The present disclosure relates to testing electronic devices. More specifically, the present disclosure relates to testing and characterizing failed devices under controlled temperature conditions on automatic test equipment (ATE) for failure analysis.
Electronic devices (cellular telephones, wireless modems, computers, digital music players, Global Positioning System units, Personal Digital Assistants, gaming devices, etc.) have become a part of everyday life. Small computing devices are now placed in everything from automobiles to housing locks. The complexity of electronic devices has increased dramatically in the last few years. For example, many electronic devices have one or more processors that help control the device, as well as a number of digital circuits to support the processor and other parts of the device.
Many different kinds of electronic devices may benefit from testing. Types of such devices include, but are not limited to, cellular telephones, wireless modems, computers, digital music players, Global Positioning System units, Personal Digital Assistants, gaming devices, etc. One group of devices includes those that may be used with wireless communication systems. As used herein, the term “mobile station” refers to an electronic device that may be used for voice and/or data communication over a wireless communication network. Examples of mobile stations include cellular phones, handheld wireless devices, wireless modems, laptop computers, personal computers, etc. A mobile station may alternatively be referred to as an access terminal, a mobile terminal, a subscriber station, a remote station, a user terminal, a terminal, a subscriber unit, user equipment, etc.
Advanced cellular handsets include a multiplicity of individual or stacked IC devices, such as a modem, power management chip, RF transmitter/receiver, video processor and a microprocessor, among others. All or some of these devices may exist in a single chip or in a single package. With increased demand for high bandwidth, high speed wireless services, today's high performance cellular IC's are required to operate at increasingly higher speeds within an ever smaller handheld package. Significant amounts of heat may be generated, at times up to 60 W, by such devices during peak operation, resulting in an increased need for effective thermal management strategies. During IC test, characterization and fault isolation similar conditions are established. In particular, during continuous loop device testing using an ATE for the purpose of fault isolation, there is a risk of device degradation and complete failure due to thermal overstress.
Similarly, numerous high speed, high power microprocessors may be utilized together for use in web-based volume data storage and internet service provider type server applications. Although the space constraints of such server based IC device applications are less restrictive than their cellular counterparts, the sheer number and density of microprocessors in a server room can far outstrip the thermal mitigation requirements of cellular systems. A standard single microprocessor IC device found in server applications may produce up to 200W during peak operation, with several hundred such processors in operation in either a mainframe or server farm configuration, resulting in a very high thermal density. As with other IC devices, during test, characterization and fault isolation similar operating conditions are established. There is a risk of device degradation and complete failure due to thermal overstress.
In addition to this, server based IC devices may have to meet very stringent robustness requirements in order to establish confidence in their long term, high reliability operation for critical applications such as web-based data storage and communications. Therefore, additional thermal mitigation and control requirements are placed upon these devices during all phases of test. In particular, thermal management must be in place allowing for a wide range of steady state temperature control during all phases of test and characterization. For example, server based IC devices may be tested at temperatures as low as −50 C and as high as +120 C to ensure high reliability under all possible conditions. Therefore, it may be beneficial for the same thermal management strategies to be in place during fault isolation in order to correctly diagnose and characterize faults which may occur under specific conditions.
This increased complexity and thermal density has led to additional testing of digital circuits and/or digital systems under more stringent conditions. Testing may be used to verify or test various parts of devices, such as pieces of hardware, software or a combination of both. Mode failure identification, fault isolation and failure analysis may depend on replication and detection of failure modes over the full range of environmental operating conditions where failure may occur.
Fault isolation techniques may include a multiplicity of methods which would benefit from such a thermal mitigation and control strategy. Examples may include, but are not limited to; Thermal imaging, emission site detection (photon, secondary electron, x-ray, etc) including in vacuum, electron beam induced voltage contrast, thermally induced voltage alteration (TIVA), light induced voltage alteration (LIVA), optical beam induced resistance change (OBIRCH), etc.
