How to choose a test jig if you’re just starting out can be pretty overwhelming. Do you go with a bed of nails fixture, or a flying probe testing solution? And what happens if you skip the PCBA testing process entirely?
Our guide on how to choose a test jig is designed to answer these questions (and a few more!), saving you time and money in the long run.
What Is a Test Jig?
A PCB test fixture, or test jig, is a piece of equipment that ensures the product is built to specification at the production stage.
Using a text fixture is highly recommended because it identifies design flaws early on, preventing these flaws from passing into the manufacturing process.
How Do PCBA Test Jigs Work?
Test jigs are often custom-made and designed to accommodate the size of your PCBA. The unit under test then sits within the fixture housing whilst the test probes make contact with the board’s test points.
Test jigs are designed to test populated PCBAs before they are assembled into products. This reduces the risk of manufacturing a faulty product, which could result in additional development time, significant costs, and loss of reputation with customers.
How Important Is It to Test PCBs Prior to Production?
Just one misplaced component on a PCB can result in a whole batch of products going out faulty. Using a test jig protects you at the vital last step in the production process, ensuring your investment pays off when you need it to.
The perceived inconvenience and costs involved with getting a PCB jig customised, set up, and run are far less hassle than the risk of dealing with a product recall.
And remember – the quality of your end product will define how customers perceive your brand. Are you someone who believes in quality and understands your customers? Or are you someone prepared to gamble on reliability and potentially waste your customer’s valuable time and money?
Your customer doesn’t see all the investment that goes into developing a reliable product, the frustrations of chip shortages or the time and planning involved. Their view of your product, and by extension your company all boils down to one thing. Does your product do what it promises to do and does it keep on doing it reliability and accurately.
If the answer is no. You’ve got a problem.
Do I Really Need a Test Jig?
For the most part, yes. It’s a sure-fire way to protect your investment and ensure your customers receive a high-quality product.
However, if your production run is less than 100 units and you’re content to test each unit manually, then this could be a more economical route.
Tales from the Electronics Industry
Advice from a Test Jig Manufacturer
We asked their Sales Manager, Michiel Ten Burren, for his advice on what to look for when choosing a test jig.
“Essentially you want to look for a safe, fast connection.
Rather than plug in lots of wires and power each time you test, you’ll want a test jig that allows you to put the board in manually or using an automated tester. You should then have all probes engaged ready for action.
This allows for swift connecting and disconnecting which in turn significantly reduces test time, which CEMS (Contract Electronic Manufacturers) will charge for, as well as increasing reliability.
In addition, for extra features, you can look for a test jig that not only tests through pins in the top and bottom but also uses side movers which allows you to close the lid and automatically insert connectors.
There is no point testing your PCBs if you are going to end up frying them with your testing equipment. Look for test fixtures which work in an ESD safe environment. A non-staticenvironment allows PCBs to be tested more safely.
The test jig should use an even spread whilst in action. This prevents the PCB from breaking when testing begins.
MG Product test fixtures are designed to be safe for high power PCBs and to not interfere in a negative way. This allows for high voltage testing. You can also lock the lid as an additional safety feature.”
Michiel Ten Buuren, MG Products
Test Jig Advice from an Engineering Manager
“Simplicity is key – more cables and harnesses to plug in increases the complexity, and therefore it’s more likely that something will go wrong. The operation in a manufacturing facility needs to be simple and repeatable so workflow is maintained on the shop floor.
Another key part is reliability, we need reliable repeatable results.”
Stephen Keetley, Ignys Ltd
Test Jig Advice from an Engineer
“Start talking to your test jig supplier/designer as early as possible.
If you’re designing a product alongside a test system, then make sure that your device to be tested (product) has the necessary features on the circuit board to allow for the test access you need, especially if you need to probe speciality signals.
For example, if you need to take some RF measurements during your end of production line test, then speak with the test jig designer about the selection of RF probes available, and which would be most suited to your application.”
Toby Lane, Ignys Ltd
Where to Find a Good Test Jig
Looking online is a good place to start but you can also attend trade shows such as Engineering Expo and ElectroTest Expo to check your options.
Also speak to people in your industry for recommendations. Seeking out test jig manufacturers with a strong reputation and background in producing quality jigs is key.
You’ll also want a partner with the right expertise to customise your test and who understands the complexities of your project. Also look at the relationship you’ll have with your first engagement with them. Are they likely to responsive?
Considerations When Choosing a Test Jig
|Speed of Deployment||Bear in mind that most test jigs have a lead time of a few months. This is due to both the customisation required and the shipping time. Therefore, it is best to start the conversation about test jigs early.|
|Your Location||Shipping is an important factor - you’ll have to consider where the test jig is coming from vs your own location. This may vary depending on your territory. You’ll want to factor in any disruptions to the current supply chain based on global factors.|
|Who will operate the test jig?||Is the test jig being used by a trained engineer or a factory worker? The level of skill and experience required will depend on what instructions are needed.
This helps the test jig manufacturer to understand what training might be needed and how easy it needs to be to use.
|What are your projected annual volumes?||Depending in the volume of products produced, you may not need to use a test jig, provided that you test each individual product manually.
If you’re at an earlier stage of development and not ready to commit to a production design, it may be more cost effective to manually test your pilot product.
|Test Points||Has your PCB had test points designed into it? If not, you will not be able to use a test fixture. It’s very important that test points are baked into the PCBA design from the start.|
|Testing Strategy||What’s your testing strategy? Have you road-mapped the process? If not, it’s worth speaking to an expert and ensuring a plan is put in place prior to testing. This will save both time and money.|
|Know your Unit-Under-Test (UUT)||Having the length, depth and width of your PCBAs allows for a far more reliable quotation.|
|Having the right files to share||The more information your test jig supplier has at their disposal, the quicker they can turn around a quote and start customising your test jig for deployment.
Useful files include Gerber files, schematics, and 3D cads.
|Do you have more than one product?||If so, you’ll need a test fixture that supports multiple cassettes.|
Other Means of PCBA Testing
Will your product be used in particularly warm or cool climates?
If so, don’t forget about environmental simulation testing. Climatic testing is a great way to check that your design can perform reliably, optimally, and safely at extreme temperatures.
If you enjoyed this article…
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- An Introduction to Test Driven Development for Embedded Systems
- Why Testing Your Own Products Can be Perilous
- Environmental Test Chambers for Condition Monitoring Technology Case Study
This article was researched and written by Hannah Ingram, with input from the engineering team and MG Products.