Failure Detection using Old and New Test Methods
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Microsectioning vs. IST Testing:
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Low number of holes tested vs. High number of holes tested
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Evaluates 1 degree of holes vs. Evaluates 360 degrees
Circumference of all connections
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Go / No Go test vs. Quantifies severity
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Poor repeatability vs.Excellent repeatability
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Operator dependent vs.Operator independent
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Visual criteria vs.Electrical criteria
PRIMARY OBJECTIVE OF IST TECHNOLOGY
The primary objectives in the design of the IST system were:
All of the criteria have been met, with the unique capability/advantage of detecting post separation as an independent failure mechanism. with the unique capability/advantage of detecting post separation as an independent failure mechanism.
Time to results:
Receiving performance data within a day (or even a shift) is critical to today's manufacturing environment, with high volumes, several levels of technology and high speed throughput, rapid time to results is a must. Process control is achievable, only if process monitoring is available! Quantifying the daily variability of the process, chemistries or materials, requires an effective tool that delivers reliable data in an efficient time frame.
: Receiving performance data within a day (or even a shift) is critical to today's manufacturing environment, with high volumes, several levels of technology and high speed throughput, rapid time to results is a must. Process control is achievable, only if process monitoring is available! Quantifying the daily variability of the process, chemistries or materials, requires an effective tool that delivers reliable data in an efficient time frame.
This immediate feedback quantifies the overall performance/integrity of the process and products. This capability to rapidly measure the total effect of the many variables is unique to
IST.
(Microsectioning will generally find the gross separations, but proves inadequate at detecting marginal separations. Microsectioning can not measure performance, all other accelerated stress test methods are too slow to be effective.)
Present users of IST technology have created performance baselines for their processes and use the methodology to monitor their daily output, resulting in immediate feedback on any changes that may influence product performance. This baseline creates the perfect reference to quantify whether engineering changes have improved or reduced the overall performance/integrity levels.
Decisions regarding product attributes, chemical or material changes can now be driven by performance data.
Reduced cost:
The combination of microsectioning and traditional thermal stress test methods, requires both investments in time to train the operators and capital to purchase the thermal stress equipment and monitoring systems. The total cost of installation, characterization, maintenance and operation, prevent it's availability to the majority of the industry. Most companies requiring thermal shock/stress testing contract independent test services to complete the work.: The combination of microsectioning and traditional thermal stress test methods, requires both investments in time to train the operators and capital to purchase the thermal stress equipment and monitoring systems. The total cost of installation, characterization, maintenance and operation, prevent it's availability to the majority of the industry. Most companies requiring thermal shock/stress testing contract independent test services to complete the work.
IST testing services price usually ranges between $3,000.00 to $5,000.00 for a
statistically valid sample size of 36 coupons. Additional activities include s IST thermal stress cycling the product to failure, identifying all failure locations, graphs of PTH & Post interconnect degradation and report writing.
The costs of a 1000 hours thermal cycling test (Delco type test), generally range between $15-$18K, this equates to $750 per sample. The cost of testing covers accelerated stress testing and report writing.
Microsections costs $85 per sample, this cost becomes excessive when the high quantities of samples required are factored into the equation.
Table 1 illustrates a comparison of IST technology to thermal cycling and liquid to liquid test methods.
TABLE 1
|
FUNCTION |
I.S.T. |
THERMAL CYCLING |
LIQUID TO LIQUID |
|
TEST TYPE |
STRESS |
STRESS |
STRESS |
|
TEMPERATURE |
25C - 260C |
-65C - 125C |
-35C - 125C |
|
FAILURE DETECTION |
EARLY |
NOT APPLICABLE |
NOT APPLICABLE |
|
*TOTAL COST OF OWNERSHIP |
$130K |
$208K |
$130K |
|
COST PER TEST COUPON |
$75.00 |
$300.00 |
$175.00 |
|
DATA COLLECTION |
INTEGRATED |
ADDITIONAL $10K |
ADDITIONAL $10K |
|
CAPABILITIES |
PWB & POST |
PWB |
PWB |
|
TIME TO RESULTS (DAYS) |
1 |
12+ |
6+ |
|
INSTALLATION |
STANDARD AC OUTLET |
HARD WIRED |
HARD WIRED |
|
MAINTENANCE |
MINIMAL |
EXTENSIVE |
ONGOING |
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COST OF MASS MICROSECTIONING |
LOW |
HIGH |
HIGH |
|
ENVIRONMENTAL |
FRIENDLY |
NITROGEN / CFC'S |
CFC'S |
*The total cost of ownership is based on calculating the cost of the initial system purchase, installation, energy utilized, consumable, floor space, maintenance costs, human resources required for operation/data analysis and failure analysis microsection requirements.
