CIS Electronic Assembly & Manufacturing Processes 3

Question 1

Which flux type leaves the least residue and typically does not require post-solder cleaning?

Accepted Answer

No-clean flux

Answer

No-clean flux is formulated to leave minimal, non-corrosive residue that does not require cleaning after soldering.

Question 2

What is the role of aperture design in stencil printing for SMT assembly?

Accepted Answer

Control the volume and location of solder paste deposited

Answer

Stencil apertures define the shape, size, and position of solder paste deposits, directly controlling paste volume on each pad.

Question 3

During wave soldering, what is the function of the preheater section?

Accepted Answer

Activate flux and bring the board near soldering temperature

Answer

The preheat section activates flux, evaporates solvents, and raises PCB temperature to reduce thermal shock during wave contact.

Question 4

What is a 'voiding' defect in solder joints?

Accepted Answer

Gas pockets trapped inside a solder joint

Answer

Voiding refers to gas or vapor pockets trapped within a solidified solder joint, which can weaken mechanical and electrical performance.

Question 5

Which process uses localized heat to solder individual through-hole components while protecting SMT components on the same board?

Accepted Answer

Selective soldering

Answer

Selective soldering applies solder only to designated areas using a miniature solder wave or laser, protecting nearby SMT components.

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