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Using the latestadvancements ininjection molded
thermally conductive plasticsLATI Industria Termoplastici S.p.A.
Business Development Unit
September the 12th, 2018
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LATICompounding solutions
LATI is a family-owned independent compounder based in Italy.In thermoplastics since 1945.
LATI portfolio:reinforced, flame retardant andspecial purpose grades.
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ELECTRICAL(45%)
TELECOMUNIC.(1%)
APPLIANCE(20%)
TRANSPORTS(20%)
INDUSTRIAL(7%)
BUILDING ANDFURNITURE (7%)
MEDICAL(1%)
Export: >70% of LATI’s business
LATIMain markets
Thermally Conductive Compoundsand heat management
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LATI Industria Termoplastici S.p.A.Business Development Unit
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Since 2003Thermally conductive compounds (TCCs)
First industrial products: year 2003First industrial application: LED modular lamp, year 2005
PA12 – 85% ceramic
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21st Century technical megatrends Managing heat build-up
Electronic miniaturization Weight reduction
Function integration Complex designCost reduction
Heat build-up Reduce number of materials
Smart designMetal replacement
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Booming industrial sectorsDissipate heat, work better
Enhanced connectivity
Electric automotive
Automation
Reducing local temperature increases performance and expected lifespan of electronics.
LED market2016 – 2 B€
2023 – 23 B€
LED lighting
Plastics vs. MetalsConduction, convection, radiation
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Metals offer higher thermal conductivity than plastics, but…
…thermal conductivity above 10 W/mK can be redundant in case of natural convection/radiation.
heat sink
heat spreader
dielectric tape
LED source
PCB
Conduction
Radiation
Convection
Plastics vs. MetalsTCCs manufacturing – a complex process
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Base resin intrinsic limits
Conductive fillers content
Particle dispersion
Property compromise
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Ceramic based
Thermal conductivity up to 10 W/mKElectrically insulative
Excellent dimensional stabilityFlame retardant versions
accepts inserts can be coloured
medical grades
LATICONTHER CPCeramics
clean: no sloughing
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Graphite based
Thermal conductivity up to 20 W/mKElectrically conductive
Excellent price/performance ratioEasy processing, good flowability
fill tiny features epoxy paintable
accept inserts can be machined
LATICONTHER GRGraphite
Plastics vs. AluminiumAdvantages of TCCs
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Less energy consumption, smaller
carbon footprint
Very low density
Complex design and function integration
No post-processing (painting, de-flashing,
machining etc.)
Colourable, chemical and corrosion resistant
Know your TCC
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Learn by doingCorrect approach, winning solution
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TCCs are not aluminum “drop-in”
Correct design requires specific knowledge
Proper moulding requires some dedicated practice
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TCC fundamentalsFillers = thermal performance
Ceramics show a rather low aspect ratio.TCC featuring ceramic fillers feature isotropic thermal behaviour.
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TCC fundamentalsFillers = thermal performance
Assuming one single value for thermal conductivity is an acceptable compromise in plane
through plane ~ 1
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TCC fundamentalsFillers = performance
TCCs featuring graphite or boron nitride show strongly anisotropic thermal behaviour because of orientation of
conductive flakes during cavity filling.
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TCC fundamentalsFillers = thermal performance
In plane vs. through plane ratio deserves accurate consideration when modelling.
in planethrough plane >> 1
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TCC fundamentalsFillers = performance
TCC featuring flake-shaped fillers may require a better description of local thermal properties.
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1 - Measuring conductivity
In plane (kx,y) and through plane (kz) thermal conductivity have to be measured as per ASTM E1530 and E1461-92 standards.Suitable specimen are prepared using injection moulded plates.
Values from TDS LATICONTHER 62 CP6/650-V0HF1
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Particle orientation is affected by wall thickness.Effects of moulding parameters (e.g. packing pressure) are less relevant.
