Rosin Flux

Finally, steps can also be taken to prevent the contaminant from ever entering the process. For example, the development of low-solids no clean rosin fluxes for soldering printed circuit boards completely eliminates the need for a cleaning process (Sapre, 1990). 

Use A detergent that removes rosins, fluxes, and resins from printed circuit boards prior to coating. It is phosphate-free and biodegradeable. 

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Milros. [Alpha Metab] Mildly activated rosin flux. 

Synonyms/Trade Names Rosin flux pyrolysis products, Rosin core soldering flux pyrolysis products ... 

Solvents, like contaminants, may be polar or nonpolar. As a general rule, polar solvents dissolve polar residues while nonpolar solvents dissolve nonpolar residues. Thus, ionic residues such as chlorides, salts, acids, acid fluxes, and alkalis are best dissolved and removed with polar solvents such as water, isopropyl alcohol, ethanol, or methylethyl ketone. Greases, oils, silicones, rosin flux, and low-molecular-weight monomers are best dissolved and removed with solvents such as hydrocarbons, Freons , hydrochloro-fluorocarbons, xylene, terpenes, and naphtha. To remove both polar and nonpolar residues, a two-step process using both types of solvents may be used or, more conveniently, an azeotrope mixture of the two solvents can be used in a one-step process. Most of the chlorofluorocarbon solvents (Freons ) and their azeotropes with alcohols, methylene chloride, or ketones are being phased out due to their high ozone-depletion potentials. Solvent blends and azeotropes of hydro-fluoroethers and hydrochlorofluorocarbons (HCFC) are now replacing these solvents. 

Precision cleaning of electronic parts in removing no-clean and rosin flux residues in vapor degreasing and cold cleaning... 

Immersion, ultrasonic, and inverted spray for removing paste and adhesives, rosin flux, no-clean flux and assembly residues... 

Table I. Rosin Flux Cleaning Power of Selected VMS Azeotropes...

A semi-aqueous cleaning process consists of a wash cycle using a mixture of different organic solvents followed by a rinse with deionized water. Organic contaminations, predominantly rosin flux residues, are removed through the lipophilic solvents, whereas the ionics are minimized by the polar rinse media. The different kinds of solvent formulations that are... 

Zestron FA/ Zestron Modified alcohol Ultrasonic, spray-under immersion, or centrifugal for low solids and rosin flux removal 40°C-45°C N/A 162-228 28.5 N/A 73 0.17 (20 C)... 

Cold joint A soldered connection that was inadequately heated, with the result that the wire is held in place by rosin flux, not solder. A cold joint is sometimes referred to as a dry joint. 

A soldered joint which looks good in visual inspection but actually is not electrically conductive. Usually it was made at too low a temperature to evaporate the rosin flux out from between the solder and the copper wire. 

Up to the mid-1970s, the predominant flux chemistry was rosin-based. Today, although rosin fluxes are still in use, great advances have been made in flux chemistries and a large variety of formulations with very different chemistries are being used. 

In the 1970s, telecommunication companies in the United States and Europe predominantly used rosin fluxes for their wave-soldering requirements. These companies had their own internal set of test methods for seleding noncorrosive rosin flux formulations. Using their selection criteria, they beUeved the fluxes to be sufficiently safe. For their applications, they cleaned only the bottom side of the assembly, where rosin residues needed to be removed to ensure good electrical contact during bed-of-naik testing. 

As the name impUes, water-soluble fluxes are soluble in water and their soldering residues are also expected to be water-soluble. These fluxes are much more active than rosin fluxes, have a wider process window, and give a higher soldering yield with reduced defects. This means that the final assembly will require less touchup or repair. On the down side, water-soluble fluxes contain corrosive residues that, if not properly removed, will cause corrosion in the field and long-term reliability problems. 

Figures 4 through 6 show several Sn/ Cu/Ni alloy solder joints of stiff lead pins. These components are attached to a large ground plane. This single-sided application uses a paper phenolic (FRl) laminate with a rosin-flux protective coating. Figure 4 was rated as B, acceptable, while Figure 6 was rated C, not acceptable. The failure mechanisms are design failures for Figure 5 due to an incorrect ratio of PCB hole-to-component lead and alloy failure (solder...

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