The present invention relates generally to shielding of electronic components and particularly to shielding of memory media and I/O device containers, and more particularly to shielding of a casing for printed circuit boards that conforms to standards set by PCMCIA, JEDIC, ISO, etc. for peripheral devices.
As computing devices are reduced in size, there is reduced available space for storage devices such as a hard disk drive or an I/O device. In order to expand a portable, laptop, or any other type of computers capacity and functioning capability, manufacturers have devised “plug-in” peripheral cards in the form of printed circuit boards contained within an exterior casing. The Personal Computer Memory Card International Association (PCMCIA) and comparable organizations have established certain size and shape standards for the construction of the peripheral cards. These peripheral cards including associated casings are termed “PCMCIA” style peripheral devices.
The PCMCIA style devices can be used to perform the functions of software, resident memory in hardware devices, or as a hard drive. The devices can be used to facilitate LAN networking and wireless networking, as flash memory, as paging devices, and as FAX modems. They may be used in cellular telephones, PROMS, EPROMS, EEPROMS, RAMS, SRAMS, and DRAMS. The devices can be used in the form of IC cards or memory cards and as I/O cards for computer communication systems.
A conventional PCMCIA style device comprises a pair of metallic top and bottom covers configured to be engaged together, a supporting frame, a circuit board, with mounted electronic components, mounted on the frame, and primary and sometimes secondary electrical connectors. The primary connector is typically referred to as an “I/O” connector. The primary connector is provided on one end of the device for interfacing the memory card, and particularly the printed circuit board contained within the PCMCIA style device, to the outside device to which the PCMCIA style device is mated. The primary connector is designed to extract the contents of the memory stored on the printed circuit board and to bus data to and from an outside device, such as a computer or other electronic device. In this fashion, data traverses the interface between the PCMCIA style device and the outside device so that the data can be efficiently transferred and used by the outside device to which the PCMCIA style device is mated for its intended purpose. In one typical assembly, the circuit board is equipped with the primary and secondary connectors at opposite ends thereof and then attached to the supporting frame before being sandwiched between the top and bottom metallic covers.
At the present time, there are three different PCMCIA style device types, as defined by PCMCIA. The three PC card types are as follows:
A new peripheral card named EXPRESS 34 has been proposed. In addition to the characteristics of the PCMCIA style device, the new peripheral card offers key advantages in terms of faster speed and smaller size. So, devices which connect the EXPRESS 34 and the PCI Express interfaces in notebook computers must have low profile interconnection and also meet the signal integrity requirement of PCI Express.
Examples of peripheral cards are described in U.S. Pat. Nos. 6,824,969; 5,397,857; 5,397,857; 6,004,144 and 6,474,998.
It is well known that electronic signals within electronic packages emit electromagnetic energy from the package, which causes electro-magnetic interference (EMI) in other electric signals. It is desired to provide a complete and efficient shielding against the emission of EMI. On the other hand, electrostatic discharge (ESD) is also another important issue because electronic components are also very sensitive to ESD and special care must be taken in handling. Radio Frequency (RF) interference can also be a problem. However, if the package is properly shielded by a conductive material, it will serve to reduce EMI, RF and ESD problems.
Given the strict thickness limitations of the aforementioned types of electronic devices, and given the desirability of fitting more components and more complex components into electronic devices, the present inventor has recognized the desirability of maximizing the usable inside volume of an electronic device by increasing the usable thickness of an electronic device for working components within the electronic device.
The invention provides an advantageous, space saving shielding arrangement for an electronic component mounted on a circuit board. Although the invention is particularly suited for peripheral devices, such as PC cards, aspects of the invention could also be incorporated generally into the design of shielding for any electronic components mounted on circuit boards. The shielding arrangement of the invention includes a sidewall composed of a plastic or polymer material oriented to be upstanding from the circuit board and surrounding the electronic component to be shielded that is mounted on the circuit board. A first cover portion substantially closes the surrounding sidewall, forming a chamber and enclosing the electronic component on the circuit board.
According to one embodiment of the invention, an electrically conductive sidewall layer or film covers an inside surface of the sidewall. Preferably, a cover portion electrically conductive layer or film also covers an inside surface of the first cover portion in a smoothly continuous fashion with the sidewall conductive layer. Thus, the entire inside surface of the chamber is covered by a conductive layer and the electronic component is shielded.
