1 esm 595 f pollution prevention in the electronics industry

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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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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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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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Operational Factors Process Control Preventive maintenance Monitoring of concentrations in air &

water Materials handling & storage Inventory control

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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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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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Step 12: Develop Material Balance for each processing area

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Electroplating Line (Microplate 9000 line)

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Oxide coating area

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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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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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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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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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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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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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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

1 esm 595 f pollution prevention in the electronics industry

Documents

assembly slide

solid slide

disclosure slide

copper waste slide

electronics industry

wet etching slide

crystal growth slide

silicon wafer slide