Post on 28-Jul-2018
PCB Strain Measurement
Chief-SI Professional System Integrator
AgendaWhy need strain gages?IPC/JEDEC-9702/9704 StandardFundamental of strain gaugeStrain measurement requirementReport functionDemo
Why need strain gages?Board flexure induced solder ball cracking, trace damage, pad lifting
Trend of PCBFiner pitch of chipThickness of PCBLead free (RoHS)
Brittle
CSP
BGA
Who should be concernedComponent suppliersTest-fixture vendorsPCB assemblersSystem manufactures
IPC StandardIPC/JEDEC-9702Monotonic Bend Characterization of
Board-Level InterconnectsJune 2004
IPC/JEDEC-9704Printed Wiring Board Strain Gage
Test GuidelineJune 2005
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
IPC-9702Universal tensile tester
Control board deflection rate
Measurement Instrument500 Hz min.Simultaneous recording strain & resistance
Copy from IPC
2008 Q1 will ready
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
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
IPC-9704Process need strain measurement
SMT assemblyComponent/connector install
Board test processesICT, Function test
Mechanical assemblySystem assembly
Shipping Environment
Copy from IPC
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)
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
Fundamental of strain gage
Copy from Vishay
What is strain?
Copy from TMLin/in
Principle of strain gage
Copy from TML
Strain gage types
Uniaxial Rosette(Tee) Rosette(Rectangular)Resistance1203501000
Axis:
MaterialSteelAluminumPlasticCompoundTemperatureRoom temperatureHigh temperature(500)
Measure direction
ApplicationResidual stressCrack detectionShear
Gage (IPC 9704)RosetteStacked Rosette Strain Gages with pre-attached wires
Planar Stacked
Gage position (IPC 9704)
Strain gage Attachment
Common question of Strain measurement
1. Strain2. Strain Gage3. Noise4.
5.
6.
How to measure strain?
Bridge Four bridge armsExcitation voltageOne Gauge system
Two-wire circuitThree-wire circuit (Lead wire compensation)
The Wheatstone BridgeFull Bridge
LoadcellStrain type AccelerometerTorque Transducer
Half BridgeStrain with Thermal compensationWeighting scale
Quarter BridgeStrain
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
==
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
===
=GF
RR
= 00024.04167
11
= 0007.01429
11
Calibration(Shunt)
Add Large ResistorSimulate Strain predeterminedExample
Rgauge=120 Rshunt=100 kR=0.1438 599.3
Shunt
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
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
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)
Our CustomerASUSCompalInventecLenovoTSMC
IntelFoxconnCHIMEIPTI
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
Easy wiring
Software for IPC-9704Graphical User InterfaceEasy WizarCalculation
Diagonal strain = e1-e2+e3Principal StrainStrainRate
Report of StrainMap
StrainMap EnhancedDemo
Thank you
Chief SI
03-59362680922855439