Description:A HEAT DISSIPATION APPARATUS FOR CCGA PACKAGE

FIELD OF THE INVENTION
This invention relates to heat sink. Particularly, this invention relates heat sink in electrical circuits for space applications.
BACKGROUND OF THE INVENTION
Electronic components, such as but not limited to integrated circuits, may be mechanically and electrically connected to electrical contact pads on a printed circuit board (PCB) by several conventional methods, including a ball grid array (BGA), or a grid array (GA) that uses pins, such as a standard pin grid array (PGA), a land grid array (LGA) that use sockets with pins, a column grid array (CGA) that uses columns, a ceramic column grid array (CCGA), or other methods. The CCGA is a commonly used type of GA used in a variety of applications, including commercial and non-commercial applications. CCGA packages use solder columns to establish electrical connections between a ceramic substrate (on which a silicon die is attached) and a printed circuit board. A problem with ceramic column grid array packages is that the solder columns are susceptible to failures due to temperature variations during CCGA device operation and Coefficient of thermal expansion (CTE) mismatch between the ceramic device package and the printed circuit board to which it is attached.
Another conventional approach for heat dissipation is by arranging cooling components disposed on a board-shaped mounting substrate, in particular SMD (Surface Mount Device) power components on a printed circuit board. These known heat removal concepts are costly in manufacturing terms and also have the disadvantage that heat dissipation by natural convection is dependent on the mounting position. Under worst case conditions a hot spot may occur which can impair the operational capability of the SMD circuit.
In view of the foregoing, there is a need in the art for an arrangement or a method for efficiently dissipating heat developed in electrical circuits specially for space applications. In addition, there is a need for such arrangement to be readily integrated with existing chip types and can be easily retrofitted to an existing circuit design.These and other needs are met by the present invention as detailed hereafter.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.

OBJECT OF THE INVENTION
The main object of the invention is to provide simple and cost-effective solution for thermal management of CCGA by withstanding the dynamic loads such as vibration and shock load.
Another object of the present invention is to provide a heatsink for the heat transfer from CCGA to housing and also to withstand the dynamic loads.
Yet another object of the present invention is to provide a heatsink in which effective transfer should happen and at the same time, the columns are not stressed after the mounting of the heatsink.
Yet another object of the present invention is to provide a heatsink which is not in direct contact with the PCB. Instead, a through hole is done in PCB through which the heatsink lug projects and attaches to the housing through TIM.
SUMMARY OF THE INVENTION
The inventive concepts presented herein are illustrated in a number of different embodiments, each showing one or more concepts, though it should be understood that, in general, the concepts are not mutually exclusive and may be used in combination even when not so illustrated.
The present invention design provides a simple and cost-effective solution for thermal management of CCGA by withstanding the dynamic loads such as vibration and shock load.
Accordingly, one aspect of the present invention provides a heat dissipation apparatus. The apparatus has a housing including a load frame. A printed circuit board (PCB) having an electronic component thereon. And a heat sink disposed on the load frame of the housing using at least one screws disposed on the heat sink and threaded into the load frame of the housing in order to secure the heat sink to the load frame and also maintain the desired thermal interface between the heatsink, the electronic component and housing to have proper contact and to reduce the thermal resistance of the assembly.
To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended figures. It is appreciated that these figures depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope.
BRIEF DESCRIPTION OF THE DRAWINGS
The above contents of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which:
FIG. 1 shows the cross-sectional view of heatsink, in accordance with one embodiment of the present invention.
FIG. 2 shows the isometric view of the heatsink with housing, in accordance with one embodiment of the present invention.
Further, skilled artisans will appreciate that elements in the figures are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the figures by conventional symbols, and the figures may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the figures with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.
DETAILED DESCRIPTION OF THE INVENTION
The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may however be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, and/or section from another element, component, region, layer, and/or section.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The invention illustratively disclosed herein suitably may be practiced in the absence of any elements that are not specifically disclosed herein.
FIG. 1 illustrates an attachment of a heat sink with housing 105 to CCGA. A circuit board assembly includes a printed circuit board 110, an electronic component such as a semiconductor chip, and an electronic connection. The electronic components which are generally packaged using electronic packages (i.e., modules) that include a module substrate to which the electronic component is electronically connected. In some cases, the module includes a cap (i.e., a capped module) which seals the electronic component within the module. In other cases, the module does not include a cap (i.e., a bare die module).The semiconductor chip is electrically connected to the module substrate. The electronic connection, which electrically connects the printed circuit board to the module substrate, may be a pin grid array (PGA), a ceramic column grid array (CCGA), a land grid array (LGA), or the like. The semiconductor chip is thermally connected with a heat sink through a thermal interface material (120, 125), which is a layer of thermally conductive material such as thermal paste, oil, or other high thermal conductivity material. In an embodiment, the thermal interface material is a Cho-therm. Typically, the thermal interface material is relatively thin so that it may easily transfer heat away from the module substrate and toward heat sink. The thickness of thermal interface material extending between heat sink and semiconductor chip is referred to as the thermal interface gap.
Heat sink is attached to electronic component using a plurality of screws or bolts. The screws pass through thru-holes in heat sink and thru-holes in the housing. Typically, each screw is arranged at each corner of the electronic component, or one on each side of the electronic component. Screws are tightened by threading a threaded portion of screws into threaded-holes in backside bolster. As screws are tightened, heat sink engages semiconductor chip through thermal interface material (TIM). Additional tightening of screws is possible as the screws are arranged or positioned in the heat sink and further attaching the housing. Due to this arrangement, the question of deflection of printed circuit board does not apply. Due to this arrangement of heat sink with the housing using the plurality of screws it overcomes the various problems associated with the conventional heatsink. For example, the invention heat sink arrangement does not affect or deflect or stresses the printed circuit board. Moreover, the invention arrangement of heat sink overcome the problem associated with the printed circuit board deflection which leads to catastrophic failure of solder joints and conductor traces on the printed circuit board.
In an embodiment, the present invention is a heat dissipation apparatus including a housing 105 having a load frame. A printed circuit board (PCB) 110 provides the installation and connection basis for electronic components by extending mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces. A heat sink 115 disposed on the load frame of the housing using at least one screws 135 disposed on the heat sink 115 and threaded into the load frame of the housing in order to secure the heat sink to the load frame and also maintain the desired thermal interface between the heatsink, the electronic component and housing to have proper contact and to reduce the thermal resistance of the assembly.
In another embodiment of the present invention, the heatsink is positioned in such a way for the effective transfer of heat can happen and at the same time, the columns are not stressed after the mounting of the heatsink.
In another embodiment of the present invention, the heatsink 115 is not in direct contact with the PCB 110, alternatively, further a through hole is done in PCB through which a plurality of heatsink lug 140 projects and attaches to the housing through thermal interface material (TIM). In an example embodiment, the arrangement has at least four heatsink lugs 140 positioned on the housing.
In an embodiment, the aluminium alloy 6061 is used for heat sink. Also, the black anodizing is done on heatsink. Moreover, M2 screws have been used to mount the heatsink.
In another embodiment of the invention, in order to determine the effect of torque on the CCGA columns, experiment has been done to ensure the safety of columns and then the torque value has been finalized for mounting heatsink.
In yet another embodiment of the present invention, thermal interface material (i.e. TIM) is used between heatsik, CCGA and housing to have proper contact and to reduce the thermal resistance of the assembly.
In yet another embodiment of the present invention, the invention arrangement of heat sink is suitable for space applications, in particular, for thermal management of the CCGA in space application.This methodology used by the invention is more reliable, easy to assemble and cost effective as fasteners are used to mount heatsink compared to other conventional methods such as copper straps or heat pipes which are mounted using only adhesive. Moreover, the invention can be used in any level of application, but preferably at low volume applications.
Following are the test conducted for the invention heat sink arrangement. Table 1 shows the sine vibration test and table 2 shows the random vibration test.

