Fluxless soldering using activated acid vapors

Conference · Wed Jan 01 00:00:00 EST 1992

OSTI ID:5982150

Frear, D R; Keicher, D M

Acid vapors have been used to fluxlessly reduce metal oxides and enhance wetting of solder on metallizations. Dilute solutions of hydrogen, acetic acid and formic acid in an inert carrier gas of nitrogen or argon were used with the sessile drop technique for 60Sn-40 Pb solder on Cu and Au/Ni metallizations. The time to reduce metal oxides and the extent of wetting as a function of acid vapor concentrations were characterized. Acetic and formic acids reduce the surface metal oxides sufficiently to form metallurgically sound solder joints. Hydrogen did not reduce oxides rapidly enough at 220{degree}C to be suitable for soldering applications. The optimum conditions for oxide reduction with formic acid was with an acid vapor concentration in nitrogen carrier gas of 4% for Cu metallizations and 1.6% on Au/Ni. The acetic acid vapor concentration, also in nitrogen, was optimized at 1.5% for both metallizations. Above a vapor concentration of 1.5%, the acetic acid combined with the bare metal to form acetates which increased the wetting time. These results indicate that acid vapor fluxless soldering is a viable alternative to traditional flux soldering.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: USDOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC04-76DP00789
• OSTI ID: 5982150
• Report Number(s): SAND-91-2743C; CONF-920247-4; ON: DE92005455
• Resource Relation: Conference: National electronics products conference (NEPCON) west, Anaheim, CA (United States), 23-27 Feb 1992
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COPPER
SOLDERING
METALLURGICAL FLUX
EVALUATION
OXIDES
REDUCTION
ACETIC ACID
FORMIC ACID
GOLD
NICKEL
SOLDERED JOINTS
VAPORS
WETTABILITY
CARBOXYLIC ACIDS
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
FABRICATION
FLUIDS
GASES
JOINING
JOINTS
METALS
MONOCARBOXYLIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
TRANSITION ELEMENTS
WELDING
360101* - Metals & Alloys- Preparation & Fabrication