Overview

General comment

QSFP28 100G SR4 optical transceiver module for short-reach datacenter applications. Uses 850nm GaAs VCSELs over multimode fiber (OM3/OM4). Lowest cost and lowest energy transceiver for rack-to-rack interconnects. 100m reach, uncooled operation, no optical isolator required.

Technology: Optoelectronics, Datacenter Transceiver
Geography: Global average data from equipment vendor specifications and industry literature

System boundary

The figure groups this dataset's unit processes by class. It is not a count of manufacturing steps — each process runs over as many passes as the flow requires, and those pass counts ship with the dataset.

Download this figure (SVG)

Data quality and references

Composite DQI 2.3 Good

Reliability

2.9

Completeness

2.3

Temporal

1.9

Geographic

2.0

Technological

2.4

How the score is calculated: Constituent datasets have more influence when they contribute a larger share of the modelled cradle-to-gate energy demand.

Pedigree scores follow the ecoinvent data-quality matrix: 1 is the best attainable, 5 the weakest. The composite is their aggregate.

Sampling procedure: Component vendor specifications, academic papers, industry literature
Coverage status: Composed from linked REEL datasets
Pedigree-scored source files: 69 — the source records behind this dataset's manufacturing operations. Each carries the five pedigree axes above; the composite DQI aggregates them.

Technosphere inputs

24 flows. Quantities are not published; they ship with the dataset on Circa.

Clock and Data Recovery IC REEL datasetwafer

Derivation basis: Calculated by the manufacturing model. The linked REEL dataset carries the upstream life cycle sources.

No source is attached to this row.
Source citations: Not stated
Upstream REEL dataset: 28nm Planar HKMG wafer, 300mm, moderate scenario
Background dataset: Modelled by REEL; see the upstream dataset above.
Notes: Wafer demand calculated from die count, rectangular wafer packing, die yield and assembly yield. Wafer manufacturing yield is already included upstream. This entry states no die yield of its own, so the sizing uses the die yield this dataset declares for that die.
Uncertainty: No range defined.
Unit: wafer

Transmitter Optical Subassembly REEL datasetwafer

Derivation basis: Calculated by the manufacturing model. The linked REEL dataset carries the upstream life cycle sources.

No source is attached to this row.
Source citations: Not stated
Upstream REEL dataset: GaAs VCSEL wafer, 100mm, United States
Background dataset: Modelled by REEL; see the upstream dataset above.
Notes: Wafer demand calculated from die count, rectangular wafer packing, die yield and assembly yield. Wafer manufacturing yield is already included upstream.
Uncertainty: No range defined.
Unit: wafer

Receiver Optical Subassembly REEL datasetwafer

Derivation basis: Calculated by the manufacturing model. The linked REEL dataset carries the upstream life cycle sources.

No source is attached to this row.
Source citations: Not stated
Upstream REEL dataset: InGaAs Photodiode wafer, 100mm, United States
Background dataset: Modelled by REEL; see the upstream dataset above.
Notes: Wafer demand calculated from die count, rectangular wafer packing, die yield and assembly yield. Wafer manufacturing yield is already included upstream. The sizing uses the die yield this dataset declares for that die rather than the one stated with the part.
Uncertainty: No range defined.
Unit: wafer

Printed Circuit Board REEL datasetm2

Derivation basis: Calculated by the manufacturing model. The linked REEL dataset carries the upstream life cycle sources.

No source is attached to this row.
Source citations: Not stated
Upstream REEL dataset: 6-Layer FR4 PCB, ENIG finish
Background dataset: Modelled by REEL; see the upstream dataset above.
Notes: Adjusted for assembly yield.
Uncertainty: No range defined.
Unit: m2

Fiber Connector REEL datasetunit

Derivation basis: Calculated by the manufacturing model. The linked REEL dataset carries the upstream life cycle sources.

No source is attached to this row.
Source citations: Not stated
Upstream REEL dataset: Fiber MPO Connector
Background dataset: Modelled by REEL; see the upstream dataset above.
Notes: Adjusted for assembly yield.
Uncertainty: No range defined.
Unit: unit

Decoupling capacitors (0201 size) REEL datasetunit

Derivation basis: Calculated by the manufacturing model. The linked REEL dataset carries the upstream life cycle sources.

