The Four Things You Need to Know About Test

Estimated reading time: 4 minutes

The electronics manufacturing process can often be extremely complex, and the costs associated with product recalls can be astronomical. A robust approach to test is key to ensuring the quality of your product and the satisfaction of your end user.

So, what do you need to know when it comes to creating a successful test strategy? And how could investing in this service early on help save you precious time (and expense) further down the line? To steal a phrase from Siemens, “Quality is when our customers come back and our products don’t.”

In this article, I explore four core truths about test that will make all the difference to the quality, reliability, and service life of your product.

1. Test Is Essential

The earlier in the manufacturing process you identify any issues or faults, the easier and less costly they’re going to be to put right. Genuine manufacturing faults should, of course, be corrected by your EMS provider at their expense. But any costs that occur as the result of design-related test failures are likely to end up back with you.

Test serves as a vital feedback loop not only between you and your production department but between you and your design team as well. The less rework that needs to be done, the higher the first-time pass rate is likely to be, and the greater the long-term reliability of your finished product.

2. There’s No One Perfect Solution

As much as it would be great if there was one single piece of test equipment that did the job of all the methods combined, it’s not usually a realistic option. To get the very best results from your test strategy, you’re often best served by a complementary approach of different techniques according to your product's needs—whether that’s in-circuit testing (ICT), flying probe, boundary scan, or functional test.

At the same time, though, there’s not likely to be many benefits in simply throwing every test strategy you have at your product and hoping for the best. And unless there’s some strong evidence to prove otherwise, your EMS partner should be looking to remove unnecessary tests and costs wherever they can.

3. AOI Isn’t a Test

It’s a fairly common misconception, but as the name suggests, automated optical inspection (AOI) isn’t a test—it’s an inspection aid. It’s also mostly limited to surface-mount electronics devices, as there’s often too much variation in through-hole device placement. 

Even so, AOI is definitely one to add to your must-have list when you’re talking to any prospective EMS provider. It offers a quick and easily repeatable way of checking for component presence, orientation, text, and (to some extent) solder joints. And being so fast, it’s a valuable part of process control on the production line, providing rapid feedback and reducing the amount of rework.

With modern systems being so quick to program and operate, there’s little excuse for an assembly house not to use AOI. And there’s no doubt that it goes a long way to making sure you have the right parts in the right places. 

4. Functional Test Isn’t A Cure-all

Functional test comes at the very end of the manufacturing and test process, which means the very next person to get their hands on the product is going to be your customer. But because functional test is usually developed by the product designer, it can make for a steep (and expensive) learning curve for an independent developer who needs to learn the product functionality before they can design the test equipment.

The sort of kit that’s suitable for the development lab is also not usually robust enough to handle the demands of an electronics manufacturing environment. And designing production fixtures may not be the best use of your product developer’s time. Functional test is also pretty slow. Debugging can be difficult and time-consuming, and it’s likely to require a high level of skill to determine the root cause if a product malfunctions—all of which adds cost.

It’s also surprising how much can be wrong at a component level and yet still pass a functional test. Floating pins on ICs, missing and wrong value components—all have the potential to escape identification. Unless those potential errors are covered elsewhere, functional tests often only ever offer false confidence.

There is, of course, a place for functional test—but it’s as a quick “final assembly” check once the (thoroughly tested) sub-assemblies have been put together. If the pass rate isn’t virtually 100%, then it may be time to take another look at your test strategy, or possibly even your product design.

Whatever approach you choose, testing can’t ever afford to be an after-thought; ideally, it should be designed in from the very beginning. Sure, it should be able to adapt to the needs of your product lifecycle, but from the start, it’s important to think about short- and long-term development costs as well as the price per unit. Further, taking a strategic approach to test will provide the reassurance that when your product is taken out of the box, it works exactly as designed, the first time.

Neil Sharp is the director of marketing for JJS Manufacturing.