Characterizing and Managing Leakage for Electronic Circuit Hardening

Abstract

The electronic system can include an electronic module and a trace circuit that provides a boundary surrounding the electronic module. A sensing circuit within the electronic system can be configured to detect a discontinuity in the boundary. In response to detecting the discontinuity in the boundary, the sensing circuit can initiate a reaction signal from a reaction device.

Description

[Technical field]

[0001] The present invention relates generally to electronic systems and, more particularly, to electronic systems configured to detect discontinuities in a perimeter surrounding an electronic module. [Background technology]

[0002] A printed circuit board (PCB) can be used to mechanically support and electrically connect electronic components using conductive paths or signal traces etched from thin sheets of copper laminated to a non-conductive substrate. Multiple copper / insulator layer pairs, also known as "cores", may be laminated together during the manufacture of a PCB. The number and arrangement of cores can be designed to suit the needs of various applications.

[0003] Vertical interconnect structures (vias) may be used to interconnect conductive signal traces between various conductive layers in a PCB. Copper shapes or areas may be used for power and ground distribution to components mounted on the PCB. Interconnect structures within a PCB can be designed to be physically and electrically compatible with the components that the PCB may be used to interconnect.

[0004] A flexible printed circuit, also known as a "flex circuit" or "flex cable," can generally be understood to resemble a PCB that is capable of bending. In practice, however, the set of design rules, such as conductor width and spacing, used in the design and manufacture of a flex circuit can be significantly different than those used in the design and manufacture of a rigid or semi-rigid PCB. In some applications, the conductors in a flex circuit may be manufactured using processes such as photo imaging or laser imaging as the pattern definition method rather than a "printing" process.

[0005] Flexible printed circuits include a metal layer of traces, often copper, bonded to a dielectric layer such as polyimide. The thickness of the metal layer can range from very thin, e.g., less than 0.0001” (0,000254 cm), to very thick, e.g., greater than 0.010” (0.0254 cm), and the thickness of the dielectric layer can similarly vary, ranging between 0.0005” (0.00127 cm) and 0.010” (0.0254 cm). Adhesive materials or other types of bonding, such as vapor deposition, may be used to bond the metal to the substrate. Because copper is prone to oxidation in the presence of air, exposed copper surfaces are often covered with a protective layer. Gold and solder are common materials used for this purpose because of their electrical conductivity and environmental resistance. For non-contacting or non-conductive areas, a dielectric material can be used to protect the circuit from oxidation or electrical shorting. Electrical leakage, i.e., leakage of electrical current, can occur through dielectric materials located between adjacent metal layers. Summary of the Invention

[0006] Embodiments may be directed to an electronic system including an electronic module, a trace circuit providing a boundary surrounding the electronic module, and a sensing circuit configured to detect a discontinuity in the boundary, the sensing circuit further configured to initiate an action from a reactive device in response to the detection.

[0007] Embodiments may also be directed to a method for designing an electronic system for managed battery life and managed electronic data security of an electronic module. The method includes receiving design requirements for the electronic system and characterizing candidate dielectric materials for use in the electronic system. The method further includes selecting a dielectric material from the candidate dielectric materials according to the design requirements and designing a trace circuit to include the selected dielectric material. The method further includes fabricating the trace circuit according to the trace circuit design and incorporating the trace circuit into the electronic system. Incorporating the trace circuit into the electronic system includes surrounding the electronic module with the trace circuit to provide a boundary surrounding the electronic module and electrically interconnecting the trace circuit to a sensing circuit.

[0008] Embodiments may also be directed to a method for operating an electronic system for managed battery life and managed electronic data security of an electronic module. The method includes applying a voltage to a trace circuit configured to provide a boundary surrounding the electronic module with a sense circuit and measuring a sense voltage on the trace circuit with the sense circuit. The method further includes comparing the sense voltage to a voltage threshold to detect a boundary discontinuity and initiating an action with a reaction device electrically interconnected to the sense circuit in response to the sense voltage indicating the boundary discontinuity.

[0009] The above summary is not intended to describe each illustrated embodiment or every implementation of the present invention.

[0010] The drawings contained herein are incorporated in and form a part of this specification. They illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. The drawings are merely illustrative of certain embodiments and are not limiting of the invention. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 illustrates an electronic system configured for managed battery life and electronic data security in accordance with an embodiment of the present invention. [Diagram 2] 1 is a flow diagram illustrating a method for designing an electronic system for managed battery life and electronic data security, according to an embodiment consistent with the figures. [Diagram 3] 11 is a graph showing dielectric leakage measurements for two dielectric materials according to an embodiment consistent with the figures. [Figure 4] 11 is a graph illustrating the variation of a sense voltage on a trace circuit according to an embodiment consistent with the figures. [Diagram 5] 1 is a flow diagram illustrating a method for operating an electronic system for managed battery life and electronic data security, according to an embodiment consistent with the figures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] While the invention is susceptible to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and are hereinafter described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. Instead, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention.

[0013] In the figures and detailed description, like numbers generally refer to like components, parts, steps and operations.

[0014] Certain embodiments of the present invention may be understood in the context of providing detection of discontinuities in boundaries surrounding electronic modules in electronic devices, such as servers, that may be used to provide data to clients coupled to the servers through a network. Such servers may include, but are not limited to, web servers, application servers, mail servers, and virtual servers. Although not necessarily limited thereto, the embodiments discussed in this context may aid in understanding various aspects of the present invention. Certain embodiments may also be directed to other devices and related applications, such as providing detection of discontinuities in boundaries surrounding electronic modules in computing systems that may be used in a variety of computing and data processing applications. Such computing systems may include, but are not limited to, supercomputers, high performance computing (HPC) systems, and other types of special purpose computers. Embodiments may also be directed to providing detection of discontinuities in boundaries surrounding electronic modules in consumer and small office / home office (SOHO) electronic devices, such as personal computers, laptops, mobile and network server devices.