No source is attached to this row.
Source citations: Not stated
Upstream REEL dataset: MLCC X7R 0201
Background dataset: Modelled by REEL; see the upstream dataset above.
Notes: Adjusted for assembly yield.
Uncertainty: No range defined.
Unit: unit

Bulk decoupling capacitors (0603 size) REEL datasetunit

Derivation basis: Calculated by the manufacturing model. The linked REEL dataset carries the upstream life cycle sources.

No source is attached to this row.
Source citations: Not stated
Upstream REEL dataset: MLCC X7R 0603
Background dataset: Modelled by REEL; see the upstream dataset above.
Notes: Adjusted for assembly yield.
Uncertainty: No range defined.
Unit: unit

Signal conditioning resistors REEL datasetunit

Derivation basis: Calculated by the manufacturing model. The linked REEL dataset carries the upstream life cycle sources.

No source is attached to this row.
Source citations: Not stated
Upstream REEL dataset: Chip Resistor 0402
Background dataset: Modelled by REEL; see the upstream dataset above.
Notes: Adjusted for assembly yield.
Uncertainty: No range defined.
Unit: unit

Power supply filtering REEL datasetunit

Derivation basis: Calculated by the manufacturing model. The linked REEL dataset carries the upstream life cycle sources.

No source is attached to this row.
Source citations: Not stated
Upstream REEL dataset: Ferrite Bead 0402
Background dataset: Modelled by REEL; see the upstream dataset above.
Notes: Adjusted for assembly yield.
Uncertainty: No range defined.
Unit: unit

Ball Lens (Glass) Materialkg · -33.3% / +46.7%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: proxy-mapped
Background dataset: flat glass, uncoated
Uncertainty: -33.3% / +46.7% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

Silver Materialkg

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: silver
Notes: From Die Attach Epoxy (conductive) (84.5% silver)
Uncertainty: No range defined.
Unit: kg

Epoxy resin, liquid Materialkg

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: epoxy resin, liquid
Notes: From Die Attach Epoxy (conductive) (15.5% epoxy)
Uncertainty: No range defined.
Unit: kg

Gold Wire (bonding) Materialkg · ±40%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: gold
Uncertainty: ±40% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

Gold Wire (wedge bonding) Materialkg · -33.4% / +66.6%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: gold
Uncertainty: -33.4% / +66.6% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

Latch Spring (301 SS) Materialkg · -30% / +40%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: steel, chromium steel 18/8, hot rolled
Uncertainty: -30% / +40% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

Nickel Plating Materialkg · ±33.3%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: nickel, class 1
Uncertainty: ±33.3% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

UV Cure Epoxy Materialkg · -28% / +40%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: epoxy resin, liquid
Uncertainty: -28% / +40% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

UV-Cure Epoxy (lens attach) Materialkg · -30% / +40%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: epoxy resin, liquid
Uncertainty: -30% / +40% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

Zinc Alloy (Zamak 3) Materialkg · -16.7% / +25%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: zamak ingot, 10% primary zinc input
Uncertainty: -16.7% / +25% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

Wafer transport, TW fab to packaging site - Air (short haul) Freight transporttkm · -47.4% / +80%

Derivation basis: Specified for this manufacturing operation and scaled to the dataset's functional unit.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: transport, freight, aircraft, dedicated freight, short haul
Notes: Freight for the part-finished product moving between REEL-modelled sites: the wafer fraction this dataset consumes, travelling from foundry fab to packaging site, cross-border. Shipped mass is that wafer fraction times the wafer mass implied by its declared diameter, times a shipping-packaging factor covering the returnable front-opening shipping box and its secondary carton; the packaging production burden is excluded as returnable, while its mass is carried because freight scales with what is actually shipped. Air freight is allocated on chargeable weight rather than actual shipped mass. The authored band holds the fixed route distance: its lower endpoint uses actual shipped mass, its central uses chargeable-weight allocation, and its upper endpoint adds the separate reusable-carrier return service, not aircraft backhaul.
Uncertainty: -47.4% / +80% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: tkm — tonne-kilometres, a transport effort rather than a mass

