1. Three types

⊙ Shear collapse: caused by continuous printing under shear force

⊙ Static collapse: collapse under shear at room temperature

⊙ Heating collapse: occurs during heating, i.e. preheating and reworking

2. Two tests

⊙ Cold decay: at room temperature

⊙ Hot decay: at 150 ℃

3. Factors affecting collapse

⊙ Composition of flux, viscosity, softening point of rosin, thixotropy, boiling point of solvent, shape of tin particle.

⊙ Process parameters of printing and mounting.

⊙ External environmental conditions

4. Collapse prone time

⊙ Mounting

⊙ Preheating process

⊙ Activation process

5. Defects caused by solder paste

⊙ Insufficient solder

*Due to the large particle size, incorrect shape, or non printability, the solder paste blocks the template hole

⊙ Solder ball

*Solder paste collapse

*Solvent splashing during reflow

*Oxidation of metal particles

*There is solder paste & solder paste slag at the bottom of the formwork

*Too much solder paste