[0015] For ease of discussion, the term "FR" is used herein to refer to a class of Fire Retardant glass-fiber-epoxy laminate materials. FR materials, particularly FR4, are widely and commonly used in the construction of various printed circuit boards (PCBs). FR4 is designed for use in high density multilayer PCBs and is suitable for high volume fine line / multilayer applications. Similarly, the term "AP" is used generally herein to refer to a class of Adhesive-less / high-Performance laminate materials, including copper clad laminates and all-polyimide composite materials of polyimide film bonded to copper foil. Such materials may be used in the construction of multilayer flex and rigid-flex applications that require advanced material performance, temperature resistance, and high reliability. The term "HT" is used generally herein to refer to a class of High Temperature laminate materials that are characterized by good material and electrical properties. Such materials have a higher glass transition temperature (T) than materials such as FR4. g ) and low loss characteristics (e.g., loss tangent).

[0016] The need for storage of secure / sensitive data and the inclusion of cryptographic functions in electronic systems has resulted in the implementation of various devices and techniques to detect and react to unauthorized attempts to tamper with such systems. Potentially vulnerable systems may include, but are not limited to, computers, servers, supercomputers, personal computers, networks, and telecommunications systems. Tampering with such systems may result in unauthorized access to confidential and / or sensitive information, such as financial, military, or classified data, sensitive personally identifiable information (PII), or cryptographic keys.

[0017] Trace circuits, including one or more layers of conductive traces fabricated in a serpentine arrangement, can be useful in detecting invasive tampering attempts of electronic devices and modules. Attempts to tamper with the trace circuit, i.e., drilling, cutting, etc., can provide detectable indications of such tampering, such as electrical discontinuities, and a responsive device, such as a processor or other circuitry, can respond in various ways to the detected tampering to alert and / or mitigate a security risk.

[0018] Electrical structures such as flexible circuits and / or PCBs that include serpentine traces can exhibit significant electrical leakage between adjacent trace layers and / or power distribution layers, especially when the serpentine traces are arranged in adjacent parallel planar orientations. In some applications, a data / crypto security system that includes one or more trace circuits may be powered by an internal battery. Electrical leakage of adjacent trace circuits to other trace circuits and / or power distribution planes can substantially reduce the life of the battery powering the security system. Such reduced battery life can compromise the security of the data within the system.

[0019] An embodiment of the present invention is directed to a system for monitoring the continuity of a trace circuit within an electronic system, such as a computer, server, supercomputer, or network system. The continuity monitoring system includes a trace circuit that acts as a boundary surrounding an electronic module and can provide an indication of discontinuities at that boundary. An embodiment includes a trace circuit constructed with one or more dielectric materials that are characterized, selected, and designed into the trace circuit to manage and minimize leakage currents. Such managed dielectric leakage currents can be particularly useful in extending and enhancing the operating life of a battery powering the trace circuit continuity monitoring system, thereby improving and enhancing security for sensitive electronically stored data and encryption keys / data. As a result of such improved security, loss of sensitive / confidential data and / or encryption capabilities can be managed and minimized.

[0020] Various aspects of the present invention may be useful for monitoring the continuity of a tracing circuit configured to provide a security boundary for an electronic system. Such monitoring may provide improved security for electronically stored data and encryption keys within the system. An electronic system configured according to embodiments may monitor the continuity of such tracing circuitry while consuming less energy and providing extended battery life compared to other similar electronic security systems. Embodiments may be configured to react to a detected tampering / violation of the security boundary of the electronic system through the transmission of a warning message, activation of an alarm or visual indicator, and destruction of secure / sensitive data and / or encryption keys. Such measures may be beneficial in improving the security of electronic data within the electronic system.

[0021] Embodiments of the present invention may also be useful for reducing the energy consumption of a security monitoring system through the reduction of dielectric leakage, thereby reducing the RC time constant (τ) of one or more trace circuits in the system. Reducing τ may be particularly useful for reducing the response time of a sensing circuit, thereby reducing both the complexity and energy consumption of such a sensing circuit. Reducing dielectric leakage may also enable a reduction in the trace circuit resistance.

[0022] Various aspects of the present invention may be useful in enabling probing of sensing circuits through the use of commonly used / available voltmeters and / or oscilloscopes with high input impedance. Embodiments of the present invention may also be useful in managing the design cost and complexity of electronic systems while using existing proven PCB design methodologies and material sets. Electronic systems designed according to certain embodiments may be compatible with existing proven computer, server, supercomputer and personal computer (PC) designs, as well as PCB / flex circuit design methodologies and material sets. Electronic perimeter security monitoring systems constructed according to embodiments of the present invention may be installed within existing electronic equipment enclosures.

[0023] Certain embodiments relate to an electronic system configured to provide managed battery life and electronic data security for an electronic module and to initiate action when a discontinuity in a boundary surrounding the electronic module is detected. Figure 1 includes consistent illustrations 100, 125, 150A, and 150B depicting an electronic system for managed battery life and electronic data security and a tracing circuit 150 according to an embodiment of the present invention.

[0024] The diagram 100 can provide an understanding of an electronic system including multiple instances of a tracing circuit 150, a sensing circuit 102, and a responsive device 120. According to an embodiment, the sensing circuit 102 is electrically interconnected with the tracing circuit 150 and configured to monitor their continuity. In response to the sensing circuit 102 detecting a discontinuity in the tracing circuit 150, the responsive device 120 can initiate actions designed to alert about and / or mitigate a data security condition / issue in the electronic system 100, 125. In such an embodiment, the electronic system 100 functions as a data security system.

