There are situations where sharp changes in temperature can have a devastating effect.
In previous posts, we have talked about the problems involved in taking a product off the market if it malfunctions in any way, and how the traditional validation process overlooks the fact that the components used today are different from those used when the product was validated, which causes many serious problems.
When we say “different”, we’re talking about the fact that their electrical or timing characteristics have changed with regards to the original specifications: the silicon wafers used may have a different composition, while shifts in manufacturing parameters or changes to machinery mean that components which share the same part number differ from one production batch to the next. Electronic components are constantly evolving and there is nothing we can do to prevent this…
Even though we can help to prevent these problems by using simulation techniques during the design stage, the complexity of the models being used means that this alternative is less effective. So, how can we bring about this variability of parameters so that we can be sure that our product won’t fail in the market?
Highly Accelerated Life Test techniques involve submitting the product to a combination of thermal shocks with cycles of vibration, thereby causing the parameters of electronic components to change and putting welding and electromechanical parts under mechanical stress.
This type of test is applied throughout the product’s life cycle:
- During the design stage, tests are used to determine the equipment’s physical operating limits. Its weaknesses are identified and it is made more robust through a test-improve-test cycle, which sees us make working conditions more difficult until the product can eventually operate correcty under the specified boundary conditions (HALT testing).
- During industrialisation, by using a greater number of samples to verify that the conditions established in the HALT tests can be applied to the mass produced product (HASS tests).
- During mass production, by taking a sample from every batch produced to ensure that none of the assembled components correspond to a faulty batch, or that none of its operating parameters vary significantly from those of the component that was orginally validated (HASA tests).
IKOR has taken the first step by purchasing equipment which allows us to carry our thermal shock tests with a 5ºC/minute ramp rate. This test can be incorporated into the production process itself. Although this appeals to all kinds of clients, it is particularly attractive for those that work in industries with high standards or high volumes. We are also looking into the possibility of introducing combined vibration and temperature tests to make this process more efficient.
If you would like to find out more about these techniques, we recommend that you read the following publication: HALT, HASS and HASA Explained, by the author Harry W. McLean.