Cover apparatus for dissipating heat and shielding electromagnetic interference

[0002] 1. Field of Invention

[0003] The invention relates to a cover apparatus and, in particular, to a cover apparatus for wireless local area network (WLAN) cards.

[0004] 2. Related Art

[0005] The electronic information industry has prospered in recent years. The use of many electronic information products also become popular. With the trend of compactness, the unnecessary voltage or current among internal systems of the products generates enormous broadband noises, which seriously affect the functions of the device. This phenomenon is generally referred as electromagnetic interference (EMI). The EMI problem inside the computer is very complicated. The interference sources include the central processing unit (CPU), motors, inverters, relays, switches, transistors, amplifiers, power supplies or other alternate circuits.

[0006] Generally speaking, to solve the EMI problem in electronic information products such as the wireless local area network (WLAN) cards, a conventional way is to use an electromagnetic (EM) shielding material to absorb or shield the EM waves. The shielding of electric field is done by disposing an electric field shielding material between two regions. The separate charges in the electric field shielding material produces a shielding effect, preventing the electric field in one region from propagating to the other. Under a high-frequency electric field, one may use materials with larger permittivity, such as metals, to make a plate cover to enclose electronic elements to be protected.

[0007] In the WLAN standards IEEE 802.11, the IEEE 802.11a transmission speed can reach as high as 54 Mbps so that it can have wider applications. IEEE 802.11a can effectively reduce multiple path attenuation and select the 5.4 GHz bandwidth with less interference. These advantages are superior to the currently used 802.11b standards (which uses a bandwidth of 2.4 GHz and has a transmission speed of 11 Mbps). Along with the advance in production techniques and the demands for larger bandwidths and higher speeds, IEEE 802.11a is seen as the high-speed WLAN standards in the next generation.

[0008] However, since the IEEE 802.11a transmissions speed and bandwidth are higher than those of IEEE 802.11b, the broadband chip for the IEEE 802.11a standards has a higher power consumption. Poor heat dissipation often affects the operation of the broadband chip. Moreover, such high-frequency electronic devices need a cover apparatus to prevent the EMI problem. Currently, conventional metal plate cover apparatuses can only shield the EM field and cannot simultaneously provide good heat dissipation.

[0009] An objective of the invention is to provide a cover apparatus for plug-in interface cards to simultaneously provide good heat dissipation and prevent EMI.

[0010] Pursuant to the above objective, the disclosed cover apparatus contains a plate, which secures on a circuit board of a plug-in interface card. The plate has at least one concave corresponding to a chip. The concave directly or indirectly contacts the chip to dissipate heat. The cover apparatus also comprises a fastener to secure the plate on the circuit board. By the concave and the fastener, the plate is able to not only shield electromagnetic interference (EMI) but also dissipate heat from the chip.

[0011] According to a preferred embodiment of the invention, the fastener secures the plate on the circuit board using nuts and bolts. A clip device and sidewalls are further employed to enhance the fixing of the plate on the circuit board, providing better EMI shielding. The material of the plate, the fastener, the clip device, and sidewalls is a metal or conductive plastic. In addition, a thermal conductive material can be disposed between the concave and the chip-contacted surface, enhancing the thermal conductivity in between.

[0012] In addition to EM shielding, the disclosed cover apparatus further utilizes the concave and the fastener to achieve heat dissipation. The invention uses several devices to secure the plate onto the WLAN card, which do not only prevent bad EM shielding and heat dissipation due to ill-assembly but also avoid the exposure of electronic components to protect the WLAN card.

[0013] These and other features, aspects and advantages of the invention will become apparent by reference to the following description and accompanying drawings which are given by way of illustration only, and thus are not to be limiting of the invention, and wherein:

[0014] FIG. 1A is a schematic view of a preferred embodiment of the invention;

[0015] FIG. 1B is a schematic view of the assembled apparatus in FIG. 1A; and

[0016] FIG. 1C is a schematic view of another preferred embodiment of the invention.

[0017] To improve the function of the cover apparatus in the conventional WLAN cards, the invention proposes a cover apparatus with the functions of heat dissipation and EMI shielding.