According to an exemplary embodiment, the first cover portion comprises a stamped metal plate, although a plastic or polymer plate, or other material plate is also encompassed by the invention. The continuous conductive layer comprising the sidewall conductive layer and the cover portion conductive layer increases the effective shielding whether or not the first cover portion is a conductive metal plate or a nonconductive plastic plate.
According to another aspect of the invention, when the first cover portion comprises a stamped metal plate, the sidewall is integrally molded with, or over molded on, the metal plate. In this regard, the stamped metal plate can have a plurality of holes therethrough, and the sidewall is molded through the holes to integrate the metal plate to the sidewall.
The invention disclosure provides an effective method of manufacturing a shield for an electronic component. The method includes the steps of: providing an enclosure having a surrounding sidewall and a first cover portion; and depositing a layer of electrically conductive material on at least an inside surface of the sidewall.
The step of depositing can be further defined in that the layer is deposited continuously on both the inside surface of the sidewall and on an inside surface of the first cover portion to effectively cover the entire inside surface of the enclosure.
Also, according to an exemplary method of the invention, the step of depositing the electrically conductive layer is a metal vacuum deposition method. According to such a method, the steps include: placing the enclosure into a chamber; arranging a supply of a metal within the chamber; heating the supply of the metal; evacuating the chamber; and depositing the conductive layer continuously on the inside surface of the surrounding sidewall and an inside surface of the first cover portion.
According to an exemplary method, the step of providing an enclosure is further defined by the steps of: providing a stamped metal plate; inserting the stamped metal plate into a mold; injecting molten polymer or plastic into the mold to form the surrounding sidewall; allowing the molten polymer or plastic to harden to integrate the sidewall with the stamped metal plate.
Once the frame and first cover portion are integrated and the conductive layer is applied to the frame and the first cover portion, the frame and the first cover portion can be applied to a circuit board in accordance with another advantageous aspect of the preferred method of the invention. The method includes the steps of: arranging a conductive adhesive continuously between facing surfaces of the sidewall and the circuit board; placing the enclosure onto the circuit board; and allowing the adhesive to cure to fix the enclosure to the circuit board.
One aspect of the invention includes the provision of a complete electronic device. The electronic device includes a circuit board and an electronic component, such as an integrated circuit or computer chip, mounted to the printed circuit board, a first frame, a first cover portion carried by the first frame, a second frame, and a second cover portion carried by the second frame. Particularly, the electronic component is mounted to a first side of the circuit board. The first frame is composed of a plastic or polymer material and secured around its perimeter to the first side of the circuit board. The first frame comprises a plurality of longitudinally arranged rails and laterally arranged rails defining at least one closed perimeter in the plane of the circuit board that surrounds the electronic component on the circuit board. The first cover portion carried by the first frame closes at least one closed perimeter to form a chamber. A layer of conductive material is adhered to and covers an inside surface of the chamber. The second frame is secured around its perimeter to an opposite side of the printed circuit board, and comprises a plurality of longitudinally extended rails and laterally extending rails partly defining a perimeter of the second frame. The second cover portion carried by the second frame closes the bottom frame.
Preferably, the first cover portion is composed of a conductive material.
Preferably, the first frame is adhesively secured to the first side of the circuit board with electrically conductive adhesive.
Preferably, the first frame comprises a plurality of closed perimeters in the plane of the circuit board, each of which surrounds one or more electronic § components mounted on the circuit board. The first portion closes the plurality of closed perimeters to form chambers. Each of the chambers is sealed to the circuit board by conductive adhesive. Each of the chambers, where shielding is desired, includes a conductive layer covering an entire inside surface of the chamber.
Preferably, the first frame and the second frame each comprise a stepped shoulder surface for fitting against an outer edge region of a respective side of the circuit board, and an outer surface located outside of a perimeter of the circuit board. The respective outer surfaces of the first and second frames are in abutting relationship to each other when the circuit board is fit between the first frame and the second frame with the respective outer edge regions abutting the respective stepped shoulder surfaces. The facing surfaces are secured preferably by a fast adhering means, such as by plastic welding, heat setting adhesive or fast curing adhesive for holding the first frame, the circuit board, the second frame, the first portion and the second portion together as a unit. This fast securing means holds the assembly together while allowing the conductive adhesive to cure for a longer period of time.
Advantageously, the device can include at least one second electronic component mounted on the second side of the printed circuit board. The second frame can be composed of a plastic material, and comprise longitudinally arranged rails and laterally arranged rails that define at least one second closed perimeter in the plane of the circuit board that surrounds the at least one second electronic component on the circuit board. The second cover portion closes the at least one closed perimeter to form a second chamber. Preferably, a second layer of conductive material covers the inside surface of the second chamber. Preferably, the second cover portion also comprises a conductive material.
