Application of "Ideal" Insulated Metal Substrates in ball grid array (BGA) packages

Insulated Metal Substrates (IMS) have been developed as one kind of packaging material in the microelectronic industry. An "Ideal" IMS uses an anodically formed oxide film on an Al plate as the insulating layer instead of epoxy, one of the advantages of which is its high thermal conductivity. Although anodic films have a high thermal performance, their thermal shock resistance is poor because of the great difference of thermal expansion coefficient between aluminum and its anodic film. This paper describes the cleaning and anodization of the aluminum and the properties of the layer - thermal shock resistance, electrical resistivity (over 1013 Q-cm), and breakdown voltage (more than 600 V). It is pointed out that BGA packages can be achieved on the IMS through electroless plating, electroplating, and photolithography methods.