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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