Wafer transport, United States – Western Grid (WECC) fab to packaging site - Air (long haul) Freight transporttkm · -47.4% / +80%

Derivation basis: Specified for this manufacturing operation and scaled to the dataset's functional unit.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: transport, freight, aircraft, dedicated freight, long haul
Notes: Freight for the part-finished product moving between REEL-modelled sites: the wafer fraction this dataset consumes, travelling from US compound-semiconductor fab to its Asian packaging site, intercontinental. Shipped mass is that wafer fraction times the wafer mass implied by the diameter, thickness and substrate its own model declares, times a shipping-packaging factor covering the returnable wafer shipping box and its secondary carton. No published container mass was found for a wafer of this diameter, so the factor carried here is the one derived for the largest diameter in this database rather than one derived for this one. The two diameters that do have a measured carrier show the factor rising as the wafer gets smaller, because a box's own mass does not fall in proportion to the wafer material it holds, so this leg's shipped mass is more likely to be understated than overstated; the packaging production burden is excluded as returnable, while its mass is carried because freight scales with what is actually shipped. Air freight is allocated on chargeable weight rather than actual shipped mass. The authored band holds the fixed route distance: its lower endpoint uses actual shipped mass, its central uses chargeable-weight allocation, and its upper endpoint adds the separate reusable-carrier return service, not aircraft backhaul. The route distance is a declared proxy: the route evidence records this vendor class's back-end location as not public and carries only a representative long-haul air lane from the United States to an Asian assembly hub, so that representative lane stands in for a site pair no public source states.
Uncertainty: -47.4% / +80% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: tkm — tonne-kilometres, a transport effort rather than a mass

Electricity, China (CN) ElectricitykWh · -19.7% / +26.6%

Derivation basis: Calculated from equipment energy across all manufacturing operations. This model includes no facility support, so the total is the manufacturing operations alone.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: electricity, medium voltage
Uncertainty: -19.7% / +26.6% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kWh

Process water WaterL · -18.5% / +26.1%

Derivation basis: Calculated from process-water and ultrapure-water demand across all manufacturing operations. This model includes no facility support, so the demand is the manufacturing operations alone. The fresh intake shown is that demand less the share reused under the water-recycling scenario this dataset assumes, and wastewater follows the same balance.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: tap water
Notes: Aggregated water demand of this dataset's production stages.
Uncertainty: -18.5% / +26.1% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: L

Nitrogen (N₂) Process gasg

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: nitrogen, liquid
Uncertainty: No range defined.
Unit: g

Outputs and waste

Lens array fallout Solid wasteg

Derivation basis: Calculated from the mass balance of spent materials and consumables, with treatment selected from the waste classification.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12 treatment route
Background dataset: treatment of inert waste, sanitary landfill
Uncertainty: No range defined.
Unit: g

Die attach failures Solid wasteg

Derivation basis: Calculated from the mass balance of spent materials and consumables, with treatment selected from the waste classification.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12 treatment route
Background dataset: treatment of inert waste, sanitary landfill
Uncertainty: No range defined.
Unit: g

Bond wire scrap Solid wasteg

Derivation basis: Calculated from the mass balance of spent materials and consumables, with treatment selected from the waste classification.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12 treatment route
Background dataset: treatment of inert waste, sanitary landfill
Uncertainty: No range defined.
Unit: g

Failed ROSA units Solid wasteg

Derivation basis: Calculated from the mass balance of spent materials and consumables, with treatment selected from the waste classification.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12 treatment route
Background dataset: treatment of inert waste, sanitary landfill
Uncertainty: No range defined.
Unit: g

Zinc runner/sprue Solid wasteg

Derivation basis: Calculated from the mass balance of spent materials and consumables, with treatment selected from the waste classification.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12 treatment route
Background dataset: market for zinc scrap, post-consumer
Uncertainty: No range defined.
Unit: g

Defective castings Solid wasteg

Derivation basis: Calculated from the mass balance of spent materials and consumables, with treatment selected from the waste classification.

