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Physical Model for Determining Failure Rates of Modules When Permeability is the Rate Controlling Step

IP.com Disclosure Number: IPCOM000079758D
Original Publication Date: 1973-Aug-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Attardo, M: AUTHOR [+2]

Abstract

A general physical model for determining the time to fail is applied to semiconductor modules under given environmental conditions and leachable chloride concentration. The model has been used to project failure rates to the field, based on accelerated temperature/humidity (T/H) data for exposures of 2000 hours or more. An accelerating factor, as a function of temperature and relative humidity, is achieved from the model's thermal and relative humidity (R.H.) factors. The thermal activation term is derived from published data on water permeability through epoxies, while the R.H. term is based on the BET isotherm for water absorption on plastic surfaces.

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Physical Model for Determining Failure Rates of Modules When Permeability is the Rate Controlling Step

A general physical model for determining the time to fail is applied to semiconductor modules under given environmental conditions and leachable chloride concentration. The model has been used to project failure rates to the field, based on accelerated temperature/humidity (T/H) data for exposures of 2000 hours or more. An accelerating factor, as a function of temperature and relative humidity, is achieved from the model's thermal and relative humidity (R.H.) factors. The thermal activation term is derived from published data on water permeability through epoxies, while the R.H. term is based on the BET isotherm for water absorption on plastic surfaces.

With the knowledge of the leachable chloride concentration and water permeation, the time to fail is determined without the need for life testing. Instead, it is determined by the critical amount of chloride solution that must reach the corrosion site to produce an open in the conductor. This critical amount, in turn, depends on the concentration of leachable chloride and water permeability.

The time to fail is expressed as:

(Image Omitted)

The model, illustrated in the figure, is general in scope and can be tailored to apply to all cases of corrosion due to internal and external contaminants, where permeability of water or pollutant is the rate limiting step.

A microprobe technique is utilized for analyzing leac...