Abstract:
Embodiments of the invention include an electrical circuit arrangement including a switchably removable bond pad extension test pad that allows improved testing of a corresponding electrical circuit device via enhanced placement of testing probes. The bond pad extension test pad is removably coupled to one of the electrical circuit device&#39;s electrical components, e.g., a bond pad. Because the bond pad extension test pad can be disconnected from the electrical component when not testing, the bond pad extension test pad does not contribute additional parasitic effects to the corresponding electrical circuit device. The electrical circuit arrangement automatically detects when a testing voltage is applied to the bond pad extension test pad, then connects the bond pad extension test pad in response to the detection of the applied testing voltage. When a testing voltage is not applied to bond pad extension test pad, the electrical circuit arrangement disconnects the test pad from the associated electrical component.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to electrical circuit devices including bond pads. More particularly, the invention relates to electrical circuit devices including bond pad extensions used for testing electrical circuit devices. 
   2. Description of the Related Art 
   Bond pads are used with wire bonding techniques for mounting electrical circuit devices, such as semiconductor integrated circuit dies, in electronic packaging. The electrical circuit devices typically include a plurality of relatively small conductive leads that are electrically connected, e.g., by ultrasonic bonding, to wire bond pads of corresponding conductors embedded in the device package. 
   Some conventional circuit device arrangements include extended bond pads, which are bond pads that have an extended area or region that allows extra room for the placement of test probes during testing of the circuit device. However, in such conventional arrangements, the extended bond pads typically remain in place after testing of the circuit device has been completed. As such, the extended bond pads can add extra capacitance or, at relatively high frequencies, add open-circuited stubs to the circuit device. Such open-circuited stubs are capacitive in nature and exhibit resonances that may result in the undesirable radiation of signals. Other conventional circuit device arrangements include extended bond pads that are broken off or peeled away from the real or original bond pad after testing is performed. However, in such arrangements, subsequent use of the extended bond pads is not possible once the extended bond pad has been permanently removed from the circuit device. 
   Therefore, a need exists for a reusable, removable, extended bond pad or bond pad extension that does not include or contribute additional parasitic effects to the existing parasitic effects of the associated electrical circuit device. 
   SUMMARY OF THE INVENTION 
   The invention is embodied in an electrical circuit arrangement that includes at least one switchably removable bond pad extension test pad that allows for improved testing of a corresponding electrical circuit device via enhanced placement of testing probes. The bond pad extension test pad is removably coupled to the electrical circuit device, e.g., via one of the electrical circuit device&#39;s bond pads, which are used for wire bonding the integrated circuit portion of the electrical circuit device to components external to the electrical circuit device. The electrical circuit arrangement includes a controllable switch coupled between the bond pad extension test pad and the bond pad or other suitable device circuitry. The controllable switch includes at least one enable control input for enabling and disabling the controllable switch, and is configured in such a way that when the controllable switch is enabled the bond pad extension test pad is electrically connected to the bond pad or other device circuitry, and when the controllable switch is disabled the bond pad extension test pad is electrically isolated from the bond pad or other device circuitry. A control circuit coupled to the controllable switch and to the bond pad extension test pad operates to enable the controllable switch when the control circuit detects a testing voltage applied to the bond pad extension test pad, and to disable the controllable switch when the control circuit detects no testing voltage applied to the bond pad extension test pad. Because the bond pad extension test pad can be disconnected from the bond pad or other device circuitry after testing, and thus removed from the electrical circuit device, the bond pad extension test pad does not contribute additional parasitic effects to the corresponding electrical circuit device. The electrical circuit arrangement automatically detects when a testing voltage is applied to the bond pad extension test pad, then connects the bond pad extension test pad in response to the detection of the applied testing voltage. When the testing voltage applied to bond pad extension test pad is removed, the electrical circuit arrangement disconnects the bond pad extension test pad from the associated bond pad or other device circuitry. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram illustrating a bond pad extension test pad arrangement according to embodiments of the invention; 
       FIG. 2  is a block diagram illustrating a bond pad extension test pad arrangement according to embodiments of the invention, including a transmission gate switch and a static random access memory (SRAM) control circuit; 
       FIG. 3  is a block diagram illustrating a bond pad extension test pad arrangement according to embodiments of the invention in use with a radio frequency (RF) transceiver; 
       FIG. 4  is a block diagram illustrating a bond pad extension test pad arrangement according to embodiments of the invention for use in radio frequency (RF) transmission power monitoring; and 
       FIG. 5  is a block diagram illustrating a method for testing an electrical circuit using a bond pad extension test pad arrangement according to embodiments of the invention. 
