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Ultrasonic Bonding of a Transparent Medium and Assembling a Liquid Crystal on a Silicon Package Using Photonic Hermetic Sealing Techniques

IP.com Disclosure Number: IPCOM000101771D
Publication Date: 2005-Mar-16
Document File: 3 page(s) / 90K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that creates an ultrasonic bond and a hermetic seal between the transparent glass and damming material that encases a liquid crystal material, which enables liquid crystal on silicon (LCoS) micro displays. Benefits include higher yields with minimized impact of thermal excursions.

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Ultrasonic Bonding of a Transparent Medium and Assembling a Liquid Crystal on a Silicon Package Using Photonic Hermetic Sealing Techniques

Disclosed is a method that creates an ultrasonic bond and a hermetic seal between the transparent glass and damming material that encases a liquid crystal material, which enables liquid crystal on silicon (LCoS) micro displays. Benefits include higher yields with minimized impact of thermal excursions.

Background

There is a need to join a transparent medium (e.g. glass or polycarbonate) to a die which has a dam enclosing liquid crystal, for which the most prominent application is micro displays. Currently, the transparent medium is joined to the dam material with an epoxy-type glue.

Figure 1 shows the current state of the art. Typically, the damming material is dispensed along the periphery of the ‘imager’, which holds the liquid crystal (LC) material in place. A small opening is left in the damming material which is later used to backfill with the LC material. The cover glass is then added on top and sealed to the dam. Under the influence of a vacuum, LC material is filled into the cavity between the cover glass and imager. The hole is then plugged with a low temperature sealant. This type of assembly limits the temperatures of the subsequent processes; because the LC material is relatively unstable at high temperatures (~90ºC), the die attach, wire bonding, and encapsulation require temperatures well below the critical temperature (i.e. the temperature at which LC becomes isotropic). With certain types of LC materials, movement above the critical temperature results in irreversible damage.

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