[0025] It will be appreciated that the electronic system 100, 125 may be incorporated into a variety of electronic devices and systems, such as computers, servers, special purpose computers, supercomputers, and personal computers (PCs). Such systems may rely on monitoring the continuity of the trace circuitry to ensure robust and ongoing data security. In some embodiments, the electronic system 100 may function as a cryptographic security system. Although particular component arrangements and interconnection schemes are depicted in the illustrations 100, 125, multiple variations of those schemes are possible, including the components depicted and described herein. The embodiments may be useful in providing an electronic system with accurate sensing of and timely response to a breach of a boundary. Such sensing and timely response may be particularly useful in preventing and providing warning of unauthorized access to secure data and / or encryption keys stored in the electronic system.

[0026] According to an embodiment, the trace circuit 150 may include one or more conductive serpentine traces that match the signal traces formed on the flexible circuit and may be used to detect boundary discontinuities. For example, a discontinuity in the trace circuit 150 may be caused by an attempt to cut, pierce, or otherwise breach the boundary provided by the cover 128 that encloses the electronic module 126. If such an action occurs, the boundary discontinuity 158 illustrated 150A may be generated. The relatively narrow conductor spacing, e.g., 4 mils, in the serpentine traces 156A, 156B may be particularly useful in generating such boundary discontinuities 158 in response to an attempt to breach / violate the boundary formed by the trace circuit 150. Resistance, e.g., R1, R2, or R3, or a combination thereof, may be sensed by the sense circuit 102 and used as an indication of the continuity of the trace circuit 150.

[0027] In an embodiment, the trace circuit 150 includes a dielectric material 154 located between and in conductive contact with two conductive layers 152A, 152B that act as electrical terminals. According to an embodiment, each of the two conductive layers 152A, 152B may be a planar structure, such as a power plane of a PCB or a flexible circuit. According to an embodiment, the trace circuit 150 may be a portion of one or more flexible circuits that at least partially surround an electronic module 126 in the electronic system 100, 125. Similarly, in some embodiments, the trace circuit 150 may correspond to a portion of a PCB that at least partially surrounds the electronic module 126, and the illustration 100 depicts three trace circuits 150 electrically interconnected in a series configuration.

[0028] In some embodiments, the electronic module 126 may be a cryptographic module and the boundary provided by the trace circuit 150 may be a secure boundary that surrounds the cryptographic module. In such embodiments, the sensing circuit 102 may be configured to detect attempts to breach the secure boundary. According to an embodiment, the placement of the trace circuit 150 attached to or adjacent to an interior surface of the cover 128 may enable it to act as a secure boundary that surrounds or partially surrounds the electronic module 126. Such a secure boundary may be particularly useful for detecting breach attempts from a variety of positions.

[0029] Resistors R1, R2, and R3 of trace circuit 150, along with resistor R, are electrically connected to sense circuit 102, sense net 112, and GND and act as a voltage divider circuit. When interconnected in such a circuit, the continuity of the series connected trace circuit 150 of FIG. 100, represented by the sum of resistors R1, R2, and R3, divides the sense voltage V at sense net 112. S can be determined by measuring with the sensing circuit 102.

[0030] According to an embodiment, the sensing circuit 102 detects an applied voltage V A to the voltage divider circuit. If there is continuity across each trace circuit 150, the sense voltage V sensed at the sense net 112 of the sense circuit 102 is S V A *(R1+R2+R3) / (R+R1+R2+R3). If there is a discontinuity in any of the trace circuits 150, the sensed voltage V S is approximately V A , for example, ≒ V DD The values ​​of R, R1, R2, and R3 are determined by the V S , V resulting from a discontinuity in any of the trace circuits 150 S can be chosen to be significantly different from such a V S The difference in values ​​is sensed by the sensing circuit 102, and the output voltage VO According to an embodiment, the sensing circuit 102 may convert, for example, the voltage V O to a logic signal, i.e., either a logic "0" or "1" value. Such a signal can be used to indicate to the responsive device 120 either intact continuity across all series-connected circuits 150, or a boundary discontinuity, e.g., 158. In some embodiments, the sensing circuit 102 can be configured to continuously sense the continuity of the tracing circuit 150, and in some embodiments, the sensing circuit 102 can be configured to periodically sense the continuity of the tracing circuit 150.

[0031] According to an embodiment, the electronic system 100 may include any number of trace circuits 150 in a series-connected configuration, as depicted, to provide a robust boundary surrounding the electronic module 126 within the cover 128. For example, in some embodiments, the electronic system 100 may include a single trace circuit 150, two trace circuits 150, or three or more trace circuits 150. The sensing circuit 102 is depicted as an exemplary circuit, and other types of sensing circuits 102 are possible. In an embodiment, the functionality of the sensing circuit 102 may be relatively simple to implement as a separate component or within an existing or new IC, such as an application specific integrated circuit (ASIC).

[0032] In some embodiments, the output 104 may be a single analog or digital signal line. In some embodiments, the sensing circuit 102 outputs an output voltage V O For example, the output voltage V O In a corresponding embodiment, the output 104 may include additional components, not shown, configured to convert the signal into another type of signal, such as a high speed serial signal representing V. O The signal may include a conductor configured to transmit a representation of the signal as a high speed serial signal, such as a Universal Serial Bus (USB) signal.

[0033] The reactive device 120 generates an output voltage V O According to an embodiment, the reactive device 120 may include, but is not limited to, a processor circuit, a service processor, an electronics module 126, and a network connected device. In some embodiments, the reactive device 120 may generate an output voltage V that indicates a lack of continuity in the trace circuit 150, such as discontinuity 158 shown at 150A. O In response to a request from the electronics module 126, the electronics module 126 may be configured to initiate an action. According to an embodiment, the action may include sending a message, such as, but not limited to, a text message, a system console message, or a short message service (SMS) message, to alert a system user or technician to a discontinuity in the boundary surrounding the electronics module 126. In some embodiments, the action may also include illuminating an indicator, such as a light emitting diode (LED), sounding an audible alarm, and / or deleting encryption keys within the electronics module 126. One or a combination of the above actions may be useful to protect the security of data and / or encryption keys maintained within the electronics module 126.

