Wave Soldering 6h2b4y
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PEM Technologies BRINGING TECHNOLOGY TO THE INDUSTRY
IMPROVING YOUR WAVE SOLDERING Igmar Grewar Technical Director PEM Technologies
Wave Soldering • Conveyor • PCB transported over the wave
The 6 Basic Steps of Wave/Selective Soldering • • • • • •
Component preparation Insert components Apply Flux Preheat PCB Soldering Cool down
Preforming THT components • Cost saving • Higher production output • Quality
The effect of hole sizes • Hole size less than 1.5 times lead thickness – bend of slightly less than 90º
• A dimple is formed on the lead for hole size more than 1.5 times lead thickness
• Raised from PCB to allow for cleaning or heat dissipation
Selective Pallets
• • • • • • •
Stable platform for PCB Eliminate masking by hand Eliminate glue dotting for SMD’s Reduce solder defects such as skips and bridging Pockets and channels promotes solder flow Standardize conveyor width – reduce setup time Multiple PCB’s on a pallet – higher throughput
The Wave Soldering Process
Picture courtesy of Cobar/Balver Zinn
Fluxing Why do we need flux? • Prevents oxidation • Acts as a wetting agent
Picture courtesy of Cobar/Balver Zinn
Fluxing – Wave Solder Two common types of fluxing methods in wave soldering: Foam fluxing
Spray fluxing
Pictures courtesy of Seho
Foam fluxing – Wave Solder
Picture courtesy of Seho
• Flux control required • Ideal area = 20mm • Ideal flux stone pore size = 3um - 10um • Air pressure 2 - 3bar • Raise or lower the whole flux station to achieve the right • Never use a foam fluxer without an air knife • Not suitable for water based fluxes
Flux Control (foam fluxer) Critical parameters: • Flux density (solid content) • Water content • Temperature • Contamination from PCB or compressed air • Replace flux in foam fluxers completely every 40 hours • Cleaning of foam pipe
Spray fluxing - Wave Solder •
• •
•
Picture courtesy of Seho
•
Single side PCB requires 100 Micro Gram per Cm2 of PCB surface (Check Flux Data Sheet) PTH PCB’s will require 20% more Check the spray pattern by wrapping a piece of photo sensitive fax paper around a bare PCB and let it run through the fluxer Combination of airflow, flux flow, moving speed, distance of nozzle to PCB Paper must be evenly gray from flux, not wet and certainly not dripping
Advantages of Spray fluxing
Picture courtesy of Seho
• Quantifiable application of the flux deposit (SPC) • No in-process QC of the flux • No thinner consumption • Direct application from can • Reduced flux consumption • No flux drippings over the preheat zone
Conversion to Spray flux • The ‘Plug ’n Spray’ sprayfluxer
Picture courtesy of Cobar/Balver Zinn
• Stand alone fluxer
Picture courtesy of Seho
Incorrect Flux Volume • Too little flux can cause soldering defects such as bridging and skips
Picture courtesy of Bob Willis
Picture courtesy of Cobar/Balver Zinn
• Excessive flux can lead to solder balling and unwanted and uncured residue left on the PCB
Flux Classification - IPC-J-STD-004
Flux Types Alcohol based (100% VOC) • • • •
Long history of reliability & process know how Modest in preheat requirements Can be applied by spray or foam High residue safety and wide process window
• Hazardous & flammable material • Contributing to the "green-house" effect
Flux Types Low-VOC (40% water / 60% alcohol) • Modest in preheat requirements • Safer to the environment • Can be applied by spray or foam • High residue safety and wide process window
Flux Types Water based (100% VOC-free) • More soldering power • Environmentally safe • Non-flammable • • • •
Requires more preheat Spray fluxing only Some process adjustments required Risk for corrosion if flux is not properly polymerized by the heat of the wave (flux under pallets, on topside or just too much flux applied)
Preheat Functions of Preheating • • •
Evaporation of the solvent in the flux Activating the flux Minimizing the Delta T between the PCB and the solder wave
