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Technical Article

Analize The Causes of Welding Cracks In SMT Assembly

Time:2020-12-27 11:38:19 Click:

Causes of welding cracks in SMT Assembly



1. The wetting of PCBA pad and component welding surface does not meet the processing requirements;


2. The use of solder paste does not meet the processing standards;


3. The thermal expansion coefficients of welding and various electric materials are not matched, and the spot welding is unstable when it condenses;


4. The setting of the reflow soldering temperature profile cannot make the organic chemical volatile organic compounds and moisture in the solder paste evaporate before entering the flow-back area;


5. The problems of lead-free ( HASL ) soldering materials in SMT Assembly are high temperature, high interfacial tension, and high viscosity. The increase of the interfacial tension will definitely make the escape of the vapor in the refrigeration process more difficult, the vapor is not easy to be discharged, and the proportion of cracks will increase. Therefore, there are more vent holes and cracks in lead-free soldering in SMT Assembly;


6. In addition, due to the lead-free soldering temperature is higher than that of leaded soldering, especially in the case of large-size, multilayer boards, and electronic devices with high thermal conductivity, the high-value temperature is usually around 260°C. The temperature difference from condensation to the indoor temperature is large, and therefore, the ground stress of lead-free soldering is also relatively large.





SMT Assembly Capability


1. The largest board: 310mm*410mm (SMT);

2. Maximum board thickness: 3mm;

3. Minimum board thickness: 0.5mm;

4. The smallest Chip parts: 0201 package or parts above 0.6mm*0.3mm;

5. The maximum weight of the mounted parts: 150 grams;

6. Maximum part height: 25mm;

7. The largest part size: 150mm*150mm;

8. Minimum lead part spacing: 0.3mm;

9. The smallest spherical part (BGA) spacing: 0.3mm;

10. The smallest spherical part (BGA) diameter: 0.3mm;

11. Maximum component placement accuracy (100QFP): 25um@IPC;

12. Mounting capacity: 3 to 4 million points/day.





Why Choosing Grande To Do PCB Assembly?


1. Strength Guarantee


▪ SMT factory: With imported SMT machines and multiple optical inspection equipment, which is able to produce 4 million points per day. Each process is equipped with QC personnel who will keep an eye on product quality.

▪ DIP production line: Two wave soldering machines and more than 10 employees who have worked for over three years. That’ s to say, these workers are highly skilled and can weld various SMT & DIP components.


2. Quality Assurance With High Cost Performance


▪ High-end equipment can paste precision special-shaped parts, BGA, QFN, 0201 package. It can also be soldered prototype pcba via SMT machine and placing bulk materials by hand.

▪ Both samples, small and large batches can be produced. And there is no SMT Machine starting cost.


3. Rich Electronic Products SMT Soldering Experience With Stable Delivery


▪ Accumulated services to thousands of electronics companies, involving SMT soldering services for various types of automotive equipment and industrial control motherboards. Furthermore, PCBA products are often exported to Europe and the United States, and the quality is able to be affirmed by new and regular customers.


4. Strong Maintenance Ability & Reliable After-Sales Service


▪ The maintenance engineers have sophisticated experience so that those defective boards caused by all kinds of smt soldering can be repaired. Meanwhile, ensuring the connectivity rate of each circuit board also make sense.

▪Order problems feedback will get response, solution and solved as soon as possible.


Previous:PCB Assembly Rework & Repair Guidelines

Next:How To Choose Coating Materials For PCBA Boards?

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