ESM 595 F
Pollution
Prevention in
the Electronics
Industry
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Electronics Industry
Fast growing sector of economy
Few 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 Growth
Wafer fabrication
Deposit of active and inactive layers
Oxidation to form silicon oxide
Photolithography
Etching
Addition 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, Ni
Non-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 masking
Electroplating
Etching
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Circuit Board Assembly
Insert components
Adhere components
Cure adhesive
Solder
Final cleaning
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Other Process Considerations
Piping of gases and corrosive liquids
Cooling water to control processing
temperature
Deionised water production
Clean room conditions
Handling 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 $19.28
Warranty, obsolescence, disclosure
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Pollution Prevention Tools
Life-Cycle Assessment/EIA
Product 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 Balances
Step 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 Tests
Step 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
issues
Step 20: Develop and Implement Action
Plan
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