One approach to characterization and failure analysis of a digital device under test (DUT) is the use of Laser Voltage Probe (LVP) (usually with a microscope) or other optical systems with a Solid Immersion Lens (SIL) or any air-gap lens. During device testing, self heating of the DUT may become problematic, especially under high frequency and high voltage test conditions. This is undesirable in that these heating effects, coupled with physical interaction by the probing system (optical, LEED, etc.), may result in perturbation of the device operation such that unwanted shifts in performance are observed, yielding invalid test results. In the worst case, a device may fail completely under testing due to overheating and/or thermal runaway caused at least in part by the LVP or other optical-type probes.
While this is somewhat of an issue for mobile devices, it may also pose a serious issue for the debug and characterization of high powered/high frequency multi-cored processors, such as those applicable to servers. Additionally, in the case of certain analytical equipment (e.g., infrared emission microscopy (IREM), thermal camera) excessive heat may also result in detector saturation and thus, device cooling may provide benefits at a system level as well. A basic solution to this problem is to provide a cooling mechanism to allow the device to be tested at maximum power and frequency without device failure or damage.
At present, two primary methods of device cooling are available: direct fluid spray cooling and direct air spray cooling. Neither of these solutions is without limitation, nor do they provide a solution suitable for all available analytical fault isolation or characterization techniques. For example, neither method would be acceptable in the instance of an analysis technique which must take place within a vacuum environment. Therefore, there is a need in the art for a solution to these shortcomings. For example, some analytical characterizations systems are preferably operable in vacuum, so therefore a cooling means is sought that can operate in vacuum as well as ambient conditions.
In a first aspect of the disclosure, an apparatus includes an electrically insulating thermally conductive carrier for supporting a device under test (DUT), one or more thermo-electric devices arranged with the carrier, and one or more conductive vias in the carrier to make electrical connection to the DUT for coupling to an external test apparatus.
In a second aspect of the disclosure, an apparatus includes electrically insulating thermally conductive carrier means for supporting a device under test (DUT), one or more solid state device means arranged with the carrier means for generating at least one of heat and cold, and one or more conductive means through the carrier means to make electrical connection to the DUT for coupling to an external test apparatus.
In a third aspect of the disclosure, a method of testing a device under test (DUT includes supporting the DUT on an electrically insulating thermally conductive carrier, arranging one or more thermo-electric devices coupled to the carrier to control the temperature of the DUT, connecting the DUT electrically to an external test apparatus through one or more conductive vias in the carrier, connecting the one or more thermo-electric devices to the external test apparatus, and characterizing with the external apparatus the DUT on the basis of the temperature of the DUT.
In a fourth aspect of the disclosure, a non-transitory computer readable media including program instructions which when executed by a processor cause the processor to perform the method, including the steps of controlling one or more thermo-electric devices coupled to a carrier to control the temperature of a device under test (DUT) arranged with the carrier, and characterizing the DUT with an external test apparatus through electrical connections between the DUT and the external test apparatus, the electrical connections including conductive vias in the carrier coupled to the DUT, and a flat top socket coupled to the vias in the carrier and to the external test apparatus.
Various aspects are now described with reference to the drawings. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects. It may be evident; however, that such aspect(s) may be practiced without these specific details.
As used in this application, the terms “component,” “module,” “system” and the like are intended to include a computer-related entity, such as, but not limited to hardware, firmware, a combination of hardware and software, software, or software in execution. For example, a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program and/or a computer. By way of illustration, both an application running on a computing device and the computing device can be a component. One or more components can reside within a process and/or thread of execution and a component may be localized on one computer and/or distributed between two or more computers. In addition, these components can execute from various computer readable media having various data structures stored thereon. The components may communicate by way of local and/or remote processes such as in accordance with a signal having one or more data packets, such as data from one component interacting with another component in a local system, distributed system, and/or across a network such as the Internet with other systems by way of the signal.
