Gas dilution method and apparatus

Abstract

A method and apparatus for preparing dilute HF for fluxless soldering, to provide very dilute anhydrous hydrogen fluoride to effect surface modification of the parts to be soldered. There are six main parts of the apparatus: a vacuum sub-system; a source gas sub-system; a dilution gas sub-system; a source gas / dilution make-up sub-system; a diluted gas storage sub-system; and a control system.

Description

[0001] This invention is disclosed in Disclosure Document No. 460022, filed Jul. 28, 1999, with the U.S. Patent Office.[0002] 1. Field of the Invention[0003] This invention relates to methods for fluxless soldering, and in particular, relates to gas dilution method and apparatus allowing fluxless soldering with very dilute hydrogen fluoride.[0004] 2. Description of the Related Art[0005] Fabrication and assembly of electronic circuits requires that certain components of the circuit, such as integrated circuits (chips) or other components such as resistors, capacitors, etc., be in electrical contact with each other. They are for this reason mounted on substrates such as printed wiring boards so that the chip and substrate make electrical contact and are held together with the substrate supporting the component.[0006] Soldering processes for connecting the components and the substrate generally involve pre-cleaning and deoxidation of surface oxides, generally using a liquid flux materi...

AI Technical Summary

Benefits of technology

[0012] It is a further object of the invention to provide a method and apparatus that achieves the dilution of anhydrous HF in a safe and controlled manner.

Problems solved by technology

This step is particularly difficult due to the small size of typical electronic components, and the difficulty of getting the cleaning agents to reach the minute areas between components.

There are problems, however, with using concentrated HF, including problems with disposal of this concentrated toxic gas, and potential problems due to the need to prevent leakage of the effluent to the environment.

Also, at high HF concentrations, if there is moisture present, undesired etching of silicon oxide (SiO.sub.2) or other metal oxides occurs.

Although water vapor can be minimized in an open environment by making sure the gases and treatment environment are dry plus the use of mild heating in the treating environment, it cannot be completely eliminated, and therefore oxide etching is a usual problem with the use of a high HF concentration as is known in the art.

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