Abstract:
Tools and methods for creating isolated or localized temperature changes on components in an electric circuit. By isolating temperature changes to individual components or small sets of components, the tools and methods allow greater control over the analysis of interactions within a board. This may allow clearer understanding of the effects of temperature on circuit component behavior. The tools and analysis advances analysis such as failure analysis and design testing.

Description:
FIELD 
       [0001]    The present invention is related to the field of electronics. More particularly, the present invention relates to the analysis of component behavior including temperature effects. 
       BACKGROUND 
       [0002]    In the field of electronics it is well known that component characteristics can vary with temperature. When investigating the behavior of an electrical circuit, the interaction of temperature-related variability of components can become very complex. For example, a circuit that functions predictably at one temperature may become unpredictable at a different temperature. 
         [0003]    Referring to the example circuit  10  of  FIG. 1 , various components of different types are included in the circuit  10 , such as components shown at  12 ,  14 ,  16 ,  18  and  20 . The behavior of any individual component at a first temperature may change at a second temperature. When investigating function, and particularly, failure, of a circuit such as that shown at  10 , changes to one component  12  may be opposite of changes of another component  14 , creating complex interactions. If the circuit  10  is not operating as expected, the complexity of temperature interactions in the circuit  10  may quickly render analysis quite difficult in the face of an unknown failure mode. 
         [0004]    A typical manner of observing temperature effects on circuit operation is shown by  FIG. 2 . An oven  30  is used to control the temperature on circuit board  32 . The circuit board  32  is placed in a chamber  34  having a controlled environment. Typical controls include dwell time  36  and temperature  38 , as well as humidity (not shown). Probes may be placed on the circuit board  32  to observe voltages on traces or across components. Because the entire circuit board  32  is subjected to a single environmental condition, however, the complex interaction of parts and their changes in response to temperature is not fully observable. 
         [0005]    Improved and alternative devices and methods for manipulating temperature control in circuit analysis are desired. 
       SUMMARY  
       [0006]    The present invention provides tools and methods for creating isolated or localized temperature changes on components in an electric circuit. By isolating temperature changes to individual components or small sets of components, the tools and methods allow greater control over the analysis of interactions within a board. This may allow clearer understanding of the effects of temperature, advancing such analysis as failure analysis and design testing. Additional embodiments may include cooling or heating an entire circuit, circuit board or substrate and then creating isolated or localized temperature changes to further analysis. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a drawing of a circuit board; 
           [0008]      FIG. 2  illustrates a prior art manner of observing temperature effects on circuit operation; 
           [0009]      FIGS. 3A-3B  show details of a passive component temperature manipulation tool; 
           [0010]      FIG. 4  shows use of the tool of  FIGS. 3A-3B ; 
           [0011]      FIG. 5  illustrates another component temperature manipulation tool; 
           [0012]      FIG. 6  shows use of the tool of  FIG. 5 ; and 
           [0013]      FIG. 7  shows another example of a tool in accordance with another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    The following detailed description should be read with reference to the drawings. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. Some of the following examples and explanations include references to issued patents and pending patent applications. These references are for illustrative purposes and are not intended to limit the present invention to the particular methods or structures from the referenced patents and patent applications. 
         [0015]      FIG. 1  is a drawing of a circuit board. Circuit boards are widely known for use in electronics of all sorts. The typical circuit board comprises a substrate having a plurality of components  12 ,  14 ,  16 ,  18 ,  20  thereon, with traces (electrically conductive lines) connecting the components.  FIG. 2  illustrates a prior art manner of observing temperature effects on circuit operation. Often it is the case that a circuit board is expected to operate at some predetermined temperature range. For example, implantable medical devices spend much of their operational lives in a body-temperature (approximately 37 degrees C.) environment. Additional variables such as humidity, pressure and cleanliness may also be controlled. Testing is sometimes performed in an oven  30 . The circuit board  32  is placed in a chamber  34  for a predetermined duration  36  at a given temperature  38 . The complex shortcomings of this approach for analyzing function and/or failure are introduced in the Background section, above. 
