PCB News - SMT content quality defects analysis

SMT content quality defects analysis:

1, Cold Welding, referring to the role spot.Features wet welding is not enough: the reason the gray, dull appearance.When viewed under a microscope, the solder joints appear granular.
Main reason: improper settings reflux temperature curve of the furnace, the furnace is too fast by the speed, product placement is too dense, solder paste damage, etc.

2, Tin, refers to two or more of the solder joints are connected together, resulting in a short circuit.
Feature: two pins are connected together.
Main reasons: even tin solder paste printing, solder paste collapse, etc.

3,False Welding, referring to the component pin and PCB pad connection.Such disorders most likely to occur in TPS welding.
Features: pin not connected to the pad, or pin covered with solder, but not connected.
Main reasons: oxidation, deformation and pollution pin components or welding pad, size mismatch design, printing and installation irregularities, inconsistent furnace temperature settings, etc.

4, Erection, also known as a monument, tombstone.
Feature: welded end components are not connected to the circuit and curved.
The main reasons: improper product design leads to uneven heating on both ends of the components, installation irregularities horizontal plane, oxidation or pollution at one end of the weld pad or pin components, leakage or printing irregularities at one end of the solder paste, etc.

5. Standing at side.Features you: although both ends of the components are connected by welding, surface perpendicular to the kinds of components PCB.
Main reasons: packing too loose components, improper equipment debugging cause SMT parts fly, and dishtowels in the process of passing furnace.

6. Turn over.Features: initially facing upwards stencil surface mount components part.Such exception below will not affect the realization of the function of the product, but it will affect maintenance.
Main reasons: packing too loose parts, improper equipment debugging leads for SMT parts fly, the products are very shaken in the process of passing through the furnace, etc.

7. Tin balls.Features: there are particles in the tin ball round the grounds of non-welded PCB area.
Main reasons: quite the return of the solder paste, improper settings reflow temperature welding, improper opening of the steel mesh, etc.

8. Pinhole.Features: no needle holes in the surface of the solder reason joints.
Main reasons: welding materials back in the humidity, the temperature returns incorrect and so on.