SMTA Southeast Asia Technical Conference April 15-16, 2015

ELECTRONIC CLEANING FLUID ADVANCEMENTS Presented By Jason Chan Kyzen Corporation

Introduction Electronic Hardware Innovations Problem Statement Exposed Metal Corrosion Potential Advanced Cleaning Agent Designs Experimental Inference from Data Findings Matching Cleaning Agent to the Process Agenda

INTRODUCTION

More interconnects Higher density Tighter pitch Low standoffs Mixed metals Modern Electronics

Residue trapped under BTCs Ionics in flux residue can exacerbate – Contamination levels under part – Flux Bridging – Creation of high resistance shorts across pads Insufficiently Cleaned Component

Surface - Yes / BTC - No Looks Can Be Deceiving Parts Removed with Heat Only Residue Pool Across Pads!!!

Dendrites (in Electronics) – Metallic tree-branch-like projection that passes current along an unintended path – Typically Constructed of Metal Ions How Dendrites are Formed/Grown Leakage Currents PCB Liquid Carrier Applied Voltage Migrating Metal Ions Metal Ions Board Terminations

Harder to clean Longer time in wash May impact metal and material compatibility Cleaning Highly Dense Assemblies

ELECTRONIC HARDWARE INNOVATIONS

Challenges – Processor and memory functions – Electronic interconnection system – Cleaning process Substrate – Key enabler – Array configured packaging – Smaller footprints – Progressively smaller outline – Mixed metal exposure Increased Signal Speed

Mixed Metals – Cu / Al / SAC LEDs

Al/Cu Pads

Copper Wire Bonds

Copper Pillar

Memory

PROBLEM STATEMENT

Require specialized materials Different alloy combinations The problem is some reactive metals exposed to the cleaning process can be Oxidized Etched Attacked There is a need for advanced cleaning fluid designs that are – Multi-metal safe – Effective at cleaning soils Electronic Circuit Innovations

EXPOSED METAL CORROSION POTENTIAL

Can affect exposed metals – Electrochemical deterioration – Chemical attack May affect – Reliability – Uninterrupted operation of electric components Harsh Cleaning Agents

4 essential factors – Anode – Cathode – Electrical connection between cathode and anode for the electron current flow – Electrolyte to facilitate ionic movement Corrosion Theory

Anodic reaction – Metal dissolution – Formation of electrons Cathodic reaction – Metals attracted to cathode – Metal forms a dendrite and grows toward anode Charges are balanced Tighter spacing increases risk of dead short Anodic / Cathodic Reaction

1.Change to a more suitable cleaning agent 2.Modifications to the environment 3.Use of protective coatings 4.Application of cathodic and anodic protection 5.Design modifications to the system or component Minimizing Corrosion Failures

ADVANCED CLEANING FLUID DESIGNS

Material Compatibility Factors

SOLVENTACTIVATORBUFFER SURFACTANT INHIBITOR Cleaning Fluid Technology Cleans Soils Material Compatibility Wide Process Window Low Cost of Ownership Removal of soils under BTCs No attack to exposed metals Dissolves Contaminants Softens contaminants for better dissolving in the solvent Maintains a very stable pH Reduces the surface tension for better penetration Protects all sensitive metals from corrosion or etch

Important driving force for o Solvating non-polar resins, rosin, and polymers Rate of dissolution depends on … o Matching up to the flux residue o Wash concentration o Wash temperature o Wash time o Impingement energy Solvency

Organic or Inorganic compounds with functional groups – Containing a polar atom – Weak or strong base Activators

Van der Waals force – Attractive / Repulsive forces between molecules – Example: Rosin flux reacts with a basic cleaning solution Converts rosin into a water soluble soap London Dispersive force – Intermolecular force – Induces a dipole / dipole interaction – Example: Induces a dipole on non-polar no clean flux residues to improve dissolution Activator Drivers

Strongly buffered solutions increase bath life Bath Life

Multi-functional ingredients that – Lower surface tension – Wet the surface Needed to penetrate low gaps – Detergency Hydrophobic ~ non-polar loving Hydrophilic ~ polar loving Surfactants

Improves the ability of the cleaning agent to penetrate and wet soil Wetting DI Water Cleaning agent in DI Water

Corrosion Mechanism Metal surface immersed in an electrolyte – Alkaline cleaning agent in water – Metal ions tend to be lost from the metal into the electrolyte – Leaves electrons behind on the metal – Continues to occur until the metal reaches its equilibrium potential – Longer exposure results in more and more metal ions being lost, resulting in continuous corrosion of the metal

Corrosion Inhibition 1. Inhibitor is adsorbed on the metal surface – Process of chemisorption / physisorption – Forms thin protective film in conjunction with metallic ions 2. Protective film over the metal – High solids rosin flux coats alloy during cleaning 3. Inhibitor ties up corrosive substance in water

EXPERIMENTAL

SEM analysis of – SAC 305 – Ni layer – Cu Pillar – Al Pad 10 min. soak 7% 60˚C Copper Pillar Die Selected

Cleaning Agents Evaluated

Cleaning Agent #1

Cleaning Agent #2

Cleaning Agent #3

Cleaning Agent #4

Cleaning Agent #5

Summary of Data Findings

INFERENCES FROM DATA FINDINGS

Equilibrium phase in an aqueous solution – No reaction – Immunity / Passive range Metals can react based on – pH of the solution Some metals are more reactive Some stable at different pH levels Some react with water Other react slowly in water – Vigorously with acid or bases Metals

Al pad is the most reactive metal Al reacts with acids and bases – Stable oxide or coating reduces attack SAC305 – Pitting corrosion from highly basic solutions Cu Pillar – Oxidizes from highly basic solutions Ni – No effect from highly basic solutions Copper Pillar Die

Adsorbs on the metal surface – Forms a protective film Form an oxide on metal – Protective film reduces corrosion effect Improves immunity Alloy specific Corrosion Inhibition

Improve cleaning effects – Attractive forces – Oxidation / Reduction – Induces a Dipole on No-Clean flux residues In the absence of these attractive forces – Reduces cleaning effects – Some soils not cleanable in an aqueous solution Low levels reduces bath life Polar Activators

Industry standards – Excellent cleaning on all soil types – Engineered Corrosion Inhibition Data Finds – Good Compatibility SAC305 Ni Cu – Corrosion potential found on Al Cleaning Agent 1 & 3

Neutral range cleaning agents – Low Levels of Polar Activators – Less Reactive to Exposed Metals – May not be as effective on some flux residues – Bath life will be shorter Data Finds – Good Compatibility SAC305 Ni Cu Al Cleaning Agent 2 & 5

Saponified cleaning agent – High levels of polar activators – Greater potential to attack exposed metals Data Finds – Good Compatibility Ni – Poor Compatibility SAC305 Cu Al Cleaning Agent 4

MATCHING CLEANING AGENT TO THE PROCESS

Engineered cleaning agent matched to – Part being cleaned – Soils – Cleaning machine Key factors – Exposed metals – Interaction potential with the cleaning process – Residue properties – Cleaning machine – Z-Axis under Bottom Termination – Advanced Cleaning Fluids design to clean under these factors Matching Cleaning Agent to Process

Thank You 54 Dr. Mike Bixenman CTO, Kyzen Corporation Jason Chan Technology Manager, Asia Haley Jones Chemist Chelsea Jewell Science/Application Technician TC Loy Sales Mgr. Malaysia