Abstract:
A housing cover to cause electrical components to engage with at least one component pad of a heat sink, the cover including a projection integrally formed from the housing cover and positioned on the cover for biasing the electrical component against the component pad, and a mechanism that permits a vertical displacement of the projection relative to the vertical displacement of the housing cover. In one example, a slot extends around at least part of the projection so as to substantially decouple a vertical displacement of the projection from a vertical displacement of the housing cover.

Description:
BACKGROUND 
   This description relates to methods and apparatus for dissipating heat from electrical components located within a housing. 
   In amplifiers and other electrical devices, various electrical components contained within the device housing generate heat while operating and require cooling for proper operation. In one example, the electrical components are integrated circuits mounted to a circuit board which are cooled by dissipating heat generated to the ambient surroundings. Improved heat transfer and cooling of the electrical components is accomplished by positioning the electrical components proximate to a heat sink. Heat sinks are generally large metallic structures made from a highly heat conductive material, such as aluminum, for example, and include an expansive surface area formed by a number of fins for improved convective heat transfer to the ambient surrounding. The heat sink itself can form the chassis for the electrical device, housing a circuit board populated with electrical components, for example. In particular, amplifiers designed for vehicle audio systems have unique cooling requirements given the typical physical limitations for mounting the amplifier in the vehicle and the relatively high power levels and number of audio channels. 
   As shown in  FIG. 1 , an amplifier  20  includes a heat sink  25  which forms a chassis for supporting the electrical components of the amplifier. The heat sink has cooling fins  30  which extend from at least one surface of the heat sink and a substantially planar housing cover  35 . As shown in  FIG. 2 , with the cover removed from the heat sink, a circuit board  40  includes one or more electrical components. Referring to  FIGS. 3A and 3B , the circuit board supports electrical components  45   a ,  45   b ,  45   c  and  45   d  (collectively  45 ), which may be integrated circuits, for example. The reverse side of the circuit board is shown in  FIG. 3B , with the corresponding locations of the electrical components  45  shown in phantom. The circuit board is disposed in the heat sink such that the electrical components are in substantial contact with component pads  50   a ,  50   b  ( FIG. 5 ). The component pads extend from the heat sink toward the electrical components to provide a conductive thermal pathway for heat dissipation to the ambient surroundings. 
   Referring to  FIG. 4 , housing cover  35  is secured to the heat sink with fasteners extending through screw holes  55  and includes projections  60   a ,  60   b ,  60   c  and  60   d  (collectively,  60 ) and can include a number of ventilation holes  70 . The location of the projections correspond to the location of the electrical components  45  on the circuit board, such that when the housing cover is fastened to the heat sink, the projections  60  engage the electrical components between the component pads  50  and the circuit board. In so doing, resistance to heat transfer from the components to the heat sink is reduced, and the heat generated in the electrical components is more effectively transferred to the heat sink. 
   With reference to  FIG. 5 , two adjacent component pads  50   a ,  50   b  can have different heights, as can the associated projections  60   a ,  60   b , when accounting for stack-up tolerances. When the electrical components  45   a ,  45   b  are adjacent to one another, the associated projections are located adjacent one another. Given the close proximity of projection  60   a  to  60   b  (and similarly,  60   c  to  60   d ), vertical movement of projection  60   a  is strongly coupled to the movement of projection  60   b . Accordingly, if projection  60   a  presses the electrical component  45   a  against component pad  50   a , projection  60   b  will be limited by projection  60   a , as both proximally extend from the same substantially rigid cover. The disparities in height noted above can lead to a gap  63  between electrical component  45   b  and projection  60   b  that interrupt or diminish proper cooling of the electrical components. 
   Attempts to reduce or bridge this gap and improve the cooling of the electrical components include the use of intermediate elements between the electrical component and the component pads such as clips, springs, gels, putty, or foam, for example. Such measures add additional components and cost to the manufacturing and assembly process and may not always maintain sufficient contact between the electrical component and the component pad, which may lead to overheating and failure of the electrical components. 
   SUMMARY 
   In general, in one aspect, the invention features an apparatus including a housing cover to cause electrical components on a circuit board to engage with at least one component pad of a heat sink, the housing cover being substantially coextensive with the circuit board, a projection integrally formed from the housing cover, the projection located on the cover to bias the electrical component against the component pad, and a mechanism that permits a vertical displacement of the projection relative to the vertical displacement of the housing cover. 
   Implementations of the inventions according to this aspect may include one or more of the following features. The mechanism can include a slot extending around at least part of the projection so as to substantially decouple a vertical displacement of the projection from a vertical displacement of the housing cover. The mechanism can also include a cantilevered tab extending from a perimeter of the housing cover. The apparatus can include two or more projections, and in one example, the projections are located proximate each other. The projections can be configured to deflect independently. The apparatus can also include a spanning element extending along the projections to substantially limit the upward vertical displacement of the projections. The spanning element can be integrally formed with the housing cover or, in another example, the attached to the housing cover by riveting, welding, bonding, or any combination thereof. 
