Tombstoning is one of the most common defects in SMT solder paste printing. When the stencil thickness does not match the pad design, the solder paste is easily pulled up during the demolding stage, forming pointed residues. If the printing speed is too fast at this time, the shear stress superimposed on the demolding tension will significantly aggravate the degree of tombstoning, leading to subsequent placement offset, reflow bridging, and even cold solder joints.

To address common solder paste defects during the dispensing process, such as stringing and paste breakage, this paper examines five key factors: viscosity, thixotropic index, metal content, flux activity, and storage temperature. By combining these factors with actual production line measurement data, it proposes an immediately actionable solder paste parameter optimization pathway, providing a direct basis for dispensing solder paste selection and process matching.

Soldering 01005 components poses extreme challenges to the accuracy of high-speed placement machines, the consistency of solder paste printing, and the uniformity of the reflow soldering thermal field. Through dual-track synchronous visual positioning, 0.02mm-level Z-axis closed-loop compensation, and a gradient temperature zone control system, Jiajinyuan equipment controls solder joint offset within ±12μm in mass production, effectively addressing typical failures such as tombstoning, cold solder joints, and uneven pad wetting during 01005 component soldering.

Solder paste selection must match the actual pad pitch and stencil aperture size. T3 to T6 solder powder particle sizes directly affect the printing accuracy and slump control of fine-pitch solder paste. Among them, T4 (25–45μm) is suitable for 0.4mm pin pitch, T5 (15–25μm) is adapted for fine-pitch solder paste applications of 0.3mm and below, while T6 (5–15μm) is only limited to CSP or FCCSP packages below 0.2mm and requires nitrogen reflow and high-precision printing equipment.

Chinese-made solder exports to ASEAN must simultaneously meet the dual requirements of China's export supervision and the technical access of ASEAN importing countries, involving the application of RCEP rules of origin, SN/T 0370.3-2018 packaging inspection, HS code 81052090 classification confirmation, and adaptation to the RoHS exemption clauses of the destination country. A batch of Jiajinyuan solder wire was fully returned during inspection by a Vietnamese customer due to flux residue failing to meet the limits of TCVN 8264:2019, exposing the problem of missing third-party SGS testing before export.

SMT printing is a key process in which SMT stencils evenly transfer solder paste to PCB pads, directly affecting placement accuracy and reflow soldering yield. In actual production lines, solder paste viscosity, stencil aperture size, squeegee pressure, and printing speed must be coordinated and matched; any slight deviation will cause typical defects such as insufficient solder, solder bridging, or misalignment.

PCBA soldering materials have complete SGS certifications, covering all categories including lead-tin alloys, lead-free solder pastes, fluxes and cleaning agents, and comply with mandatory export standards such as IEC 61249, RoHS 2.0 and REACH. They can be directly used for complete machine exports to the EU, North America, Japan and South Korea, avoiding customs clearance delays or batch returns caused by missing material qualifications.

Tin whisker growth after solder paste reflow is a critical failure mode affecting solder paste reliability. Its root causes are closely related to the silver content, grain size, flux residue, and intermetallic compound growth kinetics in the solder paste formulation. By precisely regulating the Sn/Ag/Cu ratio in the solder paste formulation, adding trace inhibitory elements, and optimizing the thermal stability of the flux, the whisker initiation time can be significantly delayed.

Automotive electronic solder maintains the mechanical strength of solder joints within a wide temperature range of -40°C to 150°C, and shows no microcracks after random vibration tests at 20G acceleration and 10Hz–2kHz, meeting the dual requirements of temperature resistance and vibration resistance for automotive electronic solder in high-reliability scenarios such as ADAS controllers and BMS main control boards.

Cold soldering is the most hidden fatal defect in SMT production lines. Insufficient reflow peak temperature prevents the solder paste from fully melting and wetting the pads, resulting in cold solder joints and false soldering. Jia Jinyuan solder paste can only complete the eutectic reaction above 183°C, and its wetting force drops sharply when the temperature is below 205°C. Cold solder joints have a gray surface without metallic luster, and the thrust test value is more than 50% lower than the standard value.

