SAC305 solder (Sn-3.0Ag-0.5Cu) SAC305

spore: profile
id: solder-sac305
spore_version: 0.2
family: low-melting-metals-and-solders
name: SAC305 solder (Sn-3.0Ag-0.5Cu)
abbreviation: SAC305
role: lead-free solder alloy
category: metals
type: heavy-metals
summary: |
  SAC305 is a lead-free solder of 96.5 % tin, 3.0 % silver and 0.5 % copper by weight. It is a hypoeutectic member of the Sn-Ag-Cu family and the most widely used composition for replacing tin-lead solder in electronics. The Indium Corporation datasheet gives a solidus of 217 °C, a liquidus of 220 °C, a density of 7.35 g/cc, a thermal conductivity of 61 W/mK and a thermal expansion coefficient of 21 ppm/°C. Tensile strength is 39.58 MPa in that datasheet and 29.7 MPa in the Henkel bar datasheet, and the sources do not explain the difference. A 2018 electrochemical study in 3.5 wt % NaCl reports a passivating surface layer of SnO, SnO2 and SnCl-.
best_for: Lead-free electronics soldering that needs the most widely documented Sn-Ag-Cu composition, at a melting range of 217 to 220 °C (Indium, Henkel)
weakest_at: 'Strength and creep: tensile strength of 29.7 to 39.58 MPa across two datasheets, and creep and stress relaxation during thermal cycling (SMTA 2025)'
identity:
  formula: 'Sn-3.0Ag-0.5Cu by weight: 96.5 % tin, 3.0 % silver, 0.5 % copper (hypoeutectic Sn-Ag-Cu alloy)'
  source: indium-256
  where: Introduction and Metallurgy sections, composition 96.5% tin, 3.0% silver, and 0.5% copper
  designations:
    - system: Trade name
      code: 97SC
      source: henkel-bar
      where: Solder Bar Typical Properties table, row Alloy 97SC (SAC305)
tags:
  applications:
    - electronics-and-chips
  stresses:
    - thermal-cycling
properties:
  - benchmark: density
    label: Density of SAC305 (Indium datasheet)
    value: 7.35
    unit: g/cc
    scope: material
    conditions:
      form: Indalloy 256 (SAC305) as printed; temperature not stated
    method: Value printed in the Selected Properties table of the product data sheet
    status: ground
    source: indium-256
    where: Indalloy 256 Properties table, Density row (7.35 g/cc)
  - benchmark: melting_point
    label: Solidus (start of melting)
    value: 217
    unit: °C
    scope: material
    conditions:
      basis: ternary alloy, 96.5% Sn, 3.0% Ag, 0.5% Cu as printed
    method: Value printed in the Selected Properties table of the product data sheet
    status: ground
    source: indium-256
    where: Indalloy 256 Properties table, Solidus row (217 °C, 423 °F)
  - benchmark: liquidus_temperature
    label: Liquidus (end of melting)
    value: 220
    unit: °C
    scope: material
    conditions:
      basis: same alloy as printed
    method: Value printed in the Selected Properties table of the product data sheet
    status: ground
    note: liquidus_temperature is not a name in property-canon.yaml; used as written.
