Miniature hearing aid amplifier

05/01/1997

Miniature hearing aid amplifier

Many semiconductor applications benefit from reduced device size and high circuit density, but some absolutely require it. The figure shows a standard hearing aid amplifier IC, flip chip-mounted to a multilayer thick film substrate. An active filter is epoxied to the top side of the flip chip and connected by wire bonding to increase circuit density and thus reduce the size of the in-ear device.

This miniature hearing aid circuit is manufactured in multiples of 144 circuits/substrate; each substrate has more than 3000, 125-?m vias. (Photo courtesy of HEI Inc., DuPont Photopolymer and Electronic Materials, and the International Microelectronics and Packaging Society)

The substrate is fabricated from silver thick film materials using Dupont`s Diffusion Patterning process. This process screen prints an imaging paste on the surface of a dried dielectric paste. Heat diffuses the imaging paste into the dielectric, defining the position of vias. An aqueous developing wash clears the patterned vias, leaving the dielectric behind. - K.D.