Bad Mark Handling: 6 Rules for SMT Panels A bad mark is a signal that tells the placement machine a unit inside the panel has already failed and must be left empty. The mark is applied after the electrical test or the inspection step that found the fault, and it…

Solder Paste Mixing: Preparation, Placement and Process Control Solder paste arrives in a jar as a thixotropic suspension of alloy powder, flux and solvent, and it is never perfectly uniform after storage. Powder settles under its own weight, solvent migrates to the surface, and the rheology a printer sees at…

Solder Paste Mixing: Practical Checks for Production Solder paste arrives in a jar as a thixotropic suspension of alloy powder, flux and solvent, and it is never perfectly uniform after storage. Powder settles under its own weight, solvent migrates to the surface, and the rheology a printer sees at the…

Stencil Clamp Force: 5 Checks for a Stable Print Stencil clamp force is what holds the stencil frame down against the printer table while the squeegee pushes paste across it. If the clamp is loose, the stencil moves a fraction of a millimetre under load, the printed pattern shifts with…

Separation Speed: A 4-Rule Guide for Clean Paste Release Separation speed is the rate at which the board drops away from the stencil at the end of the print stroke. It looks like a secondary setting next to pressure and gap, and it is the one that decides whether the…

Snap-Off Settings: A 4-Point Guide for Stencil Printing Snap-off is the small clearance a stencil printer leaves between the underside of the stencil and the surface of the board during the print stroke. The stencil is pressed down locally by the squeegee and lifts back as the blade passes, so…

Print Gap Setting: A 5-Point Guide for Stencil Printers Print gap is the clearance between the stencil and the board surface when the squeegee is not pressing them together, and it decides how the stencil behaves at the start of the stroke, at separation and everywhere in between. On most…

Specific Gravity Control for Liquid Flux: 5 Checks Before the Wave Specific gravity is the oldest measurement in a wave soldering shop and still the one most often taken without a record. A liquid flux changes as solvent evaporates from the tank and as thinners are added, and the change…

HASL Finish Quality: 6 Checks on Hot Air Solder Leveling A HASL finish protects the copper and provides the solderable surface that assembly depends on, and it is judged by how it performs rather than by how it looks. Uneven coating, a thin edge or an intermetallic layer grown during…

Paste Release From Stencil Apertures: 5 Checks for Clean Deposits Paste release is the moment the deposit stops belonging to the stencil and starts belonging to the board, and it is where most fine pitch print defects are decided. Aperture walls, area ratio, coating condition and the speed at which…