Preferably, the first cover portion and the second cover portion each comprise stamped metal plates. Each stamped metal plate has formations for integrating the stamped metal plate with the respective first and second frames when the first and second frames are over molded with the metal plates. Preferably, the formations comprise a plurality of spaced-apart holes through the stamped metal plates. Preferably, the stamped metal plates comprise elongated trough regions corresponding in extent to the longitudinally extending rails and the laterally extending rails of the respective frames. At least one of the trough regions has the spaced-apart holes therethrough. When the first and second frames are over molded onto the stamped metal plates, the first and second frames are formed through the spaced-apart holes and fill the trough regions.
Advantageously, the second frame can be configured identically to the first frame, and the second cover portion can be configured identically with the first cover portion. However this is not required as the opposite sides of the electronic device can have different component layouts and different shielding provisions.
Generally, the invention provides a shielding device for any circuit board. The shielding device includes at least one sidewall defining a closed perimeter. The closed perimeter comprises an open first face having a facing surface to be secured to a circuit board. The shielding device includes a first cover portion carried by the sidewall and closing an opposite second face of the closed perimeter, forming a chamber that is closable by being secured to a circuit board. The invention includes a conductive inside surface of the chamber. The sidewall can be composed of a plastic material. The sidewall can be molded. The sidewall can be composed of a non-conductive material with a conductive layer adhered thereto or can be composed of a conductive plastic. The first cover portion can compose a conductive material, metal or plastic, or can be a nonconductive layer adhered thereto.
Preferably, a frame defines a plurality of closed perimeters, each of the closed perimeters comprising an open first face having a facing surface to be secured to a circuit board. A plurality of first cover portions are carried by the frame and are arranged to close opposite second faces of the plurality of closed perimeters, forming a plurality of chambers each closable by the frame by being secured to a circuit board. Each chamber sidewalls and cover portion are made conductive.
Preferably, the plurality of first cover portions are formed on a single stamped metal plate. The stamped metal plate can be formed with troughs which correspond in position to portions of some of the plurality of closed perimeters of the frame. The troughs include spaced apart openings through the stamped metal plate. The frame is formed through the openings and fills the troughs to integrate the stamped metal plate with the frame. Alternately, the cover portions can have bent tabs which correspond to a portion of the closed perimeter or an interior frame wall. The tabs can be integrated with the frame by molding.
The various aspects and embodiments of the invention demonstrate the advantages of providing a cover portion and sidewall of an electronic device that includes a conductive inside surface to provide shielding for an electronic component. According to one aspect, a separate shielding element mounted beneath a device cover plate can be eliminated. A significant vertical space and lateral space can be saved to allow more room for functional electronic components. Furthermore, by compartmentalizing the device cover and frame, the casing becomes more rigid with reduced unsupported longitudinal and lateral spans across the cover. Unsupported, lengthy longitudinal and lateral spans across the cover can be more susceptible to force-induced deflection. Such deflection can lead to faults, shorts and damage to internal components.
Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.
While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated.
The top cover 12 includes a longitudinally extending trough 54, a first laterally extending trough 58 and a second laterally extending trough 62. The longitudinally extending trough 54 intersects the laterally extending trough 58. The troughs 54, 58, 62 are substantially the same depth. The side edges and the end edge of the cover 12 are turned down to a depth equal to the depth of the troughs 54, 58, 62, forming side ledges 66, 68 and an end ledge 72.
The bottom cover 14 can have a raised plain wall as shown in
The longitudinally extending intermediate rail 38 is integrated with the trough 54 by the rail 38 being formed above and below the trough 54 and filling the trough 54 and the holes 82. The rails 46, 48 are integrated with the troughs 58, 62 respectively in the same fashion as the rail 38 is integrated with the trough 54, by being formed above and below the troughs 58, 62 and filling the troughs 58, 62 and the holes 82 therethrough.
The bottom frame 22 can be a raised plain frame as shown in
In the present specification, the term conductive refers to being electrically conductive.
