Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2003-05-14
2004-12-14
Datskovsky, Michael (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S679090, C361S689000, C361S695000, C174S016100, C219S061700
Reexamination Certificate
active
06831838
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates generally to welding systems and, more particularly, to a circuit board assembly located therein.
Welding power supply housings have a front panel which includes an on/off switch as well as controls such as power adjustment dials, output gauges, and output terminals and outlets. Additionally, the housing includes a rear panel and a cover panel. Such welding power supply housings must understandably enclose the entirety of the electrical components.
The electrical components include heat generating electrical components that require cooling. The housing, being fully enclosed however, restricts natural convection cooling of these electronic components. These components are preferably cooled by attaching the components directly to a heat sink. The heat sink is exposed to a cooling flow so that the cooling flow over the fins of the heat sink effectively cools those components that are attached thereto. Additionally, the cooling flow may be polluted with particulates related to the welding process and work environment. Sensitive components of the welding device can be damaged by exposure to the polluted cooling flow.
A wind tunnel, which extends through the housing of the welding device, can be used to maintain separation between the electrical components of the device and the cooling flow. These wind tunnels must be constructed with an opening therethrough. The heat sink of the electrical assembly can then be passed through the opening of the wind tunnel such that the fins of the heat sink are exposed to the cooling flow but the electrical components thereon are not. As such, the electrical components would not be exposed to the polluted cooling flow.
The connections between the electrical components of the welding device and the heat sinks need to be physically and thermally secure. The connection between the electrical components and the heat sinks also needs to be uniform and easily repeatable. Failure to have a uniform and repeatable connection between the electrical components and the heat sinks can result in thermal hot spots in the components. These hot spots can ultimately lead to premature failure of the individual components which in turn adversely affect the operability of welding-type device and can also lead to damage of other components of the welding device. To prevent the propagation of the hot spots, and in turn protect the life expectancy of the electrical components, such electrical components need to be in constant and secure contact with a heat sink.
Additionally, the components that generate excess heat and need to be attached to a heat sink are frequently located at different distances from the circuit board as a result of variations in the construction of the individual components. The different distance from the circuit board to the bases of these components have traditionally required that each of the components be attached to separate heat sinks. An electrical assembly that requires the individual electrical components be attached to individual heat sinks presents two significant drawbacks.
The first drawback is that such a construction increases the time and cost associated with manufacturing and assembling the welding-type devices. The second drawback of having multiple independent heat sinks is that such a construction transfers stresses to localized portions of the circuit board. Heat sinks are generally large and comparatively heavy components of the electrical assembly. Having multiple heat sinks allows the circuit board to flex along several axes. Flexing of the circuit board can result in damage to the circuit traces contained thereon.
Another consideration of any circuit board assembly is the method of connection employed in connecting the individual electrical components to the board. The electrical components can be mechanically and electrically connected to the board through a variety of methods. These methods of connection include hand soldering, mechanical connectors, and wave soldering, to name a few. Of these methods, the most preferable method of connecting electrical components to a circuit board is by wave soldering. This method yields a higher quality connection between the component and the circuit board compared to hand soldering and mechanical connections.
Space restrictions are also an important consideration in circuit board assemblies. Heat sinks are comparatively large components of an electrical assembly when compared to other electrical components of the assembly. The size of the heat sink is generally determined by the amount of heat required to be transferred from the respective components mounted thereto. Having the heat sink positioned within a perimeter of the circuit board prevents use of a portion of the circuit board. The portion of the circuit board located between a first electrical component attached to the circuit board and a first heat sink and an adjacent electrical component and the adjacent components respective heat sink is often inaccessible because of the close proximity of the heat sink to the circuit board.
Therefore, it would be desirable to design a system and method capable of attaching multiple electrical components to a circuit board while having the bases of the respective components thermally connected to a common heat sink and maintaining a consistent separation between the electrical components and the cooling flow. Additionally, it would be desirable to simplify the assembly process to have a system that allows for near completion of the electrical assembly prior to attachment of the heat sink to the electrical assembly and prior to attachment of the electrical assembly to a wind tunnel of the welding-type device.
BRIEF DESCRIPTION OF INVENTION
The present invention is directed to a circuit board assembly and method of assembly that solves the aforementioned problems. The present invention provides a system and method for a circuit board assembly preferably used in a welding type power supply having a wind tunnel extending through the housing to allow cooling of the various electrical components and at the same time isolates certain electrical components from particulates that may be carried in the cooling flow. Additionally, the present invention allows the preferred electrical components to be attached to the circuit board prior to attachment of a common heat sink to the circuit board and prior to installation of the circuit board assembly within the housing of the welding type device, which allows wave soldering of these devices to the circuit board. Upon attaching the electrical components to the circuit board, the common heat sink is attached thereto in thermal communication with each of the preferred electrical components.
Therefore, in accordance with one aspect of the present invention, a circuit board configuration in a welder type device includes a common heat sink and a housing having a wind tunnel therein. The wind tunnel has an opening sized to fit the heat sink therethrough. The welding type device includes a circuit board having more than one heat generating device mounted thereon. A plurality of spacers is arranged between the more than one heat generating devices and the circuit board to ensure that the more than one heat generating devices are in proper thermal communication with the common heat sink.
In accordance with another aspect of the present invention, an electrical assembly of a welding device includes a circuit board having a plurality of components connected thereon and a plurality of fastening holes therethrough. The electrical assembly also includes a plurality of sleeves. Each sleeve has an end with a reduced outer diameter that extends through each of the fastening holes of the circuit board. A plurality of fasteners extend through the plurality of fastening holes and sleeves and secures a heat sink to the circuit board via a plurality of threaded holes therein.
In accordance with a further aspect of the present invention, a method of assembling a circuit board assembly is disclosed that includes attaching a
Datskovsky Michael
Illinois Tool Works Inc.
Ziolkowski Patent Solutions Group LLC
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