High‑Performance Lead‑Free No‑Clean Solder Paste for Fine‑Pitch and High‑Reliability SMT Assembly

How Solder Paste Composition Drives Printing Performance and Joint Reliability

In surface‑mount technology, solder paste is far more than a simple mixture of metal powder and flux. Its solder paste composition – including alloy type, powder size distribution, flux chemistry, solvent system, and rheological additives – determines every aspect of the assembly process: how well the paste releases from the stencil, how quickly it wets the terminations, how few voids remain, and how cleanly the residue behaves after reflow. Optimising the solder paste composition is the key to achieving high first‑pass yields, low defect rates, and long‑term field reliability, especially as component pitches shrink and board densities increase.

TS505 is a high‑temperature, lead‑free, no‑clean solder paste built around a carefully engineered solder paste composition. It features the Sn99Ag0.3Cu0.7 (SAC0307) alloy, Type 4 powder (20–38 µm), a flux content of 10.5 ± 0.5 %, and a halogen‑controlled flux system (L1 level, 0.085 % halogens). This precise solder paste composition provides a wide reflow window, excellent wetting on all common board finishes, extremely low voiding, minimal non‑conductive residue, and consistent print stability over long production runs. Whether you assemble telecom infrastructure, automotive ECUs, or consumer wearables, TS505’s solder paste composition delivers the robustness and predictability that modern SMT lines demand.

The Building Blocks of TS505’s Solder Paste Composition

The following tables detail the alloy chemistry, physical properties, and solder paste specifications of TS505, all verified according to JIS Z.3284 and JIS Z.3910.

Alloy Composition

Solder Paste Physical & Electrical Specifications

Core Advantages Stemming from the Solder Paste Composition

Wide Reflow Process Window

1.Thanks to the balanced activator system within the solder paste composition, TS505 supports a broad reflow profile that accommodates different board thicknesses and oven types. The recommended profile is:

2. Superior Wetting and Solder Wicking

The flux portion of the solder paste composition contains highly effective activators that quickly remove oxides from pads and component leads. Even on OSP‑coated or mildly oxidised surfaces, TS505 produces bright, full fillets with excellent capillary climb, ensuring strong intermetallic bonds and consistent joint strength.

3 Low Voiding – Enabled by Precise Solvent and Flux Ratios

Voiding is a major concern for large thermal‑mass components (QFN, LGA, thermal pads). The solder paste composition of TS505 is formulated with a carefully selected solvent system that allows volatile by‑products to escape before solder solidification, significantly reducing trapped gas. This results in void fractions well below typical industry thresholds, improving thermal and electrical performance.

4 Outstanding Printability and Stencil Life – The Role of Rheology

Thixotropic agents in the solder paste composition impart excellent shear‑thinning behaviour, ensuring smooth rolling on the stencil and clean aperture release. The paste retains its shape after printing, with minimal slump even on fine‑pitch pads (down to 0.4 mm). Moreover, the solvent evaporation rate is controlled to extend stencil life, reducing cleaning frequency and increasing uptime.

5 Minimal, Non‑Conductive Residue

After reflow, the solder paste composition leaves a dry, translucent, hard residue that is non‑hygroscopic and non‑conductive. It passes all SIR tests with wide margins, and its probe‑friendly nature allows reliable ICT testing without cleaning. This makes TS505 ideal for no‑clean processes, saving both time and cost.

Typical Applications

TS505’s solder paste composition makes it especially suitable for:

• Telecom Base Stations & Server Motherboards – large‑format PCBs with strict voiding limits.
• Automotive Electronics (ECU, BMS) – high‑reliability, thermal‑cycling environments.
• Industrial Controls & Power Modules – where insulation resistance and joint strength are critical.
• Consumer Electronics (TWS earbuds, wearables) – fine‑pitch devices (Type 4 standard; Type 5 available on request).

 Quality Assurance

Each batch of TS505 is accompanied by a Certificate of Analysis that verifies:

• Product model and batch number
• Alloy composition
• Flux content (wt%)
• Viscosity at 25 °C
• Halogen content (L1 level)

Consistent solder paste composition from lot to lot is guaranteed through rigorous testing, giving you confidence in your production process.

Packaging

Frequently Asked Questions

Q: Is TS505’s solder paste composition suitable for fine‑pitch printing?

A: Yes. The solder paste composition uses Type 4 powder (20–38 µm), which supports printing down to 0.4 mm pitch. Type 5 is also available for even finer applications.

Q: Does the residue affect ICT probing?

A: No. The residue is dry, translucent, and non‑conductive, allowing reliable probe contact without false failures.

Q: Can TS505 be used in both air and nitrogen reflow?

A: Absolutely. The solder paste composition is designed to perform consistently in both atmospheres.

Q: How does the halogen content fit into the composition?

A: Halogens are controlled at 0.085 % (L1 level), meeting low‑halogen requirements while maintaining excellent wetting activity.

 Conclusion

The solder paste composition of TS505 – with its SAC0307 alloy, Type 4 powder, halogen‑controlled flux, and advanced rheology – delivers a unique combination of print stability, wetting performance, low voiding, and clean residue. By choosing TS505, manufacturers benefit from:

• Higher first‑pass yields
• Lower rework and inspection costs
• Fewer production stoppages
• Consistent, reliable solder joints across diverse applications

For those seeking a robust, high‑quality lead‑free no‑clean solder paste, TS505 is a proven, trustworthy solution.

Contact Information

TENSAN VIETNAM CO., LTD

TS10 Road, Tien Son Industrial Park, Bac Ninh Province, Vietnam

Tel: +84‑222‑650‑8818

Email: mark@sztensan.com

For custom alloy formulations, different powder sizes, or special packaging, please contact your local Tensan sales representative.