Abstract:
An apparatus for detecting an intrusion of an environmental substance into an environmentally sealed electronic components package. The electronic components package generally includes a plastic coated or plastic enclosed electronic component, that includes a printed circuit board and/or integrated circuits. The intrusion of the environmental substance into the electronic components package can be measured by one of a plurality of monitors. The monitors can detect the presence of the environmental substance and alert a user that a break in the seal of the electronic components package has occurred.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a system to ascertain the integrity of an electronic component, and particularly relates to a system to indicate moisture ingress for accumulation in a sealed system. 
   BACKGROUND OF THE INVENTION 
   Electronic components form a large part of many modern machines and devices. Furthermore, they are often integral to the proper operation of such devices. Electronic components often include, integrated circuits that provide a very compact and efficient means for performing various electronic functions. 
   Although integrated circuit boards and chips provide an inexpensive way to provide electronic components to many vehicles and structures, they are not always impervious to the elements such as moisture and other environmental contaminants that may harm electronic components. In particular, when these components are encased in plastic, different environmental conditions may damage the circuits. The plastic of the integrated circuits and chips are not completely impervious to moisture and environmental conditions. In addition, the plastic molded parts may be damaged or harmed by other environmental conditions such as thermal shock or extent of cracking. If the electronic components, such as integrated circuit boards, become damaged, then moisture may enter the enclosure surrounding circuit boards. If moisture is able to reach the circuit board interface, then damage may occur, particularly, by shorting or corroding the internal components. 
   One commonly known solution has been to use hermetically sealed components. Using hermetically sealed components, however, often greatly increases the cost of the component. These packages generally require specific and unique materials and manufacturing processes that have associated production costs. Although hermetically sealed components are generally known and accepted to have good seal longevity, it is desired to produce a component which is cheaper and still able to have a high longevity. 
   Moreover, it is easy to determine if a hermetically sealed component has been compromised. That is, determining that a hermetically sealed component has been damaged or the components inside the part where the seal may have been damaged could be determined by fine and gross leak testing. The same is not true for integrated circuits or similar components in plastic or other enclosures. Simply, there is no easy way to determine whether the electronic component package has been compromised, thus alerting a user to a possible or impending malfunction. 
   Therefore, it is desirable to produce a structure within the component package that is able to determine if a seal, designed to protect the electronic components from environmental conditions, has been compromised. Moreover, it is desired to form such a component from inexpensive and generally available integrated circuit chips that may be integrated into the circuit board, part, or enclosure (such as a box). Using generally availably components realizes cost reductions and inventory reduction which does not require specifically producing and formulating unique components for varying applications. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to an apparatus for detecting moisture and associated environmental intrusions into an electronics package. Sensors determine whether moisture has entered an electronics package. In particular, sensors are used to determine the presence or absence of an electric current which in turn determines whether moisture is present. For example, a silver sensor is used to detect the gross or absolute intrusion of moisture into an electronics package. The presence of moisture causes silver ions to migrate and create an electrical short or conductive path in the sensor. 
   A first preferred embodiment of the present invention provides a system for monitoring a sealed electronics package for moisture or other elements that may have entered the sealed electronics package. The system includes an electronic component having a circuit. An envelope surrounds the electronic component and a monitor determines the integrity of the envelope. The monitor detects the presence of a substance in the envelope. 
   A second preferred embodiment of the present invention is directed to a system to provide substantial certainty in the detection of a substance that has entered an internal environment intended to be sealed from an external environment. The system includes a substantially sealed structure defining the internal environment. A component and a monitor are disposed in the internal environment. The monitor is able to determine the presence of a substance from the external environment in the internal environment. 
   A third embodiment of the present invention is directed to a system to determine whether an electronic components package is substantially free of an environmental substance. A structure defines an enclosed area substantially impermeable to the substance. An electronic component is disposed in the enclosed area. The electronic component becomes damaged when contacted by a critical concentration of the substance. A sensor is disposed in the enclosed area so that the monitor detects the presence of the substance before the substance reaches the critical concentration. 
   Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment(s) of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
       FIG. 1  is an elevated view of an exemplary electronic components package including a sensor, according to a first preferred embodiment of the present invention; 
       FIG. 2  is an enlarged and diagrammatic view of a substance monitor according to the first preferred embodiment of the present invention; 
       FIG. 3  is an enlarged and diagrammatic view of a substance monitor according to the first preferred embodiment of the present invention; 
       FIG. 4  is a perspective view of an electronics components package according to a second preferred embodiment of the present invention; and 
       FIG. 5  is a perspective view of an electronics component package according to a third preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
   With reference to  FIG. 1 , a system  10  in accordance with a preferred embodiment of the present invention is shown for determining the integrity of an electronic components package  11 . The electronics package  11 , typically includes a printed circuit board (PCB)  12  having traces  13  or integrated circuits (ICs)  14 , and is provided with a first seal failure monitor or sensor  16   a  and a second seal failure monitor or sensor  16   b . Overlaying the PCB  12  is a sealing layer or portion  18  of an appropriate plastic such as an epoxy substance. The sealing portion  18  overlays or encases the entire PCB  12 , or at least the portions that must be protected from environmental conditions or substances. The sealing portion  18 , the PCB  12 , and any associated ICs  14  are an example of the electronic component package  11 . 
