Aluminum EMI/RF shield with fins

A shield made from aluminum (AL) or an aluminum-based alloy coated with a solderable plating such as nickel or tin provides thermal improvement over existing shielding materials. The shield for electronic components on a circuit board comprising a base having an upper surface and one or more sidewalls extending from a perimeter of the upper surface, the sidewalls configured to engage a fence of the circuit board, and a fin array attached to the upper surface of the base, the fin array having a plurality of stackable fins, each of the stackable fins having a wall and one or more engagement tabs extending from one or more edges of the wall, the engagement tabs interlocking the plurality of stackable fins together.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an EMI/RF shield for circuitry on a circuit board and more particularly an EMI/RF shield comprised of aluminum or an aluminum-based alloy and plated with a solderable material and fins.

Related Art

Traditional EMI/RF shielding materials include but are not limited to nickel silver, tin plated cold rolled steel or SPTE, stainless steel, brass, or phosphor bronze materials which are good for formability and EMI/RF shielding but are poor from a thermal performance perspective or cost prohibitive for a shielding application.

One piece shields are typically used on thin devices where the height is a concern and replaceable lids cannot be used due to height restrictions. One piece shields are also used for cost saving solutions when compared to two piece shields. Two piece shielding solutions are generally used for reworkability and are typically higher cost.

SUMMARY

A shield made from aluminum (AL) or an aluminum-based alloy coated with a solderable plating such as nickel or tin provides thermal improvement over existing shielding materials. Plated aluminum offers enhanced thermal performance while also offering a significant weight reduction when compared to commonly used shielding materials. Due to the higher thermal conductivity of aluminum and the ability to solder the shield directly to the board, the shield will also transfer heat from the top surface down the shield side walls and “dump” the heat into the circuit board. Heat transfer is enhanced with the use of fins attached to the surface of the shield to transfer heat away from the device offering a lower operating temperature improving device life and reliability.

DETAILED DESCRIPTION OF THE INVENTION

An EMI/RF shield is made of aluminum or an aluminum-based alloy to take advantage of the thermal performance of aluminum. To allow for soldering, the aluminum material is plated with a solderable material such as nickel or tin.

FIG. 1is a side view of a heat shield made of aluminum or an aluminum-based alloy, generally indicated at10. The shield lid10is attached to a fence9which is attached to a circuit board and surrounds circuitry. Other ways of attachment of the shield10to a circuit board circuitry are considered to be written within the scope of this disclosure. The shield10includes an upper surface20and may include one or more side walls30, forming a lid that can be positioned over a circuit to provide for electromagnetic interference and radio frequency shielding. For example, the shield could have four walls and a top wall to form a five-sided lid. A benefit of using aluminum or an aluminum-based alloy is the enhanced thermal performance and weight reduction as compared to other shielding materials. Because of the thermal conductivity of the aluminum, the shield transfers heat from the top surface down the side walls of the shield and can dump the heat into the circuit board where it is dissipated.

FIG. 2is a perspective view showing two fences9on a circuit board8with shields lids10attached to the fences9. All of the shields discussed herein could be one or two piece shields that could be attached to circuit boards by attachment to fences or in other ways known in the art. The shield can be attached to the fencing in any way known in the art, such as by soldering. The attachment can be snap down or as otherwise know in the art. The shields10include top wall20and side walls30. The shields lids10are made of an aluminum or aluminum-based alloy plated with a solderable material such as nickel or tin. The fence9can be made of aluminum or an aluminum-based alloy plated with a solderable material such as nickel or tin to permit soldering of the shield. The aluminum containing shields disclosed herein can be manufactured in accordance with what is known in the art in connection with manufacturing shields of conventional shielding materials. The aluminum material can be plated with nickel, tin or another solderable material before or after being formed into a lid configuration.

FIG. 3is a perspective view showing a one piece shield10A that could be made of aluminum or an aluminum-based alloy that can be attached directly to a circuit board. The shield10A includes top wall20A and side walls30A. The shield10A is made of aluminum or an aluminum-based alloy plated with a solderable material such as nickel or tin to permit soldering of the shield directly to the circuit board. The fence9are made of aluminum or an aluminum-based alloy plated with a solderable material such as nickel or tin to permit soldering of the shield. The aluminum containing shields disclosed herein can be manufactured in accordance with what is known in the art in connection with manufacturing shields of conventional shielding materials. The aluminum material can be plated with nickel, tin or another solderable material before or after being formed into a configuration with side walls. The shield could be peelable or non-peel. If it is a peel shield and if it is re-worked and the lid is removed, the fence is left behind attached to the board requiring a replacement lid that snaps on the existing fence.

