High-activity solder paste is specifically designed for sensor soldering applications, delivering excellent wetting performance on heavily oxidized PCB pads. It effectively resolves cold solder joints and tombstoning defects caused by pad oxidation after high-temperature storage, multiple reflow cycles, or long-term exposure with conventional solder pastes. It is particularly well-suited for the fine pads and low thermal mass requirements of precision sensors such as MEMS, pressure, temperature and humidity sensors.

The pre-drying process of solder paste printing directly affects the viscosity stability of the solder paste and the formation quality of solder joints. Excessive drying will cause the flux to volatilize in advance and increase the risk of solder paste collapse, while insufficient drying can easily lead to stencil clogging and printing deviation. Based on 20 years of measured data from the Jiajinyuan production line, this paper analyzes the actual impact of different temperature zone settings on the rheological properties of printed solder paste and the void rate after reflow soldering.

During the soldering process of immersion silver boards, excessively high flux activity will accelerate the oxidative corrosion of the silver layer, leading to blackened solder joints, poor wetting, and subsequent false judgments in ICT testing. By controlling the acid value of the flux, optimizing the reflow peak temperature and nitrogen purity, and combining with the precise selection of Jiajinyuan JY-806A medium-activity rosin-based flux, silver surface discoloration can be effectively suppressed, and the first-pass soldering yield can be improved.

01005 micro component SMT soldering imposes stringent requirements on solder paste particle size, rheological properties and reflow performance. Jiajinyuan J-01005 dedicated ultra-fine powder solder paste adopts Type 7 (D50=3.5μm) metal powder and a low-volatility flux system. Under conditions of stencil aperture ≤0.12mm, squeegee pressure 0.35MPa, and printing speed 25mm/s, it can achieve a solder paste transfer rate of over 98.7%, significantly reducing bridging, insufficient solder and tombstoning defects.

The reflow oven temperature profiling board must be calibrated with a standard thermocouple once before each shift starts. If the deviation exceeds ±1.5°C, the line must be shut down immediately for adjustment; otherwise, the actual temperature profile will deviate from the set values, leading to frequent BGA cold solder joints, tombstoning, or solder balls. This is the core control point for Jia Jinyuan's production line achieving zero batch rework for three consecutive years.

Addressing the local soldering challenges of industrial control board connectors, selective wave soldering achieves high-reliability soldering through precise temperature control and solder wave positioning, while avoiding overheating damage to sensitive components across the entire board. Jiajinyuan equipment stably achieves a 99.7% first-pass yield under conditions of 0.8mm pin pitch and 12mm pad length, with a process window widened by 35% compared to traditional wave soldering, making it particularly suitable for the mixed assembly requirements of multilayer boards + high-density connectors in domestic substitution.

For the common insufficient solder defects in SMT production lines, it is necessary to wipe the bottom of the stencil with a lint-free cloth dipped in IPA after every 10 to 15 PCBs are printed, and thoroughly clean the stencil once a week with an ultrasonic cleaning machine. Meanwhile, choose the JIAJINYUAN JL-8802 series solder paste, which has a viscosity change rate of less than 8%, a slump rate of less than 12%, and a printing release stability of 99.3% at room temperature of 25℃, and can significantly reduce the incidence of insufficient solder.

To address the issues of solder paste collapse and excessive reflow void rate easily caused by the large copper foil and large pad structures of energy storage power boards, this paper is based on 20 years of measured experience on the Jiajinyuan production line, focuses on the matching of key parameters for solder paste selection, emphasizes that solder paste for large pads requires coordinated control of high thixotropic index and medium viscosity, and low-void solder paste must meet the synchronization between the flux volatilization curve and the thermal response of high heat capacity substrates, with the core focus on the wetting and spreading stability of solder paste under thick copper design.

Solder OEM contract manufacturing and customization must strictly match the customer's production line takt time and equipment compatibility. Common spool weights are 250g, 500g, and 1kg. Specifications cover combinations of diameters from 0.3mm to 1.0mm and lengths from 0.5m to 30m. Outer packaging labels must include alloy composition, rosin type, activity grade, batch number, and RoHS/REACH compliance statements. All solder OEM contract manufacturing orders from Jia Jinyuan are executed in accordance with both JIS Z 3283 and IPC J-STD-006 standards.

