EMS testing processes - ensuring your electronics are fit for purpose

Published Wednesday 23rd May, 2018

One of the marks of a professional electronics manufacturing company is the robustness of their EMS testing processes - a series of procedures that ensure OEM's products are of the highest quality.

As such a crucial step in the electronics manufacturing process, it's important to understand the methods your engineers choose and why. Let’s take a look at some of the industry standards and the processes that Daletech uses.

Inspection - the first stage of EMS testing

Before testing of the circuits and components can begin, a visual inspection is necessary to determine whether the components are correctly aligned and soldered, and that the PCBs have been manufactured to the required standards. At Daletech we use Mantis inspection equipment for our visual checks, and find its excellent ergonomics allow for fatigue-free processing of our boards - a 'must' to prevent mistakes at this stage.

Visual inspection is often carried out alongside Automated Optical Inspection (AOI), which can speed up the inspection process, but also allows your engineers to check boards directly against the manufacturing information: computer vision is much more accurate and can detect tiny imperfections that may be invisible to the naked eye. This is another method that we utilise to excellent effect.

Testing processes

There are many EMS testing processes available to your engineer, and the choices they make are often determined by requirement and personal preference:

In-circuit test (ICT) and flying probe - These are the two most common testing processes, and they generally cover the same issues (short circuits, open circuits, etc), so one or the other is generally sufficient – although we actually use neither of these, as we’ve found other methods to be better!

System functional testing - This is often the last test performed because it's essentially a 'does the board do what it says on the tin?' test. It should always be performed in conjunction with other tests because a PCB could, theoretically, pass this test and still contain faults.

Boundary scan - A reliable and speedy scan that takes advantage of the test logic already present in your digital integrated circuits to check the larger connections on your PCBs. It's a relatively expensive but elegant scan that only needs a 4-pin Test Access Port wired into your PCBA to perform the same job as an ICT and flying probe, but in much less time.

Electrical safety testing - An essential test for any product that uses electricity and one that should always be carried out. A simple portable appliance test will apply a much higher voltage than the PCB is designed to withstand, in order to determine if it can handle the stress - a well designed board should pass this easily.

Other tests such as accelerated life and environmental stress tests can also be helpful to determine a PCB's life expectancy and ability to withstand extremes of temperature and weather, but these tend to be board-specific.

Bespoke testing - product dependent

It's important that your manufacturer understands the importance of bespoke testing for each product. We always open up a dialogue with our clients to ensure that we fully understand their product and tailor our testing accordingly. This can range from a basic 'power on', to a full functional test and can often include manufacturing specific test jigs.

This level of customer service is why we have such an excellent first time pass rate: our stats for April 2018 were 98.54% of products passing our tests first time - and that tiny percentage of failures were actually due to component issues rather than manufacturing failures. We’re striving to achieve 100%, and we interrogate our product pass rate statistics to ensure that we don’t experience manufacturing process failures.

Whichever electronics manufacturer you choose, it’s pivotal to a successful relationship that their EMS testing processes are of the highest standards possible – which we absolutely guarantee when you choose us as your PCB partner.

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