Circuit cooling

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.

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 inFIG. 1, an amplifier20includes a heat sink25which forms a chassis for supporting the electrical components of the amplifier. The heat sink has cooling fins30which extend from at least one surface of the heat sink and a substantially planar housing cover35. As shown inFIG. 2, with the cover removed from the heat sink, a circuit board40includes one or more electrical components. Referring toFIGS. 3A and 3B, the circuit board supports electrical components45a,45b,45cand45d(collectively45), which may be integrated circuits, for example. The reverse side of the circuit board is shown inFIG. 3B, with the corresponding locations of the electrical components45shown in phantom. The circuit board is disposed in the heat sink such that the electrical components are in substantial contact with component pads50a,50b(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 toFIG. 4, housing cover35is secured to the heat sink with fasteners extending through screw holes55and includes projections60a,60b,60cand60d(collectively,60) and can include a number of ventilation holes70. The location of the projections correspond to the location of the electrical components45on the circuit board, such that when the housing cover is fastened to the heat sink, the projections60engage the electrical components between the component pads50and 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 toFIG. 5, two adjacent component pads50a,50bcan have different heights, as can the associated projections60a,60b, when accounting for stack-up tolerances. When the electrical components45a,45bare adjacent to one another, the associated projections are located adjacent one another. Given the close proximity of projection60ato60b(and similarly,60cto60d), vertical movement of projection60ais strongly coupled to the movement of projection60b. Accordingly, if projection60apresses the electrical component45aagainst component pad50a, projection60bwill be limited by projection60a, as both proximally extend from the same substantially rigid cover. The disparities in height noted above can lead to a gap63between electrical component45band projection60bthat 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.

Referring toFIG. 6, the housing cover75includes screw holes80and projections90a,90b,90cand90dextending from slotted tabs95a,95b,95cand95d. The cover can also include ventilation holes85. The tabs95can be attached along a peripheral edge of the cover and separated from the cover along the remaining sides by slots100a,100b,100cand100d, which can be U-shaped, for example. This configuration permits a given projection90to deflect substantially independently of the other projections and to promote thermal contact of each component pad with the corresponding electrical component. If the housing cover85is formed with a stamping process, the projections90and tabs95can be formed with a change in stamping tools, requiring no extraneous components.

Referring toFIG. 7, it is shown that the combined height of the component pad50aand electronic component45ais greater than the combined height of the component pad50band electronic component45bby a distance defined by D1. When the housing cover75is applied to the circuit board40, the height differential D1between the electronic components is accommodated by permitting a vertical displacement of the projection90arelative to the vertical displacement of the housing cover75. In one example, the projections90aand90bare substantially decoupled from the housing cover75and from each other. When the downward vertical travel of projection90ais stopped by electronic component45acontacting component pad50a, projection95bcontinues moving downward until electronic component90bcontacts component pad50b. Projection90ais cantilevered at a fixed end and separated from the housing cover75along slot100a. Projection90bis also cantilevered at a fixed end and separated from the housing cover75along slot10b. Although projections90a,90beach extend from a substantially rigid and level housing cover75, projection90bcan extend farther than projection90aby a distance given by D2. In one example, the distance D2is about equal to the distance D1. The distances shown inFIG. 7are exaggerated for clarity.

In another example, three or more electronic components (not shown) each have different heights and are proximate each other. Projections90corresponding 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 toFIG. 8, the housing cover80can include spanning elements105and110extending along the free end of adjacent tabs95aand95band adjacent tabs95cand95d, respectively. The spanning elements105can be attached to the housing cover at connections115a,115band115cand spanning element110can be attached to the housing cover at connections120a,120band120c. In some examples, elements105,110can 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 tabs95to a predetermined position.

In one example, as shown inFIG. 9, the tab95ccan deflect about a connected edge125cin the downward direction, but the movement of the tab95cis constrained in the upward direction by the spanning element110. As the spanning elements are connected along adjacent tabs, the movement of these tabs is similarly restrained.

In another example, as shown inFIG. 10, the housing cover140has screw holes145and slotted tabs150a,150b,150cand150d. The cover can include ventilation holes155. Adjacent tabs150aand150bare attached to the housing cover along a common shoulder155and are separated from the housing cover along the remaining sides by slots160aand160b. Adjacent tabs150cand150dare attached to the housing cover along a common shoulder165and are separated from the housing cover along the remaining sides by slots160cand160d. A substantially rigid linkage170connects the free edge of tabs150aand150bat connection points175a,175b, respectively, and linkage180connects the free edges of tabs150cand150dat connection points175c,175d, respectively. The linkages170,180are attached to shoulders155,165at connection points190and195, respectively. In another example, linkages170,180are integrally formed with the housing cover and extend from shoulders155,165, respectively.

As shown in the example ofFIGS. 11 and 12, an upward deflection of tab150d, relative to the cover, results in a downward deflection of adjacent tab150c, relative to the cover. Tabs150cand150d, linkage180and the shoulder160all collectively rotate about the connection point195.