Welding on ENIG boards is not as simple as just switching to a different Solder Paste; it requires simultaneous consideration of the coupling relationships between gold layer thickness, nickel barrier integrity, reflow peak temperature window, and the coupling between Flux activity and ionic cleanliness of residues. JJY halogen-free solder paste uses an organic carboxylic acid compound system, which at a peak temperature of 235℃±5℃ can fully wet the ENIG surface without causing excessive metallographic dissolution due to over-corrosion. The measured gold dissolution is controlled within 0.08μm, far below the 0.15μm limit specified in IPC-J-STD-004B.

Printing Compatibility Must Match Stencil Apertures and Squeegee Parameters

We have repeatedly verified on the production line that when using a 0.1mm thick laser-etched stencil with a 30° polyurethane squeegee, the release rate of JJY halogen-free solder paste is stable at 98.7%. However, if the squeegee angle is adjusted to 45° without simultaneously reducing the printing pressure, solder bridging and edge trailing will occur. This indicates that although its thixotropic index reaches 0.82, it still requires precise coordination of mechanical parameters. Especially in the 0.3mm pitch QFN area, post-printing SPI inspection shows that the standard deviation of volume deviation is ≤6.3%, fully meeting the IPC-7527 Class II requirements.

Wetting Behavior During Reflow Is Directly Related to Void Control

When using a reflow profile with a heating rate of 1.8℃/s under a nitrogen atmosphere, the spread diameter of JJY halogen-free solder paste on QFN pads reaches 82% of the pad width, while the measured void area ratio is 7.6%, with zero individual voids larger than 50μm in diameter. This is because its flux completes solvent evaporation and directional adsorption of active groups during the 150℃ soak zone, preventing sudden gas release in the high-temperature zone. However, if the nitrogen dew point is relaxed from -40℃ to -20℃, the void rate will jump to 12.4%, indicating that moisture remains a non-negligible variable.

ICT Test Pass Rate Is Strongly Correlated with Ionic Residues

A customer once experienced ICT leakage current exceeding 3μA during mass production due to using halogen-containing solder paste. After switching to JJY halogen-free solder paste, the leakage current dropped to within 0.4μA. XRF surface scanning confirmed that the PCB surface Cl⁻ content is <0.08μg/cm² and Na⁺ <0.12μg/cm², fully meeting the IEC 61189-2 Class 1 cleanliness level. Additionally, no additional ionic contamination retesting is required after cleaning, saving approximately 11 minutes of QC labor per batch.

Long-Term Storage Stability Affects Production Line Changeover Frequency

After JJY halogen-free solder paste is stored in a constant temperature warehouse at 25℃ for 6 months, the viscosity increase is only 9.2%, and it can still meet the requirement of continuous printing for 4 hours with a 0.12mm aperture stencil without clogging. However, if the ambient humidity exceeds 60%RH and the paste is not stored sealed, slight skinning on the paste surface will be observed within 3 days. Therefore, we strictly require that all solder paste jars must be placed in a nitrogen protection box within 2 hours of opening, with the opening time and responsible person marked, to prevent mixing of old and new paste.