Bonded Grid Arrays, BGA Heat Sinks, Solve Configuration Problems

The level of heat in today’s power electronics is ever increasing. Efforts to expand the number of fins for cooling have become necessary. Densely compact components are making the cooling system packages smaller. The increased fin count cannot add to the volume of the systems.

Heat sinks cool as heat input from a component, or mounting surface is transferred to the cooler ambient air. More heat can be removed with more heat surface area. A flat plate would increase airflow needed to dissipate heat, but the surface area needed, would be too large to fit in the available space. Adding fins to the base plate increases the amount of surface coming in contact with the air. The amount of cooling is increased without increasing the footprint occupied by the heat sink. The application is used for both natural convection and forced air.

The fins can be part of the aluminum base. As an alternative, bonded grid arrays are used. Bonded grid arrays allow a higher fin count. Taller fins than those of conventional extrusions are used.

Extruded heat seats are inexpensive and easy to manufacture. Aluminum extrusion lengths are produced, cut, and machined to the size requirement. The shaping die and extrusion tooling used in the process of manufacturing places limits on the finished product. The heat sink’s flexibility is limited by the maximum base-to-fin thickness, the minimum thickness-to-height, and the height-to-gap ratio aspect when heated aluminum is forced through the die of steel and creates the required two-dimensional shape.

Bonded grid arrays reduce the limits of fin ratios by separating base and fin extrusions. BGA heat sinks allow nearly limitless fan heights and increased cooling due to decreased center-to-center spacing. Before the recent use of BGA heat sinks, the most effective way to attach fins was the use of epoxy filled joints. The thin bond line and high conductivity of the epoxy result in a bit of thermal resistance. BGA heat sinks increase the achievable fin height-to-gap ratio to as much as 40:1

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Advantages of Extruded Aluminum Heatsinks

Using extruded aluminum heatsinks provides a greater range of convection solutions needed for high power systems and components. By forcing raw aluminum through extrusion dies, complex fin profiles have increased surface area that allows greater heat dissipation. The time and cost of an equivalent shape using block aluminum is eliminated.

The benefits of extruded aluminum heatsinks include:

•    More efficiency

•    Lower costs

•    Availability of many sizes and shapes

•    Easy customization for any application

•    Weight advantage over copper

•    Mounting tools and hardware are eliminated

The latest technology is used to test and prototype extruded aluminum heatsinks to provide the most effective thermal products. Extruded aluminum heat sinks are designed for forced air cooling and natural convection. Plating options include chromatic and anodization. Multiple extruded aluminum heatsinks can be produced. Shapes include tube, solid, semi-hollow, rod, bar, profile, and hollow. Customers can also specify unique custom shapes.

The compact designs of today require one-piece aluminum heat sink extrusions. That design prevents premature failure and limits temperature rise. Heat sink extrusions satisfy a wide range of needs for semiconductor cooling. Heat sink extrusions are customized to perform optimally for any application.

Aluminum heat sink extrusions have eliminated labor-intensive, bonded-fin heat sinks. The overall size has been reduced. The original heat sink prototype was overdesigned. A thermal analysis that used maximum operating conditions, environmental constraints and a power component layout allowed a high-ration extrusion that met the thermal requirements to be developed. 

That is the process used to find solutions to heat sink extrusion challenges. Often,  heat sink prototypes that are too expensive, too heavy, or too large can be replaced by extruded aluminum heatsinks.

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