ESM 595 F

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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