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.

What is claimed is:  
     
         1 . A method for fluxless pretreatment of a substrate comprising exposing parts to be soldered to a gas phase pretreatment of diluted anhydrous hydrogen fluoride in a dry carrier gas, said hydrogen fluoride being diluted sufficiently to avoid metallic etching during the pretreatment.  
     
     
         2 . The method of  claim 1 , further comprising adjusting the dilution of the anhydrous hydrogen fluoride based on the substrate being pretreated and on ambient environmental conditions.  
     
     
         3 . The method of  claim 1 , wherein the concentration of the diluted anhydrous hydrogen fluoride is from 30 ppm to 100,000 ppm and preferably in the range 300 ppm to 30,000 ppm.  
     
     
         4 . The method of  claim 1 , wherein the dry carrier gas is an inert gas.  
     
     
         5 . The method of  claim 4 , wherein the dry carrier gas is selected from the group consisting of dry air, dry nitrogen gas, and dry argon.  
     
     
         6 . The method of  claim 1 , wherein the carrier gas has a dew point below −40° C.  
     
     
         7 . The method of  claim 1 , wherein the pressure during pretreatment is at or near atmospheric pressure.  
     
     
         8 . An apparatus for the delivery and dilution of hydrogen fluoride to a processing tool, comprising: 
 (a) a vacuum sub-system for removing residual gases from the apparatus;    (b) a source gas sub-system for supplying anhydrous hydrogen fluoride;    (c) a dilution gas sub-system for delivering an inert dilution gas;    (d) a source gas/dilution make-up sub-system for delivering the diluted anhydrous hydrogen fluoride gas mixture to a first storage tank and to a second storage tank to form a controlled diluted anhydrous hydrogen fluoride gas mixture, and for maintaining the controlled gas mixture in the second storage tank;    (e) a diluted gas storage sub-system for containing and delivering the diluted anhydrous hydrogen fluoride gas mixture to the process tool to be soldered or otherwise treated; and    (f) a control system for controlling pressure within the apparatus, flow of gases, and vacuum evacuation of the apparatus.    
     
     
         9 . The apparatus of  claim 8 , wherein the diluted gas storage sub-system comprises a flow control valve to deliver highly diluted hydrogen fluoride to the process tool.  
     
     
         10 . The apparatus of  claim 8 , wherein the vacuum sub-system comprises a mechanically operated vacuum pump.  
     
     
         11 . The apparatus of  claim 8 , wherein the inert dilution gas is selected from the group consisting of dry air, dry nitrogen, and dry argon.  
     
     
         12 . The apparatus of  claim 8 , wherein the vacuum sub-system further comprises a vacuum source and a supply of gas for purging the apparatus.  
     
     
         13 . The apparatus of  claim 12 , wherein the gas for purging the apparatus is selected from the group consisting of dry air, dry nitrogen, and dry argon.  
     
     
         14 . The apparatus of  claim 8 , wherein the concentration of the diluted anhydrous hydrogen fluoride gas is from 30 ppm to 100,000 ppm and preferably in the range 300 ppm to 30,000 ppm.  
     
     
         15 . The apparatus of  claim 8 , wherein the carrier gas has a dew point below −40° C.  
     
     
         16 . The apparatus of  claim 8 , wherein the entire apparatus is provided with a heating means so that the apparatus may operate in a temperature range from ambient to 120 degrees C. in order to aid in maintaining a dry condition within the apparatus.