   It is desired to protect the PCB  12  and the accompanying components, such as the integrated circuits  14 , and traces  13 , from environmental conditions and substances. One environmental substance is moisture that may short or corrode the integrated circuits  14  or the traces  13  on the PCB  12 . Therefore, a leak in the electronics component package  11  may be measured by the monitors  16   a  and  16   b  and corrected before damage occurs. 
   Although it may be inherently difficult to determine whether the electronic components package  11  includes a defect, either due to manufacture or wear, the appropriate monitors  16   a  and  16   b  may be included to determine if such a failure has occurred. Although many appropriate moisture sensors may be used, comb or interdigitated monitors are particularly well suited to providing simple and accurate detection of moisture in the electronic components package  11 . 
   With reference to  FIG. 2 , the first monitor  16   a  is illustrated. The monitor  16   a , illustrated in highly simplified form as a gross moisture sensor, includes a probe  30  and a processor  32 . The probe  30  includes constituents such as silver. It will be understood that the probe  30  may be formed of many different constituents not including silver, but silver is particularly well suited for use in determining a gross moisture leak. The probe  30  generally includes an anode comb  34  and a cathode comb  36  that are in close proximity to each other. The anode comb  34  includes anode teeth or digits  38 . Similarly, the cathode comb  34  includes cathode comb teeth or digits  40 . The anode comb  34  and the cathode comb  36  are interdigitated, wherein each one of the anode digits  38  is disposed between two parallel, adjacent cathode digits  40 . Also included are an anode lead  42  and a cathode lead  44  that interconnect the probe  30  and the processor  32 . The processor  32  may then determine the presence or absence of a current in the probe  30 . Also, external readings may be taken as to current that is transferred or being conducted between the anode comb  34  and the cathode comb  36 . 
   The monitor  16   a  may be formed in an appropriate size for the application. Spacing between the associated digits  38 ,  40  may also be varied depending upon the requirements of the sensor  16   a . The more space between associated digits the greater the time or amount of moisture to provide a signal. In one preferred implementation, the spacing between digits  38  and  40  is about 2 μm (0.08 mils) to about 25 μm (1 mil). It will also be understood that the sensor  16   a  illustrated in  FIG. 2  is not illustrated to scale. The sensor  16   a , when it is made of a silver compound on an IC, is generally square and preferably between about 40 and about 80 mils on a side. 
   Also, the sensor  16   a  may be integrated into the PCB  12 . The combs  34  and  36  may be laid on the PCB  12  and the appropriate leads  42  and  44  affixed to the combs  34  and  36 . Therefore, the sensor  16  may be provided on the PCB  12  without greatly increasing the size or weight of the PCB  12 . This is particularly a concern in weight sensitive applications such as aircraft and space vehicles. 
   Alternatively, the monitor  16   a  may be first formed as a separate component IC and then added to the PCB  12 . For example, the combs  34  and  36  may first be formed on a separate PCB and then added to the PCB  12  to provide a moisture sensor to the PCB  12 . Nevertheless, the addition of this extra part does not tangibly increase the size or weight of the electronic components package  11 . Moreover, the compact dimensions of the sensor  16   a  allows a plurality of sensors  16   a  to be added to an appropriate sized PCB  12  depending upon the size and distance between the moisture sensitive components. 
   The sensors  16   a  and  16   b  may be made more sensitive to moisture than other environmental conditions. Although it will be understood that other appropriate sensors may be used to detect other environmental leakages into the electronic components package  11 . The sensor  16   a , including a silver sensor, determines a gross amount or the absolute presence of any leak of moisture into the electronic components package  11 . That is, any moisture leak, regardless of the degree, may be detected using the sensor  16   a  leading to a short. When the anode comb  34  and cathode comb  36  include silver ions, the silver ions become mobile when water is present between the digits  38  and  40  of the combs  34  and  36 . Essentially, the silver sensor has substantially no current when there is no moisture present. Upon the presence of moisture on the silver sensor  16   a , silver ions are able to transfer from one digit  38 ,  40  to another, thereby providing a current between the two combs  34 ,  36  of the silver sensor  16   a . Therefore, the presence of generally any amount of moisture, which is able to interconnect two digits of the combs  34  and  36  the sensor  16   a , causes a signal to be produced by the monitor  16   a . The processor  32  provides a potential to the monitor  16   a  and detects a current flow from the anode comb  34  to the cathode comb  36 , that only occurs when moisture is present. A user may then repair or replace the electronic components package  11  or any portion thereof. 