The side rails 34, 36 and the end rail 42 (not shown) of the upper frame 18 all include a stepped recess 120 for receiving a top edge portion of the circuit board 20. The side rails 76, 78 and the end rail 80 (not shown) of the bottom frame 22 all include a stepped recess 124 for receiving a bottom edge portion of the circuit board 20 in the same fashion. An electrically conductive adhesive 128 is applied between the surfaces 120 and 124 and the circuit board 20. Preferably, the electrically conductive adhesive 128 is applied between all of the rails 34, 36, 38, 42, 46, 48 and the circuit board. Electrically conductive adhesive 128 is applied between the rails 76, 78, 80 and the circuit board 20. If further longitudinal and lateral rails are provided on the bottom frame, electrically conductive adhesive is applied between such rails and a bottom surface of the circuit board. The side rails 34, 76, the side rails 36, 78 and the end rails 42, 80 provide facing surfaces 132, 134 outside the outer perimeter of the circuit board. The facing surfaces 132, 134 are secured together by a fast setting securing means such as a plastic weld, a sonic weld, a fast setting adhesive, a thermally setting adhesive, or the like, all indicated as the layer 136.
The rails 34, 42, 38, 46 create a closed perimeter in the plane of the circuit board which is then closed at a top face by the cover 12, forming a chamber 142. The conductive layers 110, 116 cover the inside surfaces of the rails 34, 42, 38, 46 and the inside surfaces of the cover 12. By the conductive layer being adhered to, and covering, the inside surface of the chamber 142, the chamber 142 forms an effective shielding for one or more electronic components 28 within the chamber 142. Likewise, the rails 38, 42, 36, 46 and cover 12 form a chamber 144. The conductive layers 110, 116 cover the inside surfaces of the rails 38, 42, 36, 46 and the inside surfaces of the cover 12. The conductive layer 110, 116 adhered to, and covering, the inside surface thereof forms an effective shielding for electronic component 28 within the chamber 144. The rails 34, 46, 36, 48 and the cover 12 form a chamber 146. The conductive layer 110, 116 adhered to, and covering, the inside surface thereof forms an effective shielding for electronic component 28 located within the chamber 146.
Thus, electronic components can be arranged within these separate shielded chambers 142, 144, 146 without the need for individual shields for electronic components to be applied within beneath the cover 12.
The conductive adhesive 128 beneath the shielded chambers can be arranged to make contact with a ground contact on the circuit board.
Although laterally and longitudinally extending rails and troughs are illustrated and described which form the closed perimeters for forming shielding chambers, the invention also encompasses curved rails, circular rails portions, or other shapes that can define a closed perimeter. The invention is not limited to longitudinally and laterally extending rails to form the closed perimeters.
Likewise, shielded chambers can be formed on a bottom side of the circuit board 20 utilizing the frame 22, the cover 14 and additional rails and troughs, and an inside surface conductive layer.
Materials of construction for the electronic device could be polycarbonate or a polycarbonate/ABS blend for the frames 18, 22; conventional sheet metal for the stamped metal covers 12, 14; and nickel, copper, aluminum or other conductive material for the inside conductive layer 110, 116.
Also, by compartmentalizing the top cover 12 with the troughs 54, 58, 62, and the upper frame 18 with the rails 38, 46, 48 the lateral and longitudinal unsupported span of the cover 12 is significantly reduced. Forced deflection by a pressing force on the cover 12 is reduced compared to the prior art cover having substantially unsupported width and length. Therefore, an electrical fault or short between the cover and an internal component is less likely to occur due to a pressing down of, and a deflection of, the cover 12.
The particular details of vacuum deposition methods and apparatus are well known, such as disclosed in U.S. Pat. Nos. 4,022,928; 4,306,515; 4,777,908; 6,274,014; and 6,855,236, herein incorporated by reference.
As shown in
The cover 220 is integrally molded with the frame 226. Frame material encapsulates the surrounding sidewall 232 inside and out, as shown in
The frame material is composed of electrically conductive plastic. Such plastic typically includes an electrically conductive additive. The cover can be a cold rolled steel or other electrically conductive metal.
To form the shield 200, first the cover 220 is stamped forming the top plate 234, the side wall 232 with holes 236 and the tabs 240 in a flat plane. Next, the flat plane is bent into the shape of the cover 220 having downwardly bent sidewall 232 and downwardly bent tabs 240. The sidewall 232 can be discontinuous at each corner due to the process of forming the sidewall 232. Next, the cover 220 is placed into a mold having a cavity that is shaped corresponding to the extent and contours of the desired frame 226. Molten electrically conductive plastic is injected into the cavity to form the frame 226 integrated with the cover 220.
From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred.
This application claims the benefit of U.S. Provisional Application 60/771,247 filed Feb. 8, 2006, and is a continuation of U.S. Ser. No. 11/702,729 filed Feb. 6, 2007.