Overview

General comment

Production covered

Generic flip-chip ball grid array package: a die bonded face-down onto an organic substrate by copper pillars, then underfilled and lidded, with solder balls beneath the substrate. In addition to the operations shared by the sized leaves, this wider boundary includes die-side mass reflow, a separate underfill-cure step, optional burn-in, laser marking, and tray packaging; compare totals only after aligning scope. Functional unit is one package STARTED: the reference flow is a single package entering assembly, and the activities listed run through completed assembly and final test of that package.

Modelling choices

By the count-once yield-ownership convention, the gross-up from packages started to good packages is carried by the consuming IC or component dataset, not here.

Technology: FC-BGA
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 1.9 Very good

Reliability

2.7

Completeness

2.1

Temporal

1.4

Geographic

1.9

Technological

1.5

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

Sampling procedure: Equipment vendor specifications, academic papers, industry literature
Coverage status: Partial
Pedigree-scored source files: 14 — the source records behind this dataset's manufacturing operations. Each carries the five pedigree axes above; the composite DQI aggregates them.

Technosphere inputs

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

ArF Photoresist Process chemicalg · -33.3% / +66.7%

Source citations: microsi.com (date not recorded). Flack, W.W., Nguyen, H.-A. (Ultratech), Capsuto, E. (Shin-Etsu MicroSi), Abreau, K. (STEAG Hamatech USA), "Characterization of 100 Micron Thick Positive Photoresist on 300 mm Wafers", SPIE 2005 #5753-103. PDF document.
nrf.aux.eng.ufl.edu (date not recorded). AZ 9260 PHOTORESIST (520CPS) (US) Material Safety Data Sheet, substance key SXR109902, revision date 03/03/2010. PDF document.
Upstream REEL dataset: ArF Photoresist (193nm)
Background dataset: Modelled by REEL; see the upstream dataset above.
Uncertainty: -33.3% / +66.7% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

TMAH Developer (2.38% solution) Process chemicalg · ±33.3%

Derivation basis: Developer usage

No source is attached to this row.
Source citations: Not stated
Upstream REEL dataset: TMAH Developer (2.38% solution) (N(CH3)4OH (aq))
Background dataset: Modelled by REEL; see the upstream dataset above.
Uncertainty: ±33.3% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

Water supply (municipal) Waterm3 · -38.2% / +77.5%

Derivation basis: Calculated from process-water and ultrapure-water demand across all manufacturing operations, plus facility water allocated to each finished unit. 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
Upstream REEL dataset: Water Supply (Municipal)
Background dataset: Modelled by REEL; see the upstream dataset above.
Notes: Net fresh-water intake, supplied as municipal water
Uncertainty: -38.2% / +77.5% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: m3

Electricity, Taiwan (TW) ElectricitykWh · -77% / +201.2%

Derivation basis: Calculated from equipment energy across all manufacturing operations. It also includes the assembly site's facility overhead: air handling and cleanroom conditioning, chilled water, compressed dry air, exhaust and dust collection, wastewater treatment and uninterruptible power.
REEL derivation: engineering estimate of per-package laser-marking energy from the marker system power rating and line throughput; no single published document reports this per-package value

The sources below come from the manufacturing operations behind this row.
Sources (inherited): Inherited, rolled up from the contributing process steps:

advantest.com (2024). Advantest Unveils New Ultra-High-Current Power Supply for V93000 EXA Scale SoC Test System. Web page.

teradyne.com. Titan HP | Teradyne.

directindustry.es (date not recorded). Sistema de prueba para la industria electrónica - Titan HP - Teradyne - para semiconductores / modular / de alta potencia. Web page.

electronics360.globalspec.com (date not recorded). Chip complexity drives surge in system-level testing | Electronics360. Web page.

teradyne.com (date not recorded). Titan System Level Test. Web page.
Background data: ecoinvent 3.12
Background dataset: electricity, medium voltage
Uncertainty: -77% / +201.2% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kWh

Ar Process gasg · ±76.5%

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: argon, liquid
Uncertainty: ±76.5% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