   

   DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   In the following description, like reference numerals indicate like components to enhance the understanding of the invention through the description of the drawings. Also, although specific features, configurations and arrangements are discussed hereinbelow, it should be understood that such is done for illustrative purposes only. A person skilled in the relevant art will recognize that other steps, configurations and arrangements are useful without departing from the spirit and scope of the invention. 
   Embodiments of the invention are directed to providing a bond pad extension test pad that can be used for testing a corresponding electrical circuit but then is automatically removed from the electrical circuit upon the removal of the applied testing voltage to the bond pad extension test pad. The removal of the bond pad extension test pad from the corresponding electrical circuit prevents any extra parasitic effects associated with the bond pad extension test pad from being added to the corresponding electrical circuit, such as substrate noise, substrate coupling and skin effects. For example, the bond pad extension test pad, when connected to the corresponding electrical circuit, can be used to inject high speed radio frequency (RF) test signals into the electrical circuit through lengthy transmission lines that, upon the removal of the bond pad extension test pad from the corresponding electrical circuit, do not load the actual high speed RF circuitry. 
   Referring now to  FIG. 1 , shown is a block diagram illustrating a bond pad extension test pad arrangement  10  according to embodiments of the invention. The bond pad extension test pad arrangement  10  can be coupled to an electrical circuit device  22 , via any suitable component within the electrical circuit device  22 , such as a bond pad  12 . The bond pad extension test pad arrangement  10  includes a bond pad extension test pad or test pad  14 , a controllable switch  16  coupled between the bond pad  12  and the bond pad extension test pad  14 , and a control circuit  18  coupled to the controllable switch  16  and to the bond pad extension test pad  14 . 
   It should be understood that the bond pad extension test pad arrangement  10  is useful with any suitable circuitry associated with an electrical circuit device, e.g., internal circuitry within an electrical circuit device, including bond pads. Therefore, not only can the bond pad extension test pad arrangement  10  be used for connection to and disconnection from an electrical circuit device bond pad, but also for connection to and disconnection from other internal circuitry within an electrical circuit device. Accordingly, the bond pad extension test pad arrangement  10  is useful for internal testing of electrical components within an electrical circuit device, as well as for connections to and disconnections from electrical components within an electrical circuit device. 
   The bond pad  12  can be any suitable bond pad electrically coupled to one or more integrated circuits (ICs) in an appropriate electrical circuit device  22 . Typically, the bond pad  12  is used for wire bonding the integrated circuit portion of the electrical circuit device to components (not shown) external to the electrical circuit device  22 . 
   The controllable switch  16  can be any suitable switch that can removably couple the test pad  14  to the bond pad  12  in such a way that the bond pad extension test pad  14  is electrically connected to the bond pad  12 . For example, the controllable switch  16  can be a transmission gate, as shown in  FIG. 2  and discussed in greater detail hereinbelow. A transmission gate is an electronic element that can isolate a component or components, e.g., from live signals during hot insertion or removal. 
   The control circuit  18  can be any suitable control circuit that can properly operate the controllable switch  16  in the manner discussed herein. For example, the control circuit  18  can include a static random access memory (SRAM) cell, and other control logic, as shown in  FIG. 2  and discussed in greater detail hereinbelow. In some cases, the control circuit  18  can be controlled by built-in self-test (GIST) functionality. 
   As will be discussed in greater detail hereinbelow, the control circuit  18  switchably connects the bond pad extension test pad  14  to the bond pad  12  by controlling the operation of the controllable switch  16 , i.e., by turning on the controllable switch  16  to electrically connect the bond pad extension test pad  14  to the bond pad  12  and by turning off the controllable switch  16  to electrically disconnect or electrically isolate the bond pad extension test pad  14  from the bond pad  12 . The control circuit  18  controls the operation of the controllable switch  16  based on whether or not the bond pad extension test pad  14  has a testing voltage or testing signal, e.g., from a testing probe, applied thereto. 
   Referring now to  FIG. 2 , shown is a block diagram illustrating the bond pad extension test pad arrangement  10 , in which the controllable switch  16  includes a transmission gate  24  and the control circuit  18  includes an SRAM cell  26  coupled to the transmission gate  24 . The control circuit  18  also is coupled to the bond pad extension test pad  14 , e.g., via an arrangement  28  of additional logic. According to embodiments of the invention, the bond pad extension test pad  14  can have some leakage component (not shown) added thereto, however, such is not necessary. 
