company tower banner
STIRRI® USA Company Logo
STIRRI LT HF™ is a lead-free solder paste and tacky flux designed for stencil applications on printed circuit boards. With its low viscosity and halogen-free formulation, it ensures smooth application and compliance with regulatory standards such as REACH (Europe). Ideal for both professional and DIY projects, the STIRRI LT HF™ offers reliable performance without compromising environmental safety.

Product Type: Solder Paste

Application Area: Printed Circuit Boards, Stencil

Features: Low Viscosity

Chemical Family: Rosins

Technical Data Sheet

Knowde Enhanced TDS

Identification & Functionality

Chemical Family
Product Type

Features & Benefits

Labeling Claims
Ready-to-Use Product Features
Keynotes
  • Low-solids, low viscosity chemistry designed for Sn/Bi alloys melting at low temperatures. ROL0.
  • World’s first low-temperature lead-free halogen- free solder with QC tracer glowing in UV.
  • High tack value - strong grip. REACH-compliant.
  • Halogen-free (EN14582 test method).
  • Low voiding. Clear residue. Optimal viscosity.
  • Sharp printing definition at high-speeds.
  • Instant wetting on most PCB finishes.
  • Cleans using IPA, solvents, water-based saponifiers, ultrasonic devices.

Applications & Uses

Properties

Typical Properties
ValueUnitsTest Method / Conditions
Stencil Life (at 30 - 70% R/H & 20 - 25°C)max. 12hours

Regulatory & Compliance

Certifications & Compliance

Technical Details & Test Data

Viscosity
PRINT jar/cartridge DISPENSE syringe Tacky flux Tack force (g/cm)
120-180 90-130 20-50 44-48

* Malcom @ 10 RPM @ 25°C x10³ g/cm/s

Printer Operations

Stencil printer does not require any specific optimization, should be fully adjustable based on standard in-house process requirements, including high-speed printers

Print Speed: 20-200 mm/sec (add pressure for speed)
Squeegee Pressure: 70-540 g/cm of blade (add for speed)
Stencil Vac/Wipe: Every 10-25 prints or as necessary

Automated and vacuum cleaning systems for both stencil and misprinted boards. Manual cleaning using Isopropyl alcohol (IPA), co-solvents and/or ultrasonic scrubbers, vapor degreaser.

Test Results
IPC-TM-650 Test Value Result
Corrosion 2.6.15 L: No corrosion PASS
Copper Mirror 2.3.32 L: No breakthrough PASS
ECM (No-clean) 2.6.14.1 <1 decade drop PASS
Quantitive Halides 2.3.28.1 L: <0.05% PASS
SIR Test (No-clean) 2.6.3.7 ≥100 MΩ PASS
Printing

Optimal print definition for fine pitch applications. Long stencil life of this product virtually eliminates waste of solder paste. For mesh/size determination refer to the Pitch Requirements chart below:

 

Size (micron) Type Value
75 - 45 μm T2 24 mil +
45 - 25 μm T3 16 - 24 mil
38 - 20 μm T4 12 - 16 mil
25 - 15 μm T5 < 12 mil
20 - 5 μm T6 < 8 mil
Sample Reflow Profile

STIRRI LT HF™ (No-clean Solder Paste & Tacky Paste Flux) - Sample Reflow Profile - 1

LT Profile as a starting point for low-temperature process optimization using Sn/Bi alloys like Sn42Bi48

To achieve better results with voiding or reduce tombstoning, consider using a longer soaking zone.

Packaging & Availability

Availability

STIRRI-LT-HF™- available in the following alloys of a lowoxide, spherical and uniformly sized powder: Sn42Bi58, Sn42Bi57.6Ag0.4, Sn42Bi57Ag1 and Sn43Pb43Bi14.

Packaging Information

Options with various viscosity and metal load for stencil printing and dispensing applications:

  • Printing: Jars, 1/4 NPT nozzle cartridges
  • Dispensing: Syringes, ProFlow cassettes

Storage & Handling

Shelf Life, Storage, and Handling

Refrigerated storage at 5-7°C will prolong the solder paste shelf life to no less than 6 months. Solder Paste should be allowed to reach ambient temperature, normalize for about 6-8 hours before use. Tacky flux has 24 months shelf life stored in room temperature. Refrigeration won't extend shelf life. Normalize for 4-6 hours if stored refrigerated. Paste/flux in syringes and cartridges should be kept vertically, dispensing tip pointing down.

Note :NEVER FREEZE SOLDER PASTE / FLUX!