    source: indium-256
    where: Indalloy 256 Properties table, Liquidus row (220 °C, 428 °F)
  - benchmark: melting_point
    label: Melting point range printed in the supplier SDS
    value: 217
    value_high: 218
    bound: range
    unit: °C
    scope: material
    conditions:
      form: bar or wire, massive form, as printed in section 9.1
    method: Range printed in section 9.1 of the AIM SAC305 safety data sheet
    status: ground
    source: aim-sds
    where: Section 9.1, Melting point/freezing point row (217 to 218°C)
  - benchmark: thermal_conductivity
    label: Thermal conductivity (Indium datasheet)
    value: 61
    unit: W/mK
    scope: material
    conditions:
      temperature: not stated in the datasheet
    method: Value printed in the Selected Properties table of the product data sheet
    status: ground
    source: indium-256
    where: Indalloy 256 Properties table, Thermal Conductivity row (61 W/mK)
  - benchmark: cte
    label: Coefficient of thermal expansion (Indium datasheet)
    value: 21
    unit: ppm/°C
    scope: material
    conditions:
      temperature: range not stated in the datasheet
    method: Value printed in the Selected Properties table of the product data sheet
    status: ground
    source: indium-256
    where: Indalloy 256 Properties table, CTE row (21 ppm/°C)
  - benchmark: electrical_resistivity
    label: Electrical resistivity (Indium datasheet)
    value: 13.2
    unit: μ Ohm-cm
    scope: material
    conditions:
      temperature: not stated in the datasheet
    method: Value printed in the Selected Properties table of the product data sheet
    status: ground
    source: indium-256
    where: Indalloy 256 Properties table, Electrical Resistivity row (13.2 μ Ohm-cm)
  - benchmark: elastic_modulus
    label: Young's modulus (Indium datasheet)
    value: 6.9
    unit: GPa
    scope: material
    conditions:
      test: not stated in the datasheet
    method: Value printed in the Selected Properties table of the product data sheet (1,000 ksi)
    status: ground
    source: indium-256
    where: Indalloy 256 Properties table, Young's Modulus row (6.9 GPa)
  - benchmark: poissons_ratio
    label: Poisson's ratio (Indium datasheet)
    value: 0.35
    unit: '-'
    scope: material
    conditions:
      test: not stated in the datasheet
    method: Value printed in the Selected Properties table of the product data sheet
    status: ground
    source: indium-256
    where: Indalloy 256 Properties table, Poisson's Ratio row (0.35)
  - benchmark: ultimate_tensile_strength
    label: Tensile strength (Indium datasheet)
    value: 39.58
    unit: MPa
    scope: material
    conditions:
      form: not stated in the datasheet
      test_method: not stated in the datasheet
    method: Value printed in the Selected Properties table of the product data sheet (5,740 psi)
    status: ground
    note: The Henkel bar datasheet prints 29.7 MPa for the same alloy. Test methods are not stated in either, so the two values should not be compared directly.
    source: indium-256
    where: Indalloy 256 Properties table, Tensile Strength row (39.58 MPa)
  - benchmark: ultimate_tensile_strength
    label: Tensile strength (Henkel bar datasheet)
    value: 29.7
    unit: MPa
    scope: material
    conditions:
      form: solder bar, Alloy 97SC (SAC305)
      test_method: not stated in the datasheet
    method: Value printed in the Typical Properties table of the Henkel bar datasheet (July 2013)
    status: ground
    note: The Henkel value is about 25 % below the Indium value. The datasheet does not state the test method.
    source: henkel-bar
    where: Solder Bar Typical Properties table, Tensile Strength, MPa row (29.7)
  - benchmark: yield_strength
    label: Yield strength (Indium datasheet)
    value: 22
    unit: MPa
    scope: material
    conditions:
      test: not stated in the datasheet
    method: Value printed in the Selected Properties table of the product data sheet (3,200 psi)
    status: ground
    source: indium-256
    where: Indalloy 256 Properties table, Yield Strength row (22 MPa)
  - benchmark: elongation
    label: Elongation (Indium datasheet)
    value: 49
    unit: '%'
    scope: material
    conditions:
      test: not stated in the datasheet
    method: Value printed in the Selected Properties table of the product data sheet
    status: ground
    source: indium-256
    where: Indalloy 256 Properties table, Elongation row (49 %)
corrosion:
  - environment: 3.5 wt % NaCl solution (potentiodynamic polarization)
    headline: In 3.5 wt % NaCl the SAC305 surface forms a corrosion product of SnO, SnO2 and SnCl- that the authors link to passivation.
    effect: Potentiodynamic polarization in 3.5 wt % NaCl, with SEM and XRD of the surface, found a needle-like corrosion product made of SnO, SnO2 and SnCl-. The authors say this product is responsible for the passivation behaviour of the solder. The abstract gives no corrosion rate, potential or current density.
    rating: unknown
    conditions:
      basis: laboratory electrochemical test; abstract read, full text not opened
      electrolyte: 3.5 wt % NaCl
    source: sss-nazeri2018
    where: Abstract (Solid State Phenomena 273, pp. 91-94)
risks:
  hazards:
    - text: The AIM SAC305 safety data sheet (version 1.06, issued 5/17/2024) states that the product is not classified as hazardous under Regulation (EC) 1272/2008 and has no signal word.