   The SRAM cell  26  includes a plurality of transistors M 1 -M 4 , with transistors M 2  and M 3  cross-coupled together directly and via resistors R 1  and R 2 , respectively, as shown. A data line  32  of the SRAM cell  26  is formed by the connection of transistor M 1  and transistor M 2 , and a resistor R 3 , as shown. A data bar or data complement line  34  of the SRAM cell  26  is formed by the connection of transistor M 4  and transistor M 3 , and a resistor R 4 , as shown. The data line  32  is coupled to the source voltage V CC  (i.e., tied “high”) and the data complement line  34  is coupled to ground (i.e., tied “low”). 
   The transmission gate  24  is coupled between the bond pad  12  and the bond pad extension test pad  14 . More specifically, the transmission gate  24  has an input coupled via a connection  36  to the bond pad extension test pad  14  and an output coupled via a connection  38  to the bond pad  12 . The transmission gate  24  also includes a first control or enable input coupled via a connection  42  to the SRAM cell  26  between transistors M 1  and M 2 , and a second, complementary control or enable input coupled via a connection  44  to the SRAM cell  26  between transistors M 3  and M 4 . 
   The transmission gate  24  is turned “on” when a logical “high” or logical “1” voltage is applied to the first control or enable input and a logical “low” or logical “0” is applied to the second, complementary control or enable input. When the transmission gate  24  is turned “on,” the transmission gate input is electrically connected to the transmission gate output. Thus, in this application, when the transmission gate  24  is turned “on,” the bond pad extension test pad  14 , via the connection  36 , will be electrically connected to the bond pad  12 , via the connection  38 . Also, in operation, the transmission gate  24  is turned “off” when a logical “low” or logical “0” voltage is applied to the first control or enable input and a logical “high” or logical “1” is applied to the second, complementary control or enable input. When the transmission gate  24  is turned “off,” the transmission gate input is electrically isolated or disconnected from the transmission gate output. Thus, when the transmission gate  24  is turned “off,” the bond pad  12  will be electrically isolated from the bond pad extension test pad  14 . 
   The SRAM cell  26  includes a write line (W)  46  to which the bond pad extension test pad  14  is coupled, via the appropriate logic arrangement  28 . For example, the arrangement  28  can include a NAND gate  29  with a first input coupled to the bond pad extension test pad  14 , a second input coupled to the data line  32  of the SRAM cell  26 , and an output coupled to the input of an inverter  31 , which has an input coupled to a write line  46  of the SRAM cell  26 . Alternatively, the logic arrangement  28  can be a more complex combination using D-type flip-flops or other one-shot type circuitry. 
   As discussed hereinabove, the bond pad  12  is a conventional bond pad that typically is or will be wire bonded to external circuitry (not shown). During testing of the circuitry of the electrical circuit device to which the bond pad  12  and the arrangement  10  belongs, the testing probe makes contact with the bond pad extension test pad  14  instead of the bond pad  12 . Thus, the bond pad  12  is not touched by any testing probes during any testing, therefore preserving the bonding ability of the bond pad  12 . In this manner, the bond pad extension test pad  14  can be repeatedly gouged by testing probes without adversely affecting the bonding ability of the bond pad  12 . 
   In operation, when the circuitry to which the bond pad extension test pad arrangement belongs is not powered up, the SRAM cell  26  is collapsed and not functioning. When the source voltage V cc  is applied to the circuitry to which the bond pad extension test pad arrangement belongs, e.g., for testing purposes, the SRAM cell  26  and other portions of the control circuit  18  are powered up. At this stage in the testing process, no data is written into the SRAM cell  26  because the write line  46  is not yet energized. 
   When a testing probe is applied to the bond pad extension test pad  14 , the write line  46  of the SRAM cell  26  is energized. When the write line  46  of the SRAM cell  26  becomes energized, an appropriate signal is latched in the SRAM cell  26  is such a way that the connection  42  applies a logical “high” to the first control or enable input of the transmission gate  24  and a logical “low” to the second, complementary control or enable input of the transmission gate  24 , thus turning “on” the transmission gate  24 . When the transmission gate  24  is turned “on,” test signals from the testing probe applied to the bond pad extension test pad  14  can pass between the bond pad extension test pad  14  and the bond pad  12 . As discussed hereinabove, the testing probe does not touch the bond pad  12  even though the bond pad  12  is receiving test signals. 
