Highly Accelerated Stress Testing (HAST)

HAST (Highly Accelerated Stress Test) reduces the time it takes to complete humidity testing for semiconductors. By elevating temperatures above 100°C and increasing the pressure, simulation of normal humidity tests can be made while maintaining the same failure mechanisms. Tests can be completed in days, not weeks. Any product or material testing process that requires humidity testing may benefit from switching to HAST.

Common HAST Testing Methods

• JEDEC Standard No.22-110B: Highly Accelerated Temperature and Humidity Stress Test
• JEDEC Standard No.22-118: Accelerated Moisture Resistance - Unbiased HAST
• IEC Publication 60068-2-66 (1994-6): Damp Heat Steady State
• IEC Publication 60749 Amendment 1: Damp Heat, Steady State Highly Accelerated
• EIAJ ED-4701 Method B-123: Unsaturated Vapor Pressure Test

Acceleration factors vary depending on the sample, but huge savings can be made. Typical reductions of test time to 1/50th of a standard humidity test are normal. Some people are now starting to try combining HAST with other methods, to increase the results. For example by using HALT (Highly Accelerated Life Test) methods of fast temperature cycling and random vibration, they hope to aggravate faults in parts so that when they do a HAST test, the humidity can penetrate better.