         [0016]      FIGS. 3A-3B  show details of a passive component temperature manipulation tool. As shown in  FIG. 3A , the tool  60  comprises a body section  62  sized for ready grasping, and two ends  64 ,  66 . The ends  64 ,  66  each include an extension, with the extension at end  64  being larger in diameter and the extension at  66  being smaller in diameter. As highlighted by  FIG. 3B , the central portion of the tool  60  includes a larger diameter section  68  with the two extensions  64 ,  66 . The material of the portion shown in  FIG. 3B  may be, for example, brass, or other copper based alloy having high thermal conductivity. Other materials may be used instead. In one working example, the ends  64 ,  66  were formed by removing material from the ends of a brass bar. The ends  64 ,  66  may be coated with an electrically isolative layer such as an epoxy coating. Other heat-transferring dielectrics may be used at ends  64 ,  66 ; in one illustration a diamond tip can be provided for high thermal transfer and strong dielectric characteristics. 
         [0017]    Referring again to  FIG. 3A , the body section  62  may be covered with a thermal and electrical isolator, such as a layer of rubber, leather or plastic. This protects a user from heat and/or electricity that may pass through the tool  60 . In one example a layer of Kapton® was used to isolate much of the tool  60 . In use, the entire tool  60  is placed in an oven or on a hot plate prior to use. After a period of time, typically thirty (30) seconds up to five (5) minutes, allowing it to be warmed, the tool  60  can be used as shown in  FIG. 4 . 
         [0018]      FIG. 4  shows use of the tool of  FIGS. 3A-3B . A circuit board  80  is shown with a number of components  84 ,  86 ,  88 . The tool  82 , having previously been heated, is placed in contact with one of the components  84 . A probe  90  is coupled to traces, components or pins on the circuit board  80  to allow observation of, for example, the voltage across a component on the circuit board  80 . Other suitable ways to use the probe  90  may include cutting a trace and bridging the open trace with the probe  90 , or removing a component on the circuit board  80 , for example, to analyze current flow and/or to monitor the circuit&#39;s response to selected conditions. 
         [0019]    As the tool  82  transfers heat energy to the component  84 , characteristics of the component  84  may change. For example, the circuit design may call for component  84  to operate in a narrow range of parameters (resistance, capacitance, etc.) across a temperature variation such that by heating the component  84  in isolation of the rest of the circuit board  80 , the analysis can show that the specific component  84  is or is not meeting its design requirements. The method may include iterative testing of individual components. For example, after observing any changes in operational characteristics of the circuit board  80  while component  84  is at an elevated temperature, the tool  82  is moved (and re-heated, if necessary) to components  86  and  88  to allow further testing. 
         [0020]    In some embodiments the tool  82  is heated to any suitable temperature. For example, the probe  82  may be heated to one-hundred (100) degrees C. In other embodiments, the circuit board  80  is designed for use in special applications such as medical implants, and the tool  82  is heated accordingly, for example to a range near that of body temperature. Thus, with body temperature typically at about thirty-seven (37) degrees C., the tool  82  may be heated in the range of thirty-five to forty-five (35-45) degrees C. 
         [0021]    In some embodiments, the circuit board  80  may be placed in a temperature controlled space for cooling or heating to a desired temperature, and the tool  82  can then be used to create localized temperature changes on individual components. For example, the board  80  could be heated to body temperature or operational temperature, and a component on the board  80  would then be heated or cooled using the tool  82 . In another example, the board  80  could be cooled to a desired temperature to test particular conditions (transport or extreme weather, for example) while heating one or more components with the tool  82 . 
         [0022]    The use of tool  82  may avoid problems with hot-air guns, which can disturb cleanliness and may not provide predictable or immediate behavior since air is an indirect heat transfer mechanism. Likewise, infrared light tools could be used to warm individual components, but these bring their own problems, for example, if components are light-sensitive. Further, infrared light tools can be difficult to use in some environments. The direct contact mechanism shown in  FIG. 4  provides easy control over which component is heated. 
         [0023]    In an alternative embodiment, the entire board  80  is heated, and the tool  82  is cooled, and the reverse process noted above is used. Other combinations of heating or cooling the entire board  80  while using the probe for cooling or heating as noted above may be used as well. Again, variation in response of components  84 ,  86 ,  88  can be measured by repeatedly cooling different parts of the circuit while monitoring circuit operation. 
         [0024]    If desired, more than one tool  82  may be used to allow multiple isolated components to be heated/cooled. 
