From concept to consumer, there’s a lot involved in bringing an electronic product to market. At every stage—design, development, prototyping, production, and manufacture—careful planning is the key to success. This is why it’s essential to carefully plan out your fixture design for manufacturing and testing. Well-designed fixtures ensure reliable and streamlined production processes and ultimate customer satisfaction. And this is especially true when it comes to test fixtures.
Why Focus on Fixture Design for Electronic Manufacturing?
Fixtures enable consistent and repeatable positioning of components, allowing programmed tasks to be performed with precision and accuracy, and mitigating the possibility of bottlenecks in production. When your device is ready to be produced at volume, having the fixture designs already mapped out will mean higher efficiency and throughput.
For best results, fixture design for electronic manufacturing and testing requires the engineering and design skills of a professional engineering team that’s well-versed in both DFM (Design for Manufacturability) and DFT (Design for Testability) principles. These professionals will ensure that fixtures are designed and positioned for easy testing and optimal production efficiency.
Test Fixtures: Know the Objectives, Plan the Parameters
Achieving optimum results from any test fixture will require working with a qualified electronic manufacturing services (EMS) provider to plan the test fixture’s design with the specifications of the DUT (device under test) in mind—in addition to volume, turnaround, and budget considerations. While customization and planning may add time and some initial cost to the manufacturing process, this is offset by net time saving and cost reduction per item.
Test objectives, determined by industry standards, and the product’s final use and destination will define which test parameters should be incorporated into test fixtures and testing procedures. The test fixture customization and design are planned using CAD systems and software that set test points, calibration, and the collection of data specific to your product. Whatever level of testing you would like to perform, it’s important to consult with your EMS provider regarding the basic inspection requirements your device must satisfy.
Since determination of the fixture design will depend on the functionality and complexity of your device, there are cases where a simple test fixture with few test points and minimum customization—or even an “out of the box” fixture—will be sufficient. In other cases, a more complex test fixture—one that has to be precisely positioned and aligned—may be required.
The selection and deployment of test fixtures will also depend on factors such as production volume, size of the product, and desired quality standards, as well as the overall flow of the assembly process. Costs will also vary depending on the complexity of each fixture and the number of test points that are required. In general, simple test fixtures are less expensive than complex test fixtures.
Test fixtures will not eliminate test failures, as any manufacturing process has an inherent failure rate. However, tests designed with the help of skilled SMT engineers will catch faults early and minimize failure rates.
What Are the Benefits?
Although test fixtures for different devices and products will vary in the type and number of tests required, the overarching benefits of fixture design for electronic manufacturing are consistent:
Time and Cost Savings: Test fixtures streamline the testing process by automating test procedures and identifying defects early in the manufacturing process. With this fast and efficient testing, productivity is increased, and manufacturing cycle time reduced. Test fixtures contribute to cost savings by preventing component misalignments, minimizing scrap rates, and avoiding costly rework.
High Quality Control: When a PCB fails a test, a test fixture can help isolate the specific component, connection, or circuit responsible for the failure. This facilitates troubleshooting and debugging, enabling engineers to identify and rectify issues efficiently, improving the overall manufacturing yield and product quality.
Consistent Test Methodology: Designed with precise parameters for your product, fixtures enforce a standardized test methodology across the manufacturing process and provide consistent and repeatable test conditions for devices. This promotes uniformity in performance, making it easier to identify and address any anomalies or deviations from the expected results.
Compliance with Standards and Regulations: With the final product in mind, fixtures can be designed to adhere to industry standards, safety regulations, and specific certification requirements. They help ensure that PCBs and devices meet the necessary compliance criteria, providing confidence in the reliability and safety of the electronic device.
What Test Fixtures Should You Use?
Your engineering team, working with your EMS provider, will have the best insights and expertise in determining which tests will be beneficial for your product. Here are some of the test systems that may be considered:
ICT (In-Circuit Test): This is a test system predesigned with a fixed probe layout that matches the layout of the circuit board. The benefit of the ICT test fixture is that by probing individual components and connections on densely populated circuit boards, it produces very detailed test data. It typically uses a bed-of-nails or pogo pin configuration to make contact with test points on the board.
FCT (Functional Circuit Test): This fixture test does not test single components but instead tests the overall functionality of the assembly or the function of assembly networks. A functional test fixture will evaluate the powered-on state and replicate the end application and expected functions. The test is generally conducted at the end of assembly and is helpful in product debugging and development.
Boundary Scan: Boundary scan testing, as defined by the IEEE 1149.1 standard, is primarily designed for JTAG-compatible devices. The boundary scan chain is a set of test points that are located on the edges of the PCB that can be used to test the connections between the components on the board. As a test defined by the IEEE standard, it has the advantage of ensuring consistency and compatibility across devices. The test also addresses the physical space constraints of denser boards and the loss of physical access to signals.
Environmental tests: Environmental test fixtures are used to test the PCB’s performance under the environmental conditions it’s going to be used in. This testing can be used to test the PCB’s resistance to temperature, humidity, vibration, and other environmental factors.
Burn-In Test: A burn-in test is used to detect early component failure, which is why it’s especially critical for medical or military devices. Burn-in testing involves subjecting electronic devices or components to extreme stress conditions. This usually involves running the board for 48 to 168 hours to ensure long-term reliability. A burn-in test fixture provides the necessary environment and connections for performing these tests.
Getting the Most from Fixture Design for Electronic Manufacturing
From large medical or aerospace products, to small consumer electronics, every industry relies on testing to ensure quality and reliability. Without adequate and consistent testing consumers will experience inferior products and lose confidence in the electronic devices they depend on.
No matter what tests are determined to be the best for your product, the best results will come from planning ahead with input from engineers skilled in DFM and DFT. Designing test fixtures into your assembly line will mean fewer returns and greater customer satisfaction. Customers will never see it, but they will definitely appreciate it.