Guide to Temperature Profiling for Wave, Reflow ... to Temperature Profiling for Wave, Reflow &...

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Guide to Temperature Profiling forWave, Reflow & Selective Soldering

29th October 2013

Bob Willis – Defect Database Coordinator

NPL Management Ltd - Commercial

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18th March 2014

Practical Failure Analysis in Electronics – How to Do It

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www.npl.co.uk/ei


Temperature Profiling Measurement

Reflow Soldering (Convection & VPS)

Wave Soldering

Selective Wave/Selective Soldering

Rework & Manual Soldering

Adhesive Curing

Conformal Coat Cure

Baking Printed Boards



Temperature Profilers

5


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

Reflow Time /179C 57.9 60.6 61.2 57.6 53.8 60.3 56.3

Peak Temp 209.7 210.6 218.7 212.9 208.6 215.2 213.2



BGA Temperature Profiles in 90’s


Process of Reflow Soldering

Product Size

Product Mass

Component Type

Printed Board Construction

Solder Paste Alloy

Flux Types

Solderability



Temperature Profiling Examples


Temperature Profiling Examples



What is a Thermocouple?

Two different materials are welded together to form a junction/bead. The two wire are insulated fromeach other to stop intermittent contact and false readings. The two wires are then covered with anouter cover. 1-60 micro volts can be produced between the wires which is converted to atemperature reading.


Example Thermocouple



Solid Sheath Thermocouple


Thermocouple Guide



Temperature Profiling Probes

Soldered Probes

Aluminium Foil

Kapton Tape

Epoxy Adhesive

Contact Probes

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Survey conducted on the SMART Group web site. Results from 63participantswho voted during the survey



Multilayer Design


Multilayer Design


BGA361

Temperature Profiling Probe Position

BGA361





Mounting thermocouple bead to component termination with high temperature solder is by far thebest technique. First mount the lead and secure with Kapton tape. Then solder the bead to thetermination. Its good practice to also secure other leads with high temp solder if the board will beused for double sided reflow profiling.








Care need to be taken that the thermocouple bead is in the solder jointand not on the surface. If the wires are twisted and touching this willalso give false random readings duringmeasurement



Temperature Profiling ProbesSelect 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.


Temperature Profiling POP Package



Temperature Profiling POP Package


Reflow Soldering & Profiling

Produce a slot in the surface of the board so that a bottommounted PoPwill remain flat to the surface of the board. Add a slot to the topmounted package to allow the thermocouple to be mounted betweenthe bottomand top packages



Reflow Soldering & Profiling

Aluminium tape can be used to hold the thermocouple in position onthe bottomand top package for accurateprofile measurement



Thermocouple leads from the printed boardassembly to the profiler should not be loose or flyingas could catch and tangle on the conveyor, linkedpin or centre board support mechanism

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



Wave Soldering Pre‐Heat

Single Sided Board 1.6mm Paper

Double Sided Board 1.6mm FR4

6 Layer Board 1.6mm FR4


Wave Soldering Temperature Profiles



Wave Soldering Pre‐Heat

Profile showing excessive drop intemperature prior to wave contact


Reflow Soldering Lead‐Free

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




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



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



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

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 240oC boiling fluid for vapour phasereflow. A fluid boiling at 240oC 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. Peterwas using a Galden HS240 fluid in a ASCON VP6000 system



Temperature Profiling

It is more complicated to profile a vapour phase system and not allprofiler suppliers have a cases suitable to protect the unit


Vapour Phase Soldering Lead‐Free Profile

Profile taken using a ECD profiler on SN100C intrusive reflow trial boards. Reflow conducted in avapour phase system at ACW in Wales with thermocouple mounted in three positions

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




Selective Soldering Trials

Pre-heating PCB assembly after fluxing (constant parameter)



Selective Soldering Trials

Soldering through hole terminations at 280oC & 320oC per alloy


4

1

23

5 6

Soldering Direction

PCB Direction

Selective Soldering Profiles



Selective Soldering Profiles

To run the animated graph you need a player from www.globfx.com/downloads/swfpoint/

Profiling Lead-Free Hand Soldering



Profiling Lead-Free Hand Soldering


Profiling Lead-Free De-Soldering


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


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


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/WorkshopsCleanliness 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


Guide to Temperature Profiling forWave, Reflow & Selective Soldering

29th October 2013

Bob Willis – Defect Database Coordinator

Guide to Temperature Profiling for Wave, Reflow ... to Temperature Profiling for Wave, Reflow &...

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Transcript of Guide to Temperature Profiling for Wave, Reflow ... to Temperature Profiling for Wave, Reflow &...