International
Labour Organization

Your health and safety at work

CHEMICALS IN THE WORKPLACE

Appendix X: Chemical groups

Health hazards in the electronics industry, lnternational Metalworkers' Federation, Asia Monitor Resource Centre, Hong Kong, 1985.

Chemicals used or occurring in electronics manufacturing are listed here under general groups. This chemical groups list can be used (1) to identify specific names of chemicals, and (2) to group chemicals generally according to use and type of hazard. For example, you are using certain acids, but are not sure what specific kinds. The group list for acids provides specific names which may help you to identify the acids you are using.

Acids

Acids are corrosive substances widely used throughout the industry for cleaning, etching, plating and stripping. They are usually in liquid or powder form. Most are acutely hazardous, especially when concentrated. Acids can penetrate clothing rapidly causing serious burns and damage to tissues beneath the skin. Protective gear is essential, especially for the hands, face, eyes and lungs. All corrosives should be labeled clearly with warning placards.

Alkalis (Bases)

Alkaline or base substances are used primarily for cleaning and scouring. Like acids, they are acutely hazardous, especially in concentrated form. Most have strong caustic or corrosive action, and as such should be clearly labeled with warning placards. Be sure to use protective gear especially for the face, eyes, hands and lungs.

Cryogenic gases

Cryogenic means ultra-cold. These gases are usually stored in liquid form under high pressure and are used to heat and cool ovens in the process of seminconductor wafer fabrication. Some are used as 'carrier' gases, carrying dopants into the oven chamber. Hydrogen and oxygen are extremely flammable (they ignite and burn very easily). These gases have a potential to explode and thus require special storage and handling precautions. A major leak of liquefied gas can rapidly fill the workroom displacing oxygen and causing sudden death by asphyxiation.

Cyanides

Cyanides are a group of highly irritating and rapidly acting poisons. They are used for cleaning, plating and metallizing. Notice that most cyanide compounds (salts) contain a metal or mineral molecule. The biggest risk is exposure to cyanide in gas form, although they are often stored in solid or liquid form. Cyanide is quickly absorbed through the skin and lungs. It prevents the body tissues from taking up oxygen causing sudden death by asphyxiation. Repeated low-level exposure can cause severe dermatitis, thyroid disease, and muscle incoordination. Another highly reactive and poisonous group related to the cyanides are the isocyanates. Be extremely careful with any cyanide compound, and always wear a proper respirator if the process is not completely enclosed. Be sure cyanides are labeled clearly with warning placards.

Dopants

Dopants are metal compounds in solid, liquid or gas form and are used to make chips. Dopants are sometimes called impurities. They are usually injected as a gas or vapour into ovens which are heated to extreme temperatures. When heated, the metal of the dopant is deposited in the semiconductor wafer, penetrating its surface and giving it the ability to conduct electricity. The metals more commonly used in doping include aluminum, antimony and arsenic. Boron and phosphorous are also commonly used. Dopants are considered to be potentially the most hazardous group of chemicals used in electronics. Most are highly toxic. If a leak or rupture occurs with a substance like phosphine, arsine, or the boranes, the whole factory and surrounding community can be affected with many cases of serious harm and sudden death. Argon and deuterium are sometimes used as carrier gases.

Fillers

Fillers are powders or tiny fibres added to resins (plastics, epoxies, glues, paints) to give bulk, strength and form. They are durable and some resist heat, fire and electricity. Asbestos and chromates cause cancer, and fibreglass can cause serious lung problems if breathed in over a period of time. These substances can also be highly irritating to the skin and eyes. Fillers are used to make printed circuit boards and plastics. They are easily released as harmful dusts when resin products are shaped, sawn, or drilled. Avoid breathing and direct contact.

Metals (and their compounds)

Ordinarily, people do not consider that metals are chemicals. But they are, and many can be very harmful if swallowed or if breathed in small unnoticeable amounts day after day. Because metals are good conductors of electricity, they are widely used in electronics. Metals are used or occur in many forms - such as bulk solids, powders and liquid solutions suspended in gas form, and emitted as a fume when heated and as dust when drilled, sawn, or fiied. Exposure to the more dangerous forms of metal (gases, dusts and fumes) occurs more frequently during doping, soldering, plating, tinning and other metal work.

Oxidizers

Oxidizers are highly reactive chemicals which can be used to clean or to render a metal surface free from corrosion. During oxidation, oxygen (from the oxidizer or from the air) combines with a metal or semiconductor surface to form a protective oxide layer. Some oxidizers have strong corrosive action and care must be taken to protect the eyes, skin and lungs from exposure. Oxidizers are also highly flammable and require special handling and storage arrangements.

Resins (epoxies, curing agents, plastics)

There are many kinds of resins: plastics, epoxies, glues, adhesives, paints, waxes, synthetic rubber, synthetic fibres, and many others. With obvious exception of rosin (colophony) flux used in soldering, most resins used in electronics are man-made organic polymers. Polymers are complex chemical substances. Most contain many poisonous ingredients, such as solvents, dyes, stabilizers, fillers, plasticizers, catalysts and monomer residue. Some of these ingredients cause allergies, birth defects and cancer. Polymers are formed from monomers. Epoxides (epoxy resins) are normally cured with a phenol compound, and polyesters are cured with a peroxide compound. Uncured epoxy resins or monomers are very toxic and penetrate the skin and lungs rapidly. After they are reacted, cured, or set they are much less harmful, though dust created by shaping, cutting and drilling can be harmful. Resins are widely used in electronics, particularly in making printed circuit boards, moulding plastics, bonding, encapsulating and packaging, and are also used as wire coatings and a variety of other electrical insulation materials. Resins can produce a wide variety of highly toxic vapours and gases when heated or burning. Fires caused by burning plastic are sometimes very difficult to control.

Semiconductors

Semiconductors are the basic raw material or substrate for making electronic devices. They are treated with dopants and other chemicals to give them special electrical capabilities. Semiconductor substances are sometimes made by chemical companies which specialize in supplying chemicals to the electronics industry.

cadmium sulfide

gallium arsenide

germanium

indium phosphide

silicon

Solvents

Solvents are used in nearly every phase of electronics manufacturing. They are used primarily for cleaning and degreasing, and for thinning plastics, resins, glues, inks, paints and waxes. There is a wide range of organic solvents, some very toxic and others only mildly toxic. The subgroups should be considered to have a better idea of specific hazard risks and uses.The aromatic compounds and the chlorinated hydrocarbons are perhaps the most dangerous groups of solvents since many of them are known to cause cancer and other serious diseases.