Low-smoke solder wire for connector soldering is designed for high-volume automated soldering lines, addressing the pain points of traditional solder wires such as heavy smoke, excessive spatter, and poor wettability. It significantly reduces TVOC concentrations in the operation area while ensuring high electrical conductivity and mechanical strength. Compatible with automatic wire feeders for wire diameters ranging from 0.3 to 1.2 mm, it has achieved stable continuous feeding for 8 hours without downtime on customer production lines of Jiajinyuan.

Relying on its solder ODM R&D capabilities, JJY has developed customized new solder formulations with low residue, high wettability and narrow melting range for special soldering processes such as laser solder paste jetting, vacuum reflow and low-temperature thermocompression bonding. These formulations have been successfully adapted to scenarios including 01005 component micro-pads, Cu/Ni/Au plating and dissimilar metal bonding, significantly reducing void rate and the risk of excessive IMC growth.

Dip soldering is a key process that completes batch soldering by vertically immersing PCB pins into the surface of molten solder using a manual dip soldering machine or a wave soldering machine. Its core lies in the coordinated control of solder temperature, immersion depth, and dwell time. Jiajinyuan equipment has verified in actual production lines that a temperature control accuracy of ±2℃ and a standard dip soldering window of 0.8~1.2 seconds can effectively suppress defects such as cold solder joints and bridging.

In formic acid atmosphere vacuum reflow soldering, solder paste must balance activity control and bubble removal; vacuum solder paste must have low vapor pressure, high thermal stability, and formic acid compatibility, while formic acid reflow solder paste requires a flux system that can synergistically reduce oxides with formic acid without exacerbating metal corrosion. These three factors jointly determine the void fraction and shear strength of solder joints in high-power devices.

For the first-article confirmation of the insufficient solder production line, the solder paste forming status must be visually inspected pad by pad, with a focus on identifying typical insufficient solder defects such as edge collapse, central depression, and local solder shortage. Simultaneous troubleshooting shall be conducted in combination with squeegee pressure, stencil aperture size, and solder paste rheological properties to ensure the printing stability of Jia Jinyuan solder paste under the low solder volume process window.

Solderability of immersion silver (ImAg) PCBs poses dual challenges to solder paste in terms of wetting performance and corrosion resistance. Jiajinyuan GJ-812A solder paste demonstrates excellent compatibility with silver finishes in actual production lines. Its weakly acidic flux system ensures sufficient wetting for 0.3mm fine-pitch QFN packages while avoiding excessive corrosion of the immersion silver layer. After reflow, the solder joints exhibit a clean surface and uniform IMC layer, effectively reducing the risks of cold solder joints and black pad.

During the rework soldering and BGA chip ball mounting process, an excessive void rate is the main cause of cold solder joints, increased thermal resistance, and early failures. Using low-void solder paste can significantly improve the metallurgical bonding quality of solder joints, and especially maintain structural integrity after multiple thermal cycles. In actual tests, the Jiajinyuan JGY-850 series solder paste stably controls the void rate within 8%. Combined with precise stencil aperture design and nitrogen-protected reflow, it increases the first-pass yield of rework soldering to 98.3%.

Bridging is one of the defects most likely to cause batch short circuits in the SMT process, and pre-reflow AOI inspection can intercept bridging risks before soldering, avoiding a sharp increase in rework difficulty caused by high-temperature curing. Jiajinyuan AOI equipment, through high-resolution imaging and dynamic threshold algorithms, accurately identifies micron-level bridging trends after solder paste printing and after component placement is completed but before entering the reflow oven.

In the ball mounting process, adopting a low-temperature solder paste solution can significantly reduce the thermal stress on BGA chip bodies, avoiding common production line failures such as pad peeling, silicon die microcracks, and molding compound delamination. In actual tests of the Jiajinyuan LTS series solder paste, this solution achieved ball diameter consistency of ±0.02mm at a peak temperature of 185℃, while balancing wetting and spreading performance with residue insulation properties.

For the typical solder paste defect of solder paste flux splatter contaminating PCBs, actionable improvement countermeasures that can be implemented immediately are proposed from four aspects: solder paste selection, stencil aperture design, printing parameter matching, and pre-reflow standing control. The synergistic matching of solder paste flux activity and viscosity is emphasized, avoiding reliance solely on cleaning or process compromises.