B&W Engineering Corp. is proud to present the next generation in Particle Impact Noise Detection (PIND). With the advent of economical high performance data acquisition and control products and the PC with their intuitive graphical interface, B&W has developed the most advanced and reliable PIND system available. The ease of use of the BW-LPD-DAQ4000 software and the workhorse reliability of over 30 years of the shaker and sensors, ensure this PIND tester will be on the job for many years.
Right from the start of PIND testing B&W patented the first MIL-STD compliant system outperforming the competition by over 30% better detection rate as tested by the NBS (now National Institute of Science and Technology) in a well known 1978 study (NBSIR 78-1590 NASA).
Until now there has been no significant improvement to the PIND test systems. Now the particle (or interference) is recorded in digital format and can be easily recalled for post test analysis. This advancement finally provides the ability to distinguish a particle from other noise that the PIND system has detected. The optional Transient Detector is another failsafe, detecting interference from stray RF and other sources.
The PC interface can generate test reports with percent defective per with run, serial, part and lot numbers. The many other advantages of a PC control include intuitive operation, unlimited test profiles and mixed frequency tests. The versatile Manual Mode is useful for experiments and can apply a vibration frequency sweep (to find resonances that make particle type noise) and apply shocks simultaneous with or without vibration.
How does B&W outperform the competition? According to Newton’s 1st law, a body in motion tends to stay in motion and a body at rest tends to stay at rest. B&W designed the optimum PIND system with a patented co-test shock apparatus that truly shocks simultaneously with vibration that keeps the smallest particles moving long enough to be detected and a degaussing magnet to allow detection of ferrous particles that would otherwise be immobilized by the magnetic field of the shaker.
Unfortunately the MIL-STDs were changed to allow the inferior shock technique of a non-simultaneous shock (“perturbed”), allowing the shaker to stop, shock itself into its stops with a thud and resume vibration. Even the shock duration was changed to a non-standard reference to 50% of amplitude instead of 10% as with all other shock duration measurements. This technique allows smaller particles to re-adhere before the vibration resumes, is more destructive to the device under test by over-stressing it causing micro-cracks, compromising wire bonds and other latent mechanical defects, and ultimately breaks the shaker with costly repairs and downtime.
The shock is the single most important part of the PIND test to detect the smallest particles. Small particles have a very high resonance frequency, so a high frequency shock is the most effective at knocking them loose while stressing the device under test the least. One PIND manufacturer has made the claim that an isolated test at lower frequency, higher amplitude shock at 40% of device maximum was more effective (if you cannot shock simultaneously). This claim does not agree with facts or physics.
The highest frequency mechanical shock is generated by impacting harder materials at higher velocities. For the purposes of PIND testing the minimum shock pulse duration possible is about 50 microseconds. The MIL-STD used the < less than requirement intending to minimize the shock duration, there is no such thing as a Zero Time shock except in theory and it would have infinite Amplitude. This duration will extend naturally as mass is added, so the larger package’s response to an identical shock to a smaller mass will be longer commensurate with the mass, material and geometries, creating what is referred to as the Transfer Function.