TWI developed an interconnection technique for electrical devices called wire/ribbon tape automated bonding. It is an adaptation of wire and TAB processes. The technique involves an electrical device attached to a flexible tape or rigid carrier using wire or ribbon bonding techniques. Thus it can be transported and tested before final attachment to a package or substrate.
The process involves welding or soldering a silver, gold or copper wire (4-500µm diameter) or ribbon (10µm-5mm wide) to a metallised pad on the electronic device. The wire or ribbon is then fed out and attached to a plastic or metal flexible tape or rigid carrier using welding, embedding or adhesive bonding. Next the wire or ribbon is broken or cut and the bonding machine cycled back to the next bond pad. The sequence is continued until all the connections are attached to the device. Alternatively, the bonding process can be reversed with the first bond being connected to the intermediary substrate (flexible tape or carrier) and the free end subsequently joined to the electronic device. Once the device is attached to the flexible tape or carrier it can be tested, excised and attached to a package or substrate using conventional techniques.
The novel aspect of the technique is the attachment of the wires or ribbons directly to the flexible tape or carrier.
This approach to chip interconnection combines the wire bonding with the pre-testability/burn-in and high lead count capability of TAB. This is of particular benefit for pre-production trials and low volume production and is also applicable for high volume devices.
The specific benefits are as follows:
.Standard chips can be used (no bumping necessary)
.Ag, Au or Cu connectors can be used (TAB is currently limited to plated/unplated Cu)
.The process uses conventional wire bonding equipment with its inherent flexibility. Companies will not need to invest in new equipment or expertise
.Standard tape/carrier can be used for a range of devices
.The devices can be tested prior to attachment to the substrate or package
.High lead count may be possible, particularly if ribbons are used with their small bond areas and stiffer connectors.
For information about TWI's capabilities please contact us.