rework profiles

7/21/2019 Rework Profiles

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RexPaulMark Todd



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Outline

q Thermal Quality Management (ThQM)

q Solder paste requirements

q Generating the Oven Recipe

q What’s needed to Profile

q Determine points to profile

q Attaching the T/Cs

q Performing the Profile



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Thermal Quality Management

Stage 1 Define RequirementsW h y d o w e p r o f i l e?

– Identify heat sensitive components

– Choose soldering technology

Stage 2 Machine Recipe DevelopmentW ha t i s t h e o v e n r e c i p e ?

– Develop machine settings required for production thatmeet the above requirements

– Assure all solder joints experience the requiredtemperature profile

– Assure sensitive components do not experience longterm damage

Stage 3 Collect DataH o w a r e w e d o in g ?

– Assure the temperature profile developed duringcharacterization is being repeated

– Proof your thermal process is in control

To Reduce Scrap and Increase Yields



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ThQM Definitions

Profile – The graphical plot of temperature as a function of time, asmeasured by one or more thermocouples at points of interest on a PCB

Recipe – Oven settings required to produce the desired profile

Temp

ºC

Time

• Zone set point

temperature

• Conveyor

speed

• Convection rate



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Solder paste requirements



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Solder paste requirements

RSS – “Ramp Soak Spike” profile

RTS – “Ramp to Spike” profile

Temp

ºC

Time

RSS

RTS



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Solder paste requirementsRamp – slope ºC/sec

Soak – time sec

Spike – slope ºC/sec

Time Above Liquidous (TAL) – time sec

Peak – temperature ºC

Cooling – slope ºC/sec

Ramp

Begin Temp

End Temp

Spike

Peak

Cooling

SoakLiquidous Temp

TAL

What makes a good profi le

Red = KPI



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Generating the Oven RecipeInitial recipe – Where do you start?

Software generated recipe

• Based on similar board profile characteristics

• Based on the oven characteristics

Your own recipe experience

• Use a recipe which solders a board of similar size or component density

Best to “under shoot” zone temperature set points rather than over shoot

• Lowers the risk of destroying the board

• It take less time raise the oven’s temperature then to lower it



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Generating the Oven RecipeInitial recipe – What can you control?

Three basic controls

1. Zone Temperature – Controls the profile slope in that zone

• Higher temp increases heating rate• Lower temp reduces heating rate

2. Conveyor Speed – Controls the time spent in ALL Zones

• Slower speed increases the time in all zones

• Faster speed decreases the time in all zones

3. Convection Rate (option) – Controls the flow of heat in ALL zones

• Higher rate increases heating rate at the same temp set point

• Lower rate decreases heating rate at the same temp set point

• Higher rate reduce temp differences between components



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Generating the Oven RecipeInitial recipe – Suggestions

Zone 1 2 3 4 5 6 7 8 9Leaded 150 170 180 180 180 180 205 235 250

No-lead 150 165 180 200 205 230 245 260 270

Conveyor 32 in/min



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What’s needed to ProfileWhat’s needed to prof ile1. Product to profile

2. Thermocouples

3. Profiler

4. Thermal protective barrier5. Carrier for the profiler

6. T/C attachment solder or tapes

7. Soldering iron

8. Solder wick

9. Gloves

10. Cooling fan



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Determine points to profileComponents at risk (J-STD-075)

• Capacitors: Aluminum Electrolitic, Film, Tantalum

• Crystals; Oscillators and Resonators

• Fuses

• Inductors and Transformers

• Non-Solid State Relays

• LEDs

• Connectors

• Switches



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Determine points to profileIdentifying the trouble spots

Conveyor

Direction



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Methods – Solder

High Temp Solder

• SN10 ~ 280 ºC Melting point

• SN5 ~ 305 º C Melting point

• Au80 ~ 280 º C Melting point

4000.00 / lb

Attaching the T/Cshttp://www.ecd.com/blog/index.php/category/thermocouple-attachment/

http://www.ecd.com/blog/index.php/category/thermocouple-attachment/




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Methods – Solder

1. Wick up old solder

2. Add SN5 to T/C

3. Tape down T/C

4. Touch with solder iron

5. Add a little more solder

6. Done!

0.02”






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Attaching T/Cs – Where is it?

PCB

T/C

PCB

T/C

PCB

T/C

OK

OK

OK



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Methods – Tapes and glues Aluminum Tape (Silicone adhesive)

Pro – Conforms to T/C

Pro – Hold its shape

Con – You can’t see through it

Kapton® Tape (Silicone adhesive)

Pro – You can see through it

Con – Does not hold it shape





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Methods – Tapes and gluesEpoxy® (Hi Temp)

Pro – Holds well

Con – Adds insulation

Con – Requires curing (time or UV)

AttachEZ™

Pro – Conforms to T/C

Pro – Reusable!

Con – Semi transparent







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Attaching Thermocouples - BGAs

1. Pre-drill before BGA is placed

2. Post-drill after BGA is soldered

3. Use an existing via Epoxy® Fill

BGA

PCB

Via

T/C 36 to 40ga



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Performing the ProfileLoading the Board and Profiler



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Off Loading the Board and ProfilerPerforming the Profile



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Cooling for the next runPerforming the Profile



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Checking the resultsPerforming the Profile

Ramp

Spike

Peak

Cooling

Soak

TALBegin Temp

End TempLiquidous Temp



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Performing the ProfileUse software tools to "predict" a better recipe

Prediction using actual product profiles is best because it …

… uses the actual oven recipe and its performance (Machine)

… is the actual profile of components or solder joints (Assembly)

… lets you adjust the profile to the desired specification (Process)

… assures your predictive changes will be accurately reproduced

ECD – U Classes MAP 101 or Profiling 201



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Summary

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q ThQM – Thermal Quality Management

q Solder paste requirements

q Generate an oven recipe

q What you need to profile

q Determine what points to profile

q Attach the T/Cs

q Perform a profile



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Thank you for attending today’s class

Questions? Contact: [email protected]

ECD-U Class List: www.ECD.com/ECDU

ECD Sales/Support: 503-659-6100

mailto:[email protected]

http://www.ecd.com/ECDU

http://www.ecd.com/ECDU

mailto:[email protected]



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Common questionsCan zone temperature setting fix this problem?

• Increasing the set point temp will raise both peaks

• Increase convection and lower the temperature set point

• Add a thermal shield to the hotter profile part

What causes components or traces to heat at different rates?

• Not because of their size or thermal mass

• Mostly because of their thermal resistance to heat flow

How does convection help heat different parts more equal?• It applies heat to the entire surface more or less equal

• Forced air convection is a continuous source of freshly heated air

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