Technologies for Microassembly: Selected Methods 4M 2007 Conference - - PowerPoint PPT Presentation

Technologies for Microassembly: Selected Methods

4M 2007 Conference 3-5 October 2007, Borovets, Bulgaria. ASSEMIC Invited Session

Micro-joining by hot gas stream Laser based micro-assembly system Contactless microdispensing system

Micro-joining by hot gas stream

Development of a micro-assembly system based on hot air stream joining (TU Vienna - ISAS)

Gas supply Compressor Heating tube Nozzle Substrate with µ-part Hot gas stream

• low production costs
• simplicity of use
• possibilty for integration into existing

production lines

• applicability for different materials

combinations

Development of an advanced laser based Pick and Join tool and of a micro- assembly system Innovative methods and processes for micro-welding of polymeric parts (Fraunhofer ILT)

• new laser sources
• innovative joining processes
• high flexibility and processing speed
• increased robustness
• high accuracy

Laser based micro-assembly system

Research and Solutions GmbH

A-2444 Seibersdorf, Austria, Forschungszentrum

• Tel. +43 50 550-0, Fax +43 50 550-2204

www.profactor.at

Contactless microdispensing system

Ana Almansa (Profactor Research & Solutions GmbH)

Fratila, Bou, Palfinger, Mann (Profactor R&S), Möst (PICO Dosiertechnik)

Outline

Introduction Adhesive Dispensing processes and principles Description of PROFACTOR measuring set-up First results Conclusions

Introduction

Dispensing processes- Brief introduction

Microdispensing: key process in many production processes

Packaging, automotive, … (typically automatic dispensing)

Lower volume, craft based industries, … (frequently manual dispensing

from a cartridge using e.g. sealant gun or tool)

Electronics and Microsystems (challenging task due requirement for very

high precision at high production rates)

Different types of adhesive processes Contact / contactless dispensing Single component / Multicomponent adhesive Distinct fluid properties (anisotropic, thermally conductive, IR curing….) Wide range of applications Dispensing of lubricant Adhesive processes Colour, lack, dot marking Dispensing of cleaning fluids and reactive substances Surface coating Sealing, protection, isolation

Source: PICO Dosiertechnik GmbH

Typical problems with dot dispensing

Tailing typical needle dispensing problem Tombstoning a component rises at one side during cure

because of uneven forces in the adhesive

result of an inaccurate dispense, poorly

designed process, or improperly handled materials.

Popcorning Result of air or moisture getting into the

adhesive and ‘popping’ out during the curing stage

usually results from improper handling of fluid

• r using out of date material

Satellites frequent in high speed dispensing may be caused by air bubbles Stringing break up of the adhesive between nozzle and

substrate

Consequence of too hight ejection speed for the

viscosity/cohesive strength of adhesive.

No dispense due to insufficient force next dot due to have twice nominal size)

Source: www.maths.bris.ac.uk SourceSMT magazine (4/2001)

Satellite Drop formation Tailing

Description of PROFACTOR Contactless Microdispensing System measuring set-up

Prototype implemented

Dispensing machine

DV-100 Picodostec system Contactless dispensing mode Viscosity range: 50-200.000 mPas Minimum dispensing time from 10 µs

XY Micropositioning Table

travel distance from 250 mm High accuracy Glass plate for enabling through view

USB Camera

1024x768px, 8bit

Optic

2 different telecentric objectives 5ms 10ms Exposure time 15µm 5µm Pixel Size 15/11.25mm 5/3.75mm Area T107/0.33 T50/1.0

PROFACTOR Microdispensing measuring set-up

Circular light source mounted for optimal illumination incidence angle Light difusion for enhanced light homogeneity XY Micropositioning stage integrating glass plate for enabling through view Camera and telecentric objective Drop array dispensing glass plate PICODOS contactless Microdispensing unit System Control and image processing Software Microdispensing control unit and interface Hardware

The PICODOS Microdispensing unit

The dispensing valve is actuated by two piezo-

actuators onto a rod, with a ceramic sealing ball attached to its end

Piezoactuator frequencies of up to 1000 Hz

enable dispensing amounts of down to approx. 2nl are possible

Contactless dispensing with distance of up to several centimeters (single drops or

continuous flux)

The dispensing valve integrates a heating element which allows to control the

temperature of the fluid within the needle valve (e.g. to change viscosity or attain

• perating working temperature)

PICODos dispensing valve

Microdispensing process control

The hardware developed enables remote computer control of the dispensing system and integrates galvanic isolation through 8x Optical coupling device between the computer and dispensing unit circuit (3.8 to 24 Volt)

Image processing method

Border Contrast by a total reflection light

• n the drop surface.

Sharp edge at the border of the drop

Tailing

primary beams

A challenge for image processing: Vision based analysis of transparent drops through a glass plate

Image processing Method

Illumination

• ptimized typical

Intensity profile

Imaging Manual Threshold Dilate and Erode Convolute Fill Holes Dilate and Erode

Analysis of the drops

• X,Y central position
• Perimeter & diameter
• Number of holes
• Area
• Ratio of equivalent ellipse
• Ratio of equivalent radius
• Excentricity: Outer – inner radius
• Presence and number of satellite

drops

• Statistic values
• Has the drop been adequately

dispensed?

• Are the drops homogeneous?
• Are the drops displaced from the target

position?

• Are there existing satellite drops?
• Are the drops too large or too small?
• Are there detectable faults in the

adhesive or dispensing process?

• What is the process repeatability?

The questions The answers

System control software and user interface

• System control and user

interface developed in NI LabView

• Automatic control of

positioning table and dispensing unit

• Automatic or user driven

vision based analysis of the drops

• Data exportable as excel

table

• High degree of configurability

First results

First tests – Experimental conditions

First experiments where done with oil- providing

particularly challenging conditions due to:

Low viscosity Transparency Difficulty to dispense Variability

Results of first experiments

Formation of air bubbles

The temperature increase failed to solve the

problem

Air bubbles only disappeared after few minutes The problem was solved by new optimization of

measurement set-up and program

Dynamic evolution of the drops due to low

viscosity and fluid properties (the area increased with time)

Effect was successfully measured and recorded

by PROFACTOR measuring system

Satellites were formed

Effect was detected by the measuring system and

could be corrected after readjustment of dispensing parameters

Conclusions

Conclusions

Profactor has developed in cooperation with PICO Dosiertechnik an automated system for measurement and characterization of dispensed microdrops The system has a high degree of flexibility and configurability, in order to be easily adapted to difference process conditions, fulfilling the needs of the customer. Further work is planned, in order to enable on-line measurement and integration in closed-loop dispensing processes

Acknowledgements

This work was made possible thanks to the partial support of the European Commission through the Marie Curie Actions in the 6th Framework Programme… … and to the main support and strong contribution of the company PICO Dosiertechnik GmbH.

Thank you for your attention!