Calibration Circuit - KingSheng PCBA

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Functional Testing

Functional testing is frequently utilized to calibrate or verify analog circuits. This process includes checking components within the Unit Under Test (UUT), such as the Intermediate Frequency (IF) portion of an RF circuit, to ensure proper operation. This verification may require the use of test points or test pads. One challenge encountered in high-frequency design is that the relative impedance of the test point—affected by factors such as path length and test pad size—combined with the impedance of the probe can impact circuit performance. This must be considered when setting up the test area. Automatic mechanical probes and needle bed fixtures, which will be discussed later, require a smaller test area and can help alleviate this conflict. Compared to manual operations, the precision of automated mechanisms allows testers to inspect smaller areas more effectively.

Fault Diagnosis

If functional tests are only being used as a pass/fail filter and specific calibration points are not required, you may skip this section. Typically, functional tests serve as a pass/fail check and are not very efficient in diagnosing faults, particularly when multiple failures occur. However, in certain industries—such as cellular phone manufacturing—functional testing is more integrated into the production process. Some manufacturers must take key measurements at the PCB level during assembly, prior to final assembly. This necessity arises from the fast-paced evolution of mobile phones; they are designed for low-cost assembly and are not easily disassembled. Verifying features before final testing can save on rework costs and reduce the risk of scrap due to potential damage during disassembly.

To effectively probe the PCB, adequate test points are necessary. For instance, checking the J-lead of a surface mount device with a pitch of 20 mil is inconvenient, and testing Ball Grid Array (BGA) connections is not feasible at all. According to the American Surface Mount Technology Association (SMTA), the minimum spacing between test points should be 0.040 inches, but ideally, a minimum of 0.200 inches is recommended, especially for areas requiring manual access. Clearly, test fixtures and automatic mechanical probes offer greater accuracy.

Calibration Circuit

Test Design

It is important to recognize that a design that is easy to test will facilitate production processes compared to a challenging design. Nonetheless, engineers often strive to incorporate more technology into smaller volumes at lower costs, which complicates access for online and functional testing.

The market has begun to address these challenges, offering software tools that analyze designs against established rules for assembly and testing equipment. These tools can provide recommendations to enhance the manufacturability of PCBs. It is advisable to utilize these tools to analyze each design, as they can quickly identify potential issues with test accessibility, ultimately facilitating the manufacturing of the product.

Structural Configuration to Meet High-Density Requirements

High density in PCBs may refer to their small size, a large number of circuits within the UUT, or both. The preceding sections indicate that both mechanical and electrical structures must be considered to meet testing requirements. Mechanical considerations include:
- How will the UUT be supported?
- The design of the test area.
- Testing of multilayer boards (Can the tester perform parallel testing?)
- Configurations of I/O connectors.

From an electrical perspective, if the UUT is a multilayer board, consideration must be given to whether a multi-instrument approach or a switch converter with fewer instruments is more economical. Depending on the structure of the UUT and the type of instruments required, determining the most effective solution may be complex.

Automated vs. Manual Testing

As production line output and speed increase—a key method for achieving economies of scale—consideration should be given to the automation of the test process. Automated functional testing can eliminate load/unload times and typically does not require additional testing systems. Often, the increased cost of transport equipment is overlooked when assessing enhanced production rates.

However, there are drawbacks to test automation, including the initial hardware investment, time required for integration with the production line, and whether the testing system can keep pace with production speed. If testing equipment fails, it does not directly disrupt the assembly line; products can be removed from production without hindering overall throughput. However, issues related to processing time and labor should also be taken into account.

It is important to remember that manual testing may involve connecting the UUT using several cables and connectors, which typically have shorter lifespans compared to the probes on needle bed jigs. Hence, this aspect should also be factored into the testing strategy.

Why Choose China PCBA Supplier KSPCBA as Your Calibration Circuit Manufacturer?

– Experienced and skilled team

– State-of-the-art equipment

– Strict quality control

– Excellent customer service

– Competitive price