[0034] According to an embodiment, the electronic system (side cross-sectional view) 125 may be useful in providing a visual understanding of the interconnections and arrangement of components within the electronic system 100, 125. The functions, electrical characteristics, and interconnections of the electronic system 125 are consistent with those described above with reference to the electronic system 100. The illustration 125 may be particularly useful in depicting the structural, layout, and electrical interconnection relationships between the electronic module 126, the cover 128, the trace circuit 150, the connector 136, the PCB 138, and the reaction device 120.

[0035] According to an embodiment, the electronic module 126 may be configured to store and / or process electronically stored data that is sensitive or secure. The electronic module 126 may include ICs 130, such as processors, memory devices, ASICs, and cryptographic chips, mounted on and electrically interconnected with a PCB 134. The sensing circuit 102 may be powered by a battery, e.g., 132, which may provide for continuous detection of discontinuities, e.g., 158, of the boundaries of the trace circuit 150 when the electronic module 126 is disconnected from the electronic system power source. The connector 136 provides electrical interconnection between the electronic module 126 and other components and / or devices within the electronic system 125, e.g., interconnecting the output 104 from the sensing circuit 102 to a reactive device 120 mounted on the PCB 138. According to an embodiment, the PCB 138 may be an integral part of a computer, supercomputer, server, PC, or other electronic system. In some embodiments, the electronic module 126 may be a cryptographic module.

[0036] The electronic module 126 can be surrounded by a cover 128, which can be designed to prevent visual inspection and physical access to the electronic module 126. According to an embodiment, the trace circuit 150 can be attached to an inner surface of the cover 128, for example, using an adhesive or other bonding agent or technique. In an embodiment, the dielectric layer, for example 154, can be selected by a designer based on material characterization data to comply with the design requirements of the electronic system. Such requirements can include, for example, maximum dielectric leakage specifications. The use of a dielectric layer, for example 154, having controlled and / or reduced leakage characteristics can be particularly useful in reducing the power consumption of the electronic system 100, thereby increasing and extending the life of the battery 132 used to power the electronic system 100.

[0037] The use of the trace circuit 150 can help provide cost-effective detection of unauthorized physical access to sensitive data and / or encryption keys stored in the electronic module 126. The trace circuit 150 can also be particularly useful in managing and reducing leakage between the conductive layers 152A and 152B, which can result in a managed and improved operating life of the battery 132. Exemplary dielectric material types that can be used in the dielectric layer 154 of the trace circuit 150 can include, but are not limited to, FR, HT, and AP laminate material layers. According to an embodiment, the conductive layers 152A and 152B of the trace circuit 150 can include serpentine traces 156A, 156B, respectively, that act as a boundary surrounding the electronic module 126. Depending on the PCB design and material set, the conductive layers 152A and 152B can include copper or other types of metals or both.

[0038] According to embodiments, the serpentine traces can have various patterns, as depicted at 156A, 156B in illustration 150A. The trace circuit 150 can include one or more conductive layers, e.g., 152A, 152B. In some embodiments, the conductive layers, e.g., 152A, 152B, are electrically insulated from one another by a dielectric layer, e.g., 154. In embodiments, the trace circuit 150 includes a dielectric layer 154 located adjacent to, i.e., between, both conductive layers 152A and 152B. The trace circuit 150 can include a single conductive layer, e.g., 152A, and in some embodiments, the trace circuit 150 can include two or more conductive layers, e.g., 152A and 152B, as depicted. In embodiments, various types of adhesives and / or bonding agents can be used to bond the trace circuit 150 to the inner surface of the cover 128. Although reference numeral 138 is depicted as a flexible circuit in illustration 150, in some embodiments, 138 can alternatively represent a PCB. In some embodiments, the flexible circuits or PCBs may be electrically interconnected by soldering to form a boundary that encloses multiple sides of the electronic module 126, for example the top, bottom, and sides.

[0039] 1 and the components depicted therein do not necessarily represent the actual size of the components or subcomponents used individually or collectively in the embodiments. They are not necessarily a representation of the actual size or relative size of any device, component, or subcomponent. Rather, they are intended to depict how each subcomponent of an electronic system may be arranged relative to other subcomponents in accordance with embodiments of the present invention.

[0040] FIG. 2 is a flow diagram illustrating a method 200 for designing the electronic system 100, 125 of FIG. 1 for managed battery life and electronic data security, according to an embodiment consistent with the figure. Implementation of the method 200 may be useful for designing an electronic system that can provide reliable, cost-effective, and energy-efficient data security monitoring and corrective action response for use in electronic systems such as computers and servers. With respect to a functioning electronic system, the method 200 may provide improved energy efficiency and battery operating life of the electronic system. In some embodiments, the electronic system 100 may be a cryptographic security system.

[0041] The method 200 proceeds from start 202 to operation 204. Operation 204 generally refers to receiving design requirements for the electronic system 100, 125 of FIG. 1 for managed battery life and electronic data security. According to an embodiment, the design requirements may include, for example, specified leakage characteristics of the trace circuit 150 of FIG. 1 over a range of electronic system operating temperatures and a specified impedance range across the conductive layers, e.g., 152A, 152B, of the trace circuit 150 of FIG. 1. Other design requirements may include, for example, specified maximum voltage drop, energy dissipation, and RC time constant (τ) across the conductive layers of the trace circuit 150. The design requirements may also include a minimum operating life of a battery, e.g., 132 of FIG. 1, configured to power the electronic system 100 of FIG. 1. In some embodiments, the minimum operating life of the battery may be specified by a published cryptographic security specification, such as the U.S. government Federal Information Processing Standard (FIPS) 140-2 Security Requirements for Cryptographic Modules.

[0042] According to an embodiment, each of these requirements may need to be satisfied to satisfy the overall design requirements of the electronic system. In some embodiments, the design requirements may be received by a circuit designer or an electronic design automation (EDA) system from a specification document or file. Such a document or file may have the form of, for example, a printed copy or an electronic file. The electronic file may have a variety of formats, such as a word processing document, a text file, a spreadsheet file, or a proprietary or non-proprietary specification file.