   The apparatus can include a spanning lever attached to the first projection and the second projection and to an intermediate pivot positioned between the first and second projections. The spanning lever can bias the second projection against the direction of the displacement of the first projection. In one example, a positive vertical displacement of the first projection causes a proportional negative vertical displacement of the second projection. The spanning lever can be integrally formed with the housing cover or attached to the housing cover by riveting, welding, bonding, or any combination thereof. In one example, the housing cover is substantially planar. The heat sink can be configured for an audio amplifier, and in one example, an audio amplifier for a vehicle sound system. 
   In general, in another aspect, the invention features an apparatus including a housing cover to cause electrical components to engage with at least one component pad extending from a heat sink as well as first and second projections integrally formed from the housing cover and located on the cover to bias the electrical component against at least one component pad. The apparatus also includes a mechanism that permits a vertical displacement of the projection relative to the vertical displacement of the housing cover and a spanning element lever that biases the second projection against the direction of the displacement motion of the first projection. In one example, the housing cover and heat sink are adapted for the specific requirements of an audio amplifier in a vehicle sound system. 
   In general, in another aspect, the invention features an audio amplifier configured for use in a vehicle, the amplifier including a heat sink chassis containing a circuit board and configured for dissipating heat from electrical components positioned on the circuit board to ambient surroundings, a housing cover fitted to the chassis to cause electrical components positioned on a first side of the circuit board to engage with at least one component pad extending from the heat sink chassis, a projection integrally formed from the housing cover, the projection located on the cover to bias a second side of the circuit board opposite the first side, to cause electrical component to engage the component pad, and a mechanism that permits a vertical displacement of the projection relative to the vertical displacement of the housing cover. 
   In general, in another aspect, the invention features a housing cover for a heat sink including a number of projections integrally formed from the cover, the projections located on the cover to cause integrated circuits to engage component pads extending from the heat sink, at least two of the projections being proximate each other and comprising a cantilevered tab extending from a perimeter of the housing cover and configured to deflect substantially independently, a slot extending around at least part of the projection so as to substantially decouple a vertical displacement of the projections from a vertical displacement of the housing cover; and a spanning element extending along at least one projection to substantially limit the upward deflection of the projections. 
   In general, in another aspect, the invention features a housing cover for a heat sink including first and second cantilevered projections integrally formed from the cover and located at positions on the cover for biasing integrated circuits against at least one component pad extending from the heat sink, a slot extending around at least part of the projections so as to substantially decouple a vertical displacement of the projections from a vertical displacement of the housing cover, and a spanning lever attached to the first projection and the second projection and to an intermediate pivot located between the first and second projections such that a positive vertical displacement of the first projection causes a proportional negative vertical displacement of the second projection. 
   In general, in another aspect, the invention features a method of manufacturing a housing cover for an amplifier including integrally forming the cover from a unitary work-piece, where the cover has a projection integrally formed from the housing cover and located on the cover to bias the electrical component against the component pad and a mechanism that permits a vertical displacement of the projection relative to the vertical displacement of the housing cover. 
   Implementations of the inventions according to this aspect may include one or more of the following features. The mechanism can be formed to include a slot extending around at least part of the projection so as to substantially decouple a vertical displacement of the projection from a vertical displacement of the housing cover. The can be formed with a first and second projection proximate each other. The cover can also be formed with a spanning element extending along the projections to substantially limit the upward vertical displacement of the projections. In another example, the cover can be formed with a spanning lever attached to the first projection and the second projection and to an intermediate pivot located between the first and second projections. 
   In general, in another aspect, the invention features a method for engaging electrical components on a circuit board of an audio amplifier with a portion of a heat sink by providing a unitary housing cover that is substantially coextensive with the circuit board to permit a vertical displacement of integrally formed projections relative to a vertical displacement of the housing cover, applying the cover to the amplifier housing, engaging a first electrical component with the component pad by biasing an area on a second side of the circuit board, opposite the first side of the circuit board, and engaging a second electrical component with the component pad by biasing an area on the second side of the circuit board, opposite the position of the second electrical component. 
   Other advantages and features will become apparent from the following description and from the claims. 

   
     DESCRIPTION 
       FIG. 1  is a perspective view of an amplifier, showing the heat sink and housing. 
       FIG. 2  is a perspective view of an amplifier with the housing cover removed revealing a circuit board populated with electrical components. 
       FIGS. 3A and 3B  are plan views of the circuit board of the amplifier of  FIG. 2 . 
       FIG. 4  is a plan view of a housing cover having projection for engaging portions of the circuit board of  FIGS. 3A and 3B . 
       FIG. 5  is a cross-sectional view of the circuit board of  FIG. 4  disposed between the housing cover and component pads. 
       FIG. 6  is a plan view of a housing cover including a number of projections. 
       FIG. 7  is a cross-section view taken along line A–A′ of  FIG. 6  showing adjacent projections engaging adjacent electronic components. 
       FIG. 8  is a plan view of a housing cover including projections and spanning members. 
