducing the cost of the labor needed to replace failed burn-in sockets. 
     In addition, since the spring-loaded contact pins  610  are internal to the burn-in socket  600 , the spring-loaded contact pins  610  are not susceptible to damage incurred by being struck against objects when the burn-in board is being loaded into or unloaded from testing equipment such as a burn-in oven. 
     Alternatively as shown in  FIG. 7 , the spring-loaded contact pins  712  may be built into the lid  706  of the burn in socket  700  and the electrical pads or receptacles  710  may be built into the base  702 . 
     Automated Test Equipment (ATE) usage data shows that the embodiment reliable burn-in socket  600  with spring-loaded contact pins  610  is in the range of one to two orders of magnitude more reliable than burn-in sockets  100  with flexible wires,  112  and  114  ( FIG. 1  and  FIG. 2 ). 
     An alternative reliable burn-in socket  800  is illustrated in  FIGS. 8A, 8B , and  8 C. In this burn-in socket  800  the socket lid  806  ( FIG. 8B ) is separate from the socket base  802  ( FIG. 8A ). No hinge connects the socket lid  806  to the socket base  802 . In this embodiment reliable burn-in socket  800  a packaged integrated circuit may be plugged into the IC socket  804  in the socket base  802  and the socket lid  806  may then be clamped  814  ( FIG. 8C ) to the socket base  802  during burn-in reliability testing. 
     Electrical receptacles  812  in the lid  706  ( FIG. 8B ) are connected to the heater  808  to provide electrical power. Spring-loaded contact pins  810  built into in the socket base  802  may be connected to power and ground on the circuit board on which the burn-in socket base  800  is mounted. When the socket lid  806  is clamped  814  to the socket base  802  the spring-loaded contact pins  810  come into contact with the electrical receptacles  812  in the lid  806  and provide electrical power and ground to the heater  708 . The spring-loaded contact pin  810  electrical connections in this embodiment avoid the use of flexible wires which may break. This burn-in socket design  800  also negates the need for a hinge which adds cost and is also subject to failure. This reduces the cost and manufacturing complexity of this embodiment reliable IC burn-in socket  800 . 
     Another reliable burn-in socket  900  is illustrated in  FIGS. 9A and 9B . This burn-in socket is similar to the burn-in socket illustrated in  FIGS. 8A, 8B, and 8C  except for the spring-loaded contact pins  912  are built into the socket lid  906  of the embodiment reliable burn-in socket  900  and the electrical receptacles  910  are built into the base  902 . 
     In addition to be more reliable than the wire-based burn-in socket, the wire-free burn-in sockets also improve the efficiency of burn-in testing. In one implementation, for example, an array of socket lids may be mounted on a first board whereas a corresponding array of socket bases may be stationed on a second board. By engaging the first board and the second board, multiple socket lids and socket bases are mated simultaneously. When compared to the wire-based sockets, which are opened and closed individually, the wire-free sockets facilitate more efficient set-up and reset procedures. 
     While various embodiments of the present disclosure have been described above, it should be understood that they have been presented by way of example only and not limitation. Numerous changes to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the disclosure. Thus, the breadth and scope of the present disclosure should not be limited by any of the above described embodiments. Rather, the scope of the disclosure should be defined in accordance with the following claims and their equivalents.