PCBA Testing: Solder Joint Inspection And Quality Control

In PCBA, solder joints are not only the electrical connection between components and boards, but also the physical support. Soldering quality is the cornerstone of PCBA functionality and reliability. Welding is one of the most core and critical processes in the PCBA processing flow, and its quality directly affects whether the PCBA can work properly. In the PCBA test system, the detection and management of welding quality is to ensure product quality is a key link.

Poor welding on PCBA function, life and product reliability will have a certain impact.

Components are not firmly welded or welded in the process of short-circuiting, leakage and other issues, the circuit board will be damaged. Poor soldering may lead to an increase in rework rate, which increases costs and reduces productivity. In addition, if the soldering problems on the PCB are not solved in time, it may also affect the normal service life of electronic products.

Poor soldering may lead to electrical performance problems, which may make the electronic products work unstably and fail to meet customer requirements. For example, if the solder joints appear open circuit, the electronic components on the circuit board will not work properly. If there is a short circuit in the solder joint, it may cause other electronic components on the circuit board to fail. If these problems are not solved in time, it will bring great economic loss and reputation loss.

Poor soldering can adversely affect product safety. For example, if the circuit is short-circuited or the components are overheated, it may cause safety accidents such as fire or explosion of the circuit board or electronic products. These problems will not only damage the customer's property, but also may cause casualties.

Timely detection of PCB soldering defects is one of the primary objectives of PCBA testing. The quality of welding directly depends on the level of control of the welding process during PCBA processing. PCBA factory PCB quality testing throughout the entire SMT production line.

SPI SMT placed in the automated pick and place machine before, after the SMT stencil printer. The equipment is mainly used to detect the volume, shape, position and thickness of the solder paste. As most soldering defects from poor solder paste printer, SPI is the first step in the PCBA process to prevent soldering defects is extremely critical.

Carried out after reflow oven for PCB, AOI uses a high-speed camera to capture images of the PCBA, and algorithms to detect the appearance of the solder joints, component placement (e.g., polarity, location, missing parts, wrong parts). It can detect defects such as excessive/insufficient tin, continuous tin, and false soldering (sometimes manifested as abnormal solder joint morphology). It is an effective means of rapid, batch detection of solder appearance defects after PCBA processing.

NeoDen N10p SMT production line

Inspection system Application: After stencil printing, pre/post reflow oven, pre/post wave soldering machine, FPC etc.

Program mode: Manual programming, auto programming, CAD data importing

Inspection Items:

Stencil printing: Solder unavailability, insufficient or excessive solder, solder misalignment, bridging, stain, scratch etc.
Component defect: missing or excessive component, misalignment, uneven, edging, opposite mounting, wrong or bad component etc.
DIP: Missing parts, damage parts, offset, skew, inversion, etc.
Soldering defect: excessive or missing solder, empty soldering, bridging, solder ball, IC NG, copper stain etc.

Calculation Method: Machine learning, color calculation, color extraction, gray scale operation, image contrast.

Inspection mode: PCB fully covered, with array and bad marking function.

SPC statistics function: Fully record the test data and make analysis, with high flexibility to check production and quality status.

Minimum component: 0201 chip, 0.3 pitch IC.

For BGA, QFN and other solder joints hidden in the package below the component, X-ray inspection is essential. It can "see through" the components, detect the shape of the solder ball, internal voids, even tin and pin welding. X-rays are uniquely suited for detecting invisible soldering defects, and SMT X-Ray equipment is often used for high reliability requirements or complex PCBA processing.

SMT production line

Miniaturized equipment, easy to install and operate.
Applicable to Chip, BGA/CSP, Wafer, SOP/QFN, SMT and PTU packaging, Sensors and other fields products inspection.
High resolution design to get the best image in a very short time.
Infrared automatic navigation and positioning function can select the shooting location quickly.
CNC inspection mode which can quickly and automatically inspect multi-point array.
Inclined multi-angle inspection makes it easier to inspect sample defects.
Simple softwareoperation, low operating costs.
Long lifespan

Through the probe contact with the test point on the PCBA, the open and short circuit test of the circuit and the electrical parameter measurement of the components are carried out. ICT can effectively find out the short circuit due to the connecting of the tin and the open circuit due to the false soldering and leakage of the solder. It verifies whether the connection brought by PCBA processing is correct from the electrical level.

In the simulation of the actual working environment of the PCBA and input signals, to verify that its functions are normal. Some of the virtual solder or bad solder joints may be at room temperature or static test performance is normal, but in the FCT encountered when the power, heating or vibration will be a problem, resulting in functional instability or failure. FCT can help to find these potential functional problems caused by the quality of welding.

Although less efficient and subjective factors, but in some critical areas, complex locations or as a complementary means of automated inspection, experienced inspectors can still find some welding appearance problems.

Defects accurately recorded and categorized: The establishment of a detailed defect database, recording the type, location, number of defects, found process (AOI, X-ray, ICT, FCT, etc.). Accurate classification helps subsequent analysis.
Standardized rework and retesting: Professional rework repair of detected welding defects. The rework process must strictly follow the process specifications, use the appropriate tools and materials to avoid the introduction of secondary damage. The reworked PCBA must be retested to verify that the problem has been solved and no new problems.
Root cause analysis: The high incidence or critical soldering defects for in-depth analysis to find out the real reason for their generation. This may involve solder paste printing parameters, placement machine placement accuracy, reflow temperature profile, flux activity, pad design, PCB quality, and even PCBA processing operator specifications.
Process control and optimization: Based on the results of the root cause analysis, adjust the parameters of the PCBA processing process, maintenance equipment, improve the process, strengthen personnel training. For example, adjust the temperature profile of the reflow oven to reduce voids, optimize the design of the solder paste printing stencil to solve the problem of even tin or tin amount is insufficient, strengthen the AOI inspection standards to improve the defect capture rate.
Data analysis and feedback closed loop: The use of testing and inspection systems accumulated a large amount of data, trend analysis, yield statistics, failure mode analysis. These data and analysis results timely feedback to the R&D design, PCBA processing engineering departments, the formation of a closed loop of continuous improvement, from the source to reduce the occurrence of welding quality problems.

Welding quality is the most important of PCBA reliability, strict testing and management is the core component of PCBA testing system. Defects are detected at different stages of PCBA processing through SMT SPI, AOI, X-ray and other inspection means, and its electrical function is verified by combining ICT and FCT. More importantly, the root cause analysis of the detected problems is carried out and the data is fed back to the PCBA processing for continuous improvement and optimization. Only by combining advanced inspection technology with scientific management methods to improve the welding quality of PCBA processing from the source, can we finally produce high-performance and highly reliable PCBA products.

NeoDen

1. NeoDen Tech established in 2010, 200 + employees, 27000+ Sq.m. factory.

2. NeoDen Products: Different Series PnP machines, NeoDen YY1, NeoDen4, NeoDen5, NeoDen K1830, NeoDen9, NeoDen N10P. Reflow Oven IN Series, as well as complete SMT Line includes all necessary SMT equipment

3. Successful 10000+ customers across the globe.

4. 40+ Global Agents covered in Asia, Europe, America, Oceania and Africa.

5. R&D Center: 3 R&D departments with 25+ professional R&D engineers.

6. Listed with CE and got 70+ patents.

7. 30+ quality control and technical support engineers, 15+ senior international sales, for timely customer responding within 8 hours, and professional solutions providing within 24 hours.