Patent Application
20080101037
Herein, related art may be discussed to put the invention in context. Related art labeled “prior art” is admitted prior art; related art not labeled “prior art” is not admitted prior art.
Many components of printed-circuit (PC) boards such as microprocessors and voltage regulators generate heat during operation. Heat can damage devices, impair their performance, and create a fire or explosive hazard. Heat sinks can be used to conduct and radiate heat from a device. A thermal adhesive can be used to affix the heat sink to the device, but this can be problematic for disassembly. To allow for disassembly, thermally conductive paste can be applied between the device and heat sink and a clamping mechanism or screws can be used to hold the heat sink against the device.
The screws or clamping mechanism typically require holes to be drilled through the PC board. The various conductors in the layers of the PC board must be routed around where the holes are to be formed. The present invention addresses this constraint on PC board conductor layouts. These and other features of the present invention are apparent from the description below with reference to the following drawings.
The following drawings are of an embodiment of the invention and not of the invention itself.
The present invention uses surface-mount technology to fix attachment structures to a PC board. The attachment structures are used to attach a retention device that can extend over a heat sink or other object to secure its position over a PC board. Since the attachment structures are surface-mounted, no holes are required through the PC board, simplifying layout of its conductive layers.
A computer AP1 includes a processor 101, memory 103, and input/output devices 105. Processor 101 is mounted on a PC board 107. In practice, PC board 107 can be a daughterboard mounted on a motherboard of computer AP1. A heat sink 109 is mounted on processor 101 on the side of processor 101 opposite PC board 107. A layer of thermal grease 111 ensures good thermal contact between processor 101 and heat sink 109. In alternative embodiments, heat sinks or other objects can be mounted on voltage regulators or other heat-generating devices in accordance with the invention.
Surface mount pads 113 are provided on PC board 109 adjacent opposing sides of processor 101. Hooks 115 are soldered to these pads, with the hook ends directed away from processor 101. In alternative embodiments, the hooks have other orientations. The solder forms separate “islands” 117 rather than a continuous binding layer. Such islands are conventionally used for integrated circuit devices to maintain electrical isolation between connect pins. There is no such requirement for hooks 115, but the islands serve to prevent stress fractures from propagating across the hook base. Thus, a more reliable attachment is provided for hooks 115; this is important given that the hooks can be stressed by the heat sink mass. A bale wire 119 is attached to both hooks 115 so that it contacts heat sink 109, securing its position over processor 101. In alternative embodiments, another form of strap or another type of retention device is used instead of the bale wire.
One of hooks 115 is shown in greater detail in
The present invention provides for a method 300 in which hooks or other attachment structures are surface mounted to a PC board at method segment 302. The hooks can be located and placed by current “pick and place” machinery and be secured by current solder attach methods. At method segment 304, a heat sink or other object is positioned, e.g., mounted on a processor. At method segment 306, a bale wire is attached to the attachment structures so that it contacts the heat sink and secures its position relative to the PC board.
The invention provides for many types of modifications. “Computer” herein encompasses not only general-purpose computers, but servers including multiprocessor servers, and various other devices that include embedded computers such as communications devices, appliances, medical devices, electronic “gadgets”, etc. The object to be attached can be a heat sink or any other object that needs to be attached to another object on a PC board. Where a heat sink is being attached, the underlying object can be a processor (single core or multicore), or other heat-generating integrated circuit, a power device, such as a voltage regulator, or an electro-magnetic interference (EMI) fence.
The attachment structures can be hooks, loops, or other formations suitable for attachment by a bale wire or other form of strap. Alternatively, a bridge can be formed between two, e.g., matching, solder pads. The attachment structure can be made of a single or multiple materials including metal and/or ceramic. For example, the hook can be entirely of metal, or the base and hook can be of different materials. The attachment structure can be of various heights, and diameters.
Additional hooks and straps can be used to further secure a heat sink or other object. For example, two straps (using two sets of hooks) can be arranged orthogonally to constrain movement parallel to the PC board. Also, additional hooks can provide parallel straps or wires for better securing a heat sink or other object. These and other variations upon and modifications to the illustrated embodiment are provided for by the present invention, the scope of which is defined by the following claims.
