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Contents
� Why is reliability important?
� Assembleon Reliability program 2007 – 2008
� HALT and basic principles of Reliability
� HALT case overview (Temperature)
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� HALT case overview (Temperature)
� Electrical Transients
� HALT case overview (Transients)
� Shock & Vibration
� Experience with HALT
� Mindset
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Why is reliability so important?
�Unreliable products gives:
– Customer dissatisfaction
– Warranty Costs
– Rework of parts (€ )
– Loss of Reputation
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– Loss of Reputation
– Loss of Repeat Business
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Assembleon Reliability program 2007-20081/2
� Design reviews, FMEA, functional/duration testing are NOT sufficient.
We still had FP’s (Field Problems).
� A reliability program was set up determine if the HALT technique can
provide answers to the following questions:
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provide answers to the following questions:
– How can we provoke realistic failures during design?
– How to do this within a reasonable amount of time?
– What does reliability cost?
(HALT = High Accelerated Life Testing)
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Assembleon Reliability program 2007-20082/2
� Engineering changes had to be made to various electronic boards
because of functionality expansion.
– This gave us the opportunity to try to simulate & solve known FP’s
using the HALT method.
� (Hitch-hike with the ongoing engineering process)
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� (Hitch-hike with the ongoing engineering process)
Find an answer to the unanswered questions:
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What is HALT ?� HALT is an engineering step-stress-to-fail process which can reveal
design flaws quickly (within hours of testing).
� HALT is not a compliance test and not limited by component or product
specifications.Failure
Evaluate the relevance of the failure.
Determine if stress-level is acceptible and
implement corrective action if necessary.
6Apply stress
(+/-15min/step)
Failure
Evaluate the relevance of the failure.
Determine if stress-level is acceptible and
implement corrective action if necessary. Increase stress
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Basic principles of Reliability:
Reliability of a product is determined by:
– strength (product related)
– stress (user/environment related)
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Reliability (Load & Strength interferences)
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Excluding wear-out
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Load Strength
Defect!
Ref. Patrick T.D. O’Connor – British Areospace
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Reliability (HALT principle)
..
1 • Induce failure
• Find weak-spots
Design
• Improve design
9Load Strength
Ref. Patrick T.D. O’Connor – British Areospace
Design
Margin
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HALT tests may include:
� Temperature stress
• under max. loading conditions
• In combination with power cycling
� Temperature cycling
� Voltage stress (in combination with temp.)
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� Voltage stress (in combination with temp.)
� Electric transient susceptibility stress (all cables)
� Shock & vibration
� RH%
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HALT case overview – Temperature
+100C
+140C
ModifiedChange FET type Cost: approx. 10ct
ModifiedChange IC type Cost: approx. 10ct
ModifiedChange Diode type Cost: approx. 5ct
ModifiedChange FET type Add 10uF capacitor Cost approx. 20ct
120C
85C
130C140C
X20 PCB’s
80CX20PCB’s
Case 1(Tape cutter)
100C
140C
Case 6(ITBF-EFT) 120C
Modified
Solve in FPGA
Stop test.
100C
140C
Sprocket
140C
Modified2 x pull-down resistors.Cost: negligible
ModifiedChange the BIOS settings.Cost: negligible (Implementation)
ModifiedChange res. values Cost: negligible
140CX14 PCBs130C
80C
140C
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-40C
Case 3(PCU-IC)
+50C
Re-active (learning – correlation with FP’s)
70C
Case 5(re-use F)
Case 2(PCU-FETs)
X20PCB’s
-10C
Case 8(AXPC)
Pro-active
CCB(tray
trolley)
Solve in FPGA
Cost: negligible
Case 7(BA-
Camera)
60C
Sprocket
detector
Case 9(TPR Liftcontroller)
70C
Case 4(PCU-diode)
70C
80C
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Summary: Performing Temperature HALT
� Perform Infra-red measurements (Hot-spots)
before performing HALT.
� For HALT; (Rule of Thumb): ensure a margin of at least 40C above
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specification.• (This is NOT a continuous spec!)
� It’s important to analyze all failures and to decide on: • Root cause
• Evaluate the relevance of the failure
• What is the effort/cost for improvement
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Electric transients
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� Electronic circuits with cable connections can be affected by electric transients.
� Cables can be excellent antenna’s, depending on impedances, length etc. and can
pick up such transients:
� This phenomenon deals with electromagnetic disturbances inside equipment (intra-EMC)
� The EMC regulations often concern only inter-EMC and has a more legal goal & scope
� Additional EMC performance is often necessary for reliability
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Example of an electric transient and effects
Relay switching off a load witha residue voltage.
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Possible resultant transient voltage which can be induced into nearby cables or locally on a PCB.
Possible resultant damage caused by a transient voltage disturbance.
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HALT case overview – Transients
6kV
7kV
8kV
9kV
10kV
Modified
Add 10nF cap.
Cost: negligible
Modified
Gnd. connection
Cost: negligible
At approx. 8kV,
Cable isolation gets “tricky”
10kV10kV
Modified
Shield repeater
Cost: 5 euro
8kVdefect
Modified
Gnd. connection
Cost: 10ct
6kV
Modified
Add 2x10nF caps.
Cost: negligible
Case 6(BA-
Camera)
Design integration
EMC
Cost: negligible
Design integration
EMC
Cost: negligible
8kV
Case 8(TPR)
10kV
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1kV
2kV
3kV
4kV
5kV
Re-active (learning – correlation with FP’s)
2kVCase 2
(ITBF)
mP reset
3kV3kV
3kVFET defect
Case 1
0.5kV
2.5kV
Case 4Fire-WireRepeater problem
1.5kVdefect
Case 3(Sprocket detector)
1kV
Pro-active
Camera)
4kV
0.6kV
2.8kV
Case 7(LED pcb)
Case 5(Tape cutter)
mP reset
2kV
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Transient “Rule of thumb” targets
6kV
7kV
8kV
9kV
10kV
Soft errorsHard failureEither SW
or HW
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1kV
2kV
3kV
4kV
5kV
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Shock & Vibration (placement head)
Example: Placement Head (during operation)
Test:
Vibration:10-1000Hz; 0.1g; 0.2g;… 1g; 1.2g… etc
Shock: 25g; 3msec (Sys. Limit) 30, 60, 100%
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Other tests: Non-operating; transport
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Shock & Vibration
BA Camera
Representing Optics
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Representing OpticsRepresenting Electronics
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Experience with HALT: (electro.)
� A lot of Field Problems can be provoked using the concept of HALT
testing.
� HALT testing provides results quickly (within a few hours/days).
� Experience shows that realistic failures can be provoked with minimum
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� Experience shows that realistic failures can be provoked with minimum
design impact.� Provided testing is performed early during development (pro-active).
� Now we are performing pro-active HALT testing with success.
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Reliability engineering: a matter of mindset
� The principle behind HALT is quite simple and is usually easy to
perform. The biggest challenge is setting the right MINDSET and
applying the right strategy.
� Don’t test for approval but test to find potential failures and make the
necessary improvements (It’s not a Pass/Fail test).
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� Determine HALT: plan/parameters depending on product type &
working environment.
� HALT is not a “magic solvent” but with a good test strategy and the right
mindset, it can be a very effective tool for improving the reliability of
design’s.
� Less failures gives satisfied customers
– Improved quality & less re-work