Advancements in Thermal Management at PCB … · for Electronics Design and Fabrication Presented...

Advancements in Thermal

Management at PCB Level

for Electronics Design and

Fabrication

Presented By:

Pratish Patel

Electronic Interconnect

www.eiconnect.com

[email protected]

1

http://www.eiconnect.com/

Table of Content

Challenges of the Electronics

CFD Analysis under Natural Convection

between FR4 and MCPCB.

Design Guidelines

Fabrication Guidelines

Question and Comments.

2

Challenges of the Electronics

The electronics Industry today is facing challenges such as

HOT SPOT

CTE mismatch,

solder joint stress,

thermal fatigue failure

shock and vibration issues,

“SMALLER, FASTER, STRONGER”

3

Challenges of the Thermal Management

Improve thermal performance for reduced junction temps

Heat sink design with optimized performance to weight ratios

Increase color quality and light output

Increase product lifespan

Increase energy efficiency

Save material cost by optimizing material usage

Decrease UL failures with better designs the first time

Eliminate color shift

4

A comparative study between

FR4 and other PCB’s using

CFD Analysis under Natural

Convection.

Case Study

5 5

To conduct a comparative study between FR4 and other

PCB’s using CFD Analysis under Natural Convection.

Four separate boards (FR4, Laird’s Metal clad1KA) with

different thermal conductivities were modeled.

Two different heat sources were provided to each LED (0.06

W & 0.2 W).

48 LED’s were populated on each PCB.

Two heat sink designs were proposed for each LED wattage

type (0.06 W & 0.2 W).

The ambient temperature for each model was 250 C.

OBJECTIVE

6

Thermal Model Layout

Simplified Thermal Model

Thermal Analysis 1:

- Four different PCB’s (LED = 0.06 W)

Thermal Analysis 2:

- Heat Sink Design for eight PCB’s (LED = 0.06 W)

Thermal Analysis 3:

- Four different PCB’s (LED = 0. 2 W)

Thermal Analysis 4: - Heat Sink Design for Four PCB’s (LED = 0.2 W)

Results & Conclusion 7

OUTLINE

Thermal Model Layout

Copper (k=380 W/m-K; t = 2 oz or 0.03 mm)

PCB (variable k & t values)

AL5052 (k=132 W/m-K; t = 1.5 mm)

The thermal conductivities and

thicknesses of each layer is provided

above.

PCB thickness and thermal

conductivity was variable in each

model.

FR4, 1KA, LLD, HTD, MP, NRA-8, TCB-2 & 92ML

8

Simplified Thermal Model

• The thermal model was simplified

to acquire the satisfactory results.

• In natural convection, radiation has a very important role in heat transfer. • The size of each LED was 0.25 mm 0.64 mm and the minimum radiation surface tolerance acceptable by CFD tool (Flotherm)

was 1mm (due to computer

hardware limitations), therefore, a single heat source was created to Single Heat Source

(LED) incorporate the effect of radiation.

• 48 LED’s were modeled as single

heat source with total wattage of 48

0.06 = 2.88 W & 48 0.2 = 9.60 W

9

Thermal Analysis 1:

PCBs with LED of 0.06 W

10

Thermal Analysis 1 Data

Table I

PCB with LED Wattage of 0.06 W

Boards FR4 1KA LLD HTD

Thickness (mm) 0.1 0.1 0.1 0.1

Thermal Conductivity (W/m-K) 0.25 3.0 2.0 2.2

LED Max Temp ( C) 95.7 92.7 92.8 92.8

Thermal Gradient ( C) 0.0 3.0 2.9 2.9

11

8

Thermal Analysis 1 - FR4 Board Temp Profile

LED Max Temp = 95.7 OC 12

Thermal Analysis 1 - 1KA Board Temp Profile

LED Max Temp = 92.7 C 13

Thermal Analysis 2:

PCBs + Heat Sink with LED of 0.06 W

14


Table II

PCB with Heat Sink for LED Wattage of 0.06 W


Thickness (mm) 0.1 0.1 0.1 0.1


LED Max Temp ( C) 70.5 67.1 67.2 67.2


15

Thermal Analysis 2 - Heat Sink Design

• Dimensions = 44.0 38.0 mm 16.0 mm

• Base Thickness = 3.0 mm • Fin Thickness = 1.0 mm • # Fins = 7 18

Thermal Analysis 3 :

