DISTINGUISHING ATTRIBUTES OF I.S.T.
Compared to Traditional Methods
Test 2 separate areas of same interconnects
Identifies failure hierarchy/interactions
Quantifies severity of process defects
Speed - 6X faster (minimum) than T.C.
User friendly - Automated process
Low operating/maintenance cost
No stressing beyond failure criteria
No consumables (Nitrogen/Chemicals)
Reduces extensive micro-sectioning
Excellent repeatability/reproducibility
THE TRADITIONAL TEST METHODS
The difficulty with traditional test methods has been to find a methodology with all of the following characteristics:
Automated capability that practically eliminates quality/human interpretation
Rapid time to results to permit implementation of corrective actions
Excellent repeatability and reproducibility between multiple test sites
Low operating cost
Microsectioning analysis is the most commonly used quality assessment/failure analysis tool used in the industry today. It requires extensive sampling and experience in the areas of sample preparation, polishing & etching. Microsectioning is a critical operations that uncovers the minute flaws that occur within the interconnect, the results of this operation determines a products acceptability or rejection. The fault diagnosis is generally reliant on the available knowledge and experience with numerous levels of technologies and their associated specifications. The variability of micro-sectioning can lead to different opinions or conclusions with the same situation, decisions are usually based upon opinions as opposed to being based on data.
Microsectioning determines a products acceptability or rejection based upon samples evaluated in the As Received and Solder Shocked condition. This methodology was originally designed to simulate the products ability to withstand the effects of wave soldering and/or soldering iron rework thermal stresses.
PWB interconnection technology has changed rapidly over the last decade, with the replacement/addition of through hole devices with surface mount components. PWB technology has also changed dramatically in the areas of materials and chemistries, these improvements were developed to increase the integrity/performance of products to meet an increasing array of end use requirements. Despite all of these changes, we still revert to using the same product acceptance test methodology.
There are differing opinions as to the effectiveness of the present microsectioning method and it's ability to monitor the performance and characterize the quality/ integrity of PWB products in today's fast paced manufacturing environment.
Traditional microsection sampling plans provide a low statistical evaluation of the products/production lots quality, this assessment will not provide a true statistical sampling but can be described more as a hit or miss evaluation.
Microsectioning is at best random, PWB manufacturers and users are frustrated with the following situations:
The inability to characterize the root cause of quality problems
To engineer a timely solution to resolve quality problems.
The inability to quantify the magnitude of the problem or to quantify the influence of corrective actions on product defects.
Inconsistent results between 2 or more microsection test sites
Giving assurances to customers that quality problems have been resolved