[0043] It can be appreciated that various electronic systems may have different design requirements. For example, one type of electronic system, such as electronic module 126 of FIG. 1, may be portable and / or at least partially dependent on battery power and require a relatively small maximum dielectric leakage. In some embodiments, electronic module 126 may be a cryptographic module. In contrast, another type of electronic system may not be dependent on battery power at all and may have a trace circuit 150 that is specified to be more compatible with a particular sensing circuit 102 design and may have a larger specified leakage current. Once the design requirements are received, method 200 proceeds to operation 206.

[0044] Optional operation 206 generally refers to characterizing candidate dielectric and adhesive dielectric materials for use in the electronic system 100, 125 of FIG. 1. Such dielectric materials may include, for example, thin sheets of dielectric material having metal cladding, such as copper, on one or both sides of the dielectric, and various adhesive dielectric materials. According to an embodiment, the candidate dielectric and adhesive materials may be characterized to provide PCB and circuit designers with parameters useful in making design decisions and tradeoffs. For example, the dielectric materials may be exposed to various frequencies applied to a conductive plate on a planar surface of the material, and the resulting losses may be recorded. FIG. 3 is an exemplary graph including plots of measured losses versus frequency for two dielectric materials, FR and HT. According to an embodiment, characterizing the candidate dielectric and adhesive materials may include characterizing the electrical leakage properties of the candidate dielectric and adhesive materials, including electrical leakage variations depending on temperature. In an embodiment, the candidate dielectric and adhesive materials may include, but are not limited to, FR, HT, and AP materials.

[0045] The above characterization may be performed, for example, by a vendor or supplier of the dielectric material, by a circuit or PCB designer, or by an independent test laboratory. Such characterization may be performed at one or more temperatures of interest, such as a maximum expected operating temperature, or over the operating temperature range of the electronic system. Once the candidate dielectric and adhesive materials have been characterized, method 200 proceeds to operation 208.

[0046] Operation 208 generally refers to selecting characterized dielectric and adhesive materials according to the design requirements received in operation 204. According to an embodiment, the dielectric and adhesive materials are selected by the designer from several characterized dielectric and adhesive materials, e.g., FR, HT, and AP dielectric materials. In some embodiments, the dielectric and auxiliary dielectric materials may be combined to take advantage of electrical and / or physical properties of both. The one or more dielectric materials may be selected based on various properties of the individual materials and the properties of the materials to be combined accordingly. The properties may include, for example, temperature dependent leakage and loss characteristics, dielectric constant, and adhesive properties. According to an embodiment, the selection of the dielectric material according to the design requirements may include selecting a dielectric material having a characterized electrical leakage that is less than a specified electrical leakage value. In some embodiments, the dielectric material may be selected based on a characterized electrical leakage that varies less than a specified amount over an operating temperature range. The selection of the dielectric material may be performed in conjunction with an analysis of output from an EDA program, such as a field solver or other electrical simulation program.

[0047] In some embodiments, the inherently long serpentine traces, e.g., 156A of FIG. 1, may result in a relatively large RC time constant (τ) for the trace circuit 150 of FIG. 1. A large value of τ may result in excessive settling time for the sensing circuit 102 of FIG. 1, draining energy from a battery, e.g., 132 of FIG. 1. Current leakage across the dielectric layer 154 of FIG. 1 may also act to increase τ.

[0048] According to an embodiment, selecting characterized dielectric and adhesive materials with reduced leakage according to the design requirements received in operation 204 may be particularly useful for reducing dielectric current leakage, and therefore τ. Reducing the value of τ may improve the response time of the sensing circuit 102 of FIG. 1 and the energy consumption from the battery 132 of FIG. 1. According to an embodiment, such reduction in dielectric leakage may span the range of operating temperatures of the electronic system. In an embodiment, selecting a characterized dielectric may include, for example, selecting a HT dielectric material over a FR dielectric material. Other selections may be made within the scope of the invention.

[0049] In some embodiments, by way of example, selection of characterized dielectric and adhesive materials with lower dielectric leakage can result in a reduction in τ of approximately 50%. The reduced leakage can result in a 5-fold reduction in trace circuit resistance, resulting in an overall power savings that can improve battery operating life by approximately 10%. Depending on the application, such improved operating life can result in an additional 6-9 months of battery-powered operation.

[0050] In addition to the benefit of reduced power consumption, reducing leakage current through dielectric material selection also allows detection of much higher trace resistances, thus allowing the trace circuit to be probed with commonly used or available voltmeters or oscilloscopes with input impedances in the range of 1 MΩ to 10 MΩ. According to an embodiment, the sensing circuit 102 may not be required to have hysteresis input characteristics, thereby further reducing sensing circuit complexity and power consumption.

[0051] Selecting a dielectric material based on the characterized electrical leakage can be particularly useful for managing electrical leakage from a serpentine trace, e.g., 156A of FIG. 1, to another serpentine trace, e.g., 156B of FIG. 1, or to another layer, such as a power or ground distribution layer. This managed electrical leakage can result in an improved operational life of a battery, e.g., battery 132 of FIG. 1, configured to power an electronic module, e.g., 126 of FIG. 1. Once the characterized dielectric and adhesive materials have been selected, method 200 proceeds to operation 210.

[0052] Operation 210 generally refers to designing a trace circuit to include the characterized dielectric and adhesive materials selected in operation 208. According to an embodiment, designing the trace circuit may include selecting a volume / amount of characterized dielectric material that meets a particular plane pair, dielectric leakage design requirement within a PCB or flex circuit design. The characterized dielectric material may include a combination of a dielectric material and a supplemental dielectric material. In some embodiments, more than one plane pair may be used, and in some embodiments, an EDA program such as a field solver or other type of electrical simulation program may be used in the design process. Once the trace circuit is designed, the method 200 proceeds to operation 212.