Furthermore, various aspects are described herein in connection with a terminal, which can be a wired terminal or a wireless terminal. A terminal can also be called a system, device, subscriber unit, subscriber station, mobile station, mobile, mobile device, remote station, remote terminal, access terminal, user terminal, communication device, user agent, user device, or user equipment (UE). A wireless terminal may be a cellular telephone, a satellite phone, a cordless telephone, a Session Initiation Protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device having wireless connection capability, a computing device, or other processing devices connected to a wireless modem. Moreover, various aspects are described herein in connection with a base station. A base station may be utilized for communicating with wireless terminal(s) and may also be referred to as an access point, a Node B, or some other terminology.
Moreover, the term “or” is intended to man an inclusive “or” rather than an exclusive “or.” That is, unless specified otherwise, or clear from the context, the phrase “X employs A or B” is intended to mean any of the natural inclusive permutations. That is, the phrase “X employs A or B” is satisfied by any of the following instances: X employs A; X employs B; or X employs both A and B. In addition, the articles “a” and “an” as used in this application and the appended claims should generally be construed to mean “one or more” unless specified otherwise or clear from the context to be directed to a singular form.
The techniques described herein may be used for various wireless communication networks such as Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms “networks” and “systems” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), CDMA2000, etc. UTRA includes Wideband CDMA (W-CDMA). CDMA2000 covers IS-2000, IS-95 and technology such as Global System for Mobile Communication (GSM).
An OFDMA network may implement a radio technology such as Evolved UTRA (E-UTRA), the Institute of Electrical and Electronics Engineers (IEEE) 802.11, IEEE 802.16, IEEE 802.20, Flash-OFDAM®, etc. UTRA, E-UTRA, and GSM are part of Universal Mobile Telecommunication System (UMTS). Long Term Evolution (LTE) is a release of UMTS that uses E-UTRA. UTRA, E-UTRA, GSM, UMTS, and LTE are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). CDMA2000 is described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). These various radio technologies and standards are known in the art. For clarity, certain aspects of the techniques are described below for LTE, and LTE terminology is used in much of the description below. It should be noted that the LTE terminology is used by way of illustration and the scope of the disclosure is not limited to LTE. Rather, the techniques described herein may be utilized in various application involving wireless transmissions, such as personal area networks (PANs), body area networks (BANs), location, Bluetooth, GPS, UWB, RFID, and the like. Further, the techniques may also be utilized in wired systems, such as cable modems, fiber-based systems, and the like.
During operation of the cellular telephone system 100, the base stations 110 may receive sets of reverse link signals from sets of mobile stations 108. The mobile stations 108 may be involved in telephone calls or other communications. Each reverse link signal received by a given base station 110 may be processed within that base station 110. The resulting data may be forwarded to the BSC 106. The BSC 106 may provide call resource allocation and mobility management functionality including the orchestration of soft handoffs between base stations 110. The BSC 106 may also route the received data to the MSC 102, which provides additional routing services for interfacing with the PSTN 104. Similarly, the PTSN 104 may interface with the MSC 102, and the MSC 102 may interface with the BSC 106, which in turn may control the base stations 110 to transmit sets of forward link signals to sets of mobile stations 108.
This disclosure concerns itself with a high thermal conductivity material based DUT carrier PCB and a programmable, solid state cooling device, or devices, which can also be augmented with supplementary closed loop fluid cooling that is integrated into an equally high thermally conductive material based flat top socket interface. Specifically, the DUT is mounted on a carrier board (carrier PCB) with “through via electrical connections” matching that of the DUT. The carrier PCB is mounted to a flat top socket (FTS), which then mates the carrier PCB/DUT assembly to the test head. The combination of carrier PCB and DUT provides a rigid interface between the test head's load board and the SIL of the LVP or other similar fault isolation and characterization systems. This may be necessary since the SIL is in direct contact with the DUT. It should be appreciated that in this configuration, the DUT is fully or partially de-encapsulated and that the exposed area of the IC must remain unobstructed in order to allow probing or allow detection from various circuits within the DUT and to obtain a signal for analysis. Therefore, any cooling apparatus may preferably not interfere with or obstruct the fully exposed DUT surface area in any way.
