Air based self-assembly of silicon chips on foils

1Airflow based self-assembly of silicon chips on foils | 13

Air based self-assembly of silicon chips on foils

Name: B. van LeeuwenCoach: Dr.Ir. M. TichemProfessor: Prof.dr. U. StauferSpecialisation: Production TechnologyConcern: Holst CentreCoach: Prof. Andreas Dietzel, PhDDate: 08-07-2009


Contents

• Introduction• Holst centre• Micro assembly

• Problem description• Simulation

• Dynamic simulation using COMSOL

• Dynamic simulation using Matlab• Practical test

• Test setup

• Test results• Applicability• Results


Introduction

•Joint venture of TNO and IMEC-NL•Research in future products

• System-in-foil: Low cost, flexible electronics which can be integration in disposable every day products

Holst centre

Source: Holst Centre


Introduction

• Problems appearing in micro assembly:• Scaling effect sticking effect

• Gripping and grasping difficult (delicate parts):• Solution Self-assembly

• Self-assembly: • Processes in which a disordered system of pre-existing

components forms an organized structure or pattern.

(http://en.wikipedia.org/wiki/Self-assembly)

• Self-assembly can be based on different physical phenomena:• For example: Mechanical, Fluidic or Gas based processes

Micro assembly


Problem description

• Intelligent package, produced on roll-to-roll production

• Placement of flexible chips on flexible foil

• Chip placed on first foil, than laminated with second foil• First foil makes placement possible• Second foil takes care of electrodes

and connections

Context


Problem description

• Multi scale issue (large foil, small chips, accurate positioning)

• Ultra low cost, high volume production process

Solution: Coarse placement followed by self-assembly

• Only air basedassembly treated

Target loca tion

F ina l positionFo il on ro ll

Context


Problem description

• Air flow based self-assembly• Holes in foil will allow air through foil

by backside overpressure.• Velocity gradient above surface of

foil.• Chip will float and drift to final target

location.• Different designs possible

•Main problem• Design a foil in a way that: the

chip drift to the target location by airflow

Context


Simulation

• 2D FEM simulation, solving the Navier-stokes equations using COMSOL.

• For different foil designs (velocity profiles)• Obtaining static data

• 2D motion, solving the equations of motion using Matlab.• Data form COMSOL stored in lookup tables• Motion calculated using ODE solver• Motion displayed

Dynamic simulation using COMSOL and Matlab


Simulation

The inlet velocity is imposed at the lower boundary and is defined by the friction of the nozzles:

Dynamic simulation using COMSOL

4

121

1

1

( ) ( )128 ( )

In which:

hole diameter

pressure underneath foil

( ) pressure above foil

thickness of foil

( ) pitch between holes

dynamic viscosity of air

dv p p p x

L b x

d

p

p x

L

b x


Simulation

Static simulation implemented for a certain chip position


0

0

The force in 2D on the underside of the chip:

The moment on the chip:

1 2

l

l

NF p dx m

M l p s dx N


Simulation

• Storing the obtained data lookup tables, dependent on x, y and φ

• Multiple lookup tables for:• Forces and moments• Different velocity profiles.

• Not all angle, y-position combinationspossible because of geometry

Dynamic simulation using Matlab

X

Y

P hi


SimulationDynamic simulation using Matlab

2 2

( , , ) sinF

( , , ) cosF

M

In which:

Moment of inertia [kgm ] (source:[D])3

Gravity force on chip [N]

Lift force on c

lift

x

liftgy

lift

z

g

lift

F x ym x x

mF x y

m y y Fm

MJ

J

mJ l

F m g

F

hip obtained from COMSOL [N]

Moment on chip obtained from COMSOL [Nm]liftM

The equations of motion can now be formulated


SimulationDynamic simulation using Matlab

Solving the equations of motion leads to the moving chip.

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01

-1

0

1

2

3

4

5

6

x 10-3 Motion of chip t = 2.029


Practical test

Features of test setup• Overpressure in box by fan• Foil attached on top• Pressure measurement for feedback• Events observed by camera

Test setup


Practical testTest results


ApplicabilityPractical applicability

Foil

A ir pocketA ir supply

Self alignm entprocess

Aligned chip

Movingdirection

Chip supply onreel

• Integration possibilities• Chip supply• Chip alignment• Chip fixation


Results

• Working simulation software• Dynamic simulation using an array of static FEM calculations

• Practical proof of concept• Design and build of test setup• Successful testing of foil design

• Practical applicability• Possible integration with other production steps• Manny possibilities


End of slide show, click to exit.


Simulation (backup slide)

Lookup tables for damping in y-direction:• New forces calculated with initial speed• New force subtracted from force without initial speed• Force linearization round zero becomes damping force


-0.01 v[m/s]

F lift

F lift_v1

F(v)

F [N ]


Calculation (backup slide)

Chip levitation height, foil 7 comparison

0

50

100

150

200

250

300

0 100 200 300 400 500 600

Pressure [pa]

levi

tati

on

hei

gh

t [u

m]

Foil 7, measurement

Foil 7, calc. without impulse

Foil 7, calc. with impulse

Foil 7, calc. FEM

Air based self-assembly of silicon chips on foils

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