IST has proven extremely cost effective at pre-screening product prior to submission into the 1000 hour test. Strong correlation exists between the different test methods, allowing the user to run representative samples through IST first, to ensure the product's ability to surpass the specification. This offers a major cost advantage by avoiding the risk of test failure and giving immediate feedback of potential process problems.
Cost savings can be realized through the rapid time to results capability, that delivers information to the user and avoids further processing of defective product.
Savings can also be realized with the ability to screen out defective product, especially with regard to post separations.
Repeatability & Reproducibility:
The variability of Microsections or accelerated stress test results create differences of opinion between manufacturers and their suppliers or customers. Reasons for these differences relate to the types of test methods used and the wide levels of variability that exist within these methods.
Variability of results in traditional methods is high because:
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Characterization of the thermal stress equipment is complex.
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Recreating the identical test conditions in different locations is difficult.
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Numerous test vehicle designs are used.
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Microsection analysis is highly dependent on numerous factors.
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The human factor introduces differences in the interpretation of results.
IST removes the human factor from the testing by using a computer and user friendly software to control all elements of the test protocol. The software is designed to compensate for every possible variable that influences the thermal profiles of each test vehicle, ensuring that each coupon is stressed identically.
A recent IPC (PTV Reliability Task Group) round robin confirmed that IST had superior R&R compared to all other traditional stress test methods.
Automation of test results:
IST is totally automated, the system is designed as a shop floor/operator tool, system functions are controlled by the software, the monitor displays the ongoing performance of all test vehicles.
Throughout testing the system is continuously monitoring 2 independent circuits in each test vehicle, this data is captured for graphing or is easily transferable into spreadsheets for further analysis.
IST has also been designed as an engineering tool, with which test conditions can be modified in numerous areas to create customized thermal profiles. IST can duplicate precise temperature conditions in either large or small areas by modifying the circuit geometry's within the test vehicle.
The test temperatures are easily modified by using a setup menu, test conditions are stored in libraries to allow for identical re-testing in the future.
Is IST technology a paradigm ?
The use of electrically induced stress combined with highly sensitive measurement creates the potential for increased levels of understanding with failure analysis and diagnosis.
The IST approach uses novel methods to uncover hidden variables that generally are not detected as part of the traditional product or process performance (post separation is a perfect example).
IST was developed to dramatically reduce the need for microsectioning and has proven to correlate with traditional thermal stress Technology (thermal ovens, liquid to liquid, sand bath etc.).
Several IPC studies have confirmed IST's capability to deliver accelerated time to results with good correlation and repeatability. Additional studies are ongoing that will generate the data base to determine acceptance/rejection criteria for virtually all recognized product attributes used in the industry.
To date IST has been challenged by many customers using unique technologies, chemistries and materials, the system has proven totally flexible and capable of testing all types of products.
To illustrate the systems capability, two different products were tested side by side on the same IST system: 1) 6 layer .018" PCMCIA with .006" Blind and PTH vias, 2) 24 layer .350" Backplane with .045" PTH vias. The system automatically compensated for the thermal characterizes of both products and generates the same thermal profiles for subsequent stress testing.
Because the heat is generated internally within the substrate, the system has the capability to test different technologies simultaneously, no other test methods has this capability. The internal strain can be focused at the post interconnect to determine the presence and levels of post separation. The test vehicle design is easily modified to create localized heating, that simulates the effects of high temperature components
Yes... IST Technology is a paradigm !