Picture courtesy of Cobar/Balver Zinn
Preheat Types of Preheating Infra Red elements Quartz elements
Forced Convection
Pictures courtesy of Seho
The Preheat Profile
Picture courtesy of Cobar/Balver Zinn
• • •
Preheat temperature is measured on the top side of the PCB Typical max. preheat temperature Sn/Pb = 90ºC - 120ºC Typical max. preheat temperature Pb-Free = 100ºC - 130ºC
Measuring Preheat Temperature Temperature Profiler / Thermocouples
Adhesive Temperature Strips Infrared Thermometer
Picture courtesy of TWS Automation
Picture courtesy of www.tempstrips.com
Measuring Preheat Temperature
Incorrect Preheat
Picture courtesy of Cobar/Balver Zinn
• Preheat too high or too long may break down the flux activation system and cause shorts / icicles • Preheat too low may cause problems such as skips or unwanted residues left on the PCB
Soldering Phase • Wetting Phase • Wicking Phase • Drain Phase
g
ing
in Drain
Wick
Picture courtesy of Cobar/Balver Zinn
ing Wett
W av e
- >> PCB
Soldering Phase • • • • • • • • • •
Nominal angle = 7º Width = 20 to 40mm wide for Delta Wave Width = 15mm wide for Chip Wave Dwell time Tin/Lead = 3.5 sec @ 235ºC solder pot temperature Dwell time Tin/Lead = 2.5 sec @ 250ºC solder pot temperature Dwell time Pb-Free = 2 to 5 seconds @ 260-270ºC solder pot temperature, depending on the application Conveyor speed = 0.8 – 1.5 m/min Conveyor speed (m/min) = width (cm) x Dwell time (sec) Wave height = 1/3 – 2/3 of PCB thickness High temperature glass plate is used to measure width and parallelism to the wave idth w t c a Cont
7º
Wave Nozzle Configuration Delta Nozzle • • •
Standard Nozzle for through hole components Fast moving solder moving in the opposite direction of PCB for wetting action Small volume of solder moving along with the PCB for wicking action
Picture courtesy of Bob Willis
Picture courtesy of Seho
Wave Nozzle Configuration Chip Nozzle • • • •
Turbulent wave Can be added in addition to the Delta Nozzle High Kinetic Energy Avoids shadowing
Picture courtesy of Bob Willis
Picture courtesy of Seho
Wave Nozzle Configuration Dual Wave •
• Picture courtesy of Seho
Turbulent chip wave combined with a slow moving horizontal wave overcomes the limitations of other wave types Solution for overcoming the shadow effect on SMT components not aligned to the wave
Picture courtesy of Bob Willis
Picture courtesy of Seho
Wave Nozzle Configuration Other Nozzles • For components requiring high wave pressure or high flow dynamics • For PCB’s with high thermal mass • To optimize time
Pictures courtesy of Seho
Solder Alloy Lead Containing Alloy Sn/Pb • • • • • • •
Contains Tin / Lead Sn63/Pb37 Melting point of 183ºC Solder pot temperatures from 235 - 250ºC Eutectic alloy – melts and solidifies at the same temperature Low surface tension – good wetting Low viscosity – great hole fill and top side fillet forming
Solder Alloy 4 Popular choices for Lead-Free • • • •
SAC (Tin/Silver/Copper) SAC + X (Tin/Silver/Copper + X) SnCu (Tin/Copper) SnCuNi (Tin / Copper / Nickel)
Your choice of alloy will be dependant on your specific requirements
Solder Alloy SAC • • • • • • •
Tin / Silver / Copper Typical: Sn96.5/Ag3.0/Cu0.5 Melting point of 217 - 221ºC Solder pot temperature 260ºC High silver content Solder ts looks different than Tin-Lead Dull ts due to shrinkage
Solder Alloy SAC + X • • • • • • •
Tin / Silver / Copper + X X = Co, Fe, Bi, Si, Ti, Cr, Mn, Ni, Ge, and Zn Typical: Sn98.3 Ag0.3 Cu0.7Bi0.7 Melting point of 216 - 225ºC Solder pot temperature 265ºC Lower material costs vs higher silver SAC alloys Performance and appearance similar to higher silver SAC alloys
Solder Alloy SnCu • • • • •
Tin / Copper Sn99.3/Cu0.7 Melting point of 227ºC (Eutectic alloy) No silver content - lowers alloy cost Lower tendency to leach copper - less loss of conductive copper in tracks and pads • Poor fluidity at typical lead free temperatures • Poor through-hole filling and forming of solder bridges between components