FIG. 4shows a shield generally indicated at110attached to a fence9. The shield has a top wall120and may have one or more side walls130. The shield includes heat dissipating fins generally indicated at140attached to the top wall. The fins140can be soldered to the top wall120of the shield110. The fins can be made of the same material as the shield, e.g. aluminum or an aluminum-based alloy that can be plated with nickel, tin or other solderable material. Of course the fins can be made of an entirely different material than the shield, such as a conventional non-aluminum material, if desired. The fins can be shaped as desired in accordance with what is known in the art. The fins could be plated with a solderable material before or after the fins are shaped into final form. As shown inFIG. 4, fins140can have a series of valleys142for contact to and solderable connection with the top wall120of shield110. The fins140can have a plurality of upstanding walls144and tops146connected between upstanding walls. Upstanding walls144can have further heat dissipating features such as further fins148to provide greater surface area for increased heat dissipation.

FIG. 5is a perspective view of the shield with fins shown inFIG. 4. As discussed with respect toFIG. 3, the shield110includes a top120and may include side walls130. The shield110is attached to fence9on a circuit board. Fins140include a series of valleys142wherein the fins140can be soldered to the top wall120, a plurality of upstanding walls144and a plurality of top surfaces146which interconnect adjacent upstanding walls144. Further, upstanding walls144may include further heat dissipation features such as additional fins148.

FIG. 6is a perspective view of another aluminum or aluminum-based shield with fins. The shields210includes a top wall220and may include side walls230. The shields210are attached to fences9on a circuit board8. Fins240include a series of valleys242that can be soldered to the top wall220, a plurality of upstanding walls244and a plurality of top surfaces246which interconnect adjacent upstanding walls244. As shown, the upstanding walls244can be configured to extend at right angles with respect to the top wall220.

FIG. 7is a perspective view of another aluminum or aluminum-based shield with fins. The shield310includes a top wall320and may include side walls330. The shield310is attached to fence9on a circuit board. Fins340include a series of valleys342wherein the fins340can be soldered to the top wall320, a plurality of upstanding walls344and a plurality of top surfaces346which interconnect adjacent upstanding walls344. As shown, the upstanding walls344of fins340can be configured to extend from the top wall at an angle other than a right angle from the top wall320. Further, upstanding walls344may include further heat dissipation features such as additional fins348.

The shields disclosed herein can be: single piece shields that are non-peelable or non-reworkable; single piece shields that are peelable/reworkable; two piece shields including a fence and lid both made using plated aluminum; two piece shields including a fence and lid, one component of which is plated aluminum (typically the lid) (the fence could use nickel silver, cold rolled steel or plated stainless steel); and two piece shields with soldered pre- or post-plated aluminum or copper (not limited to material selection) fin stock soldered to plated lid surface.

Low profile/low power devices such as mobile handsets, tablets, thin laptops may use either a one or two piece shield solution without soldered fin stock to the lid offering a thermal advantage over commonly used nickel silver and cold rolled shields.

High power applications such as RF modules, processor modules which typically are found in larger case structures (e.g. server chassis, wireless modems, set top boxes or cable boxes) which are typically force convection cooled. These devices can use plated fin stock to offer additional thermal improvement when used with the base plated aluminum fence and lid. Fin stock (formed, folded, stamped, etc.) is soldered to the top surface of the EMI/RF shield lid increasing thermal performance.

FIGS. 8-12are views of a shield with a fin array. More specifically,FIG. 8is a top perspective,FIG. 9is a bottom perspective,FIG. 10is a right side view,FIG. 11is a rear view, andFIG. 12is a top view of the shield410. The shield410includes an upper surface420and fin array438. The upper surface420may include one or more sidewalls430, that depend from a perimeter of the upper surface420. The sidewalls430could be continuous, or could have gaps to facilitate mounting. Further, the sidewalls430could include one or more inwardly protruding dimples432that could engage the outer surface of a fence, such that the shield410is secured to the fence and positioned over a circuit to provide electromagnetic interference and radio frequency shielding. The inner surface of sidewalls430of shield410could be sized to fit over (e.g., engage) the outer surface of a fence thereby allowing the dimples432to engage the outer surface of the fence. Alternatively, the shield410could engage the fence without the dimples432. Attachment of the shield410to the fence could by a friction fit, or welding, or other attachment.