PCBs with LED Wattage of 0.2 W

19


Table III

PCB with LED Wattage of 0.2 W


Thickness (mm) 0.1 0.1 0.1 0.1


LED Max Temp ( C) 203.0 193.0 194.0 194.0


20

Thermal Analysis 4:

PCBs + Heat Sink with LED 0.2 W

23

26


Table IV

PCB with Heat Sink for LED Wattage of 0.2 W


Thickness (mm) 0.1 0.1 0.1 0.1


LED Max Temp ( C) 75.0 65.3 65.6 65.4


24

Thermal Analysis 4 - Heat Sink Design

• Dimensions = 100.0 100.0 mm 28.0 mm

• Base Thickness = 3.0 mm • Fin Thickness = 1.0 mm • # Fins = 12

27

Results & Conclusion

Table V Thermal Analysis Data - LED Max Temp with Heat Sink

Set FR4 1KA LLD HTD MP NRA-8 TCB-2 92ML Note

Thickness (mm) 0.1 0.1 0.1 0.1 0.075 0.08 0.08 0.1

Thermal Conductivity 0.25 3.0 2.0 2.2 1.3 2.0 2.0 2.0 (W/m-K)

LED Max Temp ( C) 70.5 67.1 67.2 67.2 67.3 67.1 67.1 67.2 For 0.06 W LED & 44 38 16

Heat Sink

LED Max Temp ( C) 75.0 65.3 65.6 65.4 65.7 65.1 65.1 65.6 For 0.2 W

LED & 100×100×28

Heat Sink

28

Note: This thermal analysis is for the comparative study and not to consider the absolute

LED temps. The absolute temps will be based on the actual boundary conditions.

USA: Europe:

Asia:

www.lairdtech.com

29

Case Study: Lamp with 6 High

power LEDs

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power LEDs –cont.

31


power LEDs – cont.

32

Thermal Profile FR4 & IMPCB

33

CASE STUDY – Thermal at 40W, ST10

40Watt, Natural Convection, STABLCOR PCB running 11.2oC Cooler

www.stablcor.com

Courtesy: CONTINENTAL Automotive France SAS, Mr. Loic Bertrand

Customer Quote:

ST10 represented

a 12% to 15%

temperature

reduction

compared to FR4

dT between ST325

and ST10 PCBs

are very close to

each other

FR4 PCB STABLCOR®

ST10+FR4

NATURAL CONVECTION

40Watt

Technology Presentation-0508

34

http://www.stablcor.com/

DESIGN GUIDELINES

DESIGN GUIDELINES

35

Types of Thermal management Material?

A thermally & Electrically Conductive Composite Material

It has very good In-plane Thermal Conductivity

It can be used as a plane layer, Preferably GND plane

Thermal Interface material bonded on Metal

base plate or Carbon Core

36

BASE MATERIALS

BASE MATERIALS

Thermal

Conductivity

(W/m.K)

CTE

(ppm/C)

Tensile

Modulus

(Msi)

Density

(g/cc)

FR-4/E-glass 0.3 to 0.4 16 to 20 3.5 to 4.5 1.6-1.8

Polyimide/E-glass 0.2 to 0.4 15 to 19 3.5 to 4.5 1.5-1.7

Copper 385 17 to 20 12 8.92

CIC (Copper-Invar-Copper) 108 5 to 6 19 9.90

Aluminum 190 24 10 2.7

Carbon Composite 2*~ 75* ~4.5 to 7 ~ 9-10 1.65 to 1.7

* Theoretical calculated In-Plane values based on volume & Thermal conductivity of the composite materials

37

Additional Materials

Material CTE

(ppm/K)

Thermal

Conductivity

(W/m.K)

FR4 16-20 0.8

304 Stainless Steel 16.4 17.3

96% Alumina Ceramic 6.5 21

Aluminum (3003/6061) 23.4 173

Copper 16.5 386

38

Weight

Thickness Resistivity @ 20 C Resistivity @ 130 C

0.5 oz 0.0007” 0.956 mohm/sq. 1.367 mohm/sq.

