Optimizing test requirements: ways to eliminate test steps, cut time and optimize production through collaboration.
In developing test plans for each different assembly produced, we focus on two types of testing: functional and in-circuit testing. ICT tests are simple to perform and help define manufacturing issues by mapping exactly where the problem is occurring down to the component level, and are less technical than a functional test. The objective of the ICT test is to confirm that product is built according to customer documentation and to define manufacturing problems, such as insufficient solder, missing, incorrect or bad parts. The simplicity of the test means less downtime for troubleshooting and shorter cycle times, which decreases cost.
Functional test is more technically involved and requires more expertise to understand the methods for identifying failures. Functional testing doesn't map the problem to the component level, and because of the limited information given it can be difficult to locate the exact problem area. This requires more time for troubleshooting and longer cycle times, which increases cost. The main objective of a functional test is to verify that the assembly performs as anticipated and is intended to establish that the assembly is manufactured correctly.
We have added test points to fixtures to maximize ICT capabilities, and we have designed ICT fixtures that provide the same test coverage as functional test, often allowing us to replace functional test. Here, we outline some examples of measures taken with customers to eliminate steps in the test process, reduce test times, optimize production and reduce costs.
Splitting functional test. SMC was manufacturing an assembly for a single-phase electric meter widely used throughout the meter industry. The meter is designed to provide a two-way RF communication to utility meters. The customer required that we collaboratively develop extensive functional test systems to ensure the high reliability required. The customer had designed a single test protocol that would test RF, high-voltage circuits and programming. The single test was not optimal for troubleshooting, time optimization, line balancing and data analysis. It also used the same expensive lab instrumentation for data acquisition as is used in R & D test labs.
Working with the customer, we separated functional test into two separate phases by establishing the functionality difference of each test. Initially the separate tests helped to reduce tact time by balancing production flow, which helped lead to lower test labor content and high-volume capability with less test equipment systems. Once the test phases were established, we continuously optimized them by receiving the test data collected, adjusting test limits and eliminating test steps that brought no validity to proving the functionality of the design. As a result, we were able to eliminate two steps from the testing process. We improved the efficiency of the process and reduced cost of test equipment needed while simultaneously ensuring that production units met customer functionality requirements.
Converting functional to ICT. A leading provider of urological imaging systems collaborated with SMC to reduce production time of their product by converting a functional test to an ICT test. The customer was initially hesitant to utilize the ICT test fixture proposed by SMC engineers because of the investment they had made in functional test equipment. SMC worked with the customer to help them understand the long-term value of investing in ICT test equipment. A Teradyne test platform was used to gain 100% test coverage. The overall test time decreased; production time was reduced by two minutes, and troubleshooting became more accurate. The improvement in quality, reduction in bone pile, and reduced troubleshooting time resulted in lower cost and higher quality for the customer.
Product self-test. A provider of residential real estate lockboxes partnered with SMC to develop and support their product in all areas including design for manufacturability, design for test, test planning and development, prototyping and complete NPI. SMC test engineers worked with the customer to integrate application and test code into an ICT test that permits the assembly to be programmed one time. When the microchip is activated, it starts a self-test of the product. The application code is loaded on the final test station. Once box-build is complete, the unit is ready for use. Combining the test and application codes saved five seconds per unit in programming time during final production.
Collaboration with the OEM's engineering team with focus on testing for manufacturing and quality is just one of the ways that an EMS provider can maximize test capabilities, optimize production capabilities and reduce overall cost while maintaining high levels of quality.
Shebetey Alkhasov is test engineering manager at SMC (smcems.com); firstname.lastname@example.org.
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|Title Annotation:||Test and Inspection|
|Date:||Dec 1, 2006|
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