   Second exemplary sensor  16   b , illustrated in detail in  FIG. 3 , comprises a nichrome sensor. The nichrome sensor  16   b  includes a combination of nickel and chromium layers layered one atop the other. The nichrome sensor  16   b  is also relatively small and generally forms a rectangle having side lengths of preferably about 50 mills by about 100 mills. Again, it will be understood that the size of the nichrome sensor  16   b  may be altered depending upon the size necessary for the particular application. 
   The nichrome sensor  16   b  also includes an anode comb or labyrinth  46  and a cathode comb or labyrinth  47 . The anode comb  46  includes anode digits  48  which are associated with cathode digits  49  of the cathode comb  47 . The anode comb  46  may also include an anode lead  42 ′ and the cathode comb a cathode lead  44 ′ that interconnect the combs  46  and  47  to a processor  32 ′. Therefore, the combs  46  and  47  define a probe  30 ′ that provides a signal, or which is used by the processor  30 ′ to create a signal, based on the sensing of the probe  32 ′. 
   The nichrome sensor  16   b  comprises a more precise or quantitative moisture detector. In particular, the nichrome sensor  16   b  may determine quantitatively the amount of moisture which has leaked into the electronic components package  11 . Therefore, at least two levels of moisture detection may be provided for the electronic components package  11 . The silver sensor  16   a  provides a “gross” leak indication or absolute detection of whether moisture is present or not. The nichrome sensor  16   b , on the other hand, can determine quantitatively the amount of moisture which has entered the electronic components package  11 . 
   The nichrome sensor  16   b  provides a resistance output value when no moisture is present. The presence of moisture decreases the amount of resistance between the digits of the nichrome sensor  16   b . Therefore, as the concentration of moisture increases, the resistance measured using the nichrome sensor  16   b  decreases. Therefore, a plot or determination of the amount of resistance in the nichrome sensor  16   b  depends upon the concentration of moisture, thus allowing a quantitative measurement of moisture. 
   In addition, other appropriate sensors may be used to determine moisture leaks. For example, an integrated microchip sensitive to corrosion can be used. One such chip is the ATC04 chip produced by Sandia®. The ATC04 is an integrated chip that includes ring oscillators as moisture and corrosion sensors and other sensors such as stress and temperature sensors. Nevertheless, the inclusion of such a chip in the electronic components package  11  can be used to determine whether the seal of the electronic components package  11  has become compromised. 
   With reference to  FIG. 4 , an electronic components package  50  according to a second preferred embodiment of the present invention is illustrated. The electronic components package  50  includes a first moisture sensor  52  and a second moisture sensor  54  spaced a distance apart. The electronic package  50  includes a three dimensional box structure  55  that forms an enclosure or encasement of a sealed compartment that includes several PCBs  60  and other integrated circuit chips  62 . The electronic components package  50 , nevertheless, must be sealed from the outside ambient environment. Therefore, the presence of the moisture sensors  52  and  54  provide a means of measuring the amount of any moisture that enters the electronic components package  50 . 
   Therefore, it will be understood that the moisture sensors  16   a ,  16   b ,  52  or  54  of the present invention may be used singly or as a plurality to determine the moisture present in an electronic components package or module. As an example, if the electronic components package is larger it may be desirable to include a plurality of moisture sensors in several different areas to determine whether moisture has entered any of those areas or might be affecting any of the circuitry in separate and selected areas. Conversely, if the electronic components package or module is substantially smaller, only one or two moisture sensors may be desired. In addition, different types of moisture sensors may be provided to measure both a gross moisture leakage and to quantify the amount of moisture which is present in the electronic component package. 
   With reference to  FIG. 5  an electronic components package  70  according to a third preferred embodiment of the present invention is illustrated. The electronic components package  70  generally includes an integrated circuit which may be soldered onto a PCB, such as the PCB  12 . The electronic components package  70  includes a plurality of leads  72  which allow the interconnection between the PCB and the electronic components package  70 . Any number of circuits or resistors may be included within the electronics component package  70 . These components are then encapsulated or encased in a solid plastic case  74 . Also encapsulated within the case  74  is a sensor  76 . Although any number of the sensors  76  may be included, the electronic components package  70  is typically relatively small in size, and thus may only require one sensor  76 . Nevertheless, it will be understood that the sensor  76  is highly functional and may be placed in a very small electronic components package  70 . 
   With the present invention, electronic component packages or modules that have not been hermetically sealed may be used in sensitive applications. The use of moisture sensors allows an easy and quick means to determine whether the electronic component package seal has been compromised. From this determination, it is then known that moisture may be present that will likely disrupt the operation of the electronics in the electronic components package. 
   The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the template of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.