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Types of Defects - Electronics

Recent technology advancements have seen huge improvements in the performance of electronics. The processing power of the phone in your pocket is far beyond the capabilities of the kit that was used to send the first space shuttle to the moon!

The components are getting smaller and so the technologies required to handle them needs to be much more precise. This introduces much more room for error and the automated inspection of the processes is critical, especially when it's involved in processes such as the deployment of a drivers airbag. This article covers a few of the defects encountered and how machine vision can help prevent them.

DISPLAY CONTROL


DEAD PIXELS

INCORRECT ALIGNMENT

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 .


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 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.




BENT PIN



INCORRECT CONNECTOR

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 setup. 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



MISSING PIN

PRINTED CIRCUIT BOARDS


SOLDER BRIDGING

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.

COMPONENT MISALIGNMENT

MISSING COMPONENTS

WIRE BREAKS

OPEN SOLDER JOINTS

By using a 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.

Contact

International

STEMMER IMAGING AG
Gutenbergstraße 9–13
82178 Puchheim
Germany

+49 89 80902-0
+49 89 80902-116
info@stemmer-imaging.de


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