      ghs: []
      source: aim-sds
      where: Section 2.1, Classification and label (Not classified; No signal word)
    - text: 'PubChem''s tin record aggregates ECHA notifications: 72.9 % (695 of 953) of company reports say tin does not meet GHS criteria. Where codes were given, H319 (24.2 %) and H335 (23.1 %) appear. The record does not say which tin substance the notifications cover, so this is not a classification of SAC305.'
      ghs:
        - H319
        - H335
      source: pubchem-tin
      where: GHS Classification section, ECHA aggregated notifications (CID 5352426)
    - text: 'PubChem''s tin record also includes an H372 notification: causes damage to organs through prolonged or repeated exposure. The notification does not say which tin form it covers.'
      ghs:
        - H372
      source: pubchem-tin
      where: GHS Classification section, NITE-CMC notifications (CID 5352426)
  failure_risks:
    - mode: Thermal-cycling fatigue of solder joints
      trigger: Thermal cycling between -55 °C and 125 °C
      consequence: Over this range SAC305 sits at homologous temperatures of about 0.45 to 0.80, where creep and stress relaxation are significant and viscoplastic effects dominate.
      severity: moderate
      source: smta-libot2025
      where: Material characterisation section (stress relaxation at -55, 20 and 125 °C) and homologous temperature paragraph
    - mode: Tin whisker growth
      trigger: Pure tin plating. NASA's examples are pure tin plating, and its page does not test SAC305.
      consequence: NASA's homepage shows a tin whisker growing from a pure tin plated relay terminal. The page gives no growth rate and no test for SAC305 solder.
      severity: moderate
      source: nasa-whisker
      where: Homepage, Hot Topics list (Tin Whisker Growing from Pure Tin Plated Relay Terminal)
    - mode: Chloride-driven surface corrosion
      trigger: Chloride solution, tested in 3.5 wt % NaCl
      consequence: The laboratory test reports a passivating layer of SnO, SnO2 and SnCl-. No corrosion rate was read, so the severity is unknown.
      severity: moderate
      source: sss-nazeri2018
      where: Abstract (Solid State Phenomena 273, pp. 91-94)
  side_effects: []
  handling:
    - text: Workers should wash hands and face before eating, drinking and smoking, and remove contaminated clothing before entering eating areas.
      source: aim-sds
      where: Section 7.1, Advice on general occupational hygiene
    - text: Use strong, cut-resistant gloves suitable for handling metals. The SDS gives an occupational limit for silver of 0.1 mg/m3 over 8 hours (Romania, HG 1218/2006, as printed).
      source: aim-sds
      where: Section 8.1 (silver limit) and section 8.2 (hand protection)
  mitigations: []
uses:
  - application: electronics-and-chips
    device: Electronic assembly soldering (bar, wire and preforms)
    example: Henkel describes its SAC305 bar as a Pb-free substitute for tin/lead alloys in most electronic assembly soldering applications, and lists its features as the lowest melting point, high tin, Pb-free alloy without undesirable additions.
    source: henkel-bar
    where: Product description and Features and Benefits sections
  - application: electronics-and-chips
    device: Preforms, ribbon, wire and paste
    example: Indium offers SAC305 as preforms, ribbon, wire and paste, and calls it valued for reliability in lead-free soldering across a wide range of applications.
    source: indium-256
    where: Introduction and Available Forms sections
  - application: electronics-and-chips
    device: Solder, in U.S. tin use
    example: The USGS reports that solder took 11 % of U.S. tin use in 2025.
    source: usgs-mcs2026-tin
    where: Domestic Production and Use paragraph (uses percentages)
supply:
  - subject: Tin (mine production, world)
    producers:
      - country: China
        share_percent: 24.5
        year: 2025
      - country: Indonesia
        share_percent: 21
        year: 2025
      - country: Peru
        share_percent: 11.4
        year: 2025
      - country: Brazil
        share_percent: 9.7
        year: 2025
      - country: Congo (Kinshasa)
        share_percent: 9.3
        year: 2025
    critical_lists: []
    recycling: 'USGS: about 17,000 tons of tin from old and new scrap was recycled in 2025, which the USGS says is 22 % of apparent consumption.'