[0018] With reference to FIG. 1A, the circuit board 110 of the IEEE 802.11a WLAN card has a chip 104 producing much heat and another chip 106 producing even much heat. The plate 100 of the invention covers the chip 104 and the chip 106 on the circuit board 110 and has sidewalls 120. The sidewalls 120 extend a certain distance from the border of the plate 100 toward the chips by substantially 90 degrees, covering the peripheral area of the circuit board 110.

[0019] The position on the plate 100 corresponding to the chip 104 has a concave 102. To enhance the heat transmission effect, the lower surface of the concave 102 can directly touch the surface of the chip 104. A thermal conductive material such as the thermal conductive grease can be applied between the surface of the chip 104 and the plate 100 to lower the thermal contact resistance in between.

[0020] According to a preferred embodiment of the invention, the circuit board 110 of the WLAN card is further installed with bosses 108 and fencings 112. The bosses 108 are installed near the chip 106. As shown in FIG. 1B, screws 118 are used to fasten the plate 100 on the circuit board 110 through the screw holes 108a. Securing the plate 100 on the circuit board 110 can increase the stress between the plate 100 and the chip 104, thereby decreasing the thermal contact resistance between the plate 100 and the chip 104. Accordingly, the heat dissipation efficiency can be greatly increased.

[0021] The fencings 112 and the sidewalls 120 can be tightly combined together. In addition to increasing the electromagnetic interference (EMI) shielding effect, they also have the function for fastening the plate 100. In the current embodiment, the plate 100 further contains a engaging mechanism 114, which secures the plate 100 onto the circuit board 110 via the opening 114a. The engaging mechanism 114 is an L-shape structure installed along the peripheral of the plate 100 and having a first segment and a secondsegment The first segment of the engaging mechanism 114 is connected to the plate 100 and goes through the opening 114aon the circuit board 110, so that the second segment reaches the other surface of the circuit board 110 to assembly the plate 100 and the circuit board 110. The plate 100, the engaging mechanism 114, and the sidewalls 120 can be formed as a whole in one manufacture process to reduce the production cost.

[0022] According to a preferred embodiment of the invention, the plate 100, the bosses 108, the fencings 112, and the screws 118 are made of thermal conductive metals, such as copper and aluminum, or plastics that are both thermal and electric conductive, such as graphite fibers. All of them can provide well EMI shielding. The plate 100 is formed with several through holes 122. The heat produced by the chips is dissipated via fluid convection. Aside from the configuration introduced in the above-mentioned embodiment, the bosses 108 can be installed on the plate 100 too, as shown in FIG. 1C. The screw holes 108aare installed close to the chip 106. The screws 118 go through the screw holes 108aand grasp inside the bosses 108, securing the plate 100 onto the circuit board 110. Therefore, as long as the bosses 108 are close to the chip 106 to push the chip 106 and the plate 100 together, the thermal conductive resistance can be reduced to increase heat dissipation.

[0023] From the above preferred embodiment, one sees that the invention has the following advantages:

[0024] 1. In addition to the EMI shielding effect, the cover apparatus of the invention uses its concave and fastener to achieve heat dissipation. The lower surface of the concave directly or indirectly touches the chip to dissipate its heat. Moreover, a thermal conductive material, such as thermal conductive grease, can be disposed between the lower surface of the concave and the chip to enhance heat dissipation. The lower surface of the concave and the chip can be in direct contact to reduce the heat resistance. The screws and the bosses are installed near the chips to press the chips tightly against the plate. In this manner, the heat produced by the broadband chip with another standard can be dissipated efficiently.

[0025] 2. The invention uses several devices to assembly the cover apparatus and the WLAN card. In addition to avoid poor EMI shielding and heat dissipation effect due to the ill-assembly of its components, the invention can further prevent the electronics from being exposed to the environment, thereby protecting the circuit board.

[0026] 3. The disclosed cover apparatus can be applied to the WLAN card that requires good heat dissipation. Therefore, such WLAN cards can be used in personal computers, portable computers, WLAN equipment and wireless network access points.

[0027] Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.