Patented Non-Contact Laser Ultrasonic Technology
Our Micro Laser Ultrasonic Technology combines a pulse laser and a continuous wave laser detector forming a cause-and-effect sensing device. Simply, the pulse laser sends a single pulse of controlled light energy onto the object of interest (e.g. a ball bond that is commonly used in semiconductor interconnection processes), causing a thermoelastic excitation response. This excitation induces an ultrasonic propagation (surface and bulk waves) on and through its neighboring materials. The continuous wave laser (detector) picks up the configuration and magnitude of the surface waves, which in turn, are analyzed and correlated to the bonding status of the joined materials. A graphical demonstration of the process is illustrated (Picture Left).
This technique can be further described as the classical "pebble in the pond" scenario, whereby a pebble is dropped into the middle of the pond, which causes a "wake" or a series of waves on the surface of the water (Picture Left). This "wake" propagates outwards from the center of the pond. By observing and correlating the characteristics of the wake, one can determine the fluidity of the water in the pond, as well as the size, the height, and the velocity of the pebble.
Since our cause-and-effect device consists of well-controlled light beams, their footprints can be focused to accommodate the miniaturization trend of semiconductor materials and microcircuits. Picture Left shows the pulse (cause) and detect (effect) beams on a silicon surface next to 0.005" and 0.001" bonding sites. The beam sizes are about 0.0005 inch in diameter. Since our excitation and detection probes are in the form of light beams, they can be 'turned' to accommodate varying test point sizes and power densities as necessary.
Our Micro Laser Ultrasonic Technology is much improved from the traditional contact type methods. The test points need not be contacted, nor would its shape be modified. The excitation is much gentler than that required in a contact test. Since light is being used as a carrier of information, the speed of testing is much faster (less than a millionth of a second) than any automated wire bonding machines, lending itself to automation and real-time process control.
Instead of current pulling and shearing, materials under test can be 'steered' to the laser beams using a high speed transport stage. The bond integrity test, therefore, can be performed by a point and shoot scenario (Picture Left). With embedded machine vision, high resolution sensors, and digital signal processing algorithms, this technology can be used to automatically search, target and test the bonding integrity with no operator intervention. The operator is only required to load and unload the part under test.
Besides determining the joint integrity of inter-metallic materials (under semiconductor ball bonds), our Laser Ultrasonic Technology can be used to characterize surface material structures as well.
Our System can characterize the full spectrum of bond status of joined materials (intermetallic structures) as well as detecting the presence of voids and surface fissures. Using our proprietary software, hardware, and patented innovations, our system performs real-time pass/fail analysis, 3D imaging, and secured documentation of test results via the computer network.
User Friendly Interface
Our Windows based Graphical User Interface (GUI) integrates all necessary hardware for the system, providing a very friendly and initiative operating environment for the end users. Our system runs in 5 different operating modes:
Calibration Mode – system calibration and troubleshooting is performed under this mode.
Programming Mode – supports the part pre-programming by stepping through the part to be tested. Programs can be modified (edit, add & delete) by authorized personnel only.
Computer Assisted (Semi-Automatic) Mode - selective testing of materials by point and click using the mouse or pointing device. The test result, live image of test points and raw data can be saved for future review and evaluation.
– end user can perform production testing (multiple parts) with no
operator intervention (other than loading and unloading new parts). Pass/fail
analysis is performed automatically and documented in real-time.
Statistics can be retrieved for process control.
Data Retrieval & Analysis Mode – review test results sorted by part number, customer, and by manufacturing machine are a few of the options. Enhanced graphics for presentation is included.