Solder Wetting and Spreading

Copper Oxide Removal Activity in Nonaqueous Carboxylic Acid Solutions

“…It is important to note adipic acid is thermally stable at higher temperatures with a boiling temperature of 330 • C 8 while maleic acid decomposes at 180 • C. 13 It is also possible for some of the acid to evaporate before its boiling/decomposition point which may explain the relative change in activity. 8 The nature of the 5-10x enhancements in removal rates when acids are combined with complexing agents may be related to the removal effectiveness of Cu-carboxylate salts at the interface. FTIR spectroscopy was used to identify adsorbates and salts remaining on the surface after reaction and heat cycling.…”

“…7 Secondary acid-base and redox reactions in solution are also possible and may result in residues at the interfaces to be soldered affecting stability, wetting and reliability. 8 For example, oxalic acid is known to form Cu oxalate precipitates 9 while other organic acids may decompose at relatively low temperatures resulting in CuO x reformation. 10 In addition to the issues that affect solder wetting, the incomplete removal of oxides (or reformation of oxides) may also prevent gases from escaping the liquid solder giving rise to large voids.…”

“…For example, Cu surfaces treated with adipic acid have relatively slow solder wetting rates (456 dyn/s at 233 • C) but the acid shows relatively fast CuO x removal in practice. 8 Other analytical techniques such as weight difference and exchange current densities via polarization plots have been applied to study similar dynamic metal reactions including those used in chemical mechanical polishing (CMP) cleans and corrosion studies. [12][13][14][15] In these * Electrochemical Society Student Member.…”

Activity Of Halide-Free Carboxylic Acid Fluxes At Sn Surfaces

“…After a reflow process, new solid phases with intermetallic compounds (IMC) would be formed between the UBM and solder. The role of flux is to remove oxides and other contaminants from the substrates and to prevent the reoxidation of the substrates and solder during reflow (4). Although the other material and processes associated with flip-chip soldering are relatively well-defined (5-7), the interactions between flux and solders remain poorly understood.…”

Behavior of Halide-Free Carboxylic Acid Based Flux

“…Flux is typically a surface tarnish remover that promotes solder wetting, helps prevent solder re-oxidation and control electromigration during solder process. [1], [2] Flux chemistry and behavior has been vague from literature, where the solder fluxes are commercially obtained and the best flux is chosen based on final solder performance using process design of experiments. [2]- [4] In this work, more emphasis is laid on understanding flux chemistry and behavior in order to enhance leadfree solder reliability.…”