SnBi Eutectic Solder Paste

As a fully compliant solution for environmentally conscious electronics manufacturing, SnBi Eutectic Solder Paste combines a high‑reliability flux system with fine spherical Sn42/Bi58 alloy powder. This advanced SnBi solder paste product is engineered to deliver exceptional printability, minimal residue, and robust electrical performance – all while meeting the strictest global restrictions on hazardous substances. Its eutectic composition provides a sharp melting point at 138 °C, enabling energy‑efficient reflow and protecting temperature‑sensitive components. With a powder particle size of 25–45 μm, this paste bridges the gap between Type 3 and Type 4 classifications, making it the ideal SnBi solder paste choice for both conventional and fine‑pitch SMT assembly lines.

Solder Paste Composition

The formulation of SnBi Eutectic Solder Paste consists of a eutectic Sn42/Bi58 alloy powder and a specially developed flux system. According to the technical datasheet:

• Alloy composition: Tin 41.5–42.5%, Bismuth 57.5–58.5% – eutectic point at 138 °C (both liquidus and solidus). Lead content is < 0.001%, confirming its status as a true SnBi solder paste material.
• Flux content: 10.0 ± 1.0 wt%, with halogen content < 0.05 wt%.
• Flux composition (wt%):Hydrogenated Rosin: 45–48%S、traight‑chain C9–C12 Aliphatic Alcohol: 20–22%、Cyclical C12–C16 Ester: 9–15%、Polymerized Fatty Oil: 4–6%、Dicarboxylic Acid Activator: 4–8%、Organic Amine C8–C10: 2–3%、Antioxidant/Corrosion Inhibitor: 2–3%

This low‑ionic flux system ensures that SnBi Eutectic Solder Paste leaves minimal, non‑conductive residues after reflow, eliminating the need for post‑soldering cleaning while maintaining high surface insulation resistance (SIR) – a critical attribute for any high‑reliability SnBi solder paste product.

Printing Performance & Process Stability – Bridging Type 3 and Type 4

Designed for both conventional and fine‑pitch applications, this SnBi solder paste product features a particle size distribution of 25–45 μm, which exactly matches the Type 3 range (25–45 μm) while overlapping with the upper end of Type 4 (20–38 μm). This unique positioning enables excellent release from additive‑process stencils, whether the design calls for standard or finer geometries. The rheology is optimized to provide stable transfer efficiency and minimal slump, ensuring consistent solder deposit geometry across long production runs – a hallmark of a premium SnBi solder paste formulation that works seamlessly across both classification standards.

Recommended printing parameters (Table 3 from TDS) – fully compatible with all major printers:

Key production advantages for this SnBi solder paste:

• Minimal viscosity change during continuous printing – even after thousands of strokes, the viscosity remains within tight tolerance, ensuring uniform deposit volume for both Type‑3 and Type‑4 stencil apertures.
• Non‑hydrophilic nature allows stable operation at up to 80 % RH without moisture absorption, preventing solder ball defects – a major benefit for SnBi solder paste users in humid environments.
• Stencil life exceeds 8 hours – the paste does not dry out prematurely, reducing cleaning downtime and maximizing throughput.
• Excellent anti‑slump properties (< 0.2 mm) guarantee fine‑pitch printing without bridging, even at high squeegee speeds, making it suitable for applications that typically require Type‑4 pastes.

Flux Reliability & Electrical Performance

The flux system in SnBi Eutectic Solder Paste employs a low‑ionic activator, passing stringent tests without causing corrosion or electromigration. This makes it an ideal no‑clean solution for assemblies where post‑reflow cleaning is impractical – a key requirement for high‑volume SnBi solder paste applications.

Low‑Temperature SnBi Eutectic Advantages – with Environmental Compliance

As a fully SnBi solder paste product (Pb < 0.001 %), SnBi Eutectic Solder Paste complies with RoHS, REACH, and other global environmental regulations. Compared to conventional SAC (SnAgCu) alloys, the Sn42/Bi58 eutectic offers:

• Melting point 138 °C – approximately 80 °C lower than SAC, protecting temperature‑sensitive components and substrates, while reducing energy consumption and thermal stress on PCBs.
• Mechanical properties:Tensile strength: 55 MPa (25 °C) / 28 MPa (100 °C)、Elongation: 13 % (25 °C) / 18 % (100 °C)、Coefficient of thermal expansion: 13.4 × 10⁻⁶/°C
• Excellent creep resistance and thermal fatigue performance, verified in LED lighting, automotive sensors, and high‑frequency RF modules.

This low‑temperature profile not only enhances assembly yields but also reduces warpage on thin boards – a significant advantage for SnBi solder paste users transitioning from higher‑melting alloys, and the powder size ensures compatibility with both standard and fine‑pitch stencil designs.

Reflow Profile & Process Guidelines

To achieve optimal wetting and minimize voiding or solder balling, the following reflow profile is recommended for SnBi Eutectic Solder Paste – applicable regardless of whether the paste is prepared manually or automatically:

Handling guidelines for this SnBi solder paste:

• Thawing – Allow 4–6 hours at 25 °C before opening the container to prevent moisture condensation.
• Mixing – Stir manually (3–6 minutes) or use a standard mixer (2–5 minutes) until viscosity returns to 180 ± 20 Pa·s. The paste’s robust formulation ensures reliable performance after either method.
• Printing‑to‑placement window – Complete component placement within 3–6 hours after printing to avoid surface drying; this extended open time supports the throughput of high‑speed lines.
• Storage – Sealed at 0–10 °C, < 75 % RH; shelf life 180 days from date of manufacture.

Application Scenarios & Supply Capacity

SnBi Eutectic Solder Paste has been successfully deployed in mass production across multiple sectors, with customers relying on its proven SnBi solder paste performance:

• Consumer Electronics – TWS earbuds, smartwatches, and portable devices, where low‑temperature assembly and environmental compliance are essential, and the paste’s dual Type‑3/Type‑4 capability accommodates varied pad geometries.
• LED Lighting – COB modules and automotive interior lighting, where thermal management and reliability are critical, and the SnBi solder paste composition ensures no hazardous lead is introduced.
• Automotive Electronics – Battery management systems (BMS), in‑vehicle sensors, and infotainment, requiring high SIR and vibration resistance – all delivered by this robust SnBi solder paste product.

With over 30 active customers and a monthly production capacity exceeding 2 tons, this SnBi solder paste solution is readily available with 72‑hour delivery to support continuous SMT line operations. Our technical team provides on‑site process support to ensure seamless integration of SnBi Eutectic Solder Paste into your existing workflow, with specific guidance for stencil design optimized for this particle size range.

Safety & Environmental Compliance

• Contains no regulated hazardous substances (RoHS, REACH, Japan Industrial Safety and Health Act).
• Free from organic solvents subject to poisoning prevention regulations.
• In case of skin contact, clean immediately with ethanol‑soaked cotton, then wash with soap and water.
• Adequate ventilation is recommended during reflow to minimize fume exposure – the SnBi solder paste formulation poses no additional toxicity risks.