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Click to insert title - Arial 40pt Click to insert text; use maximum 9 lines of text per slide to make easier for audience to read Use Arial font; use bo bold ld or italics for emphasis; do not use font size smaller than 24pt Limit
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■ INTRODUC ODUCTI TION ON
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■ Zero defects – Zero rework Defects found during manufacture and test Latent defects
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■ Particles on the board before solder paste ■ Damage causes by static electricity (ESD) to components and fine tracks
Major Causes of defects
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■ PARTICL ICLE E REM EMOVAL
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■ Teknek’s SMT contact cleaner has been used for many years to efficiently remove particles and increase yields
Particles
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Areas
■ SMT2017 in the SMT Process
– Clean before solder paste print – Clean after laser marking Technology
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■ STATIC TIC EN ENVIRONM NMENT ENT
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Teknek SMT Machine and static charge
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■ All components which touch the PCB during processing must have a Surface Resistance less than 109 Ohms ■ Impedance to ground must be less than 1 XXXX ■ All non-essential insulators must be removed ■ Maximum electric field strength is 125V/25mm
ANSI ESD S20.20
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■ Removal of non-essential insulators ■ Innovative grounding for rollers ■ Reformulation of Nanocleen ■ Redesign of Adhesive
Implementation of ANSI ESD S20.20
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Removing Non-Essential Insulators
Existing Perspex Window New Metal Window
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■ Challenge: rollers both have to rotate and to be pulled out of machine
Innovative Grounding
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Tribocharging
■ Silicone rollers: -120nC/J ■ Nanocleen Rollers: +40nC/J ■ Pressure sensitive adhesive: -10nC/J ■ Epoxy Printed Circuit board: -32nC ■ Silicone/ Adhesive Triboelectric gap: 110nC/J ■ Silicone/ PCB Triboelectric gap: 88nC/J ■ Nanocleen/ Adhesive Triboelectric gap: 50nC/J ■ Nanocleen/PCB Triboelectric gap:72nC/J
Measurement Ref: www.alphalabinc.com/triboelectric-series/
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■ Included additives in the formulation to reduce the tribocharging potential of the elastomer and therefore the amount of charge generated ■ Increased shore hardness of elastomer rollers to reduce contact area between the rollers and the board and between the rollers and the Adhesive surface ■ Reformulated the elastomer to increase its conductivity
Reducing Tribocharging
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Results
30v 30v 30v 30v
90V 80V 10V 10V
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Verification
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■ EO EOS Con S Conside ideration ation
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Next stage – Electrical Overstress
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ESD vEOS
ESD discharge component failure EOS Event - Latent failure
Component threshold Potential latent damage OK Fail / dead
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■ In addition to the measures taken for ANSI ESD S20.20 ■ Adding Nanoparticle additives to standard elastomer rollers to give high conductivity ■ Altering the adhesive material to give increased conductivity ■ Reformulating the adhesive to reduce the adhesive forces between the adhesive and the Elastomer rollers reducing the tribocharging ■ Removing the static bar from the exit of the machine to reduce the risk of induced current
EOS Mitigation
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Results
30v 30v 30v 30v
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■ Cas ase e Stu tudy dy
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■ Major Scandinavian Automotive electronics Manufacturer ■ Issue: Blowing of LED’s during second side cleaning when using a Teknek SMT machine with conventional elastomer rollers and adhesive. ■ Tried the ANSI ESD S20.20 verified machine and the issue disappeared but still had a concern about static levels ■ Tested the latest developments, including removal of the static bars and decided to implement the new equipment upgrade to their Teknek machines in facilities across the world.
Case Study
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