Solder & Low-Melting Alloy Sn91Zn9-AC (Spheroidize annealed)
Heat-treated state
ISO 801 · also IEC Z90
Choose for dip, wave and solder-pot operations and for remelting; coarser as-cast eutectic lamellae give slightly lower strength.
Values for the AC condition
What is Sn91Zn9-AC?
Sn91Zn9-AC is Sn91Zn9 heat treated to AC — choose for dip, wave and solder-pot operations and for remelting; coarser as-cast eutectic lamellae give slightly lower strength. Sn91Zn9-AC has a yield strength of 34 MPa (4.93 ksi) and a tensile strength of 60 MPa (8.7 ksi) — stronger than 78% of solder & low-melting alloy grades. Elongation at break is 45% and the elastic modulus is 40 GPa (5.8 Msi). Sn91Zn9-AC has a density of 7.27 g/cm³ (0.263 lb/in³), lighter than 98% of solder & low-melting alloy grades. It melts at 199°C (390 °F).
Advantages
- Lightweight — 7.27 g/cm³ (0.263 lb/in³), better than 98% of solder & low-melting alloy grades
- Conducts heat well — 61 W/m·K (35.2 BTU/hr·ft·°F), better than 92% of solder & low-melting alloy grades
- Ductile — tolerates forming and impact — 45%, better than 84% of solder & low-melting alloy grades
- High electrical conductivity — 12.5 % IACS, better than 82% of solder & low-melting alloy grades
- High strength — 34 MPa (4.93 ksi), better than 78% of solder & low-melting alloy grades
Limitations
- Needs corrosion protection — 25/100, worse than 100% of solder & low-melting alloy grades
- Difficult to weld — 10/100, worse than 94% of solder & low-melting alloy grades
Sn91Zn9-AC properties
Typical room-temperature values for Sn91Zn9-AC; 5 are specific to this condition. Other listed values are Sn91Zn9 reference data and may not represent this condition. Bars are the position among solder & low-melting alloy grades.
Physical3
Sn91Zn9-AC has a density of 7.27 g/cm³ (0.263 lb/in³), lighter than 98% of solder & low-melting alloy grades. It melts at 199°C (390 °F).
Mechanical10
Sn91Zn9-AC has a yield strength of 34 MPa (4.93 ksi) and a tensile strength of 60 MPa (8.7 ksi) — stronger than 78% of solder & low-melting alloy grades. Elongation at break is 45% and the elastic modulus is 40 GPa (5.8 Msi).
Thermal6
Sn91Zn9-AC is rated for continuous service to 100°C (212 °F). It conducts heat at 61 W/m·K (35.2 BTU/hr·ft·°F), better than 92% of solder & low-melting alloy grades. Thermal expansion is 24 µm/m·K (13.3 µin/in·°F).
Electrical3
Sn91Zn9-AC conducts electricity at 12.5 % IACS, better than 82% of solder & low-melting alloy grades.
Chemical & Environmental3
Corrosion resistance is poor (25/100), worse than 100% of solder & low-melting alloy grades.
Sustainability4
Producing a kilogram of Sn91Zn9-AC takes about 295 MJ of energy and emits 16.5 kg of CO₂ — more than 70% of solder & low-melting alloy grades. Typical recycled content is 30%.
Manufacturability6
Sn91Zn9-AC's machinability is poor (30/100, worse than 60% of solder & low-melting alloy grades); weldability not recommended (10/100); formability excellent (85/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Sn91Zn9-AC
Is Sn91Zn9 easy to machine?
Rarely machined; extremely soft and gummy — use sharp high-rake tools, kerosene/light oil lubrication and avoid heat build-up near the 199 °C solidus.
Can Sn91Zn9 be welded?
Not a weldable structural alloy; it is the filler itself — apply at 220–260 °C with halide-activated or ZnCl2-based flux, or fluxless in N2/Ar with ultrasonic agitation for aluminium.
Can Sn91Zn9 be formed, bent or molded?
Easily extruded into wire, rolled to foil and cast to bars owing to its eutectic, narrow-freezing-range structure; work at room temperature to limit creep.
What surface finishes work on Sn91Zn9?
Do not anodize or plate; clean flux residues thoroughly (DI water or solvent) and conformally coat joints, since zinc-rich residues drive rapid corrosion in humidity.
Sn91Zn9 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Zneutectic composition ~8.9 % Zn | 8 – 10 | 9 |
| Pbimpurity limit (RoHS lead-free) | ≤ 0.05 | |
| Cuimpurity limit | ≤ 0.05 | |
| Alimpurity limit; higher Al degrades wetting | ≤ 0.01 | |
| Feimpurity limit | ≤ 0.02 | |
| Sbimpurity limit | ≤ 0.05 | |
| Biimpurity limit | ≤ 0.05 | |
| Cdimpurity limit (RoHS) | ≤ 0 | |
| Asimpurity limit | ≤ 0.03 | |
| Snbalance, ~91 % | balance |
Sn91Zn9-AC — frequently asked
What is Sn91Zn9-AC used for?
Sn91Zn9-AC is typically used for aluminum component soldering, low-cost lead-free soldering and HVAC/refrigeration joints. In short: solders aluminium reliably; silver-free, low cost; corrosion-sensitive joint.
What is the yield strength of Sn91Zn9-AC?
Sn91Zn9-AC has a typical yield strength of 34 MPa (4.93 ksi) and a tensile strength of 60 MPa (8.7 ksi) — stronger than 78% of solder & low-melting alloy grades.
Is Sn91Zn9-AC easy to machine?
Not especially — machinability is rated poor (30/100, worse than 60% of solder & low-melting alloy grades). Rarely machined; extremely soft and gummy — use sharp high-rake tools, kerosene/light oil lubrication and avoid heat build-up near the 199 °C solidus.
Can Sn91Zn9-AC be welded?
Not readily — weldability is rated not recommended (10/100). Not a weldable structural alloy; it is the filler itself — apply at 220–260 °C with halide-activated or ZnCl2-based flux, or fluxless in N2/Ar with ultrasonic agitation for aluminium.
What surface finishes work on Sn91Zn9-AC?
Do not anodize or plate; clean flux residues thoroughly (DI water or solvent) and conformally coat joints, since zinc-rich residues drive rapid corrosion in humidity.
Can Sn91Zn9-AC be formed, bent or molded?
Easily extruded into wire, rolled to foil and cast to bars owing to its eutectic, narrow-freezing-range structure; work at room temperature to limit creep.
What is the maximum service temperature of Sn91Zn9-AC?
Sn91Zn9-AC is rated for continuous use to about 100°C (212 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ISO 9453 — Soft solder alloys: chemical composition and forms (alloy 801, S-Sn91Zn9) — ISO (2020)
- IEC 61190-1-3 — Requirements for electronic grade solder alloys — IEC (2017)
- ASM Handbook Vol. 3: Alloy Phase Diagrams (Sn-Zn system) — ASM International (1992)
- NIST Database for Solder Properties with Emphasis on New Lead-Free Solders — NIST / Colorado School of Mines (2002)
- Lead-Free Solder Interconnect Reliability — ASM International (2005)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.