[0053] Operation 212 generally refers to fabricating a trace circuit according to the trace circuit design completed in operation 210. According to an embodiment, the trace circuit 150 of FIG. 1 may be fabricated according to the design of operation 210. In some embodiments, the trace circuit 150 of FIG. 1 may then be bonded to other PCB and / or flexible circuit layers. The various lamination, etching, drilling, and other process steps used in operation 212 are generally consistent with existing PCB and / or flexible circuit manufacturing and assembly processes. Once the trace circuit is fabricated, method 200 proceeds to operation 214.

[0054] Operation 214 generally refers to incorporating a trace circuit, e.g., 150 of FIG. 1, into the electronic system 100, 125 of FIG. 1. According to an embodiment, incorporating may include disposing and attaching one or more trace circuits 150 to an inner surface of the cover 128 to enclose and surround the electronic module 126 with a boundary. In some embodiments, the boundary is a secure boundary that encloses a cryptographic module, and the sensing circuit 102 is configured to detect attempts to breach the secure boundary. Various types of adhesives and / or bonding techniques may be used in the attachment process. According to an embodiment, incorporating may also include electrically interconnecting one or more trace circuits 150 in series, as represented by resistors R1, R2, and R3 of FIG. 1. Incorporating may also include electrically interconnecting the trace circuit 150 to the sensing circuit 102, for example, through solder connections to conductors in the connector 136 and the PCB 134. Once the trace circuitry has been incorporated into the electronic system, the method 200 may end at operation 216 .

[0055] 3 is a graph depicting dielectric leakage measurements as a function of frequency for two dielectric materials according to an embodiment consistent with the figure. Such dielectric materials may be used in layers such as dielectric layer 154 of FIG. 1 and included in trace circuit 150. Characterization may include a wide range of such dielectric materials, including but not limited to FR, HT, and AP dielectric layers. Characterization and measurement of properties such as dielectric leakage may provide PCB designers with valuable insight regarding which dielectric material or combination of dielectric materials to select for a particular application.

[0056] The data plot provided in FIG. 3 can provide a visual understanding of the causal relationship between measurement frequency and dielectric leakage, as well as the relative difference in leakage between various types of dielectric materials. The vertical axis of FIG. 3 corresponds to the leakage of FR and HT type dielectric materials measured in dB, with higher values ​​or positions on the vertical axis corresponding to higher leakage values. The horizontal axis at the bottom of FIG. 3 corresponds to the frequency (kHz) at which the leakage measurements were taken. As an example, the vertical axis range can range from a low of approximately -92dB to a high of -70db. Similarly, the horizontal axis range can range from approximately 0kHz to 1.0kHz. The leakage measurements can be taken at various temperatures, such as 25°C, 85°C, or 100°C.

[0057] It can be seen that the FR dielectric curve 302 and the HT dielectric curve 304 have clearly different leakage. For example, at the maximum measured frequency, the leakage difference shown between the FR dielectric curve 302 and the HT dielectric curve 304 (right side of FIG. 3) is approximately 13 dB, which corresponds to a 20-fold difference in power loss between the FR and HT dielectric materials. Measurements on other dielectric material types may yield other relative results. Characterization of dielectric material properties such as leakage as presented in FIG. 3 may be particularly useful to provide an understanding of the electrical properties of various dielectric material types that may be used in selecting among dielectric material types for inclusion in the design of the trace circuit 150.

[0058] FIG. 4 illustrates a graph of a sensed voltage, e.g., V of trace circuit 150 of FIG. 1, according to an embodiment consistent with the diagram. S1 is a graph including two illustrations 400 and 450 depicting the variation of , over a temperature range. The variation of the sense voltage may result from the variation of leakage of a dielectric material that may be included in the trace circuit 150, such as the dielectric layer 154 of FIG. 1, over a temperature range. Such materials may include, but are not limited to, FR, HT, and AP dielectric layers. Characterization of dielectric materials may provide PCB designers with valuable insight and understanding regarding the dielectric material or combination of dielectric materials to select for a particular trace circuit application. Selecting a dielectric material with minimal leakage may be particularly useful for managing and / or minimizing electrical leakage and improving the battery life of an electronic module, such as 126 of FIG. 1.

[0059] The data plot provided in Figure 4 shows the relationship between the measured temperature and the sensed voltage V S The causal relationship between the sense voltage V and the sense voltage V S The vertical axis of FIG. 4, representing temperature curve 402, corresponds to the measured temperature of the FR and HT type dielectric materials measured in units of °C, with higher values ​​or locations on the vertical axis corresponding to higher measured temperatures. The vertical axis of FIG. 4, representing voltage curves 404A and 404B, corresponds to the V of the FR and HT type dielectric materials measured in units of volts, measured over the temperature range of temperature curve 402. S A higher value or position on the vertical axis corresponds to a higher V S Voltage curve 404B corresponds to a measured sensed voltage, e.g., V S , whose dielectric leakage is nearly independent of the operating temperature. The horizontal axis at the bottom of FIG. 4 corresponds to the time at which the sense voltage measurements are taken. As an example, the temperature curve 402, i.e., T MIN -T MAX The vertical axis represents T, which is approximately -15°C. MIN T, which is approximately 75°C MAX It may extend to.

[0060] The FR dielectric curve 402 and the HT dielectric curve 404 exhibit distinctly different sensed voltages V, corresponding to different leakage depending on temperature. S It can be observed that the sensed voltage V S Characterization of dielectric materials through measurements of can be particularly useful for providing an understanding of the electrical properties of various dielectric material types that can be used when selecting from among the dielectric material types to include in the design of the trace circuit 150.

[0061] Figure 5 is a flow diagram illustrating a method 500 for operating the electronic system 100, 125 of Figure 1 for managed battery life and electronic data security of the electronic module 126 of Figure 1, according to an embodiment consistent with the figure. Performance of the method 500 can be useful for providing robust data security to the electronic system and data held within such system, while improving the effective operating life of the battery 132 of Figure 1 that powers the electronic system.

