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Survey on Lead Free Solder Systems 9 The toxicology of fluxesRosins and modified rosins The fluxes assessed in this project are composed by the following main groups of ingredients:
Some of the ingredients are multifunctional, but for simplicity they are placed in one of the main groups. Rosins and modified rosinsInhalation exposure to rosin based solder-flux fume is likely to have low systemic toxicity following single exposure (12). Inhalation exposure to rosin based solder-flux fume can lead to occupational asthma or worsen existing asthmatic conditions. Components of the fume may also give rise to allergic dermatitis (8). The available data indicate that both rosin fume and rosin itself are of low toxicity to animals. The fume is also irritating to the eyes and upper respiratory tract and on contact with the skin. Several resin acids present in solder fume from rosin flux have allergenic potential on application on the skin. There are several case reports of skin reactions being triggered in solderers following dermal exposure to solder fume, liquid fluxes or flux residues. However mode of induction of the sensitized condition is unclear (12). No toxicokinetic studies on rosin-based solder flux fume are available. Nevertheless, some conclusions can be reached from other studies in which rosin alone or resin acids were employed. Resin acids and other small molecules present in the particulate fraction of solder fume, when inhaled, are probably absorbed via the lungs and distributed throughout the body. Uptake of components via dermal and oral routes is also possible. Resin acids ar unlikely to accumulate in body tissues. Elimination of resin acids following absorption may occur via the bile (into faeces) or the urine. The environmental effects of rosins and modified rosins during the solder process or disposal of PCB´s is estimated not to have any significant environmental effects. SolventsSolvents are irritating to the respiratory tract by inhalation and are toxic to the nervous system. Inhalation of high concentrations of solvent vapors may cause acute narcotic effects, and some industrial solvents have a history of use as general anesthetics. Vapors are also irritating to eyes. Dermatological problems are well known to result from skin contact with solvents. Solvents are inrritating to the skin, mucosae and the eyes and defats the skin. Prolonged or repeated exposure to solvents may cause dermatitis. Solvents may enter the body by inhalation, intake or via the skin. Solvents may have toxic effects on the blood and cause damage to liver and kidneys. Most solvents will evaporate in the production phase of the electronic equipment. It is evaluated that solvents used during the production may cause irritation to eyes and respiratory tract, whereas neurotoxic effects are unlikely to occur due to fairly low exposure concentrations. The environmental effects of the use of solvents in the fluxes are during the solder process the production of VOC´s. By the disposal of PCB´s the solvents will not have any significant environmental effects. WaxesWaxes are generally regarded as harmless, but they may contain PAH´s if they are not well refined. PAH are suspected to be carcinogenic. Especially during heating, PAH´s may become airborne. In general the small PAH´s (Mw<202) hace low or no mutagenic effects, whereas the big PAH´s (Mw >202) is highly mutagenic (17). The environmental effects of waxes during the solder process or disposal of PCB´s is estimated not to have any significant environmental effects. AntioxidantsThe antioxidants used in the products tested in this project are very different in their chemical composition. In general they are all more or less irritants. By heating they will become airborne forming vapors that may be irritating or even toxic. The environmental effects of the antioxidants are negligible due to very low concentrations on the final PCB. ActivatorsAs for antioxidants the activators are of different chemical composition. They are though divided in to two main categories: organic acids, salts and halogen compounds. They are all strong irritants and may cause skin- and respiratory allergy. The environmental effects of the activators are negligible due to very low concentrations on the final PCB. Summary - toxicologyEach of the functional groups (e.g. solvents and activators) embraces a variety of different chemical substances, with a variety of toxicological effects. In general though the following human toxicological effects have been registered during the toxicological evaluation:
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