SMT Solder Paste Printing Parameters and Viscosity Evaluation Methods
Optimize solder paste print volume and yield by maintaining area ratios above 0.66, controlling squeegee force, and verifying viscosity stability.
Brookfield Helipath
Rotational Viscometer
Mechanically rotating vertical spindle attachment designed for measuring paste flow behavior during thick film screen printing preparation requires specialized apparatus mounted on an adjustable stand to eliminate operator interference. The brookfield helipath uses a slowly descending motor drive to lower a T bar spindle continuously through non Newtonian thixotropic solder pastes and conductive adhesives without channeling. Viscosity values derived from torque resistance during this helical descent determine whether thixotropic pastes possess adequate yield stress to hold fine line apertures after screen removal on printed circuit board production lines.
Shear Recovery
Constant mechanical agitation alters internal fluid networks inside thixotropic printing media before deposition onto copper circuit paths. Spindle translation creates continuous fresh shear planes inside the paste volume while measuring the exact force required to break down structural bonds. Recovered viscosity profiles following this downward stroke govern paste slump resistance across fine pitch component pads prior to thermal reflow operations.
Spindle Clearance
Fixture alignment tolerance dictates whether rotational measurement errors occur during automated paste verification routines. Lower limit switches halt descent before the rotating bar strikes the bottom of the sample cup, preventing mechanical damage to the drive assembly and spindle shaft. Assembly operators verify zero plane calibration daily to maintain paste dispensing repeatability across high volume surface mount technology manufacturing floors.