    substitutes:
      - 'USGS: epoxy resins are listed as a substitute for tin in solder.'
    source: usgs-mcs2026-tin
    where: World Mine Production and Reserves table, 2025e column (world total 290,000 t; shares calculated by Space Mushroom from China 71,000, Indonesia 61,000, Peru 33,000, Brazil 28,000 and Congo (Kinshasa) 27,000); Recycling; Substitutes
  - subject: Silver (mine production, world)
    producers:
      - country: Mexico
        share_percent: 24.2
        year: 2025
      - country: Peru
        share_percent: 13.8
        year: 2025
      - country: China
        share_percent: 13.1
        year: 2025
      - country: Bolivia
        share_percent: 5.8
        year: 2025
      - country: Chile
        share_percent: 5.4
        year: 2025
    critical_lists:
      - list: USGS 2025 Final List of Critical Minerals (silver added in the 2025 list)
        listed: true
    recycling: 'USGS: about 1,000 tons of silver was recovered from new and old scrap in 2025, about 11 % of apparent consumption.'
    substitutes:
      - 'USGS: the substitutes it lists for silver are digital imaging, reduced-silver film, surgical pins and plates in other metals, and stainless steel flatware. Solder is not among them.'
    source: usgs-mcs2026-silver
    where: World Mine Production and Reserves table, 2025e column (world total 26,000 t; shares calculated by Space Mushroom); critical minerals paragraph; Recycling; Substitutes
  - subject: Copper (mine production, world)
    producers:
      - country: Chile
        share_percent: 23
        year: 2025
      - country: Congo (Kinshasa)
        share_percent: 13.9
        year: 2025
      - country: Peru
        share_percent: 11.7
        year: 2025
      - country: China
        share_percent: 7.8
        year: 2025
      - country: Russia
        share_percent: 5.7
        year: 2025
    critical_lists:
      - list: USGS 2025 Final List of Critical Minerals (copper added in the 2025 list)
        listed: true
    recycling: 'USGS: about 160,000 tons of copper from old scrap and 760,000 tons from new scrap were recovered in 2025 in the United States, supplying about 30 % of U.S. copper supply.'
    substitutes:
      - 'USGS: aluminum, optical fiber, plastics, titanium and steel substitute for copper in named uses. Solder is not among them.'
    source: usgs-mcs2026-copper
    where: World Mine and Refinery Production table, mine production 2025e column (copper content, thousand metric tons; world total 23,000; shares calculated by Space Mushroom); Recycling; Substitutes
documents:
  - title: 'Indium Corporation: Indalloy 256 (SAC305) for preforms, product data sheet (form 100346 R0)'
    type: datasheet
    url: https://www.indium.com/wp-content/uploads/2025/03/Indalloy256-for-Preforms-PDS-100346-R0-1.pdf
    year: 2025
  - title: 'Henkel: Technical Data Sheet, BAR SAC305 (July 2013), copy hosted by a third party'
    type: datasheet
    url: https://cdn.eicom.ru/media/PDF/7619382.pdf
    year: 2013
  - title: 'AIM: SAC305 safety data sheet, EU (version 1.06, issued 5/17/2024)'
    type: sds
    url: https://media.eis-inc.com/m/fe37c4f9b48cc349/original/ALLOY-SAC305-AIM-Europe-EU-SDS-REACH-2020-878-2022-Romania.pdf
    year: 2024
  - title: 'Libot and Milesi: A New Efficient Thermomechanical Reliability Model for Lead-Free Solder Joints (SMTA Journal 38, issue 1)'
    type: paper
    url: https://journal.smta.org/index.php/smt/article/download/68/36/500
    year: 2025
  - title: 'Mohd Nazeri et al.: Microstructure and Phase Analyses on the Corrosion of SAC305 Solder in NaCl Solution (Solid State Phenomena 273, pp. 91-94)'
    type: paper
    url: https://www.scientific.net/SSP.273.91
    year: 2018
  - title: 'Han group (UMD): Anisotropic coefficients of thermal expansion of SAC305 grains (Acta Materialia, 2018)'
    type: paper
    url: https://terpconnect.umd.edu/~bthan/paper/CTE%20and%20CHS/2018%20SAC305%20CTE%20-%20Acta%20Materialia.pdf
    year: 2018
  - title: 'USGS Mineral Commodity Summaries 2026: Tin'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tin.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Silver'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silver.pdf
    year: 2026
  - title: 'USGS Mineral Commodity Summaries 2026: Copper'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-copper.pdf
    year: 2026
  - title: 'PubChem compound record: Tin (CID 5352426), GHS classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Tin
    year: 2026
  - title: 'Wikipedia: Solder (composition and history only)'
    type: database
    url: https://en.wikipedia.org/wiki/Solder
    year: 2026
gaps:
  - No corrosion rate, corrosion potential or current density for SAC305 was found in any source opened. The one corrosion source is the abstract of a 2018 electrochemical study; the 2023 Springer article returned a sign-in page and the Malaysian repository record could not be opened.