N₂ Process gasg · -12.2% / +14.8%

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: -12.2% / +14.8% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

Compressed air Process gasg · -10% / +15%

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: compressed air, 700 kPa gauge
Uncertainty: -10% / +15% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

Compressed air (tool) Process gasg · -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: compressed air, 700 kPa gauge
Uncertainty: -33.4% / +66.6% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

Cu plating bath (CuSO₄ + H₂SO₄) Process chemicalg · -33.3% / +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: proxy-mapped
Background dataset: copper sulfate
Uncertainty: -33.3% / +50% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

Stencil cleaner (IPA) Process chemicalg · -50% / +100%

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: isopropanol
Uncertainty: -50% / +100% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

Flux (water soluble) Process chemicalg · -40% / +100%

Derivation basis: Flux type for FOWLP solder ball attach

No source is attached to this row.
Source citations: Not stated
Background data: ecoinvent 3.12
Background dataset: flux, for wave soldering
Uncertainty: -40% / +100% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

Capillary underfill (epoxy) Process chemicalg · -33.3% / +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: ecoinvent 3.12
Background dataset: epoxy resin insulator, SiO2
Uncertainty: -33.3% / +50% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

Lid adhesive (silicone) Process chemicalg · -69% / +343.1%

Source citations: patents.google.com (date not recorded). Intel Corporation, US20210398871A1, "Integrated circuit heat spreader including sealant interface material", priority date 2020-06-18, publication date 2021-12-23. Patent.
freepatentsonline.com (date not recorded). Taiwan Semiconductor Manufacturing Company, Ltd., US20130260511A1, "Lid attach process and apparatus for fabrication of semiconductor packages", filed 2012-06-12. Patent.
freepatentsonline.com (date not recorded). Taiwan Semiconductor Manufacturing Company, Ltd., US20170076960A1, "Lid attach processes for semiconductor packages", filed 2016-11-02. Patent.
Henkel, Technical Data Sheet, LOCTITE ABLESTIK 104, December 2015, Reference 0.0, 2 pp
Henkel, Technical Data Sheet, LOCTITE(R) ABLESTIK 286, November 2024, 1 p
Background data: ecoinvent 3.12
Background dataset: silicone product
Uncertainty: -69% / +343.1% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

BT resin core + ABF buildup Materialunit · ±9.1%

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: ABF Substrate
Background dataset: Modelled by REEL; see the upstream dataset above.
Uncertainty: ±9.1% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: unit

Cu 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: copper, cathode
Uncertainty: No range defined.
Unit: kg

Thermal interface material Materialkg · -50.7% / +146.6%

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: silicone product
Uncertainty: -50.7% / +146.6% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: kg

Outputs and waste

Wastewater Wastewaterm3 · -38.2% / +77.5%

Derivation basis: Calculated from the water balance: fresh-water input minus evaporation.

No source is attached to this row.
Source citations: Not stated
Background data: carried, no background dataset
Background dataset: No treatment route recorded for this output.
Uncertainty: -38.2% / +77.5% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: m3

Spent photoresist (liquid spin-off) Solid wasteg · -33.8% / +385.1%

Source citations: microsi.com (date not recorded). Flack, W.W., Nguyen, H.-A. (Ultratech), Capsuto, E. (Shin-Etsu MicroSi), Abreau, K. (STEAG Hamatech USA), "Characterization of 100 Micron Thick Positive Photoresist on 300 mm Wafers", SPIE 2005 #5753-103. PDF document.
nrf.aux.eng.ufl.edu (date not recorded). AZ 9260 PHOTORESIST (520CPS) (US) Material Safety Data Sheet, substance key SXR109902, revision date 03/03/2010. PDF document.
epa.gov (date not recorded). US EPA, Emission Inventory Improvement Program (EIIP) Volume II, Chapter 6: Preferred and Alternative Methods for Estimating Air Emissions from Semiconductor Manufacturing, 2/24/99. PDF document.
rcrapublic.epa.gov (date not recorded). US EPA RCRA Online RO 11249, memorandum 9444.1987(18), letter to Mr. Frank Czigler, S & W Waste Inc., dated MAY 20 1987. PDF document.
pmc.ncbi.nlm.nih.gov (date not recorded). Ni, J., Zhang, Q., Zhang, X., Sun, Z., Bao, D., "Detection Method and Common Characteristics of Waste Solvent from Semiconductor Industry", Molecules 28(16):5992, 2023. Journal article.
epa.gov (date not recorded). US EPA, "Defining Hazardous Waste: Listed, Characteristic and Mixed Radiological Wastes".
Background data: ecoinvent 3.12 treatment route
Background dataset: treatment of hazardous waste, hazardous waste incineration, with energy recovery
Uncertainty: -33.8% / +385.1% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

