Patent Application
20070210820
The present invention relates apparatus and techniques used for thermal dissipation of electronic components.
High power telecommunication devices typically include a transmitter line-up including leaded high power electronic components. For example, multi-stage amplifier circuits are used to meet high level power requirements utilizing one or more high power amplifier transistors. The impedance, current drain and hence the efficiency of these components vary with frequency and transmit power level.
High power electronic components soldered to circuit boards, particularly circuit boards of portable devices, face issues with thermal dissipation and efficiency. Heat sinks are used in conjunction with these components to facilitate thermal dissipation, but depending on the load presented to the component, a parameter known as voltage standing wave ratio (VSWR) is created in the transmit path which introduces local heating of other devices on the circuit board. Depending on the magnitude and phase of the load, at certain frequencies, a significant amount of heating can occurs on the leads of the component. The heating, along with repeated cycles of transmit and receive, cause solder joints between the leads of the component and the circuit board to fail. This failure is characterized by a formation of cracks that propagate throughout the solder joint until the joint is completely cracked. The result is an open impedance at the component lead resulting in arcing and failure of the device and circuit board.
Accordingly, there is a need to reduce the propensity of the solder joints to crack and fail during cyclic loading of a leaded high power component.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of apparatus components and method steps related to thermal dissipation of high power integrated circuits. Accordingly, the apparatus components and method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.
Apparatus 100 includes at least two conductive surfaces 110, 112 disposed thereon. In the embodiment shown in
As will be shown in the figures to follow, at least one of the conductive surfaces, here conductive surfaces 110, couple to at least one lead of an integrated circuit, and the other conductive surface 112 provides a surface for contacting a heat sink.
In accordance with the present invention, bottom surface 104 can be selectively plated to provide plated geometries that align with and are reflowable to a plurality of heat generating leads of the IC without shorting the leads together. The bottom surface 104 of the substrate body 102 provides thermal dissipation from the plurality of leads to the top surface plating 106 through the substrate body 102. For the purposes of this application apparatus 100 will also be referred to as a heat dispersive apparatus or a heat dispersive member.
Referring to
The plurality of leads 204 extending from IC 202 provide a predetermined footprint. The heat dispersive apparatus of the present invention can be formed by determining which leads of an integrated generate heat, and providing a heat dispersive substrate having top, bottom and side surfaces plated such that the substrate provides independent conductive surfaces, with at least one conductive surface providing a geometry that aligns with the footprint of the IC lead(s) that generate heat. Thus, a heat dispersive member formed in accordance with the present invention can be designed to accommodate a variety of footprints and form factors.
The package 200 formed in accordance with the present invention provides a variety of benefits including improved ease of assembly, low cost and improved thermal conductivity. From a manufacturing standpoint, the package 200 can be assembled into a product using automated equipment.
Again, the conductive surfaces of heat dispersive member 100 align with at least a portion of the IC's predetermined footprint that generates heat. The heat dispersive member 100 is soldered to at least one lead of the IC via at least one conductive surface and makes contact with the heat sink 402 via the other conductive surface 112. The heat sink 404 is coupled to the printed circuit board 402 using standard soldering techniques. Heat sink 404 makes contact with both plating 112 of the heat dispersive member 100 and the metallization tab 206 of the IC 202. The thermal conductivity, electrical resistivity and dielectric strength of the heat dispersive member 100 prevent failure of the IC 202 over high temperatures as heat from heat generating lead(s) is dispersed through the dispersive member to the heat sink 402. Heat is thus dispersed through both the plating 112 and metallization tab 206.
Heat dispersive apparatus 100 can be formed to accommodate a wide variety of IC footprints through the use of selective plating such that independent signal leads are not shorted together. While the apparatus of
In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