  - Thermal conductivity and CTE rest on one datasheet (Indium Corporation). The Kappalloy and Alpha SDS pages could not be read, and the other vendor figures seen in search results were not used.
  - Tensile strength, yield strength and elongation rest on two datasheets that disagree (39.58 and 29.7 MPa tensile). Neither states a test method, so no value is recorded as a confirmed strength.
  - The Henkel datasheet prints a density of 7.4 without a unit, so it is not recorded. Only the Indium value with its unit is used.
  - The liquidus (220 °C) is recorded from the Indium datasheet only; the AIM SDS prints a melting range of 217 to 218 °C.
  - Acta Materialia (2018) reports anisotropic thermal expansion of single SAC305 grains, but no bulk CTE number was read in that paper, so it is cited for the anisotropy only.
  - The SMTA paper gives the solidus of SAC305 as about 217 °C and the homologous temperature range, but it does not give SAC305 elastic modulus or CTE values in the text read.
  - Hazards for the bare alloy rest on one SDS (AIM, 2024). Flux-cored wire, paste and preforms have their own SDS and may be classified differently; those were not read.
  - Tin whisker risk for SAC305 solder was not measured in any source opened; the NASA page is about pure tin plating.
  - Critical-mineral status of tin was not found in the USGS 2025 critical list text read (only silver and copper are stated as added). The EU critical raw materials list was not read for any of the three metals.
  - Mine shares are calculated from USGS 2025e values and are not printed by USGS as percentages.
  - No UNS, JIS or ASTM solder designation for SAC305 was found in the sources read; only the Henkel trade name 97SC is recorded.
  - No outgassing, atomic oxygen, radiation or space-exposure data for SAC305 were searched in this run.
sources:
  indium-256:
    title: Indalloy 256 (SAC305) for Preforms, product data sheet
    id: Indium Corporation, Form No. 100346 R0
    url: https://www.indium.com/wp-content/uploads/2025/03/Indalloy256-for-Preforms-PDS-100346-R0-1.pdf
    year: 2025
    kind: datasheet
    license: supplier product data sheet, cited not reproduced
  henkel-bar:
    title: Technical Data Sheet, BAR SAC305 (Alloy 97SC)
    id: Henkel, TDS BAR SAC305, July 2013
    url: https://cdn.eicom.ru/media/PDF/7619382.pdf
    year: 2013
    kind: datasheet
    license: supplier technical data sheet, cited not reproduced
  aim-sds:
    title: Safety Data Sheet, ALLOY SAC305 (AIM, EU, REACH 2020/878)
    id: Version 1.06, issued 5/17/2024
    url: https://media.eis-inc.com/m/fe37c4f9b48cc349/original/ALLOY-SAC305-AIM-Europe-EU-SDS-REACH-2020-878-2022-Romania.pdf
    year: 2024
    kind: datasheet
    license: supplier safety data sheet, cited not reproduced
  smta-libot2025:
    title: A New Efficient Thermomechanical Reliability Model for Lead-Free Solder Joints
    id: SMTA Journal, volume 38, issue 1 (2025); authors Libot and Milesi
    url: https://journal.smta.org/index.php/smt/article/download/68/36/500
    year: 2025
    kind: paper
    license: SMTA journal article, cited not reproduced
  sss-nazeri2018:
    title: Microstructure and Phase Analyses on the Corrosion of SAC305 Solder in NaCl Solution
    id: Solid State Phenomena 273, pp. 91-94, doi via Trans Tech Publications (2018); authors Mohd Nazeri et al.