Solder Alloy SnCuNi • • • • • • • • • • •
Tin / Copper / Nickel Sn99.25/Cu0.7/Ni0.05 Melting point of 227ºC Eutectic alloy – free of shrinkage Solder pot temperatures from 265ºC Does not contain silver - running costs are low Small addition of nickel in to the SnCu alloy improves fluidity Good fluidity – less bridges and better hole –filling Dross rate equal or lower than tin-lead solder Lower aggressiveness towards stainless steel Bright smooth solder ts
Solder Bath Analysis • •
For Tin-Lead, every 3 to 6 months For Lead-Free, every 4 – 6 weeks after initial fill during the first 6 months, thereafter every 3 to 6 months is recommended
Transition to Lead Free Alloys • Higher preheat temperatures required
• Corrosion of metal parts Pictures courtesy of Seho
Solutions for Lead-Free • Pause the PCB in the preheater
• Coated parts available, pumps, solder nozzles and solder pot Pictures courtesy of Seho
Cooling Phase
Picture courtesy of Cobar/Balver Zinn
• • •
Forced cooling or not? No improvement in t quality To speed up production
Nitrogen or Not? • • • • •
Displaces oxygen Reduced dross formation Increase surface tension Improved flow of solder Better wetting
Pictures courtesy of Seho
Most common causes of problems Skips Component leads too long Insufficient flux
Bridges
Insufficient Hole Fill
Blowholes
X
X
X
X
X
X
X
X X
X X
X
X
Excessive flux Flux density too low Flux density too high
Solder Balls
X
X
X
Moisture trapped in PCB Preheat temperature too low
X
X
X
X
Preheat temperature too high
X
X
X
X
X
X
X
X
X
Conveyor angle too small
X
X
Solder temperature too low
X
X
X
X
Conveyor speed too low Conveyor speed too high
Solder temperature too high
X
Solder is contaminated Uneven or erratic solder wave
X
Solder wave height too low
X
X
X
X
X
X
X
Solder wave height too high
X
X
Solder mask properties
X
X
Poor solderability of the PCB or component
X
X
X
Thank you for your Attention Any Questions?
www.smartgroupsa.org
PEM Technologies BRINGING TECHNOLOGY TO THE INDUSTRY
www.pemtech.co.za
IMPROVING YOUR WAVE SOLDERING Igmar Grewar Technical Director PEM Technologies
Wave Soldering • Conveyor • PCB transported over the wave
The 6 Basic Steps of Wave/Selective Soldering • • • • • •
Component preparation Insert components Apply Flux Preheat PCB Soldering Cool down
Preforming THT components • Cost saving • Higher production output • Quality
The effect of hole sizes • Hole size less than 1.5 times lead thickness – bend of slightly less than 90º
• A dimple is formed on the lead for hole size more than 1.5 times lead thickness
• Raised from PCB to allow for cleaning or heat dissipation
Selective Pallets
• • • • • • •
Stable platform for PCB Eliminate masking by hand Eliminate glue dotting for SMD’s Reduce solder defects such as skips and bridging Pockets and channels promotes solder flow Standardize conveyor width – reduce setup time Multiple PCB’s on a pallet – higher throughput
The Wave Soldering Process
Picture courtesy of Cobar/Balver Zinn
Fluxing Why do we need flux? • Prevents oxidation • Acts as a wetting agent
Picture courtesy of Cobar/Balver Zinn
Fluxing – Wave Solder Two common types of fluxing methods in wave soldering: Foam fluxing
Spray fluxing
Pictures courtesy of Seho
Foam fluxing – Wave Solder
Picture courtesy of Seho
• Flux control required • Ideal area = 20mm • Ideal flux stone pore size = 3um - 10um • Air pressure 2 - 3bar • Raise or lower the whole flux station to achieve the right • Never use a foam fluxer without an air knife • Not suitable for water based fluxes
Flux Control (foam fluxer) Critical parameters: • Flux density (solid content) • Water content • Temperature • Contamination from PCB or compressed air • Replace flux in foam fluxers completely every 40 hours • Cleaning of foam pipe
Spray fluxing - Wave Solder •
• •
•
Picture courtesy of Seho
•