         [0025]      FIG. 5  illustrates another component temperature manipulation tool. The tool  100  includes a handle  102  having an actuator  104 . The actuator  104  is shown as a button and may be, for example, an on-off switch. Alternatively, a slider or knob having on/off settings and/or multiple settings (Off, Low, High) may be used as actuator  104 . The actuator  104  may allow a specific temperature to be selected as well. A continuously variable control, such as a continuous knob or slider, can also be used. Other designs and locations for the actuator  104  may be used. 
         [0026]    The handle  100  is attached to an elongate probe section  110  that terminates in a probe tip  112 . The detail view in  FIG. 5  shows that at the probe tip  112  a heating element  114  and a thermocouple  116  are provided. The heating element  114  is shown as a resistive heating element; any other suitable component may be used in place of the resistor shown, such as an inductive heating element. Rather than a thermocouple  116 , any suitable heat-sensing component may be used. In one example, a thermister is used, combining the functionality of both the heating element  114  and thermocouple  116 . The combination of heating element and temperature sensor (thermocouple  116  is an example) provides closed loop control over the system. A thermal insulator may be used to insulate the rest of the elongate probe section  110  from the probe tip  112 , enhancing temperature control and isolation. In one example, a Kapton® insulator may be used to isolate elongate probe section  110  from probe tip  112 . An epoxy or other dielectric coating may be used over the probe tip  112 . These features may be optionally included in any embodiment of the present invention. 
         [0027]    A power supply  106  and temperature control circuit  108  are used to control the temperature of the probe tip  112  by coupling with the heating element  114  and thermocouple  116 . Temperature control may be effected, for example, using a system as simple as a comparator and reference voltage or potentiometer, with the output from the thermocouple fed (possibly through amplification circuitry) to one input to the comparator and a reference voltage being determined using the actuator  104 . More complex systems of temperature control are well known, using for example simple controllers. 
         [0028]    An analog or digital temperature readout may be provided on the tool  100 , if desired. Ready/not ready lights may be provided, too. The handle  102  may contain batteries that act as the power supply  104 . In an alternative embodiment, line power may be used instead. A hazard or warning indicator, such as a light, may also be provided to indicate that the probe tip  112  is too hot to touch. 
         [0029]    The temperature output, again, may vary in a wide range depending upon the desired application and use of the underlying circuit. In some examples, the temperature control  106  is designed for a range near that of body temperature for circuits directed to involve implantable medical devices. 
         [0030]    In another embodiment, rather than a heating element  114 , a cooling element may be provided, for example using a Peltier cooling circuit. A Peltier cooling circuit may, for example, heat the body  110  of the tool while cooling the tip  112 . Any suitable thermoelectric circuit can be used to modify or control the temperature of the tip  112 . To this end, the thermocouple  116  (or other temperature sensing component) may be integrated into the tip  112  while the heating or cooling element  114  is coupled closer to the body  110 , in a configuration that is reversed from what is shown in the detail view of  FIG. 5 . 
         [0031]      FIG. 6  shows use of the tool of  FIG. 5 . A tool  120  is shown relative to circuit board  130 . The tool  120  includes a tool tip  122 . To begin analysis of the circuit, the tool tip  122  is heated by the operation of the tool  120  in response to a user depressing the actuator  124 . The tool tip  122  is brought into contact with a desired one of the components  132 ,  134 ,  136 ,  138  on the circuit board  130 . The operational characteristics of the circuit board are monitored as the tool tip  122  is used to separately and independently heat the components  132 ,  134 ,  136 ,  138 . Again a separate probe  150  may be used to observe circuit operation or, alternatively, the outputs of the circuit board  130  may be monitored. 
         [0032]      FIG. 7  shows another example of a tool in accordance with another embodiment. In this example, a tool  200  is provided with a handle  202 , elongated body  204  and tip  206 . The tool  200  is coupled to a fluid supply  210  which can circulate cooling or heating fluid to the tool  200 . In accordance with this example, the tool  200  includes channels (not shown) in the elongated body  204  for circulating the cooling or heating fluid to control the temperature of the tip  206 . Temperature control may be integrated into the fluid supply  210  or can be part of the tool  200 . For example, the tool  200  may passively circulate fluid from fluid supply  210 , or it may modulate fluid flow in response to detected temperature at/near the tip  206 . 
         [0033]    Those skilled in the art will recognize that the present invention may be manifested in a variety of forms other than the specific embodiments described and contemplated herein. Accordingly, departures in form and detail may be made without departing from the scope and spirit of the present invention.