The present invention is related to an improved electronic module, comprising at least one temperature sensitive capacitor, such as an electrolytic, film, or a multi-layered ceramic (MLCC) capacitor. More specifically, the present invention is related to an electronic module comprising a temperature sensitive capacitor which is thermally stabilized by an integral thermoelectric cooler.
The demand for increased functionality of electronic products continues to expand as new technologies with greater capabilities are developed. The continued expansion of electronics in applications, once considered unsuitable, are now becoming the norm. These new applications demand high operating and processing speeds, increased electrical performance in a smaller space, and harsh environment applications such as high temperature and humidity. In electronics, increased performance is based on higher power conversion which also increases the operating temperature of the component. In the case of ceramic capacitors having specific types of dielectrics, the capacitance of a capacitor changes as the temperature of the component increases adversely affecting the performance of the capacitor. For film capacitors, the maximum operating temperature may be limited by the intrinsic stability of the film material. In electrolytic capacitors, the counterelectrode materials or the electrolyte often limit the maximum use temperature. In many cases, the temperature increase is significant enough to justify the use of heat sinks to help dissipate the increase in heat to help keep the component operating within an optimal temperature range.
The dissipation of heat from a source is an age-old endeavor. The efficiency of heat sinking has improved over the years because of improved designs, materials, and technology. Some heat sinks may be as simple as utilizing a mass of material having good thermal dissipation properties, such as copper or aluminum, and mounting a heat generating device onto the material. The addition of fins to the heat sink to increase surface area or cavities within the heat sink to circulate a cooling fluid, such as water, can also be used to increase the heat sinking capabilities. Other materials, such as AlN or BeO ceramics, are also utilized as heat sinks due to their excellent heat sinking capabilities. The amount of thermal dissipation varies with the different types of heat sinks and trying to control the dissipation may become more complicated as the degree of accuracy becomes more critical.
While heat sink technology is beneficial the use thereof is in conflict with the ongoing desire for miniaturization. As more demand is placed on electronic assemblies, and therefore electronic components, the decreasing space available for a heat sink diminishes as does the area available for circulation of a transfer medium, such as air, within the device. Furthermore, heat sinks are passive devices incapable of intermittent function and they are inadequate for use in low temperature environments wherein the temperature of the component may need to be heated to achieve adequate functionality.
There is an ongoing desire in the art for a more robust electronic module, and particularly an electronic module comprising a capacitor that has an optimal range of temperature where its capacitance remains stable. In resonator circuits containing capacitors, it is critical to maintain the capacitance within narrow limits. Since capacitance varies with temperature common heat sinks alone are not capable of achieving the temperature stability that is required. These modules are also required to have reliable performance over a wide temperature range and to eliminate failures due to thermal runaway.
The present invention is related to an improved electronic module and particularly an improved electronic module comprising an electrolytic, film, or multi-layered ceramic capacitor (MLCC) and a thermoelectric cooler (TEC) in thermal contact therewith.
More specifically, the present invention is related to an improved electronic module comprising a capacitor having stable power due to the incorporation of an integral thermoelectric cooler in thermal contact therewith.
A particular feature of the invention is the ability to maintain an electrolytic, film, or MLCC capacitor of an electronic module within a temperature range thereby improving the performance of the capacitor and electronic module.
A particular advantage is the ability to provide an electronic module comprising a capacitor with an integral safety device thereby avoiding thermal runaway.
These and other embodiments, as will be realized, are provided in an electronic module comprising at least one electronic component. A thermoelectric cooler is in thermal contact with the electronic component. A temperature controller is capable of determining a device temperature of the electronic component is provided and capable of providing current to the thermoelectric cooler proportional to a deviation of the device temperature from an optimal temperature range.
Yet another embodiment of the invention is provided in a method for controlling a device temperature of a capacitor comprising:
forming an electronic module comprising at least one capacitor wherein the capacitor comprises an optimal temperature range;
placing a thermoelectric cooler in thermal contact with the capacitor; and providing a thermal controller comprising a temperature sensor capable of measuring the device temperature of the capacitor and providing a current to the thermoelectric cooler wherein the current is proportional to a deviation of the device temperature from the optimal temperature range.