Single side PCB requires 100 Micro Gram per Cm2 of PCB surface (Check Flux Data Sheet) PTH PCB’s will require 20% more Check the spray pattern by wrapping a piece of photo sensitive fax paper around a bare PCB and let it run through the fluxer Combination of airflow, flux flow, moving speed, distance of nozzle to PCB Paper must be evenly gray from flux, not wet and certainly not dripping
Advantages of Spray fluxing
Picture courtesy of Seho
• Quantifiable application of the flux deposit (SPC) • No in-process QC of the flux • No thinner consumption • Direct application from can • Reduced flux consumption • No flux drippings over the preheat zone
Conversion to Spray flux • The ‘Plug ’n Spray’ sprayfluxer
Picture courtesy of Cobar/Balver Zinn
• Stand alone fluxer
Picture courtesy of Seho
Incorrect Flux Volume • Too little flux can cause soldering defects such as bridging and skips
Picture courtesy of Bob Willis
Picture courtesy of Cobar/Balver Zinn
• Excessive flux can lead to solder balling and unwanted and uncured residue left on the PCB
Flux Classification - IPC-J-STD-004
Flux Types Alcohol based (100% VOC) • • • •
Long history of reliability & process know how Modest in preheat requirements Can be applied by spray or foam High residue safety and wide process window
• Hazardous & flammable material • Contributing to the "green-house" effect
Flux Types Low-VOC (40% water / 60% alcohol) • Modest in preheat requirements • Safer to the environment • Can be applied by spray or foam • High residue safety and wide process window
Flux Types Water based (100% VOC-free) • More soldering power • Environmentally safe • Non-flammable • • • •
Requires more preheat Spray fluxing only Some process adjustments required Risk for corrosion if flux is not properly polymerized by the heat of the wave (flux under pallets, on topside or just too much flux applied)
Preheat Functions of Preheating • • •
Evaporation of the solvent in the flux Activating the flux Minimizing the Delta T between the PCB and the solder wave
Picture courtesy of Cobar/Balver Zinn
Preheat Types of Preheating Infra Red elements Quartz elements
Forced Convection
Pictures courtesy of Seho
The Preheat Profile
Picture courtesy of Cobar/Balver Zinn
• • •
Preheat temperature is measured on the top side of the PCB Typical max. preheat temperature Sn/Pb = 90ºC - 120ºC Typical max. preheat temperature Pb-Free = 100ºC - 130ºC
Measuring Preheat Temperature Temperature Profiler / Thermocouples
Adhesive Temperature Strips Infrared Thermometer
Picture courtesy of TWS Automation
Picture courtesy of www.tempstrips.com
Measuring Preheat Temperature
Incorrect Preheat
Picture courtesy of Cobar/Balver Zinn
• Preheat too high or too long may break down the flux activation system and cause shorts / icicles • Preheat too low may cause problems such as skips or unwanted residues left on the PCB
Soldering Phase • Wetting Phase • Wicking Phase • Drain Phase
g
ing
in Drain
Wick
Picture courtesy of Cobar/Balver Zinn
ing Wett
W av e
- >> PCB
Soldering Phase • • • • • • • • • •
Nominal angle = 7º Width = 20 to 40mm wide for Delta Wave Width = 15mm wide for Chip Wave Dwell time Tin/Lead = 3.5 sec @ 235ºC solder pot temperature Dwell time Tin/Lead = 2.5 sec @ 250ºC solder pot temperature Dwell time Pb-Free = 2 to 5 seconds @ 260-270ºC solder pot temperature, depending on the application Conveyor speed = 0.8 – 1.5 m/min Conveyor speed (m/min) = width (cm) x Dwell time (sec) Wave height = 1/3 – 2/3 of PCB thickness High temperature glass plate is used to measure width and parallelism to the wave idth w t c a Cont
7º
Wave Nozzle Configuration Delta Nozzle • • •
Standard Nozzle for through hole components Fast moving solder moving in the opposite direction of PCB for wetting action Small volume of solder moving along with the PCB for wicking action
Picture courtesy of Bob Willis
Picture courtesy of Seho
Wave Nozzle Configuration Chip Nozzle • • • •
Turbulent wave Can be added in addition to the Delta Nozzle High Kinetic Energy Avoids shadowing
Picture courtesy of Bob Willis
Picture courtesy of Seho
