The Best Fixture for your Next Application

With a wide variety of test fixtures on the market, you may not need to specify a custom built fixture. We examine key considerations when selecting test fixtures for your next project and explore whether standard or modified fixtures could be best for your application.

There are a number of stages in an electronic product’s lifecycle where testing is prudent, if not essential. When you begin to look for a cost-effective test fixture it’s important to take into account whether you are testing at the development stage or the production stage. Also the size of the printed circuit board (PCB) being tested can make a difference to the test fixture you select.

“Small toggle clamp fixtures or jigs are proving popular amongst Test Engineers looking to test development software rapidly and effectively with little outlay. They are great for up to 15 to 20 probes and are a standard fixture. Slightly more specialised jigs are needed as the PCB size gets smaller as space is generally at a premium on small boards” says Willie Lee, Technical Manager.

While a toggle jig is also useful for simple production testing, where an engineer wants to power up a product for a functional test, more sophisticated fixtures should be considered.

“The next step up from a simple toggle Jig is a Top Cam fixture. These are generally available in standard sizes with options to modify them. A common trend amongst test engineers is to ask for an open frame unit. Essentially, this is a fixture without a base can; this allows more freedom to add a range of switches or product LCD screens on the top plate of the fixture.  Top Cam fixtures are often used to test larger PCBs, or units with a higher pin count (up to 100) that would not suit a Toggle Clamp style Jig.” explains Willie.

Where a PCB needs to be tested in a wide variety of locations across the board most Test Engineers look to a Bottom Cam fixture. The operation of these test fixtures allow a higher test probe count and facilitate high precision positioning on the board being tested. Standard Bottom Cam fixtures will accommodate larger PCBS and can incorporate up to 500 probes for precise and comprehensive production testing.

“A Bottom Cam fixture not only provides a useful bed of nails type testing arrangement it can also provide a safe environment for testing regimes where high voltages are being used. Test Engineers regularly specify these fixtures with safety covers for high voltage testing and sometimes HiPOT insulation testing where the fixture can be used for both functional testing and a dielectric withstand test,” says Willie.

Test fixture design companies will have a range of standard test fixtures that can be modified to suit your next application. Understanding your testing requirements, the size of your PCB, the number of test points and the voltages you need to test at is all useful information a quality test fixture company will require to recommend the best fixture for your application. Most Test requirements can be met using standard test fixtures, sometimes with minor modifications or refinements. A fully bespoke solution is only required for a very specialised requirement, so it’s worth looking at standard fixtures first as this can offer significant savings.