Optimizing HALT Setups: The Power of Customization

Thursday, August 08 2024

When it comes to Highly Accelerated Life Testing (HALT), custom-designed setups are typical and ensure the most reliable results. Through tailored and efficient fixturing, a custom setup yields clear and swift results, allowing you to devise actionable improvements. Before getting started, though, there are several key elements to consider to ensure the utmost reliability in your outcomes. You can delve into them in detail during HALT training. In the meantime, read on for a brief overview.

Understanding Custom-Designed Setups

Custom-designed setups encompass unique product and fixture configurations to expose failure modes most effectively. With the right HALT training from a reliable provider, you’ll be able to devise optimal fixturing solutions for optimal test results. Proper fixturing will enable you to maximize the stress levels your product experiences during HALT.

The Foundation of Custom HALT Setups

Advanced planning is important before designing custom fixtures for the testing environment. To start an effective test, you must consider how the vibration and thermal stresses of HALT will be transmitted into the areas of the product where failures are expected, as well as how the fixturing is going to affect the product.  The planning process entails the following key steps: 

1. Understand How Your Product Can Affect HALT Stresses: It’s not unusual for first time users of HALT to want to test their product fully assembled in its final configuration.  However, in HALT, this may not be the best way to test the product. Typically, the failures you are looking for will occur on PCBAs or subassemblies that can be isolated from the HALT stresses by the external enclosure for the product.  When a fully assembled product is fixtured into a HALT chamber, the product case itself becomes part of the vibration fixturing, and often that case isn’t a very good vibration fixture.  This can result in poor vibration excitation of key areas of the product.  Also air flow across the internal subassemblies is usually limited by the product enclosure, reducing the effectiveness of the thermal stresses. 
   
   
2. Consider Testing Subassemblies: Often the best approach to HALT on a complex product with multiple subassemblies is to break the product up and test the subassemblies independently.  This can allow thermal and vibration stresses to be focused onto areas that otherwise might not see the stresses, making the test more effective. There is often a tradeoff with this approach since functional test may be compromised when testing subassemblies. This tradeoff will need to be evaluated as part of the testing setup. 
   
3. Consider Product Modifications: If there is concern that the product case will reduce airflow but the structure of the product demands that the case be used, simply drilling holes in the case or cutting out portions of the case can allow better airflow and better thermal change rates.  This is more effective when ducting is used to direct the chamber airflow into the custom openings in the case. 
   
4. Design an Effective Fixture: Vibration fixturing for HALT is very different from the fixturing used in other vibration tests.  Since the product is being excited by shocks from the actuators under the vibration table, a good fixture will transmit those shocks efficiently into the areas where failures are expected to occur.  Looking at the fixturing and thinking in terms of the shock path through the fixture can help you design a fixture that doesn’t dampen these shocks.
   
5. Evaluate the Performance of the Fixturing Scheme Used: Once fixturing is designed the effectiveness can be readily evaluated by using accelerometers and spectrum analysis equipment to compare the excitation seen on the subassemblies in the product to the excitation delivered by the vibration table.  If shocks are being dampened by the fixture or by the product itself it will be evident in the reduced excitation seen on the product.
   
6. Evaluate the Effect of the Fixturing on the Product: In general, a HALT fixture is designed to securely clamp an assembly to the table.  The clamping forces used are sometimes sufficient to cause cracking or deformation of the product.  It is also possible, especially when fixturing PCBAs, to leave a portion of the product unsupported so that it can experience a very high resonant response.  This can result in false failures that were induced by the fixturing. 

How Do You Know if Your Custom Setup Meets These Requirements? 

The skills and knowledge required to create an effective setup for your HALT testing are not simple or obvious.  Much of what you need to know requires experience in the field.  If you don’t have the luxury of being able to take the time to learn the nuances of HALT test setup through trial and error, then training in these techniques, delivered by an experienced and knowledgeable HALT engineer, is essential.  The engineers in ESPEC’s Customer Solutions Group have set up hundreds of tests across a wide range of products and technologies, such as: Medical devices, Automotive components, Consumer electronics, Aerospace and Defense systems, Renewable Energy technologies, and much more.  You can leverage this experience by utilizing our training services. 

Ready to Customize Your HALT Setup?

Reach out to ESPEC to understand how to set up your HALT test for success. Our solutions group offers training and consulting, while our Hobbs Engineering colleagues offer reliability educational programs that can drastically improve test results. We can support you with training that covers all aspects of an effective HALT test.  Let us help you identify what training would be best for you.