PCB Bare Board Reliability Testing Methods
- Interconnect Stress Test (IST) is an accelerated stress test method used to evaluate the integrity of the Printed Circuit Board (PCB) interconnect structure.
- Highly Accelerated Thermal Shock (HATS) system’s programmable self-contained machine does all the common reliability cycles, with a range from •55°C to +145°C in air-to-air mode.
Interconnect Stress Test (IST)
Interconnect Stress Test (IST) is an accelerated stress test method used to evaluate the integrity of the Printed Circuit Board (PCB) interconnect structure. IST creates a thermal cycle that stresses a specifically designed coupon, while simultaneously monitoring the electrical integrity of plated through holes (PTHs).
IST automatically produces data that can help determine the PCB’s ability to withstand the rigors of assembly, rework, and the end-use environment. IST gives a critical evaluation of a board’s quality and insight into the possible modes of failure.
IST works on the principle of driving a test coupon through a rapid thermal cycle between ambient temperature (21°C) and 150° C followed by forced air cooling back to ambient temperature. As the coupon thermal cycles, changes in circuit resistance are monitored. An increase of 10% is considered a failure.
The Interconnect Stress Test System (IST) is used to evaluate the reliability of the copper-plated barrel and inner-layer interconnects to the plated barrel of printed wiring boards (PWB).
The IST machine thermally cycles specially designed coupons by applying DC current to conductive patterns on the coupons to elevate the temperature to 150°C (typically) within 3 minutes and then cooling by forcing air back to ambient temperature in approximately 2 minutes.
Interconnect Stress Test
IST is an accelerated stress test method that overcomes the limitations of the thermal oven or liquid methods. IST has the capability of effectively/rapidly quantifying the integrity of both the Plated Through Hole (PTH) and the unique ability to identify the presence and levels of post separations within the multiple-layer board.
IST creates a uniform strain from within the substrate. The interconnect and its ability to distribute and redistribute this strain provide an indication of integrity. The plated barrels and inner layer junctions are “exercised ” until the initial failure mode/ mechanism is uncovered.
Basic IST Operation
Highly Accelerated Thermal Shock (HATS)
The HATS system’s programmable self-contained machine will do all the common reliability cycles, with a range from •55°C to +145°C in air-to-air mode.
It contains a 4-wire precision resistance data acquisition system connected to a demountable tray with 36 coupon slots (144 nets total) of sizes up to 1″ x 2″, including the PCQR² via module.
The HATS system provides similar results as IST and the Delphi test but in less than five days versus the traditional thermal cycling taking 21 days.
HATS Test Coupon – 2.0 x1 1.0 inch
24 Layer coupon 0.125” thick
Coupons with daisy-chained vias
- 0.010”; 0.012”; 0.0135” through vias
- 0.006” blind vias
Preconditioned
- 0, 4, or 6 reflow cycles at 260° C
500 cycles +145° C rapidly cooled to -40° C
HATS™ System
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