M h i l b h i f l i Mechanical behaviour of electronic components and assemblies studied components and assemblies studied
by full-field optical techniquesDan Borza
Ioana Nistea
Outline
Context
Full-field non-contact measurement techniques
• Interest, measured quantities
• Generally established techniques
Full-field optical measurement techniques at INSA de Rouen
• Speckle Interferometry
• Digital Holography
• Digital Image Correlation
• Application examples
Conclusion
Context
Loading in electronic assemblies :• Excess temperature (internal, environmental)• Excess current or voltage• Mechanical shock stress or impact• Mechanical shock, stress or impact• Dynamic loading• ...
Aggravating factors :• Highly inhomogeneous structures =>
materials with different thermo-mechanical properties• Increasing density of components small footprint• Increasing density of components, small footprint
Context
Mechanical failure:• Excess deformation (yielding or elastic), buckling• Ductile fracture, brittle fracture, cracking• Various types of fatigue• Various types of fatigue
Experimental analysis :Experimental analysis :• Detection and understanding of failure origins and
mechanisms, previously unknown• Development of new FEM models and testing of the existing
ones
DifferentDifferent existingexisting techniquestechniques areare oftenoften complementarycomplementary inin termsterms ofofresults,results, measuredmeasured quantities,quantities, measurementmeasurement range,range, etcetc..
Full-field non-contact techniques
Interests• Non-contact measurements, no damage to the test object
and no perturbation of the measured phenomena• High precision and high measurement sensitivityHigh precision and high measurement sensitivity• No transducer, no need for calibration• Simultaneous measurement of local values of the quantity
of interest in a large number of points => able to detectsingularities, and dynamic phenomena
Full-field non-contact techniques
Measured quantities• Kinematic quantities:
–displacementsd l i–speeds, accelerations
• Position of points (profilometry)• Material properties (indirectly):• Material properties (indirectly):
–CTEYoung's modulus–Young s modulus
–...
Full-field non-contact techniques
Techniques generally used:digital
light source
• Digital Image Correlation• Projection Moiré• IR Thermography light source
digital camera
test object
• IR Thermography• Near-Field Acoustic Holography• Shadow Moiré
CCDcamera
PZT
light source
test surface
laser
b
SignalProcessing
IR detector
∆T
SpecimenTest objecttest surface
illuminate
Processing∆T
Microphone array
view
gratingg g
Full-field optical techniques at INSA de Rouen
Interferometric techniques• Speckle Interferometry (SI)• Digital Holography• Holographic Interferometry• Holographic Interferometry
White-light techniquesWhite light techniques• Digital Image Correlation (DIC)• Fringe Projection• Structured Light Projection
Speckle Interferometry
• Continuous beam laser source (λ = 523nm)Th ibilit t d di th t t• The sensibility vector, depending on the system geometry,is either normal or tangent to the tested surface
BS1 2 beamsplitter BS1 M1BS1, 2 - beamsplitterL1, 2 - lensesM1, 2 - mirrorsIL - imaging lensPZT - piezoelectric transducer
BS1L1 M1
BS2
testPC IL
L2
Speckle Interferometry measurement Speckle Interferometry measurement setupsetup
surfacePZT M2
p yp y pp
Speckle Interferometry
• Continuous beam laser source (λ = 523nm)Th ibilit t d di th t t
BS1 M1
• The sensibility vector, depending on the system geometry,is either normal or tangent to the tested surface
BS1 2 beamsplitter BS1 M1BS1L1 M1BS1, 2 - beamsplitter
L1, 2 - lensesM1, 2 - mirrorsIL - imaging lensPZT - piezoelectric transducer
BS1L1 M1
BS2
IL
L2
testPC
ILL2
PZT M2
Speckle Interferometry measurement Speckle Interferometry measurement setupsetup
surfacePZT
p yp y pp
Speckle Interferometry
Characteristics• Spatial resolution determined by CCD detector and lens• Displacement measurement sensitivity up to several
nanometersnanometers• Sensitive to air flows and thermal gradients
Applications• Steady-state vibrations• Static, quasi-static and dynamic displacements
Speckle Interferometry
Principle:• Temporal phase stepping algorithm (four bucket)
Series of 4 specklegramsSeries of 4 specklegramsStatic displacements Steady-state vibrationsSeries of 4 specklegramsSeries of 4 specklegramsStatic displacements Steady state vibrations
Optical phase mapOptical phase map(modulo 2(modulo 2ππ) )
TAV hologramTAV hologram(Bessel fringes)(Bessel fringes)
phase unwrappingphase unwrapping specific algorithmsspecific algorithms
DisplacementDisplacementmapmap
Vibration Vibration amplitude mapamplitude map
Digital Holography
• The setup is almost identical to the one used for SI – themain difference is the absence of a camera lensmain difference is the absence of a camera lens
• We record the phase information of the interference field
BS1, BS2 - beamsplittersM1, M2 - mirrorsSF - spatial filterPZT - piezoelectric transducer
LASER BS1 lensCCD
M1
test BS2
CCD
surface BS2
PCSF
IL
Digital Holography measurement setupDigital Holography measurement setup
PC
M2PZT
g g p y pg g p y p
Digital Holography
Virtual wavefront reconstruction• We apply the same principle as in classical holography• Numerical simulation of diffraction by "illuminating" the
digital hologram with a numerical reconstruction wave (RN)digital hologram with a numerical reconstruction wave (RN)
HologramVirtual image
HologramObject
OO
((a)a) Recording (Recording (b)b) ReconstructionReconstruction
RNObserver
R
((a) a) Recording (Recording (b) b) ReconstructionReconstruction
Digital Image Correlation
• Successive images are recorded during surface deformationCh i th i l i t it t k d i d t bt i• Changes in the pixel intensity are tracked in order to obtainthe in-plane displacement map (single camera)
li ht thermal chamber
light source
digital camera
light sourcetemperaturemonitorlight source monitor
DIC measurement setup for thermal testing application DIC measurement setup for thermal testing application p g ppp g pp
Digital Image Correlation
Principle:• We determine the displacement
field between images (a) and (b)by applying a correlation algorithmy pp y g g
• Subpixel resolution can be attainedby interpolating the correlationmatrix (a)matrix
• The measurement resolutiondepends on the choice of size for
(a)
the correlation window• More complex algorithms take into
account the deformation of theaccount the deformation of thecorrelation window
(b)
Application examples (Audace)
Thermal deformations• External thermal stressing by local convection heating in
surface mount PCBs• Transient deformations induced by internal time-Transient deformations induced by internal time
dependant stress in active components
Steady state vibrations• At assembly level, board level, component level, die level
Mechanical deformations • Side effects of fastening screws
Measurement of material propertiesCTE t i lti l PCB d i PQFP• CTE measurements in multi-layer PCBs and in PQFPcomponents
Conclusion
Full-field optical techniques• Capability of experimental analysis of electronic assemblies
• Synchronous measurement of all sampled points• Synchronous measurement of all sampled points
• Ever-increasing measurement capabilities and processingg p p gpower
Each technique has specific measurement characteristics• Each technique has specific measurement characteristics,advantages/inconvenients that make it more or lessconvenient for certain applications
THANK FOR YOUR ATTENTIONATTENTION