PCBA Tech - About device cracking in SMT chip processing

In SMT assembly and production, the cracking of chip components is common in multilayer chip capacitors (MLCC) and MLCC multilayer ceramic capacitor structures. The cause of MLCC cracking failure is mainly due to stress, including thermal stress and mechanical stress. It is the cracking phenomenon of MLCC devices caused by thermal stress. Chip component cracking often occurs in the following situations.

title=The cracking problem of MLCC chip ceramic capacitor in SMT chip processing and its solution"/>

Device cracking in SMT chip processing

1. Where MLCC capacitors are used: For this capacitor, its structure is superimposed by multilayer ceramic capacitors, so its structure is fragile, low in strength, and extremely resistant to heat and mechanical shocks. This is especially true during wave soldering. obvious.

Device cracking in SMT chip processing

Cracking of MLCC chip ceramic capacitors caused by thermal stress and solutions

2. During the SMT placement process, the suction and release height of the Z-axis of the placement machine, especially some placement machines that do not have the Z-axis soft landing function, the absorption height is determined by the thickness of the chip component, not by the pressure sensor OK, so the component thickness tolerance will cause cracking.

Device cracking in SMT chip processing

3. After soldering, if there is warping stress on the PCB board, it will easily cause the components to crack

4. The stress of the split PCB will also damage the components.

5. The mechanical stress during the ICT test causes the device to crack.

Device cracking in SMT chip processing

6. The stress generated by the tightening screw during the assembly process will damage the surrounding MLCC.

Cracking of MLCC chip ceramic capacitors caused by mechanical stress and solutions

Device cracking in SMT chip processing

In order to prevent chip components from cracking, the following measures can be taken:

1. Carefully adjust the welding process curve, especially the heating rate should not be too fast.

2. Make sure that the placement machine pressure is appropriate during placement, especially for thick plates, metal substrate plates, and ceramic substrates when mounting MLCC and other brittle devices.

Device cracking in SMT chip processing

3. Pay attention to the division method and the shape of the cutter when making up.

Device cracking in SMT chip processing

4. For the warpage of the PCB, especially the warpage after soldering, targeted corrections should be made to avoid the influence of the stress caused by large deformation on the device.

Device cracking in SMT chip processing

5. MLCC and other devices should avoid high stress areas when laying out the PCB.

The reason and judgment of the wrong piece of SMT patch

All SMT work is related to welding. On the flow chart of SMT, after the placement machine is welding, this makes the placement machine not only the mechanical equipment with the highest SMT technology content, but also the last quality guarantee before welding. Therefore, the quality of the patch plays a vital role in the entire process of SMT.

In the modern production and processing concept, product quality has become the lifeblood of the company's survival. In the SMT assembly line, after the PCB passes the placement machine, it is about to face the heating and welding forming of reflow soldering, that is to say, the quality of the component's placement directly determines the quality of the entire product. This article will take the real object as a reference, so that relevant SMT practitioners can judge the quality of the patch.

Inferior, and can deal with the defects of the patch in a correct way.