ther solvents to form specialized cleaning agents for cleaning the challenges of today's electronic assembly environment.
The engineered material composition must have properties that would enhance the performance for removing the flux residues, as well as acceptable environmental and toxicity profiles. The engineered composition must contain the proper ratio and balance to form azeotropes or behave like azeotropes. For clarification, an azeotrope is a mixture of two or more components that vaporizes without a change in composition at the boiling point, and exhibits a boiling point less than any of the individual components. After evaporation, only a small difference exists between the composition of the vapor and the composition of the initial liquid phase. This difference is such that the compositions of the vapor and liquid phases are considered substantially the same.
The most effective active solvent is 1, 2-trans-dichloroethylene (DCE), which has favorable toxicological, environmental and performance properties. Proprietary fluorinated material forms an azeotrope with DCE at higher levels. This property allows the formulation of solvent blends that provides enhanced performance on the removal of many RMA, RA and low-residue resin flux residues. The resultant fluids can be formulated to have no ozone depletion, while maintaining superior cleaning ability, drying ability, low viscosity and low surface tension. In addition, desired blends will exhibit no flash point in keeping with the CFC and chlorinated-based solvents.
When building engineered fluid compositions, flash point must be a consideration. Oxygenated solvents are needed to enhance cleaning and removal of ionic contaminants. When blending oxygenated compounds within the composition, flash point is a concern. To address this concern, a more highly fluorinated compound may be added to the ternary azeotrope-like blend thus retarding the flashpoint. The addition of this highly fluorinated compound forms a unique blend of azeotropes. Being substantially constant boiling, the compositions do not tend to fractionate to any great extent upon evaporation. Since the mixtures are not easily fractionated, they are useful commercially in standard cleaning apparatuses for cold cleaning or vapor degreasing. The composition of the vapor and liquid phases are considered substantially the same and are either azeotropic or azeotrope-like in their behavior, which is a blend that is suitable for commercial use.
To better understand performance, the soil must be evaluated for suitability with the cleaning technology. Solder flux is an important engineered material that enhances solderability of electronic circuitry. A solder flux needs to perform a number of important functions at the same time. It must promote thermal transfer to the area of the solder joint, enhance wetting of the solder on the base metal, and prevent oxidation of the metal surfaces at soldering temperatures. Among those, the primary task is to remove the tarnish layer form the metal joint that is about to be soldered. The most commonly used fluxes for solder pastes include organic acids, organic bases, organic halogen compounds and organic halide salts.
The ingredients in flux are complicated. In general, fluxes comprise resins, activators, solvents and rheological additives. For certain special systems, additives such as tackifiers, surfactants, or corrosion inhibitors may also be used.
Resin refers to organic materials with medium to high molecular weight. It may include natural products, such as rosin, or synthetic materials, such as polymers. Often it is used to provide fluxing activity, tackiness, and an oxygen barrier. Sometimes it may also serve as a rheological aid. The most commonly used resins are water-white rosin or chemically modified resins. The latter type is sometimes referred to as synthetic rosin or synthetic resin by the soldering industry. These chemically modified materials can undergo polymerization, hydrogenation, or functional group modification. These changes may increase the difficul