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Guide to Temperature Profiling for Wave, Reflow & Selective Soldering 29th October 2013 Bob Willis – Defect Database Coordinator Your Delegate Webin...
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Guide to Temperature Profiling for Wave, Reflow & Selective Soldering 29th October 2013

Bob Willis – Defect Database Coordinator

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Temperature Profiling Measurement Reflow Soldering (Convection & VPS) Wave Soldering Selective Wave/Selective Soldering Rework & Manual Soldering Adhesive Curing Conformal Coat Cure Baking Printed Boards NPL Management Ltd - Commercial

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Temperature Profilers

5

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Tin/Lead Reflow Solder Profile

Zone Number:

1

2

3

4

5

6

7

8

Top Set points:

110

120

120

120

145

190

245

260

Bottom Set points:

110

120

120

120

145

190

245

260

Conveyor Speed

75

Statistics Values:

TC-1

TC-2

TC-3

TC-4

TC-5

TC-6

TC-7

Max Rising Slope

1.7

1.5

1.9

1.7

1.5

1.5

1.6

Soak Time 100-120C

68.7

68.3

65.5

71

69.8

68.8

66.1

61.2

57.6

Reflow Time /179C

57.9

60.6

Peak Temp

209.7

210.6 218.7 Ltd - Commercial 212.9 NPL Management

53.8

60.3

56.3

208.6

215.2

213.2

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BGA Temperature Profiles in 90’s

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Process of Reflow Soldering Product Size Product Mass Component Type Printed Board Construction Solder Paste Alloy Flux Types Solderability NPL Management Ltd - Commercial

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Temperature Profiling Examples

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Temperature Profiling Examples

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What is a Thermocouple?

Two different materials are welded together to form a junction/bead. The two wire are insulated from each other to stop intermittent contact and false readings. The two wires are then covered with an outer cover. 1-60 micro volts can be produced between the wires which is converted to a temperature reading. NPL Management Ltd - Commercial

Example Thermocouple

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Solid Sheath Thermocouple

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Thermocouple Guide

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Temperature Profiling Probes Soldered Probes Aluminium Foil Kapton Tape Epoxy Adhesive Contact Probes Obtain this and many more NPL reports from the Defect Database http://defectsdatabase.npl.co.uk NPL Management Ltd - Commercial

Temperature Profiling Probes

Survey conducted on the SMART Group web site. Results from 63 participants who voted during the survey NPL Management Ltd - Commercial

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Multilayer Design

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Multilayer Design

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Temperature Profiling Probe Position

BGA 361

Temperature Profiling Probe Position

BGA 361

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Temperature Profiling Probe Position

Temperature Profiling Probes

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Temperature Profiling Probes

Mounting thermocouple bead to component termination with high temperature solder is by far the best technique. First mount the lead and secure with Kapton tape. Then solder the bead to the termination. Its good practice to also secure other leads with high temp solder if the board will be used for double sided reflow profiling. NPL Management Ltd - Commercial

Temperature Profiling Probes

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Temperature Profiling Probes

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Temperature Profiling Probes

Care need to be taken that the thermocouple bead is in the solder joint and not on the surface. If the wires are twisted and touching this will also give false random readings during measurement NPL Management Ltd - Commercial

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Temperature Profiling Probes Select a printed  circuit board for profiling and an area array component for testing.  Select a thermocouple lead and place on the surface of the board. Hold the lead in position  with Kapton tape. The bead is positioned on the centre pads. Solder the bead to a group of  four pads with high  temperature solder. Hold the component firmly and locate the row of balls leading to the centre position of the  component. Remove the solder balls making sure that the area to be occupied by the thermocouple bead  position is free Place the BGA on to the surface of the board making  sure that it sits flat on the pads. If the  component sits flat then remove it and flux the pads and replace the BGA Reflow the profile board, the flux will allow the solder balls to wet the pads and hold it in  position. After initial reflow place adhesive around the four sides of the component and cure the  adhesive. This will reduce the possibility of the component coming off the board even when  reflowed up side down. NPL Management Ltd - Commercial

Temperature Profiling POP Package

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Temperature Profiling POP Package

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Reflow Soldering & Profiling

Produce a slot in the surface of the board so that a bottom mounted PoP will remain flat to the surface of the board. Add a slot to the top mounted package to allow the thermocouple to be mounted between the bottom and top packages

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Reflow Soldering & Profiling

Aluminium tape can be used to hold the thermocouple in position on the bottom and top package for accurate profile measurement

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Temperature Profiling Probes Thermocouple leads from the printed board assembly to the profiler should not be loose or flying as could catch and tangle on the conveyor, linked pin or centre board support mechanism

