News Column

Patent Issued for System with Shared Heatsink

September 10, 2014

By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventors Privitera, Concetto (Gravina di Catania, IT); Stella, Cristiano Gianluca (San Gregorio di Catania, IT), filed on June 29, 2012, was published online on August 26, 2014.

The patent's assignee for patent number 8817475 is STMicroelectronics S.r.l. (Agrate Brianza (MB), IT).

News editors obtained the following quote from the background information supplied by the inventors: "Any existing electronic component is characterized by an absorption of electrical power--generally, proportional to the product of a current passing through the same and a voltage that develops between its terminals--during an operation thereof. A portion of the absorbed power is lost as heat according to the principles of thermodynamics. In particular, heat is generated in the 'active' regions of the electronic component, i.e. where the flow of electric current occurs (e.g., with a MOSFET transistor, in a region beneath a control terminal and regions constituting the conduction terminals thereof). The heat generation concentrated in the active regions causes a rise in the temperature of the electronic component. The temperature of the active regions of the electronic component, better known as junction temperature, is a parameter that strongly affects the operation of the electronic component. In particular, a threshold voltage, typical of the electronic component (e.g., again in the case of MOSFET transistors), in relation to which the current intensity of the same is controlled, is inversely proportional to the junction temperature, as a result, with the same control voltage applied, the electronic component draws a flow of electric current which increases as the temperature increases. It is also known that, with increasing junction temperature, an increase in the electrical resistivity of the electronic component occurs, too. Consequently, the electronic component dissipates, due to the Joule effect, an increasing electric power between its terminals, and this leads to an ever rising junction temperature; in other words, a positive feedback (phenomenon called thermal runaway) is established that may cause damage or even destruction of the electronic component due to a too high junction temperature. In addition, with the rising of the junction temperature of the electronic component there is a reduction of the reliability thereof (i.e., the probability of occurrence of a structural damage during the operation increases) and generally of its operative life (i.e., the time for which the electronic component works properly).

"The miniaturization process of the electronic components (basically a reduction in the size of the electronic component, in particular of the active regions), makes it very important to contain the rise in junction temperature within an acceptable range. In fact, with the same electrical power consumption, the smaller the active area of the electronic component, the greater and more rapid the rise in junction temperature of the same (since the electrical power consumption is concentrated in a smaller volume).

"This is particularly important in the field of electronic components belonging to the 'power electronics' sector, i.e. electronic components designed to operate at voltages and currents higher than standard electronic components (for example, with operating voltages in the order of hundreds of volts and/or with operating current in the order of the amperes), which are used in circuits of apparatuses belonging to various fields of applications, for example, from computers to electro-mechanical machinery (power supply circuits of computers, actuators of electric motors, inverters for photovoltaic panels, etc.).

"Heatsinks are known and widely used to limit the rise of the junction temperature in electronic components. A heatsink is an element consisting of one or more elements in thermally conductive material (e.g., aluminum Al), which is fixed (typically by gluing and/or double-sided adhesive material tape) to a package of the electronic component. The package is essentially an insulating package (usually in plastic or ceramic) wherein contact pins are exposed (to connect the electronic component to tracks of an external circuit), and is intended to encompass and protect a chip of semiconductor material wherein the electronic component is integrated.

"Alternatively, the insulating package may also include an opening--typically formed in an upper free surface of the insulating package opposed to a mounting surface toward which the pins are oriented--for exposing a dissipation plate (made of thermally conductive material too). The dissipation plate is connected to the chip to improve heat exchange with the external environment. The heatsink can be attached directly to the dissipation plate through double-sided adhesive tapes or glues with high thermal conductivity coefficient, which conforms the contact surface, thus facilitating a conductive heat exchange between the chip and the heatsink (thanks to the increased thermal conductivity of the materials constituting the dissipation plate and the heatsink in contact with each other with respect to the plastic ones forming the insulating package).

"In greater detail, the heatsinks facilitate heat transfer by conduction (thanks to their good thermal conductivity) from the chip to themselves. In addition, heatsinks are typically formed with a structure designed to facilitate a heat transfer by convection (e.g., with a plurality of fins extending from a base through which the heatsink is fixed to the insulating package or to the dissipation plate) to the environment external to the package (i.e., transferring heat to the medium that surrounds the package, for example, air). Thus, suitably sized heatsinks allow maintaining the junction temperature below a safe temperature.

"However, heatsinks suffer from a major disadvantage, particularly when applied to small packages (e.g., to embedding miniaturized electronic components). Indeed, the heatsinks tend to be mechanically unstable, once fixed to the package. This is due to the fact that by reducing the size of the packages, an available mounting surface is proportionally reduced. This reduced mounting surface may be insufficient to ensure good mechanical stability for the heatsink on the package; therefore, the heatsink might separate from the package because of mechanical stresses, to which it may be subjected. In addition, the weight of the heatsink and the mechanical stresses might likely cause a deterioration, or even a breakage, of contacts formed between one or more pins of the package and the corresponding conductive tracks of the board to which they are attached, up to causing their detachment and the malfunction of a circuit wherein the electronic component is used.

"In circuits comprising at least two electronic components, it is highly preferable that the junction temperatures of such components be maintained as identical as possible during circuit operation. Indeed, for an effective and efficient operation of the circuit it is necessary that the temperature-dependent operating parameters (such as, for example, threshold voltages, electric currents, internal resistances, etc.) are essentially the same for all the electronic components included in the circuit.

"It is observed that heatsinks currently known in the state of the art do not allow to obtain a sufficient mechanical stability and, at the same time, to ensure sufficient uniformity in the junction temperatures of electronic components belonging to a same circuit."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "One or more aspects of a solution according to specific embodiments are set out in the independent claims, with advantageous features of the same solution that are set out in the dependent claims (with any advantageous features provided with reference to a specific object of the solution according to an embodiment which apply mutatis mutandis at any other of its aspects).

"More specifically, one aspect of a solution according to an embodiment provides a system. The system comprises a plurality of electronic devices. Each electronic device comprises an insulating package and a chip of semiconductor material embedded in the insulating package. Said chip integrates at least one electronic component. Each insulating package has a mounting surface for mounting the respective electronic device on a substrate and a free surface opposite to the mounting surface. The system also comprises a heatsink for dissipating heat generated by each electronic device of said plurality of electronic devices. The heatsink is attached to a respective base portion of the free surface of the insulating package of each electronic device.

"In a solution, the heatsink comprises at least one connection element. Each connection element connects a respective first base portion with a respective second base portion. The heatsink further comprises, for each electronic device, at least one stabilizing element extending from the respective base portion at least up to the substrate.

"Another aspect of a solution according to an embodiment provides a corresponding method for realizing such system."

For additional information on this patent, see: Privitera, Concetto; Stella, Cristiano Gianluca. System with Shared Heatsink. U.S. Patent Number 8817475, filed June 29, 2012, and published online on August 26, 2014. Patent URL:

Keywords for this news article include: Electronic Components, Electronics, STMicroelectronics S.r.l., Semiconductor.

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Source: Electronics Newsweekly

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