A list of the critical decision making metrics when migrating to a fixture based solution model.
There are many considerations to take when determining the “best” course of action in the deployment of your test configuration. The scope, cost, compatibility, in-house vs. outsourcing, and hardware capabilities are just a few. This article focuses on how ‘open-source fixture manufacturing’ and deciding on a fixture based test model can improve results in a meaningful way. Ideally, in the electronics test environment, a test fixture strives to be an all-encompassing piece of hardware tailored to the physical, mechanical, and electrical considerations required by your DUT, environment, and monitoring tools. Following is a shortlist of benefits and misconceptions commonly encountered when deciding whether or not an all-encompassing test fixture is appropriate for your project.
Think and Plan Ahead
A good place to start when evaluating the benefits of a fixture based solution is identifying the purpose(s) and scale(s) of testing to be performed; not only at the current stage in the product test cycle but also future stages. Have you evaluated the ramp-up schedule on units per hour? Have you considered the need for environmental testing or RF shielding? What additional components, sub-assemblies, or measurement tools need to be applied to the testing equation? What access will be required of the DUT at this and other stages? Although these are only a few of many questions, they should help you begin to prioritize a list of “wants” and “needs” to qualify the effectiveness of a test fixture. At this stage you should have a clearer picture of how an all-encompassing fixture can have long term benefits.
Multi DUT and Interchangeable Base for RTI’s Test Presses
The Benefits of Scalability and Universality
A custom test fixture’s reliability and serviceability are considered by many to be determining factors when migrating from a device specific to a low-medium production test fixture based environment or when there is a need to test a variety of sub-assembly designs. It’s unwise to assume that a test fixture is limited to a single device design – meaning the fixture is obsolete at the end of your DUT lifecycle. Open-source test fixture architecture offers greater longevity through its construction by employing a careful balance of common or universal design components with other DUT specific design components. This allows for a single fixture to service a variety of test processes throughout the testing lifecycle. For example, compare a test socket to an open-source test fixture. In some cases the socket itself can transcend through multiple stages in a test lifecycle but may then require new mating PCBs, socket or lid modifications, and possibly interfaces depending on the test application (i.e. FA/Engineering/Programming/Characterization/etc.) A well designed custom test fixture can offer a single piece of all-encompassing hardware designed to minimize the challenges of interoperability when applied to multiple stages throughout the test lifecycle. These common features of a fixture can remain concrete allowing for a reduction in lead times and hardware cost incurred in future projects. Design features such as: tray based loading, built-in common driver components, multi-site testing, pneumatic actuation, environmental shielding, and more can all be interchanged to meet future testing needs.
Cost Evaluation and ROI
At what point does the expense of an open-source custom fixture outweigh the limitations of an alternative? The answer to this will vary by company and project budget. OEM manufacturers with big-iron capitol and pre-established test procedures will certainly have a different opinion than that of a Lab or Contract Manufacturer. Budgeting for a well-designed and open-source platform fixture can be tricky but don’t forget about the questions you asked yourself earlier while planning ahead. Consider that one fixture can end up sparing you internal engineering time and saving you money in the long run. As the old adage goes: “Too many cooks spoil the broth” – manufacturing tolerances and/or incompatibly between various components in a widely sourced fixture solution may cause delays in your test schedule if anything need to be modified or re-designed. Weighing the value of investing in a ready-to-use product out of the box from a single source provider such as RTI versus sourcing multiple suppliers and leaning on in-house engineering time and resources should not be overlooked – especially in high-rel and custom applications.
RTI Test Press with 4 Test Sites
Test fixtures are restricted to PCB in Bed-Of-Nails applications only
Actually, test fixtures are also used to test implantable medical devices, an assortment of MEMs sensors (Gas, pressure, accelerometers, etc.) glass touch panel displays, LED/optical calibration, and sub-assemblies that incorporate combinations of these and more.
Test fixtures are simply too costly and labor intensive to consider
This is not always the case. Consider the open-source benefits and fixture longevity to meet dynamic medium to long term testing needs. In many cases an all-inclusive and specialized solutions based provider like Robson Technologies, Inc. provide on-site custom ME and PCB design/manufacturing/assembly, and full integration services.
An off-the-shelf test fixture doesn’t exist that fully meets my criteria – it must not be possible
A fixture solution is never impossible just because it can’t be discovered in a catalog of products. Nor does that mean significant internal investment to develop or modify an existing fixture. In many cases, it’s also ill advised to attempt an in house modification to a design that only partially addresses your needs. Seek a qualified fixture solutions provider that will tailor a product specific to your wants and needs while incorporating common features wherever possible.
Purchasing a test fixture is purchasing capitol equipment
Depending on the complexity, quantity, and added features incorporated in a custom test fixture, you may see pricing entering capitol range dollar values based on your company. Test fixture interfaces are rarely considered capitol equipment in themselves. Actually, some dynamic test fixtures can cost little more than a high pin test socket while offering more functionality, throughput, and accessibility.
Test fixtures are just one trick ponies
If you breed your fixture to act as a one trick pony then you will end up with a single function tool. If you plan to breed your fixture to accomplish a variety of testing goals simultaneously then you end up with a multi-function tool and resource for your lab. In short, a quality fixture should not be considered simply as a simple tool but rather a multi-functional and integrated solution.