    url: https://www.scientific.net/SSP.273.91
    year: 2018
    kind: paper
    license: abstract read; full text behind access, cited not reproduced
  acta-cte2018:
    title: Anisotropic coefficients of thermal expansion of SAC305 grains, measured by moire interferometry
    id: Acta Materialia, 2018 (accepted 14 June 2018); UMD group of B. Han
    url: https://terpconnect.umd.edu/~bthan/paper/CTE%20and%20CHS/2018%20SAC305%20CTE%20-%20Acta%20Materialia.pdf
    year: 2018
    kind: paper
    license: author-hosted preprint PDF, cited not reproduced
  usgs-mcs2026-tin:
    title: 'Mineral Commodity Summaries 2026: Tin (U.S. Geological Survey)'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tin.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-mcs2026-silver:
    title: 'Mineral Commodity Summaries 2026: Silver (U.S. Geological Survey)'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silver.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-mcs2026-copper:
    title: 'Mineral Commodity Summaries 2026: Copper (U.S. Geological Survey)'
    id: USGS MCS 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-copper.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  pubchem-tin:
    title: 'PubChem compound record: Tin (CID 5352426), GHS classification'
    id: CID 5352426; PubChem pug_view JSON
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Tin
    year: 2026
    kind: database
    license: public domain (NCBI); sections attributed to ECHA and NITE-CMC
  nasa-whisker:
    title: 'NASA Goddard Space Flight Center: Tin Whisker (and Other Metal Whisker) Homepage'
    url: https://nepp.nasa.gov/whisker/
    kind: report
    license: NASA public web page
  wiki-solder:
    title: Solder, Wikipedia (composition and history only)
    url: https://en.wikipedia.org/wiki/Solder
    kind: database
    license: CC BY-SA 4.0, linked not reproduced
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 13
  unreachable: 4
  caveats: 4
  note: 'Read by an AI assistant on 2026-10-26 from the datasheets, SDS, USGS PDFs and PubChem JSON named in each entry. Unreachable or blocked: Kappalloy TDS and product page, Alpha SDS (HTML only), Springer 2023 article (sign-in), and a Malaysian repository record. Caveats: tensile values differ between datasheets; the corrosion source is an abstract with no rate; the GHS notifications cover tin, not SAC305.'
story:
  recipe:
    line: 'SAC305 is a three-element alloy: tin with 3.0 % silver and 0.5 % copper by weight. Silver and copper form the intermetallic compounds Ag3Sn and Cu6Sn5 during soldering, which the Indium datasheet says stay finely dispersed through the joint.'
    parts:
      - name: Tin
        symbol: Sn
        share_percent: 96.5
        role: The matrix, and most of the alloy. The Ag3Sn and Cu6Sn5 compounds form within it.
      - name: Silver
        symbol: Ag
        share_percent: 3
        role: Forms Ag3Sn intermetallic compounds, which the datasheet says add mechanical strength and thermal fatigue resistance.
      - name: Copper
        symbol: Cu
        share_percent: 0.5
        role: Forms Cu6Sn5 intermetallic compounds, which the same datasheet says reinforce the joint.
  risk_groups:
    - title: For people
      level: 0
      verdict: Not classified (bare alloy)
      lead: The supplier SDS does not classify the bare alloy. Flux, core wire and paste have their own safety data sheets, so check the one for the product you use.
      points:
        - label: The alloy
          line: The AIM SDS (version 1.06, issued 5/17/2024) says the alloy is not classified as hazardous under Regulation (EC) 1272/2008 and has no signal word.
        - label: Tin records
          line: PubChem's tin record shows that 72.9 % (695 of 953) of company reports say tin does not meet GHS criteria. Where codes were given, H319 (eye irritation) and H335 (respiratory irritation) appear. The record does not say which tin substance it covers.
        - label: Silver
          line: The SDS gives an 8-hour occupational limit for silver of 0.1 mg/m3 (Romania, as printed).
