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In manual soldering, the diameter of solder wire directly affects solder joint quality and material cost. An excessively large diameter easily causes bridging, cold solder joints, and flux waste, while an excessively small diameter leads to insufficient tinning and a higher rework rate. Considering component pad size, pin pitch, and operator proficiency, 0.3mm is recommended for 0402/0603 chip resistors and capacitors, 0.5mm covers medium and low-density packages such as SOP-8/SSOP-16, and 0.8mm is suitable for power devices and through-hole components. This selection strategy has been verified in production line tests to reduce the cost of solder consumables per joint by 17% and cut rework labor hours by 23%.
Published: 2026-08-27
Solder paste slump is a post-printing deformation phenomenon in SMT soldering caused by uncontrolled solder paste rheology, which directly affects the risks of solder joint bridging and cold soldering. SMT determination requires comprehensive evaluation by combining the stencil aperture ratio, the height attenuation rate before reflow, and the edge slump angle under a microscope. The typical slump determination criteria are a height drop of more than 15% within 30 minutes after printing, continuous paste bridging between adjacent pads, and a slump angle of less than 45 degrees.
Published: 2026-08-27
Wave soldering solder bar alloy selection must focus on two core hard indicators: purity and oxidation resistance of the solder bar. High purity (≥99.95%) can reduce the generation of dross by more than 40%, while the oxidation-resistant formulation with trace rare earth elements can reduce the thickness of the oxide film on the surface of the liquid solder bath by 60%, significantly extending the service life of the solder bar and improving the wettability of through-hole solder joints.
Published: 2026-08-27
The viscosity and thixotropic index of solder paste directly affect SMT printing accuracy and solder joint yield. IPC-J-STD-005 specifies that the viscosity range of solder paste is 200–800 Pa·s (25℃), and the thixotropic index should be ≥0.75. When the measured value is below 0.65, it is easy to cause solder spikes, bridging and insufficient solder; when it is above 0.95, it will lead to poor demolding and edge collapse. The production line needs to conduct actual measurement and temperature calibration every 4 hours using a Brookfield LVDV-II+ with matching cone-and-plate rotors to avoid data drift caused by an ambient temperature difference exceeding ±2℃.
Published: 2026-08-27
Solder selection directly affects SMT first-pass yield and rework costs; solder paste, solder wire, and solder bars must be dynamically matched according to process takt, solder joint precision, and rework frequency. For example, batch mounting of 0201 components requires 3# powder solder paste paired with stainless steel stencils, while bottom rework for BGA preferentially uses 0.3mm diameter no-clean solder wire, saving over 240 hours of rework labor per production line annually.
Published: 2026-08-27
Poor solder paste wettability during SMT soldering on thick gold PCBs commonly manifests as solder joint voids, insufficient solder climb, or local dewetting. The root cause is excessive gold layer thickness leading to nickel layer passivation and excessive consumption of flux activity. Evaluation requires comprehensive judgment by combining wetting angle measurement, microscopic observation of solder joint morphology, and IMC growth state after reflow. The matching between thick gold PCBs and solder paste wettability is a key process control point to ensure first-pass yield.
Published: 2026-08-27
Restarting the machine after an SMT shutdown involves multiple risks such as reduced solder paste printing accuracy, stencil clogging, and solder paste activity attenuation. Differentiated response strategies must be developed based on the shutdown duration, ambient temperature and humidity, and solder paste type, with particular attention paid to squeegee pressure calibration, stencil cleaning frequency, and solder paste rewarming and stirring operations in the solder paste printing process.
Published: 2026-08-27
The control of the solder wire feeding angle directly affects the spatter rate of manual soldering. The industry is currently accelerating its evolution toward micro-solder joints below 0.3mm, high-density mixed-assembly PCBs, and lead-free high-temperature processes. However, the traditional fixed 45° solder feeding method can no longer match the production line reality where 0.25mm pitch QFNs and 0402 components coexist. Frontline engineers must dynamically compress the angle between the solder wire and the soldering iron tip to the 25°~35° range, while synchronously adjusting the solder feeding rhythm and the soldering iron withdrawal timing.
Published: 2026-08-27
To address the frequent solder bridging and solder spike defects of large-size QFP devices in the SMT process, this paper starts from solder paste selection, and combines printing accuracy, reflow thermal response and metal powder distribution characteristics to elaborate on special solder pastes with high thixotropy, narrow particle size distribution (D50=18.5μm) and 90.2% metal content, such as
Published: 2026-08-27
Welding of FPC flexible boards is highly sensitive to solder paste printing accuracy and mounting pressure. Based on a review of real production line failures, this paper horizontally compares the occurrence rates of bridging, tombstoning, and cold soldering under different solder paste viscosities, metal contents, thixotropic properties, and various mounting pressure ranges (0.15N～0.6N) in typical scenarios such as fine-pitch ICs, double-sided pads, and high-density blind/buried via FPCs. It is clarified that for solder paste printing, models with 4# powder, 88.5% metal content, viscosity of 220Pa·s, and thixotropic index >4.2 should be prioritized, while mounting pressure must be dynamically set according to pad size, and must not be uniformly set to 0.3N.
Published: 2026-08-27Our technical team is always ready to provide professional solder material selection advice and SMT process solutions.