Photoresist solids in NMP strip bath Solid wasteg · -33.4% / +66.6%

Source citations: microsi.com (date not recorded). Flack, W.W., Nguyen, H.-A. (Ultratech), Capsuto, E. (Shin-Etsu MicroSi), Abreau, K. (STEAG Hamatech USA), "Characterization of 100 Micron Thick Positive Photoresist on 300 mm Wafers", SPIE 2005 #5753-103. PDF document.
nrf.aux.eng.ufl.edu (date not recorded). AZ 9260 PHOTORESIST (520CPS) (US) Material Safety Data Sheet, substance key SXR109902, revision date 03/03/2010. PDF document.
rcrapublic.epa.gov (date not recorded). US EPA RCRA Online RO 11249, memorandum 9444.1987(18), letter to Mr. Frank Czigler, S & W Waste Inc., dated MAY 20 1987. PDF document.
Background data: ecoinvent 3.12 treatment route
Background dataset: treatment of hazardous waste, hazardous waste incineration, with energy recovery
Uncertainty: -33.4% / +66.6% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

Copper in wastewater-treatment sludge/recovery Solid wasteg · -2.5% / +0.5%

Source citations (dataset-level): epa.gov (date not recorded). U.S. EPA Office of Water, "Preliminary Study of the Electrical and Electronic Components Point Source Category", EPA-821-R-22-005, DCN 11197 (2022) - Table 12 indirect Cu median 0.05 / mean 0.213 / max 5.64 / min 0.00015 mg/L (67 facilities, 1,309 results, 996 detects); Table 13 direct; Table 6 named-facility treatment trains; sec. 1.2.3.1 post-1983 process additions. Government report.
Source citations (dataset-level): Inherited from this dataset's own bibliography, not tied to this row:

epa.gov (date not recorded). U.S. EPA Office of Water, "Preliminary Study of the Electrical and Electronic Components Point Source Category", EPA-821-R-22-005, DCN 11197 (2022) - Table 12 indirect Cu median 0.05 / mean 0.213 / max 5.64 / min 0.00015 mg/L (67 facilities, 1,309 results, 996 detects); Table 13 direct; Table 6 named-facility treatment trains; sec. 1.2.3.1 post-1983 process additions. Government report.
Background data: ecoinvent 3.12 treatment route
Background dataset: market for copper scrap, sorted, pressed
Uncertainty: -2.5% / +0.5% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

Flux residue on stencil 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 hazardous waste, hazardous waste incineration, with energy recovery
Uncertainty: No range defined.
Unit: g

Mixed process waste Solid wasteg

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

The sources below come from the manufacturing operations behind this row.
Sources (inherited): Inherited, rolled up from the contributing process steps:

patents.google.com (date not recorded). Intel Corporation, US20210398871A1, "Integrated circuit heat spreader including sealant interface material", priority date 2020-06-18, publication date 2021-12-23. Patent.

freepatentsonline.com (date not recorded). Taiwan Semiconductor Manufacturing Company, Ltd., US20130260511A1, "Lid attach process and apparatus for fabrication of semiconductor packages", filed 2012-06-12. Patent.

freepatentsonline.com (date not recorded). Taiwan Semiconductor Manufacturing Company, Ltd., US20170076960A1, "Lid attach processes for semiconductor packages", filed 2016-11-02. Patent.