The QFN soldering process requires precise control of solder paste volume, stencil aperture, and reflow profile. Actual measurements on Jia Jinyuan's production line show that a 0.12mm-thick stencil with 30μm trapezoidal apertures can effectively inhibit cold solder joints and bridging. Combined with reflow parameters of a peak temperature of 235℃±2℃ under nitrogen protection and a time above liquidus of 65 seconds, the first-pass yield of QFN soldering is stably maintained above 99.2%.

After multiple thawing cycles, solder paste viscosity exhibits nonlinear attenuation. After 3 thawing cycles, the viscosity decreases by approximately 28%, and after 5 cycles, the attenuation reaches 46%. Thawed solder paste is prone to causing solder skip, misalignment, and bridging in SMT production lines. Changes in solder paste viscosity directly affect squeegee pressure settings and the compatibility of stencil apertures.

The direct supply model from domestic factories for solder auxiliary materials significantly reduces intermediate costs. Jiajinyuan's full range of solder auxiliary materials, including solder paste, flux, and cleaning agents, supports orders starting from 100kg. The unit price for bulk purchases is 18% to 25% lower than that of traders, and the delivery cycle is shortened to within 7 working days, meeting the needs of high-frequency replenishment and urgent changeovers on SMT production lines.

SMT stencils directly affect solder paste release rate and void rate in optimizing the aperture ratio of pads under BGA/QFN. Actual measurements by JJY show that an aperture ratio of 0.72～0.85 can balance the filling performance of QFN thermal pads and the risk of bridging for BGA fine-pitch solder balls. Too low a ratio easily leads to cold solder joints, while too high a ratio causes tombstoning or solder balls.

In the actual production line application of ISO solder materials, the melting point deviation between batches is controlled within ±1.2℃, and the fluctuation of active residue is less than 0.03%. This is attributed to Jia Jinyuan's decomposition of ISO 9001 clauses item by item into 27 executable actions, including smelting temperature recording frequency, alloy composition quick inspection response time, and packaging sealing sampling proportion, ensuring that each batch of ISO solder materials is fully controlled from feeding to outbound.

Cold solder joint is one of the most frequent soldering defects on SMT production lines. Its cause is often misjudged as insufficient solder paste activity, but in fact, it mostly stems from the deterioration of pad solderability combined with mismatched flux activity. By specifically improving the wetting ability of the pad surface, selecting JJY JY-602 medium-high activity no-clean flux, and strictly controlling the OSP film thickness and nitrogen purity, the cold solder joint rate can be reduced from 3.2‰ to below 0.4‰ without changing the reflow profile.

Solder used in electronics manufacturing plants must achieve dynamic matching across all processes including SMT placement, wave soldering, and touch-up soldering. Jiajinyuan solder adapts to complex thermal stress scenarios with reflow peak temperature of 235℃, wave soldering temperature of 260℃, and manual touch-up soldering instantaneous temperature of 380℃ through melting point gradient design. Its active residue content is controlled within 0.012%, avoiding ICT test leakage and excessive ion contamination.

The wiping frequency of solder paste stencils directly affects the uniformity and profile clarity of printed solder paste. Excessive wiping accelerates stencil tension decay and causes insufficient solder paste deposition, while insufficient wiping easily leads to solder paste drying, aperture clogging, and induces typical defects such as solder bridging and insufficient solder. Therefore, to scientifically formulate solder paste control strategies, wiping frequency must be included as a key process parameter for dynamic calibration.

In the tin dipping process, flux selection directly affects the incidence of pinholes on the tin surface and copper exposure defects. JJY JY-806A has been verified on actual production lines to reduce the pinhole rate from 3.2% to 0.4%. Its low solid content, highly active rosin derivative system, and the characteristic of a copper surface wetting angle of less than 28° work together to significantly improve the uniformity of molten tin spreading and gas escape paths.

X-Ray inspection can penetrate BGA packages to directly observe solder ball morphology, void distribution, and bridging defects, making it an irreplaceable method for verifying the internal quality of reballing soldering after rework. Especially after reballing operations are completed on JJY rework stations, X-Ray inspection must be performed to confirm whether solder ball coplanarity, offset, and void rate comply with IPC-A-610 Class 2 standards.

Tombstoning is a typical defect of chip components where one end lifts off the pad during reflow soldering, commonly occurring in small-sized resistors and capacitors such as 0402 and 0603. It is essentially caused by the combined effect of unbalanced wetting forces at both ends and uneven solder paste shrinkage stress. The thixotropy and metal content of Jia Jinyuan solder paste directly affect the incidence of tombstoning.