The fin array438could be attached to the upper surface420of the shield410. The fin array438includes one or more stackable fins440and may include an end fin470. The fin array438could be made up of any number of stackable fins440depending on the heat shielding requirement. The stackable fins440and end fin470are spaced apart at a distance that can vary in accordance with heat shielding requirements. The stackable fins440each include nestable engagement tabs with bendable portions to interlock the stackable fins together. The stackable fins440also include non-engagement tabs which could facilitate interlocking of the stackable fins and/or provide structural support between the stackable fins440.

FIG. 13is a perspective view of a stackable fin440. The stackable fin440includes a generally planar surface or wall446having a top side446a(e.g., first side) and a bottom side446b(e.g., second side), top end tabs442aat first and second ends of the top side, bottom end tabs442bat first and second ends of the bottom side, top and bottom middle tabs444aand444b, top stackable engagement tabs448aon the top side of wall446and bottom stackable engagement tabs448bon the bottom side of wall446. Accordingly, the components of the top side446acould mirror the components of the bottom side446b. The top and bottom end tabs442aand442bcould be rectangular in shape and could extend perpendicularly, or at any other angle, from wall446. Top and bottom end tabs442aand442band top and bottom middle tabs444aand444ball extend in the same direction. Top and bottom middle tabs444aand444bcould be rectangular in shape and could extend perpendicularly, or at any other angle, from wall446. Top and bottom middle tabs444aand444bcould be longer than top and bottom end tabs442aand442b. However, top and bottom middle tabs444aand444bcould extend the same distance from wall446as top and bottom end tabs442aand442b.

Each of the two top stackable engagement tabs448aincludes a body450athat can be trapezoidal in shape and first and second arms452aand456aextend outward to form acute angles θ1with the wall446. The first arm452aincludes a bendable finger454awhich extends outward from the first arm452a. The second arm456aincludes a bendable finger458awhich extends outward from the second arm456a. The bendable fingers454aand458aextend opposite from each other. Similarly, each of the two bottom stackable engagement tabs448bincludes a body450bthat can be trapezoidal in shape and first and second arms452band456bwhich extend outward to form acute angles θ1with the wall446. As described with top stackable engagement tabs448a, the first arm452bincludes a bendable finger454bwhich extends outward from the first arm452b. Second arm456bincludes a bendable finger458bwhich extends outward from the second arm456b. The bendable finger454band458bextend opposite from each other. Each top stackable engagement tab448ais located between the top end tab442aand top middle tab444a. Similarly, each bottom stackable engagement tab448bis located between the bottom end tab442band bottom middle tab444b. Body450aand body450bare shaped to receive a trapezoidal end tab472aor472bof an end fin470(seeFIG. 14).

FIG. 14is a perspective view of an end fin470. The end fin470includes a wall476having a top side476aand a bottom side476b, top end tabs472aat first and second ends of the top side, bottom end tabs472bat first and second ends of the bottom side, top and bottom middle tabs474aand474b, top stackable end tabs478aon the top side of wall476, and bottom stackable end tabs478bon the bottom side of wall476. Accordingly, the components of the top side could mirror the components of the bottom side.

The top and bottom end tabs472aand472bcould be rectangular in shape and could extend perpendicularly from wall476, or at any other angle. Top and bottom end tabs472aand472band top and bottom middle tabs474aand474bcould be rectangular in shape and could extend perpendicularly from wall476, or at any other angle. Top and bottom middle tabs474aand474bcould extend longer (e.g., along the length of the wall) than top and bottom end tabs472aand472b. However, top and bottom middle tabs474aand474bcould extend the same distance from the wall476as top and bottom end tabs472aand472b. Top and bottom stackable end tabs478aand478bcould be trapezoidal in shape and could extend perpendicularly from wall476such that the shorter of the parallel sides of the trapezoid is attached to the wall476. Each angled side of top and bottom stackable end tabs478aand478bforms an acute angle θ2with the surface of wall476. Each top stackable end tab478ais located between the top end tab472aand top middle tab474a. Similarly, each bottom stackable end tab478bis located between the bottom end tab472band bottom middle tab474b.

FIG. 15is a perspective view showing the assembly of one or more stackable fins440of the fin array438. The fins440can be stamped from a sheet of metal (e.g., aluminum), thereby forming a wall446and tabs (442,444, and448) planar with the wall446, the tabs (442,444, and448) can then be bent to be perpendicular with the wall446. The fins440can be attached to the upper surface (not shown) of the shield and interconnected by bending. A first stackable fin440ahaving bendable fingers454′aand458′ain a planar orientation is stacked onto a second stackable fin440having bendable fingers454′band458′bin a planar orientation. The body450′aof top stackable engagement tab448′aof first stackable fin440ais inserted into and past the first arm452′band second arm456′b(and first and second bendable fingers454′band458′b) of a top stackable engagement tab448′bof second stackable fin440b. The bottom edge of the body450′aof the top stackable engagement tab448′aof the first stackable fin440acontacts (or is proximate to) the top edge of the body450′bof the top stackable engagement tab448′bof the second stackable fin440b. A top edge of each stackable engagement tab448corresponds in shape to a bottom edge of each stackable engagement tab448such that the stackable engagement tabs448nest with one another when the stackable fins440are stacked and interlocked together.