1 - Measuring conductivityEffects of geometry and moulding
Z
X
Ywal
l thi
ckne
ss
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• Conductivity through plane increases with wall thickness;
• Conductivity in plane decreases with wall thickness;
In this case, kx ≈ ky > kz
k in plane / k through plane > 10
Random orientation becomes more and more important above 4-5 mm thickness.
1 - Measuring conductivityFlakes: effects of geometry and moulding
Walls thickness
in plane
through plane
Designing with TCCs
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2 - DesigningHow and why: an exercise
LED projector2xLED COB, 25W eachopen air 25°C, free convection
Heat sink: 250x150x60 mmAverage thickness > 4mm
Material: PA6 50% graphite
Let’s try to evaluate temperature distribution on the heat sink of a 50W COB LED lamp:
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Step 1 – part geometry and boundary conditions:
2 - DesigningGeometry
Convection only: Tenv = 25°C;
Convection and radiation: Tenv = 25°C;
Heat applied: Power = 50W, with spreader
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Step 2: use adimensional numbers according to heat transport physics to obtain an acceptable evaluation of geometry capabilities.
2 - DesigningEvaluating feasibility – adimensional numbers
Description Parameters - Base Symbol Value Units
Base Width WB 0.176 m
Base Length LB 0.25 m
Base Thickness tB 0.008 m
Base Thermal Conductivity kB 8 W/mK
Base Emissivity εB 0.87 -
Base Max Temperature TB 80 °C
Power to dissipate QB 50 W
Fin / Pin efficiency
Description Parameters - Fin / Pin Symbol Value Units
Fin Width (Thickness) WF 0.004 m
Fin Length = LB LF 0.25 m
Fin Height HF 0.04 m
Number of Fins on Base Width NF 13 -
Fins Frozen Layer Guestimation TFL 10%
Distance between fins = (WB-WF*2)/(NF-1) 0.012 m
Fin Thermal Conductivity, Longitudinal kF,L 15 W/mK
Fin Thermal Conductivity, Transversal kF,T 1.2 W/mK
Fin Emissivity = εB εF 0.87 -
Fin Efficiency (Viewfactor approximation) ηF 0.076923 -
Description parameters - Environment (Fin Side) Symbol Value Units
Ambient Temperature TA 25 °C
Boundary conditions,material properties andgeometry description.
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Step 2: calculate heat transfer coefficient hconv for convective regime.
2 - DesigningEvaluating feasibility – adimensional numbers
)( ambpconvconv TTAhQ
Derived Parameters - Environment Symbol Value Units
Average Heat Transfer Coefficient = Nu*k/HF h 7.833 W/m2K
Derived Parameters - Assembly Symbol Value Units
Convective fin Heat Transfer = AF,S*ηF*h*(TAVG-TA) Qconv, F 45.53 W
Convective base and top fin Heat Transfer = AB*h*(TAVG-TA) Qconv, B 17.98 W
Radiative fin Heat Transfer = σ*ηF*AF,S*εF*(TAVG4-TA
4) [T in K] Qrad,F 7.06 W
Radiative base and top fin Heat Transfer = σ*((AB-AF,T)*εB+AF,T*εF)*(TAVG4-TA
4) [T in K]Qrad,B 15.54 W
Total Heat Transfer = Qconv+Qrad Qtot 86.10 W
)( 44ambprad TTAQ
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Step 3: run finite element analysis to evaluate part performance in actual working conditions (environmental temperature etc.).
2 - DesigningEvaluating feasibility - FEA
An aluminium spreader can be introduced simulating heat sink – PCB interface.
Test A: homogeneous isotropic thermal behaviour of TCC (10 W/mK).
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Step 3: results indicate temperature distribution (steady state).
2 - DesigningEvaluating feasibility - FEA
Test AIsotropic thermal conductivity,
natural convection
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Step 3: test B, run finite element analysis introducing radiation as well.
Heat removal by radiation can be quite relevant (>50% total).
