Force Baseline
Mechanical actuation metrics governing test pin pressure during bare board and assembly testing determine electrical contact resistance without causing physical pad damage. In flying probe test systems, flying probe contact force balances reliable oxide penetration against the risk of micro-cracking thin copper foils or solder mask boundaries. The parameter controls the z-axis drive motor current when landing tungsten or beryllium-copper needles onto test targets.
Its scope covers electrical continuity and isolation testing on printed circuit boards, ending where fixed bed-of-nails fixtures apply static spring pressure.
Deformation Mechanism
Deformation mechanism dynamics change when probe needles strike surface finishes like immersion silver, electroless nickel immersion gold or organic solderability preservatives. High needle momentum breaks through surface oxides but risks displacing soft copper, creating indentations that compromise downstream wire bonding or component placement. Lowering needle pressure preserves target geometry yet risks high contact resistance, leading to false-open test readings.
System software adjusts probe velocity and deceleration curves to optimize energy transfer upon contact.
Probe Threshold
Probe threshold limits are verified using calibrated load cell sensors positioned on test platens. Acceptance criteria specify contact pressure ranges between five and fifteen grams of force depending on target size and finish hardness. Microscopic inspection verifies that pad indentations remain below ten percent of total pad thickness.
