GAS PHASE FLUXLESS SOLDERING, CHEMISTRY AND APPLICATIONS

摘要

Gas Phase Fluxless Soldering is a pretreatment for solde coated parts or solder preforms that can eliminate the use o flux, flux residues, as well as any unwanted physical effect resulting from the volatilization of flux components during reflow. The pretreatment exposes the parts to be soldered to a fluorinating gas that weakens the bonding between surfac metal oxides (that prevent reflow and joining) and th underlying metal. The pretreatment is effective for a period of months and treated parts can be soldered with conventional equipment (e.g. solder wave or convection oven) without flux at any time during this period. If th joining process is rapid (e.g. thermode-type bonder) th reflow may be done in air. The gas phase pretreatmen process leaves no residue. The fluorination chemistry react specifically at the interface between the metal and the meta oxide and therefore adds only one to two atomic layers to the surfaces of the parts. The fluorination uses a safe an easily handled gas source; and does not affect othe materials (e.g. silicon and silicon oxides) that may b exposed during the pretreatment. The fluorination chemistry as well as process considerations and process tooling for th pretreatment will be discussed.