Welcome to Wootton Bassett! Wave Solder by Xs89U9

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									Welcome to Wootton Bassett!
 Wave Solder Process – Back To Basics
Nigel Burtt
Production Engineering Manager
Dolby Laboratories, Inc. – European HQ




                                                                               Lead-Free Wave and
                                                                                Selective Soldering
                                                                                    Workshop
            SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007
Wave solder process timeline (single-wave)


                                                                                          Solder solidified and joint
                             Flux activated, solvent                                               formed
                              evaporated, thermal
                                shock minimised                             Solder wetting complete

        Wave solder process


                                                                     wetting time
                                                                          Dwell time

      Flux             Preheat                                                Soldering                 Cooling
     Applied
                                                                                                 Solder drainage complete
 Complete coverage of
                                            Solder contact made                   Solder contact lost
 PCB and penetration of
        PTHs



                SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007                                  2
Lead-Free No-Clean Wave Solder Process Setup –
                 Five Priorities


         1) DWELL TIME
         2) CONVEYOR SPEED
         3) PREHEAT
         4) FLUX APPLICATION
         5) SOLDER TEMPERATURE


 All these parameters need to be in balance
 - some compromises will be required


          SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007   3
 Lead-Free No-Clean Wave Solder Process Setup –
            First Priority = Dwell Time
• Set dwell time in solder wave to be within about 2-4 seconds
   • Solder wave flow both forwards and backwards over the nozzle as the
     PCB comes into contact
   • Solder flow velocity should be roughly equal to the conveyor speed
   • Dross and flux residue move away from the PCB




                 SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007   4
Dwell Time
• Solder wave height and conveyor speed control the dwell time
   • Approximately a 2-4cm solder contact window is desirable as the PCB
     passes over the wave.
   • Rough rule of thumb
           Dwell time (secs)  contact window (cm) / conveyor speed (m/min)
   • The wave surface should be exactly parallel to the PCB contact window,
     contact timing across the wave should be coincident within 0.2 seconds
   • Physical adjustment of the machine level, nozzle level and conveyor
     heights may be necessary to achieve the correct parameter balance.
   • Conveyor should present PCB to wave at an angle of around 70
                                                                                          Parallel to wave
                20-40mm


                                                    70




                 SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007                      5
Dwell Time must be optimised for each PCB design




From www.wavesoldering.com



                        SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007   6
The Importance of Parallelism




From www.wavesoldering.com



                        SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007   7
 Lead-Free No-Clean Wave Solder Process Setup –
        Second Priority = Conveyor Speed
• Set conveyor speed to between 0.7-1.5m/min
   • Setting must be carefully balanced against dwell time and preheat
     requirements for each PCB design
   • Faster = less dwell time, less preheat
   • Slower = more dwell time, increased preheat




                 SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007   8
 Lead-Free No-Clean Wave Solder Process Setup –
             Third Priority = Preheat
• Set preheaters to provide a topside temperature on the PCB of
  around 90-1300C immediately before solder contact
   • Utilise the different types of preheat available to provide an even ramp rate
   • Setting must be balanced against solder dwell time
   • Preheat requirement depends on flux type and carrier solvent
   • Also dependent on PCB thickness and/or fixture thermal mass
   • PCB underside should not exceed 1500C before the wave
   • Purpose is to activate the flux and allow it time to work
   • Also brings the PCB and components up to a suitable working
     temperature to minimise thermal shock during solder contact and to
     promote wetting during soldering
   • Important that the preheat drives off the flux base solvent, to prevent
     solder spitting during wave contact.
       • Especially for VOC-free (water-based) no-clean fluxes



                  SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007   9
 Lead-Free No-Clean Wave Solder Process Setup –
             Fourth Priority = Fluxer
• Set fluxer to give complete and uniform coverage of PCB to be
  soldered and full penetration of all plated-through holes
   • Recommended application rate is approx 75ml/cm2, but depends on flux
     type and solvent carrier.
   • Too little flux will result in bridging and other such defects
   • Too much will lead to increased residue and solder balling
   • Use old thermal transfer fax paper in a fixture to check on flux coverage




                                                                                      From www.ecd.com



                  SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007                 10
 Lead-Free No-Clean Wave Solder Process Setup –
        Fifth Priority = Solder Temperature
• Set the solder pot temperature to suit your lead-free alloy
    • For SnAg3.8Cu0.7, the melting point is 2170C, but the pot will have to run
      with superheat above this temperature to optimise the flow characteristics
      of the alloy
    • If run too hot, the topside temperature on the PCB during wave contact
      may affect SMT solder joints, even causing secondary reflow in extreme
      cases.
    • Don’t rely upon the machine thermocouple to set, use a separate
      thermocouple directly in the wave to check the solder contact temperature
      accurately.
    • Typically the running wave should measure around 2600C




                  SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007   11
  Measurement Tools
                                                                                      From www.rswww.com

From www.solderstar.com




                                     From www.intertronics.co.uk


                          SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007           12
Example of Dolby Process




           SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007   13
Wetting Test PCB as final check




  SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007   14
Any Questions?


SMART Group Technical Committee
info@smartgroup.org
+44(0) 1494 465217


Nigel Burtt - Production Engineering Manager
                                                                                        (c) SMART Group 2007
Dolby Laboratories, Inc. - European HQ                                                  We accept no liability for the
                                                                                        consequence of any action taken on
                                                                                        the basis of information provided
njb@dolby.co.uk                                                                         from us.
                                                                                        The information is provided in good
+44(0) 1793 842132                                                                      faith. Any views or opinions
                                                                                        presented to you are solely those of
                                                                                        the author and reflect their
                                                                                        understanding of current good
                                                                                        practice and their interpretation of
                                                                                        guidance, regulation and standards.



               SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007                                  15

								
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