[0062] The method 500 proceeds from a start 502 to an operation 504. Operation 504 generally includes using the sensing circuit 102 to detect a voltage V A According to an embodiment, the trace circuit 150 of FIG. 1 may be configured to provide a boundary surrounding the electronic module 126 and may include several series-connected trace circuits, such as those represented by resistors R1, R2, and R3 of FIG. 1. Such trace circuits may be located adjacent to the top, bottom, or sides, or combinations, of the cover 128, for example. In some embodiments, the electronic module 126 may include a portion of the electronic system 100, 125 that is a cryptographic security system that includes a cryptographic module. The cryptographic module may include, but is not limited to, a cryptographic coprocessor, a cryptographic accelerator, a cryptographic adapter card, a cryptographic field programmable gate array (FPGA), and a memory that stores cryptographic accelerator data.

[0063] In some embodiments, the trace circuit 150 may be fabricated as a flexible circuit, and in some embodiments, the trace circuit 150 may be fabricated as a PCB. In an embodiment, the voltage V applied using the sensing circuit 102 of FIG. A For example, V DD , or another voltage selected by the circuit designer. In some embodiments, operation 504 may also include heating the trace circuit 150 to a known "reference" temperature. Such heating may be useful for detecting small temperature variations or to "normalize" the temperature of the trace circuit 150 for compatibility with the sense circuit 102. A Once is applied to the trace circuit, the method 500 proceeds to operation 506.

[0064] Operation 506 generally includes measuring a sensed voltage V across one or more trace circuits 150 of FIG. S 1 using the sense circuit 102 of FIG. According to an embodiment, if each trace circuit 150 has continuity, i.e., continuity across resistors R1, R2, and R3, then the corresponding sense voltage V S exists in the sense net 112, indicating continuity. For example, if the values ​​of resistors R1, R2, and R3 are each relatively small compared to the value of resistor R, then the corresponding sense voltage V S The value of will be approximately 0V.

[0065] If at least one trace circuit 150, e.g., resistor R1, R2, or R3, has a discontinuity, e.g., 158 in FIG. 1, a corresponding sensed voltage V S , for example, ≒ V A is present in the sense net 112. According to an embodiment, the discontinuity may be understood to represent an attempt to breach the secure boundary formed around the electronic module 126 of FIG. 1 by the trace circuit 150 of FIG. 1. The sense voltage V S Once measured, the method 500 proceeds to operation 508 .

[0066] Operation 508 generally involves using the sense circuit 102 to detect a sense voltage V S According to an embodiment, the sensed voltage V S serves as an indicator of a discontinuity in the boundary of one or more serpentine traces, e.g., 156A in FIG. 1. A boundary discontinuity, e.g., 158 in FIG. 1, may result from an unauthorized attempt to tamper with the cover 128 enclosing the electronic module 126. According to an embodiment, the sensing circuit 102 may be a comparator, an operational amplifier (opamp), or other type of comparator and / or amplifier circuit that may be implemented using separate components or integrated within an IC, such as an ASIC.

[0067] According to an embodiment, the sensing circuit 102 detects a sense voltage V S can be configured to compare V to a threshold, the threshold corresponding to continuity through the trace circuit 150. S V corresponding to a discontinuity in at least one trace circuit 150 S For example, in some embodiments, such a threshold voltage serves to distinguish between V A Following this example, the measured V S indicates continuity across the trace circuit 150 of FIG. 1, while a measured V S indicates a discontinuity across at least one of the trace circuits 150 of Figure 1. In some embodiments, the threshold voltage may be another value that depends on the values ​​of resistors R, R1, R2, and R3. Once the output voltage is compared to the voltage threshold, method 500 proceeds to operation 510.

[0068] At operation 510, the sense voltage V received by the sense circuit 102 on the sense net 112 is S A determination is made by the sense circuit 102 of FIG. 1 as to whether V indicates a discontinuity by exceeding a voltage threshold as described above. According to an embodiment, for example, V S If V is less than the voltage threshold, it may be determined that there is no discontinuity in any of the trace circuits 150. SIf V is greater than the voltage threshold, it may be determined that there is a discontinuity in at least one of the trace circuits 150. According to an embodiment, the sense circuit 102 outputs the output voltage V with a logic "0" or logic "1" value corresponding to the sensed continuity or discontinuity of the trace circuit 150. O In some embodiments, the sensing circuit 102 may be configured to drive an output voltage V O A sense voltage V is used to drive S The sense voltage V received at the sense net 112 of FIG. S If V does not indicate a discontinuity, the method 500 returns to operation 504. S If indicates a discontinuity, the method 500 proceeds to operation 512.

[0069] Operation 512 generally refers to initiating an action using the reactive device 120 of FIG. 1 in response to an indication of a discontinuity in at least one trace circuit 150. According to an embodiment, the reactive device 120 may be, for example, a processor circuit, a service processor, a network-connected device, an electronic module, such as 126 of FIG. 1, or other electronic device. The reactive device 120 may generate an output voltage V from an output 104. O Received, V O For example, the sensing circuit 102 of FIG. 1 may include circuitry / functionality for initiating one or more response actions in response to the output voltage V O , for example V DDto the reactive device 120, which indicates a discontinuity in at least one trace circuit 150. According to an embodiment, in response to receiving such a signal, the reactive device 120 may perform an action or communicate with another device, such as a computer, processor, IC, or other networked or electrically interconnected device, to initiate an action. For example, the reactive device 120 may send a message, issue an alert, or initiate an action, such as deleting an encryption key in the electronic module 126. According to an embodiment, the message sent may include, but is not limited to, an email notification, an SMS notification, or a system console message. The alert may include a visual or audible alert, such as illuminating an indicator, such as an LED or light, or activating a buzzer, horn, siren, or the like. Other types of indications of the boundary discontinuity 158 of FIG. 1 are possible within the scope of the present invention.

