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ESM 595 F
Pollution Prevention in the
Electronics Industry
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Electronics Industry
Fast growing sector of economyFew common appliances and
machines could function without electronics
Perceived as “pollution-free” since it has no smoke stacks
Environmental impacts ...
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Semiconductor Manufacture
Crystal GrowthWafer fabricationDeposit of active and inactive layersOxidation to form silicon oxidePhotolithographyEtchingAddition of impurities for special
functions
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Crystal Growth
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Silicon Wafer
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Printed Circuit Board
Patterns of Conductive Material set on a Non-conductive base
Conductive Materials: Cu, Al, Cr, NiNon-conductive: Epoxy/paper,
phenolic resin, epoxy/glass resin, teflon
Conductor can be added as lines or as a layer which is then etched
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Printed Circuit Board
Clean and prepare surface (drilling, burring, solvent wash, abrasive wash, alkaline wash)
Electroless copper plating (thin layer through holes)
Pattern printing and maskingElectroplatingEtching
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Circuit Board Assembly
Insert componentsAdhere componentsCure adhesiveSolderFinal cleaning
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Other Process Considerations
Piping of gases and corrosive liquidsCooling water to control processing
temperatureDeionised water productionClean room conditionsHandling of process wastes (gas,
liquid, solid)
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Waste Streams
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Waste Streams
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Waste Streams
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Example: Copper Waste
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Environmental Impacts
From Manufacturing Air emissions Wastewater Solids, sludges and Haz wastes
From Product Use Energy (electrical or batteries)
From Product Disposal
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Example: Pager
Disposed due to end of useful life obsolescence
To recover useful materials, need to consider: labor to disassemble segregated storage & transportation reprocessing
Balance against scrap value of materials
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Example: Pager
Circuit board is sent to a reclamation facility burn off organic materials (epoxy, paper) recover metals: Au, Ag, Pt, Pd, Cu, Al, Ni,
Cr Gold may represent less than 1% but
account for more than 90% of value Estimated value of average circuit board
is $7 per pound ($3/kg) (1992 prices)
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Example: Pager
Other reusable parts vibrator motor microprocessor oscillator crystals filters coils antennae
Valued at $19.28Warranty, obsolescence, disclosure
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Pollution Prevention Tools
Life-Cycle Assessment/EIAProduct Design
Higher density of transistors in each chip Higher density Surface Mount Technology
vs. conventional plated-hole technology Use more common plastics Reduce plastics/metals assemblies Use built-in plastic or metal clips for
assembly
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Pollution Prevention Tools
Process Design Vacuum pack after epitaxy Iron oxide masks (vs. emulsion masks) Single solvent systems (recover/reuse) Water based developer (vs. solvent) Infrared heating lamps for drying Filtering plating, etching baths Dry etching vs. wet etching
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Pollution Prevention Tools
Material Selection Aqueous cleaning materials vs. solvents Purification of solvents Eliminate use of CFCs by substitution Reduce number of acids, and use those
that result in non-toxics when neutralized (e.g. HCl vs. Trichloroacetic acid)
Lead-free solder
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Pollution Prevention Tools
Operational Factors Process Control Preventive maintenance Monitoring of concentrations in air &
water Materials handling & storage Inventory control
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Pollution Prevention Tools
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Pollution Prevention Tools
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Waste Stream Processing
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Waste Stream Processing
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Waste Stream Processing
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Waste Stream Processing
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Step-by-Step Case Study
Case Study of Pollution Prevention for Printed Circuit Board
Phase I: Preassessment Step 1: Form audit team & develop
objectives Step 2: List Unit Operations Step 3: Construct Process Flow Diagrams
with emissions and waste streams
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Case Study of Pollution Prevention for Printed Circuit Board
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Case Study of Pollution Prevention for Printed Circuit Board
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Case Study of Pollution Prevention for Printed Circuit Board
Phase 2: Material Balances Step 4: Determine Inputs Step 5: Record Water Usage Step 6: Determine Reuse/Recycle Rates Step 7: Quantify Process Outputs Step 8: Characterize wastewater streams Step 9: Account for gaseous emissions Step 10: Account for off-site wastes Step 11: Assemble Input + Output Information
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Case Study of Pollution Prevention for Printed Circuit Board
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Case Study of Pollution Prevention for Printed Circuit Board
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Case Study of Pollution Prevention for Printed Circuit Board
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Case Study of Pollution Prevention for Printed Circuit Board
Step 12: Develop Material Balance for each processing area
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Case Study of Pollution Prevention for Printed Circuit Board
Electroplating Line (Microplate 9000 line)
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Case Study of Pollution Prevention for Printed Circuit Board
Oxide coating area
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Case Study of Pollution Prevention for Printed Circuit Board
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Case Study of Pollution Prevention for Printed Circuit Board
Step 13: Evaluating the Material Balance Micro-etch rinse accounts for 90% of copper
loading in sensitizing area Micro-etch rinse accounts for 56% of total
plant rinse water copper loading to treatment plant
Other major sources of contaminated rinse water are electroplating rinse, sulfuric acid/peroxide rinse and deburrer rinse
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Case Study of Pollution Prevention for Printed Circuit Board
Step 14: Refining Material BalancesStep 15: Implementing Obvious Waste
Reduction Measures Sand filter in deburring operation was
backwashed with dirty water, leading to entrainment of copper fines throughout sand bed and release into filtered water
Bag filter captures copper fines, but these are sent to landfill. At 2.6 kg/3 days and $0.9/kg, it means $275 per year
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Case Study of Pollution Prevention for Printed Circuit Board
Step 15: Implementing Obvious Waste Reduction Measures Recirculating pumps in copper
electroplating line drip weak copper solution onto floor, which then goes to drains. Loading of about 70 g Cu/day
Alum added to wastewater in pit 1 not necessary for metal hydroxide precipitation (only useful for colloids). Increases sludge volume
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Case Study of Pollution Prevention for Printed Circuit Board
Step 15: Implementing Obvious Waste Reduction Measures Sand filters installed after sedimentation tank
were not reducing Cu in effluent (nor SS) A 50% reduction in Cu loading from sensitizing
micro-etch rinse through improved rinsing could result in a 40% reduction in rinse water loading to wastewater treatment plant, and lower Cu in outlet
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Case Study of Pollution Prevention for Printed Circuit Board
Step 16: Treatability TestsStep 17: Long-Term Waste Reduction
Options Wastewater segregation and treatment Upgrading pH adjustment, clarification,
sand filtration systems Installation of static rinse tank in electroless
copper plating bath to collect Cu electrolytically in a special treatment unit
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Case Study of Pollution Prevention for Printed Circuit Board
Step 18: Economic Evaluation Copper recovery: $3,500/yr Reduced sludge transportation and
landfilling costs: $22,000/yr Process improvements & capital
expenditures: $265,000/yr
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Case Study of Pollution Prevention for Printed Circuit Board
Step 19: Other considerations Effluent does not comply with NPDES
permit Legal action possible Time spent by upper mgmt on
wastewater issuesStep 20: Develop and Implement
Action Plan