Wave Nozzle Configuration Dual Wave •
• Picture courtesy of Seho
Turbulent chip wave combined with a slow moving horizontal wave overcomes the limitations of other wave types Solution for overcoming the shadow effect on SMT components not aligned to the wave
Picture courtesy of Bob Willis
Picture courtesy of Seho
Wave Nozzle Configuration Other Nozzles • For components requiring high wave pressure or high flow dynamics • For PCB’s with high thermal mass • To optimize time
Pictures courtesy of Seho
Solder Alloy Lead Containing Alloy Sn/Pb • • • • • • •
Contains Tin / Lead Sn63/Pb37 Melting point of 183ºC Solder pot temperatures from 235 - 250ºC Eutectic alloy – melts and solidifies at the same temperature Low surface tension – good wetting Low viscosity – great hole fill and top side fillet forming
Solder Alloy 4 Popular choices for Lead-Free • • • •
SAC (Tin/Silver/Copper) SAC + X (Tin/Silver/Copper + X) SnCu (Tin/Copper) SnCuNi (Tin / Copper / Nickel)
Your choice of alloy will be dependant on your specific requirements
Solder Alloy SAC • • • • • • •
Tin / Silver / Copper Typical: Sn96.5/Ag3.0/Cu0.5 Melting point of 217 - 221ºC Solder pot temperature 260ºC High silver content Solder ts looks different than Tin-Lead Dull ts due to shrinkage
Solder Alloy SAC + X • • • • • • •
Tin / Silver / Copper + X X = Co, Fe, Bi, Si, Ti, Cr, Mn, Ni, Ge, and Zn Typical: Sn98.3 Ag0.3 Cu0.7Bi0.7 Melting point of 216 - 225ºC Solder pot temperature 265ºC Lower material costs vs higher silver SAC alloys Performance and appearance similar to higher silver SAC alloys
Solder Alloy SnCu • • • • •
Tin / Copper Sn99.3/Cu0.7 Melting point of 227ºC (Eutectic alloy) No silver content - lowers alloy cost Lower tendency to leach copper - less loss of conductive copper in tracks and pads • Poor fluidity at typical lead free temperatures • Poor through-hole filling and forming of solder bridges between components
Solder Alloy SnCuNi • • • • • • • • • • •
Tin / Copper / Nickel Sn99.25/Cu0.7/Ni0.05 Melting point of 227ºC Eutectic alloy – free of shrinkage Solder pot temperatures from 265ºC Does not contain silver - running costs are low Small addition of nickel in to the SnCu alloy improves fluidity Good fluidity – less bridges and better hole –filling Dross rate equal or lower than tin-lead solder Lower aggressiveness towards stainless steel Bright smooth solder ts
Solder Bath Analysis • •
For Tin-Lead, every 3 to 6 months For Lead-Free, every 4 – 6 weeks after initial fill during the first 6 months, thereafter every 3 to 6 months is recommended
Transition to Lead Free Alloys • Higher preheat temperatures required
• Corrosion of metal parts Pictures courtesy of Seho
Solutions for Lead-Free • Pause the PCB in the preheater
• Coated parts available, pumps, solder nozzles and solder pot Pictures courtesy of Seho
Cooling Phase
Picture courtesy of Cobar/Balver Zinn
• • •
Forced cooling or not? No improvement in t quality To speed up production
Nitrogen or Not? • • • • •
Displaces oxygen Reduced dross formation Increase surface tension Improved flow of solder Better wetting
Pictures courtesy of Seho
Most common causes of problems Skips Component leads too long Insufficient flux
Bridges
Insufficient Hole Fill
Blowholes
X
X
X
X
X
X
X
X X
X X
X
X
Excessive flux Flux density too low Flux density too high
Solder Balls
X
X
X
Moisture trapped in PCB Preheat temperature too low
X
X
X
X
Preheat temperature too high
X
X
X
X
X
X
X
X
X
Conveyor angle too small
X
X
Solder temperature too low
X
X
X
X
Conveyor speed too low Conveyor speed too high
Solder temperature too high
X
Solder is contaminated Uneven or erratic solder wave
X
Solder wave height too low
X
X
X
X
X
X
X
Solder wave height too high
X
X
Solder mask properties
X
X
Poor solderability of the PCB or component
X
X
X
Thank you for your Attention Any Questions?
www.smartgroupsa.org
PEM Technologies BRINGING TECHNOLOGY TO THE INDUSTRY
www.pemtech.co.za
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