1.0 oz 0.0014” 0.479 mohm/sq. 0.686 mohm/sq.

2.0 oz 0.0028” 0.239 mohm/sq. 0.343 mohm/sq.

3.0 oz 0.0042” 0.160 mohm/sq. 0.229 mohm/sq.

4.0 oz 0.0056” 0.120 mohm/sq. 0.171 mohm/sq.

6.0 oz 0.01 0.080 mohm/sq 0.114 mohm/sq

Thickness and Resistivity of Std Weight Copper

39

Copper Wt. 0.5 oz 1 oz 2 oz. 3 oz. 4 oz. 6 oz.

Minimum Line

width0.005” 0.008” 0.012” 0.015” 0.020” 0.025”

Minimum Line

spacing0.005” 0.010” 0.015” 0.020” 0.025” 0.030”

Prefered Min.

Line width0.010” 0.015” 0.020” 0.020” 0.025” 0.030”

The etched copper foil tolerance is

typically +/-20% of the foil thickness.

Line Width & Edge-to-Edge Spacing

40

PROPERTIES T-preg

Thermal Conductivity, W / m oC 2 ~4

Dielectric Strength, V / mil 1,500 ~ 800

Dielectric Constant, Dk 4.2 ~ 4.8

Peel Strength, pli 6~6.5

Flammability Class 94V-0

Operating Temperature, oC 130~150

T-Preg Properties

41


42

T-preg

T-preg DSL

Copper Foil

Base Metal /Carbon Composite Material

BASIC CONSTRUCTION MATERIALS

43

T-Preg Thermally Conductive Dielectric/ Prepreg

DSL Double Sided Laminate

IMPCB’s Insulated Metal Printed Circuit Boards

Basic Construction

44

T-preg

Copper Foil

Base Metal Material

One or Multiple Layers of T-preg

Copper weight 1 to 6 ounces

Dielectric layers 4,6 or 8 mil

Base Metal Copper or Aluminum 10 to 120 mil

Single Sided Board

45

Construction Materials

• FR-4-Double-Sided PCB ( Min 0.014”)

• Metal Base

•Thermal Vias (0.025”)

PTH &

Thermal Vias

Mounting Hole

FR - 4

T-preg Metal Base

Hybrid IMPCB with FR-4/T-Preg

47

Two-Layers

• DSL internal copper weight up to 4 oz.

• T-Preg

• Metal Base

Mounting Hole

PTH &

Thermal Vias T-lam DSL

T-preg

Metal Base Construction Materials

48

49

Construction Materials:

• DS Outer copper weight up to 4 oz.

• Thermal Interface material from 4 mil

• Metal Base 0.040”

Multilayer Metal Base


DSL

Copper Foil

T-Preg

Metal Base

PTH & Thermal

Vias

Mounting Hole Buried Vias

T-lam DSL & T- preg

52

Double-Sided Metal Core


• Copper Foil

• T-preg

• Metal-Core

PTH Mounting Hole

T-preg Metal Core

53

PTH PTH & Blind

Thermal Vias

FR- 4 Multilayer

Board

Mounting

Hole

T-preg

• 4 layer FR4 PCB

• T-preg

Construction

Materials

Buried Via

Multilayer FR-4/T-preg Hybrid

54

APPLICATIONS

55

High Power LED Lighting

56

Junction Block

(Relay Box)

Electric drive unit

(DC-DC Convertor & EPS Convertor)

Headlight

58

DC / DC Converters

Mounting Hole

Thermal Vias TTC

TCP Metal Base

60

Electric Motor Controls

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Electrical & Thermal vias

Maximum Current Rating vias

Thermal Guide for performance

62


Electrical & Thermal Vias

Vias drilled prior to the Lamination.

Min. via drill 0.010” and Base metal drill 0.040”, Min

clearance 0.015”/side.

Vias wall design to carry heat & current

Not exceeding 2 holes with a 0.060 diameter, per sq

inch and a 0.060” max copper core thickness.