Henkel, Technical Data Sheet, LOCTITE ABLESTIK 104, December 2015, Reference 0.0, 2 pp

Henkel, Technical Data Sheet, LOCTITE(R) ABLESTIK 286, November 2024, 1 p

smtnet.com (date not recorded). Punit Kohli, Martin Sobczak, Jeff Bowin, Michael Matthews (Ablestik Laboratories, Rancho Dominguez, California), "Advanced Thermal Interface Materials for Enhanced Flip Chip BGA". PDF document.

Wacker Chemie AG, "WACKER(R) SILICONE PASTE P 12 -- Thermally conductive silicone paste", technical data sheet, Version 1.5, date of last alteration 14.04.2014, 2 pp

Henkel, Technical Data Sheet, LOCTITE ABLESTIK 2902, August 2021, Reference 0.5, 2 pp

amkor.com (date not recorded). MiKyeong Choi, HyunHye Jung, KwangSeok Oh, DongSu Ryu, SangHyoun Lee, WonChul Do, YoungDo Kweon, Mike Kelly, KyungRok Park, JinYoung Khim, Ron Huemoeller, "Development of an Extremely High Thermal Conductivity TIM for Large Electronics Packages in the 4th Industrial Revolution Era", 2020 IEEE 70th Electronic Components and Technology Conference (ECTC), pp. 1332-1336, DOI 10.1109/ECTC32862.2020.00211. Academic paper.
Background data: ecoinvent 3.12 treatment route
Background dataset: treatment of inert waste, sanitary landfill
Uncertainty: No range defined.
Unit: g

Emissions to air

4 elementary flows released to air by this dataset's own operations. Quantities are not published; they ship with the dataset on Circa.

Flux volatiles Emission to airg

Derivation basis: Calculated as an air release, from a mass balance on the process gases going in, with the destruction or removal efficiency of any point-of-use abatement applied.

No source is attached to this row.
Source citations: Not stated
Compartment: Air (non-urban air or from high stacks)
ecoinvent 3.12 elementary flow: NMVOC, non-methane volatile organic compounds
Uncertainty: No range defined.
Unit: g

VOCs (from underfill cure) Emission to airg

Derivation basis: Calculated as an air release, from a mass balance on the process gases going in, with the destruction or removal efficiency of any point-of-use abatement applied.

No source is attached to this row.
Source citations: Not stated
Compartment: Air (non-urban air or from high stacks)
ecoinvent 3.12 elementary flow: NMVOC, non-methane volatile organic compounds
Uncertainty: No range defined.
Unit: g

VOCs Emission to airg

Derivation basis: Calculated as an air release, from a mass balance on the process gases going in, with the destruction or removal efficiency of any point-of-use abatement applied.

No source is attached to this row.
Source citations: Not stated
Compartment: Air (non-urban air or from high stacks)
ecoinvent 3.12 elementary flow: NMVOC, non-methane volatile organic compounds
Uncertainty: A minimum-maximum range is defined for this flow. Bounds ship with the dataset on Circa.
Unit: g

Particulates (marking fume) Emission to airg

Derivation basis: Estimated from mold compound ablation

No source is attached to this row.
Source citations: Not stated
Compartment: Air (non-urban air or from high stacks)
ecoinvent 3.12 elementary flow: Particulate Matter, < 2.5 um
Uncertainty: A minimum-maximum range is defined for this flow. Bounds ship with the dataset on Circa.
Unit: g

Emissions to water

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

Cu2+ Emission to waterg

Source citations: epa.gov (date not recorded). U.S. EPA Office of Water, "Preliminary Study of the Electrical and Electronic Components Point Source Category", EPA-821-R-22-005, DCN 11197 (2022) - Table 12 indirect Cu median 0.05 / mean 0.213 / max 5.64 / min 0.00015 mg/L (67 facilities, 1,309 results, 996 detects); Table 13 direct; Table 6 named-facility treatment trains; sec. 1.2.3.1 post-1983 process additions. Government report.
Compartment: Water (surface water)
Formula: Cu
CAS number: 7440-50-8
ecoinvent 3.12 elementary flow: Copper ion
Uncertainty: A minimum-maximum range is defined for this flow. Bounds ship with the dataset on Circa.
Unit: g

