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Why PCB and PCBA testing is important and necessary

Time:2021-06-28 14:12

Printed circuit boards are commonly used in a variety of electronic devices and technologies, making them very valuable devices.  PCBs are at the heart of the effective operation of electronic devices. To ensure that the entire device operates as intended, it is important that they are thoroughly tested. If a printed circuit board is defective or has manufacturing problems, it can cause the end product to malfunction and cause inconvenience. In these cases, the manufacturer must recall the device and spend additional time and resources to resolve the failure.

Design for Manufacturing (DFM)

DFM is the process of arranging PCB layout techniques to mitigate the problems that can occur during PCB manufacturing and PCB assembly required to manufacture electronic systems.

Design for Assembly (DFA)

The goal of Design for Assembly is to determine how to design a product so that assembly is most cost effective. Design for Assembly (DFA) involves the reduction of material inputs, capital overhead costs, and labor reductions. The focus is on the application of standards to reduce production costs and shorten product development cycles.

Design for Test (DFT)

When designing new products, consider the complexity of supporting longer product life cycles, including components that are nearing end-of-life or may be obsolete. Inventory availability and spare parts sourcing are some of the variables that experienced eContract manufacturers will consider when building their customers' raw material supply chains.

On-line testing

Many PCB manufacturers prefer to use ICT for in-circuit testing (ICT). In-circuit testing (ICT) methods are a common strategy for providing troubleshooting at the component level. Manufacturers can effectively test individual components and their electrical characteristics.
 
Traditional ICT requires a "bed of nails" fixture. These lamps must be designed to fit the board. The bed-of-nails test fixture is used to access multiple test points on the underside of the PCB. With enough access points, ICT can transfer test signals in and out of the PCB at high speed to perform component and circuit evaluations.  ICT offers OEM customers the following advantages: ICT covers 100% of the test to detect all power and ground shorts.  ICT testing can enhance testing and eliminate customer debug requirements. These lights are typically expensive.  ICT is best suited for the most stable mass production endpoint testing. It is cost effective and helps identify PCB problems before integrating the PCB into larger cells.  ICT is a very accurate test process.

Flying Probe Testing

Flying probe testing, also known as fixtureless in-circuit testing (FICT), is another type of ICT. Flying probe does not require custom fixturing or additional fixturing.  FICT uses motion-based test probes (flying probes) based on the test.
 
Flying probe testing is the same as traditional ICT testing, but has the advantage of lower cost and the ability to test both sides of the PCB. If there is a defect or problem, the FICT system simply needs to be reprogrammed to generate a new part without the defect. In contrast, ICT may require a completely new fixture.
 
Programming guides the flying probe to run tests to precisely locate highly specific areas and nodes. This level of accuracy is suitable for small boards and boards with high density components.

Automated Test Equipment (ATE)

The test phase is usually a thorough one, requiring great attention to detail. Circuit boards contain a variety of complex components. These may include capacitors, resistors, transistors, diodes and fuses. These are the main components that need to be tested for any irregularities and signs of failure.
 
Automated Test Equipment (ATE) performs Manufacturing Defect Analysis (MDA). This test verifies each component on the PCB and verifies passive control measurements, diode and transistor orientation, and supply voltage. It also looks for open circuits and shorts. Testing can include basic functional process verification and "vectorless" testing to check PCB pins. Both analog and digital measurements can be tested.

Automated Optical Inspection (AOI)

PCB designs are becoming more complex and components are getting smaller. Today, the capabilities of the human eye are mostly inadequate for reliable quality control. In addition, almost all applications now require a zero-defect strategy. All these factors require inspection systems with high-performance camera modules. Such automated optical inspection (AOI) machines allow operators to perform non-contact testing of bare and assembled printed circuit boards (PCBs) at all stages of PCB assembly.
This type of AOI unit usually consists of an operating system that implements the programming of measurement and comparison functions.

Solder Paste Inspection System (SPI)

Solder paste deposition is a key process in circuit board assembly operations using SMT technology. Solder paste printing is a complex process and many factors can improve its accuracy, including the composition and rheology of the solder paste, the type of stencil and squeegee used, and the process conditions used to lay down the solder paste. Since solder paste printing is an important process, it is important to test and verify the amount and height of the printed solder paste, as micron dispersion can cause short circuits or open circuits later on.
 
SPI equipment is used in printed circuit board manufacturing to monitor and control one of the most critical steps affecting printed circuit board quality.  The SPI system measures pad height and volume prior to component application and solder melting. When used properly, it can reduce the incidence of solder-related defects to statistically insignificant numbers.  The key to SPI measurement is the accuracy of the height measurement as it is directly related to the volume of solder and the amount of defects.  The importance of accurate height measurement in SPI is that accurate solder height inspection not only helps improve the quality of the finished product, but also reduces the amount of inspection time required, which has a positive impact on productivity and thus reduces manufacturing costs.

X-ray Inspection

Automated X-ray Inspection (AXI) is a technology based on the same principles as Automated Optical Inspection (AOI). It uses X-rays, rather than visible light, as the light source to automatically inspect features that would normally be hidden from view.  ICs and BGAs are increasingly used for under-chip connections and invisibility, which makes normal optical inspection impossible. Because connections are located underneath the chip package, there is a greater need to ensure that the manufacturing process properly accommodates these chips. In addition, chips using BGA packages are often larger chips with many connections. Therefore, all connections must be correct. To meet these growing and complex needs, X-ray inspection systems are emerging for inspection.
 
In addition, X-ray inspection systems are used to detect defects anywhere by non-destructive means. It is used for a wide range of applications, including various sectors and inspection tasks, from material testing for cracks and air inclusions to foreign body inclusions and shape deviations. In the electronics industry, the increasing use of miniature enclosures and the trend toward moving components within electronic components require high-quality inspection that captures hidden defects in a cost-effective and deterministic manner.

Functional Testing (FCT)

Functional Testing (FCT) is used as the final manufacturing step. It provides a pass/fail determination of the finished PCB before it is shipped.  The purpose of FCT is to verify that the product hardware is free of defects that would otherwise adversely affect the proper operation of the product in the system application.
 
The functional tester is typically connected to the PCB under test via its edge connector or test probe point. The test simulation will use the final electrical environment of the PCB.

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