PCB Strain Roadshow -...
Transcript of PCB Strain Roadshow -...
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PCB Strain Measurement
Chief-SI Professional System Integrator
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AgendaWhy need strain gages?IPC/JEDEC-9702/9704 StandardFundamental of strain gaugeStrain measurement requirementReport functionDemo
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Why need strain gages?Board flexure induced solder ball cracking, trace damage, pad lifting
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Trend of PCBFiner pitch of chipThickness of PCBLead free (RoHS)
Brittle
CSP
BGA
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Who should be concernedComponent suppliersTest-fixture vendorsPCB assemblersSystem manufactures
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IPC StandardIPC/JEDEC-9702Monotonic Bend Characterization of
Board-Level InterconnectsJune 2004
IPC/JEDEC-9704Printed Wiring Board Strain Gage
Test GuidelineJune 2005
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IPC-9702Topics
Monotonic Bend Test
EquipmentUniversal tensile testerStrain measurement instrumentContinuity monitoring strain & resistance instrument
Recording datastrain vs. timestrain-rate vs. timestrain vs. strain-rateforce vs. timeresistance vs. time
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IPC-9702Universal tensile tester
Control board deflection rate
Measurement Instrument500 Hz min.Simultaneous recording strain & resistance
Copy from IPC
2008 Q1 will ready
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IPC-9702Test board Daisy-chainUni-axial strain gage
1.5 mm*1.5 mmPrincipal strain angle ~ longitudinal
Test speedStrain rate:5000 /s
Packagetype
PCB
Load span
Strain gageGlobal PWB Strain
Daisy-Chain
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IPC-9704Topics
Test setup and equipment requirementsStrain measurementReport format
Surface mount deviceBGA (Ball Grid Array)SOP (Small Outline Package)CSP (Chip Scale Package)
June 2005
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IPC-9704Process need strain measurement
SMT assemblyComponent/connector install
Board test processesICT, Function test
Mechanical assemblySystem assembly
Shipping Environment
Copy from IPC
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IPC-9704Strain Measurement Instrument
Simultaneous sampling500 Hz min. for impulse event
ICT, Drop, 100 Hz min. for assembly processes3-wire gage with low level excitation (typical 2V)Low Pass filterMore than 3 channels(12 or more recommend)
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IPC-9704Analysis
Principal strainPeak valueStrain rateTime history
Test FrequencyBefore any test or assembly fixture is brought online.Whenever there are modifications to a test fixture that might
alter the strain profile.Whenever there are modifications to an assembly process
that might alter the strain profile.In-process stiffener design validation.Enclosure design validation prior to hard-tooling
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Fundamental of strain gage
Copy from Vishay
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What is strain?
Copy from TMLin/in
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Principle of strain gage
Copy from TML
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Strain gage types
Uniaxial Rosette(Tee) Rosette(Rectangular)Resistance1203501000
Axis:
MaterialSteelAluminumPlasticCompoundTemperatureRoom temperatureHigh temperature(500)
Measure direction
ApplicationResidual stressCrack detectionShear
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Gage (IPC 9704)RosetteStacked Rosette Strain Gages with pre-attached wires
Planar Stacked
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Gage position (IPC 9704)
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Strain gage Attachment
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Common question of Strain measurement
1. Strain2. Strain Gage3. Noise4.
5.
6.
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How to measure strain?
Bridge Four bridge armsExcitation voltageOne Gauge system
Two-wire circuitThree-wire circuit (Lead wire compensation)
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The Wheatstone BridgeFull Bridge
LoadcellStrain type AccelerometerTorque Transducer
Half BridgeStrain with Thermal compensationWeighting scale
Quarter BridgeStrain
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Features Large excitation, large signal outputThermal consideration
Optimum excitationGauge grid areaGauge resistanceMounting surface
+2.5 VDC for StrainMap
Optimum Excitation Voltage
0 to 10 V1000
0 to 10 V350
0 to 3.125 V120
Full Bridge
0 to 10 V1000
0 to 10 V350
0 to 6.250 V120Quarter Bridge
Excitation Voltage
ResistanceConfiguration
RVIVPower
2
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Strain vs.
1 ~
4167
GF=2, R=120 , R=1
R
RGF
4167004167.02120/1
===
=GF
RR
GF=2, R=350 , R=1
1429001429.02350/1
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=GF
RR
= 00024.04167
11
= 0007.01429
11
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Calibration(Shunt)
Add Large ResistorSimulate Strain predeterminedExample
Rgauge=120 Rshunt=100 kR=0.1438 599.3
Shunt
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Principal strain and Mohrs circle
yx
xyp
xyyxyx
xyyxyxx
=
+
+=
+
++
=
2tan
222
2sin2
2cos22
22
2,1
Known: 45,,, = xyx
2,1 :Principal strainp :Principal direction
2
+0,
2yx
( )0,1( )0,2
+
2,
2max yx
2
, xyx
2, xyy
p2
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Example for 0-45-90 Rosette
45
45b
c
a x
y
480300
650
==
=
c
b
a
2.421739304
1434
max
2
1
===
=
p
450520800
===
c
b
a
80360520
===
c
b
a
4.14
1428539
889
max
2
1
=
==
=
p
5.12662111
551
max
2
1
===
=
p
:unit
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Strain Measurement SolutionStrainMap
Simultaneous sampling3 noise level2k/ch(5k/ch for PCI bus)24~128 ch
StrainMap EnhancedSimultaneous sampling5 noise level50k/chUSB24~56 chVibration Module (Option)
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Our CustomerASUSCompalInventecLenovoTSMC
IntelFoxconnCHIMEIPTI
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StrainMap advantageTotal solution
Integrate Gagemeasure & Training
Performanceaccuracy3Simultaneous sampling 2k
(5k for PCI busChannelup to 128 Chsstability
Analysis & report functionAuto-calibration (Shunt)Mohrs circle analysisExcel report
Easy wiringShort lead time & lower priceLocal service
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Easy wiring
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Software for IPC-9704Graphical User InterfaceEasy WizarCalculation
Diagonal strain = e1-e2+e3Principal StrainStrainRate
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Report of StrainMap
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StrainMap EnhancedDemo
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Thank you
Chief SI
03-59362680922855439