Sn2+ Emission to waterg

Source citations: p2infohouse.org (date not recorded). Florida Pollution Prevention Program - Electroplating Tip Sheet: Drag-Out Reduction (2000). Report.
p2infohouse.org (date not recorded). Florida Pollution Prevention Program - Electroplating Tip Sheet: Rinse Water Reduction (2000). Report.
Park et al. - Effects of the degradation of methane sulfonic acid electrolyte on the collapse failure of Sn-Ag alloy solders for flip-chip interconnections, RSC Advances, 2017
Compartment: Water (surface water)
Formula: Sn
CAS number: 7440-31-5
ecoinvent 3.12 elementary flow: Tin ion
Uncertainty: A minimum-maximum range is defined for this flow. Bounds ship with the dataset on Circa.
Unit: g

Ammonium Emission to waterg

Source citations: p2infohouse.org (date not recorded). Florida Pollution Prevention Program - Electroplating Tip Sheet: Drag-Out Reduction (2000). Report.
p2infohouse.org (date not recorded). Florida Pollution Prevention Program - Electroplating Tip Sheet: Rinse Water Reduction (2000). Report.
Park et al. - Effects of the degradation of methane sulfonic acid electrolyte on the collapse failure of Sn-Ag alloy solders for flip-chip interconnections, RSC Advances, 2017
Compartment: Water (surface water)
Formula: NH4+
CAS number: 14798-03-9
ecoinvent 3.12 elementary flow: Ammonium
Notes: TMAH biodegrades in WWTP; NH4+ mass fraction 18.04/91.15
Uncertainty: A minimum-maximum range is defined for this flow. Bounds ship with the dataset on Circa.
Unit: g

Dissolved organics (COD) Emission to waterg

Source citations: p2infohouse.org (date not recorded). Florida Pollution Prevention Program - Electroplating Tip Sheet: Drag-Out Reduction (2000). Report.
p2infohouse.org (date not recorded). Florida Pollution Prevention Program - Electroplating Tip Sheet: Rinse Water Reduction (2000). Report.
Park et al. - Effects of the degradation of methane sulfonic acid electrolyte on the collapse failure of Sn-Ag alloy solders for flip-chip interconnections, RSC Advances, 2017
Compartment: Water (surface water)
ecoinvent 3.12 elementary flow: COD, Chemical Oxygen Demand
Uncertainty: A minimum-maximum range is defined for this flow. Bounds ship with the dataset on Circa.
Unit: g

Flows not quantified

1 flow is recorded for this dataset but carries no quantity — cut off below the significance threshold, or with no background dataset available. It remains inside the declared system boundary; each is listed with its reason.

Cut off - below the significance threshold (1)

SnAg plating bath (MSA-based) Process chemicalg · -40% / +60%

Derivation basis: Solder plating bath

No source is attached to this row.
Source citations: Not stated
Background data: cut off
Background dataset: Not applicable: this flow is not quantified in the inventory.
Reason: The tin-silver plating bath is consumed in trace quantity and its formulation is complex, recorded in this inventory. This row covers the bath chemistry alone; the tin and silver the bath deposits onto the package are not carried on it. Where this dataset lists no separate deposited-solder material row, the deposited tin and silver are absent from the dataset altogether rather than accounted for elsewhere, and whether they belong inside this boundary is an open question this record does not settle. The bath chemistry falls below the declared cut-off threshold, so no upstream production dataset is attached.
Uncertainty: -40% / +60% around the published quantity. The bounds themselves ship with the dataset on Circa.
Unit: g

Limitations and unquantified flows (2)

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.

These materials are used at a step of the modelled flow and are also carried by this dataset's own material list. Each is counted once, on that list, and the step does not book it again: Complete flip-chip bumping uses Copper (anode or replenishment); TIM dispense uses Thermal Interface Material.
Some consumable pulls referenced by the modelled process steps did not resolve to an inventory row and are absent from this dataset. They are itemised in the dataset's own export audit.

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