Thermocouple leads should be bundled together using a high temperature sleeving or, alternatively, Kapton tape may be used to secure the leads

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Wave Soldering Pre‐Heat Single Sided Board 1.6mm Paper

Double Sided Board 1.6mm FR4

6 Layer Board 1.6mm FR4 NPL Management Ltd - Commercial

Wave Soldering Temperature Profiles

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Wave Soldering Pre‐Heat Profile showing excessive drop in temperature prior to wave contact

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Reflow Soldering Lead‐Free

The three row connector can be demanding thermally during intrusive reflow. The connector body and pins have different thermal demands, these are indicated by the range of temperatures from red to blue. Making successful reflow joints to meet the IPC 610 specification is fairly easy but engineers need to consider all component temperature limits and circuit board design. Pins close to the body of a connector and pin at the centre of the body will be the last to reflow in a tin/lead or lead-free process NPL Management Ltd - Commercial

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Reflow Soldering Lead‐Free

Reflow results prior to optimising the profile for the connector and increasing the  conveyor speed to improve product through put. Incomplete reflow of the solder paste is  evident in the centre of the connector and on the inner row of pins NPL Management Ltd - Commercial

Reflow Soldering Lead‐Free

Optical image after reflow before optimisation of the profile and reduction of the delta T  across the connector. The joint images from the edge to the centre show complete  reflow and progressive limited reflow of the through hole pins due to the delta T and  peak reflow temperature NPL Management Ltd - Commercial

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Reflow Soldering Lead‐Free Profiles

Profile taken using a KIC profiler on SN100C intrusive reflow trial boards. Reflow  conducted in air on a BTU reflow oven NPL Management Ltd - Commercial

To show the animated graphs use a player from www.globfx.com

Vapour Phase Reflow at ACW

Reflow of SN100C solder paste requires either a 235 or 240o C boiling fluid for vapour phase reflow. A fluid boiling at 240o C was used by Peter Barton to solder PIHR boards at ACW, Wales. ACW are a contract services provided, successfully using vapour phase for tin/lead and lead‐ free reflow. Peter was using a Galden HS240 fluid in a ASCON VP6000 system NPL Management Ltd - Commercial

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Temperature Profiling

It is more complicated to profile a vapour phase system and not all profiler suppliers have a cases suitable to protect the unit NPL Management Ltd - Commercial

Vapour Phase Soldering Lead‐Free Profile

Profile taken using a ECD profiler on SN100C intrusive reflow trial boards. Reflow conducted in a vapour phase system at ACW in Wales with thermocouple mounted in three positions NPL Management Ltd - Commercial

To show the animated graphs use a player from www.globfx.com

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Selective Soldering Trials

Pre-heating PCB assembly after fluxing (constant parameter) NPL Management Ltd - Commercial

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Selective Soldering Trials

Soldering through hole terminations at 280oC & 320oC per alloy NPL Management Ltd - Commercial

Selective Soldering Profiles

6

5

4

3

Soldering Direction PCB Direction

2

1

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Selective Soldering Profiles

To run  the animated graph you need a player from www.globfx.com/downloads/swfpoint/ NPL Management Ltd - Commercial

Profiling Lead-Free Hand Soldering

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Profiling Lead-Free Hand Soldering

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Profiling Lead-Free De-Soldering

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Temperature Profiling for Curing

Examples of coated boards after coating cure, also examples with too faster cure cycle well outside of the supplier recommendations for the ideal profile

Drying Oven/Cabinet/Enclosure

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Conformal Coating UV Inline Cure

In line curing systems can use mesh belt or pin transfer systems depending on the type of coating method and materials used in the production process

Conformal Coating Temperature Profile

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Acknowledgements

Alstom Power Conversion BTU Datapaq ECD Fujitsu KIC (Link Hamson) Loctite Multicore Roke Manor Research

Obtain this and many more NPL reports from the Defect Database http://defectsdatabase.npl.co.uk

NPL EI  Free Technology Webinars/Workshops Cleanliness Assessment Using Solvent Extract & Ionic Extraction to Improve Reliability

3rd December 2013 How to Test and Qualify Packages with Scanning Acoustic Microscopy (SAM) 4th February 2014 Effectiveness of Baking to Remove Moisture from Between PCB Ground Planes 18th March 2014 Practical Failure Analysis in Electronics – How to Do It 14th May 2014 Solderability Assessment ‐ Testing, Ageing and Practical Impact on Assembly Yield 10th June 2014

www.npl.co.uk/ei NPL Management Ltd - Commercial

Visit our web site www.npl.co.uk/ei

Guide to Temperature Profiling for Wave, Reflow & Selective Soldering 29th October 2013

Bob Willis – Defect Database Coordinator

Visit our web site www.npl.co.uk/ei