[0070] Some embodiments of the present invention may enable detection of and reaction to unauthorized testing attempts of a cryptographic module or device. Embodiments of the present invention may provide indications of attempts to physically penetrate a secure or cryptographic circuit without permanently and / or negatively affecting the functionality of the device or circuit in which it is deployed. Once action has been initiated, method 500 returns to operation 504.

[0071] The description of various embodiments of the present invention has been presented for illustrative purposes, but is not intended to be exhaustive or limited to the disclosed embodiments. Many changes and modifications will be apparent to those skilled in the art without departing from the scope of the described embodiments. The terminology used in this specification has been selected to best explain the principles of the embodiments, practical applications, or technical improvements to the technology found in the market, or to enable those skilled in the art to understand the embodiments disclosed herein.

[0072] In a preferred embodiment of the present invention, a method is provided for designing an electronic system for managed battery life and managed electronic data security for an electronic module, the method comprising receiving design requirements for the electronic system, characterizing dielectric materials that are candidates for use within the electronic system, selecting a dielectric material from the candidate dielectric materials according to the design requirements, designing a trace circuit to include the selected dielectric material, fabricating the trace circuit according to the trace circuit design, and incorporating the trace circuit into the electronic system by surrounding the electronic module with the trace circuit to provide a boundary surrounding the electronic module and electrically interconnecting the trace circuit to a sensing circuit. Preferably, the electronic system is a cryptographic security system, the electronic module is a cryptographic module, the boundary is a secure boundary surrounding the cryptographic module, and the sensing circuit is configured to detect attempts to breach the secure boundary, and the electronic system design requirements include a minimum operational life of a battery configured to power the electronic system. The minimum operational life of the battery configured to power the electronic system is preferably specified by a published cryptographic security specification. Characterizing the candidate dielectric material preferably includes characterizing the electrical leakage of the candidate dielectric material, including temperature dependent electrical leakage variation. The candidate dielectric material preferably includes a material selected from the group consisting of bonded dielectric materials and coated dielectric material sheets. The method preferably further includes selecting a supplemental dielectric material according to design requirements, and designing the trace circuit includes a dielectric material and a supplemental dielectric material. Selecting a dielectric material according to design requirements preferably includes selecting a dielectric material having a characterized electrical leakage that is less than a specified electrical leakage value, and a characterized electrical leakage that varies less than a specified amount over an operating temperature range. Designing the trace circuit preferably includes specifying an amount of dielectric material and an amount of supplemental dielectric material that results in leakage of the trace circuit less than a leakage threshold value.

Claims

1. 1. An electronic system comprising: An electronic module; a trace circuit providing a boundary surrounding the electronic module; a sensing circuit configured to detect a discontinuity in the boundary and initiate an action from the reaction device in response to the detection; Equipped with the trace circuit includes a first conductive serpentine trace and a second conductive serpentine trace electrically isolated from the first conductive serpentine trace by a dielectric layer; the dielectric layer is composed of a dielectric material having a characterized electrical leakage less than a predetermined electrical leakage value and varying less than a predetermined amount over an operating temperature range; Electronic system.

2. 2. The electronic system of claim 1, wherein the dielectric material is selected from the group consisting of FR (flame retardant fiberglass epoxy laminate), AP (adhesive-free / high performance laminate), and HT (high temperature laminate).

3. the electronic system is a cryptographic security system; the electronic module is a cryptographic module; the perimeter being a secure perimeter surrounding the cryptographic module; 3. The electronic system of claim 1, wherein the sensing circuitry is configured to detect an attempt to breach the secure perimeter.

4. 4. The electronic system of claim 1, wherein the action of notifying the boundary discontinuity is selected from the group consisting of deleting an encryption key in the electronic module, sending an email notification, sending a Short Message Service (SMS) notification, lighting an indicator, and sounding an audible alert.

5. 5. The electronic system of claim 1, wherein the sensing circuitry is configured to detect the discontinuity at the boundary by detecting a resistance of the trace circuit indicative of the discontinuity at the boundary.

6. 6. The electronic system of claim 1, wherein the reaction device is selected from the group consisting of a processor circuit, a service processor, the electronic module, and a network-connected device.

7. 1. A method for operating an electronic system for managed battery life and managed electronic data security of an electronic module, comprising: applying a voltage with a sensing circuit to a trace circuit configured to provide a boundary surrounding an electronic module, the trace circuit including a first conductive serpentine trace and a second conductive serpentine trace electrically insulated from the first conductive serpentine trace by a dielectric layer, the dielectric layer being constructed from a dielectric material having a characterized electrical leakage that is less than a specified electrical leakage value and that varies less than a predetermined amount over an operating temperature range; measuring a sense voltage on the trace circuit with the sense circuit; comparing the sensed voltage to a voltage threshold to detect a discontinuity in the boundary; initiating an action using a responsive device electrically interconnected with the sensing circuit in response to the sensed voltage indicating the discontinuity at the boundary; The method includes:

8. 8. The method of claim 7, wherein the dielectric material is selected from the group consisting of FR (fire retardant fiberglass epoxy laminate), AP (adhesive-free / high performance laminate), and HT (high temperature laminate).

9. the electronic system is a cryptographic security system; the electronic module is a cryptographic module; the reaction device is selected from the group consisting of the electronic module, a processor circuit, a network-connected device, and a service processor; the perimeter being a secure perimeter surrounding the cryptographic module; 9. The method of claim 7 or 8, wherein the sensing circuitry is configured to detect attempts to breach the secure boundary surrounding the cryptographic module.

10. 10. The method of claim 7, wherein the responsive device initiates the action selected from the group consisting of deleting an encryption key in the electronic module, sending an email notification, sending a Short Message Service (SMS) notification, lighting an indicator, and sounding an audible alarm.

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