   When the testing probe is removed from the bond pad extension test pad  14 , the write line  46  of the SRAM cell  26  no longer is energized. As such, within the SRAM cell  26 , the connection  42  to the first control or enable input of the transmission gate  24  becomes a logical “low” and the connection  44  to the second, complementary control or enable input of the transmission gate  24  becomes a logical “high,” thus turning “off” the transmission gate  24 . As discussed hereinabove, when the transmission gate  24  is turned “off,” the bond pad extension test pad  14  is electrically isolated from the bond pad  12 . 
   As the operation of the bond pad extension test pad arrangement  10  illustrates, the testing of an electrical circuit arrangement and the electrical circuit device to which the electrical circuit arrangement belongs can be performed without testing probes making contact with the bond pad  12 . Accordingly, the bond pad  12  is not subjected to the potential physical damage caused by the repeated probing and gouging of test probes, e.g., during testing processes, thus preserving the bonding ability of the bond pad  12 . 
   Although the bond pad extension test pad arrangement  10  shown in  FIG. 2  includes an SRAM cell in the control circuit  18 , other control circuit arrangements can be used according to embodiments of the invention. For example, instead of using an SRAM cell  26 , the control circuit  18  can include a circuit arrangement of NAND logic that is configured to sense applied voltages to the bond pad extension test pad  14  and to sense logical “highs” and logical “lows” on the first and second enable inputs of the transmission gate  24  to control the operation of the transmission gate  24  in the manner described hereinabove. However, the use of an SRAM cell in the control circuit  18  can be advantageous in that an SRAM cell arrangement does not include separate write line control, e.g., from a scan line test stream or other clocking signal. 
   Referring now to  FIG. 3 , shown is a block diagram illustrating a bond pad extension test pad arrangement  50  according to embodiments of the invention for providing high speed testing to high speed inputs, such as the low noise amplifier (LNA) input of an RF transceiver. The arrangement  50  includes one or more bond pads  12 , such as an RF input pad for an RF transceiver  52 . The arrangement  50  also includes a transmission gate or other appropriate controllable switch  16  coupled to the bond pad  12 , the bond pad extension test pad  14  coupled to the controllable switch  16 , and the control circuit  18  coupled to the controllable switch  16  and the bond pad extension test pad  14 . The bond pad extension test pad  14  also is coupled to an RF testing source  54 , e.g., via an input transmission line  56 . 
   The RF testing source  54  is configured to inject a high speed test signal into the low noise amplifier at the input of the RF transceiver  52 . However, the low noise amplifier (not shown) typically is sensitive to input loading, and thus the bond pad  12  should not be disturbed during active RF testing. Therefore, in operation, in the manner discussed hereinabove, when the control circuit  18  detects that a testing signal or testing voltage has been applied to the bond pad extension test pad  14  by the RF testing source  54 , the control circuit  18  enables the controllable switch  16  to allow the high speed test signal to be injected into the input of the low noise amplifier in the RF transceiver  52 . When testing is complete, i.e., when a testing signal no longer is applied to the bond pad extension test pad  14  by the RF testing source  54 , the control circuit  18  disables the controllable switch  16 , thus electrically disconnecting or isolating the RF testing source  54 , along with the transmission line  56 , from the input of the low noise amplifier in the RF transceiver  52 . 
   Referring now to  FIG. 4 , shown is a block diagram illustrating a bond pad extension test pad arrangement  60  according to embodiments of the invention for use in radio frequency (RF) transmission power monitoring. For example, the arrangement  60  illustrates a bond pad extension test pad arrangement used in an application where an RF transmitter, via a transmitter output stage  62 , is coupled to an antenna  64 , such as a printed antenna. The arrangement  60  includes a power monitor or detector  66  coupled to the bond pad extension test pad  14 , e.g., via a transmission line  68 . The bond pad extension test pad  14  is coupled to the controllable switch  16  (e.g., a transmission gate), which also is coupled to the bond pad  12 . The control circuit  18  is coupled to the controllable switch  16  and the bond pad  12  in the manner described previously herein. 
   According to embodiments of the invention, the bond pad extension test pad arrangement provides a stub for tapping off a portion of the RF transmitter output power when the power monitor  66  is applied to the bond pad extension test pad  14 . Typically, such stub or tap provided by the bond pad extension test pad arrangement is coupled to a relatively low impedance point on an output matching network  72  between the transmitter output stage  62  and the antenna  64 . Typically, the output matching network  72  is configured to have an impedance that matches or approximately matches the impedance of the transmission line  68 . 
