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SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007 Welcome to Wootton Bassett! Wave Solder Process – Back To Basics Nigel Burtt Production.

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Presentation on theme: "SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 2007 Welcome to Wootton Bassett! Wave Solder Process – Back To Basics Nigel Burtt Production."— Presentation transcript:

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

2 SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th Dwell time wetting time Wave solder process timeline (single-wave) Flux Applied Preheat Wave solder process Soldering Cooling Solder contact made Solder contact lost Solder wetting complete Flux activated, solvent evaporated, thermal shock minimised Solder solidified and joint formed Complete coverage of PCB and penetration of PTHs Solder drainage complete

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

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

5 SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 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 mm 7070 Parallel to wave

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

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

8 SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th Lead-Free No-Clean Wave Solder Process Setup – Second Priority = Conveyor Speed Set conveyor speed to between m/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

9 SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th Lead-Free No-Clean Wave Solder Process Setup – Third Priority = Preheat Set preheaters to provide a topside temperature on the PCB of around C 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 C 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

10 SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 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/cm 2, 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

11 SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th 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 C, 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 C

12 SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th Measurement Tools From From From

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

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

15 SMART Group Lead-Free Wave & Selective Soldering Workshop Dec 5th Any Questions? SMART Group Technical Committee +44(0) Nigel Burtt - Production Engineering Manager Dolby Laboratories, Inc. - European HQ +44(0) (c) SMART Group 2007 We accept no liability for the consequence of any action taken on the basis of information provided from us. The information is provided in good 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.


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