Drill clearance holes in copper core .030” to .040” larger

than drill size of the vias. The goal is to have a .015 to

.020 ring of T-preg to isolate the via from the copper

core. PTH: Min. 0.015” to 0.125” Max.

63

Maximum Current rating for vias

Vias Size

Wall Thickness

Foil Thickness

Dielectric Thickness

Maximum current of vias is limited by the

maximum vias temperature

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Thermal Guide for Performance

Function of:

Via size

Via Wall Thickness

Foil Thickness

Dielectric Thickness

Via pitch

Maximum base plate temperature

65

7mils to 10mils for Routed Edge

15mils to 20mils for Scored Edge

Copper to Edge Clearance

66

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We recommend not exceeding 2 holes with a 0.060 diameter, per

sq inch and a 0.060” maximum copper core thickness.

Drill clearance holes in copper core .030” to .040” larger than drill

size of the vias. The goal is to have a .015 to .020 ring of T-preg to

isolate the via from the copper core. PTH: Min. 0.015” to 0.125”

Max.

15mils+ per side

Surface Preparations

Exposed

Copper Surface

• Coat with Antioxidant to extend T-lam life

• Used for Aluminum ultrasonic wire bonding

Solder Resist

• Protect lines from Mechanical or Environmental damage

and contaminations

• For Heavy copper conformal coating or potting compound

can be applied

Solder coating

• Standard Hot-Air Leveling for good wetting and provides a

thin and uniform solder coating.

• 300 micro-inches thickness

68

Surface Preparations (continue)

Plating

• Reduces Oxidations, mechanical protection, improves

solder and wire bonding operations.

• Nickel, Silver, Gold, Tin, OSP are common

Nickel (Electroless)

• Use for Soldering and wire bonding

• 100 – 300 micro-inches

• Slow oxidation rate but difficult to see and remove

• Plate with 7-12% phosphorous content

ENIG

• Electroless Nickel Immersion Gold process

• Gold thickness 8-10 micro-inches, eliminate porosity

• Gold thickness 15-50 micro-inches for Wire bonding

Silver (Electroless) • Silver thickness 8-10 micro-inches, eliminate porosity

• Slow Oxidation rate but can be seen

69

FABRICATION TOLERANCES GUIDELINES

Milling/CNC or Scoring Punching

Camber or flatness +/- 0.001” per inch +/- 0.002” per inch

Cost advantage at Low volume High volume

Fix cost No Tooling cost High Tooling cost

Finish Clean Edges Burr on edges

Substract to subtract +/- 0.002” +/- 0.005”

Maximum burr 0.002” 0.007”

Corner Radius (outside (min) 0.00” 0.7t

Minimum Panel Border 0.5” 0.5”

70

FABRICATION GUIDELINES

Milling/CNC or Scoring Punching

Corner radius (inside, min.) 0.7t 0.7t

Bridge, Edge to Hole (min) 0.5t 1.5t

Hole Diameter (min) 0.2t 1.0t

Hole Tolerance. +/- 0.002” +/- 0.005”

Hole Location, Hole to holes 0.001” 0.001”

Hole Location, hole to edge 0.005” 0.001”

Wire bonding yes

High current application Less cost than FR4

71

Specify Materials in Metal core; Comapny

name and part #.

Thickness of dielectric .

Tg or Td

Metal Core

Insulation resistance & Thermal conductivity

values.

Fabrication Check List

72

Footprints OR Data sheets

Net List

Material specifications

Construction Details

Layout Guideline

Mechanical Details

Other specific requirements

Fabrication Check List

73

CONCLUSION

Reduces Hot Spot

PCB acts as a Heat Sink

Reduces Thermal Stress on Components

Operates Cooler

SS or DS with SMT NO need to change the Design

74

Acknowledgements

Thanks to following contributors:

Laird Technology

Stabcor Inc. for their Stabcor laminates

75

Thank You

Presented By:

Pratish Patel

Electronic Interconnect

www.eiconnect.com

[email protected]

76

http://www.eiconnect.com/

Advancements in Thermal Management at PCB … · for Electronics Design and Fabrication Presented...

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Transcript of Advancements in Thermal Management at PCB … · for Electronics Design and Fabrication Presented...