The present invention is related to an improved electronic module preferably comprising a capacitor which is thermally stabilized by an integral thermoelectric cooler. In particular the present invention is related to an improved electronic module comprising a multilayered ceramic capacitor (MLCC), electrolytic capacitor or film capacitor which is thermally stabilized by an integral thermoelectric cooler More specifically, the present invention allows an MLCC, electrolytic, or film capacitor or an electronic module to be maintained within a predetermined temperature range thereby improving the functionality of the capacitor and module comprising the capacitor.
A thermoelectric cooler (TEC) is a solid-state device, based on an application of Peltier Effect, which functions as a solid-state heating or cooling generator based on semi-conductor technology. When current is passed through a TEC one side becomes hot while the other side becomes cold and when the current flow is reversed the hot and cold sides flip positions thus creating a solid-state heater or cooler having no moving parts. When multiple blocks of this material are connected in series circuit, the heat generation or cooling effect can be increased by stacking the TEC with the hot side of one TEC in contact with the cold side of a second TEC.
The application described herein provides an electronic module utilizing TEC's with temperature feedback to one or multiple electronic components, preferably MLCC's, that will maintain an optimum operating temperature range. The electronic component and TEC are in thermal contact defined herein as a relationship wherein the TEC can heat or cool the capacitor in response to a current applied to the TEC. When the capacitor element is being used in a resonator circuit it is particularly essential to maintain a tight control of capacitance which in many capacitors requires a narrow range of temperature to be maintained. The TEC allows the capacitor temperature to be controlled within a narrow range by either heating or cooling.
Certain dielectrics used in MLCC's have specific dielectric properties that provide optimal capacitance properties for an MLCC. However, some dielectrics are sensitive to heat and a decrease in their capacitance can occur as the temperature of the MLCC increases. In these instances, it becomes desirable to maintain an optimum component temperature thereby allowing the component to operate at its maximum capacitance capability. This is particularly an issue with MLCC's wherein the capacitance is temperature sensitive. Temperature control can be achieved by mounting the electronic component to the TEC and utilizing surface mounted circuitry as described in U.S. Pat. No. 8,904,609, which is incorporated herein by reference, to incorporate a temperature sensing closed loop control circuit within the envelope of the electronic component.
The temperature can be determined by a predictive method, a direct method or a combination thereof. A predictive method would include a determination of temperature based on the measurement of a secondary parameter wherein the secondary parameter correlates to temperature such as current, resistance or capacitance. A direct method is a measurement of temperature by a temperature sensor which can be a contact sensor or a remote sensor. Sensors which can be employed for demonstration of the invention include a varistor, resistive temperature detector, thermistor, infrared detector, bi-metallic sensor, silicon diode, semiconductor with temperature sensitive voltage vs. current, thermocouple, optical sensor or any other temperature sensing device capable of sensing the temperature of the electronic component. It is preferable that the temperature sensor be an integral part of the temperature control circuit wherein the temperature control circuit varies the current flow to the TEC, thus, heating or cooling the electronic component to maintain an operating temperature within a preferred operating temperature range. The application of utilizing the TEC as a temperature controller can be utilized for many capacitor assembly designs and may include additional components.
In a particularly preferred embodiment a combination of predictive and direct temperature sensors can be employed. Based on parameters monitored by predictive temperature sensor the TEC may be activated before a threshold temperature is achieved and the current to the TEC may be proportional to the temperature difference relative to a predetermined temperature or temperature range thereby allowing for proportional temperature correction. The direct temperature sensor could provide redundancy or confirmation of the temperature of the electronic component.
Alternatively, the direct temperature sensor may be monitored for determination of a threshold temperature above which a predictive sensor is monitored for effectiveness of temperature alteration by the TEC.
The invention will be described with reference to the figures forming an integral component of the instant disclosure without limit thereto. Throughout the various figures similar elements will be numbered accordingly.
An embodiment of the invention is illustrated in schematic perspective view in
An embodiment of the invention will be illustrated with reference to
An embodiment of the invention is illustrated in perspective schematic view in
An embodiment of the invention is illustrated in schematic view in
An electrolytic capacitor is illustrated in schematic perspective view in
An embodiment of the invention is illustrated in cross-sectional schematic view in
The shape of the channel is not limited with the proviso that it is preferable to maximize the contact area between the TEC and channel and therefore flattened portions are preferred.