2 - DesigningEvaluating feasibility - radiation
Qin
Qrad
Qconv
)( ambpconvconv TTAhQ
)( 44ambprad TTAQ
Wall temperature Room temperature
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Step 3: contribution of radiation can be remarkable, specially for those geometries offering favourable view factors (surface exposure to radiation).
2 - DesigningEvaluating feasibility - radiation
Test bIsotropic thermal conductivity,
natural convection,radiation.
Fins offer poor view factor, radiation contribution may be low here.
Free faces radiate.
Improvement.
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Step 4: simulating flake orientation and local thermal performance.
2 - DesigningEvaluating feasibility – introducing flakes
Flake orientation is obtained by fluid-dynamic FEA simulating mould filling.
Actual viscosity and PVT curves of PA6 50% graphite available in MOLDEX3D-LATI database
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Fibre orientation tensor is used to evaluate deformation of part geometry and local mechanical performance.
Isotropic mechanical behaviour would lead to wrong assumptions.
What about thermal properties?
2 - DesigningOrientation matters
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Flakes orientation data are calculated on every element of the 3D mesh…
2 - DesigningEvaluating feasibility – introducing flakes
Orientation parameters can be mathematically processed to obtain a rough but reliable indication of local thermal conductivityFlake orientation parameter
Flake: disk, diam./thick. = 10
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Flakes orientation details describe local behavior (section cut – orientation normal to plane).
2 - DesigningEvaluating feasibility – introducing flakes
Y direction shows strong orientation along fins plane
Z direction shows strong in-plane orientation on the heat-sink base
Z Y
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Flakes orientation data can be used to evaluate local thermal conductivity values.
2 - DesigningEvaluating feasibility – introducing flakes
local thermal conductivity is translated into a specific material identity card associated to each 3D mesh element.
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Thermal FEA using local conductivity data provides a more accurate temperature distribution.
2 - DesigningEvaluating feasibility – introducing flakes
Test CLocal thermal conductivity,
natural convection.
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2 - DesigningEvaluating feasibility – confronting results
Test CLocal thermal conductivity,
natural convection.
Test AIsotropic thermal conductivity,
natural convection.
~ 45°C~ 41°C
Temperature distribution, re-scaled range 40-52°C
Enhanced contribution of fins
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2 - DesigningEvaluating feasibility – confronting results
Test CLocal thermal conductivity,
natural convection.
Test AIsotropic thermal conductivity,
natural convection.
Contribution of fins
~ 49°C~ 52°C
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2 - DesigningEvaluating feasibility – confronting results
Contribution of fins is evidenced in Test C. Flake orientation enhances heat distribution along fins.
Test CTest A
Evaluation of local thermal conductivity improves by far with mesh quality.
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3 – Other fundamental factors must be kept into consideration when designing TCC parts.
2 - DesigningNot only thermal performance
Mould layout and draft angle
Moulding equipment
Geometric features
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Deformations can be a major issue leading to poor matching between heat source and sink. Failure follows.
2 - DesigningNot only thermal performance
Warpage due to major geometric flaws in fins layout.
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Sink marks are an often neglected issue leading to poor contact between heat source and sink. Failure follows as well.
2 - DesigningNot only thermal performance
Sink mark generated by wrong fins/base thickness ratio
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This geometry features very thin walls and thicker fins.
2 - DesigningNot only thermal performance
This radiator features a thick base but fins may be too large and narrow.
TCCs as aluminum drop-in? No! Design should be optimized for TCCs…
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2 - DesigningNot only thermal performance
Pins can work better than fins once their aspect ratio and taper has been properly tuned
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3 - ConclusionsExpanding application fields
TCCs can today be used in demanding applications, but accurate design is mandatory.
The case study used in this presentation is similar to an actual industrial product available on the market.(CASTOR 2M by Electromagnetica)
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3 - ConclusionsExtended play
Proper simulation, design and moulding may allow dispersion of higher power (> 1kW).
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Any Questions?…
Thanks for your attention!
LATI Industria Termoplastici S.p.A.Business Development Unit
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