Solid state thermo-electric cooler/thermo-electric heater (TEC/TEH) devices 230 can be mounted to the metallized carrier PCB 200 to provide device cooling or heating as required. The DUT 210 may be (backside) polished to thin the silicon substrate to within acceptable thicknesses for probing and other fault isolation and characterization techniques. A slight gap may exist between the remaining encapsulation of the DUT 210 and carrier PCB surface metallization 220. The slight gap is bridged with a high thermal conductivity metallic paint or paste (such as standard silver paint, not shown), thus completing the heat transfer path between the DUT 210 and the TEC/TEH 230 mounted on the carrier PCB 200. One or more TEC/TEHs 230 can be mounted depending on the power requirements of the DUT 210.
Alternatively, during preparation of the DUT 210, further encapsulation may be removed by polishing the sides to expose unused circuitry allowing a direct thermal connection inside the device, raising the heat transfer efficiency. The TEC/TEHs 230 can be precisely controlled so that not only heat removal may be accomplished, but controlled device heating under quiescent conditions, extreme cooling or heating under nominal conditions, and nominal temperature control under full power conditions, as well as all combination of conditions in between, may be achieved for a full range of performance characterization.
A desired temperature of the DUT 210 may be monitored and controlled by enabling temperature sensors, such as thermistors, embedded in the DUT 210 and on the external carrier PCB 200 or FTS mounted thermocouples integrated for providing feedback for control of the TEC/TEHs 230. In another embodiment, the carrier PCB 200 may be constructed of standard PCB material or any other suitable material which is metallized and having one or more TEC/TEHs 230 mounted to achieve precise cooling or heating. The bridging method from DUT to metallization and TEC/TEH 230 is the same as described above. Additionally, excess cooling or heating can be achieved by addition of more, or higher power, TEC/TEHs 230 in order to overcome any reduction of heat transfer through the carrier PCB 200 itself or to simply accommodate higher power devices. For example, if 200 W of heat removal is required to dissipate 40 W of power from the DUT 210 due to inefficiencies in the thermal conductance path, multiple Peltier-type TEC/TEHs 230 may be added to accomplish the required cooling. The size and number of TEC/TEHs 230 is only limited by the potential size of the carrier PCB 200 itself which can be many times larger than the DUT 210, especially in the case of multi-core processors (e.g., in server devices) where only one or two devices may be mounted at a time for testing. Additionally, both sides of the carrier PCB 200 can be metallized so that TEC/TEHs 230 can be mounted on both sides. Known, TEC/TEHs 230 capable of about 130 W or more of cooling each (for example) are commercially available and may accommodate an appropriately sized carrier PCB 200 such that, for example, a total of 260 W of cooling for a 60 W DUT 210 is feasible. The wattages cited are for illustrative purposes only, and higher or lower power dissipation or generation may be accomplished by selection of an appropriate type and number of TEC/TEHs 230 for the test conditions.
It may be appreciated that the apparatus described is substantially uniformly temperature controlled (i.e., either for cooling or heating) throughout, not just at the DUT 210, as there is insufficient thermal path through electrical connections only, but sufficient thermal path through the carrier PCB 200 and metallization 220 may be provided with this arrangement. Furthermore, the DUT 210 may be connected to the flat-top socket by vias 310 through the carrier PCB 200, and where the through vias 310 are electrically isolated by the ceramic or other insulating base material of the PCB carrier 200.
In another embodiment, the FTS 400 may be constructed of standard plastic or any other suitable material which is metallized and which can augment the removal of heat from the DUT 210 and carrier PCB 200 in the same way as described above. Cooling flow through the FTS 400 could also comprise a multiplicity of cooling media such as water, oil, liquid nitrogen (LN2) or other refrigerants, for example.