An embodiment of the invention is illustrated in an electrical schematic view in
In operation, if the temperature sensor senses a temperature of the component which is outside a predetermined optimal temperature range an appropriate signal is relayed to the temperature control circuit and the appropriate current is applied to the TEC thereby returning the component to a temperature within the predetermined range. As would be realized the temperature of the component can be raised or lowered with a preference for lowering the temperature particularly when the component is a capacitor.
Thermoelectric materials are typically fabricated from bismuth telluride (Bi2Te3), antimony telluride (Sb2Te3), lead telluride (PbTe) or alloys thereof such as Bi0.5Sb1.5Te3 which is typically capable of achieving temperature change of about 81 K at a near ambient temperature of 300 K.
TEC's are commercially available in a variety of sizes and configurations from various companies including Marlow Industries, Inc. of Dallas, Tex. The TEC is preferably mounted to either the electronic component or circuit board by thermal epoxy, soldering, TLPS or by compression methods using thermal grease. It is preferably to control the TEC using linear proportional temperature control.
The circuit board preferably comprises a material selected from the group consisting of ceramic such as alumina such as 96% Al2O3 or 99.6% Al2O3; aluminum nitride; silicon nitride or beryllium oxide; G10; FR (Flame Retardant) materials such as FR 1-6, FR 4 which is a composite of epoxy and glass, FR2 utilizing phenolic paper or phenolic cotton and paper; Composite Epoxy Materials (CEM) such as CEM 1, 2, 3, 4, 5; insulated metal substrates such as aluminum substrates available from Berquist Mfg. and flex circuits comprising materials such as polyimide.
A test fixture was prepared comprising a TEC mounted to a Low R-theta, such as less than 1° C./watt, heat sink on one side and on the other side a stack of commercially available 3640 C0G capacitors available from KEMET having a capacitance of 0.056 μF, a rated voltage of 1000 volts and a nominal size of 9.1 mm×10.2 mm×2.7 mm. A 50.8 mm×25.4 mm FR4 substrate with copper pads was mounted to the capacitor stack opposite the TEC. A power amplifier having a circuit as illustrated schematically in
The effects of the TEC on the temperature of ten MLCC's mounted in series is provide in Table 1 measured at a frequency of 563 kHz and an ESR of 1 mΩ wherein at a given AC RMS current (I), dissipated power (DP) in watts, the termination temperature without the TEC energized (Temp 1) the TEC voltage (TEC-V), and TEC current (TEC-I) required to achieve the stated cooled temperature (Temp 2) and the TEC Power (TEC-P) in watts is provided.
As evidenced in Table 1, as the temperature of the MLCC's increases the dissipated power increases as the temperature can be lowered by the use of a TEC in thermal contact with the MLCC.
The test fixture of Example 1 was loaded with a stack of two commercially available 2220 X7R MLCC capacitors available from KEMET having a capacitance of 0.47 μF, a rated voltage of 50 volts and a nominal size of 5.70 mm×5.00 mm×1.85 mm. The effects of the TEC on the performance of the two MLCC's mounted in series is provide in Table 2 measured at a frequency of 28 kHz and an ESR of 4 mΩ wherein at a given AC RMS current (I), dissipated power (DP) in watts, the termination temperature without the TEC energized (Temp 1) the TEC voltage (TEC-V), and TEC current (TEC-I) required to achieve the stated cooled temperature (Temp 2) are reported. Capacitance Change with Reference to +25° C. and 0 VDC Applied (TCC) as a function of temperature (° C.) for a single 2220 X7R MLCC capacitor is provided in Table 3
As evidenced in Table 3, the temperature coefficient of capacitance for this representative capacitor reaches a threshold temperature at about 125° C. resulting in a significant decrease in capacitance. By maintaining the temperature of the MLCC within a predetermined optimal temperature range which is the range between a low temperature where capacitance changes to an unacceptable amount to a high temperature which is below the temperature at which thermal run-away can occur. By maintaining the temperature within the optimum temperature range thermal run-away can be avoided thereby providing a safer electronic component and ultimately a safer electronic device.
The invention has been described with reference to the preferred embodiments without limit thereto. Additional embodiments and improvements may be realized which are not specifically set forth herein but which are within the scope of the invention as more specifically set forth in the claims appended hereto.
The present application claims priority to pending U.S. Provisional Patent Application No. 62/522,297 filed Jun. 20, 2017 which is incorporated herein by reference.
Number | Date | Country | |
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Parent | 62522297 | Jun 2017 | US |
Child | 15972988 | US |