Bare Board Insulation Resistance Standard Baseline Specifications
Unpopulated printed circuit boards require baseline insulation resistance exceeding ten gigaohms under direct current bias to pass IPC Class 3 delivery criteria.
Bare Board Testing
Electrical Verification
Unpopulated printed circuit boards undergo continuity and insulation resistance measurements prior to component placement. High-voltage nets and low-resistance traces must satisfy netlist specifications before assembly. Automated flying probe systems and bed-of-nails test fixtures apply programmed test voltages across all net nodes to identify open circuits or unwanted copper shorts.
Testing ends where active or passive components join the board surface, leaving functional circuit validation to subsequent manufacturing stages.
Continuity Isolation
Signal path integrity requires rapid measurement of resistance between interconnected pad networks. Bare board testing isolates open circuits by confirming continuity along individual conductive traces below specified milliohm limits. High resistance readings trigger immediate line flags, preventing defective substrates from entering automated component pick-and-place lines.
Fixture Calibration
Mechanical alignment of test pins against small test pads dictates measurement accuracy across dense panels. Spring-loaded pogo pins in bed-of-nails fixtures must maintain uniform contact pressure without denting soft surface finishes like immersion tin or organic solderability preservatives. Pin wear, oxidation, and optical alignment errors introduce false open readings during high-volume production runs.
Standard practice requires daily verification against calibrated shorting plates to keep false rejection rates low. Flying probe systems avoid physical grid limits by using software-stepped stepper motors, though probe speed limits panel throughput compared to dedicated pin fixtures.
Bare Board Insulation Resistance Testing Thresholds
Bare board insulation resistance testing requires minimum 100MΩ thresholds at 100V DC under IPC-9252B Class 3 to prevent electrochemical migration escapes.