Page 454 - Solid Waste Analysis and Minimization a Systems Approach

432 ELECTRONICS, SEMICONDUCTORS, AND OTHER ELECTRICAL EQUIPMENT

automation, the 1-gallon bottles storing the photoresist chemicals were visually mon-
itored and replaced by the operators. Typically, operators replaced used bottles con-
taining approximately 5 cm (2 in) of photoresist in the bottom to prevent the system
from running dry. Eventually the waste from each bottle was mixed and disposed of
off-site. The time and labor required for monitoring, the high cost of new chemical,
and the disposal costs involved with the waste made these activities of concern.
An automated system was installed to provide maximum usage of photoresist from
the supply bottles and continuous operation with minimal operator assistance. The
automated system reduced photoresist waste by 50 percent.

33.6.3 EXAMPLE 3

A California semiconductor manufacturer studied approaches to reduce solvent wastes
(Briones, 2006). The conclusions indicated that solvent segregation, solvent substitu-
tion, direct solvent reuse, distillation, and evaporation could accomplish a 70 percent
solvent reduction.
Segregation of chlorinated solvents from nonchlorinated solvents was recommended to
facilitate waste reduction by increasing recyclability. Minimizing water mixing, separat-
ing chlorinated from nonchlorinated solvent wastes, separating aliphatic from aromatic
solvent wastes, and separating Freon from methylene chloride facilitated recycling.

33.7 Additional Information

1 www.dtsc.ca.gov/PollutionPrevention/P2_Semiconductor-Ind-Conf.cfm.
2 Cui, Jirang and Forssberg, Eric, “Mechanical Recycling of Waste Electric and
Electronic Equipment: A Review,” Journal of Hazardous Materials B 99, 2003,
pp 243-263.