HASS & NTF TESTING

img_test_ntf_01HASS Development

Highly Accelerated Stress Screen Development (HASS) is a process to develop and define a production screen. HASS development verifies that the screen will find manufacturing flaws and not take significant life out of the product.

 

HASS Development process defines and evaluates a specific HASS screen using the temperature and vibration operating limits determined during the HALT process. The production test setup is evaluated for thermal and vibration uniformity and repeatability by performing vibration and thermal characterization. The effectiveness of the HASS screen is then evaluated using a Proof of Screen process. This process verifies that the HASS screen is effective in finding manufacturing and process related flaws before production units are delivered to the customer. Once it is established that the HASS screen detects manufacturingand process related flaws using seeded or No Trouble Found (NTF) samples, the product is subjected to proof of life evaluation. The proof of life process evaluates the effects of the HASS screen on the end product. During proof of life evaluation, known good units are subjected to the HASS screen for a pre-determined number of runs to ensure significant life has not been removed from the unit. For example, a typical product might be subjected to the HASS screen for 15 consecutive runs. Subjecting known good units to 15 runs of the HASS screen without failure confirms that no more than 1/15th of the product’s useful life has been removed after running production units through the HASS profile.

An essential component of HASS development is root cause analysis and the identification and implementation of corrective action to ensure product integrity; thus increasing the product’s reliability and the robustness of design.

 

Goals

1. Define the HASS profile.
2. Evaluate product fixture for vibration and thermal uniformity.
3. Verify screen effectiveness.
4. Perform product life valuation.

 


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HASS Screening

Highly Accelerated Stress Screening (HASS) is approximately a two to three hour screening process utilizing rapid thermal transitions and random vibration to expose process related variations in manufacturing. HASS is used to monitor outgoing quality and improve product reliability.

 

Goals

• Uncovers component supplier quality issues and revision changes.
• Identify faults and implement corrective action to prevent future occurrences.
• Uncovers degradation in Operating Limits caused by changes to software and firmware.
• Perform HASS at chosen AQL levels to monitor process changes.
• Uncover latent defects, workmanship issues, material discrepancies and vendor part modifications.
• Maintain HASS results database and immediately report failures to contract manufacturer for root cause evaluation and corrective action implementation.

 

A screening technique used to classify No Trouble Found (NTF) units as good or defective. Defective units are sent for failure analysis and corrective action is taken to prevent future occurrences. Passing units are returned after final test and are placed into inventory as sellable goods.

 

NTF Verification Testing

A screening technique used to classify No Trouble Found (NTF) units as good or defective. Defective units are sent for failure analysis and corrective action is taken to prevent future occurrences. Passing units are returned after final test and are placed into inventory as sellable goods.