HASS Development Process

HASS is a tailor made reliability test solution for each product; the results achieved during HALT are used to determine an accurate production screen. Because HALT testing has been conducted, the products "limits" are known. This knowledge provides your company with the ability to create a production screen that won't damage good hardware, but will find process related issues.

Defining the Screen

During HALT testing the products Operating Limits are defined. Using these Operating Limits an appropriate screen is created that can be applied during mass production. There are many different varieties of HASS screen, though the two most common are precipitation and detection, and straight detection.

• Precipitation and Detection Screen

Made up of two sections: the precipitation section is designed to 'break' any dormant defect in the product by applying higher than normal stress to the product. The detection portion is designed to detect any failure by applying stress at a level the product can be functionally tested at.

• Detection Screen

A straight detection screen is designed to detect the failure by applying stress at a level the product can be functionally tested at. Typically 2-3 temperature cycles with simultaneous vibration are conducted.

Screen Selection

Our engineering consultants will work with your company to establish which type of screen is best suited to your application. There are many points to consider, and the results attained during HALT will be heavily leveraged, in order to provide the best possible base for screen development.

Screen Verification

Once the screen type has been decided upon it is time to ensure the products response to the applied stimulus is acceptable. Your product will be secured inside the HALT chamber as it would be during production screening. It is essential that any fixturing material be lightweigh, rigid, and as thermally translucent as possible.

The product is connected to all functional test equipment, as it would be in production. Thermocouples and accelerometers are connected to each unit to monitor the individual unit response to the input stimuli. The HASS begins and functional testing is carried out throughout the screen. In addition, temperature and vibration recordings are attained to ensure each product is receiving uniform response. If screen tuning, or fixture tuning is required then this process is repeated until the desired response is attained.

The defined screen will next be run on production hardware to ensure that no overstress failures occur. This process is called Proof Of Screen (POS).