FIG. 16is a close-up view of the stackable fins440of the fin array438ofFIG. 15. The edge of the top stackable engagement tab448′aof the first stackable fin440ais nested within the area formed by the body450′a, the first arm452′a, and second arm456′aof top stackable engagement tab448′a. When first stackable fin440ais stacked onto second stackable fin440bthe bendable fingers454′aand458′aof the first stackable fin440aand bendable fingers454′band458′bof second stackable fin440bare all in a planar orientation. Once stacked, bendable fingers454′band458′bof the second stackable fin440bare bent as indicated by the arrows labeled A to engage the wall446aof the first stackable fin440a. Thereby the first stackable fin440ais interlocked with the second stackable fin440bas the wall446aof the first stackable fin440ais sandwiched between bendable fingers454′band458′bof the second stackable fin440band end tabs and middle tabs (e.g., end tab442a) of second stackable fin440b. The angle at which bendable fingers454′band458′bare bent could vary.

FIG. 17is a perspective view showing the assembly of an end fin470to the fin array438. The stackable fins440each include a wall446, top end tabs442a, bottom end tabs442b, top and bottom middle tabs444aand444b, top stackable engagement tabs448a, and bottom stackable engagement tabs448b. As described, the end fin470includes a wall476, top and bottom end tabs472(e.g.,472aand472b), top and bottom middle tabs474(e.g.,474aand474b), and top and bottom stackable end tabs478(e.g.,478aand478b). The tabs (472,474, and478) extend from one or more edges of the wall476in the same direction. Top and bottom stackable end tabs478are trapezoidal in shape to engage with the first and second arms bendable fingers454′aand458′aof the first stackable fin440a. Bendable fingers454′aand458′aof the first stackable fin440aare in a planar orientation. Once stacked, bendable fingers454′aand458′aare positioned (e.g., bent) to a bent orientation to engage the wall476of the end fin470to interlock the end fin470with the stackable fins440. The stackable end tabs478interlock the end fin470with the plurality of stackable fins440by preventing movement (e.g., sliding movement) between the end fin470and the first stackable fin440a. A bottom edge of each stackable end tab478corresponds in shape to a top edge of each stackable engagement tab448of the stackable fin440to nest the stackable end tab478and stackable engagement tab448when interlocked.

FIG. 18shows an assembled view of the fin array438. The fin array438includes a plurality of stackable fins440and an end fin470. The plurality of stackable fins440are stacked and function as described inFIGS. 15-16. As described, the end fin470includes a wall476, top and bottom end tabs472(e.g.,472aand472b), top and bottom middle tabs474(e.g.,474aand474b), and top and bottom stackable end tabs478(e.g.,478aand478b). The bendable fingers454aand458aare in a bent orientation securing end fin470to fin array438, thereby preventing movement of the plurality of stackable fins440. The top edge of the stackable end tabs478are flush with the top edges of the bendable fingers454and458of the first stackable fin440once assembled, engaged, and secured.

The edge of the top stackable end tab478athat connects with the wall476is nested within the area formed by the body450a(not shown), the first arm452a, and second arm456aof top stackable engagement tab448a(not shown).

When end fin470is stacked onto the first stackable fin440the bendable fingers454and458of the first stackable fin440are all in a planar orientation. Once stacked, bendable fingers454and458of the first stackable fin440are bent to engage the stackable end tabs478of the end fin470, thereby preventing movement of the end fin470. The angle at which bendable fingers454and458are bent could vary.

The fin array438can be attached to the upper surface420of the shield on a fin by fin basis as the array438is formed, or the array438can be formed and then attached. The attachment can be by soldering or other known or developed attachment methods.

Having thus described the disclosure in detail, it is to be understood that the foregoing description is not intended to limit the spirit or scope thereof. It will be understood that the embodiments of the present disclosure described herein are merely exemplary and that a person skilled in the art may make any variations and modification without departing from the spirit and scope of the disclosure. All such variations and modifications, including those discussed above, are intended to be included within the scope of the disclosure. What is desired to be protected is set forth in the following claims.