   In operation, when the power monitor  66  is coupled to the bond pad extension test pad  14 , and the power monitor  66  is turned on or powered up, the control circuit  18  detects the presence of the power monitor  66  via the bond pad extension test pad  14  and, in response thereto, enables the controllable switch  16 , thus electrically connecting the bond pad extension test pad  14  to the bond pad  12 . With the bond pad  12  coupled to the output matching network  72 , the output power from the transmitter output stage  62  can be measured or monitored by the power monitor  66 . When the transmitter output stage  62  is not being tested, e.g., when the power monitor  66  is turned off or powered down, the control circuit  18  disables the controllable switch  16 , thus electrically disconnecting or isolating the power monitor  66  and the transmission line  68  from the transmitter output stage  62 . Otherwise, having the power monitor  66  and the transmission line  68  remaining electrically connected to the transmitter output stage  62  of the RF transmitter would be detrimental to the operation of the RF transmitter. 
   Referring now to  FIG. 5 , shown is a block diagram illustrating a method  80  for testing an electrical circuit using a bond pad extension test pad arrangement according to embodiments of the invention. The method  80  includes a step  82  of providing a bond pad extension test pad arrangement according to embodiments of the invention, e.g., an arrangement in which the bond pad extension test pad  14  is coupled to the bond pad  12  via the controllable switch  16 , and the control circuit  18  is coupled to the bond pad extension test pad  14  and coupled to the controllable switch  16 , e.g., as shown in  FIGS. 1-4  and described hereinabove. The method  80  also includes a step  84  of determining or detecting whether or not a testing signal is applied to the bond pad extension test pad  14 . For example, a testing probe configured to generate a testing signal can apply a testing signal to the bond pad extension test pad  14  by probing or contacting the testing probe to the bond pad extension test pad  14 . As discussed herein, the testing probe does not make contact with the bond pad  12 . 
   The method  80  also includes a step  86  of enabling the controllable switch  16 . As discussed hereinabove, the control circuit  18  is configured to enable the controllable switch  16  in response to the control circuit  18  detecting that a testing signal has been applied to the bond pad extension test pad  14 . If the control circuit  18  detects that a testing signal has been applied to the bond pad extension test pad  14  (Y), the control circuit  18  enables the controllable switch  16 , thus electrically connecting the bond pad extension test pad  14  to the bond pad  12 . Once the step  86  of enabling the controllable switch  16  has been performed, the method  80  returns to the step  84  of determining or detecting whether or not a testing signal is applied to the bond pad extension test pad  14 . Therefore, as long as a testing signal is applied to the bond pad extension test pad  14 , the control circuit  18  will continue to enable the controllable switch  16 , thus allowing the bond pad extension test pad  14  to be electrically coupled to the bond pad  12  and allowing the testing signal to be applied to the bond pad  12  and the electrical circuit to which the bond pad  12  belongs. 
   The method  80  also includes a step  88  of disabling the controllable switch  16 . As discussed hereinabove, the control circuit  18  is configured to disable the controllable switch  16  if the control circuit  18  does not detect a testing signal applied to the bond pad extension test pad  14 . If the control circuit  18  does not detect a testing signal applied to the bond pad extension test pad  14  (N), the control circuit  18  disables the controllable switch  16 , thus electrically isolating or disconnecting the bond pad extension test pad  14  to the bond pad  12 . Once the step  88  of disabling the controllable switch  16  has been performed, the method  80  returns to the step  84  of determining or detecting whether or not a testing signal is applied to the bond pad extension test pad  14 . Therefore, as long as no testing signal is applied to the bond pad extension test pad  14 , the control circuit  18  will keep the controllable switch  16  disabled, thus keeping the bond pad extension test pad  14  electrically isolated from the bond pad  12 . 
   As discussed hereinabove, by probing the bond pad extension test pad  14  with the testing probe instead of the bond pad  12 , the electrical circuit to which the bond pad  12  belongs can be tested without the testing probe having to make contact with the bond pad  12 , thus preserving the physical integrity and maintaining the bonding ability of the bond pad  12 . Also, by keeping the bond pad extension test pad  14  (and the control circuit  18 ) electrically isolated from the bond pad  12  when the electrical circuit to which the bond pad  12  belongs is not being tested, no additional parasitic effects that may otherwise be contributed by the bond pad extension test pad  14  are added to the electrical device to which the bond pad  12  belongs. 
   It will be apparent to those skilled in the art that many changes and substitutions can be made to the embodiments of the invention herein described without departing from the spirit and scope of the invention as defined by the appended claims and their full scope of equivalents.