Lucent Technologies Inc.

At&t Bell Laboratories

Hugh Nicholl

Peter Hartpence Read

Min-Chung Jon

Terry R McClure

Steven M Schulte

Garrett J Heyns

Mohammad F Tabrizi

Electrostatic discharges that occur during solid CO.sub.2 cleaning of a substrate (10) can be virtually eliminated by chilling the substrate so that moisture in the atmosphere, in the form of water droplets(30), condense on the substrate surface (14), thereby forming a continuous film of water (28). The water in the film (28) reacts with the solid CO.sub.2 (24) to form carbonic acid that dissociates into free ions that neutralize the charge on the solid CO.sub.2.

Mitigation of electrostatic discharges during carbon dioxide cleaning

An object (12) may be cleaned by CO.sub.2 reduced ESD by directing a first water mist (23) at a surface (14) of the object while imparting a relative motion between the object board and the mist to form a film of water on the object surface. As the relative motion is imparted between the board and the first mist (23), a second water mist (32) is injected into a stream (30) of solid CO.sub.2 particles (27) directed at the object surface downstream of the first mist. Water droplets in the second mist in the second mist combine with the CO.sub.2 particles to create carbonic acid that disassociates into charged ions that increase the conductivity of the water film, allowing for increased charge dissipation, thus reducing the incidence of ESD.

Method and apparatus for CO.sub.2 cleaning with mitigated ESD

A system for cleaning test probes attached to a probe mat fixture by propelling CO.sub.2 pellets at the test probes, by rotating the fixture so that the pellets impact different sides of the test probes, and by providing electrostatic protection for active devices mounted on the probemat fixture. The CO.sub.2 pellets are propelled so that they strike the test probes at an angle to the horizontal plane of the test probe as mounted on the probemat fixture. Electrostatic protection is provided by connecting all electrical connections to the probemat fixture to ground and by reducing electrostatic charge build up on the probemat fixture by using an ionizer to direct ions at the probemat fixture.

Probemat cleaning system using CO.sub.2 pellets

Growing community of inventors

Berthoud, CO, United States of America

Hugh Nicholl