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12 treatment route
Background dataset: market for zinc scrap, post-consumer
Uncertainty: No range defined.
Unit: g

Emissions to air

No emissions to air are recorded at this level.

Emissions to water

1 elementary flow released to water by this dataset's own operations. Quantities are not published; they ship with the dataset on Circa.

Ni (rinse water) Emission to waterg

Derivation basis: Calculated as a release to water, from a contaminant mass balance on the process chemistry.

No source is attached to this row.
Source citations: Not stated
Compartment: Water (surface water)
Formula: Ni2+
CAS number: 14701-22-5
ecoinvent 3.12 elementary flow: Nickel II
Uncertainty: No range defined.
Unit: g

Flows not quantified

10 flows are recorded for this dataset but carry no quantity — cut off below the significance threshold, or with no background dataset available. They remain inside the declared system boundary; each is listed with its reason.

Not modelled (10)

AlN Submount Materialkg · -33.3% / +41.6%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: not modelled
Background dataset: Not applicable: this flow is not quantified in the inventory.
Reason: The quantified material is retained, but its authored name does not identify a sufficiently specific background dataset or defensible proxy; background modeling remains an explicit gap.
Uncertainty: -33.3% / +41.6% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

AuSn Solder Preform Materialkg · -30% / +50%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: not modelled
Background dataset: Not applicable: this flow is not quantified in the inventory.
Reason: The quantified material is retained, but its authored name does not identify a sufficiently specific background dataset or defensible proxy; background modeling remains an explicit gap.
Uncertainty: -30% / +50% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

EMI Gasket (conductive elastomer) Materialkg · -30% / +40%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: not modelled
Background dataset: Not applicable: this flow is not quantified in the inventory.
Reason: The quantified material is retained, but its authored name does not identify a sufficiently specific background dataset or defensible proxy; background modeling remains an explicit gap.
Uncertainty: -30% / +40% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

FR4 or Ceramic Submount Materialkg · -33.3% / +46.7%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: not modelled
Background dataset: Not applicable: this flow is not quantified in the inventory.
Reason: The quantified material is retained, but its authored name does not identify a sufficiently specific background dataset or defensible proxy; background modeling remains an explicit gap.
Uncertainty: -33.3% / +46.7% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

Fiber Receptacle Materialkg · -33.3% / +40%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: not modelled
Background dataset: Not applicable: this flow is not quantified in the inventory.
Reason: The quantified material is retained, but its authored name does not identify a sufficiently specific background dataset or defensible proxy; background modeling remains an explicit gap.
Uncertainty: -33.3% / +40% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

Kovar Housing Materialkg · -30% / +40%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: not modelled
Background dataset: Not applicable: this flow is not quantified in the inventory.
Reason: The quantified material is retained, but its authored name does not identify a sufficiently specific background dataset or defensible proxy; background modeling remains an explicit gap.
Uncertainty: -30% / +40% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

Molded Lens Array (glass or polymer) Materialkg · -33.4% / +50%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: not modelled
Background dataset: Not applicable: this flow is not quantified in the inventory.
Reason: The quantified material is retained, but its authored name does not identify a sufficiently specific background dataset or defensible proxy; background modeling remains an explicit gap.
Uncertainty: -33.4% / +50% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

Multimode Fiber Pigtail (OM4) Materialkg · -30% / +40%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: not modelled
Background dataset: Not applicable: this flow is not quantified in the inventory.
Reason: The quantified material is retained, but its authored name does not identify a sufficiently specific background dataset or defensible proxy; background modeling remains an explicit gap.
Uncertainty: -30% / +40% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

TIA Die (SiGe BiCMOS) Materialkg · -40% / +60.1%

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: not modelled
Background dataset: Not applicable: this flow is not quantified in the inventory.
Reason: The quantified material is retained, but its authored name does not identify a sufficiently specific background dataset or defensible proxy; background modeling remains an explicit gap.
Uncertainty: -40% / +60.1% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

Nickel sulfamate plating bath Process chemicalg

Derivation basis: Calculated from per-operation consumption, operation counts, and manufacturing yield.

