1. As consumer electronics develop in the direction of miniaturization and high integration, the PCBA SMT SMT module process faces severe challenges: the component size has evolved from 0402 package to 01005 package (0.4mm×0.2mm), and the placement accuracy requirement has increased to ±30μm; The PCBA size of TWS earphones, smart watches, and other products is only 20×30mm, and the placement density has been greatly increased. At present, there are common problems in the industry, such as virtual soldering, wrong sticking, and less tin, and the yield rate of SMT patch is mostly 95%-98%, and the rework cost accounts for 10%-15% of the total cost of PCBA. Jiepei has high-end equipment such as 10,000-level dust-free workshop and Siemens high-speed placement machine, and has established a complete SMT SMT quality control system, achieving a yield rate of 99.98%. This article provides a practical SMT SMT optimization solution from the three dimensions of equipment selection, process optimization, and testing and control to help the production team overcome the problem of high-precision SMD.
2. Core technology analysis: key requirements for consumer electronics PCBA SMT patch
Consumer PCBA SMT patches are subject to IPC-A-610G electronic component acceptance standards (Class 2), with key requirements such as: placement offset ≤0.1mm (01005 package), solder joint voiding rate ≤5%, inscription rate ≤0.1%, and misplacement rate ≤0.01%. At the same time, it must comply with the IPC-J-STD-001 welding standard to ensure the reliability of the solder joint, and the thickness of the IMC layer (intermetallic compound layer, the core structure of solder joint reliability) is controlled at 0.5-1.5μm.
Component miniaturization: 01005 package, BGA/QFP and other high-precision IC devices are difficult to mount, and the equipment accuracy and process parameters are extremely high;
High placement density: The number of components on the small PCBA reaches hundreds, and the device spacing is only 0.3mm, which is prone to bridging and collision.
Process sensitivity: The printing amount of solder paste and the temperature curve of reflow soldering have a significant impact on the yield, and parameter fluctuations can easily lead to false soldering and continuous tin.
Through the solution of "high-end equipment + intelligent process + full-process inspection", Jepay solves the above pain points in a targeted manner, and its SMT SMT production capacity at its Guangde production base in Anhui Province reaches 10 million points/day, with a stable yield rate of 99.98%.
Jiepai is equipped with seven new Siemens SMT placement production lines, including ASM high-speed placement machine (placement accuracy ±50μm, repeatability ±30μm), GKG-G5 automatic printing machine (printing accuracy ±0.01mm), Jintuo reflow soldering (temperature accuracy ±1°C) and other high-end equipment; It has a 7500-square-meter 10,000-level dust-free workshop to control the ambient temperature and humidity (temperature 23±2°C, humidity 45%-65%) to avoid the impact of dust and static electricity; Real-time monitoring of the production process is achieved through the AI-MOMS system, and parameters can be traced and optimized.
Equipment Selection and Calibration:
Solder paste printing: GKG-G5 automatic printing machine is selected, the stencil opening is laser cutting + electropolishing process, the hole opening accuracy is ±0.005mm, and the opening size of 01005 package is 0.3mm×0.18mm (aspect ratio 1.67:1);
Placement equipment: ASM Siemens high-speed placement machine (model HS60), equipped with visual recognition system, supports 01005 package, BGA and other device placement, equipment calibration before placement, repeatability verification ≤± 30μm;
Reflow soldering: Jintuo reflow soldering furnace, the number of temperature zones ≥ 8, the heating rate is controlled at 1-3°C/s, and the cooling rate is ≤4°C/s to avoid thermal damage to components;
Material control:
Solder paste selection: SnBiAg solder (melting point 138°C), suitable for consumer electronics low-temperature soldering, solder paste viscosity controlled at 100-150Pa?s (25°C), used within 4 hours after opening;
Component control: SMT components are packaged on machines such as reels and cutting belts, and the storage environment temperature is 15-25°C and humidity ≤60% to avoid oxidation. Incoming materials pass IQC inspection to check for pin oxidation and package integrity.
Solder paste printing process:
Operation points: printing pressure 0.15-0.25MPa, printing speed 20-30mm/s, release speed 1-3mm/s; After printing, the SPI solder paste detector is used to detect the height of the solder paste (0.12-0.18mm), the area (deviation ≤±10%), and the unqualified products are automatically marked;
Data standard: solder paste printing yield ≥ 99.5%, otherwise adjust the stencil opening or printing parameters;
Placement process:
Operation points: Set the placement parameters according to the component type, 01005 package placement pressure 0.05-0.1N, placement speed 50000 points / hour; BGA device placement adopts visual alignment, and the placement deviation ≤ 0.05mm;
Intelligent optimization: The AI-MOMS system analyzes the placement data and automatically adjusts the placement parameters to reduce the offset rate.
Reflow soldering process:
Temperature curve optimization: Adopt a three-stage temperature curve, preheating zone (150-180°C, time 60-90s), constant temperature zone (180-210°C, time 60-80s), and return zone (peak temperature 235-245°C, time 10-15s) to ensure that the IMC layer is fully formed;
Nitrogen protection: For precision components, reflow soldering adopts nitrogen protection (oxygen content ≤ 1000ppm) to reduce solder joint oxidation and reduce voiding rate.
Online Testing:
AOI inspection: EAGLE 3D online AOI inspection machine is used to inspect the appearance of the installed components, identify defects such as misplacement, missing sticking, offset, and monument, with a detection accuracy of 0.01mm;
X-ray inspection: Use the daily X-RAY inspection machine to inspect solder joints that are not visible to the naked eye such as BGA and QFP to identify defects such as false welds and voids, and the void rate is ≤5% qualified;
Manual re-inspection: The QC team conducts 100% manual re-inspection of products that pass AOI and X-Ray inspection with reference to the IPC-A-610G standard, focusing on checking the solder joints of precision devices.
Rework process: The non-conforming products are reworked by professional engineers, using a heat gun (temperature 250-280°C) to accurately disassemble the components, re-mount and weld, and go through the whole process of testing again after rework;
Agile Guarantee: Establish a closed loop of "Inspection-Analysis-Optimization", generate quality reports for each batch of products, optimize process parameters for high-frequency defects, and continuously improve yields.
The core of the yield improvement of consumer electronics PCBA SMT patches is "equipment accuracy + fine process + comprehensive testing", and the production team needs to control the whole process from preliminary preparation, core process, and testing and rework. Suggestions: First, invest in high-end placement and testing equipment, which is the basis of high-precision patch; second, establish a process parameter database to optimize parameters for different product types; The third is to choose a manufacturing service provider with rich experience (such as Jeopei), whose mature quality control system can quickly solve production problems.
