1. The Demand For AOL Testing
Over the years, we have improved the requirements of AOI and automatic optical inspection, so we cannot overemphasize it. The introduction of surface mount technology and further reductions in the size of these boards have made them compact, making it easy to miss obvious faults. Several solder joints in the PCB can find most of the errors.
In the past, we have conducted a manual inspection, but the increasing complexities of modern-day PCB tired-out inspectors made manual methods unreliable and, in the end, obsolete. Hence, there is a need to know automated test inspection through the seven aspects of knowing AOI testing procedures.
2. Why Are AOI Tests Popular
Printed circuit boards are an integral part of automated optical test inspection. When ordering the board, it should immediately correct its mistake. The financial implications of such things would be disheartening.
As mentioned earlier, due to the increasing complexity of modern circuit boards, manual inspection has become obsolete. TNow points to check the circuit board by soldering automation. Contemporary markets now require high volume, top-notch products that can reach their customers as fast as possible without compromising quality inspection.
An automated test inspection is a fundamental tool in an electronics test strategy to ensure that faults are detected as fast as possible in production for products to reach the market in the shortest time possible.
3. AOI Test Detectable Defects
A wide range of errors can be detected using automated inspection test facilities. This involves using different techniques to determine if a printed circuit board fulfills all the conditions of quality or not. Some of these techniques include template matching, pattern matching, and statistical matching.
The template matching compares scanned images with the golden board. Pattern matching compares the information stored on both perfect and faulty systems. The statistical matching uses statistical data to address apparent problems.
Further advanced visual means for scanning a circuit board manufacturing defects. The systems used for fault detection, on the other hand, also make use of images, comparing them with ideal diagrams in a bid to note some glaring faults.
Welding defects can be detected in this way, for example, solder bridges, solder short circuits, the solder gap, excess solder, the solder mass, and an open circuit condition.
Component defects are also addressed, such as missing components, incorrect component value, improperly placed or misaligned components, faulty parts, lifted lead deficiencies sent when aiming to correct errors in printed circuit boards.
Also, BGA shorts and BGA open circuit connections can be detected during the AOI tests in line with approved guidelines.
4. The Technology Used When Checking or Testing
There are different technologies or means used for checking or testing for abnormalities in printed circuit boards. Some of these include In-Circuit Testing, which is a robust testing method. Designed for full coverage testing PCB design, and the user is guaranteed about 85-90% coverage that is free from human error compared to other methods.
This test actuates the entire board circuitry, and it also involves the use of probes laid out expertly in a manner that mimics the design of the circuit board. Experts have recommended that this test is ideal for a product that only needs a few revisions.
Other testing methods include:
The flying probe test: This is cost-effective when compared to in-circuit testing. It is a non-powered test that is ideal for checking for Shorts, Opens, Resistance, Inductance, Diode issues, and any related checks to be carried out.
The Burn-in Testing: This is an intensive test for printed circuit boards.Its designers to detect a load failure
The X-Ray inspection testing: This method is the best for detecting soldering defects that are not visible to the naked eyes.
Functional testing: This is a test that requires the use of external pieces of equipment, and it ensures that the PCB will power-up to perform its functions.
5. The Type of Lighting Systems Used for AOI Test
Light is one fundamental part of the automatic optical inspection layout. Choosing the most appropriate amidst the available lighting systems is very crucial for easy detection of faults. Recently in lighting technology, we have made some progress. To enhance the image-derived, reduce the time required to develop overall system status, and increase accuracy.
Many AOI systems in use have a well-defined lighting apparatus. Although this solely depends on the type of product to be tested and the operation carried out. Sometimes, when carrying out PCB quality testing, you may need to do some customizations, and the proper understanding of lighting would be required. The types of lighting used include:
LED Lighting: An LED lighting system’s use means that AOI systems can suitably adopt a stable form of lightning in carrying out random checks. By using LED lighting, we can easily control the light intensity. LEDs are better alternatives to fluorescent and incandescent lights. Although from experience, We noticed that the power of LED lights decreased over time. Nevertheless, we can add circuits to solve the problem.
Fluorescent Lighting: This is one of the most widely used light sources for AOIs; adequate lighting means checking defects on PCB. However, the main drawback of this form of lighting is that it degrades over time. It means that the optical detection system may change over time.
Ultra-violet or Infra-red light: This is useful to enhance certain defects, and third lighting systems are readily detectable.