       FIG. 9  is a cross-sectional view taken along line B–B′ of  FIG. 8  showing a tab with projections. 
       FIG. 10  is a plan view of a housing cover including linkages connecting adjacent projections. 
       FIG. 11  is a cross-sectional view taken along line C–C′ of  FIG. 10  showing two adjacent projections connected with a linkage. 
       FIG. 12  depicts the adjacent projections of  FIG. 11  engaging a circuit board. 
   

   Referring to  FIG. 6 , the housing cover  75  includes screw holes  80  and projections  90   a ,  90   b ,  90   c  and  90   d  extending from slotted tabs  95   a ,  95   b ,  95   c  and  95   d . The cover can also include ventilation holes  85 . The tabs  95  can be attached along a peripheral edge of the cover and separated from the cover along the remaining sides by slots  100   a ,  100   b ,  100   c  and  100   d , which can be U-shaped, for example. This configuration permits a given projection  90  to deflect substantially independently of the other projections and to promote thermal contact of each component pad with the corresponding electrical component. If the housing cover  85  is formed with a stamping process, the projections  90  and tabs  95  can be formed with a change in stamping tools, requiring no extraneous components. 
   Referring to  FIG. 7 , it is shown that the combined height of the component pad  50   a  and electronic component  45   a  is greater than the combined height of the component pad  50   b  and electronic component  45   b  by a distance defined by D 1 . When the housing cover  75  is applied to the circuit board  40 , the height differential D 1  between the electronic components is accommodated by permitting a vertical displacement of the projection  90   a  relative to the vertical displacement of the housing cover  75 . In one example, the projections  90   a  and  90   b  are substantially decoupled from the housing cover  75  and from each other. When the downward vertical travel of projection  90   a  is stopped by electronic component  45   a  contacting component pad  50   a , projection  95   b  continues moving downward until electronic component  90   b  contacts component pad  50   b . Projection  90   a  is cantilevered at a fixed end and separated from the housing cover  75  along slot  100   a . Projection  90   b  is also cantilevered at a fixed end and separated from the housing cover  75  along slot  10   b . Although projections  90   a ,  90   b  each extend from a substantially rigid and level housing cover  75 , projection  90   b  can extend farther than projection  90   a  by a distance given by D 2 . In one example, the distance D 2  is about equal to the distance D 1 . The distances shown in  FIG. 7  are exaggerated for clarity. 
   In another example, three or more electronic components (not shown) each have different heights and are proximate each other. Projections  90  corresponding to the locations of the electronic components first contact the circuit board and bias the electronic component for contact with corresponding components pads. In one example, the projections are formed having a predetermined amount of resistance to deflection for specific applications, based on the position and proximity of the electronic components requiring direct contact with the heat sink and any associated stack-up tolerances, for example. 
   Referring to  FIG. 8 , the housing cover  80  can include spanning elements  105  and  110  extending along the free end of adjacent tabs  95   a  and  95   b  and adjacent tabs  95   c  and  95   d , respectively. The spanning elements  105  can be attached to the housing cover at connections  115   a ,  115   b  and  115   c  and spanning element  110  can be attached to the housing cover at connections  120   a ,  120   b  and  120   c . In some examples, elements  105 ,  110  can be attached by riveting, welding or bonding, for example. In other examples, the elements can be integrally formed with the housing cover. The spanning elements limit the upward deflection of the tabs  95  to a predetermined position. 
   In one example, as shown in  FIG. 9 , the tab  95   c  can deflect about a connected edge  125   c  in the downward direction, but the movement of the tab  95   c  is constrained in the upward direction by the spanning element  110 . As the spanning elements are connected along adjacent tabs, the movement of these tabs is similarly restrained. 
   In another example, as shown in  FIG. 10 , the housing cover  140  has screw holes  145  and slotted tabs  150   a ,  150   b ,  150   c  and  150   d . The cover can include ventilation holes  155 . Adjacent tabs  150   a  and  150   b  are attached to the housing cover along a common shoulder  155  and are separated from the housing cover along the remaining sides by slots  160   a  and  160   b . Adjacent tabs  150   c  and  150   d  are attached to the housing cover along a common shoulder  165  and are separated from the housing cover along the remaining sides by slots  160   c  and  160   d . A substantially rigid linkage  170  connects the free edge of tabs  150   a  and  150   b  at connection points  175   a ,  175   b , respectively, and linkage  180  connects the free edges of tabs  150   c  and  150   d  at connection points  175   c ,  175   d , respectively. The linkages  170 ,  180  are attached to shoulders  155 ,  165  at connection points  190  and  195 , respectively. In another example, linkages  170 ,  180  are integrally formed with the housing cover and extend from shoulders  155 ,  165 , respectively. 
   As shown in the example of  FIGS. 11 and 12 , an upward deflection of tab  150   d , relative to the cover, results in a downward deflection of adjacent tab  150   c , relative to the cover. Tabs  150   c  and  150   d , linkage  180  and the shoulder  160  all collectively rotate about the connection point  195 . 
   Other implementations are within the scope of the following claims.