No source is attached to this row.
Source citations: Not stated
Background data: not modelled
Background dataset: Not applicable: this flow is not quantified in the inventory.
Reason: The quantified material is retained, but its authored name does not identify a sufficiently specific background dataset or defensible proxy; background modeling remains an explicit gap.
Uncertainty: No range defined.
Unit: g

Limitations and unquantified flows (1)

Limits this dataset declares about itself: first any limit stated in its own description, then any limit it declares flow by flow, grouped by channel. Each entry below is the model's own disclosure.

Between about a third and two thirds of the declared module mass is not itemised in this bill of materials. The optical sub-assemblies, electrical die and the housing are included; the remaining shell, gasket, thermal-interface and fastener mass is not.

The flows above are this dataset's own records. What follows are the scope rules set once for the whole database in the methodology report, repeated here so every dataset page carries them.

Database-wide boundary policy — applies to every REEL dataset

These boundaries are set once for the whole database, in Chapter 2 of the methodology report, and apply to this dataset wherever they are relevant to it. The excluded flows listed above are specific to this dataset.

Use phase: Product operation is outside the cradle-to-gate scope.
End-of-life treatment: Recycling and disposal are outside the cradle-to-gate scope.
Distribution and retail: The gate is a finished component ready for integration into a higher-level assembly.
Inbound transport of raw materials: Transport of purchased raw materials to the manufacturing facility is already inside the upstream "market for" datasets that users link to a background database, so it is not modelled a second time here. This does not cover freight between REEL production stages, which is modelled where a dataset authors it.
Returnable shipping containers: Where freight between production stages is modelled, the mass moved is the product itself. The shipping container (FOSB, SEMI M31) is returnable capital equipment whose per-trip share is unsourced, so its tare is excluded from the transport effort.
Photomask fabrication: A mask set's embodied burden is amortised across a high-volume production run and is not attributed per wafer. Users assessing low-volume production should add mask fabrication separately; the methodology report gives the basis for the exclusion.
Employee transport, administration and R&D overhead: Employee transportation, facility administration and R&D/pilot-production overhead are outside scope.
Capital goods: Manufacturing equipment, cleanroom construction and facility infrastructure are excluded, on the grounds of absent public data on equipment embodied energy, uncertainty in equipment lifetime and allocation, common practice in electronics LCA, and a focus on the operational inventory. Future versions may include capital goods when sufficient public data becomes available.
Precious metal recovery credits: Scrap recovery credits for precious metals are excluded pending data availability.
Wafer reclaim: Test wafers and scrap are outside the system boundary.

Inside the boundary, linked rather than modelled

Silicon ingot growth and wafer slicing: Inside the cradle-to-gate scope, but treated as upstream material inputs linked to background databases rather than modelled as REEL processes.
Freight between production stages: Where a dataset's product moves between REEL production stages - wafer fabrication to the packaging site, for example - that leg is authored as a transport service and linked to an ecoinvent freight activity. It is measured as a transport effort in tonne-kilometres, not as a mass. Route distances are authored per route class with a stated band; a lower bound of zero is a modelling statement that the two sites can be co-located, not a missing value.

Cut-off criteria

A flow is excluded from a process inventory when it contributes less than 1 % of the total mass of inputs to that unit process, or less than 1 % of its total energy input. The denominator is total process inputs, not product mass. That distinction matters in semiconductor manufacturing, where the input mass of water, chemicals and gases greatly exceeds the product mass, so the threshold removes only genuinely minor flows.

Included regardless of the cut-off

Perfluorocarbons (CF4, C2F6, SF6, NF3) - high GWP, EPA regulated
Heavy metals (Pb, Cd, Hg, Cr(VI)) - RoHS regulated, high toxicity
Volatile organics (photoresist solvents, PGMEA) - air quality
Precious metals (Au, Ag, Pd, Pt) - high embodied impacts
Ozone-depleting substances (legacy CFCs, HCFCs) - Montreal Protocol