Specialized test chambers are needed to perform a HALT. Typical HALT chambers are shown in Figure 1. The specification for HALT chambers is typically the following:
Liquid nitrogen (LN2) is used to cool the air temperature in HALT chambers. This allows for very rapid temperature changes of 60°C per minute and a cold temperature extreme of -100°C.
HALT chamber heating is provided by high power resistive heating elements that can produce changes of 60°C per minute and a hot temperature limit of +200°C.
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HALT procedures vary from lab to lab but are typically performed similar to DES’s procedure which is summarized below. DES’s HALT procedure is divided into 5 Stages: Stage 1 – Temperature Step Stresses, Stage 2 – Temperature Ramps, Stage 3 – Vibration Step Stresses, Stage 4 – Combined Temperature &Vibration Stresses, and Stage 5 – Temperature Destruct Limits.
Stage 1 is used to determine the HALT Operational Limits for temperature. The goal is not to cause destruction in Stage 1, but sometimes the operational and destruct limits occur simultaneously. The HALT Destruct Limits for temperature and vibration are typically found in Stages 3 to 5.
Temperature Step Stresses – Stage 1 (Figure 1)
Figure 1 – Stage 1 Temperature Steps
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Highly Accelerated Life Testing (HALT) is a rigorous reliability test method that is used to expose product weaknesses. The goal of HALT is to proactively find weaknesses and fix them, thereby increasing product reliability. Because of its accelerated nature, HALT is typically faster and less expensive than traditional testing techniques.
HALT of circuit boards in one of DES’s HALT chambers
HALT can be effectively used multiple times over a product’s life time. During product development, it can find design weakness when changes are much less costly to make. By finding weaknesses and making changes early, HALT can lower product development costs and compress time to market. When HALT is used at the time a product is being introduced into the market, it can expose problems caused by new manufacturing processes. When used after a product has been introduced into the market, HALT can be used to audit product reliability caused by changes in components, manufacturing or suppliers etc. The bottom line is that HALT can reduce product development time and cost, reduce warranty costs, improve customer satisfaction, gain market share, and increase profits.
Continue reading What Is HALT (Highly Accelerated Life Testing) And Why Perform HALT? →
Speeding up the process of device or circuit failure requires extreme inputs, those that are unlikely to occur during real-world use by customers regardless of the environment. Three common testing inputs are high and low temperatures, rapid cycling of the same and vibration along six-axes. In some cases, a highly accelerated life test (HALT) will incorporate combined temperature and vibration stresses. These inputs can result in component failure in the span of days, hours, or even minutes compared to months or years of typical usage.
While the percentages of failure based on the stress applied to a product can vary significantly, highly accelerated life testing can typically expose weaknesses faster than other means of testing. For example, of the above inputs, roughly two-thirds of failures will only come after the introduction of vibration alone or combined vibration and temperature tests. This means that during the product development process, a significant number of potential flaws would not be identified through testing that did not include these two stresses.
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A leading medical technology company contracted DES to perform Product Reliability Testing of a carrying handle. A sample of the test can be seen below and in our video library. The carrying handle had to be pulled, released, rotated and subjected to a sizable lifting force, approximately 20,000 times during its life time.
DES has considerable capability to complete product reliability testing. The main challenge for this project was that each cycle consisted of complex motion. The motion included pulling/releasing the handle to unlatch/latch a pin while rotating the handle. In order to achieve this, DES had to design fixtures and mechanisms that would reposition the carrying handle into each of the designated positions. The number of cycles was automatically counted until failure or 20,000 cycles were completed. During the test, the force to pull the handle was measured at various intervals. The Accelerated Life Testing was completed successfully demonstrating a high reliability.
Please visit our video library to see more examples of DES’s capabilities.
Random Vibration Testing is one of the more common types of vibration testing services performed by vibration test labs. A primer containing a technical explanation on random vibration testing can be found in our blog article Sinusoidal and Random Vibration Testing Primer.
Real world vibrations are usually of the random type. Vibrations from automobiles, aircraft, rockets are all random. A random vibration test can be correlated to a service life if the field vibrations are known. Since random vibration contains all frequencies simultaneously, all product resonances will be excited together which could be worse than exciting them individually as in sine testing. Sometimes random vibrations are mixed with sine vibrations in Sine-on-Random Vibration Testing. Also, a low level of broad band random vibration can be mixed with additional high levels of narrow band random vibrations in Random-on-Random Vibration Testing.
Some common test standards that have specifications for Random Vibration Testing are:
A leading commercial product manufacturer contracted DES to perform Accelerated Life Cycle Testing of a case handle. A sample of the test can be seen below and in our video library. The handle had to be opened and closed many thousands of times during its life time. In addition, two thirds of the cycles had to be completed with the sample exposed to hot and cold temperatures.
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This is a case study of a reliability test performed by Delserro Engineering Solutions, Inc.(DES) on a drawer used in a medical product. A sample of the test can be seen in our video library. DES was contacted by a leading medical equipment manufacturer to perform life cycle testing on a new product. One of the major components to be reliability tested was a drawer. This drawer had to be open and closed many thousand times during its lifetime.
First, DES developed a reliability test plan that defined how the tests would be performed, the number of samples required and how the test results would be quantified into a field life. After the plan was approved by the manufacturer, the reliability test had to be designed.
Continue reading Product Life Cycle Testing of a Drawer Used in a Medical Product →
We completed a Pyroshock test on our Mechanical Impact Pyroshock Simulator (MIPS) on equipment that will fly into outer space.
On the other end of the altitude spectrum, we completed environmental testing of components that will be used in submarines to MIL-E-917. MIL-E-917 is a military specification for Naval shipboard electric power equipment.
In the middle of the altitude range, we performed combined temperature and vibration testing on sensors that will be used in automobile engines to specification GMW 3172. GMW 3172 is a General Motors Specification for electronic component durability.
The following is a sample of some additional testing projects we have completed recently:
Product reliability is essential to success in today’s competitive global market. HALT and HASS are intensive methods used to expose and then improve design and process weaknesses. HALT and HASS are faster, less expensive and more accurate than traditional testing techniques. HALT and HASS are proven processes used to lower product development and manufacturing costs, compress time to market, reduce warranty costs, improve customer satisfaction, gain market share and increase profits. Some companies have reported savings in the millions after using HALT and HASS.
HALT and HASS can accelerate a product’s aging process from actual months into test minutes much faster than traditional testing!
Continue reading An Informational Guide to HALT and HASS →