Table 1

Table 2
Thermal Cycling with Electrical Monitoring
• Number of cycles: 1500
• Temperature: −55 °C and +100 °C,
• Dwell time: 15minutes,
• Ramp rate: Max 10 °C per minute
While the exemplary embodiments have been described in some detail, by way of example and for clarity of understanding, those of skill in the art will recognize that a variety of modification, adaptations, and changes may be employed. Hence, the scope of the present invention should be limited solely by the appending claims.
In the foregoing specification, the invention is described with reference to specific embodiments thereof, but those skilled in the art will recognize that the invention is not limited thereto. Various features, embodiments and aspects of the above-described invention can be used individually or jointly. Further, the invention can be utilized in any number of environments and applications beyond those described herein without departing from the broader spirit and scope of the specification. The specification and drawings are, accordingly, to be regarded as illustrative rather than restrictive. It will be recognized that the terms “comprising,” “including,” and “having,” as used herein, are specifically intended to be read as open-ended terms of art. , Claims:We Claim:
1. A heat dissipation apparatus comprising:
a housing (105) including a load frame;
a printed circuit board (PCB) (110) having an electronic component thereon; and
a heat sink (115) disposed on the load frame of the housing using at least one screws (135) disposed on the heat sink and threaded into the load frame of the housing (105) in order to secure the heat sink (115) to the load frame and also maintain the desired thermal interface between the heatsink (115), the electronic component and housing (105) to have proper contact and to reduce the thermal resistance of the assembly.
2. The apparatus as claimed in claim 1, wherein the heatsink (115) is positioned in such a way that the effective transfer of heat can happen and at the same time, the columns are not stressed after the mounting of the heatsink (115).

3. The apparatus as claimed in claim 1, wherein the heatsink (115) is not in direct contact with the PCB (110), alternatively, further a through hole is done in PCB (110) through which a plurality of heatsink lug (140) projects and attaches to the housing (105) through thermal interface material (TIM).

4. The apparatus as claimed in claim 1, wherein the load frame is made up of aluminium alloy 6061 which is used for heat sink and M2 screws have been used to mount the heatsink (115).

Bangalore HL NARENDRA BHATTA
17th November 2022 (INTELLOCOPIA IP SERVICES)
AGENT FOR APPLICANT
(IN/PA/1676)