Vapor Phase Soldering

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Vapor Phase Soldering

• by
• Uwe Filor

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Agenda

• 1. Physical principle
• 2. Soldering process
• 3. Heating transfer liquid
• 4. Machine speciality
• 5. Lead free soldering
• 6. Asscon production
• 7. Machines Batch and Inline
• 8. Void free soldering
• 9. Thombstoning reduction

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History
antiquated infrared
yesterday convection
today vapor phase
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1. Physical principle Step 1
process chamber
assembly
vapor
cooling
medium
heating elements
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Step 2
starting condensation
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Step 3
closed liquid film from medium around the
assembly
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Step 4
Assembly reached the vapor temperature and the
vapor goes over the assembly
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Step 5
End of the soldering process rest of medium
vaporize on the assembly
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Heating paramters
Controlled heating energy
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Temperature profile of a boardlead free
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Advantages of the process

• Heating up independence of form, colour, mass and
  mass distribution
• oxygen free solder surroundings without taken
  inert gas
• fixed end temperature
• free possibilities for the temperature gradient
  during heating up
• automatic recognition of soldering temperature
• void free soldering with vacuum technics
• min. temperature diffrences on the components
• optimum for lead free soldering process
• min. damage potetial of all soldering process

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2. Soldering process

• Assembly (PC board) is coming into the vapor
• Assembly is cooler than vapor, vapor reacts by
  condensing on the PC board
• A liquid film is around the whole PCB because the
  vapour is changing from the vapor back to the
  liquid form
• The thickness of the liquid film depends on the
  surface tension of the liquid
• Oxygen free soldering surrounding regarding the
  liquidfilm around the PCB, also under the
  components
• Film temperature is less than the vapor
  temperature, vapor molecules are attract by the
  film
• Recondensation is the opposite of the heating up
  process, vapor molecules coming in contact with
  the film and condensate immediately.
• Heat transfer in the film is from outside to
  inside, that means extreamly equal heating up the
  PCB through the film around

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Soldering process on a PCB
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Lineare energy connection
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End of the soldering process

• PCB temperature is the same as the film
  temperature is the same as the vapor temperature.
  Energy balance, no partial pressure slope between
  film and vapor
• No condensation of vapor molekules into the film,
  the soldering is ready.

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3. Heat transfer medium

• Perflouropolyether like a liquid polymer where
  the construction is carbon, fluorine and oxygen
• stable binding in region of the carbonchemistry
• Fluorine cover the carbonconstruction against
  chemicial and thermicial attack
• Asscon uses only high boiling Perflourpolyether
  from SOLVEY SOLEXIS with the product name GALDEN

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Characteristic of the liquid

• High temperature constancy
• Best material consistency
• High constancy against reactive chemicals
• Good dielectric characteristic
• low vapour pressure
• No flame point
• High vapour density
• Excellent heat transfer coefficient
• low surface tensions
• No problem with the protection of labour
• No chemical activity
• No ozone damage potential

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Application of the medium

• Medium for vapor phase soldering machines
• Lubricants for vacuum and high temperature
  applications
• Seal of building protection
• Seperation of medium
• Testmedium by the Burn-in-Test
• Mainsubstance of ointment and cosmetics
• Cooling medium for high speed computer
• Blood replacement substance
• Oxygen transfer medium by deep sea divers

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Heat transfer coeffiezient by diffrent heat
transfer forms

• Natural convection W / m² K
• Water 100 bis 1000
• Gas 3 bis 30
• Infrared Reflowsoldering
• heat radiation 50 bis 100
• Reflowsoldering with convection
• air 40 bis 120
• nitrogen 30 bis 110
• vapour phase - Reflowsoldering
• condensed vapour 500 bis 700

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Heat process of the liquid

• Activation of the heating, warm up the heat
  transfer liquid
• Heating up the liquid until reaching the boiling
  temperature of the liquid ( by taken lead free
  solderpaste 230C, by tin lead solderpaste 200 C
  )
• With more heat supply, there is no increase of
  the temperature, with results by changement from
  liquid into the vapour.
• The physical reason is the phase lump, as called
  enthalpy or heat of vaporization
• Example heat up 1 kg liquid there is a need of
  1x energy, heat up 2 kg liquid there is a need 2
  x energy
• Is the process chamber enough with vapor, the
  heat for the liquid is reducing

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4. Asscon machine specialities TGC Temperature
gradient controlling

• Temperaturgradient on the PCB depends on the
  supply of energy per time, that means how much
  vapour molecules per time can condensate into the
  liquid film
• Definition of the vapour molecules per time is
  defined in the enthalpy or in the heat of
  vaporization
• Adjustment of the energy can produce a defined
  quantity of vapor per time, only this quantity
  can condensate on the PCB
• Temperature gradient can be defined by the
  operator adjustment of the energy.

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Example variable temperature gradient
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Automatic recognition of the soldering temperature
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Automatic recognition of the soldering temperature
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ASB Automatic solder break automatic soldering
end recognition

• By restrict energy, the vapor stay on the same
  level as the PCB
• If the PCB and the vapor temperature is equal, no
  difference between film and vapor, the PCB is
  soldered
• No condensation of vapor
• By more vapor production is the level of the
  vapor coming up in the tank
• A sensor system recognizes that the vapor is
  coming up
• A PLC controls the sensor signal and finish the
  soldering process
• By the setpoint of the time for soldering results
  the exact temperature gradient
• If the time is to short, the system corrects
  automatically and give the operator a signal

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Temperature profile with vapor
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5. Lead free intermetalic zone

• Reduction the intermetalic zone
• example from 255 C to 220 C means 0,588 µm
  less

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Lead free profile vapor phase / convection
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Advantage vapor phase

• Temperature gradient in the peak zone is much
  more less than convection
• quantity of heat is less than convection (
  surface under the diagramm)
• no problem lead free, only change the liquid from
  200C to the higher liquid of 230 C in the same
  machine

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PCB lead free
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Batch systems

• VP 1000-33
• VP 1000-53
• VP 1000-56

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VP 1000
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Chip
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Flat Pack
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J-Leds
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Resistant
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9. Settlement for Tombstoning
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Ideale solderjoint
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Reduction of the Tombstoning

• Parameter
• F not variabel also max. in oxydfree
  solderingsystem
• G weight of the component not variable
• y lever distance on the pivot not variable
• x lever distance coming up moment variable by
  soldervolume
• Soldering defects reduction
• Reduction of the paste volume
• between 120 - 150 µm
• Reduction of the mask by little components
  between 15 - 20
• using coarse grained paste for reduction of the
  metal content in the printed paste volume
• Paste
• using delay melting paste, to quick melting of
  the paste is prevented

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Questions