    - title: If a joint fails
      lead: The failure routes in these sources are fatigue from thermal cycling, tin whiskers from pure tin, and a passivating corrosion layer in chloride.
      points:
        - label: Thermal cycling
          line: Between -55 and 125 °C, SAC305 sits at homologous temperatures of about 0.45 to 0.80, where creep and stress relaxation are significant (SMTA 2025).
        - label: Tin whiskers
          line: NASA's homepage shows a tin whisker growing from a pure tin plated relay terminal. The page does not test SAC305 solder.
        - label: Chloride
          line: In a 3.5 wt % NaCl test the surface formed a corrosion product of SnO, SnO2 and SnCl-, which the authors link to passivation. No rate was read.
    - title: Handling and storage
      points:
        - label: Hygiene
          line: Wash hands and face before eating, drinking and smoking, and remove contaminated clothing (AIM SDS section 7.1).
        - label: Gloves
          line: Use strong, cut-resistant gloves suitable for handling metals (AIM SDS section 8.2).
  why: SAC305 is a lead-free solder of 96.5 % tin, 3.0 % silver and 0.5 % copper. Its datasheet gives a solidus of 217 °C and a liquidus of 220 °C, low enough for general electronics assembly, which the datasheet says is still sufficient for general electronics usage. Indium says the silver and copper give a balance of strength, thermal fatigue resistance and wetting. The USGS puts solder at 11 % of U.S. tin use in 2025. Its weak points are its tensile strength, which two datasheets give as 29.7 and 39.58 MPa, and its creep under thermal cycling.
  uses:
    - where: Electronic assembly soldering
      line: Henkel calls its SAC305 bar a Pb-free substitute for tin/lead alloys in most electronic assembly soldering applications.
    - where: Preforms, ribbon, wire and paste
      line: Indium offers SAC305 in these forms and calls it valued for reliability in lead-free soldering across a wide range of applications.
    - where: Solder in U.S. tin use
      line: The USGS reports that solder took 11 % of U.S. tin use in 2025.
  can_do:
    - label: Melt low
      value: 217 °C solidus
      benchmark: melting_point
      line: Indium gives a solidus of 217 °C and a liquidus of 220 °C. The AIM SDS prints a melting point of 217 to 218 °C.
    - label: Carry heat
      value: 61 W/mK
      benchmark: thermal_conductivity
      line: Indium gives a thermal conductivity of 61 W/mK. No second value for the alloy was read.
    - label: Weight
      value: 7.35 g/cc
      benchmark: density
      line: Indium gives a density of 7.35 g/cc.
    - label: Stiffness
      value: 6.9 GPa
      benchmark: elastic_modulus
      line: Indium gives a Young's modulus of 6.9 GPa.
  compare: Indium describes the 217 to 220 °C melting range as higher than traditional tin-lead solder, yet still low enough for general electronics assembly. The higher melting point is the trade for lead-free reflow. Most of the values here come from one datasheet, so the table compares rows from the same source.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Thermal conductivity
      benchmark: thermal_conductivity
    - label: Thermal expansion
      benchmark: cte
  handling:
    - Check the SDS for the exact product. The bare alloy is not classified, but flux or core products may be.
    - Wear strong, cut-resistant gloves and wash hands before eating.
    - Keep dust and fume below the silver limit of 0.1 mg/m3 over 8 hours that the SDS prints.
  good_for:
    - Lead-free electronics assembly. Indium calls SAC305 the global standard for lead-free soldering, which gives a broad history of test data.
    - Wetting and reflow. Henkel calls SAC305 the best all-around Pb-free alternative and cites enhanced wetting.
  watch_out:
    - 'Tensile strength differs between datasheets: 29.7 MPa (Henkel) and 39.58 MPa (Indium), with no test method given.'
    - 'Thermal cycling: creep and stress relaxation are significant between -55 and 125 °C (SMTA 2025).'
    - 'Tin whiskers: NASA shows them on pure tin plating. SAC305 whisker data were not read.'
    - 'Chloride: a passivating layer forms in 3.5 wt % NaCl, but no corrosion rate was read.'
  verdict: 'SAC305 is the standard lead-free electronics solder: 217 to 220 °C melting, 61 W/mK conduction and 7.35 g/cc density in one datasheet. Its datasheets disagree on tensile strength, and the sources read give no corrosion rate, no second thermal-conductivity or CTE value, and no space-exposure data.'