Additional thermal mass for heat transfer may be added to boost cooling/heating temperature control. For example, additional thermally conductive blocks 420 (or plates) made, for example, of copper, may be bonded to the PCB 200, on which additional Peltier-type TEC/TEHs 230 can be mounted (on both top and bottom, if desired, and space permits). Where the carrier PCB 200 is ceramic, the bonding method may be brazing. For other carrier materials and/or other high thermal conductivity masses, other more appropriate bonding methods may be used. As described above, the FTS 400 may be channeled internally for cooling flow, and metallization 430 (e.g., copper, molybdenum) may provide improved thermal contact to the PCB 200. Furthermore, the DUT 210 is still connected to the FTS 400 by vias 310 through the PCB 200, so there may be no impact on the configuration of the FTS 400.
In yet another embodiment, as shown in a schematic view in
It may be appreciated that several disadvantages in current available cooling methods may be overcome, and several advantages not achievable with the current available cooling methods may be obtained. For example, there is no risk of electrical shorting of either the DUT 210 or system electronics that may occur with open fluid spray cooling. No special dielectric fluid is required to prevent electrical shorting as described above when direct spray cooling is used. Such coolants also may not be environmentally unfriendly and/or may include toxic fluorine based chemicals.
A system reconfiguration may not be required to accommodate the solid state cooling solution. Neither air spray nor other fluid spray cooling may effectively provide a method of heating the DUT 210 such as that which may be provided by a solid state device (e.g., the TEC/TEH 230). Furthermore, neither air spray nor other fluid spray cooling may be capable of providing a wide range of precise electronically controlled temperature (such as with a TEC/TEH 230 and a controller unit). The achievable precision may be to within a degree C. using a feedback loop based on embedded thermistor, thermocouple or other temperature sensor output. Whether in the case of solid state cooling/heating alone with TEC/TEHs 230, or in conjunction with an LN2/cold finger cooled FTS 400, there is no risk of coolant leakage or added vibration from high velocity air flow or fluid spray flow, which may potentially reduce the resolution and accuracy of the probing LVP microscope. Still furthermore, the LVP system detector performance may be extended and maximized by increasing the temperature range of testing to saturation and failure conditions.
In an embodiment of the apparatus, the FTS 400 is attached to a load board 510, which may have a standard layout for interfacing to an electronic test head 520 of an ATE (not shown). The PCB 200 may attach to the FTS 400 and, as described above, the DUT 210 may attach to the PCB 200, where the PCB 200 includes the DUT 210 and TEC/TEHs 230 attached thereon. The DUT 210 is arranged “face down,” i.e., with the electronic circuitry facing the PCB 200 and appropriately contacting electrical feed through vias 310 in the PCB 200, where the vias 310 are further appropriately coupled to vias in the FTS 400 for electrical connection to the electronic test head 520.
In the example of using an LVP 530, a laser source may probe the back surface of the thinned DUT 210 through either a solid immersion lens (SIL) in direct contact with the DUT 210, or through an air gap lens that is non-contact.
It may be appreciated that the combination of using a standard ATE with an adaptor means (i.e. a flat top socket FTS 400) to interface a carrier PCB 200 that includes indirect means for temperature controlling a DUT 210 (i.e., with thermally conductive coupling between the DUT 210 and the TEC/TEHs 230 through the carrier PCB 200) and simultaneously obtain quantitative optical imaging characterization of circuit performance from the thinned back of the DUT 210 may provide dynamic fault detection and failure analysis information over a full range of operating conditions not easily available otherwise.
The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for.”
It is understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented. It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the systems, methods, and apparatus described herein without departing from the scope of the claims.
This application is related to and claims priority from U.S. Provisional Patent Application Ser. No. 61/831,609 filed Jun. 5, 2013, for “INTEGRATED, SOLID STATE, PRECISION TEMPERATURE CONTROL SOLUTION FOR USE WITH A DUT ON FAILURE ANALYSIS EQUIPMENT.”
Number | Date | Country | |
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61831609 | Jun 2013 | US |