Types of Defects - Electronics
INCORRECT COLOURS / MURA EFFECTS
With the ever increasing size, resolutions and widespread use of monitors in everyday gadgets, the demand for fast and reliable automated inspection has also increased. Fortunately, the resolutions of sensors has also kept up with it, enabling inspection of even the largest 4K monitors.
The CVB Foundation Package provides all of the tools necessary for screen inspection, including colour space conversion and look-up-tables (LUTs) to allow cameras' colour response to be calibrated.
SILICON SOLAR WAFERS
When converting silicon into solar cells, the raw materials undergo very high-temperature operations before they are in their polar state, ready to be sliced into 200 micron thick wafers. They then need to be very carefully handled, cleaned, positioned and inspected to ensure they maintain their crystalline structure. Metal contacts (busbars and fingers) that help collect the electrons generated are positioned on top of the wafers. These also need to be inspected to ensure there are no breaks.
BUSBAR / FINGER BREAKS
The line scan bar is perfect for the inspection of solar wafers as the technology is suited for the high-speed inspection of flat surfaces. It's compact, self-contained design houses the sensor, lens, and light. So there's no need for any adjustments once the system is mounted.
If the solar cell is made to run a reverse bias (reverse current) it actually emits infrared light at wavelengths between 1100 to 1200nm. This electroluminescence emits at a lower intensity in regions where there are microcracks in the crystalline structure. These can be detected by using a SWIR camera before it is fully assembled into a larger unit.
HEAT DISSIPATION ANALYSIS
Electronic components can get quite hot when they are operating at their maximum loads, and they need to be checked to ensure they do not overheat. By using an infrared camera and machine vision software temperature measurements can be fully integrated into automated inspection processes.
Thermal machine vision systems are also avaliable in smart camera packages, like Automation Technology's IRSX. The IP67 smart infrared camera is completely self contained and able to communicate directly with industrial equipment.
CONNECTORS / PINS
Pin and connector checks are critical in automated production processes as they help to communicate / relay signals in operations. Incorrectly aligned pins can even cause damage to the mating connector. The pattern matching tools found in many vision tool kits can check that the correct connector is being used. They work by locating and classifying objects and patterns, providing a score based on how much they "match" the trained pattern and/or a location / rotation (so they can be used for robotic pick and place applications).
To be able to check the alignment of pins correctly, a telecentric lens is required. These lenses collimate the light, achieving equal magnification across the field of view. This removes the perspective effects that would be encountered when using a conventional lens, making it easier to check that the pins are all straight.
Adding a liquid lens to the end of the lens configuration can enable additional parts of the pins to be inspected. By moving liquid around a polymer membrane, the shape-changing lens can quickly adjust the focal point of the set-up. This means that the whole length of the pins can be inspected. Checking for the location of the bases, their height, the shape of the tips and how straight they are.
INCORRECT PIN HEIGHT
PRINTED CIRCUIT BOARDS
There are many potential sources of PCB failure. From variations in the raw materials and components used at the start, right the way through to the stresses they undergo during operational testing.
Carrying out inspections at as many points as possible during their manufacture helps to minimise losses due to adding processes/parts onto defective PCBs later on in the production process. And, wherever possible, automating these inspections helps to keep costs and missed defects down.
OPEN SOLDER JOINTS
By using an area scan or a line scan camera (or a combination of both) and machine vision software, a lot of the aformentioned defects can be identified. The LMI G2 series - 3D smart sensor can be used to check the position of the components in the vertical plane as well, ensuring they sit correctly on the boards.